Corrosion, Impact Toughness and Tensile Properties of Duplex Stainless Steels Manufactured by Directed Energy Deposition

Duplex stainless steels provide a desirable combination of corrosion resistance, strength and toughness. Additive manufacturing of duplex stainless steels can be challenging due to high cooling rates and repeated reheating, which can produce detrimental microstructural constituents. In this study, a coaxial directed energy deposition system with laser and wire was used to deposit 2205, 2209 and 2509 duplex stainless steels. Corrosion resistance, strength and impact toughness in both as-built and solution annealed condition was tested and the microstructure was characterized. Solution annealing improved impact toughness considerably, produced a slight increase in corrosion resistance and a slight decrease in tensile strength. The 2205 material surpassed all common requirements and exhibited better corrosion resistance than 2209 due to less segregation between austenite and ferrite. Segregation of alloying elements was lower in intragranular austenite than grain boundary allotriomorph and Widmanstatten austenite. The 2209 and 2509 materials provided relatively low strength, especially in the solution annealed condition. For the 2509 material, sigma phase caused low as-built corrosion resistance and impact toughness. Overmatching welding consumables were found to be less suitable as feedstock for additive manufacturing due to high austenite content in the deposited material and lower corrosion resistance than conventional duplex compositions.