Dual-grained size effect induced simultaneous enhancement of hardness-strength-toughness in TaC-modified Ti(C, N)-based cermets

Abstract

A trade-off is required to balance the hardness, strength and toughness of Ti(C, N)-based cermets, which remains a significant challenge due to the inherent contradiction between hardness (or strength) and toughness. In this work, a simple powder metallurgy process was used to prepare Ti(C, N)-based cermets with a dual-grained structure by refractory TaC modification and raw powder grading strategy. The microstructure formation process and synergistic enhancement mechanism of hardness, strength and toughness in the dual-grained Ti(C, N)-based cermets were elucidated. The formation of a dual-grained structure is attributed to selective dissolution and reprecipitation resulting from the difference in chemical potentials of both various carbonitrides and different-sized particles. As compared with conventional Ti(C, N)-based cermets prepared by only using submicron-sized raw powders, the dual-grained Ti(C, N)-based cermets modified by TaC achieve a distinct increase in Vickers hardness of about 14 %, in flexural strength of about 25 %, and in fracture toughness of 6 %. The hardness-toughness trade-off is significantly superior to those of conventional submicron-sized Ti(C, N)-based cermets using the same sintering method and even commercial Ti(C, N)-based cermets. This work offers a simple, novel and low-cost method to develop metal-ceramic composites with simultaneous enhancement of hardness, strength and toughness.