A tantalum-tungsten alloy surface ultra-high temperature oxidation-resistant double-layer gradient composite coating and a preparation method thereof

Abstract

This invention relates to the field of high-temperature protection technology for refractory metals, and discloses an ultra-high temperature anti-oxidation composite coating for tantalum-tungsten alloys and its preparation method. Addressing the challenge of severe oxidation and "pulverization" of tantalum-tungsten alloys above 600℃, this invention designs a two-layer gradient composite structure coating. The inner layer forms a dense transition zone on the surface of the tantalum-tungsten alloy substrate in situ using an embedding process, with high-melting-point silicides and borides as the main phases. The outer layer uses a composite slurry prepared from HfB2, ZrB2, TaSi2, HfSi2, and Y2O3-stabilized zirconium oxide (YSZ) as raw materials, which is then sprayed and sintered at high temperature to form a dense, erosion-resistant ultra-high temperature anti-oxidation host layer. Through the gradient design of composition and structure, this invention achieves excellent thermal expansion matching between the coating and the tantalum-tungsten substrate. This composite coating enables tantalum-tungsten alloys to effectively serve for over 400 seconds in a static oxidation environment at 2300℃ and possesses good thermal shock resistance, thus expanding the application range and service limit of tantalum-tungsten alloys in ultra-high temperature fields.

Description

Technical Field

[0001] This invention relates to the field of surface engineering technology for refractory metal materials for extreme environments, specifically to an ultra-high temperature anti-oxidation composite coating applied to the surface of tantalum-tungsten (Ta-W) alloy components and its preparation method. Background Technology

[0002] Tantalum-tungsten alloys (such as Ta-10W) are widely used in aerospace and defense industries due to their extremely high melting point (over 3000℃), excellent high-temperature strength, creep resistance and corrosion resistance. They are used in hot-end components such as nozzle throat liners, thrust chambers and gas rudders of liquid rocket engines, as well as thermal protection components of missile reentry vehicles and key structural components of nuclear weapons. They are structural materials with great potential in extreme high-temperature environments.

[0003] However, tantalum-tungsten alloys begin to oxidize severely in air above 600°C. The oxidation product, Ta₂O₅, is easily volatilized at high temperatures, and the oxidation process is accompanied by a "pulverization" phenomenon, leading to rapid material failure. This severely limits its direct application in oxygen-rich, high-temperature environments. Currently, the main approach to improving the oxidation resistance of tantalum-tungsten alloys is to apply a protective coating. This coating can construct a dense anti-oxidation barrier on the substrate surface without sacrificing the inherent excellent properties of the tantalum-tungsten alloy matrix, such as its high melting point, high-temperature strength, and good plasticity, effectively inhibiting the internal diffusion of oxygen atoms at high temperatures.

[0004] Existing technologies mainly focus on silicide coatings (such as MoSi2 and WSi2 modified coatings) at medium and low temperatures (<1800℃). However, for long-term protection at ultra-high temperatures above 2000℃, especially at 2300℃, there are still significant challenges. The main problems are: (1) high thermal stress, cracking, and peeling caused by the mismatch of the coefficient of thermal expansion (CTE) between the coating and the Ta-W substrate; (2) rapid diffusion of coating elements (such as Si) into the substrate at ultra-high temperatures, leading to the depletion and failure of the coating itself; and (3) self-volatilization, phase transformation, or softening of the coating in ultra-high temperature oxidizing environments. Therefore, developing a composite coating system that can be tightly bonded to the Ta-W substrate, has good thermal compatibility, is structurally stable at ultra-high temperatures, and is self-healing has become the key to promoting the engineering application of tantalum-tungsten alloys. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a composite coating and its preparation method that exhibits strong bonding with a tantalum-tungsten alloy substrate, excellent thermal matching, and long-term stable operation in an ultra-high temperature oxidizing environment of 2000-2300℃. The coating consists of an inner silicon / boron co-diffusion diffusion barrier layer tightly bonded to the substrate and an outer ultra-high temperature borosilicate ceramic composite layer providing the main protective layer. The core technology of this invention lies in the dual-layer structure design of "in-situ generation of a gradient diffusion layer + ultra-high temperature composite ceramic surface layer".

[0006] To achieve the above-mentioned objectives, the present invention adopts the following specific technical solution:

[0007] A high-temperature anti-oxidation composite coating for tantalum-tungsten alloy surface, characterized in that: the coating consists of a first layer (silicon / boron co-diffusion diffusion barrier layer) and a second layer (high-temperature borosilicate ceramic composite layer) from the inside out.

[0008] The first layer is an alloying layer formed in situ on the surface of the substrate by an embedding process. The composition of the embedding agent is as follows by mass percentage: Si powder: 40~55 wt%, B4C powder: 10~20 wt%, AlF3 powder: 2~5 wt%, NaF powder: 3~6 wt%, and the balance is inert filler Al2O3 powder.

[0009] The composition of the second coating material by mass percentage is as follows: HfB2 powder: 25~35 wt%, ZrB2 powder: 10~20 wt%, TaSi2 powder: 15~25 wt%, HfSi2 powder: 5~10 wt%, and the balance is Y2O3 stabilized ZrO2 powder (YSZ, Y2O3 content is 7~9 mol%).

[0010] A method for preparing an ultra-high temperature anti-oxidation composite coating on a tantalum-tungsten alloy surface, characterized by comprising the following steps:

[0011] (1) Preparation of the first layer (diffusion barrier layer): Weigh the powder of each component of the first layer embedding agent according to the proportion, add them to a V-type mixer and dry mix until there are no lumps or agglomerations in each component and the mixture is uniform; clean the tantalum-tungsten alloy matrix and completely embed it in the corundum crucible containing the embedding agent, compact the embedding agent with a glass rod and seal the crucible mouth with refractory mud; place the crucible in a tube furnace or hot-wall vacuum furnace with high-purity argon gas (purity ≥99.999%), and first heat it at 200~300 The air inside the furnace is removed by purging at a flow rate of mL / min for 15-20 minutes. Then, the temperature is increased to 1100-1250℃ at a rate of 8-12℃ / min and held for 1.5-3 hours. During the holding period, high-purity argon gas is continuously introduced to maintain an inert atmosphere. The furnace is then cooled to room temperature. The substrate is removed, and the powder adhering to the surface is removed with a soft brush. Then, it is ultrasonically cleaned with anhydrous ethanol for 5-10 minutes. After drying, a dense silicon / boron co-diffusion diffusion barrier layer is formed on the surface of the substrate.

[0012] (2) Preparation of the second layer (ultra-high temperature borosilicate ceramic composite layer) slurry: Weigh the powder of each component of the second layer coating material according to the proportion and mix it with the organic carrier (composed of anhydrous ethanol and binder polyvinyl butyral PVB, of which PVB accounts for 1.0~2.0% of the powder mass and the amount of anhydrous ethanol is 40~50% of the total powder mass), place it in a planetary ball mill, and wet ball mill at a speed of 300~400 r / min for 8~12 hours to obtain a uniform and stable spray coating slurry;

[0013] (3) Preparation and sintering of the second layer: The slurry obtained in step (2) was sprayed onto the surface of the substrate with the first layer prepared by spraying process and dried at 80~100℃. Then the sample was placed in a high-temperature vacuum atmosphere furnace, the vacuum was evacuated to ≤1.0×10⁻² Pa, the temperature was raised to 600~700℃ at 5~8℃ / min and held for 1h to remove organic agents. Then the temperature was raised to 1150~1200℃ and held for 1~1.5h under argon protection or vacuum conditions for densification sintering. Finally, the cooling rate was controlled to ≤10℃ / min to cool down to below 800℃, and then cooled to room temperature with the furnace to form a dense borosilicate ceramic composite layer with a thickness of 150~250μm.

[0014] Further preferably, in the ultra-high temperature anti-oxidation composite coating for tantalum-tungsten alloy surface according to claim 1, the particle size D of the HfB2 powder, ZrB2 powder, TaSi2 powder, HfSi2 powder, and YSZ powder used to prepare the second layer is... 90 ≤ 15μm, with a purity of not less than 99.5%; the particle size D of the Si powder and B4C powder used to prepare the first layer of penetrant is... 90 ≤ 45 μm, purity not less than 99.0%.

[0015] Further preferably, in step (1), the particle size of the inert filler Al2O3 powder is 100~200 μm and the purity is not less than 99.0%.

[0016] Further preferred, in step (1), the ball milling process parameters are a rotation speed of 200~250 r / min and a dry mixing time of 30~40 minutes.

[0017] Further preferred, in step (3), the total thickness of the final composite coating is 165~280μm.

[0018] Further preferably, a pneumatic spray gun is used as the coating spraying tool in step (3).

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention employs a gradient structure of an inner silicon / boron co-diffusion alloy layer and an outer ultra-high temperature borosilicate ceramic layer to achieve a gradient transition of thermal expansion coefficients between the substrate, inner layer, and outer layer. This significantly reduces stress concentration during high-temperature thermal cycling and solves the problem of existing coatings being prone to cracking under thermal shock conditions.

[0021] This invention achieves a functional closed loop of inner layer diffusion blocking and outer layer multi-performance synergy through precise ratio of penetrant and coating material, resulting in a composite coating with superior oxidation resistance and thermal shock resistance.

[0022] Experiments show that the present invention achieves a qualitative breakthrough in protective performance through the synergistic design of the double-layer structure and composition system, raising the upper limit of the anti-oxidation temperature to 2000~2300℃, enabling tantalum-tungsten alloy to effectively serve for more than 400 seconds in a static oxidation environment at this temperature. It has excellent thermal shock resistance and can withstand more than 15 thermal cycles from 2300℃ to room temperature water cooling without cracking or peeling.

[0023] This invention utilizes an inner silicon / boron co-diffusion barrier layer to achieve atomic-level root-cause isolation of oxygen, preventing its bulk diffusion. It also effectively inhibits the diffusion of elements such as Hf and Zr from the outer ceramic layer into the matrix, while preventing the diffusion of Ta and W from the matrix into the coating. This avoids the pitting of grain boundaries and deterioration of phase composition caused by element interdiffusion, fundamentally ensuring the long-term stability of the inner oxygen barrier structure. The outer layer achieves dense ceramic physical sealing combined with high-temperature dynamic SiO2 glass phase sealing, blocking surface penetration and microporous permeation channels for oxygen. Furthermore, the SiO2 glass phase and trace amounts of B in the coating form a SiO2-B2O3 composite glass phase, which has a lower melting point and better high-temperature fluidity compared to pure SiO2 glass phase. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the ultra-high temperature composite coating prepared in Example 1;

[0025] Figure 2 The image shows the surface scanning morphology of the ultra-high temperature composite coating prepared in Example 1.

[0026] Figure 3 The image shows the surface scanning morphology of the ultra-high temperature composite coating prepared in Example 1 after oxidation at 2100℃. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] A high-temperature anti-oxidation composite coating for tantalum-tungsten alloy surface, characterized in that: the coating consists of a first layer (silicon / boron co-diffusion diffusion barrier layer) and a second layer (high-temperature borosilicate ceramic composite layer) from the inside out.

[0030] The first layer is an alloying layer formed in situ on the surface of the substrate by an embedding and infiltration process. The composition of the embedding and infiltration agent by mass percentage is: Si powder: 40wt%, B4C powder: 15wt%, AlF3 powder: 3wt%, NaF powder: 4wt%, and the balance is inert filler Al2O3 powder.

[0031] The composition of the second coating material by mass percentage is as follows: HfB2 powder: 25t%, ZrB2 powder: 10wt%, TaSi2 powder: 20wt%, HfSi2 powder: 7wt%, and the balance is Y2O3 stabilized ZrO2 powder (YSZ, Y2O3 content is 7~9 mol%).

[0032] According to claim 1, the ultra-high temperature anti-oxidation composite coating on the surface of a tantalum-tungsten alloy is characterized in that: the particle size D of the HfB2 powder, ZrB2 powder, TaSi2 powder, HfSi2 powder, and YSZ powder used to prepare the second layer is... 90 ≤ 15 μm, with a purity of not less than 99.5%; the particle size D of the Si powder and B4C powder used to prepare the first layer of penetrant is... 90 The particle size of the inert filler Al2O3 powder is ≤ 45 μm, and the purity is not less than 99.0%.

[0033] A method for preparing an ultra-high temperature anti-oxidation composite coating on a tantalum-tungsten alloy surface, characterized by comprising the following steps:

[0034] (1) Preparation of the first layer (diffusion barrier layer): Weigh the powder of each component of the first layer embedding agent according to the proportion, add it to the V-type mixer, adjust the speed to 200~250 r / min, dry mix for 30~40 minutes until there are no lumps or agglomerations of each component, and the mixture is uniform; clean the tantalum-tungsten alloy matrix and completely embed it in the corundum crucible containing the embedding agent, compact the embedding agent with a glass rod and seal the crucible mouth with refractory mud; place the crucible in a tube furnace or hot-wall vacuum furnace with high-purity argon gas (purity ≥99.999%), and first heat it at 200~300 The air inside the furnace is removed by purging at a flow rate of mL / min for 15-20 minutes. Then, the temperature is increased to 1100-1250℃ at a rate of 8-12℃ / min and held for 1.5-3 hours. During the holding period, high-purity argon gas is continuously introduced to maintain an inert atmosphere. The furnace is then cooled to room temperature. The substrate is removed, and the powder adhering to the surface is removed with a soft brush. Then, it is ultrasonically cleaned with anhydrous ethanol for 5-10 minutes. After drying, a dense silicon / boron co-diffusion diffusion barrier layer is formed on the surface of the substrate.

[0035] (2) Preparation of the second layer (ultra-high temperature borosilicate ceramic composite layer) slurry: Weigh the powder of each component of the second layer coating material according to the proportion and mix it with the organic carrier (composed of anhydrous ethanol and binder polyvinyl butyral PVB, of which PVB accounts for 1.0~2.0% of the powder mass and the amount of anhydrous ethanol is 40~50% of the total powder mass), place it in a planetary ball mill, and wet ball mill at a speed of 300~400 r / min for 8~12 hours to obtain a uniform and stable spray coating slurry;

[0036] (3) Preparation and sintering of the second layer: The slurry obtained in step (2) was sprayed onto the substrate surface of the prepared first layer using a pneumatic spray gun as the coating spraying process, and dried at 80~100℃. Then the sample was placed in a high-temperature vacuum atmosphere furnace, and the vacuum was evacuated to ≤1.0×10⁻² Pa. The temperature was increased to 600~700℃ at 5~8℃ / min and held for 1h to remove organic agents. Then the temperature was increased to 1150~1200℃ and held for 1~1.5h under argon protection or vacuum conditions for densification sintering. Finally, the cooling rate was controlled to ≤10℃ / min to cool down to below 800℃, and then cooled to room temperature with the furnace to form a dense borosilicate ceramic composite layer with a thickness of 150~250μm.

[0037] The inner silicon / boron co-diffusion barrier layer and the outer ultra-high temperature borosilicate ceramic layer constitute an ultra-high temperature anti-oxidation composite coating, and the total thickness of the final composite coating is 175μm.

[0038] The cross-sectional view of the ultra-high temperature composite coating prepared in this embodiment is shown below. Figure 1 As shown, the surface scanning morphology is as follows Figure 2 As shown.

[0039] The surface scanning morphology of the ultra-high temperature composite coating prepared in this embodiment after oxidation at 2100℃ is shown in the figure. Figure 3 As shown, the coating has an effective service life of 750 seconds in a static oxidation environment at 2100℃ and a thermal shock life of 27 cycles. In a static oxidation environment at 2300℃, it has an effective service life of 470 seconds and a thermal shock life of 20 cycles.

[0040] Example 2

[0041] A high-temperature anti-oxidation composite coating for tantalum-tungsten alloy surface, characterized in that: the coating consists of a first layer (silicon / boron co-diffusion diffusion barrier layer) and a second layer (high-temperature borosilicate ceramic composite layer) from the inside out.

[0042] The first layer is an alloying layer formed in situ on the surface of the substrate by an embedding and infiltration process. The composition of the embedding and infiltration agent by mass percentage is: Si powder: 45wt%, B4C powder: 17wt%, AlF3 powder: 4wt%, NaF powder: 5wt%, and the balance is inert filler Al2O3 powder.

[0043] The composition of the second coating material by mass percentage is as follows: HfB2 powder: 30t%, ZrB2 powder: 15wt%, TaSi2 powder: 22wt%, HfSi2 powder: 8wt%, and the balance is Y2O3 stabilized ZrO2 powder (YSZ, Y2O3 content is 7~9 mol%).

[0044] According to claim 1, the ultra-high temperature anti-oxidation composite coating on the surface of a tantalum-tungsten alloy is characterized in that: the particle size D of the HfB2 powder, ZrB2 powder, TaSi2 powder, HfSi2 powder, and YSZ powder used to prepare the second layer is... 90 ≤ 15 μm, with a purity of not less than 99.5%; the particle size D of the Si powder and B4C powder used to prepare the first layer of penetrant is... 90 The particle size of the inert filler Al2O3 powder is ≤ 45 μm, and the purity is not less than 99.0%.

[0045] A method for preparing an ultra-high temperature anti-oxidation composite coating on a tantalum-tungsten alloy surface, characterized by comprising the following steps:

[0046] (1) Preparation of the first layer (diffusion barrier layer): Weigh the powder of each component of the first layer embedding agent according to the proportion, add it to the V-type mixer, adjust the speed to 200~250 r / min, dry mix for 30~40 minutes until there are no lumps or agglomerations of each component, and the mixture is uniform; clean the tantalum-tungsten alloy matrix and completely embed it in the corundum crucible containing the embedding agent, compact the embedding agent with a glass rod and seal the crucible mouth with refractory mud; place the crucible in a tube furnace or hot-wall vacuum furnace with high-purity argon gas (purity ≥99.999%), and first heat it at 200~300 The air inside the furnace is removed by purging at a flow rate of mL / min for 15-20 minutes. Then, the temperature is increased to 1100-1250℃ at a rate of 8-12℃ / min and held for 1.5-3 hours. During the holding period, high-purity argon gas is continuously introduced to maintain an inert atmosphere. The furnace is then cooled to room temperature. The substrate is removed, and the powder adhering to the surface is removed with a soft brush. Then, it is ultrasonically cleaned with anhydrous ethanol for 5-10 minutes. After drying, a dense silicon / boron co-diffusion diffusion barrier layer is formed on the surface of the substrate.

[0047] (2) Preparation of the second layer (ultra-high temperature borosilicate ceramic composite layer) slurry: Weigh the powder of each component of the second layer coating material according to the proportion and mix it with the organic carrier (composed of anhydrous ethanol and binder polyvinyl butyral PVB, of which PVB accounts for 1.0~2.0% of the powder mass and the amount of anhydrous ethanol is 40~50% of the total powder mass), place it in a planetary ball mill, and wet ball mill at a speed of 300~400 r / min for 8~12 hours to obtain a uniform and stable spray coating slurry;

[0048] (3) Preparation and sintering of the second layer: The slurry obtained in step (2) was sprayed onto the substrate surface of the prepared first layer using a pneumatic spray gun as the coating spraying process, and dried at 80~100℃. Then the sample was placed in a high-temperature vacuum atmosphere furnace, and the vacuum was evacuated to ≤1.0×10⁻² Pa. The temperature was increased to 600~700℃ at 5~8℃ / min and held for 1h to remove organic agents. Then the temperature was increased to 1150~1200℃ and held for 1~1.5h under argon protection or vacuum conditions for densification sintering. Finally, the cooling rate was controlled to ≤10℃ / min to cool down to below 800℃, and then cooled to room temperature with the furnace to form a dense borosilicate ceramic composite layer with a thickness of 150~250 μm.

[0049] The inner silicon / boron co-diffusion barrier layer and the outer ultra-high temperature borosilicate ceramic layer constitute an ultra-high temperature anti-oxidation composite coating, and the total thickness of the final composite coating is 190μm.

[0050] The coating has an effective service life of 850 seconds in a static oxidation environment at 2100℃ and a thermal shock life of 32 cycles. In a static oxidation environment at 2300℃, it has an effective service life of 525 seconds and a thermal shock life of 23 cycles.

[0051] Example 3

[0052] A high-temperature anti-oxidation composite coating for tantalum-tungsten alloy surface, characterized in that: the coating consists of a first layer (silicon / boron co-diffusion diffusion barrier layer) and a second layer (high-temperature borosilicate ceramic composite layer) from the inside out.

[0053] The first layer is an alloying layer formed in situ on the surface of the substrate by an embedding and infiltration process. The composition of the embedding and infiltration agent by mass percentage is: Si powder: 52wt%, B4C powder: 19wt%, AlF3 powder: 4wt%, NaF powder: 5wt%, and the balance is inert filler Al2O3 powder.

[0054] The composition of the second coating material by mass percentage is as follows: HfB2 powder: 32t%, ZrB2 powder: 17wt%, TaSi2 powder: 24wt%, HfSi2 powder: 8wt%, and the balance is Y2O3 stabilized ZrO2 powder (YSZ, Y2O3 content is 7~9 mol%).

[0055] According to claim 1, the ultra-high temperature anti-oxidation composite coating on the surface of a tantalum-tungsten alloy is characterized in that: the particle size D of the HfB2 powder, ZrB2 powder, TaSi2 powder, HfSi2 powder, and YSZ powder used to prepare the second layer is... 90 ≤ 15 μm, with a purity of not less than 99.5%; the particle size D of the Si powder and B4C powder used to prepare the first layer of penetrant is... 90The particle size of the inert filler Al2O3 powder is ≤ 45 μm, and the purity is not less than 99.0%.

[0056] A method for preparing an ultra-high temperature anti-oxidation composite coating on a tantalum-tungsten alloy surface, characterized by comprising the following steps:

[0057] (1) Preparation of the first layer (diffusion barrier layer): Weigh the powder of each component of the first layer embedding agent according to the proportion, add it to the V-type mixer, adjust the speed to 200~250 r / min, dry mix for 30~40 minutes until there are no lumps or agglomerations of each component, and the mixture is uniform; clean the tantalum-tungsten alloy matrix and completely embed it in the corundum crucible containing the embedding agent, compact the embedding agent with a glass rod and seal the crucible mouth with refractory mud; place the crucible in a tube furnace or hot-wall vacuum furnace with high-purity argon gas (purity ≥99.999%), and first heat it at 200~300 The air inside the furnace is removed by purging at a flow rate of mL / min for 15-20 minutes. Then, the temperature is increased to 1100-1250℃ at a rate of 8-12℃ / min and held for 1.5-3 hours. During the holding period, high-purity argon gas is continuously introduced to maintain an inert atmosphere. The furnace is then cooled to room temperature. The substrate is removed, and the powder adhering to the surface is removed with a soft brush. Then, it is ultrasonically cleaned with anhydrous ethanol for 5-10 minutes. After drying, a dense silicon / boron co-diffusion diffusion barrier layer is formed on the surface of the substrate.

[0058] (2) Preparation of the second layer (ultra-high temperature borosilicate ceramic composite layer) slurry: Weigh the powder of each component of the second layer coating material according to the proportion and mix it with the organic carrier (composed of anhydrous ethanol and binder polyvinyl butyral PVB, of which PVB accounts for 1.0~2.0% of the powder mass and the amount of anhydrous ethanol is 40~50% of the total powder mass), place it in a planetary ball mill, and wet ball mill at a speed of 300~400 r / min for 8~12 hours to obtain a uniform and stable spray coating slurry;

[0059] (3) Preparation and sintering of the second layer: The slurry obtained in step (2) was sprayed onto the substrate surface of the prepared first layer using a pneumatic spray gun as the coating spraying process, and dried at 80~100℃. Then the sample was placed in a high-temperature vacuum atmosphere furnace, and the vacuum was evacuated to ≤1.0×10⁻² Pa. The temperature was increased to 600~700℃ at 5~8℃ / min and held for 1h to remove organic agents. Then the temperature was increased to 1150~1200℃ and held for 1~1.5h under argon protection or vacuum conditions for densification sintering. Finally, the cooling rate was controlled to ≤10℃ / min to cool down to below 800℃, and then cooled to room temperature with the furnace to form a dense borosilicate ceramic composite layer with a thickness of 150~250 μm.

[0060] The inner silicon / boron co-diffusion barrier layer and the outer ultra-high temperature borosilicate ceramic layer constitute an ultra-high temperature anti-oxidation composite coating, and the total thickness of the final composite coating is 225μm.

[0061] The coating has an effective service life of 950 seconds in a static oxidation environment at 2100℃ and a thermal shock life of 38 cycles. In a static oxidation environment at 2300℃, it has an effective service life of 580 seconds and a thermal shock life of 28 cycles.

[0062] The above description merely illustrates 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 those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A high-temperature anti-oxidation composite coating for tantalum-tungsten alloy surfaces, characterized in that: The coating consists of a first layer (silicon / boron co-diffusion diffusion barrier layer) and a second layer (ultra-high temperature borosilicate ceramic composite layer) from the inside out. The first layer is an alloying layer formed in situ on the surface of the substrate by an embedding process. The composition of the embedding agent is as follows by mass percentage: Si powder: 40~55 wt%, B4C powder: 10~20 wt%, AlF3 powder: 2~5 wt%, NaF powder: 3~6 wt%, and the balance is inert filler Al2O3 powder. The composition of the second coating material by mass percentage is as follows: HfB2 powder: 25~35wt%, ZrB2 powder: 10~20wt%, TaSi2 powder: 15~25wt%, HfSi2 powder: 5~10wt%, and the balance is Y2O3 stabilized ZrO2 powder (YSZ, Y2O3 content is 7~9mol%).

2. The ultra-high temperature anti-oxidation composite coating on the surface of a tantalum-tungsten alloy according to claim 1, characterized in that: The particle size D of the HfB2 powder, ZrB2 powder, TaSi2 powder, HfSi2 powder, and YSZ powder used to prepare the second layer is specified. 90 ≤15μm, with a purity of not less than 99.5%; the particle size D of the Si powder and B4C powder used to prepare the first layer of penetrant is... 90 ≤45μm, purity not less than 99.0%.

3. A method for preparing an ultra-high temperature anti-oxidation composite coating on the surface of a tantalum-tungsten alloy as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of the first layer (diffusion barrier layer): Weigh the powder of each component of the first layer embedding agent according to the proportion, add them to a V-type mixer and dry mix until there are no lumps or agglomerations in each component and the mixture is uniform; clean the tantalum-tungsten alloy matrix and completely embed it in the corundum crucible containing the embedding agent, compact the embedding agent with a glass rod and seal the crucible mouth with refractory mud; place the crucible in a tube furnace or hot-wall vacuum furnace with high-purity argon gas (purity ≥99.999%), and first heat it at 200~300 The air inside the furnace is removed by purging at a flow rate of mL / min for 15-20 minutes. Then, the temperature is increased to 1100-1250℃ at a rate of 8-12℃ / min and held for 1.5-3 hours. During the holding period, high-purity argon gas is continuously introduced to maintain an inert atmosphere. The furnace is then cooled to room temperature. The substrate is removed, and the powder adhering to the surface is removed with a soft brush. Then, it is ultrasonically cleaned with anhydrous ethanol for 5-10 minutes. After drying, a dense silicon / boron co-diffusion diffusion barrier layer is formed on the surface of the substrate. (2) Preparation of the second layer (ultra-high temperature borosilicate ceramic composite layer) slurry: Weigh the powder of each component of the second layer coating material according to the proportion and mix it with the organic carrier (composed of anhydrous ethanol and binder polyvinyl butyral PVB, of which PVB accounts for 1.0~2.0% of the powder mass and the amount of anhydrous ethanol is 40~50% of the total powder mass), place it in a planetary ball mill, and wet ball mill at a speed of 300~400 r / min for 8~12 hours to obtain a uniform and stable spray coating slurry; (3) Preparation and sintering of the second layer: The slurry obtained in step (2) is sprayed onto the substrate surface of the first layer by spraying process and dried at 80~100℃. Then the sample is placed in a high-temperature vacuum atmosphere furnace and vacuumed to ≤1.0×10⁻²Pa. The temperature is raised to 600~700℃ at 5~8℃ / min and held for 1h to remove organic agents. Then the temperature is raised to 1150~1200℃ and held for 1~1.5h under argon protection or vacuum conditions for densification sintering. Finally, the cooling rate is controlled to ≤10℃ / min to cool down to below 800℃. Then the furnace is cooled to room temperature to form a dense borosilicate ceramic composite layer with a thickness of 150~250 μm.

4. The method for preparing a tantalum-tungsten alloy ultra-high temperature anti-oxidation composite coating according to claim 3, characterized in that: In step (1), the particle size of the inert filler Al2O3 powder is 100~200 μm and the purity is not less than 99.0%.

5. The method for preparing a tantalum-tungsten alloy ultra-high temperature anti-oxidation composite coating according to claim 3, characterized in that: In step (1), the ball milling process parameters are a rotation speed of 200~250 r / min and a dry mixing time of 30~40 minutes.

6. The method for preparing a tantalum-tungsten alloy ultra-high temperature anti-oxidation composite coating according to claim 3, characterized in that: In step (3), the final total thickness of the composite coating is 165~280μm.

7. The method for preparing a tantalum-tungsten alloy ultra-high temperature anti-oxidation composite coating according to claim 3, characterized in that: In step (3), a pneumatic spray gun is used as the coating spraying tool.

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