Friction and wear behavior of thin-film ceramic coatings under lubricated sliding contact

• Performance of lubricant is significantly influenced by the presence of coatings.
• Some coatings are insensitive to lubricants; same performance in all lubricants.
• Tribological performance of carbon-based coatings was good in all lubricants tested.
• The use of coatings in lubricated components should be done carefully.

Thin film ceramic coatings are increasingly being used in lubricated tribological components. Unfortunately, lubricants formulated with functional additives such as anti-wear and friction modifiers, are usually designed to interact with ferrous material to form tribochemical surface films. When these lubricants are applied to coated surfaces, the effectiveness of the additives is still largely unknown. In this study, we evaluated the friction and wear behavior of several commercially available thin-film ceramic coatings when lubricated with unformulated and fully formulated synthetic oils to assess the impact of lubricant on such coatings. A variety of behaviors were observed for different coatings which can be explained in terms of the differences in tribochemical film formation and properties on the coatings surfaces.