Enhancing ablation resistance of C/C composites above 2000 ℃ via tailored TaC/HfN_xC_1-x multi-layer coating

To address the extreme thermal challenges in ultra-high temperature scenarios, a synergistic strategy combining layered toughening and N-doped modification was adopted to enhance the ablation resistance of HfC-based coatings. This study systematically explored the relationship between phase composition, multi-layer structure and anti-ablation performance through a two-stage progressive approach. The results demonstrate that the moderate N-doping (HfN_0.25C_0.75) significantly improves ablation resistance of HfC coatings. Building upon this foundation, an innovative TaC/HfN_0.25C_0.75 multilayer coating was successfully constructed, exhibiting 18.2 % and 16.1 % reductions in mass/linear ablation rates respectively compared to monolithic coatings after 120 s ablation. Notably, it maintained low ablation rates of 0.66 mg/s and 0.84 μm/s even under cyclic ablation environment (30 s × 4). The excellent performance originates from two synergistic mechanisms: 1) Multilayer interfaces effectively release thermal stress through crack deflection, inhibiting through-thickness cracking; 2) In-situ formed Hf-Ta-O self-healing glassy phases combined with stable Hf₆Ta₂O₁₇ phases provide dual functionality of oxygen barrier and structural stabilization. This work provides new insights into designing advanced thermal protection systems through multi-scale structural engineering and composition optimization.