EP1397533B1 - Method and device for locally removing coatings from parts - Google Patents

Method and device for locally removing coatings from parts Download PDF

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Publication number
EP1397533B1
EP1397533B1 EP02740263A EP02740263A EP1397533B1 EP 1397533 B1 EP1397533 B1 EP 1397533B1 EP 02740263 A EP02740263 A EP 02740263A EP 02740263 A EP02740263 A EP 02740263A EP 1397533 B1 EP1397533 B1 EP 1397533B1
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EP
European Patent Office
Prior art keywords
coating
component
removing liquid
medium
liquid
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EP02740263A
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German (de)
French (fr)
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EP1397533A1 (en
Inventor
Anton Albrecht
Armin Eberlein
Karsten Gold
Albert Schneider
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MTU Aero Engines AG
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MTU Aero Engines GmbH
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/02—Local etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/02—Pretreatment of the material to be coated
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/44—Compositions for etching metallic material from a metallic material substrate of different composition
    • 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

Definitions

  • the invention relates to a method for local stripping of components, according to the preamble of claim 1.
  • Components of internal combustion engines have a wide variety of coatings.
  • coatings For stripping such coatings, e.g. After damage during operation, so-called dipping methods are known.
  • the component is completely immersed for stripping in an electrochemical bath, so that not only the coated, but all surfaces of the component (base material, layers, etc.) are exposed to a material attack.
  • Selective immersion of the coated areas of the device is dictated by the geometry of the device, i. the lack of accessibility to the coating, often limited.
  • the use of covers for the uncoated areas of the component leads by limited wettability to interfacial reactions and thus to an uncontrolled attack of the uncoated areas.
  • JP 59211576 A There has been known a method for locally stripping Al or Zn-coated steel substrates in which a water-absorbent substance containing an alkaline solvent is brought into contact with the area to be stripped.
  • the substance may consist of fabric, paper, cotton, sponge or a suitable chemical product.
  • Such a method may also be referred to as a "tampon method”.
  • the US-A-616,345 relates to a method for electrochemically stripping turbine blades in an acidic, electrically conductive solution.
  • the adjacent cathode of the component is adapted for a uniform material removal of the component form.
  • the component is covered in regions with a protective mask, leaving the area to be treated free.
  • the masked component is more or less completely immersed in the electrochemical bath. If only one Sohaufel tip coating / armor is to be removed, it may be sufficient to immerse only the blade tip area.
  • the object of the present invention is to provide a method with which components provided with coatings can be selectively stripped or limited to local areas.
  • a device for selective or local stripping of components is to be provided.
  • the solution according to the invention is characterized in that the component is electrochemically stripped by contact with the stripping liquid, the component being anodically switched or pulsed anodically-cathodically, and a cathode spaced from the component being provided and in contact with the decoating liquid is brought.
  • coatings of components can be removed without uncoated surfaces or the base material of the component are attacked by the decoating liquid or Stripp damkeit.
  • the coatings do not have to be completely removed, only the damaged areas are removed. If the component still has other coatings, not all, but only the damaged coatings must be removed. This leads to time and cost savings in the repair process.
  • less decoating liquid is needed than in the dipping process.
  • no additional covers for non-stratified areas of the component are required.
  • the base material below the layer is the same as that in uncoated Areas of the component not or only within the permissible limits attacked.
  • the medium may be wadding or a sponge or a porous material which may be ceramic or synthetic, e.g. synthetic fiber material can be provided.
  • the medium absorbs the liquid and stores it, so that the component is stripped on contact with the medium.
  • the medium is resistant to the Ent fürungswashkeit.
  • the medium is continuously supplied with decoating liquid.
  • the coating liquid may be continuously added to the medium, e.g. be supplied with an inflow or drip device and appropriate control, whereby the area of the component to be stripped is always wetted with decoating liquid and so a dissolution or dissolution of the coating is effected.
  • the constant flow, i. Inlet and outflow, the liquid ensures that the composition of the decoating liquid, which wets the area to be stripped, remains essentially the same.
  • the contact between the stripping fluid containing medium and the area of the component to be stripped can be maintained for a period of time which, depending on the thickness and nature of the coating, can take from a few minutes to several hours and especially from 12 to 48 hours.
  • the medium can be kept in a liquid-impermeable receptacle who the, wherein the shape of which can be formed in accordance with the shape of the component in its ent harshendem area.
  • the formation of the recording preferably takes place in such a way that the medium located during the coating process between the receptacle and the component region to be stripped hugs the component region to be stripped.
  • the receptacle may have at least one inlet, with which the medium is supplied with decoating liquid.
  • an acid or an alkali or a saline solution may be provided depending on the kind of the layer.
  • the method can be used on at least partially coated, metallic components of stationary gas turbines or aircraft engines, such as a blade or an integrally bladed rotor carrier. It can be a variety of coatings, such as hot gas corrosion or Oxidation protection layers or wear protection layers, such as hard particle blade tip armor, are selectively removed in this way or locally.
  • the period of the stripping process can be shortened, wherein with a temperature of the stripping liquid above 40 ° C and especially in the range of 40 to 60 ° C good results can be achieved with shorter stripping periods.
  • the medium and the area of the component to be stripped can be moved relative to one another. In this way, it is possible to remove fine residues on the layer or to expose surfaces of the layer that still have to be removed, with the aim of improving the surface reactions. In addition, the area to be stripped is wetted more uniformly with the stripping liquid and its constant exchange is improved. This leads to a shortening of the stripping period.
  • the solution of the problem is characterized in terms of the device according to the invention by a current source to which the component is connected anodically or by reversing anodic-cathodic, and a medium contacting the cathode.
  • the receiving device may preferably have at least one inlet for the stripping liquid and at least one outlet for liquid, so that a uniform composition of the stripping liquid contacting the areas to be stripped is ensured.
  • the apparatus may preferably have a plurality of receiving devices for simultaneously removing a plurality of coatings or coating regions of a component or have several components.
  • the blade tip armor of several blades can be stripped simultaneously without the uncoated surfaces of the rotor carrier being attacked by the stripping liquid.
  • the blade tip armor of several individual blades of gas turbines can be stripped by the corresponding number of receiving devices simultaneously.
  • the pulsation / polarity reversal can also take place over the entire decoating period.
  • the pulsation / polarity reversal allows certain atoms or molecules, e.g. Hydrogen, attach to the surface of the ent Wegenden component area, which react there to accelerate the stripping process.
  • the control of current and voltage is adapted to the base material of the component and the coating to be stripped (type, thickness, size).
  • Fig. 1 shows an integrally bladed rotor 1 of a gas turbine or an aircraft engine, on whose peripheral surface 2, a plurality of blades 3 are integrally provided.
  • the rotor 1 is a metallic component.
  • the rotor 1 and the blades 3 in the present case consist of a titanium alloy.
  • the blades 3 are provided at their blade tips 4 with (not shown) blade tip armor containing hard particles. When operating the Gas turbines may cause local damage to these blades tip armor 3 on individual blades.
  • the rotor 1 is held in a holding device (not shown) and positioned so that the area of the blade tip armor of a blade 4 to be stripped is brought into contact with a medium containing stripping liquid, wetted with desquamizing liquid and electrochemically Process is stripped.
  • a medium containing stripping liquid wetted with desquamizing liquid and electrochemically Process is stripped.
  • decoating liquid dilute sulfuric acid is used.
  • the medium is inserted into a receiving device whose shape is adapted to the blade tip 4 so that it is completely covered by the medium containing the sulfuric acid.
  • the medium consists in the present case of a synthetic fiber material.
  • the device for carrying out the method for local stripping of the rotor 1 comprises a (not shown) power source to which the rotor 1 is connected anodically.
  • the apparatus further includes a platinum-plated titanium cathode which also contacts the media with the decoating fluid.
  • the electrochemical stripping takes place at room temperature while applying a voltage of less than 10 volts over a period of 24 to 48 hours. Increasing the temperature of the decoating liquid with a heat source to 40 to 60 ° C shortens under the same boundary conditions, the period to 12 to 15 hours.
  • the medium is continuously supplied as an electrolyte serving Ent Anlagend on the blade tip 4 of the blade 3 and causes a local dissolution of the damaged blade tip armor.
  • Fig. 2 shows an embodiment with a single blade 5, which is releasably secured with its blade root 6 together with a plurality of further blades on the circumference of a blade carrier of a gas turbine.
  • the individual blade 5 (or other components to be locally coated) consists of a Ti-based alloy.
  • the individual blade 5, for example also consist of a Ni or Co base alloy.
  • the blade 5 has at its blade tip 7 a coating in the form of a blade tip armor having hard particles, on.
  • a current source (not shown) and a cathode 8 are provided.
  • the individual blade 5 is connected via the contact 9 anodically connected to the power source.
  • a receptacle 10 for the medium has an inlet 11 for a Ent fürungseckkeit, which is an electrolyte, on the inside of the receiving device 10, the electrolyte-receiving, absorbent medium is provided, which is in contact with both the blade 5 and the cathode 8.
  • the electrochemical stripping is carried out by applying a voltage at room temperature over a period of 12 to 48 hours.
  • Dilute sulfuric acid as electrolyte which wets both the area to be stratified on the blade tip 7 and the cathode 8, is constantly supplied to the absorbent medium via the inlet 11. About the flow 12 of the receiving device 10 and the absorbent medium liquid is removed.
  • only the coated regions of the component are brought into contact with the electrochemically active decoating liquid, so that the uncoated component regions are not exposed to any surface attack without additional covering.

Description

Die Erfindung betrifft ein Verfahren zum lokalen Entschichten von Bauteilen, gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a method for local stripping of components, according to the preamble of claim 1.

Bauteile von Verbrennungskraftmaschinen, wie Gasturbinen, weisen unterschiedlichste Beschichtungen auf. Zum Entschichten solcher Beschichtungen, z.B. nach einer Beschädigung im Betrieb, sind sog. Tauchverfahren bekannt. Dabei wird das Bauteil zum Entschichten vollständig in ein elektrochemisches Bad getaucht, so dass nicht nur die beschichteten, sondern sämtliche Oberflächen des Bauteils (Grundwerkstoff, Schichten etc.) einem Materialangriff ausgesetzt sind. Ein selektives Eintauchen der beschichteten Bereiche des Bauteils ist durch die Bauteilgeometrie, d.h. die fehlende Zugänglichkeit zur Beschichtung, häufig eingeschränkt. Der Einsatz von Abdeckungen für die unbeschichteten Bereiche des Bauteils führt durch eingeschränkte Benetzbarkeit zu Grenzflächenreaktionen und somit zu einem unkontrollierten Angriff der unbeschichteten Bereiche.Components of internal combustion engines, such as gas turbines, have a wide variety of coatings. For stripping such coatings, e.g. After damage during operation, so-called dipping methods are known. In this case, the component is completely immersed for stripping in an electrochemical bath, so that not only the coated, but all surfaces of the component (base material, layers, etc.) are exposed to a material attack. Selective immersion of the coated areas of the device is dictated by the geometry of the device, i. the lack of accessibility to the coating, often limited. The use of covers for the uncoated areas of the component leads by limited wettability to interfacial reactions and thus to an uncontrolled attack of the uncoated areas.

Aus Patent Abstracts of Japan, JP 59211576 A Ist ein Verfahren zum lokalen Entschichten von mit Al oder Zn überzogenen Stahlsubstraten bekannt, bei welchem eine wasserabsorbierende bzw. poröse Substanz, die ein alkalisches Lösungsmittel enthält, mit dem zu entschichtenden Bereich in Kontakt gebracht wird. Die Substanz kann aus Stoff, Papier, Baumwolle, Schwamm oder einem geeigneten chemischen Produkt bestehen. Ein derartiges Verfahren kann auch als "tampon-Verfahren" bezeichnet werden.Out Patent Abstracts of Japan, JP 59211576 A There has been known a method for locally stripping Al or Zn-coated steel substrates in which a water-absorbent substance containing an alkaline solvent is brought into contact with the area to be stripped. The substance may consist of fabric, paper, cotton, sponge or a suitable chemical product. Such a method may also be referred to as a "tampon method".

Aus der EP-A-0713957 ist eine Verfahren zum lokalen Entschichten von Bauteilen aus Inconel mit einem MCrAIY-Überzug bekannt, bei dem das abzutragende Material entweder durch chemisches Ätzen oder durch einen Aluminiumdiffusionsprozess entfernt bzw. brüchig gemacht wird. Das komplette Reparaturverfahren umfasst ein Wiederbeschichten mittels Plasmaspritzen. Vor dem chemischen Ätzen wird das jeweilige Bauteil mit Schutzlack überzogen, wobei nur die beschädigte und zu entschichtende Stelle frei bleibt. Das Bauteil wird dann in die Ätzlösung gelegt.From the EP-A-0713957 discloses a method for locally stripping Inconel components with an MCrAlY coating, in which the material to be removed is removed or made brittle either by chemical etching or by an aluminum diffusion process. The complete repair process involves recoating by plasma spraying. Before the chemical etching, the respective component is coated with protective lacquer, leaving only the damaged and to be debonded body remains free. The component is then placed in the etching solution.

Die US-A-616 345 betrifft ein Verfahren zum elektrochemischen Entschichten von Turbinenschaufeln in einer sauren, elektrisch leitfähigen Lösung. Die dem Bauteil benachbarte Kathode ist für einen gleichmäßigen Materialabtrag der Bauteilform angepasst. Für ein lokales Entschichten wird das Bauteil bereichsweise mit einer Schutzmaske überzogen, wobei die zu behandelnde Stelle frei bleibt. Das maskierte Bauteil wird in das elektrochemische Bad mehr oder weniger komplett eingetaucht. Falls nur eine Sohaufelspitzenbeschichtung/panzerung entfernt werden soll, kann es genügen, nur den Schaufelspitzenbereich einzutauchen.The US-A-616,345 relates to a method for electrochemically stripping turbine blades in an acidic, electrically conductive solution. The adjacent cathode of the component is adapted for a uniform material removal of the component form. For local de-coating, the component is covered in regions with a protective mask, leaving the area to be treated free. The masked component is more or less completely immersed in the electrochemical bath. If only one Sohaufel tip coating / armor is to be removed, it may be sufficient to immerse only the blade tip area.

Die Aufgabe der vorliegenden Erfindung besteht darin, ein Verfahren bereitzustellen, mit dem mit Beschichtungen versehene Bauteile selektiv bzw. auf lokale Bereiche beschränkt entschichtet werden können. Zudem soll eine Vorrichtung zum selektiven bzw. lokalen Entschichten von Bauteilen bereitgestellt werden.The object of the present invention is to provide a method with which components provided with coatings can be selectively stripped or limited to local areas. In addition, a device for selective or local stripping of components is to be provided.

Die Lösung dieser Aufgabe ist im Hinblick auf das Verfahren erfindungsgemäß dadurch gekennzeichnet, dass das Bauteil durch Kontakt mit der Entschichtungsflüssigkeit elektrochemisch entschichtet wird, wobei das Bauteil anodisch geschaltet bzw. anodisch-kathodisch gepulst wird, und eine zum Bauteil beabstandete Kathode bereitgestellt und in Kontakt mit der Entschichtungsflüssigkeit gebracht wird.With regard to the method, the solution according to the invention is characterized in that the component is electrochemically stripped by contact with the stripping liquid, the component being anodically switched or pulsed anodically-cathodically, and a cathode spaced from the component being provided and in contact with the decoating liquid is brought.

Dabei ist vorteilhaft, dass wie beim "Tampon-Verfahren" Beschichtungen von Bauteilen entfernt werden können, ohne dass unbeschichtete Oberflächen bzw. der Grundwerkstoff des Bauteils von der Entschichtungsflüssigkeit bzw. Strippflüssigkeit angegriffen werden. Zudem müssen die Beschichtungen nicht vollständig, sondern lediglich die beschädigten Bereiche entfernt werden. Sofern das Bauteil noch weitere Beschichtungen aufweist, müssen nicht alle, sondern lediglich die beschädigten Beschichtungen entfernt werden. Dieses führt zu Zeit- und Kosteneinsparungen beim Reparaturvorgang. Darüber hinaus wird weniger Entschichtungsflüssigkeit als beim Tauchverfahren benötigt. Ferner sind keine zusätzlichen Abdeckungen für nicht zu entschichtende Bereiche des Bauteils erforderlich. Durch das erfindungsgemäße lokale Entschichten wird der Grundwerkstoff unterhalb der Schicht ebenso wie jener in unbeschichteten Bereichen des Bauteils nicht oder nur innerhalb der zulässigen Grenzwerte angegriffen.It is advantageous that, as in the "tampon process" coatings of components can be removed without uncoated surfaces or the base material of the component are attacked by the decoating liquid or Strippflüssigkeit. In addition, the coatings do not have to be completely removed, only the damaged areas are removed. If the component still has other coatings, not all, but only the damaged coatings must be removed. This leads to time and cost savings in the repair process. In addition, less decoating liquid is needed than in the dipping process. Furthermore, no additional covers for non-stratified areas of the component are required. As a result of the local stripping according to the invention, the base material below the layer is the same as that in uncoated Areas of the component not or only within the permissible limits attacked.

In einer Ausgestaltung kann als Medium Watte oder ein Schwamm oder ein poröses Material, welches keramisch oder synthetisch , z.B. synthetisches Fasermaterial, sein kann, bereitgestellt werden. Das Medium nimmt die Flüssigkeit auf und speichert sie, so dass das Bauteil beim Kontakt mit dem Medium entschichtet wird. Als generelle Voraussetzung für diese Erfindung gilt, dass das Medium gegen die Entschichtungsflüssigkeit beständig ist. Das Medium wird dabei kontinuierlich mit Entschichtungsflüssigkeit versorgt.In one embodiment, the medium may be wadding or a sponge or a porous material which may be ceramic or synthetic, e.g. synthetic fiber material can be provided. The medium absorbs the liquid and stores it, so that the component is stripped on contact with the medium. As a general requirement for this invention is that the medium is resistant to the Entschichtungsflüssigkeit. The medium is continuously supplied with decoating liquid.

Bevorzugt kann die Beschichtungsflüssigkeit dem Medium kontinuierlich, z.B. mit einer Zufluss- oder Tropfeinrichtung und entsprechender Steuerung, zugeführt werden, wodurch der zu entschichtende Bereich des Bauteils stets mit Entschichtungsflüssigkeit benetzt wird und so ein An- oder Auflösen der Beschichtung bewirkt wird. Der ständige FluB, d.h. Zu- und Abfluß, der Flüssigkeit gewährleistet, dass die Zusammensetzung der Entschichtungsflüssigkeit, die den zu entschichtenden Bereich benetzt, im wesentlichen gleich bleibt.Preferably, the coating liquid may be continuously added to the medium, e.g. be supplied with an inflow or drip device and appropriate control, whereby the area of the component to be stripped is always wetted with decoating liquid and so a dissolution or dissolution of the coating is effected. The constant flow, i. Inlet and outflow, the liquid ensures that the composition of the decoating liquid, which wets the area to be stripped, remains essentially the same.

Der Kontakt zwischen dem entschichtungsflüssigkeitsenthaltenden Medium und dem zu entschichtenden Bereich des Bauteils kann über einen Zeitraum gehalten werden, der je nach Stärke und Art der Beschichtung einige Minuten bis mehrere Stunden und insbesondere 12 bis 48 Stunden dauern kann.The contact between the stripping fluid containing medium and the area of the component to be stripped can be maintained for a period of time which, depending on the thickness and nature of the coating, can take from a few minutes to several hours and especially from 12 to 48 hours.

Bevorzugt kann das Medium in einer flüssigkeitsundurchlässigen Aufnahme gehalten wer den, wobei deren Form entsprechend der Form des Bauteils in dessen zu entschichtendem Bereich ausgebildet werden kann. Die Ausbildung der Aufnahme erfolgt vorzugsweise so, dass sich das während des Beschichtungsvorgangs zwischen der Aufnahme und dem zu entschichtenden Bauteilbereich befindliche Medium an den zu entschichtenden Bauteilbereich anschmiegt.Preferably, the medium can be kept in a liquid-impermeable receptacle who the, wherein the shape of which can be formed in accordance with the shape of the component in its entschichtendem area. The formation of the recording preferably takes place in such a way that the medium located during the coating process between the receptacle and the component region to be stripped hugs the component region to be stripped.

Die Aufnahme kann wenigstens einen Zulauf aufweisen, mit dem das Medium mit Entschichtungsflüssigkeit versorgt wird.The receptacle may have at least one inlet, with which the medium is supplied with decoating liquid.

Als Entschichtungsflüssigkeit kann je nach Art der Schicht eine Säure oder eine Lauge oder eine Salzlösung bereitgestellt werden.As a stripping liquid, an acid or an alkali or a saline solution may be provided depending on the kind of the layer.

Das Verfahren kann an wenigstens abschnittweise mit einer Beschichtung versehenen, metallischen Bauteilen von stationären Gasturbinen oder Flugtriebwerken, wie z.B. einer Schaufel oder einem integral beschaufelten Rotorträger, eingesetzt werden. Es können unterschiedlichste Beschichtungen, wie Heißgaskorrosions- oder
-oxidationsschutzschichten oder Verschleißschutzschichten, wie Hartpartikel enthaltende Schaufelspitzenpanzerungen, auf diese Weise selektiv bzw. lokal entfernt werden.The method can be used on at least partially coated, metallic components of stationary gas turbines or aircraft engines, such as a blade or an integrally bladed rotor carrier. It can be a variety of coatings, such as hot gas corrosion or
Oxidation protection layers or wear protection layers, such as hard particle blade tip armor, are selectively removed in this way or locally.

Durch Erwärmen der Entschichtungsflüssigkeit über Raumtemperatur kann der Zeitraum des Entschichtungsvorgangs verkürzt werden, wobei mit einer Temperatur der Entschichtungsflüssigkeit oberhalb von 40 °C und insbesondere im Bereich von 40 bis 60 °C gute Ergebnisse mit kürzeren Entschichtungszeiträumen erzielt werden können.By heating the decoating liquid above room temperature, the period of the stripping process can be shortened, wherein with a temperature of the stripping liquid above 40 ° C and especially in the range of 40 to 60 ° C good results can be achieved with shorter stripping periods.

Das Medium und der zu entschichtende Bereich des Bauteils können relativ zueinander bewegt werden. Auf diese Weise lassen sich feine Rückstände auf der Schicht entfernen bzw. noch zu entschichtende Oberflächen der Schicht unter Verbesserung der Oberflächenreaktionen freilegen. Zudem wird der zu entschichtende Bereich gleichmäßiger mit der Entschichtungsflüssigkeit benetzt und deren ständiger Austausch verbessert. Dies führt zu einer Verkürzung des Entschichtungszeitraums.The medium and the area of the component to be stripped can be moved relative to one another. In this way, it is possible to remove fine residues on the layer or to expose surfaces of the layer that still have to be removed, with the aim of improving the surface reactions. In addition, the area to be stripped is wetted more uniformly with the stripping liquid and its constant exchange is improved. This leads to a shortening of the stripping period.

Die Lösung der Aufgabe ist im Hinblick auf die Vorrichtung erfindungsgemäß gekennzeichnet durch eine Stromquelle, an die das Bauteil anodisch bzw. durch Umpolung anodisch-kathodisch geschaltet ist, und eine das Medium kontaktierende Kathode.The solution of the problem is characterized in terms of the device according to the invention by a current source to which the component is connected anodically or by reversing anodic-cathodic, and a medium contacting the cathode.

Bevorzugt kann die Aufnahmeeinrichtung wenigstens einen Zulauf für die Entschichtungsflüssigkeit und wenigstens einen Ablauf für Flüssigkeit aufweisen, so dass eine gleichbleibende Zusammensetzung der die zu entschichtenden Bereiche kontaktierenden Entschichtungsflüssigkeit gewährleistet ist.The receiving device may preferably have at least one inlet for the stripping liquid and at least one outlet for liquid, so that a uniform composition of the stripping liquid contacting the areas to be stripped is ensured.

Ferner kann die Vorrichtung bevorzugt mehrere Aufnahmeeinrichtungen zum gleichzeitigen Entschichten mehrerer Beschichtungen bzw. Beschichtungsbereiche eines Bauteils oder mehrerer Bauteile aufweisen. So können z.B. bei einem integral beschaufelten Rotorträger einer Gasturbine die Schaufelspitzenpanzerungen mehrerer Schaufeln gleichzeitig entschichtet werden, ohne dass die unbeschichteten Oberflächen des Rotorträgers von der Entschichtungsflüssigkeit angegriffen werden. Ebenso können die Schaufelspitzenpanzerungen mehrerer Einzelschaufeln von Gasturbinen durch die entsprechende Anzahl von Aufnahmeeinrichtungen gleichzeitig entschichtet werden.Furthermore, the apparatus may preferably have a plurality of receiving devices for simultaneously removing a plurality of coatings or coating regions of a component or have several components. Thus, for example, in the case of an integrally bladed rotor carrier of a gas turbine, the blade tip armor of several blades can be stripped simultaneously without the uncoated surfaces of the rotor carrier being attacked by the stripping liquid. Likewise, the blade tip armor of several individual blades of gas turbines can be stripped by the corresponding number of receiving devices simultaneously.

Wird das Bauteil zeitweise, z.B. in regelmäßigen Abständen, anodisch-kathodisch umgepolt bzw. gepulst, kann die Pulsung/Umpolung auch über den gesamten Entschichtungszeitraum erfolgen. Durch die Pulsung/Umpolung lassen sich bestimmte Atome bzw. Moleküle, wie z.B. Wasserstoff, an der Oberfläche des zu entschichtenden Bauteilbereichs anlagern, die dort unter Beschleunigung des Entschichtungsvorgangs reagieren. Ferner wird beim elektrochemischen Entschichten die Steuerung von Strom und Spannung dem Grundwerkstoff des Bauteils und der zu entschichtenden Beschichtung (Art, Dicke, Größe), angepaßt.If the component is temporarily, e.g. At regular intervals, anodic-cathodic reversed polarity or pulsed, the pulsation / polarity reversal can also take place over the entire decoating period. The pulsation / polarity reversal allows certain atoms or molecules, e.g. Hydrogen, attach to the surface of the entschichtenden component area, which react there to accelerate the stripping process. Furthermore, in electrochemical stripping, the control of current and voltage is adapted to the base material of the component and the coating to be stripped (type, thickness, size).

Weitere Ausgestaltungen der Erfindung sind in den Unteransprüchen beschrieben.Further embodiments of the invention are described in the subclaims.

Im folgenden wird die Erfindung anhand je eines Ausführungsbeispiels unter Bezugnahme auf jeweils eine Zeichnung näher erläutert.In the following the invention will be explained in more detail with reference to an embodiment with reference to a respective drawing.

Es zeigen:

Fig. 1
einen integral beschaufelten Rotorträger einer Gasturbine und
Fig. 2
ein Ausführungsbeispiel einer Vorrichtung zum lokalen Beschichten eines Bauteils, mit dem das Verfahren zum lokalen Entschichten von Bauteilen durchgeführt werden kann.
Show it:
Fig. 1
an integrally bladed rotor carrier of a gas turbine and
Fig. 2
An embodiment of an apparatus for locally coating a component, with which the method for local stripping of components can be performed.

Fig. 1 zeigt einen integral beschaufelten Rotor 1 einer Gasturbine bzw. eines Flugtriebwerks, an dessen Umfangsfläche 2 eine Vielzahl von Schaufeln 3 integral vorgesehen sind. Der Rotor 1 ist ein metallisches Bauteil. Der Rotor 1 und die Schaufeln 3 bestehen vorliegend aus einer Titanlegierung. Die Schaufeln 3 sind an ihren Schaufelspitzen 4 mit (nicht dargestellten) Schaufelspitzenpanzerungen versehen, die Hartpartikel enthalten. Beim Betrieb der Gasturbine können lokale Beschädigungen dieser Schaufelspitzenpanzerungen an einzelnen Schaufeln 3 auftreten.Fig. 1 shows an integrally bladed rotor 1 of a gas turbine or an aircraft engine, on whose peripheral surface 2, a plurality of blades 3 are integrally provided. The rotor 1 is a metallic component. The rotor 1 and the blades 3 in the present case consist of a titanium alloy. The blades 3 are provided at their blade tips 4 with (not shown) blade tip armor containing hard particles. When operating the Gas turbines may cause local damage to these blades tip armor 3 on individual blades.

In einer Ausgestaltung des Verfahrens zum lokalen Entschichten wird der Rotor 1 in einer (nicht gezeigten) Halteeinrichtung gehalten und so positioniert, dass der zu entschichtende Bereich der Schaufelspitzenpanzerung einer Schaufel 4 mit einem Entschichtungsflüssigkeit enthaltenden Medium in Kontakt gebracht, mit Entschlchtungsflüssigkeit benetzt und in einem elektrochemischen Vorgang entschichtet wird. Als Entschichtungsflüssigkeit wird verdünnte Schwefelsäure eingesetzt. Das Medium ist in eine Aufnahmeeinrichtung eingesetzt, deren Form der Schaufelspitze 4 so angepasst ist, dass diese vollständig von dem die Schwefelsäure enthaltenden Medium bedeckt ist Das Medium besteht vorliegend aus einem synthetischen Fasermaterial.In one embodiment of the method for local stripping, the rotor 1 is held in a holding device (not shown) and positioned so that the area of the blade tip armor of a blade 4 to be stripped is brought into contact with a medium containing stripping liquid, wetted with desquamizing liquid and electrochemically Process is stripped. As decoating liquid dilute sulfuric acid is used. The medium is inserted into a receiving device whose shape is adapted to the blade tip 4 so that it is completely covered by the medium containing the sulfuric acid. The medium consists in the present case of a synthetic fiber material.

Die Vorrichtung zur Durchführung des Verfahrens zum lokalen Entschichten des Rotors 1 umfaßt eine (nicht dargestellte) Stromquelle, an die der Rotor 1 anodisch angeschlossen ist. Die Vorrichtung umfaBt ferner eine Kathode aus platiniertem Titan, die ebenfalls das Medium mit der Entschichtungsflüsslgkeit kontaktiert. Das elektrochemische Entschichten erfolgt bei Raumtemperatur unter Anlegen einer Spannung kleiner 10 Volt über einen Zeitraum von 24 bis 48 Stunden. Bei Erhöhung der Temperatur der Entschichtungsflüssigkeit mit einer Wärmequelle auf 40 bis 60 °C verkürzt sich bei gleichen Randbedingungen der Zeitraum auf 12 bis 15 Stunden. Dabei wird dem Medium kontinuierlich als Elektrolyt dienende Entschichtungsflüssigkeit zugeführt, die den zu entschichtenden Bereich an der Schaufelspitze 4 der Schaufel 3 benetzt und ein lokales Auflösen der beschädigten Schaufelspitzenpanzerung bewirkt.The device for carrying out the method for local stripping of the rotor 1 comprises a (not shown) power source to which the rotor 1 is connected anodically. The apparatus further includes a platinum-plated titanium cathode which also contacts the media with the decoating fluid. The electrochemical stripping takes place at room temperature while applying a voltage of less than 10 volts over a period of 24 to 48 hours. Increasing the temperature of the decoating liquid with a heat source to 40 to 60 ° C shortens under the same boundary conditions, the period to 12 to 15 hours. In this case, the medium is continuously supplied as an electrolyte serving Entschichtungsflüssigkeit, which wets the area to be debated on the blade tip 4 of the blade 3 and causes a local dissolution of the damaged blade tip armor.

Durch Vorsehen mehrerer Aufnahmeeinrichtungen, die jeweils das Medium mit dem Elektrolyten Schwefelsäure enthalten, können an mehreren Schaufeln 3 gleichzeitig beschädigte Schaufelspitzenpanzerungen entfernt werden.By providing a plurality of receptacles, each containing the medium with the electrolyte sulfuric acid, simultaneously damaged blade tip armor can be removed on several blades 3.

Fig. 2 zeigt ein Ausführungsbeispiel mit einer Einzelschaufel 5, die mit ihrem Schaufelfuß 6 zusammen mit einer Vielzahl weiterer Schaufeln am Umfang eines Schaufelträgers einer Gasturbine lösbar befestigt wird. Die Einzelschaufel 5 (oder andere lokal zu entschichtende Bauteile) besteht aus einer Ti-Basis-Legierung. Alternativ könnte die Einzelschaufel 5 z.B. auch aus einer Ni- oder Co-Basis-Legierung bestehen. Die Schaufel 5 weist an ihrer Schaufelspitze 7 eine Beschichtung in Form einer Schaufelspitzenpanzerung, die Hartpartikel aufweist, auf.Fig. 2 shows an embodiment with a single blade 5, which is releasably secured with its blade root 6 together with a plurality of further blades on the circumference of a blade carrier of a gas turbine. The individual blade 5 (or other components to be locally coated) consists of a Ti-based alloy. Alternatively, the individual blade 5, for example also consist of a Ni or Co base alloy. The blade 5 has at its blade tip 7 a coating in the form of a blade tip armor having hard particles, on.

Zum elektrochemischen Entschichten dieser im Betrieb zumindest teilweise beschädigten Schaufelspitzenpanzerung wird eine (nicht gezeigte) Stromquelle und eine Kathode 8 vorgesehen. Die Einzelschaufel 5 wird über den Kontakt 9 anodisch an der Stromquelle angeschlossen. Eine Aufnahmeeinrichtung 10 für das Medium weist einen Zulauf 11 für eine Entschichtungsflüssigkeit, die ein Elektrolyt ist, auf im Inneren der Aufnahmeeinrichtung 10 ist das den Elektrolyten aufnehmende, saugfähige Medium vorgesehen, das sowohl mit der Schaufel 5 als auch der Kathode 8 in Kontakt steht. Das elektrochemische Entschichten erfolgt durch Anlegen einer Spannung bei Raumtemperatur über einen Zeitraum von 12 bis 48 Stunden. Ober den Zulauf 11 wird dem saugfähigen Medium ständig verdünnte Schwefelsäure als Elektrolyt zugeführt, welche sowohl den zu entschichtenden Bereich an der Schaufelspitze 7 ebenso wie die Kathode 8 benetzt. Über den Ablauf 12 wird der Aufnahmeeinrichtung 10 bzw. dem saugfähigen Medium Flüssigkeit entnommen.For electrochemical stripping of this blade tip armor, which is at least partially damaged during operation, a current source (not shown) and a cathode 8 are provided. The individual blade 5 is connected via the contact 9 anodically connected to the power source. A receptacle 10 for the medium has an inlet 11 for a Entschichtungsflüssigkeit, which is an electrolyte, on the inside of the receiving device 10, the electrolyte-receiving, absorbent medium is provided, which is in contact with both the blade 5 and the cathode 8. The electrochemical stripping is carried out by applying a voltage at room temperature over a period of 12 to 48 hours. Dilute sulfuric acid as electrolyte, which wets both the area to be stratified on the blade tip 7 and the cathode 8, is constantly supplied to the absorbent medium via the inlet 11. About the flow 12 of the receiving device 10 and the absorbent medium liquid is removed.

Bei sämtlichen Ausgestaltungen des Verfahrens werden ausschließlich die beschichteten Bereiche des Bauteils mit der elektrochemisch aktiven Entschichtungsflüssigkeit in Kontakt gebracht, so dass die unbeschichteten Bauteilbereiche ohne zusätzliche Abdeckung keinem Oberflächenangriff ausgesetzt sind. Durch Vorsehen mehrerer, das saugfähige bzw. flüssigkeitsaufnehmende Medium enthaltender Aufnahmeeinrichtungen können sämtliche beschädigte Schaufelspitzenpanzerungen eines integral beschaufelten Rotors in einem Verfahrensablauf elektrochemisch entschichtet werden.In all embodiments of the method, only the coated regions of the component are brought into contact with the electrochemically active decoating liquid, so that the uncoated component regions are not exposed to any surface attack without additional covering. By providing a plurality of receiving devices containing the absorbent or liquid-receiving medium, all damaged blade tip armor of an integrally bladed rotor can be electrochemically stripped in a process sequence.

Claims (23)

  1. A method for the local removal of coatings from components, in which method a component (1, 5) which is provided, at least in certain sections, with a coating is made available, an absorbent medium is made available, the medium is supplied with a coating-removing liquid and the medium containing the coating-removing liquid is brought into contact with that region of the component (1, 5) from which the coating is to be removed, characterised in that the coating is removed from the component (1, 5) electrochemically by contact with the coating-removing liquid, the component (1, 5) begin connected anodically or pulsed anodically/cathodically and a cathode, which is at a distance from the component (1, 5), is made available and brought into contact with the coating-removing liquid.
  2. A method according to claim 1, characterised in that cotton wool or a sponge or a porous material is made available as the medium.
  3. A method according to claim 2, characterised in that the porous material is ceramic or synthetic.
  4. A method according to one of the preceding claims, characterised in that the coating-removing liquid is continuously fed to the medium and liquid is drained off from the medium.
  5. A method according to one of the preceding claims, characterised in that contact between the component (1, 5) and the coating-removing liquid is maintained over a period.
  6. A method according to claim 5, characterised by a period of a few minutes to 48 hours.
  7. A method according to claim 5 or 6, characterised by a period of 12 to 48 hours.
  8. A method according to one of the preceding claims, characterised in that the medium is positioned and held in a receptacle.
  9. A method according to claim 8, characterised in that the shape of the receptacle is constructed in a manner corresponding to the shape of the component (1, 5) in that region of the latter from which the coating is to be removed.
  10. A method according to claim 8 or 9, characterised in that the receptacle is constructed with at least one inlet and at least one outlet for liquid.
  11. A method according to one of the preceding claims, characterised in that an acid or an alkaline solution or a saline solution or a mixture of these is made available as the coating-removing liquid.
  12. A method according to claim 11, characterised in that hydrochloric acid or sulphuric acid or a mixture of these is made available as the acid.
  13. A method according to one of the preceding claims, characterised in that a metal or ceramic gas-turbine component is made available as the component (1, 5) from which the coating is to be removed.
  14. A method according to claim 13, characterised in that the gas-turbine component is a blade (5) or an integrally bladed rotor-carrier (1).
  15. A method according to one of the preceding claims, characterised in that the coating-removing liquid is heated above room temperature.
  16. A method according to claim 15, characterised in that the coating-removing liquid is heated to a temperature above 40°C.
  17. A method according to claim 15 or 16, characterised in that the coating-removing liquid is heated to a temperature in the region of 40 to 60°C.
  18. A method according to one of the preceding claims, characterised in that the coating is blade-tip armouring.
  19. A method according to one of the preceding claims, characterised in that the medium and that region of the component (1, 5) from which the coating is to be removed are moved relative to one another.
  20. A device for the local removal of coatings from components, the device having at least one holding arrangement for a component (1,5) that is provided, at least in certain sections, with a coating, and having at least one receiving arrangement (10) for an absorbent medium containing a coating-removing liquid, wherein the holding and/or receiving arrangement(s) can be so positioned that the medium containing the coating-removing liquid makes contact with that region of the component (1, 5) from which the coating is to be removed, characterised by a current source to which the component is connected anodically or is connected anodically/cathodically by pole reversal, and a cathode (8) which makes contact with the medium.
  21. A device according to claim 20, characterised in that the receiving arrangement (10) has at least one inlet (11) for the coating-removing liquid and at least one outlet (12) for liquid.
  22. A device according to claim 20 or 21, characterised by a number of receiving arrangements (10) for the simultaneous removal of a number of coatings or regions of coatings from a component or a number of components (1, 5).
  23. A device according to one of claims 20 to 22, characterised by a heat source for heating the coating-removing liquid.
EP02740263A 2001-06-14 2002-04-19 Method and device for locally removing coatings from parts Expired - Lifetime EP1397533B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10128507A DE10128507B4 (en) 2001-06-14 2001-06-14 Use of a device for the chemical or electrochemical machining of components
DE10128507 2001-06-14
PCT/DE2002/001447 WO2002103088A1 (en) 2001-06-14 2002-04-19 Method and device for locally removing coatings from parts

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EP1397533A1 EP1397533A1 (en) 2004-03-17
EP1397533B1 true EP1397533B1 (en) 2007-10-24

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EP (1) EP1397533B1 (en)
CA (1) CA2450259C (en)
DE (2) DE10128507B4 (en)
WO (1) WO2002103088A1 (en)

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Publication number Publication date
DE50211111D1 (en) 2007-12-06
EP1397533A1 (en) 2004-03-17
US20040244910A1 (en) 2004-12-09
DE10128507B4 (en) 2008-07-17
CA2450259C (en) 2010-02-09
CA2450259A1 (en) 2002-12-27
DE10128507A1 (en) 2003-01-16
WO2002103088A1 (en) 2002-12-27
US7513986B2 (en) 2009-04-07

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