In this study, the microstructure, mechanical properties and corrosion behavior of dissimilar joints of AISI 310S austenitic stainless steel to UNS 32750 duplex stainless steel were investigated. 310 S austenitic stainless steels and 32750 duplex stainless steels are connected under gas tungsten arc welding operation with negative polarity. Welding of 310S to 32750 stainless steel was performed using ER2594 filler metal at four heat input of 540, 680, 733 and 810 J/mm. Due to the microstructural changes of the weld metal due to different welding heat input, microstructural studies were performed first. Because mechanical properties such as microhardness and tensile strength change due to different microstructure, they were eva‎luated in the next step. In the microstructural studies section, microstructures of weld metal zone and heat affected zone of welding operations were performed using scanning electron microscopy (SEM) and optical microscopy. Different heat input in welding affect the general corrosion resistance, so the corrosion behavior of base metals and weld metals at heat inputs of 540 to 810 J/mm were eva‎luated. Corrosion behavior was investigated under three tests of open circuit potential (OCP), potentiodynamic polarizationon and cyclic polarization. In the results of microstructure studies, it was observed that the obtained structure is a duplex structure consisting of two-phase austenite and ferrite. Also, with increasing the inlet temperature, the percentage of austenite phase has increased and the values of the percentage of austenite phase for the heat input of 540 to 860 J/mm are 58, 67, 75 and 82%, respectively. The heat affected zone in the base metal UNS 32750 is a duplex zone consisting of 35 to 40% austenite and in the base metal 310S some delta ferrite values were observed. In hardness tests in the weld zone and in the base metal zone, UNS 32750 had higher hardness values than the 310S, and in the weld zone at heats input of 540, 660, 770 and 860 J/mm, the microhardness values were 450, 420, 410 and 398 Vickers were obtained, which increased the hardness of weld metals with increasing heat input. In corrosion polarization experiments, duplex stainless steel 32750 showed better general corrosion than stainless steel 310S and had pitting corrosion at a potential of 1100 mV. In weld metals, the general corrosion resistance decreased with increasing the heat input from 540 to 860 J/mm and moving away from the equilibrium value of ferrite and austenite, but there was not much change in the pitting corrosion resistance. Finally, the pitting corrosion resistance of welds metal up to a potential higher than 1000 mV was obtained. According to the results of the experiments, it can be said; Welding of UNS 32750 to 310S stainless steel by gas tungsten arc welding method, using filler metal ER2594 and with control of inlet temperature of about 700 J/mm, a joint can be obtained whose corrosion behavior is better than base metals.

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