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Authors:

Flore Villaret (EDF-R&D, France), Yann de Carlan (Université Paris-Saclay, CEA, France), Damien Fabrègue (Université de Lyon, France), Jérôme Garnier (Université Paris-Saclay, CEA, France), Xavier Boulnat (Université de Lyon, France)

Abstract:

The use of different steel powders allows to obtain either multi-material junctions, when they are stacked, or new duplex alloys when they are blended.This study focuses on new materials obtained by Spark Plasma Sintering (SPS) or Hot Isostatic Pressing (HIP) with an austenitic 316L steel and a martensitic Fe-9Cr steel powders. These materials are characterized at different scales: from metallography to electron microscopy with EDX and EBSD, hardness and tensile tests.The mechanical behaviour of materials cannot be described by a simple law of mixtures. To better understand this phenomenon by describing the obtained materials as a composite, Reuss and Voigt models are used and discussed.The microstructural characterizations show that during the consolidation, the diffusion of the chemical species modifies the nature and the amount of phases, which makes it possible to understand why the models do not completely account for the experimental behaviour.

DOI:

https://doi.org/10.59499/WP225371658

Authors:

E. Frutos (1), D. Cuenca-Fernandez (1), N. Encinas (1), J. Cornide (1)

1-Surface Engineering and Nanostructured Materials Research Group, Faculty of Chemical Sciences, Complutense University of Madrid, Spain

Abstract:

Strengthened high entropy alloys (HEAs), represent a new paradigm for simultaneously achieving high strength and ductility, thereby circumventing this well-known trade-off in conventional and single-phase HEAs alloys. However, dynamic strengthening mechanisms and phase-boundary interactions during external loading remain unclear for these multiphase systems. The large fraction of phase boundary significantly impacts plastic flow in these systems. In this study, the microstructure, based on a mixture of ordered FCC/BCC ((L12, L21)/B2) phases and s phase, and small-scale mechanical behaviour has been evaluated for Fe7Cr7-xNi4+xTiMo (x=0, & 2) high entropy alloys obtained from of mechanically alloyed powders by spark plasma sintering (SPS). The use of nano and macro-indentation tests has allowed us to characterize the values of hardness and fracture toughness shown by the different (L12, L21)/(B2,s)ratios presented by high-entropy Fe-rich alloys.

DOI:

https://doi.org/10.59499/EP246280981

Authors:

Alexander Mejía-Reinoso (Universidad Carlos III de Madrid, Spain), Soon-Jik Hong (Kongju National University, Korea, Republic of), JOSE MANUEL TORRALBA (Universidad Carlos III de Madrid, Spain), Monica CAMPOS (Universidad Carlos III de Madrid, Spain)

Abstract:

The microstructure of materials used in high-temperature components such as power generation, aerospace, chemical, and process plant applications must be stable at the service conditions to avoid any losses in the performance. The reduction of density and the increase of the thermal stability range of the microstructure are also two critical improvements to consider in the development of new dual Co-based superalloys. This work explored three viable choices for achieving dual ?|?’ microstructures: the Co-Al-Mo, the Co-Ni-Al-Ta-Ti-V, and the Co-Ti-V. Since the microstructural characteristics of Co-reinforced by ?' superalloys are critical for the envisioned next-generation superalloys, the morphology and coarsening behaviour of the ?' precipitates in each alloy during the sintering process have been investigated. The volume fraction of ?' and whether there is a difference in the coarsening rate of the ?' precipitates are also key factors in the behaviour of these alloys at high temperatures, has been promoted.

DOI:

https://doi.org/10.59499/WP225371699

Authors:

José Luis Aguilar-Garcia (Carlos III University, Spain), Elisa María Ruiz-Navas (Carlos III University, Spain)

Abstract:

This work explores Composite Extrusion Modeling (CEM) with aluminium as an alternative processing route for aluminium alloys. This process allows working with pellets to be deposited directly, layer-by-layer. For this reason, an initial study, necessary for the production of samples, has been carried out. The first challenge was the design of sustainable aluminium-based feedstock, and the production of pellets for additive manufacturing. Thanks to previous studies by the research group, the Powder Injection Moulding (PIM) technique was used as a first approach to produce good quality samples through a combination of water-soluble polymers with low CO2 emissions, PEG and CAB, respectively. For this, a microstructural characterization was carried out and the critical solid loading and rheological properties were studied, as well as the debinding conditions and sintering parameters. In the same way, the printing parameters were optimized for a proper material deposition and to obtain good quality samples.

DOI:

https://doi.org/10.59499/WP225371685

Authors:

Alexey Tatarinov (Riga Technical University, Latvia), Viktors Mironovs (Riga Technical University, Latvia), Viktors Kurtenoks (Riga Technical University, Latvia)

Abstract:

Although the diagnostics of cracks in sintered PM parts can be performed by resonant acoustic inspection, cracks detection in green parts still remains challenging. The problem persists due to the inapplicability of a mechanical impact to brittle green parts and a low mechanical Q-factor resulting in the absence of expressed natural resonances. Cross-correlation analysis applied to vibration spectra in healthy and damaged green PM gears obtained by laser Doppler vibrometry demonstrated minimal discrepancy between healthy parts and strong differences between healthy and cracked parts. To approach a vital industrial implementation, possibilities for an alternative simpler realization were explored. The compared testing modalities included pendulum test with a lightweight platform, contactless excitation by a pulsed electromagnetic action and frequency sweep with an electrodynamic actuator. All testing modalities along with laser vibrometry demonstrated differences in the vibration spectra between healthy and damaged green parts quantitatively assessed by cross-correlation and cross-coherence analysis.

DOI:

https://doi.org/10.59499/WP225367369

Authors:

Gerrit Hellenbrand (Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Germany), Lukas Klee (Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Germany), Jens Brimmers (Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Germany), Christian Brecher (Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Germany), Thomas Bergs (Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Germany)

Abstract:

Due to the remaining porosity of powder metallurgical (PM) gears, the highly stressed surface is post-densified in a cold rolling process to increase the wear resistance. In this report, an approach to determine the maximum possible surface densification of a demonstrator gear is presented. To realise a high degree of deformation and simultaneously avoid spalling damages at the tip area, an adaption of the process kinematic is used. Metallographic microsections are analysed to detect subsurface damages resulting from the cold rolling process. Additionally, the machine traces concerning the upcoming rolling forces over the feed-rate and number of over-rollings are evaluated. Finally, the realised densification profile is evaluated using an image-processing tool, based on the metallographic microsections and a core-density measurement. This profile can serve as an input for an FE-based tooth contact analysis with consideration of the local density profile.

DOI:

https://doi.org/10.59499/WP225372013

Authors:

Thomas Hutsch (Fraunhofer IFAM Dresden, Germany) Vicente Pacheco (Fraunhofer IFAM Dresden, Germany) Johannes Trapp (Fraunhofer IFAM Dresden, Germany) Thomas Weißgärber (Fraunhofer IFAM Dresden, Germany)

Abstract:

Field assisted Sintering Technologies (FAST) like Spark Plasma Sintering (SPS) use current-enhanced sintering kinetics combined with applied uniaxial pressure. The direct current ideally leads to volumetric Joule heating in the sample. In terms of understanding the whole process, the knowledge of pressure- and temperature-depended electrical resistance of the powder body is of fundamental interest. In the talk, an advanced method to determine the electrical resistance will be discussed. First, the pressure-depended electrical resistance at room temperature is determined. Then, the measurement strategy is implemented in the SPS process. Examples will be given for materials like pure metal and composite powders. The documented data will support the simulation of the SPS process and give the opportunity for better understanding of sintering behaviors.The adaption of the determination process to existing or future SPS equipment will be discussed.

DOI:

https://doi.org/10.59499/EP256767978

Authors:

Lennard Hermans (Fraunhofer IAPT, Germany) Jan Scheumann (Fraunhofer IAPT, Germany) Burhan Umur Avci (Fraunhofer IAPT, Germany) Ingomar Kelbassa (Institute for Industrialization of Smart Materials (ISM), Hamburg University of Technology TUHH, Germany)

Abstract:

A time-intensive challenge in material extrusion is determining process parameters for metal injection molding feedstock that enable the production of high-density components. A critical parameter is the extrusion temperature, which significantly influences the feedstock viscosity and, consequently, the material flow rate. Through in-situ measurement of the flow rate during continuous extrusion, both the initial extrusion temperature and the changes in feedstock viscosity can be determined by successively increasing the temperature. The feedstock-specific material flow rate during extrusion must be precisely adjusted to achieve the required line width in continuous deposition. Even minimal deviations in line width or feedstock viscosity can lead to bonding and layer structure defects. In this paper a closed-loop algorithm that efficiently automates time-consuming and experience-based calibration in piston-based extrusion is presented. Following the process parameter determination, ranges of suitable extrusion temperatures along with the corresponding feedstock viscosity values are provided via datasets, enabling faster production cycles.

DOI:

https://doi.org/10.59499/EP256765584

Authors:

Frederik Tischel (1), Vasily Ploshikhin (1)

1- University of Bremen, Airbus Endowed Chair for Integrative Simulation and Engineering of Materials and Processes, Germany

Abstract:

Sinter-based Additive Manufacturing (SBAM) methods, such as Metal Binder Jetting, bridge the high productivity rate of series production and freedom of design in additive manufacturing. However, SBAM requires a subsequent sintering process to achieve the desired material properties, resulting in distortion due to anisotropic shrinkage and creep distortion. Numerical simulation can be used to predict and compensate for this distortion. The numerical approach requires the determination of sintering strain and viscosity. These material parameters depend on many factors such as density, grain size, and temperature. Therefore, many experiments are necessary to specify all dependen-cies. In this study sintering strain and viscosity are determined as process-related, time-dependent mate-rial parameters directly from sinter dilatometer experiments of binder-jetted Ti-6Al-4V samples under different loads. The process-related material parameters vastly reduce the experimental effort. Fur-ther, the calculated sinter distortion is more accurate than the results using material parameters determined by complex material models.

DOI:

https://doi.org/10.59499/EP246278578

Authors:

Berend Denkena (Institute of Production Engineering and Machine Tools, Germany), Benjamin Bergmann (Institute of Production Engineering and Machine Tools, Germany)

Abstract:

The powder mixture properties determine the sintering results of vitrified bonds for grinding tools. In this paper the influence of the mixing process on porosity of the sintered bonds through the bulk density is shown. Therefore, the bulk density of the mixture and the abrasive concentration and sintering temperature and holding time were varied. Porosity, shrinkage and bending fracture stress were determined to evaluate the influence of these parameters on the sintering result. It was shown that there is no significance influence of abrasive concentration, sintering time and temperature on porosity, shrinkage and bending fracture stress. Instead the influence of the abrasive concentration on the porosity of the powder mixture and the influence of the porosity of the powder mixture on the shrinkage was shown. These outcomes are important for designing moulds and optimizing sintering results.

DOI:

https://doi.org/10.59499/WP225370589

Authors:

Motheo Sepako (1), Thuli Mkhaliphi (1), Deborah Blaine (2)

1- Department of Industrial Engineering, Stellenbosch University, South Africa

2- Department of Mechanical & Mechatronic Engineering, Stellenbosch University, South Africa

Abstract:

The study investigates the influence of Laser Powder Bed Fusion (LPBF) processing parameters on the production of AISI420 stainless steel (420SS). The research aims to determine the effect of energy density, a function of laser power, scan speed, layer height and hatching spacing on the density, porosity, microstructure, and mechanical properties of the as-built 420SS. The findings reveal that as built samples with a relative density exceeding 99% utilized volumetric energy density values ranging from 79.4 to 136.6 J/mm³ and laser power above 150 W. Samples featured porosity levels below 0.01%, characterized by isolated small spherical pores with diameters < 30 μm. The microstructure displayed retained austenite phases, with additional presence of martensite phases at the melt pool boundary, attributed to the rapid cooling associated with the LPBF process. The microhardness of the as-built samples exceeded 540 HV, surpassing that reported for cast 420SS.

DOI:

https://doi.org/10.59499/EP246281798

Authors:

Nicolas Charpentier (FEMTO-ST, France), Thierry Barrière (FEMTO-ST, France), Nathalie Boudeau (FEMTO-ST, France), Peter Vikner (Aubert & Duval, France)

Abstract:

Bio-based binder alleviate the important carbon footprint that is created during PIM-like process with a carbon cycle for the binder. Moreover, some bio-based polymer are more suited to EAM, like PLA.This work presents the different steps in developing a suitable pellets feedstock for PIM-like EAM and its optimisation to minimize porosity by tomographic observation in the final part. The work is focused in the use of a steel-tool alloy powder but using the same method other materials can broaden the field of application.

DOI:

https://doi.org/10.59499/WP225371909