Determination of Creep Parameters of the Thermal Barrier Coatings Using an Impression Creep Test

Abstract:

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

Key words:impression creep; creep parameters; coating/substrate system; weight function; finite element analysis