Oxidation resistance comparison of coating repaired mechanical cracks in carbon fibre reinforced silicon carbide composite

Oxidation resistance of carbon fibre reinforced silicon carbide composites (C/SiCs) with different coating repaired mechanical cracks was investigated. Structural integrity is critically important for the service performance of components for aerospace applications, and the coatings are reported as ideal choices to repair mechanical impact induced surface cracks. In this paper, chemical vapour deposited SiC, polysilazane (PSN) pyrolysed ceramic and slurry transformed glass coatings were introduced to investigate the oxidation resistance of repaired C/SiCs. The repair effects of various coatings were compared by weight loss and residual mechanical properties. Results showed that both SiC coated and glass coated C/SiCs exhibited preferable oxidation resistance compared with the PSN coated and uncoated specimens. Correspondingly, the former exhibited less weight loss and higher residual flexural strengths than the latter. A scanning electron microscope was employed to observe the microstructures of fracture sections, which gave an intuitive explanation for the repair effect of various coatings.