Method and device to prevent coating a dovetail of a turbine airfoil

Abstract

A method and masking assembly for masking a dovetail portion of a turbine blade during coating of an airfoil portion of the blade. The masking assembly comprises at least two masking members, each having an exterior surface and an oppositely-disposed undulatory surface complementary to one of oppositely-disposed undulatory surfaces of the dovetail portion. By mating the masking members, the undulatory surfaces thereof define an interior cavity within the masking assembly that accommodates the dovetail portion, and the undulatory surfaces of the masking members contact the undulatory surfaces of the dovetail portion to entrap the dovetail portion within the interior cavity of the masking assembly.

1 . A masking assembly for masking a dovetail portion of a turbine blade during coating of an airfoil portion of the blade, the masking assembly comprising at least two masking members, each masking member having an exterior surface and an oppositely-disposed undulatory surface complementary to one of oppositely-disposed undulatory surfaces of the dovetail portion whereby placing the dovetail portion in the masking assembly by mating the masking members causes the undulatory surfaces thereof to define an interior cavity within the masking assembly that accommodates at least part of the dovetail portion and the undulatory surfaces of the masking members contact the undulatory surfaces of the dovetail portion to entrap the dovetail portion within the interior cavity of the masking assembly. 
   
   
       2 . The masking assembly according to  claim 1 , wherein the masking members are substantially identical. 
   
   
       3 . The masking assembly according to  claim 1 , further comprising a retaining ring securing the masking members together. 
   
   
       4 . The masking assembly according to  claim 1 , wherein the masking members are formed of a material chosen from the group consisting of metallic and ceramic materials. 
   
   
       5 . The masking assembly according to  claim 1 , wherein the masking members are formed of a nickel-base superalloy. 
   
   
       6 . The masking assembly according to  claim 1 , wherein the dovetail portion is within the interior cavity of the masking assembly and secured therein by the undulatory surfaces of the masking members. 
   
   
       7 . The masking assembly according to  claim 6 , further comprising a sealant at interfaces defined by and between the masking members and by and between the dovetail portion and the masking members to prevent a coating vapor from entering the interior cavity of the masking assembly. 
   
   
       8 . The masking assembly according to  claim 7 , wherein the sealant is a masking tape, putty, or slurry. 
   
   
       9 . The masking assembly according to  claim 6 , wherein the blade further comprises a platform between the airfoil and dovetail portions, and airfoil and the platform are outside the masking assembly to enable coating of the airfoil and the platform in their entireties. 
   
   
       10 . The masking assembly according to  claim 6 , wherein the blade further comprises an internal cooling passage and the masking assembly has a passage therein through which a coating vapor can enter the internal cooling passage.