Atomic study of hydrogen behaviors at ∑3(111) grain boundary in equiatomic CoCrNi and CoCrNiFe alloys

Abstract

High-entropy alloys are potential advanced structural materials for applications in nuclear energy due to their proved high irradiation performance. However, exposing components made of structure materials to service conditions under certain nuclear environments may induce hydrogen embrittlement (HE) as one of the typical failure mechanisms. In this work, we performed density functional theory (DFT) calculations to examine the role of specific element species in HE mechanism in CoCrNi and CoCrNiFe alloys. The solution energy, binding energy and diffusion barrier of H atoms at ∑3 GBs (GBs is short for grain boundaries) are presented. Based on the DFT data, we found that Cr limits the H atom to a specific potential position, thus suppresses H segregation. The dipole moment interaction between H and Fe atoms weakens the binding of H atoms. The lattice distortion effect-induced trapping for H provides higher H diffusion barriers at ∑3 GBs than that in pure Ni.