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Abstract

To counteract H-embrittlement, more detailed knowledge on the atomistic processes involved is necessary. The hydrogen enhanced decohesion (HEDE) mechanism is expected to be most relevant at grain boundaries (GBs) and interfaces, where H is trapped, but distributed along a crystallographic plane. In a previous DFT study of a Σ5 symmetrical tilt GB it was found that HEDE in bcc Fe is probably due to the substitution of strengthening elements, such as C, by H. The aim of this work is to use ab initio calculations to improve the existing understanding of the HEDE mechanism and find alloying elements which deter the H segregation to the GB. Thus, potential alloying elements, Mn, Cr and V, in the Fe-C-H system are investigated. It was found that in systems with V, the segregation of C to the GB increases, while that of H slightly decreases, when compared to Mn and Cr. This and further possibilities of segregation engineering of steels against H-embrittlement will be discussed in detail.