A method for bulk SiC f Repair methods for SiC ceramic matrix composite components

Abstract

The application discloses a repairing method for a bulk SiC f / SiC ceramic matrix composite component, which mainly comprises the steps of machining pretreatment, fiber preform repairing, fiber line reinforcing and CVI deposition repairing. In the machining pretreatment step, the damaged material is cut into dovetail type protrusions, and the thickness of the part is slightly reduced to leave space for fiber line winding. In the fiber preform repairing step, ceramic fibers are woven into a preform with the same thickness as the dovetail type protrusions in the form of 2.5D, an internal groove matched with the preform is processed, and the preform is spliced with the material to be repaired in the form of a mortise and tenon structure. In the fiber line reinforcing step, SiC fiber lines are cross-wound in perpendicular directions to reinforce the mortise and tenon connection part. In the CVI deposition repairing step, the fiber preform and the fiber lines are deposited by means of a CVI process, so that they become SiC f / SiC ceramic matrix composite, which is closely connected with the damaged part by the cooperation of the dovetail type part, the cross-winding of the fiber lines and the mortise and tenon structure, so that the damaged material is repaired.

Description

Technical Field

[0001] This invention belongs to the field of composite material repair technology, and relates to the preparation and repair technology of ceramic matrix composites. Specifically, it is a SiC composite material repair technology that employs mortise and tenon joints, fiber cross-winding reinforcement, and CVI deposition repair processes. f Repair methods for SiC ceramic matrix composite components. Background Technology

[0002] SiC f SiC ceramic matrix composites are a new type of composite material with high strength, high temperature resistance, and corrosion resistance. They are typically made of SiC fibers as reinforcement and SiC ceramics as the matrix, prepared through processes such as chemical vapor infiltration (CVI) or liquid phase sintering (LPS). They play a vital role in the manufacture of critical structural components in aerospace, chemical industry, and vehicle manufacturing. In these applications, SiC… f The high performance of SiC composites enables them to maintain stable physical and chemical properties under extreme environments.

[0003] However, in practical engineering applications, SiC f SiC composite materials are susceptible to damage due to changes in service environment, long-term use, or sudden accidents. This damage may manifest as microcracks, voids, surface erosion, or localized fractures, affecting the material's structural integrity and performance stability, rendering it unusable and necessitating component replacement. Considering that SiC... f SiC fiber, a crucial raw material for SiC composites, has a high economic cost, and remanufacturing compliant components requires significant time and resources. Therefore, to save costs and shorten project cycles, bulk SiC fiber is preferred. f The use of repair processes for SiC ceramic matrix composites allows for the reuse of damaged materials while maintaining their performance, thus possessing certain engineering value.

[0004] Existing repair processes for bulk SiC fThe repair of SiC ceramic matrix composites mainly adopts methods such as filling repair, interlayer bonding repair, and fiber reinforcement repair. However, these processes adopted by the existing technologies have certain limitations and shortcomings in practical applications. For example: (1) The filling material used in the filling repair process needs to have a high degree of matching with the matrix material. If the material used has low matching and large performance differences, it may lead to insufficient strength of the filling interface. (2) The interlayer bonding repair process requires precise control of parameters such as adhesive concentration, temperature, and pressure. The operation is relatively complicated, and errors are easy to occur during the bonding process, affecting the experimental results. At the same time, the bonding interface relies solely on the properties of the adhesive itself to connect the repair material and the matrix material, which can easily lead to changes in the mechanical properties of the repaired material at the fracture, weakening the tensile and bending properties, and affecting the service life of the repaired material. (3) The common fiber reinforcement repair uses the damaged material as the matrix and re-weaves the material with fibers. However, for SiC f / SiC ceramic matrix composites require too much SiC fiber re-weaving, resulting in high costs. Furthermore, weaving based on damaged materials makes it difficult to handle the interface between the preform and the matrix, especially the repair of the fracture surface of the original damaged material, which is quite complicated.

[0005] In summary, existing repair techniques all have limitations in practical applications. Filler repair techniques struggle to guarantee the strength and stability of the filler interface; interlayer bonding repair techniques are complex to operate and result in unstable mechanical properties of the repaired material; fiber-reinforced repair techniques are costly and struggle to address the interface issues between the preform and the matrix. Therefore, how to repair bulk SiC... f The key technical problem to be solved is to achieve cost-effective matching between the repair material and the matrix material, stabilize the overall performance of the repaired material, and repair the fracture surface of the SiC ceramic matrix composite material. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] For existing SiC f The existing technologies for repairing SiC ceramic matrix composites suffer from defects and shortcomings, such as insufficient strength of the filling interface, complex bonding processes and unstable mechanical properties, high cost of fiber weaving and difficulty in interface treatment. To address at least one of these and other technical problems in the prior art, this invention aims to provide a method for repairing bulk SiC ceramic matrix composites. fThe method for repairing SiC ceramic matrix composite components involves machining a dovetail-shaped protrusion at the fracture surface of the damaged material and a similar dovetail-shaped groove at the connection point of the SiC fiber preform. By using the mortise and tenon joint between the two and the subsequent reinforcement with SiC fiber lines, the method addresses issues such as the mismatch between existing repair materials and raw materials, the reduced tensile and bending resistance of the repaired material, and the high repair cost. This method not only achieves a good match between the repair material and the matrix material, ensuring the overall stability of the repaired material's performance and effectively treating the fracture surface, but also significantly reduces repair costs and operational complexity. Therefore, it has significant engineering value and economic benefits in practical applications.

[0008] (II) Technical Solution

[0009] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0010] This invention provides a method for bulk SiC f Repair methods for SiC ceramic matrix composite components, used to repair bulk SiC f Damaged portions of SiC ceramic matrix composites include at least the following steps: cutting pretreatment, fiber preform repair, fiber reinforcement, and CVI deposition repair. Specifically:

[0011] SS1. Cutting Pretreatment Steps

[0012] For damaged blocky SiC f / SiC ceramic matrix composite material is cut and processed to remove the damaged part to form the material to be repaired, and a dovetail-shaped protrusion with thickness reduction is cut at the original fracture to be connected with the repair part in the form of mortise and tenon joint.

[0013] SS2. Repair steps for fiber preforms

[0014] First, the SiC fiber woven preform is processed into a shape that meets the requirements of the material to be repaired. Then, it is installed with the material to be repaired in the form of mortise and tenon joints to ensure the tensile strength of the material after repair. The shape of the SiC fiber preform is processed into the required outline of the block material, and the connection between it and the material to be repaired is processed into a groove with the same shape and similar size as the dovetail protrusion, and its thickness is consistent with the dovetail protrusion, so that a tight fit of mortise and tenon joint can be achieved during installation, and at the same time, the repaired material can have stable tensile strength.

[0015] SS3. Fiber Thread Reinforcement Steps

[0016] At the mortise and tenon connection between the SiC fiber preform and the material to be repaired, SiC fiber threads are used to reinforce the mortise and tenon connection in a cross-wrapping manner. The winding directions of the SiC fiber threads are perpendicular to each other, forming a grid structure. At the same time, the reduction in the thickness of the mortise and tenon connection provides space for the winding of the SiC fiber threads, ensuring that the repaired material will not change in size and roughness due to the presence of SiC fiber threads. Through this cross-wrapping method, the stable connection between the two is ensured while enhancing the bending resistance of the material after repair.

[0017] SS4. CVI Deposition Remediation Steps

[0018] The material to be repaired, reinforced with fiber preforms and wrapped with fiber threads, is placed in a chemical vapor deposition (CVI) furnace for CVI deposition. During the CVI process, a SiC matrix is ​​deposited on the SiC fiber preforms and SiC fiber threads, making it a ceramic matrix composite material that is identical and compatible with the material to be repaired. This ensures that the repaired material is consistent with the original damaged material in composition and structure, thereby guaranteeing performance matching and achieving the repair of damaged SiC. f Repair of SiC composite materials.

[0019] (III) Technical Effects

[0020] Compared with the prior art, the repair method for bulk SiCf / SiC ceramic matrix composite components of the present invention has the following beneficial and significant technical effects:

[0021] (1) The material to be repaired and the repaired part are connected by a mortise and tenon structure, and the connection interface is dovetail-shaped. This not only achieves a close fit between the fiber preform and the material to be repaired, but also ensures that the connection interface will not separate due to external stretching by means of the dovetail-shaped structure, thereby enhancing the tensile strength of the repaired material.

[0022] (2) SiC fiber threads are cross-wound between the material to be repaired and the repaired part to reinforce the connection and further improve the tensile strength of the repaired material. At the same time, the cross-wound fiber threads can also decompose the stress generated by bending in the material, improving the bending resistance of the repaired material. Due to the reduction in thickness of the tenon joint, space is left for the winding of SiC fiber threads, so that the repaired material will not change in size or roughness due to the SiC fiber threads.

[0023] (3) The repaired part is a fiber preform woven from SiC fibers, and the reinforcing fiber thread is also SiC fiber. Both become SiC after being deposited on a SiC matrix using the CVI process. f / SiC composite materials match the properties of the original damaged material, and the performance of the repaired material will not be affected by the difference in material properties.

[0024] (4) Since only a small amount of SiC fiber is used to make the repair and reinforcement parts that are spliced ​​with the material to be repaired, and a large amount of fiber is not used to re-weave the material to be repaired as the matrix, this method saves the economic and time costs of the repair material. Attached Figure Description

[0025] Figure 1 This is a flowchart of a repair method for bulk SiCf / SiC ceramic matrix composite components;

[0026] Figure 2 Damaged blocky SiC used in embodiments of the present invention f A schematic diagram of a SiC ceramic matrix composite material;

[0027] Figure 3 This is a schematic diagram of the cutting pretreatment steps according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the fiber preform repair steps according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the fiber reinforcement steps according to an embodiment of the present invention;

[0030] Figure 6 It is a complete block SiC after CVI deposition repair used in embodiments of the present invention. f A schematic diagram of a SiC ceramic matrix composite material.

[0031] The technical features referred to by the reference numerals in the figure are as follows:

[0032] 1. Damaged blocky SiC f 1. SiC ceramic matrix composite material; 2. Damaged area; 3. Dovetail protrusion; 4. SiC fiber preform; 5. SiC fiber thread; 6. Intact block SiC f / SiC ceramic matrix composites. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0034] For existing SiC fThe present invention addresses the shortcomings and deficiencies of SiC ceramic matrix composite repair technology, such as insufficient strength of the filling interface, complex bonding process and unstable mechanical properties, high cost of fiber weaving and difficulty in interface treatment. This invention provides a method for repairing bulk damaged SiC ceramic matrix composites. f The repair method for SiC ceramic matrix composite components mainly includes steps such as cutting pretreatment, fiber preform repair, fiber reinforcement, and CVI deposition repair. This method not only achieves a good match between the repair material and the matrix material, ensuring the overall stability of the repaired material's performance and effectively treating the repair of material fractures, but also significantly reduces repair costs and operational complexity, thus demonstrating significant engineering value and economic benefits in practical applications.

[0035] Figure 2 This is a schematic diagram of a damaged bulk SiCf / SiC ceramic matrix composite. As a specific example, such as... Figure 1 As shown, the repair method of the present invention for repairing damaged bulk SiCf / SiC ceramic matrix composites mainly includes the following specific steps:

[0036] SS1. Cutting Pretreatment Steps

[0037] For damaged blocky SiC f The SiC ceramic matrix composite material is cut and processed to remove the damaged part to form the material to be repaired. A dovetail-shaped protrusion with thickness reduction is cut at the original fracture point to be connected with the repair part in the form of mortise and tenon joint.

[0038] Specifically, such as Figure 3 As shown, for Figure 2 Damaged blocky SiC with damaged portion 2 f The SiC ceramic matrix composite material 1 undergoes a cutting pretreatment process, where the damaged part 2 is machined into a dovetail-shaped protrusion 3 and its thickness is reduced to facilitate subsequent repair and installation connection with the fiber preform.

[0039] In a more preferred embodiment, the dovetail protrusion 3 obtained by machining the damaged material should have a shape that is narrower on the inside and wider on the outside of the cross-section. To ensure stable tensile properties at the connection between the material to be repaired and the repaired part, the outer cross-sectional area of ​​the dovetail protrusion 3 should be slightly larger than the inner cross-sectional area. To prevent stress concentration, the outer contour of the dovetail protrusion should be ground into an arc-shaped curve. To ensure that the material reinforced by fiber winding has the same dimensions as the raw material, the thickness of the protrusion needs to be reduced to allow space for the subsequent fiber winding reinforcement. Furthermore, after machining the dovetail protrusion 3, it is preferable to perform laser texturing on its surface; the laser parameters are: power 100-500W, scanning speed 50-200mm / s, and spot diameter 50-200μm; by forming a microstructure on the surface, the contact area between the material to be repaired and the repaired part can be increased, and the interfacial bonding strength can be improved.

[0040] SS2. Repair steps for fiber preforms

[0041] First, the SiC fiber woven preform is processed into a shape that meets the requirements of the material to be repaired. Then, it is installed with the material to be repaired using a mortise and tenon joint to ensure the tensile strength of the material after repair. The SiC fiber preform is processed into the required outline of the block material, and the connection between it and the material to be repaired is processed into a groove with the same shape and size as the dovetail protrusion, and its thickness is consistent with the dovetail protrusion. This allows for a tight fit of the mortise and tenon joint during installation and also ensures that the repaired material has stable tensile strength.

[0042] Specifically, such as Figure 4 As shown, the SiC fiber preform 4 used for repair is processed to have a groove of the same shape and the same thickness at the connection with the dovetail protrusion 3, so as to fit tightly with the part to be repaired by mortise and tenon joint and enhance the tensile strength of the material after repair.

[0043] In a more preferred embodiment, the processed SiC fiber preform 4 is used as the repair part to ensure that the damaged material remains consistent with the original material after CVI deposition repair. After the SiC fibers are woven into a block-shaped preform with the same thickness as the dovetail protrusion 3 using a 2.5D method, a dovetail-shaped groove needs to be machined on the side of the preform 4 where it meets the material to be repaired. This allows for a tenon-and-mortise connection and precise installation with the dovetail protrusion of the material to be repaired. The dovetail-shaped groove should match the shape and size of the dovetail protrusion of the material to be repaired, and to prevent stress concentration, the inner contour should be ground into a rounded curve.

[0044] SS3. Fiber Thread Reinforcement Steps

[0045] At the mortise and tenon joint between the SiC fiber preform and the material to be repaired, SiC fiber threads are used to reinforce the mortise and tenon joint in a cross-wrapping manner. The winding directions of the SiC fiber threads are perpendicular to each other, forming a grid structure. At the same time, the reduction in the thickness of the mortise and tenon joint provides space for the winding of the SiC fiber threads, ensuring that the repaired material will not change in size and roughness due to the presence of SiC fiber threads. Through this cross-wrapping method, the stable connection between the two is ensured while enhancing the bending resistance of the material after repair.

[0046] Specifically, such as Figure 5 As shown, SiC fiber filaments 5 are used to reinforce the material on which SiC fiber preforms 4 are installed. Specifically, SiC fiber filaments 5 are used to cross-wrap the thickness reduction portion of the tenon and mortise connection, with the wrapping directions perpendicular to each other.

[0047] In a more preferred embodiment, the fiber thread 5 used for reinforcing the material to be repaired and the repaired portion should be SiC fiber to ensure that the damaged material remains consistent with the original material after CVI deposition repair. The fiber thread 5 should only be wound around the tenon-and-mortise joint where thickness reduction has occurred. During the winding reinforcement, a starting edge perpendicular to the material fracture is selected. Winding begins from this edge at a 45° angle to the material edge. Then, starting from the opposite side of the starting edge, winding continues perpendicular to the existing coil. Finally, the fiber thread used for winding is fixed. This step reinforces both the material to be repaired and the repaired portion, while also improving the bending resistance of the repaired material. Furthermore, the SiC fiber thread preferably undergoes surface modification treatment before winding, using a silane coupling agent for chemical treatment. The impregnation time is 1-3 hours at a temperature of 60-80°C to improve the interfacial bonding strength between the SiC fiber thread and the matrix, reduce interfacial debonding, and improve the overall mechanical properties of the repaired portion.

[0048] SS4. CVI Deposition Remediation Steps

[0049] The material to be repaired, reinforced with fiber preforms and wrapped with fiber threads, is placed in a chemical vapor deposition (CVI) furnace for CVI deposition. During the CVI process, a SiC matrix is ​​deposited on the SiC fiber preforms and SiC fiber threads, making it a ceramic matrix composite material that is identical and compatible with the material to be repaired. This ensures that the repaired material is consistent with the original damaged material in composition and structure, thereby guaranteeing performance matching and achieving the repair of damaged SiC. f Repair of SiC composite materials.

[0050] Specifically, such as Figure 6 As shown, the repaired material undergoes a CVI process to deposit SiC fiber preform 4 and SiC fiber wire 5 into SiC. f / SiC ceramic matrix composite material, which matches the original damaged material, and at the same time ensures a tight bond between the repaired part and the material to be repaired, becomes a complete block of SiC. f / SiC ceramic matrix composite material 6.

[0051] In a more preferred embodiment, the deposition temperature of the CVI deposition repair step is preferably controlled between 800°C and 1200°C, the deposition pressure is maintained within the range of 10-100 Pa, the deposition time is 10-20 hours, and the deposition gas should be a mixture of silicon and carbon-containing gases, specifically including methyltrichlorosilane and hydrogen, with a gas flow ratio of 1:5 to 1:10. By precisely controlling these parameters, it can be ensured that the SiC matrix is ​​uniformly deposited on the SiC fiber preform and SiC fiber lines, thereby obtaining a repair effect consistent with the properties of the raw material and improving the overall performance and service life of the repaired material. In addition, the CVI deposition process can also adopt pulsed CVI technology, that is, the flow rate and pressure of the reaction gas are periodically changed during the deposition process; the pulse period is 30-120 seconds, and the duty cycle is 40-60%; this method can increase the penetration depth of the SiC matrix inside the fiber preform, reduce porosity, and improve the density and mechanical properties of the repaired part.

[0052] In a further preferred embodiment, after completing the above steps SS1 to SS4, the repaired material can be subjected to heat treatment at a temperature of 1200-1400℃ for 2-5 hours in an inert argon atmosphere to release residual stress generated during the repair process, improve the structural stability of the material, promote interfacial bonding, and further enhance the repair effect.

[0053] In addition, after completing the above steps SS1 to SS4, the repaired material surface can be further subjected to plasma spraying treatment. The spraying material is SiC, which is the same as the substrate, and the spraying thickness is 50-200μm. This is to further seal the surface pores, improve the surface density and oxidation resistance of the material, and repair any possible surface micro-defects, thereby improving the overall performance and appearance quality of the material.

[0054] The repair block SiC of the present invention f The method of using SiC ceramic matrix composites involves creating a preform for repair and a fiber reinforcement section using a small amount of SiC fibers. By processing the connection between the repair section and the material to be repaired, the stability of the material's properties after repair is ensured, the tensile and bending resistance of the material is improved, and the economic and time costs of repair are saved.

[0055] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. A SiC f A method for repairing SiC ceramic matrix composite components, characterized in that... The repair method includes at least the following steps: SS1. For damaged blocky SiC f / SiC ceramic matrix composite material is cut and processed to remove the damaged part to form the material to be repaired, and a dovetail-shaped protrusion with thickness reduction is cut at the original fracture to be connected with the repair part in the form of mortise and tenon joint. SS2. First, the SiC fiber woven preform is processed into a shape that meets the requirements of the material to be repaired. This preform is then used as the repair part and installed in conjunction with the material to be repaired using a mortise and tenon joint. This ensures the tensile strength of the material after repair. The SiC fiber preform is processed into the required outline of the block material, and the connection between it and the material to be repaired is processed into a groove with the same shape and similar size as the dovetail protrusion. The thickness of the groove is consistent with that of the dovetail protrusion, so that a tight fit of the mortise and tenon joint can be achieved during installation, and at the same time, the repaired material has stable tensile strength. SS3. At the mortise and tenon connection between the SiC fiber preform and the material to be repaired, SiC fiber threads are used for reinforcement in a cross-wound manner. The winding directions of the SiC fiber threads are perpendicular to each other and form a grid structure. At the same time, the thickness reduction of the dovetail-shaped protrusion provides space for the winding of the SiC fiber threads, ensuring that the repaired material will not change in size and roughness due to the presence of SiC fiber threads. SS4. The material to be repaired, reinforced with SiC fiber preforms and wound with SiC fiber threads, is placed in a CVI deposition furnace for CVI deposition. During the CVI deposition process, a SiC matrix is ​​deposited on the SiC fiber preforms and SiC fiber threads, making it a ceramic matrix composite material that is identical and compatible with the material to be repaired. This ensures that the repaired material is consistent with the original damaged material in composition and structure, thereby guaranteeing performance matching and achieving the repair of damaged SiC. f Repair of SiC composite materials.

2. The repair method according to claim 1, characterized in that, In step SS1 above, the shape of the protrusion obtained by cutting the damaged material should be a dovetail-shaped protrusion with a narrower inner cross-section and a wider outer cross-section. The outer cross-sectional area of ​​the dovetail-shaped protrusion should be slightly larger than the inner cross-sectional area to enhance the tensile strength at the connection between the material to be repaired and the repaired part. In order to prevent stress concentration, the outer contour of the dovetail-shaped protrusion should be ground into an arc-shaped curve. At the same time, in order to make the material reinforced by SiC fiber winding consistent with the size of the raw material, it is necessary to reduce the thickness of the protrusion to leave space for the subsequent reinforcement by fiber winding.

3. The repair method according to claim 1, characterized in that, In step SS1 above, after the dovetail protrusion is machined, its surface is subjected to laser texturing. The laser parameters are power 100-500W, scanning speed 50-200mm / s, and spot diameter 50-200μm. By forming a microstructure on the surface, the contact area between the material to be repaired and the part to be repaired is increased.

4. The repair method according to any one of claims 1 to 3, characterized in that, In step SS2 above, the processed SiC fiber preform is used as the repair part to ensure that the damaged material remains consistent with the raw material after CVI deposition repair. After the SiC fiber is woven into a block-shaped preform with the same thickness as the dovetail protrusion using the 2.5D method, a dovetail-shaped groove needs to be processed on the side where the preform is spliced ​​with the material to be repaired. This allows for mortise and tenon connection and precise installation with the material to be repaired, which has dovetail protrusions. The dovetail-shaped groove should be consistent with the shape and size of the dovetail protrusions on the material to be repaired. In order to prevent stress concentration, the inner contour of the dovetail-shaped groove should be ground into an arc-shaped curve.

5. The repair method according to claim 1, characterized in that, In step SS3 above, the fiber thread used to reinforce the material to be repaired and the repaired part should be SiC fiber, so that the damaged material can be consistent with the original material after CVI deposition repair. The SiC fiber thread should only be wound in the tenon and mortise joint where the thickness is reduced. When reinforcing by winding, first select an edge perpendicular to the material fracture as the starting edge. Start from this edge and wind in a direction at a 45° angle to the material edge. Then start from the opposite side of the starting edge and continue winding in a direction perpendicular to the existing coil. Finally, fix the fiber thread used for winding.

6. The repair method according to claim 1, characterized in that, In step SS3 above, the SiC fiber filaments undergo surface modification treatment before winding. They are chemically treated with a silane coupling agent, with an impregnation time of 1-3 hours and a temperature of 60-80℃, in order to improve the interfacial bonding strength between the fiber filaments and the matrix and reduce interfacial debonding.

7. The repair method according to claim 1, characterized in that, In step SS4 above, the deposition temperature of the CVI deposition remediation step should be controlled between 800℃ and 1200℃, the deposition pressure should be maintained in the range of 10-100 Pa, the deposition time should be 10 to 20 hours, and the deposition gas should be a mixture of silicon and carbon-containing gases, specifically including methyltrichlorosilane (MTS) and hydrogen (H2), with a gas flow ratio of 1:5 to 1:

10.

8. The repair method according to claim 1, characterized in that, In step SS4 above, the CVI deposition process uses pulsed CVI technology, which periodically changes the flow rate and pressure of the reaction gas during the deposition process. The pulse period is 30-120 seconds and the duty cycle is 40-60% to increase the penetration depth of the SiC matrix inside the fiber preform and reduce the porosity.

9. The repair method according to claim 1, characterized in that, After completing steps SS1 to SS4 above, the repaired material is subjected to heat treatment at a temperature of 1200-1400℃ for 2-5 hours in an inert argon atmosphere to release residual stress generated during the repair process, improve the structural stability of the material, and promote interfacial bonding.

10. The repair method according to claim 1, characterized in that, After completing steps SS1 to SS4 above, the repaired material surface is subjected to plasma spraying treatment. The spraying material is SiC, which is the same as the substrate, and the spraying thickness is 50-200μm, in order to further seal the surface pores, improve the surface density and oxidation resistance of the material, and repair any possible surface micro-defects, thereby improving the overall performance and appearance quality of the material.

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