Residual stress estimation and fracture behavior of thermal barrier coatings

Protective surface coatings such as thermal barrier coatings (TBCs) are extensively utilized in gas turbines and other high-temperature applications. TBCs act as an insulating medium to shield the underlying substrate metal from damage when subjected to elevated temperature conditions. The fracture behavior of thermal barrier coating is studied in this work. The distribution of residual stress and identification of potential cracking zones in the TBC system comprising substrate material made of superalloys, bond coat (BC), alumina containing thermally grown oxide (TGO), and topcoat (TC) made of ceramic materials are analyzed using a finite element approach. Probable microstructure geometry close to the actual microstructure of TBC is used as a representative volume element in the present analysis. Temperature-dependent thermal and mechanical characteristics of TBC layers, the effect of the TGO development, and each layer’s creep deformation are considered for modeling the TBC. A finite element simulation of the TBC examines the influence of cyclic thermal loading and creep deformation on localized stress fields around the TGO interfaces. The TBC finite element analysis predicts the critical zones of crack nucleation and crack propagation, emphasizing the significance of substantial tensile stresses around and within the TGO layer, which aligns qualitatively with the observed experimental results from the existing literature.