Microstructure and polarization behavior of Ni/WC plus GO (graphene oxide) composite cladding fusion coating

Ni/WC/graphene oxide (GO) composite cladding fusion coatings were fabricated through the vacuum cladding technique on a medium carbon structure steel (45# steel) substrate whose carbon content was 0.45 +/- 0.03%. The microstructural characteristics, phase composition, and electrochemical polarization characteristics of the composite cladding fusion coatings were analyzed with scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and the electrochemical workstation CHI660E. Results show that the microstructure was compact and was micro-crack free, and without inclusions or other defects. It was comprised of four micro-zones, namely, the composite, transition, diffusion fusion, and diffusion-affected zones with thicknesses of approximately 4 mm, 1 mm, 20 mu m, and 250 mu m, respectively. The main phases of the composite coating were gamma-Ni solid solution, WC, Cr7C3, Ni2.9Cr0.7Fe0.36, Cr23C6, Ni3Fe, Ni3Si, Ni3B, W2C, and C. The self-corrosion potential of the composite coatings had increased by 0.3269 V compared with that of the substrate, and the corrosion current density of the composite coatings had decreased by nearly two orders of magnitude. The Ni-based solid solution region with relatively high C and Cr contents was difficult to dissolve.