Methods for directional solidification casting

Abstract

A method of directionally solidifying a molten alloy is presented. The molten alloy is disposed in a shell mold that has a thermal conductivity value greater than about 2 W/m-K. During the direction solidification, heat is transferred from the shell mold to a cooling region with a heat extraction rate greater than about 120 W/m 2 .

1 . A method comprising directionally solidifying a molten alloy disposed in a shell mold by transferring heat from the shell mold to a cooling region with a heat extraction rate greater than about 120 W/m 2 . 
     
     
         2 . The method of  claim 1 , wherein directionally solidifying the molten alloy comprises the steps of;
 disposing the molten alloy into the shell mold; and   contacting the shell mold containing the alloy with the cooling region.   
     
     
         3 . The method of  claim 2 , wherein contacting the shell mold with the cooling region comprises withdrawing the shell mold from a heating region into the cooling region. 
     
     
         4 . The method of  claim 3 , wherein withdrawing the shell mold comprises withdrawing the shell mold with a withdrawal rate ranging from about 50 millimeters/hour to about 400 millimeters/hour. 
     
     
         5 . The method of  claim 3 , wherein withdrawing the shell mold comprises withdrawing the shell mold with a withdrawal rate ranging from about 200 millimeters/hour to about 300 millimeters/hour. 
     
     
         6 . The method of  claim 1 , wherein directionally solidifying the molten alloy comprises maintaining a superheat of the molten alloy at least about 20 degrees Celsius. 
     
     
         7 . The method of  claim 1 , wherein the shell mold has a thermal conductivity value greater than about 2 W/m-K. 
     
     
         8 . The method of  claim 1 , wherein the shell mold has a thermal conductivity value in a range from about 5 W/m-K to about 15 W/m-K. 
     
     
         9 . The method of  claim 1 , wherein transferring heat from the shell mold to the cooling region comprises transferring heat with the heat extraction rate in a range from about 150 W/m 2  to about 300 W/m 2 . 
     
     
         10 . The method of  claim 1 , wherein the alloy comprises a nickel-based alloy, a cobalt-based alloy, or an iron-based alloy. 
     
     
         11 . The method of  claim 1 , wherein the cooling region comprises a liquid coolant. 
     
     
         12 . A method comprising directionally solidifying a molten alloy disposed in a shell mold, wherein the shell mold has a thermal conductivity value greater than about 2 W/m-K. 
     
     
         13 . The method of  claim 12 , wherein the shell mold comprises a support having a face coat disposed on an inner surface of the support and a seal coat disposed on the outer surface of the support. 
     
     
         14 . The method of  claim 13 , wherein the support comprises a material having a thermal conductivity greater than about 285 W/m-K. 
     
     
         15 . The method of  claim 14 , wherein the material comprises silicon carbide, aluminum nitride, diamond, graphite, or a combination of any of the foregoing. 
     
     
         16 . The method of  claim 12 , wherein directionally solidifying the molten alloy comprises the steps of;
 disposing the molten alloy into the shell mold; and   contacting the shell mold containing the molten alloy with a cooling region.   
     
     
         17 . The method of  claim 16 , wherein contacting the shell mold with the cooling region comprises withdrawing the shell mold from a heating region into the cooling region. 
     
     
         18 . The method of  claim 17 , wherein withdrawing the shell mold comprises withdrawing the shell mold with a withdrawal rate ranging from about 50 millimeters/hour to about 400 millimeters/hour. 
     
     
         19 . The method of  claim 17 , wherein withdrawing the shell mold comprises withdrawing the shell mold with a withdrawal rate ranging from about 100 millimeters/hour to about 300 millimeters/hour. 
     
     
         20 . The method of  claim 16 , wherein contacting the shell mold with the cooling region comprises transferring heat from the shell mold to the cooling region with a heat extraction rate greater than about 120 W/m 2 . 
     
     
         21 . The method of  claim 16 , wherein contacting the shell mold with the cooling region comprises transferring heat from the shell mold to the cooling region with a heat extraction rate in a range from about 150 W/m 2  to about 300 W/m 2 . 
     
     
         22 . The method of  claim 12 , wherein directionally solidifying the molten alloy comprises maintaining a superheat of the molten alloy at least about 20 degrees Celsius. 
     
     
         23 . The method of  claim 12 , wherein the shell mold has a thermal conductivity value in a range from about 5 W/m-K to about 15 W/m-K. 
     
     
         24 . The method of  claim 12 , wherein the alloy comprises a nickel-based, a cobalt-based, or an iron-based alloy.