Application of High-Pressure Torsion to WC–Co Ceramic-Based Composites for Improvement of Consolidation, Microstructure and Hardness

Abstract

This study shows that ultrafine-grained composites of WC–11 mass% Co are successfully consolidated by high-pressure torsion (HPT) followed by sintering at lower sintering temperatures or shorter sintering time than hot isostatic pressing (HIP) and compression and sintering. For the samples processed by HPT and successive sintering, the grain size (∼700 nm) is smaller and the hardness (∼1700 Hv) is higher when compared to those consolidated by compression and sintering and HIP. A heterogeneous microstructure consisting of nanograins of Co and WC and coarse grains of WC ceramics with high dislocation density, 2 × 10¹⁶ m⁻², is formed during HPT, but the average grain size is slightly increased by subsequent sintering. A W₃Co₃C carbide forms by sintering, while its fraction increases with increasing the shear strain or with increasing the sintering temperature.