EP3802898B1 - Density-optimized molybdenum alloy - Google Patents

Density-optimized molybdenum alloy Download PDF

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EP3802898B1
EP3802898B1 EP19739199.8A EP19739199A EP3802898B1 EP 3802898 B1 EP3802898 B1 EP 3802898B1 EP 19739199 A EP19739199 A EP 19739199A EP 3802898 B1 EP3802898 B1 EP 3802898B1
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molybdenum alloy
molybdenum
alloy
alloy according
vanadium
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French (fr)
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EP3802898C0 (en
EP3802898A1 (en
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Manja Krüger
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Otto Von Guericke Universitaet Magdeburg
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Otto Von Guericke Universitaet Magdeburg
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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
    • 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
    • C22C27/02—Alloys based on vanadium, niobium, or tantalum
    • C22C27/025—Alloys based on vanadium, niobium, or tantalum alloys based on vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
    • F01D25/005—Selecting particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/10—Metals, alloys or intermetallic compounds
    • F05D2300/12—Light metals
    • F05D2300/123—Boron
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/10—Metals, alloys or intermetallic compounds
    • F05D2300/13—Refractory metals, i.e. Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
    • F05D2300/131—Molybdenum

Definitions

  • the present invention relates to a density-optimized and high-temperature-resistant alloy based on molybdenum-silicon-boron (Mo-Si-B), a process for its production and its use as a structural material.
  • Mo-Si-B molybdenum-silicon-boron
  • the ternary Mo-Si-B alloy system not only has a very high melting temperature (beyond 2000 °C), which enables application at temperatures well above 1000 °C, but is also characterized by good oxidation resistance, excellent creep resistance and a sufficient ductile-brittle transition temperature and fracture toughness.
  • the ternary Mo-Si-B alloy system is particularly suitable as a structural material for the production of components that are operated at very high temperatures, such as turbine blades and disks in gas turbines, for highly stressed components in aerospace engineering, but also for tools in forming technology.
  • the very good oxidation resistance of this alloy system is particularly advantageous for high-temperature applications, provided the silicide content is greater than 50%.
  • Protective measures to prevent oxidation such as the use of protective gas or the application of protective layers, can therefore be omitted for materials produced using powder metallurgy or other manufactured, very fine-grained materials with a core size of less than 10 ⁇ m and homogeneous phase distribution.
  • EN 25 34 379 A1 refers to a Mo-Si-B alloy, which may also contain vanadium, among other things. However, this is an amorphous alloy that is characterized by high thermal stability, i.e. it is stable even at high temperatures and does not begin to crystallize.
  • Mo-Si-B alloy which has Mo silicide and Mo-B silicide as its main components.
  • a Mo solid solution can also be present, which can contain other elements that form a solid solution with Mo, including vanadium.
  • the other element(s) are only present in the solid solution, not in the silicides.
  • US$5,693,156 relates to molybdenum alloys with the addition of silicon and boron to improve oxidation resistance, particularly at high temperatures.
  • a consideration of weight, in particular weight reduction, is neither made nor suggested.
  • this ternary Mo-Si-B alloy system would be a promising candidate as a structural material at high temperatures also for rotating or flying applications such as turbine material.
  • the alloy Mo-9Si-8B has a density of 9.5 g/cm 3 .
  • the object of the present invention to provide an alloy system based on Mo-Si-B which has a lower density than the known Mo-Si-B alloy system and can thus be used advantageously as a structural material for rotating or flying applications, in particular in aerospace technology, for example as a turbine material. Furthermore, the alloy system should retain the advantages of the ternary alloy system Mo-Si-B, in particular with regard to oxidation resistance.
  • the molybdenum alloy according to claim 1 contains an alloy system with 5 to 25 at% silicon (Si), 0.5 to 25 at% boron (B), 3 to 40 at% vanadium (V) and the remainder molybdenum with a molybdenum content of at least 40 at%, wherein the molybdenum alloy has a molybdenum-vanadium solid solution matrix and at least one silicide phase distributed therein, and the density of the molybdenum alloy is less than 8 g/cm 3 .
  • the molybdenum alloy has a vanadium content of 10 to 50 A% and at least one silicide phase selected from (Mo, V) 3 Si, (Mo, V) 5 SiB 2 and (Mo, V) 5 Si 3 .
  • Preferred content ranges are for Si 8-15 at%, B 7-20 at% and V 10-40 at%.
  • the alloy system according to the invention has a silicide phase content of at least 30% and in particular at least 50%.
  • vanadium is one of the so-called extended refractory metals, but has a significantly lower density of 6.11 g/cm 3 at 293.15 K than molybdenum with 10.28 g/cm 3 .
  • Another advantage of vanadium is that it has a similar atomic radius (134 pm) to molybdenum (145 pm) and the same crystal structure, namely body-centered cubic. This results in good miscibility and interchangeability of these two elements in the crystal lattice and thus good alloyability of the two elements.
  • vanadium has a high ductility, so its addition does not impair the toughness of the ternary Mo-Si-B alloy.
  • the vanadium-added alloys according to the invention have a density of less than 8 g/cm 3 at 293.15 K.
  • the ternary Mo-Si-B system has a Mo solid solution matrix that inherently has good toughness. Boron is deposited on interstitial sites and silicon on regular lattice sites in the Mo phase.
  • silicide phases can form during pre-alloying, for example during very long and high-energy alloying processes or during powder atomization. Silicide phases form at the latest during compaction of the powder and/or heat treatment. These phases, in particular Mo 3 Si (A15) and Mo 5 SiB 2 (T2), give the system a high level of strength, but reduce toughness due to their brittleness. With increasing concentration of silicon and boron, the proportion of silicide phases increases, which can form the matrix phase in the structure if a critical proportion is exceeded (approx. 50% when produced via the mechanical alloying process). It is expected that this will not only reduce toughness but also lead to a Shift of the brittle-ductile transition temperature towards higher temperatures. To avoid these disadvantages, it is therefore desirable to produce alloys with Mo solid solution phase as matrix phase.
  • V does not lead to a deterioration of the toughness of Mo-Si-B alloys, but to the stabilization of the Mo solid solution phase and, with a slightly increased solid solution content, to the improvement of the toughness of the overall system.
  • the addition of vanadium to the ternary Mo-Si-B alloy system not only leads to a reduction in density, but also to an improvement in strength while maintaining the same toughness.
  • the alloy system according to the invention has a structure in which the silicide phases are distributed in a Mo solid solution matrix, even with silicide phase proportions of more than 50%.
  • titanium (Ti) can be added to the Mo-Si-B-V base alloy in an amount of 0.5-30 at%.
  • the base alloy according to the invention can contain one or more additional alloying elements selected from the group consisting of Al, Fe, Zr, Mg, Li, Cr, Mn, Co, Ni, Cu, Zn, Ge, Ga, Y, Nb, Cd, Ca and La, each in a content of 0.01 at% to 15 at%, preferably up to 10 at% and/or one or more alloying elements selected from the group consisting of Hf, Pb, Bi, Ru, Rh, Pd, Ag, Au, Ta, W, Re, Os, Ir and Pt, each in a content of 0.01 at% to preferably at most 5 at%.
  • additional alloying elements selected from the group consisting of Al, Fe, Zr, Mg, Li, Cr, Mn, Co, Ni, Cu, Zn, Ge, Ga, Y, Nb, Cd, Ca and La, each in a content of 0.01 at% to 15 at%, preferably up to 10 at% and/or one or more alloying elements selected from the group consisting of Hf,
  • the latter group consists of heavy elements with a density of more than 9 g/cm 3 , which should be added in as small an amount as possible to avoid an increase in density.
  • the alloys according to the invention can still contain interstitially soluble elements such as oxygen, nitrogen and hydrogen. These are unavoidable impurities that cannot always be completely removed from the process. However, they are only present in the ppm range.
  • the alloys according to the invention are non-eutectic but also near-eutectic and eutectic alloys.
  • Non-eutectic alloys are alloys that do not correspond to the eutectic stoichiometry.
  • Near-eutectic alloys are alloys that are close to the eutectic in terms of their composition.
  • the non-eutectic alloys according to the invention are advantageously produced using powder metallurgical processes.
  • Powder mixtures consisting of the corresponding alloy components are treated by mechanical alloying, whereby both elemental powders and pre-alloyed powders can be used.
  • Various high-energy mills can be used for mechanical alloying, such as attritors, drop mills, vibrating mills, planetary ball mills.
  • the metal powder is intensively mechanically treated and homogenized down to the atomic level.
  • pre-alloying can also be carried out by means of an atomization process under protective gas.
  • the mechanically alloyed powder can then be compacted using FAST (Field Assisted Sintering Technology).
  • FAST Field Assisted Sintering Technology
  • a suitable FAST process is carried out, for example, under vacuum at a pressure of 50 MPa and a holding time of 15 minutes at 1600 °C, with heating and cooling at 100 K/min.
  • the powders can also be compacted by cold isostatic pressing, sintering for example at 1600 °C, and hot isostatic pressing (HIP) at 1500 °C and 200 MPa.
  • FAST Field Assisted Sintering Technology
  • the FAST process is preferred because the process times for sintering are considerably shorter than for hot pressing.
  • FAST also makes it possible to achieve greater strength and hardness, expressed here as microhardness, because grain growth is prevented during the process due to the significantly shorter process times. Fine grains in the structure result in better strength than coarser grains.
  • the density-optimized alloy according to the invention can be produced using an additive manufacturing process such as selective laser melting (SLM) or laser metal deposition (LMD).
  • SLM selective laser melting
  • LMD laser metal deposition
  • the processing is carried out here on the basis of mechanically alloyed or atomized and thus pre-alloyed powders, which have a lower melting point than pure ternary Mo-Si-B alloys due to the addition of V (and possibly Ti or other alloying elements) and are therefore easier to process using such processes.
  • One advantage of the additive manufacturing process is that components close to the final structure can be obtained in a cost-, time- and material-efficient manner.
  • Near-eutectic and eutectic alloys can be processed particularly well using additive processes, as particularly fine-grained structures with good mechanical strength can be produced.
  • Such alloys have a composition range of Mo-(7..19)Si-(6... 10)B-(5... 15)V or Mo-(7..19)Si-(6... 10)B-(5... 15)V-(5... 18)Ti.
  • these alloys are also suitable for other melting metallurgical processes, including directional solidification in the well-known Bridgman process.
  • the resulting powder mixtures were ground in a planetary ball mill from Retsch GmbH (model PM 4000) with the following parameters: number of revolutions 200 rpm temperature 20 °C (293.15 K) K/P ratio 14:1 (100 balls) Grinding time 30 hours
  • the alloys obtained according to 1. were heat treated.
  • the samples were each filled into ceramic dishes and annealed under argon inert gas for the entire duration of the heat treatment.
  • the samples obtained were given the following designation: MK3-WB, MK4-WB, MK5-WB and MK6-WB
  • the MK6-WB sample was compacted using FAST.
  • the sample was compacted under vacuum at a pressure of 50 MPa and held for 10 minutes at 1100 °C and 15 minutes at 1600 °C, heating and cooling at 100 K/min.
  • the sample obtained was named MK6 FAST.
  • the microstructure and morphology of the powder particles were analyzed using a Philips ESEM (SEM) XL30 scanning electron microscope.
  • the phase contrasts were displayed using BSE contrast.
  • the phases contained were assigned using EDX analysis.
  • sample preparation small amounts of the sample powder were cold embedded in epoxy resin as follows, then wet ground with SiC sandpaper with grain sizes of 800 and 1200 and polished with diamond suspension.
  • the samples were sputtered with a thin layer of gold before embedding.
  • the structure of the alloy MK6 FAST is in binarized form in Figure 2
  • the Mo solid solution phase is white and both silicide phases are black.
  • the density of MK6 FAST was determined using Archimedes' principle to be 7.8 g/cm 3 .
  • the EDX analysis confirmed the results of the XRD measurement.
  • the silicide phases (Mo,V) 3 Si and (Mo,V) 5 SiB 2 were formed in the structure of all samples. A higher proportion of vanadium was found in the silicide phases than in the solid solution matrix.
  • MK6 FAST The evaluation of MK6 FAST showed that it has the highest proportion of silicide phases in the microstructure compared to the heat-treated samples.
  • microhardness of the mechanically alloyed (ML) samples MK3, MK4, MK5, MK6 and MK6-Fast was measured.
  • the samples were prepared as for SEM analysis (see B. 2.), but without gold sputtering.
  • the microhardness of the silicides in the FAST sample is significantly higher than that of the solid solution phase.
  • the very fine and homogeneous distribution of the silicide phases and their proportion of approx. 55% ensure a high overall hardness of the alloy.
  • the overall hardness of the FAST sample is made up of the respective microhardnesses of the individual phases Mo,V solid solution phase and the two silicide phases.

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Description

Die vorliegende Erfindung betrifft eine dichteoptimierte und hochtemperaturbeständige Legierung auf Basis von Molybdän-Silizium-Bor (Mo-Si-B), Verfahren zu deren Herstellung und Verwendung als Strukturwerkstoff.The present invention relates to a density-optimized and high-temperature-resistant alloy based on molybdenum-silicon-boron (Mo-Si-B), a process for its production and its use as a structural material.

Das ternäre Mo-Si-B-Legierungssystem weist nicht nur eine sehr hohe Schmelztemperatur auf (jenseits von 2000°C), welche eine Anwendung bei Temperaturen deutlich oberhalb von 1000 °C ermöglicht, sondern zeichnet sich darüber hinaus durch eine gute Oxidationsbeständigkeit, hervorragende Kriechbeständigkeit und eine hinreichende Duktil-Spröd-Übergangstemperatur und Bruchzähigkeit aus.The ternary Mo-Si-B alloy system not only has a very high melting temperature (beyond 2000 °C), which enables application at temperatures well above 1000 °C, but is also characterized by good oxidation resistance, excellent creep resistance and a sufficient ductile-brittle transition temperature and fracture toughness.

Aufgrund dieser Eigenschaften eignet sich das ternäre Mo-Si-B-Legierungssystem insbesondere als Strukturwerkstoff für die Herstellung von Bauteilen, die bei sehr hohen Temperaturen betrieben werden, wie zum Beispiel Turbinenschaufeln und -scheiben in Gasturbinen, für hochbelastete Bauteile in der Luft- und Raumfahrttechnik, aber auch für Werkzeuge in der Umformtechnik.Due to these properties, the ternary Mo-Si-B alloy system is particularly suitable as a structural material for the production of components that are operated at very high temperatures, such as turbine blades and disks in gas turbines, for highly stressed components in aerospace engineering, but also for tools in forming technology.

Von besonderem Vorteil für die Hochtemperaturanwendung ist die sehr gute Oxidationsbeständigkeit dieses Legierungssystems, sofern der Silizidanteil größer als 50 % ist. Schutzmaßnahmen zur Verhinderung von Oxidation, wie zum Beispiel der Einsatz von Schutzgas oder Aufbringen von Schutzschichten, können damit bei pulvermetallurgisch erzeugten Werkstoffen oder anders hergestellten, sehr feinkörnigen Werkstoffen mit einer Kerngröße von weniger als 10 µm und homogener Phasenverteilung entfallen.The very good oxidation resistance of this alloy system is particularly advantageous for high-temperature applications, provided the silicide content is greater than 50%. Protective measures to prevent oxidation, such as the use of protective gas or the application of protective layers, can therefore be omitted for materials produced using powder metallurgy or other manufactured, very fine-grained materials with a core size of less than 10 µm and homogeneous phase distribution.

Reines Molybdän als Refraktärmetall ist mit einem Schmelzpunkt von 2623 °C prinzipiell für Hochtemperaturanwendungen geeignet. Ein Problem ist jedoch dessen geringe Oxidationsbeständigkeit bereits bei Temperaturen oberhalb von 600 °C.Pure molybdenum as a refractory metal with a melting point of 2623 °C is in principle suitable for high-temperature applications. One problem, however, is its low oxidation resistance even at temperatures above 600 °C.

Durch das Zulegieren von Silizium und Bor zu Molybdän und die damit verbundene Bildung von Siliziden wurde eine signifikante Steigerung der Oxidationsbeständigkeit erzielt. Eine derartige ternäre oxidationsbeständige Mo-Si-B-Legierung ist zum Beispiel in EP 0 804 627 B1 beschrieben. Dieses ternäre Legierungssystem bildet bei Temperaturen über 540 °C eine Bor-Silikat-Schicht aus, die ein weiteres Eindringen von Sauerstoff in den Festkörper beziehungsweise das Bauteil verhindert.By alloying silicon and boron to molybdenum and the associated formation of silicides, a significant increase in oxidation resistance was achieved. Such a ternary oxidation-resistant Mo-Si-B alloy is used, for example, in EP 0 804 627 B1 This ternary alloy system forms a boron-silicate layer at temperatures above 540 °C which prevents further penetration of oxygen into the solid body or component.

DE 25 34 379 A1 betrifft eine Mo-Si-B-Legierung, die unter anderem auch Vanadium enthalten kann. Hierbei handelt es sich jedoch um eine amorphe Legierung, die sich durch eine hohe thermische Stabilität auszeichnet, das heißt, die auch bei hohen Temperaturen stabil ist und nicht zu kristallisieren beginnt. EN 25 34 379 A1 refers to a Mo-Si-B alloy, which may also contain vanadium, among other things. However, this is an amorphous alloy that is characterized by high thermal stability, i.e. it is stable even at high temperatures and does not begin to crystallize.

DE 11 55 609 A beschreibt gleichfalls Mo-Legierungen, die als zwingenden Bestandteil mindestens ein Metallborid ausgewählt unter Chromborid, Titanborid und Zirkonborid enthalten, und die Si, B sowie V aufweisen können. Keines der zahlreichen explizit aufgeführten Beispiele enthält zusätzlich zu Mo auch V. Es wird hier ausschließlich auf die Erhöhung der Oxidationsbeständigkeit und der Festigkeit abgezielt, nicht jedoch auf eine Verbesserung der Zähigkeit, wie sie erfindungsgemäß gewünscht ist. DE 11 55 609 A also describes Mo alloys which contain as a mandatory component at least one metal boride selected from chromium boride, titanium boride and zirconium boride, and which may contain Si, B and V. None of the numerous examples explicitly listed contain V in addition to Mo. The aim here is exclusively to increase oxidation resistance and strength, but not to improve toughness, as is desired according to the invention.

In WO 2005/028692 A2 ist eine Mo-Si-B-Legierung beschrieben, die als wesentliche Bestandteile Mo-Silizid und Mo-B-Silizid aufweist. Wahlweise kann auch ein Mo-Mischkristall vorhanden sein, der weitere Elemente enthalten kann, die mit Mo einen Mischkristall bilden, wobei unter anderem Vanadium genannt ist. Allerdings liegt hier das oder die weiteren Elemente ausschließlich im Mischkristall vor, nicht jedoch in den Siliziden.In WO 2005/028692 A2 A Mo-Si-B alloy is described which has Mo silicide and Mo-B silicide as its main components. Alternatively, a Mo solid solution can also be present, which can contain other elements that form a solid solution with Mo, including vanadium. However, the other element(s) are only present in the solid solution, not in the silicides.

Nach US 2016/0060734 A1 kann die Dichte einer ternären Mo-Si-B-Legierung durch teilweisen Austausch des Schwermetalls Mo durch das deutlich leichtere Metall Ti reduziert werden. Es wird jedoch darauf hingewiesen, dass der teilweise Ersatz von Mo durch Ti die Oxidationsbeständigkeit beeinträchtigt. Zur Kompensation müssen weitere Elemente, wie Eisen und/oder Yttrium, zugesetzt werden.After US 2016/0060734 A1 The density of a ternary Mo-Si-B alloy can be reduced by partially replacing the heavy metal Mo with the much lighter metal Ti. However, it should be noted that the partial replacement of Mo with Ti impairs the oxidation resistance. To compensate, other elements such as iron and/or yttrium must be added.

US 5,693,156 betrifft Molybdän-Legierungen mit einem Zusatz von Silizium und Bor zur Verbesserung der Oxidationsbeständigkeit insbesondere bei hohen Temperaturen. Zusätzlich wird vorgeschlagen, zur Einstellung verschiedener Legierungseigenschaften der Mo-Si-B-Basislegierung ein oder mehrere weitere Elemente zuzulegieren. Unter anderem wird angemerkt, dass durch Zusatz von Titan, Hafnium, Zirkon, Chrom, Wolfram, Vanadium oder Rhenium die Zugfestigkeit der Legierung verbessert werden kann. Eine Betrachtung des Gewichts, insbesondere der Gewichtsreduzierung, findet weder statt noch wird nahegelegt. US$5,693,156 relates to molybdenum alloys with the addition of silicon and boron to improve oxidation resistance, particularly at high temperatures. In addition, it is proposed to add one or more other elements to the Mo-Si-B base alloy to adjust various alloy properties. Among other things, it is noted that by adding Titanium, hafnium, zirconium, chromium, tungsten, vanadium or rhenium can improve the tensile strength of the alloy. A consideration of weight, in particular weight reduction, is neither made nor suggested.

Im Hinblick auf das vorstehend aufgezeigte hervorragende Eigenschaftsprofil wäre dieses ternäre Mo-Si-B-Legierungssystem ein vielversprechender Kandidat als Strukturwerkstoff bei hohen Temperaturen auch für rotierende oder fliegende Anwendungen wie zum Beispiel als Turbinenwerkstoff.In view of the excellent property profile outlined above, this ternary Mo-Si-B alloy system would be a promising candidate as a structural material at high temperatures also for rotating or flying applications such as turbine material.

Ein Nachteil für derartige Anwendungen, aber auch andere Anwendungen, ist hier die hohe Dichte, die typischerweise zwischen 8,5 und 9,5 g/cm3 liegt. Beispielsweise hat die Legierung Mo-9Si-8B eine Dichte von 9,5 g/cm3.A disadvantage for such applications, but also other applications, is the high density, which is typically between 8.5 and 9.5 g/cm 3 . For example, the alloy Mo-9Si-8B has a density of 9.5 g/cm 3 .

Es war daher Aufgabe der vorliegenden Erfindung, ein Legierungssystem auf Basis von Mo-Si-B bereitzustellen, das eine geringere Dichte als das bekannte Mo-Si-B-Legierungssystem aufweist, und somit vorteilhaft als Strukturwerkstoff für rotierende oder fliegende Anwendungen, insbesondere auch in der Luft- und Raumfahrttechnik, zum Beispiel als Turbinenwerkstoff, eingesetzt werden kann. Weiter soll das Legierungssystem die Vorteile des ternären Legierungssystems Mo-Si-B insbesondere in Bezug auf die Oxidationsbeständigkeit beibehalten.It was therefore the object of the present invention to provide an alloy system based on Mo-Si-B which has a lower density than the known Mo-Si-B alloy system and can thus be used advantageously as a structural material for rotating or flying applications, in particular in aerospace technology, for example as a turbine material. Furthermore, the alloy system should retain the advantages of the ternary alloy system Mo-Si-B, in particular with regard to oxidation resistance.

Diese Aufgabe wird gelöst, durch die Molybdänlegierung gemäß Anspruch 1; diese enthält ein Legierungssystem mit 5 bis 25 At% Silizium (Si), 0,5 bis 25 At% Bor (B), 3 bis 40 At% Vanadium (V) sowie der Rest Molybdän mit einem Molybdänanteil von mindestens 40 At%, wobei die Molybdänlegierung eine Molybdän-Vanadium-Mischkristallmatrix und darin verteilt mindestens eine Silizidphase aufweist, und die Dichte der Molybdänlegierung weniger als 8 g/cm3 beträgt.This object is achieved by the molybdenum alloy according to claim 1; this contains an alloy system with 5 to 25 at% silicon (Si), 0.5 to 25 at% boron (B), 3 to 40 at% vanadium (V) and the remainder molybdenum with a molybdenum content of at least 40 at%, wherein the molybdenum alloy has a molybdenum-vanadium solid solution matrix and at least one silicide phase distributed therein, and the density of the molybdenum alloy is less than 8 g/cm 3 .

Gemäß einer bevorzugten Ausführungsform weist die Molybdänlegierung einen Vanadiumgehalt von 10 bis 50 A% sowie mindestens eine Silizidphase ausgewählt unter (Mo, V)3Si, (Mo, V)5SiB2 und (Mo, V)5Si3 auf.According to a preferred embodiment, the molybdenum alloy has a vanadium content of 10 to 50 A% and at least one silicide phase selected from (Mo, V) 3 Si, (Mo, V) 5 SiB 2 and (Mo, V) 5 Si 3 .

Bevorzugte Gehaltsbereiche sind für Si 8-15 At%, B 7-20 At% und V 10-40 At%.Preferred content ranges are for Si 8-15 at%, B 7-20 at% and V 10-40 at%.

Vorzugsweise weist das erfindungsgemäße Legierungssystem einen Silizidphasenanteil von mindestens 30 % und insbesondere mindestens 50 % auf.Preferably, the alloy system according to the invention has a silicide phase content of at least 30% and in particular at least 50%.

Vanadium zählt mit einem Schmelzpunkt von 1910 °C und damit weniger als 2000 °C, zu den sogenannten erweiterten Refraktärmetallen, hat jedoch eine deutlich niedrigere Dichte von 6,11 g/cm3 bei 293,15 K als Molybdän mit 10,28 g/cm3. Ein weiterer Vorteil von Vanadium ist, dass es einen ähnlichen Atomradius (134 pm) wie Molybdän (145 pm) und die gleiche Kristallstruktur, nämlich kubisch raumzentriert, aufweist. Dadurch ergibt sich eine gute Misch- und Austauschbarkeit dieser beiden Elemente im Kristallgitter und somit eine gute Legierbarkeit der beiden Elemente.With a melting point of 1910 °C and thus less than 2000 °C, vanadium is one of the so-called extended refractory metals, but has a significantly lower density of 6.11 g/cm 3 at 293.15 K than molybdenum with 10.28 g/cm 3 . Another advantage of vanadium is that it has a similar atomic radius (134 pm) to molybdenum (145 pm) and the same crystal structure, namely body-centered cubic. This results in good miscibility and interchangeability of these two elements in the crystal lattice and thus good alloyability of the two elements.

Zudem hat Vanadium eine hohe Duktilität, sodass dessen Zusatz die Zähigkeit der ternären Mo-Si-B-Legierung nicht verschlechtert.In addition, vanadium has a high ductility, so its addition does not impair the toughness of the ternary Mo-Si-B alloy.

Die erfindungsgemäßen Legierungen mit Vanadium-Zusatz weisen eine Dichte von weniger als 8 g/cm3 bei 293,15 K auf.The vanadium-added alloys according to the invention have a density of less than 8 g/cm 3 at 293.15 K.

Es hat sich gezeigt, dass sich das hinzulegierte Vanadium in den jeweiligen Mo-Mischkristall- und Silizidphasen löst, jedoch die strukturellen Merkmale der bekannten Phasen in Mo-Si-B-Legierungen nicht verändert.It has been shown that the added vanadium dissolves in the respective Mo solid solution and silicide phases, but does not change the structural features of the known phases in Mo-Si-B alloys.

Das ternäre Mo-Si-B-System weist eine Mo-Mischkristallmatrix auf, die an sich gute Zähigkeit besitzt. Hierbei lagern sich Bor auf Zwischengitterplätzen und Silizium auf regulären Gitterplätzen in der Mo-Phase ein.The ternary Mo-Si-B system has a Mo solid solution matrix that inherently has good toughness. Boron is deposited on interstitial sites and silicon on regular lattice sites in the Mo phase.

Zusätzlich können sich bereits während des Vorlegierens Silizidphasen bilden, zum Beispiel bei sehr langen und hochenergetischen Legierungsprozessen oder beim Pulververdüsen. Spätestens bei der Kompaktierung der Pulver und/oder Wärmebehandlung entstehen Silizidphasen. Diese Phasen, insbesondere Mo3Si (A15) und Mo5SiB2 (T2), geben dem System zwar eine hohe Festigkeit, setzen aber die Zähigkeit aufgrund ihrer Sprödheit herab. Mit zunehmender Konzentration an Silizium und Bor steigt der Anteil der Silizidphasen, welche bei Überschreiten eines kritischen Anteils (ca. 50% bei Herstellung über den mechanischen Legierungsprozess) die Matrixphase in dem Gefüge bilden können. Es wird erwartet, dass sich dadurch neben einer Verringerung der Zähigkeit auch eine Verschiebung der Spröd-Duktil-Übergangstemperatur hin zu höheren Temperaturen ergibt. Zur Vermeidung dieser Nachteile ist es daher angestrebt, Legierungen mit Mo-Mischkristallphase als Matrixphase herzustellen.In addition, silicide phases can form during pre-alloying, for example during very long and high-energy alloying processes or during powder atomization. Silicide phases form at the latest during compaction of the powder and/or heat treatment. These phases, in particular Mo 3 Si (A15) and Mo 5 SiB 2 (T2), give the system a high level of strength, but reduce toughness due to their brittleness. With increasing concentration of silicon and boron, the proportion of silicide phases increases, which can form the matrix phase in the structure if a critical proportion is exceeded (approx. 50% when produced via the mechanical alloying process). It is expected that this will not only reduce toughness but also lead to a Shift of the brittle-ductile transition temperature towards higher temperatures. To avoid these disadvantages, it is therefore desirable to produce alloys with Mo solid solution phase as matrix phase.

Die Zugabe von V führt nicht zur Verschlechterung der Zähigkeit von Mo-Si-B-Legierungen, sondern zur Stabilisierung der Mo-Mischkristallphase und mit einem leicht erhöhten Mischkristallanteil zur Verbesserung der Zähigkeit des Gesamtsystems.The addition of V does not lead to a deterioration of the toughness of Mo-Si-B alloys, but to the stabilization of the Mo solid solution phase and, with a slightly increased solid solution content, to the improvement of the toughness of the overall system.

Weiterhin führt die Substitution von V-Atomen im Mo-Mischkristallgitter zu einer weiteren Verbesserung der Festigkeit.Furthermore, the substitution of V atoms in the Mo solid solution lattice leads to a further improvement in strength.

Im Ergebnis ist festzuhalten, dass der Zusatz von Vanadium zu dem ternären Mo-Si-B-Legierungssystem nicht nur zu einer Verringerung der Dichte, sondern zugleich zu einer Verbesserung der Festigkeit bei gleichbleibender Zähigkeit führt. Zudem hat das erfindungsgemäße Legierungssystem infolge des Zusatzes von V auch bei Silizidphasenanteilen von mehr als 50 % ein Gefüge bei dem die Silizidphasen in einer Mo-Mischkristallmatrix verteilt vorliegen.As a result, it can be stated that the addition of vanadium to the ternary Mo-Si-B alloy system not only leads to a reduction in density, but also to an improvement in strength while maintaining the same toughness. In addition, as a result of the addition of V, the alloy system according to the invention has a structure in which the silicide phases are distributed in a Mo solid solution matrix, even with silicide phase proportions of more than 50%.

Gemäß einer bevorzugten Ausführungsform kann der Mo-Si-B-V-Basislegierung Titan (Ti) in einer Menge von 0,5-30 At% zugesetzt werden.According to a preferred embodiment, titanium (Ti) can be added to the Mo-Si-B-V base alloy in an amount of 0.5-30 at%.

Es wurde festgestellt, dass ein Zusatz von 0,5 bis 10 At% zu einer Stabilisierung der Mischkristall-(Mo,V)3Si-(Mo,V)5SiB2-Struktur führt und ein Zusatz von 10 bis 30 At% die Herstellung einer 4-Phasenlegierung Mischkristall-(Mo,V)3Si-(Mo,V)5SiB2-(Mo,V)5Si3 begünstigt. Bei (Mo,V)5Si3 handelt es sich um die T1-Phase.It was found that an addition of 0.5 to 10 at% leads to a stabilization of the solid solution (Mo,V) 3 Si-(Mo,V) 5 SiB 2 structure and an addition of 10 to 30 at% favors the production of a 4-phase alloy solid solution (Mo,V) 3 Si-(Mo,V) 5 SiB 2 -(Mo,V) 5 Si 3 . (Mo,V) 5 Si 3 is the T1 phase.

Zudem trägt der Zusatz von Ti, das eine Dichte von lediglich 4,51 g/cm3 hat, zu einer weiteren Verringerung der Dichte bei.In addition, the addition of Ti, which has a density of only 4.51 g/cm 3 , contributes to a further reduction in density.

Je nach Bedarf kann die erfindungsgemäße Basislegierung ein oder mehrere zusätzliche Legierungselemente ausgewählt aus der Gruppe aus AI, Fe, Zr, Mg, Li, Cr, Mn, Co, Ni, Cu, Zn, Ge, Ga, Y, Nb, Cd, Ca und La, jeweils in einem Gehalt von 0,01 At% bis 15 At%, vorzugsweise bis 10 At% und/oder ein oder mehrere Legierungselemente ausgewählt aus der Gruppe aus Hf, Pb, Bi, Ru, Rh, Pd, Ag, Au, Ta, W, Re, Os, Ir und Pt jeweils in einem Gehalt von 0,01 At% bis vorzugsweise höchstens 5 At% enthalten.Depending on requirements, the base alloy according to the invention can contain one or more additional alloying elements selected from the group consisting of Al, Fe, Zr, Mg, Li, Cr, Mn, Co, Ni, Cu, Zn, Ge, Ga, Y, Nb, Cd, Ca and La, each in a content of 0.01 at% to 15 at%, preferably up to 10 at% and/or one or more alloying elements selected from the group consisting of Hf, Pb, Bi, Ru, Rh, Pd, Ag, Au, Ta, W, Re, Os, Ir and Pt, each in a content of 0.01 at% to preferably at most 5 at%.

Bei der letzteren Gruppe handelt es sich um schwere Elemente mit einer Dichte von mehr als 9 g/cm3, die zur Vermeidung einer Erhöhung der Dichte in möglichst geringer Menge zugesetzt werden sollten.The latter group consists of heavy elements with a density of more than 9 g/cm 3 , which should be added in as small an amount as possible to avoid an increase in density.

Fertigungstechnisch bedingt können die erfindungsgemäßen Legierungen noch interstitiell lösliche Elemente wie Sauerstoff, Stickstoff, Wasserstoff enthalten. Es handelt sich hierbei um unvermeidbare Verunreinigungen, die sich aus dem Prozess nicht immer vollständig fernhalten lassen. Diese liegen jedoch nur im ppm-Bereich vor.For manufacturing reasons, the alloys according to the invention can still contain interstitially soluble elements such as oxygen, nitrogen and hydrogen. These are unavoidable impurities that cannot always be completely removed from the process. However, they are only present in the ppm range.

Bei den erfindungsgemäßen Legierungen handelt es sich um nicht-eutektische aber auch um nah-eutektische und eutektische Legierungen. Nicht-eutektische Legierungen sind Legierungen, die nicht der eutektischen Stöchiometrie entsprechen. Dahingegen handelt es sich bei nah-eutektischen Legierungen um Legierungen, die sich von ihrer Zusammensetzung her in der Nähe des Eutektikums befinden.The alloys according to the invention are non-eutectic but also near-eutectic and eutectic alloys. Non-eutectic alloys are alloys that do not correspond to the eutectic stoichiometry. Near-eutectic alloys, on the other hand, are alloys that are close to the eutectic in terms of their composition.

Die Herstellung der erfindungsgemäßen nicht-eutektischen Legierungen erfolgt vorteilhafterweise mittels pulvermetallurgischer Verfahrenstechniken. Dabei werden Pulvermischungen, die aus den entsprechenden Legierungskomponenten bestehen, durch mechanisches Legieren behandelt, wobei sowohl elementare Pulver als auch vorlegierte Pulver zum Einsatz kommen können. Für das mechanische Legieren können verschiedene Hochenergiemühlen eingesetzt werden, wie zum Beispiel Attritoren, Fallmühlen, Schwingmühlen, Planetenkugelmühlen. Dabei wird das Metallpulver intensiv mechanisch behandelt und bis zum atomaren Niveau homogenisiert.The non-eutectic alloys according to the invention are advantageously produced using powder metallurgical processes. Powder mixtures consisting of the corresponding alloy components are treated by mechanical alloying, whereby both elemental powders and pre-alloyed powders can be used. Various high-energy mills can be used for mechanical alloying, such as attritors, drop mills, vibrating mills, planetary ball mills. The metal powder is intensively mechanically treated and homogenized down to the atomic level.

Das Vorlegieren kann alternativ auch mittels eines Verdüsungsprozesses unter Schutzgas erfolgen.Alternatively, pre-alloying can also be carried out by means of an atomization process under protective gas.

Anschließend kann das mechanisch legierte Pulver mittels FAST (Field Assisted Sintering Technology) kompaktiert werden. Ein geeigneter FAST-Prozess erfolgt beispielsweise unter Vakuum bei einem Druck von 50 MPa und einer Haltezeit von 15 Minuten bei 1600 °C, wobei mit 100 K/min aufgeheizt und abgekühlt wird. Alternativ dazu können die Pulver auch mittels kaltisostatischem Pressen, Sintern beispielsweise bei 1600 °C, und heißisostatischem Pressen (HIP) bei 1500 °C und 200 MPa kompaktiert werden.The mechanically alloyed powder can then be compacted using FAST (Field Assisted Sintering Technology). A suitable FAST process is carried out, for example, under vacuum at a pressure of 50 MPa and a holding time of 15 minutes at 1600 °C, with heating and cooling at 100 K/min. Alternatively, the powders can also be compacted by cold isostatic pressing, sintering for example at 1600 °C, and hot isostatic pressing (HIP) at 1500 °C and 200 MPa.

Bevorzugt ist jedoch der FAST-Prozess, da die Prozesszeiten beim Sintern im Vergleich zum Heißpressen erheblich verkürzt sind.However, the FAST process is preferred because the process times for sintering are considerably shorter than for hot pressing.

Zudem lassen sich auch bei größeren Bauteilen homogene Werkstoffeigenschaften erreichen. Auch lässt sich mit FAST eine höhere Festigkeit und Härte, hier ausgedrückt als Mikrohärte, erhalten, da aufgrund der deutlich kürzeren Prozesszeiten das Kornwachstum während des Prozesses unterbunden wird. Feine Körner im Gefüge resultieren im Gegensatz zu gröberen Körnern in einer besseren Festigkeit.In addition, homogeneous material properties can be achieved even in larger components. FAST also makes it possible to achieve greater strength and hardness, expressed here as microhardness, because grain growth is prevented during the process due to the significantly shorter process times. Fine grains in the structure result in better strength than coarser grains.

Alternativ zum pulvermetallurgischen Prozess kann die erfindungsgemäße Dichte optimierte Legierung mittels einem additiven Fertigungsverfahren wie beispielsweise Selective-Laser-Melting (SLM) oder Laser Metal Deposition (LMD) hergestellt werden. Die Verarbeitung erfolgt hier auf Grundlage von mechanisch legierten oder verdüsten und somit vorlegierten Pulvern, welche aufgrund des Hinzulegierens von V (und gegebenenfalls Ti beziehungsweise anderen Legierungelementen) einen gegenüber reinen tenären Mo-Si-B-Legierungen verringerten Schmelzpunkt aufweisen und somit über derartige Verfahren leichter verarbbeitbar sind.As an alternative to the powder metallurgy process, the density-optimized alloy according to the invention can be produced using an additive manufacturing process such as selective laser melting (SLM) or laser metal deposition (LMD). The processing is carried out here on the basis of mechanically alloyed or atomized and thus pre-alloyed powders, which have a lower melting point than pure ternary Mo-Si-B alloys due to the addition of V (and possibly Ti or other alloying elements) and are therefore easier to process using such processes.

Ein Vorteil des additiven Fertigungsverfahrens ist, dass sich endstrukturnahe Bauteile kosten-, zeit- und materialeffizient erhalten werden können.One advantage of the additive manufacturing process is that components close to the final structure can be obtained in a cost-, time- and material-efficient manner.

Derartige additive Fertigungsverfahren sind an sich bekannt und zum Beispiel in WO 2016/188696 A1 beschrieben.Such additive manufacturing processes are known per se and are used, for example, in WO 2016/188696 A1 described.

Besonders gut lassen sich nah-eutektische und eutektische Legierungen mit Hilfe der additiven Verfahren verarbeiten, da besonders feinkörnige Gefüge mit guter mechanischer Festigkeit hergestellt werden können.Near-eutectic and eutectic alloys can be processed particularly well using additive processes, as particularly fine-grained structures with good mechanical strength can be produced.

Solche Legierungen liegen in einem Zusammensetzungsbereich von Mo-(7..19)Si-(6... 10)B-(5... 15)V bzw. Mo-(7..19)Si-(6... 10)B-(5... 15)V-(5... 18)Ti. Darüber hinaus eignen sich diese Legierungen auch für andere schmelzmetallurgische Verfahren, u.a. auch für die gerichtete Erstarrung im bekannten Bridgman-Verfahren.Such alloys have a composition range of Mo-(7..19)Si-(6... 10)B-(5... 15)V or Mo-(7..19)Si-(6... 10)B-(5... 15)V-(5... 18)Ti. In addition, these alloys are also suitable for other melting metallurgical processes, including directional solidification in the well-known Bridgman process.

Das erfindungsgemäße Legierungssystem wird nachfolgend anhand von Beispielen und Figuren näher charakterisiert, dabei zeigt

  • Figur 1 ein Röntgendiffraktrogramm der Legierungsprobe MK6-FAST (Mo-40V-9Si-8B);
  • Figur 2 die Mikrostruktur der Legierungsprobe MK6 FAST gemäß Figur 1 nach der Kompaktierung mittels FAST-Verfahren dargestellt als Binärbild; und
  • Figur 3 das Ergebnis der Mikrohärteprüfung unter Berücksichtigung der Standardabweichung der Legierungsproben gemäß der Beispiele.
The alloy system according to the invention is characterized in more detail below using examples and figures, showing
  • Figure 1 an X-ray diffraction pattern of the alloy sample MK6-FAST (Mo-40V-9Si-8B);
  • Figure 2 the microstructure of the alloy sample MK6 FAST according to Figure 1 after compaction using the FAST method, represented as a binary image; and
  • Figure 3 the result of the microhardness test taking into account the standard deviation of the alloy samples according to the examples.

A) ProbenherstellungA) Sample preparation 1. Mechanisches Legieren 1. Mechanical alloying

Es wurden vier Legierungen hergestellt mit 10, 20, 30 und 40 At% Vanadium. Die atomaren Gehalte von Silizium (9 At%) und Bor (8 At%) blieben bei allen Legierungssystemen gleich. Von jedem Legierungssystem wurden 30 g hergestellt. Dafür wurden die einzelnen Legierungsbestandteile unter Argon-Schutzgasatmosphäre eingewogen und in Schutzgasatmosphäre in Mahlbehälter abgefüllt.Four alloys were produced with 10, 20, 30 and 40 at% vanadium. The atomic contents of silicon (9 at%) and boron (8 at%) remained the same for all alloy systems. 30 g of each alloy system were produced. The individual alloy components were weighed under an argon protective gas atmosphere and filled into grinding containers in a protective gas atmosphere.

Die erhaltenen Pulvermischungen wurden in einer Planetenkugelmühle der Firma Retsch GmbH (Modell PM 4000) mit folgenden Parametern gemahlen: Drehzahl 200 U/min Temperatur 20 °C (293,15 K) K-/P-Verhältnis 14:1 (100 Kugeln) Mahldauer 30 Stunden The resulting powder mixtures were ground in a planetary ball mill from Retsch GmbH (model PM 4000) with the following parameters: number of revolutions 200 rpm temperature 20 °C (293.15 K) K/P ratio 14:1 (100 balls) Grinding time 30 hours

Die erhaltenen Legierungen erhielten folgende Bezeichnungen: Bezeichnung Legierungszusammensetzung MK3 Mo-10V-9Si-8B MK4 Mo-20V-9Si-8B MK5 Mo-30V-9Si-8B MK6 Mo-40V-9Si-8B The resulting alloys were given the following names: Designation Alloy composition MK3 Mo-10V-9Si-8B MK4 Mo-20V-9Si-8B MK5 Mo-30V-9Si-8B MK6 Mo-40V-9Si-8B

2. Wärmebehandlung 2. Heat treatment

Die gemäß 1. erhaltenen Legierungen wurden wärmebehandelt.The alloys obtained according to 1. were heat treated.

Die Proben wurden jeweils in Keramikschälchen abgefüllt und über die gesamte Dauer der Wärmebehandlung unter Argon-Schutzgas geglüht.The samples were each filled into ceramic dishes and annealed under argon inert gas for the entire duration of the heat treatment.

Dafür wurden ca. 10 g jeder der im Ausgangszustand befindlichen Legierungen abgefüllt und 5 Stunden bei 1300 °C in einem Rohrofen der HTM Retz GmbH Typ Losic wärmebehandelt.For this purpose, approximately 10 g of each of the alloys in the initial state were filled and heat-treated for 5 hours at 1300 °C in a Losic type tube furnace from HTM Retz GmbH.

Die erhaltenen Proben erhielten folgende Bezeichnung:
MK3-WB, MK4-WB, MK5-WB und MK6-WBThe samples obtained were given the following designation:
MK3-WB, MK4-WB, MK5-WB and MK6-WB

3. Herstellung einer Legierungsprobe mittels FAST 3. Preparation of an alloy sample using FAST

Die Probe MK6-WB wurde mittels FAST kompaktiert. Dafür wurde die Probe unter Vakuum bei einem Druck von 50 MPa und einer Haltezeit von 10 Minuten bei 1100 °C sowie 15 Minuten bei 1600 °C, wobei mit 100 K/min aufgeheizt und abgekühlt wurde.The MK6-WB sample was compacted using FAST. The sample was compacted under vacuum at a pressure of 50 MPa and held for 10 minutes at 1100 °C and 15 minutes at 1600 °C, heating and cooling at 100 K/min.

Die erhaltene Probe erhielt die Bezeichnung MK6 FAST.The sample obtained was named MK6 FAST.

B) StrukturuntersuchungB) Structural investigation 1. Röntgendiffraktometrie (XRD) 1. X-ray diffraction (XRD)

Die Strukturuntersuchung der zu Pulver vermahlenen Proben MK3-WB, MK4-WB, MK5-WB, MK6-WB und MK6Fast wurden mittels Röntgenbeugungsanalyse mit einem Röntgendiffraktometersystem PANalytical X'pert pro durchgeführt:

  • Strahlung: Cu-K21,21,5406
  • Spannung: 40 kV
  • Strom: 30 mA
  • Detektor X' Celerator RTMS
  • Filter: Ni-Filter
  • Messbereich: 20° ≤ 2 Θ ≤ 158,95°
  • Schrittweite: 0,0167°
  • Messzeit 330,2 s (pro Schrittweite).
The structural investigation of the powder-ground samples MK3-WB, MK4-WB, MK5-WB, MK6-WB and MK6Fast was carried out by X-ray diffraction analysis with a PANalytical X'pert pro X-ray diffractometer system:
  • Radiation: Cu-K21,21,5406
  • Voltage: 40 kV
  • Current: 30 mA
  • Detector X' Celerator RTMS
  • Filter: Ni filter
  • Measuring range: 20° ≤ 2 Θ ≤ 158.95°
  • Step size: 0.0167°
  • Measuring time 330.2 s (per step size).

In allen fünf Proben wurden die Phasen Mo-V-Mischkristall, (Mo,V)3Si und (Mo, V)5Si B2 nachgewiesen.In all five samples, the phases Mo-V solid solution, (Mo,V) 3 Si and (Mo, V) 5 Si B 2 were detected.

Das Ergebnis der Analyse für MK6-FAST ist in Figur 1 dargestellt.The result of the analysis for MK6-FAST is in Figure 1 shown.

2. Gefügenuntersuchung und Dichtebestimmung 2. Structural analysis and density determination

Die Mikrostruktur und Morphologie der Pulverpartikel wurde mit einem Rasterelektronenmikroskop ESEM (REM) XL30 der Firma Philips analysiert. Die Darstellung der Phasenkontraste erfolgte mittels BSE-Kontrast. Die enthaltenen Phasen wurden mittels EDX-Analyse zugeordnet.The microstructure and morphology of the powder particles were analyzed using a Philips ESEM (SEM) XL30 scanning electron microscope. The phase contrasts were displayed using BSE contrast. The phases contained were assigned using EDX analysis.

Für die Probenherstellung wurden kleine Mengen der Probenpulver wie folgt in Epoxidharz kalt eingebettet, anschließend mit SiC-Schleifpapier mit Körnungen von 800 und 1200 nassgeschliffen und mit Diamantsuspension poliert.For sample preparation, small amounts of the sample powder were cold embedded in epoxy resin as follows, then wet ground with SiC sandpaper with grain sizes of 800 and 1200 and polished with diamond suspension.

Für die REM-Untersuchung wurden die Proben vor dem Einbetten mit einer dünnen Goldschicht besputtert.For the SEM examination, the samples were sputtered with a thin layer of gold before embedding.

Das Gefüge der Legierung MK6 FAST ist in binarisierter Form in Figur 2 dargestellt. Dabei sind die Mo-Mischkristallphase weiß und beide Silizidphasen schwarz.The structure of the alloy MK6 FAST is in binarized form in Figure 2 The Mo solid solution phase is white and both silicide phases are black.

Die Dichte von MK6 FAST wurde mittels des archimedes`schen Prinzips mit 7,8 g/cm3 bestimmt.The density of MK6 FAST was determined using Archimedes' principle to be 7.8 g/cm 3 .

C) AuswertungC) Evaluation 1. REM/ EDX-Analyse 1. SEM/ EDX analysis

Die EDX-Analyse bestätigte die Ergebnisse der XRD-Messung. Im Gefüge aller Proben haben sich neben dem Mo-Mischkristall, die Silizidphasen (Mo,V)3Si und (Mo,V)5SiB2 gebildet. Dabei wurde in den Silizidphasen ein höherer Anteil an Vanadium gefunden als in der Mischkristallmatrix.The EDX analysis confirmed the results of the XRD measurement. In addition to the Mo solid solution, the silicide phases (Mo,V) 3 Si and (Mo,V) 5 SiB 2 were formed in the structure of all samples. A higher proportion of vanadium was found in the silicide phases than in the solid solution matrix.

Die Auswertung von MK6 FAST ergab, dass diese im Vergleich zu den wärmebehandelten Proben den höchsten Anteil an Silizidphasen im Gefüge aufweist.The evaluation of MK6 FAST showed that it has the highest proportion of silicide phases in the microstructure compared to the heat-treated samples.

In der nachstehenden Tabelle sind die Prozentanteile (At.%) der Silizidphasen in den einzelnen Proben zusammengefasst. Probe Silizidphasen (At.%) M K3-WB 46,0 MK4-WB 47,8 M K5-WB 51,1 MK6-WB 52,6 MK6-FAST 55,4 The table below summarizes the percentages (at.%) of the silicide phases in the individual samples. sample Silicide phases (at.%) M K3-WB 46.0 MK4-WB 47.8 M K5-WB 51.1 MK6-WB 52.6 MK6-FAST 55.4

2. Mikrohärteprüfung 2. Microhardness test

Gemessen wurde die Mikrohärte der mechanisch legierten (ML) Proben MK3, MK4, MK5, MK6 und MK6-Fast.The microhardness of the mechanically alloyed (ML) samples MK3, MK4, MK5, MK6 and MK6-Fast was measured.

Die Mikrohärte wurde nach der Methode nach Vickers mit einem Mikroskop der Firma Carl Zeiss Microscopy GmbH (Modell Axiophod 2) bestimmt, in das ein Härteprüfer der Firma Anton Paar GmbH (Modell MHT-10) integriert war:

  • Prüfkraft: 10p
  • Prüfzeit: 10s
  • Steigung: 15 p/s.
The microhardness was determined according to the Vickers method using a microscope from Carl Zeiss Microscopy GmbH (model Axiophod 2) in which a hardness tester from Anton Paar GmbH (model MHT-10) was integrated:
  • Test force: 10p
  • Test time: 10s
  • Gradient: 15 p/s.

Die Proben wurden wie für die REM-Analyse (s. B. 2.) vorbereitet, jedoch ohne Gold-Besputterung.The samples were prepared as for SEM analysis (see B. 2.), but without gold sputtering.

Es wurden jeweils 50 Eindrücke pro Phase gesetzt und ausgewertet.50 impressions were made and evaluated per phase.

Das Ergebnis ist in Figur 3 unter Berücksichtigung der Standardabweichung gezeigt.The result is in Figure 3 taking into account the standard deviation.

Die Mikrohärte der Silizide in der FAST-Probe ist signifikant höher als die der Mischkristallphase. Die sehr feine und homogene Verteilung der Silizidphasen sowie deren Anteil von ca. 55 % sorgt für eine hohe Gesamthärte der Legierung. Die Gesamthärte der FAST-Probe setzt sich zusammen aus den jeweiligen Mikrohärten der Einzelphasen Mo,V-Mischkristallphase und der zwei Silizidphasen.The microhardness of the silicides in the FAST sample is significantly higher than that of the solid solution phase. The very fine and homogeneous distribution of the silicide phases and their proportion of approx. 55% ensure a high overall hardness of the alloy. The overall hardness of the FAST sample is made up of the respective microhardnesses of the individual phases Mo,V solid solution phase and the two silicide phases.

Claims (10)

  1. A molybdenum alloy with 5 to 25 at % silicon, 0.5 to 25 at % boron, and 3 to 40 at % vanadium with optionally titanium (Ti) in an amount of 0,5 to 30 at %, with optionally one or more alloy elements selected from the group composed of Al, Fe, Zr, Mg, Li, Cr, Mn, Co, Ni, Cu, Zn, Ge, Ga, Y, Nb, Cd, Ca, and La, each in a content of 0.01 at % to 15 at %, and/or optionally one or more alloy elements selected from the group composed of Hf, Pb, Bi, Ru, Rh, Pd, Ag, Au, Ta, W, Re, Os, Ir, and Pt, each in a content of 0.01 at % to 5 at %, as well as the remainder of molybdenum, wherein the proportion of molybdenum is at least 40 at %,
    wherein the molybdenum alloy has a molybdenum-vanadium mixed crystal matrix and at least one silicide phase distributed therein, and the density of the molybdenum alloy is less than 8 g/cm3.
  2. The molybdenum alloy according to claim 1,
    wherein at least one silicide phase is selected from (Mo,V)3Si, (Mo,V)5SiB2, and (Mo,V)5Si3.
  3. The molybdenum alloy according to one of claims 1 or 2,
    wherein the content of Ti is of 0.5 to 10 at %.
  4. The molybdenum alloy according to any of the preceding claims,
    wherein the content of vanadium is 10 to 40 at %.
  5. The molybdenum alloy according to one of the preceding claims,
    wherein the proportion of silicide phases is at least 30 %.
  6. The molybdenum alloy according to one of claims 2 to 5,
    wherein the alloy has a structure with a Mo-V mixed crystal matrix and (Mo,V)3Si and/or (Mo,V)5SiB2 distributed therein.
  7. The molybdenum alloy according to claim 6,
    wherein the phase (Mo,V)5Si3 is additionally present.
  8. A method for producing a molybdenum alloy according to one of the preceding claims,
    wherein the starting elements are mechanically alloyed in a first step, and subsequently, in a second step, are compacted by a FAST (field-assisted sintering technology) method or by means of a hot isostatic pressing method.
  9. Use of a molybdenum alloy according to one of claims 1 to 7 as a structural material for rotating or flying applications, in particular in aviation technology and aerospace technology.
  10. Use of a molybdenum alloy according to claim 9 as a turbine material.
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