Multi-component silicon-boron composite oxidation-resistant coating on surface of tantalum-tungsten alloy and preparation method thereof

Abstract

The present application relates to the technical field of refractory metal surface protection and high-temperature oxidation-resistant coating, in particular to a multi-component silicon-boron composite oxidation-resistant coating on the surface of tantalum-tungsten alloy and a preparation method thereof, the coating has a double-layer composite structure, including a boron-modified multi-component alloy transition layer close to the substrate, and a main layer composed of multi-component silicide phases and boride phases. The coating is prepared by a two-step method of vacuum pre-burning to prepare a multi-component alloy pre-coating, and then embedding and co-permeating Si-B to form phases in situ. The coating is metallurgically combined with the substrate, and after plasma beam ablation at 1600 DEG C for 2400s, the absolute value of the mass ablation rate is less than or equal to 1.2 ug / s, the absolute value of the linear ablation rate is less than or equal to 0.4 um / s, the ablation resistance is excellent, the preparation process is simple, can be adapted to complex special-shaped components, and is suitable for aerospace extreme high-temperature aerobic working conditions.

Description

Technical Field

[0001] This invention relates to the field of refractory metal surface protection and high-temperature anti-oxidation coating technology, specifically to a multi-component silicon-boron composite anti-oxidation coating for tantalum-tungsten alloy surfaces and its preparation method. Background Technology

[0002] Tantalum-tungsten alloys are typical refractory metal alloys, possessing high melting points, excellent high-temperature mechanical properties, good room-temperature plasticity, and radiation resistance. They have irreplaceable application value in fields such as hot-end structural components of hypersonic vehicles, liquid rocket engine nozzles, and high-temperature components of nuclear reactors. In particular, commercially available tungsten alloys such as Ta-5W and Ta-10W, strengthened through tungsten solid solution treatment, maintain stable mechanical strength even at high temperatures of 1000-1600℃, making them high-temperature structural materials with great engineering potential in the field of hypersonic technology.

[0003] However, the large-scale application of tantalum-tungsten alloys is limited by their extremely poor high-temperature oxidation resistance. In an oxygen-rich environment, when the temperature exceeds 1200℃, tantalum-tungsten alloys undergo severe oxidation and ablation, losing their structural integrity within a short period of time, making them completely unsuitable for direct service in oxygen-rich, high-temperature environments. Therefore, surface anti-oxidation coating technology is a core prerequisite for the engineering application of tantalum-tungsten alloys in extreme high-temperature, oxygen-rich environments.

[0004] Currently, silicide coatings are the most widely used and technologically mature protection system for high-temperature oxidation protection of refractory metals. In high-temperature, oxygen-rich environments, silicide coatings can form a dense, continuous SiO2 glass phase on the surface, effectively blocking oxygen diffusion and achieving oxidation protection in static environments of 1200-1600℃. However, with further increases in service temperature or exposure to high-speed airflow during high-temperature service, both single silicides (such as TaSi2 or MoSi2) and silicides modified with active elements (such as Ti, Cr, Al, Zr, Hf, etc.) suffer from rapid structural degradation at high temperatures and erosion of the surface SiO2 oxide film, failing to meet the requirements for safe and reliable service.

[0005] Therefore, developing a novel coating system that can provide long-term oxidation and ablation protection for tantalum-tungsten alloys at 1600°C is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-component silicon-boron composite anti-oxidation coating for the surface of tantalum-tungsten alloy and its preparation method, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy, wherein the coating has a two-layer composite structure and comprises:

[0009] The transition layer is close to the tantalum-tungsten alloy substrate, and the main layer is far away from the tantalum-tungsten alloy substrate;

[0010] The main body layer comprises a multi-component silicide phase and a boride phase. The multi-component silicide phase comprises silicides of five metal elements: Mo, Ta, W, Zr, and Hf. As the main antioxidant phase of the coating, it can form a dense and continuous SiO2 glass protective film at high temperatures, blocking the diffusion of oxygen into the substrate. On the other hand, it improves the thermal stability of the silicide structure through the multi-component effect. The boride phase comprises borides of two metal elements: Zr and Hf. As the second reinforcing phase, it can refine the coating grains, improve toughness, and enhance the coating's ablation resistance.

[0011] The transition layer is a multi-element alloy layer containing boron. The multi-element alloy contains five metallic elements: Ta, W, Mo, Zr, and Hf. It is located between the tantalum-tungsten alloy substrate and the main layer, realizing a gradient transition from the substrate to the main layer. At the same time, the coating and the substrate interface have a high-strength metallurgical bond.

[0012] As a further aspect of the present invention: in the main body layer, the volume percentage of the multi-component silicide phase is 70%-95%, and the volume percentage of the boride phase is 5%-30%, wherein the multi-component silicide phase is (Mo,Ta,W,Zr,Hf)Si2; and the boride phase is (Zr,Hf)B2.

[0013] As a further aspect of the present invention: the thickness of the main body layer is 120-150 μm, and the thickness of the transition layer is 10-30 μm.

[0014] As a further aspect of the present invention: the tantalum-tungsten alloy matrix is ​​a Ta-W binary alloy, wherein the mass percentage of tungsten is 5%-15%.

[0015] As a further aspect of the present invention: the coating is metallurgically bonded to the interface of the tantalum-tungsten alloy substrate; after being ablated by plasma beam at 1600℃ for 2400s, the absolute value of its mass ablation rate is ≤1.2μg / s, and the absolute value of its linear ablation rate is ≤0.4μm / s.

[0016] This invention also provides a method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of the tantalum-tungsten alloy. The method employs a two-step core process: first, vacuum pre-firing of a multi-component alloy substrate, followed by embedding and co-diffusion of Si-B in-situ phase formation. Specifically, the method includes the following steps:

[0017] S1. Powder preparation: Weigh Mo, Ta, W, Zr and Hf metal powders according to the preset ratio, mix them evenly to obtain multi-element alloy powder;

[0018] S2. Slurry preparation: The multi-element alloy powder is mixed with binder and solvent to prepare slurry;

[0019] S3. Coating and molding: The slurry is coated onto the surface of the tantalum-tungsten alloy substrate and dried to form a dry film coating.

[0020] S4. Pre-sintering alloying: Vacuum sintering is performed on a tantalum-tungsten alloy substrate with a dry film coating to generate a multi-element alloy pre-coating on the substrate surface.

[0021] S5. Embedding and Co-diffusion: The substrate with a multi-element alloy pre-coating is embedded in an embedding and co-diffusion agent containing a silicon source, a boron source and a halide activator. Embedding and co-diffusion is carried out under a protective atmosphere, so that silicon and boron elements diffuse into the pre-coating, and the main layer and transition layer are generated in situ.

[0022] As a further aspect of the present invention: in step S1, the mass percentage of each metal element in the multi-element alloy powder is: Mo 50%-80%, Ta 5%-10%, W 5%-10%, Zr 5%-15%, Hf 5%-15%.

[0023] As a further aspect of the present invention: in step S2, the ratio of multi-element alloy powder, binder and solvent in the slurry is (90-100g):(5-10g):(100-150mL); the binder is at least one of PVB or ethyl cellulose, and the solvent is anhydrous ethanol or isopropanol.

[0024] As a further aspect of the present invention: In step S3, multiple layered coatings are employed, with a wet film thickness of 50-70 μm for each coating. Each coating is followed by drying at room temperature for 0.5-1 h until the total dry film thickness reaches 150-200 μm. Finally, the film is dried at 60-80℃ for 10-12 h. In step S4, the vacuum sintering temperature is 1700-1750℃, the heating rate is ≤10℃ / min, the holding time is 45-60 min, and the vacuum degree is ≤1×10⁻⁶. -2 Pa.

[0025] As a further aspect of the present invention: in step S5, the embedding and infiltrating agent comprises Si powder, B powder, Al2O3 powder and NaF powder; wherein Si powder is 20-40wt%, B powder is 0.5-5wt%, NaF powder is 3-8wt%, and the balance is Al2O3 powder; the embedding and co-infiltrating temperature is 1000-1200℃, and the heat preservation time is 12-24h.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. The multi-component silicide-boride composite coating proposed in this invention consists of a host layer containing multi-component silicide and boride phases and a boron-containing multi-element alloy transition layer. Compared with single or simply modified silicides, multi-component silicides exhibit excellent microstructural thermal stability, attributed to the high-entropy effect of the multi-component structure. The finely dispersed boride second phase refines the grain size and improves toughness, and during high-temperature oxidation, it forms a high-melting-point oxide ZrO2 / HfO2 and a low-melting-point glassy phase B2O3. The former improves ablation resistance, while the latter combines with SiO2 to form a borosilicate glassy phase, which, due to its improved high-temperature fluidity, better compensates for ablation defects and maintains the continuity and density of the oxide film. Furthermore, utilizing the rapid infiltration rate of boron during Si-B co-diffusion, a boron-containing multi-element alloy transition layer is formed between the host layer and the substrate. This layer provides a gradient transition and mitigates the loss caused by Si diffusion from the host layer into the substrate.

[0028] 2. The coating prepared by this invention exhibits a metallurgical bond with the substrate interface, demonstrating excellent high-temperature resistance to oxidation and ablation. After plasma ablation testing at 1600℃ for 2400s, the absolute value of the mass ablation rate is ≤1.2μg / s, and the absolute value of the linear ablation rate is ≤0.4μm / s.

[0029] 3. The preparation process of this invention is simple. A high-quality composite coating can be obtained on the surface of tantalum-tungsten alloy using a two-step method. It can be adapted to complex irregular components and is suitable for extreme high-temperature and oxygen-containing working conditions in aerospace. Attached Figure Description

[0030] Figure 1 This is a cross-sectional BSE image and EPMA elemental distribution diagram of the multi-component silicide-boride composite coating of the present invention.

[0031] Figure 2 The image shows the XRD pattern of the multi-component silicide-boride composite coating of the present invention.

[0032] Figure 3 The temperature-time curves of the plasma ablation center of the multi-component silicide-boride composite coating of the present invention are shown, where (a) 300s, (b) 1200s, and (c) 2400s.

[0033] Figure 4 These are macroscopic morphology images of the multi-component silicide-boride composite coating of the present invention after being ablated by plasma beam at 1600℃ for different times, where (a) 300s, (b) 1200s, (c) 2400s; (Ⅰ, Ⅲ, Ⅴ) central ablation region, (Ⅱ, Ⅳ, Ⅵ) edge ablation region. Detailed Implementation

[0034] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0035] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0036]

Example 1

[0037] This embodiment provides a multi-component silicon-boron composite anti-oxidation coating on the surface of a Ta-10W tantalum-tungsten alloy and its preparation method.

[0038] 1. Pretreatment of the substrate: After grinding the surface of the Ta-10W tantalum-tungsten alloy sample, it was pickled with a mixture of hydrofluoric acid and nitric acid. The volume ratio of the acid solution was HF:HNO3:deionized water = 1:3:10. The pickling was carried out at room temperature for 5 minutes, and then rinsed repeatedly with deionized water and dried for later use.

[0039] 2. Preparation of multi-element alloy powder: Weigh 50% Mo, 10% Ta, 10% W, 15% Zr, and 15% Hf by mass percentage, with a total feed amount of 100g. Place the mixed powder into a planetary ball mill with a ball-to-powder ratio of 5:1, and wet-mill at 350 r / min for 18 h using anhydrous ethanol as the medium. After wet milling, the slurry is vacuum-dried at 70℃ for 8 h, lightly ground in an agate mortar, and then passed through a 250-mesh standard sieve to obtain multi-element alloy powder.

[0040] 3. Slurry preparation: Add 100g of multi-element alloy powder, 8g of PVB and 120mL of anhydrous ethanol according to the ratio. After initial mixing by mechanical stirring for 30min, ball mill at 250r / min for 6h to obtain a uniform slurry. Let stand for 10min to remove bubbles before use.

[0041] 4. Coating and Forming: Gravity-driven pneumatic spray guns are used for coating, with a nozzle diameter of 1.2 mm, an air pressure of 0.35 MPa, and a spraying distance of 180 mm. Coating is done in layers, with a single wet film thickness of 50-60 μm. Each layer is dried at room temperature for 45 minutes before the next layer is applied, for a total of 3 layers, resulting in a total dry film thickness of 150-180 μm. After coating, the film is vacuum dried at 70℃ for 12 hours.

[0042] 5. Vacuum pre-sintering alloying: The sample coated with the dry film coating is placed in a vacuum sintering furnace, and a vacuum of 5 × 10⁻⁶ is applied. -3 Pa. The heating curve is as follows: room temperature → 600℃ (5℃ / min, hold for 30 min for binder removal) → 1720℃ (8℃ / min, hold for 60 min). After holding, the material is cooled in the furnace to obtain a (Mo,Ta,W,Zr,Hf) multi-element alloy pre-coating with a thickness of 100-120μm.

[0043] 6. Embedding and Co-infiltration Modification: An embedding agent was prepared according to the following mass percentages: 25% Si powder, 1.5% B powder, 68.5% Al₂O₃ powder, and 5% NaF powder, with a total feed amount of 500g. The agent was dry-mixed for 3.5 hours to obtain a homogeneous embedding agent. The pre-fired sample was embedded in the embedding agent, placed in a covered crucible, and sealed. The crucible was placed in a high-temperature furnace, and under argon protection, the temperature was increased to 1150℃ at a rate of 6℃ / min and held for 18 hours. After the holding period, the sample was cooled to room temperature with the furnace, removed, and cleaned to obtain the target composite coating.

[0044] Coating structure characterization:

[0045] like Figure 1 As shown, the coating prepared in this embodiment exhibits a distinct bilayer structure. The outer layer of the coating is the main layer, composed of a gray matrix phase and a finely dispersed bright white granular phase. This is consistent with the WDS compositional analysis results. Figure 2 The XRD pattern results show that the gray matrix phase is (Mo,Ta,W,Zr,Hf)Si2, and the bright white particles are (Zr,Hf)B2. Using ImageJ image analysis software, the volume ratio of the (Mo,Ta,W,Zr,Hf)Si2 and (Zr,Hf)B2 phases is approximately 82:18. The inner layer of the coating is an alloy transition layer. EPMA elemental surface analysis results show that it is a boron-modified (Ta,Mo,W,Zr,Hf) alloy transition layer. This layer forms because during the high-temperature sintering process of the (Mo,Ta,W,Zr,Hf) multi-element alloy pre-coating, elemental interdiffusion occurred between this layer and the tantalum-tungsten alloy substrate. Furthermore, in the subsequent Si-B embedding co-diffusion process, a small amount of B preferentially diffuses into this layer, forming the boron-modified (Ta,Mo,W,Zr,Hf) alloy transition layer.

[0046] The thicknesses of each layer are as follows: the thickness of the (Mo,Ta,W,Zr,Hf)Si2+(Zr,Hf)B2 main layer is 120-150μm; the thickness of the (Ta,Mo,W,Zr,Hf) alloy transition layer is 10-30μm.

[0047]

Example 2

[0048] The only difference between this embodiment and Embodiment 1 is the ratio of the multi-element alloy powder and the conditions for embedding and co-infiltration.

[0049] Multi-element alloy powder composition: Mo 65%, Ta 8%, W 7%, Zr 10%, Hf 10%.

[0050] Embedding and co-infiltration conditions: The infiltration agent ratio is the same as in Example 1, the co-infiltration temperature is 1050℃, and the temperature is maintained for 24 hours.

[0051] The coating obtained in this embodiment also has a double-layer structure, wherein the outer layer is composed of a (Mo,Ta,W,Zr,Hf)Si2 matrix phase and a dispersed (Zr,Hf)B2 particle phase, wherein the volume ratio of the two phases is approximately 88:12; the inner layer is a B-modified (Ta,Mo,W,Zr,Hf) alloy transition layer.

[0052]

Example 3

[0053] The only difference between this embodiment and Embodiment 1 is the ratio of the multi-element alloy powder and the vacuum pre-firing temperature.

[0054] Multi-element alloy powder formulation: Mo 80%, Ta 5%, W 5%, Zr 5%, Hf 5%.

[0055] Vacuum preheating temperature: 1700℃.

[0056] The coating obtained in this embodiment has an outer layer composed of a (Mo,Ta,W,Zr,Hf)Si2 matrix phase and a dispersed (Zr,Hf)B2 particle phase, wherein the volume ratio of the two phases is approximately 90:10; and an inner layer is a B-modified (Ta,Mo,W,Zr,Hf) alloy transition layer.

[0057]

Example 4

[0058] The only difference between this embodiment and Embodiment 1 is the content of powder B in the embedding infiltrate and the co-infiltration conditions.

[0059] The encapsulation agent composition is as follows: Si powder 25%, B powder 2.5%, Al2O3 powder 67.5%, NaF powder 5%.

[0060] Co-infiltration conditions: 1100℃ for 18 hours.

[0061] The coating obtained in this embodiment has an outer layer composed of a (Mo,Ta,W,Zr,Hf)Si2 matrix phase and a dispersed (Zr,Hf)B2 particle phase, with a volume ratio of approximately 80:20 between the two phases; the inner layer is a B-modified (Ta,Mo,W,Zr,Hf) alloy transition layer, wherein the B modification is carried out in two ways: one is that B is dissolved in the (Ta,Mo,W,Zr,Hf) multi-component solid solution phase, and the other is that a small amount of (Zr,Hf)(Mo,B)2 boride phase is formed.

[0062]

Example 5

[0063] The only difference between this embodiment and Embodiment 1 is the content of powder B in the embedding infiltrate and the co-infiltration conditions.

[0064] The encapsulation agent composition is as follows: 25% Si powder, 5% B powder, 65% Al2O3 powder, and 5% NaF powder.

[0065] Co-infiltration conditions: 1050℃ for 24 hours.

[0066] The coating obtained in this embodiment has an outer layer composed of a (Mo,Ta,W,Zr,Hf)Si2 matrix phase and a dispersed (Zr,Hf)B2 particle phase, with a volume ratio of approximately 75:25 between the two phases; the inner layer is a B-modified (Ta,Mo,W,Zr,Hf) alloy transition layer, wherein the B modification is carried out in two ways: one is that B is dissolved in a (Ta,Mo,W,Zr,Hf) multi-component solid solution phase, and the other is that a (Zr,Hf)B2 boride phase is formed.

[0067] [Comparative Example]

[0068] This comparative example is used to verify the improving effect of the second phase of boride on the antioxidant ablation performance of this invention. A multi-component silicide coating (excluding boride) was prepared on the surface of a tantalum-tungsten alloy. The specific preparation steps are as follows:

[0069] The matrix pretreatment, preparation of multi-element alloy powder (same ratio as in Example 1), slurry preparation, coating molding, and vacuum pre-firing alloying were all consistent with Example 1.

[0070] Embedding and co-infiltration modification: The infiltrator composition is 25% Si powder, 70% Al2O3 powder, and 5% NaF powder (excluding B powder), dry mixed for 3.5 h; co-infiltration temperature is 1150℃, and the temperature is maintained for 18 h. The resulting coating consists of a (Mo,Ta,W,Zr,Hf)Si2 main layer and a (Ta,Mo,W,Zr,Hf)5Si3 transition layer, without boride phases.

[0071] Performance testing

[0072] In an atmospheric environment, plasma beam ablation experiments were conducted on the coating samples obtained in Example 1 and the comparative example at 1600℃. By dynamically adjusting the flow rates of argon and nitrogen and the output current of the plasma discharge system, precise control of the heat flux density on the ablation surface of the samples was achieved, ensuring that the coating stably reached the preset oxidation temperature (1600℃) within a short time. After the temperature at the center of the ablation surface was maintained at 1600±5℃, timing was started, and the ablation time was recorded at 300s, 1200s, and 2400s, respectively. The macroscopic morphological evolution of the coating surface was observed and recorded throughout the process.

[0073] Figure 3 The temperature-time curve of the coating surface during the ablation process is shown. Figure 4 The macroscopic morphology of the coating after different ablation times is shown. Figure 3 As can be seen, under the continuous action of the plasma beam, the entire ablation surface of the coating is in a red-hot state, and the oxidation ablation area covers the entire test sample. From Figure 4The real-time macroscopic image recording of the ablation process shows that in the early stage of oxidation, the composite coating exhibits a small amount of melting and bubbling, and the escape of bubbles. As the ablation time increases, the oxidation reaction gradually stabilizes, the overflow of molten bubbles decreases significantly, the ablation surface becomes smoother, and it enters a relatively stable ablation oxidation stage.

[0074] The mass ablation rate and linear ablation rate were calculated for the coating samples after ablation times of 300s, 1200s, and 2400s, respectively. The results are listed in Table 1.

[0075] Table 1 Comparison of coating ablation resistance

[0076]

[0077] Note: In the table above, both the mass ablation rate and the linear ablation rate are negative, indicating that the coating suffers mass loss and thickness reduction during high-temperature ablation. The smaller the absolute value, the better the coating's ablation resistance.

[0078] Comparing the examples and comparative examples, it can be seen that the introduction of the boride (Zr,Hf)B2 second phase in this invention can significantly improve the oxidation and ablation resistance of the silicide coating.

[0079] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy, characterized in that, The coating is a two-layer composite structure, comprising: The transition layer is close to the tantalum-tungsten alloy substrate, and the main layer is far away from the tantalum-tungsten alloy substrate; The main body layer comprises a multi-component silicide phase and a boride phase; the multi-component silicide phase comprises silicides of five metal elements: Mo, Ta, W, Zr, and Hf; the boride phase comprises borides of two metal elements: Zr and Hf. The transition layer is a multi-element alloy layer containing boron, and the multi-element alloy contains five metallic elements: Ta, W, Mo, Zr, and Hf.

2. The multi-component silicon-boron composite anti-oxidation coating on the surface of tantalum-tungsten alloy according to claim 1, characterized in that, In the main body layer, the volume percentage of the multi-component silicide phase is 70%-95%, and the volume percentage of the boride phase is 5%-30%. The multi-component silicide phase is (Mo,Ta,W,Zr,Hf)Si2, and the boride phase is (Zr,Hf)B2.

3. The multi-component silicon-boron composite anti-oxidation coating on the surface of tantalum-tungsten alloy according to claim 1, characterized in that, The thickness of the main layer is 120-150 μm, and the thickness of the transition layer is 10-30 μm.

4. The multi-component silicon-boron composite anti-oxidation coating on the surface of tantalum-tungsten alloy according to claim 1, characterized in that, The tantalum-tungsten alloy matrix is ​​a Ta-W binary alloy, wherein the mass percentage of tungsten is 5%-15%.

5. The multi-component silicon-boron composite anti-oxidation coating on the surface of the tantalum-tungsten alloy according to claim 4, characterized in that, The coating is metallurgically bonded to the tantalum-tungsten alloy substrate interface; after plasma beam ablation at 1600℃ for 2400s, its absolute mass ablation rate is ≤1.2μg / s, and its absolute linear ablation rate is ≤0.4μm / s.

6. A method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Powder preparation: Weigh Mo, Ta, W, Zr and Hf metal powders according to the preset ratio, mix them evenly to obtain multi-element alloy powder; S2. Slurry preparation: The multi-element alloy powder is mixed with binder and solvent to prepare slurry; S3. Coating and molding: The slurry is coated onto the surface of the tantalum-tungsten alloy substrate and dried to form a dry film coating. S4. Pre-sintering alloying: Vacuum sintering is performed on a tantalum-tungsten alloy substrate with a dry film coating to generate a multi-element alloy pre-coating on the substrate surface. S5. Embedding and Co-diffusion: The substrate with a multi-element alloy pre-coating is embedded in an embedding and co-diffusion agent containing a silicon source, a boron source and a halide activator. Embedding and co-diffusion is carried out under a protective atmosphere, so that silicon and boron elements diffuse into the pre-coating, and the main layer and transition layer are generated in situ.

7. The method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy according to claim 6, characterized in that, In step S1, the mass percentage of each metal element in the multi-element alloy powder is: Mo 50%-80%, Ta 5%-10%, W 5%-10%, Zr 5%-15%, Hf 5%-15%.

8. The method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy according to claim 6, characterized in that, In step S2, the ratio of multi-element alloy powder, binder, and solvent in the slurry is (90-100g):(5-10g):(100-150mL); the binder is at least one of PVB or ethyl cellulose, and the solvent is anhydrous ethanol or isopropanol.

9. The method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy according to claim 6, characterized in that, In step S3, multiple layered coatings are used, with a wet film thickness of 50-70 μm for each coating. Each coating is dried at room temperature for 0.5-1 h until the total dry film thickness reaches 150-200 μm. Finally, the film is dried at 60-80℃ for 10-12 h. In step S4, the vacuum sintering temperature is 1700-1750℃, the heating rate is ≤10℃ / min, the holding time is 45-60 min, and the vacuum degree is ≤1×10⁻⁶. -2 Pa.

10. The method for preparing a multi-component silicon-boron composite anti-oxidation coating on the surface of a tantalum-tungsten alloy according to claim 6, characterized in that, In step S5, the embedding agent comprises Si powder, B powder, Al2O3 powder and NaF powder; wherein Si powder is 20-40wt%, B powder is 0.5-5wt%, NaF powder is 3-8wt%, and the balance is Al2O3 powder. The embedding and co-infiltration temperature is 1000-1200℃, and the heat preservation time is 12-24h.

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