High temperature deformation mechanisms in cemented carbides and cermets studied by mechanical spectroscopy

Two model hardmetals, a pure WC–Co and a TiWCN–Co, have been studied by mechanical spectroscopy. In this work, the materials are studied up to 0.85Tm of cobalt. A parallel analysis of the materials shows that three domains are characterized by similar internal friction peaks. A region characterized by relaxations in Co, a region characterized by relaxations in the ceramics and a high-temperature region characterized by relaxations at grain boundaries are found. Two peaks are located at high temperatures in both materials. The first located at 1420 K in WC–Co and at 1520 K in TiWCN–Co for 1 Hz is attributed to grain boundary sliding. A very broad and high peak estimated for 1 Hz around 1600 K in WC–Co and above 1700 K in TiWCN–Co has only been directly observed in frequency. It is thermally activated and shows a high, apparent activation energy.