EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Additive manufacturing (AM) has long since evolved from its initial mode of use in rapid prototyping to commercial manufacturing. AM Ni-based superalloys have found use in the design of critical components in the aerospace industry due to its ability to retain its mechanical properties at elevated temperatures near its melting point. Furthermore, with advances in electron beam melting (EBM) powder-based AM, previously ‘hard to print’ high strength superalloys with high Al and Ti contents have been produced with no or minimal crack propagation. Currently, defect-free AM builds are achieved through highly inefficient empirical cycling of printing and/or design parameters for optimisation. This is due to the lack of a thermodynamical model for metal AM processes, which differ significantly from steady-state conditions assumed in traditional processes.

Here, we present our findings on the property and microstructural variations of AM ‘hard to weld’ Ni-based superalloy, Inconel 738, to rationalise the effects of new interface instabilities that arise with AM. We couple complementary electron microscopy, atom probe tomography and local mechanical measurement techniques to better understand structure-property relationships. The data is also used to help understand how thermal gradients influence the final microstructure and ultimately the mechanical properties in resulting EBM Inconel 738 builds.