The electrified tribological behavior of TiN coating in lubricated contacts

Abstract The excellent wear resistance and good conductivity of TiN coatings hold promising tribological applications in electrified contact systems. This work investigated the electrified tribological behavior of TiN coating when lubricated with four base oils: poly- α -olefin, mineral, rapeseed, and castor oils. The results indicated that the electric current caused fluctuating friction characteristics in lubricated contacts. The average friction coefficient under electrified conditions had a negligible change compared to the unelectrified cases when lubricated with hydrocarbon oils and rapeseed oil but a gradual decrease for castor oils. The electric current did not induce observable wear of TiN coating but promoted notable wear of steel pair. Under electrified conditions, the tribo-layers containing iron oxides and graphitized carbon were clearly observed on the surface of TiN coating for hydrocarbon oils and on the surface of steel balls for all lubricants. The enhanced adhesive transfer from steel to TiN surface was related to the electrified friction characteristics. In addition, the interfacial interactions caused by the electric field across the contact might also contribute to the electrified friction behavior of the system. These findings provide valuable insight into the application of TiN coatings in tribological protection for electrified contact components.