The aim of this study is evaluation of dissimilar welding between SAF 2507 super duplex stainless steel to Incoloy 825 superalloy. For this purpose, pulsed current (PC) and continues current (CC) gas tungsten arc welding (GTAW), using ER2594, ERNiCrMo-3 and ERNiFeCr-1 filler wires, and also friction stir welding (FSW) were employed. In order to the microstructure characterization of the samples optical microscopy, scanning electron microscopy, electron back scatter diffraction technique and X-ray diffraction analysis were used. The mechanical property and local corrosion behavior of the specimens were investigated by micro-hardness, impact toughness and tensile tests and also, cyclic polarization test at 1 M NaCl solution. Ti-rich and (Nb, Mo)-rich phases were observed in arm spacing region of the austenite dendritic for ERNiFeCr-1 and ERNiCrMo-3 welds, respectively. Cr-rich phase combine with austenite and ferrite phases was characterized at the weld metal of the sample welded by ER2594 and CCGTAW method. Tensile test results showed that it is not difference between fusion welding methods and or type of the filler metals, and in all the cases, the ductile fracture was occurred at the weaker base metal. The ERNiFeCr-1 weld metal displayed the lowest hardness values. The highest impact resistance value (87 ± 3 J) was corresponded to the samples welded by ERNiFeCr-1 and PCGTAW technique. According to the cyclic polarization tests, the ER2594 weld metals produced by PCGATW represented the highest and lowest pitting corrosion resistance and sensitivity, respectively, at the each welding passes. Positing the SAF 2507 at advancing side resulted in the better weld quality and free from any conventional FS weld defects. The dynamic recrystallization phenomenon and subsequent fine grain microstructure genarations caused in the higher hardness value at stir zones than related parent metals. In the tensile test, FS weldment showed the comparable ultimate strength (658 ± 10 MPa) to the weaker base metal. The impact test results presented that stir zones display the the higher and lower toughness than Incoloy 825 and SAF 2507 base metals, respectively. According to the cyclic polarization tests, Incoloy 825 posited under shoulder showed the highest sensitivity to the pit growth. The stir zone represented the same pitting corrosion sensitivity and resistance than SAF 2507. However, SAF 2507 located under shoulder showed the lower and higher pitting corrosion resistance comparison with SAF 2507 and Incoloy 825, respectively, due the formation of Cr-rich phase.
