A fine-grained cermet with a multi-principal alloy as a bonding metal and a preparation method thereof

Abstract

The present invention relates to a fine-grained cermet with a multi-principal alloy as a binder metal and a preparation method thereof, belonging to the field of hard materials. The present invention aims to solve the application of high- and medium-entropy alloys in the field of hard materials and the problem of high-performance cermets. The present invention optimizes the composition of TiCN-based cermets, develops core technologies such as a flaking treatment technology for atomized powders of CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys used as alloy binder metals, and a two-stage pressure sintering process for improving the wettability of the alloy system by short-term high-temperature impact, thereby obtaining a high-comprehensive-performance TiCN-based cermet with a homogeneous two-phase crystal structure, an average grain size of the hard phase less than 1.0μm, and strong adaptability to various service conditions.

Description

Technical Field

[0001] The invention relates to a fine-grained cermet with a multi-principal-element alloy as a bonding metal and a preparation method thereof, belonging to the fields of powder metallurgy and hard materials. Background Art

[0002] Achieving the ideal balance of high strength and high toughness is a key goal in the research and development of multi-principal-element alloys, namely high-entropy alloys (HEAs) and medium-entropy alloys (MEAs). The material design concepts and significant scientific and technological advances of high- and medium-entropy alloys have greatly promoted the rapid development of new materials and provided new opportunities for the development of new hard materials, such as new cemented carbides and new cermets. In the single-phase face-centered cubic crystal structure of the CoCrFeMnNi multi-principal-element alloy system, both equiatomic CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys exhibit extremely high strength and toughness, thus offering excellent potential to replace the binder metal Ni / Co in cemented carbides and TiCN-based cermets, providing a new opportunity to endow cemented carbides and cermets with unique properties that have yet to be recognized or realized.

[0003] Both CoCrFeNi high entropy alloy and CoCrNi medium entropy alloy contain Cr. Cr is an element that easily forms carbides, which can form Cr3C2, Cr7C3, Cr 23 C6, Cr2C, CrC and other carbides. If chromium carbide exists as an independent phase in the alloy, chromium carbide is very likely to grow anisotropically rapidly, thereby causing obvious microstructure defects and stress concentration to form in the alloy, significantly reducing the strength and toughness of the alloy. In the preparation of hard materials, there are strict requirements for the particle size matching between the raw material powders. Poor particle size matching can easily lead to problems such as alloy densification and microstructure homogeneity degradation. Using single element powder raw materials, preparing Fe, Co, Cr, Ni or Co, Cr, Ni multi-component metals as bonding metals (also known as "bonding metals" in the literature) of cemented carbide or cermet can solve the problem of particle size matching between powders, but due to the presence of carbon in the alloy, single substance Cr easily forms carbides during sintering, so it is very likely that the physical and mechanical properties of the alloy caused by the presence of the chromium carbide third phase are significantly reduced and the performance is unstable.

[0004] Patent application number 201210321098.1, "Titanium Carbonitride-Based Cermets with High-Entropy Alloy Binder Phase and Preparation Method Thereof," discloses that the high-entropy alloy binder phase is composed of at least four of the following: iron, cobalt, nickel, chromium, aluminum, vanadium, titanium, copper, zirconium, molybdenum, manganese, and rare earth elements. The high-entropy alloy binder phase raw materials are elemental powders or / and alloy powders thereof. The patent has 12 examples, none of which utilize high-entropy alloy powders or high-entropy alloy pre-alloy powders. The examples of the patent indicate that the "alloy powders thereof" referred to herein refer to binary master alloy powders, which are components of the high-entropy alloy.

[0005] Adding chromium to high- and medium-entropy alloy powders in a stable alloyed state is an effective measure to prevent the formation of elemental chromium carbide as a third phase during sintering. The most common method for preparing chromium-containing alloy powders is gas atomization, while the most common method for preparing pre-alloyed powders is high-energy ball milling, also known as mechanical alloying. Because Fe, Co, Cr, and Ni are highly active and readily absorb oxygen, high-energy ball milling can easily lead to significant oxygenation and incomplete alloying.

[0006] The new AlFeNiCoCr bonding metal powder involved in the invention patent with application number 201910722025.5 "A metal ceramic based on a new binder, its preparation method and application" is obtained by high-energy ball milling process of elemental powder (single metal powder).

[0007] The invention patent application number is 202111215023.0, "A high-strength and toughness medium-entropy alloy binder phase Ti(C,N)-based cermet and its preparation method", which discloses a method for preparing CoCrNi medium-entropy alloy preformed powder by mechanical alloying, and preparing cermet by a spark plasma sintering process with a pressure of 30-45MPa. There is a clear difference from the traditional sintering mechanism. During the spark plasma sintering process, under high pressure and external field, the oxygen in the CoCrNi medium-entropy pre-alloyed powder prepared by mechanical alloying can be rapidly carbon-thermally reduced. However, due to the constraints of the forming method, products with complex shapes cannot be prepared. Because cermets are mainly used as cutting tools and wear-resistant parts, the use of spark plasma sintering technology has significantly limited its industrial application.

[0008] Patent application number 201810611621.1, "Ultrafine High-Entropy Alloy Binder Phase Cermet and Preparation Method Thereof," discloses a method for using ultrafine high-entropy prealloyed powder as a binder metal for cermets. The ultrafine high-entropy prealloyed powder is composed of Cr, Ni, Fe, Co, Al, and M, where M is selected from at least one of Cu, Zr, Ti, Mo, and rare earth elements. The ultrafine high-entropy prealloyed powder is prepared by melting the components under vacuum or a protective atmosphere, crushing them, and then using high-energy ball milling to obtain a powder with a particle size of 0.4 μm or less. Comparative examples in this patent show that alloys prepared using single element powders exhibit significantly lower performance. The method of melting the components under vacuum or a protective atmosphere, crushing them, and then using high-energy ball milling to obtain a powder with a particle size of 0.4 μm or less suffers from a significantly low yield of fine powder and a tendency to significantly oxidize the powder. This method is clearly unsuitable for high-strength and tough, difficult-to-crush CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys.

[0009] The invention patent application number is 202110476018.9, "A high-strength and toughness high-entropy alloy ceramic and its preparation method", which discloses a method for preparing a metal ceramic with a mass fraction of high-entropy alloy powder as high as 30-45wt% using high-entropy alloy powder with a particle size of ≤10μm as raw material. In the comparative example, the metal ceramic was prepared according to the ratio of 18wt% high-entropy alloy powder CoCrFeNi, 72wt% Ti(C,N) matrix powder, and 10wt% WC+Mo2C strengthening additive powder. The results show that the alloy has uneven hardness distribution (HV 30 1804±15), low strength (bending strength 1434±50MPa) and other problems. Whether it is TiCN cermets or WC-based cemented carbide, the alloy that can meet the needs of actual applications must have a bonding metal mass fraction of ≤30%, usually ≤25%. The theoretical density of TiCN is less than 1 / 3 of the theoretical density of WC. Because the key parameter affecting the hardness and toughness of hard materials is the volume fraction of the bonding phase in the alloy, not the mass fraction. According to the conversion relationship between mass fraction and volume fraction, the mass fraction of bonding metal in TiCN-based cermets that can meet the needs of actual applications is usually between 15 and 25%. Because the method of this invention patent is only suitable for the preparation of cermets with a high entropy alloy bonding metal mass fraction of up to 30 to 45wt%, it is obvious that the application field of this invention patent is limited.

[0010] The mesh size corresponding to a particle size of 10 μm is 1600 mesh. Gas atomization powder production can achieve complete alloying, but there are problems such as coarse particles, difficulty in separating powders with a particle size less than 10 μm, and difficulty in matching the particle size with cemented carbide or other raw material powders of cermets. Summary of the Invention

[0011] The first purpose of the present invention is to develop a fine-grained cermet with a uniform and fine microstructure, excellent comprehensive performance, and a multi-principal alloy as a bonding metal that can better meet the needs of practical applications.

[0012] To achieve the above objectives, based on material calculations and the metal-ceramic material design database established by the inventors, as well as the design principle of alloy composition, microstructure and performance matching, the following composition characteristics of a fine-grained metal-ceramic with a multi-principal alloy as a binder metal of the present invention have been clarified through experimental verification: among the alloy components, the mass fraction of CoCrFeNi high entropy alloy or CoCrNi medium entropy alloy is less than 25% but greater than 15%, WC accounts for 1% of TiC, and the mass fraction of WC accounts for 1% of TiC. x N 1-x The mass fraction of NbC+TaC accounts for 25% to 40% of TiC. x N 1-x The mass fraction of TiC is 10-15%, NbC accounts for 0-30% of the total mass fraction of (NbC+TaC), and Mo2C accounts for 25-30% of the total mass fraction of the multi-principal alloy bonding metal; the TiC x N 1-x Refers to a single TiC 0.5 N 0.5 or TiC 0.7 N 0.3 powder, or TiC 0.5 N 0.5 and TiC 0.7 N 0.3 The multi-principal alloy is a CoCrFeNi high entropy alloy or a CoCrNi medium entropy alloy, wherein the alloy components have an equimolar ratio and constitute a metal ceramic bonding phase after sintering; the metal ceramic alloy microstructure consists of a hard phase and a bonding phase, wherein the bonding phase is uniformly distributed in the alloy without microscopic aggregation, and the average grain size of the hard phase in the alloy is less than 1.0 μm; the hard phase and the bonding phase both have a face-centered cubic crystal structure; the composition of the hard phase is (Ti, M)C x N 1-x During the sintering process, the alloy component TiC 0.5 N 0.5 and / or TiC 0.7 N 0.3 , WC, TaC, NbC, and Mo2C are formed by a multi-component solid solution reaction, where X = 0.5 to 0.7, M = W, Ta, Nb, Mo or M = W, Ta, Mo, representing the alloy components that are solid-dissolved in the hard phase lattice and occupy the position of Ti atoms.

[0013] The CoCrFeNi high-entropy alloy or CoCrNi medium-entropy alloy, i.e., the multi-principal-component alloy, is prepared using a low-cost melt atomization powder making industrialization technology in an argon atmosphere, and has a single phase composition and a face-centered cubic crystal structure; the multi-principal-component alloy powder is sieved through -250 mesh, and the maximum particle size of the powder is ≤58 μm.

[0014] The TiC 0.5 N 0.5 and / or TiC 0.7 N 0.3 The Fisher particle size of the raw material powders of TaC, NbC and Mo2C is less than 1.5 μm; the average particle size of the specific surface area of the WC raw material powder is less than 0.3 μm, and it has high reactivity during the sintering process.

[0015] The design of the alloy system of the present invention not only takes into account the matching of hardness and toughness, and the improvement of the wettability, strength, toughness, and red hardness of the alloy system, but also takes into account the complementary effect of volume expansion and stress minimization of various oxidation products during high-temperature oxidation, as well as the galvanic corrosion inhibition effect in the alloy microstructure in the presence of corrosive liquid media. Therefore, the alloy has strong adaptability to various service conditions and is also very economical.

[0016] The second purpose of the present invention is to develop a low-cost, industrialized preparation technology for fine-grained metal ceramics with a uniform and fine microstructure, excellent comprehensive performance, and a multi-principal alloy as a bonding metal that can better meet the needs of actual applications, so as to promote the quality upgrade of metal ceramics and the expansion of their application fields.

[0017] In order to achieve the above object, the present invention provides a method for preparing a fine-grained cermet with a multi-principal alloy as a binder metal, comprising the following steps:

[0018] A. Flaking of Multi-Principal Component Alloy Atomized Powders: Flaking is achieved using a stirred ball milling process under argon protection, and the wet-milled powder is dried using a vacuum drying process. The multi-principal component alloy atomized powders are CoCrFeNi high-entropy alloys or CoCrNi medium-entropy alloys, with each alloy component having an equimolar ratio. The atomized powders are sieved through -250 mesh to a maximum particle size of 58 μm or less.

[0019] B. Preparation of wet grinding mixture: The multi-principal alloy flake powder, TiC x N 1-x , WC, TaC, NbC, Mo2C are prepared, and a forming agent accounting for 2.3 to 2.5% of the total mass fraction of the powder is added for wet grinding; the result of the preparation should meet the following requirements: in the metal ceramic alloy component, the mass fraction of CoCrFeNi high entropy alloy or CoCrNi medium entropy alloy is less than 25% but greater than 15%, and WC accounts for TiCx N 1-x The mass fraction of NbC+TaC accounts for 25% to 40% of TiC. x N 1-x The mass fraction of TiC is 10-15%, NbC accounts for 0-30% of the total mass fraction of (NbC+TaC), and Mo2C accounts for 25-30% of the total mass fraction of the multi-principal alloy bonding metal; the TiC x N 1-x Refers to a single TiC 0.5 N 0.5 or TiC 0.7 N 0.3 powder, or TiC 0.5 N 0.5 and TiC 0.7 N 0.3 Mixed powder, X = 0.5 ~ 0.7; the TiC 0.5 N 0.5 and / or TiC 0.7 N 0.3 The Fisher particle size of the raw material powders of TaC, NbC and Mo2C is less than 1.5 μm, and the average particle size of the specific surface area of the WC raw material powder is less than 0.3 μm; preferably, the mass fraction of the CoCrFeNi high entropy alloy or the CoCrNi medium entropy alloy is 18-22%;

[0020] C. Drying and granulating the wet-milled mixture: using spray drying granulation or vacuum drying and mechanical granulation to prepare spherical mixture with an average particle size of less than 150 μm;

[0021] D. Powder forming: Based on the shape and size of the product, the forming method is selected in accordance with the requirements of traditional metal ceramic blank production. The forming method includes compression molding. If the product is a bar, in addition to compression molding, dry bag cold isostatic pressing and extrusion molding can also be selected;

[0022] E. Removal of forming agent and sintering: Removal of forming agent and sintering are carried out in a pressure sintering furnace; a two-stage pressure sintering process is adopted to improve the wettability of the alloy system by short-time high-temperature impact. The sintering temperature of the first stage is 1540-1560°C, and the holding time is 10-15 minutes; the sintering temperature of the second stage is 1480-1500°C, and the holding time is 60-100 minutes; after reaching the second stage sintering temperature, high-purity argon gas is introduced to increase the pressure in the sintering furnace, so that the pressure in the sintering furnace reaches 3.0-5.5MPa in the last 40-80 minutes of the holding stage.

[0023] In step A, the stirring paddle speed of the stirred ball mill is 250 to 300 rpm, the mass ratio of the cemented carbide grinding balls to the multi-principal alloy atomized powder is (15 to 20):1, alcohol is used as the wet grinding medium, the liquid level is controlled at 3 to 6 cm, the wet grinding time is 10 to 15 hours, and the ball mill barrel jacket is cooled by cooling water.

[0024] In step B, the forming agent added in the preparation of the wet-milled mixture is polyethylene glycol or paraffin wax, and a drum ball milling process is adopted.

[0025] In step E, after the forming agent is removed, vacuum sintering is carried out; when the temperature rises to 1430-1450°C, high-purity argon is introduced to make the pressure in the sintering furnace reach 5-7 kPa, and this pressure is maintained until the temperature in the sintering furnace reaches the temperature point of the second stage sintering.

[0026] The drum ball milling process adopts alcohol wet grinding medium, controls the liquid level height to be 3 to 6 centimeters, the ball mill speed is 60 to 70% of the critical speed of the ball mill, the mass ratio of carbide grinding balls to mixed materials is (4:1) to (5:1), and the wet grinding time is 50 to 60 hours.

[0027] The critical speed V of the ball mill 临界 =42.4×D -1 / 2 , D is the inner wall diameter of the ball mill barrel, in meters.

[0028] The stirred ball mill and the drum ball mill are both commercial standard equipment.

[0029] The present invention is based on the basic concept of material design and preparation that maximizes the material's properties and follows its nature. Based on the characteristics of high strength, high toughness, and high oxidation resistance of CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys, and according to the working principle of stirred ball milling, a scaly treatment technology for atomized powders of CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys has been developed. This technology enables the low-cost preparation of uniformly composed CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloy powders that match the particle size of other raw material powders of the cermet on a one-dimensional scale. Because CoCrFeNi high-entropy alloys and CoCrNi medium-entropy alloys have excellent plastic deformation capabilities and are easily deformed under forming pressure, high-strength compacts with uniform density can be obtained, which is conducive to sintering densification. Based on the characteristic parameters of the liquid phase appearance temperature and liquid phase vapor pressure of the alloy system, the limiting characteristics of the wettability improvement, and the efficient inhibition of the hard phase grain growth by the slow diffusion effect of high and medium entropy alloys, a two-stage pressure sintering process with short-time high-temperature impact to improve the wettability of the alloy system was developed. This process optimizes the wettability of the alloy system, promotes the rapid diffusion between the hard phase alloy components, promotes the rapid sintering and densification of the alloy under the condition of low liquid phase volume fraction, effectively inhibits the evaporation of the bonding phase alloy components, effectively stabilizes the bonding state of the high and medium entropy alloy components, effectively inhibits the growth of the hard phase grains, and effectively inhibits the formation of the third phase of chromium carbide in the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope photograph of -250 mesh CoCrNi medium entropy alloy gas atomized powder.

[0031] Figure 2 This is a scanning electron microscope photograph of CoCrNi medium entropy alloy powder after scaling treatment.

[0032] Figure 3 TiC in Example 1 0.5 N 0.5 -Scanning electron microscope photograph of the microstructure of 13.0WC-5.3TaC-2.2NbC-6.5Mo2C-22.0CoCrNi metal ceramics.

[0033] Figure 4 This is a scanning electron microscope image of -250 mesh CoCrFeNi high entropy alloy gas atomized powder.

[0034] Figure 5 TiC in Example 2 0.7 N 0.3 -Scanning electron microscope photograph of the microstructure of 19.0WC-5.0TaC-5.5Mo2C-22.0CoCrFeNi metal ceramics.

[0035] Figure 6 TiC in Example 40.5 N 0.5 -25.0TiC 0.7 N 0.3 -16.0WC-6.0TaC-1.5NbC-5.0Mo2C-18.0CoCrFeNi cermet (4 # alloy) (lower position) and gas atomized CoCrFeNi high entropy alloy atomized powder (upper position) and their analysis results. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0037] Example 1

[0038] -250 mesh gas atomized CoCrNi medium entropy alloy powder was used as raw material, and the scanning electron microscope photo of the powder is shown in Figure 1 The powder was flaked by a stirred ball mill crushing process under argon protection. The stirring blade speed was 250 rpm, the mass ratio of carbide grinding balls to multi-principal alloy atomized powder was 15:1, alcohol was used as the wet grinding medium, the liquid level was controlled at 6 cm, the wet grinding time was 15 hours, and the ball mill barrel jacket was cooled by cooling water. The wet-milled powder was dried by a vacuum drying process. The scanning electron microscope photo of the CoCrNi medium entropy alloy powder after flaking is shown in Figure 2 .

[0039] The CoCrNi medium entropy alloy flake powder after the above-mentioned flake treatment is used, and the Feldspar particle sizes of TiC are 1.3, 1.2, 1.4, and 1.3 μm respectively. 0.5 N 0.5 , TaC, NbC, Mo2C powder, and WC powder with an average particle size of 0.25μm are used as raw materials to prepare TiC 0.5 N 0.5 -13.0WC-5.3TaC-2.2NbC-6.5Mo2C-22.0CoCrNi metal ceramics, the values listed in the alloy composition are the mass fractions of each powder component, %.

[0040] A drum ball milling process using alcohol wet milling media was used. The liquid level was maintained at 6 cm, the mill speed was 60% of the critical speed, the mass ratio of carbide grinding balls to the mixed material was 4:1, and the wet milling time was 60 hours. During wet milling, a polyvinyl alcohol (VA) forming agent (2.3% by mass of the total powder) was added. Spherical particles with an average particle size of less than 150 μm were prepared by spray drying and granulation. Round rod specimens were prepared by dry bag cold isostatic pressing. Forming agent removal and sintering were performed in a pressure sintering furnace. After the forming agent is removed at 500°C, vacuum sintering is carried out with a heating rate of 10°C / min, and the temperature is kept at 750°C and 1200°C for 30 minutes respectively. When the temperature rises to 1430°C, high-purity argon is introduced to make the pressure in the sintering furnace reach 7kPa, and the temperature is continued to rise to 1540°C, and kept for 15 minutes. Then, the temperature is reduced to 1480°C at a cooling rate of 10°C / min, and high-purity argon is introduced to increase the pressure in the sintering furnace to 5.5MPa. The temperature is kept at this pressure for 80 minutes, and the total holding time at 1480°C is controlled to be 100 minutes, and then cooled with the furnace. The sintered round rod product will be cut into type B specimens for bending strength testing using a diamond cutting tool. The scanning electron microscope photos of the metal ceramic microstructure in this embodiment are shown in FIG. Figure 3 The test results show that the average grain size of the hard phase in the alloy is 0.8μm.

[0041] Example 2

[0042] -250 mesh gas atomized CoCrFeNi high entropy alloy powder was used as raw material. The scanning electron microscope photo of the powder is shown in Figure 4 The powder was flaked using a stirred ball milling process under argon protection. The stirring paddle speed was 300 rpm, the mass ratio of carbide grinding balls to multi-principal alloy atomized powder was 20:1, the liquid level was controlled at 3 cm, the wet milling time was 10 hours, and the ball mill jacket was cooled by cooling water. The wet-milled powder was dried using a vacuum drying process.

[0043] The CoCrFeNi medium entropy alloy flake powder after the above-mentioned flake treatment is used, and the Fe particle size of TiC is 1.4, 1.2, and 1.3 μm respectively. 0.7 N 0.3 , TaC, Mo2C powder, and WC powder with an average particle size of 0.25μm are used as raw materials to prepare TiC 0.7 N 0.3 -19.0WC-5.0TaC-5.5Mo2C-22.0CoCrFeNi metal ceramics, the values listed in the alloy composition are the mass fractions of each powder component, %.

[0044] A drum-type ball milling process using alcohol wet milling media was used. The liquid level was maintained at 6 cm, the mill speed was 70% of the critical speed, the mass ratio of carbide grinding balls to the mixed material was 5:1, and the wet milling time was 50 hours. Paraffin wax, representing 2.5% of the total powder mass fraction, was added during wet milling to form a spherical mixture with an average particle size of less than 150 μm. Vacuum drying and mechanical granulation were used to produce spherical mixtures. Type B specimens for flexural strength testing were prepared using compression molding. The forming agent was removed and sintering was performed in a pressure sintering furnace. After the forming agent was removed at 500°C, vacuum sintering was carried out with a heating rate of 10°C / min, and the temperature was kept at 780°C and 1250°C for 30 minutes respectively. When the temperature reached 1450°C, high-purity argon was introduced to make the pressure in the sintering furnace reach 5kPa, and the temperature was continued to be raised to 1560°C and kept for 10 minutes. Then, the temperature was lowered to 1500°C at a cooling rate of 10°C / min, and high-purity argon was introduced to increase the pressure in the sintering furnace to 3.0MPa. The temperature was kept at this pressure for 40 minutes, and the total holding time at 1500°C was controlled to be 60 minutes, and then the sintering furnace was cooled. The scanning electron microscope photo of the microstructure of the metal ceramic of this embodiment is shown in FIG. Figure 5 The test results show that the average grain size of the hard phase in the alloy is 0.7μm.

[0045] Example 3

[0046] A -250 mesh atomized CoCrNi medium-entropy alloy powder was used as the raw material. The powder was flaked using a stirred ball mill under argon protection. The stirring speed was 280 rpm, and the mass ratio of carbide grinding balls to atomized multi-principal alloy powder was 18:1. Alcohol was used as the wet milling medium, the liquid level was controlled at 4 cm, and the wet milling time was 12 hours. The ball mill jacket was cooled with cooling water. The wet-milled powder was then dried using a vacuum drying process.

[0047] The CoCrNi medium entropy alloy flake powder after the above-mentioned flake treatment is used, and the TiC 0.7 N 0.3 , TaC, Mo2C powder, and WC powder with an average particle size of 0.25μm are used as raw materials to prepare TiC 0.7 N 0.3 -16.0WC-6.5TaC-5.0Mo2C-18.0CoCrNi metal ceramics, the values listed in the alloy composition are the mass fractions of each powder component, %.

[0048] A drum-type ball milling process using alcohol wet milling media was used. The liquid level was maintained at 5 cm, the mill speed was 65% of the critical speed, the mass ratio of carbide grinding balls to the mixed material was 5:1, and the wet milling time was 56 hours. Paraffin wax, representing 2.3% of the total powder mass fraction, was added during wet milling to form a spherical mixture with an average particle size of less than 150 μm. Type B specimens for flexural strength testing were prepared using a compression molding process. Forming agent removal and sintering were performed in a pressure sintering furnace. After removing the forming agent at 500°C, vacuum sintering was carried out at a heating rate of 10°C / minute. The alloy was then held at 750°C and 1200°C for 30 minutes each. When the temperature reached 1440°C, high-purity argon was introduced to raise the pressure in the sintering furnace to 6kPa. The temperature was then raised to 1550°C and held for 10 minutes. The temperature was then lowered to 1490°C at a cooling rate of 10°C / minute. High-purity argon was then introduced to raise the pressure in the sintering furnace to 4MPa. The alloy was then held at this pressure for 60 minutes, with the total holding time at 1490°C controlled to 80 minutes. The alloy then cooled in the furnace. Test results showed that the average grain size of the hard phase in the alloy was 0.8μm.

[0049] Example 4

[0050] A -250 mesh atomized CoCrFeNi high-entropy alloy powder was used as the raw material. The powder was flaked using a stirred ball mill under argon protection. The stirring speed was 280 rpm, and the mass ratio of carbide grinding balls to atomized multi-principal alloy powder was 18:1. Alcohol was used as the wet milling medium, the liquid level was controlled at 5 cm, and the wet milling time was 12 hours. The ball mill jacket was cooled with cooling water. The wet-milled powder was then dried using a vacuum drying process.

[0051] The CoCrFeNi medium entropy alloy flake powder after the above-mentioned flake treatment is used, and the Fe particle size of TiC is 1.3, 1.4, 1.2, 1.4, 1.3 μm respectively. 0.5 N 0.5 、TiC 0.7 N 0.3 , TaC, NbC, Mo2C powder, and WC powder with an average particle size of 0.25μm are used as raw materials to prepare TiC 0.5 N 0.5 -25.0TiC 0.7 N 0.3 -16.0WC-6.0TaC-1.5NbC-5.0Mo2C-18.0CoCrFeNi metal ceramics, the values listed in the alloy composition are the mass fractions of each powder component, %.

[0052] A drum-type ball milling process using alcohol wet milling media was used. The liquid level was maintained at 5 cm, the mill speed was 65% of the critical speed, the mass ratio of carbide grinding balls to the mixed material was 5:1, and the wet milling time was 50 hours. Paraffin wax, representing 2.5% of the total powder mass fraction, was added during wet milling to form a spherical mixture with an average particle size of less than 150 μm. Vacuum drying and mechanical granulation were used to produce spherical mixtures. Type B specimens for flexural strength testing were prepared using compression molding. Forming agent removal and sintering were performed in a pressure sintering furnace. After removing the forming agent at 500°C, vacuum sintering was carried out at a heating rate of 10°C / minute. The alloy was then held at 780°C and 1250°C for 30 minutes each. When the temperature reached 1450°C, high-purity argon was introduced to increase the pressure in the sintering furnace to 5kPa. The temperature was then raised to 1560°C and held for 10 minutes. The temperature was then lowered to 1500°C at a cooling rate of 10°C / minute. High-purity argon was introduced to increase the pressure in the sintering furnace to 4.0MPa. The alloy was held at this pressure for 40 minutes, with a total holding time of 60 minutes at 1500°C. The alloy then cooled in the furnace. Test results showed that the average grain size of the hard phase in the alloy was 0.7μm.

[0053] X-ray phase analysis results show that the CoCrFeNi high entropy alloy and the CoCrNi medium entropy alloy have a single phase composition and a face-centered cubic crystal structure; the above four groups of alloys do not contain a third phase, and the alloys are composed of a hard phase with a face-centered cubic crystal structure and a bonding phase with a face-centered cubic crystal structure. # The X-ray diffraction phase analysis results of the alloy are shown in Figure 6 . Figure 6 In Example 4, # The X-ray diffraction pattern of the alloy is superimposed on the X-ray diffraction pattern of the gas atomized CoCrFeNi high entropy alloy powder. 0.5 N 0.5 PDF card, using TiC 0.7 N 0.3 PDF card. Since there is no PDF card for CoCrFeNi high entropy alloy, the PDF card for Ni is used. The standard X-ray diffraction peaks of Ni in the figure have been supplemented with dotted lines, and the unmarked peaks all correspond to TiC 0.7 N 0.3 . Comparative Example 4 # The X-ray diffraction patterns of the alloy and CoCrFeNi high entropy alloy show that 4 # The peak positions of the alloy's binder phase correspond well to the strongest and second-strongest peaks of the CoCrFeNi high-entropy alloy. Scanning electron microscopy results show that the corresponding alloys in the four examples all have a distinctively uniform microstructure, with no microscopic aggregation of the binder phase.

[0054] The physical and mechanical properties of the alloys were tested according to relevant national standards. The physical and mechanical properties of the alloys in the four examples are shown in Table 1. The B-type specimens used for the flexural strength test had dimensions of (20±1) mm × (6.5±0.25) mm × (5.25±0.25) mm. As shown in Table 1, all four alloys exhibit excellent physical and mechanical properties.

[0055] Table 1 Physical and mechanical properties of alloys in four examples

[0056]

[0057] Comparative Example 1

[0058] Except for the different sintering processes, the alloy composition and preparation process are the same as those in Example 1. The sintering process of the alloy is as follows: after removing the forming agent at 500°C, vacuum sintering is carried out with a heating rate of 10°C / minute, and the alloy is kept at 750°C and 1200°C for 30 minutes respectively. When the temperature reaches 1430°C, high-purity argon is introduced to increase the pressure in the sintering furnace to 7kPa. The temperature is further increased to 1540°C, and high-purity argon is introduced to increase the pressure in the sintering furnace to 5.5MPa. The alloy is kept at this pressure for 80 minutes, with the total holding time at 1540°C being controlled to be 100 minutes. The alloy is then cooled in the furnace. The sintered round rod product is cut into Type B specimens for flexural strength testing using a diamond cutting tool. Observation and analysis revealed that the alloy was significantly overburned, as evidenced by significant sintering deformation and excessive porosity. The flexural strength test results showed that the alloy had a flexural strength between 1380 and 1790MPa.

[0059] Comparative Example 2

[0060] Except for the different sintering processes, the alloy composition and preparation process are the same as those in Example 1. The sintering process of the alloy is as follows: after removing the forming agent at 500°C, vacuum sintering is carried out at a heating rate of 10°C / minute, and the temperature is maintained at 750°C and 1200°C for 30 minutes respectively. When the temperature reaches 1430°C, high-purity argon is introduced to increase the pressure in the sintering furnace to 7kPa. The temperature is further increased to 1480°C, and high-purity argon is introduced to increase the pressure in the sintering furnace to 5.5MPa. The temperature is maintained at this pressure for 80 minutes, and the total holding time at 1480°C is controlled to be 100 minutes. The alloy is then cooled with the furnace. The sintered round rod product is cut into B-type specimens for flexural strength testing using a diamond cutting tool. The flexural strength test results show that the flexural strength of the alloy is between 1802 and 2114MPa, which is significantly lower than the flexural strength of the alloy in Example 1.

[0061] Comparative Example 3

[0062] The CoCrNi medium entropy alloy was not subjected to flaking treatment, and other experimental raw materials, alloy components and preparation processes were the same as those in Example 1. The flexural strength test results showed that the flexural strength of the alloy was between 780 and 1305 MPa, which was significantly lower than the flexural strength of the alloy in Example 1.

Claims

1. A fine-grained cermet with a multi-principal alloy as a binder metal, characterized by: The multi-principal alloy refers to a CoCrFeNi high entropy alloy or a CoCrNi medium entropy alloy, wherein each alloy component has an equal molar ratio and constitutes a bonding phase of the metal ceramic after sintering; in the metal ceramic, the mass fraction of the CoCrFeNi high entropy alloy or the CoCrNi medium entropy alloy is less than 25% but greater than 15%, and WC accounts for 10% of TiC. x N 1–x The mass fraction of NbC+TaC accounts for 25~40% of TiC. x N 1–x The mass fraction of TiC is 10-15%, NbC accounts for 0-30% of the total mass fraction of (NbC+TaC), and Mo2C accounts for 25-30% of the mass fraction of CoCrFeNi high entropy alloy or CoCrNi medium entropy alloy; the TiC x N 1–x Refers to a single TiC 0.5 N 0.5 or TiC 0.7 N 0.3 powder, or TiC 0.5 N 0.5 and TiC 0.7 N 0.3 The metal ceramic structure consists of a hard phase and a binder phase, wherein the binder phase is evenly distributed in the metal ceramic without micro-aggregation, and the average grain size of the hard phase in the metal ceramic is less than 1.0 μm; the hard phase and the binder phase both have a face-centered cubic crystal structure; the composition of the hard phase is (Ti, M)C x N 1–x , during the sintering process, TiC x N 1–x , WC, TaC, NbC, and Mo2C are formed by multi-component solid solution reactions, where M = W, Ta, Nb, Mo or M = W, Ta, Mo, representing the alloy components that are solid-dissolved in the hard phase lattice and occupy the position of Ti atoms; The method for preparing the fine-grained cermet with the multi-principal alloy as the bonding metal comprises the following steps: A. Flaking of Multi-Principal Component Alloy Atomized Powders: Flaking is achieved using a stirred ball milling process under argon protection, and the wet-milled powder is dried using a vacuum drying process. The multi-principal component alloy atomized powders are CoCrFeNi high-entropy alloys or CoCrNi medium-entropy alloys, with each alloy component having an equimolar ratio. The atomized powders are sieved through 250 mesh to a maximum particle size of ≤58μm. B. Preparation of wet grinding mixture: Mix the multi-principal alloy flake powder prepared in step A with TiC x N 1–x , WC, TaC, NbC, Mo2C are mixed, and a forming agent accounting for 2.3~2.5% of the total mass fraction of the powder is added for wet grinding; the result of the mixing should meet the following conditions: in the metal ceramic, the mass fraction of CoCrFeNi high entropy alloy or CoCrNi medium entropy alloy is less than 25% but greater than 15%, and WC accounts for TiC x N 1–x The mass fraction of NbC+TaC accounts for 25~40% of TiC. x N 1–x The mass fraction of TiC is 10~15%, NbC accounts for 0~30% of the total mass fraction of (NbC+TaC), and Mo2C accounts for 25~30% of the total mass fraction of the multi-principal alloy binder metal; the TiC x N 1–x Refers to a single TiC 0.5 N 0.5 or TiC 0.7 N 0.3 powder, or TiC 0.5 N 0.5 and TiC 0.7 N 0.3 Mixed powder; the TiC x N 1–x The Fisher particle size of the raw material powders of TaC, NbC and Mo2C is less than 1.5 μm, and the average particle size of the specific surface area of the raw material powder of WC is less than 0.3 μm; C. Dry granulation of wet-milled mixture: Spray drying granulation or vacuum drying and mechanical granulation are used to prepare spherical mixture with an average particle size of less than 150 μm; D. Powder forming: Based on the shape and size of the product, the forming method is selected in accordance with the requirements of traditional metal ceramic blank production, and the forming method includes molding; E. Forming agent removal and sintering: Forming agent removal and sintering are carried out in a pressure sintering furnace; after the forming agent is removed, vacuum sintering is carried out; when the temperature rises to 1430~1450℃, high-purity argon is introduced to increase the pressure in the sintering furnace to 5~7kPa, and this pressure is maintained until the temperature in the sintering furnace reaches the temperature point of the second stage sintering. Then, a two-stage pressure sintering process is adopted to improve the wettability of the alloy system with a short high-temperature shock. The first stage sintering temperature is 1540~1560℃, and the holding time is 10~15 minutes; the second stage sintering temperature is 1480~1500℃, and the holding time is 60~100 minutes; after reaching the second stage sintering temperature, high-purity argon is introduced to increase the pressure in the sintering furnace, so that the pressure in the sintering furnace reaches 3.0~5.5MPa in the last 40~80 minutes of the holding stage.

2. The fine-grained cermet with a multi-principal alloy as a binder metal according to claim 1, characterized in that: The multi-principal component alloy is prepared by a melt atomization powder making method in an argon atmosphere, and has a single phase composition and a face-centered cubic crystal structure; the multi-principal component alloy powder is sieved through 250 meshes, and the maximum particle size of the powder is ≤58 μm.

3. The fine-grained cermet with a multi-principal alloy as a binder metal according to claim 1, characterized in that: In step A, the stirring paddle speed of the stirred ball mill is 250-300 rpm, the mass ratio of the cemented carbide grinding balls to the multi-principal alloy atomized powder is (15-20):1, alcohol is used as the wet grinding medium, the liquid level is controlled at 3-6 cm, the wet grinding time is 10-15 hours, and the ball mill barrel jacket is cooled by cooling water.

4. The fine-grained cermet with a multi-principal alloy as a binder metal according to claim 1, characterized in that: In step B, the forming agent added in the preparation of the wet-milled mixture is polyethylene glycol or paraffin wax, and a drum ball milling process is adopted.

5. The fine-grained cermet with a multi-principal alloy as a binder metal according to claim 4, characterized in that: The drum ball milling process uses alcohol wet grinding medium, controls the liquid level height to be 3 to 6 centimeters, the ball mill speed to be 60 to 70% of the critical speed of the ball mill, the mass ratio of carbide grinding balls to mixed materials to be (4:1) to (5:1), and the wet grinding time to be 50 to 60 hours.

6. The fine-grained cermet with a multi-principal alloy as a binder metal according to claim 5, characterized in that: The critical speed V of the ball mill 临界 =42.4×D –1 / 2 , D is the inner wall diameter of the ball mill barrel, in meters.

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