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

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 Cr ₃C ₂–CeO ₂–WS ₂ 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–1.2Cr ₃C ₂–1.0CeO ₂–0.4WS ₂ (alloy 2 ^#) with ultrafine dispersion phase Ce ₂O ₂S ₂ decreases by 23.7% and 15.4%, respectively, compared with WC–6Co–6Ni (alloy 1 ^#) and WC–6Co–6Ni–1.2Cr ₃C ₂ (alloy 3 ^#). The additives of Cr ₃C ₂ and CeO ₂ can promote the in situ atomic recombination in the binder phase and rapid nucleation of (Ni,Co,Cr)WO ₄. As a result, a 2.3 times and 1.6 times higher MWO ₄ (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)WO ₄ phase and the Ce ₂O ₂S ₂ 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.