Microstructural aspects of hydrogen stress cracking in seawater for low carbon steel welds produced by flux-cored arc welding

Highlights: • Hydrogen stress cracking (HSC) was compared for base metal and transverse welds. • The base metal was fractured after SSRT in the hydrogen free environment. • Tiny crack at cementite in pearlite led to HSC of the base metal. • Micro crack at granular bainite in ICHAZ led to premature rupture by HSC. • Hydrogen trapped at granular bainite affected initial deformation in ICHAZ. This study investigated the role of weld microstructures on hydrogen stress cracking (HSC) in low carbon steels. HSC behaviours were compared for base metal (BM) and transverse-weld joints (WJs) using in-situ slow strain rate testing (SSRT) with hydrogen charging. The HSC resistivity of transverse WJs was inferior to that of BM. The transverse WJs were fractured in the BM during SSRT in hydrogen-free condition. The in-situ SSRT changed the fracture location to the inter-critical heat affected zone (ICHAZ) for transverse WJs and granular bainite in ICHAZ acted as the initiation site of HSC in transverse welds.