US20100108538A1 - Method for stripping a component - Google Patents

Method for stripping a component Download PDF

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Publication number
US20100108538A1
US20100108538A1 US12/451,153 US45115308A US2010108538A1 US 20100108538 A1 US20100108538 A1 US 20100108538A1 US 45115308 A US45115308 A US 45115308A US 2010108538 A1 US2010108538 A1 US 2010108538A1
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US
United States
Prior art keywords
component
recited
electrolyte
stripped
stripping
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/451,153
Inventor
Anton Albrecht
Wolfgang Eichmann
Georgios Paronis
Thomas Uihlein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MTU Aero Engines AG
Original Assignee
MTU Aero Engines GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MTU Aero Engines GmbH filed Critical MTU Aero Engines GmbH
Assigned to MTU AERO ENGINES GMBH reassignment MTU AERO ENGINES GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: EICHMANN, WOLFGANG, UHLEIN, THOMAS, ALBRECHT, ANTON, PARONIS, GEORGIOS
Publication of US20100108538A1 publication Critical patent/US20100108538A1/en
Abandoned legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F5/00—Electrolytic stripping of metallic layers or coatings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/005—Repairing methods or devices

Definitions

  • the present invention relates to a method for stripping a component, in particular a gas turbine component, to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer.
  • gas turbine components such as rotor blades
  • special antiwear coatings are applied to the surfaces thereof.
  • gas turbine components are subject to wear or can become damaged in some other way. Repairing the damage typically requires localized, partial, or also complete removal or ablation of the antiwear coating from the component to be repaired.
  • the process of removing or ablating coatings is also described as stripping. One distinguishes among the different stripping methods according to whether the coatings are removed mechanically, chemically or electrochemically.
  • Antiwear coatings typically take the form of what is known as multilayer coatings, which are composed of a plurality of layers alternately deposited on the gas turbine component.
  • an antiwear coating in the form of a multilayer coating may include, for example, a relatively soft metallic layer and a relatively hard ceramic layer, a multiplicity of said layers being alternately deposited one above another on the gas turbine component.
  • antiwear coatings in which more than two different layers are alternately deposited one above another on the gas turbine component, such as, for example, multilayer coatings composed of four layers alternately deposited one above another on the gas turbine component, namely a first metallic layer which is adapted to the material composition of the gas turbine component and which is therefore relatively soft, a metallic layer which is composed of a metal alloy material and is also relatively soft, a third, relatively hard-grade metal-ceramic layer, and a fourth relatively hard ceramic layer.
  • the prior art has not yet disclosed a method that would allow multilayer antiwear coatings to be effectively removed without the risk of damage to the base material of the gas turbine component.
  • the present invention provides a method for stripping a gas turbine component to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer.
  • the component in order to remove the multilayer or sandwich antiwear coating, the component is placed in a bath of an alkaline electrolyte, the component placed in the electrolyte being stripped at a current density of between 1 A/dm 2 and 20 A/dm 2 .
  • the method of the present invention for stripping a component has the advantage of allowing residue-free removal of multilayer coatings from the surface of the component to be stripped without the risk of the base material thereof being attacked and thereby damaged.
  • titanium-based alloys and nickel-based alloys are not damaged during the stripping process according to the present invention.
  • Another advantage of the method of the present invention is that it allows components to be stripped in a single bath of the alkaline electrolyte.
  • the method according to the present invention for stripping a component eliminates the need to provide several different baths.
  • the component placed in the electrolyte is anodically processed at room temperature.
  • the bath contains, in addition to the alkaline electrolyte, a surfactant to reduce surface or interfacial tension.
  • a surfactant to reduce surface or interfacial tension In particular, a sodium hydroxide solution or a potassium hydroxide solution is used as the electrolyte.
  • the surfactant used is especially a fluorinated surfactant, said surfactant being used in an amount to reduce the surface or interfacial tension to a value between 20 dynes and 50 dynes.
  • the method of the present invention is used for stripping components, such as gas turbine components, which are coated with multilayer antiwear coatings composed of at least two different layers arranged alternately one above another, namely of relatively hard ceramic layers and relatively soft metallic layers arranged alternately one above another.
  • the component to be stripped in order to remove a multilayer antiwear coating from a component, and thus to strip the component, the component to be stripped is placed in a bath of an alkaline electrolyte.
  • the component placed in the alkaline electrolyte is then stripped by applying an electric current having a current density of between 1 A/dm 2 and 20 A/dm 2 .
  • stripping is accomplished electrochemically.
  • the component to be stripped is mainly processed anodically; i.e., it mainly functions as an anode during stripping.
  • the component to be stripped can also be used as a cathode at defined intervals for short periods of time in order to increase the stripping efficiency.
  • the stripping of the component placed in the alkaline electrolyte is performed at a current density of between 1 A/dm 2 and 5 A/dm 2 , and preferably at room temperature.
  • sodium hydroxide solution or potassium hydroxide solution is used as the alkaline electrolyte.
  • a bath which contains a surfactant in addition to the alkaline electrolyte.
  • the surfactant is preferably a fluorinated surfactant.
  • the amount of the surfactant is selected to reduce the surface or interfacial tension to a value between 20 dynes und 50 dynes, in particular to a value between 25 dynes und 35 dynes.
  • the portions or regions of the component that are intended not to be stripped are covered with a wax-containing or wax-like material prior to stripping. This is useful, for example, when a gas turbine blade is to be stripped only in the region of its blade, but not in the region of its root. In such a case, the blade root is covered with a wax-containing or wax-like material prior to placing the gas turbine blade in the bath.
  • the method of the present invention enables effective, low-stress stripping of multilayer coatings from components. Stripping is accomplished electrochemically, it being sufficient to use a single bath of an alkaline electrolyte. There is no risk of the base material of the component to be stripped being eroded and thus damaged.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

A method for stripping a component, in particular a gas turbine component, to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer is disclosed. According to the present invention, in order to remove the multilayer or sandwich antiwear coating, the component is placed in a bath of an alkaline electrolyte, the component placed in the electrolyte being stripped at a current density of between 1 A/dm2 and 20 A/dm2.

Description

  • This claims priority to German Patent Application DE 10 2007 022 832.7, filed May 15, 2007 through international application PCT/DE2008/000756, filed May 2, 2008, the entire disclosures of which are hereby incorporated by reference herein.
  • The present invention relates to a method for stripping a component, in particular a gas turbine component, to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer.
    • BACKGROUND OF THE INVENTION
  • To provide gas turbine components, such as rotor blades, with oxidation-resistance, corrosion-resistance or also erosion-resistance, special antiwear coatings are applied to the surfaces thereof. During operation, gas turbine components are subject to wear or can become damaged in some other way. Repairing the damage typically requires localized, partial, or also complete removal or ablation of the antiwear coating from the component to be repaired. The process of removing or ablating coatings is also described as stripping. One distinguishes among the different stripping methods according to whether the coatings are removed mechanically, chemically or electrochemically.
  • Antiwear coatings typically take the form of what is known as multilayer coatings, which are composed of a plurality of layers alternately deposited on the gas turbine component. Thus, an antiwear coating in the form of a multilayer coating may include, for example, a relatively soft metallic layer and a relatively hard ceramic layer, a multiplicity of said layers being alternately deposited one above another on the gas turbine component. In practice, there are known antiwear coatings in which more than two different layers are alternately deposited one above another on the gas turbine component, such as, for example, multilayer coatings composed of four layers alternately deposited one above another on the gas turbine component, namely a first metallic layer which is adapted to the material composition of the gas turbine component and which is therefore relatively soft, a metallic layer which is composed of a metal alloy material and is also relatively soft, a third, relatively hard-grade metal-ceramic layer, and a fourth relatively hard ceramic layer.
  • The prior art has not yet disclosed a method that would allow multilayer antiwear coatings to be effectively removed without the risk of damage to the base material of the gas turbine component.
    • SUMMARY OF THE INVENTION
  • In view of the above, it is an object of the present invention to provide a novel method for stripping a gas turbine component.
  • The present invention provides a method for stripping a gas turbine component to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer.
  • According to the present invention, in order to remove the multilayer or sandwich antiwear coating, the component is placed in a bath of an alkaline electrolyte, the component placed in the electrolyte being stripped at a current density of between 1 A/dm2 and 20 A/dm2.
  • The method of the present invention for stripping a component has the advantage of allowing residue-free removal of multilayer coatings from the surface of the component to be stripped without the risk of the base material thereof being attacked and thereby damaged. In particular, titanium-based alloys and nickel-based alloys are not damaged during the stripping process according to the present invention. Another advantage of the method of the present invention is that it allows components to be stripped in a single bath of the alkaline electrolyte. Thus, the method according to the present invention for stripping a component eliminates the need to provide several different baths.
  • Preferably, the component placed in the electrolyte is anodically processed at room temperature.
  • In an advantageous embodiment of the present invention, the bath contains, in addition to the alkaline electrolyte, a surfactant to reduce surface or interfacial tension. In particular, a sodium hydroxide solution or a potassium hydroxide solution is used as the electrolyte. The surfactant used is especially a fluorinated surfactant, said surfactant being used in an amount to reduce the surface or interfacial tension to a value between 20 dynes and 50 dynes.
    • DETAILED DESCRIPTION
  • An exemplary embodiment of the present invention is described in greater detail below.
  • The method of the present invention is used for stripping components, such as gas turbine components, which are coated with multilayer antiwear coatings composed of at least two different layers arranged alternately one above another, namely of relatively hard ceramic layers and relatively soft metallic layers arranged alternately one above another.
  • In accordance with the method of the present invention, in order to remove a multilayer antiwear coating from a component, and thus to strip the component, the component to be stripped is placed in a bath of an alkaline electrolyte. The component placed in the alkaline electrolyte is then stripped by applying an electric current having a current density of between 1 A/dm2 and 20 A/dm2.
  • Accordingly, in accordance with the present invention, stripping is accomplished electrochemically. In this process, the component to be stripped is mainly processed anodically; i.e., it mainly functions as an anode during stripping. During the stripping process, the component to be stripped can also be used as a cathode at defined intervals for short periods of time in order to increase the stripping efficiency.
  • Preferably, the stripping of the component placed in the alkaline electrolyte is performed at a current density of between 1 A/dm2 and 5 A/dm2, and preferably at room temperature.
  • Preferably, sodium hydroxide solution or potassium hydroxide solution is used as the alkaline electrolyte.
  • In order to reduce the surface or interfacial tension during stripping, it is preferred to use a bath which contains a surfactant in addition to the alkaline electrolyte. The surfactant is preferably a fluorinated surfactant.
  • The amount of the surfactant is selected to reduce the surface or interfacial tension to a value between 20 dynes und 50 dynes, in particular to a value between 25 dynes und 35 dynes.
  • If the component is to be stripped only in specific surface regions, the portions or regions of the component that are intended not to be stripped are covered with a wax-containing or wax-like material prior to stripping. This is useful, for example, when a gas turbine blade is to be stripped only in the region of its blade, but not in the region of its root. In such a case, the blade root is covered with a wax-containing or wax-like material prior to placing the gas turbine blade in the bath.
  • The method of the present invention enables effective, low-stress stripping of multilayer coatings from components. Stripping is accomplished electrochemically, it being sufficient to use a single bath of an alkaline electrolyte. There is no risk of the base material of the component to be stripped being eroded and thus damaged.

Claims (12)

1-11. (canceled)
12. A method for stripping a component, in particular a gas turbine component, to completely or partially remove a multilayer or sandwich antiwear coating from the surface of the component, the antiwear coating including at least one relatively hard ceramic layer and at least one relatively soft metallic layer, the method comprising:
in order to remove the multilayer or sandwich antiwear coating, placing the component in a bath of an alkaline electrolyte; and
stripping the component placed in the electrolyte at a current density of between 1 A/dm2 and 20 A/dm2.
13. The method as recited in claim 12, wherein the component placed in the electrolyte is stripped at a current density of between 1 A/dm2 and 5 A/dm2.
14. The method as recited in claim 12, wherein the component placed in the electrolyte is stripped anodically.
15. The method as recited in claim 12, wherein the component placed in the electrolyte is stripped at room temperature.
16. The method as recited in claim 12, wherein the bath contains, in addition to the alkaline electrolyte, a surfactant to reduce surface or interfacial tension.
17. The method as recited in claim 16, wherein the surfactant is used in an amount to reduce a surface or interfacial tension to a value between 20 dynes und 50 dynes.
18. The method as recited in claim 17, wherein the surfactant is used in an amount to reduce the surface or interfacial tension to a value between 25 dynes und 35 dynes.
19. The method as recited in claim 16, wherein the surfactant is a fluorinated surfactant.
20. The method as recited in claim 12, wherein the alkaline electrolyte is a sodium hydroxide solution.
21. The method as recited in claim 12, wherein the alkaline electrolyte is a potassium hydroxide solution.
22. The method as recited in claim 12, further comprising covering portions of the component that are intended not to be stripped with a wax-containing or wax-like material prior to placing the component in the bath.
US12/451,153 2007-05-15 2008-05-02 Method for stripping a component Abandoned US20100108538A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102007022832A DE102007022832A1 (en) 2007-05-15 2007-05-15 Process for stripping a component
DE102007022832.7 2007-05-15
PCT/DE2008/000756 WO2008138301A1 (en) 2007-05-15 2008-05-02 Method for removing the coating of a component

Publications (1)

Publication Number Publication Date
US20100108538A1 true US20100108538A1 (en) 2010-05-06

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US12/451,153 Abandoned US20100108538A1 (en) 2007-05-15 2008-05-02 Method for stripping a component

Country Status (5)

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US (1) US20100108538A1 (en)
EP (1) EP2147134A1 (en)
CA (1) CA2679308A1 (en)
DE (1) DE102007022832A1 (en)
WO (1) WO2008138301A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018145132A3 (en) * 2017-02-01 2018-10-25 Aeroment Technologies Soluton, Llc Method and apparatus for removing coatings

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102010010771A1 (en) * 2010-03-09 2011-09-15 Lufthansa Technik Ag Process for the electrochemical stripping of gas turbine components
DE102010010770A1 (en) * 2010-03-09 2011-09-15 Lufthansa Technik Ag Process for the electrochemical stripping of gas turbine components

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5624541A (en) * 1994-10-07 1997-04-29 Bayer Aktiengesellschaft Spray mist inhibitors for basic electrolysis baths
US6132520A (en) * 1998-07-30 2000-10-17 Howmet Research Corporation Removal of thermal barrier coatings
US20020074240A1 (en) * 2000-12-15 2002-06-20 Jaworowski Mark R. Feedback controlled airfoil stripping system with integrated water management and acid recycling system
US20040074783A1 (en) * 2002-10-21 2004-04-22 General Electric Company Method for partially stripping a coating from the surface of a substrate, and related articles and compositions
US20040244910A1 (en) * 2001-06-14 2004-12-09 Anton Albrecht Method and device for locally removing coating from parts
WO2005066384A1 (en) * 2004-01-09 2005-07-21 Mtu Aero Engines Gmbh Wear-resistant layer and component comprising a wear-resistant layer
US20060137995A1 (en) * 2004-12-29 2006-06-29 Sukanta Ghosh Method for removal of metal from a workpiece
US7078073B2 (en) * 2003-11-13 2006-07-18 General Electric Company Method for repairing coated components
US20060226025A1 (en) * 2005-03-16 2006-10-12 Colorado School Of Mines Electrochemical removal of die coatings
WO2007025509A1 (en) * 2005-09-02 2007-03-08 Mtu Aero Engines Gmbh Method for coating or decoating a component

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005049249B4 (en) * 2005-10-14 2018-03-29 MTU Aero Engines AG Process for stripping a gas turbine component

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5624541A (en) * 1994-10-07 1997-04-29 Bayer Aktiengesellschaft Spray mist inhibitors for basic electrolysis baths
US6132520A (en) * 1998-07-30 2000-10-17 Howmet Research Corporation Removal of thermal barrier coatings
US20020074240A1 (en) * 2000-12-15 2002-06-20 Jaworowski Mark R. Feedback controlled airfoil stripping system with integrated water management and acid recycling system
US20040244910A1 (en) * 2001-06-14 2004-12-09 Anton Albrecht Method and device for locally removing coating from parts
US20040074783A1 (en) * 2002-10-21 2004-04-22 General Electric Company Method for partially stripping a coating from the surface of a substrate, and related articles and compositions
US7078073B2 (en) * 2003-11-13 2006-07-18 General Electric Company Method for repairing coated components
WO2005066384A1 (en) * 2004-01-09 2005-07-21 Mtu Aero Engines Gmbh Wear-resistant layer and component comprising a wear-resistant layer
US20070190351A1 (en) * 2004-01-09 2007-08-16 Wolfgang Eichmann Wear-resistant coating and a component having a wear-resistant coating
US20060137995A1 (en) * 2004-12-29 2006-06-29 Sukanta Ghosh Method for removal of metal from a workpiece
US20060226025A1 (en) * 2005-03-16 2006-10-12 Colorado School Of Mines Electrochemical removal of die coatings
WO2007025509A1 (en) * 2005-09-02 2007-03-08 Mtu Aero Engines Gmbh Method for coating or decoating a component
US20090017201A1 (en) * 2005-09-02 2009-01-15 Mtu Aero Engines Gmbh Method for coating or decoating a component

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018145132A3 (en) * 2017-02-01 2018-10-25 Aeroment Technologies Soluton, Llc Method and apparatus for removing coatings

Also Published As

Publication number Publication date
WO2008138301A1 (en) 2008-11-20
CA2679308A1 (en) 2008-11-20
DE102007022832A1 (en) 2008-11-20
EP2147134A1 (en) 2010-01-27

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Owner name: MTU AERO ENGINES GMBH,GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ALBRECHT, ANTON;EICHMANN, WOLFGANG;PARONIS, GEORGIOS;AND OTHERS;SIGNING DATES FROM 20090903 TO 20090907;REEL/FRAME:023454/0246

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION