Process for forming micro cooling channels inside a thermal barrier coating system without masking material

Abstract

The present invention provides a process for forming active convection cooling micro channels within or adjacent to a bond coat layer applied to a turbine high pressure turbine airfoil. When placed adjacent or within a porous TBC, the micro channels additionally provide transpiration cooling through the porous TBC. The micro channels communicate directly with at least one cooling circuit contained within the airfoil from which they receive cooling air, thereby providing direct and efficient cooling for the bond coat layer. Because the substrate includes an actively cooled flow path surface region that can reduce the cooling requirement for the substrate, the engine can run at a higher firing temperature without the need for additional cooling air, achieving a better, more efficient engine performance. In one embodiment, a metallic bond coat is applied to an airfoil. The bond coat is grooved such that the grooves are structured, with at least one structured micro groove communicating with at least one cooling fluid supply contained within the airfoil. A TBC layer is applied over the structured grooves, resulting in the formation of hollow micro channels for the transport of the cooling fluid due to self-shadowing. In different embodiments, the location of the structured grooves, hence, the resulting micro channels are placed within the airfoil substrate at the substrate/bond coat interface or within the TBC layer.