Ablation behavior of a novel HfC-SiC gradient coating fabricated by a facile one-step chemical vapor co-deposition

To protect carbon/carbon composites against ablation at ultra-high temperature, a novel HfC-SiC gradient coating was fabricated by a facile one-step chemical vapor co-deposition. The phase composition, microstructure, bonding strength and ablation behaviour were investigated, and the mechanical properties of ablated coatings were characterized as well. The bonding strength of HfC-SiC gradient coating is 19.6?±?0.5?N (176% higher than that of HfC coating). HfC-SiC gradient coating shows excellent ablation resistance under oxyacetylene flame. The mass and linear ablation rate of HfC-SiC coating were only 0.153?±?0.02?mg·s^?1 and ?0.998?±?0.08?μm·s^?1, respectively. After ablation for 60?s, the hardness and elastic modulus of ablated HfC-SiC gradient coating are higher than those of ablated HfC coating. The excellent ablation resistance of HfC-SiC gradient coating results from its high bonding strength and the adhesion effect of Hf-Si-O sticky glass phase.