Impedance plane is one of the most important ways for presenting results in Eddy current testing, which includes major data for evaluation of results. In this study, the impedance plane was drawn for carburized steel with different surface carbon content. The influences of temperature, fill factor, and edge effect on impedance plane were investigated. The ability of Eddy current testing for determination of surface carbon content using normalized impedance was also shown. Results demonstrate a strong relationship between normalized impedance and surface carbon content (R2 = 0.82). Besides the effects of temperature, fill factor, and edge effect on determination of surface carbon content were investigated. The fill factor and temperature have the largest and the least effect on correlation coefficient between surface carbon content and impedance plane, respectively.

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