Oxidation Behavior of MuIlite‐Coated SiC and SiC/SiC Composites under Thermal Cycling between Room Temperature and 1200°‐1400°C

Refractory oxide barrier coatings are a promising approach for improving the environmental durability of silicon‐based ceramics in severe environments. The oxidation durability of a newly developed fully crystalline mullite coating on SiC and SiC/SiC composites was investigated under thermal cycling between room temperature and 1200°‐1400°C with a higher frequency (1‐ or 2‐h) and a lower frequency (20‐h) cycling for times up to 1200 h. The new mullite coating exhibited significantly improved adherence and resistance to cracking when compared to conventional mullite coatings. Current issues include oxidation of SiC‐based substrates, void formation at the coating/substrate interface, and cracking in the coating through the thickness.