SKM 2023 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 27: Hydrogen in Materials

MM 27.2: Talk

Wednesday, March 29, 2023, 10:30–10:45, SCH A 215

Ab-initio insights into hydrogen-carbide interaction in bcc Fe — Saurabh Sagar and •Poulumi Dey — Delft University of Technology, Delft, The Netherlands

Development of advanced high-strength steels is in high demand owing to its wide scale applications. The excellent mechanical properties of these steel grades are attributed to the underlying microstructure which comprises of finely dispersed nano-precipitates. However, one major factor restricting their application is their susceptibility to Hydrogen Embrittlement (HE). Experimental and theoretical work have been carried out to understand if the nano-sized carbides can aid in reducing the susceptibility to HE along with providing strengthening. Within this study, we investigated the effectiveness of finely dispersed nano-carbides (i.e., TiC, NbC and VC) to limit the diffusible hydrogen content in bcc Fe. Our study revealed that the interplay between hydrogen and carbon vacancies, local atomic environment at interface as well as interface geometry can lead to significantly increased hydrogen solubilities. Thus, the trapping at these sites leads to a reduction in concentration of diffusible hydrogen. However, the question remains whether hydrogen can populate the deepest traps (i.e., the carbon vacancies) in the bulk of these carbides. We, thus, extended our study to compute migration barriers of hydrogen across the coherent interface between bcc Fe and TiC, NbC and VC using climbing-image Nudged Elastic Band method. Furthermore, we evaluated whether a chain of interconnected carbon vacancies from the interface to the bulk of the carbides leads to a reduction in the migration barrier of hydrogen.