The design freedom offered by additive manufacturing opens up possibilities for developing novel vacuum electronic devices and radio-frequency components with integrated functionalities. High purity copper is often chosen for these applications because it combines excellent electrical and thermal conductivity. Laser powder bed fusion systems equipped with high-power green laser sources have been developed to enhance the processability of pure copper, which exhibits a low absorption rate for conventional infrared lasers. In this study, pure copper parts manufactured by green laser powder bed fusion were characterized in terms of density, impurity content, and mechanical and physical properties to assess their suitability for ultra-high vacuum applications. Additionally, vacuum membranes were produced with different wall-thicknesses and building orientations and tested for helium leakage with a detection limit of 10-10 mbar l s-1. Further microstructural characterization analyses were conducted on the tested membranes to determine the critical parameters influencing their performance in ultra-high vacuum environments, such as effective wall thickness and laser scan length, and establish the current wall thickness limits for pure copper components manufactured by green laser powder bed fusion.

Powder bed fusion of copper has been extensively investigated using both laser-based (PBF-LB/M) and electron beam-based (PBF-EB/M) additive manufacturing technologies. Each technique offers unique benefits as well as specific limitations. Near-infrared (NIR) laser-based LPBF is widely accessible; however, the high reflectivity of copper limits energy absorption, thereby resulting in a narrow processing window. Although optimized parameters can yield relative densities above 97%, issues such as keyhole porosity, incomplete melting, and anisotropy remain concerns. Green lasers, with higher absorptivity in copper, offer broader process windows and enable more consistent fabrication of high-density parts with superior electrical conductivity, often reaching or exceeding 99% relative density and 100% International Annealed Copper Standard (IACS). Mechanical properties, including tensile and yield strength, are also improved, though challenges remain in surface finish and geometrical resolution. In contrast, Electron Beam Powder Bed Fusion (EB-PBF) uses high-energy electron beams in a vacuum, eliminating oxidation and leveraging copper’s high conductivity to achieve high energy absorption at lower volumetric energy densities (~80 J/mm3). This results in consistently high relative densities (>99.5%) and excellent electrical and thermal conductivity, with additional benefits including faster scanning speeds and in situ monitoring capabilities. However, EB-PBF processes in general face their own limitations, such as surface roughness and powder smoking. This paper provides a comprehensive review of the current state of laser-based (PBF-LB/M) and electron beam-based (PBF-EB/M) powder bed fusion processes for the additive manufacturing of copper, summarizing key trends, material properties, and process innovations. Both approaches continue to evolve, with ongoing research aimed at refining these technologies to enable the reliable and efficient additive manufacturing of high-performance copper components.

Copper alloys with chromium and hafnium offer the possibility of precipitation hardening and combine enhanced strength with high electrical and thermal conductivities. The production process, which starts with raw materials, involves powder production by gas atomization and leads to additive manufacturing by laser powder bed fusion with different parameter sets. The aim is to utilize precipitation reactions afterwards in CuHf0.7Cr0.35 during temperature exposure for further property optimization. This research focuses on the low-alloyed copper alloy with hafnium and chromium, compares this with conventionally manufactured specimens, and relates the alloy to additively manufactured specimens of other benchmark alloys such as CuCr1Zr. Measurements of hardness and electrical conductivity are accompanied by metallographic investigations to understand the behavior of CuHf0.7Cr0.35 manufactured by generative methods. In the as-built condition, melting traces remain visible in the microstructure, and hardness values of 101 HV and an electrical conductivity of 17.5 MS/m are reached. Solution annealing completely recrystallizes the microstructure, and the following quenching holds further alloying elements in supersaturated solid solution, resulting in 73 HV and 16.5 MS/m. Subsequent target-oriented precipitation reactions enable peak values of about 190 HV and 42 MS/m. Future research will assess mechanical and physical properties at elevated temperatures and evaluate possible applications.

Additive Manufacturing (AM) offers different benefits such as efficient material usage, reduced production time and design freedom. Moreover, with continuous technological developments, AM expands in versatility and different material usage capabilities. Recently new energy sources have been developed for AM - green wavelength lasers, which provide better energy absorption for pure copper. Due to high thermal and electrical conductivity of copper, this novel AM technology is highly promising for various industries, particularly, there is a huge interest to use it for accelerator applications. In particular, these AM produced accelerator components should reach the associated Ultra High Vacuum (UHV) requirements. In this study, vacuum membranes of pure copper were produced by AM using a green laser source, in different thicknesses and built angles. Furthermore, a vacuum membrane helium leak tightness test was performed at room temperature by using a high-sensitivity mass spectrometer. Comparison of these test results was performed with previously established results. Through this study, novel knowledge and initial results are provided for green laser source AM technology usage for applications for UHV accelerator components.

Linear particle accelerators (Linacs) are primarily composed of radio frequency cavities (cavities). Compared to traditional manufacturing, Laser Powder Bed Fusion (L-PBF) holds the potential to fabricate cavities in a single piece, enhancing Linac performance and significantly reducing investment costs. However, the question of whether red or green laser PBF yields superior results for pure copper remains a subject of ongoing debate. Eight 4.2 GHz single-cell cavities (SCs) were manufactured from pure copper using both red and green PBF (SCs R and SCs G). Subsequently, the surface roughness of the SCs was reduced through a chemical post-processing method (Hirtisation) and annealed at 460 °C to maximize their quality factor (Q0). The geometric accuracy of the printed SCs was evaluated using optical methods and resonant frequency (fR) measurements. Surface conductivity was determined by measuring the quality factor (Q0) of the SCs. Laser scanning microscopy was utilized for surface roughness characterization. The impact of annealing was quantified using Energy-Dispersive X-ray Spectroscopy and Electron Backscatter Diffraction to evaluate chemical surface properties and grain size. Both the SCs R and SCs G achieved the necessary geometric accuracy and thus fR precision. The SCs R achieved a 95% Q0 after a material removal of 40 µm. The SCs G achieved an approximately 80% Q0 after maximum material removal of 160 µm. Annealing increased the Q0 by an average of about 5%. The additive manufacturing process is at least equivalent to conventional manufacturing for producing cavities in the low-gradient range. The presented cavities justify the first high-gradient tests.

Among metal additive manufacturing technologies, direct energy deposition (DED) processes have the advantage to be easily integrable in a manufacturing chain with other conventional technologies. This characteristic can be exploited by designing reinforcement structures to be added by DED onto pre-existing subcomponents to tailor the part’s mechanical properties while keeping the part lightweight. This study focuses on DED by means of laser beam and powder process optimization to improve material quality and geometrical accuracy of AlSi10Mg reinforcement structures while preventing excessive thermal deformations and material dilution into the substrate. These results are compared with finite elements numerical simulations of the deposition process, comprising thermo-elastic deformation and material deposition, to predict the bending and reinforcement of the processed substrate. In particular, the model includes the deterministic prediction of the deposition profile as a function of the process parameters and a few condition-specific coefficients: once calibrated, the model was used to compare the numerical and experimental residual deformation of the reinforced sample, obtaining promising agreement. The reinforcement provided to a 1.5 mm thick substrate by a single wall of deposited materials, with cross-sectional dimensions of 2 mm in width and 2.5 mm in height, was evaluated by three points bending. With the reinforcement on the tensile side of the stresses, the energy absorbed by the material plastic deformation increased by 2.4% as compared to the substrate alone, while with the reinforcement on the compression side of the stresses the energy absorption increased by 75.8% on average.

This work investigates the development of manufacturing parameters and correlations of parts manufactured via PBF-LB with AlSi10Mg using Design of Experiments (DoE). The main goal of this research is to gain a comprehensive understanding of the parameter space and find correlations of relative density with surface roughness and productivity by considering laser powers up to 400 W. The influence of different process parameters, combined and represented as the Volumetric Energy Density (VED) is investigated. Here, a density of above 99.5 % could be achieved within a wide VED range of 40 - 188 J/mm(3). The measured mean downskin surface roughness ranges from 12 - 68 mu m depending on their overhang angle and measurement method, whereas the mean top upskin surface roughness ranges between 4 - 48 mu m with different parameter combinations of laser power (P) and layer thickness (LT). The approach developed here enables the efficient development of suitable process parameters and reduces the optimization effort of the PBF-LB process through the rapid characterization of manufactured part quality in terms of density, which directly influences its mechanical strength. (c) 2024 The Authors. Published by Elsevier B.V.

The development of new high temperature materials for coatings as well as structural components is an important topic to contribute to a higher efficiency and sustainability of e.g. gas turbine engines. One promising new class of high temperature materials are NiAl-based alloys. Within this study, the microstructure and microhardness of NiAl-Ta-Cr alloys with varying Cr and Ta content were investigated. Graded specimens were fabricated by laser-based directed energy deposition utilizing an in situ alloying approach by mixing elemental Ta and Cr as well as pre-alloyed NiAl powder. Thermodynamic calculations were performed to design the alloy compositions beforehand. Inductive preheating of the substrate was used to counter the challenge of cracking due to the high brittleness. The results show that the cracking decreases with increasing preheating temperature. However, even at 700 °C, the cracking cannot be fully eliminated. Scanning electron microscopy, X-ray diffraction and electron backscatter diffraction revealed the formation of the phases B2-NiAl, A2-Cr and C14-NiAlTa within NiAl-Ta and NiAl-Cr alloys. For NiAl-Ta-Cr compositions, deviations regarding the phase formation between calculation and experiment were observed. Maximum hardness values were achieved within the NiAl-Ta and NiAl-Ta-Cr systems for the eutectic compositions at 14 at.-% Ta with maximum values above 900 HV0.1.

Zinc-based biomaterials are promising for bioresorbable applications; however, their low melting points pose challenges in laser-based additive manufacturing (AM). This study addresses this challenge by focusing on pre-heat temperature in laser-based powder bed fusion (PBF-LB) AM, a critical factor that significantly impacts final part properties. Unlike previous studies, this work systematically explores the pre-heat temperature’s role in shaping the process map, alongside laser power and scanning speed, for high-density zinc fabrication. The primary goal is to analytically generate parameter sets to avoid the vaporization temperature of zinc during the PBF-LB process and enhance the process’s stability. The proposed approach demonstrates a significant influence of the variation in pre-heat temperature on other input parameters range, such as power and scanning speed, thus enhancing the material’s processability both theoretically and next experimentally. For model validation, 20 specimens divided between three builds each with unique pre-heat temperatures were printed, revealing a direct correlation between increased pre-heat temperature and part density. Remarkably, high density was achieved even with low laser power and high scanning speed, reaching up to 99.96

Within this study, the alloy NiAl–2.5Ta–7.5Cr is investigated as a new matrix material for cBN-reinforced abrasive turbine blade tip coatings as currently used NiCoCrAlY matrix alloys suffer from insufficient strength at the high operating temperatures. Laser-based directed energy deposition with blown powder was applied to produce cBN reinforced NiAl-based coatings on monocrystalline CMSX-4 substrates. For this, powdery titanium-coated cBN and NiAl–2.5Ta–7.5Cr material were co-injected into the process zone to achieve an in situ formation of a NiAl–2.5Ta–7.5Cr/cBN composite. In order to overcome challenges such as cracking susceptibility, inductive preheating of the substrate up to 800 °C was used. Optical and scanning electron microscopy, energy dispersive X-ray spectroscopy, as well as electron backscatter diffraction were applied to analyse the fabricated samples’ microstructure. Additionally, the mechanical properties were evaluated by means of microhardness mappings. This work demonstrates the feasibility of in situ forming a metal matrix composite with a homogeneous distribution of cBN particles. The results show the beneficial effect of high-temperature preheating on the crack formation. However, the study also reveals challenges such as cracking induced by the injected cBN particles as well as severe intermixing of substrate and coating, which yields spatially resolved deviations in the chemical composition and resulting variations in microstructure and hardness.

This contribution addresses the complete process chain of an annular aerospike breadboard engine fabricated by laser powder bed fusion using the nickel-based superalloy Inconel® 718. In order to qualify the material and process for this high-temperature application, an extensive material characterization campaign including density and roughness measurements, as well as tensile tests at room temperature, 700, and 900 °C, was conducted. In addition, various geometric features such as triangles, ellipses, and circular shapes were generated to determine the maximum unsupported overhang angle and geometrical accuracy. The results were taken into account in the design maturation of the manifold and the cooling channels of the aerospike breadboard engine. Postprocessing included heat treatment to increase mechanical properties, milling, turning, and eroding of interfaces to fulfill the geometrical tolerances, thermal barrier coating of thermally stressed surfaces for better protection of thermal loads, and laser welding of spike and shroud for the final assembly as well as quality assurance. This contribution goes beyond small density cubes and tensile samples and offers details on the iterations necessary for the successful printing of large complex shaped functional parts. The scientific question is how to verify the additive manufacturing process through tensile testing, simulation, and design iterations for complex geometries and reduce the number of failed prints.

The large class science mission NewATHENA, rescoped by the European Space Agency (ESA) in November 2023, will explore the hot and energetic universe using advanced X-ray technology. The key components of the telescope will be hundreds of Silicon Porous Optics (SPO) modules arranged in an optical bench with a diameter of around 2.7 metres. Considering the overall size, the delicate cell structure and the high aspect ratio in combination with the material-related challenges of Ti6Al4V, additive manufacturing using Direct Energy Deposition (DED) is a promising alternative to conventional processing. In addition to discussing fundamental challenges (e.g. shielding), the development of a highperformance hybrid DED process and associated equipment for robust long-term production will be presented. The developed end-to-end manufacturing approach will be verified by manufacturing and analysing test specimens, geometric demonstrators and representative large breadboards [1], [2].

Zinc is a promising bioresorbable metal, yet its applications are hindered by its insufficient mechanical properties. This study investigates the impact of incorporating nanopowders into a zinc matrix for laser-based powder bed fusion (PBF-LB) additive manufacturing. Two types of nanomaterials (magnesium oxide, aluminum oxide) with different particle sizes (similar to 45 nm, 20 nm) were separately added to the zinc powder, and the mixing parameters were optimized. A significant improvement in powder flowability, particularly with smaller nanoparticles, was observed, resulting in a higher packing density in the PBF-LB process. After printing, the density of the nanocomposites was found to be lower than that of pure zinc. However, despite having the lowest density, the printed composites with the smallest nanopowders demonstrated a higher range for hardness (22.76 +/- 8.31-33.23 +/- 8.23) compared to other composite groups (18.86 +/- 5.79-28.05 +/- 9.47). This suggests a promising path for enhancing zinc mechanical properties by the addition of nanopowders.

In the current study, a combinatorial high-throughput screening approach based on CALPHAD simulations and experimental validation has been utilized to explore a Co2CrFeNi2-Al-Ti CCA-system. This technique, introduced by Kaspar et al. (High Entropy Alloys Mater. https://doi.org/10.1007/s44210-023-00023-x ), allows to perform an accelerated alloy development within a wide compositional range and automated fabrication of graded components with varying chemical composition and microstructure. Extended by semi-automated analytical characterization of the produced samples, this approach enables to design novel compositionally complex alloys (CCAs) with promising properties for specific requirements. In our current work, a multiphase design of L12 γ′-strengthened Co2CrFeNi2-Al-Ti CCAs partially tolerating the disordered BCC-A2 or ordered B2 phases in the alloy microstructure has been utilized. The samples with three different chemical compositions were manufactured by means of laser directed energy deposition (L-DED). By subsequent two-step heat treatment, different phase compositions and microstructures have been realized with a main objective to achieve a high volume fraction of L12 γ′ precipitations. Mechanical properties of investigated alloys were characterized by means of tensile tests. Depending on chemical and phase composition of the alloys, the ultimate tensile strength varied in the range of 1060-1150 MPa. The formation of BCC-B2 phase led to decreased yield to tensile strength and showed a detrimental effect on ductility of investigated alloys.

In laser-based directed energy deposition (L-DED) of Inconel 718 the microstructure of the fabricated components strongly depends on the applied process parameters and the resulting solidification conditions. Numerous studies have shown that the process parameters deposition speed and laser power have a major influences on microstructural properties, such as dendrite morphology and segregation behavior. This study investigates how changes in these process parameters affect the microstructure and hardness when the line mass, and thus the resulting layer height, are kept constant. This enables the microstructural comparison of geometrically similar specimens that were manufactured with the same number of layers but severely different process parameters. This approach yields the benefit of almost identical geometrical boundary conditions, such as the layer-specific build-height and heat conducting cross section, for all specimens. For microstructural analysis scanning electron microscopy and energy dispersive X-ray spectroscopy were applied and the results evaluated in a quantitative manner. The microstructural features primary dendritic arm spacing, fraction and morphology of precipitated Laves phase as well as the spatially resolved chemical composition were measured along the build-up direction. The occurring cooling rates were calculated based on the primary dendritic arm spacing using semi-empirical models. Three different models used by others researchers were applied and evaluated with respect to their applicability for L-DED. Finally, microhardness measurements were performed for a baseline evaluation of the influence on the materials’ mechanical properties.

In this work, a mechanical characterization of AlSi10Mg alloy processed by Direct Energy Deposition with Laser Beam of Metals (DED-LB/M) in atmospheric conditions was performed. SE(B) and ESE(T) specimens, for fracture and fatigue tests were printed and machined having the cracks in three different crack plane orientations. Microstructural and fractographic analyses were performed by FE-SEM and LOM, and it was observed that the fracture response is strongly affected by the crack plane orientation and porosity distribution. Moreover, the ESE(T) specimens were analyzed using the EBSD technique and the results shed light on the effect of melt pool boundaries, grain boundaries and crystallographic orientation of grains on the crack path for the different crack plane orientations.