USE OF BARKHAUSEN NOISE FOR DETERMINATION OF SURFACE HARDENED DEPTH

Abstract The Barkhausen noise technique is sensitive to the microstructure of the ferromagnetic materials. The parameters amplitude and position of the peak-shaped Barkhausen signal can be applied for non-destructive characterisation of steel (heat treatment, composition). For a surface treated material, the measurement of the Barkhausen signal shows two microstructural states: the bulk one and the surface one. The use of the control of the applied field yields the same condition of magnetisation for all the sample and allows us to compare the signals for different treatment depths. We establish the ability of the technique for the determination of hardened depth in the case of induction hardening, ion nitrogen hardening and case hardening.