Ablation behavior of Hf-Zr-modified silicon-based ceramic coatings prepared by polymer derived ceramics and gaseous silicon infiltration

To improve the ablation resistance of C/C composite at temperatures exceeding 2000 °C, a (Hf-Zr)C-SiC Ultra-High Temperature Ceramic (UHTC) coating was prepared by Polymer Derived Ceramics (PDCs) and Gaseous Silicon Infiltration (GSI). The linear ablation rate of the coated C/C composites was as low as 0.27 μm/s, maintaining a level as low as 10⁻⁴ mm/s. This low R_l is attributed to the formation of a well-bonded double-layered oxide scale with high thermal stability, consisting of an exterior SiO₂ glass layer and an interior Hf-Zr-Si-O complex oxide layer. Meanwhile, the dissipation of the residual Si and the C phases relieves heat accumulation, ensuring that the recorded surface temperature remains below 2000 °C, thereby enhancing the ablation resistance. Additionally, a cyclic evolution of linear ablation rate was found, due to the alternating dominant role of oxidation and mechanical denudation on the coating during ablation. This study provides theoretical and experimental support for the long-term anti-ablation design of highly dense UHTC coatings.