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Optimization of Electron Beam Melting for Production of Small Components in Biocompatible Titanium Grades
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.ORCID iD: 0000-0002-5292-2504
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Additive manufacturing (AM), also called 3D-printing, are technologies where parts are formed from the bottom up by adding material layer-by-layer on top of each other. Electron Beam Melting (EBM) is an AM technique capable of manufacturing fully solid metallic parts, using a high-intensity electron beam to melt powder particles in layers to form finished components. Compared to conventional machining, EBM offers enhanced efficiency for production of customized and patient specific parts such as e.g. dental prosthetics. However, dental prosthetics are challenging to produce by EBM, as their small sizes mean that mechanical and surface properties may be altered as part sizes decreases.

The aim of this thesis is to gain new insights that could lead to optimization for production of small sized components in the EBM. The work is focused to understand the process-property relationships for small size components production.

To improve the surface resolution and part detailing, a smaller sized powder was used for production and compared to parts made with standard sized powder. The surface-, chemical and mechanical properties were evaluated for parts produced with both types of powders. The results indicate that the surface roughness may be influenced by powder and build layer thickness size, whereas the mechanical properties showed no influence of the layer-wise production. However, the mechanical properties are dependent on part size. The outermost surface of the parts consists of a surface oxide dominated by TiO2, formed as a result of reaction between the surface and residual gases in the EBM build chamber. The surface oxide thickness is comparable to that of a conventionally machined surface, but is dependent on build height.

This work concludes that the surface resolution and component detailing can be improved by various measures. Provided that proper process themes are used, the EBM manufactured material is homogenous with properties comparable to conventional produced titanium. It has also been shown that the material properties will be altered for small components. The results point towards different ways of optimizing manufacturing of dental prosthetics by EBM, which will make dental prosthetics available for an increased number of patients.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 80 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1206
Keyword [en]
Additive Manufacturing, 3D-printing, Electron Beam Melting, Titanium alloys, Chemical properties, Mechanical properties, Surface properties
Keyword [sv]
Additiv tillverkning, 3D-skrivare, Electron Beam Melting, Titan, Kemiska egenskaper, Mekaniska egenskaper, Ytegenskaper
National Category
Production Engineering, Human Work Science and Ergonomics Metallurgy and Metallic Materials Medical Materials
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-236709ISBN: 978-91-554-9110-9 (print)OAI: oai:DiVA.org:uu-236709DiVA: diva2:765202
Public defence
2015-01-23, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2014-12-17 Created: 2014-11-21 Last updated: 2015-02-03
List of papers
1. Characterization and comparison of materials produced by Electron Beam Melting (EBM) of two different Ti-6Al-4V powder fractions
Open this publication in new window or tab >>Characterization and comparison of materials produced by Electron Beam Melting (EBM) of two different Ti-6Al-4V powder fractions
2013 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 213, no 12, 2109-2118 p.Article in journal (Refereed) Published
Abstract [en]

Electron Beam Melting (EBM) has been recognized as a revolutionary technique to produce mass-customized parts to near-net-shape from various metallic materials. The technique produces parts with unique geometries from a powder stock material and uses an electron beam to melt the powder layer-by-layer to fully solid structures. In this study we have investigated the use of two different Ti-6Al-4V powders of different size fractions in the EBM process; a larger 45-100 mu m powder, and a smaller 25-45 mu m powder. We have also investigated the effects of two build layer thicknesses, 70 mu m and 50 mu m. respectively. We hypothesize that the smaller powder has the potential to improve surface resolution of parts produced in the EBM process. The EBM as-built parts were investigated regarding surface and bulk chemistry, surface oxide thickness, macro- and microstructure, surface appearance and mechanical properties. We conclude from the results that both powders and both build layer thicknesses are feasible to use in the EBM process. The investigated material properties were not significantly affected by powder size or layer thickness within the studied range of process parameters. However, the surface appearance was found to be different for the samples made with the different powder sizes.

Keyword
Electron Beam Melting, Titanium alloy, Chemical properties, Surface analysis, Microstructure, Mechanical properties
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-210166 (URN)10.1016/j.jmatprotec.2013.06.010 (DOI)000325236200006 ()
Available from: 2013-11-04 Created: 2013-11-04 Last updated: 2017-12-06Bibliographically approved
2. Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
Open this publication in new window or tab >>Thickness dependency of mechanical properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
Show others...
(English)In: Additive Manufacturing Journal, ISSN 2214-8604Article in journal (Refereed) Submitted
Abstract [en]

Metal powder bed additive manufacturing technologies, such as the Electron Beam Melting process, facilitate a high degree of geometric flexibility and have been demonstrated as useful production techniques for metallic parts.  

However, the EBM process is typically associated with lower resolutions and higher surface roughness compared to similar laser-based powder bed metal processes. In part, this difference is related to the larger powder size distribution and thicker layers normally use As part of an effort to improve the resolution and surface roughness of EBM fabricated components, this study investigates the feasibility of fabricating components with a smaller powder size fraction and layer thickness (similar to laser based processes). The surface morphology, microstructure and tensile properties of the produced samples were evaluated. The findings indicate that microstructure is dependent on wall-thickness and that, for thin walled structures, tensile properties can become dominated by variations in surface roughness.

Place, publisher, year, edition, pages
Elsevier
Keyword
Additive Manufacturing; Electron Beam Melting; Ti-6Al-4V; Mechanical Properties
National Category
Production Engineering, Human Work Science and Ergonomics Metallurgy and Metallic Materials Medical Materials
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-236648 (URN)
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2015-02-03
3. Digital Image Correlation analysis of local strain fields on Ti6Al4V manufactured by Electron Beam Melting
Open this publication in new window or tab >>Digital Image Correlation analysis of local strain fields on Ti6Al4V manufactured by Electron Beam Melting
Show others...
2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 618, 456-461 p.Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing, or 3D-printing as it is often called, build parts in a layer-by-layer fashion. A common concern, regardless of the specific additive manufacturing technique used, is the risk of inadequate fusion between the adjacent layers which in turn may cause inferior mechanical properties. In this work, the local strain properties of titanium parts produced by Electron Beam Melting (EBM®) were studied in order to gain information about the quality of fusion of the stock powder material used in the process. By using Digital Image Correlation (DIC) the strain fields in the individual layers were analyzed, as well as the global strain behavior of the bulk material. The results show that fully solid titanium parts manufactured by EBM are homogenous and do not experience local deformation behavior, neither on local nor on a global level.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
Additive manufacturing; Electron Beam Melting; Titanium alloys; Mechanical; Characterization; Digital Image Correlation
National Category
Production Engineering, Human Work Science and Ergonomics Metallurgy and Metallic Materials
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-236653 (URN)10.1016/j.msea.2014.09.022 (DOI)000344439500055 ()
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2017-12-05Bibliographically approved
4. Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
Open this publication in new window or tab >>Thickness dependency of surface properties for thin-walled titanium parts manufactured by Electron Beam Melting (EBM®)
Show others...
(English)In: Additive Manufacturing Journal, ISSN 2214-8604Article in journal (Refereed) Submitted
Abstract [en]

The surface morphology of components produced by powder bed metal additive manufacturing is of interest for multiple industry sectors including biomedical and aerospace.  For some applications, improvements in surface finish can reduce or eliminate the requirement for secondary finishing processes. In this study, titanium alloy (Ti6Al4V) samples were manufactured using the Electron Beam Melting (EBM) process. The effect of variations in sample thickness, powder size distribution and layer thickness were measured with three different techniques, both for direct measurement and comparison of the techniques.  Ra-values in the range of 15 µm – 37 µm were obtained and varied depending on measurement technique. However, independent of technique, Ra values were found to be dependent on powder size distribution, build layer thickness, and wall thickness. Analytical transmission electron microscopy of cross sections prepared by focused ion beam milling revealed that the outermost surfaces consisted of an oxide layer of 5 nm -6 nm thickness.

Keyword
Additive Manufacturing, Electron Beam Melting, Ti-6Al-4V, Surface roughness, Surface properties, Transmission Electron Microscopy
National Category
Metallurgy and Metallic Materials Medical Materials Production Engineering, Human Work Science and Ergonomics
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-236638 (URN)
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2015-02-03
5. Surface oxidation behavior of Ti–6Al–4V manufactured by Electron Beam Melting (EBM®)
Open this publication in new window or tab >>Surface oxidation behavior of Ti–6Al–4V manufactured by Electron Beam Melting (EBM®)
Show others...
2015 (English)In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 17, no 1, 120-126 p.Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing is an emerging manufacturing technology that enables production of patient spe-cific implants, today primarily out of titanium. For optimal functionality and proper integration betweenthe titanium implant and the body tissues surface properties, such as surface oxide thickness is of partic-ular importance, as it is primarily the surface of the material which interacts with the body. Hence, in thisstudy the surface oxidation behavior of titanium parts manufactured by Electron Beam Melting (EBM®)is investigated using the surface sensitive techniques ToF-SIMS and AES. Oxide thicknesses comparableto those found on conventionally machined surfaces are found by both analysis techniques. However, abuild height dependency is discovered for different locations of the EBM®manufactured parts due to thepresence of trapped moisture in the machine and temperature gradients in the build.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Additive Manufacturing; Electron Beam Melting;Titanium alloys;Surface properties; Oxidation
National Category
Medical Materials Metallurgy and Metallic Materials Production Engineering, Human Work Science and Ergonomics
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-236651 (URN)10.1016/j.jmapro.2014.08.005 (DOI)000349885600012 ()
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2015-04-10Bibliographically approved

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