Assessing the effects of loading rate on fracture toughness of AISI 1020 and API 5L X80 steels with hydrogen charging: experimental and numeric simulation study

•Investigated the influence of loading rates on fracture toughness of AISI 1020 and API X80 steels during in-situ hydrogen charging.•Demonstrated the effect of loading rates on hydrogen concentration and its distribution along the crack front in both types of steels.•Revealed crack initiation mechanisms through actual observations of fracture morphology and numerical simulations of hydrogen distribution.•Suggested that current hydrogen compatibility standards should be modified to cover the loading rates during the actual service. This study focuses on the effect of hydrogen on fracture toughness of AISI 1020 and API 5L X80 steels using experimental measurement technique and numeric simulation. Hydrogen was introduced into Single Edge Notch Bend (SENB) specimens through in-situ electrochemical charging techniques. The study varied the loading rates (K̇) and observed a significant reduction in the fracture toughness of both types of steels with hydrogen presence, worsening as loading rates decreased. The findings illustrated that the current standards of hydrogen compatibility test, which specifies a loading rate that ranges from 0.1MPam/min to 1MPam/min in toughness tests, may produce non-conservative results by not fully capturing the degradation at lower loading rates (K̇