Periodic Reporting for period 1 - REProMag (Resource Efficient Production Route for Rare Earth Magnets)

REProMag is a European project, financed by the European Commission under the call programme ?Factories of the Future.? The project was presented under the topic FoF-02-2014: Manufacturing processes for complex structures and geometries with efficient use of materials.Our...\n\nREProMag is a European project, financed by the European Commission under the call programme ?Factories of the Future.? The project was presented under the topic FoF-02-2014: Manufacturing processes for complex structures and geometries with efficient use of materials.
Our lives become more and more dependent on the use of Rare-Earth (RE) metals, especially the use of magnets used in applications such as smartphones, headphones, (electric) cars, or micro-mechanical devices. All these products are now an integral part of modern life in Europe. Further advancement on materials and processes is required to maintain the current standard of living, while at the same time saving scarce resources and securing economically and environmentally sustainable production. However these days, Europe remains highly dependent on external sources of RE-metals. Eighty percent of the manufactured RE-metals in 2010 were made in China (only 3% in Europe) and some of the producing countries are reducing export licences. This is particularly important, as a report published by the European Commission on critical raw materials in 2012, recognised RE magnetic materials as having the highest supply risk of all rare materials crucial to EU manufacturing. Therefore, there is a need for Europe to develop processes for the efficient use of these materials from sustainable sources.
The new manufacturing route addressed in the REProMag project is called SDS process (Shaping, Debinding and Sintering). It represents an integrated solution overcoming today?s limitations in the production and use of RE-magnets. The SDS process will allow a new level of sustainability in production of magnets, as the energy efficiency along the whole manufacturing chain is increased by more than 30% and the material charge of RE-materials is reduced by 30-40% compared to conventional production routes. Furthermore, the used raw material is 100% recycled and can be recycled in the same way at the end of the lifetime of the products. Finally, the magnetic energy products can be increased by 10 to 40%, allowing the use of 3D structured parts in miniature applications. This will lead to an extremely resource efficient closed material loop for RE magnetic materials.

Specifically, the REPRoMag consortium will develop and implement the following innovative process steps:

1. Recycling: Develop and use of 100% recycled RE-metals to develop sustainable RE-powders and feedstock for SDS production.
The major goal is to guarantee sustainability in the use of critical raw materials (RE metals) by using 100% recycled raw material. The material efficiency (reduced raw material charge by 30-40% and net-shape production) and use of recycled materials of the REProMag processing route will decrease the dependency on RE metals as critical raw materials significantly and work against the risk of a shortage as a limiting market growth factor.

2. Shaping: Development of net-shape and waste-free production methods for RE-magnets with complex geometries through the SDS process, including strategies for magnetic alignment of parts to obtain high performing anisotropic magnets. Shaping techniques that are addressed are metal injection moulding and 3D-printing. In the latter, the printing variants of Fused Filament Fabrication (FFF) and Light Ceramic Processing (LCM) processes will be addressed. Thereby, current energy-intensive post sintering treatments such as machining of complex parts from bulk magnets shall be replaced, as complex parts will be produced near-net shape.

3. Debinding and Sintering: The processes of debinding and sintering are most crucial to obtain good magnetic properties in the final product. In the debinding phase the polymer binder used for the shape forming stage is removed from the part, and the sintering phase leads to the increase of density and mechanical strength of the magnets. No other post-processing phase is to be used, except an innovative coating method to avoid c\n\nTwo different types of recycled NdFeB powders were prepared and analysed in the first 18 months of the project. Different feedstock compositions have been and are currently being evaluated in terms of processibility by the SDS Metal Injection Moulding (MIM) and 3D printing processes. It has been found that the recycled and sieved powder with high Dysposium content of 4% is most suitable for the MIM processing route. Further powders will be included in the process developments in the second project period.

A main aspect of the work carried out so far was to develop appropriate debinding and sintering routes, especially due to the fact that the RE powders are very sensitive to picking up oxygen and carbon during the processes. These contaminations would always lead to poor magnetic properties, which is why special attention needs to be drawn to excluding sources of contamination. It has been found that producing the feedstock (mixing the powder and binder) under inert conditions is essential to keep oxygen pickup as low as possible. Further investigations have been conducted in order to check for the influence of gas flow rates and heating rates on carbon pickup during debinding and sintering. Processing parameters have been defined for the whole process chain from feedstock preparation over shaping to debinding and sintering of the parts, in order to keep contamination within acceptable ranges. Extensive and detailed investigations in terms of processing parameters of debinding and sintering have been conducted. In the sintered state, isotropic magnets were produced showing coercivity up to 960 kA / m. This value is competitive to today?s isotropic sintered magnets produced via the conventional pressing and sintering route, which use fresh instead of recycled powders.

For 3D-printing, a printable, debindable and sinterable feedstock made of stainless steel with full characterization in terms of thermal, rheological and mechanical properties has been developed. Furthermore the development of a 3D printer for high filled metal filaments has been successfully accomplished as well as the design and setup of a specific REProMag 3D printer for the FFF printing route. Several tests with stainless steel material have been implemented in order to test the printing behaviour. For the LCM-printing of metals the formulation has been improved and screening for the optimal powder size in terms of shape and distribution has been initiated. The stainless steel will now be replaced by the recycled RE-powder, bringing together the achievements of printing head technology, feedstock composition and debinding/sintering strategy for RE magnets.

In order to produce aligned (anisotropic) magnets by the SDS processes, three injection moulding test tools with integrated magnets to create suitable alignment fields were constructed. Extensive work was carried out on simulating the alignment fields during inside the mould cavities as a function of the arrangement of the magnets in the tools. Radial, parallel and multiaxial aligned samples were manufactured in the MIM process. Initial work on 3D-printing a magnetic powder based on strontium ferrite showed a significant alignment of parts printed on a large permanent magnet, which induced the alignment field. Based on the current results, manufacturing and characterisation of demonstrators by the SDS process will be started in the next period.

For corrosion protection of the magnets, the partners achieved an optimization of processing parameters of the coating route, e.g. temperature and hold times in order to achieve a 20┬Ám coating on sintered RE magnets. Comparative mechanical and corrosion testing of samples made by SDS and conventional sintering routes will be started in due course.

Further to the technical development, the project is taking into consideration Life Cycle Analysis (LCA) and Life Cycle Cost (LCC) of conventional sintering and SDS processing of RE magnets. The consortium is active\n\nWith the REProMag results so far, the consortium already achieved some significant progress beyond the state-of-the-art:

- Powder production and innovative feedstock systems: A production route for manufacturing powder suitable for the SDS process (MIM, FFF and LCM) has been implemented. Feedstock made of 100 % recycled RE powder was used in the MIM process for the first time. This achievement represents a considerable step to realising the envisioned 100% waste free production of SDS magnets in a closed material loop.

- Waste-free net-shape manufacturing: Using the 100% recycled powder, it has been proven that net-shape manufacturing of RE magnets in the SDS process is feasible. It was shown that magnetic properties of the samples produced reach values well in the range of sintered magnets made from fresh non-recycled material.

- Additive manufacturing: Within the REProMag projects, binder systems suitable for 3D printing of high-filled metal feedstock via the FFF and LCM routes have been developed. It was shown that the feedstock can be printed, debinded and sintered to obtain complex, net-shape metal parts via these processes for the first time. With this, SDS additive manufacturing can be further developed in the second project period to obtain the first RE printed magnets. The feasibility of magnetic aligned anisotropic magnets using non-recycled powder has already been proven in first trials.

In summary, with the progress achieved in the REProMag project so far, the basic idea of using 100 % recycled raw materials for producing RE magnets in SDS processes has been successfully validated. With this, the envisaged socio-economic and societal impact of REProMag will become a reality. For instance, the use of 100% recycled powder and feedstock will assure an independency of European industries from critical raw materials produced in Asia. Society will benefit from this development, as the consumption of energy and hazardous chemicals in the exploitation of RE materials from the ore will be considerably reduced. With the net-shape process assuring manufacturing of complex and miniaturised parts with lower material charge, European industries will be able to offer more sustainable eco-friendly products to the people, including but not limited to electrical motors, sensors, actuators, grippers and fixations in the fields of (electro-) mobility, energy, aerospace, industrial, mechanical engineering and medical technologies. The product lifecycfe ?from recycling to recycling? envisaged in the SDS process represents a closed material loop within Europe, reducing the continent?s dependency from the Asian market and thereby increasing the competitiveness of European industries. This, in turn, will lead to increased wealth and standard of living of the European people.
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Resource Efficient Production Route for Rare Earth Magnets
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