Characterization of adherence and cracking within coated materials by an acoustic emission method:: application to a WC-Co coating on a steel substrate

This note presents a characterization method of the 'adhesion' of a coating by acoustic emission technique. In situ acoustic emission measurements which were investigated in terms of amplitude, absolute energy, position of the event, etc, were performed on WC-Co coated specimens prepared by HVOF (high velocity oxy fuel) during four-point bending tests. The microscopic observations of the specimens show two types of cracks: transversal cracks (regularly spaced on the coating surface) and interfacial cracks. Acoustic emission results show two different types of acoustic events in terms of absolute energy and amplitude, which are representative of two cracking mechanisms. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.