Individual Papers

Authors:

Vania Rodriguez (Technical University of Denmark, Denmark) Naiqi Shang (Politecnico di Milano, Italy) Thomas Dahmen (Asgaard Metals ApS, Denmark) Venkata Nadimpalli (Technical University of Denmark, Denmark)

Abstract:

Binder jetting (BJ) is an emerging additive manufacturing (AM) technique offering a cost-effective route for producing complex metal parts. Compared to other AM processes, BJ does not involve rapid melting and solidification, minimizing defects and residual stresses. This makes BJ an attractive alternative for AM alloys with low-weldability such as high-carbon steels. This work explores the effect of sintering parameters on the microstructure of D2 cold work tool steel produced via BJ. Overspray powder as a bi-product from the Spray Forming process (SF) was used as a resource efficient alternative feedstock. The effects of sintering parameters on densification, linear shrinkage and microstructural evolution regarding grain size and phase composition were studied. After sintering, a density of 98% and a hardness of 680 HV were obtained. The study also discusses the potential influences of the sintered microstructure on the properties of the steel addressing opportunities for future

DOI:

https://doi.org/10.59499/EP256779530

Authors:

Vuokko Marjamaa (VTT, Finland) Atte Antikainen (VTT, Finland) Juha Lagerbom (VTT, Finland) Pentti Kalliotiura (VTT, Finland) Tomi Lindroos (VTT, Finland)

Abstract:

The effect of sintering parameters on the properties of austenitic nickel-free stainless steel was investigated using a rate-controlled sintering approach. This study focused on optimizing sintering parameters, including the influence of different gas atmospheres (argon, nitrogen, and hydrogen) with varying partial pressures of nitrogen. The goal was to explore how these parameters affect phase formation, mechanical properties, and corrosion resistance. Mechanical properties were evaluated using indentation-based methods, providing a comprehensive assessment of hardness and elastic modulus. Additionally, corrosion resistance was studied through electrochemical testing. Simulation results, calculated with Thermocal software, were used to complement and compare experimental findings. The results revealed critical insights into the relationship between sintering atmosphere, phase evolution, and material performance, offering a deeper understanding of how sintering conditions can be optimized for enhanced mechanical and corrosion properties in nickel-free stainless steel.

DOI:

https://doi.org/10.59499/EP256765960

Authors:

Yuji Shigeta (National Institute of Advanced Industrial Science and Technology (AIST), Japan) Yusuke Hirayama (National Institute of Advanced Industrial Science and Technology (AIST), Japan) Keigo Kobayashi (Mitsubishi Materials Corporation, Japan) Zheng Liu (National Institute of Advanced Industrial Science and Technology (AIST), Japan) Kenta Takagi (National Institute of Advanced Industrial Science and Technology (AIST), Japan) Jun Kato (Mitsubishi Materials Corporation, Japan) Kazuki Okada (Mitsubishi Materials Corporation, Japan)

Abstract:

Aluminum (Al) is very difficult to sinter because of the stable oxide layer on its surface. Recently we found that sinterability can be dramatically improved by adding a small amount of rare earth oxide (REO). The relative density of over 95% can be achieved by sintering of Al-REO mixed powder even without pressurization for 1 hour. Similar densities were obtained at longer sintering up to 48 hours. However, the effect of sintering time on the sintered microstructure of the mixed powder is unclear. Therefore, in this report, the change in the sintered microstructure of Al-REO mixed powder with sintering time will be discussed.

DOI:

https://doi.org/10.59499/EP256768281

Authors:

Marie Luise Scheck (1), Rui Joao Santos Batista (3), Simone Herzog (2), Anke Kaletsch (1,2), Constantin Häfner (3,4), Christoph Broeckmann (1,2)

1- Institute for Applied Powder Metallurgy and Ceramics (IAPK) at RWTH Aachen e.V., Germany

2- Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University, Germany

3- Fraunhofer Institute for Laser Technology ILT, Germany

4- Laser Technology LLT, RWTH Aachen University, Germany

Abstract:

Processing carbide-rich tool steels with laser-based powder bed fusion is challenging as cracks occur frequently. Substrate plate preheating is commonly applied to improve the processability as the temperature gradients are lowered and stresses reduced. The modified temperature gradients alter the microstructure formation of the alloy. In this study, a carbide-rich tool steel was processed at RT, 500°C and 800°C substrate plate preheating which lead to different precipitated carbide and retained austenite contents. The high substrate plate heating of 800°C significantly reduced cracking of the alloy and a fully martensitic microstructure was obtained. In the samples built at RT or 500°C, the lower diffusion hinders carbide precipitation and thus leads to austenite stabilization. These specimens show cracks despite their higher retained austenite contents. Here, the retained austenite has a high hardness, and therefore it is assumed that it is distorted, brittle and thus cannot prevent crack growth within the specimens.

DOI:

https://doi.org/10.59499/EP246281362

Authors:

Markus Schneider (GKN Sinter Metals Engineering GmbH, Germany), Herbert Danninger (Technische Universität Wien, Austria)

Abstract:

Induction hardening and induction tempering gain increasing importance for heat treating of sintered steels due to high reproducibility and the chance for subsequent soft machining of not heat-treated part regions. Due to the high heating rates and the short processing times during the inductive heating the diffusion processes have to be accelerated by higher temperature. This results in higher austenitizing and tempering temperatures compared to classical furnace heat treatments. In the presence of absorbed nitrogen higher tempering temperatures might result in blue brittleness (300 °C embrittlement), an aging effect caused by the precipitation of nitrides. Based on that working hypothesis four different sintered steels were hardened and tempered under varying conditions. The hardness and the impact toughness were analyzed to check whether a drop of the toughness can be observed at a certain tempering temperature level. Moreover, the absorbed nitrogen contents were measured.

DOI:

https://doi.org/10.59499/WP225369527

Authors:

Santiago Cano Cano (1), Johannes Bosters (1), Clemens Sperling (1), Denise Mödder (1), Johannes Stögerer (1), György Harakály (1)

1- Incus GmbH, Austria

Abstract:

Lithography-based Metal Manufacturing (LMM) is an additive manufacturing (AM) technology that delivers components with high feature resolution and surface quality. By utilizing common Metal Injection Molding grade powders (d90 <25 µm) in the process, a surface roughness of Ra < 2 µm can be achieved, with stable geometric features down to 100 µm. Although these as-printed component parameters surpass those of other metal AM technologies, some applications demand lower surface roughness. To enhance part quality, one approach is the introduction metal powders with smaller size distribution. This not only improves the surface roughness, but also augment the sintering process by facilitating better powder packing. In pursuit of this objective, steel alloys of 316L and 17-4PH with varying size distribution have been analysed, with a specific focus on their processability in the LMM technology and their effectiveness in raising the quality of the components.

DOI:

https://doi.org/10.59499/EP246281371

Authors:

Diego Monzón Martín (CEIT-BRTA, Spain) Gabriela Sarriegui (CEIT-BRTA, Spain) Nerea Burgos (CEIT-BRTA, Spain) José Manuel Martín (CEIT-BRTA, Spain) Valentina Zhukova (UPV|EHU, Spain) Arkady Zhukov (UPV|EHU, Spain)

Abstract:

This study presents a direct metallurgical approach for recycling end-of-life (EoL) sintered Nd-Fe-B magnets into competitive bonded magnets. The scrap was classified based on its rare earth content and converted into fresh recycled Nd-Fe-B powders via gas atomization. Three alloys were produced to analyze the effects of Ti and Zr additions at varying concentrations. Previous research showed that helium (He) as the atomizing gas results in finer powders with nearly fully amorphous particles. Based on this, two alloys were processed with He and one with argon (Ar), confirming that Ti and Zr enhance the glass forming ability of Nd-Fe-B alloys. After microstructural optimization by annealing, the powders exhibited improved magnetic properties. Laboratory specimens were produced by compression molding with epoxy resin as the bonding phase. Magnetic characterization of the isotropic bonded recycled Nd-Fe-B magnets revealed that this route could meet market demands for competitive bonded magnets.

DOI:

https://doi.org/10.59499/EP256767753

Authors:

Polline Mwambe (Stellenbosch University, South Africa) Natasha Sacks (Stellenbosch University, South Africa) Johannes Pötschke (2Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Germany)

Abstract:

Pure nickel (Ni) is known for its low mechanical properties, which limits its range of applications. This study explored the possibility of improving the tensile properties of Ni through the addition of titanium carbonitride (TiCN) reinforcement using laser powder bed fusion. Horizontally built tensile specimens of 100wt% Ni and Ni-10wt% TiCN were tested according to ASTM E8|E8M-21. The Ni-10wt% TiCN samples had an ultimate tensile strength (UTS) of 751.65 MPa, a yield strength (YS) of 550.30 MPa and an elongation (EL) of 11.08 %. Compared to the pure Ni, this represents an increase of 112.31 % in UTS and 79.36 % in YS respectively with a reduction of only 4.15 % in EL. The findings demonstrate that the TiCN reinforcement enhanced the tensile properties of Ni while retaining a desirable ductility. Thus, there is potential for application of these materials where currently duranickel is used, for example spring contacts.

DOI:

https://doi.org/10.59499/EP256708008

Authors:

Farnoosh Forouzan (1,2), Heike Henrich (1), Milad Zohrevand (3), Dimitris Chasoglou (1)

1- Höganäs AB, Sweden

2- Luleå university of technology, Sweden

3- Tampere university, Finland

Abstract:

In this study, the effect of high-power ultrasonic treatment (UST) in comparison with common thermal tempering of Astaloy® CrS (0.85%Cr-0.15%Mo)-0.8%C pressed and sintered samples after quenching is investigated. Results from microhardness, EBSD, and XRD show a promising level of tempering in the samples just after 4 minutes of UST by decreasing the strain level in the specimen and dislocation annihilation, while the thermal annealing at 200° C for 1 hr resulted in more softening and lower hardness level. The results of this study confirm that the Ultrasonic treatment is an effective rapid and easy method with much lower energy consumption that can be good enough to stress relief the component after quenching and substitute the traditional tempering based on the application.

DOI:

https://doi.org/10.59499/EP246269731

Authors:

Núria Cinca (1); Riberto Nunes Peres (2); Elena Tarrés (1); Olivier Lavigne (1); Assis Vicente Benedetti (2)

1- Hyperion Materials & Technologies, 08107 Barcelona, Spain

2- São Paulo State University—UNESP, Instituto de Química, Araraquara 14800-060, SP, Brazil

Abstract:

The effect of the WC grain size on the corrosion resistance of cemented carbides is not well established in the literature. In this study, the electrochemical behaviour of WC-12wt.%Co hard materials with various starting grain sizes (ultrafine, fine, and medium) were evaluated in aerated 3.5 wt.% NaCl media as well as 0.1M NaOH and 0.1M H2SO4, by means of electrochemical techniques (Electrochemical Impedance Spectroscopy, EIS, and polarization scans). Results showed that the corrosion resistance of the material is slightly dependant on the WC grain size. Based on EIS results, the corrosion resistance of the material in acidic media slightly increases when decreasing the WC grain size, while an inverse trend is observed in alkaline media. This is due to the inherent heterogeneity of the two-phase nature of these materials.

DOI:

https://doi.org/10.59499/EP235756856

Authors:

Marco Mariani (1), Luigi Montipò (1), Nora Lecis (1)

1- Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156, Milano, Italy

Abstract:

Binder jetting is a sinter-based technique that allows the production of application-oriented designs with a reduced consumption of raw materials. The employment of powders from scrap metal recycling would minimise the lifecycle impact of the process. In our work, gas atomised powders tailored for binder jetting are compared to a feedstock obtained by recycling of 316L waste. The morphological features of particles, especially sphericity and size distribution, are measured by granulometry and scanning electron microscopy. Printed components are studied at the green and sintered state to observe the influence of each feedstock and the comparative analyses on density and final microstructures (residual porosity, grain size and phases distribution) allows to determine which are the most beneficial properties of the powders. CALPHAD modelling highlights the feedstock chemical composition effects on densification mechanisms: Ni and C content are responsible for δ phase formation and solidus temperature, thus affecting diffusive processes during sintering.

DOI:

https://doi.org/10.59499/EP235764265

Authors:

Hossein Besharatloo (1,2,3), Ahmed-Ameur Zegai (4), Saghar Fooladimahani (1), Caterina Chirico (3), Luis Llanes (1), Begoña Ferrari (3), Antonio Javier Sanchez-Herencia (3)

1- CIEFMA/CMEM/EEBE - Universitat Politècnica de Catalunya, Barcelona, Spain

2- COLFEED4PRINT, Madrid, Spain

3- ICV-CSIC, Madrid, Spain

4- Laboratory of Materials Sciences and Engineering (LSGM), Faculty of Mechanical Engineering and Process Engineering, University of Sciences and Technology Houari Boumediene, Algiers, Algeria

Abstract:

The powder composition and sintering process significantly influence the microstructure, phase composition, and mechanical properties of WC-based composites. The precise control of both chemical composition and sintering conditions is crucial for tailoring these materials to meet specific requirements across diverse applications, such as cutting tools, wear-resistant components, and various industrial uses. The study comprehensively assesses: I) the impact of varying nickel content, and II) the influence of sintering methods, including conventional and Spark Plasma Sintering (SPS), on the final microstructures and mechanical properties of the WC/Ni composites. In doing so, two sets of WC/Ni composites (containing 5 and 10 vol% Ni) were sintered using SPS and conventional methods. The microstructural analysis included FESEM and XRD, while mechanical properties were evaluated at different length scales including Vickers hardness, and fracture toughness. This detailed examination contributes valuable insights for enhancing the microstructural design of WC/Ni composites.

DOI:

https://doi.org/10.59499/EP246281827