ZrCu modified CVD-SiC ablation-resistant coating and preparation method thereof

Abstract

The application discloses a ZrCu modified CVD-SiC anti-ablation coating and a preparation method thereof, and belongs to the technical field of ablation protection coatings. The preparation method can introduce Zr and Cu elements into the SiC coating through a molten salt reaction, forms a Zr-Si-Cu inlaid structure in the coating, and forms the ZrCu modified CVD-SiC anti-ablation coating with high compactness and uniform composition distribution. The method can prepare the ZrCu modified CVD-SiC anti-ablation coating with high compactness and uniform composition distribution at a relatively low temperature (1300-1500 DEG C) through simple process operation and a heat treatment device, and the preparation process is simple and easy to control without repeated deposition or multiple complex high-temperature reactions.

Description

Technical Field

[0001] This invention belongs to the field of ablation protection coating technology, specifically relating to a ZrCu modified CVD-SiC ablation-resistant coating and its preparation method. Background Technology

[0002] Carbon / carbon (C / C) composites possess advantages such as low density, low coefficient of thermal expansion, high specific strength, high specific modulus, high thermal conductivity, and good thermal shock and ablation resistance. Furthermore, as the only material whose strength increases with temperature between 1000℃ and 2400℃, it has become one of the most promising materials in the field of thermal protection. However, C / C composites are highly susceptible to oxidation in high-temperature (above 400℃) aerobic environments, exhibiting high oxidation sensitivity with increasing temperature. This leads to severe damage to the carbon fibers, matrix, and fiber-matrix interfaces during high-temperature service, resulting in a significant decrease in mechanical properties and ultimately causing C / C composite failure. Silicon-based ceramic coating technology is currently an important technology for achieving long-term effective protection of C / C composites. Among them, SiC coatings prepared by chemical vapor deposition (CVD) are ideal ablation-protective coating materials due to their high compatibility with the thermal expansion of C / C composites, relatively low preparation temperature, minimal damage to the mechanical properties of the material, and the formation of self-healing glassy SiO2 at high temperatures.

[0003] However, in ablation environments above 1700℃, the glassy SiO2 has low viscosity and high fluidity, making it easily blown off the surface of the C / C composite material by high-temperature gas flow. Above 2000℃, SiO2 volatilizes rapidly, leading to coating damage and rendering it ineffective in protecting the C / C matrix. Studies have shown that introducing ultra-high temperature refractory metal elements such as Zr into the SiC coating can stabilize SiO2, prevent the glassy SiO2 from being eroded and peeled off by gas flow, avoid coating cracking, improve the density of the SiC coating at higher ablation temperatures, and improve the coating's protective effect. In paper 1, “GHFeng,HJLi,XYYao,B.Ren,YJJia,J.Sun et al.Evaluation of ablation resistant ZrC-SiC multilayer coating for SiC coated carbon / carbon composites under oxyacetylene and laser condition[J].CorrosionScience,2022,205:110427,” a SiC transition layer was first prepared on the surface of C / C composite material using an embedding method. Then, ZrC-SiC coatings with different ZrC / SiC ratios were prepared on the SiC coating using atmospheric plasma spraying technology. The inner SiC layer alleviated the thermal mismatch phenomenon of the coating. The glassy Zr-Si-O formed by the high-temperature oxidation of ZrC-SiC sealed the pores of the coating during a short-term ablation process at a temperature as high as 2000℃, forming a dense oxide layer. However, the process of preparing the coating requires embedding, granulation, spraying and other processes, which are complicated. The SiC inner coating is prepared at a high temperature (2100℃), which will cause great damage to the C / C substrate. In addition, the coating prepared by plasma spraying has a large porosity and the protective effect of the coating is limited. Paper 2, "B.Li,HJLi,XYYao et al. Ablation behavior of the CVD-(ZrC / SiC)3 alternate coating on C / C composites under oxyacetylene torch with different heat fluxes[J].CeramicsInternational,2022,48:11756-11763," describes the preparation of an alternating (ZrC / SiC)3 coating on the surface of C / C composites using CVD. By introducing SiC between the C / C composite matrix and ZrC, as well as between adjacent ZrC coatings, the thermal mismatch of the coating is alleviated. During the ablation process, the high-melting-point ZrO2 plays a stabilizing role for the glassy SiO2. However, if the ablation temperature is too high (>2100℃), the volatilization of SiO2 in the alternating coating will form gaps, which will destroy the integrity of the coating structure.Furthermore, this process is cumbersome, and the poor adhesion between the coating and the substrate, as well as between the coatings themselves, results in poor thermal shock resistance. Patent 1, "Chen Zhaoke, Xiong Xiang, Wang Xinshuang, Sun Wei, Wang Yalei, Huang Jie. Preparation method of ZrC-SiC coating on C / C composite surface, CN201510653315.0[P].2017", employs a slurry brushing / dipping-high-temperature sintering method. First, a Zr-Si-penetrating agent-slag-forming agent ceramic slurry is prepared, then brushed onto the C / C surface, and sintered to obtain a ZrC-SiC coating. However, this preparation process is complex, the coating thickness uniformity after slurry application is poor, the reaction temperature is high, causing significant damage to the C / C substrate, and the coating porosity is high. Therefore, to effectively protect C / C composites under high-temperature ablation conditions, it is necessary to prepare a multiphase anti-ablation coating with good adhesion, excellent self-healing properties, low preparation temperature, minimal damage to the substrate, simple and controllable process, and the ability to reduce surface temperature during ablation. Summary of the Invention

[0004] The purpose of this invention is to provide a ZrCu-modified CVD-SiC ablation-resistant coating and its preparation method, so as to solve the technical problem of complex preparation process in the prior art.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating, comprising the following steps:

[0007] On the surface of the C / C composite material, a SiC coating is deposited using methyltrichlorosilane as a raw material by chemical vapor deposition to obtain a C / C composite material with a SiC coating on the surface.

[0008] ZrCu powder, ZrO2 powder, and NaCl-NaF powder were mixed to obtain a mixed powder. A C / C composite material with a SiC coating on its surface was embedded in the mixed powder and then heat-treated in an inert atmosphere. Subsequently, the material was cleaned and dried to obtain a ZrCu-modified CVD-SiC ablation-resistant coating on the surface of the C / C composite material.

[0009] Furthermore, the chemical vapor deposition is carried out using H2 as the reactant gas and Ar as the diluent gas under negative pressure.

[0010] Furthermore, the Ar flow rate is 100–400 mL / min, the H2 flow rate is 800–1500 mL / min, and the negative pressure environment pressure is 4–6 kPa; the temperature during chemical vapor deposition is 1100–1300 °C, and the flow rate of methyltrichlorosilane is 0.2–0.4 g / min.

[0011] Furthermore, the molar ratio of ZrCu powder to NaCl-NaF powder is (1:2) to (1:6); the molar ratio of ZrCu powder to ZrO2 powder is (10:1) to (1:3).

[0012] Furthermore, the NaCl-NaF powder is obtained by mixing NaCl powder and NaF powder in a molar ratio of (6:1) to (2:1).

[0013] Furthermore, the ZrCu powder has a purity of 99.9% and a particle size of 200 mesh; the ZrO2 powder has a purity of 99.5% and a particle size of 1–3 μm; and the NaCl powder and NaF powder both have a purity of 99.5%.

[0014] Furthermore, the heat treatment temperature is 1300–1500°C, and the time is 1–4 hours.

[0015] Furthermore, the inert atmosphere is an Ar atmosphere at normal pressure.

[0016] Furthermore, the cleaning is performed by ultrasonic cleaning with deionized water at 70-80°C for 12-48 hours; the drying process is carried out at a temperature of 70-80°C.

[0017] The present invention also discloses a ZrCu-modified CVD-SiC ablation-resistant coating prepared by the above preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention discloses a method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating. A C / C composite material with a SiC coating on its surface is embedded in a mixed powder composed of ZrCu powder, ZrO2 powder, and NaCl-NaF powder. Zr and Cu elements are introduced into the SiC coating through a molten salt reaction, forming a Zr-Si-Cu embedded structure within the coating. This results in a ZrCu-modified CVD-SiC ablation-resistant coating with high density and uniform composition distribution. This method can prepare a ZrCu-modified CVD-SiC ablation-resistant coating with high density and uniform composition distribution at relatively low temperatures (1300-1500℃) using simple process operations and heat treatment equipment. It eliminates the need for repeated deposition or multiple complex high-temperature reactions, and the preparation process is simple and easy to control.

[0020] This invention also discloses a ZrCu-modified CVD-SiC ablation-resistant coating prepared by the above-described method. The coating consists of an inner SiC layer and a Zr-Cu-Si layer composed of Si-rich SiC, C-rich SiC, and uniformly embedded Zr-containing and Cu-containing phases. The thickness of the Zr-Cu-Si layer can be adjusted by controlling the reaction time and temperature, and the coating density is not reduced. According to relevant experimental results, the coating exhibits good performance at a flow rate of 2.38 MW / m³. 2 After 60 s of ablation under an oxyacetylene flame, the mass ablation rate and linear ablation rate were -0.44 mg / s and -0.24 μm / s, respectively, with a surface temperature of approximately 1980 °C. This is about 200 °C lower than the surface temperature of a conventional Zr-containing coating (2160 °C), indicating a thickening of the coating. Under the stabilizing effect of ZrO2 and the cooling effect of Cu, the surface SiO2 did not undergo significant erosion. Furthermore, the surface ZrO2 showed good sintering, providing effective protection for the substrate, and the coating exhibited good ablation resistance. In contrast, under the same ablation conditions, the unmodified CVD-SiC coating exhibited intergranular loss behavior during ablation, with a large amount of surface SiO2 being consumed by airflow scouring and volatilization. The mass ablation rate and linear ablation rate reached 0.06 mg / s and 0.05 μm / s, respectively. These phenomena indicate that the ablation performance of the ZrCu-modified coating is improved compared to the SiC coating. Attached Figure Description

[0021] Figure 1 The XRD pattern of the ZrCu-modified CVD-SiC ablation-resistant coating prepared in this invention is shown.

[0022] Figure 2 SEM images of the surface and cross-section of the ZrCu-modified CVD-SiC ablation-resistant coating prepared in this invention;

[0023] Where: a - surface; b - cross section;

[0024] Figure 3 The unmodified CVD-SiC coating and the ZrCu-modified CVD-SiC ablation-resistant coating of this invention were compared at 2.38 M / Wm. 2 Surface temperature curves and mass and linear ablation rate diagrams for 60 s of ablation under oxyacetylene thermal flux.

[0025] Where: a - surface temperature curve; b - mass and linear ablation rate diagram;

[0026] Figure 4 Macroscopic morphology of the surface before and after ablation of the unmodified CVD-SiC coating and the ZrCu-modified CVD-SiC ablation-resistant coating of the present invention;

[0027] Where: a - before ablation; b - after ablation;

[0028] Figure 5 SEM images of the unmodified CVD-SiC coating and the ZrCu-modified CVD-SiC ablation-resistant coating of the present invention before and after ablation;

[0029] Wherein: a-unmodified CVD-SiC coating; b-ZrCu modified CVD-SiC coating. Detailed Implementation

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0032] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0033] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0034] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0035] The first aspect of this invention provides a method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating, comprising the following steps:

[0036] Step 1: Place the polished, cleaned and dried C / C composite material in the constant temperature zone of a vertical chemical vapor deposition furnace. Use H2 as the reaction gas, Ar as the dilution gas, and methyltrichlorosilane (MTS) as the raw material. Deposit the SiC coating using chemical vapor deposition under negative pressure to obtain a C / C composite material with a SiC coating on the surface.

[0037] Step 2: Mix ZrCu powder, ZrO2 powder and NaCl-NaF powder to obtain a mixed powder; embed the C / C composite material with SiC coating on the surface into the mixed powder and place it in a crucible; finally, seal the crucible.

[0038] Step 3: Place the sealed crucible in the constant temperature zone of a tube furnace and then perform heat treatment in an inert atmosphere at normal pressure; then perform cleaning and drying treatments in sequence to obtain a ZrCu modified CVD-SiC ablation-resistant coating on the surface of the C / C composite material.

[0039] Preferably, the Ar flow rate is 100–400 mL / min, the H2 flow rate is 800–1500 mL / min, and the negative pressure environment pressure is 4–6 kPa; the temperature during chemical vapor deposition is 1100–1300 °C, and the flow rate of methyltrichlorosilane is 0.2–0.4 g / min.

[0040] Preferably, the molar ratio of ZrCu powder to NaCl-NaF powder is (1:2) to (1:6); the molar ratio of ZrCu powder to ZrO2 powder is (10:1) to (1:3).

[0041] Preferably, the NaCl-NaF powder is obtained by mixing NaCl powder and NaF powder in a molar ratio of (6:1) to (2:1).

[0042] Preferably, the ZrCu powder has a purity of 99.9% and a particle size of 200 mesh; the ZrO2 powder has a purity of 99.5% and a particle size of 1–3 μm; and the NaCl powder and NaF powder both have a purity of 99.5%.

[0043] Preferably, the heat treatment temperature is 1300–1500°C and the time is 1–4 hours.

[0044] Preferably, the cleaning is performed by ultrasonic cleaning with deionized water at 70-80°C for 12-48 hours; the drying process is carried out at a temperature of 70-80°C.

[0045] The second aspect of the present invention discloses a ZrCu-modified CVD-SiC ablation-resistant coating prepared by the above preparation method.

[0046] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0048] Example 1

[0049] A method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating includes the following steps:

[0050] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The vacuum was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1150°C in an Ar atmosphere at a heating rate of 5°C / min. During the heating, the Ar flow rate was 200 mL / min. After reaching the temperature, H2 and MTS with flow rates of 1000 mL / min and 0.3 g / min, respectively, were introduced to deposit a SiC coating on the surface of the C / C composite material. After the deposition was completed, H2 and MTS were turned off, the power was turned off, and the Ar flow rate was maintained at 200 mL / min while the furnace was cooled down. After cooling to room temperature, a C / C composite material with a SiC coating on the surface was obtained.

[0051] 2.7g of ZrCu powder with a particle size of 200 mesh, 5.9g of NaCl powder with a particle size of 1-10μm, 2.7g of NaF powder, and 1.7g of ZrO2 powder were weighed and ground in an agate mortar for 30 minutes to obtain a mixed powder. Then, the C / C composite material with a SiC coating on its surface was embedded in the mixed powder in an alumina crucible. The crucible was then sealed and placed in the constant temperature zone of a horizontal tube furnace. It was heat-treated in Ar environment at 1300℃ for 3 hours. After the heat treatment, the heating power was turned off and the sample was cooled with the furnace. The heat-treated sample was ultrasonically cleaned multiple times in deionized water at 80℃ for 12 hours and then dried in an oven at 70℃ for 2 hours to obtain a ZrCu modified CVD-SiC ablation-resistant coating.

[0052] In this embodiment, the Zr-Cu-Si layer of the ZrCu-modified CVD-SiC ablation-resistant coating is approximately 45 μm thick.

[0053] Example 2

[0054] A method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating includes the following steps:

[0055] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The vacuum was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1250°C in an Ar atmosphere at a heating rate of 5°C / min. During the heating, the Ar flow rate was 200 mL / min. After reaching the temperature, H2 and MTS were introduced at flow rates of 1200 mL / min and 0.4 g / min, respectively, to deposit a SiC coating on the surface of the C / C composite material. After the deposition was completed, H2 and MTS were turned off, the power was turned off, and the Ar flow rate was maintained at 200 mL / min while the furnace was cooled down. After cooling to room temperature, a C / C composite material with a SiC coating on the surface was obtained.

[0056] 4.3g of ZrCu powder with a particle size of 200 mesh, 8.5g of NaCl powder with a particle size of 1-10μm, 3.9g of NaF powder, and 2.1g of ZrO2 powder were weighed and ground in an agate mortar for 30 minutes to obtain a mixed powder. Then, the C / C composite material with a SiC coating on its surface was embedded in the mixed powder in an alumina crucible. The crucible was then sealed and placed in the constant temperature zone of a horizontal tube furnace. It was heat-treated in Ar environment at 1400℃ for 4 hours. After the heat treatment, the heating power was turned off and the sample was cooled with the furnace. The heat-treated sample was ultrasonically cleaned multiple times in deionized water at 80℃ for 48 hours. Then, it was dried in an oven at 70℃ for 2 hours to obtain a ZrCu modified CVD-SiC ablation-resistant coating.

[0057] In this embodiment, the Zr-Cu-Si layer of the ZrCu-modified CVD-SiC ablation-resistant coating is approximately 120 μm thick.

[0058] Example 3

[0059] A method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating includes the following steps:

[0060] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The vacuum was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1200℃ in an Ar atmosphere at a heating rate of 5℃ / min. During the heating, the Ar flow rate was 150 mL / min. After reaching the temperature, H2 and MTS with flow rates of 900 mL / min and 0.2 g / min, respectively, were introduced to deposit a SiC coating on the surface of the C / C composite material. After the deposition was completed, H2 and MTS were turned off, the power was turned off, and the Ar flow rate was maintained at 200 mL / min while the furnace was cooled down. After cooling to room temperature, a C / C composite material with a SiC coating on the surface was obtained.

[0061] 6.5g of ZrCu powder with a particle size of 200 mesh, 13.8g of NaCl powder with a particle size of 1-10μm, 6.1g of NaF powder, and 3.8g of ZrO2 powder were weighed and ground in an agate mortar for 30 minutes to obtain a mixed powder. Then, the C / C composite material with a SiC coating on its surface was embedded in the mixed powder in an alumina crucible. The crucible was then sealed and placed in the constant temperature zone of a horizontal tube furnace. It was heat-treated in Ar environment at 1500℃ for 4 hours. After the heat treatment, the heating power was turned off and the sample was cooled with the furnace. The heat-treated sample was ultrasonically cleaned multiple times in deionized water at 80℃ for 12 hours and then dried in an oven at 70℃ for 2 hours to obtain a ZrCu modified CVD-SiC ablation-resistant coating.

[0062] In this embodiment, the Zr-Cu-Si layer of the ZrCu-modified CVD-SiC ablation-resistant coating is approximately 155 μm thick.

[0063] Example 4

[0064] A method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating includes the following steps:

[0065] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The vacuum was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1200℃ in an Ar atmosphere at a heating rate of 5℃ / min. During the heating, the Ar flow rate was 100 mL / min. After reaching the temperature, H2 and MTS with flow rates of 800 mL / min and 0.4 g / min, respectively, were introduced to deposit a SiC coating on the surface of the C / C composite material. After the deposition was completed, H2 and MTS were turned off, the power was turned off, and the Ar flow rate was kept at 100 mL / min while the furnace was cooled down. After cooling to room temperature, a C / C composite material with a SiC coating on the surface was obtained.

[0066] 6.5g of ZrCu powder with a particle size of 200 mesh, 13.8g of NaCl powder with a particle size of 1-10μm, 6.1g of NaF powder, and 3.8g of ZrO2 powder were weighed and ground in an agate mortar for 30 minutes to obtain a mixed powder. Then, the C / C composite material with a SiC coating on its surface was embedded in the mixed powder in an alumina crucible. The crucible was then sealed and placed in the constant temperature zone of a horizontal tube furnace. It was heat-treated in Ar environment at 1300℃ for 1 hour. After the heat treatment, the heating power was turned off and the sample was cooled with the furnace. The heat-treated sample was ultrasonically cleaned multiple times in deionized water at 80℃ for 48 hours. Then, it was dried in an oven at 70℃ for 2 hours to obtain a ZrCu modified CVD-SiC ablation-resistant coating.

[0067] Comparative Example 1

[0068] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The furnace was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1150°C in an Ar atmosphere at a heating rate of 5°C / min, with an Ar flow rate of 200 mL / min during the heating process. After reaching the set temperature, H2 and MTS were introduced at flow rates of 1200 mL / min and 0.35 g / min, respectively. After deposition, H2 and MTS were turned off, the power was shut off, and the Ar flow rate was maintained at 200 mL / min while the furnace cooled down. Once the temperature reached room temperature, the C / C composite material containing the SiC coating was obtained.

[0069] Approximately 6.7 g of ZrCu powder with a particle size of 200 mesh, approximately 2.9 g of NaCl with a particle size of 1–10 μm, and approximately 3.7 g of NaF were weighed and ground in an agate mortar for 30 minutes. Subsequently, the SiC-coated C / C composite material was embedded in the mixed powder in an alumina crucible, which was then sealed. The sealed crucible was placed in the isothermal zone of a horizontal tube furnace and heat-treated at 1400℃ in an Ar environment for 2 hours. After the heat treatment, the heating power was turned off, and the sample was cooled with the furnace. The heat-treated sample was ultrasonically cleaned multiple times in deionized water at 80℃, and then dried in a 70℃ oven for 2 hours. Due to severe ZrCu sintering, the sample adhered to the crucible and could not be effectively removed, resulting in severe damage to the sample surface.

[0070] Comparative Example 2

[0071] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The vacuum was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was raised to 1150°C in an Ar atmosphere at a heating rate of 5°C / min. During the heating, the Ar flow rate was 200 mL / min. After reaching the temperature, H2 and MTS were introduced at flow rates of 900 mL / min and 0.3 g / min, respectively. After the deposition was completed, H2 and MTS were turned off, the power was turned off, and the Ar flow rate was maintained at 200 mL / min while the furnace was cooled down. After cooling to room temperature, the C / C composite material containing the SiC coating was obtained.

[0072] Approximately 4.3 g of ZrCu powder with a particle size of 200 mesh, approximately 7.8 g of NaCl, approximately 3.9 g of NaF, and approximately 2.5 g of ZrO2 powder with particle sizes of 1–10 μm were weighed. These four powders were placed in an agate mortar and ground for 30 minutes. Subsequently, the SiC-coated C / C composite material was embedded in the mixed powder in an alumina crucible, which was then sealed. The sealed crucible was placed in the constant-temperature zone of a horizontal tube furnace and heat-treated at 1600℃ in an Ar environment for 2 hours. After the heat treatment, the heating power was turned off, and the sample was cooled with the furnace. The heat-treated sample was subjected to multiple ultrasonic cleanings in deionized water at 80℃, and then dried in a 70℃ oven for 2 hours. The resulting sample showed significant cracking and large-area peeling of the coating, indicating severe coating damage.

[0073] Comparative Example 3

[0074] The polished, cleaned, and dried C / C composite material was placed in the isothermal zone of a chemical vapor deposition furnace. The furnace was then evacuated to 4 kPa, and the airtightness of the equipment was tested under pressure. If the airtightness was good, the temperature of the isothermal zone was increased to 1250℃ in an Ar atmosphere at a heating rate of 5℃ / min, with an Ar flow rate of 200 mL / min during the heating process. After reaching the set temperature, H2 and MTS were introduced at flow rates of 1200 mL / min and 0.4 g / min, respectively. After deposition, H2 and MTS were turned off, the power was shut off, and the Ar flow rate was maintained at 200 mL / min while the furnace cooled down. Once the temperature reached room temperature, the C / C composite material containing the SiC coating was obtained.

[0075] Approximately 6.3 g of ZrCu powder with a particle size of 200 mesh, approximately 14.5 g of Na₂SO₄, approximately 4.9 g of K₂SO₄, and approximately 3.1 g of ZrO₂ powder with particle sizes of 1–10 μm were weighed and ground in an agate mortar for 30 min. Subsequently, the SiC-coated C / C composite material was embedded in the mixed powder in an alumina crucible, which was then sealed. The sealed crucible was placed in the isothermal zone of a horizontal tube furnace and heat-treated at 1500℃ in an Ar environment for 4 h. After the heat treatment, the heating power was turned off, and the sample was cooled with the furnace. The heat-treated sample was subjected to multiple ultrasonic cleanings in deionized water at 80℃, and then dried in a 70℃ oven for 2 h. The resulting sample showed severe corrosion of the coating, with large areas of the surface coating peeling off.

[0076] Figure 1 The image shows the XRD pattern of the ZrCu-modified CVD-SiC ablation-resistant coating prepared by this method. It can be seen from the figure that after molten salt reaction, ZrCu reacts with the SiC coating prepared by CVD to generate compounds such as Zr3Cu4Si6 and Cu4Si, which together with SiC and ZrC form a Zr-Cu-Si composite coating.

[0077] Figure 2 The surface of the ZrCu-modified CVD-SiC ablation-resistant coating prepared by this method ( Figure 2 a) and cross section ( Figure 2 b) SEM image. The image shows that the ZrCu-modified CVD-SiC ablation-resistant coating has a dense surface. The cross-section shows that the coating consists of an inner SiC layer and an outer Zr-Cu-Si composite coating. Zr3Cu4Si6 and Cu4Si are tightly embedded in the Zr-Cu-Si layer, and the coatings are tightly bonded to each other and to the substrate.

[0078] Figure 3 The surface temperature profile of the ZrCu-modified CVD-SiC coating in the oxyacetylene flame ablation test. Figure 3 a) and the quality ablation rate and linear ablation rate of the coating after ablation ( Figure 3 b) As can be seen from the figure, compared with the unmodified CVD-SiC coating, the maximum ablation temperature of the ZrCu-modified SiC coating surface decreased significantly, the coating quality and linear ablation rate were reduced, and the coating ablation performance was enhanced.

[0079] Figure 4 For unmodified CVD-SiC coating ( Figure 4 a) and ZrCu modified CVD-SiC coating ( Figure 4b) Images of the objects before and after ablation. As can be seen from the images, after ablation, the oxide layer on the surface of the unmodified CVD-SiC coating peeled off over a large area, exposing the C / C matrix at the ablation center. In contrast, the oxide layer on the surface of the ZrCu-modified CVD-SiC coating only peeled off slightly after ablation, and the oxide layer remained relatively intact.

[0080] Figure 5 For unmodified CVD-SiC coating ( Figure 5 a) and ZrCu modified CVD-SiC coating ( Figure 5 b) SEM image of the surface oxide layer after ablation. As can be seen from the image, the glassy SiO2 in the unmodified CVD-SiC coating has high fluidity during ablation and is peeled off from the sample surface after volatilization and airflow impact. After ZrCu modification, the Zr-Si-O particles in the Zr-Cu-Si composite coating have a pinning effect on the glassy SiO2. The volatilization of low-melting-point phases such as Cu in the coating reduces the ablation surface temperature, effectively reduces the loss of SiC coating, stabilizes the surface oxide film, and improves the ablation performance of SiC coating.

[0081] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating, characterized in that, Includes the following steps: On the surface of the C / C composite material, a SiC coating is deposited using methyltrichlorosilane as a raw material by chemical vapor deposition to obtain a C / C composite material with a SiC coating on the surface. The chemical vapor deposition is performed using H2 as the reactant gas and Ar as the diluent gas under negative pressure. The Ar flow rate is 100-400 mL / min, the H2 flow rate is 800-1500 mL / min, and the negative pressure environment pressure is 4-6 kPa. The temperature during chemical vapor deposition is 1100-1300 ℃, and the flow rate of methyltrichlorosilane is 0.2-0.4 g / min. ZrCu powder, ZrO2 powder, and NaCl-NaF powder were mixed to obtain a mixed powder. A C / C composite material with a SiC coating on its surface was embedded in the mixed powder and then heat-treated in an inert atmosphere. Subsequently, the mixture was cleaned and dried to obtain a ZrCu-modified CVD-SiC ablation-resistant coating on the surface of the C / C composite material. The molar ratio of ZrCu powder to NaCl-NaF powder is (1:2) to (1:6); the molar ratio of ZrCu powder to ZrO2 powder is (10:1) to (1:3); the NaCl-NaF powder is obtained by mixing NaCl powder and NaF powder in a molar ratio of (6:1) to (2:1).

2. The method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating according to claim 1, characterized in that, The ZrCu powder has a purity of 99.9% and a particle size of 200 mesh; the ZrO2 powder has a purity of 99.5% and a particle size of 1~3 μm; the NaCl powder and NaF powder both have a purity of 99.5%.

3. The method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating according to claim 1, characterized in that, The heat treatment is performed at a temperature of 1300~1500 ℃ for 1~4 h.

4. The method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating according to claim 1, characterized in that, The inert atmosphere is an Ar atmosphere at normal pressure.

5. The method for preparing a ZrCu-modified CVD-SiC ablation-resistant coating according to claim 1, characterized in that, The cleaning process involves ultrasonic cleaning with deionized water at 70-80°C for 12-48 hours; the drying process is performed at 70-80°C.

6. A ZrCu-modified CVD-SiC ablation-resistant coating, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5.

Images