Nanodiamond as an effective additive in oil to dramatically reduce friction and wear for fretting steel/copper interfaces

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 x 10(4) 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.