A refractory multi-principal element alloy strengthened by nitrides and a method for preparing the same

Abstract

This application provides a nitride-reinforced refractory multi-principal element alloy and its preparation method. The alloy composition, by weight, includes: tungsten, 63-78 parts; molybdenum, 10-20 parts; rhenium, 10-15 parts; and hafnium-zirconium composite nitride, 2-4 parts; wherein the molar ratio of hafnium to zirconium is 1:(0.5-2). The preparation method includes the following steps: preparing a precursor mixture solution by mixing tungsten, molybdenum, rhenium, hafnium, and zirconium sources with an aqueous medium; drying the precursor mixture solution to obtain a precursor composite powder; pre-calcining the precursor composite powder to obtain a mixed oxide powder; and sequentially subjecting the mixed oxide powder to nitriding and denitrification treatments to obtain the nitride-reinforced refractory multi-principal element alloy powder. The alloy contains a (Hf,Zr)N composite nitride reinforcing phase uniformly dispersed in the matrix at the nanoscale, and has broad application prospects in the field of ultra-high temperature hot-end components.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a nitride-reinforced refractory multi-principal alloy and its preparation method, and particularly to a refractory multi-principal alloy containing a hafnium-zirconium composite nitride-reinforced phase prepared by a pre-calcination synergistic nitriding-denitrification process. Background Technology

[0002] In recent years, with the continuous development of gas turbines and aero-engines towards higher power, higher speed, and higher load, the service temperature of their key hot-end components has increased to 1600-2000℃, placing more stringent requirements on the yield strength and long-term service stability of structural materials under ultra-high temperature conditions. However, existing high-temperature structural materials (such as nickel-based superalloys and refractory metals) generally suffer from a significant decrease in yield strength within this temperature range, making it difficult to meet the requirements for long-term stable service. Therefore, developing new structural materials that can maintain high strength under ultra-high temperature environments has become crucial to meeting the development needs of gas turbines and aero-engines.

[0003] Refractory multi-principal alloys, composed of various refractory metallic elements (such as W, Ta, Mo, Nb, Hf, and V), are considered promising high-temperature structural material systems due to their ability to suppress high-temperature diffusion and delay microstructural instability, thus mitigating grain coarsening and phase dissolution softening. However, above 1600℃, the thermal activation effect reduces dislocation movement resistance and accelerates crack propagation, inevitably leading to a rapid decline in yield strength. To address these shortcomings, current research has attempted to introduce nitride strengthening strategies, constructing dispersed nitride strengthening phases in the matrix to enhance the high-temperature mechanical properties of the material. Nitrides have higher melting points and hardness than oxides, effectively improving the high-temperature strength, wear resistance, and thermal stability of the material. The NbMoTaWHfN refractory multi-principal alloy designed by Cheng Yanhai et al. (Engineering 2023, 30, 110-120) achieved a yield strength of 288 MPa at 1800℃. The (HfNbTaTiV) design by Shen Baolong et al. (Adv. Eng. Mater. 2021, 2100765) 90 N 10Dual-phase alloys can achieve a yield strength of 279 MPa at 1400 °C. Anasori et al. (Acta Materialia 2021, 211, 116884) further confirmed that refractory transition metal nitrides formed by the reaction of nitrogen with the matrix can maintain stable chemical bonds above 1600 °C, endowing the material with excellent thermal stability, high-temperature stiffness, and good interfacial compatibility, thereby effectively improving the yield strength of refractory multi-principal alloys in the high-temperature range. The refractory dispersion preparation method disclosed in patent document GB1114850A allows the inclusion of nitrides of titanium, zirconium, tantalum, hafnium, aluminum, vanadium, or niobium, or mixtures of two or more of them; when different nitrides are used in combination, solid solutions and / or mixed nitrides may be formed; however, there is still a lack of clear technical guidance on how to select specific nitride combination types and ratios according to different matrix characteristics (especially for refractory multi-principal alloys), and how to further control the morphology, size, and interfacial structure of the strengthening phase.

[0004] The preparation of composite powders is fundamental to the realization of nitride-strengthened refractory multi-principal element alloys. However, existing methods for preparing such composite powders still have significant shortcomings. Mechanical alloying, as the current mainstream preparation method, generally suffers from high risks of impurity introduction, insufficient uniformity of composition and microstructure, and poor batch stability. For example, while Smeltzer et al. (Materials & Design, 2021, 210: 110070) achieved the introduction of nitrogen using cryogenic mechanical alloying with liquid nitrogen, the ball milling process introduced impurities such as Fe and C (approximately 4 at% Fe and 2.1-7.8 at% C), and the resulting alloy contained porosity and Ar bubbles. In addition, some studies have attempted to achieve breakthroughs through chemical synthesis routes. For example, Zhang et al. (Journal of Alloys and Compounds, 2025, 1024: 180264) prepared nano-W-Mo-Ta-Nb-V powder with a particle size of approximately 88 nm using a self-propagating high-temperature synthesis combined with magnesian thermal reduction. However, this method has a complex process (requiring post-treatment steps such as acid washing) and high preparation costs, making it difficult to meet the needs of industrial applications. Que et al. (International Journal of Refractory Metals and Hard Materials 2025, 128, 107044) prepared HfN-doped W-Re alloys in situ using a nitriding-denitrification method. However, their matrix was limited to W-Re binary alloys, and the reinforcing phase was only a single HfN, without involving more complex multi-principal matrix and composite reinforcing phases. The above methods still lack systematic solutions for how to achieve atomic-level homogeneous mixing of multiple components (especially high-melting-point W, Mo, Re and Hf, Zr) in the precursor stage to avoid component segregation, and how to precisely control the nanoscale size and distribution of complex nitride-reinforced phases.

[0005] To address the aforementioned issues, it is necessary to develop a novel nitride-reinforced refractory multi-principal-element alloy and its preparation method. Summary of the Invention

[0006] The purpose of this application is to provide a W-Mo-Re multi-principal alloy containing a hafnium-zirconium composite nitride strengthening phase and a preparation method based on pre-calcination-nitriding-denitrification, so as to achieve in-situ generation and uniform dispersion of the (Hf,Zr)N composite nitride strengthening phase in the W-Mo-Re multi-principal alloy matrix, thereby providing more options for the development of ultra-high temperature structural materials.

[0007] To achieve the above objectives, this application provides the following technical solution: A nitride-reinforced refractory multi-principal-element alloy, characterized in that the alloy composition, by weight, includes: tungsten, 63-78 parts; molybdenum, 10-20 parts; rhenium, 10-15 parts; hafnium-zirconium composite nitride, 2-4 parts; wherein the molar ratio of hafnium to zirconium is 1:(0.5-2).

[0008] This application also provides the following technical solutions: A method for preparing a nitride-strengthened refractory multi-principal element alloy includes the following steps: S1. Prepare a precursor mixture solution by mixing tungsten source, molybdenum source, rhenium source, hafnium source, zirconium source with an aqueous medium; S2. The precursor mixture solution is dried to obtain precursor composite powder; S3. The precursor composite powder is pre-calcined to obtain mixed oxide powder; S4. The mixed oxide powder is subjected to nitriding and denitrification treatments in sequence to obtain the nitride-reinforced refractory multi-principal-element alloy powder.

[0009] The technical solution provided in this application has the following beneficial effects: (1) The nitride-reinforced refractory multi-principal alloy provided in this application has a W-Mo-Re refractory multi-principal alloy matrix and a (Hf,Zr)N composite nitride reinforcing phase uniformly dispersed in the matrix at the nanoscale. The single solid solution reinforcing phase formed by the mutual solubility of HfN and ZrN has both high thermodynamic stability and excellent interfacial coherence. The particle size of the (Hf,Zr)N reinforcing phase in the alloy can be controlled at 2-5 nm, the oxygen content is as low as 630-720 ppm, and it has good compositional uniformity.

[0010] (2) The preparation method provided in this application uses water-soluble tungsten, molybdenum, rhenium, hafnium, and zirconium sources as raw materials to prepare a precursor mixed solution. The mixed oxide powder is first obtained by drying and pre-calcination, and then the target composite powder is obtained by nitriding-denitrification treatment. It does not require high-energy ball milling, acid washing, etc., and the process is simple and the equipment requirements are low. The nitriding-denitrification process design utilizes the significant difference in thermodynamic stability between W, Mo, Re nitrides and (Hf,Zr)N. During the denitrification process, W, Mo, and Re nitrides are selectively decomposed and alloyed to form the matrix, while the thermally stable (Hf,Zr)N is retained as a nano-reinforcing phase, realizing the in-situ generation of the composite nitride reinforcing phase in the matrix. In particular, by pre-calcining, the precursor salt is completely converted into mixed oxides before nitriding treatment, avoiding the problems of product impurity and particle agglomeration caused by residual tungsten, molybdenum, and other oxide impurities due to incomplete decomposition of the precursor salt.

[0011] (3) The nitride-strengthened refractory multi-principal alloy and its preparation method provided in this application have good potential for large-scale preparation and can be widely used in aerospace engine hot end components, nuclear reactor structural materials, ultra-high temperature electrodes and electronic packaging materials. Attached Figure Description

[0012] Figure 1 X-ray diffraction patterns of the precursor powder, nitrided powder, and denitrified composite powder prepared in Example 1.

[0013] Figure 2 This is a scanning electron microscope image of the composite powder from Example 1.

[0014] Figure 3 The elemental surface distribution EDS spectrum of the composite powder in Example 1 is shown. Invention Details 1. Terminology Explanation All patents and other publications cited herein are incorporated herein in their entirety. In the event of any conflict between any description of terminology herein and any document incorporated herein by reference, this document shall prevail.

[0016] Numerical ranges can be represented by a hyphen "-" or a tilde "~". Unless otherwise stated, the range should be understood to encompass both the endpoint values ​​and any values ​​in between. There are no particular restrictions on the type of numeric values ​​within the range, including but not limited to integers, decimals, fractions, percentages, etc., unless explicitly excluded by the context or a particular numeric type is technically unavailable. The type of numeric values ​​within the range is not limited by the specific representation of the endpoints.

[0017] The terms “including,” “containing,” and similar expressions have a non-restrictive meaning.

[0018] "Optional" is used to indicate that a certain feature (including but not limited to components, steps, parameters or structures) may be present in some embodiments, but may not appear in other embodiments, thereby providing technical flexibility for different implementations without departing from the core concept of the present invention.

[0019] "Any combination" of the enumeration items means any two or more of the enumeration items that coexist or are used together, including but not limited to any two combinations, any three combinations, any more items, and combinations of all the enumeration items, unless the context explicitly excludes it or a particular combination is technically impossible.

[0020] The use of labels such as a), b), i), ii), 1), 2), S1, S2, etc. to number the steps of a method is only for the convenience of description and reading, and does not mean that the corresponding steps must be performed in the order of the numbers, unless the text explicitly states or the information in the text can be clearly inferred that there is a logical or temporal relationship between specific steps.

[0021] The term "aqueous medium" as used herein refers to a liquid system in which water is the continuous phase. The aqueous medium may be pure water. "Pure water" refers to water with a resistivity of not less than 1 MΩ·cm at 25°C, including but not limited to deionized water, distilled water, and ultrapure water.

[0022] The term "tungsten source" as used herein refers to a tungsten-containing compound (including hydrates) that provides tungsten and can form a tungsten-containing precursor in an aqueous medium. The tungsten source includes, but is not limited to, tungstates, metatungstates, and paratungstates, specifically ammonium metatungstate, ammonium tungstate, and ammonium paratungstate.

[0023] The term "molybdenum source" as used herein refers to a molybdenum-containing compound (including hydrates) that provides molybdenum and can form a molybdenum-containing precursor in an aqueous medium. The molybdenum source includes, but is not limited to, molybdates, specifically ammonium molybdate and ammonium heptamolybdate.

[0024] The term "rhenium source" as used herein refers to a rhenium-containing compound (including hydrates) that provides rhenium and can form a rhenium-containing precursor in an aqueous medium. The rhenium source includes, but is not limited to, perrhenates and rhenates, specifically ammonium perrhenate.

[0025] The term "hafnium source" as used herein refers to a hafnium-containing compound (including hydrates) that provides hafnium and can form hafnium-containing precursors in an aqueous medium. The hafnium source includes, but is not limited to, hafnium halides, specifically hafnium tetrachloride.

[0026] The term "zirconium source" as used herein refers to a zirconium-containing compound (including hydrates) that provides zirconium and can form a zirconium-containing precursor in an aqueous medium. The zirconium source includes, but is not limited to, zirconium halides, specifically zirconium tetrachloride.

[0027] The "nitriding-denitrification" process described herein refers to the sequential nitriding and denitrification treatment of metal oxide powder. "Nitriding" refers to heating the metal oxide powder in a nitrogen-containing atmosphere, causing some or all of the metal elements to transform into corresponding nitrides. "Denitrification" refers to heat treatment under vacuum, inert atmosphere, reducing atmosphere, or low nitrogen potential atmosphere, utilizing the differences in thermal stability of different nitrides to decompose some or all of the nitrides in the material into metal atoms and alloy them, while retaining the nitrides with high thermal stability.

[0028] The "hafnium-zirconium complex nitride" mentioned in this article refers to a nitride composed of hafnium, zirconium, and nitrogen, denoted as (Hf,Zr)N. Unless otherwise specified, the (Hf,Zr)N has a single solid solution phase.

[0029] 2. Implementation Plan One embodiment of this application is as follows: A nitride-reinforced refractory multi-principal-element alloy; the composition of the alloy, by weight, includes: tungsten, 63-78 parts; molybdenum, 10-20 parts; rhenium, 10-15 parts; hafnium-zirconium composite nitride, 2-4 parts; wherein the molar ratio of hafnium to zirconium is 1:(0.5-2).

[0030] In some specific implementations, the nitride-reinforced refractory multi-principal alloy includes a refractory multi-principal alloy matrix and a nitride-reinforced phase dispersed in the matrix.

[0031] In some specific implementations, the refractory multi-principal-element alloy matrix is ​​a W-Mo-Re solid solution.

[0032] In some specific implementations, the nitride-reinforcing phase is a (Hf,Zr)N solid solution.

[0033] In some specific implementations, the particle size of the (Hf,Zr)N does not exceed 10 nm.

[0034] In some specific implementations, the oxygen content of the nitride-strengthened refractory multi-principal alloy does not exceed 800 ppm.

[0035] Another implementation scheme of this application is as follows: The preparation method of any of the aforementioned nitride-strengthened refractory multi-principal element alloys includes the following steps: S1. Prepare a precursor mixture solution by mixing tungsten source, molybdenum source, rhenium source, hafnium source, zirconium source with an aqueous medium; S2. The precursor mixture solution is dried to obtain precursor composite powder; S3. The precursor composite powder is pre-calcined to obtain mixed oxide powder; S4. The mixed oxide powder is subjected to nitriding and denitrification treatments in sequence to obtain the nitride-reinforced refractory multi-principal-element alloy powder.

[0036] In some specific implementations, the molar ratio of hafnium to zirconium is 1:1.

[0037] In some specific implementations, the tungsten source is ammonium metatungstate, ammonium tungstate, ammonium paratungstate, or any combination thereof.

[0038] In some specific implementations, the molybdenum source is ammonium molybdate, ammonium heptamolybdate, or any combination thereof.

[0039] In some specific implementations, the rhenium source is ammonium perrhenate, ammonium perrhenate, or any combination thereof.

[0040] In some specific implementations, the hafnium source is hafnium tetrachloride, hafnium oxychloride, hafnium nitrate, or any combination thereof.

[0041] In some specific implementations, the zirconium source is zirconium tetrachloride, zirconium oxychloride, zirconium nitrate, or any combination thereof.

[0042] In some specific implementation schemes, the aqueous medium is deionized water.

[0043] In some specific implementations, step S1 includes: dissolving a tungsten source, a molybdenum source, a rhenium source, a hafnium source, and a zirconium source in the same aqueous medium, and stirring at 50-80°C, preferably 60-80°C, for 0.5-1 hour to obtain a uniform and transparent precursor mixture solution.

[0044] In some specific implementations, the drying process is freeze drying.

[0045] In some specific implementations, the freeze-drying is carried out at -50°C to -20°C.

[0046] In some specific implementations, the vacuum degree of the freeze-drying is less than 10 Pa.

[0047] In some specific implementations, the freeze-drying time is 24-48 hours.

[0048] In some specific implementation schemes, the total amount of the aqueous medium corresponding to every 100 g of the tungsten source, molybdenum source, rhenium source, hafnium source and zirconium source is 200-500 mL.

[0049] In some specific implementation schemes, the pre-calcination treatment is carried out at 500-600°C.

[0050] In some specific implementations, the pre-calcination treatment is carried out in an air or oxygen atmosphere.

[0051] In some specific implementation schemes, the heat preservation time for the pre-calcination treatment is 2-4 hours.

[0052] In some specific implementations, the nitriding treatment is carried out at 650-850°C.

[0053] In some specific implementations, the nitriding treatment is carried out in an ammonia atmosphere at a flow rate of 0.2-0.5 L / min.

[0054] In some specific implementations, the holding time for the nitriding treatment is 2-4 hours.

[0055] In some specific implementations, the denitrification treatment is carried out at 850-1000°C.

[0056] In some specific implementations, the denitrification process is carried out under an argon atmosphere with an argon flow rate of 0.2-0.5 L / min.

[0057] In some specific implementation schemes, the holding time for the denitrification treatment is 2-4 hours. Detailed Implementation

[0058] The raw materials used in this application can be purchased or synthesized in-house. The following specific embodiments are used to further describe the implementation of the present invention and do not limit the scope of the invention.

[0059] Example 1: Preparation of W-10Mo-10Re-2(Hf,Zr)N nanocomposite powder (1) Preparation of precursor mixed solution: ammonium metatungstate ((NH4)6H2W 12 O 40 ·xH2O, x≈0), ammonium molybdate ((NH4)6Mo7O 24 Using 4H₂O, ammonium perrhenate (NH₄ReO₄), hafnium tetrachloride (HfCl₄), and zirconium tetrachloride (ZrCl₄) as raw materials, approximately 100 g of raw materials were weighed according to the target component weight ratio W:Mo:Re:(Hf,Zr)N = 78:10:10:2 (where the molar ratio of Hf and Zr is 1:1). The weighed powder was dissolved in 400 mL of deionized water, placed in a 1 L beaker, and heated in an 80 °C water bath with continuous stirring for 0.5 hours to obtain a clear and transparent mixed solution.

[0060] (2) Preparation of precursor composite powder: The above mixed solution was poured into stainless steel trays in batches and quickly placed in containers filled with liquid nitrogen to freeze completely into ice. The ice was then transferred to a freeze dryer and freeze-dried at -40°C and a vacuum of 5 Pa for 48 hours to obtain a loose, macroscopically uniform light yellow precursor composite powder.

[0061] (3) Preparation of mixed oxide powder: The precursor powder was placed in a tube furnace and pre-calcined in a flowing air atmosphere (flow rate 0.3 L / min) at a calcination temperature of 600 °C and a holding time of 4 hours to obtain mixed oxide powder of W, Mo, Re, Hf and Zr.

[0062] (4) Nitriding-Denitrification Treatment: The mixed oxide powder was transferred to another clean tubular furnace. Ammonia gas (flow rate 0.3 L / min) was introduced first, and the temperature was raised to 700℃ at 5℃ / min and held for 4 hours for nitriding treatment, so that Hf, Zr and some W and Mo formed nitrides. After the holding period, the ammonia gas was turned off and high-purity argon gas (flow rate 0.3 L / min) was introduced. The temperature was directly raised to 900℃ and held for 3 hours for denitrification treatment, so that the nitrides of W, Mo and Re decomposed into metal atoms and alloyed, while the thermally stable (Hf,Zr)N did not decompose and remained as a nano-reinforcing phase. After denitrification, the furnace was cooled to room temperature under argon protection to obtain W-10Mo-10Re-2(Hf,Zr)N nanocomposite powder.

[0063] (5) Characterization of alloy composition and structure: XRD pattern ( Figure 1 The results showed only a W-Mo-Re matrix solid solution phase and a (Hf,Zr)N phase, with no other impurity phases. SEM ( Figure 2 The powder particles are nearly spherical with an average particle size of 50 nm; the nano-(Hf,Zr)N reinforcing phase has a particle size of approximately 2-5 nm and is uniformly dispersed on the surface and inside the matrix particles. The powder D50 is 56 nm, and the oxygen content is 680 ppm. Elemental surface distribution EDS pattern ( Figure 3 The data showed that W, Mo, Re, Hf, and Zr elements were all uniformly dispersed with no obvious agglomeration areas, indicating good component homogeneity.

[0064] Example 2: Preparation of W-10Mo-10Re-4(Hf,Zr)N nanocomposite powder (1) Preparation of precursor mixed solution: ammonium metatungstate ((NH4)6H2W 12 O 40 ·xH2O), ammonium molybdate ((NH4)6Mo7O) 24 Using 4H₂O, ammonium perrhenate (NH₄ReO₄), hafnium tetrachloride (HfCl₄), and zirconium tetrachloride (ZrCl₄) as raw materials, approximately 100 g of raw materials were weighed according to the target component weight ratio W:Mo:Re:(Hf,Zr)N = 76:10:10:4 (where the molar ratio of Hf to Zr is 1:1). The weighed powder was dissolved in 400 mL of deionized water, placed in a 1 L beaker, and heated in an 80°C water bath with continuous stirring for 0.5 hours to obtain a clear and transparent mixed solution.

[0065] (2) Preparation of precursor composite powder: The above mixed solution was poured into stainless steel trays in batches and quickly placed in containers filled with liquid nitrogen to freeze completely into ice. The ice was then transferred to a freeze dryer and freeze-dried at -40°C and a vacuum of 5 Pa for 48 hours to obtain a loose, macroscopically uniform light yellow precursor composite powder.

[0066] (3) Preparation of mixed oxide powder: The precursor powder was placed in a tube furnace and calcined in a flowing air atmosphere (flow rate 0.3 L / min) at a temperature of 600 °C for 4 hours to obtain mixed oxide powder of W, Mo, Re, Hf and Zr.

[0067] (4) Nitriding-Denitrification Treatment: The mixed oxide powder was transferred to another clean tubular furnace. Ammonia gas (flow rate 0.3 L / min) was introduced first, and the temperature was raised to 700℃ and held for 4 hours for nitriding treatment, so that Hf, Zr and some W and Mo formed nitrides. After the holding period, the ammonia gas was turned off and high-purity argon gas (flow rate 0.3 L / min) was introduced. The temperature was directly raised to 900℃ and held for 3 hours for denitrification treatment, so that the nitrides of W, Mo and Re decomposed into metal atoms and alloyed, while the thermally stable (Hf,Zr)N did not decompose and remained as a nano-reinforcing phase. After denitrification, the furnace was cooled to room temperature under argon protection to obtain W-10Mo-10Re-4(Hf,Zr)N nanocomposite powder.

[0068] (5) Characterization of alloy composition and structure: XRD pattern showed only W-Mo-Re matrix solid solution phase and (Hf,Zr)N phase, with no other impurity phases. SEM showed that the powder particles were nearly spherical with an average particle size of 60 nm; the nano-(Hf,Zr)N reinforcing phase had a particle size of about 3-10 nm and was uniformly dispersed on the surface and inside of the matrix particles. The powder D50 was 66 nm and the oxygen content was 720 ppm. EDS pattern of elemental surface distribution showed that W, Mo, Re, Hf, and Zr elements were all uniformly dispersed with no obvious agglomeration areas, indicating good compositional homogeneity.

[0069] Example 3: Preparation of W-20Mo-15Re-2(Hf,Zr)N nanocomposite powder (1) Preparation of precursor mixed solution: ammonium metatungstate ((NH4)6H2W 12 O 40 ·xH2O), ammonium molybdate ((NH4)6Mo7O) 24 Using 4H₂O, ammonium perrhenate (NH₄ReO₄), hafnium tetrachloride (HfCl₄), and zirconium tetrachloride (ZrCl₄) as raw materials, approximately 100 g of raw materials were weighed according to the target component weight ratio W:Mo:Re:(Hf,Zr)N = 63:20:15:2 (where the molar ratio of Hf and Zr is 1:1). The weighed powder was dissolved in 400 mL of deionized water, placed in a 1 L beaker, and heated in an 80 °C water bath with continuous stirring for 1 hour to obtain a clear and transparent mixed solution.

[0070] (2) Preparation of precursor composite powder: The above mixed solution was poured into stainless steel trays in batches and quickly placed in containers filled with liquid nitrogen to freeze completely into ice. The ice was then transferred to a freeze dryer and freeze-dried at -40°C and a vacuum of 5 Pa for 48 hours to obtain a loose, macroscopically uniform light yellow precursor composite powder.

[0071] (3) Preparation of mixed oxide powder: The precursor powder was placed in a tube furnace and calcined in a flowing air atmosphere (flow rate 0.3 L / min) at a temperature of 600 °C for 4 hours to obtain mixed oxide powder of W, Mo, Re, Hf and Zr.

[0072] (4) Nitriding-Denitrification Treatment: The mixed oxide powder was transferred to another clean tubular furnace. Ammonia gas (flow rate 0.3 L / min) was first introduced, and the temperature was raised to 680℃ and held for 4 hours for nitriding treatment, so that Hf, Zr and some W and Mo formed nitrides. After the holding period, the ammonia gas was turned off and high-purity argon gas (flow rate 0.3 L / min) was switched on. The temperature was directly raised to 880℃ and held for 3 hours for denitrification treatment, so that the nitrides of W, Mo and Re decomposed into metal atoms and alloyed, while the thermally stable (Hf,Zr)N did not decompose and remained as a nano-reinforcing phase. After denitrification, the furnace was cooled to room temperature under argon protection to obtain W-20Mo-15Re-2(Hf,Zr)N nanocomposite powder.

[0073] (5) Characterization of alloy composition and structure: XRD pattern showed only W-Mo-Re matrix solid solution phase and (Hf,Zr)N phase, with no other impurity phases. SEM showed that the powder particles were nearly spherical with an average particle size of 55 nm; the nano-(Hf,Zr)N reinforcing phase had a particle size of about 2-8 nm and was uniformly dispersed on the surface and inside of the matrix particles. The powder D50 was 60 nm and the oxygen content was 630 ppm. EDS pattern of elemental surface distribution showed that W, Mo, Re, Hf, and Zr elements were all uniformly dispersed with no obvious agglomeration areas, indicating good compositional homogeneity.

[0074] Example 4: Preparation and Performance Testing of W-10Mo-10Re-2(Hf,Zr)N Alloy Bulk Using the nanocomposite powder prepared in Example 1 as raw material, alloy bulk materials were prepared by spark plasma sintering (SPS). The specific steps are as follows: (1) Filling powder: Fill about 3 g of composite powder into a graphite mold with an inner diameter of 20 mm, place graphite pads and graphite paper on the top and bottom, and place it in the SPS sintering furnace cavity.

[0075] (2) Sintering process: Evacuate the cavity until the gas pressure is below 10 Pa, heat it to 1700℃ at a rate of 100℃ / min, apply an axial pressure of 40 MPa, hold the temperature and pressure for 5 min and then release the pressure. Cool it to room temperature with the furnace to obtain a dense alloy block.

[0076] (3) Characterization of bulk properties: The density was tested using the Archimedes method, and the result was 98.6%; the room temperature hardness was measured using a Vickers hardness tester under a load of 0.5 kg and a holding pressure of 10 s, and the average hardness was HV. 0.5 482; High-temperature mechanical properties were tested under argon protection using compression testing at a strain rate of 1×10⁻⁶. -4 s -1 The yield strength at 1600℃ is 412 MPa, and the yield strength at 1800℃ is 335 MPa. The microstructure stability characterization results show that after sintering, the particle size of the (Hf,Zr)N-reinforced phase remains at 2-10 nm, without obvious coarsening, and is still dispersed in the W-Mo-Re matrix without the appearance of an interfacial reaction layer.

[0077] Example 5: Preparation and Performance Testing of W-10Mo-10Re-4(Hf,Zr)N Alloy Bulk The nanocomposite powder prepared in Example 2 was used as raw material, and sintering was carried out using the method in Example 4. The properties of the resulting bulk alloy were then characterized.

[0078] The resulting alloy bulk had a density of 98.2% and an average room temperature hardness of HV. 0.5 The yield strength at 537°C and 1800°C is 368 MPa, and the particle size of the reinforcing phase remains at 3-10 nm.

[0079] The above results indicate that by increasing the content of composite nitrides, the high-temperature strength of the alloy can be further improved while maintaining the high density of the bulk and the nanoscale of the reinforcing phase.

[0080] Comparative Example 1: Preparation of Composite Powder by Mechanical Alloying Using W, Mo, Re, HfN, and ZrN powders with purities all greater than 99.5% as raw materials, and following the same target composition W-10Mo-10Re-2(Hf,Zr)N as in Example 1, mechanical alloying was performed using a planetary ball mill. The ball-to-powder ratio was 10:1, the milling speed was 300 rpm, and the milling was carried out for 40 hours under argon protection. The resulting powder had an oxygen content as high as 3200 ppm. XRD and SEM analysis showed that the powder was a multiphase mixture with irregular particle shapes, a wide particle size distribution (D50 of approximately 1.2 μm), and some unalloyed W and Mo elemental peaks, as well as nitride particle agglomeration.

[0081] Comparative Example 2: Preparation method omitting pre-calcination Referring to the preparation method of Example 1, without pre-calcination (i.e., omitting the step of preparing mixed oxide powder), the precursor composite powder was directly transferred into a tube furnace for nitriding-denitrification treatment, and the remaining conditions were the same as in Example 1.

[0082] XRD analysis of the obtained powder revealed significant residual peaks of WO3 and MoO2 in addition to the W-Mo-Re matrix phase and (Hf,Zr)N phase, indicating that direct nitriding treatment failed to completely convert the precursor salt into the target phase, resulting in an impure product. SEM analysis showed irregular powder particle morphology, obvious sintering necks and agglomeration, with an average particle size greater than 500 nm and uneven distribution of the nano-reinforcing phase. The oxygen content was as high as 2500 ppm. These results indicate that the preparation method provided in this application, by pre-calcining before nitriding treatment, can obtain composite powders with purer components, more uniform distribution of the nano-reinforcing phase, and smaller particle size.

[0083] Comparative Example 3: Preparation of composite powders with HfN or ZrN as reinforcing phases Following the preparation method of Example 1, raw materials were weighed according to the target component weight ratio W:Mo:Re:HfN = 78:10:10:2, and other conditions remained unchanged to obtain W-10Mo-10Re-2HfN nanocomposite powder.

[0084] Following the preparation method of Example 1, the raw materials were weighed according to the target component weight ratio W:Mo:Re:ZrN = 78:10:10:2, and the other conditions remained unchanged, to obtain W-10Mo-10Re-2ZrN nanocomposite powder.

[0085] TEM observation and nanoindentation tests revealed that, compared to the (Hf,Zr)N composite reinforcing phase in Example 1, the single HfN or ZrN reinforcing phases exhibited a wider particle size distribution range (10-40 nm). Furthermore, high-magnification observation revealed minute gaps at the interface between some reinforcing phases and the matrix, indicating that the coherent / semi-coherent interfacial bonding strength might be lower than in Example 1. This suggests that the co-introduction of Hf and Zr not only utilizes the common high stability of their nitrides but also likely optimizes the interfacial matching with the W-Mo-Re matrix through the lattice distortion effect of the composite nitride, effectively suppressing the abnormal growth of reinforcing phase particles and achieving a synergistic reinforcing effect that cannot be achieved with a single component.

[0086] Comparative Example 4: Preparation of alloy bulk materials using mechanically alloyed powder The mechanically alloyed powder prepared in Comparative Example 1 was used as raw material, and sintering was carried out using the method in Example 4. The properties of the resulting bulk alloy were then characterized.

[0087] The resulting alloy bulk had a density of only 95.2% and contained a small amount of residual porosity; its average room temperature hardness was HV. 0.5 The yield strength at 395°C and 1800°C is only 240 MPa, far lower than the performance of Example 4. In addition, the nitride-reinforced phase is significantly coarsened after sintering, with some particles having a diameter exceeding 100 nm, and the strengthening effect is significantly reduced at high temperatures.

[0088] The above results indicate that the nanocomposite powder prepared in this application has superior sintering activity and thermal stability, and the density and high-temperature mechanical properties of the resulting bulk are significantly better than those of the traditional mechanical alloying route.

[0089] Comparative Example 5: The pre-calcination temperature was too low (400℃). Following the preparation method of Example 1, only the pre-calcination temperature was adjusted to 400°C, while the other process parameters remained unchanged.

[0090] XRD analysis of the obtained powder revealed weak residual peaks of WO3 and MoO2 in addition to the W-Mo-Re matrix phase and (Hf,Zr)N phase, indicating incomplete decomposition of the precursor salt and failure of some oxides to be fully converted in the subsequent nitriding-denitrification process. SEM characterization showed localized agglomeration of the powder, with an average particle size of approximately 210 nm and a D50 of 260 nm; the nano-reinforced phase had a wide particle size distribution (10-35 nm) and localized aggregation. The oxygen content of the powder was 1480 ppm, significantly higher than the 680 ppm in Example 1.

[0091] The above results indicate that a low pre-calcination temperature leads to incomplete decomposition of precursor salts, directly resulting in residual impurity phases, increased oxygen content, and decreased uniformity of reinforced phase distribution in the product, thus failing to achieve the technical effects of this application.

[0092] Comparative Example 6: Insufficient pre-calcination holding time (1 h) Referring to the preparation method of Example 1, only the pre-calcination holding time was adjusted to 1 h, while the other process parameters remained unchanged.

[0093] XRD analysis of the obtained powder revealed trace amounts of low-valence oxide impurities, indicating a lower phase purity than in Example 1. SEM characterization showed uneven powder particle morphology, with some particles exhibiting sintering and adhesion, and a D50 of 195 nm. The nano-reinforcing phase had a particle size of 8-30 nm and exhibited a small amount of localized segregation. The oxygen content of the powder was 1120 ppm, significantly higher than in Example 1.

[0094] The above results indicate that insufficient pre-calcination holding time prevents the precursor salt decomposition reaction from proceeding completely, which in turn affects the phase purity and microstructure uniformity of the final product.

[0095] All equivalent structural or procedural transformations made using the content of this application's specification, directly or indirectly applied to the same or related technical fields as this application, are included within the scope of patent protection of this application. For those skilled in the art, this invention can be implemented in a wide range with equivalent parameters, formulations, and conditions without departing from its spirit and scope, and without the need for unnecessary experimentation. Although this application includes specific conditions in its embodiments, it should be understood that the conditions of each embodiment can be combined in any suitable manner where technically feasible. To avoid unnecessary repetition, this application will not further describe the various possible combinations. In summary, any changes, modifications, substitutions, and variations made using conventional techniques known in the art based on the principles of this invention are considered to be disclosed in this application.

Claims

1. A nitride-reinforced refractory multi-principal element alloy, characterized in that, The alloy composition, by weight, includes: tungsten, 63-78 parts; molybdenum, 10-20 parts; rhenium, 10-15 parts; hafnium-zirconium composite nitride, 2-4 parts; wherein the molar ratio of hafnium to zirconium is 1:(0.5-2).

2. The nitride-strengthened refractory multi-principal element alloy according to claim 1, characterized in that, The alloy comprises a refractory multi-principal-element alloy matrix and a nitride-reinforcing phase dispersed in the matrix; The refractory multi-principal-element alloy matrix is ​​a W-Mo-Re solid solution; The nitride-reinforced phase is a (Hf,Zr)N solid solution; The particle size of the (Hf,Zr)N does not exceed 10 nm; The oxygen content of the nitride-strengthened refractory multi-principal alloy does not exceed 800 ppm.

3. A method for preparing a nitride-strengthened refractory multi-principal element alloy as described in claim 1, characterized in that, Includes the following steps: S1. Prepare a precursor mixture solution by mixing tungsten source, molybdenum source, rhenium source, hafnium source, zirconium source with an aqueous medium; S2. The precursor mixture solution is dried to obtain precursor composite powder; S3. The precursor composite powder is pre-calcined to obtain mixed oxide powder; S4. The mixed oxide powder is subjected to nitriding and denitrification treatments in sequence to obtain the nitride-reinforced refractory multi-principal-element alloy powder.

4. The method for preparing nitride-strengthened refractory multi-principal-element alloys according to claim 3, characterized in that, The tungsten source is ammonium metatungstate, the molybdenum source is ammonium molybdate, the rhenium source is ammonium perrhenate, the hafnium source is hafnium tetrachloride, and the zirconium source is zirconium tetrachloride.

5. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The aqueous medium is deionized water.

6. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The drying process is freeze-drying.

7. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The total amount of the aqueous medium used per 100g of the tungsten source, molybdenum source, rhenium source, hafnium source and zirconium source is 200-500 mL.

8. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The pre-calcination treatment is carried out at 500-600℃ in an air or oxygen atmosphere, and the holding time is 2-4 hours.

9. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The nitriding treatment is carried out at 650-850℃ in an ammonia atmosphere for 2-4 hours.

10. The method for preparing nitride-strengthened refractory multi-principal element alloys according to claim 3, characterized in that, The denitrification treatment is carried out at 850-1000℃ in an argon atmosphere for 2-4 hours.

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