Microstructure and ablation mechanism of graphite/SiC composites under oxy-acetylene flame

Graphite/SiC composites were prepared by reactive metal infiltration (RMI). The microstructure and the ablation mechanism under oxy-acetylene flame were investigated. The ablation surface was composed of a central zone, an intermediate zone and an outer zone. The surface of the intermediate zone was covered by a SiO2 layer due to the oxidation of Si and SiC. A particle layer, which consisted of SiC particles and graphite particles, was found beneath the SiO2 layer due to the large inner stress. In the central zone, an extra SiO layer was detected owing to the high temperature and the few oxygen in the particle layer. Due to the good wettability with graphite, the SiO2 layer exhibited excellent ablation resistance by inhibiting oxygen diffusion and lowering the mechanical erosion of the flame. Besides, the evolution of the gases formed inside the composite helped to improve the ablation resistance.