Fretting wear of a coated titanium alloy under free displacement

The quasi-static assemblies used in industrial applications are subjected to microsliding due to vibrations of variable amplitudes related to mechanical or aerodynamic instabilities. The titanium alloys used in such structures present extensive wear and must be protected by coatings. This article is devoted to the fretting behaviour of a coated Ti–6Al–4V alloy under free (un-imposed) displacement. The coating is made of a cupronickel alloy (CuNiIn or CuNiSi) topped by a polymer bonded solid lubricant MoS2. A fretting map was established to highlight the boundary between wear and seizure. An energetic coefficient of wear considering the global wear volume of the contact and the tribological parameters such as sliding distance and dissipated energy was established. Various morphologies of the third body observed in the contact were analyzed in terms of cohesion, ductility and adhesion. They were correlated to the tribological behaviour of the studied materials.