Fabrication and characterisation of functionally graded Ni-P coatings with improved wear and corrosion resistance

Abstract

In this study, the functionally graded Ni–P coatings with low phosphorus top most layers were deposited on the copper substrates by the electroless plating process. The surface morphology and cross-section observations were made by using scanning electron microscopy and optical microscopy. The results showed that electroless deposition of the Ni–P coatings with gradual change of phosphorus content led to a crack-free compact nodular morphology. Also, by using the graded Ni–P coatings, the wear and corrosion resistance were improved. The multilayer coating with the sequence of Ni-high P/Ni-medium P/Ni-low P layers from the substrate to the top surface exhibited the best wear and corrosion resistance.