Structure and Mechanical Properties of Austenitic Stainless Steel Prepared by Selective Laser Melting

The microstructure and mechanical properties of chromium–nickel austenitic stainless steel fabricated by selective laser melting using a Realizer SLM100 3D printer have been investigated in this work. The structure of the studied specimens has been formed by the complete melting of the initial powder and high-speed cooling of the melt. Cooling of the melt initially leads to the formation of δ ferrite, and then, polymorphic δ → γ transformation results in the formation of the final austenitic structure. The structure of δ ferrite which formed during melt crystallization has been found to exhibit a clear pattern of periodicity. The periodicity depends on the parameters of the melting process, such as the distance between neighboring bands formed during laser-beam traveling (intertrack distance) and the step of platform feeding (distance between layers). The polymorphic δ → γ transformation takes place by a disordered mechanism and no austenite texture forms. However, some structural heredity remains. It can be seen in the orientational relationship between some austenite grains and δ-ferrite grains. The steel fabricated by laser melting is shown to have high mechanical properties such as the yield strength, the ultimate tensile strength, and the tensile elongation at a strain rate of 10^–2 s^–1, which are 320, 765 MPa, and 50%, respectively. The yield strength and ultimate tensile strength of the specimens under dynamic compression by the Hopkinson–Kolskii technique at an average strain rate of 10³ s^–1 are 550 and 945 MPa, respectively.