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Electron beam freeform fabrication for cost effective near-net shape manufacturing

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Abstract

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF 3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF 3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF 3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm 3 /hr (150 in 3 /hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

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... Despite these sampling difficulties, overall, it is still clear that the grain structures were considerably finer than found in other high deposition rate processes [6], [7], [53], [54], and contained a high volume fraction of more equiaxed grains with a weaker/more random microtexture. As a result, neither the multi-track parallel, nor orthogonal lattice sample CEWAM β textures were anywhere near as strong as seen in these alternative processes, which are typically > 20 MRD. ...
... The strong <001>β || ND fibre texture and very coarse columnar β-grain structures normally found in Ti64 parts built with most current high deposition rate DED AM processes (e.g. Fig. 1) are frequently reported in the literature [6], [7], [53], [54] [6], [7], [19], [21], [22], [26], [50], [51]. Overall, all the samples studied produced by the CEWAM process had considerably finer primary β-grain structures and both a weaker β-solidification and α-transformation texture. ...
... It has previously been shown in most AM processes with Ti64 that the melt pool solidification conditions are located in the columnar region on the solidification diagram proposed by Kobryn and Semiatin [30], and subsequently widely used by numerous authors [2], [44], [55], [56]. An estimate of the power input relative to the volume of wire melted (Table 1) shows that the CEWAM process employs an energy density of 30 -40 J mm -3 and this is at the bottom end of the range typically used for WAAM that operates around 30 -60 J mm -3 , and other DED processes, such as the Sciaky electron beam AM process [6], use even higher power inputs. ...
Article
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High-deposition-rate, directed-energy-deposition additive manufacturing (DED-AM) processes typically produce Ti-6Al-4V (Ti64) components with coarse columnar β-grain structures that lead to undesirable mechanical anisotropy, as well as a fine heterogeneous lamellar transformation microstructure, which is very different to that seen standard wrought products. This arises because of the intrinsic lack of constitutional undercooling at the solidification front, and the subsequent high cooling rates and rapid thermal cycling experienced by the deposited material. In this work, the more refined primary β-grain solidification structures and textures seen in components built with the novel coaxial electron beam wire DED AM (CEWAM) process have been characterised in detail, for the first time, with the aim of investigating the potential for this technology to directly replicate the β-annealed damage-tolerant microstructure used in large Ti64 aerospace forgings. Due to its different lower energy density solidification conditions, it has been confirmed, by electron backscatter diffraction (EBSD) analysis and β-grain reconstruction in three orthogonal cross-sections, that the CEWAM process changes the melt conditions to promote β-grain nucleation ahead of the solidification front, which can result in a highly refined, equiaxed, β-grain structure. However, the conditions for refinement were marginal and a mixed grain structure was commonly observed in thicker sections. Additionally, the subsequent grain-growth stability during β-annealing was investigated. It is shown that an equivalent microstructure can be achieved to that seen in a standard β-forged component, by grain structure homogenisation and slow cooling through the β transus, to promote α colony nucleation, allowing direct part substitution. This was made possible by the refined primary β-grain structure achieved during deposition with the CEWAM solidification conditions which, importantly, are also shown to lead to a weaker texture than in a typical forging.
... Process design papers aim to into establish [Hirt et al., 1997, Chitkara and Bhutta, 1995, Chitkara and Kim, 1996, Jeon and Kim, 1999, Qi et al., 2010, Mamalis et al., 1998, Taminger and Hafley, 2006, optimize [Netto et al., 1996, Siegert et al., 1997, Kapranos et al., 2000, Kim et al., 2005b or enhance [Li, 1995, Kang et al., 2003, Dirba et al., 2014 process capabilities in terms of technological quality [Hirt et al., 1997, Chitkara and Bhutta, 1995, Chitkara and Kim, 1996, Li, 1995, Kang et al., 2003, Dirba et al., 2014, Kapranos et al., 2000, geometric capabilities [Chitkara and Kim, 2001, Chitkara and Bhutta, 1996, Jeon and Kim, 1999, Qi et al., 2010, Mamalis et al., 1998], workable material [Netto et al., 1996, Siegert et al., 1997, Taminger and Hafley, 2006 or waste reduction. Investigations are mainly empirical (experimental and case studies) and analytical [Chitkara and Bhutta, 1995, Chitkara and Kim, 2001, Jeon and Kim, 1999, Netto et al., 1996. ...
... Process design papers aim to into establish [Hirt et al., 1997, Chitkara and Bhutta, 1995, Chitkara and Kim, 1996, Jeon and Kim, 1999, Qi et al., 2010, Mamalis et al., 1998, Taminger and Hafley, 2006, optimize [Netto et al., 1996, Siegert et al., 1997, Kapranos et al., 2000, Kim et al., 2005b or enhance [Li, 1995, Kang et al., 2003, Dirba et al., 2014 process capabilities in terms of technological quality [Hirt et al., 1997, Chitkara and Bhutta, 1995, Chitkara and Kim, 1996, Li, 1995, Kang et al., 2003, Dirba et al., 2014, Kapranos et al., 2000, geometric capabilities [Chitkara and Kim, 2001, Chitkara and Bhutta, 1996, Jeon and Kim, 1999, Qi et al., 2010, Mamalis et al., 1998], workable material [Netto et al., 1996, Siegert et al., 1997, Taminger and Hafley, 2006 or waste reduction. Investigations are mainly empirical (experimental and case studies) and analytical [Chitkara and Bhutta, 1995, Chitkara and Kim, 2001, Jeon and Kim, 1999, Netto et al., 1996. ...
... Investigations are mainly empirical (experimental and case studies) and analytical [Chitkara and Bhutta, 1995, Chitkara and Kim, 2001, Jeon and Kim, 1999, Netto et al., 1996. The empirical ones focus on forming, particularly on enhancing and optimizing SSMC processes in terms of the techno-logical quality [Kapranos et al., 2000, Kang et al., 2003, Hirt et al., 1997 or for additive layer manufacturing processes establish workable materials [Taminger and Hafley, 2006] or geometric capabilities [Qi et al., 2010]. Analytical papers are focused on determining achievable geometries [Chitkara and Kim, 2001, Chitkara and Bhutta, 1996, Jeon and Kim, 1999] and technological quality Bhutta, 1995, Chitkara andKim, 1996] as well as optimizing workable materials [Netto et al., 1996] in forging process applications. ...
Thesis
Full-text available
The adoption of innovative Near Net Shape (NNS) manufacturing technologies can dramatically reduce costs and lead times in established manufacturing processes. However identifying candidate NNS processes and optimizing their implementation is frequently done in an adhoc manner without the benefits of a structured process of discovery and assessment. Motivated by the need for more robust assessment of potential NNS applications this thesis presents a methodology for selecting NNS manufacturing technologies and optimizing their implementation in established manufacturing processes. The literature review highlights a lack of systematic methodologies that support a holistic approach to assessing the impact of an NNS process (in terms of machining time and raw material consumption) on an established manufacturing chain. The methodology (known as the Near Net Shape Operative(NeNeShO) Protocol) is a three step pipeline that first creates a short-list of candidate processes, before selecting and, lastly, optimising the operational parameters. The first phase (Product Geometry, Manufacturing and Material Matching (ProGeMa3) is a quantitative methodology that selects a set of viable primary shaping process using a unique form of Process Selection Matrix (ProSMa), that associates processes with a range of materials and product geometry they can shape. ProGeMa3 ranks the candidate processes (using fuzzy logic) by their ability to achieve target product requirements (e.g. tolerances, mechanical properties) in relationship to current process capabilities. The second phase (Differential Cost and Feasibility Analysis - DFCA) ii combines technological feasibility (i.e. analytical, numerical or experimental approaches) and economic feasibility (theoretical, statistical derived, analogous cost models) to establish the ability of an NNS process to deliver the specified product requirements. The process models used in phase two are also applied in the third phase (Conditional Design Optimization - CoDeO) and, depending on the selected route, optimization algorithms (e.g. genetic algorithms) or statistical methods (e.g. Design of Experiment) are used to refine the implementation. Case study applications.
... The raster was done in a circular pattern with a frequency of 10 kHz. Heat input was calculated assuming 95% electron beam energy efficiency [17]. . . . . 71 Any phase change must be accompanied by a decrease in the free energy of the system in order for the phase change to proceed. ...
... EBF 3 provides many advantages to AM of aerospace components, including direct cost savings through EBF 3 -based repair, higher process efficiency, and better material performance through the fabrication of functionally graded microstructures. EBF 3 is a remarkably efficient process, achieving close to 100% efficiency in material consumption and 95% in energy efficiency [17]. EBF 3 is also capable of metal deposition rates of over 2450 cm 3 /hr [143]. ...
... 17: Intergranular misorientation map of the solid wire EBF 3 2 vol.% AD build. ...
Thesis
Full-text available
High-strength wrought aluminum alloys are extensively used in aerospace and automotive applications for their high strength-to-weight ratios. Further improvements to properties, including specific modulus, can be achieved by the introduction of discontinuous particulates into the Al matrix, creating a metal matrix composite (MMC). The introduction of particulates can also minimize the propensity for solidification cracking that certain Al alloys possess as a result of large solidification temperature ranges and high coefficients of thermal expansion. To overcome the limitations of conventional manufacturing processes, additive manufacturing (AM) of these alloys and MMCs is emerging as a promising solution to meet the demands of the aerospace and automotive industries. In this work, Al MMCs were created in situ via exothermic reaction synthesis powders that produce ceramic and intermetallic inoculant particulates. Powder-cored tubular wires (PCTWs) were made using the reaction synthesis powders to produce varying amounts of inoculant content during electron beam freeform fabrication (EBF3) AM deposition. The EBF3 materials were compared with builds produced by laser-powder bed fusion (L-PBF). The inoculant particulates significantly refined the microstructure of the AM materials, achieving mean grain diameters as small as 9 and 2 µm in EBF3 and L-PBF, respectively. Additionally, for both AM processes, the solidification morphology was shifted to an equiaxed grain structure, which was found to be more resistant to solidification cracking. XRD and TEM were used to identify the most potent inoculants present as TiB2, TiC, and Al3Ti. Percent density in the EBF3 materials was found to decrease with increasing inoculant content, which was attributed to nucleation of vaporized Mg on poorly wetted particles. Mechanical testing showed optimal impact toughness to occur at 2 vol.% inoculant, while the highest ultimate tensile strengths of 308±6 MPa and 368±2 MPa and Young's moduli of 86±0.2 GPa and 92.8±1.6 GPa were achieved at 10 vol.% inoculant for T6 heat treated solid wire EBF3 and L-PBF builds, respectively. These materials showed a marked improvement over the UTS of uninoculated EBF3 and L-PBF builds, which were 186±6 MPa and 35±3 MPa.
... This growth demonstrates the need to find solutions that are better suited for mass manufacturing rather than rapid prototyping. AM has significant potential in the medical field, particularly for custom designs, aerospace, and automotive for lightweight construction and functionally critical parts manufactured locally at distant locations [2,3]. However, uncertainties regarding component quality currently delay the full introduction of AM technology in these areas. ...
... Theoretical background on the convolutional neural networks is given in Sects. 3 ...
Article
Full-text available
Additive manufacturing of metal components with laser-powder bed fusion is a very complex process, since powder has to be melted and cooled in each layer to produce a part. Many parameters influence the printing process; however, defects resulting from suboptimal parameter settings are usually detected after the process. To detect these defects during the printing, different process monitoring techniques such as melt pool monitoring or off-axis infrared monitoring have been proposed. In this work, we used a combination of thermographic off-axis imaging as data source and deep learning-based neural network architectures, to detect printing defects. For the network training, a k-fold cross validation and a hold-out cross validation were used. With these techniques, defects such as delamination and splatter can be recognized with an accuracy of 96.80%. In addition, the model was evaluated with computing class activation heatmaps. The architecture is very small and has low computing costs, which means that it is suitable to operate in real time even on less powerful hardware.
... Additive manufacturing offers the potential to save significant amounts of energy and resources (Ref. 3,4) and overcome some limitations of traditional manufacturing methods such as casting, forging and machining. The use of the Plasma Arc welding process for additive manufacturing promises to produce low cost products from vitally important metal alloys (Ref. ...
... Vol. [2][3][4][5][6]2014 International Educative Research Foundation and Publisher © 2014 pg. 115 Deposit walls were built by placing individual weld layers were placed one atop the previous layer (Fig. 3). ...
Article
Full-text available
Additive manufacturing has the potential to produce near-net shape parts directly from weld metal. Prior work has proved that it is possible to directly manufacture components with complex geometric features and with good productivity. However, under high productivity conditions, deposit temperature increases to a level that it is no longer possible to develop appropriate deposit microstructure and therefore mechanical properties. In this study, Plasma Arc welding was used to produce experimental deposits of 1018 low carbon steel under various conditions. An analytical heat flow model was developed to study the influence of interlayer wait time on deposit temperature and therefore grain size and hardness. The results of the model indicated that as wall height increased, the rate of deposit heat removal by conduction to the substrate decreased leading to a higher preheat temperature after a fixed interlayer wait time causing grain size to increase as wall height increased. However, the model results also show that as wall height increased, the deposit surface area from which heat energy is lost via convection and radiation increased. The model also demonstrated that the use of a means of forced convection to rapidly remove heat from the deposit could be an effective way to boost productivity and maintain smaller grain size and therefore higher hardness and strength in the deposit.
... This includes the presence of α allotriomorphs on the β GBs and an associated single variant 'colony' α GB layer, along with multi-variant α colonies forming in the matrix (the so-called basket weave microstructure) [30] that have a restricted set of variant orientations (typically three) related by the BOR to their parent β grain. Furthermore, the high temperature gradients and multiple thermal cycles experienced during deposition can lead to additional microstructural variation [19,21,[23][24][25][26][27][31][32][33][34]. With sequential deposition passes in AM, each layer experiences a complex cyclic thermal history that can result in systematic variation in the local microstructural parameters. ...
... With sequential deposition passes in AM, each layer experiences a complex cyclic thermal history that can result in systematic variation in the local microstructural parameters. In particular, heat affected zone (HAZ) 'bands', with a regular spacing equivalent to the layer height, are commonly observed in wire-based AM processes [19,21,[23][24][25][26][27][31][32][33][34]. The microstructure divergence in the HAZ band regions results from re-heating to temperatures below the β transus, but within the β approach curve, where substantial coarsening of α can occur [15]. ...
Article
Full-text available
Ti–6Al–4V microstructures produced by high deposition rate Wire Arc Additive Manufacturing (WAAM) can be both heterogeneous and anisotropic. Key features of the as-built microstructures include; large columnar ß grains, an α transformation texture inherited from the β solidification texture, grain boundary (GB) α colonies, and Heat Affected Zone (HAZ) banding. The effect of this heterogeneity on the local strain distribution has been investigated using Digital Image Correlation (DIC) in samples loaded in tension; parallel (WD), perpendicular (ND) and at 45° (45ND) to the deposited layers. Full-field surface strain maps were correlated to the underlying local texture. It is shown that loading perpendicular to the columnar β grains leads to a diffuse heterogeneous deformation distribution, due to the presence of regions containing hard, and soft, α microtextures within different parent β grains. The ‘soft’ regions correlated to multi-variant α colonies that did not contain a hard α variant unfavourably orientated for basal or prismatic slip. Far more severe strain localisation was seen in 45° ND loading at ‘soft’ β grain boundaries, where single variant α GB colonies favourably orientated for slip had developed during transformation. In comparison, when loaded parallel to the columnar ß grains, the strain distribution was relatively homogeneous and the HAZ bands did not show any obvious influence on strain localisation at the deposit layer-scale. However, when using high-resolution DIC, as well as more intense shear bands being resolved at the β grain boundaries during 45° ND loading, microscale strain localisation was observed in HAZ bands below the yield point within the thin white-etching α colony layer.
... The process was termed electron beam freeform fabrication (EBF 3 ) and was commercialized as a method for rapid metal deposition (Taminger and Hafley, 2003). Figure 1 shows a schematic of the primary components in an EBF 3 system based on Taminger and Hafley (2006). ...
... The EBF 3 technique has drawn a great deal of attention in the AM field, as it can work efficiently with a variety of weldable alloys, including any electrically conductive materials, even highly reflective alloys (Taminger and Hafley, 2006). The EBF 3 process can fabricate timely and cost-effective parts with complex shapes. ...
Article
Full-text available
Purpose The purpose of this study is to simulate the temperature distribution during an electron beam freeform fabrication (EBF ³ ) process based on a fully threaded tree (FTT) technique in various scales and to analyze the temperature variation with time in different regions of the part. Design/methodology/approach This study presented a revised model for the temperature simulation in the EBF ³ process. The FTT technique was then adopted as an adaptive grid strategy in the simulation. Based on the simulation results, an analysis regarding the temperature distribution of a circular deposit and substrate was performed. Findings The FTT technique was successfully adopted in the simulation of the temperature field during the EBF ³ process. The temperature bands and oscillating temperature curves appeared in the deposit and substrate. Originality/value The FTT technique was introduced into the numerical simulation of an additive manufacturing process. The efficiency of the process was improved, and the FTT technique was convenient for the 3D simulations and multi-pass deposits.
... The buy-to-fly ratio of typical aerospace machined components may range from 10:1 to 20:1. In contrast, AM can significantly reduce material waste and the consequent total manufacturing costs of expensive materials compared to traditional processing routes [16]. AM technology, in particular SLM, has shown the capability to produce complex components in their net or near-net shapes with little machining required to be put into service [16]. ...
... In contrast, AM can significantly reduce material waste and the consequent total manufacturing costs of expensive materials compared to traditional processing routes [16]. AM technology, in particular SLM, has shown the capability to produce complex components in their net or near-net shapes with little machining required to be put into service [16]. ...
Article
Full-text available
Due to its vast benefits, Additive Manufacturing (AM) has attracted a great deal of attention during the last two decades. Selective Laser Melting (SLM) is one of the most increasingly used AM techniques in the world. The machinability of SLM-manufactured Ti6Al4V parts in as-built (SLM-AB) and stress-relief (SLM-SR) conditions was studied in this work via toroidal milling. A conventional processed Ti6Al4V alloy was tested as a reference. SLM process parameters for producing near fully dense parts were optimized to yield a volumetric energy density of 46.4 J/mm³. Relative density, microstructure, hardness, residual stresses, surface roughness, cutting forces, tool wear, and chip morphology were evaluated. The SLM-manufactured parts gave a relative density of 99.70 % and higher hardness values than those of the conventional parts by a factor of about 1.2. The conventional, SLM-AB, and SLM-SR Ti6Al4V alloys exhibited microstructures consisting of α and β phases, acicular α′ martensite, α′ martensite and some amounts of α + β phases, respectively. The conventional alloy had the lowest residual stress. SLM-AB had considerable residual tensile stress in the 0° direction of measurement, whereas SLM-SR had the highest compressive stress in both 0° and 90° directions. The lowest cutting force was observed in the conventional alloy and the highest in the SLM-SR alloy. The SLM-AB alloy featured the highest flank wear. However, no significant difference in flank wear was observed in the conventional and SLM-SR alloys.
... New and existing material are combined in a melt pool by a focused electron beam, undergoing a temperature increase of O(10 3 ) K/s and decrease of over 10 4 K/s [30], resulting in rapid solidification. The combination to prevent dissipation of the e-beam lead this process to achieve nearly 100% material efficiency and 95% energy efficiency [29]. The use of different wire diameters allows the creation of fine details and/or bulk deposition, while the overall size of the component is bound by the dimensions of the vacuum chamber. ...
... ELECTRON BEAM FREEFORM FABRICATION (EBF3) SCHEMATIC. REPRINTED FROM[29] ...
Conference Paper
This paper discusses the design of axisymmetric structures with self-supporting features that can be additively manufactured without requiring internal support structures. This is motivated by wire-fed additive manufacturing processes, many of which can fabricate designs with enclosed pores that inherently exist in many axisymmetric structures, such as double walled pressure vessels. Although enclosed pores are possible, features that rise at shallow angles from the build plate typically cannot be fabricated without the use of support structures, which require removal and thus are unfavorable in such applications. In this paper, an overhang constraint is applied to ensure that all designed features rise at a designer-prescribed self-supporting angle to eliminate the need for such support structures. This is achieved by coupling the projection-based overhang constraint approach with topology optimization and axisymmetric finite elements whose stiffness is interpolated using Solid Isotropic Material with Penalization (SIMP). Gradients are computed with the adjoint method and the Method of Moving Asymptotes (MMA) is employed as the gradient-based optimizer. Two numerical examples related to a canonical pressure vessel and an optical mirror support structure are used to demonstrate the approach. Solutions are shown to satisfy minimum feature size requirements and designer-prescribed (process dependent) overhang constraint angles, while providing clear and crisp representations of topology. As observed in past works on overhang constraints, a clear trade-off is illustrated between the magnitude of the overhang constraint angle and the structural performance (mass or stiffness), with more strict requirements producing designs with lower performance.
... feeding rate is directly related to the speed of the carrier gas, the geometry of the nozzle and the properties of the powder [18,31]. An increased print speed is the outcome of high material feed rates which lead in a rapid construction of the product, but could potentially result to the reduced quality of the final object as explained in the next section [32,33]. ...
... In general, DED procedures possess inferior surface quality compared to powder-feed procedures. In particular, there are many articles which declare that the surface roughness could rise even up to ten times higher [31,45]. As mentioned in Table 5, the feeding orientation and feeding angle are two essential factors that affect the quality of a printed part. ...
Article
Full-text available
Metal additive manufacturing (AM) has been recently acknowledged as a method to produce metal parts with complex geometries and unique characteristics. In general, metal AM components are used in applications where enhanced mechanical properties are required; thus it is essential to optimize the parameters that affect the metal AM processes. The immense advantages of metal AM technologies in the fields of production and manufacturing placed these technologies in the forefront of scientific sectors relevant to engineering, biomedical science and electronics. In recent years, many studies have been published analyzing the parameters which influence metal AM techniques to achieve advanced overall quality and optimized mechanical behavior of the fabricated products. Existing research has individually studied the influence of various factors on metal AM methods such as feedstock material properties, build orientation, printing conditions, infill patterns and post-processing procedures. The present study aims to review the research carried out until today identifying and classifying all parameters affecting metal AM, based on their impact on the quality of the final product. This survey intents to establish a process map of the categories which influence metal AM components. Additional recommendations, research gaps and directions towards the improvement of metal AM are also provided.
... Bu yöntemle, ortopedik implantlar, uçak parçaları, türbin kanatları gibi parçalar üretilmektedir. [42][43][44]. ...
... Large-Scale Additive Manufacturing (LSAM) technologies aimed at fabrication industrial large-scale component blanks have been a subject of keen interest in recent years. Among LSAM methods, Wire-feed Electron Beam Additive Manufacturing (EBAM) (also referred to as Electron Beam Free Form Fabrication, EBF 3 ) is one of the most prospective technologies [18,19]. The key benefits of wire-feed EBAM (being a type of direct energy deposition techniques) are extremely high deposition rates (up to 2500 cm 3 /h) and nearly 100% efficiency in feedstock consumption. ...
Article
Comparison of the microstructure and the phase composition of the Ti-6Al-4V alloy parts built by various additive manufacturing technologies was carried out by optical and transmission scanning electron microscopy, as well as X-ray diffraction analysis. It was shown that the martensitic αʹ phase, formed due to the melt pool fast cooling rate, determined the accommodation mechanisms of shear deformation of the as-built Ti-6Al-4V AM fabricated samples under uniaxial quasi-static tension and impact bending (and, accordingly, their mechanical properties). The effect of microstructure on impact toughness, ultimate impact strength, as well as the crack initiation and propagation energy was investigated by the impact bending tests with recording impact load diagram (force–displacement graph). It was concluded that impact toughness of the Ti-6Al-4V samples built by wire-feed electron beam additive manufacturing was significantly higher than that of ones manufactured by selective laser melting and electron beam melting of a powder. Matching the mechanical properties and SEM micrographs of the fracture surfaces of the as-built Ti-6Al-4V AM fabricated samples enabled to reveal the crack initiation and propagation mechanisms during their quasi-static and dynamic loading. Discussion of the results was carried out using the concept of scale levels of plastic deformation.
... Schematics for each process are shown in Figure 1. EBF 3 is a wire-fed AM process developed by NASA-Langley Research Center (LaRC) that uses an electron beam to maintain a molten pool into which the wire feedstock is deposited [20]. Conversely, L-PBF uses a powder feedstock that is raked in from a reservoir into the powder bed containing the component that is consolidated using a laser beam. ...
Article
Full-text available
In this work, aluminum 6061-based powder blend feedstocks with reactive Ti-B/C additions were employed in two different additive manufacturing processes, laser powder bed fusion (L-PBF) and electron beam freeform fabrication (EBF3), to create micro- and nanoscale ceramic and intermetallic inoculants in situ and to examine the effect of feedstock inoculant content on microstructure and mechanical properties. Products of the reaction synthesis process were identified with X-ray diffraction and energy-dispersive spectroscopy to include Al3Ti, TiC, and TiB2. Electron back-scatter diffraction revealed significant grain refinement up to 74×, mitigation of solidification cracking, and formation of an equiaxed grain structure with the addition of just 2 vol.% inoculant. Inoculants formed in situ were seen to induce approximately 5× more grain refinement than pre-existing inoculants. The highest ultimate tensile strength and Young’s modulus of 368 ± 2 MPa and 92.8 ± 1.6 GPa, respectively, were achieved at 10 vol.% inoculant in the L-PBF process. Strengthening mechanism calculations and the tensile data suggest a higher strengthening contribution via modulus mismatch and Orowan strengthening from the particles created by reaction synthesis than from Hall–Petch strengthening through grain refinement.
... Nowadays, AM technology used for not only prototyping but also small batch production with improved repeatability and reliability. According to the Wohlers Report, the market of AM manufactured parts has grown to $2.9 bn as compared to $2.1 bn in 2016 [2]. In recent years, growing demand for AM parts pushed for industrial development for better quality assurance and monitoring of the process. ...
Article
Direct metal laser sintering, an additive manufacturing technique, has a huge growing demand in industries like aerospace, biomedical, and tooling sector due to its capability to manufacture complex parts with ease. Despite many technological advancements, the reliability and repeatability of the process is still an issue. Therefore, there is a demand for in‐line automatic fault detection and post‐processing tools to analyze the acquired in‐situ monitoring data aiming to provide better quality assurance to the user. This study focuses on the treatment of the data obtained using the EOSTATE Optical Tomography monitoring system. A balanced dataset is obtained with the help of computer tomography of the certified part (Stainless Steel CX cylindrical samples), through which a feature matrix is prepared, and the layers of the part are classified either having “Drift” or “No‐drift”. The model is trained with the feature matrix and tested on benchmark parts (Maraging Steel) and on an industrial part (knuckle, automotive part) manufactured in AlSi10Mg. The proposed semi‐supervised approach shows promising results for presented case studies. Thus, the semi‐supervised machine learning approach, if adopted, could prove to be a cost‐effective and fast approach to post‐process the in‐situ monitoring data with much ease. This article is protected by copyright. All rights reserved.
... d) A large structure manufactured by WAAM from Cranfield University [56]. e) 2219 Al airfoil produced by DED [57]. f) As-deposited sample made by wire-feed LAM (AeroMet) with "stair stepping" surfaces and g) shows the sample after surface machining [52] 11 1 State of the art ...
Thesis
This thesis was dedicated to the study of 316L stainless steel additively manufactured or repaired specimens by Directed Energy Deposition (DED). Different configurations were manufactured under optimal process parameters. The novelty of this work is the observation of the microstructural strain localization. This experiment combined an in situ tensile test inside a scanning electron microscope with high resolution digital image correlation and an electron backscatter diffraction map. These results allowed for a fresh interpretation of monotonic tensile tests as well as of self-heating experiments under cyclic loading and the failure patterns observed at the surface of specimens. The first objective was to understand the deformation mechanisms at the grain scale which could explain the observed macroscopic anisotropy of the tensile properties as reported in literature. Two loading directions, along and perpendicular, were considered with respect to the printing direction for fully printed specimens. We observed that for a tensile load perpendicular to the printing direction, the strain localization is mainly situated at some interlayers. For a tensile load along the printing direction, the strain localization was observed in some particular regions of large grains. The second objective was the assessment of DED as a repair technology. Dog bone shaped repaired specimens (half hot rolled sheet and half printed) were designed and they exhibited an important hierarchical microstructural gradient. We noticed that the interface is not a weak area during a monotonic tensile test. Moreover, while homogeneous strain was observed in the substrate half, the printed half showed a strain heterogeneity, with the highest localization found at some interlayers. An unstrained zone was observed at both sides of the interface and was associated with higher hardness. The last objective was to evaluate the fatigue properties by self-heating tests. The experiment has proven that the difficulties due to the small dimensions of the single-track thickness specimens can be overcome by careful construction of the experimental set-up. The results revealed a certain correlation between the pattern of the microstructure, the deformation pattern at this scale and the self-heating results. Anisotropy was highlighted during these cyclic tests where specimens tested perpendicularly to the printing direction showed higher fatigue limits in comparison to the ones tested along the printing direction. Post mortem analysis revealed a multitude of cracks at interlayers for the specimens tested perpendicularly to the printing direction creating several sites of heat diffusion. For the specimens tested along the printing direction, a more classical fatigue scenario was observed with one dominating crack and thus a localized heat dissipation.
... Direct energy deposition additive manufacturing (AM) processes, like wire-arc AM (WAAM) with titanium alloys such as Ti-6Al-4V (Ti64), have been the focus of recent research due to their high deposition rate and ability to produce near-net-shape components with size envelopes of several metres [1][2][3][4][5][6][7][8] . However, in Ti64 WAAM under standard conditions, epitaxial growth during solidification typically produces cm-long columnar grains, with a < 001 > fibre texture, which can sometimes extend throughout the entire build height [6 , 9-14] . ...
Article
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The coarse columnar β grains in Ti-6Al-4V WAAM can be refined by relatively low strain inter-pass deformation. Simulation, with rapid heating, has shown this may partly occur by a novel recrystallization mechanism that involves twinning during β regrowth through the α-β transus, as a result of the prior deformation promoting faults in the α-β interface, which produces a unique micro-texture in each parent β grain. Here, this potential mechanism has been investigated further, using a different deformation mode – uniaxial tensile deformation rather than plane-strain compression – to enable the texture contribution from conventional recrystallization to be more unambiguously discriminated. The tensile-deformed samples are shown to produce the same unusual unique micro-texture seen previously, at low strains, despite the different deformation mode, but this disappeared at higher strains, which provides more evidence in support of this new rapid heating β recrystallization mechanism.
... The specific details were to place the printer horizontally (perpendicular to the direction of gravity) and inverted (opposite to the direction of gravity) to print the product that the same as the normal one [2]. In 2002, it developed the second generation electron beam free forming (EBF3) system which realizes the microgravity manufacture of titanium, nickel, aluminum, and other metals [3,4]. In 2014, Made In Space installed a 3D printer in the International Space Station and used molten deposition technology to print plastic parts. ...
... The main advantages of the additive manufacturing are related to reduced material consumption and shorter production times due to obtaining the reduced allowances for machining. Depending upon the type of an energy source mainly used for melting the metallic materials, the AM is classified into laser- [9][10][11], arc- [12,13], or electron beam-based [14][15][16][17][18] processes. An alternative classification may be based on the type of source material used such as powder or wire. ...
Article
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Electron beam wire-feed additive manufacturing is given less attention in research community compared with other additive manufacturing methods, despite it allows higher deposition rate and less porosity. However, both gas and shrinking porosity are still met even with this method especially if applied to light alloys. The excess heat input may be the reason for evaporation of volatile metals, and forming the gas pores especially in the top layers of the built sample where cooling rate is reduced. Therefore, exponential decay heat input was used to grow AA5356 samples. Microstructural and mechanical characterization of the samples obtained at mean low, medium, and high heat input levels was carried out. An optimal heat input gradient was determined which allowed growing a defect-free metal in the bottom part of the sample and forcing out the shrinkage cavities to the top part. Shrinkage and gas pore structure formation was analyzed as a function of the heat input gradient and along the building direction. Gas pores resulted at two higher heat input regimes as a result of evaporation of magnesium as supported by the results of EDS and XRD. Tensile test showed the ultimate strength of the defect-free part equal to that of the base AA5356.
... Wire-fed, high power (> 2 kW) directed energy deposition (DED) AM processes are capable of efficiently producing parts with kilogram-per-hour deposition rates and build envelopes of several metres, which makes these processes particularly attractive for the manufacture of larger-scale aerospace components [3]. Such processes employ lasers [4], electron beams [5,6], or arc-plasma welding torches [7][8][9][10][11][12], as directed energy heat sources to deposit layers 1-2 mm thick. However, because of the larger melt pool dimensions, the solidification and cooling rates are considerably lower (< 10 2°C s −1 ) than experienced in powder bed technologies (10 4-5°C s −1 ) [13][14][15][16][17] and as a consequence, components produced by high deposition rate DED can suffer from more severe microstructural heterogeneity and mechanical anisotropy [7,14,18]- [27]. ...
Article
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Relatively low levels of inter-pass deformation have been found to be very effective in refining the coarse columnar grain structures normally seen in Ti-6Al-4V components, built using wire-fed high-deposition-rate additive manufacturing processes. The most important process parameters that control the level of β recrystallization – the final grain size and micro-texture – were systematically investigated by simulating the deformation and high heating rate conditions in controlled samples, to develop the process knowledge required to optimise inter-pass deformation and obtain predictable grain sizes. Overall, it was found that the level of β-grain refinement achieved by inter-pass deformation was surprisingly insensitive to the ranges of deformation temperatures, deformation speeds, and changes to the as-deposited α + β microstructure, expected within the WAAM process window, provided a minimum plastic strain of only 14% was achieved in each added layer. Conversely, the final component grain size was shown to be strongly affected by rapid grain growth on re-heating above the β transus. The texture results obtained were consistent with previous work which suggested that, with fine AM transformation microstructures, new β-grain orientations may be produced during the α → β transformation from the development of twinning faults, induced by the prior deformation and rapid heating. In contrast, greatly increasing the starting α lamellar spacing – to be more similar to that found in a wrought material – greatly reduced the level of recrystallization and also appeared to change the recrystallization mechanism to favour new β orientations produced largely by local lattice rotation.
... Directed energy deposition (DED) wire-fed AM processes are suitable for such applications because of their high material efficiency and productivity [2À4]. Wire-based processes under development include; laser [5] and E-beam based technologies (NASA, Sciaky TM [6,7]), and Wire-Arc Additive Manufacturing (WAAM) (e.g., Cranfield University, Norsk Titanium [8À12]). All of these processes employ a directed heat source and have melt pool sizes 2À10 mm wide, with a layer height of 1À2 mm [3À10,13]. ...
Article
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Additive Manufacture (AM) of Ti–6Al–4V frequently leads to undesirable, coarse, columnar β-grain structures with a strong <100> fibre texture. In Wire-Arc AM (WAAM), it has been found that the application of a low plastic strain, by methods such as inter-pass rolling, can disrupt β columnar growth and produce a refined, equiaxed grain structure that is more randomly orientated. The origin of this desirable effect has been investigated by thermo-mechanical simulation, direct in-situ EBSD observation, as well as by real-time synchrotron X-ray diffraction (SXRD) during rapid heating. These complementary approaches have shown that, when starting with a WAAM microstructure, the grain refinement process produces a unique micro-texture represented by a four-pole motif symmetrically centred on the parent grain {100} orientations. These new β-grain orientations can be reproduced by a double {112}<111> twinning operation, which produces 12 new, unique, β-orientation variants. High-resolution orientation-mapping techniques and in-situ SXRD heating simulations suggest that the prior β does not twin during deformation, but rather the grain refinement and related texture may be caused by annealing twinning during β re-growth on rapid re-heating of the deformed AM microstructure. Although this is the first time such a unique texture has been observed in a deformed and β annealed Ti–6Al–4V material, it was only found to dominate under the unusual conditions that occur in AM of rapid heating – a fine, lightly deformed α transformation microstructure, with a very coarse starting β-grain structure.
... Analogue to the general accepted acronym WAAM for Wire Arc Additive Manufacturing it is suggested to use WEBAM in the case of electron beam. In first reports by NASA this technology was called Electron Beam Freeform Fabrication (EBF 3 ) [3,4], an expression not implemented in the last 20 years by the DED community. ...
Conference Paper
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Wire Electron Beam Additive Manufacturing (WEBAM) facilitates great opportunities to provide semi-finished products of certain materials, where other additive manufacturing technologies experience great challenges. The advantages of WEBAM are related to the specific properties and capabilities of the electron beam, and to the operation in a high vacuum. An overview of the WEBAM activities at pro-beam with different geometries and a variety of materials such as titanium, stainless steel, Inconel and copper is shown.
... The vacuum chamber size is 1 m 3 and the maximum part size possible is 300 Â 300 Â 150 m 3 . The power of the beam is 2-3 kW, 15 kV (Taminger and Hafley, 2006). 5.2.3.2 ...
Article
Purpose Electron beam-based additive manufacturing (EBAM) is an emerging technology to produce metal parts layer-by-layer. The propose of this paper is to systematically address the research and development carried out for this technology, up till now. Design/methodology/approach This paper identifies several aspects of research and development in EBAM. Findings Electron beam has several unique advantages such as high scanning speed, energy efficiency, versatility for several materials and better part integrity because of a vacuum working environment. Originality/value This paper provides information on different aspects of EBAM with the current status and future scope.
... Wire-feed AM can also be classified into different processes depending on how the metal is disposed (Karunakaran, Suryakumar, Pushpa, & Akula, 2010). It has higher material usage efficiency and faster disposal rate than the powder-feed process which means waste is reduced in the process and the risk of using powder metals is eliminated (Taminger & Hafley, 2006). In addition, wires are less costly than powder. ...
Article
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At a time when construction projects are increasing in complexity and costs are constantly rising, 3D concrete printing have emerged as a revolutionary technology in construction. However, reinforcing 3D printed concrete elements has posed technical issues in research and practice. This paper introduces a methodology for 3D printing nonstandard steel rebar shapes together with 3D concrete printing. The new process can revolutionize the construction industry's approach to reinforced concrete design, as it provides a high degree of flexibility in both concrete and steel free-form creation, which is a key difference from traditional methods that only utilize standard steel reinforcement shapes. In addition, the proposed method will provide an even higher degree of automation in the concrete 3D printing construction process. An agent based model using Any Logic © was developed to simulate and optimize the printing of retaining and shear walls for a floor in a reinforced concrete building. Results show the optimization ratios of steel printing heads to concrete printing heads using the current technology and promise significant reductions in time and cost while providing a cleaner, safer, more automated, and an unbounded construction process. Findings from this research call for an in-depth investigation of the capabilities of steel 3D printing and its utilization in construction. It also highlights the importance of considering the application of new construction tools that would cope with the rapid growth of computational capabilities, and their adoption in design practices.
... Bu yöntemle, ortopedik implantlar, uçak parçaları, türbin kanatları gibi parçalar üretilmektedir. [42][43][44]. ...
Article
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ÖZET: Eklemeli üretim, bir 3B CAD modelinin, malzemenin tabakalar halinde birleştirilerek fiziksel bir parçaya dönüştürüldüğü üretim işlemidir. Eklemeli üretim son yıllarda oldukça önem kazanmış ve gelecekte daha çok hayatımızda rol alması beklenen son derece önemli bir teknolojidir. Eklemeli üretim, günümüzde otomotiv, havacılık, uzay, sağlık-inşaat sektörleri, enerji gibi alanlarda devrim yaratmış bir yöntemdir. Dolayısıyla, eklemeli üretim teknolojisini anlayabilmek günümüz için oldukça stratejik bir konudur. Bu çalışmada, eklemeli üretime ait genel bilgi verilmiş ve günümüzde en fazla ticari olarak kullanılan eklemeli üretim yöntemleri anlatılmıştır. Çalışmada ayrıca, eklemeli üretimin kullanım alanlarından bahsedilerek, gelecekteki potansiyeli değerlendirilmiştir. Anahtar kelimeler: Eklemeli üretim (EÜ), Üretim yöntemleri, Eklemeli üretim yöntemleri, Eklemeli üretimin kullanım alanları, Eklemeli üretimin geleceği ABSTRACT Additive manufacturing is a manufacturing process in which a 3D CAD model is combined into the layer by layer and converted into a physical part. Additive manufacturing has gained considerable importance in recent years and is an extremely important technology that will play a role in our lives in the future. Additive manufacturing is a revolutionary method in the automotive, aerospace, health and construction sectors, energy and more. Therefore, understanding of additive manufacturing technology is a very strategic issue for today. In this study, general information about additive manufacturing is given and the most commercially used additive manufacturing methods are explained. Then, the usage areas of additive manufacturing are mentioned and its future potential is evaluated.
... These weld beads can then be stacked laterally and vertically to fabricate a 3D metal component. Using wire instead of powder has several advantages, which include higher deposition rates [Taminger and Hafley (2006) reported values up to 330 g/min for stainless steel], efficient material use (because nearly 100 per cent of the wire can be potentially used) and ease of wire production resulting in relatively lower material costs. However, there is often a trade-off between deposition rate and dimensional accuracy, and parts produced using wire-feed AM generally have lower accuracy as compared to powder bed processes that limit applicability to fabricating large parts with moderate complexity. ...
Article
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Purpose Using wire as feedstock has several advantages for additive manufacturing (AM) of metal components, which include high deposition rates, efficient material use and low material costs. While the feasibility of wire-feed AM has been demonstrated, the accuracy and surface finish of the produced parts is generally lower than those obtained using powder-bed/-feed AM. The purpose of this study was to develop and investigate the feasibility of a fine wire-based laser metal deposition (FW-LMD) process for producing high-precision metal components with improved resolution, dimensional accuracy and surface finish. Design/methodology/approach The proposed FW-LMD AM process uses a fine stainless steel wire with a diameter of 100 µm as the additive material and a pulsed Nd:YAG laser as the heat source. The pulsed laser beam generates a melt pool on the substrate into which the fine wire is fed, and upon moving the X–Y stage, a single-pass weld bead is created during solidification that can be laterally and vertically stacked to create a 3D metal component. Process parameters including laser power, pulse duration and stage speed were optimized for the single-pass weld bead. The effect of lateral overlap was studied to ensure low surface roughness of the first layer onto which subsequent layers can be deposited. Multi-layer deposition was also performed and the resulting cross-sectional morphology, microhardness, phase formation, grain growth and tensile strength have been investigated. Findings An optimized lateral overlap of about 60-70% results in an average surface roughness of 8-16 µm along all printed directions of the X–Y stage. The single-layer thickness and dimensional accuracy of the proposed FW-LMD process was about 40-80 µm and ±30 µm, respectively. A dense cross-sectional morphology was observed for the multilayer stacking without any visible voids, pores or defects present between the layers. X-ray diffraction confirmed a majority austenite phase with small ferrite phase formation that occurs at the junction of the vertically stacked beads, as confirmed by the electron backscatter diffraction (EBSD) analysis. Tensile tests were performed and an ultimate tensile strength of about 700-750 MPa was observed for all samples. Furthermore, multilayer printing of different shapes with improved surface finish and thin-walled and inclined metal structures with a minimum achievable resolution of about 500 µm was presented. Originality/value To the best of the authors’ knowledge, this is the first study to report a directed energy deposition process using a fine metal wire with a diameter of 100 µm and can be a possible solution to improving surface finish and reducing the “stair-stepping” effect that is generally observed for wires with a larger diameter. The AM process proposed in this study can be an attractive alternative for 3D printing of high-precision metal components and can find application for rapid prototyping in a range of industries such as medical and automotive, among others.
... Traditional manufacturing methods typically include subtractive procedures such as milling, which wastes a lot of material, or precision casting (lost wax method), which takes a long time and costs a lot of money [1,2]. AM methods, which were first introduced as a tool for the rapid prototyping of industrial components, have acquired substantial traction in recent years for commercial fabrication [3][4][5]. When adopting AM technologies for the small-volume manufacturing of filigree components, the fundamental principle of three-dimensional component manufacturing using an input CAD model enables great design freedom [6]. ...
Article
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One of the fundamental challenges in L-PBF of filigree geometries, such as aortic stents used in biomedical applications, is the requirement for a robust yet easily removable support structure that allows each component to be successfully fabricated without distortion. To solve this challenge, an integrative experimental approach was attempted in the present study by identifying an optimal support structure design and an optimized support removal strategy for this design. The specimens were manufactured using four different support structure designs based on the geometry exposed to the laser beam during the L-PBF. Support removal procedures included sand blasting (SB), glass bead blasting (GB), and electrochemical polishing (ECP). The two best-performing designs (line and cross) were chosen due to shorter lead times and lower material consumption. As an additional factor that indicates a stable design, the breaking load requirement to remove the support structures was determined. A modified line support with a 145° included angle was shown to be the best support structure design in terms of breaking load, material consumption, and manufacturing time. All three procedures were used to ensure residue-free support removal for this modified line support design, with ECP proving to be the most effective.
... The maximum size of EBAM-fabricated samples is limited only by the size of the vacuum chamber. The most distinctive feature of EBAM is that this method combines extremely high deposition rates with very little material waste [4]. There is also the opportunity to use dual material suppliers to increase the efficiency of the EBAM process [5]. ...
Article
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The inferior mechanical properties of EBAM Ti-6Al-4V samples are due to the coarse columnar grains containing coarse lamellar structures. One can expect that water cooling of the build platform will increase the cooling rate of the molten pool during the build-up process, causing microstructure refinement. In the present work, the substrate cooling effects on the microstructure and phase composition of EBAM Ti-6Al-4V samples are studied using optical, scanning electron, and scanning transmission microscopy, as well as X-ray diffraction analysis. It is shown that the microstructure of the EBAM Ti-6Al-4V samples built on the substrate without water cooling consists predominantly of columnar prior β grains with lateral sizes ranging up to 2000 µm, while cooling of the build platform causes the appearance of equiaxed prior β grains measuring 1000 µm. Moreover, the refinement of the martensite structure and the precipitation of α″ martensite platelets within a laths occur in the EBAM Ti-6Al-4V samples built on the water-cooled build platform. An explanation of the mechanisms underlying the α′→α + β and α′→α + α″ + β transformations during the building process is provided based upon ab initio calculations. The fragmentation of the a laths under the residual compressive stresses is discussed.
... The AM, formerly known as 3D printing or rapid prototyping, has been used for a few decades. Nowadays industries like aerospace, automotive, defence and medical are showing an increasing demand for applying this technology to make their products [29,30,31,32]. ...
Thesis
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Nowadays, titanium alloys are widely used in a variety of industries like automotive and aerospace due to their high strength to weight ratio. Ti-5%Al-5%V-5%Mo-3%Cr is a metastable near beta titanium alloy with excellent fatigue performance and corrosion resistance. Hence, it is mainly used in the airframe structure and the landing gear components. As the additive manufacturing (AM) industry grows everyday, so does the interest in printing of strategic Titanium alloys. Selective Laser Melting (SLM) is a powder-bed fusion process utilizing the laser power as the heat source which scans over a compact powder layer along a pre-de fined path. In this study, the printability of Ti-5553 by pulsed-laser SLM is investigated, thoroughly. To this end, a batch of powder was first characterized in terms of size distribution, porosity level, chemical composition and microstructure. Afterwards, the effect of Volumetric Energy Density (VED), sample geometry and scanning strategy was evaluated on the microstructure and properties of the printed parts. Various tests such as Archimedes method, Nano-CT scanning, surface roughness, Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Electron backscattered diffraction (EBSD) and hardness mapping were applied. Results showed that the virgin plasma-atomized powder had a high quality with a mean sphericity of 0.95 and porosity of less than 0.01%. In addition, it was observed that there was an optimized VED range leading to a nearly fully dense part, i.e. 99.7%, with a smooth surface. Low and High VEDs resulted in a lack of fusion and spattering, respectively, both undermining the density of the printed parts. Moreover, high VEDs provided the energy required for the beta to alpha transformation and caused in-situ precipitation hardening. This in-situ heat treatment is not desired due to the lack of homogeneity. Furthermore, the sample geometry, i.e. cubic or cylindrical, was determined to have negligible effects on the achieved properties while the choice of scanning strategy directly affected the texture and density of the printed parts. It was seen that the chessboard, stripes and total ll strategies led to the optimized, medium and poor properties, respectively. Finally, the best density of 99.94% was achieved by using the VED of 112 J/mm3 and the chessboard scanning strategy. The sample showed a homogeneous hardness distribution with an average of 295 ±10 HV. The TEM analysis determined that the sample was in the beta to omega phase transformation stage. Also, it had a columnar grain structure elongated parallel to the building direction indicating a highly crystallographically textured part. The EBSD analysis supported these fi ndings by suggesting a preferred growth direction with crystal texture seven times higher than the random intensity. The melt pool shape of the optimized sample was seen to be goblet-like with a lower penetration compared to the sample printed by the stripes strategy.
... EBF3 is similar to direct laser deposition but based on electron beam welding. 49 Metal wire feedstock-due to the difficulty in using powder in a vacuum-is melted in a 30-40 kW electron beam within a vacuum. It generates a focused electron beam in a highvacuum chamber offering 100% feedstock consumption with 95% energy efficiency due to excellent electron coupling to the metal melt pool. ...
Article
Crucial to permanent occupation of the Moon will be the ex- ploitation of local resources to build a lunar infrastructure. We examine 2 processes—the Metalysis Fray Farthing Chen (FFC) process and metal three-dimensional (3D) printing—as the backbone of a robust and sustainable industrial ecology on the Moon to exploit its raw material resources with husbandry. The Metalysis FFC process is an electrochemical technique that can extract near pure metals from their oxide and silicate forms through cathodic reduction. An anode (graphite) and cathode (metal oxide to be reduced) reside in a bath of molten salt CaCl2 at 900–1,100�C. A voltage is applied and the metal oxide re- leases oxygen ions into the molten salt, and oxygen is released at the cathode and transferred to the anode as CO or CO2 gas if the anode is graphite. At the cathode, the metal oxide is reduced into metal plus oxygen through a series of intermediate steps. We outline how the Metalysis FFC process can be leveraged through a handful of chemical preprocessing methods to exploit its versatility. We have demonstrated some preliminary experiments in extracting Ti metal powder from rutile through the Metalysis FFC process, which was subsequently 3D printed into Ti test structures using selective laser sintering. These 2 methods—Metalysis FFC and metal 3D printing—offer unprecedented cap- abilities for a lunar infrastructure manufacturing chain. In par- ticular, we take note of their high-energy efficiency that will be crucial to lunar in situ resource utilization.
Article
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Digital product processing and the utilization of novel, tissue-friendly materials allow the use of fixed dentures for patients. Its basis is a titanium plate fixed to the cortical bone surface at given screw positions. A digital dental cast is created from the existing bone surface, and modelling and necessary statistical analyses are carried out in a virtual environment. Safety of the welded joint is evaluated with mechanical methods. When designing the fixing points, an idealized denture is used that was previously designed for the patient. The number and position of pillar elements used for screw fixation of the denture are determined by the complex geometry of the denture itself, and the location, direction, and articulating position of existing teeth. The additively manufactured implant and the machined pillar sleeves are joined with laser-welding at given nesting positions. Homogeneity of the metallic material structure at the welded joint zone of the product is examined with micro-CT. Due to this implementation method, surgical time decreases together with complication rates and post-operative problems.
Article
The Inconel 718 (IN718) alloy coatings were successfully fabricated using electron beam wire-feeding deposition technology. The macrostructure, microstructure and elemental analysis of the deposited coatings were characterized by OM, SEM and EDS. Moreover, the hardness and wear resistance were also investigated experimentally. The results showed that the cross section of the deposited coatings can be divided into three different regions: clad zone (CZ), fusion zone (FZ) and heat affected zone. Equiaxed dendrites appeared in the CZ while columnar dendrites occurred in the FZ, and discrete fine Laves phase particles were formed under low beam current while continuous coarse Laves phase particles were found under high beam current. The EDS results showed that the degree of Nb segregation in FZ is higher than that in CZ. More importantly, the microstructure coarsened and the degree of Nb segregation increased with the increase of beam current. The deposited coating under the lowest beam current (10 mA) has the highest hardness (263 HV0.2) and the minimum specific wear rate (3.95391 × 10⁻¹⁵ m³/Nm), which is corresponding to the fine microstructure, discrete Laves phase particles and low degree of Nb segregation under low beam current. Graphic Abstract Open image in new window
Chapter
Acoustic emission (AE) testing was carried out in the TC4 titanium alloy manufactured by electron-beam free-form fabrication. The acoustic emission signal parameter distribution, localization characteristics, and frequency spectrum characteristic are analyzed in this chapter. The results indicated that there are many AE signals during the tensile deformation of the EBF³ TC4 titanium alloy material. The frequency of its AE signals shows it has a wide frequency band from 50 to 500 kHz, with a peak value of 150 kHz. The AE amplitudes are mainly distributed in 50–60 dB. The AE technique could be used as an effective means for the safety evaluation of the EBF³ TC4 titanium alloy material.
Thesis
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Metal additive manufacturing can be used for producing complex and functional components in the aerospace industry. This thesis deals with the process-structure-property relationships in selective laser melting of three aerospace alloys: Invar 36, stainless steel 316L, and Ti-6Al-4V. These alloys are weldable but hard to machine, which make them good candidates for the selective laser melting process. Invar 36 has a very low coefficient of thermal expansion because of its nickel concentration of 36% and stainless steel 316L contains 16-18% chromium that gives the alloy a corrosion resistance property. Ti-6Al-4V offers high strength-to-weight ratio, high biocompatibility, and outstanding corrosion resistance. Any changes in the chemical composition of these materials could affect their performance during application. In this thesis, a full factorial design of experiments is formulated to study a wide range of laser process parameters. The bulk density, tensile mechanical properties, fractography, microstructure, material composition, material phases, coefficient of thermal expansion, magnetic dipole moments, and residual stresses of the parts produced are experimentally investigated. An optimum process window has been suggested for each material based on experimental work. The thermal cycle, residual stresses, and part distortions are examined using a thermo-mechanical finite element model. The model predicts the residual stress and part distortion after build plate removal. The thesis introduces two laser energy densities for each material: brittle-ductile transition energy density, ET, and critical laser energy density, EC. Below the brittle-ductile transition energy density, the parts exhibited void formation, low density, and brittle fracture. Above the critical energy density, the parts showed vaporization of some alloying elements that have low boiling temperatures. Additionally, real-time measurements were taken using a pyrometer and a high-speed camera during the selective laser melting process. The trends found in the numerical results agree with those found experimentally.
Article
This paper used the Wire Oscillating Laser Additive Manufacturing (O-WLAM) process to deposit 2319 aluminum alloy samples. Optimization of deposition process parameters made it possible to obtain samples with a smooth surface and extremely low porosity. The effect of deposition parameters on the formability and evolution of microstructure and mechanical properties before and after heat treatment were studied. The oscillating laser deposition of 2319 aluminum alloy, especially the circular oscillation mode, significantly reduced the porosity and improved the process stability and formability compared to non-oscillating laser deposition. There were clear boundaries between deposition units in the deposition state, whose interior was dominated by columnar crystals with many rod- and point-shaped precipitates. After heat treatment, the θ phase was largely dissolved. The residual dot- and rod-shaped θ ' phases were dispersedly distributed, showing an obvious precipitation hardening effect. Samples in the as-deposited state had a 245∼265MPa tensile strength, about 12.6% elongation, and an 87HV microhardness. After heat treatment at 530°C for 20 h and aging at 175°C for 18 h, the tensile strength, elongation, and microhardness values reached 425∼440MPa, about 10%, and 153HV, respectively. The performance was notably improved without significant anisotropy. Compared with samples produced by the wire arc additive manufacturing(WAAM), the tensile strength was increased by about 10%, and the strength and microhardness were significantly improved.
Article
Wire-arc additive manufacturing (WAAM) has recently attracted researchers to produce metal components with a highdeposition rate. Many researchers are trying to establish the WAAM process as a high-deposition metal additive manufacturing (AM) process. A computationally efficient mathematical model used for the metal-AM process yields a framework for component qualification as per international standards. Since heat transaction in the AM process can control the thermal-field generated through continuous heat deposition. Therefore, the present study focuses on the critical review of multi-physics continuum modelling of WAAM at a macro-scale level. Thermo-mechanical model for WAAM has been discussed extensively, i.e., heat-source models, materials models, meshing strategy, and boundary conditions. Further, a review of the simulation results discussed as thermal fields, residual stress and distortion, and experimental validation to provide a critique of reallife experiments. Also, various residual stress/distortion mitigation techniques used in the WAAM have been compiled to provide a framework for future directions.
Article
Wire arc additive manufacturing (WAAM) is a new manufacturing technique in which large metal components can be fabricated layer by layer. A method is related apparatus for fabricating a three-dimensional object under a computer-aided design of the object in a layer-by-layer but not point-by-point fashion. Providing a work surface lying substantially parallel feeding a first layer of a first powder to this work surface by screw feeding. Feeding a second layer of a second powder onto the first layer, repeating the feeding, spraying and directing steps to build successive layers along the Z-direction in a layer-wise fashion under the design for forming multiple layers of the object; the main objective of the paper is screw feeding setup and experimenting the microstructure, grain size & hardness of the manufactured composites with different reinforcement ratios.
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Nickel-titanium alloys are the most widely used shape memory alloys due to their outstanding shape memory effect and superelasticity. Additive manufacturing has recently emerged in the fabrication of shape memory alloy but despite substantial advances in powder-based techniques, less attention has been focused on wire-based additive manufacturing. This work reports on the preliminary results for the process-related microstructural and phase transformation changes of Ni-rich nickel-titanium alloy additively manufactured by wire-based electron beam freeform fabrication. To study the feasibility of the process, a simple 10-layer stack structure was successfully built and characterized, exhibiting columnar grains and achieving one-step reversible martensitic-austenitic transformation, thus showing the potential of this additive manufacturing technique for processing shape memory alloys.
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Approaches Composite Apart from your power of additive manufacturing producing (AM) processes in generating elements with intricate geometries, two key intricacies of the manufacturing procedure which can be not worth mentioning would be its versatility in getting united together with additional production processes in addition to usage of the sort of substances in one manufacturing stage to create multi-material and mix services and products. Tests of substances in structures was demonstrated to boost the overall features, from excess fat loss and combining production and the assembly alter the procedures. Approaches in the direction of alteration of procedures aimed to accomplish mix or multi-material parts have been examined inside this paper.
Chapter
Directed Energy Deposition (DED) is a method for melting material as it is being deposited layer-by-layer. Material in wire or powder form is delivered along with the energy required to melt it. Although it has been shown that a number of material types can be processed this way, DED is almost exclusively applied to metals in both research and commercialized instantiations. DED presents unique advantages and disadvantages that make it particularly suited for repair and feature addition to an existing part. DED is gaining industrial interest because of its ability to create near-net-shape, large freeform structures more quickly and inexpensively than traditionally made near-net-shape castings and forgings.
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Wire and arc additive manufacturing (WAAM) has proven that it can produce medium to large components because of its high-rate deposition and potentially unlimited build size. Like all additive manufacturing (AM) technologies, however, an optimized process planning that provides uniform, defect-free deposition is key for the production of parts. Moreover, AM, particularly WAAM, is no longer just a prototyping technology, and most of today's attention is on its transformation to a viable and cost-effective production. With this transformation, a number of issues need to be addressed, including the accuracy and effectiveness of the manufactured components. Therefore, the emphasis should be on dimensional precision and surface finish in WAAM. This paper covers heat input and management concept, related to the resulting shrinkage, deformation, and residual stresses, which is particularly critical. In addition, we focus on process planning including build orientation, slicing, and path planning, as well as the definition of process parameter selection from a single track to multi-track and multilayer, and finally geometric features from a thin-wall to lattice structures with several case studies. Central to addressing component quality and accuracy, we summarize guiding designs and future needs through numerous WAAM-specific issues, which require for manufacturing of complex components.
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Metal additive manufacturing technologies, such as powder bed fusion process, directed energy deposition (DED) process, sheet lamination process, etc., are one of promising flexible manufacturing technologies due to direct fabrication characteristics of a metallic freeform with a three-dimensional shape from computer aided design data. DED processes can create an arbitrary shape on even and uneven substrates through line-by-line deposition of a metallic material. Theses DED processes can easily fabricate a heterogeneous material with desired properties and characteristics via successive and simultaneous depositions of different materials. In addition, a hybrid process combining DED with different manufacturing processes can be conveniently developed. Hence, researches on the DED processes have been steadily increased in recent years. This paper reviewed recent research trends of DED processes and their applications. Principles, key technologies and the state-of-the art related to the development of process and system, the optimization of deposition conditions and the application of DED process were discussed. Finally, future research issues and opportunities of the DED process were identified.
Article
Additive manufacturing (AM) processes have widely varying thermal environments, which dictate the solidification of alloys during solidification. Here, we use binder jet 3D printing (BJ3DP), electron beam freeform fabrication (EBF3), and direct metal laser sintering (DMLS) to fabricate samples of Inconel 625, displaying the significant differences in microstructure brought about purely by the thermal gradients produced in each manufacturing method. Dislocation density and elastic strain are measured using high-resolution electron backscatter diffraction and the spatial relationship between these features is analyzed with respect to the relative thermal environments of each AM technique, with DMLS exhibiting microstructure typical of high thermal gradients and rapid solidification. Increasing thermal gradient and solidification rate results in a stronger spatial dependence of microscale elastic strain on GND density. Our results also demonstrate the use of statistical techniques to quantify microstructural features in relation to processing, which has potential for informing frameworks which can predict microstructure and material properties of AM components.
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The nature of the chemical mixing and microstructure gradients that occur across the interface transition, when manufacturing tailored components with the two high-performance dissimilar titanium alloys (Ti-6Al-4V (Ti-64) and Ti-5Al-5V-5Mo-3Cr (Ti-5553)) by the wire-arc additive manufacturing (WAAM) process, are reported. It has been shown that a relatively long-range chemical gradient occurs during the transition between layers produced with the two different titanium alloys, due to convective mixing in the melt pool between the substrate layers and new alloy wire. This resulted in a stepwise exponential decay composition profile normal to the layers, the width of which can be described by a simple dilution law, with steep local composition gradients seen within the boundary layers at the fusion boundary of each individual layer. The alloy-alloy composition gradients had little effect on the β-grain structure. However, they strongly influenced the transformation microstructure, due to their effect on the parent β-phase stability and the β → α transformation kinetics and reaction sequence. The microstructure gradient seen on transitioning from Ti-64 → Ti-5553 was significantly more abrupt, compared to when depositing the two alloys in the reverse order. Under WAAM thermal conditions, Ti-64 appears to be more sensitive to the effect of adding β-stabilising elements than when Ti-5553 is diluted by Ti-64, because at high cooling rates, stabilisation of the β phase readily suppresses α nucleation when cooling through the β transus, and the normal Ti-64 lamellar transformation microstructure is abruptly replaced by finer scale α laths generated by precipitation during subsequent reheating cycles.
Article
In this paper, an alternating current (AC) was added to filling wire in the arc deposition process. The effect of alternative current on grains size and microstructure of Ti-6Al-4V cladding layers were studied. The microstructure evolution, grain size distribution, texture, and crystal twining of cladding layers with the addition of alternative current were studied in detail using metallographic microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscope (TEM). The results reveal that the addition of AC can effectively inhibit β grain growth, the grains size decrease with the increase of AC value. The enhancement of microstructure uniformity and decrease of texture intensity have been realized by electromagnetic force produced by alternative current. Additionally, the {10-10}<10-12> compression twins system was observed in cladding layer at 45A.
Article
This work explores the possibility of using friction stir processing to harden the Ti-6Al-4V titanium alloy material produced by wire-feed electron beam additive manufacturing. For this purpose, thin-walled workpieces of titanium alloy with a height of 30 cm were printed and, after preparation, processed with an FSW-tool made of heat-resistant nickel-based superalloy ZhS6U according to four modes. Studies have shown that the material structure and properties are sensitive to changes in the tool loading force. In contrast, the additive material’s processing direction, relative to the columnar grain growth direction, has no effect. It is shown that increasing the axial load leads to forming a 𝛽-transformed structure and deteriorates the material strength. At the same time, compared to the additive material, the ultimate tensile strength increase during friction stir processing can achieve 34–69%.
Chapter
This study proposes and discusses a methodology for the formation of a list of products for a company or a group of companies recommended to be transferred to additive manufacturing (AM). This methodology covers already manufactured products (parts and assembly units) and products being put into production. With this technique, the entire considered set of products is divided into two subsets—the first consisting of parts and assembly units, which are not economically feasible to be transferred to AM, while for the second set it is potentially beneficial. The second subset is divided into product groups that can be obtained by the same method of additive shaping and using the equipment of the same type. Time priorities can be defined for each group to prepare schedule for planning the transfer of products to AM. It is noted that the production processes of modern mechanical engineering production are inherently additive–subtractive, and it is proposed to consider the operation (or a group of operations) for obtaining the AM workpiece as a separate stage in the product's entire production process. The organizational side of the proposed methodology is based on the creation of an expert group (designers, production engineers, and economists), who jointly assign identification codes to each product of the second set, which indicates whether the product can be produced by AM.
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Micro-plasma transfer arc metal additive manufacturing (μ-PTAMAM) process is a unique direct energy deposition (DED) type additive manufacturing (AM) process capable of manufacturing three-dimensional metallic components through simultaneous use of wire and powder forms of AM material. DED process yields an uneven surface on the manufactured components which necessitates their further post-processing to attain the required surface finish, dimensional accuracy, and geometrical accuracy. This research focuses on using machine learning algorithm, namely, K-nearest neighbors (KNN), to predict the surface roughness. The data of surface roughness for training KNN algorithm was generated by depositing multi-layer single-track depositions yielding wall-like structures using Stellite-6 as AM material in powder and wire forms. It was found that surface roughness increases with an increase in power supply to micro-plasma and AM material feed rate whereas it decreases with an increase in traverse speed of the deposition head for both powder and wire of the AM material. Surface roughness of the walls for powder form of the AM material is smaller (i.e., 118 to 149 μm) than that obtained by the wire form (i.e., 195 to 227 μm). Surface roughness prediction error for KNN algorithm is found to be from − 6.2 to 2.8% for powder form and − 5.8 to 2.3% for wire form of the AM material proving capability of KNN algorithm for accurate prediction of surface roughness produced by μ-PTAMAM process. Since the prediction error depends on number of data set used to train KNN algorithm, therefore, it can be further reduced by increasing number of training data set.
Article
3D printing or Additive manufacturing or Rapid prototyping is a technology where 3D structures are designed and printed which is currently doing good for the manufacturing sector of many industries such as automotive, aerospace, medical, jewellery, constructions etc. Additive Manufacturing is a fast-emerging technology which has been exceedingly used for mass customization and fabrication of free design sourced products. Additive manufacturing is a method where the materials are put together in a desired shape via a certain process with the appropriate material type. The property of the materials used for 3D printing is highly dependent on the type and composition of the material. The various types and compositions of materials hugely impacts their implementation in potential applications which is discussed in this paper. The dominantly used materials, their composition, their properties, their applications and their future scope are discussed. This paper gives a clear overview on the material technology used in the additive manufacturing industry.
Conference Paper
1. Einleitung Der industrielle Einsatz von additiv gefertigten, metallischen Bauteilen steigt stetig. Die Hauptgründe dafür sind folgende: 1. Die Realisierung von Bauteilgeometrien, die mit traditionellen Herstellungsmethoden gar nicht, oder nur zeit-und kostenintensiv erzielt werden können. 2. Die Reduktion von Grundmaterialverbrauch und mechanischer Verarbeitung durch die endkon-turnahe Herstellung von Halbzeugen, beziehungsweise Bauteilen. 3. Die Bereitstellung von Halbzeugen, die nicht auf dem Markt erhältlich sind oder eine sehr große Lieferzeit haben. 4. Die Kombination unterschiedlicher Materialien, gegebenenfalls mit gradierten Eigenschaften. 5. Der Einsatz einer Hybridbauweise, die auf dem additiven Aufbau komplexer Strukturen auf einfa-chen Geometrien basiert. 6. Die Möglichkeit zur Reparatur von hochwertigen Bauteilen. Zurzeit sind etwa 18 unterschiedliche Technologien für die additive Fertigung von metallischen Bautei-len in der Entwicklung. Von diesen können fünf als soweit technologisch ausgereift bezeichnet werden, dass sie für den industriellen Einsatz in Frage kommen [1]. Dies sind Pulverbettmethoden und Techno-logien mit Materialauftrag durch gerichtete Energieeinbringung (DED: directed energy deposition) [2]. Wie aus Tabelle 1 ersichtlich, sind der Laser, der Lichtbogen/Plasma und der Elektronenstrahl mögliche Energiequellen. Als Ausgangsmaterial kommt Pulver oder Draht zum Einsatz. Tabelle 1: Industriereife Technologien für die additive Fertigung von Metallbauteilen Bezeichnung des Verfahrens Technologie Energiequelle Materialform Laser beam powder bed fusion LB-PBF Pulverbett Laser Pulver Electron beam powder bed fusion EB-PBF Pulverbett Elektronenstrahl Pulver Laser-DED DED Laser Draht/Pulver Wire arc additive manufacturing WAAM DED Lichtbogen/Plasma Draht Wire electron beam additive manufacturing WEBAM DED Elektronenstrahl Draht Pulverbett und DED bedienen dabei in der Regel unterschiedliche Märkte, da die Pulverbettmethoden detailreichere und kleinere Bauteile, aber mit niedrigeren Produktionsraten als die DED-Methoden lie-fern. DED dagegen wird bevorzugt bei größeren Bauteilen und Halbzeugen eingesetzt, wobei gegebe-nenfalls eine mechanische Endbearbeitung sinnvoll sein kann. Obwohl der Einsatz des Elektronenstrahls für die drahtbasierte additive Fertigung bereits vor etwa 20 Jahren in Berichten von der NASA vorgestellt wurde [3; 4], sind WAAM und Laser-DED generell wesent-lich bekannter im industriellen Einsatz. Daher soll in diesem Dokument das Potential von WEBAM im Vergleich zu den anderen DED-Technologien diskutiert werden. 2. WEBAM Alle DED-Technologien verwenden eine Energiequelle, um zugeführtes Material durch Schmelzen auf-zutragen [2] (Abb. 1). Dabei wird das Bauteil schichtweise durch eine Relativbewegung der Materialzu-führung zu einer Grundplatte beziehungsweise einem Grundkörper aufgebaut. Dies erfolgt in der Regel
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Wire feeding can be combined with different heat sources, for example, arc, laser, and electron beam, to enable additive manufacturing and repair of metallic materials. In the case of titanium alloys, the vacuum operational environment of electron beam systems prevents atmospheric contamination during high-temperature processing and ensures high performance and reliability of additively manufactured or repaired components. In the present work, the feasibility of developing a repair process that emulates refurbishing an “extensively eroded” fan blade leading edge using wire-feed electron beam additive manufacturing technology was examined. The integrity of the Ti6Al4V wall structure deposited on a 3 mm thick Ti6Al4V substrate was verified using X-ray microcomputed tomography with a three-dimensional reconstruction. To understand the geometrical distortion in the substrate, three-dimensional displacement mapping with digital image correlation was undertaken after refurbishment and postdeposition stress relief heat treatment. Other characteristics of the repair were examined by assessing the macro- and microstructure, residual stresses, microhardness, tensile and fatigue properties, and static and dynamic failure mechanisms.
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Researchers at NASA Langley Research Center are developing a new electron beam freeform fabrication (EB F3) technique to fabricate metal parts. This process introduces metal wire into a molten pool created by a focused electron beam. Potential aerospace applications for this technology include ground-based fabrication of airframe structures and on-orbit construction and repair of space components and structures. Processing windows for reliably producing high quality 2219 aluminum parts using the EB F3 technique are being defined. The effects of translation speed, wire feed rate, and beam power on the resulting microstructures and mechanical properties are explored. Tensile properties (ultimate tensile strength, yield strength, and elongation) show little effect over the range of processing conditions tested. Basic processing-microstructure-property correlations are drawn for the EB F3 process.
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Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF 3 ), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF 3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Thus far, this technique has been demonstrated on aluminum and titanium alloys of interest for aerospace structural applications; nickel and ferrous based alloys are also planned. Deposits resulting from 2219 aluminum demonstrations have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm3/hr (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs. Background
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NASA's Langley Research Center and Johnson Space Center are developing a solid freeform fabrication system utilizing an electron beam energy source and wire feedstock. This system will serve as a testbed for exploring the influence of gravitational acceleration on the deposition process and will be a simplified prototype for future systems that may be deployed during long-duration space missions for assembly, fabrication, and production of structural and mechanical replacement components. Critical attributes for this system are compactness, minimal mass, efficiency in use of feedstock material, energy use efficiency, and safety. The use of a low-voltage (
Conference Paper
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Recent developments on Laser Cladding and Rapid Prototyping have led to Solid Freeform Fabrication (SFF) technologies that produce net shape metal components by laser fusion of metal powder alloys. These processes are known by various names such as Directed Light Fabrication (DLF{trademark}), Laser Engineered Net Shaping (LENS{trademark}), and Direct Metal Deposition (DMD{trademark}) to name a few. These types of processes can be referred to as direct laser powder deposition (DLPD). DLPD involves fusing metal alloy powders in the focal point of a laser (or lasers) that is (are) being controlled by Computer Aided Design-Computer Aided Manufacturing (CAD-CAM) technology. DLPD technology has the capability to produce fully dense components with little need for subsequent processing. Research and development of DLPD is being conducted throughout the world. The list of facilities conducting work in this area continues to grow (over 25 identified in North America alone). Selective Laser Sintering (SLS{trademark}) is another type of SFF technology based on laser fusion of powder. The SLS technology was developed as a rapid prototyping technique, whereas DLPD is an extension of the laser cladding technology. Most of the effort in SLS has been directed towards plastics and ceramics. In SLS, the powder is pre-placed by rolling out a layer for each laser pass. The computer control selects where in the layer the powder will be sintered by the laser. Sequential layers are sintered similarly forming a shape. In DLPD, powder is fed directly into a molten metal pool formed at the focal point of the laser where it is melted. As the laser moves on the material it rapidly resolidifies to form a shape. This talk elaborates on the state of these developments.
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Electron beam freeform fabrication (EBF3) parts exhibit a ridged surface finish typical of many layer-additive processes. Thus, post-processing is required to produce a net shape with a smooth surface finish. High speed milling, wire electrical discharge machining (EDM), electron beam glazing, and glass bead blasting were performed on EBF(3)-built 2219 aluminum alloy parts to reduce or eliminate the ridged surface features. Surface roughness, surface residual stress state, and microstructural characteristics were examined for each of the different surface treatments to assess the quality and effect of the surface treatments on the underlying material. The analysis evaluated the effectiveness of the different surface finishing techniques for achieving a smooth surface finish on an electron beam freeform fabricated part.
Article
Recently, a precision metal deposition (PMD) process which provides capabilities for rapid and precise net-shape manufacturing of three-dimensional dense metal structures was developed. This patented process developed by H&R Technology involves laser energy that simultaneously melts and fuses a solid metal flat wire to a substrate. As a result, the PMD process produces metal parts with an order of magnitude less heat input into the part.
Article
Ultrasonic consolidation is a newly commercialized rapid tooling process in which aluminum tooling is fabricated in a single operation, on a single machine. The tools are suitable for any application, including injection molding, extrusion, vacuum forming, and other. Thus, ultrasonic consolidation is a micro-friction process. It differs substantially from other direct metal fabrication processes in that it applie the technologies of ultrasonic joining to produce true metallurgical bonds between thin layers of metal in the solid state.
Conference Paper
For many years, Sandia National Laboratories has been involved in the development and application of rapid prototyping and direct fabrication technologies to build prototype parts and patterns for investment casting. Sandia is currently developing a process called Laser Engineered Net Shaping (LENS™) to fabricate fully dense metal parts directly from computer-aided design (CAD) solid models. The process is similar to traditional laser-initiated rapid prototyping technologies such as stereolithography and selective laser sintering in that layer additive techniques are used to fabricate physical parts directly from CAD data. By using the coordinated delivery of metal particles into a focused laser beam, a part is generated. The laser beam creates a molten pool of metal on a substrate into which powder is injected. Concurrently, the substrate on which the deposition is occurring is moved under the beam/powder interaction zone to fabricate the desired cross-sectional geometry. Consecutive layers are additively deposited, thereby producing a three-dimensional part. This process exhibits enormous potential to revolutionize the way in which metal parts, such as complex prototypes, tooling, and small-lot production parts, are produced. The result is a complex, fully dense, near-net-shape part. Parts have been fabricated from 316 stainless steel, nickel-based alloys, HI3 tool steel, and titanium. This talk will provide a general overview of the LENS™ process, discuss potential applications, and display as-processed examples of parts.
Article
A study was conducted to evaluate the relative significance of input parameters on Ti- 6A1-4V deposits produced by an electron beam freeform fabrication process under development at the NASA Langley Research Center. Five input parameters where chosen (beam voltage beam current, translation speed, wire feed rate, and beam focus), and a design of experiments (DOE) approach was used to develop a set of 16 experiments to evaluate the relative importance of these parameters on the resulting deposits. Both single-bead and multi-bead stacks were fabricated using 16 combinations, and the resulting heights and widths of the stack deposits were measured. The resulting microstructures were also characterized to determine the impact of these parameters on the size of the melt pool and heat affected zone. The relative importance of each input parameter on the height and width of the multi-bead stacks will be discussed.
A Brief History of Rapid Prototyping & Manufacturing: The Growth Years
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Ti-6Al-4V, Code 3707, Aerospace Structural Metals Handbook
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Direct Laser Powder Deposition – State of the Art Powder Materials: Current Research and Industrial Practices
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