Role of impact on determination of interfacial toughness measurement by indentation for thermal barrier coating systems

The measurement of interfacial toughness by an indentation method was proposed several years ago. It has been shown that this method is very simple and reliable for the calculation of interfacial toughness. For this reason, many studies were performed for different substrate and coating combinations. Numerical models also supported these studies. Unfortunately, the success of this method depends on the hardness of the substrate. In most studies, the coating was ceramic and the substrate was steel. The substrate must be hard enough to get a circular crack around the indentation zone. If the substrate is not hard enough, the circular crack cannot be seen. In the light of the experiments performed for different combinations of substrate and coating, the use of the method was restricted to a very narrow range of materials that are mainly used for thermal barrier coating systems. In the present study, this method is used even for a medium hardness substrate. In order to get a circular crack, loading is performed with constant acceleration instead of static loading. The success of the method is shown to be considerably increased.