Mechanical and Corrosion Properties of 254SMO-2507 Dissimilar Stainless Steel Joints Welded by Double-Sided TIP TIG Arc Welding

The microstructure, mechanical properties, and corrosion resistance of 254SMO-2507 dissimilar joints welded using double-sided TIP TIG arc welding (DSTTAW) with ERNiCrMo-3 filler wire were systematically analyzed. Results demonstrate that DSTTAW process can produce 254SMO-2507 joint with excellent appearance and performance. The weld metal solidifies in a single-phase austenitic solidification, with solidification grain boundary and solidification sub-grain boundary observed in fusion zone. The transition zone from 2507 SDSS contains δ-Fe, grain boundary austenite, Widmänstten-type austenite (WA), and intragranular austenite. Mechanical test reveals that the 254SMO-2507 dissimilar joints exhibit higher average tensile strength and hardness compared to 254SMO base metal, though lower than 2507 base metal due to its ferrite content. The joints fracture at the weld zone in the ductile mode with decreased elongation due to the existing WA, but remains suitable for engineering application. In terms of corrosion resistance, the 254SMO-2507 joint shows a slight reduction compared to the base metals but achieves pitting corrosion resistance comparable to the 254SMO SASS base metal. After polarization curves test, pitting corrosion mainly occurred in the 2507 base metal area. Both the joint and base metals exhibit as n-p-type semiconductor behavior, but the passive film on 254SMO-2507 joint surface is less stable than that of the base metals.