Effect of Sn addition on microstructure evolution, corrosion behavior and wear resistance of CoFeNiSn high-entropy alloys

The microstructure evolution, corrosion behavior and wear resistance of CoFeNiSn x high-entropy alloys (HEAs) were investigated in the Sn fraction range of 0-1.25. The addition of Sn facilitated the transition from single FCC phase to BCC+HCP eutectic structure. The CoFeNiSn 0.25 HEA exhibited excellent corrosion resistance in a 3.5wt% NaCl solution, displaying the passive film thickness of 3.74 nm and n -type semiconductor properties. The presence of Sn enhanced the surface potential in FCC phase and suppressed the contact potential difference ( V CPD ) at the phase interface, reducing the sensitivity of pitting and galvanic corrosion. The wear rate of CoFeNiSn x HEAs significantly decreased with the increase of Sn content, and the main wear mechanism shifted from adhesive wear to oxidative wear. This was attributed to the synergistic effect brought by Sn content to promote the gradual formation and integrity of the Fe-rich frictional oxide layer, together with the lubrication properties of SnO 2 .