Investigation of the hydrogen-induced cracking of E690 steel welded joint in simulated seawater

Hydrogen-induced cracking (HIC) behavior and mechanism of E690 welded joint in simulated seawater were studied via microstructure observations, electrochemical hydrogen charging, slow strain rate tension (SSRT) tests and hydrogen content measurement. The results show that the welded joint of E690 steel has a higher HIC susceptibility than that of base metal, in which the inter-critical heat affected zone (ICHAZ) is composed of polygonal ferrite and granular bainite is the final fracture location in the joint. ICHAZ with the lowest yield strength deformed preferentially under the tensile stress, and subsequently, the proliferating dislocations with the deformation strengthening and the continuously charged hydrogen led to the HIC and brittle fracture at the ICHAZ of the welded joint. Moreover, the HIC susceptibility was linearly dependent on the logarithm of total hydrogen concentration in the steel, and the hydrogen concentration had a more obvious effect on the welded joint than the base metal. The higher density of piled dislocations adjoining the M/A islands in the welded joint exhibited a significant effect on the hydrogen agglomeration and diffusion, which enhanced the HIC susceptibility.