# US 5,702,288 A · Method of removing excess overlay coating from within cooling holes of aluminide coated gas turbine engine components

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- Number: US 5,702,288 A
- Document ID: US5702288A
- Status: Granted
- Kind: A
- Application number: 08/521,199
- Filed: 1995-08-30
- Granted: 1997-12-30
- Earliest claimed: 1995-08-30
- Assignees: United Technologies Corporation
- Inventors: William R. Liebke; David R. Dawson; Mark A. Fredette; Mark B. Goodstein
- Web page: https://patentgrep.com/patent/US5702288A

## CPC

- B24B 31/116: using plastically deformable grinding compound, moved relatively to the workpiece under the influence of pressure
- B23P 2700/06: Cooling passages of turbine components, e.g. unblocking or preventing blocking of cooling passages of turbine components
- B24B: MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING (grinding of gear teeth B23F, of screw-threads B23G1/36; by electro-erosion B23H; abrasive or related blasting B24C; tools for grinding, buffing or sharpening B24D; polishing compositions C09G1/00; abrasives C09K3/14; electrolytic etching or polishing C25F3/00; grinding arrangements for use on assembled railway tracks E01B31/17); DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B23P: METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS (arrangements for copying or controlling B23Q)

## Abstract

A method of removing excess MCrAlY overlay coating from within a cooling hole of an aluminide coated gas turbine engine component is disclosed. The method includes providing a gas turbine engine component having an internal surface (4), an outer surface (6) and a root end (8). The component also includes at least one cooling hole (10) extending from the internal surface (4) to the outer surface (6), wherein the internal surface(4) of the component is coated with a corrosion resistant aluminide coating. An MCrAlY overlay coating (12) is also located on the outer surface (6) and inside a portion of the cooling hole (10). An abrasive slurry is forced into the gas turbine engine component from the outside of the component to the inside of the component, through the cooling hole (10), such that the slurry flows through the internal surface (4) of the component and removes at least a portion of the overlay coating (12) located inside the cooling hole (10) without adversely affecting the internal surface (4) of the component. The abrasive slurry subsequently exits the component through the root end (8).

## Claims

### Claim 1

A gas turbine engine component repaired by providing a gas turbine engine component having an internal surface, an outer surface and a root end, the component also having at least one cooling hole extending from the internal surface to the outer surface, wherein the internal surface of the component is coated with an aluminide coating, the component further including a MCrAlY overlay coating on the outer surface and inside a portion of the cooling hole; and
forcing an abrasive slurry of semi-solid plastic flowable material comprising abrasive grits into the gas turbine engine component from the outer surface of the component to the internal surface of the component, through the cooling hole, wherein the slurry flows through the cooling hole and removes at least a portion of the overlay coating located inside the cooling hole without adversely affecting the aluminide coating on the internal surface of the component such that airflow through the component is within +/-12.5 percent of a target nominal airflow level, the slurry subsequently, exiting the repaired component through the root end.

### Claim 2

A method of repairing a gas turbine engine component by removing excess MCrAIY overlay coating from within a cooling hole of an aluminide coated gas turbine engine component comprising the steps of:
providing a gas turbine engine component having an internal surface, an outer surface and a root end, the component also having a plurality of cooling holes extending from the internal surface to the outer surface, wherein the internal surface of the component is coated with an aluminide coating, the component further including a MCrAlY overlay coating on the outer surface and inside a portion of the cooling holes;
masking a portion of the cooling holes to prevent flow there through;
inserting the component into an abrasive flow machining device; and
forcing an abrasive slurry into the gas turbine engine component from the outer surface of the component to the internal surface of the component, through the cooling holes, wherein the slurry flows through the cooling holes and removes at least a portion of the overlay coating located inside the cooling holes without adversely affecting the aluminide coating on the internal surface of the component, such that airflow through the component is within design limits, +/-12.5 percent of a target nominal airflow level, the slurry subsequently exiting the repaired component through the root end.

### Claim 3 (depends on 2)

The method of claim 2 wherein the masking step includes applying an ultraviolet curable polymer over the cooling holes.