| 1. |
- Brueckner, Frank, et al.
(författare)
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Enhanced manufacturing possibilities using multi-materials in laser metal deposition
- 2018
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Ingår i: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 26:2, s. 10-12
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Tidskriftsartikel (refereegranskat)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. |
- Brueckner, Frank, et al.
(författare)
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Fabrication of metallic multi-material components using Laser Metal Deposition
- 2017
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Ingår i: Solid Freeform Fabrication 2017. - : The University of Texas at Austin. ; , s. 2530-2538
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Meanwhile, Laser Metal Deposition (LMD) is a well-known Additive Manufacturing technology used in various industrial branches as energy, tooling or aerospace. It can be used for the fabrication of new components but also repair applications. So far, volume build-ups were mostly carried out with one single material only. However, loading conditions may strongly vary and, hence, the use of more than one material in a component would yield major benefits. By means of multi-material build-ups, cost-intensive alloys could be used in highly-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 thermo-physical and mechanical properties. Within this contribution, possibilities of material combinations by LMD and selected examples of beneficial multi-material use are presented.
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| 3. |
- Eberle, Sebastian, et al.
(författare)
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Additive manufacturing of an AlSi40 mirror coated with electroless nickel for cryogenic space applications
- 2018
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Ingår i: International Conference on Space Optics—ICSO 2018. - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)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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| 4. |
- Lopez, Elena, et al.
(författare)
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Evaluation of 3D-printed parts by means of high-performance computer tomography
- 2018
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Ingår i: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 30:3
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Moritz, Juliane, et al.
(författare)
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Hybrid manufacturing of titanium Ti-6Al-4V combining laser metal deposition and cryogenic milling
- 2020
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 107:7-8, s. 2995-3009
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid manufacturing, which, e.g., combines additive manufacturing with conventional machining processes, can be a way of overcoming limitations currently encountered in additive manufacturing. Cryogenic milling might be a viable option for hard-to-cut materials, as it leaves a contamination-free surface and can increase surface quality and tool life compared to conventional cooling concepts. In this study, the influence of cryogenic milling with carbon dioxide on titanium Ti-6Al-4V specimens manufactured with laser metal deposition (LMD) was investigated regarding tool wear and surface integrity in comparison to dry machining and machining with cooling lubricants. Moreover, additional layers of material were deposited on top of conventionally and cryogenically machined surfaces by means of LMD. The interface zone was then examined for defects. The milling process was closely monitored by means of thermal and high-speed imaging. Optical and tactile surface analysis provided evidence that lower roughness values and improved surface qualities could be obtained with cryogenic machining in comparison to dry machining. Moreover, significantly less tool wear was observed when a cryogenic cooling medium was applied. Although the utilization of conventional cooling lubricants resulted in satisfying surface qualities, substantial residual contamination on the milled surface was detected by means of fluorescence analysis. These contaminants are suspected to cause defects when the next layer of material is deposited. This is supported by the fact that pores were found in the weld bead applied on top of the milled specimens by means of LMD. Conversely, cryogenic machining resulted in very clean surfaces due to the residue-free evaporation of the coolant. Hence, a good metallurgical bonding between the weld bead and the milled substrate could be achieved. The results indicate the great potential of cryogenic milling in hybrid manufacturing, especially in terms of intermediate machining, as it provides residue-free surfaces for subsequent material deposition without an additional cleaning step and can significantly prolongate tool life.
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| 6. |
- Mueller, Michael, et al.
(författare)
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Microstructural, mechanical, and thermo-physical characterization of hypereutectic AlSi40 fabricated by selective laser melting
- 2019
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 31:2
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Tidskriftsartikel (refereegranskat)abstract
- The powder bed additive manufacturing process selective laser melting (SLM) enables designers and engineers to overcome restrictions of conventional manufacturing technologies. The potential of fabricating complex lightweight structures and processing advanced materials is a key feature for enhancing further development of high performance components for space applications. Due to a high specific stiffness and a thermal expansion coefficient very close to electroless nickel, which is an advantageous optical coating material, the hypereutectic aluminum-silicon alloy AlSi40 shows great potential for the manufacturing of optical mirrors for space applications. In prior investigations, Hilpert et al.showed the feasibility to process AlSi40 by SLM [E. Hilpert and S. Risse, Materials Science & Technology Conference and Exhibition MS&T'15, Columbus, Ohio, 4–8 October 2015(Association for Iron & Steel Technology, Warrendale, PA, 2015) and E. Hilpert, “Struktur und Eigenschaften von additiv gefertigten hypereutektischen Aluminum-Siliciumlegierungen,” in Werkstoffwoche 2017, Dresden, Germany, 28 September 2017 (Deutsche Gesellschaft für Materialkunde e.V., Berlin, 2017)]. Nevertheless, in order to qualify this material for space applications, the manufacturing process and fabricated samples need to be thoroughly investigated in terms of microstructural, mechanical, as well as thermo-physical characterization. The authors present results of the SLM process development for manufacturing dense AlSi40 samples with a relative density above 99.50%. The effect of various process parameters, such as hatch distance, preheating, and scanning strategy, on the formation of defects was investigated by destructive [e.g., optical microscopy (OM)] and nondestructive (e.g., computed tomography) testing. In addition, the effect of several thermal post-treatments on the AlSi40 microstructure was profoundly analyzed by multiple methods such as OM, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. Moreover, mechanical and thermo-physical testing of manufactured specimens was conducted to provide material characteristics for component design. In conclusion, the determined material properties of AlSi40 samples fabricated by SLM were compared to bulk material properties. The gained knowledge and testing data were evaluated in order to identify correlations and dependencies.
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| 7. |
- Poelzl, Gerhard, et al.
(författare)
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Repetitive use of levosimendan in advanced heart failure : need for stronger evidence in a field in dire need of a useful therapy
- 2017
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 243, s. 389-395
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Tidskriftsartikel (refereegranskat)abstract
- Patients in the latest stages of heart failure are severely compromised, with poor quality of life and frequent hospitalizations. Heart transplantation and left ventricular assist device implantation are viable options only for a minority, and intermittent or continuous infusions of positive inotropes may be needed as a bridge therapy or as a symptomatic approach. In these settings, levosimendan has potential advantages over conventional inotropes (catecholamines and phosphodiesterase inhibitors), such as sustained effects after initial infusion, synergy with beta-blockers, and no increase in oxygen consumption. Levosimendan has been suggested as a treatment that reduces re-hospitalization and improves quality of life. However, previous clinical studies of intermittent infusions of levosimendan were not powered to show statistical significance on key outcome parameters. A panel of 45 expert clinicians from 12 European countries met in Rome on November 24-25, 2016 to review the literature and envision an appropriately designed clinical trial addressing these needs. In the earlier FIGHT trial (daily subcutaneous injection of liraglutide in heart failure patients with reduced ejection fraction) a composite Global Rank Score was used as primary end-point where death, re-hospitalization, and change in N-terminalprohormone-brain natriuretic peptide level were considered in a hierarchical order. In the present study, we tested the same end-point post hoc in the PERSIST and LEVOREP trials on oral and repeated i.v. levosimendan, respectively, and demonstrated superiority of levosimendan treatment vs placebo. The use of the same composite end-point in a properly powered study on repetitive levosimendan in advanced heart failure is strongly advocated.
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| 8. |
- Seidel, André, et al.
(författare)
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Added value by hybrid additive manufacturing and advanced manufacturing approaches
- 2018
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Ingår i: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 26:2, s. 6-8
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Seidel, André, et al.
(författare)
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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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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 49:9, s. 3812-3830
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Seidel, André, et al.
(författare)
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Hybrid Additive Manufacturing of Gamma Titanium Aluminide Space Hardware
- 2018
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Ingår i: Contributed Papers from Materials Science and Technology 2018 (MS&T18). - : Association for Iron and Steel Technology (AISTECH). ; , s. 13-21
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Konferensbidrag (refereegranskat)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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