Investigation on Properties of Electroless Ni-P-W/Al2O3 Composite Coatings Deposited on Sintered NdFeB Permanent Magnet

Abstract

The Ni-P-W/Al2O3composite coatings were deposited on the surface of sintered NdFeB permanent magnet by electroless plating method. The morphology and the phases of Ni-P-W/Al2O3composite coatings were investigated using scanning electron microscopy and X-ray diffraction respectively. The hardness and the corrosion resistance of the composite coatings were also tested. The results indicated that the composite coatings morphology appears closely nodules morphology, and the microhardness increases linearly with increasing incorporation of Al2O3ratio. Compared with NdFeB magnet and Ni-P-W amorphous alloy coating, the corrosion resistance of the composite coatings was superior to that of the NdFeB magnet and the amorphous alloy coating obviously. However, for the corrosion resistance of Ni-P-W/Al2O3composite coatings with different Al2O3concentration, there is not a linear increase with the Al2O3concentration increasing. The self-corrosion potential of Ni-P-W/Al2O3composite coatings reaches the highest value while increasing incorporation of Al2O3ratio up to 10 g/L.