Effects of TiB₂ Content on the Microstructures and Mechanical Properties of Low-Cobalt Ti(C,N)-TiB₂ Cermets Fabricated by Vacuum Hot Pressing

Abstract

Ti(C,N)-TiB₂ cermets were fabricated from Ti(C,N), TiB₂, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB₂ content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB₂ contents, two types of core-rim microstructures were present in the Ti(C,N)-TiB₂ cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB₂ content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB₂ cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB₂ cermets with 20 wt% TiB₂ content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 H V, 7.92 MPa·m^1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.

Keywords

Ti(C,N)-TiB₂ cermets / vacuum hot pressing / mechanical properties / fracture behavior