Ablation resistance of C/C–Hf_1-xZr_xC composites under an oxyacetylene flame at above 2700 °C

To the better application of C/C composites in thermal components of vehicles above 2700 °C, C/C–Hf_1-xZr_xC composites were prepared by CLVD, and the ablation behavior of composites was investigated. The results show that C/C–Hf_0.5Zr_0.5C has excellent ablation properties with linear and mass ablation rates of −0.23 μm/s and −0.31 mg/(s·cm²), respectively. ZrO₂ molten phase and Hf_xZr_1-xO₂ particles are generated on the surface of C/C–Hf_1-xZr_xC composites during ablation. During the ablation process, defects are healed by the ZrO₂ molten phase due to its mobility, which inhibits the diffusion of oxygen into the substrate. The ZrO₂ molten phase is stabilized by the pinning effect of the Hf_xZr_1-xO₂ particles, which makes the ZrO₂ molten phase better resistant to the scouring of the air stream. A relatively complete oxide layer is generated on the C/C–Hf_0.5Zr_0.5C surface, with a moderate amount of Hf_xZr_1-xO₂ exerting a pinning effect to hold the ZrO₂ molten phase.