Additive Manufacturing

Project B2 explores selective electron beam melting, which belongs to the additive manufacturing technologies, for the processing of single-crystalline superalloys. Especially the potential of the inherent high cooling rates is investigated. These lead to an ultra-fine and directional solidified microstructure. The main challenge of this project is to develop innovative processing strategies based on a sound theoretical process understanding in order to produce crack-free and preferably single crystalline samples, also with higher geometric complexity.
 

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Metamaterials are artificial structures with extraordinary properties as result of their internal architecture. We are investigating mechanical metamaterials manufactured by SEBM. We investigate auxetic materials characterized by a negative Poisson’s ratio as well as phononic band gap materials. Structure design rests upon basic knowledge about mechanisms generated by numerical simulation.

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Selective electron beam melting represents an interesting alternative to laser melting in the field of powder-based additive manufacturing methods. The evacuated build chamber and the overall high performance allow for the production of components with excellent properties. The almost inertia free deflection and focusing of the electron beam by electromagnetic lenses facilitates extremely high construction speeds at very high precision levels.
This project has the goal to optimize electron beam properties and to provide a better understanding of the melting process and of other influences in order to tap the full potential of this process, both with regard to energy input and process speed.   Here, process monitoring plays an important role. Process influences, such as temperature distribution, scanning strategies, and electron beam properties are investigated using both a thermal and a high-speed camera.  In addition, the existing field of parameters will be expanded to include high scanning rates (up to 10 m/s). The influence of powder properties, e.g., particle size distribution and bulk density, different scanning strategies, e.g., the multi-beam strategy, will be evaluated in order to tailor component properties.

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The basic mechanisms that are essential in the powder based selective beam melting process are poorly understood. Most of the existing analytical and numerical models describing the process of consolidation in a homogenized image, i.e. individual powder particles are not resolved. This approach is suitable for information on averages, but cannot capture the local influence of the powder, i.e. the powder size distribution, the stochastic effect of the powder bed, the wetting of the powder by the melt and the formation of the melt. The actual selective melting process and thereby acting mechanisms can only be understood on the scale of the powder particles, with the help of numerical simulation on the mesoscopic scale. The aim of this project is to provide a numerical tool for mesoscopic simulation of selective beam melting and to use it to develop innovative process strategies. The mesoscopic scale allows the prediction of defects, surface quality and accuracy of the structure for different materials as a function of material parameters (powder form, bulk density, ...) and the process parameters (beam shape, energy per unit length, speed, ...).
In the first phase, a tool for the 2D simulation of selective electron beam melting was developed and validated with experimental results. The main task was the modeling of the entire build process with its different time scales (pre-heating, melting, applying new powder layer). Among other things, the complex coupling of the beam in the powder bed, radiation losses at the surface, mass and energy loss through evaporation and the deformation of the molten bath by the evaporation pressure is taken into account. The software is now able to simulate assembly processes, taking into account different scanning strategies on many layers. Such process strategies as the remelt strategy and the refill strategy are investigated. The verification of the numerical results is done in close cooperation with subproject B2.
In the second phase, the previous model is transferred to polymers. For this purpose, the absorption of the laser beam in the partially transparent stochastic powder bed and the highly viscous, viscoelastic material behavior must be described. Development and verification of the model is carried out in cooperation with subproject B3. In a further step, a method of 3D simulation of the grain structure in the selective beam melting of metals is implemented, in order to predict the texture of the materials as a function of process strategy.

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Fundamental understanding of a new and innovative process combining sheet metal forming with additive manufacturing is the main goal of this research work.

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Electron beam melting additive manufacturing is used to produce successive layers of a part in a powder bed and offers the ability to produce components closest to their final dimensions, with good surface finish. At this time the process is faster than any other technique of comparable quality, however the parts are not produced at sufficient rate to make them economically viable for any but very high value specific applications. One key output of the project will be the knowledge surrounding the use of the high powder electron beam gun, including the process control, and modeled and validated understanding of beam-powder bed interaction. The target objectives is the transfer of the 2D model to a 3D model and its parallel implementation. The outcome of the simulation will be compared with real experimental data and therefore the model parameters are adjusted in such a way that the resulting numerical melt pool sizes correspond to the experimental ones.

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The overarching goal of AMAZE is to rapidly produce large defect-free additively-manufactured (AM) metallic components up to 2 metres in size, ideally with close to zero waste, for use in the following high-tech sectors namely: aeronautics, space, automotive, nuclear fusion and tooling.

Four pilot-scale industrial AM factories will be established and enhanced, thereby giving EU manufacturers and end-users a world-dominant position with respect to AM production of high-value metallic parts, by 2016. A further aim is to achieve 50% cost reduction for finished parts, compared to traditional processing.

The project will design, demonstrate and deliver a modular streamlined work-flow at factory level, offering maximum processing flexibility during AM, a major reduction in non-added-value delays, as well as a 50% reduction in shop-floor space compared with conventional factories.

AMAZE will dramatically increase the commercial use of adaptronics, in-situ sensing, process feedback, novel post-processing and clean-rooms in AM, so that (i) overall quality levels are improved, (ii) dimensional accuracy is increased by 25% (iii) build rates are increased by a factor of 10, and (iv) industrial scrap rates are slashed to <5%.

Scientifically, the critical links between alloy composition, powder/wire production, additive processing, microstructural evolution, defect formation and the final properties of metallic AM parts will be examined and understood. This knowledge will be used to validate multi-level process models that can predict AM processes, part quality and performance.

In order to turn additive manufacturing into a mainstream industrial process, a sharp focus will also be drawn on pre-normative work, standardisation and certification, in collaboration with ISO, ASTM and ECSS.

The team comprises 31 partners: 21 from industry, 8 from academia and 2 from intergovernmental agencies. This represent the largest and most ambitious team ever assembled on this topic.

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Raney-copper is a catalyst made from a copper base alloy containing at least one less noble element than copper (e.g. zinc). After fabricating the base material via a casting process consisting of a melt and a quenching step the alloy can be converted into a nanoporous and catalytically active structure using an alkaline solution.

During this project a Raney-copper type alloy will be processed using the selective electron beam melting process (SEBM). The main goal of this project is to utilize the process’ specific characteristics like a high cooling rate and geometric freedom to build periodic cellular catalyst structures. Those cellular structures surface will then be made catalytically active for their application in the methanol synthesis process using a leaching step. In contrast to other yet fabricated cellular metal catalyst structures the Raney-copper ones do not need any further coating with active species like e.g. palladium.

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Additive manufacturing of components is a key technology of the future. The powder bed based selective electron beam melting process allows to produce complex components from high performance alloys. Nevertheless, the highly dynamic melting process is not fully understood and suffers from binding faults, changes of the alloy composition and process instabilities. Aim of the project is to understand the basic mechanisms during selective electron beam melting and to use this knowledge to predict and to influence the resulting materials quality. In order to reach this aim, the selevtive electron beam melting process takting selective vaporation phenomena into account is simulated based on a Lattice Boltzmann Model. Evaporation leads to material loss, has influence on the melt pool dynamics and changes the alloy composition. Simulation on the scale of the powder particles reveals phenomena which result from the complex interplay between beam, powder and melt pool. The numerical results are varified by experiments by an exemplary alloy.

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Ziel dieses Projektes ist es, die Einschränkungen der bisherigen Elektronenstrahlkanone und eingeschränkten Prozesskontrolle zu überwinden, um damit einen großen Entwicklungsschritt in dieser Technologie zu vollziehen. Dazu ist geplant, die Elektronenstrahlkanone einer bei WTM vorhandenen Arcam S12 (diese wird geopfert) durch eine erheblich leistungsfähigere Elektronenstrahlkanone zu ersetzen. Auf dem Markt sind Kanonen mit sehr viel höherer Leistung bei gleichbleibend…

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Titanaluminde haben durch das Ersetzen deutlich schwererer Nickelbasislegierungen großes Potential für Kraftstoffeinsparungen in zukünftige Generationen von Flugzeug- und Kraftwerksturbinen. Die Verarbeitung dieser Materialien gestaltet sich allerdings äußerst schwierig, da die Materialeigenschaften stark von der Mikrostruktur und chemischen Homogenität des Endproduktes abhängen. Im vorliegenden Vorhaben soll ein Rapid Manufacturing Prozess, das selektive Elektronenstrahlschmelzen,…

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The electron beam offers the potential for innovative selective beam melting process strategies due its inertia-free deflection at extremely high speed.

A deep understanding of the process is developed with the help of different methods of in-situ process monitoring (thermal imaging and high speed camera). In particular, the potential to tailor the microstructure, grain structure and texture of the material with the help of the extremely high beam velocity is explored. In addition, we investigate the mechanisms of evaporation induced material displacement and the possibility to use this effect to realize hollow structures within components.

CRC DFG 814 “Additive Manufacturing”  (http://www.sfb814.forschung.uni-erlangen.de/).

A further focus is on processing of single crystalline nickel-base alloys. We are designing building strategies to avoid cold and hot crack formation. The main challenge is to control directional and rapid solidification in order to realize single crystals directly developing from powder particles without any seed material. We are now able to realize large single crystals out of nickel-base alloys with unique homogeneity by selective electron beam melting. 

CRC DFG TR 103 “From Atom to Turbine Blade” (http://www.sfb-transregio103.de/).

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We investigate the potential of SEBM for processing of technical alloys based on Iron Aluminides, Nickel and Copper as well as amorphous metals.

For Iron aluminides, the focus is on the influence of additional elements such as Boron and Titanium on the workability, the microstructure and the resulting properties.  

Concerning pure Copper and Copper alloys our focus is on the influence of minor elements or contaminations such as Oxygen or Phosphorus on the resulting properties, in particular the achievable heat conductivity

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Commercial available EBSM machines show strong limitations with respect to the beam power, beam quality and beam control. To overcome these limitations, the electron gun and control system of an Arcam S12 System was renewed. The resulting machine is equipped with a 6 kW electron beam gun and a backscattering electron detector for process monitoring. This is the first electron beam AM machine where the electron beam serves for both, processing and analyzing.

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We investigate new alloys for structural catalysts that serve as carrier material and simultaneously as catalytically active material in structured reactors. The active catalyst (Raney copper type) develops from the AM manufactured structure by leaching. Thus, geometric restrictions of complex coating processes for catalytic functionalization disappear. The direct generation of the catalytically active material on the carrier structure is expected to show advantages with respect to thermal management. In order to demonstrate the potential of structural catalysts we consider the methanol synthesis.

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We use combinatorial methods for the development of new alloys that allow the creation of large material libraries based on thermodynamic predictions. To do this, the Chair of WTM is currently establishing a laser metal deposition machine from the company InssTek. This machine is equipped with four powder hoppers in a glove box with inert gas atmosphere. Besides materials libraries we are also able to realize multi-material and graded components.

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Target oriented material development has to be based on a profound understanding of process-inherent mechanisms. This project aims on in-situ observation of the material consolidation process during additive manufacturing.

This includes particular phase transformations and the nucleation and growth of precipitates. The observation of these phenomena is a big challenge due to their high temporal dynamics. New experimental environments allow the observation of the formation of the microstructure of a material under AM conditions. Access to this accelerator based experimental environment allows the competence anchor DESY-FAU DHW, a cooperation between FAU and the Helmholtz centers DESY and DHW.

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We examine the possibility to process high performance alloys such as non-weldable Nickel-base alloys or special Copper alloys by means of SEBM. There are also experiences in the processing of Titanium alloys, in particular for medical applications, Titanium aluminides and steels.

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