Process parameter optimization for selective laser melting of Inconel 718 superalloy and the effects of subsequent heat treatment on the microstructural evolution and mechanical properties

Abstract

• Laser power, scanning speed and overlap rate were coupled into energy density. • Heat treatments led to the correspondingly microstructural evolution. • The microhardness, tensile strength and wear resistance of SLMed samples were investigated. The Inconel 718 superalloy (IN718) was fabricated by selective laser melting (SLM) successfully in this work. The optimization of process parameters and effects of three heat treatment processes on the microstructures and mechanical properties of samples were also systematically investigated. The relationship equation between relative density (RD) of SLMed samples and energy density (ED) coupled by laser parameters was determined. After the solution aging (SA) heat treatment, a large amount of needle-like δ phases precipitated and the precipitation of ultrafine spherical γ'/γ” strengthening phases as well as complete recrystallization appeared after homogenization + solution aging (HSA) heat treatment. The overall performances of SLMed IN718 samples were improved significantly using the HSA treatment, with the increase of tensile strength from 946 MPa to 1570 MPa.