Hot isostatic pressing and post-hot isostatic pressing of SiC-β-sialon composites

Abstract

SiC-β-sialon two-phase composites with various compositions were formed by hot isostatic pressing (HIP) and treated by post-hot isostatic pressing (post-HIP). The bending strength of the HIP specimens reached the highest values when the Z-value (Si 6−ZAl ZO ZN 8−Z) of the second phase, β-sialon, was 2.0, while the highest values of hardness were reached at Z = 1.5. Scanning electron microscopy (SEM) observations of the fracture surface revealed that a fine and homogeneous microstructure was obtained by HIP. Surface nitriding of the HIP specimens by post-HIP in a N 2 atmosphere resulted in significant improvement in the bending strength. The maximum value of bending strength reached 950 MPa at Z = 1.0 for β-sialon. The formation of a dense microstructure, with rod-like grains in the surface layer, and other strengthening mechanisms may be responsible for the improvement.