Tribochemical characterisation of duplex hard coatings with additional ion implantation

Abstract

Tribochemical wear occurs at the interface between a contact surfaces as a result of chemical and mechanical interactions in a tribological contact. Evidence of this type of wear is found by analysing residual surface debris and the near-surface material exposed to the tribological contact. In the present investigation the wear resistance of duplex-coated high-speed steel and surface modified with ion implantation, was studied under dry sliding condition. A typical duplex process involves plasma nitriding and the coating treatment of steels. The physical vapour deposition (PVD) and ion beam-assisted deposition (IBAD) coating under investigation was TiN. Ion implantation, after treatment, was provided with N2+ ions to change surface properties. The three basic points that are considered fundamental to studies of friction are the surface area and nature of the intimate asperity contacts, the surface adhesion and shear strength, and the nature of deformation and energy dissipation occurring at the asperity junctions. Conventional tribofilm analysis in the wear tracks was performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy. Wear resistance and exchanges of friction coefficient were measured with online specially designed tribology equipment. Finally, the results were correlated with properties determined from mechanical and tribological characterisation.