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 whi ch were investigated in terms of amplitude, absolute energy, position of th e event, etc, were performed on WC-Co coated specimens prepared by HVOF (hi gh velocity oxy fuel) during four-point bending tests. The microscopic obse rvations of the specimens show two types of cracks: transversal cracks (reg ularly spaced on the coating surface) and interfacial cracks. Acoustic emis sion results show two different types of acoustic events in terms of absolu te energy and amplitude, which are representative of two cracking mechanism s. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsev ier SAS.