Residual stresses in thermal barrier coatings: effects of interface asperity curvature/height and oxide thickness

The effects of curvature and height of the interface asperity on residual thermal stresses in a plasma-sprayed thermal barrier coating were numerically simulated. In the tip region of a convex asperity, the residual stress normal to the interface, σy is tensile in the ceramic top coat and increases with both curvature and height of the asperity. However, this residual tensile stress is lower for a periodic array of asperities than for an isolated asperity. The effects of thickness of the thermally grown oxide at the top coat–bond coat interface on residual thermal stresses were also numerically simulated. In the tip region of a convex asperity, σy in the ceramic top coat is tensile for a thin oxide but becomes compressive for a thick oxide. In the tip region of a concave asperity, σy in the ceramic top coat is compressive for a thin oxide and becomes less compressive for a thick oxide. The physical meaning of the above trend was qualitatively interpreted using an analytical model of three concentric circles.