Effect of Ta Content on Microstructure and Properties of (Ti,W)C-Based Cermets

Abstract

(Ti,W)C-based cermets are an ideal material for the preparation of high-performance cutting tools due to their excellent mechanical properties, high temperature oxidation resistance, and corrosion resistance. However, their lower toughness limits the application of cutting tools. In order to solve the problem of low toughness faced by the current materials used in tools, in this study, a (Ti,W)C solid solution was used as the hard phase to prepare cermets with high toughness via vacuum sintering. The effects of Ta content on the composition, morphology, and microstructure of the cermets were analyzed through XRD analysis and SEM and EDS characterization methods. The mechanical properties such as hardness, transverse fracture strength, and the fracture toughness of the cermets and corrosion resistance in an HNO3 solution were also investigated. The results show that the microstructure of (Ti,W)C solid solution-based cermets exhibit simpler core-rim (single-rim) and acyclic structures, which weaken the formation and propagation of cracks at the interface. The relative density and grain size of cermets increases and decreases, respectively, with the greater amount of Ta addition, while excessive Ta addition leads to a decrease in the relative density and agglomeration between grains. The cermet with 3 wt.% Ta addition possessed excellent mechanical properties with a Vickers hardness, transverse rupture strength, and fracture toughness of 13 GPa, 1907.4 MPa, and 15.5 MPa m1/2, respectively. The addition of Ta leads to the formation of a Ta-rich protective layer on the surface of the cermet under the corrosion of the acidic solution, and with the increase in the Ta content, the corrosion resistance of the cermet gradually improves.