A design of sintered Nd-Fe-B magnet exhibiting superior corrosion resistance based on the metallurgical behavior of Ni and Cr

The improvement of corrosion resistance for sintered Nd-Fe-B magnets is usually focused on the modification of grain boundary phase. The main phase is similarly a key point to enhance corrosion resistance. In this work, a novel sintered Nd-Fe-B magnet is designed with the addition of Ni and Cr. This kind of sintered Nd-Ni-Fe-Cr-B magnet maintains a typical 2:14:1 tetragonal phase, and the metallurgical behavior of Ni and Cr is characterized by the distribution of Ni in the grain boundary and Cr in the main phase. Accelerated corrosion and electrochemical corrosion tests were conducted to compare the corrosion resistance of traditional sintered Nd-Fe-B magnet and Nd-Ni-Fe-Cr-B magnet. Results show that sintered Nd-Ni-Fe-Cr-B magnet exhibits superior corrosion resistance. It is found that the corrosion resistance of the grain boundary phase and the main phase is simultaneously increased. Moreover, the reduced potential difference between the grain boundary phase and the main phase further enhances the corrosion resistance of sintered Nd-Ni-Fe-Cr-B magnet. This work could provide an insight into the research aimed at improving the corrosion resistance of uncoated sintered Nd-Fe-B magnets.