Microstructure and Corrosion Properties of Austenitic and Duplex Stainless Steel Dissimilar Joints

Abstract

In several applications duplex stainless steels should be joint welded to conventional austenitic stainless steels. In this research LDX 2101 lean duplex stainless steel sheets were welded to conventional 304 austenitic stainless steels, using gas tungsten arc welding. For the welded joints three different welding rods were used: ER 308L, ER 309LSi, and ER 2209. For gas shielding two different shielding gases were used: argon and argon +2% nitrogen. It was found that the nitrogen addition to the shielding gas promoted austenite formation in the weld metal. It was also found Schaeffler-diagram modified by Outokumpu showed a very good estimation to the ferrite content and chemical composition of the weld metal. The ferrite content estimated by the Outokumpu-diagram, showed a close correlation to measured ferrite contents, the highest error was 30%. In case of the chemical composition of the weld metal, the Cr- and Ni-contents were estimated with a maximum of 15% error. In terms of the corrosion resistance, the best pitting corrosion resistance was achieved using the 308L welding rod with argon shielding gas, where the weight loss was 1.6% after the 24 hours immersion test.