Oxidation behavior of C/SiC composite with CVD SiC-B₄C coating in a wet oxygen environment

A two-layered self healing coating with a B₄C internal layer and a SiC external layer is prepared on C/SiC composite by chemical vapor deposition (CVD). Microstructure and component of the coating was analyzed by SEM, EDS, and XRD. Oxidation behavior of SiC-B₄C coated C/SiC composite was compared with SiC-SiC coated C/SiC in an environment of P _H2O/P_O2/P_Ar = 14/8/78 at at 700°C, 1,000°C and 1,200°C for 100 h, respectively. It is demonstrated that the SiC-B₄C coating is more efficient to protect the composite from oxidation than SiC-SiC coating below 1,000°C due to the self healing behavior. After oxidized at 700°C for 100 h, the residual flexural strength of SiC-B₄C coated C/SiC is about 86%, and that of SiC-SiC coated is about 64%. While after oxidized at 1,200°C, the former is about 86% and the later is about 89%. This is due to the enhanced evaporation of B ₂O₃ at higher temperature.