Mo content-depended competition between Cr2O3 enrichment and selective dissolution of CoCrFeNiMox high entropy alloys

Abstract The corrosion and passivation behavior of the as-cast CoCrFeNiMo x ( x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) high entropy alloys (HEAs) are investigated. With the addition of Mo, increasing Mo and Cr riched σ phase precipitates from the primary FCC phase. The corrosion resistance of the CoCrFeNiMo x HEAs strongly depends on the phase structure and the passive film. Generally, Mo promotes the selective dissolution of the FCC phase and the enrichment of Cr 2 O 3 in the passive film, the former deteriorates the corrosion resistance while the latter enhances it. Interestingly, the hypoeutectic Mo 0.6 exhibits a higher corrosion resistance than that of Mo 0.4 , eutectic Mo 0.8 , and hypereutectic Mo 1 . Analysis of surface passive film and the composition of alloy phases implies that the Cr 2 O 3 enrichment dominates in Mo 0.6 while selective dissolution governs in Mo x ( x = 0.4, 0.8, and 1.0). Mo content-depended competition between the Cr 2 O 3 enrichment and selective dissolution is discussed.