Document Type

Conference Proceeding


Review of Progress in Quantitative Nondestructive Evaluation

Publication Date



Kingston, RI


This paper reports on an eddy current (EC) study aimed at detecting anomalous machining damages in Inconel 718 and Ti 6–4 samples, including (i) surface discontinuities such as re‐depositing of chips onto the machined surface, and (ii) microstructural damages manifested as a white surface layer and a subsurface layer of distorted grains, typically tens of microns thick. A series of pristine and machine‐damaged coupons were studied by EC scans using a differential probe operated at 2 MHz to detect discontinuous surface anomalies, and by swept high frequency EC (SHFEC) measurements from 0.5 MHz to 65.5 MHz using proprietary detection coils to detect surface microstructural damages. In general, the EC c‐scan data from machine‐damaged surfaces show spatial variations with larger standard deviations than those from the undamaged surfaces. In some cases, the c‐scan images exhibit characteristic bipolar indications in good spatial correlation with surface anomalies revealed by optical microscopy and laser profilometry. Results of the SHFEC measurements indicate a reduced near‐surface conductivity of the damaged surfaces compared to the undamaged surfaces.


Copyright 2010 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

This article appeared in AIP Conference Proceedings 1211 (2010): 1639–1645 and may be found at

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American Institute of Physics




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