A method of forming at least one concavity of a selected size and shape
within a surface of an internal passageway of a metallic component
comprises: depositing a ceramic-based material by a direct-write
technique onto a ceramic core which is suitable for forming the internal
passageway during a casting process to form the metallic component,
wherein the ceramic-based material is deposited as a positive feature;
heat-treating the deposited ceramic-based material; forming the metallic
component by a casting process in which the ceramic core is incorporated
into the casting, in a position selected as a desired position for the
internal passageway; and then removing the ceramic core from the metal
component after the casting process is complete, thereby forming the
internal passageway, with the concavity contained within the surface of
the passageway, said concavity formed by removal of the positive feature
of the ceramic-based material.