Impact of introducing SiC and Si on microstructure and oxidation resistance of MoSi₂/SiC coated C/C composites prepared by SAPS

In order to evaluate and compare the differences of their anti-oxidation and thermal shock performances, two kinds of coatings including MoSi₂–SiC and MoSi₂–Si were deposited on the surface of SiC coated carbon/carbon composites (C/C composites) by supersonic air plasma spraying (SAPS), respectively. Their microstructures and phase components were observed by SEM, EDS and XRD. The results showed that the porosity and bonding strength of MoSi₂–Si/SiC coating were 4.27% and 15.7 N, while the MoSi₂–SiC/SiC coating were 10.58% and 12.56 N. Due to form more glassy SiO₂ layer on the surface of the MoSi₂–Si/SiC coating, it could effectively protect C/C composites from oxidation for 178 h in air at 1500 °C with a weight loss of 0.58% and concurrently withstood 15 times thermal shock cycling. However, the MoSi₂–SiC/SiC coating had a weight loss of 0.98% after oxidation for 127 h in the same experimental condition. The failure mechanisms of the two coatings were investigated.