Effect of CeO2 on microstructure and properties of Ni–Co-based coatings

Abstract

To improve the property and service life of continuous casting copper mould, Ni–Co–CeO2 composite coatings were prepared on the surface of the copper plate by electroplating technology. The effect of CeO2 addition on the phase composition, microstructure, hardness, wear resistance at 600 °C and corrosion resistance of the coatings was studied using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) combined with an energy dispersive X-ray spectroscopy (EDS), microhardness tester, electrochemical workstation, high-temperature friction and wear tester. The results indicated that the appropriate amount of CeO2 can increase the Co content of Ni–Co–CeO2 composite coatings with a kind of dense cellular surface structure. CeO2 particles accelerated the deposition rate of the coatings and the coatings thickened with an increase of CeO2 particles added in the bath. The maximum Vickers hardness of Ni–Co–CeO2 composite coating was obtained after 5 g/L CeO2 was added in the electroplating bath, which was 51% higher than that of Ni–Co alloy coating. The corrosion rate of Ni–Co–CeO2 (10 g/L) composite coating was 83% lower than that of Ni–Co alloy coating, and the impedance of the coating was much higher than that of the others. Ni–Co–CeO2 composite coatings with uniform structure exhibit excellent high-temperature wear resistance at 600 °C. The minimum wear volume appeared in the Ni–Co–CeO2 (10 g/L) composite coating, which was 40% lower than that of Ni–Co alloy coating. The high-temperature wear resistance at 600 °C and corrosion resistance of the Ni–Co–CeO2 coatings have been improved because of the CeO2 particle addition.