Method for forming shaped holes

Abstract

A method of forming a shaped hole in a substrate, including substrates protected by coatings, as is the case where an air-cooled component has a thermal barrier coating for protection from a hostile thermal environment, such as the turbine, combustor and augmentor sections of a gas turbine engine. In particular, cooling holes are formed in an air-cooled component after a ceramic layer has been deposited on the surface of the component without damaging or spalling the ceramic layer. Processing steps generally include forming a hole through the ceramic layer and a substrate protected by the ceramic layer, thereby defining an opening at the surface of the ceramic layer. The diameter of the hole is less than the final size required for the cooling hole. A high-pressure abrasive fluid stream is then directed into the hole to enlarge the cross-section of the hole and impart a noncircular shape to the opening by removing portions of the substrate and ceramic layer without removing the ceramic layer surrounding the resulting noncircular-shaped opening. In a preferred embodiment, the abrasive fluid stream is traversed across the surface of the ceramic through a series of nested patterns that are not concentric with the central axis of the hole. Preferably, the hole acquires the desired noncircular shape in the ceramic layer, but retains a circular shape in the substrate.

Dependencies are inferred from the claim text.