Protective barrier coatings

Patent metadata

Field	Value
Publication number	US-9644273-B2
Application number	US-70444707-A
Country	US
Kind code	B2
Filing date	Feb 9, 2007
Priority date	Feb 9, 2007
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

Exemplary embodiments of the invention provide barrier coated substrates and methods of coating a substrate with a barrier coating derived from sol gels. An example includes a barrier coated aerospace component that is subject to hot salt corrosion during use. The barrier coating is derived from oxidation of a coating composition that includes at least one sol gel. The barrier coating resists hot salt corrosion for an incubation period of such duration that an uncoated superalloy substrate under the same conditions would suffer corrosion to a depth of about 2.0 mils. Methods of applying the barrier coating include the steps of selecting a first liquid sol gel and wetting surfaces of the superalloy substrate with the selected first liquid sol gel. The wetted surfaces of the superalloy substrate are subjected to heat treatment. The heat treatment includes sintering of sol gel to oxide to produce a barrier coating.

First claim

What is claimed is:

1. A method of applying a barrier coating on a superalloy substrate having an external surface and an internal passageway, the method comprising:
selecting a first liquid sol gel comprising a precursor to be used in a sol-gel process to form a solid, oxide-based first layer of a first sol gel selected from the group consisting of zirconia, silica, alumina, titanium oxide, yttria, hafnia, and tantala, and combinations thereof, the first liquid sol gel having a viscosity at or below 1 centipoise;
wetting the external surface and the internal passageway of the superalloy substrate with the selected first liquid sol gel to form a wetted substrate, the first liquid sol gel transforming into the oxide-based first layer in situ on the superalloy substrate by a chemical reaction with moisture in the surrounding atmosphere, the oxide-based first layer comprising a first sol gel layer;
heating the oxide-based first layer on the external surface and the internal passageway of the superalloy substrate to a first temperature in a range of about 150° C. to about 600° C. to drive off volatile organic compounds from the oxide-based first layer;
selecting a second liquid sol gel comprising a precursor to be used in the sol gel process to form a solid, oxide-based second layer of a second sol gel different from the first sol gel and selected from the group consisting of zirconia, silica, alumina, titanium oxide, yttria, hafnia, and tantala, and combinations thereof, the second liquid sol gel having a viscosity at or below 1 centipoise;
applying the second liquid sol gel over the oxide-based first layer, the second liquid sol gel transforming into the solid, oxide-based second layer in situ on the oxide-based first layer on the superalloy substrate by a chemical reaction with moisture in the surrounding atmosphere, the oxide-based second layer comprising a second sol gel layer;
heating the oxide-based second layer to the first temperature in a range of about 150° C. to about 600° C. to drive off volatile organic compounds from the oxide-based second layer;
applying a third liquid sol gel over the oxide-based second layer, the first, second and third sol gel layers comprising a layered sol gel coating on the superalloy substrate; and
subjecting the superalloy substrate including the layered sol gel coating to a heat treatment at a higher second temperature in a range of about 550° C. to about 1200° C., the heat treatment comprising sintering the layered sol gel coating to produce the barrier coating, the barrier coating resisting hot salt corrosion for an incubation period of such duration that an uncoated superalloy substrate under the same conditions will corrode to a depth of about 2.0 mils,
wherein the sintering of the layered sol gel coating is in a reducing atmosphere and the method further comprises subsequent to the sintering of the layered sol gel coating, oxidizing the barrier coating to produce an equilibrium oxide barrier coating, and
wherein the step of wetting the external surface and the internal passageway of the superalloy substrate comprises adding a surface tension modifier to reduce a surface tension of the selected first liquid sol gel to form the wetted substrate on the external surface and the internal passageway of the superalloy substrate.

2. The method of claim 1 , wherein the barrier coating comprises a thickness in a range from about 0.5 to about 5.0 microns.

3. The method of claim 1 , further comprising, prior to wetting the surfaces of the superalloy substrate, applying a first coating comprising at least one of diffusion aluminide, platinum aluminide, and cobalt-nickel-chrome-aluminum-yttrium.

4. The method of claim 1 wherein the barrier coating comprises a zirconium silicate barrier coating and the first sol gel coating comprises one of silica or zirconia and the second sol gel coating comprises the other of zirconia or silica and the step of subjecting the superalloy substrate to a heat treatment at a higher second temperature comprises heating to about 1000° C.

5. The method of claim 1 , wherein the superalloy substrate comprises an object selected from the group of gas turbine components consisting of airfoils, turbine blades, turbine nozzles, disks, seals, ducts, and liners.

6. A method of producing a barrier coated substrate, the method comprising:
(a) selecting a superalloy substrate to be coated, the superalloy substrate having an external surface and a serpentine internal passageway;
(b) selecting a first liquid sol gel to be used in a sol-gel process to form a solid, oxide-based first layer, the first liquid sol gel comprising a precursor to a first sol gel selected from the group consisting of zirconia, silica, alumina, titanium oxide, yttria, hafnia, and tantala, and combinations thereof;
(c) wetting the external surface and the internal passageway of the selected substrate with the selected first liquid sol gel to form a wetted external surface and a wetted internal passageway of the selected substrate, the first liquid sol gel transforming into the solid, oxide-based first layer in situ on the superalloy substrate by a chemical reaction with moisture in the surrounding atmosphere, the oxide-based first layer comprising a first sol gel layer selected from the group consisting of zirconia, silica, alumina, titanium oxide, yttria, hafnia, and tantala, and combinations thereof;
(e) heating the oxide-based first layer to a first temperature in a range of about 150° C. to about 600° C. to drive off volatile organic compounds from the oxide-based first layer;
(f) selecting a second liquid sol gel that is different from the first liquid sol gel and applying the second liquid sol gel over the oxide-based first layer, the second liquid sol gel comprising a precursor to a second sol gel selected from the group consisting of zirconia, silica, alumina, titanium oxide, yttria, hafnia, and tantala, and combinations thereof, the first and second sol gels being different;
(g) sintering the oxide-based first layer and the second liquid sol gel at a higher second temperature in a range of about 550° C. to about 1200° C. to form a mixed oxide barrier coating; and
(h) repeating steps (b) to (g); or repeating steps (b) to (f) and carrying out step (g) after a final repeating of steps (b) to (f),
wherein the step of wetting the external surface and the internal passageway of the superalloy substrate comprises adding a surface tension modifier to reduce a surface tension of the selected first liquid sol gel to form the wetted external surface and the wetted internal passageway of the selected substrate,
wherein the sintering of the oxide-based first layer and the second liquid sol gel is in a reducing atmosphere and the method further comprises subsequent to step (g), oxidizing the mixed oxide barrier coating to produce an equilibrium oxide barrier coating.

7. The method of claim 6 , wherein the step of repeating steps (b) to (g) or repeating steps (b) to (f) comprises selecting a different sol gel in at least one repetition of step (b), step (f), or both.

8. The method of claim 6 , further comprising subjecting the external surface and the internal passageway to a vacuum of about 0.10 of an atmosphere during the step of wetting the external surface and the internal passageway.

Assignees

• Raybould Derek
• Strangman Thomas E
• Delacruz Christian
• Honeywell Int Inc

Inventors

• Raybould Derek
• Strangman Thomas E
• Delacruz Christian

Classifications

• C23C28/321

  with at least one metal alloy layer · CPC title

• C23C24/08 Primary

  by application of heat or pressure and heat (C23C24/04 takes precedence) · CPC title

• F05D2230/90

  Coating; Surface treatment · CPC title

• C23C18/1241

  Metallic substrates · CPC title

• C23C18/04

  Pretreatment of the material to be coated (C23C18/06 takes precedence) · CPC title