Microstructure evolution of 2205 duplex stainless steel (DSS) and inconel 718 dissimilar welded joints and impact on corrosion and mechanical behavior

The Inconel 718/2205 DSS dissimilar welding is widely used in subsea pipelines. In order to investigate the influence of high-density energy sources on the microstructure and properties of welded joints, a 2205 DSS/ Inconel 718 dissimilar joint was fabricated using laser beam welding (LBW). The microstructure of the joint was analyzed using scanning electron microscopy (SEM). The results indicate that a large number of irregular Laves phases were formed in the weld zone, with good fusion between IN718 and the weld zone, while the interface between 2205 and the weld was clear, forming a transition zone. The corrosion behavior and characteristics of the weld and base material in a 3.5 wt% NaCl solution were studied using electrochemical methods. Compared to the base material IN718, the passivation current density of the welded joint decreased by 18.6 %, and the corrosion current density decreased by 41 %. More corrosion products were generated in the welded joint, which is the main reason for the improved corrosion resistance. The hardness and tensile properties of the joint were evaluated, showing that due to the formation of Laves phases, the hardness of the welded joint increased by 19.1 % compared to IN718. However, the large Laves phases are prone to fracture during plastic deformation, leading to a decrease in the elongation of the welded joint. The research findings of this study are of significant importance for the application of stainless steel and nickel-based alloy welded joints in engineering.