Method for repairing surface defects of carbon-based composite material

Abstract

The invention discloses a method for repairing surface defects of a carbon-based composite material, and belongs to the technical field of composite materials. The method comprises the following steps: coating the defect part or the surface of a composite material base material with slurry, wherein the slurry comprises silica sol, repairing powder matched with the composite material base material, and chopped cellulose; according to the slurry, the chopped cellulose serves as a framework material, the supporting and strengthening effects can be achieved at the defect position, the repairing powder is matched with the material of the composite material base material, and meanwhile the silica sol has the bonding effect. According to the repairing slurry, coating repairing is carried out on defects of acceptable sizes on the surface of a base material, and compared with direct replacement of a new carbon-based composite material, the cost is reduced by 90% or above. On the basis of preparing the carbon-based composite material by adopting a reactive infiltration process, the composite material prepared by adopting a subsequent process disclosed by the invention is excellent in ablation resistance, the performance of the scouring-resistant and ablation-resistant carbon-based composite material can be quickly and specifically repaired, and the time cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a method for repairing surface defects of carbon-based composite materials. Background Art

[0002] Carbon / carbon (C / C) composites have the advantages of low density, high specific strength, and high-temperature mechanical properties, and are often used as key thermal structural materials in ultra-high temperature extreme use environments. However, C / C composites begin to oxidize in an aerobic environment at 370°C, and the oxidation rate increases rapidly when it exceeds 400°C, which intensifies the loss of its mechanical properties and eventually leads to material failure, severely limiting its application in high-temperature oxidation and airflow scouring environments. Therefore, it is urgent to improve the thermal protection performance of carbon / carbon composites.

[0003] At present, the preparation methods of ablation-resistant carbon-based composites mainly include two processes: coating modification and matrix modification. Among them, the matrix modification process can effectively improve the erosion resistance and ablation resistance of C / C composites. Among them, processes such as precursor impregnation pyrolysis and reactive infiltration are widely used in the matrix modification treatment of C / C composites. However, each process has its inevitable shortcomings. The preparation cycle of precursor impregnation pyrolysis is long, the time cost is high, the introduced ceramic particles are loose, and the erosion resistance is poor. The reactive infiltration process has the remarkable characteristics of short preparation time, strong bonding between ceramics and matrix, and near-net size molding, and has great application prospects. However, the reactive infiltration process is often accompanied by large thermal stress, and cracks are prone to occur on the surface of the sample. At the same time, due to the brittleness of the ceramic itself during the processing process, the carbon-based composites prepared by ultra-high temperature ceramic modification may crack or even collapse and fall off during processing. This limits the application of reactive infiltration technology in some fields.

[0004] At present, the solution to the surface defects of ablation-resistant carbon-based composite materials is often to replace them with new ablation-resistant carbon-based composite materials, which leads to a sharp increase in costs. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for repairing surface defects of carbon-based composite materials, so as to solve the problem that in the prior art, new anti-ablation carbon-based composite materials with surface defects are usually used, which has a high cost.

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

[0007] A method for repairing surface defects of a carbon-based composite material comprises the following steps:

[0008] S1, pretreating the substrate, wherein the pretreating process includes grinding, cleaning and drying; the substrate is an ultra-high temperature ceramic composite material or a carbon / carbon composite material;

[0009] S2, mixing silica sol, deionized water and repair powder, stirring evenly to obtain slurry, adding short-cut carbon fiber to the slurry, and obtaining repair slurry after ultrasonic vibration;

[0010] S3, brushing the repair slurry on the defects or surface of the substrate to fill the defects, repeatedly drying after brushing, and drying after the last drying to obtain a substrate coated with the repair slurry;

[0011] S4, placing the substrate coated with the repair slurry in a heating furnace to deposit carbides, and obtaining a repaired carbon-based composite material after deposition.

[0012] A further improvement of the present invention is:

[0013] Preferably, in S1, the ultrahigh temperature ceramic composite substrate is Zr-based, Hf-based or Si-based.

[0014] Preferably, in S1, the grinding process is to grind with 50 mesh, 400 mesh and 1000 mesh sandpaper in sequence; the cleaning is to ultrasonically clean with deionized water for several times; the drying temperature is 60-100° C., and the drying time is 8-12 hours.

[0015] Preferably, in S2, the mass ratio of silica sol, deionized water and repair powder is (1-3):(1-3):(1-3).

[0016] Preferably, in S2, the volume ratio of the slurry to the carbon fiber is 10:(0.5-3).

[0017] Preferably, in S2, the ultrasonic oscillation time is 30 min to 90 min.

[0018] Preferably, in S3, the repair slurry is applied multiple times and dried after each application.

[0019] Preferably, in S3, the drying temperature is 60-100° C., and the drying time is 8-12 hours.

[0020] Preferably, in S4, the carbide is one or more of SiC, HfC, ZrC, TaC, TiC or PyC.

[0021] Preferably, in S4, the deposition temperature is 900-1200° C., and the deposition time is 10-40 hours.

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

[0023] The present invention discloses a method for repairing surface defects of carbon-based composite materials. The method comprises coating a slurry on the defect or surface of a composite material substrate. The slurry comprises silica sol, a repair powder matching the composite material substrate material, and short-cut cellulose. The slurry uses short-cut cellulose as a skeleton material, and can play a certain supporting and reinforcing role at the defect. The repair powder matches the material of the composite material substrate, and the silica sol plays a certain bonding role. The repair slurry is coated and repaired for defects of acceptable size on the surface of the substrate. Compared with directly replacing a new carbon-based composite material, the cost is reduced by more than 90%. Based on the preparation of carbon-based composite materials by a reaction infiltration process, the composite material prepared by the subsequent process of the present invention still has excellent anti-ablation performance, and can quickly and targetedly repair the performance of erosion-resistant and anti-ablation carbon-based composite materials, saving time and cost. The method also has the advantages of designable surface composition, etc., and is a good choice for surface defect repair, with broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a process flow chart of the present invention;

[0025] Figure 2 This is the XRD spectrum of the sample surface after coating in the present invention;

[0026] Figure 3 This is the surface XRD spectrum of the sample after coating and SiC deposition treatment in the present invention;

[0027] Figure 4 The surface SEM picture of the coated sample of the present invention after being treated with deposited SiC. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0030] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0032] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0033] Ablation-resistant carbon-based composite materials are materials with heat resistance and wear resistance, and are generally used in applications in high-temperature environments. It is composed of carbon fiber and a high-temperature resin matrix, and has excellent anti-oxidation and anti-thermal expansion properties. Because of its excellent performance, this type of material is often used in aerospace, aeroengines, rocket propulsion systems and other high-temperature applications. Correspondingly, the service conditions of this type of material are relatively harsh, and the integrity of the material is required to be high. Once a certain proportion of defects appear on the surface, this type of material cannot be used and needs to be replaced as a whole. In response to this type of problem, the present invention can, on the one hand, target ablative carbon-based composite materials with surface defects, and on the other hand, it can also serve as a strengthening layer, infiltrated into the surface of the ablative carbon-based composite material, and overall improve the thermal protection performance of the material.

[0034] See also Figure 1 The present invention proposes a surface defect repair method for an anti-ablation carbon-based composite material based on a slurry brushing method, and the specific process includes the following steps:

[0035] Step 1: Select an ablation-resistant carbon-based composite material as the substrate. The substrate is an ultra-high temperature ceramic-based composite material (any one of Zr-based, Hf-based or Si-based) prepared by RMI process or 1.7-1.8 g / cm 3 The carbon / carbon composite material has a profiled surface or a flat surface.

[0036] It should be understood that the RMI process is a reactive melt infiltration process.

[0037] The above-mentioned samples may be samples with defects on the surface, which need to be repaired; or they may be samples without obvious defects or without defects, which need to enhance the overall surface of the sample.

[0038] It should be understood that the defects referred to in the present invention are defects that are visible to the naked eye but are within an appropriate size range. For large defects in such materials, considering the service environment of the material itself and the impact of the defects, the workpiece itself will not be repaired and will be directly scrapped and replaced with a new one.

[0039] Step 2: Use 50-mesh, 400-mesh and 1000-mesh sandpaper to polish the defects in turn to keep the sample surface smooth, then use deionized water for ultrasonic cleaning, the cleaning time is 30-60 minutes, the number of cleanings is 3-5 times, and the sample is dried in an electric blast drying oven at a temperature of 60-100°C for 8-12 hours for use.

[0040] Step 3: Mix silica sol: deionized water: repair powder in a mass ratio of (1-3): (1-3): (1-3), and use a magnetic stirrer to mix them evenly into a slurry for 3-6 hours. Then add chopped carbon fibers to the slurry, the volume ratio of the slurry to the chopped carbon fibers is 10: (0.5-3), and use ultrasonic vibration to evenly disperse the chopped carbon fibers in the slurry for 30 minutes to 90 minutes to obtain a repair slurry.

[0041] In some embodiments of the present invention, the repair material is a mixture of one or more of silicon powder, hafnium oxide, zirconium oxide, silicon oxide, tantalum oxide, and titanium oxide. The selection of the repair material is usually required to match the matrix material, such as having a similar expansion coefficient, C / C composite material (α (C / C) ≈1.0×10 -6 / ℃) and HfC composites (α HfC ≈6.7×10-6 / ℃) of thermal expansion coefficient (CTE) mismatch generates huge thermal stress which will destroy the material performance. To solve this problem, SiC (α SiC ≈4.4×10 -6 / ℃) ceramics are often used to alleviate thermal mismatch problems, reduce thermal mismatch, and improve the bonding strength between the repair material and the substrate. Secondly, the repair material can also be adjusted according to the use environment of the original sample to improve the material's anti-ablation, erosion resistance, anti-oxidation and other properties.

[0042] It should be understood that the short-linked cellulose in the above-mentioned repair slurry can play the role of a skeleton in the slurry for repairing defects, so that the slurry can repair defects, and the silica sol can be used as a binder to combine the repair slurry and the material matrix. The repair powder is used as a filling material to mainly improve the thermal protection performance of the repair material. It should be noted that different materials are selected for the repair powder according to different matrix materials and the requirements for thermal protection performance. The thermal expansion coefficient of the repair powder itself needs to match that of the matrix material to ensure thermal adaptability. It should be understood that the amount of short-linked cellulose added to the above-mentioned repair powder should not be too much to prevent the short-linked cellulose from agglomerating.

[0043] Step 4: Apply the slurry evenly to the defects, and then place the sample in a drying oven at 60-100°C for 30-60 minutes. Apply once and dry once. The number of times of application and drying is based on the leveling of the defects. The specific number of applications depends on the size of the defects on the sample surface. It is necessary to ensure that the defects after application are flush with the sample surface. After all the applications are completed, place the sample in a drying oven at 60-100°C for 8-12 hours to obtain the coated substrate.

[0044] The purpose of drying during the painting process is to prevent the previously applied coating from being damaged during the subsequent painting process. The final drying can dry out the deionized water inside the sample and the residual moisture in the silica sol.

[0045] Step 5: Place the coating sample in step 4 in a low-temperature deposition furnace to deposit carbides on its surface. The carbides are one or more of SiC, HfC, ZrC, TaC, TiC or PyC. The deposition temperature is 900-1200°C and the deposition time is 10-40 hours. After cooling in the furnace, take it out to finally obtain a repaired erosion-resistant and ablation-resistant carbon-based composite material sample.

[0046] In this process, the repair powder can be recombined with the matrix material. The damaged matrix exposes the carbon material inside the matrix. The chopped fibers introduced into the matrix can ensure the existence of sufficient carbon source in the subsequent process. In the deposition process, firstly, high-temperature heat treatment is performed to make the carbon phase in the matrix material and the carbon phase in the repair material react with the Si-based Hf-based, and the atomic diffusion between the phases is performed to improve the bonding strength between the repair material and the matrix material. Secondly, the coating after deposition can ensure the uniformity of the external surface of the material, further reducing the possibility of the repair material becoming an obvious defect.

[0047] The following is further described in conjunction with specific embodiments.

[0048] Example 1

[0049] Step 1: Set the density to 1.75 g / cm 3 The 2.5DC / C composite material is processed into a round cake with a diameter of 28mm and a thickness of 10mm. A groove with a diameter of 10mm and a depth of 5mm is dug in the center area of ​​the round cake.

[0050] Step 2: The C / C sample with grooves was polished with 50-mesh, 400-mesh and 1000-mesh sandpaper in turn to keep the sample surface smooth, and then ultrasonically cleaned with deionized water for 30 minutes and 5 times, and dried in an electric blast drying oven at 80°C for 8 hours for use.

[0051] Step 3: Weigh a certain mass of Si and C powders in a mass ratio of 5:1, ball-mill them to make them fully mixed, and then place them in an oven for drying for 8 hours.

[0052] Step 4: Spread the prepared powder on the bottom of the graphite crucible, put the sample into the graphite crucible, then add powder to fully fill the sample, and finally seal the graphite crucible with graphite paper.

[0053] Step 5: Place the graphite crucible in an ultra-high temperature heat treatment furnace, raise the temperature to 2000°C under argon protection, keep it warm for 1 hour, then turn off the power and cool it down. Take out the sample after it cools to room temperature.

[0054] Step 6: Prepare a slurry with a mass ratio of 1:2:1 for silica sol, deionized water and SiC powder. Use a magnetic stirrer to mix the slurry thoroughly for 1 hour. Then mix the slurry and chopped carbon fiber in a volume ratio of 10:1. Use ultrasonic vibration to evenly disperse the chopped carbon fiber in the slurry for 60 minutes.

[0055] Step 7: Apply the slurry obtained in step 6 to the groove of the C / C composite material coated with SiC coating, and then place the sample after application in a drying oven at 80°C for 30 minutes. Apply the slurry 4 times until the groove is filled and leveled. After application, place the sample in a drying oven at 80°C for 12 hours. Perform XRD spectrum analysis on the dried sample. The results are as follows: Figure 2 As shown, the detected phases on the sample surface are α-SiC and C.

[0056] Step 8: Place the sample obtained in step 7 in a low-temperature deposition furnace and deposit SiC on its surface. The deposition temperature is 1200°C and the deposition time is 20 hours. After cooling in the furnace, take it out and finally obtain a repaired erosion-resistant and ablation-resistant carbon-based composite material sample. Then, perform XRD spectrum analysis on the sample. The results are as follows: Figure 3 As shown in the figure, the main phase of the sample surface component is β-SiC, indicating that a dense silicon carbide coating on the surface has been successfully prepared. Some carbon can also be detected in the XRD spectrum. This is due to the presence of a certain amount of short-cut carbon fibers in the repair component, which also indirectly proves the introduction of short-cut carbon fibers. The microscopic morphology of the sample surface after repair is shown in the figure. Figure 4 As shown, the surface of the sample is a SiC coating formed by dense SiC particles, which indicates that the repair of the surface defects of the sample is successful.

[0057] The composite material obtained in this embodiment has a dense surface. Referring to the GJB323A-96 standard, at a heat flux density of 2.4 MW / m 2After being ablated in an oxyacetylene flame for 30 seconds, the mass ablation rate and line ablation rate were 0.0031 g / s and 0.028 mm / s, respectively, showing excellent anti-ablation performance.

[0058] Example 2

[0059] Step 1: Set the density to 1.75 g / cm 3 The 2.5DC / C composite material is processed into a round cake with a diameter of 28mm and a thickness of 10mm. A groove with a diameter of 10mm and a depth of 5mm is dug in the center area of ​​the round cake.

[0060] Step 2: Grind the round C / C sample with 50-mesh, 400-mesh and 1000-mesh sandpaper in turn to keep the sample surface smooth, then use deionized water for ultrasonic cleaning for 30 minutes and 5 times, and dry it in an electric blast drying oven at 80°C for 8 hours for use.

[0061] Step 3: Weigh a certain mass of Si and C powders in a mass ratio of 5:1, ball-mill them to make them fully mixed, and then place them in an oven for drying for 8 hours.

[0062] Step 4: Spread the prepared powder on the bottom of the graphite crucible, put the sample into the graphite crucible, then add powder to fully fill the sample, and finally seal the graphite crucible with graphite paper.

[0063] Step 5: Place the graphite crucible in an ultra-high temperature heat treatment furnace, raise the temperature to 2000°C under argon protection, keep it warm for 1 hour, then turn off the power and cool it down. Take out the sample after it cools to room temperature.

[0064] Step 6: Prepare a slurry with a mass ratio of 1:2:1 for silica sol, deionized water and SiC powder. Use a magnetic stirrer to mix the slurry thoroughly for 1 hour. Then mix the slurry and chopped carbon fiber in a volume ratio of 10:1. Use ultrasonic oscillation to evenly disperse the chopped carbon fiber in the slurry for 60 minutes.

[0065] Step 7: Apply the slurry obtained in step 6 to the surface of the C / C composite material coated with the SiC coating, and then place the sample after application in a drying oven at a temperature of 80°C for 30 minutes, and apply the sample three times. After the application, place the sample in a drying oven at a temperature of 80°C for 12 hours.

[0066] Step 8: Place the sample obtained in step 7 in a low-temperature deposition furnace and deposit SiC on its surface. The deposition temperature is 1200°C and the deposition time is 20 hours. After cooling in the furnace, take it out and finally obtain a repaired erosion-resistant and ablation-resistant carbon-based composite material sample.

[0067] Example 3

[0068] Step 1: Set the density to 1.20 g / cm 3 The 2.5DC / C composite material is processed into a round cake with a diameter of 30mm and a thickness of 10mm. A groove with a diameter of 10mm and a depth of 5mm is dug in the center area of ​​the round cake.

[0069] Step 2: The C / C sample with grooves was polished with 50-mesh, 400-mesh and 1000-mesh sandpaper in turn to keep the sample surface smooth, and then ultrasonically cleaned with deionized water for 30 minutes and 5 times, and dried in an electric blast drying oven at 80°C for 12 hours for use.

[0070] Step 3: The C / C composite material is modified by a reactive infiltration process. The sample is buried in the infiltration powder and heat treated at 2000°C for 1 hour in an argon protective atmosphere. The power is then turned off and the temperature is lowered to obtain an ultra-high temperature ceramic modified C / C composite material.

[0071] Step 4: The obtained C / C-HfC-SiC composite material was polished with 50 mesh, 400 mesh and 1000 mesh diamond grinding discs in turn to ensure that the sample surface was smooth and free of protrusions. The sample was then ultrasonically cleaned with deionized water. The cleaning times were 3 times, and each cleaning time was 60 minutes.

[0072] Step 5: Prepare a slurry with silica sol, deionized water and HfC powder in a mass ratio of 1:2:3, use a magnetic stirrer to fully mix the slurry, the stirring time is 6 hours, and then use ultrasonic vibration to evenly disperse the HfC ceramic powder in the slurry for 90 minutes. Then mix the slurry and chopped carbon fiber in a volume ratio of 10:1. Use ultrasonic vibration to evenly disperse the chopped carbon fiber in the slurry for 90 minutes.

[0073] Step 6: Apply the slurry obtained in step 5 to the C / C-HfC-SiC composite material, and then place the sample after application in a drying oven at a temperature of 100°C for 30 minutes, and apply the sample three times. After application, place the sample in a drying oven at a temperature of 100°C for 12 hours.

[0074] Step 7: Place the sample in step 6 in a low-temperature deposition furnace and deposit SiC on its surface. The deposition temperature is 1200°C and the deposition time is 20 hours. After cooling in the furnace, take it out and finally obtain a repaired erosion-resistant and ablation-resistant carbon-based composite material sample.

[0075] Example 4

[0076] In this embodiment, in step 2, the drying temperature is 60° C., the drying time is 12 h, and the other parameters are the same as in embodiment 1.

[0077] Example 5

[0078] In this embodiment, in step 2, the drying temperature is 100° C., the drying time is 8 h, and the other parameters are the same as in embodiment 1.

[0079] Example 6

[0080] In this embodiment, in step 6, silica sol, deionized water, and SiC powder are configured into a slurry in a mass ratio of 3:2:3, the ultrasonic time is 60 min, the volume ratio of the slurry to the carbon fiber is 10:3, and the other parameters are the same as in embodiment 1.

[0081] Example 7

[0082] In this embodiment, in step 6, silica sol, deionized water, and SiC powder are configured into a slurry in a mass ratio of 2:3:1, the ultrasonic time is 30 minutes, the volume ratio of the slurry to the carbon fiber is 10:2, and the other parameters are the same as in embodiment 1.

[0083] Example 8

[0084] In this embodiment, in step 6, silica sol, deionized water, and SiC powder are configured into a slurry in a mass ratio of 2:1:2, the ultrasonic time is 90 minutes, the volume ratio of the slurry to the carbon fiber is 10:1.5, and the other parameters are the same as in embodiment 1.

[0085] Example 9

[0086] In this embodiment, in step 7, the drying temperature is 60° C., the drying time is 12 h, and the other parameters are the same as in embodiment 1.

[0087] Example 10

[0088] In this embodiment, in step 7, the drying temperature is 100° C., the drying time is 8 h, and the other parameters are the same as in embodiment 1.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for repairing surface defects of carbon-based composite materials, It is characterized in that The following steps are involved: S1, pretreating the substrate, wherein the pretreating process includes grinding, cleaning and drying; the substrate is an ultra-high temperature ceramic composite material or a carbon / carbon composite material; S2, mixing silica sol, deionized water and repair powder, stirring evenly to obtain slurry, adding short-cut carbon fiber to the slurry, and obtaining repair slurry after ultrasonic vibration; S3, brushing the repair slurry on the defects or surface of the substrate to fill the defects, repeatedly drying after brushing, and drying after the last drying to obtain a substrate coated with the repair slurry; S4, placing the substrate coated with the repair slurry in a heating furnace to deposit carbides, and obtaining a repaired carbon-based composite material after deposition.

2. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S1, the ultra-high temperature ceramic composite substrate is Zr-based, Hf-based or Si-based.

3. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S1, the grinding process is to grind with 50 mesh, 400 mesh and 1000 mesh sandpaper in sequence; the cleaning is to ultrasonically clean with deionized water for several times; the drying temperature is 60-100° C., and the drying time is 8-12 hours.

4. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S2, the mass ratio of silica sol, deionized water and repair powder is (1-3):(1-3):(1-3).

5. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S2, the volume ratio of slurry to carbon fiber is 10:(0.5-3).

6. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S2, the ultrasonic oscillation time is 30 min to 90 min.

7. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S3, the repair slurry is applied multiple times and dried after each application.

8. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S3, the drying temperature is 60 to 100° C., and the drying time is 8 to 12 hours.

9. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S4, the carbide is one or more of SiC, HfC, ZrC, TaC, TiC or PyC.

10. A method for repairing surface defects of a carbon-based composite material according to claim 1, It is characterized in that In S4, the deposition temperature is 900-1200° C., and the deposition time is 10-40 hours.

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