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Authors:

Marco Mitterlehner (voestalpine Böhler Edelstahl GmbH & Co KG, Austria), Harald Gschiel (voestalpine Böhler Edelstahl GmbH & Co KG, Austria), Michael Schatz (voestalpine Böhler Edelstahl GmbH & Co KG, Austria), Helena Weingrill (Anton Paar GmbH, Austria), Timothy Aschl (Anton Paar GmbH, Austria)

Abstract:

When it comes to the characterization and processing of metal powders used in laser beam powder bed fusion (LB-PBF) processes, moisture has been a recurring topic for quite some time. In general, a distinction must be made between water from the air surrounding the metal powder and water adsorbed on the metal powder surface. To investigate the actual influence of these two water sources, a gas atomized superalloy powder BÖHLER L718 AMPO was exposed to different humidity levels and examined under these conditions. Thus, the correlation between the prevailing air humidity and the adsorbed water content on the metal powder surface and further, the influence on well-known (flow time and apparent density) as well as modern (shear cell parameters such as the flowability coefficient) powder characteristics was investigated. The water content adsorbed on the metal powder surface was determined by Karl Fischer titration.

DOI:

https://doi.org/10.59499/WP225372079

Authors:

Christian Berger (1), Johannes Pötschke (1), Uwe Scheithauer (1), Markus Krause (2), David Wonn (2)

1- Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Winterbergstraße 28, 01277 Dresden, Germany

2- ExOne GmbH, Daimlerstrasse 22, 86368 Gersthofen, Germany

Abstract:

For some years now, the production of WC-Co hardmetals via the powder-based additive manufacturing process binder jetting has been pursued. Compared to alternative AM processes Binder jetting offers the possibility of high production. Due to the powder-based process, the green bodies usually have a low green density, which means that only higher Co contents with lower resulting hardness’s are possible. By choosing the right starting powder and a suitable post-processing, the previous limits can be extended, and the appropriate powder can be chosen depending on the application. In the context of this study, the correlation between different WC-Co starting powders with different morphologies is investigated and evaluated for their processability in the BJT process and for the resulting mechanical properties of sintered components.

DOI:

https://doi.org/10.59499/EP235765382

Authors:

Alexandre Mégret (1), Loïc Prince (1), Véronique Vitry (1), Fabienne Delaunois (1)

1- Metallurgy Unit, Faculty of Engineering, University of Mons, Belgium

Abstract:

Recycling end-of-life tungsten carbide tools is important to encounter the issues linked to critical raw materials (CRM). Indeed, cobalt and tungsten have been listed as critical by the European Commission since 2011. Previous studies have characterized a recycled powder in terms of densification, microstructure, and mechanical properties, leading to interesting properties compared to conventional powders. The study of corrosion and tribological properties was not characterized although they are essential to understand the interactions between the cemented carbide tool and other materials. In this study, parts made from recycled tungsten carbide powder containing 7.5 wt.% cobalt have been sintered to evaluate their corrosion properties (open-circuit potential, polarizations…) and their tribological properties (friction coefficient, wear mechanisms…).

DOI:

https://doi.org/10.59499/EP246278304

Authors:

Mariana Pinto (1), Juliana Almeida (1), Alexandre Bastos (1), Joaquim Sacramento (2), Filipe Oliveira (1), Luís Filipe Malheiros (3), Pedro Pereira (2)

1- Department of Materials and Ceramic Engineering, CICECO, Aveiro, Portugal

2- DURIT, Metalurgia Portuguesa do Tungsténio, Lda., Portugal

3- INEGI, Department of Metallurgical and Materials Engineering, University of Porto, Portugal

Abstract:

The unfavourable corrosion behaviour of some hardmetal compositions is a main drawback for many applications. In wear parts operating in acidic media, cobalt (Co) is usually partially or totally substituted by nickel (Ni) and chromium (Cr) to increase the corrosion resistance. In hardmetals for metal forming tools, where high-volume fractions of binder are needed, the use of alternative binders, namely alloys of CoNiCr, is practically unexplored. Studying the corrosion and wear behaviour of hardmetals with high contents of these compositions is increasingly necessary for those applications. The degradation of mechanical properties induced by corrosion and wear damage that can decrease the service time of forming tools is an additional motivation for this research. This work studies the influence of binder composition in the performance of hardmetals with high binder contents in different tribological and corrosive environments, assessing the effects of partially replacing Co with simultaneous additions of Ni and Cr.

DOI:

https://doi.org/10.59499/EP246285835

Authors:

Facundo Masari (Universidad Carlos III de Madrid, Spain), Luis Antonio Diaz-Rodriguez (Nanomaterials and Nanotechnology Research Centre, Spain), Jose M. Torralba (Universidad Carlos III de Madrid|IMDEA Materials Institute, Spain)

Abstract:

It is possible to increase the operating pressure and temperature of power plants to improve efficiency and reduce CO2 emissions per unit of the generated electricity. To accomplish this, new materials must be identified to resist high-temperature corrosion. As an alternative to commercial Alumina-Forming-Austenitic (AFA) steels, new alumina-forming ferritic-martensitic or plain martensitic steels with nano-precipitates are studied. Their significant corrosion resistance is attributed to the formation of a protective Al2O3 layer. This makes it possible to be used at higher temperatures and for longer periods than conventional stainless steels that form a Cr2O3 surface layer. Based on thermodynamic simulations, two promising compositions, Fe-14.5Cr-12Ni-3.5Al and Fe-13Cr-10.5Ni-3.5Al were selected. Once atomized, were consolidated by field-assisted sintering techniques. Oxidation behaviour at high temperatures and experiments at lower temperatures and longer times have been performed at operating temperatures of around 750 °C. The further nano-precipitation of MX particles will provide a mechanical behaviour advantage.

DOI:

https://doi.org/10.59499/WP225371630

Authors:

Prabin A (1); Anvitha K S (1); Sathish R (1)

1-Kennametal India Limited, India

Abstract:

Cemented tungsten carbide (WC-Co) materials are made of tungsten-carbide grains embedded in a cobalt matrix and are used for making metal cutting and mining tools through powder metallurgical processes. Cobalt is known to be prone to corrosion in aqueous environments. Various surface preparation processes for cemented carbide exposes the cobalt phase in multiple aqueous environments where the corrosion mechanism is not well understood. Therefore, this study aims to understand the corrosion behavior of cemented carbides with different inhibitors in varying pH and temperature environments. The study also evaluates conditions where the corrosion inhibitor can be removed or reduced for different surface conditions for cemented carbide processes, and for alternate corrosion inhibitors with lesser health and environmental impacts. The results of this study will help improve cemented carbide tool performance in highly demanding service conditions and applications in oil and gas extraction in tetra-phasic conditions (seawater, sand, liquid, and gaseous hydrocarbons).

DOI:

https://doi.org/10.59499/EP235763660

Authors:

Masari F. (1), Pär Olsson (2), Peter Szakálos (2), Torralba JM (1,3), Campos M. (1)

1- Universidad Carlos III De Madrid, Leganes Madrid, Spain

2- KTH Royal Institute of Technology, Stockholm, Sweden

3- IMDEA Materials Institute, Getafe Madrid, Spain

Abstract:

The use of molten lead as a heat exchange fluid poses important critical issues, both in terms of corrosion resistance and creep resistance, due to the temperatures and structural stresses reached during operation. The objective of this work has been the investigation of the corrosion resistance and mechanical properties of new experimental compositions of alumina-forming stainless-steel candidates for these applications. The exposures to stagnant liquid lead were carried out for 500 and 1,000 hours, at temperatures of 550 and 650 °C, with controlled amounts of oxygen dissolved in the liquid lead. In comparison with the AISI 316L and T91 both tested as reference materials, the studied alloys showed highly promising corrosion behavior and mechanical properties. According to these results, the proposed steels are appropriate for components that will operate in liquid lead at elevated temperatures without corrosion, while maintaining good mechanical properties.

DOI:

https://doi.org/10.59499/EP246282505

Authors:

Beñat Arejita (EXOM Engineering, Spain), Iker Garmendia (TEKNIKER, Spain), Aitzol Zuloaga (UPV|EHU, Spain)

Abstract:

The complex nature of an LMD process demands advanced control mechanisms in order to compensate for the deviations that occur in the growth direction of the material. Consequently, every layer must be scanned to measure the 3D profile as layers are deposited, either by complicated in-situ measurement techniques or by performing intra-layer measurements after each layer deposition. Additionally, the digitization of the process allows the extraction and logging of relevant data and available process control and state variables for an ex-post analysis of the manufactured object. The quality of the extracted data directly affects the quality of the process itself, and typically high-end surface profilers are used, resulting in costly solutions. This work proposes an LMD process control solution that applies sensor fusion techniques to extract and integrate data from several cost-effective sensors. As a result, data-rich layer information is generated by combining process metadata and measured layer profiles using.

DOI:

https://doi.org/10.59499/WP225372133

Authors:

Emma Gil (1); Raúl Gómez (1); Fermin Garciandia (1); Maria San Sebastian (1); Ane Miren Mancisidor (1)

1- LORTEK, Arranomendi Kalea 4A, 20240 Ordizia, Spain

Abstract:

CM247LC alloy is a precipitation strengthened nickel-based superalloy commonly used in aeronautic sector due to its outstanding mechanical, oxidation, creep and wear properties at room and at high temperatures. However, there is a big challenge in obtaining a crack free material during PBF-LB/M processing. High contents of Al and Ti induce cracking. Four batches of CM247LC powders with different compositions were analysed and processed by PBF-LB/M. In this study, different approaches were employed to mitigate crack susceptibility of the alloy, namely, alloy modification, process modification and post-processing by HIP. The influence of the elements on cracking was assessed as well as the process parameters modification, including modification of the laser scanning strategies. Microstructure before and after post-processing, namely heat treatments and HIPping, was evaluated and cracking mechanism was studied in the light of microstructural observations.

DOI:

https://doi.org/10.59499/EP235762584

Authors:

Markus Schneider (GKN Sinter Metals Engineering GmbH, Germany), Christos Radis (GKN Sinter Metals Engineering GmbH, Germany), Robert Maassen (GKN Sinter Metals Engineering GmbH, Germany)

Abstract:

The Kitagawa-Takahashi approach combines two different reliability concepts. In classical high cycle fatigue testing the material is assumed as undamaged and the testing itself is responsible for the crack initiation. Depending on the failure criterion, very often defined as drop of the stiffness or resonance frequency, the subsequent crack propagation phase is not investigated. Crack propagation experiments by means of da|dN curves continue the testing in the damaged condition. If both reliability concepts are combined, a critical defect size can be defined. This critical defect size is of major importance since it defines the limit resolution of non-destructive testing methods. The loading ratio affects both testing procedures, e.g. over crack closure|opening effects and must be examined carefully. A typical sintered alloy was chosen for that study due to its large range of application. The derived critical defect sizes were compared with the maximum apparent 2D pore sizes.

DOI:

https://doi.org/10.59499/WP225369531

Authors:

Sandra Wieland (1); Lea Reineke (1); Julius Eckel (1); Jonathan Giel (1); Sebastian Boris Hein (1)

1- Fraunhofer IFAM, Wiener Straße 12, 28359 Bremen, Germany

Abstract:

Along the Metal Binder Jetting process chain, the metal powder is subjected to interactions with the binder, which is often water-based, and with air at elevated temperature during the curing step. This can lead to corrosion or oxidation reactions, especially for non-corrosion-resistant materials like typical tool steels. In order to investigate the interaction of non-corrosion resistant steels and different binders as well as the curing behaviour, two commonly used tool steels (PM-V10 and M2) are combined with three different binders. Measurements are carried out on the wetting behaviour of all powder-binder combinations, by determining the saturation rate and equilibrium binder saturation. Curing temperatures are set according to the respective binder composition, and both curing in air as well as in protective atmosphere is tested. The evaluation includes the shape of the resulting green parts and the density, microstructure, and carbon and oxygen content of parts after debinding and sintering.

DOI:

https://doi.org/10.59499/EP235764652

Autors; 

S. Fooladi Mahani (1); C. Liu (2); F. García-Marro (1,3); X.K. Cai (2); E.Jiménez-Piqué (1,3); L. Llanes (1,3)

1- CIEFMA, Department of Materials Science and Engineering, Universitat Politècnica de Catalunya - BarcelonaTech, Campus Diagonal Besòs-EEBE, Barcelona 08019, Spain

2- Xiamen Tungsten Co., Ltd., 361009 Xiamen, China

3- Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya - BarcelonaTech, Campus Diagonal Besòs, 08019 Barcelona, Spain

Abstract:

Resistance to contact loading is a key issue to consider for microstructural design of cemented carbides to be used as tools and wear components. In this work, Vickers, conical and Hertzian indentation has been implemented to assess contact damage response for three microstructurally different WC-Co cemented carbides. Deformation and damage linked to induced imprints were inspected at both surface and subsurface levels, the latter through sequential tomography. Results are presented as damage maps as a function of applied load. It is found that critical load values for emergence of cracks as well as for their subsequent evolution are strongly dependent on indenter geometry (linked to specific stress field) and fracture toughness of the material. Practical implications of these findings, in terms of future damage tolerance studies, are finally discussed.

DOI:

https://doi.org/10.59499/EP235761011