A Si-Mo oxidation protective coating for C/SiC coated carbon/carbon composites

A novel Si Mo alloy coating was prepared on the surface of C/SiC coated carbon/carbon (C/C) composites by pack cementation to fill the C/SiC gradient inner layer, which was expected to protect C/C composites at 1773 K in air for long-term application. The microstructure, oxidation resistance and thermal shock resistance of the as-received coatings were also investigated. The cross-section SEM image of the as-obtained coating revealed that the C/SiC/Si Mo multi-coating is about 150 lm in thickness and there are no penetration cross-cracks or big holes in the coating. The coating can effectively protect C/C composites for more than 100 h in air at 1773 K and undergo the thermal cycling between 1773 K and room temperature for 40 cycles. The excellent oxidation resistance and thermal shock resistance of the coating can be attributed to the free silicon phase and C/SiC gradient inner layer, which can suppress the generation of the thermal stresses in the coating.