Improvement of tensile properties through Nb addition and heat treatment in additively manufactured 316L stainless steel using directed energy deposition

Abstract

Metal additive manufacturing (AM) has been applied in various fields because it allows the manufacture of parts with complex shapes. In this study, 316 L stainless steel specimens with 0 and 2 wt% Nb were fabricated using direct energy deposition, and heat treatment was performed at various temperatures. The addition of Nb changed the microstructure of the steel, including the grain size and Nb segregation. When heat treatment was performed, microstructural evolution of the cell boundary, dislocation density, and deformation twin density occurred. These microstructural changes improved the tensile properties of the heat-treated specimens containing Nb. The yield strength, tensile strength, and elongation of the specimens containing Nb with heat treatment at 800 °C were 530 MPa, 757 MPa, and 39%, respectively, which represent great improvements compared to specimens without Nb. These results show that the addition of Nb to 316 L stainless steel together with heat treatment at an appropriate temperature endow the additively manufactured stainless steel with excellent tensile properties.