Effect of heat sources on microstructure and properties of duplex stainless steels fabricated by additive manufacturing

The balanced two-phase microstructure of austenite and ferrite endows duplex stainless steels (DSSs) excellent mechanical properties and high corrosion resistance. Additive manufacturing (AM) has been applied to the fabrication of DSS structures with the increased use of DSSs in corrosive environment. Direct energy deposition (DED) technologies, including laser metal deposition (LMD) and wire arc additive manufacturing (WAAM), have been regarded as the promising AM processes considering the industrial requirement of cost and size. The formation quality, microstructure evolution, mechanical properties and corrosion resistance largely depends on the heat sources used in AM processes. Super DSS 2594 powder and wire were used as feedstocks respectively for LMD and WAAM. A single-wall body of multiple layers was built with few defects. The chemical composition and microstructure were characterized. The effect of heat sources on mechanical and electrochemical properties was compared. The LMD samples exhibited relatively lower mechanical properties and weaker corrosion resistance than WAAM samples, which was resulted by more element loss due to the higher energy intensity during the LMD process. The results indicated that a proper content and uniform distribution of alloying element is critical to AM DSS parts.