Improved Wear Resistance of a Heterogeneous CoCrNi Medium-Entropy Alloy at Cryogenic Temperature

Medium-entropy alloys (MEAs) exhibit excellent mechanical properties and unique deformation mechanism at cryogenic temperatures. However, limited studies have been conducted to explore their cryogenic temperature wear behaviors and thus hinder their further cryogenic applications. Here, we report a mono-phased heterogeneous CoCrNi MEA composed of fully recrystallized grains and non-recrystallized grains that shows a favorable combination of strength and ductility. Meanwhile, a decreased coefficient of friction and improved wear resistance are revealed with the decreasing temperatures (0 °C → –120 °C). The wear mechanism shows an apparent transition from brittle fracture to mild plastic deformation when temperature decreases. The enhancement of strength-ductility for heterogeneous CoCrNi MEA at lower temperature leads to a reduction of ploughing coefficient and superior plastic response, thus resulting in excellent wear resistance. The present work provides a convenient route for preparing strength-ductility balanced and wear-resistant alloys for cryogenic applications. Graphical Abstract