| 1. |
- Brueckner, Frank, et al.
(author)
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Enhanced manufacturing possibilities using multi-materials in laser metal deposition
- 2018
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In: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 26:2, s. 10-12
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Journal article (peer-reviewed)abstract
- Additive manufacturing (AM) addresses various benefits as the buildup of complex shaped parts, the possibility of functional integration, reduced lead times or the use of difficult machinable materials compared to conventional manufacturing possibilities. Beside these advantages, the use of more than one material in a component would strongly increase the field of applications in typical AM branches as energy, aerospace, or medical technology. By means of multi-material buildups, cost-intensive alloys could be only used in high-loaded areas of the part, whereas the remaining part could be fabricated with cheaper compositions. The selection of combined materials strongly depends on the requested thermophysical but also mechanical properties. Within this contribution, examples (e.g., used in the turbine business) show how alloys can be arranged to fit together, e.g., in terms of a well-chosen coefficient of thermal expansion. As can be seen in nature, the multi-material usage can be characterized by sharp intersections from one material to the other (e.g., in case of a thin corrosion protection), but also by graded structures enabling a smoother material transition (e.g., in case of dissimilar materials which are joined together without defects). The latter is shown for an example from aerospace within this paper. Another possibility is the simultaneous placement of several materials, e.g., hard carbide particles placed in a more ductile matrix composition. These particles can be varied in size (e.g., TiC versus WC). Also the ratio between carbides and matrix alloy can be adjusted depending on its application. Especially, nozzle-based free form fabrication technologies, e.g., laser metal deposition, enable the utilization of more than one material. Within this contribution, possibilities to feed more than one filler material are demonstrated. In addition, results of multi-material processes are shown. Finally, this work focuses on different (potential) applications, mainly on power generation, but also for medical technology or wear resistant components.
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| 2. |
- Eberle, Sebastian, et al.
(author)
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Additive manufacturing of an AlSi40 mirror coated with electroless nickel for cryogenic space applications
- 2018
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In: International Conference on Space Optics—ICSO 2018. - : SPIE - International Society for Optical Engineering.
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Conference paper (peer-reviewed)abstract
- Advanced Manufacturing (AM) has the potential to improve existing technologies and applications in terms of performance, light-weighting and costs. In the context of the SME4ALM initiative, launched by DLR and ESA, the company Kampf Telescope Optics GmbH (KTO) in cooperation with the Fraunhofer Institute for Material and Beam Technology (IWS) have assessed the feasibility of AM to build a high-performance optical mirror for space applications. For the assessment of the AM potentials, a mirror design concept for cryogenic instruments for observations in the IR and NIR range was baselined. In a second step, Nickel-Phosphorus (NiP) was selected as optical coating. The combination of coating and mirror material is a primary design driver for optical performance. Both materials must have a very similar CTE as well as be compliant to modern optical manufacturing (diamond turning, polishing). As a promising candidate for NiP coating the AlSi40 was selected for the mirror structure. The potential advantages of AM for optical mirrors in terms of mechanical performance, cost, and manufacturing time were exploited. The achievement of those objectives was / will be demonstrated by:1. verifying AM material properties and manufacturability of AM mirrors by material sample tests and subcomponent tests2. designing AM mirror demonstrator by structural, thermal, and optical performance analysis3. applying and elaborating AM specific design methods (topology optimization, sandwich structures with internal microstructures, monolithic design, etc.)4. manufacturing, assembling, and testing AM mirror demonstrator to verify manufacturability and optical performance5. comparing optical and mechanical performance of the AM mirror demonstrator to a conventional mirror by numerical analysis to exploit potential advantages of AM
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| 3. |
- Lopez, Elena, et al.
(author)
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Evaluation of 3D-printed parts by means of high-performance computer tomography
- 2018
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In: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 30:3
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Journal article (peer-reviewed)abstract
- Conventional tactile and optical testing methods are not capable to detect complex inner geometries or complex surface shapes. Detecting porosities in parts is also not possible with those nondestructive methods. Among other material parameters, geometrical accuracy is essential to determine part's quality. Additive manufacturing processes also have to be optimized regarding geometry deviations caused by distortion or unfavorable orientation in the build chamber. For additive manufactured parts that incorporate previously mentioned features, high-performance computer tomography is the more suitable nondestructive testing method. Components of different materials such as plastics, ceramics, composites, or metals can be completely characterized. This nondestructive testing method was used for porosity analysis regarding the shape and local distribution of pores in an additive manufactured part to find correlations concerning the most suitable process conditions. The measured part data were also compared to original CAD files to determine zones of deviation and apply specific process strategies to avoid distortion. This paper discusses the results of integrating high-performance computer tomography (power: 500 W, max. part size: Ø 300 mm, 300 × 430 mm2) in a productionlike environment of additively manufactured parts for a wide range of technologies (i.e., electron beam melting and selective laser melting). I. INTRODUCTION
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| 4. |
- Seidel, André, et al.
(author)
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Added value by hybrid additive manufacturing and advanced manufacturing approaches
- 2018
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In: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 26:2, s. 6-8
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Journal article (peer-reviewed)abstract
- In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive manner, but can also be done in a complementary way. This complementary approach is often used for the processing of difficult-to-machine materials with particular regard to high-tech parts or components. Hybrid machining processes or, more general, advanced machining processes can be brought to the point that the results would not be possible with the individual constituent processes in isolation [Hybrid Machining Processes Perspectives on Machining and Finishing (Springer International Publishing AG, 2016)]. Hence, the controlled interaction of process mechanisms and/or energy sources is frequently applied for a significant increase of the process performance [Advanced Machining Processes of Metallic Materials: Theory, Modelling, and Applications, 2nd ed. (2016)] and will be addressed within the present paper. A via electron beam melting manufactured gamma titanium aluminide nozzle is extended and adapted. This is done via hybrid laser metal deposition. The presented approach considers critical impacts like processing temperatures, temperature gradients, and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking [Laser-Based Manufacturing of Components using Materials with High Cracking Susceptibility (Laser Institute of America–LIA), pp. 586–592; Ti-2015: The 13th World Conference on Titanium, Symposium 5]. Furthermore, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, the results will be evaluated. This will also be done in the perspective of other applications.
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| 5. |
- Seidel, André, et al.
(author)
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Additive Manufacturing of Powdery Ni-Based Superalloys Mar-M-247 and CM 247 LC in Hybrid Laser Metal Deposition
- 2018
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In: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 49:9, s. 3812-3830
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Journal article (peer-reviewed)abstract
- The present paper addresses the phenomena of hot cracking of nickel-based superalloys in the perspective of hybrid Laser Metal Deposition (combined application of induction and laser). This includes an extract of relevant theoretical considerations and the deduction of the tailored approach which interlinks material–scientific aspects with state-of-the-art manufacturing engineering. The experimental part reflects the entire process chain covering the manufacturing strategy, important process parameters, the profound analysis of the used materials, the gradual process development, and the corresponding hybrid manufacture of parts. Furthermore, hot isostatic pressing and thermal treatment are addressed as well as tensile testing at elevated temperatures. Further investigations include X-ray CT measurements, electron backscattered diffraction (EBSD), and scanning electron microscopy (SEM) as well as light optical microscope evaluation. The fundamental results prove the reliable processibility of the high-performance alloys Mar-M-247 and Alloy 247 LC and describe in detail the process inherent microstructure. This includes the grain size and orientation as well as the investigation of size, shape, and distribution of the γ′ precipitates and carbides. Based on these findings, the manufacturing of more complex demonstrator parts with representative dimensions is addressed as well. This includes the selection of a typical application, the transfer of the strategy, as well as the proof of concept.
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| 6. |
- Seidel, André, et al.
(author)
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Hybrid Additive Manufacturing of Gamma Titanium Aluminide Space Hardware
- 2018
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In: Contributed Papers from Materials Science and Technology 2018 (MS&T18). - : Association for Iron and Steel Technology (AISTECH). ; , s. 13-21
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Conference paper (peer-reviewed)abstract
- A major part of laser additive manufacturing focuses on the fabrication of metallic parts for applications in the space and aerospace sector. Especially the processing of the very brittle titanium aluminides can be particularly challenging [1-2].In the present paper a gamma titanium aluminide (γ-TiAl) nozzle, manufactured via Electron Beam Melting (EBM), is extended and adapted via hybrid Laser Metal Deposition (LMD). The presented approach considers critical impacts like processing temperatures, temperature gradients and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking [3-6]. Furthermore, the potential of microstructural tailoring is going to be addressed by the process-specific manipulation of the composition and/or microstructure.In addition to this, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, post manufacturing and surface modification are briefly addressed.
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