Mechanical properties and corrosion behaviour of duplex stainless steel weldment using novel electrodes

Abstract

Abstract Mechanical and corrosion properties of welded duplex stainless steel (DSS) structures are of paramount consideration in many engineering applications. The current research investigates the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, using optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715–732 MPa and that of the E2 electrode was found to be 606–687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with E1 electrode coated with basic flux has better mechanical properties. The steel structure in 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed on the basis of the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes.