History and Manufacturing Techniques
In 1982, General Motors (GM) and Sumitomo Special Metals discovered the Nd2Fe14B compound. The effort was principally driven by the high material cost of the SmCo permanent magnets, which had been developed earlier. GM focused on the development of melt-spun nanocrystalline Nd2Fe14B magnets, while Sumitomo developed full-density sintered Nd2Fe14B magnets. GM commercialized its inventions of isotropic Neo powder, bonded Neo magnets, and the related production processes by founding Magnequench in 1986. Magnequench, now part of the Neo Materials Technology, Inc., supplies melt-spun Nd2Fe14B powder to bonded magnet manufacturers. The Sumitomo facility has become part of the Hitachi Corporation and currently manufactures and licenses other companies to produce sintered Nd2Fe14B magnets. Hitachi holds more than 600 patents covering Neodymium magnets.
Sintered Nd2Fe14B tends to be vulnerable to corrosion. In particular, corrosion along grain boundaries may cause deterioration of a sintered magnet. This problem is addressed in many commercial products by adding a protective coating. Nickel plating or two-layered copper-nickel plating are the standard methods, although plating with other metals or polymer and lacquer protective coatings is also in use.
Read more about this topic: Neodymium Magnet
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