Contribution of Additive Manufacturing of Rare Earth Material to the Increase in Performance and Resource Efficiency of Permanent Magnets

Abstract

Powerful permanent magnets are of essential meaning for electric drives as well as for environmental friendly energy conversion in general. The main requirements for these applications are high energy products, coercivity and remanent polarization, thermal stability as well as affordable price. As state of the art, rare earth permanent magnets, frequently consisting of NdFeB based alloys, meet these requirements. When complex geometric shapes like arcs, shells or freeform surfaces are required by the application, a trade-off has to be taken into account between magnetic performance and post magnet-fabrication processing steps. Either bonded magnets can be produced with great variety of geometries while accepting low magnetic performance due to a significant amount of nonmagnetic plastic binder matrix, or sintered blocks with great magnetic performance have to be machined out to the specified shape accepting great effort for grinding or wire cutting as well as a significant loss of valuable material. To overcome the drawback of both conventional established magnet manufacturing processes, Laser Beam Melting (LBM) is investigated to provide an alternative process route for magnet production. This innovative Additive Manufacturing (AM) process offers tool less production of nearly any thinkable geometry by use of a metal powder bed fusing process. Due to the challenging material behavior, a detailed parameter study is presented including a systematic design of experiment (DoE) approach. The connection between process parameters, density and key performance indicators on the B/H-curve is broken down.