Abstract: A multilayered ceramic topcoat of a thermal barrier coating system is useful for high temperature corrosive applications such as hot section components in gas turbine engines. The ceramic topcoat includes at least two layers, each having generally columnar grain microstructures with different grain orientation directions. A preferred method of producing the multilayered ceramic topcoat includes positioning a superalloy substrate at a first angled orientation relative to a ceramic vapor cloud in an electron beam physical vapor deposition apparatus for a time sufficient to grow a first ceramic layer. The substrate is then reoriented to a second, different angled orientation for a time sufficient to grow a second ceramic layer. The ceramic layers exhibit columnar microstructures having respective grain orientation directions which are related to the first and second substrate orientations.

Abstract: Disclosed is an improved bond coat of a thermal barrier coating system useful for enhancing adhesion of a ceramic topcoat to a superalloy substrate. The bond coat includes about 13 to 30 weight percent aluminum, between trace and about 3 weight percent of a reactive element selected from the group consisting of yttrium, zirconium, lanthanum, and scandium, and mixtures thereof, and balance selected from the group consisting of nickel, cobalt, iron and mixtures thereof, wherein said bond coat is further characterized by absence of added chromium. A preferred method includes plasma spraying a prealloyed powder of the bond coat composition on the substrate followed by alumina formation and ceramic topcoat deposition. Uses include thermal barrier coating systems on gas turbine engine hot section components such as turbine blade and vane airfoils, combustors, and exhaust nozzles.