Investigation on microstructure evolution and properties of duplex stainless steel joint multi-pass welded by using different methods
By Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei
Published in Materials & Design
2016
Abstract
Abstract 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. N2-supplemented shielding gas during the {GTAW} process significantly facilitated austenite formation and reduced amounts of chromium nitride (Cr2N) precipitation tendency, thereby resulting in an improvement in impact toughness. The heat-affected zone (HAZ) had relatively low toughness because of an insufficient austenite content and Cr2N and ?-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 N2-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.