Upgrading aluminide coating on used turbine engine component

Inactive Publication Date: 2005-02-17
GEN ELECTRIC AVIATION SERVICE OPERATION PTE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The operating environment within a gas turbine engine is both thermally and chemically hostile.
Significant advances in high temperature alloys have been achieved through the formulation of iron, nickel and cobalt-base superalloys, though components formed from such alloys often cannot withstand long service exposures if located in certain sections of a gas turbine engine, such as the turbine, combustor and augmentor.
In the latter situation, hot corrosion typically occurs on hot section turbine blades and vanes under conditions where salt deposits on the surface as a solid or liquid.
The salt deposits can break down the protective alumina scale on the aluminide coating, resulting in rapid attack of the coating.
A disadvantage

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example

EXAMPLE 1

[0055] Two high-pressure turbine blades, originally coated with CODEP aluminide coating and returned from service, are cleaned to remove hot corrosion products by immersing in an aqueous solution comprising about 4-8% acetic acid for about 2 hours. The solution has a temperature of about 150-175° F. (about 66-77° C.) and is agitated using ultrasonic energy. A layer of platinum is then deposited on the blades using an electroplating process, as described above. The thickness of the new platinum layer deposited on top of the existing CODEP coating is about 0.0002-0.0004 inches (about 5-10 microns).

[0056] The platinum-plated blades are then heat treated at 1900-1950° F. (about 1038° C.-1066° C.) for 35 minutes in a vacuum furnace so that the platinum interdiffuses with the base material. A second aluminide coating is then formed on the blades by a pack cementation process at 1900° F. (about 1038° C.) for 2 hours using titanium-aluminide donor as the aluminum source. The thic...

Example

EXAMPLE 2

[0058] Two blades are processed as described in Example 1 except that the aluminiding process is an over-the-pack process using chromium-aluminum donor at 1975° F. (about 1079° C.) for 6 hours (VPA process). Blades coated by this method also have oxidation resistance equivalent to that of blades stripped of their original aluminide coatings and then coated by a conventional platinum aluminide process.

Example

EXAMPLE 3

[0059] Two blades are cleaned, platinum-plated and aluminided as described in Example 1, except that the diffusion vacuum heat treatment step is not performed. Two additional blades are cleaned, platinum-plated and aluminided as described in Example 2, except that the diffusion vacuum heat treatment step is not performed.

[0060] Sample blades coated by these methods are oxidized in static air at 2050° F. (about 1121° C.) for 47 hours. The blades have oxidation resistance equivalent to that of blades stripped of their aluminide coatings and recoated by conventional platinum aluminide processes.

[0061] Various embodiments of this invention have been described. However, this disclosure should not be deemed to be a limitation on the scope of the invention. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the claimed invention.

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Abstract

A method of upgrading an aluminide coating on a used turbine engine component to a platinum aluminide coating. The method involves cleaning at least one surface of the component to remove hot corrosion products from the surface without damaging the aluminide coating. In one embodiment, the cleaning step involves immersing the component in a heated solution comprising acetic acid while agitating the solution using ultrasonic energy. A layer of platinum is then deposited onto the cleaned surface of the component. A second aluminide coating is then formed on the surface of the component to upgrade the component. The invention also relates to a turbine engine component, e.g., a turbine blade, having a metal-based substrate and a platinum aluminide coating on at least one surface thereof, which coating has been upgraded from an aluminide coating originally on the component using the above method.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to a method for upgrading an aluminide coating on a used turbine engine component to a platinum aluminide coating. More particularly, this invention is directed to such a method that comprises cleaning at least one surface of the component to remove hot corrosion products from the surface without damaging the aluminide coating, depositing a layer of platinum onto the cleaned surface, and then forming a second aluminide coating on the surface of the component. The invention also relates to such an upgraded used turbine engine component. [0002] The operating environment within a gas turbine engine is both thermally and chemically hostile. Significant advances in high temperature alloys have been achieved through the formulation of iron, nickel and cobalt-base superalloys, though components formed from such alloys often cannot withstand long service exposures if located in certain sections of a gas turbine engine, such as the tu...

Claims

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Application Information

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IPC IPC(8): F01D25/00C23C4/00C23C4/02C23C28/00C23G1/02C23G1/14C23G1/28C25D5/34F01D5/28F02C7/00
CPCC23C4/00C23C4/02C23C28/021C23G1/02C23G1/14C23G1/28F05D2300/611F01D5/288Y02T50/672F05D2230/30F05D2230/80F05D2230/90F05D2300/143C25D5/34Y02T50/60
Inventor CHEN, KENG NAMNGIAM, SHIH-TUNG
Owner GEN ELECTRIC AVIATION SERVICE OPERATION PTE
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