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

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

Fingerprint

Magnetic leakage
Permanent magnets
Magnets
Corrosion
Fluxes
Caustics
Magnetic flux
Dissolution
Grain boundaries
Electron microscopes
Magnetic fields
Scanning
Degradation
Oxidation
Monitoring

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

Cite this

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title = "Development of magnetic losses during accelerated corrosion tests for Nd-Fe-B magnets used in permanent magnet generators",
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.",
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",
author = "Elisa Isotahdon and Elina Huttunen-Saarivirta and Veli-Tapani Kuokkala",
year = "2016",
doi = "10.5006/2037",
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journal = "Corrosion",
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Development of magnetic losses during accelerated corrosion tests for Nd-Fe-B magnets used in permanent magnet generators. / Isotahdon, Elisa (Corresponding Author); Huttunen-Saarivirta, Elina; Kuokkala, Veli-Tapani.

In: Corrosion, Vol. 72, No. 6, 2016, p. 732-741.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Development of magnetic losses during accelerated corrosion tests for Nd-Fe-B magnets used in permanent magnet generators

AU - Isotahdon, Elisa

AU - Huttunen-Saarivirta, Elina

AU - Kuokkala, Veli-Tapani

PY - 2016

Y1 - 2016

N2 - 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.

AB - 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.

KW - Corrosion

KW - Corrosion losses

KW - Highly accelerated stress test (HAST test)

KW - Improved corrosion resistance sintered Nd-Fe-B magnets

KW - Improved stability sintered Nd-Fe-B magnets

KW - Nd-Fe-B

KW - Permanent magnet

KW - Scanning electron microscopy

KW - Thermal losses

KW - Wind power

U2 - 10.5006/2037

DO - 10.5006/2037

M3 - Article

VL - 72

SP - 732

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JO - Corrosion

JF - Corrosion

SN - 0010-9312

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ER -