Method of forming concavities in the surface of a metal component, and related processes and articles
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.
1. 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, comprising the following steps:
(a) 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 in a shape which, as cured, is inverse to the shape of the concavity;
(b) heat-treating the ceramic-based material deposited in step (a);
(c) 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
(d) 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.
2. The method of claim 1 , wherein the direct-write technique is selected from the group consisting of thermal spray, laser CVD, ink jet, laser particle guidance, matrix assisted pulsed laser evaporation (MAPLE), pen dispensing techniques, and combinations of any of the foregoing.
3. A method according to claim 1 for forming a pattern of concavities, corresponding to a pattern of ceramic-based material deposited as positive features in step (a).
4. The method of claim 3 , wherein the positive features are in a shape selected from the group consisting of diamonds, cones, hemispheres, hemispherical sections, circular pins, elongate hexahedrons, elongate semi-cylinders, and combinations thereof.
5. The method of claim 1 , wherein step (c) is carried out by an investment casting process.
6. The method of claim 1 , wherein the ceramic-based material deposited in step (a) is heat-treated in step (b) under thermal conditions sufficient to sinter the material and bond it securely to the ceramic core.
7. The method of claim 1 , wherein the ceramic core is in a green state during the deposition of the ceramic-based material in step (a).
8. The method of claim 7 , wherein the ceramic core is heat-treated during step (b), with the ceramic-based material deposited thereon, under sintering conditions.
9. The method of claim 1 , wherein the heat treating of step (b) occurs during at least a portion of the depositing of step (a).