Spheroidization of Nd-Fe-B Powders by RF Induction Plasma Processing

The present study described the synthesis of spheroidized Nd-Fe-B powders using a radio frequency (RF) inductively coupled plasma (ICP) torch with irregular feedstock materials. The effect of the power feed rate and the particle size of the feedstock material on spheroidization was analyzed. Scanning electron microscopy was used to examine the morphologies and the cross sections of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed in the spheroidization processing. The loose densities and the particle size distributions of both the raw materials and the spheroidized powders were characterized. The results show that almost 100% of spheroidization percentage could be achieved. The loose density and powder flowability are enhanced greatly after plasma-treating. The loose density rises from 2.778 g/cm3 to 3.785 g/cm3. The powder flowability increases from 43.3 s/50 g to 27.5 s/50 g. Due to the good flowabitity and high loose density of the spherical powders, plasma-treated Nd-Fe-B powders have been used as the feedstock for gel-casting and injection molding.