Process for repairing sulfidation damaged turbine components
View Patent ↗A process is provided for cleaning a surface of an internal cavity of a gas turbine component having sulfidation or sulfur bearing deposits comprising: inserting into the internal cavity a fluoride salt; and heating the fluoride salt and the component in an inert atmosphere for a time and at a temperature to clean the sulfidation or sulfur bearing deposits on the surface. In a preferred embodiment the cleaned internal surface is then coated with a metallic coating.
1. A process for cleaning a surface of an internal cavity of a gas turbine component having sulfidation or sulfur bearing deposits comprising:
inserting into the internal cavity a fluoride salt in solid form; and
heating the fluoride salt and the component in an inert atmosphere for a time and at a temperature effective to remove the sulfidation or sulfur bearing deposits on the surface.
2. A process of claim 1 wherein the fluoride salt is selected from the group consisting of alkali fluoride salt, alkali earth fluoride salt and metal fluoride salt.
3. A process of claim 1 wherein the gas turbine component is a low pressure turbine component.
4. A process of claim 1 wherein the sulfur bearing deposits contain an alumina silicate.
5. A process of claim 1 wherein the inert atmosphere is an argon atmosphere.
6. A process of claim 2 wherein the fluoride salt is in the form of a powder.
7. A process of claim 2 wherein the fluoride salt and component are heated to a temperature from about 1100 to 1500° F. for about ¼ to 4 hours to remove the sulfidation or sulfur bearing deposits.
8. A process of claim 4 wherein the component is a high pressure turbine blade.
9. A process of claim 6 wherein the fluoride salt is selected from the group consisting of ammonium bifluoride, potassium fluoride, aluminum fluoride, sodium fluoride and ammonium fluoride.
10. A process of claim 9 wherein the fluoride salt is ammonium bifluoride.
11. A process of claim 10 wherein the cleaning process chemically removes substantially all of the sulfidation or sulfur bearing deposits.
12. A process for repairing a surface of an internal cavity of a gas turbine component having sulfidation or sulfur bearing deposits comprising:
inserting into the internal cavity a fluoride salt in solid form;
heating the fluoride salt and the component in an inert atmosphere for a time and at a temperature effective to remove the sulfidation or sulfur bearing deposits on the surface; and
coating the cleaned surface with a metallic coating.
13. A process of claim 12 wherein the metal coating is applied to the surface by inserting a metal coating powder containing an activator into the cleaned internal cavity; and
heating the coating powder and the component for a time and at a temperature to coat the surface with the metal coating; and
removing any residual of the coating powder from the internal cavity.
14. A process of claim 12 wherein the fluoride salt is selected from the group consisting of alkali fluoride salt, alkali earth fluoride salt and metal fluoride salt.
15. A process of claim 12 wherein the metal coating is a chromide coating.
16. A process of claim 12 wherein the gas turbine component is a high pressure turbine component.
17. A process of claim 13 wherein the cleaning process chemically removes substantially all of the sulfidation or sulfur bearing deposits.
18. A process of claim 13 wherein the metal coating is applied by inserting into the internal cavity a coating mixture which comprises from about 10 to 30 wt % of a metal powder, about 70 to 90 wt % of an inert filler powder and about 1 to 2 wt % of a halide activator.
19. A process of claim 14 wherein the fluoride salt is in the form of a powder.
20. A process of claim 14 wherein the fluoride salt and component are heated to a temperature from about 1100 to 1500° F. for about ¼ to 4 hours to remove the sulfidation or sulfur bearing deposits.
21. A process of claim 18 wherein the metal powder is a chromium powder and the inert filler powder is alumina.
22. A process of claim 18 wherein the coating mixture and component are heated at a temperature of about 1850 to 2000° F. for 2 to 15 hours to coat the surface of the internal cavity.
23. A process of claim 19 wherein the fluoride salt selected from the group consisting of ammonium bifluoride, potassium fluoride, aluminum fluoride, sodium fluoride and ammonium fluoride.
24. A process of claim 21 wherein the halide activator is ammonium chloride or ammonium bifluoride.
25. A process of claim 21 wherein the gas turbine component is a low pressure turbine component.
26. A process of claim 23 wherein the fluoride salt is ammonium bifluoride.