Migration of Liquid Phase in Dual-Layer WC-9Ni Cemented Carbides

Abstract

The liquid phase migration (LPM) in the sintering process of WC-9Ni dual-layer cemented carbides and its mechanism were investigated and discussed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) system. Moreover, the effect of sintering temperature and WC grain size on micro-structure changes of the samples was also studied. The results indicated that the LPM of dual-layer cemented carbide at different stages in the sintering process was mainly dominated by capillary force, the decrease of inter-facial energy in fine WC layer (FWC layer) and Ni content concentration gradient in the coarse WC layer (CWC layer). During the sintering process, liquid phase first migrated from FWC layer to CWC layer due to the effect of capillary force. With the temperature increase, the liquid phase in turn flowed from CWC layer to FWC layer resulted from the decrease of inter-facial energy of FWC layer. A high temperature sintering (1450 °C) might lead to the formation of an abnormal WC grain growth layer (AWC layer) with relative high Ni content and many pool defects in the CWC layer next to the interface. With the increase of WC particle size in the CWC layer, the quantity of the pool defects in the CWC layer near the interface increased, so did the size.