Ablation behavior of C/C-ZrC-SiC composites prepared by reactive melt infiltration under oxyacetylene torch at two heat fluxes

C/C-ZrC-SiC composites were prepared by reactive melt infiltration and tested using an oxyacetylene torch with the heat fluxes of 4.18 and 2.38 MW/m². The results showed that compared to C/C and C/C-SiC at the heat flux of 4.18 MW/m², the mass ablation rates of C/C-ZrC-SiC were decreased by 60.8% and 44.8%, respectively. Its linear ablation rate was 7.3% higher than that of C/C, but was 13.5% lower than that of C/C-SiC. The C-SiC matrix and fibers of C/C-SiC in the center region were severely depleted by the high ablation temperature. C/C-ZrC-SiC composites experienced the temperature exceeding 2400 °C associated with intense mechanical scouring of gas flow. The severe depletion of SiC and carbon fibers on the surface led to the formation of the porous ZrO₂ layer. The spallation of ZrO₂ occurred in the center of the ablated surface as a result of mechanical denudation of high temperature gas flow. At the heat flux of 2.38 MW/m², the mass and linear ablation rates of C/C-ZrC-SiC were decreased by 76.8% and 88.4% (C/C), 66.9% and 58.3% (C/C-SiC), respectively. The oxide was slightly peeled off in the center region of C/C-SiC. The surface temperatures of C/C-SiC and C/C-ZrC-SiC were lower than that of C/C composites. The island-like ZrO₂ and SiO₂ layer were formed on the ablated surface of C/C-ZrC-SiC and acted as effective barriers to shield the ablation heat and slow inward transport of oxygen to the underlying material.