CURABLE MASKING MATERIAL FOR PROTECTING A PASSAGE HOLE IN A SUBSTRATE

• US 20010007708A1
• Filed: 11/27/1998
• Published: 07/12/2001
• Est. Priority Date: 12/03/1996
• Status: Active Grant

• Current Assignee: James Anthony Brewer, Lawrence Edward Szala, Marcus Preston Borom, Venkat Subramaniam Venkataramani, Wayne Charles Hasz
• Original Assignee: James Anthony Brewer, Lawrence Edward Szala, Marcus Preston Borom, Venkat Subramaniam Venkataramani, Wayne Charles Hasz
• Inventors: VENKATARAMANI, VENKAT SUBRAMANIAM, BREWER, JAMES ANTHONY, SZALA, LAWRENCE EDWARD, BOROM, MARCUS PRESTON, HASZ, WAYNE CHARLES
• Granted Patent: US 6,335,078 B2
• Time in Patent Office: Days
• US Class Current: 428/139
• CPC Class Codes: B05D 1/32 using means for protecting parts of a surface not to be coated, e.g. using stencils, resists
• CPC Class Codes: B23P 2700/06 Cooling passages of turbine components, e.g. unblocking or preventing blocking of cooling passages of turbine components
• CPC Class Codes: C23C 14/042 using masks
• CPC Class Codes: C23C 4/01 Selective coating, e.g. pattern coating, without pre-treatment of the material to be coated
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10T 428/12361 having aperture or cut
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24281 Struck out portion type
• CPC Class Codes: Y10T 428/24289 Embedded or interlocked
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24339 Keyed

Abstract

A method for temporarily protecting at least one passage hole in a metal-based substrate from being obstructed by at least one coating applied over the substrate is disclosed. The method includes the following steps:

(a) filling and covering the hole with a curable masking material which forms a protrusion over the hole;

(b) curing the masking material;

(c) applying at least one coating over the substrate and the masking material, wherein the coating does not substantially adhere to the protrusion; and then

(d) removing the masking material to uncover the passage hole.

Usually, there are an array of holes, and they serve as conduits for cooling gasses for an engine component. The curable masking material exhibits substantially non-Newtonian flow characteristics which make it especially suitable for forming protrusions of the proper size and shape on the coating-side of an engine part.

Another embodiment of this invention relates to a the curable masking material itself, and to articles which include such a material.

Claims

1. A method for temporarily protecting at least one passage hole in a metal-based substrate from being obstructed by at least one coating applied over the substrate, comprising the following steps:

(a) filling and covering the hole with a curable masking material which forms a protrusion over the hole;

(b) curing the masking material;

(c) applying at least one coating over the substrate and the masking material, wherein the coating does not substantially adhere to the protrusion; and

then

(d) removing the masking material to uncover the passage hole.

2. The method of

claim 1

, wherein the hole is filled and covered by an extrusion technique.

3. The method of

claim 1

, wherein the metal-based substrate has a first surface and a second surface, and the masking material is extruded from the first surface, through the length of the passage hole, to extend beyond the second surface.

4. The method of

claim 3

, wherein the extrusion is carried out by applying a layer of the masking material over the first surface, and then forming a pressure differential between the first surface and the second surface, causing the material to move to the second surface.

5. The method of

claim 3

, wherein the masking material is extruded under a pressure of about 1 psi to about 30 psi.

6. The method of

claim 3

, wherein a sheet of material is placed over the first surface after the masking material has been applied to the first surface for extrusion, and extrusion is then carried out by applying pressure on the sheet of material.

7. The method of

claim 6

, wherein the sheet of material comprises a rubber or a saran-type material.

8. The method of

claim 1

, wherein the average height of the protrusion above the substrate is at least about 50% greater than the expected thickness of the coating subsequently applied in step (c).

9. The method of

claim 1

, wherein the curable masking material exhibits a substantially non-Newtonian flow characteristic.

10. The method of

claim 9

, wherein the curable masking material exhibits a Bingham solid characteristic.

11. The method of

claim 9

, wherein the curable masking material comprises a thermosetting resin and at least one additive selected from the group consisting of fillers, plasticizers, and liquid crystal materials.

12. The method of

claim 11

, wherein the thermosetting resin is selected from the group consisting of epoxy resins and alkyd resins.

13. The method of

claim 12

, wherein the epoxy is derived from bisphenol A.

14. The method of

claim 11

, wherein the thermosetting resin is a phenolic.

15. The method of

claim 14

, wherein the phenolic is a phenol-formaldehyde polymer.

16. The method of

claim 11

, wherein the filler is an organic material or a mixture of an organic material and an inorganic material.

17. The method of

claim 16

, wherein the organic material comprises a substance selected from the group consisting of rubber, wax, gums, cellulosic materials, wood, sawdust, walnut shell powder, and any combination of the foregoing.

18. The method of

claim 11

, wherein the filler comprises an inorganic material.

19. The method of

claim 18

, wherein the inorganic material is selected from the group consisting of graphite, silica, alumina, magnesium oxide, talc, alkaline earth carbonates, zirconium basic carbonate, sulfates, sulfides, halides, phosphates, borates, borosilicates, slate flour, clay, and any combination of the foregoing.

20. The method of

claim 10

, wherein the curable masking material comprises a thermoplastic resin and at least one additive selected from the group consisting of fillers, plasticizers, and liquid crystal materials.

21. The method of

claim 20

, wherein the thermoplastic resin is selected from the group consisting of acrylic resins, thermoplastic polyesters, polyamides, thermoplastic polyimides, polycarbonates, polyphenylene ethers, polyolefins, styrene-based resins, copolymers of any of the foregoing;

and mixtures of any of the foregoing.

22. The method of

claim 21

, wherein the filler is an organic material or a mixture of an organic material and an inorganic material.

23. The method of

claim 1

, wherein the masking material is removed in step (d) by a technique which comprises pyrolysis.

24. The method of

claim 1

, wherein the masking material is substantially removed in step (d) by treatment with a solvent which dissolves the material.

25. The method of

claim 1

, wherein the metal-based substrate is a superalloy.

26. The method of

claim 1

, wherein the metal-based substrate is a component of a gas turbine engine.

28. The method of

claim 1

, wherein the coating applied in step (c) comprises a thermal barrier coating.

29. The method of

claim 1

, wherein the substrate contains a row of passage holes.

30. The method of

claim 1

, wherein the substrate contains an array of passage holes.

31. The method of

claim 3

, wherein the second surface is a hot surface exposed to elevated temperature, and the first surface is a cold surface exposed to a temperature less than that to which the hot surface is exposed.

32. The method of

claim 31

, wherein the hot surface is exposed to a temperature of at least about 1200°

C.

33. The method of

claim 31

, wherein the passage holes are cooling holes.

34. The method of

claim 1

, wherein step (c) comprises applying a bond coat and then a thermal barrier coating over the bond coat.

27. The method of 26, wherein the component is a combustion chamber.

35. A method for applying a thermal barrier coating to a high-temperature alloy substrate which includes cooling holes, wherein the cooling holes remain clear after the thermal barrier coating has been applied, comprising the following steps:

(i) filling and covering the holes with a curable masking material which forms a protrusion over each hole;

(ii) curing the masking material;

(iii) applying a thermal barrier coating over the exposed masking material, wherein the thermal barrier coating does not substantially adhere to the protrusions; and

then

(iv) removing the masking material to uncover the cooling holes.

36. The method of

claim 35

, wherein a bond coating is applied between steps (ii) and (iii), and the bond coating also does not substantially adhere to the protrusions.

37. The method of

claim 35

, wherein the holes are filled and covered by an extrusion technique.

38. The method of

claim 35

, wherein the curable masking material exhibits a substantially non-Newtonian flow characteristic.

39. The method of

claim 36

, wherein the average height of the protrusion above the substrate is at least about 50% greater than the expected, total thickness of the bond coating and the thermal barrier coating.

40. The method of

claim 35

, wherein the substrate is subjected to an adhesion-enhancing pre-treatment between step (ii) and step (iii).

41. The method of

claim 40

, wherein the pre-treatment comprises abrasion of the substrate surface.

42. The method of

claim 36

, wherein the bond coating and the thermal barrier coating are independently applied by a plasma technique or by electron beam-chemical vapor deposition.

43. The method of

claim 35

, wherein the masking material is removed in step (iv) by a technique which comprises pyrolysis.

44. A method for repairing a damaged thermal barrier coating applied over a substrate which includes at least one passage hole extending from a first surface to a second surface on which the thermal barrier coating had been applied, comprising the following steps:

(A) removing the damaged thermal barrier coating from the second surface, uncovering any passage hole in the substrate;

(B) filling and covering the hole with a curable masking material which forms a protrusion over the hole;

(C) curing the masking material;

(D) applying additional thermal barrier coating material over the substrate and the masking material, wherein the coating does not substantially adhere to the protrusion; and

then

(E) removing the masking material to uncover the passage hole.

45. A curable masking material for protecting at least one passage hole in a metalbased substrate from being obstructed by the subsequent application of at least one coating to the substrate, wherein said masking material comprises an extrudable resin composition which is thermally stable at elevated temperatures, and wherein the masking material, when cured, does not serve as an adhesion site for any coating which is subsequently applied.

46. The curable masking material of

claim 45

, comprising a thermosetting resin and at least one rheology-modifying additive, wherein the weight-ratio of thermosetting resin to the total amount of additive is in the range of about 90:

10 to about 50;

50.

47. The curable masking material of

claim 46

, wherein the thermosetting resin is an epoxy resin or a phenolic resin.

48. The curable masking material of

claim 45

, comprising a thermoplastic resin and at least one rheology-modifying additive.

49. An article, comprising:

(I) a substrate which includes at least one passage hole extending from a first surface to a second surface;

(II) a curable masking material which fills the passage hole and covers the hole to form a protrusion on the second surface over the hole; and

(III) at least one coating applied over the second surface, wherein the coating does not substantially adhere to the protrusion.