Methods for repairing ceramic cores

Abstract

A method is provided for repairing defects in a ceramic core adapted for use in a casting process. The ceramic core is formed from a slurry comprising at least one refractory powder material suspended in a liquid vehicle. The method includes forming a repair mixture comprising a liquid diluent and the at least one refractory powder material suspended in the liquid vehicle of the slurry. The repair mixture is applied to a region of the ceramic core that includes at least one defect and then the ceramic core is fired to burn off the liquid vehicle in the repair mixture and form a ceramic composition that closes the defect.

1 . A method for repairing defects in a ceramic core adapted for use in a casting process, the ceramic core being formed from a slurry comprising at least one refractory powder material suspended in a liquid vehicle, the method comprising:
 forming a repair mixture comprising a liquid diluent and the at least one refractory powder material suspended in the liquid vehicle of the slurry;   applying the repair mixture to a region of the ceramic core, the region comprising at least one defect; and   firing the ceramic core to burn off the liquid vehicle in the repair mixture and form a ceramic composition that closes the defect.   
     
     
         2 . The method of  claim 1 , wherein the at least one refractory powder material comprises a silica refractory powder and a zircon refractory powder. 
     
     
         3 . The method of  claim 1 , wherein the liquid vehicle comprises a siloxane binder. 
     
     
         4 . The method of  claim 1 , wherein the liquid diluent is a siloxane diluent. 
     
     
         5 . The method of  claim 1 , wherein the liquid diluent is an additional amount of the liquid vehicle. 
     
     
         6 . The method of  claim 1 , wherein the repair mixture further comprises a catalyst capable of cross-linking the liquid vehicle and the liquid diluent. 
     
     
         7 . The method of  claim 1 , wherein the repair mixture comprises, by volume, about 30 to about 50 percent of the refractory powder material and about 50 to about 70 percent of the liquid vehicle and the liquid diluent combined. 
     
     
         8 . The method of  claim 7 , wherein the repair mixture comprises up to about 100 ppm of a catalyst capable of cross-linking the liquid vehicle and the liquid diluent. 
     
     
         9 . The method of  claim 1 , further comprising wetting the region with the liquid diluent prior to applying the repair mixture. 
     
     
         10 . The method of  claim 1 , wherein the ceramic core comprises a wall defining at least one cavity therein. 
     
     
         11 . The method of  claim 10 , further comprising injecting the repair mixture into the cavity to close at least one opening in the wall of the ceramic core prior to firing. 
     
     
         12 . The ceramic core repaired by the method of  claim 1 . 
     
     
         13 . A method for repairing defects in a silica-containing ceramic core adapted for use in a casting process, the silica-containing ceramic core being formed from a slurry comprising at least one refractory powder material and a siloxane binder, the method comprising:
 forming a repair mixture comprising a siloxane diluent and the at least one refractory powder material and the siloxane binder of the slurry;   applying the repair mixture to a region of the silica-containing ceramic core ( 10 ), the region comprising at least one defect; and   firing the silica-containing ceramic core to burn off the siloxane binder and the siloxane diluent in the repair mixture and form a silica-containing ceramic composition that fills the defect.   
     
     
         14 . The method of  claim 13 , wherein the repair mixture comprises a catalyst capable of cross-linking the siloxane binder. 
     
     
         15 . The method of  claim 13 , wherein the siloxane diluent has the same composition as the siloxane binder. 
     
     
         16 . The method of  claim 13 , wherein the at least one refractory powder material comprises a silica refractory powder and/or a zircon refractory powder. 
     
     
         17 . The method of  claim 13 , wherein the silica-containing ceramic core comprises a wall defining at least one cavity therein. 
     
     
         18 . The method of  claim 17 , further comprising injecting the repair mixture into the cavity to close at least one opening in the wall of the silica-containing ceramic core prior to firing. 
     
     
         19 . The method of  claim 13 , wherein the silica-containing ceramic core is adapted for use in casting a component for installation in a gas turbine engine. 
     
     
         20 . The method of  claim 13 , wherein the repair mixture comprises, by volume, about 30 to about 50 percent of the silica refractory powder and the zircon refractory powder combined, about 50 to about 70 percent of the siloxane binder and the siloxane diluent combined, and optionally up to about 100 ppm of a catalyst capable of cross-linking the siloxane binder and the siloxane diluent.