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  • 1.
    Akbari, Saeed
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Johansson, Jan
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Johansson, Emil
    Adaxis, France.
    Tönnäng, Lenny
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Large-Scale Robot-Based Polymer and Composite Additive Manufacturing: Failure Modes and Thermal Simulation2022In: Polymers, E-ISSN 2073-4360, Vol. 14, no 9, article id 1731Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM) of large-scale polymer and composite parts using robotic arms integrated with extruders has received significant attention in recent years. Despite the contributions of great technical progress and material development towards optimizing this manufacturing method, different failure modes observed in the final printed products have hindered its application in producing large engineering structures used in aerospace and automotive industries. We report failure modes in a variety of printed polymer and composite parts, including fuel tanks and car bumpers. Delamination and warpage observed in these parts originate mostly from thermal gradients and residual stresses accumulated during material deposition and cooling. Because printing large structures requires expensive resources, process simulation to recognize the possible failure modes can significantly lower the manufacturing cost. In this regard, accurate prediction of temperature distribution using thermal simulations is the first step. Finite element analysis (FEA) was used for process simulation of large-scale robotic AM. The important steps of the simulation are presented, and the challenges related to the modeling are recognized and discussed in detail. The numerical results showed reasonable agreement with the temperature data measured by an infrared camera. While in small-scale extrusion AM, the cooling time to the glassy state is less than 1 s, in large-scale AM, the cooling time is around two orders of magnitudes longer. © 2022 by the authors

  • 2.
    Claesson, Åsa
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Lyckfeldt, Ola
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Lindqvist, Jonas
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kardeby, Victor
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Lejon, Erik
    Gestamp HardTech AB, Sweden.
    Ulfberg, Petter
    Proximion AB, Sweden.
    Rendall, Helen
    Proximion AB, Sweden.
    Hedin, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ottosson, Peter
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ohlsson, David
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kvarned, Anders
    Uddeholms AB, Sweden.
    Karamchedu, Seshendra
    Uddeholms AB, Sweden.
    Brinkfeldt, Klas
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Hosseini, Seyed
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    lntegrated Optical Fiber Sensors in Additive Manufactured Metal Components for Smart Manufacturing Applications2019In: Smart Systems Integration; 13th International Conference and Exhibition on Integration Issues of Miniaturized Systems, 2019Conference paper (Refereed)
    Abstract [en]

    This work combines fiber optic sensors with additive manufacturing to enable integration of temperature and strain sensors in metal components. In this paper, we present a fiber optic sensor network integrated in press hardening tools to monitor the contact between the tool and the metal sheet during forming operation. The tools are manufactured through metal powder bed fusion using laser melting processes (PBF-SLM), after which the tools are prepared for sensor integration. A demonstrator press hardening tool with integrated fiber optic sensors was heated using an electric heat foil and the sensor measurements was compared to a thermal simulation model. The sensor technology is based on Fiber Bragg Gratings (FBGs), integrated at several positions along the optical fiber. FBGs are in-fiber sensors that are multiplexed. lt is possible to place hundreds of FBG sensors along one single fiber, thus allowing for quasidistributed sensing of temperature or strain. The optical fiber itself can be less than 100 micrometer in diameter, allowing for sensing at several points in a minimally invasive way, when integrated in a tool or component.

  • 3.
    Flys, Olena
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Johansson, M.
    RISE Research Institutes of Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production.
    Berglund, Johan
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Hatami, Sepehr
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Oikonomou, C.
    Uddeholm AB, Sweden.
    Rosen, B. -G
    Halmstad University, Sweden.
    Heat transfer and flow performance in additively manufactured cooling channels with varying surface topography2020In: Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering, ISSN 0912-0289, Vol. 86, no 1, p. 71-79Article in journal (Refereed)
    Abstract [en]

    The flexibility in respect of design and manufacturing freedom that additive manufacturing (AM) offer are key driving factors for many industrial scctors. For example, designing and manufacturing unique internal conformal cooling/heating channels with enhanced functionalities for various applications like tools and heat cxchangcrs. However, for the majority of the metal AM-processes in the as-build condition, AM is associated with high surface roughness, which has a measurable impact e.g on the heat transfer and flow properties. Hence, proper characterization of the fluid flow and heat transfer is vital to understand how the AM surfaces should be optimized for maximum output. The current study considers the cffcct of surface roughness and channels dimensions on the pressure drop and heat transfer. An experimental investigation was made of cooling channels produced by Powdcr-Bcd-Fusion using Lascr-Bcam-Mclting (PBF-LBM) additive manufacturing technique. Cooling channels with as-build surfaces was compared to post-processed cooling channels such as extrude honing and drilled channels, respectively. Results showed the lowest pressure drop for extrude honed channels compare to drilled and as-build channels, while heat transfer showed the same trend for as-build and extrude honed channels. The complexity of surface topography of as-build channels need to be described by parameters suitable for the detection of fluid interaction. Combination of different parameters remains to be investigated.

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  • 4.
    Götelid, Sareh
    et al.
    Swerim AB, Sweden.
    Ma, Taoran
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Lyphout, Christophe
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Vang, Jesper
    Swerim AB, Sweden.
    Stålnacke, Emil
    Swerim AB, Sweden.
    Holmberg, Jonas
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Strondl, Annika
    Swerim AB, Sweden.
    Effect of post-processing on microstructure and mechanical properties of Alloy 718 fabricated using powder bed fusion additive manufacturing processes2021In: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 27, no 9, p. 1617-1632Article in journal (Refereed)
    Abstract [en]

    Purpose: This study aims to investigate additive manufacturing of nickel-based superalloy IN718 made by powder bed fusion processes: powder bed fusion laser beam (PBF-LB) and powder bed fusion electron beam (PBF-EB). Design/methodology/approach: This work has focused on the influence of building methods and post-fabrication processes on the final part properties, including microstructure, surface quality, residual stresses and mechanical properties. Findings: PBF-LB produced a much smoother surface. Blasting and shot peening (SP) reduced the roughness even more but did not affect the PBF-EB surface finish as much. As-printed PBF-EB parts have low residual stresses in all directions, whereas it was much higher for PBF-LB. However, heat treatment removed the stresses and SP created compressive stresses for samples from both PBF processes. The standard Arcam process parameter for PBF-EB for IN718 is not fully optimized, which leads to porosity and inferior mechanical properties. However, impact toughness after hot isostatic pressing was surprisingly high. Originality/value: The two processes gave different results and also responses to post-treatments, which could be of advantage or disadvantage for different applications. Suggestions for improving the properties of parts produced by each method are presented.

  • 5.
    Holmberg, Jonas
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Berglund, Johan
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Brohede, Ulrika
    Swerim AB, Sweden.
    Åkerfeldt, Pia
    Luleå university of Technolgy, Sweden.
    Sandell, Viktor
    Luleå university of Technology, Sweden.
    Rashid, Amir
    KTH Royal institute of Technology, Sweden.
    Zhao, Xiaoyu
    KTH Royal institute of Technology, Sweden.
    Dadbakhsh, Sasan
    KTH Royal institute of Technology, Sweden.
    Fischer, Marie
    Chalmers university of Technology, Sweden.
    Hryha, Eduard
    Chalmers university of Technology, Sweden.
    Wiklund, Urban
    Uppsala university, Sweden.
    Hassila, Carl Johan Karlsson
    Uppsala university, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Machining of additively manufactured alloy 718 in as-built and heat-treated condition: surface integrity and cutting tool wear2023In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 130, no 3-4, p. 1823-1842Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM) using powder bed fusion is becoming a mature technology that offers great possibilities and design freedom for manufacturing of near net shape components. However, for many gas turbine and aerospace applications, machining is still required, which motivates further research on the machinability and work piece integrity of additive-manufactured superalloys. In this work, turning tests have been performed on components made with both Powder Bed Fusion for Laser Beam (PBF-LB) and Electron Beam (PBF-EB) in as-built and heat-treated conditions. The two AM processes and the respective heat-treatments have generated different microstructural features that have a great impact on both the tool wear and the work piece surface integrity. The results show that the PBF-EB components have relatively lower geometrical accuracy, a rough surface topography, a coarse microstructure with hard precipitates and low residual stresses after printing. Turning of the PBF-EB material results in high cutting tool wear, which induces moderate tensile surface stresses that are balanced by deep compressive stresses and a superficial deformed surface that is greater for the heat-treated material. In comparison, the PBF-LB components have a higher geometrical accuracy, a relatively smooth topography and a fine microstructure, but with high tensile stresses after printing. Machining of PBF-LB material resulted in higher tool wear for the heat-treated material, increase of 49%, and significantly higher tensile surface stresses followed by shallower compressive stresses below the surface compared to the PBF-EB materials, but with no superficially deformed surface. It is further observed an 87% higher tool wear for PBF-EB in as-built condition and 43% in the heat-treated condition compared to the PBF-LB material. These results show that the selection of cutting tools and cutting settings are critical, which requires the development of suitable machining parameters that are designed for the microstructure of the material.

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  • 6.
    Holmberg, Jonas
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF. University West, Sweden.
    Palosaari, Mikko
    Stresstech OY, Finland.
    Hosseini, Seyed
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF.
    Larjosuo, Henri
    Stresstech OY, Finland.
    Andersson, Pär
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF. RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Round Robin Study on Residual Stresses Using X-RayDiffraction for Shot-Peened Tool Steel Specimens2018Conference paper (Refereed)
    Abstract [en]

    Residual stress measurements using x-ray diffraction is a well established methodused within the industrial and academic community to verify the performance of differentprocesses for metallic materials. The measurement gives an absolute value of the stress statewhich can be used to design and optimize the process route to induce beneficial compressiveresidual stresses and avoid detrimental tensile stresses. Investigating the uncertainty andaccuracy of the measurement system, operator and the material is therefore of high relevanceboth from an industrial and scientific point of view. Round robin testing is an important way toquantify the uncertainties that could affect the quality of the measured results and hence how aprocess is optimized and tuned. Such an investigation allows the operator to understand andreduce variations. Current round robin test includes results from five different laboratories usingcomparable equipments located in Sweden, Finland, Germany and United States. This workfocuses on five shot-peened tool steel specimens produced with identical process settings.Additionally, an investigation of the repeatability of the system, influence of the operator,variations within the specimen, and the long time stability of the specimens has been measured.

  • 7.
    Hosseini, Seyed
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, IVF.
    Karlsson, B.
    Chalmers University of Technology.
    Vuoristo, T.
    Scania CV AB.
    Dalaei, K.
    Chalmers University of Technology.
    Determination of Stresses and Retained Austenite in Carbon Steels by X-rays - A Round Robin Study2011In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 51, no 1, p. 59-69Article in journal (Refereed)
    Abstract [en]

    Residual stresses and retained austenite are two important process-related parameters which need to be controlled and monitored carefully during production and heat treatment of products. X-ray diffraction techniques are normally used in this context, and the purpose of the present study was to investigate the reproducibility and accuracy of these methods for medium and high carbon steels. The work was carried out as a round robin study including nine different laboratories in Sweden and Finland. Stress measurements were carried out on three specimens etched to three different depths, 0 μm, 230 μm and 515 μm. Retained austenite measurements were carried out on three specimens containing approximately 11, 17 and 30 vol.-% of this phase. The stress measurements showed good reproducibility with standard deviations of typically 4% on flat and smooth surfaces and not more than about 8% on etched surfaces. Estimations revealed that specimen misalignment and improper X-ray spot location were the main sources behind the variation in the stress recordings. The determination of retained austenite showed a standard deviation of typically 15% between the different contributors. However, by using identical evaluation methods for all raw data, the data spread could be narrowed by a factor of 3 to 4 despite the fact that different experimental settings were used in the individual laboratories. © 2010 Society for Experimental Mechanics.

  • 8.
    Hosseini, Seyed
    et al.
    RISE Research Institutes of Sweden, Materials and Production. Chalmers University of Technology, Sweden.
    Klement, U.
    Chalmers University of Technology, Sweden.
    A descriptive phenomenological model for white layer formation in hard turning of AISI 52100 bearing steel2021In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 32, p. 299-310Article in journal (Refereed)
    Abstract [en]

    This paper investigates the characteristics and the formation of white layers and dark layers induced by hard turning of through-hardened AISI 52,100 steel. The investigation showed that different types of white layers exist e.g., formed predominantly through excessive thermal or mechanical energy loading. The thermally induced white layer is formed when the cutting temperature is above the critical austenitisation temperature for the material. The nano-sized microstructure is initiated through dynamic recovery, which transitions to dynamic recrystallisation when the temperature rises above the onset temperature for dynamic recrystallisation. The corresponding white layer is characterised by a higher retained austenite content compared to the unaffected material, and the presence of a dark layer beneath the white layer. The white layer and the adjacent dark layer are found to be ∼12% harder and 14% softer, respectively, compared to the unaffected material. On the other hand, the mechanically induced white layer is formed through severe plastic deformation, where the formation is controlled by dynamic recovery and results in an elongated and broken-down substructure. Neither austenite nor an adjacent dark layer could be found for such white layers. The mechanically induced white layer is ∼26% harder than the unaffected material. For both types of white layer, (Fe, Cr)3C carbides are found in the microstructure. The investigation shows that the heating rate, cooling rate, pressure, and duration of contact between the cutting tool and workpiece surface should also be considered to understand the underlying formation mechanisms. The characteristics of the examined white layers and the cutting conditions are summarised in a descriptive phenomenological model in order to create a systematic approach for the definition of the different types of white layers. 

  • 9.
    Hosseini, Seyed
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes. Chalmers University of Technology, Sweden.
    Mallipeddi, D.
    Chalmers University of Technology, Sweden.
    Holmberg, Jonas
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Rännar, L. -E
    Mid Sweden University, Sweden.
    Koptyug, A.
    Mid Sweden University, Sweden.
    Sjöström, W.
    Mid Sweden University, Sweden.
    Krajnik, P.
    Chalmers University of Technology, Sweden.
    Klement, U.
    Chalmers University of Technology, Sweden.
    Comparison of machining performance of stainless steel 316L produced by selective laser melting and electron beam melting2022In: Procedia CIRP, Elsevier B.V. , 2022, p. 72-77Conference paper (Refereed)
    Abstract [en]

    Powder bed fusion processes based additively manufactured SS 316L components fall short of surface integrity requirements needed for optimal functional performance. Hence, machining is required to achieve dimensional accuracy and to enhance surface integrity characteristics. This research is focused on comparing the material removal performance of 316L produced by PBF-LB (laser) and PBF-EB (electron beam) in terms of tool wear and surface integrity. The results showed comparable surface topography and residual stress profiles. While the hardness profiles revealed work hardening at the surface where PBF-LB specimens being more susceptible to work hardening. The investigation also revealed differences in the progress of the tool wear when machining specimens produced with either PBF-LB or PBF-EB. .

  • 10.
    Hosseini, Seyed
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF, Tillverkningsprocesser. Chalmers University of Technology, Sweden; AB SKF, Sweden.
    Thuvander, Mattias
    Chalmers University of Technology, Sweden.
    Klement, Uta
    Chalmers University of Technology, Sweden.
    Sundell, Gustav
    Chalmers University of Technology, Sweden.
    Ryttberg, Kristina
    AB SKF, Sweden.
    Atomic-scale investigation of carbon atom migration in surface induced white layers in high-carbon medium chromium (AISI 52100) bearing steel2017In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 130, p. 155-163Article in journal (Refereed)
    Abstract [en]

    The microstructure and chemical composition of white layers (WLs) formed during hard turning of AISI 52100 steel were studied using atom probe tomography (APT) and transmission electron microscopy (TEM). APT analyses revealed a major difference in the re-distribution of the carbon (C) atoms between WLs formed above and below the Ac1 temperature, i.e. T-WL and M-WL, respectively. In T-WL, the C-atoms segregate to grain boundaries (GBs) forming interconnected or isolated C-rich clusters, ∼5 nm, with a concentration of 9.8 ± 0.3 at.%C. Apart from the GB segregation, in M-WLs, large C-rich regions were found with 24.8 ± 0.4 at.%C. Owing to the chemical composition (stoichiometry) and element partitioning of such regions, they were assigned as θ-carbides (cementite). The APT results reveal that the original θ-carbides remain un-dissolved in the M-WLs, but might be plastically deformed due to the excessive strain that exists in hard machining process. The obtained results are in good agreement with the temperatures that are reached during formation of M-WLs. The isolated nano-sized C-clusters were assigned as off-stoichiometric carbides whereas the interconnected C-rich clusters were attributed to Cottrell atmospheres, evident by the linear shape of the C-enrichment as observed in the APT reconstructions. The C-contents in the nano-sized martensitic and ferritic grains were estimated to 0.50 ± 0.06 at.%C and ∼0.46 ± 0.02 at.%C, respectively. The C-content in the ferritic grains, beyond the C-solubility limit in ferrite (<0.1 at.%) is governed by the high dislocation density inside the grains, supported by the favorable binding energy between dislocations and C-atoms compared to C-atoms and Fe in carbides. No other evidence of redistribution of the substitutional alloying elements was observed. TEM analyses showed that T-WLs comprises of an equiaxed and nano-sized grains with well-defined cell boundaries, whereas the structure in the M-WLs comprised of elongated sub-grains formed via re-orientation of the original martensite followed by breakage/partitioning into elongated sub-grains.

  • 11.
    Liu, Yan
    et al.
    Simtec Soft Sweden AB, Sweden.
    Adolfsson, Erik
    RISE Research Institutes of Sweden.
    Christoffersson, Örjan
    TurnTime Technologies AB, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes. TurnTime Technologies AB, Sweden.
    Yan, Zhenghua
    Simtec Soft Sweden AB, Sweden.
    Simulation and Additive Manufacturing of Complexly Designed Aircraft Component2023In: Euro PM2023 Proceedings, European Powder Metallurgy Association (EPMA) , 2023Conference paper (Refereed)
    Abstract [en]

    An innovative component used for the cargo handling systems of Boeing 737 aircraft is developed to improve loaders’ working conditions and protect cargo spaces, passenger luggage, and goods from damage. Since the design of the component makes it difficult to manufacture using conventional techniques, metal Binder Jetting, an Additive Manufacturing technique both faster and more cost-effective compared to the conventional laser/electron beam techniques, is used. However, there is a risk of thermally induced distortion in connection with the post-processing, specifically the sintering step. To address this, a 3D computational fluid dynamics simulation model is developed and simulations are made to identify where and when unwanted distortions may occur during the sintering process. In the simulation, the sintering process follows about 15 hours full sintering cycle with all the heating, holding and cooling stages. The simulations are compared with experiments to validate the numerical results. 

  • 12.
    Martin Vilardell, Anna
    et al.
    Karlstad University, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production.
    Åsberg, M.
    Karlstad University, Sweden.
    Dahl-Jendelin, Anton
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Krakhmalev, P.
    Karlstad University, Sweden.
    Oikonomou, C.
    Uddeholms AB, Sweden.
    Hatami, Sepehr
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Evaluation of post-treatments of novel hot-work tool steel manufactured by laser powder bed fusion for aluminum die casting applications2021In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 800, article id 140305Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing is a good alternative to conventional methods for the production of near net shape geometries with high geometric complexity shorter lead times, being a good option for the manufacturing of dies for die casting process. In this research, a novel hot-work tool steel for aluminum die casting applications manufactured by laser powder bed fusion was investigated. As-built and stress-relieved (AS-B + SR) state was established and used as the reference condition, and subsequent post-treatments were added and compared to the reference condition. Test parts were evaluated using tensile, impact, hardness and thermal fatigue testing. Compared to the reference condition, heat treatment (HT), significantly increased the hardness, yield and ultimate tensile strengths of the material, due to the obtained tempered martensite microstructure. Hot isostatic pressing (HIP) prior to HT significantly increased the impact toughness and ductility, and slightly increased the yield and ultimate tensile strength values compared to the HT condition. The addition of nitriding treatment after HT, without intermedium HIP step, resulted in the highest surface hardness and lowest impact toughness. Thermal fatigue was mostly affected by the hardness and the softening of the material during the thermal fatigue testing. Results showed that a high surface hardness resulted in a higher thermal fatigue crack nucleation, meanwhile conditions with a high softening during thermal fatigue performance resulted in a higher crack propagation.

  • 13.
    Pant, Prabhat
    et al.
    Linköping University, Sweden.
    Proper, Sebastian
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Luzin, Vladimir
    ANSTO, Australia; University of Newcastle, Australia.
    Sjöström, Sören
    Linköping University, Sweden.
    Simonsson, Kjell
    Linköping University, Sweden.
    Moverare, Johan
    Linköping University, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production.
    Pacheco, Victor
    Uppsala University, Sweden.
    Peng, Ru Lin
    Linköping University, Sweden.
    Mapping of residual stresses in as-built Inconel 718 fabricated by laser powder bed fusion: A neutron diffraction study of build orientation influence on residual stresses2020In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 36, article id 101501Article in journal (Refereed)
    Abstract [en]

    Manufacturing of functional (ready to use) parts with the powder bed fusion method has seen an increase in recent times in the field of aerospace and in the medical sector. Residual stresses (RS) induced due to the process itself can lead to defects like cracks and delamination in the part leading to the inferior quality of the part. These RS are one of the main reasons preventing the process from being adopted widely. The powder bed methods have several processing parameters that can be optimized for improving the quality of the component, among which, build orientation is one. In this current study, influence of the build orientation on the residual stress distribution for the Ni-based super-alloy Inconel 718 fabricated by laser-based powder bed fusion method is studied by non- destructive technique of neutron diffraction at selected cross-sections. Further, RS generated in the entire part was predicted using a simplified layer by layer approach using a finite element (FE) based thermo-mechanical numerical model. From the experiment, the part printed in horizontal orientation has shown the least amount of stress in all three directions and a general tendency of compressive RS at the center of the part and tensile RS near the surface was observed in all the samples. The build with vertical orientation has shown the highest amount of RS in both compression and tension. Simplified simulations results are in good agreement with the experimental value of the stresses. © 2020 The Authors

  • 14.
    Pant, Prabhat
    et al.
    Linköping University, Sweden.
    Salvemini, Filomena
    ANSTO, Australia.
    Proper, Sebastian
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Luzin, Vladimir
    ANSTO, Australia; University of Newcastle, Australia.
    Simonsson, Kjell
    Linköping University, Sweden.
    Sjöström, Sören
    Linköping University, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Peng, Ru Lin
    Linköping University, Sweden.
    Moverare, Johan
    Linköping University, Sweden.
    A study of the influence of novel scan strategies on residual stress and microstructure of L-shaped LPBF IN718 samples2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 214, article id 110386Article in journal (Refereed)
    Abstract [en]

    Process parameters in laser-based powder bed fusion (LBPF) play a vital role in the part quality. In the current study, the influence of different novel scan strategies on residual stress, porosities, microstructure, and crystallographic texture has been investigated for complex L-shape parts made from nickel-based superalloy Inconel 718 (IN718). Four different novel scanning strategies representing total fill, re-melting, and two different sectional scanning strategies, were investigated using neutron diffraction, neutron imaging, and scanning electron microscopy techniques. These results were compared with the corresponding results for an L-shape sample printed with the conventional strategy used for achieving high density and more uniform crystallographic texture. Among these investigated novel strategies, the re-melting strategy yielded approximately a 25% reduction in surface residual stress in comparison to the reference sample. The other two sectional scanning strategies revealed porosities at the interfaces of the sections and due to these lower levels of residual stress were also observed. Also, variation in crystallographic texture was observed with different scan strategies. © 2022 The Author(s)

  • 15.
    Pant, Prabhat
    et al.
    Linköping University, Sweden.
    Sjöström, Sören
    Linköping University, Sweden.
    Simonsson, Kjell
    Linköping University, Sweden.
    Moverare, Johan
    Linköping University, Sweden.
    Proper, Sebastian
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production.
    Luzin, Vladimir
    ANSTO, Australia; University of Newcastle, Australia.
    Peng, Rulin
    Linköping University, Sweden.
    A simplified layer-by-layer model for prediction of residual stress distribution in additively manufactured parts2021In: Metals, ISSN 2075-4701, Vol. 11, no 6, article id 861Article in journal (Refereed)
    Abstract [en]

    With the improvement in technology, additive manufacturing using metal powder has been a go-to method to produce complex-shaped components. With complex shapes being printed, the residual stresses (RS) developed during the printing process are much more difficult to control and manage, which is one of the issues seen in the field of AM. A simplified finite element-based, layer-by-layer activation approach for the prediction of residual stress is presented and applied to L-shaped samples built in two different orientations. The model was validated with residual stress distributions measured using neutron diffraction. It has been demonstrated that this simplified model can predict the trend of the residual stress distribution well inside the parts and give insight into residual stress evolution during printing with time for any area of interest. Although the stress levels predicted are higher than the measured ones, the impact of build direction on the development of RS during the building process and the final RS distributions after removing the base plate could be exploited using the model. This is important for finalizing the print orientation for a complex geometry, as the stress distribution will be different for different print orientations. This simplified tool which does not need high computational power and time can also be useful in component design to reduce the residual stresses. © 2021 by the authors.

  • 16.
    Xu, Jinghao
    et al.
    Linköping University, Sweden.
    Ma, Taoran
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Peng, Ru Lin
    Linköping University, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes.
    Effect of post-processes on the microstructure and mechanical properties of laser powder bed fused IN718 superalloy2021In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 48, article id 102416Article in journal (Refereed)
    Abstract [en]

    The post-processing on the additively manufactured component is of huge interest as the key to tailor the microstructure to obtain certain mechanical properties. In this present study, the effects of hot isostatic pressing, as well as heat treatment on the microstructure, phase configuration and mechanical properties of laser powder bed fused (LPBF) IN718 superalloy were systematically investigated. Three different post-processes were studied such as hot isostatic pressing (HIP), heat treatment (HT), and HIP followed by HT (HIP+HT). The HIP process effectively eliminated the Laves phase remained in the as-built microstructure and brought uniformly distributed super fine γ″ precipitates in nano-meter size. In the heat-treated microstructure, larger γ″ precipitates were promoted directly from the as-built material. In comparison the HIP+HT process caused a moderate growth of γ″. In the latter two cases, the developed γ″ significantly strengthened the material. Yield strength of IN718 was increased from 738 MPa in as-built condition to 1015 MPa and 1184 MPa after HT and HIP+HT, respectively. On the contrary the ductility in the as-built IN718 condition was reduced by more than 40% after HT and HIP+HT. This can be compared to an increase in the ductility by almost 30% when subjected the as-built specimens to only HIPping. Finally, the correlation between microstructure evolution and mechanical properties is discussed in detail. © 2021 The Authors

  • 17.
    Yuan, M.
    et al.
    Chalmers University of Technology, Sweden.
    Cao, Y.
    Chalmers University of Technology, Sweden; Central South University, China.
    Karamchedu, S.
    Uddeholms AB, Sweden.
    Hosseini, Seyed
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes. Chalmers University of Technology, Sweden.
    Yao, Y.
    Chalmers University of Technology, Sweden.
    Berglund, Johan
    RISE Research Institutes of Sweden, Materials and Production, Manufacturing Processes. Chalmers University of Technology, Sweden.
    Liu, L.
    Central South University, China.
    Nyborg, L.
    Chalmers University of Technology, Sweden.
    Characteristics of a modified H13 hot-work tool steel fabricated by means of laser beam powder bed fusion2022In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 831, article id 142322Article in journal (Refereed)
    Abstract [en]

    In the present study, a modified H13 hot-work tool steel (M-H13) was fabricated by laser beam powder bed fusion (LB-PBF). The effect of two types of post processing, direct tempering from as-built condition (DT) and conventional quenching followed by tempering (QT), on the microstructure and mechanical properties was evaluated. The typical microstructure in QT condition was tempered martensite with carbides along lath boundaries. In DT condition, melt pool boundaries and cellular structure from as-built condition were still observed. While comparable tensile properties and hardness were obtained, DT samples exhibited significantly lower impact toughness compared to QT samples. This was attributed to the difference in work hardening ability and strain rate sensitivity originating from different microstructures obtained under these two heat treatment conditions. The study was also focused on the softening behavior and the correlation with the microstructure of the two post treatments at the elevated temperatures. It was found that the DT samples showed lower thermal softening compared to QT samples. The evolution of carbides was discussed based on the microanalysis results and the JMatPro simulation. © 2021 The Authors

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