Microstructural and mechanical properties of electron beam welded super duplex stainless steel

Abstract The electron beam welding of super duplex stainless steels is associated with challenges due to the concentrated heat input and the nitrogen loss that result in a predominantly ferritic structure after the solidification. This study presents an approach to overcome this issue by feeding nickel-based filler wire into the melt pool in welding of 2507 super duplex stainless steel. Results showed that the high-frequency beam oscillation combined with a multi-beam technique led a good mixing between the base metal and the filler wire, even at a large depth-to-width ratio. Additionally, the weld geometry was characterized by near-parallel fusion lines and a narrow heat-affected zone. The nickel addition resulted in a balanced microstructure in the weld metal with ferrite fractions of 35–55 %, despite a significant nitrogen loss, consequently leading to impact energy values of 215 ± 15 J and hardness values of 285 ± 15 HV. The findings of this investigation allow fabricators to effectively design electron beam welding processes for producing thick-walled super duplex stainless steel components.