Coating materials for diffusing into magnet of NdFeB and a method of making it

A method for fabricating a magnet with a coating material, wherein the coating material comprises an alloy powder A having a rare earth element and a metal powder B, wherein the method comprises following steps:

• providing a rare earth magnet;
• providing a slurry comprising the coating material;
• coating the slurry on a surface of the rare earth magnet;
• performing a two-stage diffusion heat treatment on the coated rare earth magnet;
• and
• annealing the rare earth magnet;
• wherein the rare earth magnet comprises a neodymium-iron-boron (NdFeB) magnet;
• wherein a melting point of the metal powder B is lower than a melting point of the alloy powder A;
• and
• wherein the metal powder B in the coating material is arranged to be in a range of 3-10% by weight;
• the rare earth element in the alloy powder A comprises Dysprosium (Dy) and/or Terbium (Tb) in a form of a rare earth-metal-hydrogen alloy (RMH) powder;
• metal M of the alloy powder A is an alloy composed of Fe and Co, and a mass ratio of the Fe and Co elements is 1:1 to 2:1;
• an average particle size of the alloy powder A is in a range of 1 to 5 μm, and an average particle size of the metal powder B is in a range of 0.1 to 0.5 μm;
• wherein performing the two-stage diffusion heat treatment comprises:
• performing, in a first stage, diffusion at 600-800° C. for 5-15 hours;
• and
• performing, in a second stage, diffusion at 850-1000° C. for 10-20 hours.