Ablation mechanism of ZrB₂-SiC and Csf/ZrB₂-SiC ultra-high temperature ceramic composites

ZrB₂-SiC and Csf/ZrB₂-SiC, two kinds of ultra-high temperature ceramic composites were fabricated by hot-pressing. The ablation behavior of them was studied by oxyacetylene torch test at a heat flux of 4186.8 kW/m² for 180 s. For ZrB₂-SiC, the surface temperature increases to 2406°C during torch test and the average mass loss is -0.14%, linear ablation rate is -1 × 10^-3 mm/s. For Csf/ZrB₂-SiC, the maximum surface temperature is 1883°C, and the average mass loss is -0.19%, linear ablation rate is -4 × 10^-4 mm/s. From the surface and cross section analysis it is found that loosen ZrO₂ oxidation layer, SiC rich layer and unaltered layer form from outer layer to inner layer in ablated ZrB₂-SiC microstructure, where SiC rich layer has oxidation resistance. For Csf/ZrB₂-SiC, ZrO₂-SiO₂ oxidation layer, SiC depletion layer and unaltered layer distribute from outer layer to inner layer, where the SiO₂ filled ZrO₂ oxidation layer formed in the surface can prevent oxygen effectively.