Life prediction for thermal barrier coating systems in gas turbine vanes

Thermal barrier coatings (TBC) are widely used in turbines for propulsion and power generation. Expanded application to more demanding scenarios requires that their basic thermal fatigue characteristic be understood and quantified. In previous works, the plate and tube specimens with TBC have been studied under thermal cyclic load. The thermal fatigue life of vanes with TBC was seldom investigated. In present work, first the thermal fatigue experiments of tube specimens were carried out under different pre-oxidation time. By means of the WALKER constitutive model implemented in ABAQUS/UMAT, the stress-strain state of the interface between the bond coat and top coat was analysed at the meso-scale. The life prediction for TBC system was verified. Then the 3D finite element method (FEM) of a vane was modelled and analysed, negating the TGO thickness and the interface shape because of cross-scale thickness distribution in TBC system. The strain at critical location of the vane was obtained. Finally, the equivalent coefficient with relevance to the macro-and meso-scale FEM results was proposed. As a result, the thermal fatigue life of turbine vanes with TBC was determined.