Microstructure and mechanical properties of Inconel 718 thin walls prepared by laser direct energy deposition and selective laser melting

Abstract

This paper systematically investigates the microstructure, crystal structure and related mechanical properties of Inconel 718 thin walls prepared by two different methods, laser direct energy deposition (LDED) and selective laser melting (SLM), which are representative technologies for laser additive manufacturing of high-performance metal parts, and compares with conventional forged parts. The microstructure of SLM-part consists of columnar and equiaxed crystals with disordered growth directions, while LDED-part is mainly composed of coarse columnar crystals that grow perpendicular to the plane of the molten pool free surface. Unlike a strong 〈001〉 texture in the LDED-part, the SLM-part has a {110} texture in the XY plane, achieving stronger tensile strength due to different grain boundary strengthening and dislocation strengthening effects, which is found by comparing with LDED and forged Inconel 718 alloy. In addition, the difference in crystallographic texture between SLM and LDED-parts results in the different mechanical property anisotropy. The comparative study of two laser additive manufacturing technologies provides guidance for an in-depth understanding about the mechanism of laser additive manufacturing high-performance metal parts.