Microstructure Formation and Its Effect on Mechanical Properties for Duplex Stainless Steel 2205 Plasma Arc Welded Joint

The control of phase balance has always been a tough challenge for the welding of duplex stainless steel, which heavily restricts its optimal serving performance in engineering. The microstructure development and mechanical characteristics of SAF2205 plasma arc welded joints were thoroughly examined in this paper. It was proven that the phase balance can be well controlled by plasma arc welding, and the austenite content of the welded joints was about 60%. Despite successful phase control, there was still grain coarsening and distortion; i.e., at the center of the welded zone, the gain size was about eight times that of the base metal, and the austenite was mainly in the form of grain boundary austenite and intragranular austenite, while more Widmanstatten austenites were found in the heat-affected zone. In addition, a transition region between the heat affected zone and the center exhibited columnar ferritic grains. Furthermore, the plasticity and toughness of the welded joints were significantly decreased, especially the elongation in the longitudinal direction, which is about 10% lower than that of the base metal, and transversal tensile strength remained comparable to the base metal, with only a slight reduction in longitudinal tensile strength. Lastly, the formation mechanism of microstructure and its correlation with mechanical properties were revealed. This investigation offers valuable insights into the structural integrity of duplex stainless steel welded joints in engineering applications.