Abstract:The feasibility of dissimilar friction stir welding (FSW) between the SAF 2507 super duplex stainless steel and the Incoloy 825 Ni-based superalloy was evaluated. The microstructure and mechanical behavior of the weldments were examined too. The results showed that the alloys were successfully welded together by positioning the SAF 2507 on the advancing side. The nuggets displayed higher hardness than the base metals, due to the occurrence of dynamic recrystallization and the subsequent refinement of the microstructures. The welded sample obtained the similar strength to the Incoloy 825 parent metal, showing the ductile fracture mode after the tensile tests by SEM. Moreover, the weld zone (31 J) exhibited higher and lower toughness than the Incoloy 825 (23 J) and SAF 2507 (42 J) parent metals, respectively. Based on the obtained results, the FSW method could be recommended to weld the super duplex stainless steel/Ni-based superalloy joints.

Key words: friction stir welding; dissimilar welds; nickel; stainless steel; microstructure; mechanical property