Microstructure Development in Track-by-Track Melting of EBM-Manufactured Alloy 718Show others and affiliations
2018 (English)In: PROCEEDINGS OF THE 9TH INTERNATIONAL SYMPOSIUM ON SUPERALLOY 718 and DERIVATIVES: ENERGY, AEROSPACE, AND INDUSTRIAL APPLICATIONS, SPRINGER INTERNATIONAL PUBLISHING AG , 2018, p. 643-654Conference paper, Published paper (Refereed)
Abstract [en]
Electron beam melting (EBM) is a powder-bed fusion process within the group of additive manufacturing (AM) technology that is used to fabricate high performance metallic parts. Nickel-Iron base superalloys, such as Alloy 718, are subjected to successive heating and cooling at temperatures in excess of 800 degrees C during the EBM process. Characterization of the dendritic structure, carbides, Laves and delta-phase were of particular interest in this study. These successive thermal cycles influence the microstructure of the material resulting in a heterogeneous structure, especially in the building direction. Hence, the aim of this study was to gain increased fundamental understanding of the relationship between the processing history and the microstructure formed within a single layer. Different numbers of tracks with equal heights were for this purpose produced, varying from one to ten tracks. All tracks used the same process parameters regardless of number and/or position. Microstructure characteristics (sub-grain structure, grain structure and phases) were analyzed by optical microscopy, scanning electron microscopy equipped with energy disperse spectroscopy and electron backscatter diffraction. The direction of dendrites changed in the overlap zones within the tracks due to re-melting of material in the overlap zone. The primary dendrite arm spacings slightly increased along multi-tracks owing to a slight decrease in cooling rate by addition of the next tracks. Epitaxial growth of grains were observed in all samples due to partial re-melting of grains in previous layers and surface nucleation was also found to occur in all tracks.
Place, publisher, year, edition, pages
SPRINGER INTERNATIONAL PUBLISHING AG , 2018. p. 643-654
Series
Minerals Metals & Materials Series, ISSN 2367-1181
Keywords [en]
Additive manufacturing; Electron beam melting; Alloy 718 Microstructure; Track-by-Track
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-152111DOI: 10.1007/978-3-319-89480-5_42ISI: 000445800500042ISBN: 978-3-319-89480-5 (electronic)ISBN: 978-3-319-89479-9 (print)OAI: oai:DiVA.org:liu-152111DiVA, id: diva2:1256657
Conference
9th International Symposium on Superalloy 718 and Derivatives - Energy, Aerospace, and Industrial Applications
Note
Funding Agencies|European Regional Development Fund; SiCoMap; KK foundation
2018-10-172018-10-172018-10-17