Microstructures of FeCoNiMo and CrFeCoNiMo Alloys, and the Corrosion Properties in 1 M Nitric Acid and 1 M Sodium Chloride Solutions

FeCoNiMo and CrFeCoNiMo equimolar alloys were prepared by arc-melting. The microstructures of the as-cast alloys were examined by SEM, HREM and XRD; and a potentiodynamic polarization test of the as-cast alloys was undertaken to evaluate the corrosion resistance in the solutions. Results showed that both of FeCoNiMo and CrFeCoNiMo equimolar alloys had a dendritic structure. The dendrites of these two alloys were a single phase which was a simple cubic (SC) structure with large lattice constant; and the interdendrities of these two alloys had a dual-phased eutectic structure in which the phases were face-centered cubic (FCC) and simple cubic (SC). The hardness of CrFeCoNiMo alloy was higher than that of FeCoNiMo alloy. Additionally, the potentiodynamic polarization test showed that CrFeCoNiMo alloy was better than FeCoNiMo alloy in 1 M nitric acid and 1 M sodium chloride solutions. Adding chromium into FeCoNiMo alloy could increase corrosion resistance in these two solutions. All of the results indicated that the CrFeCoNiMo alloy surpassed FeCoNiMo alloy.