Development of magnetic losses during accelerated corrosion tests for Nd-Fe-B magnets used in permanent magnet generators

Elisa Isotahdon (Corresponding Author), Elina Huttunen-Saarivirta, Veli-Tapani Kuokkala

    Research output: Contribution to journalArticleScientificpeer-review

    1 Citation (Scopus)

    Abstract

    Sintered Nd-Fe-B magnets are critical components in permanent magnet wind generators. They are the strongest permanent magnets available and thus enable the construction of light and effective devices, but their stability in corrosive environments is limited. In this work, the formation of corrosion losses in two types of Nd-Fe-B alloys was studied. Magnets were in a magnetized state during the corrosion test, enabling monitoring of the development of losses in magnetic flux along with those in weight. Parallel flux and weight loss measurements conducted during corrosion tests showed that percentage weight losses were lower than the total flux losses. Scanning electron microscope studies of corroded specimens disclosed that the magnets first underwent dissolution of the grain-boundary phase, followed by the detachment and movement of the loosened grains in the magnetic field. The degradation was accelerated by oxidation of the matrix phase, which introduced further damage by volume expansion.
    Original languageEnglish
    Pages (from-to)732-741
    JournalCorrosion
    Volume72
    Issue number6
    DOIs
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Corrosion
    • Corrosion losses
    • Highly accelerated stress test (HAST test)
    • Improved corrosion resistance sintered Nd-Fe-B magnets
    • Improved stability sintered Nd-Fe-B magnets
    • Nd-Fe-B
    • Permanent magnet
    • Scanning electron microscopy
    • Thermal losses
    • Wind power

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