Improving the high temperature oxidation resistance of high entropy alloy by surface modification

In the current study, we report an excellent high temperature oxidation resistance of AlCoCrFeNi high entropy alloy (HEA) following surface modification. The surface properties of HEA were tailored through a severe surface deformation technique. The as cast HEA exhibited coarse grain B2/BCC microstructure. In contrast, processed specimen showed significant grain refinement along with B2/BCC to FCC phase-transition. The processed specimen demonstrated 11-67% reduction in the oxidation kinetics. Cr2O3 and Al2O3 were the predominant oxides formed in all the oxidized specimens. In addition, Cr, Fe and Co rich spinels were also found in the as cast oxidized specimens. The superior oxidation resistance of the processed specimen is attributed to the microstructural refinement resulting in the formation of protective dense chromia layer.