A nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder and its preparation method

Abstract

This invention relates to a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder and its preparation method. The invention employs mechanical alloying technology to prepare refractory high-entropy alloy powder. A certain mass fraction and particle size of nano-Al2O3 ceramic particles are mixed into the mechanically alloyed powder, and then wet-mixed ball milling is used to prepare nano-refractory high-entropy metal-ceramic powder, forming a unique and fine multiphase reinforced microstructure. This invention simultaneously disperses nano-Al2O3 ceramic particles into the mechanically alloyed nano-refractory high-entropy alloy powder, enhancing its application potential. The powder prepared using this method can be used in processes such as vacuum hot pressing sintering, spark plasma sintering, or laser cladding after spray granulation.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy, specifically to a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder and its preparation method. Background Technology

[0002] The high-temperature environments faced by cutting-edge fields such as aerospace, nuclear reactors, and ground-based gas turbines are becoming increasingly harsh and complex. Nickel-based superalloy structural materials, as mature materials in these fields, have shown significant deficiencies in high-temperature stability and resistance (the ultimate service temperature of superalloys is ~1350℃). In 2010, Senkov et al. at the U.S. Air Force Research Laboratory developed two pioneering classic refractory high-entropy alloys, NbMoTaW and NbMoTaWV. Their mechanical properties differ from traditional nickel-based superalloys. In high-temperature environments of ~800℃, the yield strength of these two refractory high-entropy alloys remains almost unchanged, while many superalloys (such as Inconel 718 and Haynes 230) soften in this temperature range. Furthermore, these two refractory high-entropy alloys still possess a yield strength greater than 400 MPa at 1600℃. In the design and development of alloy materials, it is generally necessary to follow the interaction between dislocations and crystal defects. Traditional strengthening theories in metallic materials science, such as solid solution strengthening, deformation strengthening, grain refinement strengthening, precipitation strengthening, dispersion strengthening, and second-phase strengthening, can still serve as the theoretical foundation for the research of refractory high-entropy alloys. In terms of material preparation, the technique of dispersively incorporating nano-ceramic particles (such as Al2O3, ZrB2, HfN, TiB2, etc.) is employed to further control the room-temperature and high-temperature mechanical properties of these refractory high-entropy alloys, obtaining refractory high-entropy alloy composite materials with fully synergistically strengthened and toughened fine nano-microstructures. These composites have the potential to replace nickel-based superalloys as ideal ultra-high-temperature load-bearing structural materials (service standards for ultra-high-temperature load-bearing structural materials >1800℃). Currently, one research direction in this field is to develop new schemes for refractory high-entropy alloys that can improve both room-temperature and high-temperature mechanical properties. Summary of the Invention

[0003] The purpose of this invention is to provide a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder and its preparation method. This method prepares mechanically alloyed nano-refractory high-entropy alloy powder while simultaneously dispersing nano-Al2O3 ceramic particles, thereby improving its application potential and enhancing its room temperature and high temperature mechanical properties.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0005] A method for preparing a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder, characterized by comprising the following steps:

[0006] S1: Dry, weigh, and proportion the refractory high-entropy metal powder, which consists of 5+X metal elements, including 5 mandatory metal elements, namely Nb, Mo, Ta, W, and V, and X optional metal elements, where X is an integer between 0 and 5. The optional metal elements are selected from Hf, Re, Cr, Zr, and Ti; the mass fraction of each metal element is 0.8-1.2.

[0007] S2: Place the weighed refractory high-entropy metal powder into a ball mill jar, add cemented carbide grinding balls according to the ball-to-powder ratio, and add process control agent to increase powder flowability and prevent oxidation;

[0008] S3: After evacuating the ball mill jar, fill it with argon or nitrogen gas, and repeat 2-4 times;

[0009] S4: The ball mill jar is placed on the ball mill and the ball milling is carried out in an intermittent rotation mode with alternating forward and reverse low-speed and low-energy ball milling to mix and refine the powder; each ball milling session lasts 30-60 minutes, followed by a 15-minute rest, and then the ball milling is carried out alternately in forward and reverse directions. The rotation speed of the ball mill is 250-300 r / min, and the process is carried out for a total of 5-10 hours.

[0010] S5: The ball milling jar is placed on the ball mill and subjected to intermittent rotary high-energy ball milling to achieve mechanical alloying; each ball milling session lasts 30-60 minutes, followed by a 15-minute rest period, and then alternating forward and reverse ball milling. The ball mill rotation speed is 450-580 r / min, and the process lasts for 50-70 hours.

[0011] S6: The ball mill jar is left to stand in an inert gas atmosphere for 24 hours, and then the top cover of the ball mill jar is opened for passivation. The passivation time is not less than 24 hours.

[0012] S7: Remove the ball mill jar, add an appropriate amount of ball milling media to the ball mill jar, place it on the ball mill and ball mill at low speed and low energy for 2 hours. The rotation speed of the ball mill is 150-200 r / min, until the powder is in the form of a slurry.

[0013] S8: Place the ball mill jar in a vacuum drying oven at 50-80℃ and dry for 12 hours;

[0014] S9: Place the ball mill jar on the ball mill and ball mill at low speed and low energy for 1 hour. The rotation speed of the ball mill is 150-200 r / min. The powder adhering to the inside of the jar and the grinding balls is crushed by impact and eventually completely detached.

[0015] S10: Take the powder out of the ball mill jar and place it in an agate bowl to grind and break up the agglomerated powder.

[0016] S11: Place the powder in an agate ball mill jar; place 10nm-50nm nano-alumina in the agate mill jar, the amount of nano-alumina added is 1-10wt% of the total amount of refractory high-entropy metal powder;

[0017] S12: Place the agate ball milling jar on a ball mill and use the wet grinding and powder mixing method for ball milling. Add zirconium dioxide grinding balls according to the ball-to-material ratio, along with grinding media and powder binder. The ball mill rotation speed is 150-300 r / min. The ball milling time is 10-40 h. The powder binder is used to ensure that the nano-reinforced phase is tightly coated on the surface of the refractory high-entropy alloy phase.

[0018] S13: Place the agate ball milling jar in a vacuum drying oven at 50-80℃ and dry for 12 hours;

[0019] S14: Place the agate ball milling jar on the ball mill and ball mill at low speed and low energy for 1 hour. The rotation speed of the ball mill is 150-200 r / min.

[0020] S15: Take the powder out of the agate ball mill jar, put it in the agate round bowl, and grind it into powder;

[0021] S16: Use a 400-mesh stainless steel inspection sieve for sieving, separation, and packaging.

[0022] To optimize the above technical solution, the specific measures also include:

[0023] Furthermore, in step S2, the total amount of refractory high-entropy metal powder occupies 1 / 3 of the ball mill jar space, and the internal operating space occupies 1 / 3 of the ball mill jar space.

[0024] Furthermore, in step S2, cemented carbide grinding balls of different diameters are added at a ball-to-material ratio of 8:1 to 15:1.

[0025] As a preferred option, one ball configuration involves adding 16 cemented carbide grinding balls of two different diameters. Carbide grinding balls and 100 Carbide grinding balls.

[0026] As a preferred option, one ball configuration involves adding 5 different diameter cemented carbide grinding balls: 2 Carbide grinding balls, 13 Carbide grinding balls, 56 Carbide grinding balls, 56 Carbide grinding balls and 18 Carbide grinding balls.

[0027] Further, in step S2, the process control agent is a mixture of industrial anhydrous ethanol and stearic acid, wherein the industrial anhydrous ethanol accounts for 2.0-3.0 wt% of the total amount of refractory high entropy metal powder, and the stearic acid accounts for 0.5%-3.0 wt% of the total amount of refractory high entropy metal powder.

[0028] Furthermore, in step S7, the milling media is industrial anhydrous ethanol, and the amount of milling media used is 8-12 wt% of the total amount of refractory high-entropy metal powder.

[0029] Further, in step S12, the ball-to-material ratio is 2:1-5:1; preferably, 100 balls can be used. Zirconia grinding balls, 16 Zirconia grinding balls.

[0030] Further, in step S12, the ball milling media is industrial anhydrous ethanol, and the volume ratio of the total amount of refractory high-entropy metal powder to industrial anhydrous ethanol is 1:2; the powder binder is polyvinyl butyral resin (PVB) or polyvinyl alcohol, and the amount of powder binder is 1.0 to 2.0 wt% of the total amount of refractory high-entropy metal powder.

[0031] This invention also protects the nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder prepared by the above method.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention uses mechanical alloying technology to prepare refractory high-entropy alloy powder. A certain mass fraction and a certain particle size of nano-Al2O3 ceramic particles are mixed into the mechanically alloyed powder, and nano-refractory high-entropy metal ceramic powder is prepared by wet mixing ball milling, forming a special and fine multiphase reinforced microstructure.

[0034] The material of this invention further modulates its room temperature and high temperature strength and toughness with nano-Al2O3, ultimately forming a multiphase nano-ceramic phase dispersion-strengthened nano-metal ceramic powder. This material has the application potential to prepare ideal ultra-high temperature load-bearing structural materials.

[0035] The powder prepared using the method of the present invention can be used in processes such as vacuum hot pressing sintering, spark plasma sintering, or laser cladding after spray granulation, which helps to increase mechanical properties such as strength and toughness, and can also improve antioxidant properties. Attached Figure Description

[0036] Figure 1 XRD pattern of NbMoTaWV refractory high-entropy alloy prepared in Example 1 as a function of ball milling time.

[0037] Figure 2 Example 1: Surface scanning EDS energy dispersive spectroscopy analysis of NbMoTaWV refractory high entropy alloy powder after 70 hours of mechanical alloying.

[0038] Figure 3 Example 1: Powder map of nano-Al2O3 (~10nm) uniformly dispersed in NbMoTaWV refractory high-entropy alloy.

[0039] Figure 4 Example 2: Powder map of nano-Al2O3 (~10nm) uniformly dispersed in NbMoTaWV refractory high-entropy alloy. Detailed Implementation

[0040] The present invention will be further described in detail below through embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0042] Example 1

[0043] Preparation of a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder:

[0044] S1: Dry, weigh, and proportion the refractory high-entropy metal powder. The refractory high-entropy metal powder is composed of refractory elements Nb, Mo, Ta, W, and V, with a mass ratio of 1:1:1:1:1.

[0045] S2: Place the weighed refractory elemental powders into a ball mill jar, and add five different diameter cemented carbide grinding balls at a ball-to-powder ratio of 8:1. (2) (13) (56), (56), (18); the powder volume occupies 1 / 3, and the internal operating space occupies 1 / 3; in order to increase the flowability of the powder and prevent oxidation, process control agents of 2.0 wt% industrial anhydrous ethanol and 0.5 wt% stearic acid are used.

[0046] S3: After evacuating the ball mill jar, fill it with argon or nitrogen, and repeat twice;

[0047] S4: The ball mill jar is placed on the ball mill and the ball milling is carried out in an intermittent rotation mode with alternating forward and reverse directions at low speed and low energy to mix and refine the powder; each ball milling session lasts 30 minutes, with a 15-minute break in between, alternating forward and reverse directions; the ball milling is carried out at low speed and low energy for 5 hours, and the ball mill rotation speed is 300 r / min.

[0048] S5: The ball mill jar is placed on the ball mill for high-energy ball milling and mechanical alloying. The ball milling time is 70 hours, and the ball mill rotation speed is 580 r / min. The ball milling still adopts an intermittent rotation mode, with 30 minutes of ball milling followed by a 15-minute rest, alternating between forward and reverse rotation.

[0049] S6: The ball mill jar is left to stand in an argon glove box for 24 hours, and then the top cover of the ball mill jar is opened for passivation. The passivation time is not less than 24 hours.

[0050] S7: Add industrial anhydrous ethanol to the ball mill jar, the amount of which is 8wt% of the total amount of refractory high entropy metal powder. Place it on the ball mill and rotate it at low speed for 2 hours. The rotation speed of the ball mill is 200r / min, until the powder is in the form of a slurry.

[0051] S8: Place the ball mill jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0052] S9: Place the grinding jar on the ball mill and rotate it at low speed and low energy for 1 hour. The ball mill rotates at 200 r / min. The powder adhering to the inside of the jar and the grinding balls is crushed by impact and eventually completely detached.

[0053] S10: Place the refractory high-entropy alloy powder in an agate mortar and grind it thoroughly to break up any agglomerated powder.

[0054] S11: Place the refractory high-entropy alloy powder in an agate ball milling jar; place 10nm nano-alumina, comprising 1wt% of the total amount of the refractory high-entropy metal powder, into the aforementioned agate milling jar;

[0055] S12: Place the agate ball mill jar on a ball mill and use the wet grinding method to ball mill the powder. Use zirconium dioxide grinding balls with a ball-to-powder ratio of 2:1. Use industrial anhydrous ethanol as the grinding media (volume ratio: powder / anhydrous ethanol = 1 / 2). The ball milling speed is 300 r / min. The ball milling time is 10 h. The powder binder is PVB (2 wt% of the total amount of refractory high entropy metal powder).

[0056] S13: Place the agate ball milling jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0057] S14: Place the agate ball milling jar on the ball mill and ball mill at low speed and low energy for 1 hour. The rotation speed of the ball mill is 200 r / min.

[0058] S15: Place the refractory high-entropy metal-ceramic composite powder in an agate bowl and grind it into powder.

[0059] S16: Separate the samples by sieving them through a 200mm diameter laboratory standard stainless steel test sieve (400 mesh) and then seal them in a plastic bottle or vacuum bag.

[0060] Example 2

[0061] Preparation of a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder:

[0062] S1: Dry, weigh, and proportion the refractory high-entropy metal powder. The refractory high-entropy metal powder is composed of refractory elements Nb, Mo, Ta, W, and V, with a mass ratio of 1:1:1:1:1.

[0063] S2: Place the weighed elemental powders into a ball mill jar, and add two types of carbide grinding balls of different diameters at a ball-to-powder ratio of 15:1. (16); (100 pieces); To increase the flowability of the powder and prevent oxidation, process control agents of 3.0 wt% industrial anhydrous ethanol and 3.0 wt% stearic acid were used.

[0064] S3: After evacuating the ball mill jar, fill it with argon or nitrogen gas, and repeat 4 times;

[0065] S4: The ball mill jar is placed on the ball mill and the ball milling is carried out in an intermittent rotation mode with alternating forward and reverse directions at low speed and low energy to mix and refine the powder; each ball milling session lasts 30 minutes, with a 15-minute break in between, alternating forward and reverse directions; the ball milling is carried out at low speed and low energy for 5 hours, and the ball mill rotation speed is 250 r / min.

[0066] S5: The ball mill jar is placed on the ball mill for high-energy ball milling and mechanical alloying. The ball milling time is 50 hours, and the ball mill rotation speed is 500 r / min. The ball milling still adopts an intermittent rotation mode, with 30 minutes of ball milling followed by a 15-minute rest, alternating between forward and reverse rotation.

[0067] S6: The ball mill jar is left to stand in an argon glove box for 24 hours, and then the top cover of the ball mill jar is opened for passivation. The passivation time is not less than 24 hours.

[0068] S7: Add industrial anhydrous ethanol to the ball mill jar, the amount of which is 10wt% of the total amount of refractory high entropy metal powder, place it on the ball mill and rotate it at low speed for 2 hours. The ball mill rotation speed is 150r / min, until the powder is in the form of a slurry.

[0069] S8: Place the ball mill jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0070] S9: Place the ball mill jar on the ball mill and ball mill at low speed and low energy for 1 hour. The ball mill rotates at 150 r / min. The powder adhering to the inside of the jar and the grinding balls is crushed by impact and eventually completely detached.

[0071] S10: Place the refractory high-entropy alloy powder in an agate mortar and grind it thoroughly to break up any agglomerated powder.

[0072] S11: Place the refractory high-entropy alloy powder in an agate ball milling jar; place 5 wt% of the total amount of refractory high-entropy metal powder, consisting of 10 nm nano-alumina, into the aforementioned agate milling jar;

[0073] S12: Place the agate ball mill jar on a ball mill and use the wet grinding method to ball mill the powder. Use zirconium dioxide grinding balls with a ball-to-powder ratio of 2:1. Use industrial anhydrous ethanol as the grinding media (volume ratio: powder / anhydrous ethanol = 1 / 2). The ball milling speed is 300 r / min. The ball milling time is 20 h. The powder binder is PVB (1.0 wt%).

[0074] S13: Place the agate ball milling jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0075] S14: Place the agate ball mill jar on the ball mill and rotate it at a low speed and low energy for 1 hour. The rotation speed of the ball mill is 200 r / min.

[0076] S15: Place the refractory high-entropy metal-ceramic composite powder in an agate bowl and grind it into powder.

[0077] S16: Separate the samples by sieving them through a 200mm diameter laboratory standard stainless steel test sieve (400 mesh) and then seal them in a plastic bottle or vacuum bag.

[0078] Example 3

[0079] Preparation of a nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder:

[0080] S1: Dry, weigh, and proportion the refractory high entropy metal powder. The refractory high entropy metal powder is composed of refractory elements Nb, Mo, Ta, W, V, and Re, with a mass ratio of 1:1:1:1:1:1.

[0081] S2: Place the weighed powders of several elements into a ball mill jar, and add two types of cemented carbide grinding balls of different diameters at a ball-to-powder ratio of 8:1; to increase the flowability of the powder and prevent oxidation, use 2.0 wt% industrial anhydrous ethanol and 0.5 wt% stearic acid as process control agents.

[0082] S3: After evacuating the ball mill jar, fill it with argon or nitrogen, and repeat twice;

[0083] S4: The ball mill jar is placed on the ball mill and the ball milling is carried out in an intermittent rotation mode with alternating forward and reverse directions at low speed and low energy to mix and refine the powder; each ball milling session lasts 60 minutes, with a 15-minute break in between, alternating forward and reverse directions; the ball milling is carried out at low speed and low energy for 10 hours, and the rotation speed of the ball mill is 300 r / min;

[0084] S5: The ball mill jar is placed on the ball mill for high-energy ball milling and mechanical alloying. The ball milling time is 70 hours, and the ball mill rotation speed is 580 r / min. The ball milling still adopts an intermittent rotation mode, with 60 minutes of ball milling followed by a 15-minute rest period, alternating between forward and reverse rotation.

[0085] S6: The ball mill jar is left to stand in an argon glove box for 24 hours, and then the top cover of the ball mill jar is opened for passivation. The passivation time is not less than 24 hours.

[0086] S7: Add industrial anhydrous ethanol to the ball mill jar, the amount of which is 12wt% of the total amount of refractory high entropy metal powder, place it on the ball mill and rotate it at low speed for 2 hours. The ball mill rotation speed is 200r / min, until the powder is in the form of a slurry.

[0087] S8: Place the ball mill jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0088] S9: Place the grinding jar on the ball mill and rotate it at low speed and low energy for 1 hour. The ball mill rotates at 200 r / min. The powder adhering to the inside of the jar and the grinding balls is crushed by impact and eventually completely detached.

[0089] S10: Place the refractory high-entropy alloy powder in an agate mortar and grind it thoroughly to break up any agglomerated powder.

[0090] S11: Place the refractory high-entropy alloy powder in an agate ball milling jar; place 8 wt% of the total amount of refractory high-entropy metal powder, consisting of 50 nm nano-alumina, in the above-mentioned agate milling jar;

[0091] S12: Place the agate ball mill jar on a ball mill and use the wet grinding and powder mixing method for ball milling. Use zirconium dioxide grinding balls with a ball-to-powder ratio of 5:1. Use industrial anhydrous ethanol as the grinding medium (volume ratio: powder / anhydrous ethanol = 1 / 2). The ball milling speed is 150 r / min. The ball milling time is 40 h. The powder binder is polyvinyl alcohol (1.0 wt%).

[0092] S13: Place the agate ball milling jar in an 80℃ vacuum drying oven and dry for 12 hours;

[0093] S14: Place the agate ball mill jar on the ball mill and rotate it at low speed and low energy for 1 hour. The rotation speed of the ball mill is 150 r / min.

[0094] S15: Place the refractory high-entropy metal-ceramic composite powder in an agate bowl and grind it into powder.

[0095] S16: Separate the samples by sieving them through a 200mm diameter laboratory standard stainless steel test sieve (400 mesh) and then seal them in a plastic bottle or vacuum bag.

[0096] Example 4

[0097] The XRD pattern of the nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder prepared in Example 1 was determined, as follows: Figure 1 The study showed the evolution of the phase and microstructure of NbMoTaWV refractory high-entropy alloy with increasing ball milling time (0–70 h).

[0098] In Example 1, the melting points of the five refractory metal elements, from highest to lowest, are W→Ta→Nb→Mo→V. X-ray diffraction was used to detect the basic characteristics of the phase and microstructure evolution of this refractory high-entropy alloy, as shown in Table 1. With the extension of the high-energy ball milling mechanical alloying time, the powder underwent significant mechanical alloying and refinement. After 70 hours of high-energy ball milling mechanical alloying, the powder grain size reached a scale of 30 nm.

[0099] Table 1. Evolution characteristics of phases and microstructure of NbMoTaWV refractory high-entropy alloys

[0100]

[0101] EDS energy dispersive spectroscopy analysis to determine the mutual solubility of the five refractory metal elements in Example 1, such as... Figure 2 This shows that the five refractory metal elements are basically homogeneous and miscible.

[0102] The results of ball milling wet mixing methods in Examples 1 and 2, with the addition of 1 wt% and 5 wt% of 10 nm nano-Al2O3 respectively, showed the uniform dispersion distribution of the nano-Al2O3. Figure 3 , Figure 4 The nano-Al2O3 ceramic reinforcing phase is dispersed in the refined NbMoTaWV refractory high-entropy alloy powder. The nano-Al2O3 is encapsulated and agglomerated on the surface of the NbMoTaWV refractory high-entropy alloy nanocrystals with a large number of defects. The nano-Al2O3 and NbMoTaWV refractory high-entropy alloy have good adsorption and binding properties, which fully prepares the preparation for the preparation of nano-Al2O3-coated NbMoTaWV refractory high-entropy cermets by spray granulation.

[0103] Example 5

[0104] The nano-alumina-coated reinforced refractory high-entropy metal-ceramic composite powder prepared in Example 1 was used to prepare nano-Al2O3-coated NbMoTaWV refractory high-entropy metal-ceramics by spray granulation, forming particles with a certain particle size distribution to meet the process requirements of laser cladding.

[0105] The refractory high-entropy metal ceramic powder (which still retains the nanoscale) after high-speed homogeneous stirring and dispersion cannot be synchronously fed into laser cladding due to its low particle mass. Spray granulation is required to achieve the ideal powder particle size distribution that meets the requirements of the laser cladding process.

[0106] The process parameters for centrifugal spray drying granulation are as follows: inlet air temperature: 150~190℃; outlet air temperature: 90~95℃; feed pump pressure: 1~3MPa;

[0107] After the spray granulation process, the powder needs to be sieved using an ultrasonic-assisted standard vibrating screen, and the powder particle size should be controlled at 150 mesh (106μm).

[0108] Then, refractory high-entropy alloy composites were prepared using laser cladding. The room temperature and high temperature mechanical properties of the refractory high-entropy alloy composites are evaluated as follows:

[0109] Room temperature yield strength σs≥3000MPa, 1600℃ yield strength σs≥700MPa, 1800℃ yield strength σs≥500MPa; room temperature fracture strain ε≥14%, 1600℃ fracture strain ε≥15%, 1800℃ fracture strain ε≥15%; room temperature compressive strength ≥2000MPa, 1600℃ compressive strength ≥500MPa, 1800℃ compressive strength ≥400MPa; room temperature microhardness: ~1200HV.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a nanometer alumina-coated refractory high-entropy metal ceramic composite powder, characterized in that: The method comprises the following steps: ​ S1: drying, weighing and proportioning refractory high-entropy metal powder, wherein the refractory high-entropy metal powder is composed of 5+X kinds of metal elements, including 5 kinds of metal elements, namely Nb, Mo, Ta, W and V, and X kinds of optional metal elements, wherein X is an integer between 0 and 5, and the optional metal elements are selected from Hf, Re, Cr, Zr and Ti; the mass fraction of each metal element is 0.8-1.2; S2: placing the weighed refractory high-entropy metal powder into a ball mill tank, adding hard alloy grinding balls according to the ball-to-material ratio, and adding a process control agent; S3: after the ball mill tank is vacuumized, argon or nitrogen is filled in, and the operation is repeated 2-4 times; S4: the ball mill tank is placed on a ball mill to adopt an intermittent rotation mode of low-speed and low-energy ball milling in a forward and reverse alternating manner; wherein each ball milling is performed for 30-60 min, followed by a 15-min rest, then the ball milling is performed in a forward and reverse alternating manner, the rotation speed of the ball mill is 250-300 r / min, and the ball milling is performed for a total of 5-10 h; S5: the ball mill tank is placed on a ball mill to adopt an intermittent rotation mode of high-energy ball milling; wherein each ball milling is performed for 30-60 min, followed by a 15-min rest, then the ball milling is performed in a forward and reverse alternating manner, the rotation speed of the ball mill is 450-580 r / min, and the ball milling is performed for a total of 50 h-70 h; S6: the ball mill tank is placed in an inert gas atmosphere for 24 h, then the upper cover of the ball mill tank is opened for passivation, and the passivation time is not less than 24 h; S7: the ball mill tank is taken out, an appropriate amount of ball milling medium is added into the ball mill tank, the ball mill tank is placed on a ball mill for low-speed and low-energy ball milling for 2 h, and the rotation speed of the ball mill is 150-200 r / min, until the powder is in a slurry state; S8: the ball mill tank is placed in a 50-80℃ vacuum drying box for drying for 12 h; S9: the ball mill tank is placed on a ball mill for low-speed and low-energy ball milling for 1 h, and the rotation speed of the ball mill is 150-200 r / min; S10: the powder in the ball mill tank is taken out and placed in a agate bowl, and the agglomerated powder is fully ground and crushed; S11: the powder is placed in an agate ball mill tank, and 10 nm-50 nm nano-aluminum oxide is placed in the agate ball mill tank, and the addition amount of the nano-aluminum oxide is 1-10wt% of the total amount of the refractory high-entropy metal powder; S12: the agate ball mill tank is placed on a ball mill to adopt a wet milling and powder mixing method, zirconium dioxide grinding balls are added according to the ball-to-material ratio, and ball milling medium and a powder binder are added; the rotation speed of the ball mill is 150-300 r / min; and the ball milling time is 10-40 h; S13: the agate ball mill tank is placed in a 50-80℃ vacuum drying box for drying for 12 h; S14: the agate ball mill tank is placed on a ball mill for low-speed and low-energy ball milling for 1 h, and the rotation speed of the ball mill is 150-200 r / min; S15: the powder in the agate ball mill tank is taken out and placed in a agate bowl, and the agglomerated powder is fully ground and crushed; S16: the powder is separated by sieving through a 400-mesh stainless steel sieve and is packaged. In step S12, the ball milling medium is industrial absolute ethanol, the volume ratio of the total amount of refractory high-entropy metal powder to industrial absolute ethanol is 1:2; the powder binder is polyvinyl butyral resin or polyvinyl alcohol, and the amount of the powder binder is 1.0-2.0 wt% of the total amount of refractory high-entropy metal powder.

2. The method for preparing nano-alumina coated refractory high-entropy metal ceramic composite powder according to claim 1, characterized in that: In step S2, the total amount of refractory high-entropy metal powder accounts for 1 / 3 of the space of the ball milling jar, and the running space in the jar accounts for 1 / 3 of the space of the ball milling jar.

3. The method of claim 1, wherein the method is characterized by: In step S2, the hard alloy milling balls of different diameters are added according to a ball-to-powder ratio of 8:1-15:

1.

4. The method of claim 3, wherein the method is characterized by: One ball arrangement scheme is to add hard alloy milling balls of two diameters: 16 φ10 hard alloy milling balls and 100 φ6 hard alloy milling balls.

5. The method of claim 3, wherein the method is characterized by: One ball arrangement scheme is to add hard alloy milling balls of five diameters: 2 φ10 hard alloy milling balls, 13 φ9 hard alloy milling balls, 56 φ8 hard alloy milling balls, 56 φ7 hard alloy milling balls and 18 φ7 hard alloy milling balls.

6. The method of claim 1, wherein the method is characterized by: In step S2, the process control agent is a mixture of industrial absolute ethanol and stearic acid, the amount of industrial absolute ethanol is 2.0-3.0 wt% of the total amount of refractory high-entropy metal powder, and the amount of stearic acid is 0.5%-3.0 wt% of the total amount of refractory high-entropy metal powder.

7. The method of claim 1, wherein the method is characterized by: In step S7, the ball milling medium is industrial absolute ethanol, and the amount of the ball milling medium is 8-12 wt% of the total amount of refractory high-entropy metal powder.

8. The method of claim 1, wherein the method is characterized by: In step S12, the ball-to-powder ratio is 2:1-5:

1.

9. The nano-alumina coated refractory high-entropy metal ceramic composite powder prepared by the method of any one of claims 1-8.

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