A high-entropy alloy-based composite material and its preparation method

Abstract

This invention discloses a high-entropy alloy-based composite material and its preparation method, belonging to the field of additive manufacturing composite material technology. The preparation method of the high-entropy alloy-based composite material of this invention includes the following steps: preparing a high-entropy alloy powder matrix; coating the surface of the high-entropy alloy powder matrix with carbide and / or nitride powder to obtain a cemented composite powder; subjecting the cemented composite powder to reduction treatment to obtain an oxygen-free cemented composite powder; subjecting the oxygen-free cemented composite powder to plasma spheroidization treatment to obtain a high-entropy alloy-based composite powder; and using the high-entropy alloy-based composite powder for additive manufacturing to obtain a high-entropy alloy-based composite material precursor. This invention, through full-chain technological innovation, effectively solves the core problems of uneven distribution of reinforcing phases, weak interfacial bonding, and poor process stability in additive manufacturing of high-entropy alloy-based composite materials, significantly improving the high-temperature tensile strength and creep resistance of the material, making it particularly suitable for hot-end components of aero-engines.

Description

Technical Field

[0001] This application belongs to the field of additive manufacturing composite material technology, and specifically relates to a high-entropy alloy-based composite material and its preparation method. Background Technology

[0002] With the continuous improvement of thrust-to-weight ratio and thermal efficiency in aero-engines, the requirements for the material properties of hot-end components (such as turbine blades and combustion chamber liners) are becoming increasingly stringent. These components operate in extreme environments, requiring materials to not only possess excellent high-temperature tensile strength to withstand enormous centrifugal forces and aerodynamic loads, but also outstanding high-temperature creep resistance to ensure dimensional stability and service life under long-term high-temperature stress. Although traditional nickel-based and cobalt-based superalloys have undergone many years of development, their performance improvements have approached theoretical limits, making it difficult to meet the requirements of next-generation aero-engines for higher service temperatures (above 1200°C) and longer service life.

[0003] High-entropy alloys, with their unique multi-principal element design and high-entropy effects, lattice distortion effects, and hysteresis diffusion effects, offer a new paradigm for the development of next-generation ultra-high temperature structural materials. In particular, high-entropy alloy systems composed of multiple alloying elements, such as Ni, Co, Cr, W, Mo, Nb, and Al, possess excellent high-temperature microstructural stability and mechanical property potential, making them ideal candidate materials for hot-end components of aero-engines. However, to fabricate them into dense components that meet extreme operating conditions using additive manufacturing technology, a series of interrelated process bottlenecks still need to be overcome.

[0004] First, achieving high standards for raw material powders and uniform preparation of composite powders are fundamental challenges. Additive manufacturing requires powders with excellent flowability and high purity. However, an even more critical challenge lies in how to uniformly coat the micro-ceramic reinforcing phase onto the surface of the matrix powder. Traditional simple mixing cannot achieve precise control and easily leads to agglomeration of the reinforcing phase, becoming a source of defects in subsequent processes.

[0005] Secondly, the melting and solidification behavior and heterogeneous interface control during additive manufacturing are the core determinants of performance. In the rapid melting and solidification process of laser or electron beam, the wettability and degree of reaction between ceramic particles and the molten metal directly determine the quality of interfacial bonding. Without active control, it is difficult to form a transition layer in situ, and without a strong and toughened interface, the reinforcing phase cannot achieve diffuse distribution and effective load-bearing, and the potential high-temperature strength and creep resistance of the material will be greatly reduced.

[0006] Finally, post-processing to eliminate additive manufacturing defects and achieve customized microstructure and properties is crucial. Pores are unavoidable within additively manufactured parts, resulting in low density in the printed state and severely compromising mechanical reliability. General hot isostatic pressing (HIP) processes are difficult to apply directly; specific parameters tailored to the material system are necessary to effectively close the pores and increase the density to over 99.5% without damaging the already formed fine interfaces.

[0007] In summary, existing technologies have gaps and shortcomings in three key aspects: preparation of high-quality composite powders, active interface control during additive manufacturing, and targeted densification post-treatment. Summary of the Invention

[0008] The purpose of this invention is to provide a high-entropy alloy-based composite material and its preparation method, which solves the technical problems of uneven distribution of reinforcing phase, weak interfacial bonding and poor process stability in the additive manufacturing of high-entropy alloy-based composite materials in the prior art.

[0009] To achieve the above objectives, one embodiment of the present invention provides a method for preparing a high-entropy alloy-based composite material, comprising the following steps:

[0010] Preparation of high-entropy alloy powder matrix;

[0011] A cemented composite powder is obtained by coating a high-entropy alloy powder matrix with carbide and / or nitride powders.

[0012] The adhesive composite powder was reduced to obtain an oxygen-free adhesive composite powder.

[0013] The oxygen-free adhesive composite powder was subjected to plasma spheroidization treatment to obtain high-entropy alloy-based composite powder.

[0014] High-entropy alloy-based composite powder was used to obtain a precursor for high-entropy alloy-based composite materials through additive manufacturing.

[0015] The high-entropy alloy-based composite material precursor was subjected to hot isostatic pressing to obtain the high-entropy alloy-based composite material.

[0016] In one preferred embodiment of the present invention, the high-entropy alloy powder matrix comprises the following components in the following mass percentage ratios: Ni: 20%-23%, Co: 27%-30%, Cr: 15%-17%, W: 14%-16%, Mo: 7%-9%, Nb: 4%-13%, Al: 1%-4%.

[0017] In one preferred embodiment of the present invention, the high-entropy alloy powder matrix has a particle size of 15μm-120μm, a sphericity of not less than 0.85, a flowability of not more than 30s / 50g, and a loose packing density of not less than 4.00g / cm³. 3 The tapped density is not less than 4.4 g / cm³.3 The hollow powder rate is no more than 1%, the number of impurities in the powder is no more than 3 particles / 100g, and the oxygen content is less than 0.01%.

[0018] One preferred embodiment of the present invention is the preparation of a high-entropy alloy powder matrix, comprising: preparing the high-entropy alloy powder matrix by argon atomization or plasma rotating electrode method.

[0019] One preferred embodiment of the present invention involves coating a high-entropy alloy powder matrix with carbide and / or nitride powders to obtain a cemented composite powder, comprising:

[0020] The carbide and / or nitride powders are mixed with the adhesive to obtain a suspension;

[0021] The suspension and high-entropy alloy powder matrix are mixed and stirred, and then dried to obtain a glued composite powder.

[0022] In one preferred embodiment of the present invention, the particle size of the carbide and / or nitride powder is 2μm-6μm, wherein the carbide in the carbide and / or nitride powder is at least one of TiC, SiC, ZrC and WC, and the nitride is at least one of Si3N4 and TiN.

[0023] In one preferred embodiment of the present invention, the adhesive is at least one of polyvinylpyrrolidone, polyacrylic acid, ammonium citrate and polyvinyl alcohol.

[0024] In one preferred embodiment of the present invention, the mass ratio of carbide and / or nitride powder to adhesive is 5:2-3, and the viscosity of the suspension is 1.2 Pa·s-1.8 Pa·s.

[0025] In one preferred embodiment of the present invention, the ceramic phase content of the adhesive composite powder is 2%-22%, and the coating layer thickness of the adhesive composite powder is less than 1μm.

[0026] One preferred embodiment of the present invention is to reduce the adhesive composite powder to obtain an oxygen-free adhesive composite powder, comprising: spreading the adhesive composite powder in a container and purging it; after purging, heating and reducing the adhesive composite powder; and cooling it to obtain an oxygen-free adhesive composite powder.

[0027] During the heating and reduction process, the gas flow rate was set to 0.5 m³ / s. 3 / h-1.5m 3 At a rate of 5℃ / min-10℃ / min, the temperature is increased to 600℃-700℃ and held for 1-2 hours. After holding, the temperature is increased to 1000℃-1100℃ at a rate of ≤5℃ / min and held for 2-3 hours.

[0028] One preferred embodiment of the present invention involves plasma spheroidizing the oxygen-free adhesive composite powder to obtain a high-entropy alloy-based composite powder. The process includes: during spheroidizing, the plasma beam current is 610A-360A, the main gas flow rate is 115SCFH-130SCFH, the auxiliary gas flow rate is 9SCFH-11SCFH, the carrier gas flow rate is 9SCFH-13SCFH, and the powder feeding rate is 80g / min-120g / min. After spheroidizing, the powder is sieved through a 125-800 mesh screen. During sieving, the single sieving load is 100g-300g, the amplitude is 10mm-20mm, and the time is 20min-40min.

[0029] One preferred embodiment of the present invention includes an additive manufacturing process comprising laser melting deposition, laser selective melting, and electron beam selective melting. The laser melting deposition process parameters include: laser power of 500W-1300W, scanning speed of 400mm / min-1300mm / min, powder feed tray rotation speed of 700r / min-2800r / min, and carrier gas flow rate of 3L / min-11L / min. The laser selective melting process parameters include: laser power of 190W-350W, scanning speed of 800mm / s-1600mm / s, scanning spacing of 0.08mm-0.12mm, and auxiliary powder layer thickness of 2μm-4μm. The electron beam selective melting process parameters include: vacuum degree of 1.5×10⁻⁶. -3 ±1.2×10 -4 mbar, operating voltage 55kV-60kV, electron beam power 3000W-6000W, auxiliary powder layer thickness 50μm-60μm, preheating temperature 300℃-1100℃.

[0030] One preferred embodiment of the present invention is hot isostatic pressing, comprising: a heat preservation and pressure preservation treatment at a temperature of 1100℃-1250℃, a pressure of 140MPa-160MPa, and a time of 1.75h-2.25h.

[0031] The present invention also discloses a high-entropy alloy-based composite material, which is prepared by the above-described preparation method.

[0032] In one preferred embodiment of the present invention, the density of the high-entropy alloy-based composite material is 99.0%-99.9%.

[0033] Compared with the prior art, this application has the following advantages:

[0034] 1. The preparation method of the high-entropy alloy-based composite material of the present invention involves coating a high-entropy alloy powder matrix with carbide and / or nitride powder to obtain a cemented composite powder. The cemented composite powder is then subjected to reduction treatment, plasma spheroidization treatment, additive manufacturing, and hot isostatic pressing treatment to ultimately achieve a multi-scale, dispersed ceramic reinforcing phase and a strongly bonded nano-interface layer in the formed part. This significantly improves the tensile strength, durability, and microstructure stability of the material under high-temperature conditions, thereby meeting the extreme requirements of hot-end components of aero-engines for material performance.

[0035] 2. The preparation method of the high-entropy alloy-based composite material of this invention achieves precise, uniform, and toughened composite of the reinforcing phase in the matrix, laying the foundation for a leap in performance. Specifically, by preparing a suspension of ceramic powder with a specific adhesive and mixing it, and by strictly controlling the particle size of the ceramic powder, the content of the ceramic phase in the final composite powder, and the coating thickness, the problem of ceramic particle agglomeration caused by traditional mechanical mixing is fundamentally solved. The dehydrogenation reduction treatment ensures the purity of the bonded composite powder. At the same time, the subsequent plasma spheroidization treatment further ensures the sphericity and flowability of the composite powder, making it fully meet the stringent requirements of various additive manufacturing processes for raw materials, and ensuring the uniform dispersion of the reinforcing phase from the source.

[0036] 3. The preparation method of the high-entropy alloy-based composite material of the present invention significantly improves the high-temperature load-bearing capacity of the material by actively controlling the melting and solidification process and constructing a strong and tough interface in situ. Specifically, under the optimized additive manufacturing process parameters (such as laser / electron beam power and scanning strategy), the present invention utilizes the interaction between the high-energy beam and ceramic particles with a specific interface transition layer design to actively guide the formation of a gradient transition layer with a thickness of 50-200nm around the ceramic particles in situ. This transition layer can effectively promote load transfer and alleviate thermal mismatch stress, thereby allowing the dispersed ceramic particles to fully exert the second-phase strengthening effect, so that the composite material has higher tensile strength and creep performance at high temperatures, meeting the extreme service requirements of hot-end components of aero-engines.

[0037] 4. This invention provides a complete closed-loop process that thoroughly eliminates internal defects and obtains a stable and optimized final microstructure. Specifically, addressing the porosity problem commonly found in additive manufacturing components, this invention employs a specific hot isostatic pressing (HIP) process. This effectively increases the density of the component from approximately 97.0% in the printed state to over 99.5% without damaging the microstructure, greatly eliminating the harmful effects of defects on fatigue and durability. This complete technology chain, from precursor powder to post-processing, ensures high reproducibility of material properties and high reliability of the components.

[0038] 5. This invention defines precise standards for high-performance matrix powders, ensuring consistency at the starting point of the process. Specifically, this invention not only clarifies the optimal composition range of high-entropy alloy matrices (Ni-Co-Cr-W-Mo-Nb-Al system), but also specifies the physical properties of its powders (particle size, sphericity, flowability, density, purity, etc.). This set of quantitative indicators provides a clear basis for preparing high-quality raw materials suitable for additive manufacturing and is the fundamental prerequisite for achieving all subsequent process effects and performance goals.

[0039] 6. This invention achieves synergistic optimization of material microstructure and macroscopic properties by constructing a complete technical chain of "uniform composite powder preparation—surface modification treatment—precise energy input and metallurgical reaction control." This chain successfully combines the potential of high-entropy alloy matrices with the high-temperature hardness and strength advantages of ceramic phases such as TiC, SiC, ZrC, WC, TiN, and Si3N4 through an in-situ generated strong and tough transition layer, transforming it into a reliable performance advantage for components under extreme high-temperature environments. This invention has significant technological advancements and clear engineering application value, providing an ideal material solution for the manufacturing of hot-end components of next-generation aero-engines.

[0040] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description and the accompanying drawings. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic flowchart of a method for preparing a high-entropy alloy-based composite material in one embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of the high-entropy alloy powder matrix in Embodiment 1 of the present invention;

[0044] Figure 3 This is a schematic diagram of the adhesive composite powder in Embodiment 1 of the present invention;

[0045] Figure 4The images shown are transmission electron microscope (TEM) images of the microstructure of the high-entropy alloy-based composite powder in Example 1 of this invention, where (a) is a dark-field phase photograph, (b) is the electron diffraction pattern in region A, (c) is the electron diffraction pattern in region B, and (d) is the electron diffraction pattern in region C.

[0046] Figure 5 This is a scanning electron microscope image of the microstructure of the high-entropy alloy-based composite material in Example 1 of the present invention;

[0047] Figure 6 This is a scanning electron microscope image of the microstructure of the high-entropy alloy-based composite material in Example 2 of the present invention;

[0048] Figure 7 This is a scanning electron microscope image of the microstructure of the high-entropy alloy-based composite material in Example 3 of the present invention;

[0049] Figure 8 This is a scanning electron microscope image of the microstructure of the high-entropy alloy-based composite material in Example 4 of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0052] This invention discloses a method for preparing high-entropy alloy-based composite materials, such as... Figure 1 As shown, it includes the following steps:

[0053] Step (1): Prepare high-entropy alloy powder matrix; specifically, prepare high-entropy alloy powder matrix using argon atomization or plasma rotating electrode method to ensure high purity and excellent spherical morphology of the material; wherein, the high-entropy alloy powder matrix includes the following components in the following mass percentage ratio: Ni: 20%-23%, Co: 27%-30%, Cr: 15%-17%, W: 14%-16%, Mo: 7%-9%, Nb: 4%-13%, Al: 1%-4%, this composition ratio is intended to synergistically optimize the strength, corrosion resistance and high temperature stability of the alloy;

[0054] Preferably, the high-entropy alloy powder matrix has a particle size of 15μm-120μm, a sphericity of not less than 0.85, a flowability of not more than 30s / 50g, and a loose packing density of not less than 4.00g / cm³. 3 The tapped density is not less than 4.4 g / cm³. 3 The hollow powder ratio is no more than 1%, the number of inclusions in the powder is no more than 3 particles / 100g, and the oxygen content is less than 0.01%. These characteristics enable the high-entropy alloy powder matrix to have both good fluidity and dense powder spreading effect, and it can be directly adapted to a variety of additive manufacturing processes.

[0055] Step (2): Coating carbide and / or nitride powders onto the surface of a high-entropy alloy powder matrix to obtain a bonded composite powder; specifically, using a surface bonding process to firmly attach fine carbide and / or nitride powders to the surface of the high-entropy alloy powder matrix.

[0056] Includes the following steps:

[0057] Step (201): Mix carbide and / or nitride powder and adhesive to obtain a suspension; wherein, the carbide and / or nitride powder, as the reinforcing phase of the composite material, exists in the form of fine powder, and the mass ratio of carbide and / or nitride powder to adhesive is 5:2-3; preferably, the particle size of the carbide and / or nitride powder is 2μm-6μm, which belongs to the micro-nano scale, aiming to achieve uniform dispersion and good interfacial bonding of the reinforcing phase in the alloy matrix; the adhesive is at least one of polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), ammonium citrate and polyvinyl alcohol (PVA); the viscosity of the suspension is 1.2 Pa·s-1.8 Pa·s;

[0058] Furthermore, the carbide and / or nitride powder contains at least one of TiC, SiC, ZrC and WC as the carbide and at least one of Si3N4 and TiN as the nitride.

[0059] Step (202): Mix and stir the suspension and the high-entropy alloy powder matrix, and dry to obtain the adhesive composite powder; specifically, put the suspension and the high-entropy alloy powder matrix into the mixing equipment and stir them thoroughly, so that the nano-ceramic powder adheres evenly to the surface of the high-entropy alloy powder matrix particles under the action of the adhesive. After stirring, the mixture is separated into solid and liquid, and the obtained solid product is dried at low temperature under controlled conditions to completely remove volatile components, and finally obtains the adhesive composite powder of high-entropy alloy particles and carbide / nitride ceramic phase bonded by adhesive.

[0060] The prepared cemented composite powder has a specific microstructure. The powder has a core of high-entropy alloy particles, and its surface is uniformly coated with a mixture of carbide and / or nitride nano-ceramic particles, thus forming a core-shell structure. The ceramic coating layer is continuous and dense, and its thickness is precisely limited to less than 1 micrometer through process control. This submicrometer-level thin-layer coating design aims to ensure that the ceramic phase and the metal matrix can achieve good interfacial bonding and performance synergy in the subsequent spheroidization and forming process.

[0061] Preferably, the ceramic phase content of the adhesive composite powder is 2%-22%, and the coating layer thickness of the adhesive composite powder is less than 1μm;

[0062] Step (3): The adhesive composite powder is subjected to reduction treatment to obtain oxygen-free adhesive composite powder; wherein, the reduction treatment is hydrogen reduction treatment, including the following steps:

[0063] Step S1: Sample loading: Spread the adhesive composite powder from step (2) evenly in the alumina crucible, with a thickness of about 3-5 mm;

[0064] Step S2: Purging: Place the crucible in the constant temperature zone of the tube furnace, seal the furnace tube, and purge with Ar / N2 for more than 30 minutes;

[0065] Step S3: Heating and Reduction: Switch to H2 (or H2 / Ar mixture), set the flow rate to 1m³ / s. 3 / h; simultaneously, raise the temperature to 600-700℃ at a rate of 5-10℃ / min, hold for 1-2 hours (pre-reduction), and continue to raise the temperature to 1000-1100℃ at a rate of ≤5℃ / min, hold for 2-3 hours (deep reduction).

[0066] Step S4: Cooling: After the heat preservation is completed, the furnace is cooled to below 200°C in an H2 atmosphere, and then Ar / N2 is used to purge to room temperature;

[0067] Step S5: Sampling: After the furnace temperature drops to room temperature, take out the powder to obtain oxygen-free adhesive composite powder;

[0068] Step (4): The oxygen-free cemented composite powder is subjected to plasma spheroidization treatment to obtain high-entropy alloy-based composite powder; specifically, the oxygen-free cemented composite powder obtained in step (3) is sent into an inductive plasma device for spheroidization treatment, wherein the plasma beam current is controlled at 610-630A, the main gas (Ar) flow rate is 115-130SCFH, the auxiliary gas (H2) flow rate is 9-11SCFH, the carrier gas (Ar) flow rate is 9-13SCFH, and the powder feeding rate is 80g / min-120g / min; after spheroidization, the powder is then sieved. The powder undergoes precise classification, sieving using 125-800 mesh sieves under conditions of 100-300g load, 10-20mm amplitude, and 20-40 minutes per sieving cycle. This process yields high-entropy alloy / carbide / nitride composite additive manufacturing powder with high sphericity and uniform composition. This process facilitates the in-situ formation of a transition layer composed of (Ti,W)C and Ti(C,N) phases on the powder surface. This transition layer is present on the surface of the carbide and nitride particles. Preferably, the thickness of the transition layer is between 80-400nm.

[0069] High-entropy alloy-based composite powders generate (Ti,W)C solid solution and Ti(C,N) composite structures in situ on the surface of their particles through a process. This structure forms a dense ceramic / solid solution composite film on the powder surface. This surface design gives the powder material dual functional advantages: on the one hand, it significantly improves its oxidation resistance, and on the other hand, it achieves interfacial strengthening between the matrix and the reinforcing phase, thereby optimizing the overall performance of the final formed part.

[0070] Step (5): High-entropy alloy-based composite powder is additively manufactured to obtain a high-entropy alloy-based composite material precursor. Specifically, the additive manufacturing process includes laser melting deposition, laser selective melting, and electron beam selective melting. The laser melting deposition process parameters include: laser power of 500W-1300W, scanning speed of 400mm / min-1300mm / min, powder feed tray rotation speed of 700r / min-2800r / min, and carrier gas flow rate of 3L / min-11L / min. The laser selective melting process parameters include: laser power of 190W-350W, scanning speed of 800mm / s-1600mm / s, scanning spacing of 0.08mm-0.12mm, and auxiliary powder layer thickness of 2μm-4μm. The electron beam selective melting process parameters include: vacuum degree of 1.5×10⁻⁶. -3 ±1.2×10 -4mbar, working voltage of 55kV-60kV, electron beam power of 3000W-6000W, auxiliary powder layer thickness of 50μm-60μm, and preheating temperature of 300℃-1100℃; through the above process, carbide and nitride ceramic particles are melted and precipitated in the molten pool, dispersed in the composite material, and form a transition layer;

[0071] Step (6): The high-entropy alloy-based composite material precursor is subjected to hot isostatic pressing to obtain the high-entropy alloy-based composite material. Specifically, the additively manufactured part is placed in a hot isostatic pressing equipment and kept at a temperature of 1100-1250℃ and a pressure of 140MPa-160MPa for 2h±15min. After the treatment, the pressure is first reduced to below 100±10MPa, and then argon gas is introduced to cool it down. This treatment can significantly increase the material density from about 97.0% in the printed state to more than 99.5%.

[0072] Through the above complete steps (1) to (6), a high-performance high-entropy alloy-based composite material is finally prepared.

[0073] During the melting and solidification process in laser additive manufacturing, high-entropy alloy matrix composites undergo rapid melting and solidification, leading to in-situ dissolution and re-precipitation of the ceramic phase on their surface. Ultimately, this results in the formation of TiC, TiN, ZrC, SiC, WC, Si3N4, and M within the alloy matrix. 23 The C6-based multi-element ceramic reinforcing phase exhibits multi-scale particle size characteristics and is dispersed throughout the matrix. Meanwhile, a metallurgically well-bonded nanoscale transition layer with a thickness of 80-400 nanometers is formed between the ceramic phase and the high-entropy alloy matrix through interfacial reaction, effectively achieving load transfer and interfacial strengthening.

[0074] During laser processing, carbide and nitride ceramic particles with specific particle sizes and ratios undergo an in-situ metallurgical reaction with a high-entropy alloy powder matrix. This reaction promotes the decomposition of some ceramic particles, ultimately generating a ceramic reinforcing phase dispersed in multiple scales (from nanometer to submicron) within the high-entropy alloy matrix. Simultaneously, at the interface between the reinforcing phase and the matrix, a tightly bonded submicron-level interfacial transition layer is formed through element interdiffusion. This structure achieves effective load transfer and a significant improvement in interfacial strength.

[0075] The present invention also discloses a high-entropy alloy-based composite material, which is prepared by the above-described preparation method, and the density of the obtained high-entropy alloy-based composite material is 99.0%-99.9%.

[0076] This invention effectively solves the core problems of uneven distribution of reinforcing phase, weak interfacial bonding and poor process stability in high-entropy alloy-based composite materials in additive manufacturing through whole-chain technological innovation. It significantly improves the high-temperature tensile strength and durability of the material, and is particularly suitable for hot-end components of aero-engines.

[0077] Example 1

[0078] A method for preparing a high-entropy alloy-based composite material includes the following steps:

[0079] (1) In the powder preparation stage, a high-entropy alloy is first prepared according to the mass ratio of Ni 22%, Co 28.5%, Cr 16%, W 15%, Mo 8%, Nb 8.5%, and Al 2%. This high-entropy alloy spherical matrix powder with a particle size of 15-120 micrometers and an oxygen content of less than 0.008% is obtained by argon atomization. Figure 2 As shown. Subsequently, TiC, SiC, ZrC, WC, Si3N4, and TiN powders with median particle sizes of 4.2 μm, 4.6 μm, 3.6 μm, 4.0 μm, 3.8 μm, and 4.2 μm, respectively, were weighed and uniformly dispersed in an aqueous solution of polyvinyl alcohol binder at a mass ratio of 3:2:1.5:1.5:1:1 to form a suspension with a viscosity of 1.5 Pa·s. Using a planetary mixing process, this suspension was coated onto the surface of each high-entropy alloy powder particle under an inert atmosphere. After coating, the wet powder was vacuum dried at 90 °C for 3 hours, and then heat-treated at 350 °C for 1.5 hours under argon protection to obtain a cemented composite powder with a uniform core-shell structure. Figure 3 As shown. In this batch of cemented composite powder, the total mass percentage of the ceramic phase is 10%. The obtained cemented composite powder was subjected to hydrogen reduction treatment to obtain oxygen-free cemented composite powder. Finally, the powder was spheroidized using 10kW inductive plasma, which optimized the sphericity and flowability of the powder, and generated a dense (Ti,W)C solid solution and Ti(C,N) composite film in situ on the particle surface, resulting in a high-entropy alloy-based composite powder, as shown. Figure 4 As shown (where (a) is a dark-field phase photograph, (b) is the electron diffraction pattern of region A, (c) is the electron diffraction pattern of region B, and (d) is the electron diffraction pattern of region C), the preparation of high-performance composite additive manufacturing powder is completed.

[0080] (2) In the additive manufacturing and microstructure control stage, laser selective melting technology was used for forming. Based on the optimized process parameters (laser power 280W, scanning speed 1200mm / s, layer thickness 40μm, substrate preheating 150℃), the above composite powder was processed. The processed high-entropy alloy matrix composite precursor was then subjected to hot isostatic pressing to obtain the high-entropy alloy matrix composite. Under the precise energy input of the laser, the ceramic coating layer on the powder surface and the high-entropy alloy matrix underwent a controllable in-situ metallurgical reaction. After the molten pool solidified rapidly, a ceramic reinforcing phase with TiC, SiC, ZrC, WC, Si3N4, and TiN as the main components and a multi-scale dispersed distribution in the size range of 50nm-2μm was formed in the matrix, and M was formed with the matrix elements. 23 C6 and other carbides, such as Figure 5 As shown. Simultaneously, through elemental interdiffusion, a metallurgical bonding interface layer with a thickness of approximately 80-400 nanometers and a gradient composition is formed between the reinforcing phase and the matrix;

[0081] (3) During the performance verification stage, high-temperature mechanical tests were conducted on the molded specimens: at 850℃, the tensile strength of the material reached 860MPa, and the yield strength was 810MPa, which is about 35% higher than that of the unreinforced material. The creep life under the conditions of 900℃ / 300MPa reached 220 hours. Fracture analysis showed that the reinforcing phase and the matrix were well bonded, with no obvious interface debonding. Microstructure observation confirmed that the effective obstruction of dislocation movement by the multi-scale reinforcing phase and the load transfer capability of the strong and tough transition layer are the fundamental reasons why the material obtains excellent high-temperature tensile and creep properties. This implementation method fully verifies the effectiveness of the entire technology chain from composite powder design and preparation to high-performance component molding.

[0082] Example 2

[0083] This embodiment aims to verify the forming ability of the composite powder of the present invention in the laser selective melting process and the high-temperature mechanical properties of the obtained material.

[0084] A method for preparing a high-entropy alloy-based composite material, comprising:

[0085] 1. Composite Powder Preparation: First, a high-entropy alloy master ingot was prepared according to the mass ratio of Ni 22%, Co 28.5%, Cr 16.5%, W 15%, Mo 8%, Nb 6%, and Al 4%. This ingot was then atomized with argon gas to obtain low-oxygen spherical matrix powder. Subsequently, 40 g of TiC powder with a median particle size of 3.8 μm, 30 g of TiN powder with a median particle size of 4.3 μm, 15 g of SiC powder with a median particle size of 3.2 μm, 5 g of ZrC powder with a median particle size of 4.6 μm, 5 g of WC powder with a median particle size of 4.0 μm, and 5 g of Si3N4 powder with a median particle size of 3.6 μm (total additives) were weighed out. 100 grams of a substrate powder was added as a reinforcing phase and uniformly coated onto the surface of 1.0 kg of matrix powder using a surface bonding process to form a core-shell structure precursor powder with a ceramic phase mass fraction of 9.1%. The core-shell structure precursor powder was then subjected to hydrogen reduction treatment. Finally, after spheroidization treatment in 9 kW induction plasma, a final composite powder with excellent flowability (flowability ≤ 25 s / 50 g) was obtained, and a continuous (Ti,W)C / Ti(C,N) composite film was formed on its surface.

[0086] 2. Forming Process and Microstructure Analysis: Standard mechanical property test specimens were prepared using a laser selective melting (SLM) system. The specific parameters for the SLM process were: laser power 275W, scanning speed 1250mm / s, scanning interval 0.105mm, powder layer thickness 40μm, oxygen content in the forming chamber controlled below 80ppm, and substrate preheating temperature 180℃. The formed specimens underwent hot isostatic pressing (HIP): holding temperature and pressure at 1180℃ and 150MPa for 2 hours.

[0087] Metallographic and transmission electron microscopy (TEM) analyses revealed that the material matrix contained uniformly dispersed ceramic reinforcing phases, primarily composed of TiC and TiN, with sizes ranging from 80 nm to 1.2 μm. An interfacial transition layer of approximately 70-260 nm thickness was formed between the reinforcing phases and the high-entropy alloy matrix, exhibiting clear metallurgical bonding characteristics. The microstructure was further analyzed using scanning electron microscopy (SEM) images as follows. Figure 6 As shown.

[0088] 3. High-Temperature Mechanical Properties: High-temperature tensile tests were conducted at 850℃ in an atmospheric environment. The material's yield strength was 825 MPa, tensile strength was 870 MPa, and elongation after fracture was 8.2%. A high-temperature creep rupture test was performed at 900℃ under a stress of 320 MPa, with a fracture time of 230 hours. Performance data indicate that the material prepared using the process described in this embodiment exhibits over 40% improvement in high-temperature strength and creep rupture life compared to unreinforced high-entropy alloys of the same composition. This is mainly attributed to the effective inhibition of dislocation movement by the multi-scale reinforcing phases and the load transfer strengthening effect brought about by the strong and tough interface.

[0089] Example 3

[0090] This embodiment focuses on examining the applicability of the composite powder of the present invention in laser melting deposition process and its performance in high temperature.

[0091] A method for preparing a high-entropy alloy-based composite material, comprising:

[0092] 1. Powder Preparation and Characterization: To meet the requirements of laser melting deposition process for powder delivery, the powder preparation parameters were adjusted. The high-entropy alloy matrix composition was the same as in Example 1. During the argon atomization stage, the melting temperature was controlled at 1650℃, the atomization pressure was set to 3.8MPa, the guide tube diameter was 4.0mm, and the atomization tower height was 2.5m, resulting in a spherical high-entropy alloy powder matrix with a D50 of 68 micrometers and a wide particle size distribution. The reinforcing phase remained nano-TiC, SiC, ZrC, WC, Si3N4, and TiN (consistent with the reinforcing phase in Example 1). By optimizing the surface bonding process, the amount of adhesive (polyvinyl alcohol) was adjusted to 1.2% of the total mass of the ceramic powder, and the mixture was stirred at 280rpm for 45 minutes in a planetary mixer to ensure the formation of a complete and firm ceramic coating layer on the surface of the coarser alloy particles. After plasma spheroidization, the powder flowability was ≤23s / 50g, meeting the requirements for stable powder delivery.

[0093] 2. Deposition and Microstructure Characterization: Multilayer single-pass deposition experiments were conducted using a laser melting deposition system to prepare bulk materials. The laser melting deposition process parameters were: laser power 1100W, scanning speed 500mm / min, corresponding powder feed tray rotation speed of approximately 2000r / min, carrier gas flow rate 7L / min, and the deposition process was carried out under argon protection, with interlayer cooling to below 150℃.

[0094] The microstructure of the deposited material was observed after undergoing the same hot isostatic pressing treatment: due to the relatively slow cooling rate of the molten pool in laser melting deposition, the size of the reinforcing phase was slightly coarsened, mainly distributed between 0.3-1.8 micrometers, but with good uniformity. The transition layer thickness was approximately 120-300 nanometers, with tight bonding. The microstructure is shown in the scanning electron microscope image below. Figure 7 As shown.

[0095] 3. Performance Verification: High-temperature performance tests were conducted on the deposited material: its high-temperature tensile strength was 935 MPa at 800℃. Its fracture life under 750 MPa stress reached 120 hours, far exceeding that of the matrix material (<40 hours), demonstrating the material's enormous potential for long-term service at high temperatures.

[0096] The results of this embodiment show that the composite powder prepared by the present invention is fully applicable to laser melting deposition process. The prepared material not only has high high-temperature strength, but also exhibits good durability, and has application potential in the fields of repair or coating.

[0097] Example 4

[0098] This embodiment aims to study the microstructure evolution and ultra-high temperature properties of the material system of the present invention under the typical vacuum high-temperature forming environment of electron beam selective melting.

[0099] A method for preparing a high-entropy alloy-based composite material, comprising:

[0100] 1. Powder Adaptability Preparation: Considering that electron beam selective melting processes typically use coarser powders and higher preheating temperatures, targeted adjustments were made to the powder preparation. The composition ratio of the high-entropy alloy matrix powder was the same as in Example 1, and the D50 of the obtained high-entropy alloy matrix powder was adjusted to 82 micrometers. The ratio of the nano-ceramic reinforcing phase remained unchanged as in Example 2. The coating layer thickness was precisely controlled to approximately 0.9 micrometers in the surface bonding process to balance the dissolution and precipitation behavior of the ceramic phase during the forming process. After inductive plasma spheroidization, the powder met the powder laying requirements of the electron beam equipment.

[0101] 2. Vacuum High-Temperature Forming Process: Test samples are prepared in an electron beam selective melting device. The key process parameters are: maintaining a vacuum level of 1.8 × 10⁻⁶. -3 The parameters are: mbar, accelerating voltage 60kV, electron beam focusing current corresponding to power 4800W, scanning speed 900mm / s, and powder layer thickness 60μm. A key feature is the constant substrate preheating temperature of 700℃ to minimize thermal stress.

[0102] 3. Microstructure and Ultra-high Temperature Performance: Benefiting from the vacuum environment and high preheating temperature, the sample exhibits extremely high density (>99.98%). Scanning electron micrographs of the microstructure are shown below. Figure 8 As shown, microstructural analysis reveals a uniform distribution of the reinforcing phase. However, due to significant thermal cycling, the average size of the in-situ precipitated phase is larger than that obtained by laser processing, with the main phase size ranging from 0.4 to 2 micrometers. Simultaneously, high-density nanoscale secondary carbides precipitate in the matrix. The transition layer thickness is approximately 150-220 nanometers, exhibiting high interfacial bonding strength.

[0103] The material underwent rigorous ultra-high temperature performance testing: at 1000℃, its high-temperature tensile strength remained at 625 MPa. Under stress conditions of 980℃ and 200 MPa, its creep rupture life reached 150 hours, demonstrating considerable load-bearing capacity and durability even near the temperature limits of traditional nickel-based superalloys. This embodiment verifies the excellent compatibility of the material system of this invention with electron beam selective melting technology and its great potential in hot-end component applications requiring higher operating temperatures.

[0104] Example 5: Changing the composition ratio of high-entropy alloy matrix

[0105] The high-entropy alloy was prepared according to the following mass percentages: Ni 25%, Co 32%, Cr 12%, W 10%, Mo 12%, Nb 5%, and Al 4%. The remaining preparation steps were the same as in Example 1, including coating with the same proportion of ceramic phase (TiC, etc.), plasma spheroidization, and laser selective melting processes.

[0106] Results Comparison: Cracks appeared during the forming process, and the density decreased. The high-temperature (850℃) tensile strength was 520MPa, and the creep rupture life (900℃ / 300MPa) was only 45 hours. Although high-entropy alloy-based composite materials can be prepared, their performance is far lower than that of Example 1 (860MPa, 220 hours).

[0107] Analysis: Compositional imbalance leads to coarsening of the precipitated phase, decreased thermal stability, increased mismatch between the thermal expansion coefficients of the matrix and the ceramic phase, and poorer interfacial bonding.

[0108] Example 6: Changing the ceramic phase content

[0109] High-entropy alloy matrix powder with the same composition ratio as in Example 1 was used. The total addition amount of ceramic phase (TiC, SiC, etc.) was increased to 30% (mass fraction), and the coating process was the same as in Example 1. The plasma spheroidization and laser selective melting process parameters were kept consistent with those in Example 1.

[0110] Results Comparison: The powder had poor flowability (flowability test > 50s / 50g), unstable powder feeding, and high porosity in the formed parts. The reinforcing phase aggregated, forming brittle ceramic clusters in some areas, and the high-temperature tensile properties decreased (tensile strength only 610MPa), lower than in Example 1.

[0111] Analysis: Excessive ceramic content leads to uneven coating, powder agglomeration, and the ceramic phase in the molten pool cannot fully dissolve / diffuse, resulting in structural defects.

[0112] Example 7: Changing plasma spheroidization parameters

[0113] The same adhesive composite powder as in Example 1 was used. During plasma spheroidization, the beam current was set to 300A, the main gas flow rate was set to 100SCFH, and the remaining steps were the same as in Example 1.

[0114] Results comparison: The sphericity was low, the powder still contained many irregular particles, and the flowability was ≤40s / 50g. Laser absorption was unstable during the forming process, the molten pool fluctuated greatly, and incomplete fusion defects appeared inside the sample.

[0115] Analysis: Insufficient plasma beam current and gas flow rate lead to insufficient energy, preventing the powder from fully melting and spheroidizing, which affects the stability of subsequent additive manufacturing processes. Although high-entropy alloy-based composite materials can still be prepared, their performance is far lower than that of Example 1.

[0116] Example 8: Changing additive manufacturing process parameters

[0117] The same high-entropy alloy-based composite powder as in Example 1 was used. During selective laser melting, the laser power was set to 150W, the scanning speed was maintained at 1200mm / s, and the remaining steps were consistent with those in Example 1.

[0118] Results Comparison: Insufficient penetration depth, poor interlayer bonding, and reduced density. The ceramic phase could not fully integrate into the matrix, resulting in a weak reinforcing effect. The high-temperature strength was comparable to that of the matrix alloy (approximately 600 MPa), but lower than that of Example 1.

[0119] Analysis: Insufficient energy input leads to a short molten pool life, insufficient in-situ reaction between the ceramic phase and the matrix, and indistinct multi-scale dispersed strengthening phase and gradient interface.

[0120] Comparative example: Elimination of the plasma spheroidization step

[0121] The coated adhesive composite powder from Example 1 was directly used for laser selective melting (without plasma spheroidization). All other process parameters were the same as in Example 1.

[0122] Results comparison: The powder morphology was irregular, the flowability was poor (≥60s / 50g), the auxiliary powder was uneven, and the surface roughness of the molded parts was high. The distribution of the reinforcing phase was extremely uneven, and local enrichment led to the initiation of microcracks, resulting in a high-temperature durability of less than 30 hours.

[0123] Analysis: Plasma spheroidization not only improves powder flowability, but also promotes interfacial bonding by forming a dense ceramic composite film in situ at high temperature; skipping this step will prevent the achievement of core-shell structure uniformity and interfacial strengthening.

[0124] in conclusion

[0125] A comparison of the proportions and examples shows that: when the high-entropy alloy composition is within the preferred range of this application, it can ensure the thermal stability of the matrix and the compatibility with the ceramic phase; the ceramic phase content is controlled at 2%-22%, which can optimize the process and will not lead to structural defects; the plasma spheroidization parameters are within the preferred range of this application, which can ensure the sphericity of the powder and the interface reaction; the use of a special inorganic adhesive can form a strong and tough interface; the additive manufacturing process window is within the preferred range of this application, which can ensure sufficient metallurgical reaction in the molten pool; the plasma spheroidization step is indispensable, otherwise the core-shell structure optimization and interface strengthening cannot be achieved.

[0126] The above embodiments and comparative examples further confirm that, when carried out within the range of components, process parameters and steps defined in the claims of this invention, high-entropy alloy-based composite materials with uniform structure, strong and tough interfaces and high performance can be obtained.

[0127] In summary, this invention, through full-chain technological innovation, effectively solves the core problems of uneven distribution of reinforcing phases, weak interfacial bonding, and poor process stability in additive manufacturing of high-entropy alloy-based composite materials, significantly improving the high-temperature tensile strength and durability of the materials, making them particularly suitable for hot-end components of aero-engines.

[0128] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a high-entropy alloy-based composite material, characterized in that, Includes the following steps: Preparation of high-entropy alloy powder matrix; A cemented composite powder is obtained by coating a high-entropy alloy powder matrix with carbide and / or nitride powders. The adhesive composite powder was reduced to obtain an oxygen-free adhesive composite powder. The oxygen-free adhesive composite powder was subjected to plasma spheroidization treatment to obtain high-entropy alloy-based composite powder. High-entropy alloy-based composite powder was used to obtain a precursor for high-entropy alloy-based composite materials through additive manufacturing; The high-entropy alloy matrix composite precursor was subjected to hot isostatic pressing to obtain the high-entropy alloy matrix composite material. The process of coating a high-entropy alloy powder matrix with carbide and / or nitride powder to obtain a cemented composite powder includes: The carbide and / or nitride powders are mixed with the adhesive to obtain a suspension; The suspension and the high-entropy alloy powder matrix were mixed and stirred, and then dried to obtain the adhesive composite powder. The mass ratio of the carbide and / or nitride powder to the adhesive is 5:2-3, and the viscosity of the suspension is 1.2 Pa·s-1.8 Pa·s; The ceramic phase content of the adhesive composite powder is 2%-22%, and the coating layer thickness of the adhesive composite powder is less than 1μm. The reduction treatment of the adhesive composite powder to obtain anaerobic adhesive composite powder includes: spreading the adhesive composite powder in a container and purging it; after purging, heating and reducing the adhesive composite powder; and cooling it to obtain anaerobic adhesive composite powder. During the heating and reduction process, the gas flow rate was set to 0.5 m³ / s. 3 / h-1.5m 3 / h, increase the temperature to 600℃-700℃ at a rate of 5℃ / min-10℃ / min, hold for 1h-2h, and after holding, continue to increase the temperature to 1000℃-1100℃ at a rate of ≤5℃ / min, and hold for 2h-3h. The process of plasma spheroidizing the oxygen-free adhesive composite powder to obtain high-entropy alloy-based composite powder includes: during the spheroidizing process, the plasma beam current is 610A-360A, the main gas flow rate is 115SCFH-130SCFH, the auxiliary gas flow rate is 9SCFH-11SCFH, the carrier gas flow rate is 9SCFH-13SCFH, and the powder feeding rate is 80g / min-120g / min; after the spheroidizing process, the powder is sieved through a 125-800 mesh sieve, with a single sieve load of 100g-300g, an amplitude of 10mm-20mm, and a time of 20min-40min.

2. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that, The high-entropy alloy powder matrix comprises the following components in the following mass percentage ratios: Ni: 20%-23%, Co: 27%-30%, Cr: 15%-17%, W: 14%-16%, Mo: 7%-9%, Nb: 4%-13%, Al: 1%-4%.

3. The method for preparing a high-entropy alloy-based composite material as described in claim 1 or 2, characterized in that: The high-entropy alloy powder matrix has a particle size of 15μm-120μm, a sphericity of not less than 0.85, a flowability of not more than 30s / 50g, and a loose packing density of not less than 4.00g / cm³. 3 The tapped density is not less than 4.4 g / cm³. 3 The hollow powder rate is no more than 1%, the number of impurities in the powder is no more than 3 particles / 100g, and the oxygen content is less than 0.01%.

4. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that: The preparation of the high-entropy alloy powder matrix includes: preparing the high-entropy alloy powder matrix using argon atomization or plasma rotating electrode method.

5. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that: The particle size of the carbide and / or nitride powder is 2μm-6μm, and the carbide in the carbide and / or nitride powder is at least one of TiC, SiC, ZrC and WC, and the nitride is at least one of Si3N4 and TiN.

6. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that: The adhesive is at least one of polyvinylpyrrolidone, polyacrylic acid, ammonium citrate, and polyvinyl alcohol.

7. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that: The additive manufacturing process includes laser melting deposition, laser selective melting, and electron beam selective melting. The laser melting deposition process parameters include: laser power of 500W-1300W, scanning speed of 400mm / min-1300mm / min, powder feed tray rotation speed of 700r / min-2800r / min, and carrier gas flow rate of 3L / min-11L / min. The laser selective melting process parameters include: laser power of 190W-350W, scanning speed of 800mm / s-1600mm / s, scanning spacing of 0.08mm-0.12mm, and auxiliary powder layer thickness of 2μm-4μm. The electron beam selective melting process parameters include: vacuum degree of 1.5×10⁻⁶. -3 ±1.2×10 -4 mbar, operating voltage 55kV-60kV, electron beam power 3000W-6000W, auxiliary powder layer thickness 50μm-60μm, preheating temperature 300℃-1100℃.

8. The method for preparing a high-entropy alloy-based composite material as described in claim 1, characterized in that: The hot isostatic pressing process includes: a temperature of 1100℃-1250℃, a pressure of 140MPa-160MPa, and a time of 1.75h-2.25h.

9. A high-entropy alloy-based composite material, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

10. The high-entropy alloy-based composite material as described in claim 9, characterized in that: The density of the high-entropy alloy-based composite material is 99.0%-99.9%.

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