Stress corrosion cracking behavior of SUS301L-MT stainless steel laser-arc hybrid welded joints

Highlights: • Laser-arc hybrid welding (LAHW) has potentially employed for the excellent welding of cold rolled SUS301L stainless steel, promising for new generation subway vehicles underframe, due to its low heat input and high welding speed. However, the stress corrosion cracking (SCC) behavior of this type welded joints is still unclear, which seriously obstructs its wide applications. • In our works, in combination with the fracture morphologies, microstructures and potentiodynamica polarization of the weld metal (WM), heat affect zone (HAZ) and base matel (BM), the facile slow strain rate tensile (SSRT) technology were applied to systematically investigate its SCC behavior in 3.5 wt.% NaCl solution by using 8 mm thick LAHW-based SUS301L-MT stainless steel as BM. • As a result, the SCC susceptibility index (I_SSRT) of welded joints is as low as 0.09, lowering 2.56 times compared with that of BM (0.23). So low I_SSRT should be mainly attributed to the cathodic protection of austenite originated from the corroding δ-γ interfaces. • We believe that the disclosure of SCC behavior will heavily facilitate the wide applications of LAHW for new generation subway vehicles underframe as well as others high strength welding structures. - Abstract: Laser-arc hybrid welding (LAHW) has potentially employed for the excellent welding of cold rolled SUS301L stainless steel, promising for the new generation subway vehicles underframe, due to its low heat input and high welding speed. However, the stress corrosion cracking (SCC) behavior of this type welded joints is still unclear, which may be a potential risk for its applications. Here, in combination with the fracture morphology, microstructure and potentiodynamic polarization of the weld metal (WM), heat affect zone (HAZ) and base metal (BM), the slow strain rate tensile (SSRT) method was applied to systematically investigate its SCC behavior of LAHW-based SUS301L-MT stainless steel in 3.5 wt.% NaCl solution. The result indicated that the SCC susceptibility index ($I_{SSRT}$) of welded joints is 0.09, much lower than that of BM (0.23). The low $I_{SSRT}$ should be mainly attributed to the cathodic protection of austenite originated from the corroding δ-γ interfaces. We believe that this study will help to facilitate the wide applications of LAHW for new generation of subway vehicles underframe and others high strength welding structures.