Abstract: Al₂O₃-O’-SiAlON-SiC composite was prepared from tabular corundum (aggregates and fines), ultra-fine α-Al₂O₃ and Si powder as starting materials at 1 500 ℃ for 3 h in carbon embedded condition. The effects of thermal shock and thermal shock cycle on oxidation behavior of the composite were investigated. The results show that the weight gain ratio of the composite increases with temperature increasing from 900 ℃ to 1 300 ℃ with and without thermal shock condition. The weight gain ratio with thermal shock is more than that without thermal shock, and the weight gain ratio increases with the increase of thermal shock cycle, indicating that thermal shock can promote the oxidation of Al₂O₃-O’-SiAlON-SiC composite. The oxidation curves exhibit parabolic-like without thermal shock, and the curves are linear-like with thermal shock. O’-SiAlON and SiC are oxidized on the surface of sample to form a dense protective film which retards oxygen diffusion into the inner of sample without thermal shock. However, the oxidation protective film is broken under thermal shock condition, which provides passages for oxygen to enter the inner part of the samples, accelerating the oxidation of the composite.

Key words: refractory, Al₂O₃-O’-SiAlON-SiC composite, thermal shock, oxidation behavior, phase composition, microstructure