Corrosion behavior of sintered duplex stainless steel manufactured from gas-atomized powders discarded from laser powder bed fusion

Powder metallurgy duplex stainless steel (PM DSS) was fabricated using gas-atomized powders discarded from laser powder bed fusion (LPBF), and the mechanisms governing its corrosion behavior were clarified. We demonstrate that although sintering refines pore morphology—reducing the population of large pores and increasing circularity—the resulting improvement in corrosion resistance is governed primarily by microstructural evolution rather than porosity changes. Prolonged sintering significantly refines grains, increases the fraction of low-angle boundaries, and elevates the geometrically necessary dislocation density, which collectively accelerate chromium transport and promote the formation of a Cr 2 O 3 -enriched passive film. The Cr 2 O 3 content rises from 23.64% to 40.91%, and the Cr/Fe ratio increases from 0.24 to 0.32, leading to a substantial enhancement in passive-film resistance and pitting resistance (E pit from 0.323 to 0.890 V SCE ). Meanwhile, improved pore morphology reduces capacitive effects and charge-transfer pathways inside pores, but its contribution remains secondary. These findings provide new mechanistic insight into how porosity and microstructure competitively influence corrosion in PM DSS, and demonstrate that LPBF-discarded powders can be effectively reused to produce stainless steels with excellent corrosion performance.