Effect of substrate preheating on the microstructure, mechanical properties, and corrosion resistance of DED-deposited super duplex stainless steel

The effect of substrate preheating on changes in the microstructure, phase composition, mechanical properties and corrosion resistance of super duplex stainless steel (UNS S32750) deposited via a directed energy deposition method is investigated in this study. Microstructures including austenite content and precipitation of undesirable phases and their impact on mechanical and corrosion properties were evaluated in samples deposited on the substrate preheated to 300 °C and 500 °C and compared to the samples as-built and solution annealed states. The deposition of DSS on the substrate preheated to the temperature of 500 °C led to an increased austenite content, resulting in homogeneous microstructure with excellent tensile properties and corrosion resistance in aggressive chloride environments. In contrast, deposition on a substrate preheated to 300 °C resulted in slightly higher austenite content compared to samples deposited on a non-preheated substrate, accompanied by increased tensile strength and hardness, reduced elongation, and decreased corrosion resistance in the DL-EPR test.