Effect of Heat Treatment on Strength of β-Sialon

Abstract

β-sialon was fabricated from α-Si₃N₄ and aluminum-iso-propoxide by hot-pressing. Bending specimens of hot-pressed β-sialon were heat treated at 800° to 1400°C for 0.5 to 10h in air, and effect of heat treatment on the bending strength was examined. Free and fractured surfaces were observed by optical and scanning electron microscope after heat treatment under different temperature-time conditions. The strength, when heat treated for 2h, increased with increase in the heat treating temperature and showed the maximum value of 150kg/mm² at 1200°C. But the strength decreased a little at 1400°C. The strength did not decreased with heat treating time up to 10h at 1200°C. Most of the specimens fractured from surface flaw generated by grinding. The observed increase in strength by heat treatment at 800° and 1000°C was ascribed to the blunting of crack tips, and that at 1200°C was to the blunting of crack tips and also to the coating of surface flaws with oxide layer.