Authors:
Yang Tian (Monash University, Australia), Derui Jiang (Monash University, Australia), Xinhua Wu (Monash University, Australia)
Abstract:
Metal powder characteristics can affect the build quality of laser powder bed fusion produced (LPBF) parts. In this study, two batches of Hastelloy X powder with different powder characteristics including powder chemical compositions, morphologies, amounts of inclusions, and size distributions were compared in terms of the subsequent flowability, printing quality, and microstructures. Metal powder with irregular surface morphologies and large number of inclusions was found to be undesirable to the building quality. This was mainly attributed to the poor powder spreading quality on the build plate. Whereas metal powder with uniform circular morphology and less inclusions showed the best printing quality. Cracking issue was found in the LPBF produced HX microstructure, which was sensitive to the amount of Si, Mn and C contents.
DOI:
https://doi.org/10.59499/WP225366563
Authors:
J. B. Lee (1), J. Y Jeong (1), B. G. Lim (2), H. G. Jeong (1)
1- Korea Institute of Industrial Technology, Republic of Korea
2- AMOTECH co. ltd., Republic of Korea
Abstract:
Commercial hydrothermally synthesized BaTiO3 powder with a cubic structure was annealed in a temperature range of ~900 ℃, and the cubic-tetragonal structure transition and microstructure evolution of the powder were investigated in relation to the sintering processes. The BaTiO3 powder used had a cubic structure below an annealing temperature of 900 ℃ and a tetragonal structure above 900 ℃. The pre-annealed powders with a cubic structure were transformed into powders with a tetragonal structure by sintering above 900 ℃, irrespective of the environment.
DOI:
https://doi.org/10.59499/EP235762595
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Authors:
Aitor Amatriain (CEIT, Spain), Ernesto Urionabarrenetxea (CEIT, Spain), Martin José M. (CEIT, Spain)
Abstract:
Computer simulation of metal powder gas atomisation aims to better understand the complex phenomena involved in the interaction between gas and liquid metal, in order to maximize productivity and to avoid common issues. An efficient axisymmetric simulation of primary and secondary atomisation is proposed, which reduces calculation time in conventional desktop computer to the range of few hours. Primary atomisation is modeled using a Eulerian model that predicts the gas|liquid ratio in the neighborhood of the melt delivery tube. The secondary atomisation uses a Lagrangian particle tracking approach with a multimodal breakup model to predict particle breakup, and thus particle size distribution. Transition from the primary to the secondary atomisation takes place at the iso-surface of void fraction equal to 90%, which is adopted as injection surface. Particle size distributions of gas-atomised copper powder obtained with simulations are compared with experimental results.
DOI:
https://doi.org/10.59499/WP225371452
Authors:
Paul Baret (1,2), Xavier Boulnat (2), Yann de Carlan (1), Laurent Chaffron (1), Damien Fabrègue (2), Joël Malaplate (1)
1- Université Paris-Saclay, CEA, Service de Recherche en Matériaux et procédés Avancés, France
2- Université Lyon, CNRS, INSA-Lyon, MATEIS UMR5510, France
Abstract:
Austenitic steel was the reference cladding material in sodium cooled fast neutron nuclear reactors. These alloys exhibit good high temperature mechanical properties and they can withstand very high irradiation doses. To further increase the performance of these alloys, two distinct ways of improvement are possible: oxides dispersion strengthening or ultra fine grain microstructure. In order to achieve the desired enhanced material, powder metallurgy and in particular mechanical alloying route is promising. However, the high ductility of austenitic steel significantly reduces the powder production yield and worsens the supersaturation of oxides during mechanical alloying. To overcome this issue, multiple batches were produced using high-energy horizontal attritor at times ranging from 5 to 40 hours and consolidated by Spark Plasma Sintering (SPS). This paper tackles the characterization of powders after mechanical alloying and SPS compacts.
DOI:
https://doi.org/10.59499/EP246274627
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Authors:
García de la Cruz Lucía (1), Lagos Miguel (2), Alvaredo Paula (1), Torralba José Manuel (1,3), Campos Mónica (1)
1- Universidad Carlos III de Madrid, Leganés, Spain
2- TECNALIA, Donostia-San Sebastián, Spain
3- IMDEA Materials Institute, Madrid, Spain
Abstract:
Electrical resistance sintering (ERS) is an ultrafast sintering process that uses high current densities and pressure to consolidate samples in a few seconds. These conditions enable the consolidation of powder partially retaining its original characteristics. Such characteristics can be modified by low energy mechanical milling, deforming superficially the powder while retaining its spherical shape. CoCrMo alloy is widely used for biomedical applications and requires a good combination of strength and ductility, which can be achieved with customized microstructure that features the proper phase distribution and grain size. This research investigates the use of ERS as a promising tool to fabricate CoCrMo samples from powder processed at different milling times, for exceptional mechanical properties. Microstructures are studied by means of SEM/EBSD and XRD and mechanical properties evaluated in terms of hardness.
DOI:
https://doi.org/10.59499/EP235764663
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Authors:
G.P. De Gaudenzi (1); S. Tedeschi (1); F. Pirone (1); D. Ruggiero (1); F. Tavola (2); and B. Bozzini (2)
1-F.I.L.M.S. S.p.A., Italy
2-Dept. of Energy, Politecnico di Milano, Italy
Abstract:
Circular use of the main hardmetal constituents is mandatory for European industrial economy. Over the past 20 years some recovery processes have been integrated in the extractive metallurgy or directly in the hardmetal production processes. Among attempted recovery routes, electrochemical methods have been studied since the ‘70’s, although they never climbed to the level of an industrial process. In this work, we present the crucial electrochemical knowledge-base that has enabled the definition of an electrochemical demolition process, claiming to overcome the productivity barrier that, so far, has hindered the industrial application of electrochemical scrap treatments. In particular, in this contribution, we concentrate on the systematic investigation of the electrochemical response of HM in the pseudopassive and transpassive condition, an appropriate sequence of which is adopted in our electrochemical demolition process. As a worst-case benchmark, this study revolves around a representative series of corrosion-resistant grades.
DOI:
https://doi.org/10.59499/EP235763766
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Authors:
Fredrik Olsson (Höganäs AB, Sweden), Maheswaran Vattur Sundaram (Höganäs AB, Sweden)
Abstract:
The enhanced strength and performance of the PM steels are attributed to its martensitic microstructure from heat treatment process. However, in the as-quenched state, the metastable martensite is brittle, and to improve the toughness and the phase stability, tempering is performed. In PM steels, the performance can be further enhanced by the addition of Ni and heat treatment after sintering in form of casehardening by low-pressure carburizing (LPC). The combined effect on the obtained microstructure needs to be understood and optimized to maximize the overall performance. This paper investigates the effect of microstructural changes due to tempering a chromium pre-alloyed PM steel with and without Ni additions after LPC utilizing Electron Backscatter Diffraction (EBSD).
DOI:
https://doi.org/10.59499/WP225371528
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Authors:
A. Kirchner (1), U. Gaitzsch (1), D. Dorow-Gerspach (2), B. Distl (3), M. Franke-Jurisch (1), C. Zhong (1), T. Weißgärber (1,4)
1- Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Branch Lab Dresden, Germany
2- Forschungszentrum Jülich, Institut für Energie- und Klimaforschung - Plasmaphysik, Germany
3- Plansee SE, Austria
4- Institute of Materials Science, Technische Universität Dresden, Germany
Abstract:
For refractory metals additive manufacturing of near net shape parts represents an attractive opportunity, in particular for complex geometries. The combination of high melting point, thermal conductivity and brittleness represents a challenge for fusion processes. Electron beam powder bed fusion (PBF-EB) facilitates preheat temperatures above 1000°C and vacuum processing with negligible oxygen contamination. Elemental tungsten and molybdenum were PBF-EB processed to high density from spherical and non-spherical powders. The resulting microstructure is characterized by large grains elongated in build direction and texture. Accordingly, the potential for the mechanical strength of defect-free PBF-EB refractory metals corresponds to conventionally fabricated material in recrystallized condition. The cracking behavior of tungsten tiles under extreme thermal shock was analyzed. Generated test geometries include thin-walled components and lattice structures. The Mo9Si8B alloy required 1100°C preheat temperature for crack-free processing. The microstructure is fine-grained with coarsening in the lower part. The bending strength exceeds 1200 MPa at 1000°C.
DOI:
https://doi.org/10.59499/EP246281479
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Authors:
Alex Wehrli (Osterwalder AG, Switzerland)
Abstract:
Energy cost and overall equipment efficiency have triggered the development of large electric powder compacting presses.Additionally, several OEMs have announced the implementation of stronger regulations in their supply chain with the aim to reduce the grey energy.With the increased complexity and precision of PM parts, hydraulic CNC presses have replaced the mechanical presses. By implementing high|low-pressure systems, fast movement actuators and intelligent pump technology, the energy efficiency was increased, but there remains a very high energy demand compared to the actual net energy required for compacting a part.In this study the energy consumption of hydraulic and electric drive systems for the upper ram and the die of a compacting press is calculated and compared with the actual net energy demand of a compaction part.It will be shown why and by what amount the electric drive outperforms the hydraulic drive when it comes to energy efficiency.
DOI:
https://doi.org/10.59499/WP225367791
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Authors:
Karl-Heinz Leitz (1), Bernhard Valentini (1)
1- PLANSEE SE, 6600 Reutte, Austria
Abstract:
High temperature vacuum furnaces for heat treatment typically have operation powers of several hundred kilowatts. They are generally equipped with a fast-cooling system that has to assure that cooling rates, required for certain heat treatment processes, are uniformly met in the whole load. In this contribution thermo-electric and thermo-fluid dynamic analyses of a high temperature vacuum furnace with a refractory metal hot zone are applied to show potentials for energy savings without losing cooling efficiency. The simulation results are validated by experimental data. The results show that an optimization of the gas system allows energy savings of up to 20 % without losing cooling efficiency.
DOI:
https://doi.org/10.59499/EP235764058
Authors:
Maheswaran Vattur Sundaram (Höganäs AB, Sweden) Michael Andersson (Höganäs AB, Sweden) Philipp Scholzen (Höganäs AB, Sweden)
Abstract:
Astaloy® CrS is a sustainable alternative to Fe-Cu-C PM steels that can also be heat treated in a conventional way with gas carburization and oil quenching. When heat treated this material has the potential to reach performance levels of Mo-prealloyed PM steels. To achieve improved fatigue performances, the evaluation was performed in two stages. First by varying the heat treatment parameters such as carburisation temperature and holding time. Secondly, Ni and graphite amounts were varied, applying carburisation at low temperature, to realise the full potential of this material. The performance was benchmarked against other materials. By optimising heat treatment and mix compositions, fatigue performance has significantly improved, making Astaloy CrS superior to Fe-Cu-C and equivalent to that of Mo-prealloyed PM steels.
DOI:
https://doi.org/10.59499/EP256767821
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Authors:
Patrick Korir (1,2,3), Maheswaran Vattur Sundaram (1), Kumar Babu Surreddi (2), Farnoosh Forouzan (1,2), Dimitris Chasoglou (1), Marta-Lena Antti (2,3)
1- Höganäs AB, Sweden
2- Division of Materials Science, Luleå University of Technology, Sweden
3- Wallenberg Initiative Materials Science for Sustainability, Division of Materials Science, Luleå University of Technology, Sweden
Abstract:
In PM steels, alloying through master alloy (MA) addition enables the introduction of oxygen-sensitive elements such as Cr, Mn, and Si. These elements offer cost-effective and sustainable alternatives to Cu and Ni, enhancing hardenability and performance. This study investigates the atomisation of Fe-Cr-Mn-Si-C MA powders using three different techniques: water atomisation, gas atomisation, and gas atomisation-water cooling. The MA powders were sieved into two size fractions and mixed with Fe – 0.85 wt.% Mo pre-alloyed base powder and graphite. MA powder characterisation, compressibility, and dilatometry-sintering experiments were performed to evaluate the different atomisation techniques, and liquid phase formation at various sintering temperatures. Additionally, industrial sintering trials were conducted, and mechanical properties were assessed to understand the behaviour of sintered samples. The results indicate that MA addition improves the hardenability and performance, especially after sintering above 1200°C, once the MA melting and alloy homogenisation have occurred.
DOI:
https://doi.org/10.59499/EP246281345
