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Um fossile Brennstoffe in der industriellen Pulverlackbeschichtung zu ersetzen, kann Infrarottrocknung eingesetzt werden. Für komplexe Geometrien, bei denen eine Verschattung die Effizienz der Infrarot-Aushärtung mindert, sind die Anordnung der Infrarotstrahler in der reflektierenden Heizkammer, deren Geometrie und die Verweilzeit der Bauteile die Schlüssel für erfolgreiche Prozesse.
Industrial processes need to be transformed into sustainable alternatives. For powder coatings, which traditionally rely on gas or oil heating systems, infrared radiation can deliver the required process heat. The aim of the NAPUBEST project is to evaluate the possibilities of infrared radiation in the powder coating process. In our laboratory, we realized a prototype of an IR oven for test measurements.
In line with the energy transition, it is desirable to replace fossil fuels in the curing process of industrial powder coatings. Infrared heating is the considered method here. IR-emitter arrangement in the reflective heating chamber, their geometry and the dwell time of the components are crucial for a successful and efficient process. Process optimization has to consider the optical parameter variation of the powder coating during the procedure. Measurements in the NAPUBEST prototype are compared with optical simulations of the setup to get the simulation parameters in agreement with reality and to provide a foundation for the layout of industrial processes.
A report is made on a study of mechanical properties and fractographic characteristics of laser powder bed fusion (PBF‐LB/M)‐built Inconel 718, performing heat treatments and hot‐isostatic pressing. For this, tensile components are heat‐treated by different processes, as namely stress relief (SR), SR and double aging (SR + DA), and hot‐isostatic pressing are conducted. For the mechanical testing, the ultimate tensile strength (UTS) as well as the fatigue behavior are evaluated, examining differences in maximum load behavior, elongation, and the different regimes of fatigue. As changes in material structure can be observed, the sole SR leads to a diminished UTS, while the combination of SR + DA develops an UTS of Rm = 1277 MPa. Within the fatigue behavior, the HIP shows a very balanced material structure with an increased high cycle and very high cycle regime, as the texture gets homogenized during the heat treatment. The metallographic analysis can quantify the material changes, as the density and the hardness are improved by virtue of the heat treatments. Furthermore, the fractographic analysis shows the differences in fracture behavior, arising due to the microstructural changes, as crack initiation points, crack propagation, and forced fractures can be categorized by scanning electron microscopy.
As the correlation between design rules and process limitations is of the upmost importance for the full exploitation of any manufacturing technology, we report a design guide for hybrid-additive manufacturing of Inconel 718. Basic limitations need to be evaluated for this particular hybrid approach that combines laser powder bed fusion (PBF-LB/M) and in situ high-speed milling. Fundamental geometric limitations are examined with regard to the minimum feasible wall thickness, cylinders, overhanging structures, and chamfers. Furthermore, geometrical restrictions due to the integrated three-axis milling process with respect to inclinations, inner angles, notches, and boreholes are investigated. From these findings, we derive design guidelines for a reliable build process using this hybrid manufacturing. Additionally, a design guideline for the hybrid-additive manufacturing approach is presented, depicting a step-to-step guide for the adjustment of constructions. To demonstrate this, a powder nozzle for a direct energy deposition (DED-LB/M) process is redesigned following the previously defined guidelines. This redesign encompasses analysis of the existing component and identification of problematic areas such as flat angles, leading to a new construction that is suitable for a hybrid-additive manufacturing approach.
The recent energy crisis revealed the dependence of many manufacturing companies on fossil fuels Industrial processes need to be transformed into sustainable alternatives For powder coatings, which traditionally rely on gas or oil heating systems, infrared radiation can deliver the required process heat The strong dependence of the IR absorption on the geometry of the irradiated parts as well as on the color and sort of the coating powder has to be considered before the implementation of this innovative heating The aim of the NAPUBEST project (German abbreviation for Nachhaltige Pulverbeschichtungs Technologie which means “Sustainable Powder Coating Technology”) is to get a better understanding of these correlations In our laboratory, we realized a prototype of an IR oven for test measurements The high reflectivity of silver coated reflector sheets facilitates the concentration of infrared radiation inside the oven. On the other hand, the absorption of powder coated samples in different paint colors has an impact on the heating efficiency First tests of the equipment and measurements of the angular dependence of the reflectivity of various coated samples are presented.
Im Rahmen der Energiewende sollen fossile Brennstoffe auch im Heizofen einer industriellen Pulverlackbeschichtung ersetzt werden. In der Stahlindustrie ist die Infrarottrocknung von ebenen Stahlband-Oberflächen ein bereits seit Jahren bewährtes Verfahren. Pulverlack-Beschichtungen werden jedoch oft auf komplexe Geometrien aufgetragen, bei denen eine Verschattung die Effizienz der Infrarot-Aushärtung mindert. Die Anordnung der Infrarotstrahler in der reflektierenden Heizkammer, deren Geometrie und die Verweilzeit der Bauteile sind daher die Schlüssel für erfolgreiche Prozesse. Zur Verfahrensoptimierung müssen zudem die optischen Parameter der Pulverlacke während des Prozesses bekannt sein, um die nötige Strahlungsleistung an Bauteile und unterschiedliche Lacke anpassen zu können. Messungen in der NAPUBEST-Prototypanlage werden daher mit optischen Simulationen des Aufbaus abgeglichen, um die Simulationsparameter an die Messergebnisse anzupassen und damit die Grundlage für die Auslegung von industriellen Prozessen zu gewährleisten. Hierbei wird Infrarotstrahlung mehrerer Wellenlängen berücksichtigt, um in unterschiedlichen Ofenzonen benötigte Aufheiz- und Haltephasen zu verwirklichen.
The enhanced use of sustainable energy sources entails strong fluctuations in the availability of electric power. As we need new approaches for energy distribution and energy storage systems, hydrogen is often discussed as a promising energy carrier. PEM electrolysis can be used to transform electrical energy from renewable sources into hydrogen. One challenge in this context is the need for catalysts, as these contribute significantly to the performance of the electrolysis cell. The commonly used platinum group metal (PGM) catalysts like Iridium are quite scarce and therefore expensive. A possible approach to reduce the Ir content is the application of magnetron sputtering for catalyst generation. By selecting the right process parameters, the desired layer properties can be set very precisely during sputtering. This ensures a large surface area with reduced material usage. The introduction of carbon can increase the surface area of the catalyst further and enhance its effectiveness. First results of investigations on the catalytic effect of sputtered Ir catalyst layers will be presented.
Poly-dopamine - an organic material for X-ray mirror coatings and other technical applications
(2024)
Although the organic molecule dopamine (3,4-dihydroxyphenethylamine) is commonly known as the “hormone of happiness”, thin polymer films of poly-dopamine also have interesting technical properties. When produced by dip coating, these self-organizing layers grow in a reproducible thickness of single or multiple molecule monolayers of a few nanometre thickness only. One application is the use of thin poly-dopamine overcoatings to increase the soft X-ray reflectivity of astronomical X-ray mirrors. We thereby introduce a method of determining the layer thickness of poly-dopamine, which is based on spectroscopic ellipsometry measurements and applies an optical model for the poly-dopamine layers including their dielectric function. Furthermore, we give an outlook to other technical applications for this promising material, presenting this bio-inspired organic polymer as an innovative technical solution for the future.
Bessel beams are advantageous tools for micro drilling applications due to their diffraction-free properties, their long focal length, and their small focal spot diameter. However, their application in industry is limited because they are challenging to integrate into flexible beam shaping systems. This work is intended to overcome limitations in flexibility by presenting a new approach paving the way to high-aspect ratio freeform holes. Therefore,
a spatial light modulator was integrated into an axicon-based setup to merge diffraction-free ablation with the flexibility of holographic spatial beam shaping. A dynamic change of the phase hologram displayed on the spatial light modulator during the process allows for the generation of arbitrary ablation geometries. In contrast to other holographic approaches, the diffraction-free nature of the Bessel beam allows ablation over an extended focal
depth without any focus control needed. The applicability of the approach was demonstrated by processing arbitrary hole shapes, such as ellipses, squares, or star-shapes. The hole sizes of the freeform holes range from 4 μm to 80 μm. Furthermore, up-scaling of the process is demonstrated by using the setup for generation of multi-Bessel spots.