Influence of Welding Processes on the Microstructure and Mechanical Properties of Duplex Stainless Steel Parts Fabricated by Wire Arc Additive Manufacturing

Direct energy deposition (DED) is an advanced additive manufacturing (AM) technique for producing large metal components in structural engineering. Its cost-effectiveness and high deposition rates make it suitable for creating substantial and complex parts. However, the mechanical and microstructural properties of these components can be influenced by the varying heat input and repeated thermal treatments associated with different welding procedures used during the deposition process. This study employed gas metal arc welding (GMAW) and cold metal transfer (CMT) arc welding techniques to fabricate cylindrical components from 2209 duplex stainless steel (DSS). The research investigated the impact of these welding methods on the microstructure and mechanical properties of the 2209 DSS cylinders. The intricate thermal cycles and cooling rates inherent in the DED process significantly influenced the primary phase balance, ideally comprising 50% austenite and 50% ferrite. In components processed using GMW, sigma-phase formation was noted at the grain boundaries. Additionally, a slower cooling rate and extended time for solid-state phase transformations led to an increase in austenite content from the bottom to the top of the component. The cylinder fabricated using the CMT process exhibited fine austenite morphologies and a higher ferrite content compared to the GMW-processed cylinder. Furthermore, the cylinder produced using the CMT process showed consistent properties across the building direction, unlike the components manufactured with the GMW process. In terms of tensile properties, hardness, and impact toughness, the cylinder produced using the CMT technique outperformed the one made with the GMW process.