Effect of CVI SiC content on ablation and mechanism of C/C-SiC-ZrC-Cu composites

C/C-SiC-ZrC-Cu composites were fabricated by chemical vapor infiltration, precursor infiltration-pyrolysis and vacuum-pressure infiltration methods. During Cu infiltration, the Cu6.69Si and Cu3Si new phases are generated through reaction between SiC and molten Cu. The formed Cu6.69Si, Cu3Si, ZrC and SiC phases can improve the wettability and interface combination between Cu and the doped carbon matrix. The ablation tests demonstrate that the CVI SiC content significantly affects the structure of protective oxide layer, and induces inverse effects in ablation center at 2500 degrees C and 3000 degrees C. The relatively high CVI SiC content enhances the ablation resistance of composites at 2500 degrees C, but increases the linear ablation rate at 3000 degrees C due to the excessive evaporation and mechanical denudation. During ablation, the formed Si-Zr-C-O layer underneath ablation center and the Si-Cu-CO layer on transition or marginal areas can prevent carbon matrix from serious oxidation. After ablation for 20 s, the C/C-SiC-ZrC-Cu composites with high CVI SiC content display the best anti-ablation property at 2500 degrees C, and the ablation rates are 3.5 +/- 0.1 mu m/s and 3.4 +/- 0.1 mg/s.