Corrosion coating for turbine blade environmental protection

Abstract

The present invention is a gas turbine engine turbine blade comprising an airfoil section having at least an exterior surface, a platform section having an exterior surface, an under platform section having an exterior surface, and a dovetail section having an exterior surface, the exterior surface of the dovetail section comprising a shank exterior surface and a serrated exterior surface. The blade further comprises a silicon-modified diffusion aluminide layer a surface of a turbine blade section selected from the group consisting of the exterior surface of the under platform section, the exterior surface of the dovetail section, and combinations thereof, the silicon modified diffusion aluminide layer having a concentration of silicon at a surface of the silicon-modified diffusion aluminide layer in the range of about 1 weight percent to about 10 weight percent and a concentration of aluminum at the surface of the silicon modified diffusion aluminide layer in the range of about 5 weight percent to about 25 weight percent. The present invention is also a method for making such a gas turbine engine blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow chart illustrating the application of the corrosion resistant coating of the present invention.

FIG. 2 is perspective view of an embodiment of a turbine blade coated with the corrosion resistant coating of the present invention.

FIG. 3 is a schematic view of a corrosion resistant coating of the present invention deposited on a substrate.

Claims

1. A method for coating a portion of a gas turbine engine blade, the method comprising the steps of: providing a gas turbine blade comprising a superalloy selected form the group consisting of nickel-base superalloys, cobalt-base superalloys, iron-base superalloys, and combinations thereof, the blade further comprising: an airfoil section having at least an exterior surface;a platform section having an exterior surface;an under platform section having an exterior surface; anda dovetail section having an exterior surface, the exterior surface of the dovetail section comprising a shank exterior surface and a serrated exterior surface;applying a layer of silicon-modified aluminum composition to a preselected exterior surface selected from the group consisting of the under platform exterior surface, the dovetail shank exterior surface, and combinations thereof, the silicon-modified aluminum composition comprising a silicon and aluminum particulate component and an additional component selected from the group consisting of a fugitive binder component, a liquid carrier component, at least one chromium-containing salt component, and combinations thereof, the silicon and aluminum particulate component comprising:from about 10 weight percent to about 20 weight percent silicon and balance aluminum;heating the gas turbine blade to a preselected temperature in the range of about 600° C. to about 800° C. in a an environment selected from the group consisting of a vacuum and a protective atmosphere;holding the temperature of the gas turbine blade at the preselected temperature for a preselected length of time in the range of about 0.5 hours to about 4 hours to diffuse the aluminum and silicon particulates into the preselected exterior surface to form a silicon-enriched diffusion aluminide coating;cooling the gas turbine blade; andcleaning the gas turbine blade.

2. The method of claim 1, wherein the superalloy is a nickel-base superalloy.

3. The method of claim 2, wherein the nickel-base superalloy comprises less than about 12 weight percent chromium.

4. The method of claim 1, wherein the thickness of the coating is in the range of about 0.1 mils to about 5 mils.

5. The method of claim 5, wherein the thickness of the coating is in the range of about 0.5 mils to about 4 mils.

6. The method of claim 1, wherein the additional component is at least the chromium-containing salt component, wherein the at least one chromium-containing salt comprises up to about 10 weight percent of the silicon-modified composition.

7. The method of claim 1, wherein the gas turbine blade is selected from the group consisting of a new make blade, repaired used blade, an upgraded used blade, and a restored used blade.

8. The method of claim 1, further comprising masking a preselected portion of the gas turbine blade, leaving the preselected exterior surface unmasked.

9. The method of claim 8, further comprising roughening the non-masked surface after the step of masking and prior to the step of applying the layer of silicon-modified aluminum composition.

10. The method of claim 1, wherein the silicon-modified aluminum composition comprises about 35 weight percent aluminum particulates; about 6 weight percent silicon particulates; about 12 weight percent binder salts, and balance water.

11. The method of claim 8, further comprising the step of removing the masking after the step of applying the layer of silicon-modified aluminum composition and prior to the step of heating.

12. The method of claim 1, further comprising the step of heating the gas turbine blade at second preselected temperature in the range of about 700° C. to about 900° C. for a second preselected length of time in the range of about 1 hour to about 4 hours to further diffuse the aluminum into the preselected exterior surface after the step of holding.

13. The method of claim 2, wherein the thickness of the coating is in the range of about 0.5 mils to about 4 mils.

14. A method for coating a portion of a gas turbine engine blade, the method comprising the steps of: providing a gas turbine blade comprising a nickel-base superalloy, the blade further comprising: an airfoil section having at least an exterior surface;a platform section having an exterior surface;an under platform section having an exterior surface; anda dovetail section having an exterior surface, the exterior surface of the dovetail section comprising a shank exterior surface and a serrated exterior surface;applying a layer of silicon-modified aluminum composition to a preselected exterior surface selected from the group consisting of the under platform exterior surface, the dovetail shank exterior surface, and combinations thereof, the silicon-modified aluminum composition comprising: about 35 weight percent aluminum particulates;about 6 weight percent silicon particulates;about 12 weight percent binder salts; andbalance water;heating the gas turbine blade to a preselected temperature in the range of about 600° C. to about 800° C. in a an environment selected from the group consisting of a vacuum and a protective atmosphere;holding the temperature of the gas turbine blade at the preselected temperature for a preselected length of time in the range of about 0.5 hours to about 4 hours to diffuse the aluminum and silicon particulates into the preselected exterior surface to form a silicon-enriched diffusion aluminide coating, wherein the silicon-enriched diffusion aluminide coating has a thickness in the range of about 0.5 mils to about 4 mils;cooling the gas turbine blade; andcleaning the gas turbine blade.

15. The method of claim 14, wherein the gas turbine engine blade is a new make blade.

16. The method of claim 14, wherein the gas turbine blade is selected from the group consisting of a repaired used blade, an upgraded used blade, and a restored used blade.

17. A gas turbine engine turbine blade comprising: A superalloy selected from the group consisting of nickel-base superalloys, iron-base superalloys, and cobalt-base superalloys, and combinations thereof;an airfoil section having at least an exterior surface;a platform section having an exterior surface;an under platform section having an exterior surface; anda dovetail section having an exterior surface, the exterior surface of the dovetail section comprising a shank exterior surface and a serrated exterior surface; anda silicon-modified diffusion aluminide layer a surface of a turbine blade section selected from the group consisting of the exterior surface of the under platform section, the exterior surface of the dovetail section, and combinations thereof, the silicon modified diffusion aluminide layer having a concentration of silicon at a surface of the silicon-modified diffusion aluminide layer in the range of about 1 weight percent to about 10 weight percent and a concentration of aluminum at the surface of the silicon modified diffusion aluminide layer in the range of about 5 weight percent to about 25 weight percent.

18. The gas turbine engine blade of claim 17, wherein the blade is a new make blade.

19. The gas turbine engine blade of claim 17, wherein the blade is selected from the group consisting of a repaired used blade, an upgraded used blade, and a restored used blade.

20. The gas turbine engine blade of claim 17, wherein the blade comprises a nickel-base superalloy.