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Abstract This study reports on fretting friction and wear behaviors of steel/copper test pairs lubricated in the nanodiamond-dispersed oil with a flat-on-flat configuration at 106 N. After 4 × 104 fretting cycles, results show that an addition of 0.2 wt% nanodiamonds in oil reduces the friction torque from 0.12 Nm of pure oil to 0.08 Nm. Particularly, the wear volume is decreased by an order of magnitude compared to that tested in pure oil. Microstructural analyses reveal that the substantial friction and wear reduction is attributed to collective effects including the formation of robust nanodiamond-strengthened tribofilms, wear-induced twin boundaries, and good mechanical bonding interface between tribofilms and the substrate. Highlights • Dispersing nanodiamonds (NDs) in oil dramatically reduced friction for fretting. • Wear volume was decreased by an order of magnitude after dispersing NDs in oil. • This can be attributed to formation of a robust nanodiamond-strengthened tribofilm. • Wear-induced TBs in the substrate also promoted to the high wear resistance. [ABSTRACT FROM AUTHOR]

The present research describes a study to explore the possibility to improve the wear resistance by healing microcracks that initiated under fretting wear. To this aim Ti 3 SiC 2 coatings prepared at different plasma powers (33 and 34 kW) were investigated comparatively under fretting. The results showed that the amount of Ti 3 SiC 2 phases was higher at the lower plasma power, leading to a major difference on fretting wear properties. Coatings with a higher content of Ti 3 SiC 2 phases exhibited a remarkable decrease in the friction coefficient and an enhancement in the wear resistance. The enhanced wear resistance was mainly attributed to the healed cracks by selective oxidation of Ti 3 SiC 2 . The reduced friction coefficient was strongly related to the formation of tribo-induced oxides. [ABSTRACT FROM AUTHOR]