Severe-to-Mild Wear Transition of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si Alloy Accelerated by Fe-Rich Oxide Tribo-layers

Abstract

Tribo-oxides (especially Fe-rich oxides) and tribo-layers usually play an important role in dry sliding wear and wear transition of titanium alloys against steels. To accelerate the transfer of Fe-rich oxides onto a titanium alloy and induce the rapid formation of the protective tribo-layer, a soft counterface of AISI 52100 steel (30 HRC) was used to slide against Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy (37 HRC) in air at 1–4 m/s under 20–50 N. Another comparative test of a hard counterface of AISI 52100 steel (60 HRC) against the titanium alloy was also performed with the same parameters. The roles of tribo-oxides and tribo-layers on the dry sliding wear of the titanium alloy were explored. As the titanium alloy slid against the soft counterface, the wear rates of the titanium alloy successively decreased from 1 to 4 m/s. However, in the case of the hard counterface, the wear rates were relatively high at 1–3 m/s (especially at 2 m/s), but sharply decreased at 4 m/s (except under 50 N). The sliding velocity-induced transition of severe-to-mild wear appeared at 2 m/s and 4 m/s for the soft and hard counterfaces, respectively. The load-induced transition of mild-to-severe wear emerged under 40 N at 2 m/s and under 50 N at 4 m/s for the soft and hard counterfaces, respectively. The Fe-rich oxide tribo-layers, rapidly induced by the soft counterface, accelerated the severe-to-mild wear transition at a lower sliding velocity of 2 m/s. The destruction of tribo-oxide layers caused the mild-to-severe wear transition under a high load.