Composite seals for turbomachinery

Abstract

The present application provides composite seals for reducing leakages between adjacent components of turbomachinery. The composite seals may include a metallic shim, a metallic support structure and a ceramic, glass or enamel coating. The shim and the support structure may be bonded or fused together. The support structure may include internal voids or gaps, and the coating may be applied to the shim and the support structure such that the coating is provided within the voids or gaps of the support structure, between portions of the support structure and the shim, and substantially over the outer surface of the support structure. The support structure may thereby provide a mechanical attachment between the shim and the coating. In use, the coating provides thermal and/or chemical insulation to the metallic shim and the support structure of the seal.

We claim: 
     
         1 . A seal assembly for positioning within a seal slot formed at least partially by adjacent turbomachinery components to seal a gap extending between the components, the seal assembly comprising:
 a metallic shim including a sealing surface and a support surface;   a porous metallic support structure bonded to the support surface of the metallic shim; and   a ceramic, glass or enamel coating extending over and within the porous metallic support structure such that the coating substantially covers the support surface side of the metallic shim and the support structure, and   wherein portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure.   
     
     
         2 . The seal assembly of  claim 1 , wherein portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure in a direction extending away from the support surface to mechanically couple the coating to the metallic shim via the metallic support structure. 
     
     
         3 . The seal assembly of  claim 2 , wherein the direction extending away from the support surface is substantially normal to the support surface. 
     
     
         4 . The seal assembly of  claim 1 , wherein the metallic shim is a substantially solid metallic shim. 
     
     
         5 . The seal assembly of  claim 1 , wherein the coating is chemically bonded to the support structure. 
     
     
         6 . The seal assembly of  claim 1 , wherein at least one of the support surface of the metallic shim and the metallic support structure includes a protective outer coating configured to prevent oxidation of the respective metallic component. 
     
     
         7 . The seal assembly of  claim 1 , wherein the metallic support structure is diffusion bonded to the metallic shim via at least one braze. 
     
     
         8 . The seal assembly of  claim 1 , wherein the metallic support structure is a mesh structure. 
     
     
         9 . The seal assembly of  claim 1 , wherein portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure that are bonded to the support surface of the metallic shim. 
     
     
         10 . The seal assembly of  claim 1 , wherein portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure that are not bonded to the support surface of the metallic shim. 
     
     
         11 . The seal assembly of  claim 10 , wherein the portions of the metallic support structure that are not bonded to the support surface of the metallic shim extend from or are coupled to portions of the metallic support structure that are bonded to the support surface of the metallic shim. 
     
     
         12 . The seal assembly of  claim 1 , wherein the coating is bonded to at least one of the support surface of the shim and the support structure. 
     
     
         13 . The seal assembly of  claim 1 , further comprising:
 a second porous metallic support structure bonded to the sealing surface of the shim; and   a second ceramic, glass or enamel coating extending over and within the second porous metallic support structure such that the second coating substantially covers the sealing surface side of the metallic shim and the second support structure, and   wherein portions of the second coating are positioned between the sealing surface of the metallic shim and portions of the second metallic support structure.   
     
     
         14 . A method of forming a seal assembly for use within a seal slot formed at least partially by adjacent turbomachinery components to seal a gap extending between the components, the method comprising:
 bonding at least one portion of a porous metallic support structure to a metallic shim;   applying ceramic, glass or enamel coating material to the porous metallic support structure such that the coating material overlies the support surface side of the metallic shim and the support structure, and includes portions that are positioned between the support surface of the metallic shim and portions of the metallic support structure; and   densifying the ceramic, glass or enamel coating material to form a ceramic, glass or enamel coating mechanically fixed to the metallic shim via the metallic support structure.   
     
     
         15 . The method of  claim 14 , wherein bonding at least one portion of the metallic support structure to the support surface of the metallic shim includes diffusion bonding at least one portion of the metallic support structure to the support surface of the metallic shim. 
     
     
         16 . The method of  claim 14 , wherein applying ceramic, glass or enamel coating material to the porous metallic support structure comprises applying a high viscosity castable ceramic composition by screen printing or toweling. 
     
     
         17 . The method of  claim 16 , further comprising removing a portion of the ceramic composition applied to the support structure via a doctor blade, and wherein densifying the ceramic composition comprises curing and heat treating the applied ceramic composition. 
     
     
         18 . The method of  claim 14 , wherein applying ceramic, glass or enamel coating material to the porous metallic support structure comprises applying a glass or enamel based composition in a paintable form by painting, dip coating or spray coating. 
     
     
         19 . The method of  claim 18 , wherein densifying the glass or enamel based composition comprises drying and heat treating the applied glass or enamel based composition. 
     
     
         20 . A turbomachine comprising:
 a first turbine component and a second turbine component adjacent the first turbine component, the first and second turbine components forming at least a portion of a seal slot extending across a gap between the turbine components; and   a seal positioned within the seal slot of the first and second turbine components and extending across the gap therebetween, the seal comprising:
 a metallic shim including a sealing surface and a support surface; 
 a porous metallic support structure bonded to the support surface of the metallic shim; and 
 a ceramic, glass or enamel coating provided on and within the metallic support structure such that the coating substantially covers the support surface side of the metallic shim and the support structure, and portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure. 
   
     
     
         21 . The turbomachine of  claim 20 , wherein the ceramic, glass or enamel coating of the seal is positioned against a first side of the seal slot that is collectively formed by a first side of the first turbine component and a first side of the second turbine component. 
     
     
         22 . The turbomachine of  claim 20 , wherein the metallic shim is a substantially solid metallic shim, and the porous metallic support structure is a metallic mesh structure. 
     
     
         23 . The turbomachine of  claim 20 , wherein portions of the coating are positioned between the support surface of the metallic shim and portions of the metallic support structure in a direction extending substantially normal to the support surface to mechanically couple the coating to the metallic shim via the metallic support structure.