In this research Taguchi method (DOE technique) has been used to optimize welding parameters in dissimilar joint between duplex stainless steel UNS32750 and austenite stainless steel AISI321 for achieving highest corrosion resistance. Pulse current 110, 120 and 130 A, background current 50, 60 and 70 A, % on time 70, 80 and 90 %, current frequency 1, 3 and 5 Hz were considered as welding parameters. Welding conditions were based on L 9 Taguchi’s orthogonal array design of experiment. Pulsed current gas arc welding (PCGTAW) with ER2594 electrode was used. Welding speed and voltage were 140 mm/min and 13 V, respectively. Microstructural characterization of joint was determined by optical and scanning electron microscope. The pitting potential was evaluated by potentiodynamic polarization test in 3.5 % NaCl solution at room temperature. Mechanical properties of optimal joint were determined by impact test and vickers microhardness. According to the results of Taguchi method, pulse current of 130 A, Background current of 60 A, % on time of 90 % and current frequency of 3 Hz were obtained as optimal conditions inwhich heat input were 0.685 KJ/mm. The reason of the difference between pitting potential in Taguchi specimens were heat input. In accordance with the result of analysis of variance, the percentage contributions of pulse current (most effective parameter) and % on time (less effective parameter) were 38.01% and 6.6%, respectively. Based on cyclic polarization test, pitting potential of weldment under optimal conditions welded with PCGTAW and CCGTAW were 1.03 and 0.8 V, respectively. Whereas, the corrosion resistance of CCGTAW were better than PCGTAW as a result of precipitate of Cr 2 N in PCGTAW weldment. Microstructural evaluation shows that the equal amount of ferrite and austenite were obtained in PCGTAW weldment. While in CCGTAW weldment fraction of phases changed to 40% ferrite and 60% austenite. The analysis of Taguchi specimens show that chi phase was precipitated in weld zone. TiN precipitations were formed in fusion line of CCGTAW weldment in optimal conditions. The average values of hardness in PCGTAW and CCGTAW weld zone were 241 and 225 HV 0.2 , respectively. The higher amount of ferrite in PCGTAW weldment in comparison with CCGTAW weldment were the reason of upper hardness average. The toughness of PCGTAW and CCGTAW were 106 and 102 J, respectively.
