Wire arc additively manufactured super duplex stainless steel: microstructural and property evolution under thermal aging and solution treatment

A super duplex stainless steel (SDSS) structure was fabricated using wire arc additive manufacturing (WAAM) with cold metal transfer (CMT) welding. In the as-deposited (AD) condition, the structure exhibited grain-boundary chromium carbides, and subsequent thermal aging at 850°C for 24 h promoted the precipitation of Cr- and Mo-rich intermetallic sigma (σ) phase along the α/γ interfacial regions. This σ-phase increased yield and tensile strength but caused severe loss of ductility, reducing elongation from 38% (as-deposited) to 4% (aged). Pitting corrosion resistance also deteriorated significantly, as indicated by a drop in pitting potential from 1006 mV to 625 mV (∼38% loss). A subsequent solution treatment at 1050°C for 1 h dissolved the precipitates, restoring the austenite-ferrite balance and enhancing both mechanical and corrosion properties. This study highlights the influence of post-fabrication thermal aging and subsequent solution treatment in mitigating detrimental effects, ensuring the structural integrity and performance of WAAM-fabricated SDSS components.