WO2016096382A1

WO2016096382A1 - Method for repairing damage to a turbine blade by means of templates

Info

Publication number: WO2016096382A1
Application number: PCT/EP2015/078014
Authority: WO
Inventors: Martin Bremer; Matthias Kuhlee; Britta Laux; Uwe Paul; Radan RADULOVIC
Original assignee: Siemens Aktiengesellschaft
Priority date: 2014-12-16
Filing date: 2015-11-30
Publication date: 2016-06-23
Also published as: DE102014226055A1

Abstract

The invention specifies a method (1) for repairing damage (2) to a turbine blade (4), there being provided a predefined template (12c) which completely covers at least the damage (2), wherein in the region of the damage (2) the material of the turbine blade (4) is removed forming a removal region (22) with a shape predefined by the template (12c), and hereby at least the damage (2) is excavated in the removal region (22), wherein a repair piece (14) in the shape of the template (12c) is inserted into the removal region (22), and wherein the repair piece (14) is connected to the turbine blade (4) at a surface (28) bounded by the removal region (22). The invention also specifies a turbine blade (4) having a removal region (22) and a template-like repair piece (14) which is inserted therein in a form-fitting manner and which is connected to the turbine blade (4) at a surface (28) bounded by the removal region (22).

Description

description

PROCESS FOR IMPROVING DAMAGE TO A TURBINE BLADE THROUGH TEMPLATES

The invention relates to a method for repairing damage to a turbine blade.

In a gas turbine, the efficiency increases with increasing combustion temperature for thermodynamic reasons. A higher efficiency also means is that the power transmitted to the individual turbine stages rotational energy increases ^¬. Because their efficiency is the key parameter for its economy for long-term operation of a gas turbine, all measures are preferable to check their Auswir ^¬ effects on the efficiency out in the planning and construction ei ^¬ ner gas turbine, and the gas ^¬ turbine for a interpreted continuous operation with the highest possible We ^¬ ciency back.

For the individual turbine stages, this means that in particular ^¬ sondere the respective components of the blading to receive the highest possible torque have to have a particularly high mechanical strength, as well as to demonstrate A possible ^¬ lichst high thermal resistance ^¬ th order for a favorable efficiency high combustion - to allow temperaturn.

These two goals are often not material both technically sufficiently well to realize. In the construction of turbine blades for gas turbines, therefore, mechanical resistance to thermal resistance is usually prioritized first, and the latter subsequently improved by means of a corresponding aftertreatment, for example, by means of corresponding coatings. A turbine blade usually consists of a profiled wing, which is closed at both ends in each case by a platform. For a high mechanical Strength of the wing and the platforms are made together of a metal, usually a nickel-based alloy. After this production, depending on the maximum temperature of the turbine stage, for which the turbine blade is provided, one or more bonding layers and / or thermal barrier coatings can be applied.

Each turbine stage consists of a set of vanes and a set of blades, wherein in each set the blades of the turbine blade are arranged in a spoke shape to each other, and the platforms of Turbinenschau ^¬ blades of a set each form an inner or an outer ring. The vanes are arranged stationary in the turbine, the individual blades of the same turbine stage are mutually rigidly mounted, and rotatably mounted as a common set with respect to the axis of the gas turbine.

Despite a conventional coating of the turbine blades to improve their heat resistance, it comes over the Be ^¬ operating time of the gas turbine often cause damage to the turbine blades due to corrosion. For reasons of flow technology, this affects in particular the platforms of the turbine blades, which are arranged on the outer ring, since there the hot gas action is particularly high. This heat-induced corrosion occurs, in particular, at the ^edges on which two adjacent platforms of the same turbine stage and the same set close to one another, since there the hot gas can diffuse between the platforms.

In order to prevent such diffusion into the gap between two be ^¬ adjacent platforms as possible, corresponding column of profiled sheets versie possible ^¬ gel. From be reasons of fluidic turbulence in the region behind the wings of the turbine blades, there is this measure is often not sufficiently effective. The Ausbes ^¬ tion of such damage to the most cast or forged turbine blades is due to the high Requirements, in particular their mechanical strength, so far not satisfactorily solved. Turbine blades with the above-mentioned damage are therefore usually exchanged, which on the one hand results in undesirably high costs for the provision of new turbine blades, and on the other hand the old turbine blades can be disposed of as scrap not least because of the non-reusable coatings, possibly resulting in even ^greater costs can arise.

The invention is therefore based on the object to provide a method for repairing damage to a turbine blade, which takes into account the material structure of the turbine blade and should be feasible as inexpensively.

The invention further has for its object to provide a ^turbine blade which can be used following damage again for high performance applications.

The first object is achieved by a method for repairing damage to a turbine blade, wherein a predefined template is ^{bereitge ¬} provides, which completely covers at least the damage, wherein in the region of damage, the material of the turbine blade to form a Abtragungsbereiches with a through the Sten predetermined form is removed and thereby at least the damage is removed in the ablation region, wherein a repair piece in the form of the template is inserted into the Abtragungsbereich, and wherein the repair piece is connected to the turbine blade on ei ^¬ ner limited by the ablation region surface. Advantageous and partly inherently inventive embodiments of the method are the subject of the dependent claims.

The second object is achieved by a turbine blade with a removal area and a in a form-fitting inserted stencil-like repair piece, which is connected to the turbine blade at a limited by the ablation area surface. The advantages mentioned for the method and its developments can be transferred analogously to the turbine blade.

The damage is present a deviation from a preferably defined by the condition of the turbine blade prior to commissioning local target geometry. The BE ^¬ reitzustellende template is present as a geometrical ^¬ ULTRASONIC patterns understood that at the surface of the ^turbine blade in the region of the damage can reproduce local Sollgeo ^¬ metry. The at least complete covering of the damage by the template is in this sense understood that the geometrically ^reproduced by the template geometric pattern in a correct positioning in the region of damage this is completely covered in the geometric pattern. This means that by a decision-fernung of the material of the turbine blade in the area of Be ^¬ damage in the form imposed by the template as well as the damage is also removed.

In particular, the damage may be on a platform of the turbine blade, and in particular, the damage includes corrosion of the material of the turbine blade at the corresponding location.

The invention proceeds from the consideration that due to the high demands on the strength and the heat resistance of a turbine blade, the repair of a Beschä ^¬ ending has to be made such that it at the repaired place the material structure of the turbine blade before the smallest possible deviation from the condition the start-up would take should have, and on the other hand, a nachträg ^¬ Liche heat protection coating is again possible, if necessary. A common practice in repairing components of gas turbines is to use a presintered preform ("pre-sintered preform"). sintered preform ", hereafter PSP) over a location with wear and tear, and after appropriate fixation under the influence of pressure and heat to connect to the component.However, this approach does not bring sufficient connection quality of the PSP at certain points of a turbine blade in the case of corrosive damage these only covered, but not effectively eliminated, which may have a negative impact on the strength in the corre ^¬ sponding area and also carries the risk of detachment of the PSP, whereby a repeated mending, possibly after an uner ^¬ desirably short maintenance interval would be required. About ^¬ this occur on a turbine blade damage in the area of tight manufacturing tolerances, whereby the mere addition of a PSP may be disadvantageous.

A surprising finding is now that a removal of the material in the region of the damage according to a given template with such high precision is possible that a correspondingly shaped repair piece in the area of the removed material accurately, ie without significant play can be used. By such a passge ^¬ naues inserting a repair piece, a sufficiently smooth transition can be Herge ^¬ situated between the turbine blade and the ver ^¬-bound with this in a suitable manner repair piece to the desired geometry reproducing surface so that tight manufacturing tolerances can be met. Moreover, if necessary, a heat protection coating can be repaired on the smooth surface without much effort.

In a further step will now be recognized that from strö ^¬ mung technical reasons and because of the symmetries in a gas turbine, a plurality of possible and normally occurring on the surface of the turbine blade Beschädi ^¬ conditions are relatively similar, and also in each case to ver ^¬ parable points of the turbine blades occur. The provision of a repair piece in the form of a front Finished template and the removal of material of the Turbi ^¬ nenschaufel in appropriate form uses this fact during mending, so that parts of the repair process - eg the prefabrication of the repair piece and a pre-defined in a plant process for removing the material on the turbine blade in the field of damage - can be automated, resulting in increased efficiency and cost savings in mending. Moreover, in the first place given a satisfactory repaired raturmöglichkeit for a plurality of possible or üblicherwei ^¬ se appearing at the surface of the turbine blade Be ^¬ damage by mending with an accurately inserted into a previously processed removal area repair piece which a premature Aussortie ^¬ ren Damaged turbine blade is able to prevent. Thus, the life of the turbine blade can be wesent ^¬ Lich extend, which in the long term leads to cost savings in the operation of a gas turbine.

Conveniently, the template is provided by selecting from a plurality of predetermined, mutually different templates. In the continuous operation of gas turbines tre ^¬ th due to a precisely predetermined flow path in a plurality of individual turbine blades often comparable damage to the same places, from point to place of a turbine blade, the ^{Beschädigun ¬} conditions can each vary more. Pretending mutually different templates and the ability to select for the repair of a single damage a particular template from this makes it possible to react flexibly when repairing the possible local differences in Beschädi ^¬ supply, and at the same time take advantage of a series of prefabrication in claim to be able to.

It proves to be advantageous if, as a criterion for selecting the template, a minimization of the damage to be removed to form the removal region around the damage Quantity of the material of the turbine blade is used. Depending on the type through which the material of the turbine blade is removed to form the ablation zone in the area of damage to the process, which to-remove amount of material can affect the speed and also the Ener ^¬ gieeffizienz the process decisively. In particular, this applies to a removal of the material. Eg ^¬ ne minimization of this amount thus allows the process to perform as cost effective and time-saving.

Conveniently, the material of the turbine blade is removed in the region of the damage by means of spark erosion. Spark erosion allows the removal of metal with a precision of a few micrometers. Thereby, the denudation can be adapted to the repair piece supply area particularly accurately so that subsequently reaches a particularly firm Ver ^¬ tying the repair piece to the turbine who can ^¬. Conveniently, the material of the turbine blade in the area of the Be ^¬ damage by means of mechanical milling and / or laser cutting is removed. By milling can be removed relatively quickly and energetically favorable ver ^¬ tively large amounts of material. The laser cutting is in particular advantageous if a removal area comprises the full thickness of a portion of the turbine blade to be repaired, for example, the platform, so that the supply area Abtra ^¬ herausge ^¬ can be easily separated by means of laser cutting. For this purpose, only the material in the region of the cutting point of the laser must be melted, the expenditure of energy for melting and / or removal of lying closer to the damage material can thus be saved. In particular, the said processes can also be combined to remove the material. Thus, for example, for damage to a platform of the turbine blade, first an area can be milled off, and then fine machining of the removal area by spark erosion. In an advantageous embodiment of the invention, a pre-sintered preform (PSP) is recognized as ^¬ repair piece. Alternatively, it may be advantageous if a repair piece of a similar, in particular crystalline monolithic material is used. A PSP be ^¬ stands typically consist of a mixture of a metalli ^¬ rule granules with a solder with a proportion of the granules of 40-75 wt .-%, preferably 50-65 wt .-%, by weight and a Lotanteil of 25-60. -%, preferably 35-50 wt .-%. The granules and the solder are sintered in the PSP to a solid shape, so that the remaining during the sintering process microscopic spaces between the metallic granules are filled by the solder. Preferred repair piece of the metal granules is in this case matched to the material of the turbine blade with respect to the intrinsic properties ^¬ during joining in the case of egg ner PSP. Particularly preferred is the granules of an alloy of components included in the material of the turbine blade. In the case of a fully crystalline repair piece, the touchup ^¬ piece is preferably made of the same material as the turbine show ^¬ fel.

Depending on the geometry of the damage and the resulting removal area, in particular its surface, at which the repair piece is to be connected to the material of the turbine blade, one of the two options is also selected according to time, energy and cost parameters, the latter may also depend on the geometry of the damage. A patching piece of a fully crystalline material has in itself a higher Fes ^¬ ACTION to as a PSP, but the quality or strength of the connection between the repair piece and the turbine blade due to the higher strength is also higher by the geometry of the surface of the ablation preparation ^¬ ches Depending on which the patch has contact with the turbine blade, which may possibly speak for a PSP in individual cases. As a further advantage it proves to be when the off ^¬ improvement piece is connected to the turbine blade by welding and / or brazing and / or sintering. In particular, combinations of the mentioned process techniques are also advantageous. In this case, the selection and possibly the ^{sequence of} the or each process for connecting the repair piece to the turbine blade is preferably ^adapted to the material and the internal structure of the repair piece. In particular, in the application of a plurality of said process techniques in a first step, a connection to the intended contact surfaces of the turbine blade and the repair piece in isolated locations or surface, but of lesser strength to achieve. The strength of the compound to be achieved by this first step should preferably favor a further step.

Conveniently, in this case, the repair piece is first connected to the turbine blade at a number of isolated locations on the surface defined by the ablation area by spot welding, in particular resistance spot welding, and then the repair piece is connected to the rest of the area delimited by the ablation area in a soldering process with the turbine blade , The spot welding here has the advantage that at the welding points already a compound of high strength ent ^¬ stands, so that the repair ^piece is fixed sufficiently for the subsequent soldering in the removal area. The soldering process is preferably adapted to the material and the internal structure of the repair piece. Is given by a PSP the patching piece, can verzich to an intended contact surface due to the presence in the PSP solder on the application of a solder to be ^¬ sätzlichen ^¬ tet, which has a low process technology. In the case of a repair piece made of a fully crystalline material, a solder or an inert substance, in particular a thin layer of a PSP, is preferably applied to a contact surface provided on the turbine blade or the repair piece before the spot welding. An embodiment of the invention will be explained in more detail with reference to a drawing. 1 shows a diagram of the sequence of a method for

Repair damage to a turbine blade.

1 shows a schematic diagram of the sequence of a method 1 for repairing a damage 2 at a

Turbine blade 4 shown. The turbine blade 4 has a platform 6 and a seated on the platform 6 profiled wing 8. At an edge 10 of the platform 6, the material is locally corroded, which has caused damage 2. The damage 2 to the platform 6 is now to be repaired by the material of the platform ^¬ form 6 is removed in this area, and then new ^¬ material used in the resulting gap, and is connected to the material of the platform 6.

This is now done by a stencil 12 is selected for the form ei ^¬ nes repair piece 14 of the employed material from ^¬. In the process of selecting a template 12 for the material to be removed in the region of the damage 2 to the platform 6 is assumed by a plurality of predetermined, mutually different shapes for the individual templates 12 and thus for the shape of the possible repair ^¬ piece 14. From this plurality of possible template shapes 12, the one which on the one hand completely covers the damage 2 and which on the other hand minimizes the material to be removed on the platform 6 in the region of the damage 2, in order to arrive there on a shape complementary to the selected template. Concretely, in the present example, the template 12b would not be sufficient to completely cover the damage 2, since in a material removal on the platform 6 according to the template 12b, the damage 2 further into the depth would be enough. The selection mask 12a would certainly guaranteed ^¬ provide that, with a corresponding removal of the material of the platform 6, the damage 2 would be removed completely, but this is ensured even when using the template 12c. Since only a smaller area of undamaged material of the platform 6 is removed with a removal according to the template 12c than with a removal according to the template 12a, the template 12c is selected for the further course of the method. By means of spark erosion or milling, 16 18 or 20 laser cutting the material of the platform 6 will be removed in the area around the damaged or removed 2 around such that a mask 12c for Komple ^¬ mentärer removal area arises 22nd

Furthermore, a repair piece 14 in the form of

Template 12c provided. The repair piece 14 can be present as a PSP 24, in which a

granular material of a nickel superalloy is processed with a solder. Alternatively, 26 can be present as nickel-based superalloy, the Ausbesse ^¬ extension piece 14 also in the form of a fully crystalline material. The Ausbesse ^¬ extension piece 14 is now inserted into the removal area 22, where it is connected with the platform 6 at the Abtragungsbe ^¬ rich 22 bounding surface 28th In order to fix the repair piece 14 to the platform 6 immediately after insertion into the removal area 22, the repair piece 14 is firstly fastened at isolated locations of the surface 28 delimiting the removal area 22 by means of resistance spot welding 30. By the individual weld spots of resistance spot welding 30, a sufficient fixing of the repair pad 14 in Abtra ^¬ supply region 22 is ensured for the final bonding process. For the complete connection of the repair piece 14 with the platform 6 at the surface 28 delimiting the removal area 22, the repair piece 14 is involved in a soldering process 32 under the action of pressure and heat joined the platform 6. If the repair piece 14 is given as a PSP 24, the solder processed in the PSP for the soldering process 32 is sufficient. If the Ausbesse ^¬ extension piece 14 of a fully crystalline material 26, then at the limiting this surface preferably also apply an additional solder 28 prior to insertion of the repair pad 14 in the supply area Abtra ^¬ 22nd

Although the invention in detail by the preferred embodiment has been illustrated and described in detail, the invention is not by this embodiment is ^¬ limits. Other variations can be deduced therefrom by those skilled in the art without departing from the scope of the invention.

Claims

claims

1. A method (1) for repairing damage (2) on a turbine blade (4),

wherein a predefined template (12c) is provided, which completely covers at least the damage (2), wherein in the region of the damage (2) the material of the turbine blade (4) is formed with a removal region (22) through the template (12c). predetermined form is removed and thereby in the removal area (22) at least the damage (2) is dissolved out,

wherein a repair piece (14) in the form of the template (12c) in the removal area (22) is inserted, and

wherein the repair piece (14) is connected to the turbine blade (4) at a surface (28) defined by the removal area (22).

2. Method (1) according to claim 1,

wherein the template (12c) is provided by selecting from a plurality of predetermined mutually different templates (12a-12c).

3. Method (1) according to claim 2,

wherein criterion for selecting the template (12c) is a minimization of the amount of the material of the turbine blade (4) to be removed in order to form the removal area (14) around the damage (2).

4. The method (1) according to any one of the preceding claims, wherein the material of the turbine blade (4) in the region of

Damage (2) is removed by means of spark erosion (16).

5. The method (1) according to any one of the preceding claims, wherein the material of the turbine blade (4) in the region of the damage (2) by means of mechanical milling (18) and / or laser cutting (20) is removed.

6. Method (1) according to one of the preceding claims wherein a pre-sintered preform (24) is used as a repair piece (14).

7. Method (1) according to one of claims 1 to 5,

wherein a repair piece (14) made of a fully crystalline material (26) is used.

A method (1) according to any one of the preceding claims, wherein the repair piece (14) is joined to the turbine blade (4) by welding (30) and / or brazing (32) and / or sintering.

9. Method (1) according to claim 8,

wherein the repair piece (14) with the turbine blade (4) first at a number of isolated locations of the surface (28) bounded by the removal area (22)

Spot welding (30) is connected, and then the Aus ^¬ correcting piece (14) on the other by the Abtragungsbereich (22) limited surface (28) in a soldering process (30) with the turbine blade (4) is connected.

10. turbine blade (4) having a removal area (22) and a stencil-like repair piece (14) inserted therein in a form-fitting manner, which is connected to the turbine blade (4) at a surface (28) delimited by the removal area (22).

11. turbine blade (4) according to claim 10,

wherein the repair piece (14) is connected to the turbine blade (4) by welding (30) and / or brazing (32) and / or sintering.