Mechanical and Corrosion Properties of Super Austenitic Stainless Steel Joint for Double-Sided Synchronous TIP TIG Arc Butt Welding

Super austenitic stainless steel 254SMO (254SMO SASS) plates are joined by double-sided double-arc synchronous TIP TIG butt welding (DSSTTABW) using ER NiCrMo3 wire, and the micro-structure, mechanical and corrosion properties of 254SMO SASS joints are investigated subsequently. Results show that solidification grain boundary and solidification sub-grain boundary can be observed in fusion zone. A small amount of sigma phase precipitates in the weld, while chi phase is found in the transition zone, but no solidification crack occurs in weld and heat affected zone (HAZ). 254SMO SASS joint has higher micro-hardness and lower tensile strength and elongation compared to base metal. During transverse tensile process, 254SMO SASS joints fail in the weld zone in a ductile mode. Electrochemical corrosion performance tests indicate that 254SMO SASS joint achieve equivalent pitting corrosion resistance and similar passive mechanism to base metal in 3.5 wt% NaCl solution. The passivation film on the surface of both joint and base metal display as n-p semi-conductive character, but the film stability of 254SMO joint surface is slightly poorer compared to base material. The surface passivation film of 254SMO joint primarily consists of oxides of Fe, Cr, and Mo before potentiodynamic polarization, while hydroxides of Fe and Cr are also observed after polarization. Double-sided synchronous TIP TIG arc welding was introduced to butt joint 4 mm thick 254SMO super austenitic stainless steel without groove. Sound joint with excellent appearance, mechanical and corrosion properties was achieved. The passive film of 254SMO joint and base metal both display as n-p semi-conductive character, which consists of metal oxides and hydroxides of Cr and Mo.image (c) 2024 WILEY-VCH GmbH