Oxidation resistance of a La-Mo-Si-O-C coating prepared by Supersonic Atmosphere Plasma Spraying on the surface of SiC-coated C/C composites

To prevent the oxidation of carbon/carbon (C/C) composites at high temperature, a La-Mo-Si-O-C coating was prepared on the surface of a porous SiC-coated C/C composites by Supersonic Atmosphere Plasma Spraying method. The surface microstructure, interface construction and high temperature oxidation behavior of the prepared coated C/C composites were investigated. Results show that the La-Mo-Si-O-C coating has a significant anti-oxidation property that could protect C/C composites for 85 h at 1773 K in air environment. La acted as the penetration enhancer could accelerate the sintering of Mo-Si-O-C ceramic coating and increase the penetrating capacity of the coating components into SiC coating. After oxidation, the as-prepared coating was dense with free-cracks and glass phases La2O3, La2SiO5, SiO2, with low oxygen permeability. The glass phases were formed on the surface of coating, and could effectively obstruct the diffusion of oxygen into the inner of coating.