Additive manufacturing of duplex stainless steels - A critical review

Duplex stainless steels (DSSs) are promising materials in many fields due to their excellent corrosion resistance and mechanical properties, which are resulted from their microstructure consisted of a roughly equal amount of austenite and ferrite phases. As a revolutionary production technology, additive manufacturing (AM) has exhibited tremendous advantages for the fabrication of metal parts of complicated or customized geometry. Wire arc additive manufacturing (WAAM), laser metal deposition (LMD) and laser powder bed fusion (L-PBF) have been utilized to fabricate DSSs. However, it is of a great challenge to achieve expected formation quality and microstructure at the same time, considering the complicated layer-upon-layer process. A delicate control of processing conditions is highly required based on the understanding of DSS materials and AM processes. In this work, an overview of the up-to-date research status and future perspectives on the AM of DSSs is presented from extensive viewpoints including materials, processing, microstructure and properties. The microstructure evolution during the AM processes is highlighted in detail, which explains the change of mechanical properties and corrosion resistance, and provides the direction of processing optimization.