Enhancing austenite formation in directed energy deposition-arc fabrication of duplex stainless steel using nitrogen-bearing shielding gas

Directed energy deposition-arc (DED-arc) of duplex stainless steels faces challenges in achieving a balanced ferrite/austenite ratio in the as-deposited condition. Consequently, solution annealing is often necessary to optimize the microstructure and attain good mechanical and corrosion properties. This study explores an approach to improve the phase balance using AM 2205 wire and Ar + 2% N2 as shielding gas. Thin-walled structures comprising 10 layers were fabricated using a waveform-controlled gas metal arc welding (GMAW) process at two different travel speeds and arc power levels. Additionally, reference samples were produced with Ar + 2.5% CO2 to quantify the influence of shielding gas composition on austenite formation. Microstructural investigations revealed that samples produced with nitrogen-containing shielding gas had an average austenite fraction ranging from 39 to 46 vol.%, depending on the travel speed and arc power combination. This represents an average increase of 3-9 vol.% compared to traditional shielding gas.