Abstract
The nickel coatings have been used successfully for mild steel protection against corrosion and wear, and provide a surface that is resistant to corrosion and wear. The substrate materials used in the present investigation are AISI 1020, 4140 steel, and CuZn30 brass. All these substrates were coated with electroplating process in nickel sulphamate solutions used for the deposition of functional coatings. The hardness of the AISI 1020, 4140 steel with normalised and CuZn30 brass before and after Ni coating were measured. The microstructural characterisations of uncoated and coated substrates were obtained using optical microscope, Scanning Electron Microscope (SEM). The wear tests of the AISI 1020, 4140 steel and CuZn30 brass before and after Ni coating were performed in Pin-on-disc tribotester. It was observed that the substrate type has effect on the wear behaviour of Ni coatings. In addition, the wear behaviour of Ni coatings on the substrates with high hardness was found better. Also, an increase of hardness in the coating was observed depending on the substrate hardness. While the lowest friction coefficient was recorded in pairs with Ni coated AISI steel substrate with the highest hardness, the highest friction coefficient was recorded in Ni coated CuZn30 substrate having a low hardness.

Key words
electroplating, wear, substrate type, pin-on-disc

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