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Home » Technologies & Materials » 40th Hagen Symposium: Powder Metallurgy – Diverse Processes and Materials

40th Hagen Symposium: Powder Metallurgy – Diverse Processes and Materials

As the key conference on Powder Metallurgy in the German-speaking area, the Hagen Symposium has proven over the last 40 years that it has always kept pace with the times and taken up current topics from science, industry and society. In the last few years, for instance, issues like energy and resource efficiency, electromobility, and sustainability have been addressed. But very fundamental topics have also been regularly included in the programme of papers. This wealth of different topics underscores the great diversity in Powder Metallurgy, which is reflected especially in a wide spectrum of materials and a large number of different manufacturing processes.

Introduction

To illustrate the dynamism and innovation in Powder Metallurgy, this year the programme commission placed special focus on new processes and material developments, without, however, leaving out papers on the further development of established materials and processes. Additive Manufacturing has grown in importance over the past years. Especially binder-based Additive Manufacturing offers great potential for Powder Metallurgy as – apart from the actual forming process – the process chains are the same as those in established Powder Metallurgy. In the subject area of carbides, besides reviewing current material developments in nanostructured binders, the symposium addressed cobalt-free and alternative binders. The honour of the SKAUPY lecture this year went to Dr Uwe Schleinkofer from the company CERATIZIT/LU, who is an acknowledged expert in the field of carbides. The laudation for the SKAUPY Award Winner in 2022 was given by Thierry Wolter, CERATIZIT S.A. In his role as Chair of the Powder Metallurgy Committee, Prof. Dr-Ing. Christoph Broeckmann (RWTH University of Aachen/DE) was able to welcome over 150 attendees as well as 42 exhibitors in the Stadthalle Hagen on 24.–25.11.2022. SKAUPY Award Winner 2022 The SKAUPY lecture was entitled Carbide and Coating – from Science to Shaping the Future. For 100 years, the composite carbides and, for around 60 years, coatings have been major factors influencing the speed of development of industrial machining processes. Here, the requirements for the material system of substrate/ coating manufactured in a Powder Metallurgy process are constantly increasing, driven by more complex component geometries, the novel materials that have to be machined, cost and efficiency pressure in manufacturing as well as higher quality requirements. Modern analytical methods allow insights into the material down to atomic level and enable, with the support of simulation processes, tailored design of the material properties. In this paper, key scientific milestones with regard to this material system were reviewed and the latest findings presented. Moreover, an outlook was given and discussed with regard to even more efficient processes in manufacture and application, but also in respect of the very important aspect of sustainability.

Papers

Dr Patrick Koehnen (GKN Additive/DE) reported on Binder Jetting in Series Manufacture: Potential and Challenges. Metal Binder Jetting (MBJ) is a free-jet-based Additive Manufacturing (AM) process with high application potential for industrial series manufacturing of complex components (>10 000 components/a). The key feature of MBJ technology is the application of a liquid binder for the selective bonding of metal powder layers. The green body produced is then compacted to relative densities of up to 99 % in a sintering process. On the one hand, with utilisation of the advantages of Powder Metallurgy, materials like, for example, high-carbon tool steels can be processed, which can be difficult to achieve with other AM processes. On the other hand, isotropic material properties can be adjusted and residual stresses reduced. To improve component properties and process robustness, besides specific MBJ material development, the correlation of pressure and sintering parameters is a key factor for the metallurgical properties, and digitalization of the process chain is posnecessary. In this paper, current possibilities, obstacles and future potential of MBJ technology for series manufacture were discussed. 3D Printing of Ceramic Components – Wish and Reality was presented by Dr Dieter Nikolay (WZR ceramic solutions GmbH/DE). The expectation in the use of 3D printing is to obtain a material equivalent to that produced with established shaping processes. Often, however, the required geometries have been designed for other shaping processes. The currently available commercial 3D printing processes for ceramics were presented and assessed against the background of the expectations. With reference to case studies, the speaker explained how different the result obtained with the different processes can be even if the ceramic processed is the same. Lithography-Based Metal Manufacturing (LMM) was discussed by Denise Mödder (Incus GmbH/AT). Lithography- Based Metal Manufacturing (LMM) is an Additive Manufacturing technology for the production of functional metal components with smooth surface aesthetics, high resolution and complex shapes that cannot be accomplished with other Additive Manufacturing technologies for metals. LMM is based on the concept of photopolymerization, in which metal powder is homogeneously dispersed in a light-sensitive resin and selectively polymerized layer by layer by means of exposure. To obtain the ultimate metallic properties, the green parts require a debinding and sintering step, similar to other sintering-based processes, like, for example, metal injection moulding. Filament-Based 3D-Pressure for Metals, Carbides and MMC was discussed by Dr Christian Kukla (Montanuniversität Leoben/AT). In the wide range of 3D printing processes, filament-based 3D printing is the process with the widest distribution, because the necessary equipment is very reasonable in terms of cost and easy to handle. This applies mainly for polymers. For other materials, like metals, carbides and MMC, this process plays only a minor role, but is suitable for the production of green parts, which can be subsequently sintered to compact components. To provide an insight into the strengths and weaknesses of this process, the speaker presented an overview, and from this he elaborated the special features of filament-based 3D printing for metals, carbides and MMC. In addition, the speaker also addressed related processes that do not work on the basis of filaments. Metal Binder Jetting as a Technology Complementing MIM – Common Features, Differences and their Consequences was discussed by Dr Sebastian Boris Hein (Fraunhofer IFAM Bremen/DE). In recent years, Metal Binder Jetting has shifted into the focus of powder technology as it shows great potential to close the gap from prototype to series manufacture. The process is perceived increasingly as complementary to metal powder injection, which has become clearly established as a series manufacturing process. That was examined in detail, not only based on component piece numbers, but from scientific, technical and economic perspective along the respective process chains. Common features and differences in the processes were explained and the speaker demonstrated how these impact research, development and application. Dr Robert Feher (Graphit Kropfmühl GmbH/ DE) spoke on Potential Applications of Graphite in E-Mobility. The predicted growth in exclusively electrically driven vehicles in the next few years will have significant effects on the raw materials markets. In this context, the EU has also classified graphite as a critical raw material. The speaker gave an overview on the possible uses of the mineral in the automotive sector in general, and specifically for electric vehicles. While for the latter group, the spotlight is on the applications of graphite in and around the battery in terms of volume, there are certainly prospects for vehicle components manufactured with the PM route. In the manufacturing processes for steel, graphite acts as an additive that is not present as such in the finished part, but nevertheless plays an important role for the properties of the finished part. Powder Metallurgical Production and Characterisation of Al-B4C Sheets for Nuclear Applications were explained by Dr Stefan Pretterhofer (voestalpine Böhler Bleche GmbH & Co KG, Mürzzschlag/AT). The nuclear industry’s demand for materials for neutron-shielding applications that exhibit increased neutron absorption, while possessing at the same time higher thermal conductivity and lower density than the stainless steels used so far, has increased substantially in the last few years. For this reason, a powder metallurgical process was developed for the manufacture of boroncarbide- reinforced aluminium precursor. The sheets rolled from this material were then characterised in respect of their mechanical, physical and chemical properties. Here, the speaker was able to point out the major influence of the process parameters on the one hand and the selected matrix alloy on the other.

From Research to Industry: Applications and Latest Developments in FAST/SPS Sintering was the subject addressed by Jens Huber (Dr. Fritsch Sondermaschinen GmbH/DE). The FAST/SPS sintering process is registering strong growth rates and increasingly replacing conventional hot pressing, especially in new applications. Most of the installed FAST/SPS systems have been used for decades in industrial mass production. On account of the complex requirements today, the development of new applications often requires close cooperation between industry and/or research institutes as well as FAST/SPS manufacturers. Referencing the example of a new generation of solidstate batteries that is to be developed, the speaker showed how such cooperation can look and what motivates customers today to choose FAST/SPS rather than conventional hot pressing. Dr Igor Konyashin (Element Six GmbH/DE) reported on Coarse-Grained Carbides with Nanostructured Binders. Coarsegrained WC–Co carbides are used on a large scale for various applications, e.g. in the mining and construction industries. The main disadvantage of such carbides with the WC mean particle size of around 3–5 μm is, however, the low hardness and wear resistance of the interlayers. To solve this problem, novel carbides with nano-reinforced binders were developed and used industrially on large scale. The microstructure of the carbides consists of rounded WC grains with thick and uniform interlayers of the binder, as a result of which high fracture toughness is achieved. The carbide binder phase is strengthened and hardened with nanoparticles of metastable Co–W–C phase with cubic crystal lattice and a mean size of around 3 nm. As a result of the nano- reinforced binder, the service lifetime of the carbide inserts for mining and construction is lengthened significantly. Current Developments in Carbides with Alternative Binders were presented by Dr-Ing. Johannes Pötschke (Fraunhofer IKTS Dresden/DE). Carbides on the basis of tungsten carbide as a hard material and cobalt as a bonding metal exhibit excellent mechanical properties and the use of cobalt allows detailed, non-destructive testing of the microstructure and phase components. On account of the classification of cobalt as a critical raw material, as CMR material (carcinogenic, mutagenic and toxic to reproduction) as well as price increases on account of the use of cobalt in battery production, there is great interest in the use of alternative binder metals. In the scope of the talk, besides an overview and examples of both commercial and novel metal binder systems still under development, a historical review and a classification of the properties in comparison with conventional WC–Co-based carbides were provided. Dr Alexander Leonhard Meijer (TU Dortmund University – Institute of Machining Technology/DE) spoke on New Tool and Process Developments for Flexible Micro-Milling-Based Production of Heavy-Duty Moulds. Micromilling offers great potential for tool and mould making. It enables the production of very small moulding elements with simultaneous adjustment of the surface finish in respect of, for example, roughness and residual stress state of the boundary zone. Even hardened Powder Metallurgy highspeed steels and carbides used for the production of heavy-duty moulds can be manufactured with suitable process and tool design to meet very high quality and functional requirements in a safe and reliable process. To this end, current investigations on the process configuration and tool design on the basis of the analysis of the cutting forces, resulting surface topographies and residual stress states were presented. This also included the evaluation of an approach for tool modification by means of cutting edge conditioning to enhance the potential performance of milling tools with very small dimensions for micro-hard machining. Powder Metallurgical Material and Process Solutions for Aviation Applications were presented by Ingolf Langer (Schunk Sintermetalltechnik GmbH/DE). Complex-shaped and heavy-duty components manufactured by means of Metal Injection Moulding (MIM) have been successfully introduced into aviation applications and specifically in engine technology. With reference to selected examples, the speaker presented the materials used and applications. The success is motivating manufacturers and users to apply the MIM strategy to other materials and applications. In the paper, current material developments were considered. Parallel to this, additional shaping technologies for the production of green parts, like, for instance, powder-based Additive Manufacturing technologies (AM) were evaluated with regard to their suitability for the short-term provision of prototypes with comparable properties. Inductive Heat Treatment of Sintered Steels in the Industrial Environment was presented by Alexander Ulferts (Inductoheat Europe GmbH/DE). In times of onepiece- workflow processes and inline manufacturing, in the manufacturing network, integrated thermal treatment processes, like inductive hardening and inductive tempering, are increasing in importance in Powder Metallurgy, too. Unlike steels from conventional production, for inductive heat treatment of the components made of sintered steel additional process influences and requirements result, which were examined and analysed more closely. Beginning with the basis of inductive heating processes of steels and the analysis of their main influences, the special features of the inductive heating process and the subsequent aqueous quenching process on water- polymer basis were outlined and rated in terms of their importance. An FEMbased analysis of the occurring electromagnetic and resulting thermal fields in the component provides information on the influence of geometric interfering contours on the heating behaviour during active thermal treatment and thus offers the possibility of the classification of real boundary areas. Finally, there was a description and discussion of inductive hardening processes in practice according to state-of-the-art based on real components, and an outlook on current research and development activities in practice was given. New Approaches for a Calculated Strength Verification for Machine Components Made of Sintered Steel given by Karl Burkamp (RWTH University of Aachen – Institute of Material Applications in Machine Engineering/DE). Up to now, there has not been any process for strength verification, as exists, for instance, for other material groups in the FKM directive. In some cases, users apply their own, not always soundly based processes to evaluate the strength. The establishment of a generally acknowledged strength verification for sintered steels would make this material group accessible to a wider circle of users than has been the case so far. On the basis of a comprehensive literature research, it has been possible to develop initial calculation models that allow strength verification based on the FKM directive. It is now possible to generate a synthetic or a design Wöhler curve for any sintered steels on the basis of hardness, density and local stress parameters (high-stressed volume and stress ratio). The calculation models are independent of the material and return results for any material compositions. The results were obtained in the scope of an FKM/AiF research project with the goal of developing a general strength verification for sintered steels. Harald Leitner (voestalpine Böhler Edelstahl GmbH & Co. KG/AT) spoke on Powder Metallurgy Material Concepts for Cold Work Applications. The requirements in different cold work applications have risen significantly in recent years. On the one hand, the complexity and dimensional accuracy of the manufactured components have increased considerably, on the other hand the mechanical properties of the materials to be machined are on a high level and continue to increase. All these facts lead to increased stress on the tools and consequently high requirements for the tool material and its surface quality. During application, the tool materials are exposed to very high mechanical stresses so that during application various wear phenomena, material nicks and chipping occur. This cannot be avoided completely and to ensure an acceptable lifetime for the tools, therefore, improved and new material concepts are needed. In the scope of this paper, modern material concepts for cold work applications on the basis of powder metallurgical production were described and discussed. Andreas Frehn (Materion Brush GmbH/DE) reported on Particle-Reinforced Aluminium Materials for High-Performance Applications. Particle-reinforced materials generally offer better properties than monolithic materials with the same base material. Certain properties can be selectively controlled and improved, with the type of the base or particle material, the content of added particles, their size and distribution being used as control mechanisms. In the paper, various particle-reinforced materials on aluminium basis were presented for which a special alloying process was used to achieve a very homogeneous distribution of the particles, which in turn leads to very homogeneous or near-isotropic properties. With reference to various interesting examples, the speaker examined the materials used and the requirements they must meet. The 41st Hagen Symposium will be organised in the Stadthalle Hagen on 30.11.– 01.12.2023.


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