Spheroidization of Rare-Earth Magnetic Powder by Induction Plasma

Rare-earth (RE) permanent magnets have found a wide range of applications in electronic components such as laptops, speakers, and hard drives as well as electric products like hybrid and electric vehicles and wind turbines [1, 2]. As such, the production of permanent magnets via advanced manufacturing techniques, including metal additive manufacturing (metal AM), injection molding, and spark plasma sintering, among others, has been the topic of research and development in the past couple of decades [3, 4]. It is well known that the feedstock powder for these manufacturing techniques shall meet strict chemical and morphological specifications, including particle sphericity. Sadly, one of the most common RE magnets, NdFeB, is produced as powder by strip casting and jet milling or by hydrogen decrepitation process, both of which yield irregular/angular powders. Such irregular powders exhibit low flowability making them unfit for most advanced manufacturing techniques. This work presents the use of an induction plasma system to spheroidize irregular NdFeB powders. The effect of plasma conditions on the sphericity of the powder is discussed. It is shown that highly spherical powder can be obtained at an optimum plasma condition. Crystalline structure and apparent density of NdFeB powder, prior to and post-plasma treatment, are obtained and compared.