Thermal barrier coatings (TBCs) are applied to hot gas path surfaces to reduce metal temperatures and thermal stresses for improved turbine component durability. Improvements in engine performance are achieved when TBCs enable reductions in cooling air usage and turbine blade tip-shroud clearances.
This paper describes the development of thick TBCs with superior strain tolerance. A pattern of grooves or slant steps incorporated into the surface to be coated enables the development of shadow gaps in the ceramic layer during plasma spray deposition. These gaps segment the TBC, permitting ceramic-metal thermal expansion mismatch and thermal strains to be accommodated by free expansion.