Oxidation behavior of C/SiC composites with a SiC/Mo–Si multilayer coating

A SiC/Mo-Si multilayer coating was prepared on the surface of C/SiC composites by chemical vapor deposition (CVD) combined with slurry painting. The coating was composed of a dense CVD SiC coating alternating with a porous Mo-Si layer. From inside to outside the coating consisted of CVD SiC,Mo-Si,CVD SiC,Mo-Si and CVD SiC. The coating remained intact and no obvious failure such as destruction or spalling was found during oxidation at 1 400 ℃ and thermal shock between 1 400 ℃ and room temperature. The mass loss and mass loss rate of the coated sample were only 0.25% and 6.61×10-6 g·cm-2·h-1,respectively after oxidation at 1 400 ℃ for 150 h. The flexural strength retention was 95.73% and 81.61% after 25 and 50 thermal cycles respectively and mass of the coating generally increased after oxidation. The SiC/Mo-Si multilayer coating showed excellent anti-oxidation ability and a thermal shock resistance and could effectively protect the C/SiC composites at 1 400 ℃ for a long time.