US-12617735-B2 - Methods to remove an EBC from a substrate and to repair a coated component

Abstract

A method is provided for removing an environmental barrier coating from a coated component. The method may include contacting the coated component with an etchant liquid that comprises 5% by volume to 70% by volume of hydrogen fluoride and a solvent. The hydrogen fluoride reacts with silicon oxide in a thermally grown oxide layer positioned between a bondcoat and the environmental barrier coating. The bondcoat is positioned within the coated component between a silicon-containing substrate and the thermally grown oxide layer, and the bondcoat comprises a silicon-containing material.

Inventors

• Anant Achyut Setlur
• Julin Wan
• Andrea Vozar
• James Edward Murphy

Assignees

• GENERAL ELECTRIC COMPANY

Dates

Publication Date

20260505

Application Date

20240207

Claims (20)

1. 1 . A method for removing an environmental barrier coating from a coated component that includes a silicon-containing substrate, a bondcoat on the silicon-containing substrate and comprising a silicon-containing material, an environmental barrier coating on the bondcoat, and a thermally grown oxide layer positioned between the bondcoat and the environmental barrier coating, the method comprising: contacting the coated component with an etchant liquid comprising 5% by volume to 70% by volume of hydrogen fluoride and a solvent, wherein the hydrogen fluoride reacts with silicon oxide in the thermally grown oxide layer to thereby remove the thermally grown oxide layer and the environmental barrier coating from the bondcoat.
2. 2 . The method of claim 1 , wherein the bondcoat comprises elemental silicon.
3. 3 . The method of claim 1 , wherein the bondcoat comprises at least 75% by weight of elemental silicon.
4. 4 . The method of claim 1 , wherein contacting the coated component with the etchant liquid comprises submerging the coated component within the etchant liquid.
5. 5 . The method of claim 1 , wherein the etchant liquid comprises 25% by volume to 49% by volume of the hydrogen fluoride.
6. 6 . The method of claim 1 , wherein the solvent comprises water.
7. 7 . The method of claim 6 , wherein the etchant liquid consists essentially of the hydrogen fluoride and water.
8. 8 . The method of claim 1 , wherein the etchant liquid further comprises hydrogen chloride, nitric acid, fluorosilicic acid, hydrogen peroxide, or mixtures thereof.
9. 9 . The method of claim 1 , wherein the etchant liquid further comprises a wetting agent.
10. 10 . The method of claim 1 , wherein contacting the coated component with the etchant liquid, with the etchant liquid having a treatment temperature of 20° C. to 60° C.
11. 11 . The method of claim 1 , further comprising: after contacting the coated component with the etchant liquid, removing the bondcoat to expose a surface of the silicon-containing substrate.
12. 12 . The method of claim 11 , wherein removing the bondcoat from the substrate comprises contacting the coated component with a mechanical etchant to remove the bondcoat and expose a surface of the silicon-containing substrate.
13. 13 . The method of claim 12 , wherein contacting the coated component with the mechanical etchant comprises mechanically blasting the bondcoat with a plurality of particles for removal of the bondcoat.
14. 14 . The method of claim 13 , wherein the plurality of particles comprises grit particles, glass particles, metal particles, or a mixture thereof.
15. 15 . A method of repairing a coated component, the method comprising: forming an intermediate component by removing an environmental barrier coating from the coated component according to the method of claim 1 to expose the bondcoat and define an exposed bondcoat; forming a replacement environmental barrier coating on the intermediate component.
16. 16 . The method of claim 15 , wherein the replacement environmental barrier coating is formed directly on the exposed bondcoat.
17. 17 . The method of claim 15 , further comprising: after exposing the bondcoat, removing the bondcoat to expose a surface of the silicon-containing substrate to define an exposed silicon-containing substrate; and forming a replacement bondcoat on the exposed silicon-containing substrate, wherein the replacement environmental barrier coating is formed on the replacement bondcoat.
18. 18 . The method of claim 17 , wherein removing the bondcoat comprises contacting the intermediate component with a mechanical etchant.
19. 19 . The method of claim 18 , wherein contacting the intermediate component with the mechanical etchant comprises mechanically blasting the bondcoat with a plurality of particles.
20. 20 . The method of claim 17 , wherein the replacement bondcoat comprises mullite.

Description

FIELD The present disclosure generally relates to methods for removal of an environmental barrier coating layer(s) from a substrate. BACKGROUND Silicon-based materials are employed for high temperature components of gas turbine engines such as, for instance, airfoils (e.g., blades, vanes), combustor liners, and shrouds. The silicon-based materials may include silicon-based monolithic ceramic materials, intermetallic materials, and composites. For example, silicon-based ceramic matrix composites (CMCs) may include silicon-containing fibers reinforcing a silicon-containing matrix phase. BRIEF DESCRIPTION OF THE DRAWINGS A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended Figs., in which: FIG. 1 is a cross-sectional schematic view of an exemplary coated component including a substrate coated with a silicon-containing bondcoat, a thermal barrier coating, and an EBC; FIG. 2 shows the exemplary coated component of FIG. 1 submerged within an etchant liquid according to one embodiment of a method described herein; FIG. 3A shows a cross-sectional schematic view of the exemplary coated component of FIG. 1 after removal from the etchant liquid and showing that the silicon-containing bondcoat remains on the substrate while the thermal barrier coating and the EBC are removed; FIG. 3B shows a cross-sectional schematic view of an optional removal of the remaining silicon-containing bondcoat of the component in FIG. 3A; FIG. 4A shows a cross-sectional schematic view of an exemplary repaired component with a replacement environmental barrier coating on the remaining silicon-containing bondcoat of FIG. 3A; FIG. 4B shows a cross-sectional schematic view of an exemplary repaired component with a replacement environmental barrier coating on a replacement silicon-containing bondcoat; FIG. 5A shows a flow chart diagram of an exemplary method for removing an EBC from an exemplary coated component that includes a silicon-containing bondcoat, a thermal barrier coating layer, and an EBC; FIG. 5B shows a flow chart diagram of an exemplary method for removing an EBC from an exemplary coated component that includes a silicon-containing bondcoat, a thermal barrier coating layer, and an EBC; FIG. 6 is a cross-sectional schematic view of an exemplary coated component including a substrate coated with a mullite-containing bondcoat and an EBC; FIG. 7 shows the exemplary coated component of FIG. 6 submerged within an etchant liquid according to one embodiment of a method described herein; FIG. 8 shows a cross-sectional schematic view an optional method of removing the remaining mullite-containing bondcoat after contact with the etchant liquid; FIG. 9 shows an exemplary repaired component with a replacement environmental barrier coating on the remaining silicon-containing bondcoat; and FIG. 10 shows a method of removing an EBC from an exemplary coated component that includes a mullite-containing bondcoat and a thermal barrier coating. Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. Definitions As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. Chemical elements are discussed in the present disclosure using their common chemical abbreviation, such as commonly found on a periodic table of elements. For example, hydrogen is represented by its common chemical abbreviation H; helium is represented by its common chemical abbreviation He; and so forth. As used herein, “RE” refers to a rare earth element or a mixture of rare earth elements. More specifically, the “RE” refers to the rare earth elements of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), or mixtures thereof. As used herein, “alumina” refers to an aluminum oxide in the form of Al2O3. As used herein, “silica” refers to a silicon oxide in the form of SiO2. Conversely, “elemental silicon” refers to silicon without any alloying materials present, outside of incidental impurities. It is sometimes referred to in the art as “silicon metal.” Elemental silicon has a melting point of about 1414° C. As used herein, the term “mullite” generally refers to a mineral containing alumina and silica. That is, mullite is a chemical compound of alumina and silica with an alumina (Al2O3) and silica (SiO2) ratio of about 3 to 2 (e.g., within 10 mole % of 3 to 2 of alumina to silica). However, a ratio of about 2 to 1 has also been reported as mullite (e.g., within 10 mo