High temperature wear behavior of refractory high entropy alloys based on 4-5-6 elemental palette

Abstract Refractory high entropy alloys (RHEAs) have recently attracted significant attention for structural applications because of their excellent high-temperature mechanical properties. However, there are few reports and limited understanding of their tribological behavior at elevated temperatures. Here, the sliding and reciprocating behavior of two newly developed RHEAs, namely HfTaTiVZr and TaTiVWZr, based on 4-5-6 elemental palette were investigated from 298 K to 723 K against Si3N4 counterface and compared with stainless steel. The steady state friction coefficient was in the range of 0.23–0.35, which are among the lowest values reported for RHEAs. The wear rates for HfTaTiVZr and TaTiVWZr were observed to be on the order of 10−4 mm3/N.m. With increasing temperature there was initially an increase in wear rate for the RHEAs up to the temperature of 423 K followed by decrease in wear rate with further increase in temperature. Detailed microscopic characterization of the wear tracks and the counterface showed a transition from abrasive to oxidative wear mechanism with increase in temperature with the formation of stable oxides and subsurface deformation in the contact region by shear mixing of the oxides.