Assessment of Microstructural and Mechanical Properties of 420 Stainless Steel Fabricated by Laser Powder Bed Fusion

Abstract

In this work, fabricated samples of additively manufactured 420 stainless steel (420SS) via laser powder bed fusion (LPBF) process were analyzed. The microstructural features, grain morphology, crystallographic texture, phase composition, and tensile properties were evaluated for both as-printed and heat-treated conditions. The as-printed condition exhibits a yield strength of 1083 MPa and a tensile elongation of 21.2%. Microstructure analysis revealed that its comparable ductility is due to the presence of 15.2 % of retained austenite. After the successive heat treatment procedure, the yield strength improved significantly to 1388 MPa while decreasing the tensile elongation to 12.4 %. The yield strength obtained in the heat-treated condition was superior to previously reported literature values of precipitation hardening stainless steels fabricated by LPBF, and 420SS fabricated using different additive manufacturing processes. This improvement in yield strength is attributed to the coarsening of martensite laths and needles, elimination of retained austenite phase, and the carbide precipitation of 1.9 vol. % in the microstructure. The results in this work proved that the tensile properties and microstructure were greatly influenced by laser parameters and can be tailored accordingly using different heat treatment techniques.