Experimental and finite element investigation on hybrid GTAW-GMAW of duplex stainless steel

In this paper, 2205 DSS sheets with equal amounts of ferrite and austenite joined by GTAW, GMAW(1) (equal welding speed with hybrid welding), GMAW(2) (equal input heat with hybrid welding), and hybrid GTAW-GMAW. Then, heat distribution, maximum temperature, and cooling time during welding obtained from finite element simulation and the results were validated. Finally, the effect of input heat, cooling time, and welding method condition on quality and final microstructure of the joint were investigated. In addition to having a very good appearance, hybrid welding also has the highest ratio of weld depth to weld width. Also, due to the effect of using two arcs, on a same input, it has a lower maximum temperature comparing GMAW(2). The average cooling time in hybrid welding is 26.5 s, which is less than GMAW(2) and more than GTAW and GMAW(1), and this has caused the weld metal microstructure to have approximately equal amounts of ferrite and austenite (48% austenite). This has caused the hardness of the weld zone in hybrid welding to be higher than the hardness of GMAW(2) and close to the hardness of GTAW. Microstructural studies also revealed that the main morphology of austenite in fusion zone of hybrid welding is Widmanstatten. The size of ferrite grains in HAZ for hybrid welding is 204.3 mu m, which is smaller than GMAW(2) and larger than GTAW and GMAW(1). The reason for this is the shorter cooling time in hybrid welding compared to welding GMAW(2).