Oxidation resistance of SiC/Si-B₄C coating on C/C compositesat 500-1 500℃ in air

In order to improve the oxidation behavior of C/C composites in a wide range of temperature, a new SiC/Si-B₄C coating was developed. The oxidation resistant mechanism of the SiC/Si-B₄C coated composites was studied by thermogravimetric analysis in the temperature range from room temperature to 1 500℃. After oxidation at 1 500℃ in air for 2 h, the mass gain of sample is 2.21%. The oxidation behaviors of SiC, Si and B₄C were also studied in the temperature range from 500℃ to 1 500℃, respectively, and the effective oxidation resistant temperature ranges of SiC, Si and B₄C were explained. By analyses of oxidation kinetics, activation energies for the oxidation of SiC and Si are 196.7 kJ/mol and 167.3 kJ/mol, respectively. Because of the synergistic oxidation resistant mechanism of SiC, Si and B₄C, the SiC/Si-B₄C coating shows self-healing ability and excellent oxidation resistance in the temperature range from 600℃ to 1 500℃.