Abstract
Directed energy deposition is an additive manufacturing technology which usually relies on prototype machines or hybrid systems, assembled with parts from different producers. Because of this lack of standardization, the optimization of the process parameters is often a mandatory step in order to develop an efficient building process. Although, this preliminary phase is usually expensive both in terms of time and cost. The single scan approach allows to drastically reduce deposition time and material usage, as in fact only a stripe per parameters combination is deposited. These specimens can then be investigated, for example in terms of geometrical features (e.g. growth, width) and microstructure to assess the most suitable process window. In this work, Ti-6Al-4V single scans, produced by means of directed energy deposition, corresponding to a total of 50 different parameters combinations, were analyzed, focusing on several geometrical features and relative parameters correlations. Moreover, considering the susceptibility of the material to oxygen pick-up, the necessity of an additional shielding gas system was also evaluated, by comparing the specimens obtained with and without using a supplementary argon flow. A process window, which varies according to the user needs, was found together with a relationship between microstructure and process parameters, in both shielding scenarios.Graphic
Highlights
Directed Energy Deposition (DED) is a laser-based Additive manufacturing (AM) technology which allows the production of metallic components from a feedstock material, usually in the form of prealloyed powder [1]
DED techniques differ from Powder Bed Fusion (PBF) systems mainly due to the material disposition method: while the former implies the delivery of the powder through carrier gas from nozzles directly on the building platform, in the latter, a layer of powder completely covers the whole platform each time a new layer is added [2]
The beneficial effect of the additional shielding gas system was due to augmented overall gas flow of the overall apparatus, which reduced the possibility for the powder to flow outside of the melting area, to the results found in literature
Summary
Directed Energy Deposition (DED) is a laser-based Additive manufacturing (AM) technology which allows the production of metallic components from a feedstock material, usually in the form of prealloyed powder [1]. DED techniques differ from Powder Bed Fusion (PBF) systems mainly due to the material disposition method: while the former implies the delivery of the powder through carrier gas from nozzles directly on the building platform, in the latter, a layer of powder completely covers the whole platform each time a new layer is added [2]. PBF technologies, such as Laser Powder Bed Fusion (LPBF), grant the possibility to build more complex components, characterized by a lower surface roughness, when compared to DED [3]. DED allows building rates more than 10 times greater, in addition to the ability to manufacture bigger components [4]. DED is well-suited for some specific applications, such as remanufacturing/repairing of pre-existing pieces and gradedmaterials production [3].
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