Microstructure and mechanical properties improvements in cemented carbides by (Cr,Mo,Ta)2(C,N) inhibitors

Abstract

Grain growth inhibitors can effectively suppress the grain size of tungsten carbide (WC), and consequently improve the hardness and strength of the cemented carbides; however, the toughness, one of the most important properties, usually deteriorates with inhibitors. Here, (Cr,Mo,Ta)2(C,N) synthesized by carbothermal reduction–nitridation was used as a novel inhibitor, and its effects on the microstructure and mechanical properties of the cemented carbides were investigated. The results showed that the cemented carbides containing (Cr,Mo,Ta)2(C,N) outperformed its counterpart comprising the traditional inhibitors in comprehensive mechanical properties, which was mainly attributed to the better inhibition performance provided by the (Cr,Mo,Ta)2(C,N) solid-solution powders. With the content of (Cr,Mo,Ta)2(C,N) increasing from 0 wt% to 1.25 wt%, the average grain size of WC in the cemented carbides decreased from 0.85 to 0.60 μm firstly, and then increased to 0.64 μm. With 1.00 wt% (Cr,Mo,Ta)2(C,N) addition, the cemented carbides with the best performance of hardness (HV30) of 15.55 GPa, transverse rupture strength of 4272 MPa, fracture toughness of 13.91 MPa·m1/2 were obtained. The electron backscattered diffraction (EBSD) measurements showed that cemented carbides with (Cr,Mo,Ta)2(C,N) processed more amount of Σ2 boundary compared with the other specimens, which contributed to better fracture resistance.