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Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0001-6610-1486
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-7663-9631
Linköping University, Division of Engineering Materials, Department of Management and Engineering, Linköping, 581 83, Sweden.
University of Chalmers, Division of Materials and Manufacture, Industrial and Materials Science, Gothenburg, 412 96, Sweden.
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2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 99, no S1, p. 2903-2913Article in journal (Refereed) Published
Abstract [en]

Effects of build layout and orientation consisting of (a) height from the build plate (Z-axis), (b) distance between samples, and (c) location in the build plate (X-Y plane) on porosity, NbC fraction, and hardness in electron beam melted (EBM) Alloy 718 were studied. The as-built samples predominantly showed columnar structure with strong ˂001˃ crystallographic orientation parallel to the build direction, as well as NbC and ÎŽ-phase in inter-dendrites and grain boundaries. These microstructural characteristics were correlated with the thermal history, specifically cooling rate, resulted from the build layout and orientation parameters. The hardness and NbC fraction of the samples increased around 6% and 116%, respectively, as the height increased from 2 to 45 mm. Moreover, by increasing the height, formation of ÎŽ-phase was also enhanced associated with lower cooling rate in the samples built with a greater distance from the build plate. However, the porosity fraction was unaffected. Increasing the sample gap from 2 to 10 mm did not change the NbC fraction and hardness; however, the porosity fraction increased by 94%. The sample location in the build chamber influenced the porosity fraction, particularly in interior and exterior areas of the build plate. The hardness and NbC fraction were not dependent on the sample location in the build chamber. © 2018, The Author(s).

Place, publisher, year, edition, pages
2018. Vol. 99, no S1, p. 2903-2913
Keywords [en]
3D printers, Cooling, Electron beam melting, Electron beams, Grain boundaries, Hardness, Location, Niobium compounds, Porosity, Alloy 718, Build direction, Columnar structures, Crystallographic orientations, Micro-structural characteristics, Micro-structural characterization, Orientation parameter, Sample location, Porous plates
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-13043DOI: 10.1007/s00170-018-2621-6ISI: 000452076900065Scopus ID: 2-s2.0-85053670925OAI: oai:DiVA.org:hv-13043DiVA, id: diva2:1259278
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Note

First Online: 17 September 2018

Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2019-05-28Bibliographically approved
In thesis
1. Electron beam melting of Alloy 718: Influence of process parameters on the microstructure
Open this publication in new window or tab >>Electron beam melting of Alloy 718: Influence of process parameters on the microstructure
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM) is the name given to the technology of building 3D parts by adding layer-by-layer of materials, including metals, plastics, concrete, etc. Of the different types of AM techniques, electron beam melting (EBM), as a powder bed fusion technology, has been used in this study. EBM is used to build parts by melting metallic powders by using a highly intense electron beam as the energy source. Compared to a conventional process, EBM offers enhanced efficiency for the production of customized and specific parts in aerospace, space, and medical fields. In addition, the EBM process is used to produce complex parts for which other technologies would be either expensive or difficult to apply. This thesis has been divided into three sections, starting from a wider window and proceeding to a smaller one. The first section reveals how the position-related parameters (distance between samples, height from build plate, and sample location on build plate) can affect the microstructural characteristics. It has been found that the gap between the samples and the height from the build plate can have significant effects on the defect content and niobium-rich phase fraction. In the second section, through a deeper investigation, the behavior of Alloy 718 during the EBM process as a function of different geometry-related parameters is examined by building single tracks adjacent to each other (track-by-track) andsingle-wall samples (single tracks on top of each other). In this section, the main focus is to understand the effect of successive thermal cycling on microstructural evolution. In the final section, the correlations between the main machine-related parameters (scanning speed, beam current, and focus offset) and the geometrical (melt pool width, track height, re-melted depth, and contact angle) and microstructural (grain structure, niobium-rich phase fraction, and primary dendrite arm spacing) characteristics of a single track of Alloy 718 have been investigated. It has been found that the most influential machine-related parameters are scanning speed and beam current, which have significant effects on the geometry and the microstructure of the single-melted tracks.

Place, publisher, year, edition, pages
Trollhättan: University West, 2018. p. 65
Series
Licentiate Thesis: University West ; 22
Keywords
Additive manufacturing; Powder bed fusion; Electron beam melting; Part’s orientation; Microstructure development; Single track; Energy input; Focus offset; Geometrical features, Alloy 718
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13140 (URN)978-91-88847-08-9 (ISBN)978-91-88847-07-2 (ISBN)
Presentation
2018-11-21, C120, Högskolan Väst, Trollhättan, 10:00 (English)
Supervisors
Available from: 2018-11-21 Created: 2018-11-19 Last updated: 2018-11-19

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Karimi Neghlani, PariaSadeghimeresht, EsmaeilAndersson, JoelNylen, Per

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