Enhancement of mechanical properties of NbCN-Ni cermets via WC addition

Abstract

In this study, the microstructural and mechanical properties of sintered NbCN-Ni cermets with various WC contents were investigated. The density and grain size of the NbCN-Ni cermets increased with an increase in the sintering temperature from 1420 to 1510 °C, whereas after WC addition, the average grain size of NbCN decreased significantly. The added WC was initially dissolved in the binder phase and then dissolved in NbCN crystals and formed a white W-rich (Nb,W)CN shell phase and gray Nb-rich (Nb,W)CN core phase structure for WC contents up to 10 wt%. Meanwhile, the formation of the shell-core structure enabled the morphology of NbCN grains to gradually change from polygonal to spherical, which can be attributed to the high solubility of WC in the Ni binder. The hardness and transverse rupture strength (TRS) of the cermets first increased and then decreased with increasing sintering temperature and WC content. At a WC content of 10 wt% and sintering temperatures of 1480 and 1450 °C, the HV10 and TRS of the cermets reached maximum values of 1405 kg/mm2 and 1280 MPa, respectively. The friction coefficient of the NbCN-Ni cermets decreased from 0.7 to 0.55–0.6 after WC addition. Hence, the cermets exhibited excellent wear resistance because the introduction of WC decreased their friction coefficient and increased their hardness.