Sliding friction and wear performance of Ti6Al4V in the presence of surface-capped copper nanoclusters lubricant

The friction and wear properties of Ti6Al4V sliding against AISI52100 steel ball under different lubricative media of surface-capped copper nanoclusters lubricant—Cu nanoparticles capped with O,O′-di-n-octyldithiophosphate (Cu-DTP), rapeseed oil and rapeseed oil containing 1 wt% Cu-DTP was evaluated using an Optimol SRV oscillating friction and wear tester. The wear mechanism was examined using scanning electron microscopy (SEM) and X-ray photoelectron spectrosmeter (XPS). Results indicate that Cu-DTP can act as the best lubricant for Ti6Al4V as compared with rapeseed oil and rapeseed oil containing 1 wt% Cu-DTP. The applied load and sliding frequency obviously affected the friction and wear behavior of Ti6Al4V under Cu-DTP lubricating. The frictional experiment of the Ti6Al4V sliding against AISI52100 cannot continue under the lubricating condition of rapeseed oil or rapeseed oil containing 1 wt% Cu-DTP when the applied load are over 100 N. Surprisingly, the frictional experiment of Ti6Al4V sliding against AISI52100 steel can continue at the applied load of 450 N under Cu-DTP lubricating. The tribochemical reaction film containing S and P is responsible for the good wear resistance and friction reduction of Ti6Al4V under Cu-DTP at the low applied load. However, a conjunct effect of Cu nanoparticle deposited film and tribochemical reaction film containing S and P contributes to the good tribological properties of Ti6Al4V under Cu-DTP at the high-applied load.