Effect of environments on the tribological behaviour of pure and graphene coated nickel against stainless steel counterpart

Friction and wear are a major cause of failure experienced by the mechanical components. Service life of these components can be improved by the application of different surface modifications and lubricating techniques. In this research work, tribological investigation of pure and graphene coated nickel specimens, in contact with stainless steel ball was conducted using pin-on-disc (PoD) tribometer test setup. Multilayered graphene coatings, approximately 20 nm in thickness, were applied using atmospheric pressure chemical vapor deposition (APCVD). Tests were conducted under similar loading conditions in four different environments: dry ambient, distilled water, saline water (3% NaCl) and mineral oil. Maximum coefficient of friction (COF), wear debris and wear track width were observed when pure nickel specimens were tested under dry ambient conditions. Graphene coating caused significant reduction in COF as well as in the width of wear scars. A minimum COF of 0.05 was achieved in graphene coated specimens under dry and mineral oil environments. Abrasive wear was the dominant phenomenon in case of pure nickel and stainless steel tribopair, while adhesive wear was observed in graphene coated and stainless steel tribopair. Microscopic analysis also revealed corrosive phenomenon in NaCl environment.