C / C 复合材料表面 SiC-ZrB₂ 涂层的缺陷修复与抗烧蚀性能

Defects such as cracks, pits and holes, appear in the coatings of carbon / carbon (C / C) composite materials during the preparation and service process, which make coatings lose their integrity and lead to protection failure. Replacing the integral coating as a commonly used solution is expensive, complicated and time-consuming. Therefore, a fast and efficient repairing technology for minor defects on coatings is an effective way to solve this problem. Defects are pre-fabricated on the surface of SiC-ZrB₂ (SZ) coated C / C composites by supersonic atmospheric plasma flame. To repair the defects of the SZ coating, isopropanol and boron-containing polynitrosilane adhesive with stable performance at high temperatures are used as repairing agents. SiC-ZrB₂ and Al₂O₃ are used as modified filler and sintering aid, respectively. The microstructure and ablation resistance of the coating before and after repair are studied. The results show that circular pit defects appear in the center of the coating sample after plasma flame ablation, exposing the C / C composite substrate. For the coating sample after repair, SiBCN ceramics and modified ceramic fillers generated by the pyrolysis of the repair agent cover the defects evenly, and thus the coating sample maintains high integrity. A dense SiO₂ glass film can be formed under oxyacetylene ablation, which effectively blocks oxygen diffusion and protect C / C composites from mechanical erosion. The repaired coating sample shows a better ablation resistance under oxyacetylene flame flow. After ablated for 60 s, its line ablation rate and mass ablation rate are 0.65 μm / s and -0.28 mg / s, respectively, which decrease by 83.54% and 129.47% compared with the unrepaired coating samples, suggesting that the ablation resistance of the repaired coating is significantly improved.