Counter-bored film-cooling holes and related method

Abstract

A turbine component includes a plurality of film-cooling holes formed in a region of the component to be cooled, the cooling holes having specified diameter, each hole at an exit thereof formed with a counter-bore of predetermined depth; the component having a coating applied thereto at least in the region, wherein the counter-bore provides an area for excess coating material to accumulate without reducing the specified diameter. A method of maintaining cooling efficiency of film-cooling holes in a turbine component where the film-cooling holes have specified diameters and the turbine component has a protective coating therein comprising: a) before coating, forming each film-cooling hole with a counter-bore and an exit end of the film-cooling hole; and b) spraying the coating onto the turbine component at least in areas surrounding the film-cooling holes such that excess coating material accumulates in the counter-bore without reducing the specified diameter of the cooling holes.

1 . A turbine component having a plurality of film-cooling holes formed in a region of the component to be cooled, said cooling holes having specified diameter, each hole at an exit thereof formed with a counter-bore of predetermined depth; said component having a coating applied thereto at least in said region, wherein the counter-bore provides an area for excess coating material to accumulate without reducing the specified diameter.  
   
   
       2 . The turbine component of  claim 1  wherein, for a specified diameter of about 0.033 inch, the counter-bore has a diameter of about 0.053 inch.  
   
   
       3 . The turbine component of  claim 2  wherein the counter-bore has a depth of about 0.030 inch.  
   
   
       4 . The turbine component of  claim 2  wherein said coating comprises a first bondcoat layer and a second thermal barrier coating layer.  
   
   
       5 . The turbine component of  claim 4  wherein the bondcoat layer is an NiAl-based material.  
   
   
       6 . The turbine component of  claim 5  wherein the thermal barrier coating layer is a yttria stabilized zirconium material.  
   
   
       7 . The turbine component of  claim 1  wherein the turbine component comprises a gas turbine bucket having an airfoil portion and a shank portion, and wherein said region comprises the airfoil portion.  
   
   
       8 . The turbine component of  claim 7  wherein, for a specified diameter of about 0.033 inch, the counter-bore has a diameter of about 0.053 inch; and wherein the counter-bore has a depth of about 0.030 inch.  
   
   
       9 . The turbine component of  claim 7  wherein said coating comprises a first bondcoat layer and a second thermal barrier coating layer; and wherein the bondcoat layer is an NiAl-based material.  
   
   
       10 . A gas turbine bucket having an airfoil portion and a shank portion, said airfoil portion having a plurality of film-cooling holes therein, each hole at an exit thereof formed with a counter-bore of predetermined depth; said component having a coating applied thereto at least in said region, wherein the counter-bore provides an area for excess coating material to accumulate without reducing the specified diameter; and wherein said coating comprises a first bondcoat layer and a second thermal barrier coating layer.  
   
   
       11 . The gas turbine bucket of  claim 10  wherein the bondcoat layer is an NiAl-based material.  
   
   
       12 . The gas turbine bucket of  claim 11  wherein the thermal barrier coating layer is a yttria-stabilized zirconium layer.  
   
   
       13 . A method of maintaining cooling efficiency of film-cooling holes in a turbine component where the film-cooling holes have specified diameters and the turbine component has a protective coating therein comprising: 
 a) before coating, forming each film-cooling hole with a counter-bore and an exit end of the film-cooling hole; and    b) spraying the coating onto the turbine component at least in areas surrounding the film-cooling holes such that excess coating material accumulates in the counter-bore without reducing the specified diameter of the cooling holes.