Effect of Nitrogen-Added Shielding Gas on Microstructure Evolution of Welded Joints by Gas Tungsten Arc Welding Process in Duplex Stainless Steel 2205

Duplex stainless steels (DSS), due to their high corrosion resistance, primarily attributed to their austenite-ferrite duplex microstructure, are widely used in industrial sector such as petrolchimical and gas natural industries. Maintaining this microstructure is crucial during manufacturing processes, including welding which presents the challenge of minimizing ferritization in the heat-affected zone (HAZ) or weld zone (WZ), as it can significantly reduce their corrosion resistance. This work aims to describe the influence of nitrogen gas in the Ar-N2 shielding atmosphere when depositing beads on 2205 DSS plates, using a gas tungsten arc welding (GTAW) process. It is observed that at low nitrogen load (98%Ar-2%N2), the austenite content reaches 49% in WZ and 29% in HAZ. When the nitrogen percentage is increased (50%Ar-50%N2), the austenite content rises to 67% and 37%, respectively. The joint is evaluated macro- and microstructurally to observe the atmosphere impact on weld bead geometry and microstructural development. Additionally, hardness is assessed throughout the weld bead. The work demonstrates that, with a 50%Ar-50%N2 shielding gas mixture, it is possible to limit the formation of ferrite in the WZ and HAZ of DSS during the welding process, without altering the microhardness trend of the welded joint. A challenge in welding duplex stainless steels is to limit ferritization in the heat-affected zone to ensure high corrosion resistance. The work describes the influence of nitrogen gas in the Ar-N2 shielding atmosphere during a gas tungsten arc welding process. The 50%Ar-50%N2 gas mixture allows the austenite to be increased without altering the microhardness trend of the weld.image (c) 2024 WILEY-VCH GmbH