Microstructure and Corrosion Resistance of Ni-Co Based Cladding Layers on Surface of ZG45 Steel

The Ni-Co based cladding layers with different proportions of Ni and Co and those with different mass fractions of WC, graphite (G)+WC were fabricated on the surface of ZG45 steel substrate by vacuum cladding technique. The microstructures, phase composition and corrosion resistance in NaCl solution of the cladding layers were studied. The results show that all the cladding layers had dense microstructures and were metallurgically bonded to the substrate. The main phases of the G+WC/Ni-Co alloy cladding layer were Cr₇C₃, Cr₂₃C₆, Ni₃Si, CrB, FeW₃C, WC, C and γ-Ni-C solid solution. The corrosion resistance of Ni-Co alloy cladding layers was better than that of substrate and increased with the Co content increasing. The free corrosion current density of both WC/Ni-Co alloy cladding layer and G+WC/Ni-Co alloy cladding layer decreased and then increased with the increase of WC or G content. Localized corrosion mainly occurred on the surface of G+WC/Ni-Co alloy cladding layer, and the localized corrosion pits appeared in the WC and G particle concentrated area.