Sintered-bonded high temperature coatings for ceramic turbomachine components

Abstract

A coated turbomachine component includes a ceramic component body having a principal surface. The component includes a high temperature coating. The high temperature coating includes a sintered coating body bonded directly to and intimately contacting the principal surface of the ceramic component body. The sintered coating body has a minimum porosity adjacent the principal surface and a maximum porosity at a location further from the principal surface, as taken along an axis orthogonal to the principal surface.

What is claimed is: 
     
         1 . A coated turbomachine component, comprising:
 a ceramic component body having a principal surface; and   a high temperature coating comprising a sintered coating body bonded directly to and intimately contacting the principal surface of the ceramic component body,   wherein the sintered coating body has a minimum porosity adjacent the principal surface and a maximum porosity at a location further from the principal surface, as taken along an axis orthogonal to the principal surface.   
     
     
         2 . The coated turbomachine component of  claim 1  wherein the minimum porosity is less than 10% by volume, while the maximum porosity is between 20% and 40% by volume. 
     
     
         3 . The coated turbomachine component of  claim 1  wherein the sintered coating body comprises:
 about 80% to 100% of at least one rare earth silicate by weight; and 
 0% to about 20% of at least one glass sintering aid by weight. 
 
     
     
         4 . The coated turbomachine component of  claim 1  wherein the principal surface of the ceramic component body is substantially free of oxide contaminants and has an average surface roughness exceeding 0.1 microns. 
     
     
         5 . The coated turbomachine component of  claim 1  wherein the ceramic component body comprises a turbine shroud body, which is composed of a silicon-ceramic material and which has an inner peripheral surface over which the high temperature coating is formed. 
     
     
         6 . The coated turbomachine component of  claim 1  wherein the sintered coating body is composed of a plurality of coating layers, with a base layer bonded directly to the principal surface, at least one intermediate coating layer formed on the base layer and an outermost coating layer formed on the at least one intermediate coating layer. 
     
     
         7 . The coated turbomachine component of  claim 6  wherein the base layer has the minimum porosity, which is less than a porosity of the at least one intermediate coating layer. 
     
     
         8 . The coated turbomachine component of  claim 6  wherein the outermost coating layer has a porosity that is less than a porosity of the at least one intermediate coating layer. 
     
     
         9 . The coated turbomachine component of  claim 6  wherein a topcoat is formed over the outmost coating layer, and topcoat has a porosity that is less than a porosity of the outermost coating layer. 
     
     
         10 . The coated turbomachine component of  claim 6  wherein the at least one intermediate coating layer has the maximum porosity. 
     
     
         11 . A coated turbomachine component, comprising:
 a ceramic component body having a principal surface; and   a high temperature coating comprising a sintered coating body bonded directly to and intimately contacting the principal surface of the ceramic component body, the sintered coating body composed of a plurality of coating layers, with a base layer bonded directly to the principal surface, at least one intermediate coating layer formed on the base layer and an outermost coating layer formed on the at least one intermediate coating layer,   wherein the base layer has a minimum porosity, and the sintered coating body has a maximum porosity at a location further from the principal surface, as taken along an axis orthogonal to the principal surface.   
     
     
         12 . The coated turbomachine component of  claim 11  wherein the outermost coating layer has a porosity that is less than a porosity of the at least one intermediate coating layer. 
     
     
         13 . The coated turbomachine component of  claim 11  wherein a topcoat is formed over the outmost coating layer, and the topcoat has a porosity that is less than a porosity of the outermost coating layer. 
     
     
         14 . The coated turbomachine component of  claim 11  wherein the at least one intermediate coating layer has the maximum porosity. 
     
     
         15 . The coated turbomachine component of  claim 11  wherein the minimum porosity is less than 10% by volume, while the maximum porosity is between 20% and 40% by volume. 
     
     
         16 . The coated turbomachine component of  claim 11  wherein the sintered coating body comprises:
 about 80% to 100% of at least one rare earth silicate by weight; and 
 0% to about 20% of at least one glass sintering aid by weight. 
 
     
     
         17 . The coated turbomachine component of  claim 11  wherein the principal surface of the ceramic component body is substantially free of oxide contaminants and has an average surface roughness exceeding 0.1 microns. 
     
     
         18 . The coated turbomachine component of  claim 11  wherein the ceramic component body comprises a turbine shroud body, which is composed of a silicon-ceramic material and which has an inner peripheral surface over which the high temperature coating is formed.