Comparative Study on Tribological Behaviors of Two TiZr-Based Alloys in Vacuum

In this study, the vacuum tribological behaviors of the two TiZr-based alloys were investigated. The results show that the coefficient of friction of Ti-47Zr-5Al-3V alloy (T47Z)/ steel counterpart was lower at 0.59 m/s, while that of Ti-20Zr-6.5Al-4V alloy (T20Z)/ steel counterpart was lower when the sliding velocity was increased to 1.17 m/s. The wear volume of T47Z alloy was higher regardless of the tribological conditions. Zirconium content, normal load and sliding velocity were evaluated based on wear volume using the Taguchi method and ANOVA analysis, and they contributed 18.11, 53.79, and 14.44%, respectively. SEM was used to analyze the worn surface morphology. For T20Z alloy, the wear mechanisms varied from mild abrasive wear to delamination wear. However, the dominant wear mechanisms of T47Z alloy changed from mild abrasive wear and plastic flow to severe delamination wear and fatigue wear. The microstructural evolution of TiZr-based alloys was determined using TEM. At lower tribological parameters, the dislocation density of both alloys increased compared with unworn specimens. Under 30 N, 1.17 m/s condition, the SAED results show that only the β-phase was elongated in T20Z alloy. In contrast, subgrains, even nanograins, were formed in T47Z alloy under the same condition.