Method for joining blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors

A method is provided for joining blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors. A blade and a blade root or rotor disk that is to be joined to the blade are supplied, and provided with a thickening in sections that are to be joined together. The sections of the blade and the blade root or rotor disk that are to be joined together are machined so as to form recesses and; c) are then aligned relative to each other, opposite recesses defining at least one groove-shaped seam preparation. The blade and the blade root or rotor disk are joined in the area of the or each seam preparation by means of laser power build-up welding and the joined blade and blade root or rotor disk are machined so as to provide a gas turbine blade or an integrally bladed gas turbine rotor having a predefined geometrical profile.

FIELD OF THE INVENTION

The present invention relates to a method for joining blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors.

BACKGROUND

Gas turbines, such as aircraft engines, for example, have at least one compressor, as well as at least one turbine, the or each compressor, as well as the or each turbine having at least one stage, and the or each stage of each compressor, as well as of each turbine being constituted of a stationary guide vane ring, as well as of a rotating rotor blade ring. The rotor blades forming the or each rotating rotor blade ring each have an aerodynamically shaped blade, the blade of each rotor blade either being anchored by a blade root in corresponding recesses of a rotor disk, or being permanently joined to the rotor disk, forming an integrally bladed gas turbine rotor. Integrally bladed gas turbine rotors are also referred to as blisks (bladed disks) or blings (bladed rings).

The rotor blades of a gas turbine, in particular, are exposed to heavily oxidizing, corroding or also eroding conditions during operation of the gas turbine, so that they are subjected to substantial wear. Thus, the need may arise, for example, when working with integrally bladed rotors, to replace a damaged blade in order to repair the integrally bladed gas turbine rotor. This then requires joining a new blade to the rotor disk of the gas turbine rotor at the location where a damaged blade had been removed. When rebuilding integrally bladed gas turbine rotors, all of the blades must be joined to the rotor disk. When individual gas turbine blades are rebuilt, it is necessary to join a blade to a corresponding blade root.

The related art method provides for using linear friction welding or inductive high-frequency pressure welding to join blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors. Both linear friction welding, as well as inductive high-frequency pressure welding are costly, particularly when working with high-temperature resistant materials, and they pose risks in terms of process safety.

SUMMARY OF THE INVENTION

Against this background, an object of the present invention is to devise a novel method for joining blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors. For ease of reference, the term “blade support” is used herein to mean either a blade root or a rotor disk.

In accordance with an embodiment of the present invention, a method for joining blades to blade roots or rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors includes the steps of: a) prefabricating a blade and a blade root to be joined to the blade, or a rotor disk to be joined to the blade, the blade and the blade root or the rotor disk having a thickened region at portions of the same to be joined; b) machining the portions of the blade and blade support (i.e. the blade root or the rotor disk) to be joined together, to form recesses; c) subsequently mutually aligning the blade and the blade support to be joined to the blade, mutually opposing recesses delimiting at least one groove-shaped weld preparation; d) joining the blade and blade support in the area of the or each weld preparation by employing laser powder build-up welding; e) machining the mutually joined blade and blade support to prepare a gas turbine blade or an integrally bladed gas turbine rotor having a predefined geometric profile. In the case of a method for repairing gas turbine blades or integrally bladed gas turbine rotors, the blade support (i.e., the blade root or rotor disk) may be prefabricated in step (a) by performing laser powder build-up welding to form a thickened region at least in a separating region of a damaged blade, and separating the damaged blade from a gas turbine along the separating region to form the prefabricated blade support having a thickened region.

DETAILED DESCRIPTION

FIG. 1athrough1gclarify one specific embodiment of the method according to the present invention for joining blades to a rotor disk when repairing an integrally bladed gas turbine rotor. In accordance with the method of the present invention, the following procedure is used when repairing an integrally bladed gas turbine rotor:

FIG. 1ashows an integrally bladed gas turbine rotor10having a damaged blade11, the aim being to remove damaged blade11from a rotor disk12of gas turbine rotor10and to replace it with a new blade, in order to repair gas turbine rotor10shown inFIG. 1a. Before cutting off damaged blade11from rotor disk12of integrally bladed gas turbine rotor10, a thickened region13is prepared at least in the area of a later separation site by employing laser powder build-up welding both on the intake side, as well as on the thrust side of blade11, to ensure a most continuous or uniform possible thickness profile over the entire region of the separation site. Damaged blade11is subsequently separated from rotor disk12along parting cut14shown as a dashed line inFIG. 1a. The separation of damaged blade11from rotor disk12yields the structure shown inFIG. 1b, thickened region13produced beforehand by laser powder build-up welding extending in the area of a portion15of rotor disk12, where a new, prefabricated blade is to be attached in order to repair gas turbine rotor10.

The thus prepared portion15of rotor disk12, to which a new blade16(seeFIG. 1dthrough1g) is to be attached, is machined along the lines of the present invention in such a way that at least one recess17is formed in portion15. In this connection, in the exemplary embodiment ofFIG. 1athrough1g, merely one recess17is incorporated in portion15, this recess17extending over the entire axial length of portion15. This may be inferred, in particular, fromFIG. 1c.

The new, prefabricated blade16is likewise provided with a corresponding recess19in the area of a portion18, via which blade16is to be attached to portion15of rotor disk12, as may be inferred fromFIG. 1d, portion18of blade16also being provided with a corresponding thickened region20, in order to prepare a continuous or uniform thickness profile on portion18of new blade16. Likewise introduced into blade16, merely on one side and in the area of portion18, is a recess19, which, in turn, extends over the entire axial length of blade16.

As may be inferred fromFIG. 1d, rotor disk12and new blade16are subsequently mutually aligned in a way that permits a positionally correct joining thereof, recesses17and19of regions15and18of rotor disk12and blade16opposing one another and forming a groove-shaped weld preparation21. Groove-shaped weld preparation21extends, in turn, over the entire axial length of blade16and rotor disk12in the area of portions15and18to be joined together, and, to be precise, in the exemplary embodiment ofFIG. 1athrough1g, merely on one side of blade16, this side either being the intake side or the thrust side of blade16.

Blade16, aligned relative to rotor disk12along the lines ofFIG. 1d, is subsequently joined to rotor disk12by employing a laser powder build-up welding process in the area of weld preparation21. Thus, in hatched shading,FIG. 1eshows weld preparation21filled in by laser powder build-up welding, blade16being thereby joined to rotor disk12at portions15and18in the area of weld preparation21.

In the exemplary embodiment ofFIG. 1athrough1g, another groove-type weld preparation22(seeFIG. 1f) is subsequently introduced to the opposite side of blade16, where blade16is not yet joined to rotor disk12, and thus on the rear side of weld seam introduced into weld preparation21. If weld preparation21, where blade16is already joined to rotor disk12, is located on the thrust side of blade16, then an additional weld preparation22is introduced into the intake side accordingly. In the process, additional weld preparation22is introduced into portions15and18of rotor disk12and of blade16to be joined together, in such a way that nicks and/or imperfections in the area of a root of the weld seam introduced into weld preparation21by laser powder build-up welding are eliminated.

As shown inFIG. 1g, a laser powder build-up welding process is subsequently carried out in the region of additional weld preparation22and, in this region as well, a weld joint is prepared between blade16and rotor disk12.

Blade16joined on both sides to rotor disk12, as well as rotor disk12are subsequently machined in the area of thickened regions13and20, respectively, in such a way that an integrally bladed gas turbine rotor having a predefined, geometric, aerodynamically favorable profile is finally made ready for use. This is preferably accomplished by milling, in particular by adaptive milling. In this context, thickened regions13and20in the area of mutually joined portions15and18of rotor disk12and of blade16are ablated in a way that yields the contour illustrated by a dashed line inFIG. 1gin the area of rotor disk12and of blade16. Thickened regions13and20not only extend in the area of the two sides (intake side and thrust side) of blade16and of rotor disk12, but also in the area of a flow inlet edge and flow outlet edge, so that the material provided by thickened regions13and20, in excess of the dashed-line contour, is removed on all sides.

It should be pointed out here again that, in the exemplary embodiment ofFIG. 1athrough1g, to repair an integrally bladed gas turbine rotor10, blade16and rotor disk12are welded in such a way that they are first joined on one side by employing laser powder build-up welding and, on the side that is not yet joined, an additional weld preparation is subsequently formed, where a separate laser powder build-up welding process is then carried out to completely join blade16to rotor disk12. It is also emphasized at this point that, in the context of the present invention, it is understood that the process of joining blade16to rotor disk12may also be carried out on both sides simultaneously. This then requires introducing corresponding recesses on both sides of portions15and18of blade16and rotor disk12to be joined together, so that a positionally correct, mutual alignment of blade16and of rotor disk12yields groove-type weld preparations on both sides. In this case, blade16may be simultaneously welded to rotor disk12by laser powder build-up welding.

FIG. 2athrough2dillustrate a second exemplary embodiment of the method according to the present invention when joining a blade23to a blade root24in order to manufacture a gas turbine blade25.

To this end, in accordance withFIG. 2a, a blade root24is prefabricated, which, at a portion26, where blade23having a portion27is to be attached or joined, has a thickened region28. In the same way, portion27of blade23has a corresponding thickened region29. The purpose of thickened regions28and29is, in turn, to provide a uniform or continuous thickness distribution at portions28and29of blade23and blade root24to be joined to one another.

Blade23, as well as blade root24(see, in particular,FIGS. 2band2c), are subsequently machined at portions26and27in such a way that recesses30and, respectively,31are produced. In the process, in the exemplary embodiment ofFIG. 2athrough2d, two recesses30are introduced in the area of portion26of blade root24, each of these two recesses extending on one side, namely both on the thrust side, as well as on the intake side, over the entire axial length of portion26. Likewise introduced into portion27of blade23are two recesses31, which also extend on both sides of blade23over the entire axial length of the same. Once blade23and blade24are accurately positionally aligned (seeFIG. 2c), groove-type weld preparations32and33are formed on both sides, thus both on the thrust side, as well as on the intake side, and extend over the entire axial length thereof. Blade23is then joined to blade root24, simultaneously on both sides of blade23, by employing laser powder build-up welding in the area of these two groove-type weld preparations32and33. In a hatched shading,FIG. 2dshows weld preparations32and33filled with a weld seam produced by laser powder build-up welding.

Once blade23is joined to blade root24in the manner described above, they are then machined in the area of thickened regions28and29to prepare a gas turbine blade having a predefined geometric profile, as is shown by dashed lines inFIG. 2d. This machining operation is preferably accomplished, in turn, by milling, in particular by adaptive milling.

The method according to the present invention makes it possible to produce high-strength bonds between blades and blade roots and, respectively, between blades and rotor disks when manufacturing and/or repairing gas turbine blades or integrally bladed gas turbine rotors. The method according to the present invention is also especially suited when the components to be joined together are manufactured from high-temperature resistant materials.

One skilled in the art whom this technical teaching concerns is already familiar with the details pertaining to laser powder build-up welding, so that no further explanation of this process is needed. It should be merely noted here that, particularly when repairing integrally bladed rotor disks along the lines of the method of the present invention, laser welding heads must be used which permit a beam deflection of up to 90°, since minimal space is available between adjacent blades of an integrally bladed rotor. The laser light, as well as the powdery material required for laser powder build-up welding are externally supplied from the radial direction in this case, and must be deflected in the area of the groove-type weld preparations by up to 90°, to enable the laser light, as well as the powdery material to be introduced into the weld preparations in a manner characterized by positional accuracy.