Combinatorial study of process parameters, microstructure and mechanical properties in Inconel 718 parts produced by additive manufacturing

Research output: ThesisMaster's Thesis

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Abstract

Functional properties of Ni-basis Inconel 718 alloy components synthetized using selective laser melting depend on a variety of process parameters. In this thesis, the effects of the laser power, the scanning velocity and the layer thickness on the surface quality, the mechanical properties, the microstructure and the residual stress gradients in a variety of as-built structures are analyzed. Based on an experimental design schema, first, 41 process parameter combinations were systematically selected and applied to manufacture the structures. The combinatorial study has indicated complex correlations between the process and the sample parameters. Surfaces roughnesses were optimized to mean values of ~14 and 19 µm for vertical, 45°-upskin and 45°-downskin oriented surfaces, respectively. A maximal ultimate tensile strength of ~670 MPa and a strain at fracture of up to ~33.5 % were obtained in the as-built structures without further surface post-processing. Secondly, the results were used to select representative conditions for the production of six near-product sample geometries, which were further analyzed at the synchrotron beamline P07 of DESY in Hamburg. Three specimens were produced using constant deposition conditions and, for another three geometries, the volumetric energy density was varied during the building process. Horizontal and vertical synchrotron scanning experiments were performed to characterize stress and texture evolutions across the samples. The correlation of the experimental data allowed the understanding of the influence of the specific process parameters on the mechanical properties, the microstructure, the residual stress distributions and the surface quality. Finally, this multi-parameter study based on a variety of experimental techniques and applied process conditions demonstrate that it is actually possible to perform knowledge-based design of the functional properties and the corresponding microstructure of as-built components by applying purposefully selected input parameters during the additive manufacturing process.
Translated title of the contributionKombinatorische Studie der Prozessparameter und deren Auswirkungen auf die Gefügeentwicklung und die mechanischen Eigenschaften in mittels generativer Fertigung hergestellten Bauteilen aus Inconel 718
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Keckes, Jozef, Supervisor (internal)
Award date23 Mar 2018
Publication statusPublished - 2018

Bibliographical note

embargoed until 17-11-2022

Keywords

  • additive manufacturing
  • selective laser melting
  • powder bed
  • Inconel 718
  • nickel-basis alloy
  • residual stress distribution
  • design of experiments
  • multi-parameter study

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