Aluminizing composition and method for application within internal passages

1. An aluminizing composition comprising

an aluminum-based powder;

a binder selected from the group consisting of colloidal silica, at least one organic resin, and combinations thereof; and

an inert organic pyrolysable solid particulate thickener.

2. The composition of claim 1 wherein a structure of the pyrolysable thickener is selected from the group consisting of beads, yarns, strings, fibers, and combinations thereof.

3. The composition of claim 2 wherein the pyrolysable thickener comprises acrylic.

4. The composition of claim 1 wherein the pyrolysable thickener comprises polymeric microbeads.

5. The composition of claim 1 wherein the pyrolysable thickener comprises poly(methyl methacrylate) beads.

6. The composition of claim 1 wherein the aluminum-based powder has an average particle size in the range of about 0.5 micron to about 200 microns.

7. The composition of claim 1 wherein the aluminum-based powder comprises an alloy of aluminum and silicon.

8. The composition of claim 7 wherein the silicon is present in an amount sufficient to decrease the melting point of the aluminum-silicon alloy to below about 610° C.

9. The composition of claim 7 wherein the silicon is present at a level in the range of about 1% by weight to about 20% by weight, based on the combined weight of the silicon and aluminum.

10. The composition of claim 9 silicon is present at a level in the range of about 10% by weight to about 15% by weight, based on the combined weight of the silicon and aluminum.

11. The composition of claim 7 wherein the aluminum-silicon alloy comprises substantially spherical powder particles.

12. The composition of claim 1 further comprising a liquid carrier selected from the group consisting of water, alcohols, halogenated hydrocarbon solvents, and compatible mixtures thereof.

13. The composition of claim 12 further comprising at least one additive selected from the group consisting of pigments, diluents, curing agents, dispersants, deflocculants, anti-settling agents, anti-foaming agents, binders, plasticizers, emollients, surfactants, driers, extenders, and lubricants.

14. The composition of claim 1 wherein the composition is substantially free of hexavalent chromium.

15. The composition of claim 1 , wherein the composition comprises less than about 10% by weight of phosphoric acid and phosphoric acid derivatives, based on the weight of the entire composition.

16. An aqueous-based slurry coating composition according to claim 1 .

17. The composition of claim 1 wherein the aluminum-based powder further comprises at least one metal selected from the group consisting of platinum group metals, rare earth metals, scandium, yttrium, iron, chromium, and cobalt.

18. The composition of claim 1 further comprising aluminum flakes.

19. The composition of claim 1 wherein the binder comprises colloidal silica.

20. The composition of claim 19 wherein the binder comprises colloidal silica present at a level in the range of about 5% by weight to about 20% by weight, based on silica solids as a percentage of the entire composition.

21. The composition of claim 19 wherein the silica in the colloidal silica has an average particle size in the range of about 10 nanometers to about 100 nanometers.

22. The composition of claim 19 further comprising at least one organic stabilizer which includes at least two hydroxyl groups.

23. The composition of claim 22 wherein the organic stabilizer includes at least three hydroxyl groups.

24. The composition of claim 22 wherein the organic stabilizer is selected from the group consisting of alkane diols, glycerol, pentaerythritol, fats, and carbohydrates.

25. The composition of claim 24 wherein the carbohydrate is a sugar compound.

26. The composition of claim 22 wherein the organic stabilizer is present in an amount sufficient to chemically stabilize the aluminum-based powder during contact with any aqueous component present in the composition.

27. The composition of claim 22 wherein the organic stabilizer is present at a level in the range of about 0.1% by weight to about 20% by weight, based on the total weight of the composition.

28. The composition of claim 1 wherein the binder comprises at least one organic resin.

29. The composition of claim 28 further comprising at least one organic solvent.

30. The composition of claim 29 wherein the organic solvent is selected from the group consisting of alcohols, glycols, ketones, aldehydes, aromatic compounds, dimethylformamide, mineral spirits, naphtha, nitrated hydrocarbons, chlorinated hydrocarbons, and combinations thereof.

31. The composition of claim 28 wherein the organic resin is selected from the group consisting of epoxy resins, silicone resins, alkyd resins, acrylic resins, polyurethane resins, polyvinyl chloride resins, phenolic resins, polyester resins, urethane resins, polyamide resins, polyolefin resins, and combinations thereof.

32. The composition of claim 31 wherein the organic resin comprises a reaction product of phthalic anhydride and glycerol.

33. The composition of claim 28 wherein the organic resin comprises bisphenol A.

34. The composition of claim 28 wherein the organic resin comprises a modified or unmodified silicone varnish.

35. The composition of claim 28 wherein the organic resin comprises at least one organopolysiloxane.

36. The composition of claim 28 wherein the organic resin comprises a silicone alkyd, a silicone epoxy, or a silicone polyester.

37. A slurry coating composition for providing aluminum to an internal passage of a turbine component formed from a material comprising a nickel-based superalloy, wherein the composition is substantially free of hexavalent chromium, and comprises a binder selected from the group consisting of colloidal silica, at least one organic resin, and combinations thereof, particles of an aluminum-silicon alloy which has an average particle size in the range of about 1 micron to about 50 microns, and inert organic pyrolysable solid particulate thickener beads.

38. The composition of claim 37 wherein the thickener beads comprise acrylic.

39. The composition of claim 37 wherein the thickener beads comprise poly(methyl methacrylate) beads.

40. The composition of claim 37 wherein the binder comprises colloidal silica present at a level in the range of about 5% by weight to about 20% by weight, based on silica solids as a percentage of the entire composition; and the amount of aluminum in the composition exceeds the amount of aluminum present in the surface region of the internal passage by up to about 65 atomic %.

41. The composition of claim 37 wherein the binder comprises colloidal silica and an organic stabilizer which includes at least two hydroxyl groups.

42. The composition of claim 41 wherein the organic stabilizer is selected from the group consisting of glycerol, at least one dihydroxy alcohol, and combinations thereof.

43. The composition of claim 41 wherein

the organic stabilizer is present at a level in the range of about 0.1% by weight to about 20% by weight, based on the total weight of the composition;

the colloidal silica is present at a level in the range of about 5% by weight to about 20% by weight, based on silica solids as a percentage of the entire composition; and

the amount of aluminum in the composition exceeds the amount of aluminum present in the surface region of the internal passage by up to about 65 atomic %.

44. The composition of claim 37 wherein the binder comprises an organic resin selected from the group consisting of epoxy resins, silicone resins, alkyd resins, acrylic resins, polyurethane resins, polyvinyl chloride resins, phenolic resins, polyester resins, urethane resins, polyamide resins, polyolefin resins, and combinations thereof.