Influence of the L-PBF Process Atmosphere on the Microstructure and Tensile Properties of AISI 318LN Duplex Stainless Steel

Duplex stainless steels (DSSs) have excellent mechanical properties, owing to their austenitic-ferritic microstructure. The phase equilibrium strongly depends on solidification conditions and chemical composition, where elemental nitrogen significantly stabilizes the austenitic phase. When DSSs are processed by laser powder bed fusion (L-PBF) under an argon atmosphere, rapid cooling rates result in undesirable fully ferritic To better understand microstructure formation, this study examined influence of L-PBF process atmosphere porosity, microstructure, properties DSS AISI 318LN. Gaseous were used as a protective specimens analyzed as-built post-processed via optical electron microscopy, backscatter diffraction, tensile testing. Specimens showed lower initial density conditions, tended form more lack-of-fusion gas pores compared argon. different defect types nitrogen-processed still present after solution-annealing quenching, leading 13% strength 43% elongation at fracture. Differences caused could not be established. All differences porosity can minimized hot isostatic pressing, thus resulting comparable argon- specimens.