Control of the Microstructure and Mechanical Properties of a Super Duplex SAF 2507 Steel Produced by Additive Manufacturing

Two-phase duplex stainless steels are widely used in transport industry due to their good fatigue and corrosion properties. Although these steels are investigated when they are produced and/or shaped by conventional processes, few research works have characterized duplex steels obtained by additive processes. This paper concerns the elaboration and characterization of super duplex steel SAF 2507 obtained by laser powder bed fusion (LPBF). Firstly, the printability of this steel is discussed by analyzing the impact of certain process parameters on the density and microstructure of the material. This as-built microstructure being ferritic and not very ductile, various heat treatments (HT) are, then, applied in order to obtain the typical two-phase microstructure and thus improve the ductility. Afterward, the impact of the different phases (austenite and ferrite) on its mechanical behavior is analyzed. This work has shown the possibility of obtaining an austenitic-ferritic microstructure close to 50–50 with different grain morphologies with an appropriate post-fabrication TTH. The resulting mechanical properties are satisfactory compared to those of duplex steel obtained by conventional processes.