Improvement of high-temperature oxidation resistance of WC–Co–Ni alloy by Cr3C2–CeO2–WS2 mixed additives and its mechanism

Abstract

Whether used as hot rollers or hot forging dies, the high-temperature oxidation resistance of cemented carbides is closely related to their lifetime. In the context of the above applications, a WC–Co–Ni alloy with Cr3C2–CeO2–WS2 mixed additives is designed based on the principles of oxidation resistance and self-lubrication at elevated temperatures. The results of continuous oxidation at 700 °C for 16 h show that the oxidation rate of WC–6Co–6Ni–1.2Cr3C2–1.0CeO2–0.4WS2 (alloy 2#) with ultrafine dispersion phase Ce2O2S2 decreases by 23.7% and 15.4%, respectively, compared with WC–6Co–6Ni (alloy 1#) and WC–6Co–6Ni–1.2Cr3C2 (alloy 3#). The additives of Cr3C2 and CeO2 can promote the in situ atomic recombination in the binder phase and rapid nucleation of (Ni,Co,Cr)WO4. As a result, a 2.3 times and 1.6 times higher MWO4 (M = Co, Ni, Cr) in quantity is formed on the oxidized surfaces compared with the counterpart alloy 1# and alloy 3#. The high proportion of dense (Ni,Co,Cr)WO4 phase and the Ce2O2S2 third phase resistant to high-temperature oxidation can form a double obstacle to the diffusion of oxygen atoms and delay the kinetic process of oxidation reaction.