Known for its corrosion resistance, 2507 duplex stainless steel is widely applied in sectors like marine, chemical, and petrochemical industries. To adapt this material for more complex structures, additive manufacturing is being investigated as a fabrication method. However, to get the best of the properties of this material, the microstructure needs to be composed of an approximately equal amount of ferrite and austenite. But additive manufacturing processes generate sharp thermal gradients, which significantly impact the microstructure and so the mechanical properties of duplex stainless steel. That is why the aim of this work was to test several heat treatments, characterize their results and identify the most suitable one.

To do so, several samples were heat treated in a furnace at 1100°C, for 30 min to 1h30, some were quenched in water after 10 seconds in ambient air and some were directly quenched. Microstructure, phase fraction and detrimental phases were observed using an optical microscope. Hardness was also measured using Vickers method on a hardness tester. Heat treatments were found to be essential as additive manufacturing of this material was leading to a non-uniform microstructure composed of highly ferritic regions and re-heated regions that showed more balanced phase fraction. As-built material was exhibiting chromium nitrides that needed to be dissolved.

Heat treating at 1100°C for at least 1h obtained satisfying austenite and ferrite balance. Cooling in ambient air for 10 seconds before quenching was found essential to not precipitate chromium nitrides. Hardness of the heat-treated samples were found to be low compared to wrought material and further studies are needed to obtain better hardness values.