Improved Mechanical Properties and Thermal Stability of Sm-Co High Temperature Magnets Resulting From Surface Modifications

Improved mechanical properties and thermal stability of Sm-Co high temperature magnets resulting from surface modifications are reported. Compared to un-modified magnets, the modification with 15 μm sulfamate-Ni plating improved the fracture toughness by 76% and the thermal stability by 143% in vacuum and 861% in air for aging at 500 °C for up to 3000 hours. Microstructures of some specimens with and without modification were studied using SEM with EDS, and showed different fracture patterns. The improvements in mechanical properties were resulted by closing the infinite crack-origin sites on the surface of the brittle magnets with ductile metal. The striking improvement in thermal stability was achieved by sealing the Sm-Co magnets with corrosion resistive metal to limit oxidation. The adhesive bond strength between the magnet and the modified surface plays an important role in these improvements.