METHOD OF RESTORING NEAR-WALL COOLED TURBINE COMPONENTS

1 . A method for restoring a coated component, which has been exposed to engine operation, comprising:

providing an engine run component including a base metal substrate made of a nickel-based alloy having superficial outer cooling channels partly defined by an outer wall comprising outer wall layers of a thermal barrier coating system, the thermal barrier coating system comprising a diffusion bond coat on the base metal substrate and a top ceramic thermal barrier coating;

injecting a polymeric preform material effective to fill the outer cooling channels;

removing the outer wall layers of the component, exposing in part the preform material filling the outer cooling channels;

applying a new bond coat to the component in one or more layers, wherein the new bond coat covers at least part of the exposed preform material without deforming it;

applying a new thermal barrier coating over the new bond coat; and

removing the preform material without destroying the new bond coat and the new thermal barrier coating.

2 . The method of claim 1 additionally comprising plugging a venting passage in the engine run component with a venting passage material prior to removing the outer wall layers, and removing the venting passage material when removing the preform material.

3 . The method of claim 2 additionally comprising pre-cooling the component prior to applying the at least one of the new bond coat and the new thermal barrier coating.

4 . The method of claim 1 wherein the preform material in the cooling channels retains the shape(s) of tubulators so as to provide cooling channel contours providing a desired flow pattern.

5 . The method of claim 1 , wherein the preform material provides a desired degree of roughness in an interior surface of at least one of the outer channels, effective to provide a non-laminar flow of fluids there through.

6 . The method of claim 1 wherein the applying comprises a high velocity oxy-fuel spraying process.

7 . The method of claim 6 , additionally comprising selecting a preform material having a melting temperature of at least 300° C., effective to withstand the applying.

8 . The method of claim 1 , additionally comprising cooling the component while applying at least one of the new bond coat and the new thermal barrier coating.

9 . The method of claim 8 , wherein the cooling is provided from one or more air jets disposed on a spray gun used for applying the new bond coat.

10 . The method of claim 8 , wherein the cooling is provided from at least one cooling flow source disposed to direct a cooling flow across a surface of the component being coated during said applying.

11 . A method for restoring a near-wall cooled component which has been exposed to engine operation, comprising the steps:

providing an engine run near-wall cooled component comprising a metal substrate having an internal cooling system including superficial cooling channels partly defined by an outer wall comprising outer wall layers applied over the substrate;

filling the internal cooling system with a preform material effective to fill the superficial cooling channels;

removing the outer wall layers of the component, exposing in part the preform material filling the superficial cooling channels and a surface of the substrate;

applying at least one new outer layer to form a new outer wall; and

removing the preform material without destroying the new outer wall.

12 . The method of claim 11 , additionally comprising plugging a venting passage in the engine run near-wall cooled component with a venting passage material prior to removing the outer wall layers, and removing the venting passage material when removing the preform material.

13 . The method of claim 11 additionally comprising pre-cooling the component prior to applying the at least one outer layer.

14 . The method of claim 11 wherein the preform material in the superficial cooling channels retains the shape(s) of tubulators or trip-strips so as to provide cooling channel contours providing a desired flow pattern.

15 . The method of claim 11 , wherein the preform material provides a desired degree of roughness in an interior surface of at least one of the superficial channels, effective to provide a non-laminar flow of fluids there through.

16 . The method of claim 11 , wherein the applying comprises a high velocity oxy-fuel spraying process.

17 . The method of claim 11 , additionally comprising cooling the component while applying the at least one new outer layer to form the new outer wall.

18 . The method of claim 11 , wherein the cooling is provided from one or more air jets disposed on a spray gun used for applying the at least one new outer layer.

19 . The method of claim 11 , wherein the cooling is provided from at least one cooling flow source disposed to direct a cooling flow across a surface of the component being coated during said applying.

20 . A method for restoring a near-wall cooled component of a gas turbine engine, which has been exposed to engine operation, comprising:

filling cooling channels of the component with a polymeric preform material;

removing existing outer wall layers of the component, exposing in part the preform material;

applying new outer wail layers over the component; and

removing the preform material without destroying the new outer wall layers.