Modeling of the effect of Al2O3 interlayer on residual stress due to oxide scale in thermal barrier coatings

The thermally grown oxide (TGO) formed at the bondcoat/topcoat interface has been characterized as the driving force for coating spallation when a thermal barrier coating system is exposed to high temperature environment. To improve the oxidation resistance of the system, a plasma-sprayed Al2O3 interlayer was applied between the bondcoat and topcoat, as an oxygen barrier layer. This article discusses the effects of the additional Al2O3 layer on the residual stress induced by a TGO. Analytical modeling, coupled with finite element analysis, shows that the incorporation of a thin Al2O3 interlayer reduces residual stress at the interface. Hence, considering the oxygen–penetration–inhibiting role of the interlayer, this multilayered system was proposed as one potential alternative in improving TBC reliability.