Mullite whisker-mullite/yttrium aluminosilicate oxidation protective coatings for SiC coated C/C composites

A novel mullite whisker-mullite/yttrium aluminosilicate coating was designed and prepared through a three-step process including molten salt, supersonic atmospheric plasma spraying and sol-hot dipping. The mullite whiskers were used to enhance the interface bonding between mullite and SiC layer. A dense yttrium aluminosilicate outer coating was employed to seal the microholes in mullite coating. Results show that the bonding strength of the as-prepared coating was enhanced and the coating present a dense and crack-free microstructure. After 30 thermal-shock cycles from 1773 K to room temperature and oxidized for 185 h in atmospheric environment at 1773 K, the coated sample was only at a weight loss of 1.08% and 1.58%, respectively.