Additive manufacture of superduplex stainless steel using WAAM

Abstract

Superduplex stainless steels have been used in the oil and gas industry for a couple of decades due to the combination of excellent mechanical properties and corrosion resistance. The present investigation addresses the applicability of wire and arc additive manufacturing for this steel grade. Due to the inherent rapid heating and cooling, the initial base metal microstructure will be substantially altered, and complex thermal cycles may cause the formation of brittle secondary phases, among which the frequently observed intermetallic sigma phase is most harmful. However, no intermetallic phases have been observed, which is consistent with the low heat input employed, and the high Ni content in the wire. The microstructure observations in terms of ferrite volume fraction, Cr nitrides precipitation and the formation of secondary austenite are discussed together with the hardness measurements, tensile testing and notch toughness testing. It is concluded that additive manufacturing of superduplex stainless steels by wire and arc process is feasible.