Relationship Between Morphology of Hierarchical Structure and Mechanical Properties of Ni-Based Superalloy Printed via Metal Additive Manufacturing

Ni-based superalloys with excellent high temperature strength and oxidation resistance are used for turbine blades in aircraft engines. A recent study reported the formation of a unique hierarchical structure in Ni-based superalloys fabricated by laser beam-powder bed fusion (LB-PBF). This unique structure is composed of a meso-scale crystallographic lamellar microstructure (CLM) and a nanoscale cellular structure. While such a unique microstructure leads to excellent mechanical properties, the influence of process parameters on the morphology of the hierarchical structure has not yet been clarified in detail, nor has the relationship between the morphology of the hierarchical structure and mechanical properties been established.<br/>This study examined the influence of input energy density on the morphology of the hierarchical structure in Inconel 718 alloys fabricated by LB-PBF, focusing on the cell spacing. The effect of cell spacing on the room temperature strength was also examined by tensile tests and <i>in-situ</i> neutron diffraction analyses. We found for the first time that the cell spacing increases with increasing input energy density. Furthermore, it was revealed that the tensile strength strongly depends on the cell spacing.