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Resource Efficient Production Route for Rare Earth Magnets

Periodic Reporting for period 2 - REProMag (Resource Efficient Production Route for Rare Earth Magnets)

Reporting period: 2016-07-01 to 2017-12-31

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. Shaping techniques that were addressed are metal injection moulding and 3D-printing. In the latter, the printing variants of ME (material extrusion) and Vat polymerisation (LMM) processes were be addressed. 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.
Different types of recycled NdFeB powders were prepared and analysed and made into different feedstock compositions: These were 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 are suitable for the MIM processing route. To compensate for oxidation of EoL magnets, the addition of small percentages of Nd material either in hydrided form or as a master alloy is beneficial for the magnetic properties, allowing to reach properties of non-recycled virgin material.

A main aspect of the work carried out 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. Extensive and detailed investigations in terms of processing parameters of debinding and sintering have been conducted, in order to keep contamination within acceptable ranges. In the sintered state, isotropic magnets were produced showing coercivity up to 95% of the starting material.
The achieved values are competitive to today’s isotropic sintered magnets produced via the conventional pressing and sintering route, which use fresh instead of recycled powders. In order to produce aligned (anisotropic) magnets by the SDS processes, injection moulding test tools with integrated magnets to create suitable alignment fields were simulated, constructed and built. Radial, parallel and multiaxial aligned samples were manufactured, with the strength of the alignment field being optimised for maximum alignment.

For 3D-printing, a printable, debindable and sinterable feedstock system has been developed. The design and setup of a specific ME printer has been successfully accomplished, being tested with stainless steel, Ti and NdFeB material, which led to magnets with minimised C-contents. However, as the printing was done under air, an oxygen contamination of the NdFeB could not be avoided, leading to improvable magnetic properties. Work under protective atmospheres is ongoing.
For the LMM-printing of metals, also a new type of printer and a corresponding feedstock system has been developed. Printing of NdFeB type material could not be achieved, due to a catalytic reaction between the photopolymeric binder and Nd. However, the route has proved to be an excellent method to shape other metals, e.g. stainless steel and Ti with high precision.
An alignment system for the ME-3D-printer was constructed and tested. For NdFeB, the initial alignment looks promising, the work is ongoing.
For corrosion protection of the magnets, an optimized coating which combines a LPPS (low pressure pack sublimation) with electroplating was developed. Comparative mechanical and corrosion testing of samples made by SDS and conventional sintering routes with standard and optimised coatings were carried out.
A comprehensive Life Cycle Analysis (LCA) and Life Cycle Cost (LCC) assessment of SDS processing of RE magnets was carried out.
The consortium was active in dissemination and publication of results, while at the same time carefully protecting generated knowledge and IP, with one patent being filed and a lot of substantial technical know-how was created with all partners.
REProMag was selected as a winner of the German Innovation Price for Raw Material Efficiency 2017 and the EcoTech Award for Resource Efficiency 2017 of the German State of Baden-Württemberg.
A production route for manufacturing powder suitable for the SDS process has been implemented. Feedstock made of 100 % recycled RE powder was used in the MIM process for the first time, representing a considerable step to realising the envisioned 100% waste free production of SDS magnets in a closed material loop.

Using 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.

The ME and LMM routes for 3D printing of metals have been developed. It was shown for the first time that these processes are suitable to obtain complex, net-shape metal parts and that the ME route can be further developed to obtain the first fully dense printed RE magnets.

With these achievements, the envisaged socio-economic and societal impact of REProMag will become a reality. 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 magnetic products.
The product lifecycle “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.
SDS magnets are complexely shaped and strong
The SDS process is a circular approach