A HfSiO₄-based coating with stronger oxidation resistance defending C/C composites at 1773 K and 1973 K in air

The high-temperature oxidation of Carbon/carbon (C/C) composites limits their application as hot-end structural materials in the aerospace industry. To solve this problem, a HfSiO₄-based coating with strong oxygen blocking ability on the C/C composites was fabricated by a compound method of slurry brushing and in-situ oxidation sintering. The C/C composites were protected by the coating for 2257 h at 1773 K, 121 h at 1973 K in air, with a mass loss of about 0.50 wt%, respectively. Such good performance was attributed to the Hf-Si-O oxygen barrier layer with abundant and uniformly distributed HfSiO₄ particles (Volume accounting for over 65 %). The HfSiO₄ particles could reduce the volatile mass of the SiO₂ glass, and relieve the difference of coefficient of thermal expansion (CTE) between the SiC inner coating and SiO₂ in the outer coating. More importantly, the oxygen diffusion resistance of the Hf-Si-O layer with HfSiO₄ as the main phase was significantly enhanced, providing a basis for optimizing the composition of oxidation resistance coatings at 1973 K and above in air.