Evolution mechanism of microstructure and properties for 2205 duplex stainless steel joints under “oscillation + pulse” laser-induced arc hybrid welding

Abstract

The key to high efficiency welding and corrosion resistance of 2205 duplex stainless steel lies in balancing both properties during the welding process. Laser-induced arc hybrid welding effectively balances the relationship between microstructure and corrosion while pursuing welding efficiency. This study proposes a “oscillation + pulse” double hybrid effect laser to induce an arc and investigates its impact on the microstructure and properties of 2205 duplex stainless steel joints. The results indicate that “oscillation + pulse” laser-induced arc hybrid welding, with circular scanning, induces a more vigorous stirring effect on the molten pool, promoting the conversion from columnar to equiaxial crystal structures. This process also reduces the formation of hard brittle Widmanstätten austenite. In addition, fine and fragmented intragranular austenite precipitates within the ferrite grain boundaries, resulting in a significant increase in elongation, from 15.04 % to 26.91 %. Electron backscatter diffraction analysis reveals that, compared to TIG welding, the average grain size of the austenite decreases from 31.2 μm to 12.9 μm, while the ferrite grain size decreases from 224.5 μm to 110.6 μm. This grain refinement improves corrosion resistance, reducing the corrosion rate by 76.6 % compared to TIG welding.