Microstructure-property gradients in Ni-based superalloy (Inconel 738) additively manufactured via electron beam powder bed fusion

Abstract

Electron beam powder bed fusion (E-PBF) can produce nickel-based superalloy components with minimal cracking and post-processing. This is due to the reduced thermal gradients and high print temperatures accessible through innovative beam scanning strategies compared to other AM processes. However, variations in thermal signature along the build direction inherent in alloys printed using E-PBF can drive significant changes in the microstructure and associated mechanical properties. In this work, through complementary local property measurements we observed a 127 – 145% increase in mean elastic modulus and 7–9% increase in mean hardness, as a function of build height, of an as-fabricated non-weldable Ni-based superalloy, Inconel 738. These properties were attributed primarily to variations in the γ′ character with build height, revealed through a multi-scale microstructural characterisation. The results highlight the influence of the thermal signatures on the microstructural-property relationships of E-PBF Inconel 738.