EFFECT OF WELDING ON MICROSTRUCTURE AND CORROSION PROPERTIES OF SAF 2507 SUPER-DUPLEX STAINLESS-STEEL JOINTS

In this paper, SAF 2507 super-duplex stainless steel (SDSS) was welded using laser-beam welding (LBW). laser gas-metal hybrid arc welding (LGH) and gas-tungsten arc welding (GTAW). Heat-input calculation results showed that LBW had the lowest heat input, while GTAW had the highest heat input. The correlation of the heat input during the welding with the microstructure, nanoindentation properties and corrosion behaviors of the three types of welded joints of SAF 2507 SDSS was studied. The hardness of the welded joints decreased as the heat input increased. Microstructural analyses showed that these welded joints were composed of the ferrite phase and austenite phase. and that the fraction of the austenite phase increased with the heat input. Electrochemical studies indicated that the heat input had a minor influence on the corrosion behavior of these joints. A slight increase in the passive-current density and acceptor/donor density in the passive film suggested that the heat input slightly increased the corrosion susceptibility by changing the structure and property of the passive film formed on the surface of the welded joints.