Effect of surface oxidation at 1500°C on flexural strength and thermal shock resistance of the ZrB_2-SiC-ZrC ceramic

摘要

The isothermal oxidation of the ZrB_2-SiC-ZrC ceramic was carried out in static air at a constant temperature of 1500±15°C for 20 min. Compared with the original strength of 580 MPa, the strength of the oxidized specimen increased to 655±45 MPa, because the flaws in the surface of the specimen were sealed by the oxide layer. The thermal shock resistance of the specimens before and after the oxidation was measured by the water quenching. The measured ΔTcrit for the oxidized specimen was 641°C that was obviously greater than 348°C for the unoxidized specimen. The improvement in the thermal shock resistance was attributed to the formation the oxide layer on the surface of the specimen. The results here pointed to a promising method for improving strength and thermal shock resistance of ZrB_2-based ceramics.