Ablation Mechanism of ZrB_2-SiC and C_(sf)/ZrB_2-SiC Ultra-high Temperature Ceramic Composites

ZrB_2-SiC and C_(sf)/ZrB_2-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 4186.8kW/m~2 for 180s.For ZrB_2-SiC,the surface temperature increases to 2406℃during torch test and the average mass loss is -0.14%,linear ablation rate is -1×10~(-3)mm/s.For C_(sf)/ZrB_2-SiC, the maximum surface temperature is 1883℃,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 ZrO_2 oxidation layer,SiC rich layer and unaltered layer form from outer layer to inner layer in ablated ZrB_2-SiC microstructure,where SiC rich layer has oxidation resistance.For C_(sf)/ZrB_2-SiC,ZrO_2-SiO_2 oxidation layer,SiC depletion layer and unaltered layer distribute from outer layer to inner layer,where the SiO_2 filled ZrO_2 oxidation layer formed in the surface can prevent oxygen effectively.