Method for removing the coating from a gas turbine component

Patent metadata

Field	Value
Publication number	US-9212555-B2
Application number	US-8880006-A
Country	US
Kind code	B2
Filing date	Oct 10, 2006
Priority date	Oct 14, 2005
Publication date	Dec 15, 2015
Grant date	Dec 15, 2015

Abstract

A method for removing the coating from a gas turbine component, namely for the complete or partial removal of a multilayer wear protection coating from the surface of the gas turbine component, the wear protection coating having at least one relatively hard ceramic layer and at least one relatively soft metallic layer, wherein, in order to remove the multilayer wear protection coating, the gas turbine component is alternately positioned in two different chemical baths, a first bath being used exclusively for the removal of each relatively hard ceramic layer, and a second bath being used exclusively for the removal of each relatively soft metallic layer of the wear protection coating.

First claim

The invention claimed is:

1. A method for removing a wear protection coating from a surface of a gas turbine component, the wear protection coating having at least one relatively hard ceramic layer and at least one relatively soft metallic layer, the method comprising:
alternately positioning the gas turbine component in two different chemical baths for at least partially removing the wear protection coating from the gas turbine component without damaging the surface of the gas turbine component by removing a portion of the surface, a first bath being used exclusively for the removal of each relatively hard ceramic layer of the wear protection coating, and a second bath being used exclusively for the removal of each relatively soft metallic layer of the wear protection coating, the component being sequentially positioned in the respective first and second baths corresponding to the disposition of the at least one relatively hard ceramic layer and the at least one soft metallic layers on the component,
wherein said first bath is an acid consisting of a hydrogen peroxide solution and at least one sodium salt and/or potassium salt of an organic acid contained therein, and wherein said first bath has a pH value between 3 and 5; and
wherein said second bath is formed from a 5 w/v % to 50 w/v % alkali hydroxide solution.

2. The method as recited in claim 1 , wherein said first bath is the hydrogen peroxide solution having 10 g/l to 100 g/l sodium salts of organic acids.

3. The method as recited in claim 1 , wherein said first bath, which is used exclusively for the removal of each relatively hard ceramic layer, is an acid made up of a hydrogen peroxide solution and an organic compound containing nitrogen contained therein.

4. The method as recited in claim 3 , wherein said first bath is the hydrogen peroxide solution having 1 g/l to 10 g/l of the nitrogen-containing compound.

5. The method as recited in claim 1 , wherein said first bath, which is used exclusively for the removal of each relatively hard ceramic layer, is an acid made up of a hydrogen peroxide solution, at least one sodium salt and/or potassium salt of an organic acid contained therein, and a nitrogen-containing organic compound contained therein.

6. The method as recited in claim 5 , wherein said first bath is the hydrogen peroxide solution having 10 g/l to 100 g/l sodium salts of organic acids and 1 g/l to 10 g/l of the nitrogen-containing organic compound.

7. The method as recited in claim 1 , wherein said first bath is a mixture of hydrofluoric acid and nitric acid, and in addition contains at least one sodium salt and/or potassium salt of an organic acid and/or a nitrogen-containing organic compound.

8. The method as recited in claim 1 , wherein said removal of a relatively hard ceramic layer, the gas turbine component is positioned in the first bath at a temperature between 10° C. and 70° C. for a duration of 1-60 minutes per 1 nm thickness of the layer that is to be removed.

9. The method as recited in claim 1 , wherein said second bath, which is used exclusively for the removal of each relatively soft metallic layer, is a base made up of an aqueous solution of at least one alkali hydroxide or earth alkali hydroxide containing silicon or silicon compounds and/or phosphorus or phosphorus compounds.

10. The method as recited in claim 9 , wherein said second bath is the alkali hydroxide solution having 1 g/l to 200 g/l silicon or silicon compounds and/or 10 g/l to 100 g/l phosphorus or phosphorus compounds.

11. The method as recited in claim 9 , wherein said second bath, which is used exclusively for the removal of each relatively soft metallic layer, has a pH value greater than 12.

12. The method as recited in claim 1 , wherein in said removal of a relatively soft metallic layer, the gas turbine component is positioned in the second bath at a temperature between 20° C. and 150° C. for a duration of 10-120 minutes per 1 nm thickness of the layer that is to be removed.

13. A method for removing a wear protection coating from a surface of a gas turbine component, the wear protection coating having at least one relatively hard ceramic layer and at least one relatively soft metallic layer, the method comprising:
alternately positioning the gas turbine component in two different chemical baths for at least partially removing the wear protection coating from the gas turbine component without damaging the surface of the gas turbine component by removing a portion of the surface, a first bath being used exclusively for the removal of each relatively hard ceramic layer of the wear protection coating, and a second bath being used exclusively for the removal of each relatively soft metallic layer of the wear protection coating, the component being sequentially positioned in the respective first and second baths corresponding to the disposition of the at least one relatively hard ceramic layer and the at least one soft metallic layers on the component, said first bath is an acid solution taken from the group consisting of a hydrogen peroxide solution, a hydrogen peroxide solution and organic compound containing nitrogen contained therein, and a hydrofluoric acid and a nitric acid, and at least one sodium salt and/or potassium salt of an organic acid contained therein, wherein said first bath has a pH value between 3 and 5, and said second bath is a base formed from a 5 w/v % to 50 w/v % alkali hydroxide solution containing silicon or silicon compounds and/or phosphorus or phosphorus compounds.

14. The method as recited in claim 1 , wherein said second bath has a pH of at least 12.

15. The method as recited in claim 13 , wherein said second bath has a pH of at least 12.

Assignees

• Manier Karl-Heinz
• Uihlein Thomas
• Thöne Carl-Stefan
• Mtu Aero Engines Gmbh
• Solut Chemie Gmbh Ab

Inventors

• Manier Karl-Heinz
• Uihlein Thomas
• Thöne Carl-Stefan

Classifications

• C23F1/44

  Compositions for etching metallic material from a metallic material substrate of different composition · CPC title

• F01D5/288

  Protective coatings for blades · CPC title

• C23G1/106

  refractory metals · CPC title

• F01D5/005 Primary

  Repairing methods or devices · CPC title