A parametric study of damage initiation and propagation in EB-PVD thermal barrier coatings

In this paper, finite element models are used to investigate catastrophic failure of thermal barrier coatings (TBCs) due to delaminations along susceptible interface between thermally grown oxide (TGO) and the ceramic top coat. The top coat crack initiation and propagation is investigated using a thermo-elastic finite element model with bond coat creep. Cracks are assumed to initiate when the maximum principal stress exceeds rupture stress of the top coat. A sensitivity analysis estimates the contribution of geometric and material parameters. Subsequently, crack propagation simulations using a hysteretic cohesive zone model are performed for parametric combinations which initiate top coat cracks. A parametric relationship is established for assessing crack initiation in terms of geometric and material parameters of the TBC that helps identify the fail-safe design space for TBC. The finite element predictions are also compared to the experimental observations of failure.