Oxidation behavior of ZrB2-SiC-ZrC at 1700 °C

The oxidation behaviors of four compositions of ZrB2-SiC-ZrC and one composition of ZrB2-SiC were studied at 1700 °C in air and under low oxygen partial pressure. Volatility diagrams for ZrB2-SiC-ZrC and ZrB2-SiC were used to thermodynamically elucidate the oxidation mechanisms. SiO2 and ZrO2 layers formed on the surfaces of ZrB2-SiC-ZrC and ZrB2-SiC oxidized at 1700 °C. A SiC-depleted layer only formed on the surface of the ZrB2-SiC oxidized under low oxygen partial pressure. The oxide layer thickened with increasing ZrC volume content during oxidation in air and under low oxygen partial pressure. The ZrB2-SiC-ZrC oxide surface exploded in air when the ZrC volume content was more than 50%. Under low oxygen partial pressure, the oxide surfaces of all the ZrB2-SiC-ZrC specimens bubbled.