Ablation behavior of sharp-shape C/C-SiC-ZrB₂ composites under oxyacetylene flame

C/C-SiC-ZrB₂ composites with sharp leading edge shape were prepared by reactive melt infiltration, and their ablation behavior was investigated by subjected to the oxyacetylene flame with a heat flux of 2.38 MW/m² for 60 s. The results show that after adding ZrB₂ particles the mass and linear ablation rates of the C/C-SiC composites could be reduced by 36% and 52%, respectively. The ablated regions of the composites can be divided into two regions according the ablated features: brim ablation region and center ablation region. In the brim ablation region, a kind of ‘embedding structure’ of Zr-O-Si glass layer was formed on the surface of the C/C-SiC-ZrB₂ composites, and the ablated surface of the C/C-SiC composites was covered by a melting SiO₂ layer. In the center ablation region, the molten SiO₂ layer cannot resist the intensive impact of high-temperature, speed and pressure oxyacetylene flame, resulting in the failure of the protective coating for C/C-SiC composites. The surface of C/C-SiC-ZrB₂ composites was covered by a sintered ZrO₂ layer, which acted as an effective oxygen species and heat flux barrier and protected the composites against further ablation, resulting in an excellent configurational stability of C/C-SiC-ZrB₂ composites.