Super duplex stainless steel fabricated by arc-based directed energy deposition

Super duplex stainless steels (SDSSs) are often used in corrosive environments owing to their combination of good strength (>450 MPa yield strength and > 600 MPa ultimate tensile strength) and corrosion resistance (PREN > 40). In additive manufacturing (AM), the challenge is achieving phase balance and minimizing microsegregation to reduce sigma phase formation. This work employs multi-phase-field simulations to understand the solidification of a SDSS under AM, and experimental tests to analyze the microstructure and properties of a SDSS (AWS ER2594) deposited wall. Phase field solidification simulations showed epitaxial growth of δ dendrites, followed by solute segregation of ferritizing and austenitizing elements into the δ dendrite cores and interdendritic liquid, promoting γ phase nucleation. The deposited wall showed an almost 50/50 ferrite/austenite phase balance and minimum of 0.3 % of sigma phase, by ANOVA and Tukey analysis no significant difference between phase fraction at different regions, and a variation in microhardness values between the base (273 HV1) and upper (262 HV1) regions of the wall. These results indicate good homogenization and well-chosen AM process parameters for producing a SDSS wall. Nevertheless, this work improves the understanding of solidification, thus microstructural evolution, of SDSS under AM, and provides input for future models of solid-state transformations.