Friction and wear behavior of a single-phase equiatomic TiZrHfNb high-entropy alloy studied using a nanoscratch technique

Abstract

In this study, friction and wear of a body-centered cubic equiatomic TiZrHfNb high-entropy (HE) alloy were investigated using a nanoscratch method. Scratch tests, under both ramping and constant load modes, were conducted to evaluate the coefficient of friction (COF) and wear rate of the alloy. The effects of scratch rate on the friction and wear were also studied. The morphology such as the surface profile and depth of scratched tracks was examined using scanning electron microscopy (SEM) and scanning probe microscopy (SPM). It was found that, whilst wear behavior, including wear rate and wear resistance, could be described by Archard equation, friction of the alloy appeared to be more complicated. Experimental results revealed that the friction of the alloy could be divided into two distinct regimes - elastic and plastic. The COF decreased rapidly with increasing normal load in the elastic regime, but became essentially constant in the plastic regime, indicating a transition of friction mechanism. In this study, scratch tests were also performed on pure Nb and a solid-solution strengthened Nb-based C103 alloy to make a direct comparison. The TiZrHfNb HE alloy apparently exhibited an improved wear resistance and lower COF as compared to its traditional alloy counterparts. The better wear resistance and lower COF were discussed in lights of the acting plowing and adhesion mechanisms during wear.