A C/SiC gradient oxidation protective coating for carbon/carbon composites

In order to eliminate the mismatch of the thermal expansion coefficient between SiC coating and C/C composites, a C/SiC gradient oxidation protective coating has been produced by a two-step technique. The first step is to prepare a slurry coated carbon layer, and the second one is to obtain a dense C/SiC concentration gradient coating by a pack cementation technique. The structures of the coatings were characterized by XRD, SEM and EDS analyses. Oxidation behaviour of the C/SiC coated C/C composites was also investigated. It was found that the as-prepared C/SiC gradient coating could effectively improve the oxidation resistance of SiC coating and could protect C/C composites from oxidation at 1773 K in air for 35 h with a weight loss of 2.46%. The gradient distributions of Si and C elements in the coating, which can suppress the generation of the thermal stresses, induce the excellent anti-oxidation ability of the C/SiC gradient coating.