Mild and Severe Wear of Titanium Alloys

Dry sliding wear tests were performed for TC4 and TC11 alloys on a pin-on-disk wear tester at room temperature and various sliding velocities. TC4 and TC11 alloys shared almost the same wear regularity as a function of sliding velocity and contact pressure. The titanium alloys were noticed to reveal not only severe wear, but also mild wear at room temperature. Severe and mild wear alternated to appear at the sliding velocity of 0.75-4 m/s. With an increase in the contact pressure, a mild-to-severe wear transition occurred at 1.5 and 2.68 m/s, especially significantly at 2.68 m/s. However, a mild wear appeared throughout at 0.75 and 4 m/s. When titanium alloys slid at 4 m/s and then at 2.68 m/s, the originally high wear rate at 2.68 m/s was markedly reduced. That is, a severe-to-mild wear transition occurred in the originally severe wear regime by means of pre-sliding at 4 m/s. The appearance of mild wear was confirmed to be attributed to the formation of tribo-oxide layers. Oxidative mild wear prevailed in mild wear regime; delamination wear did in severe wear regime.