Method of estimating the lifetime of thermal barrier coatings

摘要

A method of estimating the lifetime of a thermal barrier coating (14), which is applied to the surface of a member subjected to cyclical thermal loads, especially a vane and/or blade of a gas turbine, by means of a bond coat (12) lying in between, leads to more accurate results with simplified calculation by determining, in a first step, the amplitude of the normal stress (DELTAsigman) perpendicular to the interface between the bond coat (12) and the thermal barrier coating (14) during cyclical loading, and calculating, in a second step, the number Ni of cycles to failure for every normal stress amplitude (DELTAsigman) in accordance with the formula 1 $N_i={\left(Cit\left(\frac{{\mathrm{\Delta sigma}}_n}{{\mathrm{sigma}}_0}\right)\right)}^m$ where sigma0 is a stress reference value and C(deltaox) and m(deltaox) are material parameters, which depend on the thickness (deltaox) of an oxide layer (13), which is located between the thermal barrier layer (14) and the bond coat (12) and grows with the cyclical loading.