Effect of multipass TIG welding on the corrosion resistance and microstructure of a super duplex stainless steel

• Published in: Materials and corrosion 2017-04, Vol.68 (4), p.405-415
• Main Authors: Hosseini, V. A., Hurtig, K., Karlsson, L.
• Format: Article
• Language: English
• Subjects: Alloys; Base metal; Boundaries; Corrosion; Corrosion resistance; Duplex stainless steels; Manufacturing and materials engineering; Melting; Microstructure; pitting corrosion; Produktions- och materialteknik; resistance; Stainless steel; super duplex stainless steel; thermal cycling; TIG welding; Weld metal; Welded joints; Welding
• ISSN: 0947-5117; 1521-4176; 1521-4176
• DOI: 10.1002/maco.201609102

This is a study of the effect of repetitive TIG (tungsten inert gas) welding passes, melting and remelting the same material volume on microstructure and corrosion resistance of 2507 (EN 1.4410) super duplex stainless steel. One to four weld passes were autogenously (no filler added) applied on a plate using two different arc energies and with pure argon shielding gas. Sensitization testing showed that multipass remelting resulted in significant loss of corrosion resistance of the weld metal, in base material next to the fusion boundary, and in a zone 1 to 4 mm from the fusion boundary. Metallography revealed the main reasons for sensitization to be a ferrite‐rich weld metal and precipitation of nitrides in the weld metal, and adjacent heat affected zone together with sigma phase formation at some distance from the fusion boundary. Corrosion properties cannot be significantly restored by a post weld heat treatment. Using filler metals with higher nickel contents and nitrogen containing shielding gases, are therefore, recommended. Welding with a higher heat input and fewer passes, in some cases, can also decrease the risk of formation of secondary phases and possible corrosion attack. A super duplex stainless steel was subjected to multiple tungsten inert gas welding passes with two different heat inputs. Sensitization testing showed significant loss of corrosion resistance of the weld metal, in base material next to the fusion boundary, and in a zone 1 to 4 mm from the fusion boundary due to nitrogen loss and precipitation of secondary phases.