Oxidation resistance and self-sealing property of ceramic coatings for C/C composites

The oxidation behavior and damage mechanism of modifiers and compounds of many types of ceramic coatings were investigated experimentally. A MoSi₂/SiC coating was produced by infiltration process. The oxidation behavior of the coated-C/C composites was studied at various temperatures below 1650°C. The oxidation results showed that the MoSi₂/SiC coating for thermal-protection of C/C composites has high oxidation resistance at temperature up to 1650°C. In the present work, a new model of an oxidation protective, self-sealing multi-layer coating system was proposed for C/C composites. The multi-layer coating possessing the self-sealing property was obtained by pack cementation and infiltration process. The protection coating system for C/C composites consists of an inner layer of SiC and an outer layer of porous refractory oxides filled by modified SiO₂ glass. Isothermal and cyclic thermal oxidation tests showed the multi-layer coating was capable of protecting the C/C composites in an oxidizing atmosphere at temperature up to 1800°C.