Oxidation resistant graded multiphase coating for carbon/carbon composites

A double layer TaB2-TaSi2-SiC-Si/TaC-SiC coating was prepared on the surface of C/C composites to improve the oxidation resistance of the composites, which was prepared by in situ reaction method through pack cementation technique. The phase composition and microstructures of the multiphase coating were characterized by XRD and SEM-EDS. The inner coating is composed of TaC and SiC, while the outer multiphase coating is composed of TaB2, TaSi2, SiC and Si. The multilayer coating is about 200 μm in thickness and does not display penetrating crack or big cavities. The coating could protect C/C from oxidation at 1773 K in air for 330 h with only 0.9% weight loss, thanks to the formed silicate glass layer containing SiO2 and tantalum oxides.