Revealing the B addition on tribology performance in TiZrHfTa0.5 refractory high-entropy alloy at ambient and elevated temperature.

TiZrHfTa 0.5 refractory high-entropy alloy (RHEA) shows great strength and ductility trade-off at ambient temperature, and has a lot of potential for use at elevated temperature. In this work, the effect of B element addition on the wear properties at different temperatures was thoroughly investigated. The results revealed that 1 at% B addition sample presents the best tribological properties at elevated temperatures, and borides exhibit a morphology evolution from blocky to acicular with the increasing B content. The wear rates at ambient and elevated temperatures successfully decrease with the increasing B content, which is ascribed to the increasing hardness, the solution strengthening, and the pinning effect at the grain boundaries induced by the second phase. In addition to the B content, the wear test temperature also significantly affects wear properties. With the analysis of the wear behavior and worn surface, it is demonstrated that the lowest wear rate at 600 ℃ is attributed to the continuous and densified oxide layer, while the serious wear at 400 ℃ results from the uncovered matrix and loose oxide layer. This work offers a new method to improve the wear properties of RHEAs at ambient and elevated temperatures. • The addition of B element for TiZrHfTa 0.5 RHEA results in the preferable wear performance at RT, 400 ℃ and 600 ℃. • The wear performance at 600 ℃ for four types of samples present the lowest wear rate. • The continuous and densified oxide layer formed at 600 ℃ contributes to the lowest wear rate. • The loose oxide layer formed in 400 ℃ leads to more metal fragments and more serious wear. [ABSTRACT FROM AUTHOR]