Sliding wear of CoCrNi medium-entropy alloy at elevated temperatures: Wear mechanism transition and subsurface microstructure evolution

Abstract

To gain a comprehensive understanding of the wear mechanism and the combined effect of low stacking fault energy (SFE) and external elevated temperature on sliding-induced plastic deformation of CoCrNi medium-entropy alloy (MEA), herein, we report on the wear response of fine-grained CoCrNi MEA against Inconel alloy 718 counterparts between room temperature (RT) and 300 °C, with particular focus on the wear mechanism transition and sliding-induced subsurface microstructure evolution. The results show that the hardness of the MEA and coefficients of friction (CoFs) start to decrease at 200 °C, but wear rates monotonously decrease with rising temperatures. The wear mode changes from abrasive wear at RT to oxidative and adhesive wear at 200 °C. Between RT and 150 °C, stacking faults and deformation twins play a significant role in the formation of gradient subsurface microstructure. The improved wear resistance is mainly attributed to the thermal softening of the mating material and the increased contribution of adhesive wear. However, at 200 °C and above, the reduced wear rates and CoFs are associated with the formation of glaze layer. The present findings provide insights into understanding the wear mechanism and sliding-induced deformation of metallic alloys with low SFE at elevated temperatures.