Effect of the Rare Earth Oxide CeO2 on the Microstructure and Properties of the Nano-WC-Reinforced Ni-Based Composite Coating

In this study, the addition of the rare earth oxide CeO2 was investigated to alter the microstructural properties of the nano-WC-reinforced Ni-based composite coatings. The reinforced composite was prepared on the 42CrMo steel surface using a semiconductor laser. The morphology and microstructure of coatings were analyzed using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Further, the digital microhardness tester and high-temperature friction and wear tester were used to observe the mechanical properties. The results indicated that the addition of CeO2 eliminated the cracks from the surface of the coatings and effectively reduced the number of pores. The phases were mainly observed as γ-Ni(Fe) in a solid solution, and some residual WC and W2C phases were observed. In addition, Fe3C, Cr23C6, M6C (M = W, Fe, and Ni), SiC and Cr7C3 composite carbides, Si2W and NiW tungsten compounds, and CeFe2- and CeNi2-containing Ce complex compounds were formed on the coating. The rare earth oxide CeO2 composite-modified coating mainly comprised dendrites, crystal cells, strips, and massive microstructures. The reinforced phases of the modified coating presented uniform dispersion distribution with the addition of 1% CeO2, and the structures were significantly refined. The maximum microhardness of the modified coating was approximately 1560 HV0.2, which was approximately 20% higher than that of the unmodified composite coating. The minimum wear loss of the modified coating was 6.1 mg and the minimum frictional coefficient was approximately 0.23, which were better than those of the unmodified coating. The wear mechanism of the nano-WC-reinforced Ni-based coating was primarily adhesive, whereas that of the CeO2 composite modified coating was mainly abrasive particle wear, which accompanied adhesive wear.