Optimization of Coating Process Parameters to Improve Microhardness of Ni-P-TiO2 Composite Coatings

Abstract

The presence of nickel, phosphorus and second phase particles significantly affects on the hardness, tribological properties and microstructure ofelectroless composite coatings. Heat treatment plays important role in changing the microstructure of composite coating from amorphous to crystalline. The present study deals with investigating the effect of heat treatment and coating process parameters on the micro-hardness of Ni-P-TiO2 composite coating using Taguchi technique. Nickel sulphate, sodium hypophosphite, TiO2 particles is considered as coating parameters along with annealing temperature are fitted in the L27orthogonal array. From experimental result, it is confirmed that annealing temperature has the most significant effect on hardness of composite coating, while TiO2 particles has the significant effect. The scanning electron microscopy, energy-dispersive X-ray analysis and X- ray diffraction analyzer are used to study the microstructure, composition and phase structure of composite coating respectively.