Oxidative ablation resistance behavior of HfC-based ultra-high temperature ceramics

The HfC-SiC composites with different volume ratio were prepared by hot press sintering. Then, the resultant samples were ablated by the supersonic speed gas flow for 600 s at 2300 K and 2500 K, respectively. The microstructure and composition of the ablated materials were analyzed by SEM and EDS. As can be seen, HfC-SiC composites have excellent oxidation and ablation resistance. The ablation resistance property of 30vol%SiC-HfC is superior to that of 50vol%SiC-HfC and pure HfC ceramics, which depends on the oxidation layer produced by HfC_xO_y and SiO₂. Due to the weak adhesion, the oxidation layer and matrix have separated from each other, which can be resolved by adding SiC. With the temperature rising, the ablation resistance ability decreases and the thickness of ablation layer increases. Meanwhile, Si will lose as the temperature rises, which will result in the low density of oxide layer. As SiC is 50vol%, inner HfC_xO_y skeleton becomes looser and the ablation becomes serious.