Determination of creep parameters of the thermal barrier coatings using an impression creep test

An extensive accurate finite element (FE) analysis of the impression creep test was performed for two material systems, i.e. a single phase half infinite system and a coating/substrate system. For each case, the FE analysis was carried out for different classes of punch sizes aimed to develop methods to separate creep properties of a coating from a coating/substrate system. The study emphasis was placed on understanding how the punch size influenced the impression creep exponent of a certain coating/substrate system. A weight expression was proposed to quantify the coating's and the substrate's contributions to the impression creep exponent of the coating/substrate system. The results of finite element analysis show that the value of the weight expression exhibits a good power-law dependence on the radius of the punch for a certain coating/substrate system. The weight function proposed allows developing an analytic approach to separate coating's creep exponent from a coating/substrate system. Then a numerical approach including procedures of fitting the curve of n vs R/Tc and extrapolating to R=0 was put forward to determine the coating's creep exponent. Both of the results obtained by the two methods agree reasonably well with the input FE model.