Long-term oxidation behaviors of Si-Cr-W multiphase coating on SiC coated C/C composites at 1773 K and 1973 K

To obtain long-term oxidation protection for C/C composites at high temperatures, a dense Si-Cr-W multiphase ceramic coating was prepared on the surface of SiC coated C/C composites by a combined method of slurry brushing, heat treatment and liquid silicon infiltration, which drastically enhanced the oxidation resistance of SiC coated C/C composites at 1773 K and 1973 K in air. The microstructure evolution, phase composition and oxidation behavior of the multiphase coating were analyzed before and after oxidation. Results display that the Si-Cr-W coating with a thickness of ~ 115 µm possessed a dense and uniform multiphase mosaic structure (WSi₂, CrSi₂, Cr₅Si₃, SiC and Si). The mass loss of the coated sample was only 1.08 mg/cm² after oxidation for 325 h at 1773 K in air owing to the formation of the compact compound glass layer (SiO₂, Cr₂O₃ and WO₃) acted as an oxygen diffusion barrier. The coating can effectively protect C/C substrate from oxidation for 76 h at 1973 K in air, demonstrating its outstanding high-temperature oxidation protective ability.