Abstract
Hydrogen is promoted, as a clean energy carrier, to play an important role in achieving carbon neutrality. A possible mode of transportation for hydrogen gas are steel pipelines. Hydrogen embrittlement is a threat to structural integrity of these lines. The mechanisms of hydrogen embrittlement remain unclear and more efforts are still needed, including how hydrogen interacts with the microstructure and in particular when plasticity is involved which can come from various sources (installation, damage, etc…).
The focus of this work is to understand how hydrogen interacts with the steel microstructure and see how these interactions are modified after plastic deformation of the material. The material of interest is an API 5L steel grade that was plastically deformed up to approximately 5%.
Thermal Desorption Spectroscopy after gas charging revealed that at least two microstructural contributions to the H pick-up are present in the material before deformation. After deformation, two contributions remain but with a much higher signal (i.e higher H pick-up), sign of an increased number of hydrogen traps. Diffusivity of hydrogen, measured by electro-chemical permeation, is strongly delayed with a much higher sub-surface hydrogen concentration consistent with the TDS results. These modifications are discussed in terms of the different microstructural parameters (grain size, dislocation density, etc..) that have been quantified by Electron BackScatter Diffraction.