Patent ID: 6681639
Filing Date: 2004-01-27
Classification: C23C,G01N

Abstract:
A method of estimating the lifetime of a thermal barrier coating, 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 a bond coat lying in between the coating and the member, the method comprising:in a first step, determining the amplitude of the normal stress (&Dgr;&sgr;n) perpendicular to the interface between the bond coat and the thermal barrier coating during cyclical loading; and, in a second step, calculating the number Ni of cycles to failure for every normal stress amplitude (&Dgr;&sgr;n) in accordance with the formula Ni&it;â€ƒ=C&af;(&bigtriangleup;ÏƒnÏƒ0)mwhere &sgr;0 is a stress reference value and C(&dgr;ox) and m(&dgr;ox) are material parameters, which depend on the thickness (&dgr;ox) of an oxide layer, which is located between the thermal barrier layer and the bond coat and grows with the cyclical loading.