Effects of Hydrogen in Linepipe Steels

Zero carbon energy systems are needed urgently. Gas is used for heating in 85% of households in the UK and this could be replaced by hydrogen supplied through the existing national transmission system (NTS). Assessing the potential effects of hydrogen on pipeline steels is a necessary part of the safety case. A variety steel grades are used in the main high-pressure pipelines with varying proportions of of ferrite, pearlite, and bainite present. Higher strength steels are used in valve and spring components in lower volume.  All of these will neccessarily be exposed to hydrogen and the potential debit to mechanical properties needs to be determined, understood and if neccessary mitigated.  Potential detrimental effects include hydrogen embrittlement and accelerated fatigue failure (crack initiation and crack growth).
This project will compare the mechanical behaviour of linepipe steels currently in service within the NTS with and without hydrogen charging. The focus will be on improving mechanistic understanding of the micromechanical response.  Combinations of nanoindentation, ex-situ and in-situ mechanical testing, with digital image correlation (optical and SEM imaging), will be used along with HR-EBSD, EDX and possibly AFM characterisation.  The strategy will be to determine the differing effects of hydrogen on the individual microstructural components and from that build understanding of the steel as a whole.  There will be scope for crystal plasticity modelling work.  The work may expand to look at effects of hydrogen on potential replacement materials for existing steels.
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