Effect of selected laser-powder bed fusion parameters on the as-built properties of Inconel 718

Stellenbosch University, Department of Mechanical and Mechatronic Engineering, Stellenbosch, South Africa

^* Corresponding author: melzvanrooyen@sun.ac.za

Abstract

Laser-powder bed fusion (L-PBF) is a form of additive manufacturing that makes use of a laser beam to melt a desired planar geometry into a powder bed, layer by layer, to form a three-dimensional part. This technology has rapidly become an attractive manufacturing method of complex parts made from nickel superalloys, such as Inconel® 718 (IN718), for aerospace applications due to the associated economic and environmental benefits. The as-built material properties are, however, dependent on the L-PBF process parameters. With sustainability in mind, ideal combinations of process parameters should produce dense, mechanically sound, and isotropic parts while minimising the amount of required energy input. This study highlights the effect of laser power and scanning speed on the as-built density, grain size and hardness of L-PBF fabricated IN718 specimens. Density and grain size values did not vary significantly beyond experimental scatter over the range of volumetric energy densities (VED) considered in this work (62 – 72 J/mm³). Near 100 % relative densities, refined grain sizes and reduced hardness anisotropy was observed at VED values that are lower than the VED value based on the standard process parameter set. This implies potential energy savings (lower laser powers) and faster build times (faster scanning speeds) for the aerospace industry.