Towards Recycling of NdFeB Permanent Magnets in a Circular Economy

Abstract

This study provides a comprehensive analysis of recycling NdFeB permanent magnets within the framework of a circular economy. Its goal is to address the increasing demand for sustainable resource management driven by the rising need for rare earth elements (REEs), particularly neodymium, a material classified as critical by European standards. These magnets are essential to various high-tech applications, but their dependence on scarce and geopolitically sensitive REEs poses significant supply risks. This research focuses on developing and optimizing innovative recycling processes, mainly through additive manufacturing. The investigation covers the entire recycling circuit, starting with demagnetizing and dismantling end-of-life (EOL) rotors. The study explores hydrogen decrepitation, a technique that converts bulk magnets into powder, and the subsequent additive manufacturing of bonded magnets using this recycled powder. Throughout these stages, special attention is given to pre-processing steps, such as optimizing demagnetization temperatures and hydrogen desorption times, which are crucial for maintaining the magnetic properties of the recycled NdFeB powders. A comparative analysis is conducted between powders produced via hydrogen decrepitation and those obtained through industrial milling. The research highlights significant differences in magnetic properties, microstructural characteristics, and overall process efficiency, underscoring the strengths and weaknesses of each powder production method. The findings demonstrate the potential of the proposed recycling technologies to upcycle EOL magnets into newly additively manufactured magnets that are suitable for various applications while reducing reliance on virgin REEs. This work successfully demonstrates a complete, high-throughput recycling circuit, emphasizing the importance of Extended Producer Responsibility and eco-design principles to enhance the sustainability of NdFeB magnet production and recycling.