Effect of Alumina Dispersion on Microstructural and Nanomechanical Properties of Pulse Electrodeposited Nickel–Alumina Composite Coatings

Nickel-gamma alumina (Ni–γAl2O3) composite coatings were synthesized by pulsed electrodeposition technique with different concentrations of alumina (0, 10, 20 and 50 g/L) in Watt's bath. Both ultrasonic vibration and magnetic-stirring were utilized to disperse Al2O3 and to achieve its optimum loading. Microstructure shows that agglomerates occur at higher loadings, but 10 g/L Al2O3 addition in bath has shown uniform dispersion of alumina with improved mechanical properties such as hardness, Young's modulus and yield strength by 40%, 46% and 35%, respectively, when compared to that of pure Ni coating. Further, elasto-plastic indentation mechanics has shown that strength at 29% strain is enhanced to 110.5 GPa for 10 g/L Al2O3 electrophoretically deposited Ni–γAl2O3 coating when compared to that of electrodeposited Ni (81.8 GPa).