Effect of surface oxidation on 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 1000 ± 15 ℃, 1200 ± 15 ℃ and 1400 ± 15 ℃ for 30 min, respectively. Compared with the original strength of 580 MPa, the strength for the specimen oxidized at 1000 ℃, 1200 ℃ and 1400 ℃ for 30 min increased to 609 MPa, 656 MPa and 660 MPa, respectively, 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 △Tcrit for the specimen oxidized at 1000 ℃, 1200 ℃ and 1400 ℃ were 352 ℃, 453 ℃ and 623 ℃, respectively, which was obviously higher than 270 ℃ 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 ZrB2-based ceramics.