Effect of Sn addition on the tribological behaviors of CoCrFeNi high entropy alloys

The present work investigated the effect of Sn on the microstructure, hardness, and tribological behaviors of CoCrFeNi high entropy alloys fabricated via vacuum arc melting. The results showed that Sn addition in CoCrFeNi alloys led to a distinct structure change from single FCC to dendritic microstructure in which Ni3Sn2 phase was distributed between the FCC dendrites. With the increase in Sn content, the volume fraction of Ni3Sn2 phase increased and thus brought about the improved hardness due to the second phase strengthening. The friction and wear test indicated that the best tribological performance was achieved by Sn1 alloy under a load of 2 N (the friction coefficient and wear rate were as low as 0.21 and 2.7 × 10−5 mm3/N∙m, respectively), which was attributed to the competitive effect between the applied load and Sn content. Moreover, the wear mechanisms of CoCrFeNiSnx alloys during sliding were carefully discussed.