Study of Alternating Current Potential Drop testing on the evaluation of case depth on carburized steel

As part of a project to identify nondestructive techniques to determine the surface hardness and case depth of carburized steel, Alternating Current Potential Drop (ACPD) testing has been evaluated. ACPD is an optimized eddy current technique. Compared to the traditional eddy current testing, the four-pin ACPD sensor contacts the surface of the conductive material directly. A constant value alternating current is applied to the two outer pins, and the potential drop of the two inner pins is measured. Conductivity and permeability are obtained by ACPD to evaluate the properties of the carburized steel. For this study, samples of 1018 and 8620 were carburized to selected hardness and case depths. ACPD was determined to be an effect method to detect the case depth. In this paper, results of this method will be presented and discussed.