Distinct Evidence of Hydrogen-Enhanced Defect Formation on Pre-Strained Nickel Alloy 625 during In Situ Electrochemical Nanoindentation Test

In the present work, in situ electrochemical nanoindentation was utilized to investigate the hydrogen effect on the nanomechanical properties of tensile pre-strained nickel alloy (0%, 5% and 20%). The study reveals that hydrogen-induced hardening occurs during cathodic polarization due to hydrogen incorporation and softening behavior during anodic polarization; this is due to the irreversible microstructure modification induced in the presence of hydrogen solutes. Their respective contributions were quantified by fitting the elastoplastic part of the load-displacement data. In addition, the differences in their plastic behaviors were investigated in detail by examining the dislocation structure underneath the indents. This study aims to shed light on hydrogen’s interaction with pre-existing defects.