Patent ID: 7291403

Claim:
A thermal barrier coating system on a surface of a component, the thermal barrier coating system comprising: a bond coat on the surface of the component; an alumina scale on the bond coat; and a multilayer thermal barrier coating consisting of: a thermal-sprayed first ceramic layer on the alumina scale, the first ceramic layer consisting essentially of partially stabilized zirconia so as to comprise the tetragonal and cubic phases of zirconia, the first ceramic layer being essentially free of vertical microcracks; a thermal-sprayed noncolumnar second ceramic layer overlying the first ceramic layer and being the outermost layer of the thermal barrier coating system and defining the outermost surface of the component, the second ceramic layer having a thickness greater than the first ceramic layer, the second ceramic layer consisting essentially of fully stabilized zirconia so as to consist essentially of the cubic phase of zirconia, the fully stabilized zirconia of the second ceramic layer being less erosion resistant than the partially stabilized zirconia of the first ceramic layer, the second ceramic layer being in an as-thermal sprayed condition to have a microstructure characterized by irregular flattened grains and a degree of inhomogeneity and porosity, and to have vertical microcracks that extend through the thickness of the second ceramic layer in an amount of at least twenty-five cracks per linear inch of surface thereof to cause the second ceramic layer to be more erosion resistant than the first ceramic layer; and optionally one or more intermediate layers between the first and second ceramic layers, the one or more intermediate layers providing a compositional gradient between the first and second ceramic layers whereby concentrations of partially and fully-stabilized zirconia decrease and increase, respectively, in the direction toward the second ceramic layer, wherein in the absence of the one or more intermediate layers the second ceramic layer overlies and contacts the first ceramic layer.