Dry wear characteristics of TC21 titanium alloy at elevated temperatures

Abstract

TC21 alloy is a new type of high damage tolerance titanium-based alloy, but its elevated-temperature wear characteristics such as wear mechanism and wear transition are still unknown. In present study, dry wear tests of TC21 alloy were carried out at experimental temperatures of 20-300oC under various applied loads. Volumetric wear rate was plotted against experimental temperature under each applied load to exhibit its variation trend and mild-severe wear transition. Scanning electron microscopy was used to examine worn surface morphologies. Confocal scanning laser microcopy and Vickers microhardness tester were utilized for characterizing the friction-affected microstructure and mechanical property in the subsurfaces. Four wear mechanisms, namely abrasion, adhesion, mild surface deformation and severe surface deformation, were observed. Severe surface deformation was found responsible for severe wear behavior, and it was aroused by the near-surface softening originating from dynamic recrystallization (DRX). The severe wear transition temperature was found to be decreased linearly with increasing applied load. By linearly fitting the relation between applied load and transition temperature, a critical surface temperature of 399.4oC for severe wear transition is estimated, and it is further deduced to be the critical temperature for DRX realization of surface material during sliding.