Effect of multipass welding on the microstructure of superduplex stainless steel

This work studies the influence of thermal cycles on the microstructure of a 2507 superduplex stainless steel (2507 SDSS) after being multipass-welded using the GMAW process with ER 2209 filler metal and two shielding gasses (Ar and Ar-6%N). To calculate the thermal cycles experienced during welding, the heat flow equation for a thin plate was used. All samples were analyzed by optical microscopy and scanning electron microscopy to identify phases. The results showed particles of sigma phase in both the heat affected zone (HAZ) and welding metal (WM) in the ferrite/austenite grain boundary and intragranular, resulting in the loss of the microstructural balance of the superduplex stainless steel.