Xu Min, Guo Lingjun, Wang Hanhui
State Key Laboratory of Solidification Processing, Carbon/Carbon Composites Research Center, Northwestern Polytechnical University, Xi'an 710072, China.
Materials (Basel). 2021 Dec 16;14(24):7780. doi: 10.3390/ma14247780.
A SiC ceramic coating was prepared on carbon/carbon composites by pack cementation. The phase composition and microstructure of the coated specimens were characterized using X-ray diffraction instrument and scanning electron microscope. The results showed that the mass-loss percentage of the coated specimen was 9.5% after being oxidized for 20 h. The oxidation failure of the SiC ceramic coating at 1773 K was analysed by non-destructive X-ray computed tomography. The effective self-healing of cracks with widths below 12.7 μm introduced during the coating preparation process and generated while the specimens cooled down from the high oxidation temperature prevented the oxidation of carbon/carbon composites. X-ray computed tomography was used to obtain three-dimensional images revealing internal damage caused by spallation and open holes on the coating. Stress induced by heating and cooling caused the formation, growth and coalescence of cracks, which in turn led to exfoliation of the coating and subsequent failure of oxidation protection.
通过包埋渗金属法在碳/碳复合材料上制备了碳化硅陶瓷涂层。使用X射线衍射仪和扫描电子显微镜对涂层试样的相组成和微观结构进行了表征。结果表明，涂层试样在1773K氧化20小时后的质量损失率为9.5%。利用无损X射线计算机断层扫描技术分析了碳化硅陶瓷涂层在1773K时的氧化失效情况。在涂层制备过程中引入的宽度小于12.7μm的裂纹以及试样从高氧化温度冷却时产生的裂纹的有效自愈，防止了碳/碳复合材料的氧化。利用X射线计算机断层扫描技术获得了三维图像，揭示了涂层剥落和开孔引起的内部损伤。加热和冷却引起的应力导致裂纹的形成、扩展和合并，进而导致涂层剥落和随后的氧化保护失效。
