Effect of Ultrafine Powder Reduction Combined with Hydrogen Sintering on Magnetic Properties of NdFeB Permanent Magnets for Brushless DC Motors

Abstract

NdFeB permanent magnets are pivotal components for offshore wind turbines and electric vehicles, both of which demand exceptional magnetic properties. This study presents an innovative fabrication method for NdFeB magnets that eliminates the need for heavy rare earths in grain boundary diffusion. Through ultrafine powder reduction and an optimized sintering process, we achieved magnets with superior magnetic characteristics. The modified process, which includes secondary fine pulverization and slow heating in an argon atmosphere, yielded magnets with impressive magnetic properties: _iH_c = 16.04 kOe, (BH)_max = 52.46 MGOe, and BHH = 68.50. These values exceed those of magnets produced by conventional methods, which achieve _iH_c = 12.50 kOe, (BH)_max = 51.28 MGOe, and BHH = 63.78 by 22.07%, 2.25%, and 6.89%, respectively. Consequently, magnets produced by the modified process are upgraded from the N52 to the N50H grade, significantly enhancing their performance in high-temperature applications.