EFFECT OF Mo₂C ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF (Ti,W)C–Ni CERMETS

Abstract

(Ti, W)C–Ni cermets with different contents of Mo₂C were produced by the spark plasma sintering (SPS) method. The grain size (GS), composition of ceramic phases, and mechanical properties of the sintered cermets were investigated. The amount of Mo₂C had a significant influence on the microstructure and mechanical properties of as-prepared cermets. GS and fracture toughness (K_Iс) were decreased as a result of increasing the amount of Mo₂C. By increasing the amount of Mo₂C, the transverse rupture strength (TRS) and hardness (HRA) were enhanced. However, above 10 wt.%, the TRS was reduced. The conventional black cores observed by field-emission scanning electron microscopy (FE–SEM) in backscattered electron imaging (BSE) in (Ti, W)C–Ni cermets will be partially turned into some white cores which contain higher Mo, except for Ti and W elements, when content of Mo₂C reaches ~15 wt.%. Batch mechanical tests indicate that cermets with some white cores have refined microstructure and higher hardness, but relatively lower transverse rupture strength (TRS) and fracture toughness (K_Iс) at room temperature.