Ti and Cr nitride coating/steel adherence assessed by acoustic emission wavelet analysis

Wavelet Transform (WT) was applied to Acoustic Emission (AE) signals from scratch tests on stainless steel samples with Cr or Ti nitride coatings obtained by physical vapor deposition, in order to characterize the coating adherence failure mechanisms. The WT, employed to analize the essentially non-stationary AE signals, was adequate to identify different stages of failure (transversal coating microfractures and coating/matrix debonding microfractures), which could be precisely delimited by a unique parameter.