Mechanism of ablation of 3D C/ZrC–SiC composite under an oxyacetylene flame

► Mass loss and linear recession rate of C/ZrC–SiC are 0.0089g/s and 0.0136mm/s. ► A five-layers structure formed after ablation. ► The glassy ZrO2–SiO2 layer inhibited inward transportation of oxygen. ► Four kinds of ablation behavior controlled ablation rate. Ablation behavior of 3D C/ZrC–SiC composite was tested under an oxyacetylene flame and an ablation mechanism was proposed. A five-layer microstructure formed after ablation, including the ZrO2-melting layer, the porous layer, the SiO2-rich layer, the SiC-depleted layer and the composite substrate. The ablation rate is controlled by oxidations of carbon fibers, SiC and ZrC in the first stage, and then controlled by the scouring away of ZrO2–SiO2 binary melt by gas flow and the oxygen diffusion through the glassy ZrO2–SiO2 layer. Finally the evaporation of SiO2 controls the ablation rate cooperative with the last mentioned two ablation behavior.