EP3688200B1 - Molybdenum sintered part and method of manufacturing - Google Patents
Molybdenum sintered part and method of manufacturing Download PDFInfo
- Publication number
- EP3688200B1 EP3688200B1 EP18789316.9A EP18789316A EP3688200B1 EP 3688200 B1 EP3688200 B1 EP 3688200B1 EP 18789316 A EP18789316 A EP 18789316A EP 3688200 B1 EP3688200 B1 EP 3688200B1
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- EP
- European Patent Office
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- ppmw
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- molybdenum
- boron
- carbon
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- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 title claims description 122
- 229910052750 molybdenum Inorganic materials 0.000 title claims description 93
- 239000011733 molybdenum Substances 0.000 title claims description 90
- 238000004519 manufacturing process Methods 0.000 title description 14
- 229910052796 boron Inorganic materials 0.000 claims description 79
- 229910052799 carbon Inorganic materials 0.000 claims description 75
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 74
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 70
- 229910052760 oxygen Inorganic materials 0.000 claims description 40
- 239000000523 sample Substances 0.000 claims description 36
- 239000001301 oxygen Substances 0.000 claims description 35
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 34
- 239000000843 powder Substances 0.000 claims description 34
- 238000005245 sintering Methods 0.000 claims description 22
- 239000012535 impurity Substances 0.000 claims description 20
- 239000010936 titanium Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 14
- 229910052721 tungsten Inorganic materials 0.000 claims description 14
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 13
- 239000010937 tungsten Substances 0.000 claims description 13
- 229910052735 hafnium Inorganic materials 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- 230000008569 process Effects 0.000 claims description 11
- 229910052702 rhenium Inorganic materials 0.000 claims description 11
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 10
- 238000003325 tomography Methods 0.000 claims description 10
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 9
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 9
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 9
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 9
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 229910052700 potassium Inorganic materials 0.000 claims description 8
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 claims description 8
- 239000010703 silicon Substances 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 239000011591 potassium Substances 0.000 claims description 7
- 238000003825 pressing Methods 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- 239000004411 aluminium Substances 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- PPWPWBNSKBDSPK-UHFFFAOYSA-N [B].[C] Chemical compound [B].[C] PPWPWBNSKBDSPK-UHFFFAOYSA-N 0.000 claims description 2
- 238000011109 contamination Methods 0.000 claims 6
- 238000012360 testing method Methods 0.000 description 30
- 238000005452 bending Methods 0.000 description 20
- 239000000463 material Substances 0.000 description 20
- 238000011161 development Methods 0.000 description 19
- 230000018109 developmental process Effects 0.000 description 19
- 238000003466 welding Methods 0.000 description 18
- 125000004429 atom Chemical group 0.000 description 16
- 238000004458 analytical method Methods 0.000 description 12
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 238000007792 addition Methods 0.000 description 10
- 150000001875 compounds Chemical class 0.000 description 10
- 230000000694 effects Effects 0.000 description 10
- 239000000654 additive Substances 0.000 description 9
- 238000001887 electron backscatter diffraction Methods 0.000 description 9
- 238000002844 melting Methods 0.000 description 9
- 230000008018 melting Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
- 238000005242 forging Methods 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- 238000005096 rolling process Methods 0.000 description 7
- 230000007704 transition Effects 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 239000000945 filler Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 238000004663 powder metallurgy Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000009864 tensile test Methods 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 229910001182 Mo alloy Inorganic materials 0.000 description 4
- 238000000137 annealing Methods 0.000 description 4
- 238000013001 point bending Methods 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 229910002091 carbon monoxide Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000011835 investigation Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000000376 reactant Substances 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 241001522319 Chloris chloris Species 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910039444 MoC Inorganic materials 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- LGLOITKZTDVGOE-UHFFFAOYSA-N boranylidynemolybdenum Chemical compound [Mo]#B LGLOITKZTDVGOE-UHFFFAOYSA-N 0.000 description 2
- 238000009838 combustion analysis Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 238000010884 ion-beam technique Methods 0.000 description 2
- 238000005272 metallurgy Methods 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005211 surface analysis Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- QIJNJJZPYXGIQM-UHFFFAOYSA-N 1lambda4,2lambda4-dimolybdacyclopropa-1,2,3-triene Chemical compound [Mo]=C=[Mo] QIJNJJZPYXGIQM-UHFFFAOYSA-N 0.000 description 1
- 241001270131 Agaricus moelleri Species 0.000 description 1
- 229910000521 B alloy Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000001389 atom probe field ion microscopy Methods 0.000 description 1
- 238000001636 atomic emission spectroscopy Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- QROVMOADHGTXCA-UHFFFAOYSA-N dimolybdenum monoboride Chemical compound B#[Mo]#[Mo] QROVMOADHGTXCA-UHFFFAOYSA-N 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000156 glass melt Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000004573 interface analysis Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 238000010943 off-gassing Methods 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 238000012549 training Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
- C22C27/04—Alloys based on tungsten or molybdenum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/045—Alloys based on refractory metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2201/00—Treatment under specific atmosphere
- B22F2201/01—Reducing atmosphere
- B22F2201/013—Hydrogen
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2207/00—Aspects of the compositions, gradients
- B22F2207/01—Composition gradients
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2302/00—Metal Compound, non-Metallic compound or non-metal composition of the powder or its coating
- B22F2302/45—Others, including non-metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
- B22F3/04—Compacting only by applying fluid pressure, e.g. by cold isostatic pressing [CIP]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
Definitions
- the present invention relates to a powder-metallurgical molybdenum sintered part in the form of a solid body and a method for producing such a molybdenum sintered part.
- molybdenum Due to its high melting point, low thermal expansion coefficient and high thermal conductivity, molybdenum is suitable for various high-performance applications, such as a material for glass melting electrodes, for furnace components of high-temperature furnaces, for heat sinks and for X-ray anodes.
- a frequently used and large-scale process for the production of molybdenum and molybdenum-based materials is the powder metallurgical production route, in which the corresponding starting powders are pressed and then sintered, with the pressing step typically being preceded by mixing the powders in the case of several powders.
- molybdenum produced by powder metallurgy (hereinafter "powder metallurgy") is characterized by the fact that the structure is finer-grained and more homogeneous due to the comparatively low sintering temperature (sintering temperature ⁇ 0.8*melting point). There is no liquid phase segregation and the powder metallurgy fabrication route allows for a greater variety of preforms (in geometric terms) to be produced.
- molybdenum with its body-centered cubic crystal structure, has a transition from ductile to brittle behavior depending on the processing state - at or above room temperature (e.g. at 100°C) and is very brittle below this transition temperature. Furthermore, undeformed molybdenum and recrystallized molybdenum have a relatively low strength, especially in relation to bending and tensile loads, which also limits the area of application (through forming, such as rolling or forging, these properties can also be improved with conventional molybdenum, with increasing recrystallization however, they deteriorate again).
- molybdenum cannot be welded, which either requires complex connection methods (riveting, flanging, etc.) or - to improve the welding properties - the addition of alloying elements (e.g. rhenium or zirconium) to the Mo base material or the use of welding filler materials (e.g. rhenium).
- alloying elements e.g. rhenium or zirconium
- welding filler materials e.g. rhenium
- 2017/0044646 A1 which contains certain proportions of vanadium (V), carbon (C), niobium (Nb), titanium (Ti), boron (B), tungsten (W), tantalum (Ta), hafnium (Hf) and ruthenium (Ru ) teaches in combination known.
- V vanadium
- carbon C
- niobium Nb
- titanium Ti
- boron B
- Ta tantalum
- Ru ruthenium
- the object of the present invention is to provide a molybdenum-based material that has high strength and good weldability and can be used universally in different applications.
- the molybdenum sintered part according to the invention has significantly increased ductility and increased strength, in particular with regard to bending and tensile loads. This is particularly true when compared to conventional molybdenum in the undeformed and/or (fully or partially) recrystallized condition.
- conventional molybdenum the Forming larger components is problematic due to the low grain boundary strength.
- forging thick bars e.g. with starting diameters of 200-240 mm
- rolling thick sheets e.g.
- the molybdenum sintered part according to the invention can also be produced and further processed on an industrial scale.
- the molybdenum sintered part according to the invention With the molybdenum sintered part according to the invention, the forming of large components, such as the forging of thick rods and the rolling of thick sheets, is possible while avoiding internal defects and grain boundary cracks.
- the molybdenum sintered part according to the invention eg in the form of sheet metal
- the low strength of conventional molybdenum is attributed to low grain boundary strength, which leads to intergranular fracture behavior.
- the grain boundary strength of molybdenum is known to be reduced by segregation of oxygen and possibly other elements, such as nitrogen and phosphorus, in the area of the grain boundaries.
- the invention is based on the finding that even low levels of carbon and boron in combination lead to significantly increased grain boundary strength and have a favorable effect on the flow behavior of the material (responsible for the high ductility) if the oxygen content is low and the content of other impurities ( and W) are below the specified limits.
- the carbon content of the Oxygen content can be kept low in the sintered part.
- the boron content large amounts of carbon are not required, which would be problematic, especially in the case of glass melting components, due to the increased outgassing that then occurs.
- a low proportion of boron in combination with a comparatively low proportion of carbon is sufficient to achieve the desired high ductility and strength values.
- a powder-metallurgical molybdenum sintered part is understood to mean a component whose production includes the steps of pressing corresponding starting powder to form a compact and sintering the compact.
- the manufacturing process can also have further steps, such as mixing and homogenizing (e.g. in a plowshare mixer) the powder to be pressed, etc Specialist is readily recognizable.
- This microstructure is characterized by its fine grain (typical grain sizes in particular in the range of 30-60 ⁇ m). Furthermore, the pores are distributed uniformly over the entire cross section through the sintered part.
- the powder-metallurgical molybdenum sintered part according to the invention can also have been subjected to further processing steps, such as forming (rolling, forging, etc.), so that it is then in a formed structure, subsequent annealing, etc.. It can also be coated and / or connected to other components, such as by welding or soldering.
- the details of the proportions according to the invention and the details regarding the further developments explained below relate to the respective taken element (eg Mo, B, C, O or W), regardless of whether this is present in the molybdenum sinter in elemental or combined form.
- the proportions of the different elements are determined by chemical analysis.
- the proportions of most metallic elements e.g. Al, Hf, Ti, K, Zr, etc.
- the ICP-MS analysis method mass spectroscopy with inductively coupled plasma
- the boron proportion using the ICP-OES analysis method optical emission spectroscopy with inductively coupled plasma
- the carbon content via combustion analysis combustion analysis
- oxygen content via hot extraction analysis carrier gas hot extraction
- ppmw expresses the proportion by weight multiplied by 10 -6 .
- the specified limit values can also be stably maintained over thick components; in particular, the advantageous properties can be realized on an industrial scale independently of the respective component geometry, sheet metal thickness, etc. It was observed that the boron content and the carbon content decrease slightly towards the surface of the sintered part, while the oxygen content is relatively constant through the sintered part thickness. A slight decrease in the boron content and/or the carbon content towards the surface or a slight increase in the oxygen content towards the surface, even if the limit values may not be in an area close to the surface (with a thickness of 0.1 mm, for example).
- a grading of the composition can optionally only occur during subsequent treatment steps of the molybdenum sintered part, such as during reshaping (rolling, forging, extrusion, etc.), during subsequent annealing, during a welding process, etc., occur or increase further.
- the boron content and the carbon content are each ⁇ 5 ppmw.
- certified content information for boron and carbon can typically be specified above 5 ppmw.
- boron and carbon below a respective proportion of 5 ppmw can also be clearly detected and their proportions can be determined quantitatively (at least if the respective proportion is ⁇ 2 ppmw), but the proportions in in this area - depending on the analysis method - sometimes no longer specified as a certified value.
- the total proportion "BuC" of carbon and boron is in the range of 25 ppmw ⁇ "BuC" ⁇ 40 ppmw.
- the boron content "B” is in the range of 5 ppmw ⁇ "B" ⁇ 45 ppmw, more preferably in the range of 10 ppmw ⁇ "B" ⁇ 40 ppmw.
- the proportion of carbon “C” is in the range of 5 ⁇ “C” ⁇ 30 ppmw, more preferably in the range of 15 ⁇ “C” ⁇ 20 ppmw.
- both elements (B, C) are contained in the molybdenum sintered part in such a high and at the same time in such a sufficient quantity that their advantageous interaction is clearly noticeable, but at the same time the carbon and the boron contained does not yet have a negative effect in the various applications.
- the effect of carbon is to keep the oxygen content low in the molybdenum sinter and of boron to allow a sufficiently low carbon content while achieving high ductility and high strength.
- the oxygen content "O" is in the range of 5 ⁇ "O" ⁇ 15 ppmw. According to current knowledge, the oxygen accumulates in the area of the grain boundaries (segregation) and leads to a reduction in grain boundary strength. Accordingly, an overall low oxygen content is advantageous. Setting such a low oxygen content is possible both by using starting powders with a low oxygen content (eg ⁇ 600 ppmw, in particular ⁇ 500 ppmw), sintering in the Vacuum, under protective gas (eg argon) or preferably in a reducing atmosphere (especially in a hydrogen atmosphere or in an atmosphere with H 2 partial pressure), and by providing a sufficient proportion of carbon in the starting powders.
- a low oxygen content eg ⁇ 600 ppmw, in particular ⁇ 500 ppmw
- protective gas eg argon
- a reducing atmosphere especially in a hydrogen atmosphere or in an atmosphere with H 2 partial pressure
- the maximum proportion of impurities from zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminum (Al) is ⁇ 50 ppmw in total.
- the proportion of each element of this group (Zr, Hf, Ti, V, Al) is preferably ⁇ 15 ppmw.
- the maximum proportion of impurities from silicon (Si), rhenium (Re) and potassium (K) is ⁇ 20 ppmw in total.
- the proportion of each element of this group (Si, Re, K) is preferably ⁇ 10 ppmw, in particular ⁇ 8 ppmw.
- the effect attributed to potassium is that it reduces the grain boundary strength, which is why the lowest possible proportion is desirable.
- Zr, Hf, Ti, Si and Al are oxide formers and could in principle be used to counteract an enrichment of oxygen in the area of the grain boundaries by binding the oxygen (oxygen getter) and thus in turn to increase the grain boundary strength. In some cases, however, they are suspected of reducing ductility, especially when they are present in large quantities.
- a ductilizing effect is ascribed to Re and V, ie they could in principle be used to increase the ductility.
- the addition of additives means that they can also have a disruptive effect depending on the application and conditions of use of the Mo sintered part.
- the molybdenum sintered part has a total proportion of molybdenum and tungsten of ⁇ 99.97% by weight.
- the proportion of tungsten within the specified limit values ( ⁇ 330 ppmw) is not critical for the previously known applications and is typically already due to the Mo extraction and powder production.
- the molybdenum sintered part has a molybdenum content of ⁇ 99.97% by weight, ie it consists almost entirely of molybdenum.
- the carbon and the boron are in total at least 70% by weight, based on the total content of carbon and boron, in dissolved form (they do not therefore form a separate phase).
- Investigations on sintered molybdenum parts according to the invention have shown that a small proportion of the boron may be present as the Mo 2 B phase, although this is not critical to a small extent.
- the carbon and the boron are at least to a large extent (eg ⁇ 70% by weight, in particular ⁇ 90% by weight) in solution, they can segregate at the grain boundaries and fulfill the effect explained above to a particularly high degree.
- each of the elements B and C individually also satisfies the specified limit values.
- the boron and the carbon are finely distributed in the Mo base material and enriched in the area of the large-angle grain boundaries.
- a high-angle grain boundary is present when an angular difference of ⁇ 15° is required to match the crystallographic alignment of adjacent grains, which can be determined by EBSD (electron backscatter diffraction). Due to the fine distribution and the enrichment in the area of the large-angle grain boundaries, boron and carbon can exert their positive influence on the grain boundary strength to a particularly high degree.
- An essential aspect for achieving this fine distribution and a high enrichment at least along as many large-angle grain boundaries as possible (and possibly also along small-angle grain boundaries) is that the boron and carbon are added to the starting powders during powder metallurgical production as the purest possible element (B , C) or as a compound that is as pure as possible, ie with as few other impurities as possible (apart from the compound partner of B and/or C that may be added, such as Mo, N, C, etc.), and as a powder that is as fine as possible.
- Boron for example, as molybdenum boride (Mo 2 B), as boron carbide (B 4 C), as boron nitride (BN) or elementary as amorphous or crystalline boron.
- Carbon can be added, for example, as graphite or as molybdenum carbide (MoC, Mo 2 C).
- the sintering conditions temperature profile, maximum sintering temperature, Holding times, sintering atmosphere
- boron and carbon if they are freely available at the temperatures in question, react at least partially with oxygen from the starting powders and possibly also with oxygen from the sintering atmosphere and escape as gas. In order to still achieve the desired boron and carbon content in the finished molybdenum sintered part, correspondingly higher amounts of boron- and/or carbon-containing powders must be added to the starting powders.
- the tendency for it to volatilize during the sintering process and be emitted into the atmosphere as an environmentally harmful gas can be counteracted by matching the boron-containing powder and the sintering conditions in such a way that the boron is only released after such a Duration and / or after such a temperature increase as a reactant is available (e.g. because only then does the boron-containing compound decompose or the boron-containing powder only releases the boron due to its morphology, coating, etc. to the reaction) if the Oxygen from the starting powders has at least largely reacted with different reactants (e.g. hydrogen, carbon, etc.) and has escaped as a gas.
- reactants e.g. hydrogen, carbon, etc.
- a gradation of the composition across the thickness of the Mo sintered part can be largely suppressed by keeping the oxygen content as low as possible in the starting powders and only using a moderately increased amount of carbon and boron-containing powders (compared to the achievable C and B portions in the Mo sintered part) is added, preferably a reducing atmosphere (H 2 atmosphere or H 2 partial pressure), alternatively a protective gas (e.g argon) or a vacuum is selected during the sintering process and the boron-containing powder and the temperature profile during the sintering process are coordinated in such a way that the boron is only released when the oxygen from the starting powders has already reacted, at least to a large extent, with other reactants Has.
- a protective gas e.g argon
- the total proportion of carbon and boron in the area of the grain boundary section is at least one and a half times as high as in the area of the grain interior of the adjacent grain;
- the proportion of carbon and boron in total in the area of the grain boundary section is at least twice as high, more preferably at least three times as high as in the area of the grain interior of the adjacent grain.
- each of the elements B and C satisfies the specified relationships.
- the proportions of the individual elements (B, C) and the sum of the elements (B and C) are each determined in atomic percent (at%) by means of three-dimensional atom probe tomography.
- a three-dimensional, cylindrical region with a cylinder axis running perpendicular to the grain boundary section and with a thickness of 5 nm (nanometers) running along the cylinder axis is selected for the region of the grain boundary section, which is placed centrally around the grain boundary section in relation to the cylinder axis direction (According to the measurement method that is decisive here and explained in detail below, this is the range of 5 nm thickness within which the sum of the measured concentrations of B and C is maximum).
- the cylinder axis runs perpendicularly to the plane that is spanned by the grain boundary section in the region to be examined.
- a mean plane that maintains a minimum distance to the grain boundary section over the observed area is to be used (for the orientation and positioning of the cylindrical region to be examined).
- a three-dimensional cylindrical region spaced with its center by 10 nm in the cylinder axis direction from the grain boundary portion (or, if necessary, from the associated average plane) becomes the same Dimensions and the same orientation (ie the same alignment and position of the cylinder axis of the cylinder-shaped area to be examined) is used. It is important to ensure that the region of the interior of the grain is at the same time sufficiently spaced apart from other large-angle grain boundaries, preferably by at least 10 nm.
- the three-dimensional, cylindrical areas (of the grain interior as well as the grain boundary section) each have a (circular) diameter of 10 nm, with the associated circular area of the cylindrical areas being aligned perpendicular to the associated cylinder axis (resulting from the cylindrical shape).
- the proportion of boron and carbon is determined in atomic percent. Subsequently, the proportions determined in this way, either of boron and carbon in total or alternatively also of the individual elements, are set in relation to the area of the grain boundary section and the area of the interior of the grain, as will be explained in more detail below.
- Atom probe tomography is a high-resolution characterization method for solids. Needle-shaped tips ("sample tip") with a diameter of about 100nm are cooled to temperatures of about 60K and removed by field evaporation. The position of the atom and the mass-to-charge ratio for each detected atom (ion) is determined using a position-sensitive detector and time-of-flight mass spectrometer. A more detailed description of atom probe tomography can be found in MK Miller, A Cerezo, MG Hetherington, GDW Smith, Atom probe field ion microscopy, Clarendon Press, Oxford, 1996 .
- a three-dimensional reconstruction of the sample tip used in the molybdenum sintered part according to the invention is first carried out (cf. also figure 5 and their description). At least elements B and C are displayed. Based on the knowledge that these elements accumulate in the area of the large-angle grain boundaries, the position of the large-angle grain boundary can be made visible in the three-dimensional reconstruction by the compression of elements B and C occurring there.
- a measuring cylinder which is relevant for the evaluation and has a diameter of 10 nm (according to the information given above), is positioned in the three-dimensional reconstruction in such a way that a grain boundary section (as flat as possible and spaced sufficiently far from other large-angle grain boundaries) of the Large-angle grain boundary within the measuring cylinder is that the cylinder axis of the measuring cylinder - as described above for the cylindrical areas to be examined - is aligned perpendicular to the plane spanned by the grain boundary section.
- the grain boundary section is preferably located essentially in the center of the measuring cylinder in relation to the cylinder axis of the measuring cylinder.
- the measuring cylinder must be positioned and its length (along the cylinder axis) chosen so long (e.g. 30 nm) that not only the cylindrical area of the grain boundary section, but also the cylindrical area of the grain interior, each of which has a thickness of 5 nm and whose centers are spaced apart by 10 nm along the cylinder axis, each lie entirely within the measuring cylinder.
- a one-dimensional concentration profile is then determined (cf. 6 and the associated description).
- the measuring cylinder is divided along its cylinder axis into cylindrical disks with a respective disk thickness of 1 nm (diameter 10 nm in each case corresponding to the diameter of the measuring cylinder).
- the concentration (in atomic percent) of at least the elements B and C (and optionally other elements such as O, N, Mo, etc.) is determined for each of these discs.
- the concentration of at least the elements B and C (individually and possibly also in total) determined for each disk is plotted against the length of the cylinder axis in a diagram (see. 6 ), whereby one measuring point per nanometer is to be entered according to the subdivision.
- the five adjacent discs of the measuring cylinder where the sum of the measured concentrations of B and C (B and C calculated for each measuring point in total) is maximum are selected as the cylindrical area of the grain boundary section to be examined.
- the five adjacent disks are selected, the central disk of which is spaced by 10 nm from the central disk of the cylindrical region of the grain boundary section.
- the proportions of B, C and the sum of B and C are determined for the area of the grain boundary section and correspondingly for the area of the interior of the grain by calculating the proportions (in atomic percent) of these elements (B, C, or B and C in total ) is summed up for the five relevant panes of the area to be examined and then the sum is divided by five.
- the values thus obtained for the area of the grain boundary section can then be related to the area of the grain interior.
- the molybdenum sintered part according to the invention can also be subjected to further processing steps, in particular forming (rolling, forging, extrusion, etc.).
- the sintered molybdenum part is deformed at least in sections and has a preferred orientation of the large-angle grain boundaries and/or large-angle grain boundary sections perpendicular to the main direction of deformation, which can be determined by means of EBSD analysis of a metallographic microsection of a cross-sectional plane along the direction of deformation, in which the (e.g. circumferential high angle grain boundaries formed around a grain and the high angle grain boundary sections (e.g. formed with an open beginning and end) visualized can be determined.
- the molybdenum sintered part according to the invention can be shaped particularly well and with a low scrap rate. Even when forging thick bars (e.g. with starting diameters in the range of 200-240 mm) and rolling thick sheets (e.g. with starting thicknesses in the range of 120-140mm), cracking, which occurs more frequently with conventional molybdenum, in the core of the bars/sheets, avoided.
- the molybdenum sintered part a deformed structure, i.e. there are typically no clear large-angle grain boundaries surrounding individual grains, as they occur immediately after the sintering step, but only large-angle grain boundary sections, each of which has an open beginning and an open end.
- sections of the large-angle grain boundaries of the original grains are still recognizable as they were immediately after the sintering step.
- Dislocations and new large-angle grain boundary sections are also formed as a result of the deformation.
- the original grains, as they were immediately after the sintering step, if they are still recognizable, are severely squashed and distorted due to the deformation.
- the preferred direction of the recognizable large-angle grain boundary sections runs perpendicular to the main direction of deformation. In particular, a larger proportion (e.g.
- At least 60%, in particular at least 70%) of the large-angle grain boundary sections in terms of length is more inclined to the direction perpendicular to the main forming direction (or in some cases exactly parallel to it) than inclined to the main forming direction, which is EBSD analysis of a metallographic micrograph of a cross-sectional plane along the main forming direction, in which the high-angle grain boundary sections are made visible.
- a heat treatment e.g. stress-relief annealing at temperatures in the range of 650-850°C and a duration in the range of 2-6 h; recrystallization annealing at temperatures in the range of 1000-1300°C and a duration in range of 1-3 hours.
- a heat treatment e.g. stress-relief annealing at temperatures in the range of 650-850°C and a duration in the range of 2-6 h; recrystallization annealing at temperatures in the range of 1000-1300°C and a duration in range of 1-3 hours.
- the molybdenum sintered part according to the invention is at least partially (if necessary also completely ) in a partially or fully recrystallized structure. Compared to conventional molybdenum with a partially or fully recrystallized structure, significantly higher ductility and strength values are achieved.
- the sintered molybdenum part (in particular in the form of sheet metal) is connected to a further sintered molybdenum part (in particular in the form of sheet metal) via a welded joint, with both sintered molybdenum parts being formed in accordance with the present invention and optionally in accordance with one or more of the further developments and wherein a weld zone of the welded joint has a molybdenum content of ⁇ 99.93% by weight.
- the molybdenum sintered parts according to the invention can be welded much better than conventional molybdenum. As is evident from the specified molybdenum content of the weld zone, no filler material is required.
- the welded connection has high ductility and strength values, in particular, depending on the welding process and the welding conditions, elongations of >8% in the tensile test (according to DIN EN ISO 6892-1 Verf.B) and bending angles of up to 70° in bending tests according to DIN EN ISO 7438) measured. Significant improvements have been achieved in particular in laser beam welding and TIG welding (tungsten inert gas welding).
- the powders containing boron and carbon can likewise be molybdenum powder, which contains a corresponding proportion of boron and/or carbon. It is essential that the starting powder used for pressing the green compact contains sufficient amounts of boron and carbon and that these additives are distributed as evenly and finely as possible in the starting powder.
- the sintering step comprises a heat treatment for a residence time of from 45 minutes to 12 hours (h), preferably from 1-5 h, at temperatures in the range of 1800°C - 2100°C.
- the sintering step is carried out in a vacuum, under a protective gas (eg argon) or preferably in a reducing atmosphere (in particular in a hydrogen atmosphere or in an atmosphere with H 2 partial pressure).
- the molybdenum sintered parts had the following compositions (if relevant to the present invention): 30B15C 15B15C 30B B70 B150 C70 C150 Mon in B portion [ppmw] 30 15 30 70 150 ⁇ 5 ⁇ 5 ⁇ 5 C content [ppmw] 15 15 9 8th 9 70 150 6 O content [ppmw] 9 9 8th 5 6 7 ⁇ 5 14 W component [ppmw] ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 ⁇ 330 330 330 330 330 330 330 330 Other impurities. [ppmw] ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇ 300 ⁇
- test specimens designed according to the invention achieve significantly higher bending angles at the same test temperature.
- test sample "30B15C” achieves a bending angle of 99°
- test sample "15B15C” a bending angle of 94°
- test sample "Mo pure” only a bending angle of approx. 2.5°.
- test specimen "30B15C” achieves a bending angle of 82°, test specimen “15B15C” a bending angle of 40° and test specimen "Mo pure” only a bending angle of approx. 2.5°.
- the transition from ductile to brittle behavior in molybdenum sintered parts according to the invention can be shifted to significantly lower temperatures, in particular from 110° C. for "Mo pure” to -10° C. for "30B15C”. and at 0°C at "15B15C”.
- the transition from brittle to ductile behavior is assigned to the temperature at which a bending angle of 20° is reached for the first time.
- test samples "30B15C” and “15B15C” show that a slightly higher addition of boron leads to a further increase in ductility, especially in the temperature range from approx. -20°C to 50°C, while the ductility is comparable in the remaining temperature ranges is.
- a B content of 15 ppmw and a C content of 15 ppmw will already be sufficient for many applications, especially if the aim is to keep the content of additional elements as low as possible.
- FIG 5 is a three-dimensional reconstruction of a sample tip of a molybdenum sintered part according to the invention, determined by atom probe tomography "15B15C" shown.
- the position of the C atoms in the tip of the sample is shown in red in this representation, that of the B atoms in violet, that of the O atoms in blue and that of the N atoms in green.
- the Mo atoms are indicated as small dots in order to visualize the shape of the tip of the sample.
- the positions of the various atoms are also clearly recognizable in a gray scale representation (taken place in the patent specification) on the basis of the different gray scales.
- the three-dimensional reconstruction is also described qualitatively in the following and also quantitatively by the one-dimensional concentration profile of the 6 added.
- a measuring cylinder 4 is placed in the three-dimensional reconstruction by the measuring software in such a way that its cylinder axis 6 is perpendicular to the the grain boundary section 2 spanned plane runs.
- a measuring cylinder 4 with a length of 20 nm (along the cylinder axis) and a diameter of 10 nm was selected.
- the grain boundary section 2 lies centrally (relative to the cylinder axis 6) within the measuring cylinder 4.
- those five adjacent disks (each having a thickness of 1 nm) of the measuring cylinder 4 are selected as the three-dimensional cylindrical region representative of the grain boundary section, in which the sum of the measured concentrations of B and C is maximum. In the present case, these are the measured values at the "distances" of 9, 10, 11, 12 and 13 nm.
- the five adjacent disks are selected as the cylindrical region of the interior of the grain to be examined, the central disk of which is 10 nm away from the central disk of the cylindrical Area of the grain boundary portion is spaced. This would be in the representation of 6 the measured values at the distances 3, 2, 1, 0, -1 (the latter value is not covered by the measuring cylinder in this case). Subsequently, for these two areas (of the grain boundary section as well as of the grain interior), the total proportions of B, C and of B and C are determined and set in relation to one another, as described in detail above.
- the proportion of carbon and boron, both individually and in total, in the area of the grain boundary section is at least three times as high as in the area of the interior of the adjacent grain. Furthermore is off 6 (as well as from figure 5 ) it can be seen that B and C (particularly in the interior of the grain) are finely and evenly distributed and are strongly enriched in the area of the large-angle grain boundaries.
- Molybdenum powder which was produced by hydrogen reduction, was used for the powder-metallurgical production of a molybdenum sintered part according to the invention.
- the grain size according to Fisher (FSSS according to ASTM B330) was 4.7 ⁇ m.
- the molybdenum powder had impurities of 10 ppmw carbon, 470 ppmw oxygen, 135 ppmw tungsten and 7 ppmw iron.
- the compacts produced in this way (round rods of 480 kg each) were sintered in indirectly heated sintering plants (i.e. heat transfer to the sintered material via thermal radiation and convection) at a temperature of 2050°C for a period of 4 hours in a hydrogen atmosphere and then cooled.
- the sintered rods obtained in this way had a boron content of 22 ppmw, a carbon content of 12 ppmw and an oxygen content of 7 ppmw.
- the tungsten content and the content of other metallic impurities remained unchanged.
- the sintered molybdenum rods according to the invention were deformed on a radial forging machine at a temperature of 1200° C., the diameter being reduced from 240 to 165 mm.
- the ultrasonic examination of the 100% dense bar showed no cracks on the inside either, and metallographic sections confirmed this finding.
- a cross-sectional area is produced through the molybdenum sintered part to be examined.
- a corresponding ground surface is prepared in particular by embedding, grinding, polishing and etching the cross-sectional area obtained, with the surface then being ion-polished (to remove the deformation structure on the surface caused by the grinding process).
- the measuring arrangement is such that the electron beam strikes the prepared ground surface at an angle of 20°.
- the distance between the electron source (here: field emission cathode) and the sample is 16.2 mm and the distance between the sample and the EBSD camera (here: "DigiView IV” ) is 16 mm.
- the information given in parentheses relates to the device types used by the applicant, although in principle other device types that enable the functions described can also be used in a corresponding manner.
- the acceleration voltage is 20 kV
- a magnification of 500x is set and the distance between the individual pixels on the sample, which are scanned one after the other, is 0.5 ⁇ m.
- large-angle grain boundaries e.g. formed circumferentially around a grain
- large-angle grain boundary sections e.g. formed with an open beginning and end
- a grain boundary angle that is greater than or equal to the minimum rotation angle of 15°
- the scanning electron microscope large-angle grain boundaries or large-angle grain boundary sections are always determined and displayed between two grid points within the examined sample surface if an orientation difference of the respective crystal lattices of ⁇ 15° is determined between the two grid points.
- the smallest angle that is required to convert the respective crystal lattices that are present at the grid points to be compared into one another is used as the orientation difference.
- This process is performed on each raster point in relation to all raster points surrounding it. In this way, a grain boundary pattern of high-angle grain boundaries and/or high-angle grain boundary sections is obtained within the examined sample area.
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Description
Die vorliegende Erfindung betrifft ein pulvermetallurgisches, als Festkörper vorliegendes Molybdän-Sinterteil sowie ein Verfahren zum Herstellen solch eines Molybdän-Sinterteils.The present invention relates to a powder-metallurgical molybdenum sintered part in the form of a solid body and a method for producing such a molybdenum sintered part.
Molybdän eignet sich aufgrund seines hohen Schmelzpunktes, seines niedrigen thermischen Ausdehnungskoeffizienten und seiner hohen Wärmeleitfähigkeit für unterschiedliche Hochleistungsanwendungen, wie zum Beispiel als Material für Glasschmelzelektroden, für Ofenbauteile von Hochtemperaturöfen, für Wärmesenken und für Röntgenanoden. Ein häufig angewendetes und großtechnisches Verfahren zur Herstellung von Molybdän und Molybdän-basierten Materialien ist die pulvermetallurgische Herstellungsroute, bei der entsprechende Ausgangspulver gepresst und anschließend gesintert werden, wobei im Falle von mehreren Pulvern dem Pressschritt typischerweise noch ein Mischen der Pulver vorangeht. Gegenüber schmelzmetallurgisch hergestelltem Molybdän zeichnet sich pulvermetallurgisch hergestelltes (nachfolgend "pulvermetallurgisches") Molybdän dadurch aus, dass das Gefüge aufgrund der vergleichsweise niedrigen Sintertemperatur (Sintertemperatur ≈ 0,8*Schmelztemperatur) feinkörniger und homogener ist. Es kommt zu keiner Entmischung in der flüssigen Phase und die pulvermetallurgische Herstellungsroute erlaubt die Herstellung einer größeren Vielfalt an Vorformen (in geometrischer Hinsicht).Due to its high melting point, low thermal expansion coefficient and high thermal conductivity, molybdenum is suitable for various high-performance applications, such as a material for glass melting electrodes, for furnace components of high-temperature furnaces, for heat sinks and for X-ray anodes. A frequently used and large-scale process for the production of molybdenum and molybdenum-based materials is the powder metallurgical production route, in which the corresponding starting powders are pressed and then sintered, with the pressing step typically being preceded by mixing the powders in the case of several powders. Compared to molybdenum produced by melting metallurgy, molybdenum produced by powder metallurgy (hereinafter "powder metallurgy") is characterized by the fact that the structure is finer-grained and more homogeneous due to the comparatively low sintering temperature (sintering temperature ≈ 0.8*melting point). There is no liquid phase segregation and the powder metallurgy fabrication route allows for a greater variety of preforms (in geometric terms) to be produced.
Eine Herausforderung stellt dabei dar, dass Molybdän mit seiner kubisch raumzentrierten Kristallstruktur einen Übergang von duktilem zu sprödem Verhaltenabhängig von dem Bearbeitungszustand - um bzw. über der Raumtemperatur (z.B. bei 100°C) aufweist und unterhalb dieser Übergangstemperatur sehr spröde ist. Weiterhin weisen unverformtes Molybdän sowie rekristallisiertes Molybdän eine relativ niedrige Festigkeit, insbesondere gegenüber Biege- und Zugbelastungen, auf, wodurch der Anwendungsbereich ebenfalls eingeschränkt wird (durch Umformen, wie z.B. Walzen oder Schmieden, lassen sich diese Eigenschaften auch bei herkömmlichem Molybdän verbessern, mit zunehmender Rekristallisation verschlechtern sie sich jedoch wieder). Schließlich lässt sich Molybdän nicht schweißen, was entweder aufwändige Verbindungsverfahren (Nieten, Bördeln, etc.) oder aber - zur Verbesserung der Schweißeigenschaften - die Zugabe von Legierungselementen (z.B. Rhenium oder Zirconium) in das Mo-Grundmaterial oder den Einsatz von Schweißzusatzwerkstoffen (z.B. Rhenium) erfordert.One challenge is that molybdenum, with its body-centered cubic crystal structure, has a transition from ductile to brittle behavior depending on the processing state - at or above room temperature (e.g. at 100°C) and is very brittle below this transition temperature. Furthermore, undeformed molybdenum and recrystallized molybdenum have a relatively low strength, especially in relation to bending and tensile loads, which also limits the area of application (through forming, such as rolling or forging, these properties can also be improved with conventional molybdenum, with increasing recrystallization however, they deteriorate again). After all, molybdenum cannot be welded, which either requires complex connection methods (riveting, flanging, etc.) or - to improve the welding properties - the addition of alloying elements (e.g. rhenium or zirconium) to the Mo base material or the use of welding filler materials (e.g. rhenium).
In dem US-Patent
Durch derartige Zugaben von zusätzlichen Legierungselementen sowie durch den oben beschriebenen Einsatz von Schweißzusatzwerkstoffen können zwarje nach zugegebenem Zusatz (Element/Verbindung) - die Duktilität erhöht, die Festigkeit erhöht und/oder die Schweißbarkeit verbessert werden, je nach Anwendung ist jedoch die Zugabe von Zusätzen mit Nachteilen verbunden. So führt zum Beispiel ein erhöhter Kohlenstoffanteil bei Glasschmelzkomponenten (z.B. bei Glasschmelzelektroden) zu unerwünschter Bläschenbildung an der Oberfläche der Glasschmelzkomponente, da unter anderem der Kohlenstoff aus dem Mo-Material mit Sauerstoff aus der Glasschmelze zu Kohlendioxid (CO2) und Kohlenmonoxid (CO) reagiert. Beim Einsatz von Schweißzusatzwerkstoffen können im Bereich der Schweißzone Änderungen des Schmelzpunktes, des thermischen Ausdehnungskoeffizienten und/oder der Wärmeleitfähigkeit im Vergleich zu dem Mo-Grundmaterial auftreten.Depending on the additive (element/compound) added, such additions of additional alloying elements and the use of welding filler materials described above can increase ductility, increase strength and/or improve weldability, but depending on the application, the addition of additives with associated disadvantages. So For example, an increased proportion of carbon in glass melting components (e.g. in glass melting electrodes) leads to undesirable bubble formation on the surface of the glass melting component, since, among other things, the carbon from the Mo material reacts with oxygen from the glass melt to form carbon dioxide (CO 2 ) and carbon monoxide (CO). When using welding filler materials, changes in the melting point, the thermal expansion coefficient and/or the thermal conductivity can occur in the area of the welding zone compared to the Mo base material.
Dementsprechend besteht die Aufgabe der vorliegenden Erfindung darin, einen Molybdän-basierten Werkstoff bereitzustellen, der eine hohe Festigkeit sowie eine gute Schweißbarkeit aufweist und universal in unterschiedlichen Anwendungen einsetzbar ist.Accordingly, the object of the present invention is to provide a molybdenum-based material that has high strength and good weldability and can be used universally in different applications.
Die Aufgabe wird durch ein pulvermetallurgisch hergestelltes (nachfolgend: "pulvermetallurgisches"), als Festkörper vorliegendes Molybdän-Sinterteil gemäß Anspruch 1 sowie durch ein Verfahren zur Herstellung eines Molybdän-Sinterteils gemäß Anspruch 13 gelöst. Vorteilhafte Weiterbildungen der Erfindung sind in den abhängigen Ansprüchen angegeben.The object is achieved by a sintered molybdenum part produced by powder metallurgy (hereinafter: "powder metallurgy") and present as a solid body according to
Gemäß der vorliegenden Erfindung wird ein pulvermetallurgisches, als Festkörper vorliegendes Molybdän-Sinterteil bereitgestellt, aus nachfolgender Zusammensetzung bestehend aus folgenden Anteilen:
- a. einem Molybdänanteil von ≥ 99,93 Gew.%,
- b. einem Boranteil "B" von ≥ 3 ppmw und einem Kohlenstoffanteil "C" von ≥ 3 ppmw, wobei der Gesamtanteil "BuC" an Kohlenstoff und Bor im Bereich von 15 ppmw ≤ "BuC" ≤ 50 ppmw, insbesondere im Bereich von 25 ppmw ≤ "BuC" ≤ 40 ppmw, liegt,
- c. einem Sauerstoffanteil "O" im Bereich von 3 ppmw ≤ "O" ≤ 20 ppmw,
- d. einem maximalen Wolframanteil von ≤ 330 ppmw und
- e. einem maximalen Anteil an sonstigen Verunreinigungen von ≤ 300 ppmw, wobei vorzugsweise der maximale Anteil an Verunreinigungen durch Zirconium (Zr), Hafnium (Hf), Titan (Ti), Vanadium (V) und Aluminium (Al) in Summe ≤ 50 ppmw beträgt und vorzugsweise der maximale Anteil an Verunreinigungen durch Silicium (Si), Rhenium (Re) und Kalium (K) in Summe ≤ 20 ppmw beträgt.
- a. a molybdenum content of ≥ 99.93% by weight,
- b. a boron content "B" of ≥ 3 ppmw and a carbon content "C" of ≥ 3 ppmw, the total content "BuC" of carbon and boron in the range of 15 ppmw ≤ "BuC" ≤ 50 ppmw, in particular in the range of 25 ppmw ≤ "BuC" ≤ 40 ppmw, lies,
- c. an oxygen content "O" in the range of 3 ppmw ≤ "O" ≤ 20 ppmw,
- i.e. a maximum tungsten content of ≤ 330 ppmw and
- e. a maximum content of other impurities of ≤ 300 ppmw, with preferably the maximum content of impurities from zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminum (Al) totaling ≤ 50 ppmw and preferably the maximum proportion of impurities due to silicon (Si), rhenium (Re) and potassium (K) is ≦20 ppmw in total.
Das erfindungsgemäße Molybdän-Sinterteil weist gegenüber herkömmlichem, pulvermetallurgischem, reinem Molybdän (Mo) (nachfolgend "herkömmlichem Molybdän") eine deutlich erhöhte Duktilität sowie eine erhöhte Festigkeit, insbesondere gegenüber Biege- und Zugbelastungen, auf. Dies gilt insbesondere im Vergleich zu herkömmlichem Molybdän im unverformten und/oder (vollständig oder teilweise) rekristallisierten Zustand. Bei herkömmlichem Molybdän ist die Umformung größerer Bauteile aufgrund der geringen Korngrenzenfestigkeit problematisch. Insbesondere beim Schmieden dicker Stäbe (z.B. mit Ausgangsdurchmessern von 200-240 mm) und beim Walzen dicker Bleche (z.B. mit Ausgangsdicken im Bereich von 120-140 mm) ist eine Rissbildung, die verstärkt im Kern der Stäbe/Bleche auftritt, problematisch. Demge genüber lässt sich das erfindungsgemäße Molybdän-Sinterteil auch in großtechnischem Maß herstellen und weiterverarbeiten. Das Umformen großer Bauteile, wie beispielsweise das Schmieden dicker Stäbe und das Walzen dicker Bleche, ist bei dem erfindungsgemäßen Molybdän-Sinterteil unter Vermeidung von inneren Fehlern und Korngrenzenrissen möglich. Weiterhin lässt sich das erfindungsgemäße Molybdän-Sinterteil (z.B. in Blechform) gut verschweißen, so dass nicht wie bei herkömmlichem Molybdän auf aufwändige Verbindungskonstruktionen oder auf den Einsatz von Schweißzusatzwerkstoffen zurückgegriffen werden muss.Compared to conventional, powder-metallurgical, pure molybdenum (Mo) (hereinafter "conventional molybdenum"), the molybdenum sintered part according to the invention has significantly increased ductility and increased strength, in particular with regard to bending and tensile loads. This is particularly true when compared to conventional molybdenum in the undeformed and/or (fully or partially) recrystallized condition. With conventional molybdenum, the Forming larger components is problematic due to the low grain boundary strength. Especially when forging thick bars (e.g. with starting diameters of 200-240 mm) and rolling thick sheets (e.g. with starting thicknesses in the range of 120-140 mm), cracking, which occurs more frequently in the core of the bars/sheets, is problematic. demge on the other hand, the molybdenum sintered part according to the invention can also be produced and further processed on an industrial scale. With the molybdenum sintered part according to the invention, the forming of large components, such as the forging of thick rods and the rolling of thick sheets, is possible while avoiding internal defects and grain boundary cracks. Furthermore, the molybdenum sintered part according to the invention (eg in the form of sheet metal) can be easily welded, so that complex connection constructions or the use of welding filler materials do not have to be resorted to, as is the case with conventional molybdenum.
Die niedrige Festigkeit von herkömmlichem Molybdän wird auf eine niedrige Korngrenzenfestigkeit, die zu einem interkristallinem Bruchverhalten führt, zurückgeführt. Die Korngrenzenfestigkeit von Molybdän wird bekanntlich durch eine Segregation von Sauerstoff und ggf. von weiteren Elementen, wie z.B. von Stickstoff und Phosphor, im Bereich der Korngrenzen erniedrigt. Während unter anderem aus den oben angeführten Dokumenten des Standes der Technik bekannt ist, durch Zugabe erheblicher Mengen von Zusätzen (Elementen/Verbindungen), welche die Korngrenzenfestigkeit und/oder die Duktilität von Molybdän erhöhen, die Eigenschaften von Molybdän-basierten Werkstoffen zu verbessern, werden die ausgezeichneten Eigenschaften des erfindungsgemäßen Molybdän-Sinterteils (hohe Festigkeit, hohe Duktilität, gute Schweißbarkeit) durch die vergleichsweise niedrigen Bor (B) -, Kohlenstoff (C) - und Sauerstoff (O) - Gehalte in Kombination mit den niedrigen Maximalgehalten an sonstigen Verunreinigungen (und an Wolfram (W)) eingestellt. Damit ist der Anteil an weiteren (d.h. von Mo abweichenden) Elementen, die sich je nach Anwendung störend auswirken, gering und das erfindungsgemäße Molybdän-Sinterteil ist universell in den unterschiedlichsten Anwendungen einsetzbar.The low strength of conventional molybdenum is attributed to low grain boundary strength, which leads to intergranular fracture behavior. The grain boundary strength of molybdenum is known to be reduced by segregation of oxygen and possibly other elements, such as nitrogen and phosphorus, in the area of the grain boundaries. While it is known, inter alia from the prior art documents cited above, by adding significant amounts of additives (elements/compounds) which increase the grain boundary strength and/or the ductility of molybdenum, the properties of molybdenum-based materials are improved the excellent properties of the molybdenum sintered part according to the invention (high strength, high ductility, good weldability) due to the comparatively low boron (B), carbon (C) and oxygen (O) contents in combination with the low maximum contents of other impurities ( and set to tungsten (W)). The proportion of other elements (i.e. other than Mo), which have a disruptive effect depending on the application, is low and the molybdenum sintered part according to the invention can be used universally in a wide variety of applications.
Die Erfindung beruht auf der Erkenntnis, dass bereits geringe Gehalte an Kohlenstoff und Bor in Kombination zu einer deutlich erhöhten Korngrenzenfestigkeit führen und das (für die hohe Duktilität verantwortliche) Fließverhalten des Werkstoffs günstig beeinflussen, wenn gleichzeitig der Sauerstoffgehalt niedrig und der Gehalt an sonstigen Verunreinigungen (und W) unterhalb der angegebenen Grenzwerte liegen. Insbesondere kann durch den Kohlenstoffanteil der Sauerstoffanteil in dem Sinterteil niedrig gehalten werden. Auf der anderen Seite bedarf es aufgrund des Boranteils keiner großen Mengen an Kohlenstoff, die gerade bei Glasschmelzkomponenten aufgrund der dann verstärkt auftretenden Ausgasung problematisch wären. Bei den erfindungsgemäßen niedrigen Anteilen an Sauerstoff, an sonstigen Verunreinigungen und an W reicht im Ergebnis also bereits ein geringer Boranteil in Kombination mit einem vergleichsweise niedrigen Kohlenstoffanteil aus, um die gewünschten hohen Duktilitäts- und Festigkeitswerte zu erreichen.The invention is based on the finding that even low levels of carbon and boron in combination lead to significantly increased grain boundary strength and have a favorable effect on the flow behavior of the material (responsible for the high ductility) if the oxygen content is low and the content of other impurities ( and W) are below the specified limits. In particular, the carbon content of the Oxygen content can be kept low in the sintered part. On the other hand, due to the boron content, large amounts of carbon are not required, which would be problematic, especially in the case of glass melting components, due to the increased outgassing that then occurs. With the low proportions of oxygen, other impurities and W according to the invention, a low proportion of boron in combination with a comparatively low proportion of carbon is sufficient to achieve the desired high ductility and strength values.
Unter einem pulvermetallurgischen Molybdän-Sinterteil wird dabei ein Bauteil verstanden, dessen Herstellung die Schritte des Pressens entsprechender Ausgangspulver zu einem Pressling und des Sinterns des Presslings umfasst. Darüber hinaus kann das Herstellungsverfahren auch noch weitere Schritte aufweisen, wie z.B. das Mischen und Homogenisieren (z.B. in einem Pflugscharmischer) der zu pressenden Pulver, etc.. Das pulvermetallurgische Molybdän-Sinterteil weist damit eine für die pulvermetallurgische Herstellung typische Mikrostruktur auf, die für den Fachmann ohne weiteres erkennbar ist. Diese Mikrostruktur zeichnet sich durch seine Feinkörnigkeit aus (typische Korngrößen insbesondere im Bereich von 30-60 µm). Ferner sind die Poren gleichmäßig über den gesamten Querschnitt durch das Sinterteil verteilt. Bei einer "guten" oder "vollständigen" Sinterung (die Dichte ist dann bei Molybdän ≥ 93 % der theoretischen Dichte und es gibt keine offene Porosität) erscheinen diese Poren an den Korngrenzen sowie als abgerundete Hohlräume im Inneren der entstandenen Sinterkörner. Die Untersuchung dieser charakteristischen Merkmale erfolgt im Querschliff in lichtmikroskopischer oder elektronenmikroskopischer Aufnahme). Das erfindungsgemäße pulvermetallurgische Molybdän-Sinterteil kann auch noch weiteren Bearbeitungsschritten unterzogen worden sein, wie z.B. einer Umformung (Walzen, Schmieden, etc.), so dass es anschließend in einer Umformstruktur vorliegt, einer anschließenden Glühung, etc.. Ferner kann es auch beschichtet und/oder mit weiteren Bauteilen verbunden werden, wie beispielsweise durch Schweißen oder Löten.A powder-metallurgical molybdenum sintered part is understood to mean a component whose production includes the steps of pressing corresponding starting powder to form a compact and sintering the compact. In addition, the manufacturing process can also have further steps, such as mixing and homogenizing (e.g. in a plowshare mixer) the powder to be pressed, etc Specialist is readily recognizable. This microstructure is characterized by its fine grain (typical grain sizes in particular in the range of 30-60 µm). Furthermore, the pores are distributed uniformly over the entire cross section through the sintered part. With "good" or "complete" sintering (the density is then ≥ 93% of the theoretical density for molybdenum and there is no open porosity), these pores appear at the grain boundaries and as rounded cavities inside the resulting sintered grains. The examination of these characteristic features is carried out in the cross-section in light microscopic or electron microscopic images). The powder-metallurgical molybdenum sintered part according to the invention can also have been subjected to further processing steps, such as forming (rolling, forging, etc.), so that it is then in a formed structure, subsequent annealing, etc.. It can also be coated and / or connected to other components, such as by welding or soldering.
Die erfindungsgemäßen Angaben der Anteile sowie die Angaben bzgl. der nachfolgend erläuterten Weiterbildungen beziehen sich auf das jeweils in Bezug genommene Element (z.B. Mo, B, C, O oder W), unabhängig davon, ob dieses in dem Molybdän-Sinterteil in elementarer oder gebundener Form vorliegt. Die Anteile der verschiedenen Elemente werden über chemische Analyse bestimmt. Bei der chemischen Analyse werden insbesondere die Anteile der meisten metallischen Elemente (z.B. Al, Hf, Ti, K, Zr, etc.) über das Analyseverfahren ICP-MS (Massenspektroskopie mit induktiv gekoppeltem Plasma), der Boranteil über das Analyseverfahren ICP-OES (optische Emissionsspektroskopie mit induktiv gekoppeltem Plasma), der Kohlenstoffanteil über Verbrennungsanalyse (Combustion Analysis) und der Sauerstoffanteil über Heißextraktionsanalyse (carrier gas hot extraction) ermittelt. Die Angabe "ppmw" drückt dabei den Gewichtsanteil multipliziert mit 10-6 aus. Die angegebenen Grenzwerte können grundsätzlich auch über dicke Bauteilstärken hinweg stabil eingehalten werden, insbesondere sind die vorteilhaften Eigenschaften unabhängig von der jeweiligen Bauteil-Geometrie, Blechdicke, etc. großtechnisch realisierbar. Beobachtet wurde, dass der Boranteil und der Kohlenstoffanteil zur Oberfläche des Sinterteils hin leicht abnehmen, während der Sauerstoffanteil durch die Sinterteil-Dicke hindurch relativ konstant sind. Eine leichte Abnahme des Boranteils und/oder des Kohlenstoffanteils zur Oberfläche hin oder aber auch eine leichte Zunahme des Sauerstoffanteils zur Oberfläche hin, auch wenn die Grenzwerte dann ggf. in einem oberflächen-nahen Bereich (mit einer Dicke von z.B. 0,1 mm) nicht mehr eingehalten werden, ist insbesondere dann unkritisch und solche Molybdän-Sinterteile werden auch dann noch von der vorliegenden Erfindung umfasst, wenn ein ausreichend dicker Kern bzw. allgemeiner mindestens eine ausreichend dicke Lage des Sinterteils verbleibt, in dem/der die beanspruchten Grenzwerte erfüllt sind, so dass zumindest in diesem Kern bzw. in dieser Lage eine Rissbildung oder ein Rissfortschritt (z.B. aufgrund eines Umformschrittes) vermieden bzw. deutlich verlangsamt wird. Dies ist insbesondere dann der Fall, wenn - bezogen auf die Gesamtdicke des Mo-Sinterteils - ein erfindungsgemäß ausgebildeter Kern mindestens doppelt so dick ist wie die Gesamtdicke der oberflächen-nahen Bereiche, innerhalb derer die beanspruchten Grenzwerte ganz oder teilweise nicht mehr erfüllt sind. Eine Gradierung der Zusammensetzung kann gegebenenfalls auch erst bei nachfolgenden Behandlungsschritten des Molybdän-Sinterteils, wie beispielsweise bei einer Umformung (Walzen, Schmieden, Extrudieren, etc.), bei einer nachfolgenden Glühung, bei einem Schweißvorgang, etc., auftreten bzw. sich noch weiter verstärken.The details of the proportions according to the invention and the details regarding the further developments explained below relate to the respective taken element (eg Mo, B, C, O or W), regardless of whether this is present in the molybdenum sinter in elemental or combined form. The proportions of the different elements are determined by chemical analysis. In the chemical analysis, the proportions of most metallic elements (e.g. Al, Hf, Ti, K, Zr, etc.) are determined using the ICP-MS analysis method (mass spectroscopy with inductively coupled plasma), the boron proportion using the ICP-OES analysis method ( optical emission spectroscopy with inductively coupled plasma), the carbon content via combustion analysis (combustion analysis) and the oxygen content via hot extraction analysis (carrier gas hot extraction). The specification "ppmw" expresses the proportion by weight multiplied by 10 -6 . In principle, the specified limit values can also be stably maintained over thick components; in particular, the advantageous properties can be realized on an industrial scale independently of the respective component geometry, sheet metal thickness, etc. It was observed that the boron content and the carbon content decrease slightly towards the surface of the sintered part, while the oxygen content is relatively constant through the sintered part thickness. A slight decrease in the boron content and/or the carbon content towards the surface or a slight increase in the oxygen content towards the surface, even if the limit values may not be in an area close to the surface (with a thickness of 0.1 mm, for example). is not critical, and such molybdenum sintered parts are also covered by the present invention if a sufficiently thick core or, more generally, at least one sufficiently thick layer of the sintered part remains, in which the claimed limit values are met, so that at least in this core or in this layer, crack formation or crack propagation (eg due to a forming step) is avoided or significantly slowed down. This is particularly the case when - based on the total thickness of the Mo sintered part - a core designed according to the invention is at least twice as thick as the total thickness of the regions near the surface within which the claimed limit values are no longer met in whole or in part. A grading of the composition can optionally only occur during subsequent treatment steps of the molybdenum sintered part, such as during reshaping (rolling, forging, extrusion, etc.), during subsequent annealing, during a welding process, etc., occur or increase further.
Gemäß einer vorteilhaften Weiterbildung betragen der Boranteil und der Kohlenstoffanteil jeweils ≥ 5 ppmw. Bei den gängigen Analyseverfahren sind typischerweise oberhalb von 5 ppmw auch zertifizierte Gehaltsangaben von Bor und Kohlenstoff angebbar. In Bezug auf niedrige Bor- und Kohlenstoffanteile ist anzumerken, dass Bor und Kohlenstoff unterhalb von einem jeweiligen Anteil von 5 ppmw zwar auch eindeutig nachweisbar und deren Anteile quantitativ bestimmbar sind (zumindest sofern der jeweilige Anteil ≥ 2 ppmw ist), jedoch sind die Anteile in diesem Bereich - je nach Analyseverfahren - teilweise nicht mehr als zertifizierter Wert angebbar. Gemäß einer Weiterbildung liegt der Gesamtanteil "BuC" an Kohlenstoff und Bor im Bereich von 25 ppmw ≤ "BuC" ≤ 40 ppmw. Gemäß einer Weiterbildung liegt der Boranteil "B" im Bereich von 5 ppmw ≤ "B" ≤ 45 ppmw, noch bevorzugter im Bereich von 10 ppmw ≤ "B" ≤ 40 ppmw. Gemäß einer Weiterbildung liegt der Kohlenstoffanteil "C" im Bereich von 5 ≤ "C" ≤ 30 ppmw, noch bevorzugter im Bereich von 15 ≤ "C" ≤ 20 ppmw. Bei diesen Weiterbildungen und in besonderer Weise bei den engeren Bereichsangaben sind beide Elemente (B, C) in so hoher und gleichzeitig in so ausreichender Menge in dem Molybdän-Sinterteil enthalten, dass ihre vorteilhafte Wechselwirkung deutlich spürbar ist, sich gleichzeitig aber der enthaltene Kohlenstoff und das enthaltene Bor noch nicht nachteilig in den unterschiedlichen Anwendungen auswirken. Insbesondere besteht die Wirkung von Kohlenstoff darin, den Sauerstoffanteil in dem Molybdän-Sinterteil niedrig zu halten, und von Bor darin, einen ausreichend niedrigen Kohlenstoffanteil zu ermöglichen und gleichzeitig eine hohe Duktilität und eine hohe Festigkeit zu erzielen.According to an advantageous development, the boron content and the carbon content are each ≧5 ppmw. With the usual analysis methods, certified content information for boron and carbon can typically be specified above 5 ppmw. With regard to low boron and carbon contents, it should be noted that boron and carbon below a respective proportion of 5 ppmw can also be clearly detected and their proportions can be determined quantitatively (at least if the respective proportion is ≥ 2 ppmw), but the proportions in in this area - depending on the analysis method - sometimes no longer specified as a certified value. According to a further development, the total proportion "BuC" of carbon and boron is in the range of 25 ppmw≦"BuC"≦40 ppmw. According to a development, the boron content "B" is in the range of 5 ppmw≦"B"≦45 ppmw, more preferably in the range of 10 ppmw≦"B"≦40 ppmw. According to a development, the proportion of carbon “C” is in the range of 5≦“C”≦30 ppmw, more preferably in the range of 15≦“C”≦20 ppmw. In these developments and in particular in the narrower ranges, both elements (B, C) are contained in the molybdenum sintered part in such a high and at the same time in such a sufficient quantity that their advantageous interaction is clearly noticeable, but at the same time the carbon and the boron contained does not yet have a negative effect in the various applications. In particular, the effect of carbon is to keep the oxygen content low in the molybdenum sinter and of boron to allow a sufficiently low carbon content while achieving high ductility and high strength.
Gemäß einer Weiterbildung liegt der Sauerstoffanteil "O" im Bereich von 5 ≤ "O" ≤ 15 ppmw. Nach bisheriger Erkenntnis sammelt sich der Sauerstoff im Bereich der Korngrenzen an (Segregation) und führt zu einer Erniedrigung der Korngrenzenfestigkeit. Dementsprechend ist ein insgesamt niedriger Sauerstoffanteil vorteilhaft. Die Einstellung eines derart niedrigen Sauerstoffanteils gelingt sowohl durch die Verwendung von Ausgangspulvern mit niedrigem Sauerstoffanteil (z.B. ≤ 600 ppmw, insbesondere ≤ 500 ppmw), die Sinterung im Vakuum, unter Schutzgas (z.B. Argon) oder vorzugsweise in reduzierender Atmosphäre (insbesondere in Wasserstoffatmosphäre oder in einer Atmosphäre mit H2-Teildruck), sowie durch die Vorsehung eines ausreichenden Kohlenstoffanteils in den Ausgangspulvern.According to a development, the oxygen content "O" is in the range of 5≦"O"≦15 ppmw. According to current knowledge, the oxygen accumulates in the area of the grain boundaries (segregation) and leads to a reduction in grain boundary strength. Accordingly, an overall low oxygen content is advantageous. Setting such a low oxygen content is possible both by using starting powders with a low oxygen content (eg ≦600 ppmw, in particular ≦500 ppmw), sintering in the Vacuum, under protective gas (eg argon) or preferably in a reducing atmosphere (especially in a hydrogen atmosphere or in an atmosphere with H 2 partial pressure), and by providing a sufficient proportion of carbon in the starting powders.
Gemäß der Erfindung beträgt der maximale Anteil an Verunreinigungen durch Zirconium (Zr), Hafnium (Hf), Titan (Ti), Vanadium (V) und Aluminium (Al) in Summe ≤ 50 ppmw. Vorzugsweise ist dabei der Anteil von jedem Element dieser Gruppe (Zr, Hf, Ti, V, Al) jeweils ≤ 15 ppmw. Gemäß einer Weiterbildung beträgt der maximale Anteil an Verunreinigungen durch Silicium (Si), Rhenium (Re) und Kalium (K) in Summe ≤ 20 ppmw. Vorzugsweise ist dabei der Anteil von jedem Element dieser Gruppe (Si, Re, K) jeweils ≤ 10 ppmw, insbesondere ≤ 8 ppmw. Kalium wird die Wirkung zugeschrieben, dass es die Korngrenzenfestigkeit herabsetzt, weshalb ein möglichst niedriger Anteil anzustreben ist. Zr, Hf, Ti, Si und Al sind Oxidbildner und könnten grundsätzlich eingesetzt werden, um durch Bindung des Sauerstoffs (Sauerstoffgetter) einer Anreicherung von Sauerstoff im Bereich der Korngrenzen entgegenzuwirken und damit wiederum die Korngrenzenfestigkeit zu erhöhen. Teilweise stehen sie jedoch im Verdacht, dass sie - gerade wenn sie in größeren Mengen vorhanden sind - die Duktilität herabsetzen. Re und V wird eine duktilisierende Wirkung zugeschrieben, d.h. sie könnten grundsätzlich zur Erhöhung der Duktilität eingesetzt werden. Jedoch bedingt die Zugabe von Zusätzen (Elemente/Verbindungen), dass sie sich je nach Anwendung und Einsatzbedingung des Mo-Sinterteils auch störend auswirken können. Solche, teilweise auch nur Anwendungs-abhängig auftretende, nachteilige Wirkungen der oberhalb genannten Zusätze werden gemäß der vorliegenden Erfindung und insbesondere gemäß dieser Weiterbildung vermieden, indem weitgehend auf diese Elemente verzichtet wird. Gemäß einer Weiterbildung weist das Molybdän-Sinterteil einen Gesamtanteil an Molybdän und Wolfram von ≥ 99,97 Gew.% auf. Der Anteil von Wolfram innerhalb der angegebenen Grenzwerte (≤ 330 ppmw) ist für die bisher bekannten Anwendungen unkritisch und ist typischerweise bereits durch die Mo-Gewinnung und Pulverherstellung bedingt. Insbesondere weist das Molybdän-Sinterteil einen Molybdän-Anteil von ≥ 99,97 Gew.% auf, d.h. es besteht fast ausschließlich aus Molybdän. Bei allen in diesem Absatz diskutierten Weiterbildungen ist der Anteil an sonstigen Verunreinigungen sehr gering. Dementsprechend wird gemäß dieser Weiterbildungen - jeweils für sich genommen und in besonderem Maße in Kombination - ein breit einsetzbares Molybdän-Sinterteil mit hoher Reinheit bereitgestellt.According to the invention, the maximum proportion of impurities from zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminum (Al) is ≦50 ppmw in total. The proportion of each element of this group (Zr, Hf, Ti, V, Al) is preferably ≦15 ppmw. According to a development, the maximum proportion of impurities from silicon (Si), rhenium (Re) and potassium (K) is ≦20 ppmw in total. The proportion of each element of this group (Si, Re, K) is preferably ≦10 ppmw, in particular ≦8 ppmw. The effect attributed to potassium is that it reduces the grain boundary strength, which is why the lowest possible proportion is desirable. Zr, Hf, Ti, Si and Al are oxide formers and could in principle be used to counteract an enrichment of oxygen in the area of the grain boundaries by binding the oxygen (oxygen getter) and thus in turn to increase the grain boundary strength. In some cases, however, they are suspected of reducing ductility, especially when they are present in large quantities. A ductilizing effect is ascribed to Re and V, ie they could in principle be used to increase the ductility. However, the addition of additives (elements/compounds) means that they can also have a disruptive effect depending on the application and conditions of use of the Mo sintered part. Such disadvantageous effects of the above-mentioned additives, which sometimes only occur depending on the application, are avoided according to the present invention and in particular according to this development by largely dispensing with these elements. According to a development, the molybdenum sintered part has a total proportion of molybdenum and tungsten of ≧99.97% by weight. The proportion of tungsten within the specified limit values (≤ 330 ppmw) is not critical for the previously known applications and is typically already due to the Mo extraction and powder production. In particular, the molybdenum sintered part has a molybdenum content of ≧99.97% by weight, ie it consists almost entirely of molybdenum. For all of the further training courses discussed in this paragraph, the proportion of other impurities very low. Accordingly, a molybdenum sintered part with high purity that can be used widely is provided according to these developments—in each case taken individually and to a particular degree in combination.
Gemäß einer Weiterbildung liegen der Kohlenstoff und das Bor in Summe zu mindestens 70 Gew.% bezogen auf den Gesamtgehalt an Kohlenstoff und Bor in gelöster Form vor (sie bilden also keine separate Phase aus). Untersuchungen an erfindungsgemäßen Molybdän-Sinterteilen haben gezeigt, dass gegebenenfalls ein kleiner Anteil des Bor als Mo2B-Phase vorliegt, wobei dies in einem niedrigen Ausmaß unkritisch ist. Liegen der Kohlenstoff und das Bor zumindest zu einem hohen Anteil (z.B. ≥ 70 Gew.%, insbesondere ≥ 90 Gew.%) in Lösung, so können sie sich an die Korngrenzen segregieren und die oberhalb erläuterte Wirkung in besonders hohem Maß erfüllen. Vorzugsweise werden die angegebenen Grenzwerte auch durch jedes der Elemente B und C einzeln eingehalten.According to a further development, the carbon and the boron are in total at least 70% by weight, based on the total content of carbon and boron, in dissolved form (they do not therefore form a separate phase). Investigations on sintered molybdenum parts according to the invention have shown that a small proportion of the boron may be present as the Mo 2 B phase, although this is not critical to a small extent. If the carbon and the boron are at least to a large extent (eg ≧70% by weight, in particular ≧90% by weight) in solution, they can segregate at the grain boundaries and fulfill the effect explained above to a particularly high degree. Preferably, each of the elements B and C individually also satisfies the specified limit values.
Gemäß einer Weiterbildung sind das Bor und der Kohlenstoff in dem Mo-Grundmaterial fein verteilt und im Bereich der Großwinkel-Korngrenzen angereichert. Eine Großwinkel-Korngrenze liegt dann vor, wenn eine Winkeldifferenz von ≥15° erforderlich ist, um die kristallographische Ausrichtung benachbarter Körner in Deckung zu bringen, was über EBSD (engl.: electron backscatter diffraction; deutsch: Elektronenrückstreubeugung) bestimmbar ist. Durch die feine Verteilung und die Anreicherung im Bereich der Großwinkel-Korngrenzen können Bor und Kohlenstoff ihren positiven Einfluss auf die Korngrenzenfestigkeit in besonders hohem Ausmaß ausüben. Ein wesentlicher Aspekt zur Erzielung dieser feinen Verteilung und einer hohen Anreicherung zumindest entlang möglichst aller Großwinkel-Korngrenzen (und gegebenenfalls auch entlang von Kleinwinkel-Korngrenzen) ist, dass das Bor und der Kohlenstoff den Ausgangspulvern im Rahmen der pulvermetallurgischen Herstellung als möglichst reines Element (B, C) oder als möglichst reine Verbindung, d.h. mit möglichst wenigen, sonstigen Verunreinigungen (abgesehen von dem gegebenenfalls hinzutretenden Verbindungspartner von B und/oder C, wie z.B. Mo, N, C, etc.), sowie als möglichst feines Pulver zugesetzt werden. Bor kann beispielsweise als Molybdänborid (Mo2B), als Borkarbid (B4C), als Bornitrid (BN) oder auch elementar als amorphes oder kristallines Bor zugesetzt werden. Kohlenstoff kann beispielsweise als Graphit oder als Molybdäncarbid (MoC, Mo2C) zugesetzt werden. Vorzugsweise werden das Bor-haltige Pulver (Verbindung/Element, Korngröße, Kornmorphologie, etc.) und das Kohlenstoff-haltige Pulver (Verbindung/Element, Korngröße, Kornmorphologie, etc.), die Mengen derselben sowie die Sinterbedingungen (Temperaturprofil, maximale Sintertemperatur, Haltezeiten, Sinteratmosphäre) derart aufeinander abgestimmt, dass das Bor und der Kohlenstoff nach dem Sintervorgang möglichst gleichmäßig und fein verteilt mit dem jeweils gewünschten Anteil und in möglichst konstanter Konzentration über die Dicke des jeweiligen Molybdän-Sinterteils hinweg vorliegen. Dabei ist einzubeziehen, dass Bor und Kohlenstoff, sofern sie bei den fraglichen Temperaturen frei verfügbar sind, zumindest anteilig mit Sauerstoff aus den Ausgangspulvern und ggf. zusätzlich mit Sauerstoff aus der Sinteratmosphäre reagieren und als Gas entweichen. Um dennoch den gewünschten Bor- und Kohlenstoffanteil in dem fertigen Molybdän-Sinterteil zu erzielen, müssen den Ausgangspulvern entsprechend höhere Mengen an Bor- und/oder Kohlenstoff-haltigen Pulvern zugesetzt werden. Speziell bei Bor kann der Tendenz, dass es sich während des Sintervorgangs verflüchtigt und als umweltschädliches Gas in die Atmosphäre ausgestoßen wird, dadurch entgegen gewirkt werden, dass das Bor-haltige Pulver und die Sinterbedingungen derart aufeinander abgestimmt werden, dass das Bor erst nach solch einer Zeitdauer und/oder nach solch einem Temperaturanstieg als Reaktionspartner zur Verfügung steht (z.B. weil sich erst dann die Bor-haltige Verbindung zersetzt oder das Bor-haltige Pulver das Bor aufgrund seiner Morphologie, Beschichtung, etc. erst dann zur Reaktion freigibt), wenn der Sauerstoff aus den Ausgangspulvern zumindest zu einem Großteil mit abweichenden Reaktionspartnern (z.B. Wasserstoff, Kohlenstoff, etc.) reagiert hat und als Gas entwichen ist. Weiterhin kann eine Gradierung der Zusammensetzung über die Dicke des Mo-Sinterteils hinweg weitgehend unterdrückt werden, indem in den Ausgangspulvern der Sauerstoffanteil möglichst niedrig gehalten wird und auch nur eine moderat erhöhte Menge an Kohlenstoff- und Bor-haltigen Pulvern (im Vergleich zu den zu erzielenden C- und B-Anteilen in dem Mo-Sinterteil) zugesetzt wird, vorzugsweise eine reduzierende Atmosphäre (H2-Atmosphäre oder H2-Teildruck), alternativ ein Schutzgas (z.B. Argon) oder ein Vakuum beim Sintervorgang gewählt wird und indem das Bor-haltige Pulver sowie das Temperaturprofil beim Sintervorgang derart aufeinander abgestimmt sind, dass das Bor erst dann freigesetzt wird, wenn der Sauerstoff aus den Ausgangspulvern zumindest zu einem großen Anteil bereits mit abweichenden Reaktionspartnern reagiert hat.According to a further development, the boron and the carbon are finely distributed in the Mo base material and enriched in the area of the large-angle grain boundaries. A high-angle grain boundary is present when an angular difference of ≥15° is required to match the crystallographic alignment of adjacent grains, which can be determined by EBSD (electron backscatter diffraction). Due to the fine distribution and the enrichment in the area of the large-angle grain boundaries, boron and carbon can exert their positive influence on the grain boundary strength to a particularly high degree. An essential aspect for achieving this fine distribution and a high enrichment at least along as many large-angle grain boundaries as possible (and possibly also along small-angle grain boundaries) is that the boron and carbon are added to the starting powders during powder metallurgical production as the purest possible element (B , C) or as a compound that is as pure as possible, ie with as few other impurities as possible (apart from the compound partner of B and/or C that may be added, such as Mo, N, C, etc.), and as a powder that is as fine as possible. Boron, for example, as molybdenum boride (Mo 2 B), as boron carbide (B 4 C), as boron nitride (BN) or elementary as amorphous or crystalline boron. Carbon can be added, for example, as graphite or as molybdenum carbide (MoC, Mo 2 C). Preferably, the boron-containing powder (compound/element, grain size, grain morphology, etc.) and the carbon-containing powder (compound/element, grain size, grain morphology, etc.), the amounts thereof, and the sintering conditions (temperature profile, maximum sintering temperature, Holding times, sintering atmosphere) coordinated with one another in such a way that after the sintering process the boron and carbon are distributed as evenly and finely as possible with the desired proportion and in a concentration that is as constant as possible over the thickness of the respective molybdenum sintered part. It must be taken into account that boron and carbon, if they are freely available at the temperatures in question, react at least partially with oxygen from the starting powders and possibly also with oxygen from the sintering atmosphere and escape as gas. In order to still achieve the desired boron and carbon content in the finished molybdenum sintered part, correspondingly higher amounts of boron- and/or carbon-containing powders must be added to the starting powders. In the case of boron in particular, the tendency for it to volatilize during the sintering process and be emitted into the atmosphere as an environmentally harmful gas can be counteracted by matching the boron-containing powder and the sintering conditions in such a way that the boron is only released after such a Duration and / or after such a temperature increase as a reactant is available (e.g. because only then does the boron-containing compound decompose or the boron-containing powder only releases the boron due to its morphology, coating, etc. to the reaction) if the Oxygen from the starting powders has at least largely reacted with different reactants (e.g. hydrogen, carbon, etc.) and has escaped as a gas. Furthermore, a gradation of the composition across the thickness of the Mo sintered part can be largely suppressed by keeping the oxygen content as low as possible in the starting powders and only using a moderately increased amount of carbon and boron-containing powders (compared to the achievable C and B portions in the Mo sintered part) is added, preferably a reducing atmosphere (H 2 atmosphere or H 2 partial pressure), alternatively a protective gas (e.g argon) or a vacuum is selected during the sintering process and the boron-containing powder and the temperature profile during the sintering process are coordinated in such a way that the boron is only released when the oxygen from the starting powders has already reacted, at least to a large extent, with other reactants Has.
Gemäß einer Weiterbildung gilt zumindest an einem Korngrenzenabschnitt einer Großwinkel-Korngrenze und dem daran angrenzenden Korn: der Anteil an Kohlenstoff und Bor in Summe ist im Bereich des Korngrenzenabschnitts mindestens eineinhalb mal so hoch wie im Bereich des Korninneren des angrenzenden Korns; insbesondere ist der Anteil an Kohlenstoff und Bor in Summe im Bereich des Korngrenzenabschnitts mindestens zwei mal so hoch, noch bevorzugter mindestens drei mal so hoch, wie im Bereich des Korninneren des angrenzenden Korns. Vorzugsweise werden die angegebenen Relationen auch durch jedes der Elemente B und C einzeln erfüllt. Die Anteile der Einzelelemente (B, C) und der Summe der Elemente (B und C) werden jeweils bestimmt in Atomprozent (at.-%) mittels dreidimensionaler Atomsonden-Tomographie. Dabei wird für den Bereich des Korngrenzenabschnitts ein dreidimensionaler, zylinderförmiger Bereich mit einer senkrecht zu dem Korngrenzenabschnitt verlaufenden Zylinderachse und mit einer entlang der Zylinderachse verlaufenden Dicke von 5 nm (Nanometer), der bezogen auf die Zylinderachsen-Richtung zentral um den Korngrenzenabschnitt gelegt wird, ausgewählt (nach dem hier maßgeblichen und nachfolgend noch im Detail erläuterten Messverfahren ist dies der Bereich von 5 nm Dicke, innerhalb dem die Summe der gemessenen Konzentrationen an B und C maximal ist). Die Zylinderachse verläuft insbesondere senkrecht zu der Ebene, die durch den Korngrenzenabschnitt in dem zu untersuchenden Bereich aufgespannt wird. Im Falle eines (leicht) gekrümmten Korngrenzenabschnitts ist (für die Ausrichtung und Positionierung des zu untersuchenden, zylinderförmigen Bereichs) eine gemittelte Ebene, die über die betrachtete Fläche hinweg einen minimalen Abstand zu dem Korngrenzenabschnitt einhält, heranzuziehen. Für den Bereich des Korninneren wird ein mit seinem Zentrum um 10 nm in Zylinderachsen-Richtung von dem Korngrenzenabschnitt (beziehungsweise gegebenenfalls zu der zugehörigen, gemittelten Ebene) beabstandeter dreidimensionaler, zylinderförmiger Bereich gleicher Abmessungen und gleicher Orientierung (d.h. gleicher Ausrichtung und Lage der Zylinderachse des zu untersuchenden, zylinderförmigen Bereichs) herangezogen. Dabei ist darauf zu achten, dass der Bereich des Korninneren gleichzeitig auch von weiteren Großwinkel-Korngrenzen ausreichend, vorzugsweise um mindestens 10 nm, beabstandet ist. Die dreidimensionalen, zylinderförmigen Bereiche (des Korninneren wie des Korngrenzenabschnitts) weisen insbesondere jeweils einen (kreisförmigen) Durchmesser von 10 nm auf, wobei die zugehörige Kreisfläche der zylinderförmigen Bereiche jeweils senkrecht zu der zugehörigen Zylinderachse ausgerichtet ist (ergibt sich aus der Zylinderform). Innerhalb dieser Bereiche wird jeweils der Anteil von Bor und Kohlenstoff in Atomprozent bestimmt. Anschließend werden die so bestimmten Anteile, entweder von Bor und Kohlenstoff in Summe oder alternativ auch jeweils von den Einzelelementen, jeweils von dem Bereich des Korngrenzenabschnitts zu dem Bereich des Korninneren ins Verhältnis gesetzt, wie nachfolgend noch weiter im Detail erläutert wird.According to one development, the following applies at least to a grain boundary section of a large-angle grain boundary and the adjacent grain: the total proportion of carbon and boron in the area of the grain boundary section is at least one and a half times as high as in the area of the grain interior of the adjacent grain; In particular, the proportion of carbon and boron in total in the area of the grain boundary section is at least twice as high, more preferably at least three times as high as in the area of the grain interior of the adjacent grain. Preferably, each of the elements B and C satisfies the specified relationships. The proportions of the individual elements (B, C) and the sum of the elements (B and C) are each determined in atomic percent (at%) by means of three-dimensional atom probe tomography. A three-dimensional, cylindrical region with a cylinder axis running perpendicular to the grain boundary section and with a thickness of 5 nm (nanometers) running along the cylinder axis is selected for the region of the grain boundary section, which is placed centrally around the grain boundary section in relation to the cylinder axis direction (According to the measurement method that is decisive here and explained in detail below, this is the range of 5 nm thickness within which the sum of the measured concentrations of B and C is maximum). In particular, the cylinder axis runs perpendicularly to the plane that is spanned by the grain boundary section in the region to be examined. In the case of a (slightly) curved grain boundary section, a mean plane that maintains a minimum distance to the grain boundary section over the observed area is to be used (for the orientation and positioning of the cylindrical region to be examined). For the region of the grain interior, a three-dimensional cylindrical region spaced with its center by 10 nm in the cylinder axis direction from the grain boundary portion (or, if necessary, from the associated average plane) becomes the same Dimensions and the same orientation (ie the same alignment and position of the cylinder axis of the cylinder-shaped area to be examined) is used. It is important to ensure that the region of the interior of the grain is at the same time sufficiently spaced apart from other large-angle grain boundaries, preferably by at least 10 nm. The three-dimensional, cylindrical areas (of the grain interior as well as the grain boundary section) each have a (circular) diameter of 10 nm, with the associated circular area of the cylindrical areas being aligned perpendicular to the associated cylinder axis (resulting from the cylindrical shape). Within these ranges, the proportion of boron and carbon is determined in atomic percent. Subsequently, the proportions determined in this way, either of boron and carbon in total or alternatively also of the individual elements, are set in relation to the area of the grain boundary section and the area of the interior of the grain, as will be explained in more detail below.
Die Atomsonden-Tomographie ist eine hochauflösende Charakterisierungsmethode für Festkörper. Nadelförmige Spitzen ("Probenspitze") mit einem Durchmesser von etwa 100nm werden auf Temperaturen von etwa 60K gekühlt und mittels Feldverdampfung abgetragen. Die Position des Atoms und das Massezu-Ladungsverhältnis für jedes detektierte Atom (Ion) wird mittels positionssensitivem Detektor und Flugzeitmassenspektrometer bestimmt. Eine weitergehende Beschreibung der Atomsonden-Tomographie findet sich in
Im Rahmen der Atomsonden-Tomographie wird zunächst eine dreidimensionale Rückkonstruktion der eingesetzten Probenspitze des erfindungsgemäßen Molybdän-Sinterteils durchgeführt (vgl. auch
Anschließend wird ein eindimensionales Konzentrationsprofil bestimmt (vgl.
Wie bereits oberhalb ausgeführt wurde, kann das erfindungsgemäße Molybdän-Sinterteil auch noch weiteren Bearbeitungsschritten unterzogen werden, insbesondere einer Umformung (Walzen, Schmieden, Extrudieren, etc.). Gemäß einer Weiterbildung ist das Molybdän-Sinterteil zumindest abschnittsweise umgeformt und weist eine Vorzugsorientierung der Großwinkel-Korngrenzen und/oder Großwinkel-Korngrenzenabschnitte senkrecht zur Hauptumformrichtung auf, was mittels EBSD-Analyse eines metallographischen Schliffbildes einer Querschnittsebene entlang der Umformrichtung, bei welchem die (z.B. umlaufend um ein Korn ausgebildeten) Großwinkel-Korngrenzen und die (z.B. mit einem offenen Anfang und Ende ausgebildeten) Großwinkel-Korngrenzenabschnitte sichtbar gemacht werden, bestimmbar ist. Versuche haben dabei gezeigt, dass das erfindungsgemäße Molybdän-Sinterteil sich besonders gut und mit niedriger Ausschussrate umformen lässt. Selbst beim Schmieden dicker Stäbe (z.B. mit Ausgangsdurchmessern im Bereich von 200-240 mm) und beim Walzen dicker Bleche (z.B. mit Ausgangsdicken im Bereich von 120-140mm) wird eine Rissbildung, die bei herkömmlichem Molybdän verstärkt im Kern der Stäbe/Bleche auftritt, vermieden. Infolge des Umformens weist das Molybdän-Sinterteil eine Umformstruktur auf, d.h. es sind typischerweise keine klaren, um einzelne Körner umlaufenden Großwinkel-Korngrenzen, wie sie unmittelbar nach dem Schritt des Sinterns auftreten, mehr zu erkennen, sondern nur Großwinkel-Korngrenzenabschnitte, die jeweils einen offenen Anfang und ein offenes Ende aufweisen. Zum Teil sind dabei (je nach Umformgrad) auch noch Abschnitte der Großwinkel-Korngrenzen der ursprünglichen Körner, wie sie unmittelbar nach dem Sinterschritt vorlagen, erkennbar. Weiterhin bilden sich durch die Umformung Versetzungen und neue Großwinkel-Korngrenzenabschnitte aus. Die ursprünglichen Körner, wie sie unmittelbar nach dem Sinterschritt vorlagen, sofern sie noch erkennbar sind, sind aufgrund der Umformung stark gequetscht und verzerrt. Die Vorzugsrichtung der erkennbaren Großwinkel-Korngrenzenabschnitte verläuft dabei senkrecht zur Hauptumformrichtung. Insbesondere verläuft ein längenmäßig größerer Anteil (z.B. mindestens 60%, insbesondere mindestens 70%) der Großwinkel-Korngrenzenabschnitte stärker zu der Richtung senkrecht zur Hauptumformrichtung hin geneigt (bzw. zum Teil auch genau parallel dazu), als zu der Hauptumformrichtung hin geneigt, was mittels EBSD-Analyse eines metallographischen Schliffbildes einer Querschnittsebene entlang der Hauptumformrichtung, bei welchem die Großwinkel-Korngrenzenabschnitte sichtbar gemacht werden, bestimmbar ist.As already explained above, the molybdenum sintered part according to the invention can also be subjected to further processing steps, in particular forming (rolling, forging, extrusion, etc.). According to a further development, the sintered molybdenum part is deformed at least in sections and has a preferred orientation of the large-angle grain boundaries and/or large-angle grain boundary sections perpendicular to the main direction of deformation, which can be determined by means of EBSD analysis of a metallographic microsection of a cross-sectional plane along the direction of deformation, in which the (e.g. circumferential high angle grain boundaries formed around a grain and the high angle grain boundary sections (e.g. formed with an open beginning and end) visualized can be determined. Experiments have shown that the molybdenum sintered part according to the invention can be shaped particularly well and with a low scrap rate. Even when forging thick bars (e.g. with starting diameters in the range of 200-240 mm) and rolling thick sheets (e.g. with starting thicknesses in the range of 120-140mm), cracking, which occurs more frequently with conventional molybdenum, in the core of the bars/sheets, avoided. As a result of the forming, the molybdenum sintered part a deformed structure, i.e. there are typically no clear large-angle grain boundaries surrounding individual grains, as they occur immediately after the sintering step, but only large-angle grain boundary sections, each of which has an open beginning and an open end. In some cases (depending on the degree of deformation), sections of the large-angle grain boundaries of the original grains are still recognizable as they were immediately after the sintering step. Dislocations and new large-angle grain boundary sections are also formed as a result of the deformation. The original grains, as they were immediately after the sintering step, if they are still recognizable, are severely squashed and distorted due to the deformation. The preferred direction of the recognizable large-angle grain boundary sections runs perpendicular to the main direction of deformation. In particular, a larger proportion (e.g. at least 60%, in particular at least 70%) of the large-angle grain boundary sections in terms of length is more inclined to the direction perpendicular to the main forming direction (or in some cases exactly parallel to it) than inclined to the main forming direction, which is EBSD analysis of a metallographic micrograph of a cross-sectional plane along the main forming direction, in which the high-angle grain boundary sections are made visible.
Weiterhin kann im Anschluss an den Umformschritt auch noch eine Wärmebehandlung (z.B. Spannungsarmglühen bei Temperaturen im Bereich von 650-850°C und einer Dauer im Bereich von 2-6 h; Rekristallisationsglühen bei Temperaturen im Bereich von 1000-1300°C und einer Dauer im Bereich von 1-3 h stattfinden. Mit zunehmender Temperatur und Dauer einer Wärmebehandlung findet schrittweise ein Kornwachstum von Körnern mit um die einzelnen Körner umlaufenden Großwinkel-Korngrenzen statt (Rekristallisation). Gemäß einer Weiterbildung liegt das erfindungsgemäße Molybdän-Sinterteil zumindest abschnittsweise (gegebenenfalls auch vollständig) in einer teilweise oder vollständig rekristallisierten Struktur vor. Gegenüber herkömmlichem Molybdän mit teilweiser oder vollständig rekristallisierter Struktur werden dabei deutlich höhere Duktilitäts- und Festigkeitswerte erzielt.Furthermore, following the forming step, a heat treatment (e.g. stress-relief annealing at temperatures in the range of 650-850°C and a duration in the range of 2-6 h; recrystallization annealing at temperatures in the range of 1000-1300°C and a duration in range of 1-3 hours. With increasing temperature and duration of a heat treatment, there is a gradual grain growth of grains with large-angle grain boundaries surrounding the individual grains (recrystallization). According to a further development, the molybdenum sintered part according to the invention is at least partially (if necessary also completely ) in a partially or fully recrystallized structure. Compared to conventional molybdenum with a partially or fully recrystallized structure, significantly higher ductility and strength values are achieved.
Gemäß einer Weiterbildung ist das (insbesondere in Blechform ausgebildete) Molybdän-Sinterteil über eine Schweißverbindung mit einem weiteren (insbesondere in Blechform ausgebildeten) Molybdän-Sinterteil verbunden, wobei beide Molybdän-Sinterteile gemäß der vorliegenden Erfindung und gegebenenfalls gemäß einer oder mehrerer der Weiterbildungen ausgebildet sind und wobei eine Schweißzone der Schweißverbindung einen Molybdänanteil von ≥ 99,93 Gew.% aufweist. Die erfindungsgemäßen Molybdän-Sinterteile lassen sich gegenüber herkömmlichem Molybdän deutlich besser verschweißen. Wie durch den spezifizierten Molybdänanteil der Schweißzone deutlich wird, ist keine Zugabe eines Schweißzusatzwerkstoffes erforderlich. Dadurch können die Materialeigenschaften von reinem Molybdän auch im Bereich der Schweißzone beibehalten werden. Die Schweißverbindung weist dabei hohe Duktilitäts- und Festigkeitswerte auf, insbesondere wurden abhängig vom Schweißverfahren und den Schweißbedingungen Dehnungen von >8% im Zugversuch (gemäß DIN EN ISO 6892-1 Verf.B) und Biegewinkel von bis zu 70°bei Biegeversuchen gemäß DIN EN ISO 7438) gemessen. Erhebliche Verbesserungen wurden insbesondere beim Laserstrahlschweißen und beim WIG-Schweißen (Wolframinertgasschweißen) erzielt.According to a further development, the sintered molybdenum part (in particular in the form of sheet metal) is connected to a further sintered molybdenum part (in particular in the form of sheet metal) via a welded joint, with both sintered molybdenum parts being formed in accordance with the present invention and optionally in accordance with one or more of the further developments and wherein a weld zone of the welded joint has a molybdenum content of ≧99.93% by weight. The molybdenum sintered parts according to the invention can be welded much better than conventional molybdenum. As is evident from the specified molybdenum content of the weld zone, no filler material is required. As a result, the material properties of pure molybdenum can also be retained in the area of the welding zone. The welded connection has high ductility and strength values, in particular, depending on the welding process and the welding conditions, elongations of >8% in the tensile test (according to DIN EN ISO 6892-1 Verf.B) and bending angles of up to 70° in bending tests according to DIN EN ISO 7438) measured. Significant improvements have been achieved in particular in laser beam welding and TIG welding (tungsten inert gas welding).
Die vorliegende Erfindung betrifft ferner ein Verfahren zum Herstellen eines Molybdän-Sinterteils, das aus einem Molybdänanteil von ≥ 99,93 Gew.%, einem Boranteil "B" von ≥ 3 ppmw und einem Kohlenstoffanteil "C" von ≥ 3 ppmw, wobei der Gesamtanteil "BuC" an Kohlenstoff und Bor im Bereich von 15 ppmw ≤ "BuC" ≤ 50 ppmw liegt, einem Sauerstoffanteil "O" im Bereich von 3 ppmw ≤ "O" ≤ 20 ppmw, einem maximalen Wolframanteil von ≤ 330 ppmw und einem maximalen Anteil an sonstigen Verunreinigungen von ≤ 300 ppmw besteht, wobei vorzugsweise der maximale Anteil an Verunreinigungen durch Zirconium (Zr), Hafnium (Hf), Titan (Ti), Vanadium (V) und Aluminium (AI) in Summe ≤ 50 ppmw beträgt und vorzugsweise der maximale Anteil an Verunreinigungen durch Silicium (Si), Rhenium (Re) und Kalium (K) in Summe ≤ 20 ppmw beträgt, wobei durch nachfolgende Schritte:
- a. Pressen einer Pulvermischung aus Molybdänpulver und Bor- und Kohlenstoff-haltigen Pulvern, zu einem Grünling;
- b. Sintern des Grünlings in einer vor Oxidation schützenden Atmosphäre mit einer
Verweildauer von mindestens 45 Minuten bei Temperaturen im Bereich von 1.600 °C - 2.200°C.
- a. pressing a powder mixture of molybdenum powder and powders containing boron and carbon into a green body;
- b. Sintering of the green compact in an atmosphere protecting against oxidation with a residence time of at least 45 minutes at temperatures in the range of 1,600 °C - 2,200 °C.
Bei dem erfindungsgemäßen Verfahren werden die oberhalb in Bezug auf das erfindungsgemäße Molybdän-Sinterteil erläuterten Vorteile in entsprechender Weise erzielt. Ferner sind entsprechende Weiterbildungen, wie sie oberhalb erläutert wurden, auch bei dem erfindungsgemäßen Verfahren möglich. Bei den Bor- und Kohlenstoff-haltigen Pulvern kann es sich ebenfalls um Molybdänpulver handeln, das einen entsprechenden Bor- und/oder Kohlenstoff-Anteil enthält. Wesentlich ist, dass das Ausgangspulver, das zum Pressen des Grünlings eingesetzt wird, ausreichende Mengen an Bor und Kohlenstoff enthält und diese Zusätze möglichst gleichmäßig und fein in dem Ausgangspulver verteilt sind.In the method according to the invention, the advantages explained above in relation to the molybdenum sintered part according to the invention are achieved in a corresponding manner. Furthermore, corresponding further developments, as explained above, are also possible with the method according to the invention. The powders containing boron and carbon can likewise be molybdenum powder, which contains a corresponding proportion of boron and/or carbon. It is essential that the starting powder used for pressing the green compact contains sufficient amounts of boron and carbon and that these additives are distributed as evenly and finely as possible in the starting powder.
Insbesondere umfasst der Schritt des Sinterns eine Wärmebehandlung für eine Verweildauer von 45 Minuten bis zu 12 Stunden (h), vorzugsweise von 1-5 h, bei Temperaturen im Bereich von 1.800 °C - 2.100 °C. Insbesondere wird der Sinterschritt im Vakuum, unter Schutzgas (z.B. Argon) oder vorzugsweise in reduzierender Atmosphäre (insbesondere in Wasserstoffatmosphäre oder in einer Atmosphäre mit H2-Teildruck) durchgeführt.In particular, the sintering step comprises a heat treatment for a residence time of from 45 minutes to 12 hours (h), preferably from 1-5 h, at temperatures in the range of 1800°C - 2100°C. In particular, the sintering step is carried out in a vacuum, under a protective gas (eg argon) or preferably in a reducing atmosphere (in particular in a hydrogen atmosphere or in an atmosphere with H 2 partial pressure).
Weitere Vorteile und Zweckmäßigkeiten der Erfindung ergeben sich anhand der nachfolgenden Beschreibung von Ausführungsbeispielen unter Bezugnahme auf die beigefügten Figuren.Further advantages and advantages of the invention result from the following description of exemplary embodiments with reference to the attached figures.
Von den Figuren zeigen:
- Fig. 1:
- Diagramm-Darstellung eines 3-Punkt-Biegeversuchs von Proben unterschiedlicher Molybdän-Sinterteile;
- Fig. 2:
- Entsprechende Diagramm-Darstellung wie in
Fig. 1 unter Aufnahme weiterer Proben von Molybdän-Sinterteilen; - Fig. 3:
- Diagramm-Darstellung der Bruchdehnung unterschiedlicher Molybdän-Sinterteile im Zugversuch;
- Fig. 4:
- Diagramm-Darstellung der Bruchfestigkeit unterschiedlicher Molybdän-Sinterteile im Zugversuch;
- Fig. 5:
- Über Atomsonden-Tomographie bestimmte dreidimensionale Rückkonstruktion einer Probenspitze eines erfindungsgemäßen Molybdän-Sinterteils "15B15C", wobei die Elemente Kohlenstoff (C), Bor (B), Sauerstoff (O) und Stickstoff (N) dargestellt sind; und
- Fig. 6:
- Diagrammdarstellung des linearen bzw. eindimensionalen Konzentrationsprofils der Elemente C, B, O und N entsprechend der in
Fig. 5 dargestellten, dreidimensionalen Rückkonstruktion entlang der inFig. 5 eingezeichneten Zylinderachse.
- Figure 1:
- Diagram representation of a 3-point bending test of samples of different molybdenum sintered parts;
- Figure 2:
- Corresponding diagram representation as in
1 including further samples of molybdenum sintered parts; - Figure 3:
- Diagram representation of the elongation at break of different molybdenum sintered parts in the tensile test;
- Figure 4:
- Diagram showing the breaking strength of different molybdenum sintered parts in a tensile test;
- Figure 5:
- Three-dimensional reconstruction of a sample tip of a molybdenum sintered part "15B15C" according to the invention, determined by atom probe tomography, the elements carbon (C), boron (B), oxygen (O) and nitrogen (N) being represented; and
- Figure 6:
- Diagram representation of the linear or one-dimensional concentration profile of the elements C, B, O and N according to the in
figure 5 illustrated, three-dimensional reconstruction along the infigure 5 marked cylinder axis.
In
Die in den
Wie die Gegenüberstellung der erfindungsgemäßen Molybdän-Sinterteile "30B15C", "15B15C" gegenüber dem herkömmlichen Molybdän-Sinterteil "Mo rein" in
Wie die Gegenüberstellung mit den weiteren Prüfproben "B70", "B150", "C70", "C150" in
In den
In
Wie ferner oberhalb in Bezug auf die Atomsonden-Tomographie beschrieben wurde und in
Anschließend wurde das lineare Konzentrationsprofil der Elemente C, B, O und N entlang der Zylinderachse 6 des Messzylinders 4 so, wie es oberhalb in Bezug auf die Atomsonden-Tomographie erläutert wurde, ermittelt.
Im Folgenden wird noch konkret anhand der
Für die pulvermetallurgische Herstellung eines erfindungsgemäßen Molybdän-Sinterteils wurde Molybdänpulver, welches durch Wasserstoff-Reduktion hergestellt wurde, verwendet. Die Korngröße nach Fisher (FSSS nach ASTM B330) betrug 4,7 µm. Das Molybdänpulver wies Verunreinigungen von 10 ppmw Kohlenstoff, 470 ppmw Sauerstoff, 135 ppmw Wolfram und 7 ppmw Eisen auf. Unter Einberechnung der nach der Reduktion im Molybdänpulver bereits vorhandenen Menge an B und C (vorliegend: C-Anteil von 10 ppmw; B nicht nachweisbar) wurden solche Mengen an C- und B-haltigem Pulver (39 ppmw C und 31 ppmw B) zugegeben, dass ein Gesamtanteil von 49 ppmw an Kohlenstoff und von 31 ppmw an Bor im Molybdänpulver eingestellt wurde. Die Pulvermischung wurde durch eine 10 minütige Mischung in einem Pflugscharmischer homogenisiert. In weiterer Folge wurde diese Pulvermischung in entsprechende Schläuche gefüllt und kaltisostatisch bei einem Pressdruck von 200 MPa bei Raumtemperatur über eine Dauer von 5 Minuten gepresst. Die so erzeugten Presslinge (runde Stäbe von jeweils 480 kg) wurden in indirekt beheizten Sinteranlagen (d.h. Wärmeübertragung auf das Sintergut über Wärmestrahlung und Konvektion) bei einer Temperatur von 2050°C über eine Zeitdauer von 4 Stunden in einer Wasserstoffatmosphäre gesintert und anschließend abgekühlt. Die so erhaltenen Sinterstäbe wiesen einen Bor-Anteil von 22 ppmw, einen Kohlenstoff-Anteil von 12 ppmw und einen Sauerstoff-Anteil von 7 ppmw auf. Der Wolframanteil und der Anteil an sonstigen metallischen Verunreinigungen blieb unverändert.Molybdenum powder, which was produced by hydrogen reduction, was used for the powder-metallurgical production of a molybdenum sintered part according to the invention. The grain size according to Fisher (FSSS according to ASTM B330) was 4.7 μm. The molybdenum powder had impurities of 10 ppmw carbon, 470 ppmw oxygen, 135 ppmw tungsten and 7 ppmw iron. Taking into account the amount of B and C already present in the molybdenum powder after the reduction (present: C content of 10 ppmw; B not detectable), such amounts of C and B-containing powder (39 ppmw C and 31 ppmw B) were added that a total of 49 ppmw of carbon and 31 ppmw of boron was set in the molybdenum powder. The powder mixture was homogenized by mixing in a plowshare mixer for 10 minutes. Subsequently, this powder mixture was filled into appropriate hoses and cold isostatically pressed at a pressure of 200 MPa at room temperature for a period of 5 minutes. The compacts produced in this way (round rods of 480 kg each) were sintered in indirectly heated sintering plants (i.e. heat transfer to the sintered material via thermal radiation and convection) at a temperature of 2050°C for a period of 4 hours in a hydrogen atmosphere and then cooled. The sintered rods obtained in this way had a boron content of 22 ppmw, a carbon content of 12 ppmw and an oxygen content of 7 ppmw. The tungsten content and the content of other metallic impurities remained unchanged.
Die erfindungsgemäßen Molybdän-Sinterstäbe wurden auf einer Radialschmiedemaschine bei einer Temperatur von 1200°C verformt, wobei eine Durchmesserreduktion von 240 auf 165 mm vorgenommen wurde. Die Ultraschalluntersuchung des 100% dichten Stabes zeigte auch im Inneren keine Risse und metallografische Schliffe bestätigten diesen Befund.The sintered molybdenum rods according to the invention were deformed on a radial forging machine at a temperature of 1200° C., the diameter being reduced from 240 to 165 mm. The ultrasonic examination of the 100% dense bar showed no cracks on the inside either, and metallographic sections confirmed this finding.
Erfindungsgemäße Molybdän-Sinterteile in Blechform wurden über ein Laser-Schweißverfahren miteinander verschweißt. Folgende Schweißparameter wurden dabei eingestellt:
- Lasertyp: Trumpf TruDisk 4001
- Wellenlänge: 1030nm
- Laserleistung: 2.750 W (Watt)
- Fokusdurchmesser: 100 µm (Mikrometer)
- Schweißgeschwindigkeit: 3.600 mm/min (Millimeter pro Minute)
- Fokuslage: 0 mm
- Schutzgas: 100% Argon
- Laser type: Trumpf TruDisk 4001
- Wavelength: 1030nm
- Laser power: 2,750 W (watts)
- Focus diameter: 100 µm (microns)
- Welding speed: 3,600 mm/min (millimeters per minute)
- Focus position: 0 mm
- Shielding gas: 100% argon
Gefügeuntersuchungen zeigten, dass auch im Bereich der Schweißzone ein gleichmäßiges, relativ feinkörniges Gefüge ausgebildet war. Die verschweißten Molybdän-Sinterteile wiesen auch im Bereich der Schweißverbindung eine vergleichsweise hohe Duktilität auf, was im Biegeversuch, bei dem Biegewinkel von > 70'° erzielt wurden, bestätigt wurde.Structural investigations showed that an even, relatively fine-grained structure was also formed in the area of the weld zone. The welded sintered molybdenum parts also showed a comparatively high ductility in the area of the welded joint, which was confirmed in the bending test, in which bending angles of >70° were achieved.
Nachfolgend wird die mit einem Rasterelektronenmikroskop durchführbare EBSD-Analyse erläutert. Hierzu wird im Rahmen der Probenpräparation eine Querschnittfläche durch das zu untersuchende Molybdän-Sinterteil hergestellt. Die Präparation einer entsprechenden Schlifffläche erfolgt insbesondere durch Einbetten, Schleifen, Polieren und Ätzen der erhaltenen Querschnittfläche, wobei die Oberfläche im Anschluss noch ionenpoliert wird (zur Entfernung der durch den Schleifvorgang entstandenen Verformungsstruktur auf der Oberfläche). Die Messanordnung ist derart, dass der Elektronenstrahl unter einem Winkel von 20° auf die präparierte Schlifffläche auftrifft. Bei dem Rasterelektronenmikroskop (vorliegend: Carl Zeiss "Ultra 55 plus") beträgt der Abstand zwischen der Elektronenquelle (vorliegend: Feldemissionskathode) und der Probe 16, 2 mm und der Abstand zwischen der Probe und der EBSD-Kamera (vorliegend: "DigiView IV") beträgt 16 mm. Die in Klammern gemachten Angaben betreffen jeweils die von der Anmelderin verwendeten Gerätetypen, wobei grundsätzlich auch anderweitige Gerätetypen, welche die beschriebenen Funktionen ermöglichen, in entsprechender Weise verwendbar sind. Die Beschleunigungsspannung beträgt 20 kV, es wird eine 500-fache Vergrößerung eingestellt und der Abstand der einzelnen Pixel auf der Probe, die nacheinander abgetastet werden, beträgt 0,5 µm.The EBSD analysis that can be performed with a scanning electron microscope is explained below. For this purpose, as part of the sample preparation, a cross-sectional area is produced through the molybdenum sintered part to be examined. A corresponding ground surface is prepared in particular by embedding, grinding, polishing and etching the cross-sectional area obtained, with the surface then being ion-polished (to remove the deformation structure on the surface caused by the grinding process). The measuring arrangement is such that the electron beam strikes the prepared ground surface at an angle of 20°. With the scanning electron microscope (here: Carl Zeiss "Ultra 55 plus"), the distance between the electron source (here: field emission cathode) and the sample is 16.2 mm and the distance between the sample and the EBSD camera (here: "DigiView IV" ) is 16 mm. The information given in parentheses relates to the device types used by the applicant, although in principle other device types that enable the functions described can also be used in a corresponding manner. The acceleration voltage is 20 kV, a magnification of 500x is set and the distance between the individual pixels on the sample, which are scanned one after the other, is 0.5 µm.
Im Rahmen der EBSD-Analyse können dabei (z.B. umlaufend um ein Korn ausgebildete) Großwinkel-Korngrenzen und (z.B. mit einem offenen Anfang und Ende ausgebildete) Großwinkel-Korngrenzenabschnitte mit einem Korngrenzenwinkel, der größer oder gleich dem Mindest-Rotationswinkel von 15° ist, innerhalb der untersuchten Probenfläche sichtbar gemacht werden. Durch das Rasterelektronenmikroskop werden innerhalb der untersuchten Probenfläche nämlich Großwinkel-Korngrenzen bzw. Großwinkel-Korngrenzenabschnitte immer dann zwischen zwei Rasterpunkten bestimmt und dargestellt, wenn zwischen den beiden Rasterpunkten ein Orientierungsunterschied der jeweiligen Kristallgitter von ≥ 15° festgestellt wird. Als Orientierungsunterschied wird jeweils der kleinste Winkel herangezogen, der benötigt wird, um die jeweiligen Kristallgitter, die an den zu vergleichenden Rasterpunkten vorliegen, ineinander überzuführen. Dieser Vorgang wird bei jedem Rasterpunkt in Bezug auf alle, ihn umgebenden Rasterpunkte durchgeführt. Auf diese Weise wird innerhalb der untersuchten Probenfläche ein Korngrenzenmuster aus Großwinkel-Korngrenzen und/oder Großwinkel-Korngrenzenabschnitten erhalten.Within the framework of the EBSD analysis, large-angle grain boundaries (e.g. formed circumferentially around a grain) and large-angle grain boundary sections (e.g. formed with an open beginning and end) with a grain boundary angle that is greater than or equal to the minimum rotation angle of 15°, can be made visible within the examined sample area. With the scanning electron microscope, large-angle grain boundaries or large-angle grain boundary sections are always determined and displayed between two grid points within the examined sample surface if an orientation difference of the respective crystal lattices of ≥ 15° is determined between the two grid points. The smallest angle that is required to convert the respective crystal lattices that are present at the grid points to be compared into one another is used as the orientation difference. This process is performed on each raster point in relation to all raster points surrounding it. In this way, a grain boundary pattern of high-angle grain boundaries and/or high-angle grain boundary sections is obtained within the examined sample area.
Claims (13)
- Powder-metallurgical sintered molybdenum part which is present as solid body from a composition consisting of the following amounts:a. a molybdenum content of ≥ 99.93% by weight,b. a boron content "B" of ≥ 3 ppmw and a carbon content "C" of ≥ 3 ppmw, with the total content "BaC" of carbon and boron being in the range of 15 ppmw ≤ "BaC" ≤ 50 ppmw,c. an oxygen content "O" in the range of 3 ppmw ≤ "O" ≤ 20 ppmw,d. a maximum tungsten content of ≤ 330 ppmw ande. a maximum proportion of other impurities of ≤ 300 ppmw, wherein preferably the maximum proportion of contamination by zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminium (Al) is ≤ 50 ppmw in total, and preferably the maximum proportion of contamination by silicon (Si), rhenium (Re) and potassium (K) is ≤ 20 ppmw in total.
- Sintered molybdenum part according to Claim 1, characterized in that the boron content "B" is in the range of 5 ≤ "B" ≤ 45 ppmw.
- Sintered molybdenum part according to Claim 1 or 2, characterized in that the carbon content "C" is in the range of 5 ≤ "C" ≤ 30 ppmw.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that the oxygen content "O" is in the range of 5 ≤ "O" ≤ 15 ppmw.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that
the maximum proportion of contamination by zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminium (Al) is ≤ 50 ppmw in total and in that the maximum proportion of contamination by silicon (Si), rhenium (Re) and potassium (K) is ≤ 20 ppmw in total. - Sintered molybdenum part according to anyone of the preceding claims, characterized in that it has a total content of molybdenum and tungsten of ≥ 99.97% by weight.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that the carbon and the boron are present in dissolved form in a total amount of at least 70% by weight based on the total content of carbon and boron.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that the following applies at least at a grain boundary section (2) of a large angle grain boundary and the adjoining grain: the total proportion of carbon and boron in the region of the grain boundary section (2) is at least one and a half times that in the region of the grain interior of the adjoining grain, measured in atom per cent by means of three-dimensional atom probe tomography, where a three-dimensional, cylindrical region having a cylinder axis (6) running perpendicular to the grain boundary section (2) and a thickness running along the cylinder axis (6) of 5 nm which, relative to the cylinder axis direction, is laid centrally around the grain boundary section (2) is selected for the region of the grain boundary section (2) and a three-dimensional, cylindrical region having the same dimensions and the same orientation and having its centre 10 nm away from the grain boundary section (2) in the cylinder axis direction is employed for the region of the grain interior.
- Sintered molybdenum part according to Claim 7, characterized in that the total proportion of carbon and boron in the region of the grain boundary section (2) is at least three times that in the region of the grain interior of the adjoining grain.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that it has been formed at least in sections and has a preferential orientation of the large angle grain boundaries and/or large angle grain boundary sections perpendicular to the main forming direction.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that it has, at least in sections, a partially or fully recrystallized structure.
- Sintered molybdenum part according to anyone of the preceding claims, characterized in that it is joined via a weld connection to a further sintered molybdenum part which is configured according to anyone of the preceding claims, with a weld zone of the weld connection having a molybdenum content of ≥ 99.93% by weight.
- Process for producing a sintered molybdenum part consisting of a molybdenum content of ≥ 99.93% by weight, a boron content "B" of ≥ 3 ppmw and a carbon content "C" of ≥ 3 ppmw, with the total content "BaC" of carbon and boron being in the range of 15 ppmw ≤ "BaC" ≤ 50 ppmw, an oxygen content "O" in the range of 3 ppmw ≤ "O" ≤ 20 ppmw, a maximum tungsten content of ≤ 330 ppmw and a maximum proportion of other impurities of ≤ 300 ppmw, wherein preferably the maximum proportion of contamination by zirconium (Zr), hafnium (Hf), titanium (Ti), vanadium (V) and aluminium (Al) is ≤ 50 ppmw in total, and preferably the maximum proportion of contamination by silicon (Si), rhenium (Re) and potassium (K) is ≤ 20 ppmw in total, with the following steps:a. pressing of a powder mixture composed of molybdenum powder and boron- and carbon-containing powders to give a green body;b. sintering of the green body in an atmosphere which protects against oxidation for a residence time of at least 45 minutes at temperatures in the range 1600°C-2200°C.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ATGM217/2017U AT15903U1 (en) | 2017-09-29 | 2017-09-29 | Molybdenum sintered part |
PCT/AT2018/000071 WO2019060932A1 (en) | 2017-09-29 | 2018-09-07 | Sintered molybdenum part |
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EP3688200A1 EP3688200A1 (en) | 2020-08-05 |
EP3688200B1 true EP3688200B1 (en) | 2022-06-22 |
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EP18789316.9A Active EP3688200B1 (en) | 2017-09-29 | 2018-09-07 | Molybdenum sintered part and method of manufacturing |
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US (1) | US11925984B2 (en) |
EP (1) | EP3688200B1 (en) |
JP (1) | JP7273808B2 (en) |
CN (1) | CN111164227B (en) |
AT (1) | AT15903U1 (en) |
ES (1) | ES2923151T3 (en) |
TW (1) | TWI763918B (en) |
WO (1) | WO2019060932A1 (en) |
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AT17259U1 (en) * | 2020-11-13 | 2021-10-15 | Plansee Se | HIGH TEMPERATURE FORMING TOOL |
CN113637884B (en) * | 2021-07-20 | 2022-07-08 | 深圳大学 | High-performance molybdenum alloy and preparation method thereof |
CN113418946B (en) * | 2021-07-30 | 2022-08-09 | 贵研检测科技(云南)有限公司 | High-calibration-rate EBSD sample preparation method for ruthenium metal |
CN115261634B (en) * | 2022-07-25 | 2024-02-06 | 金堆城钼业股份有限公司 | Low-potassium molybdenum matrix, preparation method and application |
CN115418517B (en) * | 2022-09-15 | 2024-05-14 | 宁波江丰电子材料股份有限公司 | Preparation method of molybdenum-copper alloy for electronic packaging |
CN115572877B (en) * | 2022-10-08 | 2023-06-09 | 郑州大学 | Preparation method of molybdenum-niobium or molybdenum-tantalum alloy |
CN118166230B (en) * | 2024-05-15 | 2024-07-19 | 安庆瑞迈特科技有限公司 | Improved tungsten/molybdenum alloy material powder metallurgy method |
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AT285966B (en) * | 1968-10-11 | 1970-11-25 | Plansee Metallwerk | Sintered molybdenum-boron alloy |
JPS4940763B1 (en) * | 1969-09-10 | 1974-11-05 | ||
JPS54116313A (en) | 1978-03-02 | 1979-09-10 | Nat Res Inst Metals | Production of molybdenum material or sintered molybdenum material with excellent low temperature tenacity |
JPS55164071A (en) * | 1979-06-08 | 1980-12-20 | Sumitomo Electric Ind Ltd | Manufacture of coated and sintered alloy parts |
JPS5853703B2 (en) | 1980-07-08 | 1983-11-30 | 株式会社東芝 | Molybdenum material with excellent hot workability |
AT377584B (en) * | 1981-06-25 | 1985-04-10 | Klima & Kaelte Gmbh | CORNER CONNECTION TO METAL FRAME |
JPS59116356A (en) * | 1982-12-22 | 1984-07-05 | Toshiba Corp | Molybdenum alloy |
JP4199406B2 (en) | 2000-03-29 | 2008-12-17 | 株式会社アライドマテリアル | Molybdenum material and manufacturing method thereof |
JP2006002178A (en) * | 2004-06-15 | 2006-01-05 | Hitachi Metals Ltd | Method for producing pure molybdenum or molybdenum alloy thin strip |
DE102005003445B4 (en) * | 2005-01-21 | 2009-06-04 | H.C. Starck Hermsdorf Gmbh | Metal substrate material for the anode plates of rotary anode X-ray tubes, method for producing such a material and method for producing an anode plate using such a material |
TWI471436B (en) | 2007-01-12 | 2015-02-01 | Nippon Steel & Sumikin Mat Co | Mo sputtering target plate and its manufacturing method |
JP5484756B2 (en) | 2009-03-13 | 2014-05-07 | 株式会社アライドマテリアル | Molybdenum plate and method for manufacturing molybdenum plate |
TW201103987A (en) * | 2009-07-22 | 2011-02-01 | China Steel Corp | Method for manufacturing molybdenum based sheet |
CN102703788B (en) * | 2012-06-26 | 2014-01-22 | 洛阳爱科麦钨钼制品有限公司 | Boron-doped TZM (molybdenum-titanium-zirconium) alloy |
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2018
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- 2018-09-07 EP EP18789316.9A patent/EP3688200B1/en active Active
- 2018-09-07 CN CN201880063038.XA patent/CN111164227B/en active Active
- 2018-09-07 US US16/649,489 patent/US11925984B2/en active Active
- 2018-09-07 JP JP2020517783A patent/JP7273808B2/en active Active
- 2018-09-07 WO PCT/AT2018/000071 patent/WO2019060932A1/en unknown
- 2018-09-07 ES ES18789316T patent/ES2923151T3/en active Active
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TAKIDA TOMOHIRO ET AL: "Mechanical Properties of Fine-Grained, Sintered Molybdenum Alloys with Dispersed Particles Developed by Mechanical Alloying", MATERIALS TRANSACTIONS, vol. 45, no. 1, 1 January 2004 (2004-01-01), JP, pages 143 - 148, XP055854647, ISSN: 1345-9678, DOI: 10.2320/matertrans.45.143 * |
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TWI763918B (en) | 2022-05-11 |
EP3688200A1 (en) | 2020-08-05 |
US20200306832A1 (en) | 2020-10-01 |
CN111164227B (en) | 2022-07-26 |
CN111164227A (en) | 2020-05-15 |
JP7273808B2 (en) | 2023-05-15 |
US11925984B2 (en) | 2024-03-12 |
JP2020535318A (en) | 2020-12-03 |
WO2019060932A1 (en) | 2019-04-04 |
TW201920707A (en) | 2019-06-01 |
AT15903U1 (en) | 2018-08-15 |
ES2923151T3 (en) | 2022-09-23 |
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