Surface morphology evolution and ablation mechanism of SiC–Si multiphase ceramic coating on graphite under oxy-acetylene flame

• The surface temperature drops about 300 °C after applying SiC–Si coating.
• The relation between the surface temperature and the microstructure is researched.
• The morphology evolution of the ablation surface of SiC–Si coating is explained.
• The relation between the ablation mechanism and ablation time is uncovered.

A dense SiC–Si coating with average thickness of 580 μm was prepared on graphite by pack cementation. The surface morphology evolution and ablation mechanism of the coating at about 1780 °C were investigated by oxy-acetylene flame. After applying SiC–Si coating, the ablation surface temperature dropped about 300 °C. The ablation products SiO2 presented high viscosity and provided good protection in the early-to-middle stage of the ablation. The mechanical denudation gradually became severe with the ablation time increasing. Finally, the convection between the gases formed in the subsurface and the ablative gases turned out to be the primary ablation barrier.