Effect of heat flux on ablation behaviour and mechanism of C/C–ZrB2–SiC composite under oxyacetylene torch flame

•C/C–ZrB2–SiC composite was prepared by a three-step process.•The ablation performance decreased with the increase of heat flux.•The formation of oxides provides ablation protection for prepared composite.•The ablation mechanism changes from chemical erosion to mechanical denudation.

The ablation property of C/C–ZrB2–SiC composite under oxyacetylene torch flame with different heat flux was investigated. The ablation performance decreased with the increase of heat flux from 2400 to 4200 kW/m2 and the ablation mechanism changed from chemical erosion to mechanical denudation. The good ablation resistance under 2400 kW/m2 is attributed to the formation of SiO2–ZrO2 mixture. When heat flux is 3200 kW/m2, the formation of ZrO2 can partly prevent the diffusion of oxygen and provide ablation protection. But with heat flux increasing, the increase of mechanical denudation results in the reduction of ablation performance.