Optimization of Sensitivity and Reliability of Magnetic Barkhausen Technique for Detecting Hardness Differences on Quenched and Tempered AISI 4140 Steels

Date

2015-06-18

Author

Arslan, Ebru
Davut, Kemal
Şimşir, Caner

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Magnetic Barkhausen noise (MBN) technique offers fast and non-destructive inspection of parts against grinding burns. Moreover, the applicability of the technique to evaluate residual stresses, microstructure heterogeneity, hardness, and heat treatment faults has been subject of intense research for the past 10 years. However, the influence of measurement parameters on the sensitivity and reliability of this technique has yet to be studied in detail. The present work aims at comparing the MBN response of quenched and tempered steels at different magnetizing frequency and voltages. For that purpose identical specimens from an AISI 4140 steel bar were quenched and the tempered at various temperatures between 200oC and 600oC. The microstructures were characterized by metallographic examinations and hardness measurements. A linear relation is expected between mechanical hardness and MBN activity due to the linear relation between magnetic coercive force and hardness. The reliability of the MBN measurements were, therefore, evaluated using Pearson’s correlation coefficient between MBN signals and the hardness. In addition sensitivity of the MBN technique was evaluated by comparing the MBN response of the hardest and softest samples; namely the as quenched sample and the sample tempered at 600oC. The MBN activity of the samples was quantified by calculating the root-mean-square (RMS) value of the noise signal obtained. Too low magnetizing voltages cause the MBN signal to be indistinguishable from background noise. Increasing the magnetizing voltage, increases the sensitivity of the MBN. However; saturation magnetization is exceeded in the pick-up coil when too high magnetizing voltages are used. Therefore the most sensitive response of MBN is obtained at an intermediate magnetizing voltage. This optimization work showed that the validity, reliability and sensitivity of Barkhausen noise technique strongly depends on the selection of measurement parameters.

URI

https://hdl.handle.net/11511/79343

Conference Name

11th Int Conf on Barkhausen Noise Micromagnetic Testing (ICBM 11)

Collections

Department of Metallurgical and Materials Engineering, Conference / Seminar

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Citation Formats

E. Arslan, K. Davut, and C. Şimşir, “Optimization of Sensitivity and Reliability of Magnetic Barkhausen Technique for Detecting Hardness Differences on Quenched and Tempered AISI 4140 Steels,” presented at the 11th Int Conf on Barkhausen Noise Micromagnetic Testing (ICBM 11), İzmir, Türkiye, 2015, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/79343.