A SiC f Method for laser repair of near-surface damage in SiC / SiC composites

Abstract

This invention relates to the field of materials technology, and provides a SiC f Laser repair methods for near-surface damage in SiC composite materials specifically include: laser repair of SiC composite materials with near-surface damage. f The SiC composite material undergoes pretreatment; silicon carbide ceramic particles and carbon source powder are acid-washed and then formulated into a dispersion solution, which is ultrasonically stirred to obtain a repair slurry; the repair slurry is introduced into the damaged area to form a ceramic skeleton network; placed in a vacuum environment, melting powder is simultaneously delivered to the damaged area, and a laser beam is manipulated to focus on the area for scanning to achieve reactive melting infiltration of the damaged area. This invention ensures the cleanliness and activation of the damaged interface through systematic pretreatment, constructs a porous skeleton network with high ceramic content and modulus matching that of the base material using particle gradation technology, and finally achieves precise filling and reactive bonding of the skeleton network by the melt in a vacuum environment using laser selective area synchronous powder delivery melting infiltration technology.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and more specifically, to a SiC... f Laser repair method for near-surface damage of SiC composite materials. Background Technology

[0002] Silicon carbide ceramics and their composites possess excellent properties such as low density, high thermal conductivity, high breakdown electric field strength, oxidation resistance, and high temperature resistance, making them widely used in strategic fields such as aerospace, automotive, photovoltaic semiconductors, and new energy. However, silicon carbide ceramics and their composites are highly susceptible to near-surface damage throughout their manufacturing-service lifecycle, leading to premature failure of critical components. If entire components are scrapped due to minor damage, it not only results in severe resource waste but also significantly increases the overall cost of the supply chain, creating a sharp contradiction with the concept of green manufacturing.

[0003] Near-surface damage is the primary source of material service failure and is located at the interface of direct environmental corrosion, thus presenting a window of opportunity for repair. Currently, there are three main reported material repair methods: (1) endowing the material with self-healing capabilities; (2) preparing repair agents to repair the damaged area; and (3) using advanced additive manufacturing technology to remanufacture the damaged material.

[0004] Literature "J. Dai, L. He, Z. Xu, et al. Oxidation behavior of SiC f / SiC minicomposites with multilayered (BN / SiC)n interfacial coatings under humidenvironment[J]. Journal of Materials Engineering and Performance, 2022, 31(12): 10343–10353.” By introducing boron into the composite material, the boron reacts with silica after oxidation to form a borosilicate glass phase with viscous flow characteristics, which can effectively heal microcracks and improve the material's oxidation resistance. However, the self-healing ability of the material is limited, and it can only achieve self-healing of microcracks, making it difficult to cope with the repair function of macroscopic damage.

[0005] Patent No. CN202210523145.4 discloses a method for repairing ceramics under high-temperature thermal conditions and its application. The invention repairs cracked surfaces by applying a high-temperature resistant silicate inorganic adhesive and sintering it, and can be used to repair ceramics under high-temperature thermal conditions. However, the adhesive material and the ceramic substrate have significantly different coefficients of thermal expansion and elastic modulus, easily leading to thermal stress concentration at the repair interface. This repair process mainly targets macroscopic cracked surface damage and lacks the ability to repair near-surface defects such as microcracks and pits, limiting its application scenarios. Furthermore, the adhesive can only physically fill surface defects, lacking sufficient penetration and bonding strength to cover hidden damage such as micron-level pores within the ceramic, making it difficult to guarantee the structural integrity after repair.

[0006] Patent CN202510341886.4 discloses a laser repair process for ductile iron surfaces. This process repairs ductile iron using laser cladding technology and optimizes the bonding quality between the cladding layer and the base material through pre-coating combined with silicone oil immersion treatment, effectively reducing interface defects. This process utilizes the characteristic of metallic materials to partially melt under laser irradiation, promoting metallurgical bonding between the cladding material and the substrate, thereby ensuring compatibility of the repaired area. However, this method is primarily for repairing metallic materials, and its mechanism relies on the melting-solidification behavior of the repair material and the base material. Ceramic materials, due to their high melting point and significant differences in thermal properties, cannot achieve effective bonding between the repair layer and the base material using the same process; therefore, specialized process design is required for ceramic materials.

[0007] Patent CN202010267085.5 discloses a method for repairing SiC coatings on carbon / carbon composite materials. This technology repairs coating defects by applying a slurry made of a mixture of Si, SiC, and C to the damaged coating surface and then using laser cladding technology to locally prepare a SiC coating in the damaged area. Patent CN202011360860.8 uses the same repair method to clad modified glass material onto the damaged coating surface, significantly improving the material's absorption rate in the laser band, enhancing cladding quality, and improving the material's oxidation resistance. Because carbon / carbon composite materials themselves have excellent high-temperature resistance, they can withstand the high temperatures generated during laser melting of silicon powder. However, for SiC... f For SiC composites, the maximum temperature that the fibers can withstand is 1400 ℃. When using laser cladding, the temperature in the molten pool region significantly exceeds the fiber's temperature limit, causing irreversible changes in the fiber's internal structure and resulting in a significant degradation of the material's mechanical properties. Therefore, repair methods used for carbon / carbon composite coatings cannot be directly applied; it is necessary to develop methods suitable for SiC. f Repair schemes and material systems for SiC composite materials.

[0008] In summary, current research on SiC fRepair technology for SiC composite materials is currently lacking, making it difficult to achieve microstructural reconstruction and performance restoration. Therefore, there is an urgent need to develop new ceramic repair technologies to overcome material application bottlenecks, extend the service life of components, and thus ensure the stability, safety, and economy of high-end equipment, contributing to the sustainable development of China's manufacturing industry. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a SiC f A laser repair method for near-surface damage in SiC composite materials, the laser repair method specifically includes the following steps: Step S1, Pretreatment: Pretreatment of SiC with near-surface damage. f / SiC composite material is pretreated; Step S2: Preparation of repair slurry: After acid washing of silicon carbide ceramic particles and carbon source powder, a dispersion solution is prepared and then ultrasonically stirred to obtain the repair slurry. Step S3: Introduce the repair slurry: Introduce the repair slurry obtained in step S2 into the SiC pretreated in step S1. f The damaged area of ​​the / SiC composite material is formed, and a ceramic skeleton network is formed in the damaged area; Step S4, Laser Selective Repair: Placed in a vacuum environment, melt-infiltrating powder is simultaneously delivered to the damaged area, and the laser beam is controlled to focus on the area for scanning to achieve reactive melt-infiltrating of the damaged area.

[0010] Compared with existing technologies, this invention ensures the cleanliness and activation of the damaged interface through systematic pretreatment, constructs a porous framework network with high ceramic content and modulus matching that of the base material using particle size distribution technology, and finally achieves precise filling and reactive bonding of the framework network by the melt in a vacuum environment using laser selective powder feeding and infiltration technology. This solution overcomes the difficulty of repairing SiC using traditional methods. f The bottleneck of near-surface damage in SiC composites is addressed by precisely controlling the thermal field with lasers, strictly confining the high-temperature reaction to the damaged area and effectively avoiding damage to the fibers from overall heat exposure. The repair process is controllable, the repaired area is dense and well-bonded to the matrix, significantly improving the integrity and performance recovery rate of the repaired structure. This provides a reliable technical path for achieving in-situ, precise, and efficient life-extending repair of such high-end ceramic components.

[0011] In one possible implementation, step S1 includes pretreatment comprising sequential ultrasonic cleaning, acidic solution ultrasonic cleaning, and low-temperature plasma cleaning; wherein, The parameters for ultrasonic cleaning are as follows: the cleaning solution is an organic solvent, and the cleaning time is 1-3 hours. The parameters for ultrasonic cleaning with acidic solution are as follows: the acidic solution is a 5-10 wt% hydrofluoric acid solution, and the time is 5-12 h; The parameters for low-temperature plasma cleaning are as follows: gas is hydrogen, power is 300-500 W, and time is 10-15 min.

[0012] Compared with existing technologies, this invention achieves a progressively deep purification of damaged surfaces, from macroscopic contaminants to microscopic oxide layers, through a three-step synergistic process of organic solvent cleaning, acidic solution ultrasonic cleaning, and low-temperature plasma cleaning. Its advantages lie not only in effectively removing surface debris and impurities, but more importantly, in thoroughly eliminating interfacial adsorbed functional groups and trace oxide layers through hydrofluoric acid etching and plasma activation, significantly improving the surface energy and chemical activity of the damaged area. This clean and activated surface state greatly promotes the wetting, spreading, and penetration of subsequent repair slurry, and provides a highly reactive interface for the melting and infiltration process. This reduces porosity and bonding defects between the repair layer and the base material from the source, laying a crucial foundation for obtaining a dense and robust repair effect.

[0013] In one possible implementation, in step S2, the particle size range of the silicon carbide ceramic particles is 0.2-20 μm, the particle size ratio of the three-stage gradation is D1:D2:D3=1:(5-7):(10-20), and the corresponding mass ratio is m1:m2:m3=1:(2-5):(7-10).

[0014] Compared with existing technologies, this invention, through precise particle size and mass ratio design, enables ceramic particles of different sizes to form a densest packing structure, thereby constructing a ceramic skeleton network with low porosity and good continuity in the damaged area. Its core advantage lies in the fact that this highly dense prefabricated skeleton can maximize the acceptance of ceramic phases generated by subsequent infiltration reactions, while significantly reducing the residue of low-melting-point alloy melts, ensuring an extremely high ceramicization rate in the repair area. This not only ensures a good match between the mechanical modulus of the repair area and the parent material, guaranteeing the continuity of load transfer, but also lays the foundation for the high density, high strength, and high thermal stability of the repair from a microstructural perspective.

[0015] In one possible implementation, in step S2, the carbon source powder is selected from at least one of graphite powder, carbon black, and pyrolytic carbon.

[0016] Compared with existing technologies, this invention introduces graphite powder, carbon black, or pyrolytic carbon as the reactive carbon source, which can fully react with molten silicon alloy during laser infiltration to generate a silicon carbide ceramic phase in situ. This not only significantly improves the ceramicization rate of the repaired area and effectively avoids the residue of low-melting-point alloy phases, but also ensures that the newly formed ceramic phase is tightly bonded to the graded framework, further optimizing the composition and structure of the repaired area. This ensures that the repair has higher thermal stability, better mechanical properties, and thermophysical properties that are more compatible with the base material, thereby guaranteeing the long-term service reliability of the repaired area.

[0017] In one possible implementation, in step S2, the mass ratio of silicon carbide ceramic particles to carbon source powder is (3-5):1.

[0018] Compared to existing technologies, the aforementioned mass ratio design optimizes the balance between ceramic framework construction and carbon reaction source supply. Its advantages lie in ensuring a sufficiently dense structural framework to support the mechanical properties of the repair area, while also providing an appropriate amount of carbon source for complete reaction with the infiltrated alloy. This maximizes ceramic conversion efficiency, reduces low-melting-point alloy residue, and ultimately yields a restoration with properties highly matched to the parent material.

[0019] In one possible implementation, in step S2, ultrasonic stirring is performed simultaneously with pickling, and the pickling parameters are as follows: the pickling solution is a hydrofluoric acid solution with a concentration of 5-10 wt%, the temperature is 60-80 ℃, and the time is 12-24 h.

[0020] Compared with existing technologies, the pickling process of this invention is carried out under ultrasonic assistance and heating conditions, which can efficiently and thoroughly remove adsorbed functional groups and trace oxide layers from the surface of silicon carbide particles and carbon source powder. This treatment significantly improves the surface chemical activity and cleanliness of the powder, thereby ensuring that it can achieve highly uniform dispersion in subsequent slurry preparation and enhancing its compatibility with the dispersion medium.

[0021] In one possible implementation, in step S2, the dispersion system of the dispersion solution is selected from one of sodium carboxymethyl cellulose aqueous solution, phenolic resin solution, and sol containing monomer-crosslinking agent system.

[0022] Compared with existing technologies, this invention, by selecting a suitable dispersion medium, not only ensures that the slurry has good stability, wettability and filling ability for complex damage morphologies, but also can be efficiently transformed into a structurally stable porous ceramic skeleton in subsequent processing, thus providing a reliable and adaptable prefabricated foundation for laser infiltration repair.

[0023] In one possible implementation, in step S2, the ceramic solids content of the repair slurry is 30-40 vol.%.

[0024] Compared with existing technologies, the above-mentioned ceramic solid content ensures that the slurry has good fluidity and sufficient filling ability for the damaged morphology, while also guaranteeing the formation of a porous ceramic skeleton with sufficient density and strength after drying or curing. This provides an ideal prefabricated structure for the subsequent infiltration process and is a key prerequisite for obtaining a dense and robust restoration.

[0025] In one possible implementation, in step S3, the method for introducing the repair slurry is either a slurry coating method or a vacuum pressure impregnation method; wherein... When near-surface damage presents as pits, a slurry coating method is used to introduce repair slurry. When the near-surface damage morphology is a crack or fissure with depth characteristics, the repair slurry is introduced using a vacuum pressure impregnation method.

[0026] Compared with existing technologies, this invention differentiates the introduction method based on the damage morphology characteristics (shallow pits or deep cracks), achieving precise and efficient filling of defects by the repair slurry. Its advantage lies in the targeted process selection ensuring that the slurry can fully penetrate and adhere to damage areas of different morphologies, laying a crucial foundation for the subsequent construction of a uniform and complete ceramic skeleton network. This significantly improves the integrity and reliability of the repair, effectively avoiding weak points in the repair caused by incomplete filling.

[0027] In one possible implementation, in step S3, the method for forming the ceramic framework network is selected from one of the following: freeze-drying, curing-pyrolysis composite method, and sol-gel conversion combined with heat treatment; wherein, When the dispersion system of the dispersion solution is an aqueous solution of sodium carboxymethyl cellulose, a ceramic framework network is formed by freeze drying. When the dispersion system of the dispersion solution is a phenolic resin solution, a ceramic framework network is formed by a curing-pyrolysis composite method. When the dispersion system of the dispersion solution is a sol containing a monomer-crosslinking agent system, a ceramic framework network is formed by sol-gel conversion combined with heat treatment.

[0028] Compared with existing technologies, this invention ensures that the slurry can be efficiently and completely transformed into a porous ceramic framework with a stable structure and suitable porosity by precisely matching the most suitable framework forming process for different dispersion systems (water-based slurry - freeze-drying, resin-based slurry - curing pyrolysis, sol system - gel conversion heat treatment). Its advantage lies in the fact that this systematic process design fully utilizes the characteristics of each material system, making the framework forming process controllable and reliable. This provides an ideal preform with uniform structure and good strength for subsequent melt infiltration repair, thereby fundamentally guaranteeing the compactness, bonding strength, and final performance of the repaired area.

[0029] In one possible implementation, the parameters of the freeze-drying method are as follows: temperature from -40 to -20 °C, time from 24 to 48 h; The parameters of the curing-pyrolysis composite method are as follows: curing temperature is 120-200 ℃, time is 1-2 h, pyrolysis temperature is 900-1100 ℃, time is 2-5 h, and the protective gas is argon. The specific operation of the sol-gel conversion combined with heat treatment method is as follows: the sol gelation temperature is 60-80 ℃, after gelation, it is placed at room temperature for drying for 12-24 h, and the dried material is placed in a heat treatment furnace and heated to 400-600 ℃ at a rate of 1 ℃ / min to remove the sol and obtain a ceramic skeleton network.

[0030] Compared with existing technologies, this invention can effectively suppress skeleton cracking, deformation or performance degradation caused by stress concentration, component oxidation or rapid shrinkage during drying or pyrolysis by strictly controlling key parameters such as temperature, time and atmosphere at each stage. This ensures that an ideal ceramic skeleton network with complete structure, interconnected pores and sufficient strength is finally obtained, laying a solid foundation for subsequent high-quality melt infiltration repair.

[0031] In one possible implementation, in step S4, the vacuum level of the vacuum environment is ≤200 Pa, the laser power is 300-600 W, the scanning speed is 3-7 mm / s, and the spot diameter is 3-5 mm.

[0032] Compared with existing technologies, the parameters used in this invention, through matching and optimizing laser energy input and a stringent vacuum environment, achieve precise control of the thermal field during the repair process. Specifically, this ensures that the melting and infiltration reaction proceeds fully, guaranteeing complete filling and bonding of the melt to the precast skeleton, while effectively suppressing fiber damage and harmful phase formation caused by excessive temperature or oxidation. Thus, while successfully repairing the damage, it maximizes the protection of the original properties and structural integrity of the parent material.

[0033] In one possible implementation, in step S4, the infiltrated powder is a low-melting-point silicon-containing eutectic alloy powder.

[0034] Compared with existing technologies, this invention uses low-melting-point silicon-containing eutectic alloy powder as the infiltration material, and its core advantage lies in significantly reducing the temperature required for the repair process. This not only effectively avoids thermal damage to the SiC fiber reinforcement caused by the high temperature of the laser and protects the mechanical properties of the base material, but also ensures that the alloy melt has good fluidity and wettability, thereby achieving full reaction with the carbon source powder and complete penetration into the prefabricated ceramic skeleton, ultimately forming a dense and firmly bonded repair zone.

[0035] It is worth mentioning that the selected infiltration powders include, but are not limited to, low-melting-point silicon-containing eutectic alloy powders such as Si-8.5at%Hf, Si-16at%Ti, and Si-18at%Y.

[0036] Furthermore, to avoid internal stress and deformation caused by a large temperature difference between the repair area and the base material during the repair process, a heating stage was installed at the bottom of the sample to reduce the temperature gradient. In addition, a CNC system was installed inside the equipment to achieve gradual increase and decrease of laser power, thereby reducing the concentration of thermal stress in the repair area. Attached Figure Description

[0037] Figure 1 This shows the packing of SiC particles in the matrix after gradation. Figure 2 A process roadmap for laser repair of near-surface damage in silicon carbide ceramics and their composites; Figure 3 These are photos of the composite material before and after laser repair. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0039] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0041] Example 1 This embodiment provides a SiC based on particle size distribution.f The specific steps for repairing near-surface pits in SiC composite materials are as follows: Step 1, Damaged Surface Treatment: Treating SiC with Damaged Near-Surface f The SiC composite material was ultrasonically cleaned in acetone for about 2 hours to remove residual debris and impurities on the damaged surface. Then it was acid-washed in dilute hydrofluoric acid solution for 12 hours to remove excess functional groups at the interface. Finally, it was cleaned by low-temperature plasma for 15 minutes to complete the treatment of the damaged surface. Step 2, Preparation of Repair Slurry: Silicon carbide particles with particle sizes of 0.5 μm, 2 μm, and 10 μm were mixed and graded at a mass ratio of 1:5:10. Then, the graded silicon carbide particles and 1 μm carbon black were respectively placed in dilute hydrofluoric acid for acid washing for 12 h. Next, the dried ceramic powders were added sequentially to a 1 wt.% sodium carboxymethyl cellulose dispersion at a mass ratio of 1:4 to prepare a solution with a ceramic content of 40 vol.%. The mixed solution was then treated by ultrasonic stirring for 24 h to obtain a uniformly dispersed ceramic repair slurry. Step 3, Repair slurry coating: The ceramic repair slurry is introduced into the microcracks on the surface of the material by vacuum pressure impregnation, so that the ceramic repair slurry penetrates evenly into the crack. The water in the ceramic slurry is removed by freeze drying process, and a porous skeleton structure is formed. Step 4, Laser Selective Repair: Place the repair material in the reaction chamber, evacuate to below 200 Pa, set the laser power to 400 W, scanning speed to 5 mm / s, and spot diameter to 3 mm. Feed yttrium silicon powder into the chamber using a powder feeder. A robotic arm controls the laser to focus on the damaged area, and the equipment is started to achieve reaction penetration in the selected area according to the set scanning path. Repaired SiC f The SiC composite material has a complete structure and its flexural strength is restored to 83% of the original parent material strength.

[0042] Example 2 This embodiment provides a SiC based on particle size distribution. f The specific steps for repairing near-surface cracks in SiC composite materials are as follows: Step 1, Damaged Surface Treatment: Treating SiC with Damaged Near-Surface f The SiC composite material was placed in isopropanol for ultrasonic cleaning for about 3 hours to remove residual debris and impurities on the damaged surface. Finally, it was cleaned by low-temperature plasma for 15 minutes to complete the surface treatment. Step 2, Preparation of Repair Slurry: Silicon carbide particles with particle sizes of 0.5 μm, 2 μm, and 10 μm were mixed and graded at a mass ratio of 1:5:10. The graded silicon carbide particles and 1 μm carbon black were respectively placed in dilute hydrofluoric acid for acid washing for 12 h. Then, the dried ceramic powders of the two types were added to a 20 wt.% phenolic resin solution at a mass ratio of 1:3 to prepare a solution with a ceramic content of 40 vol.%. The mixed solution was treated by ultrasonic stirring for 24 h to obtain a uniformly dispersed ceramic repair slurry. Step 3, Repair slurry impregnation: The ceramic repair slurry is introduced into the microcracks on the surface of the material through vacuum pressure impregnation, so that the ceramic repair slurry penetrates evenly into the crack. Through the curing-pyrolysis composite process, the phenolic resin in the ceramic slurry is converted into amorphous carbon and forms a porous skeleton structure. Step 4, Laser Selective Repair: Place the repair material in the reaction chamber, evacuate to below 200 Pa, set the laser power to 300 W, scanning speed to 3 mm / s, and spot diameter to 3 mm. Feed the silicon-aluminum powder through the powder feeder. The robotic arm controls the laser to focus on the damaged area, and the equipment is started to achieve reaction penetration in the selected area according to the set scanning path. Repaired SiC f The SiC composite material has a complete structure and its flexural strength is restored to 85% of the original parent material strength.

[0043] Comparative Example 1 This comparative example provides a SiC f The specific steps for repairing near-surface pits in SiC composite materials are as follows: Step 1, Damaged Surface Treatment: Treating SiC with Damaged Near-Surface f The SiC composite material was ultrasonically cleaned in anhydrous ethanol for about 1 hour to remove residual debris and impurities on the damaged surface. Then it was acid-washed in dilute hydrofluoric acid solution for 12 hours to remove excess functional groups at the interface. Finally, it was cleaned by low-temperature plasma for 10 minutes to complete the treatment of the damaged surface. Step 2, Preparation of Repair Slurry: 5 μm silicon carbide particles and 1 μm graphite powder were respectively placed in dilute hydrofluoric acid for acid washing for 12 h. Then, the dried ceramic powders were added to a 1 wt.% sodium carboxymethyl cellulose dispersion solution at a mass ratio of 3:1 to prepare a solution with a ceramic content of 40 vol.%. The mixture was then treated with ultrasonic stirring for 24 h to obtain a uniformly dispersed ceramic repair slurry. Step 3, Applying the repair slurry: Apply the ceramic repair slurry to the damaged surface of the material, so that the ceramic repair slurry is evenly spread on the pit damaged surface. Remove the water in the ceramic slurry through a freeze-drying process and form a porous skeleton structure. Step 4, Laser Selective Repair: Place the repair material in the reaction chamber, evacuate to below 200 Pa, set the laser power to 600 W, scanning speed to 5 mm / s, and spot diameter to 3 mm. Feed the silicon-yttrium alloy powder through the powder feeder. The robotic arm controls the laser to focus on the damaged area, and the equipment is started to achieve reaction penetration in the selected area according to the set scanning path. Repaired SiC f The SiC composite material has a complete structure, and its flexural strength is restored to 71% of the original parent material's strength.

[0044] Based on the comparison results of the above embodiments and comparative examples, it can be seen that the flexural strength recovery rate of the repaired material using particle gradation technology (Examples 1 and 2) (83% and 85%) is significantly higher than that of the comparative example (71%) without gradation technology. This strongly demonstrates that constructing a high ceramic content and dense precast skeleton through precise particle gradation is the core of achieving high-performance repair. This technical solution can effectively ensure the modulus matching and structural integrity between the repair area and the base material. Combined with an optimized slurry system and laser process, it achieves efficient and reliable repair of near-surface pits and cracks, thus extending the lifespan of SiC. f This provides a practical process path for extending the service life of key SiC composite components.

[0045] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A SiC f A laser repair method for near-surface damage in SiC composite materials, characterized in that... The laser repair method specifically includes the following steps: Step S1, Pretreatment: Pretreatment of SiC with near-surface damage. f / SiC composite material is pretreated; Step S2: Preparation of repair slurry: After acid washing of silicon carbide ceramic particles and carbon source powder, a dispersion solution is prepared and then ultrasonically stirred to obtain the repair slurry. Step S3: Introduce the repair slurry: Introduce the repair slurry obtained in step S2 into the SiC pretreated in step S1. f The damaged area of ​​the / SiC composite material is formed, and a ceramic skeleton network is formed in the damaged area; Step S4, Laser Selective Repair: Placed in a vacuum environment, melt-infiltrating powder is simultaneously delivered to the damaged area, and the laser beam is controlled to focus on the area for scanning to achieve reactive melt-infiltrating of the damaged area.

2. The laser repair method as described in claim 1, characterized in that, In step S1, the pretreatment includes sequential ultrasonic cleaning, acidic solution ultrasonic cleaning, and low-temperature plasma cleaning; wherein, The parameters for ultrasonic cleaning are as follows: the cleaning solution is an organic solvent, and the cleaning time is 1-3 hours. The parameters for ultrasonic cleaning with acidic solution are as follows: the acidic solution is a 5-10 wt% hydrofluoric acid solution, and the time is 5-12 h; The parameters for low-temperature plasma cleaning are as follows: gas is hydrogen, power is 300-500W, and time is 10-15min.

3. The laser repair method as described in claim 1, characterized in that, In step S2, the particle size range of silicon carbide ceramic particles is 0.2-20 μm, and the particle size ratio of the three-stage gradation is D1:D2:D3=1:(5-7):(10-20), with a corresponding mass ratio m1:m2:m3=1:(2-5):(7-10).

4. The laser repair method as described in claim 1, characterized in that, In step S2, the carbon source powder is selected from at least one of graphite powder, carbon black, and pyrolytic carbon; and / or, In step S2, the mass ratio of silicon carbide ceramic particles to carbon source powder is (3-5):

1.

5. The laser repair method as described in claim 1, characterized in that, In step S2, ultrasonic stirring is performed simultaneously with pickling, and the pickling parameters are as follows: the pickling solution is a hydrofluoric acid solution with a concentration of 5-10 wt%, the temperature is 60-80 ℃, and the time is 12-24 h.

6. The laser repair method as described in claim 1, characterized in that, In step S2, the dispersion system of the dispersion solution is selected from one of the following: sodium carboxymethyl cellulose aqueous solution, phenolic resin solution, and sol containing monomer-crosslinking agent system; and / or, In step S2, the ceramic solid phase content of the repair slurry is 30-40 vol.%.

7. The laser repair method as described in claim 1, characterized in that, In step S3, the method for introducing the repair slurry is either a slurry coating method or a vacuum pressure impregnation method; wherein... When near-surface damage presents as pits, a slurry coating method is used to introduce repair slurry. When the near-surface damage morphology is a crack or fissure with depth characteristics, the repair slurry is introduced using a vacuum pressure impregnation method.

8. The laser repair method as described in claim 1, characterized in that, In step S3, the method for forming the ceramic framework network is selected from one of the following: freeze-drying, curing-pyrolysis composite method, and sol-gel conversion combined with heat treatment; wherein... When the dispersion system of the dispersion solution is an aqueous solution of sodium carboxymethyl cellulose, a ceramic framework network is formed by freeze drying. When the dispersion system of the dispersion solution is a phenolic resin solution, a ceramic framework network is formed by a curing-pyrolysis composite method. When the dispersion system of the dispersion solution is a sol containing a monomer-crosslinking agent system, a ceramic framework network is formed by sol-gel conversion combined with heat treatment.

9. The laser repair method as described in claim 8, characterized in that, The parameters for the freeze-drying method are as follows: temperature -40 to -20 ℃, time 24-48 h; The parameters of the curing-pyrolysis composite method are as follows: curing temperature is 120-200 ℃, time is 1-2 h, pyrolysis temperature is 900-1100 ℃, time is 2-5 h, and the protective gas is argon. The specific operation of the sol-gel conversion combined with heat treatment method is as follows: the sol gelation temperature is 60-80 ℃, after gelation, it is placed at room temperature for drying for 12-24 h, and the dried material is placed in a heat treatment furnace and heated to 400-600 ℃ at a rate of 1 ℃ / min to remove the sol and obtain a ceramic skeleton network.

10. The laser repair method as described in claim 1, characterized in that, In step S4, the vacuum level of the vacuum environment is ≤200 Pa, the laser power is 300-600 W, the scanning speed is 3-7 mm / s, and the spot diameter is 3-5 mm; and / or, In step S4, the infiltrated powder is a low-melting-point silicon-containing eutectic alloy powder.

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