Abstract
Ni and its alloys are susceptible to hydrogen embrittlement (HE). In this work, we perform a systematic density functional theory (DFT)-based investigation on the hydrogen-enhanced decohesion (HEDE) mechanism of HE for the case of the special Σ5(012) grain boundary (GB) in Ni containing C and Mo impurity atoms. Segregation and co-segregation energy profiles of H along with C and Mo solute elements are investigated in detail and used to analyze the effect of Mo and C solutes on HEDE in Ni within the framework of the Rice-Thomson-Wang theory. We show that H, C, and Mo segregate to the GB in Ni. H demonstrates the GB embrittling effect while C and Mo solutes strengthen the GB in Ni. The results also show that H–Mo and H–C interactions in the bulk and at the GB are very similar and can be neglected in most of cases of co-segregation.
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