Additive manufacture of superduplex stainless steel using WAAM

Superduplex stainless steels have been utilized in the oil and gas sector for several decades owing to their exceptional mechanical properties and corrosion resistance. This study investigates the feasibility of wire and arc additive manufacturing (WAAM) for this particular steel grade. The inherent rapid thermal cycles of the WAAM process significantly alter the initial microstructure of the base metal and can result in the formation of brittle secondary phases, with the intermetallic sigma phase being notably detrimental. However, observations indicate that no intermetallic phases developed, likely due to the low heat input used and the high nickel content of the wire employed. The evaluation of microstructural characteristics such as ferrite volume fraction, chromium nitrides precipitation, and secondary austenite formation was undertaken alongside assessments of hardness, tensile strength, and notch toughness. The findings confirm that the application of additive manufacturing techniques like WAAM for superduplex stainless steels is not only possible but also practical.