Metal Injection Moulding of NdFeB Based on Recycled Powders

• Published in: European Congress and Exhibition on Powder Metallurgy. European PM Conference Proceedings pp. 1 - 7
• Main Authors: Imgrund, Philipp, Weber, Oxana, Schlauf, Thomas, Pischang, Karsten, Pickering, Lydia, Walton, Allan, Gonzalez-Gutierrez, Joamin, Kukla, Christian, Burkhardt, Carlo
• Format: Conference Proceeding
• Language: English
• Published: Shrewsbury The European Powder Metallurgy Association 01.01.2016
• Subjects: Binder removal; Boron; Carbon; Coercivity; Heat treatment; Hydrogen; Hydrogen decrepitation; Injection molding; Magnetic properties; Magnetism; Neodymium; Permanent magnets; Rare earth elements; Raw materials; Recycling; Remanence; Sintering; Sintering (powder metallurgy); Solvents

Over the last ten years several groups have been carrying out research into metal injection moulding (MIM) of neodymium-iron-boron (NdFeB) powders to produce isotropic or anisotropic rare earth magnets with higher complexity than in the conventional press and sintering approaches. However, difficult processability due to the high affinity of the powder to oxygen and carbon pickup remains problematic in terms of obtaining sufficient remanence and coercivity. In this paper, a new approach to MIM of NdFeB magnets is presented. It is based on the use of powder obtained from recycling of used rare earth magnets by the hydrogen decrepitation (HD) process. Different types of binder systems have been used for producing mouldable MIM feedstock. Influence of debinding and sintering conditions on interstitial contents and magnetic properties of sintered MIM parts are presented and discussed. Magnets with a remanence of 570 mT, a coercivity of 970 kA/m and an energy product of 57 kJ/m3 could be produced without additional heat treatment.