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- Directed energy deposition (4)
- Recycling (4)
- Resistance spot welding (4)
- Additive manufacturing (3)
- Grinding chips (3)
- Hardness (3)
- Artificial intelligence (2)
- Comminution (2)
- Directed Energy Deposition (2)
- Finite element modelling (2)
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During the production of ship propellers, considerable quantities of grinding chips from nickel aluminium bronze areproduced. This paper examines the mechanical comminution of such chips via impact whirl milling and the utilization of twochip-powder batches as feedstock for a laser-based directed energy deposition process. The materials are characterized viadigital image analysis, standardized flowability tests, scanning electron microscopy and energy dispersive X-ray spectroscopyand are compared to conventional, gas atomized powder. The specimens deposited via directed energy deposition areanalyzed for density, hardness and microstructure and tensile properties for vertical and horizontal build up directions arecompared. At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favorableflow properties and particle size distribution, making them suitable to deposit additive specimens. The microstructureexhibited characteristic martensitic phases due to the high cooling rates of the additive manufacturing process. The presenceof ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanicalproperties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa intensile strength, 455 MPa in yield strength and 12.6 % elongation at break. The findings of this study indicate that recyclingof machining chips to additive manufacturing feedstock can be a viable option for reducing material costs and environmentalimpact.
Die additive Fertigung gewinnt für industrielle Anwendungen zunehmend an Bedeutung. In diesem Zusammenhang sind Verfahren der Directed Energy Deposition (DED) besonders gefragt, um hohe Aufbauraten zu erreichen. Neben den bekannten laserstrahlbasierten Verfahren hat auch der Elektronenstrahl die industrielle Marktreife erreicht. Das Wire Electron Beam Additive Manufacturing bietet zum Beispiel Vorteile bei der Verarbeitung von Kupferwerkstoffen. In der Literatur wird die höhere Energieeffizienz und die daraus resultierende Verbesserung der CO2-Bilanz des Elektronenstrahls hervorgehoben. Es fehlt jedoch an praktischen Studien mit Messdaten, um das Potenzial der Technologie zu quantifizieren. In dieser Arbeit wird eine vergleichende Ökobilanz zwischen der additiven Fertigung mit Draht und Elektronenstrahl (DED-EB) und der additiven Fertigung mit Laserstrahl und Pulver (DED-LB) durchgeführt. Dazu werden die Ressourcen für die Herstellung ermittelt, ein Testbauteil mit beiden Verfahren hergestellt und der gesamte Energieverbrauch gemessen. Die Umweltauswirkungen werden dann mit den Faktoren Treibhauspotenzial (GWP100), Ozonbildungspotenzial (POCP), Versauerungspotenzial (AP), Eutrophierungspotenzial (EP) abgeschätzt. Es zeigt sich, dass das Wire Electron Beam Additive Manufacturing durch einen deutlich geringeren Energiebedarf gekennzeichnet ist. Darüber hinaus gewährleistet die Verwendung von Draht eine größere Ressourceneffizienz, was zu insgesamt besseren Ökobilanzergebnissen führt.
Manual welding of structures requires highly skilled welders due to the large heat-affected zone of arc-based processes, that can negatively impact microstructure and cause distortion. Handheld laser beam welding is a promising alternative with high welding velocity and a concentrated heat input. However, its current use in industry is limited to parts with aesthetic requirements, often made of high-alloyed steel. To extend the use of handheld laser beam welding to low-cost steels with good mechanical properties, this study investigates the influence of laser power on the melt pool shape for micro-alloyed steel with a thickness of 1.5 mm. Tested joint geometries are T-joints welded with filler wire as well as butt joints and overlap joints without filler wire, which are typically found in assemblies under mechanical load. Weld quality is assessed by weld porosity analysis. The results show that the handheld laser beam welding with filler wire produces T-joints with a very good external appearance, but with porosity between level C and D in the cross sections according to DIN EN ISO 13919-1. By increasing the laser power, a deep penetration of the T-joint zone can be achieved without increasing the actual throat thickness. For handheld laser beam welding of butt joints a full penetration weld of the highest quality class can be reached. Overlap joints can be welded with full or partial penetration depending on the laser power selected, with quality classes between B and C in terms of porosity.
Additive Fertigungstechnologien wie das Laser-Pulverbett-Verfahren bieten großes Potenzial für die Fertigung von Neu und Ersatzteilen für stationäre Gasturbinen aus Nickelsuperlegierungen wie Inconel 939 (IN939). Um die Integration in bestehende Baugruppen zu ermöglichen und Bauraumbeschränkungen zu überwinden, muss die Prozesskette der additiven Fertigung um geeignete Fügetechniken erweitert werden. Die vorliegende Arbeit beschäftigt sich daher mit dem Schweißen von Inconel 939. Hierbei werden Bleche aus Gussmaterial und der additiven Herstellung mittels Laser im Pulverbett beim Elektronenstrahlschweißen verglichen. Im Fokus der Untersuchung stehen die erreichbare Nahtqualität im Hinblick auf geometrische Unregelmäßigkeiten sowie innere Defekte in Form von Mikrorissen in der Wärmeeinflusszone. Bei der Auswertung der geschweißten Proben zeigen sich keine Unterschiede in der Ausbildung der Nahtform zwischen dem additiv gefertigten Material und dem Gusswerkstoff. Für beide Materialien ließ sich bei hohen Vorschubgeschwindigkeiten von 20 mm/s die höchste Bewertungsgruppe für Strahlgeschweißte Nähte nach DIN EN ISO 13919-1 erreichen. Unabhängig von der Herstellungsart zeigen beide Materialien eine Zunahme der Rissneigung mit steigendem Vorschub. Das Material aus der additiven Herstellung weist aufgrund seiner Mikrostruktur insgesamt jedoch deutlich weniger Mikrorisse auf, was Potenzial für die Anwendung in der Praxis eröffnet.
This study investigates the occurrence and mitigation of liquid metal embrittlement occurring during resistance spot welding in deep-drawn automotive components, specifically focusing on an S-Rail made from advanced high-strength steel. A simulation-based liquid metal embrittlement risk criterion based on local major component stresses was established and used to quantify and compare liquid metal embrittlement risks between different tests. Experimental and numerical analyses were conducted, revealing that springback significantly impacts liquid metal embrittlement formation. Adjustments in electrode geometry and hold time post-welding were found to mitigate liquid metal embrittlement risks. The effects of stack-up configuration and related parameter settings on liquid metal embrittlement occurrence were identified and liquid metal embrittlement was effectively prevented across both stack-up configurations. These findings advance the understanding of liquid metal embrittlement mechanisms and provide practical approaches to enhance the spot weld quality in AHSS-based body-in-whites.
During the production of ship propellers, considerable quantities of grinding chips from nickel aluminium bronze are produced. This paper examines the mechanical comminution of such chips via impact whirl milling and the utilization of two chip-powder batches as feedstock for a laser-based directed energy deposition process. The materials are characterized via digital image analysis, standardized flowability tests, scanning electron microscopy and energy dispersive X-ray spectroscopy and are compared to conventional, gas atomized powder. The specimens deposited via directed energy deposition are analyzed for density, hardness and microstructure and tensile properties for vertical and horizontal build up directions are compared. At elevated mill rotation speeds, the comminution with impact whirl milling produced rounded particles, favorable flow properties and particle size distribution, making them suitable to deposit additive specimens. The microstructure exhibited characteristic martensitic phases due to the high cooling rates of the additive manufacturing process. The presence of ceramic inclusions was observed in both the powder and on the tensile fracture surfaces, partly impairing the mechanical properties. However, specimens in the vertical build-up direction (Z) showed competitive tensile results, with 775 MPa in tensile strength, 455 MPa in yield strength and 12.6 % elongation at break. The findings of this study indicate that recycling of machining chips to additive manufacturing feedstock can be a viable option for reducing material costs and environmental impact.
The production of conventional metal powders for additive manufacturing process is energy intensive and costly. This study introduces a sustainable alternative by recycling stainless steel milling chips as feedstock for laser-powder directed energy deposition. The recycling process employs a three-stage mechanical comminution method utilizing a fine impact mill UPZ100 from Hosokawa Alpine AG. Characterization of the resulting powders is conducted through particle morphology analysis, flowability tests, and mechanical property assessments. The chip-derived powders exhibit comparable aspect ratios and sphericity to conventional water atomized powders, though with reduced flowability due to a pronounced fine fraction content. Elevated levels of oxides are observed, leading to the formation of an oxide layer on specimen blocks, without impairing the mechanical properties. Analyses of porosity, microstructure, and hardness indicate no significant differences when compared to conventional powders from water or gas atomization. This recycling approach not only mitigates waste but also enhances the potential for a circular and sustainable manufacturing process in the additive manufacturing industry and beyond.
The finite element analysis (FEA) simulation of directed energy deposition (DED) processes offers many potential cost savings during the build job optimization process, through, e.g., distortion predictions. However, the biggest challenge is the long calculation time, frequently exceeding the actual build time. One way of simplifying the simulation with the aim of reducing the calculation times is the inherent strain method. While this method is already used commercially in the simulation of powder bed-based processes and conventional welding technologies, its use in DED is still the subject of research. In this work, an inverse determination of an inherent strain is carried out on a 20-layer-high, single-track-wide wall, common theories are reviewed, and an approach based on thermal strain is introduced. As a result, the calculation time could be reduced by 83% and the accuracy remained at 92%.
Abstract
In the post-processing of large maritime components, a considerable amount of waste in the form of milling and grinding chips is produced. At the same time, additive manufacturing technologies have shown great potential in producing high-volume parts for maritime applications, allowing novel design approaches and short lead times. In this context, this study presents a sustainable approach to recycle and use aluminium bronze waste material, generated during post-processing of large cast ship propellers, as feedstock for laser-powder directed energy deposition. The recycling technology used to produce powder batches is inductive re-melting in combination with ultrasonic atomization. The derived metal powders are characterized using digital image analysis, powder flowability tests, scanning electron microscopy as well as energy dispersive X-ray spectroscopy. Compared to conventional metal powders produced by gas atomization, the recycled material shows excellent sphericity and a powder size distribution with a higher content of finer and coarser particles. Metallographic sections of deposited additively produced specimens show an increased hardness and reduced ductility, but also competitive densities and higher yield and ultimate tensile strength compared to cast material. The process chain shows high potential for the maritime sector to enable circular and sustainable manufacturing.
In recent years, new solutions have been explored to reduce the weight of components for the automotive, railway, and aerospace industries. For this reason, Carbon Fiber Composites (CFCs) have increasingly replaced metals in products that need to be lightweight. However, due to their poor thermal conductivity, CFCs have limited use in applications requiring efficient heat dissipation. In such applications, conventionally manufactured metal alloys are typically utilized. To address these limitations, a novel approach using a combination of additively manufactured aluminum and CFCs is proposed to exploit the distinct advantages of both materials. These innovative hybrid structures aim to combine good structural and thermal management properties with reduced weight compared to conventionally produced metal products. In this study, additively manufactured aluminum alloy (AlSi10Mg) and short carbon fiber Polyamide 6 composite (sCF-PA6) are utilized to produce metal–polymer pairs using electron beam energy to bond the two materials. Direct irradiation of short CFCs with electron beam leads to polymer degradation. Thus, a novel method “Electron Beam Bonding” for joining CFCs with aluminum alloy in various joint configurations using electron beam technology is demonstrated. This innovative approach presents a promising solution for creating metal–polymer multi-materials for lightweight applications.
