Nondestructive determination of case depth and hardness profile by the investigation of the parts response to the induction current

The eddy current test is a non-destructive technique which can be performed rapidly. Since the eddy current response is sensitive to the chemical composition and microstructure of the materials، it can be used to determine case depth of induction hardened parts due to the difference in magnetic properties of the hardened layer and the core of the specimen. In the present study، identical rods of CK45 carbon steel were case hardened using induction hardening method. Plotting of hardness profile was done، and the effective and total case depths were also determined. In order to investigate the applicability of the eddy current technique، the relation between effective and total case depths and eddy current outputs (primary and secondary voltages، normalized impedance and phase angle) have been studied. Good correlations between these findings indicate an acceptable level of accuracy of this method in comparison with destructive methods.