CN117340251A - High-density tungsten alloy and preparation method thereof - Google Patents
High-density tungsten alloy and preparation method thereof Download PDFInfo
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- CN117340251A CN117340251A CN202311295627.XA CN202311295627A CN117340251A CN 117340251 A CN117340251 A CN 117340251A CN 202311295627 A CN202311295627 A CN 202311295627A CN 117340251 A CN117340251 A CN 117340251A
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- 229910001080 W alloy Inorganic materials 0.000 title claims abstract description 99
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 238000005245 sintering Methods 0.000 claims abstract description 137
- 238000000034 method Methods 0.000 claims abstract description 60
- 239000007791 liquid phase Substances 0.000 claims abstract description 51
- 239000007790 solid phase Substances 0.000 claims abstract description 47
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 49
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 33
- 238000010438 heat treatment Methods 0.000 claims description 30
- 239000000843 powder Substances 0.000 claims description 29
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 25
- 229910052759 nickel Inorganic materials 0.000 claims description 20
- 238000007731 hot pressing Methods 0.000 claims description 17
- 238000003825 pressing Methods 0.000 claims description 17
- 229910000863 Ferronickel Inorganic materials 0.000 claims description 14
- 229910052742 iron Inorganic materials 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 8
- 238000009694 cold isostatic pressing Methods 0.000 claims description 6
- UGKDIUIOSMUOAW-UHFFFAOYSA-N iron nickel Chemical compound [Fe].[Ni] UGKDIUIOSMUOAW-UHFFFAOYSA-N 0.000 claims description 3
- 238000007723 die pressing method Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 230000008569 process Effects 0.000 description 36
- 239000012071 phase Substances 0.000 description 31
- 229910052721 tungsten Inorganic materials 0.000 description 26
- 239000010937 tungsten Substances 0.000 description 26
- 239000002245 particle Substances 0.000 description 22
- 238000001816 cooling Methods 0.000 description 18
- 229910045601 alloy Inorganic materials 0.000 description 17
- 239000000956 alloy Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 7
- 238000004321 preservation Methods 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 6
- 238000004663 powder metallurgy Methods 0.000 description 6
- 210000003739 neck Anatomy 0.000 description 5
- 238000001513 hot isostatic pressing Methods 0.000 description 4
- 238000000280 densification Methods 0.000 description 3
- 238000011534 incubation Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000000748 compression moulding Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005489 elastic deformation Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000002490 spark plasma sintering Methods 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910017061 Fe Co Inorganic materials 0.000 description 1
- 229910003271 Ni-Fe Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000012536 packaging technology Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- B22F3/14—Both compacting and sintering simultaneously
-
- 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
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
-
- 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
- B22F3/1035—Liquid phase sintering
-
- 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
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention discloses a high-density tungsten alloy and a preparation method thereof, wherein a tungsten alloy compact is heated to a presintering temperature in vacuum, pressurized when reaching the presintering temperature, presintered under 15-20MPa, depressurized to 5-15MPa after presintering is finished, then heated to a solid phase sintering temperature, subjected to solid phase sintering, depressurized to 0MPa after the solid phase sintering is finished, then heated to a liquid phase sintering temperature, and subjected to liquid phase sintering to obtain the tungsten alloy; the presintering temperature is 850-950 ℃, the solid phase sintering temperature is 1200-1300 ℃, and the liquid phase sintering temperature is 1450-1500 ℃, and the tungsten alloy with the relative density more than or equal to 99.5% can be prepared by the method.
Description
Technical Field
The invention belongs to the field of powder metallurgy liquid phase sintering tungsten alloy, and particularly relates to a high-density tungsten alloy and a preparation method thereof.
Background
Tungsten alloy is a composite material, typically consisting of high strength and high hardness tungsten particles and a soft binder phase. The tungsten alloy has high strength (more than 900 MPa), high hardness (more than 400 HV), high toughness (elongation rate more than 20 percent) and high density (more than 17 g/cm) 3 ) And the like. These advantages have led to the widespread use of tungsten alloys in the field of military defense, such as bullets, shells, grenades and artillery parts, and in particular their high density, making them the best material for armor piercing. The tungsten alloy armor piercing bullet has extremely high kinetic energy and excellent armor piercing capability, and can break down multi-layer composite armor and large-dip angle armor. The tungsten alloy armor-piercing bomb has the remarkable advantages of no radiation, no pollution, low cost and the like compared with the depleted uranium bomb.
Because the melting point of tungsten is higher, the tungsten-based material prepared by using a smelting method has coarse grains and reduced performance. Thus, tungsten alloys are typically produced by powder metallurgy. The powder metallurgy method for preparing tungsten alloy is required to be subjected to three steps of powder mixing, compression molding and sintering. In the compression molding process, the compaction degree of the pressed compact can only be improved to 60-65% by adopting modes such as mould pressing, cold isostatic pressing and the like, and a large number of holes can be formed in the pressed compact in the sintering process, so that the relative density of the tungsten alloy can be effectively improved by pressurizing in the sintering process. Meanwhile, the sintering process can seriously affect the performance of the tungsten alloy. Common tungsten alloy powder metallurgy methods are spark plasma sintering, hot isostatic pressing sintering, and vacuum hot pressing sintering. Among them, the spark plasma sintering method can make the powder finish alloying in a short time under a larger current and a higher pressure. However, since the liquid phase damages the discharge plasma sintering equipment, the solid phase sintering method is generally adopted to sinter at a lower temperature, and the performance and the compactness of the alloy are poor. Hot isostatic pressing sintering may apply isostatic pressure at high temperatures to obtain dense tungsten alloys at lower sintering temperatures. However, the hot isostatic pressing sintering requires a higher packaging technology, and the hot isostatic pressing sheath has higher cost and is difficult to use on a large scale. The vacuum hot-pressed sintering has the remarkable characteristics of low cost, high efficiency, simple equipment and the like, and is commonly used for preparing various powder metallurgy materials. However, vacuum hot-press sintering generally avoids the generation of liquid phase to prevent damage to equipment and dies, which makes it possible to prepare tungsten alloys only by solid-phase sintering, which has low alloy density and poor performance.
201810255013.1 in the improved tungsten alloy and the method for preparing the same, the sintering steps of the tungsten alloy are disclosed as follows: sintering, namely placing the pressed formed tungsten alloy into a sintering furnace for sintering, heating to 900 ℃ at a heating rate of 450 ℃/h, preserving heat for 4 hours at the temperature of 900 ℃, heating to 1400 ℃ from 900 ℃ at a heating rate of 75 ℃/h, and preserving heat for 4 hours, wherein the sintering process in the period of time is a solid-phase sintering process; then heating from 1400 ℃ to 1440 ℃, wherein the heating rate is 40 ℃/h, and preserving heat for 1h, and the sintering process in the period of time is a liquid phase sintering process; the above sintering stage is carried out with continuous hydrogen supply. Finally, the temperature is reduced to 1100 ℃ from 1440 ℃, hydrogen is converted into nitrogen at 1100 ℃, the prepared tungsten alloy is taken out from 1100 ℃ to natural temperature, and the 60W-28Ni-12Fe alloy is obtained. However, since no pressure is applied to the sample during sintering, the tungsten alloy has lower density (relative density 83-87.2%), and the alloy has extremely poor tensile strength (less than 265 MPa) and elongation (less than 2.3%).
Disclosure of Invention
Aiming at the problems that powder metallurgy tungsten alloy cannot be pressurized and the relative density of the alloy is poor in the vacuum hot-pressing sintering process in the prior art, the first aim of the invention is to provide a preparation method of high-density tungsten alloy.
A second object of the present invention is to provide a high-density tungsten alloy prepared by the above-mentioned preparation method.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the invention relates to a preparation method of a high-density tungsten alloy, which comprises the steps of heating a tungsten alloy compact to a presintering temperature under vacuum, pressurizing when reaching the presintering temperature, presintering under the pressure of 15-20MPa, reducing the pressure to 5-15MPa after presintering, heating to a solid-phase sintering temperature, performing solid-phase sintering, reducing the pressure to 0MPa after the solid-phase sintering is completed, heating to a liquid-phase sintering temperature, and performing liquid-phase sintering to obtain the tungsten alloy; the presintering temperature is 850-950 ℃, the solid phase sintering temperature is 1200-1300 ℃, and the liquid phase sintering temperature is 1450-1500 ℃.
The pressure provided in the invention is the relative pressure, namely the normal pressure relative to the vacuum gauge at 0MPa.
The preparation method of the invention adopts a method of vacuum and hot pressing and solid-liquid phase multistage sintering, firstly, the temperature is raised under vacuum, the gas in the compact is discharged under vacuum environment, the gas is discharged to facilitate the connection and contact among tungsten particles, the vacuum environment can reduce the melting point of each component in the compact, the formation of sintering necks among tungsten particles is facilitated, then the compact is pressurized when the compact reaches the presintering temperature, the compact is presintered under 15-20MPa, the pressure sintering is carried out under presintering, the formation of sintering necks among tungsten powder is further promoted, the formation of tungsten skeleton in the tungsten alloy is promoted, then the compact is depressurized to 5-15MPa, then the compact is raised to 1200-1300 ℃ for solid phase sintering, and the compact sintering is realized, on the one hand, the strength of the tungsten alloy bonding phase is reduced due to the temperature rise, the proper pressure reduction can be facilitated, on the other hand, the strength of the tungsten alloy bonding phase is reduced, a certain pressure is maintained, the compact is realized through applying the pressure of 5-15MPa, the compact is well deformed to fill gaps in the tungsten skeleton, the compact is realized through the sintering, the compact is fully heated to the compact, the compact phase is finally, the compact is realized through the compact sintering, and the compact density of the compact is realized through the compact sintering, and the compact phase is realized through the compact phase.
The preparation method of the invention promotes the formation of sintering necks by pre-sintering under pressure, only the metallurgical bonding among tungsten particles occurs in the pre-sintering process, so that the solid-phase sintering temperature is reduced, the solid-phase sintering can be carried out at a lower temperature of 1200-1300 ℃, the pressurizing during the solid-phase sintering can be realized due to the larger interval between the solid-phase sintering temperature and the liquid-phase sintering temperature, the pressurizing during the liquid-phase sintering is not realized, if the pre-sintering is not carried out under the pressurizing, the solid-phase sintering densification is carried out at a higher temperature, and at this time, the liquid phase appears in advance in the pressed compact due to the fluctuation of a thermal field and the segregation of local components of a binding phase because the temperature is close to the melting point of gamma- (Ni, fe) phase. The liquid phase which occurs in advance is rapidly extruded under pressure, which can lead to collapse, deformation of the compact. At the same time, the extruded liquid phase also reacts with the pressurized die (typically graphite), light weight leading to difficult die removal and heavy weight leading to damage to the die and even the equipment.
In the whole preparation process of the invention, the temperature and pressure need to be effectively controlled, such as the temperature is lower during presintering, the bonding phase does not form stable gamma- (Ni, fe) phase through diffusion, and a large amount of nickel and iron powder still exist in a particle form. At the moment, the particles can move due to the excessively high pressure, and the macroscopic green compact edge can crack and remove powder; while too little pressure is insufficient to achieve initial contact between the tungsten particles; the formation of the sintering neck cannot be effectively promoted; the high solid phase sintering temperature can lead to the mutual combination of a large number of tungsten particles, so that large tungsten particles still exist among the large tungsten particles, and the subsequent liquid phase is difficult to fill the pores due to the blocking effect of the closed tungsten particles, so that the structure is unfavorable for the subsequent densification sintering, and the high solid phase sintering temperature is unfavorable for the pressurization during the solid phase sintering, and the liquid phase is not pressurized.
In a preferred scheme, the tungsten alloy pressed compact is obtained by mixing tungsten powder and ferronickel-based powder and then pressing and forming.
Further preferably, in the tungsten alloy compact, the mass fraction of tungsten powder is 85-95%.
Further preferably, the nickel-iron-based powder comprises nickel and iron, wherein the total mass ratio of the nickel to the iron is more than or equal to 85%, and meanwhile, the nickel is as follows: iron=6-8: 2-4.
The sintering method is suitable for both W-Ni-Fe alloy and W-Ni-Fe-Co base alloy, but the total mass ratio of nickel and iron needs to be controlled to be more than or equal to 85 percent.
Further preferably, the press forming mode is die pressing or cold isostatic pressing.
In a preferred scheme, the compactness of the tungsten alloy pressed compact is more than or equal to 55%, preferably more than or equal to 60%.
In a preferred scheme, firstly, a tungsten alloy pressed compact is placed in a vacuum hot-pressing sintering furnace, and is vacuumized, so that the vacuum degree is less than 5 multiplied by 10 - 3 At Pa, starting to raise the temperature to the presintering temperature at a heating rate of 5-15 ℃/min, and controlling the vacuum degree to be less than 1 multiplied by 10 during the heating period -2 Pa。
Preferably, when the presintering temperature is reached, the pressure is increased to 15-20MPa within 5-10 min.
The inventor finds that the pressure is slowly increased within 5-10min, so that the pressed compact is not cracked, and meanwhile, the sufficient deformation and filling among the powders are facilitated, and finally, the density of the tungsten alloy is improved.
Preferably, the presintering time is 1-1.5h.
In a preferred embodiment, after the burn-in is completed, the pressure is reduced to 5-15MPa, preferably 5-10MPa, within 5-10 min.
In the invention, solid-phase sintering is carried out under the pressure of 5-15MPa, during solid-phase sintering, ferronickel in a bonding phase forms a stable gamma- (Ni, fe) phase through rapid solid-phase diffusion at a high temperature stage, the gamma- (Ni, fe) phase can be uniformly wrapped on a tungsten skeleton by applying proper pressure, gaps in the tungsten skeleton are well filled through deformation of the gamma- (Ni, fe) phase, the density of a pressed compact is rapidly improved through solid-phase sintering and heat preservation, and the strength of a tungsten alloy bonding phase is reduced due to the high temperature stage, so that the maintenance of the tungsten skeleton can be facilitated by slowly reducing the pressure to 5-15MPa within 5-10min, and if the smaller pressure is insufficient for plastically deforming the gamma- (Ni, fe) phase; while the high temperature causes the gamma- (Ni, fe) phase to soften, at this time, too high a pressure is applied to collapse the newly formed tungsten skeleton.
The inventors found that the solid phase sintering was performed by heating to the solid phase sintering temperature at a rate of 5 to 8 ℃/min.
In the invention, the temperature rise is carried out at the speed of 5-8 ℃/min, which is helpful for stabilizing the thermal field in the furnace and reducing the thermal stress caused by uneven temperature rise.
Preferably, the solid phase sintering time is 2-3h.
When solid phase sintering is carried out at 1200-1300 ℃, the strength of a binding phase mainly comprising nickel-iron base is greatly reduced, and gaps in a tungsten skeleton can be well filled through deformation by applying pressure of 5-15MPa, and the density of a pressed compact is rapidly improved by heat preservation for 2-3 hours.
In a preferred scheme, after the solid phase sintering is completed, the pressure is reduced to 0MPa within 10-20 min.
The inventors found that reducing the pressure to 0MPa within 10-20min can avoid elastic deformation of the binder phase, allowing it to adequately fill the voids.
In a preferred scheme, the temperature is increased to the liquid phase sintering temperature at a speed of 5-8 ℃/min, and the liquid phase sintering is carried out. The inventors found that the use of a slow ramp rate of 5-8 deg.c/min also helps to heat the sample evenly.
Preferably, the liquid phase sintering time is 0.5-1.5h. In the invention, the liquid phase sintering is finally carried out at 1450-1500 ℃, the complete liquefaction of the ferronickel-based binding phase can be realized, the tungsten particles can be fully dissolved in the liquid phase for a sufficient time through the heat preservation time of 0.5-1.5h in the liquid phase sintering, meanwhile, the liquid phase also has sufficient time to further fill the tiny gaps among the tungsten particles through capillary action, and densification is realized, but the heat preservation time at the stage is not suitable to be too long, because the too long heat preservation time can lead to coarsening of the structure, which is unfavorable for the final performance of the alloy.
Further preferably, the temperature of the liquid phase sintering is 1480 ℃ and the time of the liquid phase sintering is 1h.
In a preferred scheme, after the liquid phase sintering is completed, the temperature is reduced to 850-950 ℃ at a speed of 5-10 ℃/min, and then the temperature is cooled to room temperature along with a furnace.
Because a certain linear expansion coefficient difference exists between tungsten and a binding phase in a high-temperature stage, the interface thermal stress can be relieved by reducing the temperature to 900 ℃ at the speed of 5-10 ℃/min. And when the temperature is below 900 ℃, tungsten particles are completely separated out, the alloy performance is basically stable, and the energy consumption can be reduced by switching off heating and cooling along with the furnace.
The invention also provides the tungsten alloy with high density prepared by the preparation method.
The relative density of the tungsten alloy is more than or equal to 99.5 percent.
Advantageous effects
The preparation method of the invention adopts a method of vacuum+hot pressing and solid-liquid phase multistage sintering, firstly, the temperature is raised under vacuum, the pressure is increased when the temperature reaches the presintering temperature, the presintering is carried out under the pressure of 15-20MPa, the pressure sintering is carried out under the presintering, the formation of sintering necks between tungsten powder can be promoted, the formation of tungsten frameworks in tungsten alloy is promoted, then the pressure is reduced to 5-15MPa, the temperature is raised to 1200-1300 ℃ for solid phase sintering, on the one hand, the strength of the bonding phase of the tungsten alloy is reduced due to the rise of the temperature during the solid phase sintering, the proper pressure is reduced, the maintenance of the tungsten frameworks can be facilitated, on the other hand, the strength of the bonding phase of the tungsten alloy is reduced, the certain pressure is maintained, the gaps in the tungsten frameworks can be well filled through the deformation, the solid phase sintering is carried out for heat preservation, the density of the pressed blank is rapidly improved, finally the pressure is reduced to 0MPa, the liquid phase sintering temperature is raised, the elastic deformation of the bonding phase can be avoided, the bonding phase is fully filled into the gaps, and finally the tungsten alloy with high density is obtained through the liquid phase sintering.
According to the preparation method, the tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering is realized through the presintering process, the powder pre-pressurizing process, the solid phase pressure sintering process, the liquid phase sintering process and the cooling process, and the relative density of the sintered tungsten alloy reaches more than 99%.
Drawings
FIG. 1 is a process flow diagram of the present invention.
FIG. 2 shows the microstructure morphology of the tungsten alloy prepared by the method of example 1. As shown in fig. 1, the tungsten alloy consists of white body centered cubic tungsten particles and black face centered cubic binder phase, wherein the binder phase is responsible for plastic deformation and the tungsten particles provide strength support for the alloy. No significant hole defects were seen in the alloy. Tungsten particles are spherical and are dispersed in the binding phase in a fine and uniform state, and no obvious adhesion phenomenon exists among the tungsten particles.
Detailed Description
Example 1
The tungsten alloy pressed compact used in the embodiment is obtained by mixing tungsten powder and ferronickel powder and then performing cold isostatic pressing forming, wherein the tungsten powder accounts for 90% of the tungsten alloy in the tungsten alloy pressed compact. In the ferronickel powder, the mass ratio of nickel to iron is 7: and 3, the density of the tungsten alloy compact is 62.5%.
A tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering method comprises the following steps:
step one: and (5) a presintering process.
Placing the tungsten alloy pressed compact obtained by powder mixing-pressing into a vacuum hot-pressing sintering furnace, and reducing the vacuum to 5 x 10 -3 Heating the green compact at Pa or below, while maintaining the vacuum degree at 1×10 -2 Under Pa, the temperature is raised to 900 ℃ at a speed of 10 ℃/min, and the temperature is kept for 1h.
Step two: and (3) a powder pre-pressurizing process.
When the temperature in hot press sintering reaches 900 ℃, the pressurizing operation of the pressed compact is started. The pressure of 20MPa is applied to the pressed compact, and the pressure is slowly increased to 20MPa within 10 min.
Step three: and (3) a solid-phase pressure sintering process.
The pressure was slowly reduced to 10MPa over 10min, then the temperature in the furnace was increased to 1300 ℃ at a rate of 5 ℃/min, during which time the pressure was maintained at 10MPa. Thereafter, the temperature in the furnace was maintained at 1300℃and kept for 3 hours.
Step four: and (3) a liquid phase sintering process.
The pressure was reduced to 0MPa within 20min, then the temperature within the furnace was increased to 1480℃at a rate of 5℃per min, and incubated for 1h.
Step five: and (5) cooling.
Cooling to 900 ℃ at a speed of 5 ℃/min, then closing heating, and cooling to room temperature along with the furnace.
The tungsten alloy obtained in example 1, as shown in fig. 1, consists of white body-centered cubic tungsten particles and black face-centered cubic binder phase, wherein the binder phase is responsible for plastic deformation and the tungsten particles provide strength support for the alloy. No significant hole defects were seen in the alloy. Tungsten particles are spherical and are dispersed in the binding phase in a fine and uniform state, and no obvious adhesion phenomenon exists among the tungsten particles.
Example 2
The tungsten alloy pressed compact used in the embodiment is obtained by mixing tungsten powder and ferronickel powder and then performing cold isostatic pressing forming, wherein the tungsten powder accounts for 90% of the tungsten alloy in the tungsten alloy pressed compact. In the ferronickel powder, the mass ratio of nickel to iron is 7: and 3, the density of the tungsten alloy compact is 62.3%.
A tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering method comprises the following steps:
step one: and (5) a presintering process.
Placing the tungsten alloy pressed compact obtained by powder mixing-pressing into a vacuum hot-pressing sintering furnace, and reducing the vacuum to 5 x 10 -3 Heating the green compact at Pa or below, while maintaining the vacuum degree at 1×10 -2 Pa or below. The temperature was raised to 950℃at a rate of 10℃per minute and incubated for 1.5h.
Step two: and (3) a powder pre-pressurizing process.
When the temperature in hot press sintering reached 950 ℃, the pressing operation of the green compact was started. The pressed compact was subjected to a pressure of 15MPa, which was slowly raised to 15MPa within 5 min.
Step three: and (3) a solid-phase pressure sintering process.
The pressure was slowly reduced to 5MPa over 5min, then the temperature in the furnace was increased to 1300 ℃ at a rate of 5 ℃/min, during which the pressure was maintained at 5MPa. Thereafter, the temperature in the furnace was maintained at 1300℃and kept for 3 hours.
Step four: and (3) a liquid phase sintering process.
The pressure was reduced to 0MPa within 20min, then the temperature within the furnace was increased to 1480℃at a rate of 5℃per min, and incubated for 1h.
Step five: and (5) cooling.
Cooling to 900 ℃ at a speed of 5 ℃/min, then closing heating, and cooling to room temperature along with the furnace.
Example 3
The tungsten alloy pressed compact used in the embodiment is obtained by mixing tungsten powder and ferronickel powder and then pressing and forming the mixture in a mould pressing mode, wherein the tungsten powder accounts for 90% of the tungsten alloy in the tungsten alloy pressed compact. In the ferronickel powder, the mass ratio of nickel to iron is 7: and 3, the density of the tungsten alloy compact is 61.8%.
A tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering method comprises the following steps:
step one: and (5) a presintering process.
Placing the tungsten alloy pressed compact obtained by powder mixing-pressing into a vacuum hot-pressing sintering furnace, and reducing the vacuum to 5 x 10 -3 Heating the green compact at Pa or below, while maintaining the vacuum degree at 1×10 -2 Pa or below. The temperature was raised to 950℃at a rate of 10℃per minute and incubated for 1.5h.
Step two: and (3) a powder pre-pressurizing process.
When the temperature in hot press sintering reached 950 ℃, the pressing operation of the green compact was started. The pressed compact was subjected to a pressure of 15MPa, which was slowly raised to 15MPa within 5 min.
Step three: and (3) a solid-phase pressure sintering process.
The temperature in the furnace was raised to 1200 c at a rate of 8 c/min, during which the pressure was maintained at 15MPa. Thereafter, the temperature in the furnace was maintained at 1200℃and kept at that temperature for 3 hours.
Step four: and (3) a liquid phase sintering process.
The pressure was reduced to 0MPa within 10min, then the temperature within the furnace was increased to 1500℃at a rate of 8℃per min, and incubated for 0.5h.
Step five: and (5) cooling.
Cooling to 900 ℃ at a speed of 10 ℃/min, then closing heating, and cooling to room temperature along with the furnace.
Example 4
The tungsten alloy pressed compact used in the embodiment is obtained by mixing tungsten powder and ferronickel powder and then performing cold isostatic pressing forming, wherein the tungsten powder accounts for 90% of the tungsten alloy in the tungsten alloy pressed compact. In the ferronickel powder, the mass ratio of nickel to iron is 7: and 3, the density of the tungsten alloy compact is 62.1%.
A tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering method comprises the following steps:
step one: and (5) a presintering process.
Placing the tungsten alloy pressed compact obtained by powder mixing-pressing into a vacuum hot-pressing sintering furnace, and reducing the vacuum to 5 x 10 -3 Heating the green compact at Pa or below, while maintaining the vacuum degree at 1×10 -2 Pa or below. The temperature was raised to 900℃at a rate of 10℃per minute and incubated for 1.5h.
Step two: and (3) a powder pre-pressurizing process.
When the temperature in hot press sintering reaches 900 ℃, the pressurizing operation of the pressed compact is started. The pressed compact was subjected to a pressure of 15MPa, which was slowly raised to 15MPa within 5 min.
Step three: and (3) a solid-phase pressure sintering process.
The pressure was slowly reduced to 10MPa over 5min, then the temperature in the furnace was increased to 1250 ℃ at a rate of 5 ℃/min, during which time the pressure was maintained at 10MPa. Thereafter, the temperature in the furnace was maintained at 1250℃and maintained for 2.5 hours.
Step four: and (3) a liquid phase sintering process.
The pressure was reduced to 0MPa within 15min, and then the temperature within the furnace was increased to 1500℃at a rate of 5℃per min, and incubated for 1h.
Step five: and (5) cooling.
Cooling to 900 ℃ at a speed of 5 ℃/min, then closing heating, and cooling to room temperature along with the furnace.
Example 5
The tungsten alloy pressed compact used in the embodiment is obtained by mixing tungsten powder and ferronickel powder and then pressing and forming the mixture in a mould pressing mode, wherein the tungsten powder accounts for 90% of the tungsten alloy in the tungsten alloy pressed compact. In the ferronickel powder, the mass ratio of nickel to iron is 7: and 3, the density of the tungsten alloy compact is 62.2%.
A tungsten alloy vacuum hot-pressing solid-liquid phase multistage sintering method comprises the following steps:
step one: and (5) a presintering process.
Placing the tungsten alloy pressed compact obtained by powder mixing-pressing into a vacuum hot-pressing sintering furnace, and reducing the vacuum to 5 x 10 -3 Heating the green compact at Pa or below, while maintaining the vacuum degree at 1×10 -2 Pa or below. The temperature was raised to 850℃at a rate of 5℃per minute and incubated for 1h.
Step two: and (3) a powder pre-pressurizing process.
When the temperature in hot press sintering reaches 850 ℃, the pressing operation of the pressed compact is started. The pressed compact was subjected to a pressure of 15MPa, which was slowly raised to 15MPa within 5 min.
Step three: and (3) a solid-phase pressure sintering process.
The pressure was slowly reduced to 5MPa over 5min, then the temperature in the furnace was increased to 1200 ℃ at a rate of 5 ℃/min, during which time the pressure was maintained at 5MPa. Thereafter, the temperature in the furnace was maintained at 1200℃and kept for 2 hours.
Step four: and (3) a liquid phase sintering process.
The pressure was reduced to 0MPa within 10min, then the temperature in the furnace was increased to 1450℃at a rate of 5℃per min, and the temperature was maintained for 0.5h.
Step five: and (5) cooling.
Cooling to 900 ℃ at a speed of 5 ℃/min, then closing heating, and cooling to room temperature along with the furnace.
Comparative example 1
The difference from example 1 is that at 900℃the pressurizing operation was not performed, after 1 hour of incubation at 900℃the pressure was directly increased to 10MPa and increased to 1300℃at 5℃per minute and the operation of step three was continued, the rest of the operations being the same as in example 1.
Comparative example 2
Unlike example 1, the first and second steps were not performed. After heating to 900 ℃, the pressure was directly increased to 10MPa without heat preservation and pressurization, and was increased to 1300 ℃ at 5 ℃/min and the operation of step three was continued, the rest of the operations being the same as in example 1.
Comparative example 3
Unlike example 1, no pressurizing operation was performed after 900 ℃. After incubation at 900℃for 1h, the pressure was reduced to 0MPa within 20 min. Thereafter, the temperature was raised to 1300℃at 5℃per minute and kept at that temperature for 3 hours, and the other operations were the same as in example 1.
Comparative example 4
The difference from example 1 is that no incubation operation is performed at 1300 ℃. After the temperature was raised to 1300 ℃, the pressure was reduced to 0MPa in 20min, and the temperature was continued to be raised to 1480 ℃, and the rest of the operation was the same as in example 1.
Comparative example 5
Unlike example 1, step four was not performed. After the green compacts were incubated at 1300℃for 3 hours, the pressure was directly reduced to 0MPa within 20 minutes, and then the operation of the fifth step was started, and the other operations were the same as in example 1.
Comparative example 6
The difference from comparative example 5 is that the sample was not subjected to the pressurizing operation, was raised to 1300 c at 5 c/min and was kept at the temperature for 3 hours, was cooled to 900 c at a speed of 5 c/min directly, and then was turned off to be heated, followed by cooling to room temperature in the furnace. This comparative example demonstrates that the method described in this patent can effectively reduce the solid phase sintering temperature of tungsten alloys.
The results of the sample measurements for examples 1-5 and comparative examples 1-5 are shown in Table 1:
from the measurements of the samples of examples 1 to 5 and comparative examples 1 to 6, it can be seen that the alloy obtained in example 1 is almost fully dense and the grain size is fine. The first, second and third steps have good improvement effect on the relative density of the alloy, and the relative density of the alloy can not reach more than 99% without any step. And step four, the influence on the relative density of the alloy is the greatest, and the tungsten alloy which is not subjected to liquid phase sintering is difficult to reach satisfactory density.
Claims (10)
1. A preparation method of a high-density tungsten alloy is characterized by comprising the following steps: heating the tungsten alloy pressed compact to a presintering temperature under vacuum, pressurizing when reaching the presintering temperature, presintering under 15-20MPa, reducing the pressure to 5-15MPa after presintering is finished, heating to a solid phase sintering temperature, performing solid phase sintering, reducing the pressure to 0MPa after solid phase sintering is finished, heating to a liquid phase sintering temperature, and performing liquid phase sintering to obtain the tungsten alloy; the presintering temperature is 850-950 ℃, the solid phase sintering temperature is 1200-1300 ℃, and the liquid phase sintering temperature is 1450-1500 ℃.
2. The method for preparing a high-density tungsten alloy according to claim 1, wherein:
the tungsten alloy pressed compact is obtained by mixing tungsten powder and ferronickel-based powder, pressing and forming,
in the tungsten alloy pressed compact, the mass fraction of tungsten powder is 85-95%;
the nickel-iron-based powder comprises nickel and iron, and the total mass ratio of the nickel to the iron is more than or equal to 85%; meanwhile, according to the mass ratio, the nickel: iron=6-8: 2-4.
The pressing and forming mode is die pressing or cold isostatic pressing.
3. The method for preparing a high-density tungsten alloy according to claim 1, wherein: the density of the tungsten alloy pressed compact is more than or equal to 55 percent.
4. The method for preparing a high-density tungsten alloy according to claim 1, wherein: firstly, placing the tungsten alloy pressed compact into a vacuum hot-pressing sintering furnace, vacuumizing, and when the vacuum degree is less than 5 multiplied by 10 -3 At Pa, starting to raise the temperature to the presintering temperature at a heating rate of 5-15 ℃/min, and controlling the vacuum degree during the heating period1×10 -2 Pa。
5. The method for producing a high-density tungsten alloy according to claim 1 or 4, wherein: pressurizing to 15-20MPa within 5-10min when reaching presintering temperature;
the presintering time is 1-1.5h.
6. The method for preparing a high-density tungsten alloy according to claim 1, wherein: after presintering, reducing the pressure to 5-15MPa within 5-10 min;
raising the temperature to the solid-phase sintering temperature at a speed of 5-8 ℃/min, and carrying out solid-phase sintering; the solid phase sintering time is 2-3h.
7. The method for preparing a high-density tungsten alloy according to claim 1, wherein:
after the solid phase sintering is completed, the pressure is reduced to 0MPa within 10-20 min.
8. The method for producing a high-density tungsten alloy according to claim 1 or 7, wherein: heating to the liquid phase sintering temperature at a speed of 5-8 ℃/min, and performing liquid phase sintering; the liquid phase sintering time is 0.5-1.5h.
9. The method for preparing a high-density tungsten alloy according to claim 1, wherein: after the liquid phase sintering is finished, the temperature is firstly reduced to 850-950 ℃ at the speed of 5-10 ℃/min, and then the temperature is reduced to room temperature along with the furnace.
10. A high density tungsten alloy produced by the method of any one of claims 1 to 9.
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