World PM2022 Proceedings

Authors:

Silvia Baselli (University of Trento, Italy), Alberto Molinari (University of Trento, Italy)

Abstract:

The thermodynamic driving force of sintering is the decrease of the Gibbs free energy related to the excess of specific surface area of the powder. Nevertheless, for cold compacted green parts, the mass transport mechanisms which allow atoms to move to form the neck are promoted by the deformation in compaction that acts as a mechanical driving force expressed through the geometrical and structural activity. The powder particles are in contact over a surface, condition that affects the geometrical relationships in the neck region. The material is strain hardened, the concentration of structural defects is higher than that in the starting powder (enhanced diffusivity). The effect on sintering shrinkage of the geometrical activity has been explained in previous works and a theoretical model is available. To highlight how structural activity acts, a dilatometry study has been carried out on ferrous materials (plain iron and AISI 316L) and different powder morphology.

DOI:

https://doi.org/10.59499/WP225372160

Authors:

Mihai Iovea (Accent PRO 2000 s.r.l., Romania), Gabriela Mateiasi (Accent PRO 2000 s.r.l., Romania), Marian Neagu (Accent PRO 2000 s.r.l., Romania), Alexandru Enciu (Accent PRO 2000 s.r.l., Romania), Andrei Stanciulescu (Accent PRO 2000 s.r.l., Romania), Mihaela Poterasu (Accent PRO 2000 s.r.l., Romania), Monica Mirea (Accent PRO 2000 s.r.l., Romania)

Abstract:

We present our X-ray high-resolution sintered and additive manufactured parts in-line NDT investigations based on various mini|microfocus X-ray set-ups. We are introducing also our latest development, an industrial combined X-ray scanner and a Laser-based 3D profiler machine for sintered parts in-line NDT control in one short pass. With the new equipment design we combined two advanced control techniques: the Laser-based profiler for getting the parts 3D shape measurement with 2-3% accuracy, followed by an X-ray digital imaging system for parts internal defects identification, based on a minifocus X-rays source and a TDI (Time Delayed Integration) X-ray detector. The system is able to compute also the sample' local density for sintered ceramic ballistic plates and to NDT analyse the transmission digital Xray images at a pixel size of 60 microns for detecting the internal defects.

DOI:

https://doi.org/10.59499/WP225370755

Authors:

Malte Becker (Fraunhofer IAPT, Germany), Ina Ludwig (Fraunhofer IAPT, Germany)

Abstract:

Additive Manufacturing (AM) stands out in lightweight construction, material efficiency and geometric freedom. But as it is still a relatively young technology only a small number of alloys has been developed and thus there is a lack of material diversity especially for highly stressed AM components.One way to increase mechanical properties is using composite alloys that are reinforced by ceramic particles.Subject of this investigation are the effects of reinforcing AlSi10Mg with different volume fractions of silicon carbide (SiC), by either mixing or milling and the processability of the reinforced powder in a LPBF process.The used powders are characterized including optical inspection, particle size distribution, particle morphology and flowability. The manufactured parts analyzed regarding the density and tested for their mechanical properties. Based on the results correlations between the powder manufacturing process, alloy composition and mechanical properties are evaluated.

DOI:

https://doi.org/10.59499/WP225371733

Authors:

Carl Jonsson (The University of Melbourne, Australia), Tesfaye Molla (The University of Melbourne, Australia)

Abstract:

Interest in the field of alternate binders for WC hardmetals has increased due to the health implications surrounding the use of cobalt as a binder material. Here, an Integrated Computational Materials Engineering (ICME) approach was used to search for alternate binder compositions using a reduced order model. The model was derived by combining the densification mechanisms present in cobalt containing compacts with the rate enhancing factors governing early onset densification. The model incorporates thermodynamic and kinetic components coupled to a multi-objective genetic algorithm. It allows alloys with compositions optimized for sintering to be ranked against those optimized for mechanical properties to form Pareto sets. By incorporating the sinterability and mechanical properties of the system simultaneously, alternatives that are manufacturable using existing procedures can be determined.

DOI:

https://doi.org/10.59499/WP225371931

Authors:

Oliver Levano Blanch (The University of Sheffield, United Kingdom), Beatriz Fernandez Silva (The University of Sheffield, United Kingdom), Martin Jackson (The University of Sheffield, United Kingdom)

Abstract:

Titanium alloys are well known for their high strength to weight ratio. However, its use is restricted in many sectors simply due to its high cost when processed through the conventional route. Powder metallurgy has been proven as an alternative way to reduce the cost of near-net shape titanium components. The cost of powder is related to its source, but technologies like additive manufacturing (AM) produce large quantities of surplus powder that can be reused with alternative technologies. Alternatively, the option to use titanium machining swarf as a feedstock material is also explored to further reduce the price of titanium components.In this work, Ti-6Al-4V swarf and surplus AM powder has been consolidated using field-assisted sintering technology (FAST) and hot isostatic pressing (HIP). The consolidation, microstructure and hardness has been assessed to explore and compare the potential of these technologies in the production of low-cost titanium near-net shape parts.

DOI:

https://doi.org/10.59499/WP225372019

Authors:

Louise Rosenblad (KTH, Sweden), Per-Lennart Larsson (KTH, Sweden), Henrik Larsson (KTH, Sweden)

Abstract:

From a previously developed constitutive model of cemented carbide, the powder size- and configuration can be used to simulate the densification during the sintering process. However, small differences in experimental execution cannot be accounted for in the simulation, making the model sensitive. Here, we study how well the developed constitutive model can capture the experimental results of a dilatometer test. Three different experiments were performed where the only difference was the transition between the debinding and sintering process. From parameter adjustments, it is seen that the constitutive model is more suited to a certain experimental setup, which is a limitation of the model.

DOI:

https://doi.org/10.59499/WP225372032

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:

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:

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:

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:

Karin Frisk (Innomat AB, Sweden)

Abstract:

Computational alloy design based on the CALPHAD approach involves physically based models and therefore successfully predicts properties of complex multicomponent metallic materials. When remelting metal powder by laser the effect of rapid solidification on microstructures often requires adjustments of composition, as compared to those of conventionally produced material, to reach adequate properties and avoid cracks. Searching for new compositions outside the common ranges of alloying elements, can benefit from using design criteria and data analysis. The design criteria can for example be hardenability, solidification ranges, corrosion resistance, precipitation hardening. The calculations provide the dataset to be analysed. A few examples of what is possible for Fe- and Al-based alloys, are given. The models, but also the background data, used for the calculations is critical, and this will be illustrated and discussed.

DOI:

https://doi.org/10.59499/WP225372044

Authors:

Felix-Christian Reissner (Fraunhofer Institute for Structural Durability and System Reliability LBF, Germany), Etienne Haberlick (Fraunhofer Institute for Structural Durability and System Reliability LBF, Germany), Karl Burkamp (RWTH Aachen University, Germany)

Abstract:

This paper describes a data-driven methodology to derive reliable S-N curves for PM components that take the hardness, the highly stressed volume, the stress ratio and the density into account. The methodology aims for a fatigue assessment approach applicable for all PM steels. For this, a large database with approximately 800 S-N curves, 20.000 S-N experiments and a broad spectrum of different geometries, materials, loading conditions, sinter conditions etc. is set up. The methodology is based mainly of known analytical functions, such as the Bal’shin equation and the Haigh diagram. The parameters for the fatigue assessment are obtained by optimization of the used analytical functions. As a result, the model leads to a highly reliable fatigue assessment of PM components.

DOI:

https://doi.org/10.59499/WP225371463