Microstructure evolution of in-situ SiC-HfB2-Si ternary coating and its corrosion behaviors at ultra-high temperatures

An in-situ SiC-HfB2-Si ternary coating was deposited on C/C composites (C/Cs) via slurry panting plus gaseous Si infiltration composite method, to improve the oxidation and ablation resistance of C/Cs above 1773 K. The coating formation mechanism was investigated by microstructural analyses and thermo-dynamic calculations. The oxidation behavior of the coated specimens subjected either to high-temperature testing at 1773 K and 1973 K in static air furnace or to ablation testing with oxyacetylene torch upon ultra-high temperature service were studied, base on thermo-dynamic computations, numerical simulations and microstructure evolution. The SiCHfB2-Si coating protected C/Cs against oxidation at 1773 K for more than 1507 h which is longer than that of the reported SiC-HfB2-based coatings, due to the as-prepared compact mosaic coating filled with HfB2-rich Si-based multiphase and the consequently formed dense Hf-Si-O oxide layer. Moreover, a good ablation resistance with relatively low linear and mass ablation rates of -0.72 mu m/s and 0.07 mg/s, respectively, was achieved due to the stable oxide scale with high viscosity.

Automated summary

In this study, an in-situ SiC-HfB2-Si ternary coating was deposited on C/C composites using slurry panting and gaseous Si infiltration composite method to enhance oxidation and ablation resistance at temperatures above 1773K. The coating exhibited effective protection against oxidation due to the compact mosaic structure filled with HfB2-rich Si-based multiphase and the dense Hf-Si-O oxide layer. Additionally, the coating showed good ablation resistance with low linear and mass ablation rates, attributed to the stable oxide scale with high viscosity.