Eddy currents to control steel decarburising

Abstract

The work presented in the present paper aims at evaluating the opportunity of the eddy current method to characterise the decarburising extent which can occur during usual heat treatments of steel like austenising. The present work is based on previous studies highlighting the ability of eddy current to detect superficial defects such as cracks, pores or the possibility to corroborate its signal intensity with the mechanical microhardness modifications generated by carburising of steel. That is why eddy current is used here to systematically compare non-affected sample with the decarburised ones at different levels of decarburising. Among the techniques available to characterise the extent of decarburising, i.e. optical observations and microhardness profile, the eddy current technique provides a non-destructive method which is often required from an industrial control point of view. The results obtained show a strong correlation between the eddy current signal and the decarburised depth of the samples. As a consequence, they open realistic perspectives to characterise decarburising industrially.