Proceedings

Authors:

João Teixeira Oliveira de Menezes (1), Federico Matias de la Vega (1), Enrique Mariano Castrodeza (1), Matteo Zanon (2), Tom Pelletiers (3), Riccardo Casati (1)

1- Department of Mechanical Engineering, Politecnico di Milano, Italy

2- Kymera International, Ecka Granules Germany, Germany

3- Kymera International / SCM Metal Products, USA

Abstract:

Binder Jetting of Al alloys can open new scenarios for the additive manufacturing of many alloys that cannot be processed by laser-based printing technologies because of the susceptibility to hot cracking (e.g., 2xxx, 6xxx and 7xxx series alloys). In this study, 6061 Al alloy samples were produced by Binder Jetting. The debinding and sintering parameters were fine-tuned and the tensile and fracture properties of the samples were assessed. Compact tension C(T) fracture specimens were notched in three different crack-plane orientations. Microstructural and fractographic analyses were performed using FE-SEM and LOM. The Al 6061-T6 alloy produced by BJ exhibited very low mechanical anisotropy. The tensile properties are in line with those reported for wrought Al 6061-T6, with a lower elongation at fracture. Brittle fracture occurred in all the crack orientations, with negligible stable crack growth and toughness values corresponding to half of those for hot-extruded Al 6061-T6 along the longitudinal direction.

DOI:

https://doi.org/10.59499/EP235765587

Authors:

Jean-Michel Missiaen (Univ. Grenoble Alpes, France), Mathilde Labonne (Univ. Grenoble Alpes, France), Olivier Lavigne (Hyperion Materials & Technologies, Spain), Luis Garcia (Hyperion Materials & Technologies, Spain)

Abstract:

Cemented carbides are widely used for cutting and drilling tools. They usually combine a WC hard carbide phase and a Co-based ductile binder. NbC-Ni materials are considered as a possible alternative, especially for wear applications. The advantageous economic situation for raw materials sourcing, their interesting mechanical properties and low density have raised a new interest for these materials. However, mechanical properties can be limited by the rapid grain growth during liquid phase sintering, as compared to WC-Co. Grain growth can be controlled by the addition of secondary carbides such as Mo2C. In this paper, a quantitative EBSD analysis of grain growth is performed for NbC-12vol%Ni materials sintered at 1360°C with controlled addition of Mo2C. The average grain size decreases continuously with Mo2C content. The results are discussed based on a more detailed interface characterization and on a previous model for the cooperative migration of phase boundaries and grain boundaries.

DOI:

https://doi.org/10.59499/WP225371483

Authors:

W. Limberg (1), T. Ebel (1), R. Willumeit-Römer (1)

1- Institute of Metallic Biomaterials, Helmholtz-Zentrum Hereon, Max-Planck-Straße 1, 21502 Geesthacht, Germany

Abstract:

For this study, tensile test specimens and rectangular shaped fatigue test specimens were produced by MIM, using a mixture of hydride de-hydride (HDH) Ti-6Al-4V powder with high oxygen content (4200 µg/g) and 20% gas atomized Ti-6Al-4V powder with 1600 µg/g oxygen. Due to the oxygen-scavenging effect, the addition of 0.5 wt.-% yttrium powder with a particle size < 45 µm to the powder mixture led to a strong increase of ductility from 4.5% to 13.5%. The results of the fatigue tests, conducted by 4-point bending at room temperature with a load ratio of 0.2 show a totally different behaviour. While the ductility is increasing, the fatigue endurance limit drops from 420 MPa for the pure Ti-6Al-4V down to 350 MPa by the addition of yttrium. This decrease of fatigue strength is caused by the large irregular shaped Y2O3 filled pore clusters, which are forming during sintering. DOI:

https://doi.org/10.59499/EP235763904

Authors:

Annalisa Fortini (1), Ottavia Vezzani (1), Michele Gragnanini (1), Gian Luca Garagnani (1), Mattia Merlin (1)

1- University of Ferrara, Department of Engineering, Italy

Abstract:

Powder metallurgy (PM) steels containing diffusion-bonded Ni are characterized by microstructural inhomogeneities related to the lack of Ni diffusion during sintering. As a result of sinter-hardening treatment a martensitic microstructure with Ni-rich austenite areas is obtained. Aiming at homogenizing the Ni distribution by diffusion, in the present study two different post-sintering treatments were performed, consisting in a vacuum quenching at 900 °C for 1 h and 3 h, respectively, followed by inert gas cooling. Microstructural evolution was investigated through hardness tests, optical and scanning electron microscopy, coupled with image analysis techniques. The mechanical properties of sinter-hardened and heat-treated samples were evaluated through Charpy impact, tensile and pin-on-disk tribological tests. The main effect on material properties was given by austenite content reduction and the resulting formation of Ni-rich martensite.

DOI:

https://doi.org/10.59499/EP246281385

Authors:

Thierry Baffie (CEA-LITEN, Univ.Grenoble Alpes, France), Guilhem Roux (CEA-LITEN, Univ.Grenoble Alpes, France), Mathieu Soulier (CEA-LITEN, Univ.Grenoble Alpes, France), Michel Pellat (CEA-LITEN, Univ.Grenoble Alpes, France), Claudia Salvan (CEA-LITEN, Univ.Grenoble Alpes, France), Claudie De Vernon (TOLECTRO SAS, France)

Abstract:

Recently, we showed that >99% dense CuCrZr parts can be produced by Laser Powder Bed Fusion (L-PBF) process using a large power range (270 to 480W) [1,2]. The as-built (AB) microstructure is anisotropic showing columnar grains aligned along building direction (BD). After a solution annealing and age hardening (SA+AH), solidification cells disappear and the dislocations density decrease, whereas partial recrystallization, twins and Cr nano-precipitates are observed. Even if the microstructure is not fully similar to wrought CuCrZr one, yield strengths are equivalent. This work aimed to develop further the process by: (i) evaluating the impact of incoming powders and lasing parameters on the AB microstructure, (ii) analyzing the microstructural effects of SA+AH and (iii) comparing the mechanical, thermal and electrical properties in both conditions for three powders.[1] C.Salvan et al., Proceedings EuroPM2019, Oct.13-17 2019[2] C.Salvan et al., Mat. Sci. & Eng. A 826 (2021) 141915

DOI:

https://doi.org/10.59499/WP225371437

Authors:

Eshwara Nidadavolu (1), Martin Wolff (1), Thomas Ebel (1), Regine Willumeit-Römer (1)

1- Institute of Metallic Biomaterials, Helmholtz-Zentrum Hereon, Germany

Abstract:

Liquid phase sintered biodegradable Mg-0.6Ca alloy generally exhibits an isotropic microstructure with homogenously restricted grain size of 30 µm, even after long sintering durations of 60 h at 625 °C. Such sintered microstructures reveal the presence of numerous impurity oxide particles at the grain boundaries, which are evident also on the initial gas atomized powder surfaces. However, after a mechanical powder sieving treatment for 20 min, the surface SiO2 concentration dropped from initially 220 ppm to 85 ppm, resulting in heterogeneous grain coarsening after sintering for 18 h at 625°C. For the use of Mg-Ca materials as biodegradable implants, reproducibility of in vitro degradation results is a prerequisite, for which a homogenous grain structure is desired. However, the lowered oxide-pinning effect at certain grain boundaries created heterogeneous grain coarsening and this indicates the necessity for the careful handling of fine powders to ensure repeatability in degradation and mechanical properties.

DOI:

https://doi.org/10.59499/EP246281669

Authors:

G. Gaillard (1), M. Soulier (1), C. Flament (1), P. Faucherand (1), V. Bonnefoy (1), V. Chastand (2), C. Marchand-Maillet (2), G. Bonnefont (3)

1-Université Grenoble Alpes, CEA, LITEN, France

2-Dassault Aviation Argonay, France

3-AddUp SAS, France

Abstract:

Powder characteristics in a laser powder bed fusion (LPBF) process have a major impact on the quality of the parts produced [1] [2]. An in-depth study was done to assess the effect of powder properties on LPBF-densified materials, focusing on two alloys (titanium and aluminum). Both powders were processed in a wide range of conditions in order to determine their induced effects: batch variability at specification thresholds, powder after multiple reuses and storage-aged powder. For each configuration, the powders and the LPBF-densified materials were subjected to physical, chemical, microstructural and mechanical analyses. The study of the effects of powder characteristics led to define recommendations for the management of supply, reuse and storage so as to optimize production costs while maintaining an acceptable quality level.

DOI:

https://doi.org/10.59499/EP246277018

Authors:

Anok Babu Nagaram (Chalmers University of Technology, Sweden), Eduard Hryha (Chalmers University of Technology, Sweden), Johannes Gårdstam (Quintus Technologies AB, Sweden), Maheswaran Vattur Sundaram (Höganäs AB, Sweden), Michael Andersson (Höganäs AB, Sweden), Zhuoer Chen (Chalmers University of Technology, Sweden)

Abstract:

In this study, compacts of Cr-prealloyed steel with admixed nickel and graphite, fabricated through cold isostatic pressing (CIP), were sintered in low vacuum at 1150 °C and at 1250 °C in a HIP furnace, followed by the capsule-free hot isostatic pressing (HIP) at 1150 °C in the same HIP furnace using argon at 100 MPa. Microstructures of these compacts sintered at 1250 °C revealed the complete closure of interconnected porosity, after which densification to full bulk density was achieved by final HIP stage. Hardness measurements and chemical analysis were also employed. Carbon as a reducing agent played a crucial part to reach very low oxygen content of 0.02% after sintering and capsule-free HIP. This study demonstrates the possibility of achieving full density in high performance powder metallurgy (PM) steels through novel approach of CIP and in-situ vacuum sintering in combination with capsule-free HIP using a two-stage densification process.

DOI:

https://doi.org/10.59499/WP225372077

Authors:

Antonio Pennacchio (1), Federico Simone Gobber (1), Marco Actis Grande (1)

1- Polytechnic University of Turin – Dept. of Applied Science and Technology (DISAT), C.so Duca degli Abruzzi, 24 10129 Torino, ITALY

Abstract:

Super duplex stainless steels (SDSS) combine the advantages of ferritic and austenitic steels and reach an excellent combination of mechanical and corrosion properties. In addition, high-level mass fractions of chromium, molybdenum, and intermediate nitrogen mass fractions have enabled the higher Pitting Resistance Equivalent Number of SDSS. One of the main goals of the research activity is to evaluate the possible nitrogen variation into the UNS S32760 (X2CrNiMoCuWN25-7-4, AISI F55, 1.4501) super duplex stainless steel powders produced by Vacuum induction melting Inert Gas Atomization (VIGA) (starting from metals scraps and wastes) with two different melt chamber gas atmospheres, Ar or N2. Another study objective concerns the influence of different atomisation gas, Ar or N2 (in combination with the two different melt chamber atmospheres), on powder properties. The identification of the optimal gas process parameters necessary to obtain AISI F55 powders with the correct chemistry composition, especially in terms of nitrogen content, is essential for any subsequent process techniques (L-PBF, 3D printing, MIM, …) to get the best pitting resistance and a good balance in the α ferrite/austenite phase, crucial for the mechanical properties. Therefore, after sieving, the effect of the different gas process parameters on the characteristics of the final powder, in terms of granulometry, morphology, microstructure, chemical composition (also taking into account light elements such as N, O, H, C, and S) and rheology, was investigated.

DOI:

https://doi.org/10.59499/EP235765086

Authors:

Peter Vikner (Aubert & Duval, France), Charlotte Mayer (Aubert & Duval, France), Corrado Muner (Texer design, Italy)

Abstract:

TS700 is a new precipitation hardening steel with high temperature resistance and excellent hot hardness developed for additive manufacturing of aluminium die casting tooling.TS700 parts were produced by L-PBF on a plate made in H11 tool steel treated at 45HRC. The interface between TS700 and H11 is investigated, as well as the microstructure evolution versus energy density (for different laser powers and scan speeds). The evolution of the microstructure with subsequent heat treatments is presented as well as some mechanical properties associated to the different microstructures obtained.

DOI:

https://doi.org/10.59499/WP225371564

Authors:

Federico Simone Gobber (Politecnico di Torino, Italy), Marco Actis Grande (Politecnico di Torino, Italy)

Abstract:

Duplex stainless steels represent a very promising alternative when aggressive|marine atmospheres characterize the component’s final application. In this frame, grades with higher Pitting Resistance Equivalent Number (40 or above) may be used in hydrogen sulphide and chloride-containing environments. UNS 32760 Duplex Stainless Steel powders have been obtained by means of close coupled gas atomization, starting from wrought bars. The paper analyses the effect of different parameters on the characteristics of the final powder, in terms of granulometry, orphology, microstructure, and chemical composition (compared to the starting material), also taking into account light elements as N, O, H, C, and S.

DOI:

https://doi.org/10.59499/WP225372042

Authors:

Yongkwan Lee (1,2), JaeJin Sim (1,3), SungGue Heo (1,2), Soong Ju Oh (2), MiHye Lee (1), JaeHong Shin (1), Seok-Jun Seo (2), KyoungTae Park (1)

1- Korea Institute for Rare Metals, Korea Institute of Industrial Technology, Incheon 21655, Korea

2- Department of Materials Science and Engineering, Korea University, Seoul 02841, South Korea

3- Department of Advanced Materials Engineering, In-Ha University, Incheon 22212, Korea

Abstract:

Tungsten carbide (WC) is the main raw material of cemented carbide (WC-Co) and is mainly used for cutting tools, wear-resistant tools, and impact-resistant tools because of its excellent high-temperature hardness and high strength. The properties of cemented carbide are greatly affected by the particle size of the tungsten carbide powder, and the development of particle size control technology of the tungsten carbide powder is being actively developed to improve the performance of the tool material. This study evaluated the characteristics according to the amount of reducing agent and carbon input to control the particle size of tungsten carbide powder. The phase composition and morphology evolution of synthesized powders has been examined by X-ray diffraction, scanning electron microscope, and particle size analyser. As a result, WC powder with a particle size of about 200 nm was manufactured under optimized experimental conditions through the control of the reducing agent and carbon content.

DOI:

https://doi.org/10.59499/EP235764653