Effect of nickel and heat input on microstructure and mechanical properties of duplex stainless steel via dual-wire directed energy deposition

• The dual-wire DED-arc method successfully fabricates DSS with a new Ni content. • Ni content (5.2–6.9 wt%) is controlled by adjusting feeding ratio of two wires. • Reducing Ni content and heat input lowers austenite ratio; Ni has greater effect. • A phase balanced DSS with near-optimal strength has been achieved. Achieving controlled ferrite–austenite balance remains challenging in duplex stainless steel (DSS) fabricated by directed energy deposition via arc (DED-arc). Commercial wires ER2209 (8.6 wt% nickel (Ni)) yields > 65 % austenite, while ER2205 (5.2 wt% Ni) yields < 44 %, indicating optimal Ni levels lie between 5.2–8.6 wt%. However, DSS wires within this range have not yet been commercialized, leading to high trial-and-error costs. This study introduces a dual-wire DED-arc (DW-DED-arc) method, blending ER2205 and ER2209 wires for precise Ni control. The effects of heat input and Ni content are systematically investigated. When Ni content is 6.9 wt%, reducing heat input from 657 J/mm to 355 J/mm decrease austenite content from 81.2 % to 62.8 %, increasing tensile strength but reducing elongation. At constant 600 J/mm, lowering Ni content from 6.9 wt% to 5.2 wt% reduces austenite content from 78.0 % to 53.7 %, similarly increasing strength and decreasing elongation. Crucially, at 600 J/mm, DSS with 5.2 wt% Ni (53.7 % austenite) and 6.1 wt% Ni (61.3 % austenite) achieved near-balanced phases while exhibiting optimal tensile properties. The DW-DED-arc method effectively controls DSS microstructure and provides an innovative approach for developing new material compositions from existing wires, offering valuable insights for DED-arc fabricated DSS.