Effect of Molybdenum Additives on Corrosion Behavior of (CoCrFeNi)100-xMox High-Entropy Alloys

The present work investigates the influence of micro-alloyed Mo on the corrosion behavior of (CoCrFeNi)(100-x)Mo-x high-entropy alloys. All of the (CoCrFeNi)(100-x)Mo-x alloys exhibit a single face-centered cubic (FCC) solid solution. However, the (CoCrFeNi)(97)Mo-3 alloy exhibits an ordered sigma (sigma) phase enriched in Cr and Mo. With the increase of x (the Mo content) from 1 to 3, the hardness of the (CoCrFeNi)(100-x)Mo-x alloys increases from 124.8 to 133.6 Vickers hardness (HV), and the compressive yield strength increases from 113.6 MPa to 141.1 MPa, without fracture under about a 60% compressive strain. The potentiodynamic polarization curve in a 3.5% NaCl solution indicates that the addition of Mo has a beneficial effect on the corrosion resistance to some certain extent, opposed to the sigma phase. Furthermore, the alloys tend to form a passivation film in the 0.5 M H2SO4 solution in order to inhibit the progress of the corrosion reaction as the Mo content increases.