Investment casting process and apparatus to facilitate superior grain structure in a DS turbine bucket with shroud

Abstract

An investment casting process that enables directionally solidified tip shrouded turbine blades or buckets to have a continuous grain structure that extends through the tip shroud in addition to increasing the quantity of grains in the root of the part.

1 . An investment casting process for forming a directionally solidified blade comprising:
 providing a blade mold, said mold being oriented so that a portion of a mold cavity thereof for forming a base of said blade is at a base thereof and a portion of the mold cavity for forming a tip of the blade is at a vertically upper end thereof;   providing a heat removal feature to extend below said mold;   flowing molten metal into said mold cavity of said mold; and   allowing said blade to solidify from the base upwardly.   
   
   
       2 . The investment casting process of  claim 1 , wherein said molton metal is fed to a base of said mold cavity. 
   
   
       3 . The investment casting process of  claim 1 , further comprising providing a sprue adjacent to said blade mold and providing a feeder tube for flowing molten metal from said sprue to said mold cavity. 
   
   
       4 . The investment casting process of  claim 3 , wherein said molten metal flows through said feeder tube from said sprue into the base of said mold cavity. 
   
   
       5 . The investment casting process of  claim 3 , wherein said sprue is vertically oriented, adjacent and parallel to said blade mold. 
   
   
       6 . The investment casting process of  claim 5 , wherein said molten metal flows through said feeder tube from said sprue into the base of said mold cavity. 
   
   
       7 . The investment casting process of  claim 5 , wherein said flowing molten metal comprises flowing molten metal into the vertically upper end of the sprue before said flowing through said feeder tube. 
   
   
       8 . The investment casting process of  claim 1 , wherein the mold is configured for forming a turbine bucket, the base of said mold cavity is configured to form a dovetail/shank of the turbine bucket and the vertically upper end of said mold cavity is configured to form a tip shroud of the turbine bucket. 
   
   
       9 . An investment casting assembly for molding a directionally solidified blade comprising:
 a blade mold, said mold being oriented so that a portion of a mold cavity thereof for forming a base of said blade is at a base thereof and a portion of the mold cavity for forming a tip of the blade is at a vertically upper end thereof;   a heat removal feature disposed to extend below said mold; and   a plumbing system for flowing molten metal into said mold cavity of said mold,   whereby the molded blade will solidify from the base upwardly.   
   
   
       10 . The investment casting assembly of  claim 9 , wherein said plumbing system comprises a sprue adjacent to said blade mold and a feeder tube for flowing molten metal from said sprue to said mold cavity. 
   
   
       11 . The investment casting assembly of  claim 10 , wherein said feeder tube extends from said sprue to the base of said blade mold. 
   
   
       12 . The investment casting assembly of  claim 10 , wherein said sprue is substantially vertically oriented, adjacent and parallel to said blade mold. 
   
   
       13 . The investment casting assembly of  claim 12 , wherein said feeder tube extends from said sprue to the base of said blade mold. 
   
   
       14 . The investment casting assembly of  claim 12 , further comprising a pour cup at the vertically upper end of the sprue for receiving molten metal. 
   
   
       15 . The investment casting assembly of  claim 9 , wherein the mold is configured for forming a turbine bucket, the base of said mold cavity is configured to form a dovetail/shank of the turbine bucket and the vertically upper end of said mold cavity is configured to form a tip shroud of the turbine bucket.