Oxidation/ablation behaviors of hafnium carbide-silicon carbonitride systems at 1500 and 2500 C

The oxide scales of hafnium carbide (HfC) typically exhibit a porous structure after oxidation/ablation due to the release of gas oxidation products, which allows oxygen penetration to promote the rapid oxidation of the HfC matrices. Here, we report that the oxidation/ablation resistance of HfC was enhanced by the incorporation of amorphous silicon carbonitride (SiCN). HfC-SiCN ceramics with 10 vol. % SiCN showed a significant improvement in the oxidation/ablation resistance compared with pure HfC. The HfC-10 vol. % SiCN ceramic has a higher density with good mechanical properties. After being oxidized at 1500 °C for 2 h, a dense and homogeneous HfO2-HfSiO4 layer with low oxygen permeability is formed. The ablation resistance of the HfC-10 vol. % SiCN ceramic is improved due to the formation of the triple-layer structure oxide with good thermal stability and mechanical scouring resistance. After ablation under an oxyacetylene flame for 60 s, the mass and linear ablation rates of HfC-10 vol. % SiCN ceramic are -0.019 mg cm−2 s−1 and -0.156 μm s−1, respectively.