Methods to remove an EBC from a substrate and to repair a coated component
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.
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 . The method of claim 1 , wherein the bondcoat comprises elemental silicon.
3 . The method of claim 1 , wherein the bondcoat comprises at least 75% by weight of elemental silicon.
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 . The method of claim 1 , wherein the etchant liquid comprises 25% by volume to 49% by volume of the hydrogen fluoride.
6 . The method of claim 1 , wherein the solvent comprises water.
7 . The method of claim 6 , wherein the etchant liquid consists essentially of the hydrogen fluoride and water.
8 . The method of claim 1 , wherein the etchant liquid further comprises hydrogen chloride, nitric acid, fluorosilicic acid, hydrogen peroxide, or mixtures thereof.
9 . The method of claim 1 , wherein the etchant liquid further comprises a wetting agent.
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 . 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 . 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 . 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 . The method of claim 13 , wherein the plurality of particles comprises grit particles, glass particles, metal particles, or a mixture thereof.
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 . The method of claim 15 , wherein the replacement environmental barrier coating is formed directly on the exposed bondcoat.
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 . The method of claim 17 , wherein removing the bondcoat comprises contacting the intermediate component with a mechanical etchant.
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 . The method of claim 17 , wherein the replacement bondcoat comprises mullite.