Effects of in situ amorphous graphite coating on ablation resistance of SiC fiber reinforced SiBCN ceramics in an oxyacetylene flame

The effects of in situ amorphous graphite coating on ablation behavior of SiC fiber reinforced SiBCN ceramics in an oxyacetylene flame are explored. The ablation products for both the monoliths and composites are similar, comprising amorphous SiO2 and cristobalite. The ablation resistance stems from formation of dense, passivating oxide scale of B2O3 containing amorphous SiO2. In different ablation stages, the ablation rates are synergistically controlled by various mechanisms. Interfacial structure and degradation of SiC fibers both deteriorate ablation resistance. The crystallization of SiC fibers leading to strength reduction is the main reason for poorer performance vs monoliths.