Thermal aging of melt-spun NdFeB magnetic powder in hydrogen

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:417

Article

Pinkerton, Frederick E.¹  Balogh, Michael P.¹  Ellison, Nicole¹  Foto, Aldo²  Sechan, Martin³  Tessema, Misle M.³  Thompson, Margarita P.³ 

[1] Gen Motors Res & Dev Ctr, Chem & Mat Syst Lab, Warren, MI 48092 USA

[2] Element Mat Technol Wixom Inc, Wixom, MI 48393 USA

[3] Gen Motors LLC, GFL VE PT Mat Engn, Powertrain Mat Fluids AMPPD Engn & Lab, Pontiac, MI 48340 USA

关键词: Permanent magnets;    Neodymium-iron-boron;    Thermal aging;    Melt-spun;    Injection molding;   

DOI  :  10.1016/j.jmmm.2016.05.068

来源: Elsevier

【 摘 要 】

High energy product neodymium-iron-boron (NdFeB) magnets are the premier candidate for demanding electrified vehicle traction motor applications. Injection molded (IM) or compression molded (CM) magnets made using NdFeB powders are promising routes to improve motor efficiency, cost, and manufacturability. However, IM and CM NdFeB magnets are susceptible to substantial thermal aging losses at motor operating temperatures when exposed to the automatic transmission fluid (ATF) used as a lubricant and cooling medium. The intrinsic coercivity H-ci, of NdFeB IM and CM magnets degrades by as much as 18% when aged for 1000 h in ATF at 150 degrees C, compared to a 3% loss when aged in air. Here we report aging studies of rapidly quenched NdFeB powder in air, ATF, and H-2 gas. Expansion of the NdFeB crystal lattice in both ATF and H-2 identified hydrogen dissociated from the ATF during aging and diffused into the primary NdFeB phase as the probable cause of the coercivity loss of IM and CM magnets. (C) 2016 Elsevier B.V. All rights reserved.

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