Effect of Process Parameters on Microhardness of Ni-P-Al2O3 Composite Coatings

Abstract

Electroless Ni-P-Al2O3 composite coatings have found wide range of applications due to their high hardness and wear resistance. The present study triesto investigate the influence of coating process parameters on the microhardness of electroless Ni-P-Al2O3 composite coating with the help ofTaguchi analysis. Four parameters, namely, concentration of nickel sulphateas a nickel source, concentration of sodium hypophosphite as a reducing agent, concentration of Al2O3 particles as concentration of second phase particles, and annealing temperature, are considered and fitted into an L27 orthogonal array to find out the optimized condition for improvedhardness of the coating. The optimized condition is found to yield about 20.47% improvement in hardness of the coating comparedto the initial condition. The significance of the process parameters and their interactions on the hardness of electroless Ni-P-Al2O3 composite coating isstudied with the help of analysis of variance, which revealed that annealing temperature and concentration of second phase particles (Al2O3 particles) have significant influence on the hardness characteristics of electroless Ni-P-Al2O3 composite coating. The compositional, microstructural, andphase structure analyses are conducted with the help of energy-dispersive X-ray analysis, scanning electron microscope, and X-raydiffraction analyzer, respectively.