Micromagnetic techniques since years have been used to characterize the microstructure and to analyse residual stress states in magnetizable materials, i.e. steels [1,2]. Applying a dynamic sinusoidal magnetization in the frequency range 50 mHz ≦ f ≦ 110 Hz with field strength maxima up to 150 A/cm irreversible (magnetic Barkhausen noise) and reversible (incremental permeability) micromagnetic processes (Bloch-wall-jumps, rotations) give independent nd-quantities together with a derived coercivity. The question arises as to whether these techniques can be adapted for the characterization of surface-hardened materials for the estimation of the hardening depth.