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

Abstract

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.