Effects of Heat Treatment on Morphology and Hardness of Electroless Ni-P Coating: Impact of Temperature and Concentrations

Abstract

This study examines the effects of heat treatment on the morphology and micro-hardness of Electroless Nikel-Phosphorus (Ni-P) coating. The coatings were deposited at various levels of Nickel source concentration, reducing agent concentration and bath temperature. The coated samples were considered for heat treatment at 300 ℃, 400 ℃ and 500 ℃ for one hour. The hardness of the samples was evaluated with a Vickers microhardness tester and the morphology of the samples has been studied with scanning electron microscopy (SEM). Energy dispersive spectroscopic (EDS) analysis for elemental mapping was done by the coating delamination of the substrate. The samples deposited at conditions of low Ni source concentration and high P concentration and high bath temperature condition, showed the maximum microhardness when heat treated at 300 ℃. A sample with high Ni source concentration and low P concentration at low bath temperature conditions showed a gradual reduction in micro-hardness with an increase in heat treatment temperature. SEM observed the least agglomeration at a heat treatment temperature of 300 ℃. The coatings deposited at low P conditions showed severe cracks at 500 °C