EP0318886B1 - Procédé de décapage électrolytique d'une couche protectrice, ayant une haute teneur en chromium et nickel et/ou cobalt, recouvrant un substrat d'un objet fait en superalliage - Google Patents

Procédé de décapage électrolytique d'une couche protectrice, ayant une haute teneur en chromium et nickel et/ou cobalt, recouvrant un substrat d'un objet fait en superalliage Download PDF

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Publication number
EP0318886B1
EP0318886B1 EP88119777A EP88119777A EP0318886B1 EP 0318886 B1 EP0318886 B1 EP 0318886B1 EP 88119777 A EP88119777 A EP 88119777A EP 88119777 A EP88119777 A EP 88119777A EP 0318886 B1 EP0318886 B1 EP 0318886B1
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Prior art keywords
parts
protective layer
electrolyte
weight
following composition
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EP88119777A
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German (de)
English (en)
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EP0318886A1 (fr
Inventor
Vladimir Sova
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BBC Brown Boveri AG Switzerland
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BBC Brown Boveri AG Switzerland
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    • 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
    • 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

Definitions

  • the blade is a critical component, with protective layers against erosion, wear, corrosion and oxidation becoming more important at high temperatures.
  • the protective layer usually has a shorter lifespan than the core material of the blade, which is why the renewability of the former is becoming increasingly important.
  • the invention relates to the further development of methods for repairing, repairing and renewing components of thermal machines which have been rendered unusable by erosion, wear, corrosion, oxidation or mechanical damage and are provided with protective layers.
  • the old existing protective layer must first be removed, which can basically be done mechanically or chemically.
  • the electrochemical method as a reverse process to the galvanic coating has a special position.
  • it relates to a method for the electrolytic detachment of a surface protective layer having a high Cr and Ni and / or Co content from the base body of a component consisting of a nickel or cobalt-based superalloy.
  • Electrolytic dissolution has hitherto not been practically used for such alloys.
  • Some methods are known for removing metals from their substrates by reversing the method of electroplating.
  • US-A-2 907 700 it is known to electrolytically remove coatings of metals (Ag, Ni, Cd, Zn, In) from a plutonium substrate.
  • Sulfuric acid or sodium phosphate solution is used as the electrolyte.
  • An electrolytic process is known from DE-B-21 46 828 for detaching metal coatings (Cr, Au, Cd, Cu, Ag, Zn, Sn, Ni) from stainless Cr / Ni steel.
  • Bromine-containing solutions of nitrates, acetates, chlorides etc. are used as electrolytes.
  • the attack on the substrate is said to be low.
  • coatings of metals Ni, Cr, Zn, Sn, Cu, Cd, Ag
  • nitric acid or nitrate-containing solutions with iodine content as electrolytes, to which organic chlorine compounds are additionally added will.
  • the invention is based on the object of specifying a method for detaching a surface protection layer based on a Ni and / or Co alloy with a high Cr content from the base body of a component, which consists of a chromium-containing Ni and / or Co base alloy.
  • the surface layer should be completely removed without the material of the base body being attacked, removed or damaged or its chemical-physical properties and its behavior with regard to compatibility being impaired or changed, particularly when a surface protective layer is subsequently reapplied (renewed).
  • 1 shows a schematic cross section through the active part of an electrolytic cell for carrying out the method.
  • 1 is the cathode (usually a sheet made of corrosion-resistant Cr / Ni steel), 2 the electrolyte (indicated by horizontal lines), 3 the anode consisting of the base body and surface protection layer.
  • the base body (substrate) 4 consists of a nickel or cobalt-based superalloy, which is usually present as an unchanged part 5 (core material).
  • a diffusion zone 6 is located in the base body 4 at the boundary with the surface protective layer 7.
  • the surface protection layer 7 in turn is composed of an originally unchanged part 8 and a diffusion zone 9.
  • the latter generally forms after the protective layer 7 has been applied by diffusion annealing in production, but at the latest when the high temperatures in operation are reached. It is usually characterized by a depletion of chromium and an enrichment in nickel.
  • the main ions present in the present example H+; Ni2+; Co2+, NO 2nd 3rd ⁇
  • the electrochemical attack is first carried out on the surface of the protective layer 7 by NO 2nd 3rd ⁇ Ions, which mainly release the nickel (through with NO 2nd 3rd ⁇ And Ni2+ marked arrows). This loosens the protective layer 7, which is indicated by the formation of the pores 10.
  • the attack of the electrolyte can be carried forward deeper inside the protective layer 7.
  • the chromium is mainly oxidized by the oxidizing attack and has a passivating effect.
  • the Cr2O3 particles formed fall out successively mechanically from the loosened dressing (indicated by an arrow).
  • the chromium-depleted and nickel-enriched diffusion zone 9 of the surface protection layer 7, which is electrochemically negative compared to the neighboring regions, is preferably attacked by oxidizing the chromium and mechanically falling out as Cr2O3 (indicated by the arrow).
  • the diffusion zone 9 of the surface protective layer 7 sets itself electronegatively with respect to the regions adjacent to it (indicated by -).
  • Curve “a” shows the course of the chromium content
  • curve “b” that of the nickel content as a function of depth x.
  • the values are highly schematic mean values of numerous samples. The course can assume other values quantitatively, but always shows the same picture of the Cr depletion and the Ni enrichment in the diffusion zone 9.
  • FIG. 3 shows a flow diagram in the form of a block diagram of a possible embodiment of the method.
  • the diagram is self-explanatory and requires no further explanation.
  • Electrolytic separation processes are based on the difference in the separation or dissolution potential of the components and / or phases involved.
  • the potentials of the base body (substrate) 4 and the surface protective layer 7 are normally close together, since they are each nickel alloys with chromium contents that do not differ significantly from one another.
  • the protective layer 7 can be detached without simultaneously attacking the base body 4, since the ions are the same.
  • the thermal treatment of coated components even with very related alloys for the protective layer and base body, causes significant differences in concentration and potential due to diffusion. Interdiffusion forms an intermediate layer (diffusion zone 9) which (in an oxidizing electrolysis bath) assumes a negative electrochemical potential with respect to its surroundings and is therefore more easily attacked and detached.
  • the core material of the gas turbine blade consisted of a nickel-based wrought superalloy with the trade name Nimonic 80A with the following composition: Cr 19.5% by weight Al 1.4% by weight Ti 2.4% by weight Zr 0.06% by weight Mn 0.30% by weight Si 0.30% by weight B 0.003% by weight C. 0.06% by weight Ni rest
  • the surface protective layer with a thickness of 100 to 150 ⁇ m had been applied to the core material by plasma spraying and had the following composition: Cr 17% by weight Si 4.5% by weight Fe 4.5% by weight B 3.5% by weight Ni rest
  • the gas turbine blade was cleaned by placing it in a solution of 20% NaOH at a temperature of 100 ° C. for 2 hours, rinsing it and treating it again in concentrated HCl. Then the shovel was brushed with a steel brush.
  • the bucket was activated. For this purpose, it was again placed in 20% NaOH and then placed in concentrated HCl for 2 h.
  • a sheet made of corrosion-resistant 18 Cr / 8 Ni steel served as the cathode.
  • Electrolysis was then carried out under a cell voltage of 1000 mV at an anodic current density of 0.2 A / dm 2 for a period of 144 h.
  • the bath temperature was 25 ° C.
  • the scoop was removed from the bath, rinsed, brushed and dried.
  • the core material had the trade name IN 939 from INCO, was a nickel-based casting superalloy and had the following composition: Cr 22.4% by weight Co 19.0% by weight Ta 1.4% by weight Nb 1.0% by weight Al 1.9% by weight Ti 3.7% by weight Zr 0.1% by weight C. 0.15% by weight Ni rest
  • the approx. 120 ⁇ m average surface protection layer had the following composition: Cr 49% by weight Si 6% by weight Fe 2% by weight Ni rest
  • a sheet made of corrosion-resistant Cr-Ni steel served as the cathode.
  • the electrolytic detachment of the surface protective layer was carried out under a cell voltage of 1100 mV at an anodic current density of 0.2 A / dm 2 for 120 h.
  • the bath temperature was 20 ° C.
  • the dimensions of the airfoil were the same as in example 1.
  • the core material of the airfoil consisted of a nickel-based casting superalloy with the trade name IN 738 from INCO with the following composition: Cr 16.0% by weight Co 8.5% by weight Mon 1.75% by weight W 2.6% by weight Ta 1.75% by weight Nb 0.9% by weight Al 3.4% by weight Ti 3.4% by weight Zr 0.1% by weight B 0.01% by weight C. 0.11% by weight Ni rest
  • the protective layer had an average thickness of 100 ⁇ m and had the following composition: Cr 20% by weight Fe 2% by weight B 3% by weight Ni rest
  • Example 2 As in Example 1, a sheet made of corrosion-resistant 18/8 steel was used as the cathode.
  • the cell voltage was 1050 mV, the current density at the anode was 0.2 A / dm2. Electrolysis was carried out at a bath temperature of 22 ° C. for 140 h.
  • the core material of a gas turbine blade with the blade dimensions according to Example 2 consisted of a nickel-based wrought superalloy with the trade name IN 105 from INCO with the following composition: Cr 13.5% by weight Co 18% by weight Al 4.2% by weight Mon 4.5% by weight Ti 0.9% by weight Mn 1% by weight Si 1% by weight C. 0.2% by weight Ni rest
  • the protective layer had an average thickness of 140 ⁇ m and had the following composition: Cr 10% by weight Si 6% by weight Fe 4% by weight Co 20% by weight Ni rest
  • a sheet made of corrosion-resistant 18 Cr / 8 Ni steel served as the cathode. It was electrolyzed under a cell voltage of 1100 mV with an anodic current density of 0.18 A / dm2 for 150 h. Bath temperature 24 ° C. After the treatment, the component was rinsed, brushed and dried in the usual way.
  • a sheet of corrosion-resistant 18/8 steel served as the cathode.
  • the invention is not restricted to the exemplary embodiments.
  • the method relates specifically to the electrolytic detachment of surface protective layers with a high Cr content and with a high Ni or Co content or at the same time a high Ni and Co content. It is therefore a matter of high-chromium nickel or cobalt-based alloys or those based on a nickel / cobalt mixture.
  • Activation is carried out by 20% NaOH and subsequent immersion in concentrated HCl for 2 h at 40 ° C.
  • the component is then placed as an anode in an electrolyte that contains oxygen-releasing, oxidizing components. There it is subjected to electrolysis until the surface protective layer has completely dissolved and fallen off.
  • the surface protective layer is optionally pretreated by grinding and / or sand or shot peening before electrolysis. In stubborn cases, pulsed cell voltage is used.
  • the stationary cell voltage is intermittent at intervals of 10 to 30 min. over a period of 5 to 10 seconds, an additional overvoltage of 1500 to 2000 mV is superimposed on the cell voltage.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Electrochemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)

Claims (7)

  1. Procédé pour la dissolution électrolytique d'un film protecteur formant couche superficielle (7) présentant un contenu élevé de Cr et Ni et/ou Co, d'une substance de base (4) d'un élément composé d'un super-alliage à base de nickel ou de cobalt, caractérisé en ce que l'élément recouvert d'un film protecteur (7) est d'abord plongé, pour activation, dans une solution de NaOH à 20% et ensuite à 40 °C, pendant 2 heures, dans une solution de HCl concentré, et en ce que l'élément est placé, avec son film protecteur activé (7), en tant qu'anode dans un électrolyte aqueux (2), qui contient en outre un acide oxygéné oxydant et le cas échéant des sels d'un tel acide et est soumis a électrolyse jusqu'à totale dissolution et complète séparation du film protecteur (7).
  2. Procédé selon la revendication 1, caractérisé en ce que l'électrolyte (2) a la composition suivante :
       30 parties de HNO₃ concentré
       2 parties de Ni(NO₃)₂
       1 partie de Co(NO₃)₂
       70 parties de H₂O.
  3. Procédé selon la revendication 1, caractérisé en ce que le film protecteur (7) est préalablement traité par ponçage et/ou jets de sable ou de billes avec d'être plongé dans l'électrolyte (2) et que ce dernier a la composition suivante :
       10 parties de HNO₃ concentré
       5 parties de AgNO₃
       90 parties de H₂O.
  4. Procédé selon la revendication 1, caractérisé en ce que l'électrolyte (2) a la composition suivante :
       20 parties de CrO₃
       80 parties de H₂O.
  5. Procédé selon la revendication 1, caractérisé en ce que l'électrolyte (2) a la composition suivante :
       10 parties de H₂SO₄
       10 parties de Na₂S₂O₈
       80 parties de H₂O.
  6. Procédé selon la revendication 1, caractérisé en ce que l'électrolyte (2) a la composition suivante :
       30 parties de HNO₃
       70 parties de H₂O
       10 g/l de AgNO₃
       20 g/l de NH₄HF₂.
  7. Procédé selon la revendication 1, caractérisé en ce que pendant le processus d'électrolyse, on superpose une surtension additionnelle à la tension cellulaire stationnaire, de façon intermittente à des intervalles de 10 à 30 min et pendant une durée de chaque fois 5 à 10 sec.
EP88119777A 1987-12-01 1988-11-28 Procédé de décapage électrolytique d'une couche protectrice, ayant une haute teneur en chromium et nickel et/ou cobalt, recouvrant un substrat d'un objet fait en superalliage Expired - Lifetime EP0318886B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH467387 1987-12-01
CH4673/87 1987-12-01

Publications (2)

Publication Number Publication Date
EP0318886A1 EP0318886A1 (fr) 1989-06-07
EP0318886B1 true EP0318886B1 (fr) 1992-07-22

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EP88119777A Expired - Lifetime EP0318886B1 (fr) 1987-12-01 1988-11-28 Procédé de décapage électrolytique d'une couche protectrice, ayant une haute teneur en chromium et nickel et/ou cobalt, recouvrant un substrat d'un objet fait en superalliage

Country Status (3)

Country Link
US (1) US4894130A (fr)
EP (1) EP0318886B1 (fr)
DE (1) DE3873038D1 (fr)

Cited By (1)

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Publication number Priority date Publication date Assignee Title
US6969457B2 (en) 2002-10-21 2005-11-29 General Electric Company Method for partially stripping a coating from the surface of a substrate, and related articles and compositions

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GB9700819D0 (en) * 1997-01-16 1997-03-05 Gkn Westland Helicopters Ltd Method of and apparatus for removing a metallic component from attachmet to a helicopter blade
US6176999B1 (en) * 1998-12-18 2001-01-23 United Technologies Corporation Feedback controlled stripping of airfoils
US6352636B1 (en) * 1999-10-18 2002-03-05 General Electric Company Electrochemical system and process for stripping metallic coatings
US6428683B1 (en) * 2000-12-15 2002-08-06 United Technologies Corporation Feedback controlled airfoil stripping system with integrated water management and acid recycling system
US6497968B2 (en) * 2001-02-26 2002-12-24 General Electric Company Oxidation resistant coatings for molybdenum silicide-based composite articles
DE10259364A1 (de) * 2002-12-18 2004-07-08 Siemens Ag Verfahren zum Entfernen von zumindest einem Oberflächenbereich eines Beuteils
DE10259363A1 (de) * 2002-12-18 2004-07-08 Siemens Ag Verfahren zum Entfernen von zumindest einem Oberflächenbereich eines Bauteils
DE102004002763A1 (de) * 2004-01-20 2005-08-04 Mtu Aero Engines Gmbh Verfahren zum elektrochemischen Entschichten von Bauteilen
EP1870497A1 (fr) * 2006-06-23 2007-12-26 Siemens Aktiengesellschaft Procédé d'enlèvement électrochimique d'un revêtement métallique d'un substrat
EP1890004A1 (fr) 2006-08-08 2008-02-20 Siemens Aktiengesellschaft Procédé pour la production d'un revêtement à partir du matériau d'un revêtement recyclé
DE102006044416A1 (de) * 2006-09-18 2008-03-27 Siemens Ag Verfahren zum elektrochemischen Be- oder Entschichten von Bauteilen
EP2053145A1 (fr) * 2007-10-19 2009-04-29 Siemens Aktiengesellschaft Procédé d'enlèvement d'une couche métallique à l'aide de FIC dans une étape intermédiaire
US7875200B2 (en) * 2008-05-20 2011-01-25 United Technologies Corporation Method for a repair process
EP2166125A1 (fr) * 2008-09-19 2010-03-24 ALSTOM Technology Ltd Procédé pour la configuration des services d'un réseau personnel
CN110670115B (zh) * 2019-09-30 2021-11-30 飞而康快速制造科技有限责任公司 一种适用于沉积态gh3536合金的腐蚀剂及其腐蚀方法
CN114075690B (zh) * 2020-08-14 2022-11-22 中国科学院金属研究所 一种电化学退除MCrAlY涂层的方法
CN115573023A (zh) * 2022-09-23 2023-01-06 中国航发哈尔滨东安发动机有限公司 一种铝合金表面铬层去除方法

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Publication number Priority date Publication date Assignee Title
US6969457B2 (en) 2002-10-21 2005-11-29 General Electric Company Method for partially stripping a coating from the surface of a substrate, and related articles and compositions

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Publication number Publication date
DE3873038D1 (de) 1992-08-27
US4894130A (en) 1990-01-16
EP0318886A1 (fr) 1989-06-07

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