Low-frequency magnetic incremental permeability for the non-destructive evaluation of hardness profile after carburization treatment with large case hardening depth

Carburization treatment with large case hardening depth is a technical process to enhance steel parts' surface hardness and wear resistance. Accurate evaluation of this metallurgical treatment is crucial to prevent critical mechanical failures. Low-frequency magnetic incremental permeability (LF-MIP) emerges as a non-destructive surface technique well-suited for this purpose in the case of ferromagnetic parts. Although correlations between magnetic indicators obtained through LF-MIP characterization and deep carburization treatment have been demonstrated, they remain qualitative. In this study, we propose an innovative method to assess the entire hardness profile based on LF-MIP characterization. Experimental results and simulation data are integrated into a reference chart used for post-processing, enabling the prediction of hardness profiles for specimens in a blind test. With a relative Euclidean distance of less than 6 % between the method's predictions and destructive tests conducted on specimens treated with medium, deep, and intense intensities, we consider the method validated.