Process development and process adaption guidelines for the deposition of thin-walled structures with IN718 using extreme high-speed directed energy deposition (EHLA3D)

Abstract

Extreme high-speed directed energy deposition (EHLA) is a modified variant of the laser based directed energy deposition (DED-LB) and is being applied as an efficient coating process for rotational symmetric components. Characteristics of EHLA processes are feed rates of up to 200 m/min, which result in smaller weld bead deposition and thinner layer thicknesses compared to conventional DED-LB. When transferred to additive manufacturing, this characteristic utilizes the potential of depositing thin-walled filigree structures at deposition rates, which are comparable to typical DED-LB processes (EHLA3D). The results of this work were achieved with an EHLA3D machine, which is a modified CNC-type machine capable of operating feed rates with vf = 30 m/min. In this work, process parameters were developed for the deposition of thin-walled filigree structures with the Ni-based superalloy IN718. Single tracks with constant feed rates and a variation in the beam diameter and powder mass flow were deposited and analyzed regarding the resulting weld bead dimension and dilution zone. Then, process parameters were selected and transferred to the deposition of thin walls, and guidelines of the parameter adaption toward thin-walled deposition were defined. Two parameter sets were developed to assess the feasible wall-thicknesses deposited by EHLA3D. Depending on the developed parameter sets, wall thicknesses between 300 and 500 μm are achieved. To characterize the resulting thin-walls, surface roughness measurements and metallographic cross sections were conducted.