Method of forming concavities in the surface of a metal component, and related processes and articles

Abstract

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 modifying the surface of a ceramic core, comprising the step of depositing a ceramic-based material by a direct-write technique onto the surface of the ceramic core, according to a pre-selected pattern.  
     
     
         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 . The method of  claim 2 , wherein the thermal spray technique is a plasma spray process or a high velocity oxy-fuel (HVOF) process.  
     
     
         4 . The method of  claim 2 , wherein the pen-dispensing technique is carried out with a robotic pen which itself comprises: 
 (i) a computer-controlled machine which includes a stage for mounting the ceramic core for rotation and orthogonal translation, and an elevator for translation from the stage;    (ii) a pen tip rotatably mounted to the elevator; and    (iii) a dispenser joined in flow communication with the pen tip, for ejecting a stream of material onto at least one surface of the ceramic core.    
     
     
         5 . The method of  claim 4 , wherein the stage includes a first table for translating the core in a first linear axis; a second table for translating the core in a second linear axis orthogonal to the first linear axis; and a spindle for rotating the core in a first rotary axis; 
 wherein the pen tip is mounted to the elevator for translation in a third linear axis orthogonal to the first and second linear axes, and for rotation in a second rotary axis coordinated with the first rotary axis, for orienting the pen tip relative to the core.    
     
     
         6 . The method of  claim 1 , wherein the ceramic-based material is deposited as a pattern of positive features on the core surface.  
     
     
         7 . The method of  claim 6 , 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.  
     
     
         8 . The method of  claim 1 , wherein the ceramic-based material comprises at least one refractory oxide.  
     
     
         9 . The method of  claim 1 , wherein the ceramic-based material comprises at least one constituent selected from the group consisting of alumina, alumina-aluminum; silica, silicon carbide, silicon nitride, magnesium oxide; silicates, yttria; zirconia, and silica-zircon.  
     
     
         10 . The method of  claim 9 , wherein the ceramic-based material further comprises at least one binder.  
     
     
         11 - 19 . (canceled)  
     
     
         20 . A metallic component containing at least one internal passageway and at least one concavity of a selected size and shape within a surface of the internal passageway, said component being formed by a method which comprises: 
 (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.    
     
     
         21 . A method of applying a pattern of positive features on the surface of a ceramic core used in an investment casting process to form a turbine engine airfoil with internal cooling passages which contain concavities inverse to the positive features, comprising the step of depositing a ceramic-based material to the surface of the ceramic core by a direct-write technique, according to a pre-selected pattern for the positive features.