Investigation on the oxidation and ablation behaviors of HfB₂-SiC-Si/SiC-Si coatings for carbon/carbon composites

Oxidation and ablation behaviors of HfB₂-SiC-Si/SiC-Si coatings fabricated by dipping-carbonization joint gaseous silicon infiltration on cubic and nose-shaped carbon/carbon substrates were investigated. After 30 thermal cycles between 1500 °C and room temperature, the mass gain of the coated sample was 0.91 %, and the mass gain was 2.62 % after oxidation at 1500 °C for 870 h. The coated nose-shaped sample exhibited good anti-ablation properties at 1800 °C–2000 °C under oxyacetylene flame. Especially at 1800 °C, the mass ablation rate was −0.073 mg/s. Although the nose tip suffered the most serious corrosion, HfO₂ scale surrounded by Hf-Si-O glass could withstand the oxyacetylene torch scouring.