Evaluation of carburization depth in service exposed ferritic steel using Magnetic Barkhausen Noise analysis

The feasibility of using Magnetic Barkhausen Noise (MBN) measurement for the evaluation of carburization depth in ferritic steels has been reported in this paper. MBN measurements were carried out on samples from service exposed 0.5Cr-0.5Mo ferritic steel tube at different depths (cross section) from carburised ID surface to simulate the variation in carbon concentration gradient within the skin depth of MBN with increasing time of exposure to carburization. It has been observed that the MBN level increases with increasing depth of measurement. An inverse relation between MBN level and carbon content/hardness value has been observed. This study suggests that, the MBN measurements on the carburized surface can be correlated with the concentration gradient within the skin depth of the MBN which would help in predicting the approximate depth of the carburized layer with proper prior calibration.