In industrial case hardening, the temporal and local non-destructive characterization of occurring microstructural constituents creates new possibilities for automating manufacturing processes showing a high level of process reliability. Furthermore, component properties within the scope of quality assurance and product liability can be fully documented. By analyzing the higher harmonics of eddy current testing, the structure-specific magnetic properties can be used to differentiate between the microstructural constituents formed. The eddy current sensor can be integrated into the cooling path. This enables in-situ test signal recording in order to continuously monitor the graded microstructure formation in the peripheral zone as well as deeper in the component for quality assurance. An increasing carbon content leads, among other things, to a higher proportion of residual austenite. This results in a lower test signal amplitude, which, for example, can be correlated with the hardening depth. The results of this testing method, used for the first time for graded components, are presented here.