Removing coatings from ceramic matrix composite substrates

Patent metadata

Field	Value
Publication number	US-11053578-B2
Application number	US-201715786057-A
Country	US
Kind code	B2
Filing date	Oct 17, 2017
Priority date	Oct 21, 2016
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A method for removing a coating including a rare earth silicate from a substrate including a ceramic or ceramic matrix composite may include contacting a coating comprising a rare earth silicate with a liquid comprising an active species. The active species may include at least one of a mineral acid or a base. The method also may include working the coating to cause removal of at least a portion of the coating.

First claim

The invention claimed is:

1. A method comprising:
removing a portion of a coating using an abrasive material or a liquid jet, wherein the coating comprises a rare earth silicate, and wherein the coating is on a substrate comprising a ceramic or ceramic matrix composite;
after removing the portion of the coating using the abrasive material or the liquid jet, contacting the coating with a liquid comprising an active species, wherein the active species comprises a mineral acid, and wherein the mineral acid comprises at least one of hydrochloric acid (HCl), nitric acid (HNO 3 ), phosphoric acid (H 3 PO 4 ), hydrobromic acid (HBr), hydroiodic acid (HI), sulfuric acid (H 2 SO 4 ), or sulfamic acid (H 3 NSO 3 ); and
working the coating to cause removal of at least a portion of the coating.

2. The method of claim 1 , wherein the liquid jet comprises a water jet at a pressure of between about 100 pounds per square inch (psi) and about 5,000 pounds per square inch (psi).

3. The method of claim 1 , further comprising, while contacting the coating comprising the rare earth silicate with the liquid, agitating the liquid.

4. The method of claim 1 , further comprising, while contacting the coating comprising the rare earth silicate with the liquid, electrically connecting the substrate to an electrode submerged in the liquid, wherein the electrode has a greater natural potential than the substrate.

5. The method of claim 4 , wherein the electrode comprises at least one of graphite, gold, platinum, or a nickel-based corrosion resistant alloy.

6. The method of claim 1 , further comprising heating the liquid at a temperature between about 30° C. and about 80° C.

7. The method of claim 1 , wherein the rare earth silicate comprises a rare earth monosilicate or a rare earth disilicate.

8. The method of claim 1 , wherein the rare earth silicate comprises a ytterbium silicate.

9. The method of claim 1 , wherein the substrate comprises at least one of a SiC/SiC ceramic matrix composite or a SiC/Si—SiC ceramic matrix composite.

10. The method of claim 1 , further comprising:
after contacting the coating comprising the rare earth silicate with liquid, recovering a rare earth element removed from the coating.

11. The method of claim 10 , wherein recovering the rare earth element removed from the coating comprises:
heating the liquid to remove excess active species and form a concentrate;
filtering the concentrate through a filter to obtain filtered residue; and
distilling the filtered residue to recover the rare earth element.

12. The method of claim 11 , wherein the recovered rare earth element is in salt form.

Assignees

• Rolls Royce Corp

Inventors

• Fairbourn David C
• Chang Sunny
• Grubbs Johnny D

Classifications

• C04B41/91 Primary

  involving the removal of part of the materials of the treated articles, e.g. etching · CPC title

• C04B41/5353

  Wet etching, e.g. with etchants dissolved in organic solvents · CPC title

• C04B41/009

  characterised by the material treated · CPC title

• F01D5/288

  Protective coatings for blades · CPC title

• C23G1/10

  Other heavy metals · CPC title