Microstructure and anti-oxidation property of Si–W–Cr coating for SiC coated carbon–carbon composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, a Si–W–Cr coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructure and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. The coating obtained by first step pack cementation was porous α-SiC structure. New phases of WSi2 and CrSi2 together with α-SiC deposited on the porous SiC inner layer. Oxidation test shows that the weight loss of single SiC coated C/C is up to 8.21% after 9 h in air at 1773 K, while the weight loss of Si–W–Cr/SiC coated C/C composites is only 2.26% after 51 h. After thermal cycling between 1773 K and room temperature for 40 times, the weight loss is only 3.36%. The weight loss of coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating.