A SiC / HfB2-SiC dual-phase mosaic coating, its preparation method and application

Abstract

This invention discloses a SiC / HfB2-SiC biphase mosaic coating, its preparation method, and its application. The method includes: adding a mixed powder of HfO2 and B4C to a polyvinyl butyral alcohol solution and stirring to obtain a slurry; uniformly coating the slurry onto the surface of a SiC coating using a brushing process, drying, and allowing it to stand for pre-curing to obtain an HfO2-B4C pre-coating; subjecting the HfO2-B4C pre-coating to high-temperature heat treatment to form a porous framework layer containing HfB2; and infiltrating SiC into the porous framework layer using a low-temperature chemical vapor infiltration process to obtain the SiC / HfB2-SiC biphase mosaic coating. In this invention, the porous framework layer containing HfB2 is prepared in one step via a carbon-boron thermal reduction reaction. The pore size and distribution are relatively uniform and interconnected, thus facilitating the infiltration of SiC and avoiding the formation of a crust on the SiC surface and the resulting non-dense coating due to uneven pore size.

Description

Technical Field

[0001] This invention belongs to the field of carbon / carbon composite material anti-oxidation technology, and relates to a SiC / HfB2-SiC dual-phase mosaic coating, its preparation method and application. Background Technology

[0002] Carbon / carbon composites possess excellent properties such as low density, high specific strength, and high specific modulus, and their mechanical properties even increase under high-temperature inert environments, making them highly promising for applications in aerospace, aviation, and military fields. However, carbon / carbon composites are prone to oxidation in aerobic environments exceeding 450°C. This high-temperature aerobic sensitivity significantly reduces their mechanical properties, limiting their applications. Therefore, it is urgent to solve the problem of high-temperature oxidation of carbon / carbon composites, and surface coating technology is considered an effective method to avoid high-temperature oxidation of carbon / carbon composites.

[0003] Currently, silicon-based ceramic coatings, represented by SiC coatings, are the most widely studied. These coatings, after oxidation, can form a SiO2 protective film on the surface, exhibiting an extremely low oxygen diffusion coefficient and fluidity at high temperatures. This allows them to heal cracks and pores on the coating surface, further providing protection for the material. However, as the service temperature continues to rise (above 1600℃), the SiO2 glass layer formed after oxidation on the coating surface gradually volatilizes, reducing its thickness and leading to further oxidation of the inner coating layer. Therefore, in high-temperature, oxygen-rich environments, a single SiC coating is insufficient to provide long-term effective protection for carbon / carbon composite materials.

[0004] Among ultra-high temperature ceramic borides, HfB2 has the highest melting point, reaching 3250℃. After oxidation, the HfB2-SiC coating generates SiO2, HfO2, and B2O3. The oxide particles, as high-temperature refractory phases, are embedded in the glass layer, which can play a "pinning" role, improve the thermal stability of the multiphase glass at high temperatures, and inhibit the propagation of cracks in the glass, thereby enhancing the high-temperature protection capability of the coating.

[0005] The literature “Zhu X, Zhang Y, Qiang X, et al. An oxidation protective coating prepared by SiC densifying HfB2-SiC skeleton for SiC-coated C / C composites at 1473, 1773, and 1973 K [J]. Corrosion Science, 2022, 207: 110559” describes the preparation of HfB2-SiC ceramic coatings. SiO2 hollow microspheres were introduced into the original powder as a pore-forming agent. The pore-forming agent was removed by high-temperature heat treatment to form a porous coating. Due to the non-uniform particle size of the SiO2 hollow microspheres, unevenly sized pores appeared in the coating. During subsequent low-temperature chemical vapor infiltration, this caused surface crusting and closed pores, which is detrimental to the densification of the coating. Furthermore, in a high-temperature aerobic environment, oxygen rapidly diffuses into the coating, and the resulting oxide film structure becomes unstable. Summary of the Invention

[0006] The purpose of this invention is to provide a SiC / HfB2-SiC dual-phase mosaic coating, its preparation method and application, to solve the problem of uneven pore size caused by pore-forming agent treatment in the prior art, which leads to an undense coating.

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

[0008] A method for preparing a SiC / HfB2-SiC dual-phase mosaic coating, comprising:

[0009] HfO2 and B4C mixed powders were added to a polyvinyl butyral alcohol solution and stirred to obtain a slurry.

[0010] The slurry was uniformly coated onto the SiC coating surface using a brushing process, dried, and allowed to stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0011] The HfO2-B4C pre-coating was subjected to high-temperature heat treatment to form a porous framework layer containing HfB2.

[0012] SiC was infiltrated into a porous framework layer using a low-temperature chemical vapor infiltration process to obtain a SiC / HfB2-SiC dual-phase mosaic coating.

[0013] Furthermore, the molar ratio of HfO2 to B4C powder is 1:0.7 to 1.

[0014] Furthermore, the mass of the HfO2 and B4C mixed powder is 20% to 50% of the mass of the polyvinyl butyral alcohol solution.

[0015] Furthermore, the purity of the HfO2 powder is ≥99.9%, the purity of the B4C powder is ≥99%, and the particle size of both the HfO2 and B4C powders is 1–3 μm.

[0016] Furthermore, the thickness of the HfO2-B4C pre-coating is 30–80 μm.

[0017] Furthermore, the high-temperature heat treatment is carried out at a temperature of 1500–2100°C for a reaction time of 1–3 hours.

[0018] Furthermore, the deposition temperature of the low-temperature chemical vapor infiltration process is 1000–1200℃, the deposition time is 3–7 h, the hydrogen gas flow rate is 100–350 ml / min, and the argon gas flow rate is 200–800 ml / min.

[0019] The SiC / HfB2-SiC dual-phase mosaic coating prepared by the above preparation method includes an inner coating and an outer coating, wherein the inner coating is a SiC coating and the outer coating is an HfB2-SiC dual-phase mosaic coating.

[0020] Application of a SiC / HfB2-SiC dual-phase mosaic coating in oxidation resistance of carbon / carbon composites.

[0021] A carbon / carbon composite material having the aforementioned SiC / HfB2-SiC biphase mosaic coating on its surface.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention provides a method for preparing a SiC / HfB2-SiC biphase mosaic coating. Based on a process combining slurry coating-high-temperature heat treatment and low-temperature chemical vapor infiltration, the method first prepares an HfO2-B4C pre-coating on the surface of the SiC inner coating using a slurry coating method. Next, this coating material undergoes high-temperature heat treatment, resulting in a carbon-boron thermal reduction reaction to form a porous framework layer containing HfB2. During this process, a large amount of gas (B2O3, CO, etc.) is released. When the gas escapes from the coating surface, it forms through-pores, meaning that uniformly sized and distributed through-pores can be formed on the coating surface without the need for pore-forming agents. Finally, SiC is filled into the porous framework layer using a low-temperature chemical vapor infiltration process. In this invention, the HfB2-containing porous framework layer is obtained in one step through a carbon-boron thermal reduction reaction. The pore size and distribution are relatively uniform, and the pores are through-pores, thus facilitating the infiltration of SiC and avoiding the phenomenon of SiC crusting on the surface and non-dense coating caused by uneven pore size. Meanwhile, under the synergistic effect of preparing HfB2 porous framework by carbon-boron thermal reduction reaction and low-temperature chemical vapor infiltration of SiC, a dual-phase embedded coating with uniformly distributed HfB2 and dense structure is finally formed. The two phases of HfB2 and SiC are uniformly distributed, and a structurally stable oxide film is generated during high-temperature oxidation, which uniformly improves the viscosity of the oxide film. It is expected to overcome the problem of effective oxidation resistance of carbon / carbon composite materials at high temperature for a long time.

[0024] Furthermore, the raw materials used are HfO2 and B4C powder. Compared with using HfB2 directly, the raw material cost is significantly reduced. Moreover, the coating prepared by the slurry brushing process can effectively disperse HfO2 and B4C powder, making HfO2 and B4C evenly distributed. The distribution of HfB2 in the in-situ formed porous framework layer is also relatively uniform and the content is high.

[0025] Furthermore, the porous framework layer containing HfB2 is obtained through high-temperature reaction sintering, which results in a more compact sintering between grains compared to directly mixing and sintering HfB2 with SiC powder.

[0026] Furthermore, by setting the molar ratio of HfO2 to B4C to 1:0.7-1, a porous HfB2 framework layer with uniform pore size and content distribution can be obtained, which is more conducive to the subsequent infiltration of SiC.

[0027] Furthermore, the deposition temperature of the low-temperature chemical vapor infiltration process is 1000–1200℃, the deposition time is 3–7 h, the hydrogen gas flow rate is 100–350 ml / min, and the argon gas flow rate is 200–800 ml / min. By controlling the low-temperature chemical vapor infiltration process, especially the deposition temperature, the deposition efficiency of SiC can be directly and effectively controlled, thereby obtaining a uniformly distributed and dense HfB2-SiC biphase embedded antioxidant coating. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a diagram illustrating the preparation process of the SiC / HfB2-SiC dual-phase mosaic coating of the present invention.

[0030] Figure 2 SEM image of the HfB2 porous framework layer prepared in Example 1 of the present invention.

[0031] Figure 3 The X-ray diffraction pattern of the HfB2 porous framework layer prepared in Example 1 of the present invention.

[0032] Figure 4 The X-ray diffraction pattern of the HfB2-SiC dual-phase mosaic coating prepared in Example 1 of the present invention.

[0033] Figure 5 The image shows the surface morphology of the HfB2-SiC dual-phase mosaic coating prepared in Example 1 of this invention.

[0034] Figure 6 The image shows the cross-sectional morphology SEM image of the SiC / HfB2-SiC dual-phase mosaic coating prepared in Example 1 of this invention.

[0035] Figure 7 This is a SEM image of the surface morphology of the coating prepared in Comparative Example 1 of the present invention.

[0036] Figure 8 This is a SEM image of the cross-sectional morphology of the coating prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.”

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The present invention will now be described in further detail:

[0045] See Figure 1 This invention provides a method for preparing a SiC / HfB2-SiC dual-phase mosaic coating, comprising the following steps:

[0046] Step 1: Mix HfO2 with a purity ≥99.9% and B4C powder with a purity ≥99% at a molar ratio of 1:0.7~1 as the raw powder, and use anhydrous ethanol as the dispersion medium. Place the mixture in a planetary ball mill for ball milling, and after sieving, obtain a mixed powder with a particle size of 1~3μm for later use.

[0047] Step 2: Add 20% to 50% of the mass of the polyvinyl butyral (PVB) alcohol solution to the mixed powder obtained in Step 1, and stir thoroughly to obtain a slurry;

[0048] Step 3: The slurry obtained in Step 2 is uniformly coated onto the surface of the SiC coating using a slurry brushing process. The coating thickness is 30-80 μm. The coating is then allowed to air dry naturally at room temperature and allowed to stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0049] Step 4: Place the HfO2-B4C pre-coating obtained in Step 3 into a high-temperature heat treatment furnace under inert atmosphere protection for high-temperature heat treatment to form a porous skeleton layer containing HfB2.

[0050] Step 5: Place the coating material obtained in Step 4 in a chemical vapor deposition furnace, and infiltrate SiC into the porous framework layer through a low-temperature chemical vapor infiltration process to obtain a SiC / HfB2-SiC dual-phase mosaic coating.

[0051] Preferably, in step 4, the high-temperature heat treatment process parameters are: heating rate of 5-20℃ / min, heat treatment temperature of 1500-2100℃, holding time of 1-3h, cooling rate of 3-10℃ / min, and cooling with the furnace after cooling to 1200℃.

[0052] Preferably, in step 5, the low-temperature chemical vapor infiltration process parameters are: deposition temperature of 1000–1200℃, deposition time of 3–7 h, hydrogen gas flow rate of 100–350 ml / min, and argon gas flow rate of 200–800 ml / min. By controlling the above-mentioned low-temperature chemical vapor infiltration process (especially the deposition temperature), the deposition efficiency of SiC can be directly and effectively controlled, thereby obtaining a uniformly distributed and dense HfB2-SiC biphase embedded antioxidant coating.

[0053] The present invention will be further described in detail below with reference to specific embodiments:

[0054] Example 1:

[0055] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.85 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0056] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 20% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0057] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 20 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0058] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2000℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0059] Step 5. Place the coating material prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1000℃, time 5h, hydrogen gas flow rate 150ml / min, argon gas flow rate 350ml / min, and finally obtain SiC / HfB2-SiC dual-phase mosaic coating.

[0060] Example 2:

[0061] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.8 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0062] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 40% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0063] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 15 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0064] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 1900℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0065] Step 5. Place the coating material prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1100℃, time 3h, hydrogen gas flow rate 160ml / min, argon gas flow rate 400ml / min, and finally obtain SiC / HfB2-SiC dual-phase mosaic coating.

[0066] Example 3:

[0067] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.75 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0068] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 50% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0069] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 15 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0070] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2050℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0071] Step 5. Place the coating material prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1100℃, time 6h, hydrogen gas flow rate 180ml / min, argon gas flow rate 450ml / min, and finally obtain SiC / HfB2-SiC dual-phase mosaic coating.

[0072] Comparative Example 1:

[0073] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.85 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0074] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 20% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0075] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 20 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0076] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2000℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0077] Step 5. Place the coating material with HfB2 skeleton prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 900℃, time 5h, hydrogen gas flow rate 200ml / min, and argon gas flow rate 600ml / min.

[0078] Comparative Example 2:

[0079] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.8 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0080] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 20% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0081] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 20 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0082] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2000℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0083] Step 5. Place the coating material with HfB2 skeleton prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1300℃, time 5h, hydrogen gas flow rate 200ml / min, and argon gas flow rate 600ml / min.

[0084] Comparative Example 3:

[0085] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:0.5 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0086] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 20% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0087] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 20 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0088] Step 4. Place the HfO2-B4C pre-coated material into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2000℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool the material with the furnace.

[0089] Step 5. Place the material prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1050℃, time 5h, hydrogen gas flow rate 200ml / min, and argon gas flow rate 600ml / min.

[0090] Comparative Example 4:

[0091] Step 1. Weigh HfO2 powder and B4C powder with a molar ratio of 1:1.5 as raw materials, and use anhydrous ethanol as the dispersion medium. Place them in a planetary ball mill for ball milling, and then sieve them for later use.

[0092] Step 2. Take the above mixed powder and add it to the PVB alcohol solution at 20% of the mass of the PVB alcohol solution. Stir thoroughly under a magnetic stirrer to obtain a slurry.

[0093] Step 3. Immerse the SiC inner coating in the above solution, wait 1-2 seconds, then pull it out and let it stand for pre-curing. Repeat the above steps 20 times, then let it air dry at room temperature and let it stand for pre-curing to obtain the HfO2-B4C pre-coating.

[0094] Step 4. Place the HfO2-B4C pre-coated layer into a high-temperature heat treatment furnace under argon protection. The heating rate is 5℃ / min. After reaching 2000℃, hold the temperature for 2 hours. The cooling rate is 3℃ / min. After cooling to 1200℃, cool with the furnace to form a porous framework layer containing HfB2.

[0095] Step 5. Place the material prepared in Step 4 into a chemical vapor deposition furnace to infiltrate SiC. The process parameters are: temperature 1050℃, time 4h, hydrogen gas flow rate 200ml / min, and argon gas flow rate 600ml / min.

[0096] Depend on Figure 2 As can be seen, in Embodiment 1 of the present invention, during the high-temperature heat treatment process, HfO2 and B4C undergo a carbon-boron thermal reduction reaction, releasing a large amount of gas (B2O3, CO, etc.), forming relatively uniform pores on the coating surface, and thus forming a porous framework layer in situ. The X-ray diffraction pattern of the porous framework layer is shown below. Figure 3 As shown, the phase of the porous framework layer is HfB2, indicating that HfO2 and B4C undergo a carbon-boron thermal reduction reaction to generate HfB2 in situ. Figure 4 The X-ray diffraction pattern of the SiC / HfB2-SiC dual-phase mosaic coating obtained in Example 1 is shown below. Figure 4As can be seen, the coating material forms a SiC phase on its surface after undergoing a low-temperature chemical vapor infiltration process. For example... Figure 5 As shown, the surface of the porous framework layer after a low-temperature chemical vapor infiltration process exhibits a typical cauliflower-like morphology, dense and free of pores and cracks. Figure 6 The image shows the cross-sectional morphology of the porous framework layer after a low-temperature chemical vapor infiltration process. Figure 6 It can be seen that a dense dual-phase embedded HfB2-SiC coating was prepared, with the white HfB2 phase being uniformly distributed and having a high content in the coating.

[0097] The deposition temperature of Comparative Example 1 was 900℃, from which... Figure 7 As shown in the SEM image of the coating surface morphology, after the deposition temperature was reduced in this comparative example, SiC exhibited a coiled growth pattern, resulting in low SiC deposition efficiency. The surface was loose with many pores and did not show a dense cauliflower-like morphology, which was not conducive to the densification of the coating.

[0098] The deposition temperature of Comparative Example 2 was 1300℃, from Figure 8 As shown in the SEM image of the coating surface morphology, after increasing the deposition temperature in this comparative example, the deposition efficiency of SiC is relatively high, and it will be rapidly deposited on the surface of the porous framework layer. This is not conducive to the penetration of SiC into the internal porous framework layer, resulting in a crust formation on the coating surface, and finally forming a sandwich structure of SiC inner coating, HfB2 porous framework layer and SiC outer coating.

[0099] Comparative Example 3 increased the HfO2 content (HfO2:B4C was 1:0.5). This comparative example could not obtain a single HfB2 phase after high-temperature heat treatment, and ultimately could not prepare a dual-phase embedded HfB2-SiC coating.

[0100] Comparative Example 4 increased the B4C content (HfO2:B4C was 1:1.5). After high-temperature heat treatment, the coating of this comparative example was tested by XRD. It was found that in addition to the HfB2 phase, there was a certain amount of B4C in the coating. In the end, the dual-phase embedded HfB2-SiC coating could not be prepared.

[0101] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a SiC / HfB2-SiC dual-phase mosaic coating, characterized in that, include: HfO2 and B4C mixed powders were added to a polyvinyl butyral alcohol solution and stirred to obtain a slurry. The SiC inner coating is immersed in the above slurry, pulled out, and left to stand for pre-curing to obtain the HfO2-B4C pre-coating. The HfO2-B4C pre-coating was subjected to high-temperature heat treatment to form a porous framework layer containing HfB2. SiC was infiltrated into a porous framework layer by a low-temperature chemical vapor infiltration process to obtain a SiC / HfB2-SiC dual-phase mosaic coating. The molar ratio of HfO2 to B4C powder is 1:(0.7~1). The high-temperature heat treatment is performed at a temperature of 1500~2100℃ for a reaction time of 1~3h.

2. The method for preparing a SiC / HfB2-SiC dual-phase mosaic coating according to claim 1, characterized in that, The mass of the HfO2 and B4C mixed powder is 20% to 50% of the mass of the polyvinyl butyral alcohol solution.

3. The method for preparing a SiC / HfB2-SiC dual-phase mosaic coating according to claim 1, characterized in that, The purity of the HfO2 powder is ≥99.9%, the purity of the B4C powder is ≥99%, and the particle size of both the HfO2 and B4C powders is 1~3μm.

4. The method for preparing a SiC / HfB2-SiC dual-phase mosaic coating according to claim 1, characterized in that, The thickness of the HfO2-B4C pre-coating is 30~80μm.

5. The method for preparing a SiC / HfB2-SiC dual-phase mosaic coating according to claim 1, characterized in that, The deposition temperature of the low-temperature chemical vapor infiltration process is 1000~1200℃, the deposition time is 3~7h, the hydrogen gas flow rate is 100~350ml / min, and the argon gas flow rate is 200~800ml / min.

6. A SiC / HfB2-SiC dual-phase mosaic coating prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It includes an inner coating and an outer coating, wherein the inner coating is a SiC coating and the outer coating is an HfB2-SiC dual-phase damascene coating.

7. The application of the SiC / HfB2-SiC dual-phase mosaic coating as described in claim 6 in the oxidation resistance of carbon / carbon composite materials.

8. A carbon / carbon composite material, characterized in that, The surface has a SiC / HfB2-SiC dual-phase damascene coating as described in claim 6.

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