Reinforced ceramic investment casting shell mold and method of making such mold

Abstract

A reinforced ceramic investment casting shell mold and method of making such mold. The ceramic investment casting shell mold includes alternate, repeating layers of a ceramic material and a ceramic stucco defining an overall thickness of the shell mold. A fibrous reinforcing material is disposed in the alternate, repeating layers at an intermediate thickness of the shell mold. The fibrous reinforcing material has high tensile strength at elevated temperature and a coefficient of thermal expansion that is less than the coefficient of thermal expansion of the ceramic material and the ceramic stucco. The fibrous reinforcing material is preferably woven into a twisted yarn and disposed in a generally spiral configuration.

What is claimed is: 
     
       1. A method of making a ceramic investment casting shell mold, said method comprising the steps of: providing a pattern having the shape of the desired casting;   dipping said pattern into a ceramic slurry to form a coating on said pattern;   applying a ceramic stucco on said coating;   repeating said dipping step and said applying step to build up said shell mold to an intermediate thickness, said intermediate thickness being less than the desired overall thickness of said shell mold;   .[.disposing.]. .Iadd.winding .Iaddend.a .Iadd.substantially continuous .Iaddend.fibrous reinforcing material around said shell mold;   building up said shell mold to the desired overall thickness by repeating said dipping step and said applying step over said reinforcing material; and   firing said shell mold, said fibrous reinforcing material having high tensile strength at elevated temperature such that said reinforcing material remains an integral part of said shell mold after firing and said fibrous reinforcing material having a coefficient of thermal expansion that is less than the coefficient of thermal expansion of the ceramic materials comprising said ceramic slurry and said ceramic stucco.   
     
     
       2. The method of claim 1, wherein said step of .[.disposing.]. .Iadd.winding .Iaddend.a fibrous reinforcing material around said shell mold is performed after said dipping step and said applying step having been alternately repeated approximately 6 to 9 times. 
     
     
       3. The method of claim 1, wherein said reinforcing material is an alumina-based or mullite-based ceramic composition having a tensile strength of at least 200,000 psi and a coefficient of thermal expansion that is approximately one-half the coefficient of thermal expansion of the ceramic materials comprising said ceramic slurry and said ceramic stucco. 
     
     
       4. The method of claim 1, wherein said step of .[.disposing.]. .Iadd.winding .Iaddend.said reinforcing material around said shell mold further comprises: Wrapping said reinforcing material around said shell mold in a generally spiral configuration.   
     
     
       5. The method of claim 4, wherein said reinforcing material is .[.wrapped.]. .Iadd.wound .Iaddend.around said shell mold in a substantially continuous spiral leaving a space between successive .[.wraps.]. .Iadd.windings .Iaddend.of said reinforcing material around said shell mold. 
     
     
       6. The method of claim 5, wherein said space is in the range of from about 0.2 inch to about 2.0 inches. 
     
     
       7. The method of claim 1, wherein said reinforcing material is a woven twisted yarn. 
     
     
       8. The method of claim 1, wherein said reinforcing material is a woven tape product. 
     
     
       9. The method of claim 7, wherein said yarn reinforcing material is an open net-like member. 
     
     
       10. A ceramic investment casting shell mold, said shell mold comprising: alternate, repeating layers of a ceramic material and a ceramic stucco defining an overall thickness of said shell mold; and   a .Iadd.substantially continuous .Iaddend.fibrous reinforcing material .[.disposed.]. .Iadd.wound around said shell mold .Iaddend.in said alternate, repeating layers at an intermediate thickness of said shell mold, said reinforcing material being comprised of an alumina-based or mullite-based ceramic composition having high tensile strength of at least 200,000 psi and having a coefficient of thermal expansion that is approximately one-half the coefficient of thermal expansion of said ceramic material and said ceramic stucco.   
     
     
       11. The ceramic investment casting shell mold of claim 10, wherein said reinforcing material is .[.disposed.]. .Iadd.wound .Iaddend.in said alternate, repeating layers at an intermediate thickness of 6 to 9 alternate, repeating layers. 
     
     
       12. The ceramic investment casting shell mold of claim 10, wherein said reinforcing material is wound in a generally spiral configuration. 
     
     
       13. The ceramic investment casting shell mold of claim 12, wherein said reinforcing material is .[.disposed.]. .Iadd.wound .Iaddend.in said shell mold in substantially continuous spiral leaving a space between successive wraps of said reinforcing material. 
     
     
       14. The ceramic investment casting shell mold of claim 13, wherein said space is in the range of from about 0.2 inch to about 2.0 inches. 
     
     
       15. The ceramic investment casting shell mold of claim 10, wherein said reinforcing material is a woven twisted yarn. 
     
     
       16. The ceramic investment casting shell mold of claim 10, wherein said reinforcing material is a woven tape product. 
     
     
       17. The ceramic investment casting shell mold of claim 15, wherein said yarn reinforcing material is woven into an open net-like member.