Effect of laser energy per unit powder feed on Hastelloy-X walls built by laser directed energy deposition based additive manufacturing

Abstract Laser Directed Energy Deposition (LDED), an additive manufacture process, has many inherent advantages and is attractive particularly for fabrication of thin walled components. The present work focuses on LDED of Hastelloy-X (Hast-X) walled structures built at three different values of Laser Energy per unit Powder Feed (LEPF), i.e., 8.2 kJ/g, 10.7 kJ/g and 13.2 kJ/g. The effect of LEPF on the built walls is examined for the geometry, microstructure and mechanical properties. The variations in built wall geometry are analyzed using statistical tools along the length, cross-section and build direction. The maximum deviation along wall height and width are found at LEPF of 13.2 kJ/g and 8.2 kJ/g, respectively. The examination along the build direction shows the maximum deviation in profile at lower layers with 8.2 kJ/g and at top layers with 13.2 kJ/g. The defect free deposits having dendritic growth at all conditions is observed. The dendrites size increases with increase in LEPF. A marginal reduction in mechanical properties, i.e., average microhardness (~8%), yield strength (~3.7%) and ultimate strength (~4%) are observed with increase in LEPF. Further, temperature distribution from finite element analysis based numerical simulation is used to understand the effect of LEPF on the wall structures. An increase in preheat temperature on previous layers with increase in number of layers and LEPF is observed. The study provides an understanding on the effect of process parameters on LDED built Hast-X wall structures.