A High-Temperature Oxidation-Resistant Gradient Coating on the Surface of Tantalum-Tungsten Alloy and Its Preparation Method

Abstract

The present invention relates to the field of high-temperature oxidation-resistant coatings, particularly to a high-temperature oxidation-resistant gradient coating on a tantalum-tungsten alloy surface and its preparation method. The coating comprises three layers of oxidation-resistant coatings with gradient composition, ensuring matching thermal expansion coefficients between the coating and substrate, and between the coatings, thereby reducing residual and thermal stresses. The coating is produced by slurry sintering and embedding siliconization, using materials including ZrB2, HfB2, 8YSZ, SiC, SiO2, La2Zr2O7, and Si. Specifically, a coating material is mixed with ethanol, a binder, and a halide, then wet-mixed in a ball mill to form a coating slurry. This slurry is then sprayed onto the substrate surface, filled with embedding powder, and sintered in a vacuum tube furnace to produce the coating. The two subsequent coating processes are repeated to produce the high-temperature oxidation-resistant gradient coating. The developed coating exhibits strong bonding with the tantalum-tungsten alloy substrate, protecting the tantalum-tungsten alloy substrate from oxidative corrosion or slowing down the oxidation rate at elevated temperatures (above 1900°C) for 250 to 1800 seconds.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature anti-oxidation coatings, and in particular to a high-temperature anti-oxidation gradient coating on the surface of a tantalum-tungsten alloy and a preparation method thereof. Background Art

[0002] Tantalum-tungsten alloy has a melting point of up to 3080°C and exhibits excellent high-temperature strength, wear resistance, and creep resistance in high-temperature environments. In the aerospace field, tantalum-tungsten alloy is an excellent material for missile warheads and an ideal candidate for hot components such as valve stems, valve cores, cylinders, and support plates in fast-sealing valves in hypersonic wind tunnel systems.

[0003] However, at 500°C in atmospheric conditions, Ta10W alloys react with oxygen, causing "pest" oxidation. As the temperature rises, the alloy will eventually completely pulverize and break down, limiting the service life and application range of tantalum-tungsten alloys. There are two methods to improve the oxidation resistance of tantalum-tungsten alloys: alloying and surface coating. While alloying affects other alloy properties, coating does not alter the matrix composition, preserving the alloy's high-temperature mechanical properties to the greatest extent possible.

[0004] Research on high-temperature protective coatings for tantalum-tungsten alloys, both domestically and internationally, has primarily focused on temperatures below 1900°C, with little research on protective coatings suitable for temperatures above 1900°C. Furthermore, some tantalum-based alloy components require operating temperatures as high as 1800°C, sometimes requiring short periods of use at 2200°C. These components also require high allowable stresses at high temperatures to ensure safety and reliability in high-temperature, high-pressure environments. Therefore, improving the high-temperature oxidation and thermal shock resistance of tantalum-based alloys above 1900°C is crucial to enabling their application in these high-temperature environments. Summary of the Invention

[0005] The present invention relates to a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy and a preparation method thereof. The coating is composed of three layers of oxidation-resistant coatings with gradient composition changes, so that the thermal expansion coefficients of the coating and the substrate, and between the coatings, are matched, thereby reducing residual stress and thermal stress. The coating can protect the tantalum-tungsten alloy substrate from oxidation corrosion or slow down the oxidation rate at high temperatures for a short period of time.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following raw materials: a first coating material, a second coating material, and a third coating material stacked in sequence;

[0008] The composition of the first coating material is: ZrB2 is 35-40wt%, HfB2 is 5-10wt%, 8YSZ is 11-16wt%, SiC is 2-5wt%, SiO2 is 2-4wt%, and the balance is Si;

[0009] The composition of the second coating material is: ZrB2 is 30-35wt%, HfB2 is 10-15wt%, 8YSZ is 11-16wt%, SiC is 2-5wt%, SiO2 is 2-4wt%, La2Zr2O7 is 5-10wt%, and the balance is Si;

[0010] The components of the above-mentioned third coating material are: ZrB2 is 25~30wt%, HfB2 is 15~20wt%, 8YSZ is 11~16wt%, SiC is 2~5wt%, SiO2 is 2~4wt%, La2Zr2O7 is 10~15wt%, and the balance is Si.

[0011] The present invention provides a method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following steps:

[0012] (1) mixing the first coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a coating slurry;

[0013] (2) spraying the coating slurry obtained in step (1) onto the surface of the substrate, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1100°C to 1300°C for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the first layer of anti-oxidation coating;

[0014] (3) mixing the second coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a coating slurry;

[0015] (4) spraying the coating slurry obtained in step (3) onto the surface of the substrate having the first layer of anti-oxidation coating, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200°C to 1450°C, and keeping the temperature for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form a second layer of anti-oxidation coating;

[0016] (5) mixing the third coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a coating slurry;

[0017] (6) The coating slurry obtained in step (5) is sprayed onto the surface of the substrate having the first and second layers of anti-oxidation coating, and the sprayed substrate is filled with embedding powder and placed in a vacuum tube furnace for sintering. The sintering temperature is 1200°C to 1450°C, and the temperature is kept for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the third layer of anti-oxidation coating.

[0018] More preferably, the particle sizes of the ZrB2 powder, HfB2 powder, 8YSZ powder, SiC powder, SiO2 powder, La2Zr2O7 powder and Si powder are all less than 50 μm, and the purity is greater than 99.9%.

[0019] Further preferably, the binder added in step (1), step (3) and step (5) is 0.3-0.5 wt% of polyvinyl pyrrolidone, the halide is 0.3-0.5 wt% of sodium fluoride, and the embedding powder added in step (2), step (4) and step (6) comprises 30 wt% of silicon powder, 15 wt% of sodium fluoride and 55 wt% of aluminum oxide.

[0020] More preferably, the substrate in step (2), step (4) and step (6) is tantalum-tungsten alloy.

[0021] More preferably, the ball milling process parameters of step (1), step (3) and step (5) are 400 / min and the milling time is 5 to 6 hours.

[0022] More preferably, the total thickness of the high-temperature anti-oxidation gradient coating finally prepared on the surface of the substrate in step (6) is 160 μm to 200 μm.

[0023] More preferably, the steps (2), (4) and (6) use a pneumatic spray gun as the coating spraying tool.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The coating prepared by the present invention is composed of three layers of anti-oxidation coatings with gradient component content. The thermal expansion coefficient changes in a gradient, which effectively alleviates the mismatch between the thermal expansion coefficients of the coating and the alloy, reduces residual stress and thermal stress, and at the same time, there is a certain degree of mutual diffusion between the interlayer structure of the coating and between the coating and the alloy at high temperature, which enhances the bonding strength and anti-shedding ability of the coating.

[0026] (2) The present invention optimizes the proportion of the gradient coating spray slurry and the spraying process through a large number of experiments, so that the prepared coating has better oxidation resistance and thermal shock resistance.

[0027] (3) Tests show that the static anti-oxidation life of the gradient coating specimen prepared by the present invention at 1900°C is not less than 0.5h, and the thermal shock life from 1900°C to room temperature (water cooling) is greater than 50 times; the static anti-oxidation life at 2200°C is not less than 250s, and the thermal shock life from 2200°C to room temperature (water cooling) is greater than 15 times.

[0028] (4) The coating prepared by the present invention generates SiO2 and B2O3 during the oxidation process, which fill the skeleton of ZrO2 and ZrSiO4, and can effectively block the penetration of oxygen, so that the coating exhibits good oxidation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The surface scanning morphology of the coating of Example 1 (probe analysis × 1000);

[0030] Figure 2 This is the X-ray diffraction pattern of the coating surface of Example 1;

[0031] Figure 3 This is the surface scanning morphology of the coating in Example 1 after oxidation at 1900°C (probe analysis ×2000);

[0032] Figure 4 This is the surface X-ray diffraction pattern of the coating in Example 1 after oxidation at 1900°C. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Example 1

[0035] The present invention provides a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following raw materials: a first coating material, a second coating material, and a third coating material;

[0036] The composition of the first coating material is: ZrB2 40wt%, HfB2 10wt%, 8YSZ 16wt%, SiC 5wt%, SiO2 4wt%, and the balance is Si;

[0037] The composition of the second coating material is: ZrB2 is 35wt%, HfB2 is 14wt%, 8YSZ is 16wt%, SiC is 5wt%, SiO2 is 4wt%, La2Zr2O7 is 10wt%, and the balance is Si;

[0038] The components of the third coating material are: ZrB2 is 30wt%, HfB2 is 18wt%, 8YSZ is 16wt%, SiC is 5wt%, SiO2 is 4wt%, La2Zr2O7 is 15wt%, and the balance is Si.

[0039] The particle sizes of ZrB2 powder, HfB2 powder, 8YSZ powder, SiC powder, SiO2 powder, La2Zr2O7 powder and Si powder in the above three coating materials are all less than 50 μm, and the purity is greater than 99.9%.

[0040] The present invention provides a method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following steps:

[0041] (1) Mixing the first coating material with ethanol, a binder, and a halide, placing the mixture in a ball mill and wet-mixing at a speed of 400 r / min for 6 h to prepare a coating slurry;

[0042] (2) using a pneumatic spray gun to spray the coating slurry obtained in step (1) onto the surface of the tantalum-tungsten alloy substrate, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1100° C. for 90 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the first layer of anti-oxidation coating;

[0043] (3) Mix the second coating material with ethanol, a binder, and a halide, place the mixture in a ball mill, and wet-mix at a speed of 400 r / min for 6 h to prepare a coating slurry;

[0044] (4) using a pneumatic spray gun to spray the coating slurry obtained in step (3) onto the surface of the substrate having the first layer of anti-oxidation coating, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200° C. for 90 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form a second layer of anti-oxidation coating;

[0045] (5) Mix the third coating material with ethanol, a binder, and a halide, place the mixture in a ball mill, and wet-mix at a speed of 400 r / min for 6 h to prepare a coating slurry;

[0046] (6) Using a pneumatic spray gun, the coating slurry obtained in step (5) is sprayed onto the surface of the substrate having the first and second layers of anti-oxidation coatings, and the sprayed substrate is filled with embedding powder and placed in a vacuum tube furnace for sintering. The sintering temperature is 1200°C and the temperature is kept for 90 minutes. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form a third layer of anti-oxidation coating.

[0047] The first anti-oxidation coating, the second anti-oxidation coating and the third anti-oxidation coating constitute a high-temperature anti-oxidation gradient coating with a total thickness of 160 μm.

[0048] The surface scanning morphology (probe analysis ×1000) and surface X-ray diffraction patterns of the high-temperature antioxidant gradient coating prepared in this embodiment are as follows: Figure 1 and Figure 2 shown.

[0049] In the above-mentioned high-temperature anti-oxidation gradient coating material on the surface of tantalum-tungsten alloy and its preparation method, the binder added in step (1), step (3) and step (5) is 0.3wt% of polyvinyl pyrrolidone, the halide is 0.3wt% of sodium fluoride, and the embedding powder added in step (2), step (4) and step (6) is composed of 30wt% silicon powder, 15wt% sodium fluoride and 55wt% aluminum oxide.

[0050] The surface scanning morphology (probe analysis × 2000) and surface X-ray diffraction pattern of the high-temperature oxidation-resistant gradient coating prepared in this embodiment after oxidation at 1900°C are shown as follows: Figure 3 and Figure 4 As shown, the coating specimen has a life of 1800s in a static oxidation test at 1900°C and a thermal shock life of 52 times; the coating specimen has a life of 360s in a static oxidation test at 2200°C and a thermal shock life of 15 times.

[0051] Example 2

[0052] The present invention provides a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following raw materials: a first coating material, a second coating material, and a third coating material;

[0053] The composition of the first coating material is: ZrB2 is 35wt%, HfB2 is 5wt%, 8YSZ is 11wt%, SiC is 2wt%, SiO2 is 2wt%, and the balance is Si;

[0054] The composition of the second coating material is: ZrB2 is 30wt%, HfB2 is 10wt%, 8YSZ is 11wt%, SiC is 2wt%, SiO2 is 2wt%, La2Zr2O7 is 5wt%, and the balance is Si;

[0055] The components of the third coating material are: ZrB2 is 25wt%, HfB2 is 15wt%, 8YSZ is 11wt%, SiC is 2wt%, SiO2 is 2wt%, La2Zr2O7 is 10wt%, and the balance is Si.

[0056] The particle sizes of ZrB2 powder, HfB2 powder, YSZ powder, SiC powder, SiO2 powder, La2Zr2O7 powder and Si powder in the above three coating materials are all less than 50 μm, and the purity is greater than 99.9%.

[0057] The present invention provides a method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following steps:

[0058] (1) Mixing the first coating material with ethanol, a binder, and a halide, placing the mixture in a ball mill and wet-mixing at a speed of 400 r / min for 5 h to prepare a coating slurry;

[0059] (2) using a pneumatic spray gun to spray the coating slurry obtained in step (1) onto the surface of the tantalum-tungsten alloy substrate, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200° C. for 80 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the first layer of anti-oxidation coating;

[0060] (3) Mix the second coating material with ethanol, a binder, and a halide, place the mixture in a ball mill, and wet-mix at a speed of 400 r / min for 5 h to prepare a coating slurry;

[0061] (4) using a pneumatic spray gun to spray the coating slurry obtained in step (3) onto the surface of the substrate having the first layer of anti-oxidation coating, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1300° C. for 70 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form a second layer of anti-oxidation coating;

[0062] (5) Using a pneumatic spray gun, the third coating material is mixed with ethanol, a binder, and a halide, and the mixture is placed in a ball mill and wet-mixed at a speed of 400 r / min for 5 h to prepare a coating slurry;

[0063] (6) The coating slurry obtained in step (5) is sprayed onto the surface of the substrate having the first and second layers of anti-oxidation coating, and the sprayed substrate is filled with embedding powder and placed in a vacuum tube furnace for sintering. The sintering temperature is 1400°C and the temperature is kept for 60 minutes. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the third layer of anti-oxidation coating.

[0064] The first anti-oxidation coating, the second anti-oxidation coating and the third anti-oxidation coating constitute a high-temperature anti-oxidation gradient coating with a total thickness of 200 μm.

[0065] In the above-mentioned high-temperature anti-oxidation gradient coating material on the surface of tantalum-tungsten alloy and its preparation method, the binder added in step (1), step (3) and step (5) is 0.4wt% of polyvinyl pyrrolidone, the halide is 0.4wt% of sodium fluoride, and the embedding powder added in step (2), step (4) and step (6) is composed of 30wt% silicon powder, 15wt% sodium fluoride and 55wt% aluminum oxide.

[0066] The coating specimen has a life of 1900s in a static oxidation test at 1900℃ and a thermal shock life of 53 times; the coating specimen has a life of 420s in a static oxidation test at 2200℃ and a thermal shock life of 17 times.

[0067] Example 3

[0068] The present invention provides a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following raw materials: a first coating material, a second coating material, and a third coating material;

[0069] The composition of the first coating material is: ZrB2 37wt%, HfB2 7wt%, 8YSZ 13wt%, SiC 3wt%, SiO2 3wt%, and the balance is Si;

[0070] The composition of the second coating material is: ZrB2 is 32wt%, HfB2 is 12wt%, 8YSZ is 13wt%, SiC is 3wt%, SiO2 is 3wt%, La2Zr2O7 is 7wt%, and the balance is Si;

[0071] The components of the third coating material are: ZrB2 is 27wt%, HfB2 is 17wt%, 8YSZ is 13wt%, SiC is 3wt%, SiO2 is 3wt%, La2Zr2O7 is 12wt%, and the balance is Si.

[0072] The particle sizes of ZrB2 powder, HfB2 powder, YSZ powder, SiC powder, SiO2 powder, La2Zr2O7 powder and Si powder in the above three coating materials are all less than 50 μm, and the purity is greater than 99.9%.

[0073] The present invention provides a method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, comprising the following steps:

[0074] (1) Mixing the first coating material with ethanol, a binder, and a halide, placing the mixture in a ball mill and wet-mixing at a speed of 400 r / min for 5.5 h to prepare a coating slurry;

[0075] (2) using a pneumatic spray gun to spray the coating slurry obtained in step (1) onto the surface of the tantalum-tungsten alloy substrate, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200° C. for 75 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the first layer of anti-oxidation coating;

[0076] (3) Mix the second coating material with ethanol, a binder, and a halide, place the mixture in a ball mill, and wet-mix at a speed of 400 r / min for 5.5 h to prepare a coating slurry;

[0077] (4) using a pneumatic spray gun to spray the coating slurry obtained in step (3) onto the surface of the substrate having the first layer of anti-oxidation coating, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1300° C. for 75 minutes. During the sintering process, when the temperature is below 1000° C., the vacuum gauge pressure in the vacuum tube furnace is less than 0.1 Pa. When the temperature is greater than 1000° C., high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form a second layer of anti-oxidation coating;

[0078] (5) Using a pneumatic spray gun, the third coating material is mixed with ethanol, a binder, and a halide, and the mixture is placed in a ball mill and wet-mixed at a speed of 400 r / min for 5.5 h to prepare a coating slurry;

[0079] (6) The coating slurry obtained in step (5) is sprayed onto the surface of the substrate having the first and second layers of anti-oxidation coating, and the sprayed substrate is filled with embedding powder and placed in a vacuum tube furnace for sintering. The sintering temperature is 1300°C and the temperature is kept for 75 minutes. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the substrate is cooled with the furnace to form the third layer of anti-oxidation coating.

[0080] The first anti-oxidation coating, the second anti-oxidation coating and the third anti-oxidation coating constitute a high-temperature anti-oxidation gradient coating with a total thickness of 170 μm.

[0081] In the above-mentioned high-temperature anti-oxidation gradient coating material on the surface of tantalum-tungsten alloy and its preparation method, the binder added in step (1), step (3) and step (5) is 0.4wt% of polyvinyl pyrrolidone, the halide is 0.4wt% of sodium fluoride, and the embedding powder added in step (2), step (4) and step (6) is composed of 30wt% silicon powder, 15wt% sodium fluoride and 55wt% aluminum oxide.

[0082] The coating specimen has a static oxidation test life of 1800s at 1900℃ and a thermal shock test life of 50 times; the coating specimen has a static oxidation test life of 250s at 2200℃ and a thermal shock test life of 15 times.

[0083] The above description merely represents the preferred embodiments of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications, improvements, and substitutions without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy, characterized by: The high-temperature anti-oxidation gradient coating is composed of a first coating material, a second coating material and a third coating material stacked in sequence; The composition of the first coating material is: ZrB2 is 35-40wt%, HfB2 is 5-10wt%, 8YSZ is 11-16wt%, SiC is 2-5wt%, SiO2 is 2-4wt%, and the balance is Si; The second coating material comprises: 30-35 wt% ZrB2, 10-15 wt% HfB2, 11-16 wt% 8YSZ, 2-5 wt% SiC, 2-4 wt% SiO2, 5-10 wt% La2Zr2O7, and the balance Si; The components of the third coating material are: ZrB2 is 25-30wt%, HfB2 is 15-20wt%, 8YSZ is 11-16wt%, SiC is 2-5wt%, SiO2 is 2-4wt%, La2Zr2O7 is 10-15wt%, and the balance is Si.

2. The high-temperature oxidation-resistant gradient coating on the surface of tantalum-tungsten alloy according to claim 1, characterized in that: The particle sizes of the ZrB2 powder, HfB2 powder, 8YSZ powder, SiC powder, SiO2 powder, La2Zr2O7 powder and Si powder are less than 50 μm and the purity is greater than 99.9%.

3. The method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy according to claim 1 or 2, characterized in that: The steps include: (1) Mixing the first coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a first coating slurry; (2) spraying the first coating slurry obtained in step (1) onto the surface of the substrate, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1100°C to 1300°C for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the substrate is cooled with the furnace to form the first layer of anti-oxidation coating; (3) Mixing the second coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a second coating slurry; (4) spraying the second coating slurry obtained in step (3) onto the surface of the substrate having the first anti-oxidation coating, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200°C to 1450°C for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the second anti-oxidation coating; (5) Mixing the third coating material with ethanol, a binder, and a halide, and placing the mixture in a ball mill for wet mixing to prepare a third coating slurry; (6) spraying the third coating slurry obtained in step (5) onto the surface of the substrate having the first and second anti-oxidation coatings, filling the sprayed substrate with embedding powder, and placing it in a vacuum tube furnace for sintering at a sintering temperature of 1200°C to 1450°C for 60min to 90min. During the sintering process, when the temperature is below 1000°C, the vacuum gauge pressure in the vacuum tube furnace is less than 0.1Pa. When the temperature is greater than 1000°C, high-purity argon gas is introduced. After the heating is completed, the furnace is cooled to form the third anti-oxidation coating; The first anti-oxidation coating layer, the second anti-oxidation coating layer and the third anti-oxidation coating layer connected in sequence constitute a high-temperature anti-oxidation gradient coating.

4. The method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy according to claim 3, characterized in that: The binder added in step (1), step (3) and step (5) is 0.3-0.5 wt% of polyvinyl pyrrolidone, the halide is 0.3-0.5 wt% of sodium fluoride, and the embedding powder added in step (2), step (4) and step (6) comprises 30 wt% of silicon powder, 15 wt% of sodium fluoride and 55 wt% of aluminum oxide.

5. The method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy according to claim 3, characterized in that: The ball milling process parameters of step (1), step (3) and step (5) are 400 r / min and grinding for 5 to 6 hours.

6. The method for preparing a high-temperature oxidation-resistant gradient coating material on the surface of a tantalum-tungsten alloy according to claim 3, characterized in that: The total thickness of the high-temperature anti-oxidation gradient coating finally prepared on the surface of the substrate in step (6) is 160 μm to 200 μm.

7. The method for preparing a high-temperature oxidation-resistant gradient coating on the surface of a tantalum-tungsten alloy according to claim 3, characterized in that: In the steps (2), (4) and (6), a pneumatic spray gun is used as a coating spraying tool.

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