Effect of the surface oxidation on the flexural strength of the ZrB2–SiC–ZrC ceramic

The isothermal oxidation of the ZrB2–SiC–ZrC ceramic was carried out at a constant temperature of 1000 ± 2 °C, 1200 ± 5 °C and 1400 ± 5 °C, respectively, for different times in static air. The surface oxidation was favorable to increase the flexural strength of the ZrB2–SiC–ZrC ceramic because the flaws on the surface of the specimen were healed by the glass layer. The distribution of strength significantly decreased as the oxidation time increased in spite of the oxidation temperature. The analysis on the mechanism of the strength increase indicated that the strength increased as the reaction rate increased, and the increase in strength was related to change rate in volume induced by reaction, the initial crack geometry, elastic modulus and the surface free energy and so on.