Influence of Process Parameters on Multiple Roughness Characteristics of Ni–P–TiO2 Composite Coatings

Abstract

The electroless nickel-phosphorus based composite coatings are popular because of their outstanding hardness, yield strength, better resistance to wear, frictional resistance, corrosion resistance, and good lubricity. In the present study attempts is made to investigate the influence of process parameters on the surface roughness of Ni–P–TiO2 composite coatings with the help of Grey analysis and the Taguchi method. Different surface roughness parameters considered in the analysis are Ra, Rq, Rsk, Rku and Rsm. The coating parameters considered nickel sulpahte as nickel source, sodium hypophosphite as a reducing agent and concentration of TiO2 particles as second phase particles are fitted into L27 orthogonal array to find out the optimum level of process parameters to minimize the surface roughness of the composite coatings. It is observed from the experimental result that the concentration of the second phase particles, i.e. titanium particles has significant influence and amount of reducing agent has moderate influence in controlling roughness parameters of composite coatings. The surface structure and compositional analysis with the phase structure of the composite coatings are analyzed by using SEM, EDAX and XRD analysis respectively. The experimental result confirmed that weight percentage of TiO2 particles increase with increase in TiO2 content in electrolysis bath. Similarly from SEM images it is confirmed that the composite particles are uniformly distributed over the coated surface. From the XRD analysis, it is observed that composite coating without heat treatment has single broad peak it means that the coating is amorphous in nature.