(19)
(11)EP 2 116 691 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
02.05.2018 Bulletin 2018/18

(21)Application number: 09250802.7

(22)Date of filing:  23.03.2009
(51)International Patent Classification (IPC): 
F01D 5/00(2006.01)
B23K 9/04(2006.01)

(54)

Method for repairing a stator assembly of a gas turbine engine and gas turbine engine component

Verfahren zum Reparieren einer Statoranordnung einer Gasturbine sowie Gasturbinenbauteil

Procédé de réparation d'un ensemble de stator d'une turbine à gaz et composant d'une turbine à gaz


(84)Designated Contracting States:
DE GB

(30)Priority: 05.05.2008 US 114836

(43)Date of publication of application:
11.11.2009 Bulletin 2009/46

(73)Proprietor: United Technologies Corporation
Farmington, CT 06032 (US)

(72)Inventors:
  • Hasselberg, Timothy P.
    Middletown, CT 06457 (US)
  • Rose, William M.
    West Brookfield Maine 01585 (US)
  • Rutz, David A.
    Glastonbury, CT 06033 (US)

(74)Representative: Hull, James Edward et al
Dehns St. Bride's House 10 Salisbury Square
London EC4Y 8JD
London EC4Y 8JD (GB)


(56)References cited: : 
EP-A2- 1 621 816
US-A- 4 657 171
US-A- 5 553 370
US-B1- 6 568 077
WO-A1-2006/125234
US-A- 4 903 888
US-B1- 6 468 367
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND OF THE DISCLOSURE



    [0001] This disclosure relates to a method for repairing a worn surface of a gas turbine engine component.

    [0002] Gas turbine engines typically include a compressor section, a combustor section and a turbine section. Air is pressurized in the compressor section, and is mixed with fuel and burned in the combustor section to energize and expand the air and accelerate the airflow into the turbine section. The hot combustion gases that exit the combustor section flow downstream through the turbine section, which extracts kinetic energy from the expanding gases and converts the energy into mechanical power to drive the compressor section.

    [0003] The compressor section of the gas turbine engine typically includes multiple compression stages to obtain high pressure levels. Each compressor stage consists of alternating rows of stator assemblies that include stationary airfoils called stator vanes followed by rotor assemblies including moving airfoils called rotor blades. The stator vanes direct incoming airflow to the next set of rotor blades.

    [0004] During operation, portions of the stator assemblies may become worn as a result of rubbing that occurs between the stator assemblies and surrounding components of the gas turbine engine. The rubbing may wear and stress portions of the stator assemblies.

    [0005] Replacing an entire stator assembly is expensive due to material and machining costs. Accordingly, stator assemblies are often repaired instead of replaced. The repairs generally involve removing the worn surfaces of the stator assembly, and then restoring them with weld filler or similar material on a surface of the component. The material build-up is machined to an appropriate shape to form a restored surface.

    [0006] A known gas tungsten arc (GTA) welding process is generally used to repair worn surfaces of gas turbine engine components. The GTA welding process may be performed manually or robotically to deposit weld material on a worn area of the component. However, GTA welding is a relatively slow build-up process that, because of the inherent heat input, can cause unacceptable component distortion. These aspects have prompted the aerospace industry to seek faster and less heat intensive welding processes,

    [0007] A prior art method, having the features of the preamble of claim 1, is disclosed in US-6468367. Other prior art methods are shown in US-5553370 and US-4903888. CMT (Cold Metal Transfer) welding is disclosed in chapter "Weld repair of turbine blades" in the MSc thesis by Benoit Courtot, "Repair welding of high temperature nickel superalloy castings", Cranfield University, 2007.

    SUMMARY OF THE INVENTION



    [0008] According to the present invention, there is provided a method as claimed in claim 1 and a gas turbine engine component as claimed in claim 10.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0009] 

    Figure 1 is a schematic view of an example gas turbine engine;

    Figure 2 illustrates a gas turbine engine component including a worn surface;

    Figure 3 illustrates an example method for repairing the gas turbine engine component illustrated in Figure 2;

    Figure 4A shows an initial step in an example repair process;

    Figure 4B shows a subsequent step of the repair process; and

    Figure 4C illustrates yet another step in the repair process.


    DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT



    [0010] Figure 1 schematically illustrates an example gas turbine engine 10 that is circumferentially disposed about an engine centerline axis A. The gas turbine engine 10 includes (in serial flow communication) a fan section 12, a low pressure compressor 14, a high pressure compressor 16, a combustor section 18, a high pressure turbine 20, and a low pressure turbine 22. During operation, airflow is drawn into the gas turbine engine 10 by the fan section 12, and is pressurized in the low pressure compressor 14 and the high pressure compressor 16. Fuel is mixed with the pressurized air and combusted within the combustor section 18. The combustion gases are discharged through the high pressure turbine 20 and the low pressure turbine 22, which extract energy from the combustion gases for powering the compressor sections 14, 16 and the fan section 12.

    [0011] The low pressure compressor 14 and the high pressure compressor 16 include a plurality of alternating rows of rotor assemblies 24 having blades 26 and stator assemblies 28 including vanes 30. It should be understood that the various features and example illustrations presented herein are not limited to a gas turbine engine of this particular architecture. That is, the present disclosure is applicable to any engine architecture, and for any application.

    [0012] Figure 2 illustrates an example gas turbine engine component 15 having at least one worn surface 32. In this example, the gas turbine engine component 15 is a stator assembly 28 of the high pressure compressor 16. The stator assembly 28 includes a plurality of vanes 30 that extend between a radially inward honeycomb 34 and a radially outward flange 36. The flange 36 includes an outer diameter surface 38 and a plurality of featherseal slots 40 (one shown in Figure 2).

    [0013] The worn surfaces 32 may occur at any location of the stator assembly 28, including but not limited to, the flange 36, the outer diameter surface 38 and/or the featherseal slot 40. In one example, the worn surface 32 includes a crack in the outer diameter surface 38. The worn surfaces 32 may be caused by the rubbing, vibration and/or extreme temperatures that occur during gas turbine engine 10 operation. The worn surfaces 32 are repairable utilizing a gas metal arc welding operation, as is further discussed below. Although the disclosed examples are illustrated with respect to a stator assembly 28 of a high pressure compressor 16, it should be understood that the disclosed examples may be applied to any gas turbine engine component.

    [0014] Figure 3, with continued reference to Figures 1 and 2, illustrates an example method 100 for repairing a gas turbine engine component 15. The method 100 begins at step block 102 where a worn surface 32 of the gas turbine engine component 15 is removed. In one example, the worn surface 32 is removed by utilizing a machining operation. A person of ordinary skill in the art having the benefit of this disclosure would be able to select an appropriate machining operation for removal of the worn surfaces 32 of the gas turbine engine component 15. In one example, the worn surface 32 is machined down to remove any damaged portion of the gas turbine engine component 15 (See Figure 4A).

    [0015] Next, at step block 104, additional material is secured to the gas turbine engine component 15 utilizing gas metal arc welding, The gas metal arc welding includes cold metal transfer. Cold metal transfer is a process developed by the Fronius Corporation and is known. However, cold metal transfer has not been utilized to repair a worn surface of a gas turbine engine component 15, such as a stator assembly 28 of a high pressure compressor 16, for example. The additional material is secured to the gas turbine engine component 15 in an area of the removed worn surface 32.

    [0016] At step block 106, a portion of the additional material is removed from the gas turbine engine component 15. In one example, the portion of the additional material is removed via a machining operation. The additional material is removed down to a pre-defined dimension. In one example, the predefined dimension includes an original dimension of the gas turbine engine component.

    [0017] Figures 4A - 4C describe an example implementation of the method 100. Referring to Figure 4A, an initial step in the repair of the gas turbine engine component 15 includes machining the worn surface 32 down to a predefined dimension D. Machining the worn surface 32 down to the predefined dimension D includes removal of sufficient material to remove any damaged portion of the gas turbine engine component 15, in this example. The actual predefined dimension D will vary depending upon design specific parameters including, but not limited to, the degree of damage to the gas turbine engine component.

    [0018] As shown in Figure 4B, additional material 44 is secured to the gas turbine engine component 15 utilizing a gas metal arc welder 46, for example. In one example, the additional material 44 is secured to the gas turbine engine component with a manually controlled gas metal arc welder 46. In another example, the additional material 44 is secured using a robotically controlled gas metal arc welder 46. As described above, the gas metal arc welder 46 includes cold metal transfer. The additional material 44 is secured to a revealed area 48 of the gas turbine engine component 15. The revealed area 48 is provided by removal of the worn surface 32, in one example.

    [0019] Figure 4C illustrates removal of a portion of the additional material 44 from the gas turbine engine component 15. The additional material 44 is removed down to a predefined dimension D2 to provide a repaired section 50 of the gas turbine engine component 15. In one example, the predefined dimension D2 relates to an original dimension of the gas turbine engine component 15.

    [0020] The example gas metal arc welding operation of the present disclosure facilitates a low heat input, high deposition, and spatter free weld process for repairing worn surfaces of a gas turbine engine component. For example, the gas metal arc welding operation may be utilized to repair a worn surface of a stator assembly of a gas turbine engine.


    Claims

    1. A method for repairing a stator assembly (28) of a gas turbine engine, comprising the steps of:

    a) removing a worn surface (32) of the stator assembly to provide a revealed area; and

    b) securing additional material (44) to the revealed area of the stator assembly utilizing gas metal arc welding,

    characterised in that:

    the gas metal arc welding includes cold metal transfer; and

    said surface (32) is a flange (36) or a featherseal slot (40) of said stator assembly (28).


     
    2. The method as recited in claim 1, wherein said step a) includes the step of machining the worn surface (32) down to a predefined dimension (D).
     
    3. The method as recited in claim 2, wherein the step of machining the worn surface (32) down to the predefined dimension (D) includes removal of sufficient material to remove any damaged portion of the stator assembly (28).
     
    4. The method as recited in any preceding claim, wherein said step b) includes the step of securing the additional material (44) to the revealed area (48) of the stator assembly (28).
     
    5. The method as recited in any preceding claim, comprising the step of:

    c) removing a portion of the additional material (44).


     
    6. The method as recited in claim 5, wherein said step c) includes the step of machining the additional material (44) down to a predefined dimension.
     
    7. The method as recited in any preceding claim, wherein the stator assembly (28) is a component of a high pressure compressor (16) of the gas turbine engine (10).
     
    8. The method as recited in any preceding claim, wherein the additional material (44) is applied manually to the stator assembly (28).
     
    9. The method as recited in any of claims 1 to 7, wherein the additional material (44) is applied robotically to the stator assembly (28).
     
    10. A gas turbine engine component (15), comprising:

    a stator assembly (28) having at least one repairable surface (32); and

    a repaired section (50) of said stator assembly (28), wherein additional material (44) is deposited on said at least one repairable surface to fabricate said repaired section (50) using gas metal arc welding,

    characterised in that:

    the gas metal arc welding includes cold metal transfer; and

    said surface (32) is a flange (36) or a featherseal slot (40) of said stator assembly (28).


     
    11. The component as recited in claim 10, wherein said gas turbine engine component (15) is a high pressure compressor stator assembly (28).
     
    12. The method or component as recited in any preceding claim, wherein said surface (32) includes a crack in said stator assembly (28).
     


    Ansprüche

    1. Verfahren zum Reparieren einer Statoranordnung (28) einer Gasturbine, umfassend die folgenden Schritte:

    a) Entfernen einer abgenutzten Fläche (32) der Statoranordnung, um einen freigelegten Bereich bereitzustellen; und

    b) Befestigen von zusätzlichem Material (44) an dem freigelegten Bereich der Statoranordnung unter Verwendung von Schutzgas-Metall-Lichtbogenschweißen,

    dadurch gekennzeichnet, dass:

    das Schutzgas-Metall-Lichtbogenschweißen Kaltmetalltransfer beinhaltet; und

    die Fläche (32) ein Flansch (36) oder ein Federabdichtungsschlitz (40) der Statoranordnung (28) ist.


     
    2. Verfahren nach Anspruch 1, wobei der Schritt a) den Schritt des spanabhebenden Bearbeitens der abgenutzten Fläche (32) auf eine vordefinierte Abmessung (D) beinhaltet.
     
    3. Verfahren nach Anspruch 2, wobei der Schritt des spanabhebenden Bearbeitens der abgenutzten Fläche (32) auf die vordefinierte Abmessung (D) das Entfernen von genügend Material beinhaltet, um einen beschädigten Teil der Statoranordnung (28) zu entfernen.
     
    4. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Schritt b) den Schritt des Befestigens des zusätzlichen Materials (44) an dem freigelegten Bereich (48) der Statoranordnung (28) beinhaltet.
     
    5. Verfahren nach einem der vorhergehenden Ansprüche, umfassend den folgenden Schritt:

    c) Entfernen eines Teils des zusätzlichen Materials (44) .


     
    6. Verfahren nach Anspruch 5, wobei der Schritt c) den Schritt des spanabhebenden Bearbeitens des zusätzlichen Materials (44) auf eine vordefinierte Abmessung beinhaltet.
     
    7. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Statoranordnung (28) ein Bauteil eines Hochdruckverdichters (16) des Gasturbinentriebwerks (10) ist.
     
    8. Verfahren nach einem der vorhergehenden Ansprüche, wobei das zusätzliche Material (44) manuell auf die Statoranordnung (28) aufgebracht wird.
     
    9. Verfahren nach einem der Ansprüche 1 bis 7, wobei das zusätzliche Material (44) durch einen Roboter auf die Statoranordnung (28) aufgebracht wird.
     
    10. Gasturbinenbauteil (15), umfassend:

    eine Statoranordnung (28), die mindestens eine zu reparierende Fläche (32) aufweist; und

    einen reparierten Abschnitt (50) der Statoranordnung (28), wobei das zusätzliche Material (44) auf die mindestens eine zu reparierende Fläche aufgetragen wird, um unter Verwendung von Schutzgas-Metall-Lichtbogenschweißen den reparierten Abschnitt (50) zu erzeugen,

    dadurch gekennzeichnet, dass:

    das Schutzgas-Metall-Lichtbogenschweißen Kaltmetalltransfer beinhaltet; und

    die Fläche (32) ein Flansch (36) oder ein Federdichtungsschlitz (40) der Statoranordnung (28) ist.


     
    11. Bauteil nach Anspruch 10, wobei das Gasturbinenbauteil (15) eine Statoranordnung (28) eines Hochdruckverdichters ist.
     
    12. Verfahren oder Bauteil nach einem der vorhergehenden Ansprüche, wobei die Fläche (32) einen Riss in der Statoranordnung (28) beinhaltet.
     


    Revendications

    1. Procédé pour réparer un ensemble de stator (28) d'une turbine à gaz, comprenant les étapes suivantes :

    a) le retrait d'une surface usée (32) de l'ensemble de stator pour fournir une zone dévoilée ; et

    b) la fixation d'une matière supplémentaire (44) à la zone dévoilée de l'ensemble de stator en utilisant un soudage à l'arc sous gaz avec fil plein,

    caractérisé en ce que :

    le soudage à l'arc sous gaz avec fil plein inclut un transfert de métal froid ; et

    ladite surface (32) est une bride (36) ou une fente à languette d'étanchéité (40) dudit ensemble de stator (28).


     
    2. Procédé selon la revendication 1, dans lequel ladite étape a) inclut l'étape d'usinage de la surface usée (32) par enlèvement jusqu'à une dimension prédéfinie (D).
     
    3. Procédé selon la revendication 2, dans lequel l'étape d'usinage de la surface usée (32) par enlèvement jusqu'à la dimension prédéfinie (D) inclut le retrait de matière suffisante pour retirer toute portion endommagée de l'ensemble de stator (28).
     
    4. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite étape b) inclut l'étape de fixation de la matière supplémentaire (44) à la zone dévoilée (48) de l'ensemble de stator (28).
     
    5. Procédé selon l'une quelconque des revendications précédentes, comprenant l'étape suivante :

    c) le retrait d'une portion de la matière supplémentaire (44).


     
    6. Procédé selon la revendication 5, dans lequel ladite étape c) inclut l'étape d'usinage de la matière supplémentaire (44) par enlèvement jusqu'à une dimension prédéfinie.
     
    7. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'ensemble de stator (28) est un élément d'un compresseur haute pression (16) de la turbine à gaz (10).
     
    8. Procédé selon l'une quelconque des revendications précédentes, dans lequel la matière supplémentaire (44) est appliquée manuellement à l'ensemble de stator (28).
     
    9. Procédé selon l'une quelconque des revendications 1 à 7, dans lequel la matière supplémentaire (44) est appliquée de manière robotisée à l'ensemble de stator (28).
     
    10. Élément de turbine à gaz (15), comprenant :

    un ensemble de stator (28) ayant au moins une surface réparable (32) ; et

    une section réparée (50) dudit ensemble de stator (28), dans lequel une matière supplémentaire (44) est déposée sur ladite au moins une surface réparable pour fabriquer ladite section réparée (50) en utilisant un soudage à l'arc sous gaz avec fil plein,

    caractérisé en ce que :

    le soudage à l'arc sous gaz avec fil plein inclut un transfert de métal à froid ; et

    ladite surface (32) est une bride (36) ou une fente à languette d'étanchéité (40) dudit ensemble de stator (28).


     
    11. Élément selon la revendication 10, dans lequel ledit élément de turbine à gaz (15) est un ensemble de stator de compresseur haute pression (28).
     
    12. Procédé ou élément selon l'une quelconque des revendications précédentes, dans lequel ladite surface (32) inclut une fissure dans ledit ensemble de stator (28).
     




    Drawing














    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description