Cyclic ablation and oxide-layer evolution of YF3/YSi2 co-modified C/C–ZrC–SiC composites

Ultra-high-temperature ceramic-modified C/C composites are vital for hypersonic vehicles, but their repeated service capability is hindered by oxide-scale degradation during cyclic ablation. This study evaluates the reusability of C/C-ZrC-SiC composites via cyclic oxy-acetylene ablation tests. Three Y-modification configurations were investigated: coating-only, matrix-only, and dual-integration. Results indicate that the dual-modified composite exhibited optimal resistance after three 60 s ablation cycles at ∼2600°C, achieving a linear ablation rate of −0.015 μm/s and a mass ablation rate of −0.016 mg/s (a 108% improvement over the reference). Mechanistically, the YSi 2 -modified coating rapidly formed a viscous Y 2 Si 2 O 7 -containing oxide layer during the initial stage to seal surface defects. In subsequent cycles, YF 3 in the matrix continuously replenishes the damaged scale with Y-containing species, promoting the formation of stable Zr 0 . 82 Y 0 . 18 O 1 . 91 and suppressing the martensitic transformation of ZrO 2 . This internal-external synergistic self-healing mechanism substantially enhances the reusability and long-term reliability of aerospace thermal structural components.