Additive Fertigung
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- 2018 (15) (entfernen)
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- Additive manufacturing (9)
- ProMoAM (3)
- Thermography (3)
- Computed tomography (2)
- Laser Beam Melting (2)
- Laser beam melting (2)
- Laser metal deposition (2)
- Selective laser melting (2)
- 316L (1)
- AGIL (1)
Organisationseinheit der BAM
- 8 Zerstörungsfreie Prüfung (11)
- 8.5 Röntgenbildgebung (8)
- 9 Komponentensicherheit (5)
- 5 Werkstofftechnik (4)
- 8.0 Abteilungsleitung und andere (4)
- 9.3 Schweißtechnische Fertigungsverfahren (3)
- 1 Analytische Chemie; Referenzmaterialien (2)
- 4 Material und Umwelt (2)
- 4.2 Material-Mikrobiom Wechselwirkungen (2)
- 9.4 Integrität von Schweißverbindungen (2)
Additive manufacturing (AM) offers a range of novel applications. However, the manufacturing process is complex and the production of defect-free parts with a high reliability is still a challenge. Thermography is a valuable tool for process surveillance, especially in metal AM processes. The high process temperatures allow one to use cameras usually operating in the visible spectral range. Here, we compare the results of first measurements during the manufacturing process of a commercial laser metal deposition (LMD) setup using a MWIR camera with those from a VIS high-speed camera with band pass filter in the NIR range.
Additive manufacturing (AM) opens the route to a range of novel applications.However, the complexity of the manufacturing process poses a challenge for the production of defect-free parts with a high reliability. Since process dynamics and resulting microstructures of AM parts are strongly influenced by the involved temperature fields, thermography is a valuable tool for process surveillance. The high process temperatures in metal AM processes allow one to use cameras usually operating in the visible spectral range to detect the thermally emitted radiation from the process. In our work, we compare the results of first measurements during the manufacturing processes of a commercial laser metal deposition (LMD) setup and a laser beam melting (LBM) setup using a MWIR camera with those from a VIS high-speed camera with band pass filter in the NIR range.
Sintered bioactive glass scaffolds of defined shape and porosity, e.g. made via additive manufacturing, must provide sufficient bioactivity and sinterability. As higher bioactivity is often linked to high corrosion and crystallization tendency, a certain compromise between sintering ability and bioactivity is therefore required. Groh et al. developed a fluoride-containing bioactive glass (F3), which allows fiber drawing and shows a bioactivity well comparable to that of Bioglass®45S5.
To study whether and to what extent the sinterability of F3 glass powder is controlled by particle size, coarse and fine F3 glass powders (300-310µm and 0-32µm) were prepared by crushing, sieving and milling. Sintering, degassing and phase transformation during heating were studied with heating microscopy, vacuum hot extraction (VHE), DTA, XRD, and SEM.
For the coarse glass powder, sintering proceeds slowly and is limited by surface crystallization of primary Na2CaSi2O6 crystals. Although the crystallization onset of Na2CaSi2O6 is shifted to lower temperature, full densification is attained for the fine powder. This finding indicate that certain porosity might be tuned via particle size variation. Above 900°C, intensive foaming is evident for the fine powder. VHE studies revealed that carbon species are the main foaming source.
Influence of deposition hatch length on residual stress in selective laser melted Inconel 718
(2018)
The present study aims to evaluate the bulk residual stresses in SLM parts by using neutron diffraction measurements performed at E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. Together with microstructure characterization and distortion measurements, it is possible to describe the stress state throughout the whole sample. The sample was measured in as-build condition (on a build plate) and after releasing from the build plate. The used material is the nickel based superalloy 718. This alloy is widely used in aerospace and chemical industries due to its superior corrosion and heat resistant properties.
Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component. The normal and transversal component exhibits a rather compressive behavior while the longitudinal was tensile in the center part of the sample and became compressive towards the tip. As expected, the absolute values of all stress components decreased after releasing the sample from the building plate. A surface scan utilizing a coordinate-measuring machine (CMM) allowed us to present top surface distortion before and after releasing. The top surface showed a distortion around ±80µm after releasing. Microstructure evolution in the scanning-building cross-section is largely dominated by columnar grains. In addition, many small random orientated grains are prominent in the regions of a laser overlap during SLM.
In summary, for the sample of superalloy 718 manufactured by SLM, a small distortion occurred when removing the sample from the build plate whereby the residual stress state decreases. Moreover, the observed columnar grains in the building direction could give a reason for the lowest stress values in that normal direction. However, the most important parameter controlling the residual stresses is the temperature gradient. Hence, future investigations are planned for a different scan strategy to distribute the laser impact in a more homogenous manner.
Compact nuclear magnetic resonance (NMR) instruments make NMR spectroscopy and relaxometry accessible in industrial and harsh environments for reaction characterization and process control. Robust field integration of NMR systems have to face explosion protection or integration into process control systems with short set-up times. This paves the way for industrial automation in real process environments.
The design of failsafe, temperature and pressure resistant flow through cells along with their NMR-specific requirements is an essential cornerstone to enter industrial production plants and fulfill explosion safety requirements. Additionally, if fast reactions are monitored, suitable mixing devices need to be placed in close vicinity to the measuring volume to mix the reactants properly.
NMR-specific requirements aim at full quantitative pre-magnetization and acquisition with maximum sensitivity while reducing sample transfer times and dwell-times. All parameters are individually dependent on the applied NMR instrument.
Luckily, an increasing number of applications are reported together with an increasing variety of commercial equipment. However, these contributions have to be reviewed thoroughly.
The performance of sample flow cells commonly used in online analytics and especially for low-field NMR spectroscopy was experimentally and theoretically investigated by 1H-NMR experiments and numerical simulations. Especially, the applicability of 3D printed zirconium dioxide for innovative flow cell designs was of interest. Here, we demonstrate and discuss an automated test method to determine the critical parameters of flow through cells for quantitative online NMR spectroscopy. The setup is based on randomized setpoints of flow rates in order to reduce temperature related effects. Five flow cells and tubing were assessed and compared for high-field as well as low-field NMR spectrometers.
Additive manufacturing (AM) offers an effective solution to the medical sector. It enables the production, on demand, of customised implants which match the patient’s anatomy, with grafts that promote bone growth, as well as surgical guides that help the surgeons. The objective of this project is to provide a comprehensive basis to enable the safe use of medical AM products with traceable and reliable dimensionalmeasurements. This will guarantee the reliability of medical AM products to notified bodies and facilitate acceptance of AM in the medical sector for a better quality of life.
Additive manufacturing (AM) offers an effective solution to the medical sector. It enables the production, on demand, of customised implants which match the patient’s anatomy, with grafts that promote bone growth, as well as surgical guides that help the surgeons.
The objective of this project is to provide a comprehensive basis to enable the safe use of medical AM products with traceable and reliable dimensionalmeasurements. This will guarantee the reliability of medical AM products to notified bodies and facilitate acceptance of AM in the medical sector for a better quality of life.
The quality of components made by laser beam melting (LBM) additive manufacturing is naturally influenced by the quality of the powder bed. A packing density < 1 and porosity inside the powder particles lead to intrinsic voids in the powder bed. Since the packing density is determined by the particle size and shape distribution, the determination of these properties is of significant interest to assess the printing process. In this work, the size and shape distribution, the amount of particle’s intrinsic porosity as well as the packing density of micrometric powder used for LBM have been investigated by means of synchrotron X-ray computed tomography (CT). Two different powder batches were investigated: Ti-6Al-4V produced by plasma atomization and Stainless Steel 316L produced by gas atomization. Plasma atomization particles were observed to be more spherical in terms of the mean anisotropy compared to particles produced by gas atomization. The two kinds of particles are comparable in size according to the equivalent diameter. The packing density is lower (i.e. the powder bed contains more voids in between particles) for the Ti-6Al-4V particles. The comparison of the tomographic results with laser diffraction, as another particle size measurements techniques, proved agreement.
Additive Manufacturing (AM) offers the opportunity to produce easier geometrically complex parts compared to traditional production technologies. An important AM technology for metals is selective laser melting (SLM) where a part is produced by melting and solidifying powder in layers. This technique is known to cause a pronounced texture in the produced AM products due to the specific heat flow and the associated solidification of the material during SLM deposition. In order to evaluate the influence of the deposition hatch length during SLM of nickel based superalloy Inconel 718 samples on the texture and in order to identify any preferred crystallographic direction, we performed monochromatic neutron radiography scans (using wavelength from 1.6 Å to 4.4 Å, step size 0.05 Å) to image the samples while rotating it through 90°. Samples produced with short hatch length showed fine textured columnar grains oriented along the sample building direction in high-resolution radiographs. Whereas processing the sample using a ten-fold longer hatch length reduced the texture. The neutron radiographic experiments were accompanied by scanning electron microscopy including electron back-scattered diffraction to visualize and verify the microstructure and texture.
Additive Manufacturing by Selective Laser Melting (SLM) offers an ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses (RS) developed during the processing can reduce the load bearing capacity as well as induce unwanted distortion, limiting the life time and the application of SLM parts.
Due to the advantages of additive manufacturing (AM), it has been increasingly integrated into many industrial sectors.
The application of AM materials for safety-critical parts requires the detailed knowledge about their microstructure stability under thermo-mechanical or mechanical load and knowledge on ageing process mechanisms. Ageing processes are characterized by change of the material microstructure that is to be initially investigated. This work deals with the Investigation of 316L stainless steel manufactured by selective laser melting (SLM). Describing Parameters must be defined and applied on the microstructure of these materials in their initial state and after loads were applied. The findings of this work form the basis for the investigation of AM material ageing.
The layer-by-layer Additive Manufacturing (AM) by means of Selective Laser Melting (SLM) offers many prospects regarding the design of a part used in aeroplane components and gas turbines. However, structural deviations from the nominal morphology are unavoidable. The cooling of the finished part leads to shrinkage and a high surface roughness is induced by attached powder particles affecting the part volume too.
The integrity and load-bearing capacity of a SLM produced lattice structure (see Fig.1) has been investigated by means of in-situ X-ray computed tomography during compression. The lattice structure was compressed by 10 % in height with an applied maximum force of 5 kN. Additionally, a single strut has been investigated ex-situ as a component of the lattice structure. With the higher resolution achieved on the single strut, the pore distribution (size and location) as well as the surface roughness were assessed. One of the main results coming from the in-situ analysis was that the nodes were identified as the weakest points in the lattice structure.
BAM ensures and represents high standards for safety in technology and chemistry. Additive manufacturing (AM) changes the requirements for conventional non-destructive testing (NDT) as new processes of defect creation occur. Especially in safety critical areas, such as aerospace and automotive, new manufacturing processes and materials always require reliability tests and new standards which is a big challenge for NDT.