Evaluation of Interfacial Adhesive Toughness by Simulation of Crack Propagation in Interfacial Indentation Test

Abstract

Abstract One of the methods used for the evaluation of coating adherence consists of determining an apparent interfacial fracture toughness through interfacial indentation in the cross-section of the coated system. In the present paper the interfacial crack propagation in a thermal spray coated system, during interfacial indentation test, was studied by finite element method. A Vickers indenter was applied at the coating/substrate interface to perform indentation test. In order to simulate the cracking, an initial semi-circular crack lying at the interface between the substrate and the coating was considered. Since the cracks resulting from interfacial indentation test have been reported to have a semi-circular shape, the crack was forced to advance by a uniform distance normal to the crack front in the plane of interface at each step of calculation. In these conditions it was shown that the interfacial crack has a mixed fracture mode. An apparent interfacial fracture energy Jca was calculated by this method to evaluate the interfacial adhesive toughness. The model was applied to study the crack propagation at the interface between a Cr3C2-NiCr HVOF coating and a grey cast iron substrate. A reasonable agreement between the calculation results and reported experimental data was found.