Reading depth of the magnetic Barkhausen noise. II. Two-phase surface-treated steels

• Published in: Journal of magnetism and magnetic materials Vol. 513; p. 167239
• Main Authors: Stupakov, A., Perevertov, A., Neslušan, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-11-2020; Elsevier BV
• Subjects: Barkhausen effect; Barkhausen noise; Coils; Decarburizing; Noise; Surface sensitivity; Surface treatment; Thickness measurement; Barkhausen noise; Surface treatment; Surface sensitivity
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.167239

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•We tested two-phase steels with soft ferrite and hard milled layers of different thicknesses.•We clarified the effective depth from which the magnetic Barkhausen noise is detected.•For soft ferrite steels, the reading depth of both detection coils is about 200 micrometers.•For hard fine materials, the depth of the surface-mounted coils can drop up to 50 micrometers.•Overlapping of the noise pulses has a strong impact on the signal detected by the surface coils.
This second part of the work estimates the reading depth of the magnetic Barkhausen noise, testing surface-treated steels. The concomitant changes of the surface microstructure result in a pronounced two-peak profile of the Barkhausen noise signal: an additional peak arising from the surface-treated layer suppresses the initial peak generated in the bulk material. To confirm and explain the results obtained for semi-hard steel ribbons in the first part of this work (Stupakov et al., 2020), the steels with opposite surface treatments (soft decarburized and hard milled layers of different thickness) have been measured by commonly used detection sensors: classical sample-wrapping and industrial surface-mounted coils. To obtain physically accurate data, dynamic variations of the Barkhausen noise signal have been corrected using the recently proposed dH/dt normalization of its rms envelopes.