Hydrogen Embrittlement (HE) is one of the causes mainly evoked in premature rupture of industrial components exposed to aggressive environment. Many studies have been conducted in order to understand the mechanisms involved during this degradation. However the effects of the grain boundaries (GBs), triple junction (TJs) and several defects (dislocations, vacancies ...) in FCC materials and their interactions with hydrogen on the mechanisms of metal damages remain controversy. In fact, several works suggest that in FCC materials the grain boundaries represent preferential paths for hydrogen (short-circuit diffusion), and that hydrogen diffusion along GBs is higher than interstitial diffusion. However, GBs contain different defects, particularly, dislocations and vacancies. These defects are able to trap hydrogen affecting the diffusion mechanisms. The density and configuration of these defects are accommodated by the character of grain boundaries. Indeed, we distinguish different GBs classes. GBs with small misorientation (LAGB) that are accommodated by one dislocation network, and GBs with large misorientation (HAGB), which can be defined or not by coincidence site lattice network (CSL). In this study, we have several bicrystals of pure nickel with different grain boundary classes (according to misorientation and CSL index). For each bicrystal (grain boundary), we evaluated the hydrogen diffusion and trapping mechanisms using the electrochemical permeation (EP) coupled to the thermal desorption spectroscopy (TDS). The results will allow us to associate the short-circuit diffusion and trapping phenomena to the grain boundaries character.
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