High temperature tribology of nanocrystalline Ni–P–Ag coating

Abstract

In this study, silver particles were embedded in Ni–P matrix by electroless deposition on medium carbon steel substrates to produce Ni–P–Ag composite coating. The structure of as plated and heat treated coatings were evaluated by X-ray diffraction analysis. Tribological properties of the coatings were investigated by pin on disc test method using 52100 steel pin as counter body at room and high temperatures. Three-dimensional optical profiler was employed to determine wear rate of the deposits. Surface morphology, cross-section of coatings and wear scars were studied by using scanning electron microscopy equipped with EDS analysis. The results showed that nanocrystalline Ni–P–Ag composite coating had a self-lubricating property at room and high temperatures. It was concluded that diffusion and nucleation of silver on the surface of Ni–P–Ag coating and also formation of a silver thin layer on the sliding surface led to decrease the friction coefficient of Ni–P–Ag coating.