Surface refinement of additively manufactured components: Improving the mechanical properties and the oxidation behaviour

The additive manufacturing of metallic components has become increasingly interesting to industry and research. One of the numerous manufacturing processes is Selective Laser Melting (SLM). Here the components are built layer by layer in a powder bed by spreading layers of metallic powder on the basis and melting it with a laser source. The additively manufactured components may feature complex geometries, however they often show high surface roughness and remaining porosity. Both factors can have a negative effect on the oxidation behaviour and particularly on the mechanical properties of the components.

The present AiF project of DECHEMA-Forschungsinstitut and Neue Materialien Bayreuth GmbH therefore pursues the goal of refining the surface of SLM-manufactured metallic samples by using pack cementation, a classical representative of chemical vapour deposition. The general idea is to use the Al- or Cr-rich protective coating formed at high temperatures to close surface-near pores (sealing coat) as well as minimizing the pronounced surface roughness. The experiments are conducted on Fe- and Ni-base alloys (e.g. Alloy 800H, Alloy 625 etc.) with high Cr content, which are primarily used for high temperature applications in the chemical industry. Besides primary baseline investigations of deposition properties of pack cementation coatings on SLM components, their improved oxidation resistance will be investigated in thermocyclic and isothermal exposure tests. This allows a direct comparison between coated and uncoated SLM samples as well as, additionally, with conventionally manufactures components, which are regarded as a reference. Furthermore, tensile and fatigue tests will be conducted in order to assess the influence of coatings on the mechanical properties in more detail.

Das IGF-Vorhaben Nr. 21431 der Forschungsvereinigung DECHEMA e.V., Theodor-Heuss-Allee 25, 60486 Frankfurt am Main wurde über die AiF im Rahmen des Programms zur Förderung der industriellen Gemeinschaftsforschung (IGF) vom Bundesministerium für Wirtschaft und Klimaschutz aufgrund eines Beschlusses des Deutschen Bundestages gefördert.