Investigation on microstructure evolution and properties of duplex stainless steel joint multi-pass welded by using different methods

We investigated the microstructure, impact toughness, and pitting corrosion resistance of duplex stainless steel (DSS) welding joints fabricated by using gas tungsten arc welding (GTAW) and flux-cored arc welding (FCAW) with different shielding gas compositions. N-2-supplemented shielding gas during the GTAW process significantly facilitated austenite formation and reduced amounts of chromiumnitride (Cr2N) precipitation tendency, thereby resulting in an improvement in impact toughness. The heat-affected zone (HAZ) had relatively lowtoughness because of an insufficient austenite content and Cr2N and sigma-phase precipitation. Dimple fracture was the main fracture mode of the weld metal. Large irregular inclusions resulting in discontinuous dimple fractures mainly contributed to the lowest level of toughness in the FCAW weld metal. The HAZ fracture mode was dominated by the ferrite quasi-cleavage fracture. The base metal exhibited a mixed fracture mode of alternating dimple and quasi-cleavage. Furthermore, the pitting resistance of the whole joint was predominated by the HAZ. The N-2-supplemented shielding gas significantly improved the pitting resistance of the GTAW joint. The pits were prone to form in the secondary austenite and around Cr2N. Moreover, an abundance of inclusions in the FCAW weld metal resulted in adverse effects on the pitting resistance. (C) 2016 Elsevier Ltd. All rights reserved.