Nd-Fe-B permanent magnets (thick films) produced by a vacuum-plasma-spraying process

Thick, hard-magnetic Nd-Fe-B films (similar to 1 mm) were deposited on different substrates (Cu, steel) by a low-pressure plasma-spraying process. The properties of the applied Nd-Fe-B powders (e.g., grain size, composition) and the conditions of the spraying process were optimized with respect to the mechanical and magnetic properties of the films. Film thicknesses up to 1.2 mm were achieved with good adhesive properties (bond strength > 40 MPa). Cracks at the interface or within the films during the deposition process could be suppressed by adjusting the temperature profile of the substrate and controlling the deposition rate. Depending on the maximum temperature of the substrate and the thickness of the Nd-Fe-B films, either amorphous or microcrystalline structures were obtained. In general, the magnetic properties were improved by a postdeposition annealing treatment. Coercivities H-cJ up to 16 kA/cm and isotropic remanences of about 0.6 T were achieved. (C) 2000 American Institute of Physics. [S0021-8979(00)22108-7].