Metallic coating for non-line of sight areas

Abstract

A disclosed process for coating a turbine vane includes the steps of applying a coating to line of sight surfaces with a thermal spraying process and applying a slurry coating to non-line of sight surfaces to provide oxidative protection and desired thermal protection. Moreover, the applied coating on both the line of sight and non-line of sight surfaces provides a bond layer for the application of a ceramic coating.

1 . A process of coating a component comprising the steps of:
 applying a spray coating to at least one first surface of a component reachable by a thermal spraying process;   applying a slurry coating to at least one second surface of the component, wherein the second surface is not reachable by the spray coating process utilized to coat the first surface; and   heat-treating the component to release undesired portions of the slurry from the component.   
     
     
         2 . The process as recited in  claim 1 , including the step of diffusing the applied spray coating and the slurry coating into the first and second surface of the component. 
     
     
         3 . The process as recited in  claim 2 , wherein the spray coating on the at least one first surface and the slurry coating on the at least one second surface comprise a metallic coating that provides oxidative resistance and creates a bonding layer onto which a subsequently applied ceramic coating bonds. 
     
     
         4 . The process as recited in  claim 3 , including the step of applying a ceramic coating to the component after diffusion of the spray coating and the slurry coating. 
     
     
         5 . The process as recited in  claim 1 , wherein the application of the spray coating comprises a thermal spraying operation. 
     
     
         6 . The process as recited in  claim 1 , wherein the slurry coating comprises a suspension including one of nickel based alloy particles and MCrAlY based alloy particles. 
     
     
         7 . The process as recited in  claim 6 , wherein the one of the nickel based alloy particles and the MCrAlY based alloy particles are smaller than 25 microns and are suspended in an organic binder. 
     
     
         8 . The process as recited in  claim 1 , wherein the component comprises a turbine vane assembly. 
     
     
         9 . The process as recited in  claim 1 , including the step of mechanically treating at least one surface of the component. 
     
     
         10 . A process of surface treating a turbine vane comprising the steps of:
 applying a metallic coating with thermal spraying process to surfaces of the turbine vane accessible by the thermal spraying process;   preparing a slurry coating including metallic particles suspended in an organic binder;   applying the slurry coating to at least some of the surfaces of the component that are not accessible by the thermal spraying process; and   heat-treating the component to diffusion bond the metallic particles to the component.   
     
     
         11 . The process as recited in  claim 10 , wherein the step of preparing a slurry coating comprise preparing a oxidation resistant composition capable of bonding with a subsequently applied ceramic coating. 
     
     
         12 . The process as recited in  claim 11 , wherein the slurry coating comprises a material that produces a thermally grown oxide that provides for bonding to the subsequently applied ceramic coating. 
     
     
         13 . The process as recited in  claim 10 , including the step of applying a ceramic coating to the turbine vane to the surfaces coated with the metallic coating and the slurry coating on both the surfaces accessible from an exterior of the turbine vane and the surfaces not accessible from the exterior of the turbine vane after heat-treating. 
     
     
         14 . The process as recited in  claim 10 , wherein the heat-treating step includes diffusing the slurry coating and the metallic coating applied with the thermal spraying process onto the surface of the turbine vane. 
     
     
         15 . The process as recited in  claim 13 , wherein the metallic coating applied with the thermal spraying process and the coating applied with the slurry coating form a bond layer to which the ceramic coating bonds. 
     
     
         16 . The process as recited in  claim 10 , wherein the thermal spraying process includes the step of propelling coating material heated with a plasma torch onto the surface of the turbine vane. 
     
     
         17 . The process as recited in  claim 10 , wherein the turbine vane includes at least one airfoil and at least one surface on which a coating cannot be applied using the thermal spraying process, and coating the at least one surface on which a coating cannot be applied using the thermal spraying process with the slurry coating. 
     
     
         18 . The process as recited in  claim 10 , wherein the step of preparing a slurry coating comprises preparing a suspension of nickel based alloy particles within the organic binder. 
     
     
         19 . The process as recited in  claim 18 , wherein the step of preparing the slurry comprises suspending nickel based alloy particles no larger than 25 microns in the organic binder. 
     
     
         20 . The process as recited in  claim 10 , wherein the heat-treating of the turbine vane comprises removing the organic binder from the turbine vane.