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/m(2). The results showed that compared to C/C and C/C-SiC at the heat flux of 4.18 MW/m(2), 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 degrees 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/m(2), 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.