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Impact of magnetization state on the corrosion of sintered Nd-Fe-B magnets for e-motor applications

Moore, M. and Sueptitz, R. and Gebert, A. and Schultz, L. and Gutfleisch, O. (2013):
Impact of magnetization state on the corrosion of sintered Nd-Fe-B magnets for e-motor applications.
In: Materials and Corrosion, WILEY-VCH Verlag GmbH & Co. KGaA, pp. n/a-n/a, ISSN 09475117,
[Online-Edition: http://dx.doi.org/10.1002/maco.201206978],
[Article]

Abstract

We have created an accelerated corrosion environment for sintered Nd–Fe–B magnets in e-motor applications. E-motor working conditions are complex, and standard magnet corrosion tests only cover a small subset of possible parameters (e.g., samples are usually tested in the demagnetized state). In this work magnetized and demagnetized sintered Nd–Fe–B magnets were placed in gearbox oil, and exposed to temperature cycles (θmax = 130 °C) using an autoclave. Beforehand the magnets were pre-immersed in saturated water-based salt solution to account for water and de-icing salt that might interfuse gearbox oil over time. The corrosive behavior was studied for two commercial magnet grades, “high grade” (8.9 wt% dysprosium) and “low grade” (3.1 wt% dysprosium); and monitored by weight loss, structural analysis (scanning electron microscopy and energy dispersive X-ray) as well as magnetic characterization. The magnetized samples corroded significantly faster than their demagnetized counterparts. Strong differences in the corrosion rates of the “low grade” and “high grade” material are discussed. We concluded that the magnetization state is one key parameter that needs to be considered in corrosion tests for e-motor applications.

Item Type: Article
Erschienen: 2013
Creators: Moore, M. and Sueptitz, R. and Gebert, A. and Schultz, L. and Gutfleisch, O.
Title: Impact of magnetization state on the corrosion of sintered Nd-Fe-B magnets for e-motor applications
Language: English
Abstract:

We have created an accelerated corrosion environment for sintered Nd–Fe–B magnets in e-motor applications. E-motor working conditions are complex, and standard magnet corrosion tests only cover a small subset of possible parameters (e.g., samples are usually tested in the demagnetized state). In this work magnetized and demagnetized sintered Nd–Fe–B magnets were placed in gearbox oil, and exposed to temperature cycles (θmax = 130 °C) using an autoclave. Beforehand the magnets were pre-immersed in saturated water-based salt solution to account for water and de-icing salt that might interfuse gearbox oil over time. The corrosive behavior was studied for two commercial magnet grades, “high grade” (8.9 wt% dysprosium) and “low grade” (3.1 wt% dysprosium); and monitored by weight loss, structural analysis (scanning electron microscopy and energy dispersive X-ray) as well as magnetic characterization. The magnetized samples corroded significantly faster than their demagnetized counterparts. Strong differences in the corrosion rates of the “low grade” and “high grade” material are discussed. We concluded that the magnetization state is one key parameter that needs to be considered in corrosion tests for e-motor applications.

Journal or Publication Title: Materials and Corrosion
Publisher: WILEY-VCH Verlag GmbH & Co. KGaA
Uncontrolled Keywords: corrosion, e-motor, magnetic field, Nd–Fe–B magnets
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 10 Mar 2014 08:49
Official URL: http://dx.doi.org/10.1002/maco.201206978
Additional Information:

Early View (Online Version of Record published before inclusion in an issue)

Identification Number: doi:10.1002/maco.201206978
Funders: Funded by industry as part of the “CO2-Sonderforschungsprogramm” of the “Forschungsvereinigung Antriebstechnik e.V. (FVA)”, Funded by “Forschungsvereinigung Verbrennungskraftmaschinen e.V. (FVV).”
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