Ablation performance of Ta_0.8Hf_0.2C-SiC coating fabricated via pack cementation for carbon/carbon composites

Ta_0.8Hf_0.2C solid solution combines the excellent oxidation and ablation resistance of TaC and HfC, making it ideal for ultra-high temperature applications. Herein, a Ta_0.8Hf_0.2C-SiC coating was fabricated on carbon/carbon (C/C) composites via pack cementation, with the volume fraction of Ta_0.8Hf_0.2C being only 0.57 %. The coating provided over 350 s of thermal protection at 2.4 MW/m² (2150 ℃) and 170 s at 6.2 MW/m² (2400 ℃) for C/C composites, demonstrating exceptional ablation resistance with low addition of Ta_0.8Hf_0.2C. The mass and linear ablation rates were only 0.5110 mg/s and 0.0277 μm/s at 2150 ℃, and 0.3947 mg/s and 0.6229 μm/s at 2400 ℃, respectively. The solid solution structure of Ta_0.8Hf_0.2C ensures uniform atomic-scale distribution of Ta and Hf, which facilitaes the in-situ pinning of liquid-phase Ta₂O₅ by HfO₂/Hf₆Ta₂O₁₇ particles.