Effects of hydrogen and microstructure on tensile properties and failure mechanism of 304L K-TIG welded joint

The effects of hydrogen on the mechanical properties of 304L keyhole tungsten inert gas welded joint were investigated in the study. The presence of hydrogen resulted in a significant decrease in the macroscopic ductility of the weld metal, and fracture may be initiated at the sites of clustered dislocations due to hydrogen atoms. Moreover, it is found that hydrogen may result in more severe loss in ductility and noticeable decrease in the flow stress and strength of the base metal, because of the interplay between the hydrogen atoms and strain-induced α′ martensite. Strain-induced α′ martensitic transformation and phase boundaries in the base metal may provide more sites for the accumulation of hydrogen and dislocations, leading to an appreciable decrease in the ductility and strength of the base metal.