Journal articles: 'PBF-LB/M'

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Schneck, Matthias, Max Horn, Maik Schindler, and Christian Seidel. "Capability of Multi-Material Laser-Based Powder Bed Fusion—Development and Analysis of a Prototype Large Bore Engine Component." Metals 12, no. 1 (December 25, 2021): 44. http://dx.doi.org/10.3390/met12010044.

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Additive Manufacturing (AM) allows the manufacturing of functionally graded materials (FGM). This includes compositional grading, which enables the allocation of desired materials corresponding to local product requirements. An upcoming AM process for the creation of metal-based FGMs is laser-based powder bed fusion (PBF-LB/M) utilized for multi-material manufacturing (MM). Three-dimensional multi-material approaches for PBF-LB/M are stated to have a manufacturing readiness level (MRL) of 4 to 5. In this paper, an advancement of multi-material technology is presented by realizing an industry-relevant complex part as a prototype made by PBF-LB/M. Hence, a multi-material injection nozzle consisting of tool steel and a copper alloy was manufactured in a continuous PBF-LB/M process. Single material regions showed qualities similar to the ones resulting from mono-material processes. A geometrically defined transition zone between the two materials was achieved that showed slightly higher porosity than mono-material regions. Nevertheless, defects such as porosity, cracks, and material cross-contamination were detected and must be overcome in further MM technology development.

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Heiland, Steffen, Benjamin Milkereit, Kay-Peter Hoyer, Evgeny Zhuravlev, Olaf Kessler, and Mirko Schaper. "Requirements for Processing High-Strength AlZnMgCu Alloys with PBF-LB/M to Achieve Crack-Free and Dense Parts." Materials 14, no. 23 (November 25, 2021): 7190. http://dx.doi.org/10.3390/ma14237190.

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Processing aluminum alloys employing powder bed fusion of metals (PBF-LB/M) is becoming more attractive for the industry, especially if lightweight applications are needed. Unfortunately, high-strength aluminum alloys such as AA7075 are prone to hot cracking during PBF-LB/M, as well as welding. Both a large solidification range promoted by the alloying elements zinc and copper and a high thermal gradient accompanied with the manufacturing process conditions lead to or favor hot cracking. In the present study, a simple method for modifying the powder surface with titanium carbide nanoparticles (NPs) as a nucleating agent is aimed. The effect on the microstructure with different amounts of the nucleating agent is shown. For the aluminum alloy 7075 with 2.5 ma% titanium carbide nanoparticles, manufactured via PBF-LB/M, crack-free samples with a refined microstructure having no discernible melt pool boundaries and columnar grains are observed. After using a two-step ageing heat treatment, ultimate tensile strengths up to 465 MPa and an 8.9% elongation at break are achieved. Furthermore, it is demonstrated that not all nanoparticles used remain in the melt pool during PBF-LB/M.

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Martucci, Alessandra, Alberta Aversa, and Mariangela Lombardi. "Ongoing Challenges of Laser-Based Powder Bed Fusion Processing of Al Alloys and Potential Solutions from the Literature—A Review." Materials 16, no. 3 (January 26, 2023): 1084. http://dx.doi.org/10.3390/ma16031084.

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Their high strength-to-weight ratio, good corrosion resistance and excellent thermal and electrical conductivity have exponentially increased the interest in aluminium alloys in the context of laser-based powder bed fusion (PBF-LB/M) production. Although Al-based alloys are the third most investigated category of alloys in the literature and the second most used in industry, their processing by PBF-LB/M is often hampered by their considerable solidification shrinkage, tendency to oxidation, high laser reflectivity and poor powder flowability. For these reasons, high-strength Al-based alloys traditionally processed by conventional procedures have often proved to be unprintable with additive technology, so the design and development of new tailored Al-based alloys for PBF-LB/M production is necessary. The aim of the present work is to explore all the challenges encountered before, during and after the PBF-LB/M processing of Al-based alloys, in order to critically analyse the solutions proposed in the literature and suggest new approaches for addressing unsolved problems. The analysis covers the critical aspects in the literature as well as industrial needs, industrial patents published to date and possible future developments in the additive market.

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Huber, Florian, Dominic Bartels, and Michael Schmidt. "In-Situ Alloy Formation of a WMoTaNbV Refractory Metal High Entropy Alloy by Laser Powder Bed Fusion (PBF-LB/M)." Materials 14, no. 11 (June 4, 2021): 3095. http://dx.doi.org/10.3390/ma14113095.

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High entropy or multi principal element alloys are a promising and relatively young concept for designing alloys. The idea of creating alloys without a single main alloying element opens up a wide space for possible new alloy compositions. High entropy alloys based on refractory metals such as W, Mo, Ta or Nb are of interest for future high temperature applications e.g., in the aerospace or chemical industry. However, producing refractory metal high entropy alloys by conventional metallurgical methods remains challenging. For this reason, the feasibility of laser-based additive manufacturing of the refractory metal high entropy alloy W20Mo20Ta20Nb20V20 by laser powder bed fusion (PBF-LB/M) is investigated in the present work. In-situ alloy formation from mixtures of easily available elemental powders is employed to avoid an expensive atomization of pre-alloyed powder. It is shown that PBF-LB/M of W20Mo20Ta20Nb20V20 is in general possible and that a complete fusion of the powder mixture without a significant number of undissolved particles is achievable by in-situ alloy formation during PBF-LB/M when selecting favorable process parameter combinations. The relative density of the samples with a dimension of 6 × 6 × 6 mm3 reaches, in dependence of the PBF-LB/M parameter set, 99.8%. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements confirm the presence of a single bcc-phase. Scanning electron microscopy (SEM) images show a dendritic and/or cellular microstructure that can, to some extent, be controlled by the PBF-LB/M parameters.

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Kessler, Olaf, Evgeny Zhuravlev, Sigurd Wenner, Steffen Heiland, and Mirko Schaper. "Correlation between Differential Fast Scanning Calorimetry and Additive Manufacturing Results of Aluminium Alloys." Materials 15, no. 20 (October 15, 2022): 7195. http://dx.doi.org/10.3390/ma15207195.

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High-strength aluminium alloy powders modified with different nanoparticles by ball milling (7075/TiC, 2024/CaB6, 6061/YSZ) have been investigated in-situ during rapid solidification by differential fast scanning calorimetry (DFSC). Solidification undercooling has been evaluated and was found to decrease with an increasing number of nanoparticles, as the particles act as nuclei for solidification. Lower solidification undercooling of individual powder particles correlates with less hot cracking and smaller grains in the material produced by powder bed fusion of metals by a laser beam (PBF-LB/M). Quantitatively, solidification undercooling less than about 10–15 K correlates with almost crack-free PBF-LB/M components and grain sizes less than about 3 µm. This correlation shall be used for future purposeful powder material design on small quantities before performing extensive PBF-LB/M studies.

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Wimmer, Andreas, Baturay Yalvac, Christopher Zoeller, Fabian Hofstaetter, Stefan Adami, Nikolaus A. Adams, and Michael F. Zaeh. "Experimental and Numerical Investigations of In Situ Alloying during Powder Bed Fusion of Metals Using a Laser Beam." Metals 11, no. 11 (November 16, 2021): 1842. http://dx.doi.org/10.3390/met11111842.

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Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M) is increasingly utilized for the fabrication of complex parts in various industrial sectors. Enabling a robust and reproducible manufacturing process is one of the main goals in view of the future success of PBF-LB/M. To meet these challenges, alloys that are specifically adapted to the process are required. This paper demonstrates the successful interplay of simulation studies with experimental data to analyze the basic phenomena of in situ alloying. The meshless Smoothed-Particle Hydrodynamics (SPH) method was employed for the numerical simulation of two-component powder systems considering both thermodynamics and fluid mechanics in the solid and the melt phase. The simulation results for the in situ alloying of stainless steel 316L blended with the aluminum alloy AlSi10Mg were enriched and validated with the data from a novel experimental test bench. The combination of both approaches can enhance the understanding of the process for in situ alloying. Therefore, future investigations of the PBF-LB/M process with multi-component powder systems can benefit from detailed numerical studies using SPH.

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Wimmer, Andreas, Fabian Hofstaetter, Constantin Jugert, Katrin Wudy, and Michael F. Zaeh. "In situ alloying: investigation of the melt pool stability during powder bed fusion of metals using a laser beam in a novel experimental set-up." Progress in Additive Manufacturing 7, no. 2 (October 31, 2021): 351–59. http://dx.doi.org/10.1007/s40964-021-00233-y.

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AbstractThe limited access to materials for the Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M) is compensated by in situ alloying. Individual melt pool characteristics can be specifically influenced to improve the mechanical properties of the final part. However, conventional PBF-LB/M machines allow only limited access for detailed observation of the process zone and, in particular, the melt pool. This paper presents a methodology for systematically analyzing the melt pool in the cross section to determine the in situ variation of the melt pool depth. A custom PBF-LB/M test bench was devised to enable investigation of the process zone using high-speed infrared cameras. The image data were processed automatically using a dedicated algorithm. The methodology was applied to analyze the effect of additives on the melt pool stability. Stainless steel 316L powder was blended with the aluminum alloy AlSi10Mg by up to 20 wt.%. It was found that the blended powder significantly reduced the variation of the melt pool depth.

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Schmitt, Matthias, Albin Gottwalt, Jakob Winkler, Thomas Tobie, Georg Schlick, Karsten Stahl, Ulrich Tetzlaff, Johannes Schilp, and Gunther Reinhart. "Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion." Metals 11, no. 6 (May 31, 2021): 896. http://dx.doi.org/10.3390/met11060896.

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The carbon content of steel affects many of its essential properties, e.g., hardness and mechanical strength. In the powder bed fusion process of metals using a laser beam (PBF-LB/M), usually, pre-alloyed metal powder is solidified layer-by-layer using a laser beam to create parts. A reduction of the carbon content in steels is observed during this process. This study examines adding carbon particles to the metal powder and in situ alloying in the PBF-LB/M process as a countermeasure. Suitable carbon particles are selected and their effect on the particle size distribution and homogeneity of the mixtures is analysed. The workability in PBF-LB is then shown. This is followed by an evaluation of the resulting mechanical properties (hardness and mechanical strength) and microstructure in the as-built state and the state after heat treatment. Furthermore, potential use cases like multi-material or functionally graded parts are discussed.

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Huber, Florian, Michael Rasch, and Michael Schmidt. "Laser Powder Bed Fusion (PBF-LB/M) Process Strategies for In-Situ Alloy Formation with High-Melting Elements." Metals 11, no. 2 (February 16, 2021): 336. http://dx.doi.org/10.3390/met11020336.

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In-situ alloy formation by Laser Powder Bed Fusion (PBF-LB/M) from mixtures of easily available elemental powders is an appealing approach for developing and qualifying new alloys for laser based additive manufacturing of metals. However, especially when dealing with high-melting elements, like W, Ta, Mo, or Nb, it is difficult to achieve a homogeneous element distribution and a complete fusion of the powder particles. The aim of this work was to understand the effects of the PBF-LB/M process parameters (laser power, scan speed, laser spot diameter) and three different single- and double-exposure strategies on the fusion of high-melting W, Ta, Mo, and Nb particles in a Ti-matrix. For this purpose, 220 samples with 10 vol.% of the high-melting particle fraction were prepared and analyzed by optical light microscopy and automated image processing, as well as by scanning electron microscopy (SEM). The results are discussed in the context of current research on the process dynamics of PBF-LB/M. Based on that process strategies to support a complete fusion of high-melting particles during in-situ alloy formation are derived. It is shown that the number of unmolten particles can be at least decreased by a factor of ten compared to the most unfavorable parameter combination. For the lower melting elements, Nb and Mo, a complete fusion without any remaining particles visible in the microsections was achieved for certain parameter combinations. The results prove the feasibility of in-situ alloy formation with high-melting alloying elements, but they also demonstrate the necessity to adjust the PBF-LB/M process strategy to achieve a complete dissolution of the alloying elements.

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Bartsch, K., and C. Emmelmann. "Enabling Cost-Based Support Structure Optimization in Laser Powder Bed Fusion of Metals." JOM 74, no. 3 (December 16, 2021): 1126–35. http://dx.doi.org/10.1007/s11837-021-05055-5.

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AbstractSupport structures are essential to laser powder bed fusion (PBF-LB/M). They sustain overhangs, prevent distortion, and dissipate process-induced heat. Their removal after manufacturing is required, though, increasing the overall costs. Therefore, optimization is important to increase the economic efficiency of PBF-LB/M. To enable optimization focused on the support structures’ costs, a cost model is developed. The whole production process, including the design, manufacturing, and post-processing of a part, is considered by deriving formulas for the individual costs. The cost model is applied to a previously developed benchmark procedure. Additionally, a case study investigating different support layout strategies is conducted.

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Nammalvar Raja Rajan, Aravindh, Marcel Krochmal, Thomas Wegener, Abhishek Biswas, Alexander Hartmaier, Thomas Niendorf, and Ghazal Moeini. "Micromechanical Modeling of AlSi10Mg Processed by Laser-Based Additive Manufacturing: From as-Built to Heat-Treated Microstructures." Materials 15, no. 16 (August 13, 2022): 5562. http://dx.doi.org/10.3390/ma15165562.

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The unique microstructure of the alloy AlSi10Mg produced by the laser-based powder bed fusion of metals (PBF-LB/M) provides high-strength and high-strain-hardening capabilities of the material. The microstructure and mechanical properties of 3D-printed, i.e., additively manufactured, AlSi10Mg are significantly altered by post-building heat-treatment processes applied in order to tailor the final properties of the parts. Using an accurate computational model to predict and improve the mechanical performance of 3D-printed samples considering their microstructural features can accelerate their employment in envisaged applications. The present study aims to investigate the correlation between microstructural features and the mechanical behavior of as-built, direct-aged, and T6 heat-treated samples of PBF-LB/M AlSi10Mg under tensile loading using experiment and microstructure-sensitive modeling approaches. Nanoindentation tests are used to calibrate the parameters of the constitutive models for the Al and Si-rich phases. The experimental investigations revealed that heat treatment significantly changes the sub-grain morphology of the Si-rich phase, and this can have a considerable effect on the mechanical behavior of the components. The effect of the modeling of the Si-rich phase in the representative volume elements on the prediction of mechanical behavior is investigated using the J2 plasticity model. The combination of the crystal plasticity model for Al and the J2 plasticity model for the Si-rich phase is used to predict the tensile properties of the as-built and heat-treated states. The predicted results are in good agreement with the experimental results. This approach can be used to understand the microstructure–property relationship of PBF-LB/M AlSi10Mg and eventually tailor heat treatment for PBF-LB/M AlSi10Mg based on the requirement of the application.

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Bartels, Dominic, Julian Klaffki, Indra Pitz, Carsten Merklein, Florian Kostrewa, and Michael Schmidt. "Investigation on the Case-Hardening Behavior of Additively Manufactured 16MnCr5." Metals 10, no. 4 (April 21, 2020): 536. http://dx.doi.org/10.3390/met10040536.

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Additive manufacturing (AM) technologies, such as laser-based powder bed fusion of metals (PBF-LB/M), allow for the fabrication of complex parts due to their high freedom of design. PBF-LB/M is already used in several different industrial application fields, especially the automotive and aerospace industries. Nevertheless, the amount of materials being processed using AM technologies is relatively small compared to conventional manufacturing. Due to this, an extension of the material portfolio is necessary for fulfilling the demands of these industries. In this work, the AM of case-hardening steel 16MnCr5 using PBF-LB/M is investigated. In this context, the influences of different processing strategies on the final hardness of the material are studied. This includes, e.g., stress relief heat treatment and microstructure modification to increase the resulting grain size, thus ideally simplifying the carbon diffusion during case hardening. Furthermore, different heat treatment strategies (stress relief heat treatment and grain coarsening annealing) were applied to the as-built samples for modifying the microstructure and the effect on the final hardness of case-hardened specimens. The additively manufactured specimens are compared to conventionally fabricated samples after case hardening. Thus, an increase in both case-hardening depth and maximum hardness is observed for additively manufactured specimens, leading to superior mechanical properties.

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Höfflin, Dennis, Christian Sauer, Andreas Schiffler, and Jürgen Hartmann. "Process Monitoring Using Synchronized Path Infrared Thermography in PBF-LB/M." Sensors 22, no. 16 (August 9, 2022): 5943. http://dx.doi.org/10.3390/s22165943.

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Additive manufacturing processes, particularly Laser-Based Powder Bed Fusion of Metals (PBF-LB/M), enable the development of new application possibilities due to their manufacturing-specific freedom of design. These new fields of application require a high degree of component quality, especially in safety-relevant areas. This is currently ensured primarily via a considerable amount of downstream quality control. Suitable process monitoring systems promise to reduce this effort drastically. This paper introduces a novel monitoring method in order to gain process-specific thermal information during the manufacturing process. The Synchronized Path Infrared Thermography (SPIT) method is based on two synchronized galvanometer scanners allowing high-speed and high-resolution observations of the melt pool in the SWIR range. One scanner is used to steer the laser over the building platform, while the second scanner guides the field of view of an IR camera. With this setup, the melting process is observed at different laser powers, scan speeds and at different locations with respect to the laser position, in order to demonstrate the positioning accuracy of the system and to initially gain thermal process data of the melt pool and the heat-affected zone. Therefore, the SPIT system shows a speed independent overall accuracy of ±2 Pixel within the evaluated range. The system further allows detailed thermal observation of the melt pool and the surrounding heat-affected zone.

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Bierwisch, C., A. Butz, B. Dietemann, A. Wessel, T. Najuch, and S. Mohseni-Mofidi. "PBF-LB/M multiphysics process simulation from powder to mechanical properties." Procedia CIRP 111 (2022): 37–40. http://dx.doi.org/10.1016/j.procir.2022.08.111.

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Harbig, Jana, Johannes Geis, Philip Sperling, Jens Musekamp, Holger Merschroth, Matthias Oechsner, Matthias Weigold, and Eckhard Kirchner. "Referenzieren von Prozessüberwachungsdaten mit CT-Daten/Using CT data to reference process-monitoring data – Quality assurance in PBF-LB/M." wt Werkstattstechnik online 113, no. 01-02 (2023): 48–52. http://dx.doi.org/10.37544/1436-4980-2023-01-02-52.

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Die Qualitätssicherung beim pulverbettbasierten Laserstrahlschmelzen (PBF-LB/M) ist kostenintensiv und eine der großen Barrieren für eine breite industrielle Anwendung. Neue Ansätze der digitalen Qualitätssicherung durch Überwachungssysteme sollen dieses Problem lösen. Um diese Systeme für die lokale Fehlererkennung auslegen zu können, wird eine Methode zur Verknüpfung von Prozessüberwachungsdaten mit einer CT-Visualisierung der Probe vorgestellt. Quality assurance in powder bed fusion with a laserbeam (PBF-LB/M) is cost-intensive and remains one of the major barriers to widespread industrial application. New approaches of digital quality assurance through monitoring systems are expected to solve this problem. To design these systems for use in local defect detection, a method for linking process-monitoring data to the CT visualization of the sample is presented.

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Griemsmann, Tjorben, Arvid Abel, Christian Hoff, Jörg Hermsdorf, Markus Weinmann, and Stefan Kaierle. "Laser-based powder bed fusion of niobium with different build-up rates." International Journal of Advanced Manufacturing Technology 114, no. 1-2 (March 12, 2021): 305–17. http://dx.doi.org/10.1007/s00170-021-06645-y.

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AbstractNiobium is an important material for high temperature applications, in space, in superconductors or in chemical process constructions. Laser-based powder bed fusion of niobium (PBF-LB/M/Nb) offers new opportunities in design, though it is still an expensive technique. The build-up rate is an important factor for economical manufacturing using PBF-LB/M/Nb. It is largely influenced by variation of process parameters, affecting the heat flow during the manufacturing process. In this work, an empirical model for PBF-LB/M/Nb is developed. Based on this model, manufacturing parameter sets using different volume build-up rates are predicted and confirmed. They enable the manufacture of parts with homogeneous and crack-free microstructure with more than 99.9% relative density. Tensile and hardness tests of specimens, which were manufactured using different parameter sets, are performed to determine the effects of the build-up rate—and thus the heat flow during manufacturing—on different mechanical properties. The ultimate tensile strength and yield strength of as-manufactured specimens reach values up to 525 MPa and 324 MPa, respectively, while the elongation at break ranges between approximately 8 and 16%. The Vickers hardness of all specimens was in the range of 149 ± 8 HV0.1. In addition, the microstructure of the manufactured samples is investigated by means of light as well as scanning electron microscopy.

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Zhang, Wenxuan, Wenyuan Hou, Luc Deike, and Craig Arnold. "Understanding the Rayleigh instability in humping phenomenon during laser powder bed fusion process." International Journal of Extreme Manufacturing 4, no. 1 (January 14, 2022): 015201. http://dx.doi.org/10.1088/2631-7990/ac466d.

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Abstract The periodic undulation of a molten track’s height profile in laser-based powder bed fusion of metals (PBF-LB/M) is a commonly observed phenomena that can cause defects and building failure during the manufacturing process. However a quantitative analysis of such instabilities has not been fully established and so here we used Rayleigh–Plateau theory to determine the stability of a single molten track in PBF-LB/M and tested it with various processing conditions by changing laser power and beam shape. The analysis discovered that normalized enthalpy, which relates to energy input density, determines whether a molten track is initially unstable and if so, the growth rate for the instability. Additionally, whether the growth rate ultimately yields significant undulation depends on the melt duration, estimated by dwell time in our experiment.

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Cui, Chengsong, Louis Becker, Eric Gärtner, Johannes Boes, Jonathan Lentz, Volker Uhlenwinkel, Matthias Steinbacher, Sebastian Weber, and Rainer Fechte-Heinen. "Laser Additive Manufacturing of Duplex Stainless Steel via Powder Mixture." Journal of Manufacturing and Materials Processing 6, no. 4 (July 2, 2022): 72. http://dx.doi.org/10.3390/jmmp6040072.

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Laser additively manufactured duplex stainless steels contain mostly ferrite in the as-built parts due to rapid solidification of the printed layers. To achieve duplex microstructures (ferrite and austenite in roughly equal proportions) and, thus, a good combination of mechanical properties and corrosion resistance, an austenitic stainless steel powder (X2CrNiMo17-12-2) and a super duplex stainless steel powder (X2CrNiMoN25-7-4) were mixed in different proportions and the powder mixtures were processed via PBF-LB/M (Laser Powder Bed Fusion) under various processing conditions by varying the laser power and the laser scanning speed. The optimal process parameters for dense as-built parts were determined by means of light optical microscopy and density measurements. The austenitic and ferritic phase formation of the mixed alloys was significantly influenced by the chemical composition adjusted by powder mixing and the laser energy input during PBF-LB/M. The austenite content increases, on the one hand, with an increasing proportion of X2CrNiMo17-12-2 in the powder mixtures and on the other hand with increasing laser energy input. The latter phenomenon could be attributed to a slower solidification and a higher melt pool homogeneity with increasing energy input influencing the phase formation during solidification and cooling. The desired duplex microstructures could be achieved by mixing the X2CrNiMo17-12-2 powder and the X2CrNiMoN25-7-4 powder at a specific mixing ratio and building with the optimal PBF-LB/M parameters.

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Hantke, Nick, Felix Großwendt, Anna Strauch, Rainer Fechte-Heinen, Arne Röttger, Werner Theisen, Sebastian Weber, and Jan Torsten Sehrt. "Processability of a Hot Work Tool Steel Powder Mixture in Laser-Based Powder Bed Fusion." Materials 15, no. 7 (April 4, 2022): 2658. http://dx.doi.org/10.3390/ma15072658.

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Powder bed fusion of metals using a laser beam system (PBF-LB/M) of highly complex and filigree parts made of tool steels is becoming more important for many industrial applications and scientific investigations. To achieve high density and sufficient chemical homogeneity, pre-alloyed gas-atomized spherical powder feedstock is used. For high-performance materials such as tool steels, the number of commercially available starting powders is limited due to the susceptibility to crack formation in carbon-bearing steels. Furthermore, scientific alloy development in combination with gas-atomization is a cost-intensive process which requires high experimental effort. To overcome these drawbacks, this investigation describes the adaption of a hot work tool steel for crack-free PBF-LB/M-fabrication without any preheating as well as an alternative alloying strategy which implies the individual admixing of low-cost aspherical elemental powders and ferroalloy particles with gas-atomized pure iron powder. It is shown that the PBF-LB/M-fabrication of this powder mixture is technically feasible, even though the partly irregular-shaped powder particles reduce the flowability and the laser reflectance compared to a gas-atomized reference powder. Moreover, some high-melting alloying ingredients of the admixed powder remain unmolten within the microstructure. To analyze the laser energy input in detail, the second part of the investigation focuses on the characterization of the individual laser light reflectance of the admixed alloy, the gas-atomized reference powder and the individual alloying elements and ferroalloys.

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Łuszczek, Jakub, Lucjan Śnieżek, Krzysztof Grzelak, Janusz Kluczyński, Janusz Torzewski, Ireneusz Szachogłuchowicz, Marcin Wachowski, and Marcin Karpiński. "Processability of 21NiCrMo2 Steel Using the Laser Powder Bed Fusion: Selection of Process Parameters and Resulting Mechanical Properties." Materials 15, no. 24 (December 15, 2022): 8972. http://dx.doi.org/10.3390/ma15248972.

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With the development and popularization of additive manufacturing, attempts have been made to implement this technology into the production processes of machine parts, including gears. In the case of the additive manufacturing of gears, the availability of dedicated materials for this type of application is low. This paper summarizes the results of research on the implementation of 21NiCrMo2 low-alloy steel, which is conventionally used to produce gears as a feedstock in the PBF-LB/M process. The work presents research on the selection of process parameters based on porosity measurements, static tensile tests, and hardness measurements. In addition, the article includes a mathematical model based on the quadratic regression model, which allows the estimation of the percentage of voids in the material depending on the assumed values of independent variables (laser power, scanning velocity, and hatch distance). The paper includes a range of process parameters that enable the production of elements made of 21NiCrMo2 steel with a density of over 99.7%. Additionally, comparative tests were carried out on PBF-LB/M-manufactured steel (in the state after printing and the state after heat treatment) and conventionally manufactured steel in terms of its mechanical and microstructural properties. The results showed that the steel exhibited similar mechanical properties to other carburizing steels (20MnCr5 and 16MnCr5) that have been used to date in PBF-LB/M processes and it can be used as an alternative to these materials.

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Rasch, Michael, Johannes Heberle, Maximilian A. Dechet, Dominic Bartels, Martin R. Gotterbarm, Lukas Klein, Andrey Gorunov, et al. "Grain Structure Evolution of Al–Cu Alloys in Powder Bed Fusion with Laser Beam for Excellent Mechanical Properties." Materials 13, no. 1 (December 23, 2019): 82. http://dx.doi.org/10.3390/ma13010082.

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Powder Bed Fusion with Laser Beam of Metals (PBF-LB/M) is one of the fastest growing technology branches. More and more metallic alloys are being qualified, but processing of aluminum wrought alloys without cracks and defects is still challenging. It has already been shown that small parts with low residual porosity can be produced. However, suffering from microscopic hot cracks, the fracture behavior has been rather brittle. In this paper different combinations of temperature gradients and solidification rates are used to achieve specific solidification conditions in order to influence the resulting microstructure, as well as internal stresses. By this approach it could be shown that EN AW-2024, an aluminum-copper wrought alloy, is processable via PBF-LB/M fully dense and crack-free with outstanding material properties, exceeding those reported for commonly manufactured EN AW-2024 after T4 heat treatment.

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Bartels, Dominic, Tobias Novotny, Andreas Mohr, Frank van Soest, Oliver Hentschel, Carsten Merklein, and Michael Schmidt. "PBF-LB/M of Low-Alloyed Steels: Bainite-like Microstructures despite High Cooling Rates." Materials 15, no. 17 (September 5, 2022): 6171. http://dx.doi.org/10.3390/ma15176171.

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Laser-based powder bed fusion of metals (PBF-LB/M) is an emerging technology with enormous potential for the fabrication of highly complex products due to the layer-wise fabrication process. Low-alloyed steels have recently gained interest due to their wide potential range of applications. However, the correlation between the processing strategy and the material properties remains mostly unclear. The process-inherent high cooling rates support the assumption that a very fine martensitic microstructure is formed. Therefore, the microstructure formation was studied by means of scanning electron microscopy, hardness measurements, and an analysis of the tempering stability. It could be shown that additively manufactured Bainidur AM samples possess a bainitic microstructure despite the high process-specific cooling rates in PBF-LB/M. This bainitic microstructure is characterized by an excellent tempering stability up to temperatures as high as 600 °C. In contrast to this, additively manufactured and martensitic-hardened specimens are characterized by a higher initial hardness but a significantly reduced tempering stability. This shows the potential of manufacturing products from Bainidur AM for high-temperature applications without the necessity of a post-process heat treatment for achieving the desired bainitic microstructure.

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Großwendt, Felix, Louis Becker, Arne Röttger, Abootorab Baqerzadeh Chehreh, Anna Luise Strauch, Volker Uhlenwinkel, Jonathan Lentz, et al. "Impact of the Allowed Compositional Range of Additively Manufactured 316L Stainless Steel on Processability and Material Properties." Materials 14, no. 15 (July 22, 2021): 4074. http://dx.doi.org/10.3390/ma14154074.

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This work aims to show the impact of the allowed chemical composition range of AISI 316L stainless steel on its processability in additive manufacturing and on the resulting part properties. ASTM A276 allows the chromium and nickel contents in 316L stainless steel to be set between 16 and 18 mass%, respectively, 10 and 14 mass%. Nevertheless, the allowed compositional range impacts the microstructure formation in additive manufacturing and thus the properties of the manufactured components. Therefore, this influence is analyzed using three different starting powders. Two starting powders are laboratory alloys, one containing the maximum allowed chromium content and the other one containing the maximum nickel content. The third material is a commercial powder with the chemical composition set in the middle ground of the allowed compositional range. The materials were processed by laser-based powder bed fusion (PBF-LB/M). The powder characteristics, the microstructure and defect formation, the corrosion resistance, and the mechanical properties were investigated as a function of the chemical composition of the powders used. As a main result, solid-state cracking could be observed in samples additively manufactured from the starting powder containing the maximum nickel content. This is related to a fully austenitic solidification, which occurs because of the low chromium to nickel equivalent ratio. These cracks reduce the corrosion resistance as well as the elongation at fracture of the additively manufactured material that possesses a low chromium to nickel equivalent ratio of 1.0. A limitation of the nickel equivalent of the 316L type steel is suggested for PBF-LB/M production. Based on the knowledge obtained, a more detailed specification of the chemical composition of the type 316L stainless steel is recommended so that this steel can be PBF-LB/M processed to defect-free components with the desired mechanical and chemical properties.

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Seidler, A., S. Holtzhausen, H. Korn, P. Koch, K. Paetzold, and B. Müller. "Proposal for Load Adaptive Design of Microlattice Structures Suitable for PBF-LB/M Manufacturing." Proceedings of the Design Society 2 (May 2022): 1461–70. http://dx.doi.org/10.1017/pds.2022.148.

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AbstractIn this paper, a proposal for a new method to design load-adaptive microlattice structures for PBF-LB/M manufacturing is presented. For this purpose, a method was developed to stiffen microlattice structures in particular by using self-similar sub-cells to ensure their manufacturability. The quality of the stiffness increase was investigated and verified by finite element simulations. Subsequently, the simulation results were critically discussed with respect to their potential for future design processes for architected materials.

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Deckers, Tobias, Thomas Ammann, Pierre Forêt, Sophie Dubiez-Le-Goff, Kai Zissel, and Gerd Witt. "Einfluss heliumhaltiger Prozessgase auf den Laser-Strahlschmelzprozess." Zeitschrift für wirtschaftlichen Fabrikbetrieb 117, no. 7-8 (August 1, 2022): 452–55. http://dx.doi.org/10.1515/zwf-2022-1094.

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Abstract Kann das Prozessgas bei der Optimierung des PBF-LB/M-Prozesses (z. B. Schichtstärke, Belichtungsgeschwindigkeit oder Prozessierbarkeit neuer Materialen) eine Schlüsselrolle einnehmen? Dieser Beitrag liefert einen Einblick über den aktuellen Forschungsstand der Linde GmbH in Bezug auf heliumhaltige Prozessgase und Vorstellung des neuartigen Prozessgases ADDvance® Laser230. Aufgrund seiner Zusammensetzung ermöglicht das Gasgemisch, die Prozessproduktivität und -stabiliät entscheidend zu verbessern.

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Martucci, A., A. Aversa, F. Bondioli, P. Fino, and M. Lombardi. "Synergic strategies to improve the PBF-LB\M processability of a cracking-sensitive alloy." Materials & Design 224 (December 2022): 111396. http://dx.doi.org/10.1016/j.matdes.2022.111396.

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Diller, Johannes, Dorina Siebert, Christina Radlbeck, and Martin Mensinger. "PBF-LB/M/316L vs. hot-rolled 316L – comparison of cyclic plastic material behavior." Procedia Structural Integrity 42 (2022): 58–65. http://dx.doi.org/10.1016/j.prostr.2022.12.006.

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Götz, Dominik, Andreas Bachmann, Andreas Wimmer, and Michael F. Zäh. "Topologieoptimierung beim Laser-Strahlschmelzen." Zeitschrift für wirtschaftlichen Fabrikbetrieb 116, no. 1-2 (February 1, 2021): 70–74. http://dx.doi.org/10.1515/zwf-2021-0014.

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Abstract Das Laser-Strahlschmelzen (PBF-LB/M) bietet bei der Verarbeitung von Metallen Vorteile gegenüber konventionellen Herstellungsverfahren, wie z. B. eine hohe geometrische Gestaltungsfreiheit. Allerdings sind bereits bei der Bauteilgestaltung einige Fertigungsrestriktionen zu beachten, welche bei der Topologieoptimierung im Gegensatz zur Bauteilmasse oft unberücksichtigt bleiben. Im Projekt OptProLaS * werden temperaturabhängige Fertigungsrestriktionen ermittelt und durch die Kopplung einer Topologieoptimierung mit einer Prozesssimulation bei der Bauteilauslegung berücksichtigt.**

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29

Pisarek, Marcin, Robert Ambroziak, Marcin Hołdyński, Agata Roguska, Anna Majchrowicz, Bartłomiej Wysocki, and Andrzej Kudelski. "Nanofunctionalization of Additively Manufactured Titanium Substrates for Surface-Enhanced Raman Spectroscopy Measurements." Materials 15, no. 9 (April 25, 2022): 3108. http://dx.doi.org/10.3390/ma15093108.

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Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.

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Pisarek, Marcin, Robert Ambroziak, Marcin Hołdyński, Agata Roguska, Anna Majchrowicz, Bartłomiej Wysocki, and Andrzej Kudelski. "Nanofunctionalization of Additively Manufactured Titanium Substrates for Surface-Enhanced Raman Spectroscopy Measurements." Materials 15, no. 9 (April 25, 2022): 3108. http://dx.doi.org/10.3390/ma15093108.

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Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.

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31

Pisarek, Marcin, Robert Ambroziak, Marcin Hołdyński, Agata Roguska, Anna Majchrowicz, Bartłomiej Wysocki, and Andrzej Kudelski. "Nanofunctionalization of Additively Manufactured Titanium Substrates for Surface-Enhanced Raman Spectroscopy Measurements." Materials 15, no. 9 (April 25, 2022): 3108. http://dx.doi.org/10.3390/ma15093108.

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Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.

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32

Pannitz, Oliver, Felix Großwendt, Arne Lüddecke, Arno Kwade, Arne Röttger, and Jan Torsten Sehrt. "Improved Process Efficiency in Laser-Based Powder Bed Fusion of Nanoparticle Coated Maraging Tool Steel Powder." Materials 14, no. 13 (June 22, 2021): 3465. http://dx.doi.org/10.3390/ma14133465.

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Research and development in the field of metal-based additive manufacturing are advancing steadily every year. In order to increase the efficiency of powder bed fusion of metals using a laser beam system (PBF LB/M), machine manufacturers have implemented extensive optimizations with regard to the laser systems and build volumes. However, the optimization of metallic powder materials using nanoparticle additives enables an additional improvement of the laser–material interaction. In this work, tool steel 1.2709 powder was coated with silicon carbide (SiC), few-layer graphene (FLG), and iron oxide black (IOB) on a nanometer scale. Subsequently, the feedstock material and the modified powder materials were analyzed concerning the reflectance of the laser radiation and processed by PBF-LB/M in a systematic and consistent procedure to evaluate the impact of the nano-additivation on the process efficiency and mechanical properties. As a result, an increased build rate is achieved, exhibiting a relative density of 99.9% for FLG/1.2709 due to a decreased reflectance of this modified powder material. Furthermore, FLG/1.2709 provides hardness values after precipitation hardening with only aging comparable to the original 1.2709 material and is higher than the SiC- and IOB-coated material. Additionally, the IOB coating tends to promote oxide-formation and lack-of-fusion defects.

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33

Vu, Hoang Minh, Steffen Meiniger, Björn Ringel, Holger Claus Hoche, Matthias Oechsner, Matthias Weigold, Matthias Schmitt, and Georg Schlick. "Investigation of Material Properties of Wall Structures from Stainless Steel 316L Manufactured by Laser Powder Bed Fusion." Metals 12, no. 2 (February 5, 2022): 285. http://dx.doi.org/10.3390/met12020285.

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To make powder bed fusion (PBF) via laser beam (-LB) for metals (/M) available for highly regulated components such as pressure equipment according to the Pressure Equipment Directive, system-specific qualification methods need to be established to deal with process- and geometry-dependent inhomogeneous material behavior. Therefore, the material properties of austenitic stainless steel (316L) and their influences on normative acceptable qualification strategies were investigated in this study. Flat tensile test specimens were produced by two manufacturing systems identical in construction and were compared to specimens produced from conventionally rolled sheet material. Specimens were compared in the horizontal and vertical building directions in relation to different slope angles, wall thicknesses and cross-sectional areas. Despite identical process setups, parameters and powder feedstock, differences in mechanical behavior could be seen. Furthermore, the mechanical properties, surface roughness and density showed dependencies on the wall thickness and slope angle. In particular, the influence of wall thickness has not been covered in publications about PBF-LB/M before. These results suggest that geometry- and system-dependent components can be designed based on associated data from qualification processes. Therefore, a new qualification method based on wall structure properties is suggested for standard qualification processes of components with wall structures, such as pressure equipment.

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Pannitz, Oliver, and Jan T. Sehrt. "Transferability of Process Parameters in Laser Powder Bed Fusion Processes for an Energy and Cost Efficient Manufacturing." Sustainability 12, no. 4 (February 19, 2020): 1565. http://dx.doi.org/10.3390/su12041565.

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In the past decade, the sales of metal additive manufacturing systems have increased intensely. In particular, PBF-LB/M systems (powder bed fusion of metals using a laser-based system) represent a technology of great industrial interest, in which metallic powders are molten and solidified layer upon layer by a focused laser beam. This leads to a simultaneous increase in demand for metallic powder materials. Due to adjusted process parameters of PBF-LB/M systems, the powder is usually procured by the system’s manufacturer. The requirement and freedom to process different feedstocks in a reproducible quality and the economic and ecological factors involved are reasons to have a closer look at the differences between the quality of the provided metallic powders. Besides, different feedstock materials require different energy inputs, allowing a sustainable process control to be established. In this work, powder quality of stainless steel 1.4404 and the effects during the processing of metallic powders that are nominally the same were analyzed and the influence on the build process followed by the final part quality was investigated. Thus, a correlation between morphology, particle size distribution, absorptivity, flowability, and densification depending on process parameters was demonstrated. Optimized exposure parameters to ensure a more sustainable and energy and cost-efficient manufacturing process were determined.

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35

Diller, Johannes, Lukas Rier, Dorina Siebert, Christina Radlbeck, Frank Krafft, and Martin Mensinger. "Cyclic plastic material behavior of 316L manufactured by laser powder bed fusion (PBF-LB/M)." Materials Characterization 191 (September 2022): 112153. http://dx.doi.org/10.1016/j.matchar.2022.112153.

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Fiegl, Tobias, Martin Franke, Ahmad Raza, Eduard Hryha, and Carolin Körner. "Effect of AlSi10Mg0.4 long-term reused powder in PBF-LB/M on the mechanical properties." Materials & Design 212 (December 2021): 110176. http://dx.doi.org/10.1016/j.matdes.2021.110176.

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YAMADA, Shinnosuke, Mitsugu YAMAGUCHI, and Tatsuaki FURUMOTO. "Effect of Powder Shear Property on PBF-LB/M Powder Bed Quality of Tool Steels." Journal of the Japan Society for Precision Engineering 88, no. 10 (October 5, 2022): 795–800. http://dx.doi.org/10.2493/jjspe.88.795.

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Kleszczynski, Stefan, and Arno Elspaß. "Influence of isolated structural defects on the static mechanical properties of PBF-LB/M components." Procedia CIRP 94 (2020): 188–93. http://dx.doi.org/10.1016/j.procir.2020.09.036.

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Grünewald, Jonas, Pirmin Clarkson, Ryan Salveson, Georg Fey, and Katrin Wudy. "Influence of Pulsed Exposure Strategies on Overhang Structures in Powder Bed Fusion of Ti6Al4V Using Laser Beam." Metals 11, no. 7 (July 15, 2021): 1125. http://dx.doi.org/10.3390/met11071125.

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Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a reduction of downskin roughness and overhang angle can be achieved in PBF-LB/M of Ti6Al4V. Starting from cw exposure, the limits of overhang angle and surface roughness at the downskin surface are investigated as a reference. Subsequently, the influence of laser power, scanning speed, and hatch distance with fixed pulse duration (τpulse = 25 µs) and repetition rate (υrep = 20 kHz) on surface roughness Ra is investigated. Pulsed exposure strategies enable the manufacturing of flatter overhang angles (≤20° instead of ≥25°). Furthermore, a correlation between the introduced volume energy density and the downskin roughness can be observed for pulsed exposure. As the reduction in volume energy density causes an increase in porosity, the combination of pulsed downskin exposure and commercial cw infill exposure is investigated. The larger the gap in volume energy density between the infill area and downskin area, the more challenging it is combining the two parameter sets. By combining cw infill and pulsed downskin exposure, flatter overhang structures cannot be manufactured, and a reduction in roughness can be achieved.

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Rothfelder, Richard, Florian Huber, and Michael Schmidt. "Influence of beam shape on spatter formation during PBF-LB/M of Ti6Al4V and tungsten powder." Procedia CIRP 111 (2022): 14–17. http://dx.doi.org/10.1016/j.procir.2022.08.105.

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41

Hovig, Even W., Amin S. Azar, Klas Solberg, and Knut Sørby. "An investigation of the anisotropic properties of heat-treated maraging steel grade 300 processed by laser powder bed fusion." International Journal of Advanced Manufacturing Technology 114, no. 5-6 (March 27, 2021): 1359–72. http://dx.doi.org/10.1007/s00170-021-06938-2.

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AbstractIn order to explore the possibilities enabled by laser beam powder bed fusion of metals (PBF-LB/M), reliable material models are necessary to optimize designs with respect to weight and stiffness. Due to the unique processing conditions in PBF-LB/M, materials often develop a dominating microstructure that leads to anisotropic mechanical properties, and thus isotropic material models fail to account for the orientation-dependent mechanical properties. To investigate the anisotropy of 18Ni300 maraging steel, tensile specimens were built in seven different orientations. The specimens were heat treated at two different conditions and tested for their tensile properties using digital image correlation (DIC) technique. The microstructure and fracture surfaces are investigated with scanning electron microscope and electron backscatter diffraction. The tensile properties are typical for the material, with a yield strength in the range of 1850 MPa to 1950 MPa, and ultimate tensile strength in the range of 1900 MPa to 2000 MPa. The elastic modulus is 180 GPa, and the elongation at fracture is in the range of 2–6% for all specimens. The strain fields analysed with DIC reveals anisotropic straining in both the elastic and plastic parts of the flow curve for both direct ageing and solution treatment plus ageing specimens. In the former condition, the elastic anisotropy is dictated by the fraction of melt pool boundaries on the transverse surfaces of the specimens. When the material is solution treated prior to ageing, the melt pool boundary effect was supressed.

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Stavropoulos, Panagiotis, Georgios Pastras, Thanassis Souflas, Konstantinos Tzimanis, and Harry Bikas. "A Computationally Efficient Multi-Scale Thermal Modelling Approach for PBF-LB/M Based on the Enthalpy Method." Metals 12, no. 11 (October 29, 2022): 1853. http://dx.doi.org/10.3390/met12111853.

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Laser-Based Powder Bed Fusion is one of the most widely used additive manufacturing processes, mainly due to its high-quality output. End users would greatly benefit from a virtual simulation of the process; however, the modelling of the process is very complicated and slow and therefore restricted mainly to academic users. In this work, a computationally efficient approach to the thermal modelling of PBF-LB/M is presented. This approach is based on the enthalpy method and the division of the simulation into three characteristic scales of the process. Despite the small runtime of the simulations, the model captures the critical phenomena of the process achieving sufficient accuracy.

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43

Schneider, M., D. Bettge, M. Binder, K. Dollmeier, M. Dreyer, K. Hilgenberg, B. Klöden, T. Schlingmann, and J. Schmidt. "Reproducibility and Scattering in Additive Manufacturing: Results from a Round Robin on PBF-LB/M AlSi10Mg Alloy." Practical Metallography 59, no. 10 (September 24, 2022): 580–614. http://dx.doi.org/10.1515/pm-2022-1018.

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Abstract The round robin test investigated the reliability users can expect for AlSi10Mg additive manufactured specimens by laser powder bed fusion through examining powder quality, process parameter, microstructure defects, strength and fatigue. Besides for one outlier, expected static material properties could be found. Optical microstructure inspection was beneficial to determine true porosity and porosity types to explain the occurring scatter in properties. Fractographic analyses reveal that the fatigue crack propagation starts at the rough as-built surface for all specimens. Statistical analysis of the scatter in fatigue using statistical derived safety factors concludes that at a stress of 36.87 MPa the fatigue limit of 107 cycles could be reached for all specimen with a survival probability of 99.999 %.

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Fuchs, C., L. Kick, O. Leprevost, and M. F. Zaeh. "ASSESSMENT OF FINISH MACHINING AND MASS FINISHING AS POST-PROCESSING METHODS FOR PBF-LB/M-MANUFACTURED 316L." MM Science Journal 2021, no. 5 (November 3, 2021): 5187–94. http://dx.doi.org/10.17973/mmsj.2021_11_2021137.

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Additive manufacturing techniques are increasingly used in industry. However, the direct usage of additively manufactured parts is limited due to their relatively low surface quality. Especially to achieve functional surfaces, post-processing has to be carried out. Post-processing methods include traditional mechanical cutting processes as well as electrical and chemical processes. Since previously deposited material is removed and additional manufacturing time is necessary, post-processing leads to increased manufacturing costs. Therefore, if additive manufacturing is to be competitive with traditional manufacturing processes, choosing the correct post-processing method is vital. Decision parameters, for example, are the achievable surface quality, the amount of material removal, and the preservation of the shape. In this article, the suitability of two traditional manufacturing processes, milling and mass finishing, as post-processing methods for parts from 316L, manufactured with powder bed fusion using a laser beam, is described. It is characterized how the depth of material removal influences the surface quality. For the milling process, it is determined that a depth of material removal of 0.2 mm leads to a stable surface quality. Finally, the processes' effectiveness as post-processing methods is assessed by comparing the achievable surface quality, showing that mass finishing processes are an economic post-processing option in specific cases.

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Emminghaus, Nicole, Sebastian Fritsch, Hannes Büttner, Jannes August, Marijan Tegtmeier, Michael Huse, Marius Lammers, Christian Hoff, Jörg Hermsdorf, and Stefan Kaierle. "PBF-LB/M process under a silane-doped argon atmosphere: Preliminary studies and development of an innovative machine concept." Advances in Industrial and Manufacturing Engineering 2 (May 2021): 100040. http://dx.doi.org/10.1016/j.aime.2021.100040.

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46

Ghosh, Abhi, Amit Kumar, Nithin Joy, Anne-Marie Kietzig, and Mathieu Brochu. "Characterization of femtosecond laser micromachined specimens extracted from PBF-LB/M microstruts: Analyzing surfaces fabricated via internally linked machined kerfs." Materialia 20 (December 2021): 101260. http://dx.doi.org/10.1016/j.mtla.2021.101260.

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47

Cui, Chengsong, Felix Stern, Nils Ellendt, Volker Uhlenwinkel, Matthias Steinbacher, Jochen Tenkamp, Frank Walther, and Rainer Fechte-Heinen. "Gas Atomization of Duplex Stainless Steel Powder for Laser Powder Bed Fusion." Materials 16, no. 1 (January 3, 2023): 435. http://dx.doi.org/10.3390/ma16010435.

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Duplex stainless steel powders for laser additive manufacturing have not been developed extensively. In this study, the melts of a super duplex stainless steel X2CrNiMoCuWN25-7-4 (AISI F55, 1.4501) were atomized with different process gases (Ar or N2) at different atomization gas temperatures. The process gas N2 in the melting chamber leads to a higher nitrogen dissolution in the steel and a higher nitrogen content of the atomized powders. The argon-atomized powders have more gas porosity inside the particles than the nitrogen-atomized powders. In addition, the higher the atomization gas temperature, the finer the powder particles. The duplex stainless steel powders showed good processability during PBF-LB/M (Laser powder bed fusion). The gas entrapment in the powder particles, regardless of the gas chemistry and the gas content, appears to have a negligible effect on the porosity of the as-built parts.

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48

Rasch, Michael, Dominic Bartels, Shoujin Sun, and Michael Schmidt. "AlSi10Mg in Powder Bed Fusion with Laser Beam: An Old and Boring Material?" Materials 15, no. 16 (August 17, 2022): 5651. http://dx.doi.org/10.3390/ma15165651.

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Powder bed fusion with laser beam of metals (PBF-LB/M) is a widely used technology to produce parts with a high freedom in design paired with excellent mechanical properties. The casting alloy AlSi10Mg features a wide process window and a microstructure with excellent mechanical properties which are not obtainable through conventional manufacturing. One possibility for achieving this is by influencing the solidification which then directly affects the local part properties. In this study, the effect of different laser beam profiles with gaussian and top-hat intensity distributions, as well as the influence of varying parameter sets on the microstructure and microhardness within the same specimen, was examined. A test specimen consisting of many small cubes was built with different parameters. It was found that the local properties can be varied in a wide range. Build-height-dependent in-situ aging effects can thereby be exploited for tailoring the local material properties. Thus, an extra degree of freedom is added to the design of additively manufactured parts.

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Paraschiv, Alexandru, Gheorghe Matache, Mihaela Raluca Condruz, Tiberius Florian Frigioescu, and Laurent Pambaguian. "Laser Powder Bed Fusion Process Parameters’ Optimization for Fabrication of Dense IN 625." Materials 15, no. 16 (August 21, 2022): 5777. http://dx.doi.org/10.3390/ma15165777.

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This paper presents an experimental study on the influence of the main Laser Powder Bed Fusion (PBF-LB) process parameters on the density and surface quality of the IN 625 superalloy manufactured using the Lasertec 30 SLM machine. Parameters’ influence was investigated within a workspace defined by the laser power (150–400 W), scanning speed (500–900 m/s), scanning strategy (90° and 67°), layer thickness (30–70 µm), and hatch distance (0.09–0.12 µm). Experimental results showed that laser power and scanning speed play a determining role in producing a relative density higher than 99.5% of the material’s theoretical density. A basic set of process parameters was selected for generating high-density material: laser power 250 W, laser speed 750 mm/s, layer thickness 40 µm, and hatch distance 0.11 mm. The 67° scanning strategy ensures higher roughness surfaces than the 90° scanning strategy, roughness that increases as the laser power increases and the laser speed decreases.

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Karlsson, Jussi, Aki Piiroinen, Markus Korpela, and Antti Salminen. "Surface roughness variance on different levels of surface inclination of powder bed fused tool steel 1.2709." IOP Conference Series: Materials Science and Engineering 1135, no. 1 (November 1, 2021): 012020. http://dx.doi.org/10.1088/1757-899x/1135/1/012020.

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Abstract Evolution of additive manufacturing has allowed increased flexibility and complexity of designs over conventional manufacturing e.g. formative and subtractive manufacturing. Restricting factor of laser powder bed fusion of metals (PBF-LB/M) additive manufacturing is the as-built surface quality. To promote an understanding of the surface roughness and suitable surface measuring technologies octagon shaped tool steel 1.2709 samples was developed and manufactured. Different surface measuring technologies was also literary reviewed. Studied samples were manufactured with commercially available laser-based powder bed fusion system using standard parameter set provided by the system manufacturer. Surface roughness was measured from top and down skins from multiple different building angles in a way that process specific effects, such as direction of movement of the powder re-coater, was considered. Based on these measuring results of the samples the effect surface inclination are discussed. The results show that building angle strongly affects to surface roughness of laser-based powder bed fused parts. Surface roughness was measured to be more than five times worse in unsupported angle manufactured down facing surfaces when compared with vertical walls.

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Journal articles on the topic 'PBF-LB/M'

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