Effect of solution treatment on the microstructure and properties of UNS S32750 super duplex stainless steels prepared by selective laser melting

The ferritic stainless steels with the ultra-high strength and certain ductility were successfully prepared by selective laser melting (SLM), using the UNS S32750 duplex stainless steel spherical powders with the particle size of 15~53 μm prepared by electrode induction-melting gas atomization. The microstructure, mechanical properties, and corrosion resistance of the duplex stainless steels before and after solution treatment were studied. The results indicate that, the microhardness, tensile strength, yield strength, elongation, and impact absorption energy of the printed samples are HV 449, 1475 MPa, 1265 MPa, 11.6%, and 25.99 J, respectively. After the solution treatment at 1150 ℃, the area fraction of α phase and γ phase are 55.2% and 44.8%, respectively, showing the ratio of approximately 1:1. The microhardness, tensile strength, yield strength, elongation, and impact absorption energy of the solution treated samples are HV 329, 913 MPa, 601 MPa, 34.0%, and 231.82 J, respectively, showing the decrease of strength and microhardness and the improvement of plasticity and toughness. The self-corrosion potential and pitting potential of the solution treated samples are higher than those of the printed samples, but the self-corrosion current density becomes lower.