Abstract
Hydrogen enhanced decohesion is expected to play a major role in ferritic steels, especially at grain boundaries. Here, we address the effects of some common alloying elements C, V, Cr, and Mn on the H segregation behaviour and the decohesion mechanism at a Σ 5 ( 310 ) [ 001 ] 36.9 ∘ grain boundary in bcc Fe using spin polarized density functional theory calculations. We find that V, Cr, and Mn enhance grain boundary cohesion. Furthermore, all elements have an influence on the segregation energies of the interstitial elements as well as on these elements’ impact on grain boundary cohesion. V slightly promotes segregation of the cohesion enhancing element C. However, none of the elements increase the cohesion enhancing effect of C and reduce the detrimental effect of H on interfacial cohesion at the same time. At an interface which is co-segregated with C, H, and a substitutional element, C and H show only weak interaction, and the highest work of separation is obtained when the substitute is Mn.
Highlights
Hydrogen being one of the most abundantly available elements is one of the most complicated to understand
In the study at hand, we investigate the co-segregation of H and typical alloying elements in ferritic steels, C, V, Cr, and Mn to shed some light on their combined effects on grain boundary embrittlement
Mn decreases the grain boundaries (GBs) energy and is more strongly attracted to the GB than Cr and V. From both γseg and the decrease in γGB, we find that Cr and V at 5 at% do not show a clear preference for the GB
Summary
Hydrogen being one of the most abundantly available elements is one of the most complicated to understand. Grain boundaries (GBs) are likely trapping sites for H [3,4] but are prone to suffer from hydrogen enhanced decohesion (HEDE) [5]. Both the segregation tendency of H to grain boundaries and the effect of H on GB cohesion can be influenced by alloying elements [6,7]. In the study at hand, we investigate the co-segregation of H and typical alloying elements in ferritic steels, C, V, Cr, and Mn to shed some light on their combined effects on grain boundary embrittlement.
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