Effect of hydrogen-induced surface steps on the nanomechanical behavior of a CoCrFeMnNi high-entropy alloy revealed by in-situ electrochemical nanoindentation

The effect of hydrogen on the nanomechanical properties of CoCrFeMnNi high-entropy alloy was investigated by in-situ electrochemical nanoindentation testing. The changes in surface morphology, elastic modulus, pop-in load, and hardness during hydrogen ingress and egress processes were systematically evaluated. The results show that hydrogen charging leads to the formation of irreversible slip lines accumulated as surface steps. Furthermore, the irreversible reduced pop-in load and elastic modulus, and reversible increased hardness are detected. In this paper, the mechanisms of hydrogen-induced surface steps together with their further influences on the nanomechanical properties are discussed in detail.