A method for repairing damaged SiC coated carbon / carbon composites

Abstract

The present application relates to a kind of repair methods for damaged SiC coating carbon / carbon composite, SiO2-Nd2O3 / Si-SiC repair system for damaged SiC coating carbon / carbon composite and its preparation method, based on laser cladding technology, using SiO2-Nd2O3 / Si-SiC double-layer system to locally repair SiC coating damage part.The Si-SiC inner coating has good physical and chemical compatibility with C / C composite substrate and the SiC coating of undamaged part, which is beneficial to the recovery of oxidation protection performance of repaired sample;SiO2-Nd2O3 outer coating presents strong reflection characteristics to laser in 1 μm band, which can effectively reduce the absorption of laser energy and heat generation of material, thereby effectively protecting the secondary damage of laser to SiC coating.

Description

Technical Field

[0001] This invention belongs to the field of protective coating technology, and relates to a repair method for damaged SiC coating carbon / carbon composite materials, and to a SiO2-Nd2O3 / Si-SiC repair system and method for damaged SiC coating carbon / carbon (C / C) composite materials. Background Technology

[0002] SiC-coated C / C composites are often used as thermal structural components in extreme environments due to their advantages such as high specific strength, excellent high-temperature resistance, and outstanding oxidation resistance. However, SiC coatings have poor resistance to ablation by lasers in the 1μm wavelength range. Under laser irradiation, the cumulative thermal effect can cause a dramatic temperature rise and ablation failure of the SiC coating. If the damaged coating is not repaired in time, it will lead to oxidation of the C / C composite matrix and a significant deterioration of its mechanical properties, potentially causing serious accidents. Therefore, research on the repair of damaged SiC coatings is urgently needed.

[0003] Reference 1, "Repair of SiC coating on carbon / carbon composites by laser cladding technique, Hanhui Wang, Hejun Li, Xiaohong Shi, Xuesong Liu, Jing'an Kong, Hang Zhou, Ceramics International, 2020, 46: 19537-19544," proposes using laser cladding technology, which features precise positioning and rapid forming, for the damage repair of SiC-coated C / C composites. By locally preparing a Si-SiC coating with good physicochemical compatibility with the SiC coating at the damaged site, the basic restoration of both the geometric dimensions and oxidation protection performance of the repaired area is achieved. Therefore, using Si-SiC as an inner coating helps to obtain a repair system that has good bonding with the C / C composite matrix and excellent oxidation resistance.

[0004] Reference 2, "Ablation behavior of graphite / SiO2 composite irradiated by high-intensity continuous laser, Wenzhi Li, Lihong Gao, Zhuang Ma, Fuchi Wang, Journal of the European Ceramics Society, 2017, 37: 1331-1338," confirms that SiO2 has a strong reflection and dissipation effect on lasers in the 1μm band. Using it as an outer coating of the repair system can effectively reduce the absorption of laser energy and the generation and accumulation of heat, thereby significantly improving the laser ablation resistance of the repaired area and avoiding the catastrophic consequences of secondary laser damage.

[0005] Reference 3, "Design and preparation of composite coatings with increased reflectivity under high-energy continuous wave laser ablation," Weiye Xu, Lihong Gao, Chen Ma, Zhuang Ma, Taotao Wu, Alexandr A. Rogachev, Fuchi Wang, Ceramics International, 2020, 46: 23457-23462, reveals that the laser ablation resistance of the protective coating significantly increases with increasing reflectivity. Considering that doping with rare earth element Nd can further enhance the reflectivity of SiO2 to lasers of specific wavelengths, the repair system with SiO2-Nd2O3 as the outer coating theoretically has a more ideal laser protection effect.

[0006] Therefore, the invention and research of the SiO2-Nd2O3 / Si-SiC bilayer repair system for damaged SiC coating C / C composites based on laser cladding method has important theoretical and practical significance. Summary of the Invention

[0007] Technical problems to be solved

[0008] To overcome the shortcomings of existing technologies, this invention proposes a repair method for damaged SiC-coated carbon / carbon composites, and provides a SiO2-Nd2O3 / Si-SiC repair system and its preparation method for damaged SiC-coated C / C composites. Specifically, a Si-SiC inner coating and a SiO2-Nd2O3 outer coating are prepared at the damaged SiC coating site using laser cladding technology. The Si-SiC inner coating exhibits good physicochemical compatibility with both the C / C composite matrix and the undamaged SiC coating, which is beneficial for restoring the oxidation protection performance of the repaired sample. The SiO2-Nd2O3 outer coating, through Nd doping, enhances the reflectivity of lasers in the 1μm wavelength range, thereby strengthening the laser ablation resistance at the repaired site and ultimately achieving the goal of effectively protecting the SiC coating from secondary laser damage.

[0009] Technical solution

[0010] A method for repairing damaged SiC-coated carbon / carbon composite materials, characterized in that: the damaged SiC coating is provided with a Si-SiC inner coating and a SiO2-Nd2O3 outer coating, and the repair steps are as follows:

[0011] Step 1, Pretreatment: Along the surface of the damaged area, the damaged area of ​​the SiC-coated C / C composite material is filed and polished to remove the coating in that area until the C / C composite material matrix is ​​exposed.

[0012] Step 2, Powder preparation: Mix 50-70% Si powder, 15-30% SiC powder and 5-15% C powder by ball milling to make the inner coating powder.

[0013] SiO2 powder with a mass percentage of 95-100% and Nd2O3 powder with a mass percentage of 0-5% were ball-milled and then placed in a muffle furnace. The furnace temperature was raised from room temperature to 1573-1773K in an air environment and heat-treated for 1-2 hours. The mixture was then removed and air-cooled to obtain SiO2-Nd2O3 bulk material, which was then ground into powder and used as an outer coating powder.

[0014] Step 3, Damage Repair: Anhydrous ethanol is used as a solvent to magnetically stir the inner coating powder and then applied to the pretreated area in Step 1. After drying to remove the solvent, laser cladding is performed using a fiber laser in an argon atmosphere to obtain the Si-SiC inner coating. Anhydrous ethanol is used as a solvent to magnetically stir the outer coating powder and then applied to the surface of the Si-SiC inner coating. After drying to remove the solvent, laser cladding is performed using a CO2 laser in an argon atmosphere to obtain the SiO2-Nd2O3 outer coating.

[0015] The laser cladding parameters for the inner coating are: power 200-400W, scanning speed 2-5mm / s, and spot diameter 3-5mm; the laser cladding parameters for the outer coating are: power 100-200W, scanning speed 10-16mm / s, and spot diameter 6-10mm.

[0016] The ball milling process takes 2-4 hours.

[0017] The magnetic stirring is carried out for 2-4 hours.

[0018] Beneficial effects

[0019] This invention proposes a repair method for damaged SiC-coated carbon / carbon composites. Specifically, it focuses on the SiO2-Nd2O3 / Si-SiC repair system and its preparation method for damaged SiC-coated carbon / carbon composites. Based on laser cladding technology, a SiO2-Nd2O3 / Si-SiC bilayer system is used to locally repair the damaged areas of the SiC coating. The Si-SiC inner coating exhibits good physicochemical compatibility with both the C / C composite matrix and the undamaged SiC coating, which is beneficial for restoring the oxidation protection performance of the repaired sample. The SiO2-Nd2O3 outer coating exhibits extremely strong reflectivity to laser light in the 1μm wavelength range, effectively reducing the absorption of laser energy and the generation of heat, thereby effectively preventing secondary damage to the SiC coating from laser light.

[0020] The present invention has the following effects:

[0021] 1) Laser cladding technology has been successfully used to repair damaged areas with coatings. It has high process stability, precise positioning, high coating preparation efficiency, short cycle and low cost, and is expected to be applied in large-scale engineering.

[0022] 2) such as Figure 1 As shown, the SiO2-Nd2O3 material provided by this invention exhibits excellent laser reflectivity. Compared to SiO2 and SiC materials, its reflectivity is increased by 8% and 43.3%, respectively, demonstrating the significant modification effect of Nd.

[0023] 3) such as Figure 2 As shown, the SiO2-Nd2O3 / Si-SiC laser protective coating provided by the present invention has a smooth surface and dense structure, without defects such as cracks or holes, and no interface cracking, indicating good preparation effect.

[0024] 4) such as Figure 3 As shown, the SiO2-Nd2O3 / Si-SiC repair system provided by this invention exhibits optimal resistance to laser ablation. Compared to unmodified SiO2 / Si-SiC coated samples and undamaged SiC coated samples, the SiO2-Nd2O3 / Si-SiC sample demonstrates superior resistance to laser ablation at 23.89 MW / m².2 With 39.81MW / m 2 The mass loss was minimal under both heat flux densities after 7 seconds of continuous irradiation, at 0.14% and 0.31%, respectively. Attached Figure Description

[0025] Figure 1 The reflectance curves of SiC, SiO2 and SiO2-Nd2O3 powders provided in Example 1 of the present invention.

[0026] Figure 2 (a) Surface morphology and (b) cross-sectional morphology of the SiO2-Nd2O3 / Si-SiC laser protective coating provided in Embodiment 1 of the present invention.

[0027] Figure 3 The (a) 23.89MW / m² provided for Embodiment 1 of the present invention 2 (b) 39.81MW / m 2 Curve showing the change in laser ablation quality under heat flux density. Detailed Implementation

[0028] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0029] Example 1:

[0030] 1) Pretreatment: Along the surface of the damaged area, the damaged area of ​​the SiC-coated C / C composite material is filed to remove the coating in that area until the C / C composite material matrix is ​​exposed. The sample is then ultrasonically cleaned and dried for later use.

[0031] 2) Powder preparation: Weigh 55% Si powder, 30% SiC powder and 15% C powder by mass, and ball mill them together for 4 hours to prepare as inner coating powder. In addition, weigh 95% SiO2 powder and 5% Nd2O3 powder by mass, ball mill them together for 4 hours and place them in a muffle furnace. Heat the mixture from room temperature to 1773K in air and continue heat treatment for 2 hours. Then remove it and air cool it to obtain SiO2-Nd2O3 bulk material. To facilitate subsequent repair use, grind it into powder and prepare it as outer coating powder.

[0032] 3) Damage Repair: Anhydrous ethanol was used as a solvent to prepare an inner coating slurry with the inner coating powder. After magnetic stirring for 4 hours, the slurry was applied to the pretreated area of ​​the sample obtained in step 1). After drying to remove the solvent, laser cladding was performed using a fiber laser in an argon atmosphere to obtain the Si-SiC inner coating. Anhydrous ethanol was used as a solvent to prepare an outer coating slurry with the outer coating powder. After magnetic stirring for 4 hours, the slurry was applied to the surface of the Si-SiC inner coating. After drying to remove the solvent, laser cladding was performed using a CO2 laser in an argon atmosphere to obtain the SiO2-Nd2O3 outer coating. The laser cladding parameters for the inner coating were: power 300W, scanning speed 2mm / s, and spot diameter 4mm; the laser cladding parameters for the outer coating were: power 100W, scanning speed 10mm / s, and spot diameter 10mm.

[0033] 4) Ablation Test: To test the laser protection performance of the repaired SiC-coated C / C composite material, fiber lasers with wavelengths of 1060-1090 nm were used to perform laser ablation tests on both the repaired and undamaged SiC coatings, and the results were compared. Two laser heat flux densities were selected, namely 23.89 MW / m². 2 With 39.81MW / m 2 Irradiation durations of 1, 3, 5, and 7 seconds were performed, and the weight loss percentage for each ablation was calculated.

[0034] Example 2:

[0035] 1) Pretreatment: Along the surface of the damaged area, the damaged area of ​​the SiC-coated C / C composite material is filed to remove the coating in that area until the C / C composite material matrix is ​​exposed. The sample is then ultrasonically cleaned and dried for later use.

[0036] 2) Powder preparation: Weigh 55% Si powder, 30% SiC powder and 15% C powder by mass, and ball mill them together for 4 hours to prepare as inner coating powder. In addition, weigh 95% SiO2 powder and 5% Nd2O3 powder by mass, ball mill them together for 4 hours and place them in a muffle furnace. Heat the mixture from room temperature to 1773K in air and continue heat treatment for 2 hours. Then remove it and air cool it to obtain SiO2-Nd2O3 bulk material. To facilitate subsequent repair use, grind it into powder and prepare it as outer coating powder.

[0037] 3) Damage Repair: Anhydrous ethanol was used as a solvent to prepare an inner coating slurry with the inner coating powder. After magnetic stirring for 4 hours, the slurry was applied to the pretreated area of ​​the sample obtained in step 1). After drying to remove the solvent, laser cladding was performed using a fiber laser in an argon atmosphere to obtain the Si-SiC inner coating. Anhydrous ethanol was used as a solvent to prepare an outer coating slurry with the outer coating powder. After magnetic stirring for 4 hours, the slurry was applied to the surface of the Si-SiC inner coating. After drying to remove the solvent, laser cladding was performed using a CO2 laser in an argon atmosphere to obtain the SiO2-Nd2O3 outer coating. The laser cladding parameters for the inner coating were: power 400W, scanning speed 4mm / s, and spot diameter 4mm; the laser cladding parameters for the outer coating were: power 200W, scanning speed 15mm / s, and spot diameter 10mm.

[0038] 4) Ablation Test: To test the laser protection performance of the repaired SiC-coated C / C composite material, fiber lasers with wavelengths of 1060-1090 nm were used to perform laser ablation tests on both the repaired and undamaged SiC coatings, and the results were compared. Two laser heat flux densities were selected, namely 23.89 MW / m². 2 With 39.81MW / m 2 Irradiation durations of 1, 3, 5, and 7 seconds were performed, and the weight loss percentage for each ablation was calculated.

[0039] Example 3:

[0040] 1) Pretreatment: Along the surface of the damaged area, the damaged area of ​​the SiC-coated C / C composite material is filed to remove the coating in that area until the C / C composite material matrix is ​​exposed. The sample is then ultrasonically cleaned and dried for later use.

[0041] Powder preparation: Weigh 55% Si powder, 30% SiC powder and 15% C powder by mass, and ball mill them together for 4 hours to prepare as the inner coating powder. Separately, weigh 95% SiO2 powder and 5% Nd2O3 powder by mass, ball mill them together for 4 hours and place them in a muffle furnace. Heat the mixture from room temperature to 1773K in air and continue heat treatment for 2 hours. Then remove it and air cool it to obtain SiO2-Nd2O3 bulk material. To facilitate subsequent repair use, grind it into powder and prepare it as the outer coating powder.

[0042] 3) Damage Repair: Anhydrous ethanol was used as a solvent to prepare an inner coating slurry with the inner coating powder. After magnetic stirring for 4 hours, the slurry was applied to the pretreated area of ​​the sample obtained in step 1). After drying to remove the solvent, laser cladding was performed using a fiber laser in an argon atmosphere to obtain the Si-SiC inner coating. Anhydrous ethanol was used as a solvent to prepare an outer coating slurry with the outer coating powder. After magnetic stirring for 4 hours, the slurry was applied to the surface of the Si-SiC inner coating. After drying to remove the solvent, laser cladding was performed using a CO2 laser in an argon atmosphere to obtain the SiO2-Nd2O3 outer coating. The laser cladding parameters for the inner coating were: power 350W, scanning speed 3mm / s, and spot diameter 4mm; the laser cladding parameters for the outer coating were: power 150W, scanning speed 13mm / s, and spot diameter 10mm.

[0043] 4) Ablation Test: To test the laser protection performance of the repaired SiC-coated C / C composite material, fiber lasers with wavelengths of 1060-1090 nm were used to perform laser ablation tests on both the repaired and undamaged SiC coatings, and the results were compared. Two laser heat flux densities were selected, namely 23.89 MW / m². 2 With 39.81MW / m 2 Irradiation durations of 1, 3, 5, and 7 seconds were performed, and the weight loss percentage for each ablation was calculated.

Claims

1. A method for repairing damaged SiC-coated carbon / carbon composite materials, characterized in that: The damaged SiC coating area is treated with a Si-SiC inner coating and a SiO2-Nd2O3 outer coating. The repair steps are as follows: Step 1, Pretreatment: Along the surface of the damaged area, the damaged area of ​​the SiC-coated C / C composite material is filed and polished to remove the coating in that area until the C / C composite material matrix is ​​exposed. Step 2, Powder preparation: Mix 50-70% Si powder, 15-30% SiC powder and 5-15% C powder by ball milling to make the inner coating powder. SiO2 powder with a mass percentage of 95% and Nd2O3 powder with a mass percentage of 5% were ball-milled and then placed in a muffle furnace. The furnace temperature was raised from room temperature to 1573-1773K in an air environment and heat-treated for 1-2 hours. The mixture was then removed and air-cooled to obtain SiO2-Nd2O3 bulk material, which was then ground into powder and used as an outer coating powder. Step 3, Damage Repair: Anhydrous ethanol is used as a solvent to magnetically stir the inner coating powder and then applied to the pretreated area in Step 1. After drying to remove the solvent, laser cladding is performed using a fiber laser in an argon atmosphere to obtain the Si-SiC inner coating. Anhydrous ethanol is used as a solvent to magnetically stir the outer coating powder and then applied to the surface of the Si-SiC inner coating. After drying to remove the solvent, laser cladding is performed using a CO2 laser in an argon atmosphere to obtain the SiO2-Nd2O3 outer coating. The laser cladding parameters for the inner coating are: power 200-400W, scanning speed 2-5mm / s, and spot diameter 3-5mm; the laser cladding parameters for the outer coating are: power 100-200W, scanning speed 10-16mm / s, and spot diameter 6-10mm.

2. The method for repairing damaged SiC-coated carbon / carbon composite materials according to claim 1, characterized in that: The ball milling process takes 2-4 hours.

3. The method for repairing damaged SiC-coated carbon / carbon composite materials according to claim 1, characterized in that: The magnetic stirring is carried out for 2-4 hours.

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