Oxidation and ablation resistant properties of pack-siliconized Si-C protective coating for carbon/carbon composites

Uniformly SiC coating was established on carbon/carbon (C/C) composites using halide activated pack cementation (HAPC). The siliconizing temperature in HAPC process played an evident effect on the deposition efficiency and oxidation behavior of SiC coating. The SiC coating revealed a typical crystalline structure with limited porosity and combined well with the substrate. Oxidation tests showed that the coating can withstand the 25 h of continuous isothermal oxidation at 1773 K and 10 thermal cycles between 1773 K and room temperature due to the good self-healing ability of formed glassy SiO₂ scale. An oxyacetylene flame test demonstrated that the SiC coating can effectively protect C/C composites from ablation for 45 s. The ablation central region presented a discontinuous and damaged morphology due to the volatilization of oxides and thermos-mechanical denudation, while a continuous glassy SiO₂ layer as the primary ablation barrier availably prevented the transitional region from being heavily oxidized.