The Study on Suspension Plasma Spraying Grain Boundary Diffusion of Nd–Fe–B Magnets

To improve the coercivity of sintered Nd–Fe–B magnets, this study proposed a combined technology of suspension plasma spraying and grain boundary diffusion (GBD). First, suspension plasma spraying technology was used to deposit a Dy ₂ O ₃ precoating on magnet surfaces, followed by GBD modification via annealing‐tempering processes with varied parameters. Test results showed the average bonding strength between the Dy ₂ O ₃ coating and magnet reached 108.2 N, laying a solid foundation for subsequent GBD. When the Dy ₂ O ₃ precoating mass was controlled at 0.7 wt.% (relative to the magnet's mass), its coercivity increased by 2.35 kOe (15% higher than the original). Microstructural and compositional characterizations confirmed uniform Dy diffusion within 200 μm from the surface and a distinct Dy‐rich core–shell structure at grain boundaries. In the 20°C–120°C range, the coercivity temperature coefficient of GBD‐treated magnets was −0.624%/°C, lower than the original (−0.735%/°C). Thus, this combined approach is feasible for Nd‐Fe‐B performance optimization, exhibiting significant practical application potential.