Effect of current density, MoS2 content and bath agitation on tribological properties of electrodeposited nanostructured Ni-MoS2 composite coatings

Abstract

ABSTRACTNanostructured nickel coatings with molybdenum disulphide particles were electrodeposited to form composite coatings. Three different current densities, i.e. 3, 5 and 7 A/dm2 were investigated initially. The best results were obtained with 5 A/dm2 for codeposition of nanostructured Ni-MoS2 composite coatings. With the addition of 1–4 g/L molybdenum disulphide to the bath, the weight percentages of MoS2 particles in the coatings were 23–38%. This increase of MoS2 content was accompanied with decrease in friction coefficient of the coatings from 0.35 to 0.08. Wear resistance of the coatings was increased with increasing MoS2 content and the weight loss was decreased from 1.4 to 0.7 mg. Hardness was decreased from 585 to 400 VHN with increasing the MoS2 content. By increasing bath agitation speed up to 150 rpm, more MoS2 particles were embedded in the matrix and the coatings showed better wear resistance. However, increase of agitation speed from 150 to 200 rpm caused a decrease of MoS2 particles in the nickel matrix due to the turbulent motion of particles in the bath. Overall, it was shown that the lubricating effect of MoS2 in the coating was more influential than the nanocrystallinity of the nickel matrix in improving tribological properties of these composite coatings.