Effects of surface treatments and coatings on tribological performance of Ti–6Al–4V in the mixed fretting and gross slip regimes

• Ti–MoS2 and TiC–aC coatings on Ti–6Al–4V reduce wear and friction in fretting contact.
• Ti–MoS2 undergoes a hydrodesulfurization tribochemical wear process with NiPO4.
• NiPO4 is a very compatible counterface for TiC–aC.
• The best material pairing observed in this study is MnPO4 versus Ti–MoS2 coated Ti–6Al–4V.

Although titanium alloys are chemically resistant and have desirable mechanical properties, these materials are known to experience high wear rates and friction when they are in contact and in relative motion with themselves or most other materials. In this study, titanium-containing MoS2 and Ti containing amorphous carbon coatings have been applied to Ti–6Al–4V discs and were examined in mixed fretting and gross slip regimes against uncoated, NiPO4, and MnPO4 coated AISI 52100 counterfaces. Experiments were carried out at two different temperatures and wear coefficients were obtained for the various material pairs. Whereas the smallest friction and wear coefficients were obtained for MnPO4/Ti–MoS2 pairs at both high and low temperatures, the NiPO4/Ti–MoS2 coupling is incompatible. On the other hand, NiPO4/Ti–aC appears to be a very compatible material pair.