Effect of Shielding Gas and Post-Welding Heat Treatment on the Mechanical and Corrosion Performances of Duplex and Super Duplex Stainless Steels’ Low Heat-Input Welded Joints

The purpose of this paper is to study the weldability of two specific steels, UNS S31803 (duplex) and UNS S 32760 (super duplex), by making heterogeneous butt joints using gas tungsten arc welding technology. These materials are widely used in applications that take advantage of their superior corrosion resistance, strength, or both, such as chemical plants, oil and gas equipment, offshore sector, marine and other high-chloride environments. Although the joining technique of DSS and SDSS steels is a well-established industrial method, there are several process parameters that can play a key role in the correct execution of welds and in their final achievable properties. Starting from this assumption, this paper investigates some specific aspects such as the influence of heat input and shielding gas composition on the joint's microstructure and the consequent changes in the ferrite/austenite ratio, also after post-welding heat treatments. Effects on both mechanical and corrosion resistance properties of the alloys are addressed.