Wear Behavior of Electroless Ni-P Coatings in Brine Solution and Optimization of Coating Parameters

The present paper studies the wear behavior of electroless Ni-P coating in brine medium and optimization of the coating process parameters for minimum wear using Taguchi method based on L27 orthogonal array. The study is carried out using different combinations of four coating process parameters, namely, concentration of nickel source (A), concentration reducing agent (B), bath temperature (C) and annealing temperature (D). The wear tests are conducted with a pin-on-disk Wear & Friction Monitor. The optimum combination of process parameters for minimum depth of wear is obtained. ANOVA is performed to find out the significance of the coating parameters and their interactions. The surface morphology and composition of coatings are studied with the help of scanning electron microscopy (SEM), energy dispersed X-ray (EDX) analysis and X-ray diffraction (XRD) analysis. It is found that Ni-P coating is amorphous in as-deposited condition but gradually turns crystalline with heat treatment. The worn surface morphology reveals abrasive as well as corrosive wear mechanism.