Microstructural evolution of coating-modified 3D C/SiC composites after annealing in wet oxygen at different temperatures

Two types of coating-modified 3D C/SiC, coated with CVD SiC/SiC/SiC (type I) and CVD SiC/amorphous-BC/SiC (type II), are subjected to a 14 vol.% H₂O/8 vol.% O₂/78 vol.% Ar atmosphere at 700, 1000 and 1200 °C up to 100 h. Microstructure and corrosion behaviour are investigated using a variety of characterization techniques. The type II shows a better oxidation resistance than type I during annealing at relatively low temperatures. Nevertheless, residual strength of the type I annealed above 1000 °C is enhanced by healing of many micron-sized defects. Interfacial bond strength of the composites is reasonably improved after annealing.