Fretting wear and friction reduction of CP titanium and Ti–6Al–4V alloy by ultrasonic nanocrystalline surface modification

Application of surface modification techniques is expected to be a viable solution to mitigate fretting damage and to reduce friction. In this paper, the aim was to improve the fretting wear and friction characteristics of commercially pure titanium (CP Ti) and Ti–6Al–4V alloy by using an ultrasonic nanocrystalline surface modification (UNSM) technique. Lubricated fretting wear and friction tests were conducted with a ball-on-flat configuration on untreated and UNSM-treated specimens using silicon nitride (Si3N4) balls. The results showed that the fretting wear and friction coefficient characteristics of the UNSM-treated specimens were improved compared to those of the untreated specimens. Moreover, it was found that the fretting wear scar diameter and depth of the UNSM-treated specimens were smaller and shallower compared to those of the untreated specimens. Surface analysis was performed using a scanning electron microscope (SEM).