ZrO2/ZrN MULTILAYERS ON BARE SINTERED NdFeB MAGNETS BY ION-PLASMA DEPOSITION WITH PULSED BIASING

摘要

Surface modification with nanocrystalline ZrO2/ZrN multilayers was performed on bare sintered NdFeB permanent magnets to improve their corrosion properties. The multilayers were deposited by ion-plasma vacuum-arc evaporation technique with curvilinear magnetic filter reducing amount of macro-particles emitted from cathode spots and using pulsed biasing mode for elimination of micro-arcs formation. The structure, chemical and phase compositions have been investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM) with energy-dispersive X-ray analysis (EDX) and X-ray fluorescence (XRF) methods. Mechanical and tribological properties were evaluated using a ball-on-disc method, Vickers microhardness and nanoindentation tests, respectively. The influence of the obtained coatings in terms of their barrier properties for corrosion in a quasi-physiological 0.9% NaCl solution has been studied. The coating had a thickness of 10 mu m and achieved hardness of up to 26-30 GPa. The proposed technology, in particular, would be prospective for application of buffer multilayered coatings on NdFeB magnets used as repelling devices in orthodontics.