Fracture and electrochemical behavior of S355 steel welded joint under High-Frequency vibration

•Effects of high-frequency vibration on residual stress, impact toughness and electrochemical performance of S355 steel welded joint are studied.•The mechanism of the high-frequency vibration on the impact toughness and the electrochemical corrosion resistance is discussed.•The residual tensile stress is effectively decreased, the impact toughness is improved, and the electrochemical performance is improved by high-frequency vibration. The influences of the high-frequency vibratory stress relief (VSR) on the surface residual stress, the impact toughness, the fracture morphology, the chemical composition, the microstructure, and the electrochemical corrosion resistance of S355 steel welded joints were analyzed. The improvement mechanism of the high-frequency vibration on the impact toughness and the electrochemical corrosion resistance were discussed. The SEM and EDS results indicated that the plasticity of the metal material was enhanced since the size and depth of the dimples in each region of the impact specimens were increased, the uniformity was better. In this case, the impact toughness of the S355 steel welded joints after the high-frequency VSR was improved. Moreover, the electrochemical corrosion resistance of the heat affected zone of the S355 steel welded joints was improved by the high-frequency VSR. Meanwhile, the grain size and the microstructure morphology of the S355 steel welded joints remained almost the same before and after the high-frequency VSR. The findings confirm that the reduced residual tensile stress could improve the impact toughness and the electrochemical corrosion resistance of the S355 steel welded joints.