A MoSi2-SiOC-Si3N4/SiC anti-oxidation coating for C/C composites prepared at relatively low temperature

In this study, SiC coating for C/C composites was prepared by pack cementation method at 1773 K, and MoSi2-SiOC-Si3N4 as an outer coating was successfully fabricated on the SiC coated samples by slurry method at 1273 K. The microstructure and phase composition of the coatings were analyzed. Results showed that a porous β-SiC inner coating and a crack-free MoSi2-SiOC-Si3N4 coating are formed. Effect of Si3N4 content on the oxidation resistance of the coated C/C composites at 1773 K in air was also investigated. The weight loss curves revealed that introducing the appropriate proportion of Si3N4 could improve the oxidation resistance of coating. The MoSi2-SiOC/SiC coated C/C sample had an accelerated weight loss after oxidation in air for 20 h. However, the coating containing 45% Si3N4 could protect C/C composition from oxidation for 100 h with a minute weight loss of 0.63%.