Comparative study on the ablation behavior of C/C-Ta_1-xHf_xC (x=0, 0.46, 1)-SiC composites at 2300 ℃

To elucidate the respective roles of TaC and HfC constituents within Ta_1-xHf_xC solid solutions during ablation, C/C-TaC-SiC (CTS), C/C-HfC-SiC (CHS), and C/C-Ta_1-xHf_xC-SiC (CTHS) composites were fabricated via chemical liquid vapor deposition. After exposure to an oxyacetylene torch with a heat flux of 4.18 MW/m² for 100 s, the phase composition, microstructure, and ablation behavior were analyzed. The results show that CTHS has the best ablation resistance, indicated by the lowest mass ablation rate (0.09 mg/s) and linear ablation rate (0.58 μm/s). During ablation, the solid skeleton composed of HfO₂ and Hf₆Ta₂O₁₇ effectively pins the highly mobile molten phase, suppressing its migration and loss. Simultaneously, the abundant molten phase formed by SiO₂, Ta₂O₅, and partially molten Hf₆Ta₂O₁₇ fills the pores and voids within the solid skeleton to enhance the oxide layer’s compactness. The combined mechanism provides enhanced protection for CTHS in the harsh oxyacetylene torch environment.