Austenite phase evolution in duplex stainless steels printed using laser directed energy deposition

Direct energy deposition–laser beam (DED-LB) was performed using duplex stainless steel (DSS) 2507 powders. Single and multilayer samples were printed to determine how reheating from additional layers affects austenite formation. Unlike laser powder bed fusion (PBF-LB) of DSS producing negligible austenite, DED-LB-printed DSS exhibited ~ 20% austenite in the single layer that increased to ~ 25% after printing subsequent layers. Transient-thermal numerical simulations and thermodynamic calculations were performed to predict phase formation. The calculations suggest that the increased austenite is due to solid-state (ferrite to austenite) phase formation after solidification and subsequent reheating followed by relatively slower cooling rates.