EP2240293A1 - Method for fusing curved surfaces, and a device - Google Patents

Abstract

Components comprising both flat and curved surfaces are often difficult to weld. According to the inventive method, the orientation of the laser welding appliance (16) in relation to the curved surface (7) of the substrate (4) is varied according to the curvature of the surface (7).

Description

 Method for melting curved surfaces and a device

The invention relates to a method for melting curved surfaces according to the preamble of claim 1 and a corresponding device.

Surfaces of components are repaired by a laser powder deposition process by supplying material to the surface, which is melted by the laser.

Likewise, it may be possible to remelt cracks in the component or remelt already welded portions a second time to achieve a desired microstructure, or to repair cracks in the weld,

Both flat and curved surfaces are repaired.

However, in such components, which have both flat or curved surfaces, there are always unsatisfactory welding results.

It is therefore an object of the invention to solve the above-mentioned problem.

The object is achieved by a method according to claim 1, in which the direction of the energy beam is adapted to the curvature of the surface, and a device according to claim 15.

In the dependent claims further advantageous measures are listed, which can be combined with each other in order to achieve further advantages. Show it:

1 shows a method according to the prior art,

Figure 2 schematically shows the sequence of the invention

Method, Figure 3 is a gas turbine,

FIG. 4 shows in perspective a turbine blade FIG. 5 in perspective a combustion chamber and FIG. 6 shows a list of superalloys.

The figures and the description show only exemplary embodiments of the invention.

FIG. 1 shows the schematic sequence of the method according to the prior art with different positions of an energy source 16, in particular a welding apparatus, over a component 1, 120, 130, 155 (FIGS. 4, 5) in a direction of translation (in the drawing from the left to the right) .

A substrate 4 of the component 1, 120, 130, 155 has a curved surface 7 with a normal n (perpendicular). The direction of the normal n changes along the curved surface 7.

The curved surface 7 is intended to be thrown up or remelted by energy beams 13.

This is done by means of an energy source 16, preferably by means of a plasma or by means of a laser emitting laser beams 13.

The state of the art and the invention described below are described by way of example only by means of laser welding.

Relative to a planar surface 22 of the substrate 4, a laser beam 13 strikes the surface 22 at an angle. The position of the laser 16 is not changed relative to the substrate 4, even if the laser beam 13 moves away from the curved surface 7, so that the angle γ between the normal paint ή the surface 7 and the laser beam 13 is changed.

This often leads to cracks during remelting or to uneven melting depths, in particular during the restructuring of directionally solidified (DS, SX) components 120, 130.

FIG. 2 shows schematically the course of the method according to the invention.

When the laser beam 13 strikes the curved surface 7, which is preferably U-shaped, the position of the laser beam 13 relative to the substrate 4 is changed so that the angle γ between the laser beam 13 and the normal n of the surface 7 is preferably remains constant.

The change can preferably be adjusted continuously.

Likewise, it may be that the position of the laser beam 13 is only changed if by displacement of the laser 16 and substrate 4 against each other in the translation direction an angle change Δγ and a certain angle change Δγ between the energy beam 13 and normal n, preferably of Δγ = 3 °, in particular of 1 °, in particular of 0.5 ° is exceeded, so that only a quasi-continuous change of the laser beam 13 to the surface 7 takes place. In the case of a curved surface 7 as in FIG. 2, the position of the laser beam 13 with respect to the curved surface 7 is changed at least three times. So there is a quasi-continuous adjustment of the angle.

By varying the angle γ, the local variability of the laser power and the local speed is reduced. Since the temperature signal of the welding spot generated by the laser beam is influenced by the change in the angle γ, preferably also no percentage control of the temperature of the melt takes place.

The angle γ is preferably between 8 ° and 12 °, preferably 10 °.

The laser power is preferably 750W. The preheating temperature is preferably from 500 ⁰ C.

The travel speed is preferably 50 mm / min.

Such curved surface regions 7 are, in the area of the turbine blade 120, 130, the transition between the blade leaf 406 and the blade blade 403.

Likewise, preferably, the distance of the laser 16 to the surface 7 can be adjusted, in particular kept constant, since the curvature of the surface 7, the distance to the laser 16 changes. As a result, the energy input into the substrate 4 remains uniform.

Similarly, the method can be applied to convex surfaces.

Furthermore, weld metal can be supplied to the substrate 4, which is melted and fills cracks or reinforced component walls.

In particular, the method is advantageous in a directionally solidified substrate 4, the columnar solidified grains (DS) or monocrystalline (SX) is formed, since there the crystal orientation plays an important role, which is influenced by the application of temperature gradients.

Substrates 4 preferably have a superalloy according to FIG. FIG. 3 shows by way of example a gas turbine 100 in a longitudinal partial section.

The gas turbine 100 has inside a rotatably mounted about a rotation axis 102 rotor 103 with a shaft, which is also referred to as a turbine runner.

Along the rotor 103 follow one another an intake housing 104, a compressor 105, for example, a toroidal combustion chamber 110, in particular annular combustion chamber, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109th

The annular combustion chamber 110 communicates with an annular annular hot gas channel 111, for example. There, for example, four turbine stages 112 connected in series form the turbine 108.

Each turbine stage 112 is formed, for example, from two blade rings. In the flow direction of a working medium

As can be seen in the hot gas duct 111 of a guide blade row 115, a row 125 formed of rotor blades 120 follows.

The guide vanes 130 are fastened to an inner housing 138 of a stator 143, whereas the moving blades 120 of a row 125 are attached to the rotor 103 by means of a turbine disk 133, for example.

Coupled to the rotor 103 is a generator or work machine (not shown).

During operation of the gas turbine 100, air 105 is sucked in and compressed by the compressor 105 through the intake housing 104. The compressed air provided at the turbine-side end of the compressor 105 is guided to the burners 107 and mixed there with a fuel. The mixture is then burned to form the working fluid 113 in the combustion chamber 110. From there, the working medium flows 113 along the hot gas channel 111 past the guide vanes 130 and the blades 120. On the blades 120, the working medium 113 expands in a pulse-transmitting manner, so that the blades 120 drive the rotor 103 and this drives the machine coupled to it.

The components exposed to the hot working medium 113 are subject to thermal loads during operation of the gas turbine 100. The guide vanes 130 and rotor blades 120 of the first turbine stage 112, viewed in the flow direction of the working medium 113, are subjected to the greatest thermal stress in addition to the heat shield elements lining the annular combustion chamber 110. To withstand the prevailing temperatures, they can be cooled by means of a coolant.

Likewise, substrates of the components may have a directional structure, i. they are monocrystalline (SX structure) or have only longitudinal grains (DS structure).

As the material for the components, in particular for the turbine blade 120, 130 and components of the combustion chamber 110, for example, iron-, nickel- or cobalt-based superalloys are used.

Such superalloys are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949.

Also, the blades 120, 130 may be anti-corrosion coatings (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and represents yttrium (Y) and / or silicon , Scandium (Sc) and / or at least one element of the rare earth or hafnium). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1. On the MCrAlX may still be a thermal barrier layer, and consists for example of Zrθ2, Y2Ü3-Zrθ2, that is, it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide. Suitable coating processes, such as electron beam evaporation (EB-PVD), produce stalk-shaped grains in the thermal barrier coating.

The vane 130 has a guide vane foot (not shown here) facing the inner housing 138 of the turbine 108 and a vane head opposite the vane foot. The vane head faces the rotor 103 and fixed to a mounting ring 140 of the stator 143.

FIG. 4 shows a perspective view of a moving blade 120 or guide blade 130 of a turbomachine that extends along a longitudinal axis 121. The turbomachine may be a gas turbine of an aircraft or a power plant for power generation, a steam turbine or a compressor.

The blade 120, 130 has along the longitudinal axis 121 consecutively a fastening region 400, a blade platform 403 adjacent thereto and an airfoil 406 and a blade tip 415.

As a guide blade 130, the blade 130 may have at its blade tip 415 another platform (not shown). In the mounting region 400, a blade root 183 is formed, which serves for attachment of the blades 120, 130 to a shaft or a disc (not shown). The blade root 183 is designed, for example, as a hammer head. Other designs as fir tree or Schwäbwschwanzfuß are possible. The blade 120, 130 has a leading edge 409 and a trailing edge 412 for a medium flowing past the airfoil 406.

In conventional blades 120, 130, for example, massive metallic materials, in particular superalloys, are used in all regions 400, 403, 406 of the blade 120, 130.

Such superalloys are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949.

The blade 120, 130 can hereby be manufactured by a casting process, also by directional solidification, by a forging process, by a milling process or combinations thereof.

Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed to high mechanical, thermal and / or chemical stresses during operation.

The production of such monocrystalline workpieces takes place e.g. by directed solidification from the melt. These are casting processes in which the liquid metallic alloy is transformed into a monocrystalline structure, i. to the single-crystal workpiece, or directionally solidified.

Here, dendritic crystals are aligned along the heat flow and form either a columnar grain structure (columnar, ie grains that run the entire length of the workpiece and here, for general language use, referred to as directionally solidified) or a monocrystalline structure, ie the whole workpiece consists of a single crystal. In these processes, one must avoid the transition to globulitic (polycrystalline) solidification, since undirected growth necessarily forms transverse and longitudinal grain boundaries which negate the good properties of the directionally solidified or monocrystalline component. The term "directionally solidified structures" generally refers to single crystals that have no grain boundaries or at most small-angle grain boundaries, as well as stem crystal structures that have grain boundaries running in the longitudinal direction but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures.

Such methods are known from US Pat. No. 6,024,792 and EP 0 892 090 A1.

Likewise, the blades 120, 130 may have coatings against corrosion or oxidation, e.g. M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare ones Earth, or hafnium (Hf)). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1.

The density is preferably 95% of the theoretical

Density.

On the MCrAlX layer (as an intermediate layer or as the outermost layer)

Layer) forms a protective aluminum oxide layer (TGO = thermal grown oxide layer).

Preferably, the layer composition comprises Co-30Ni-28Cr-8A1-0, 6Y-0, 7Si or Co-28Ni-24Cr-10Al-0, 6Y. Besides these cobalt-based protective coatings, nickel-based protective layers such as Ni-10Cr-12Al-0.6Y-3Re or Ni-12Co-21Cr-IIAl-O, 4Y-2Re or Ni-25Co-17Cr-1OAl-O, 4Y-I are also preferably used , 5Re.

On the MCrAlX may still be present a thermal barrier coating, which is preferably the outermost layer, and consists for example of ZrC> 2, Y2Ü3-Zrθ2, ie it is not, partially ^¬ or fully stabilized by yttria and / or calcium oxide and / or magnesium oxide , The thermal barrier coating covers the entire MCrAlX layer. Suitable coating processes, such as electron beam evaporation (EB-PVD), produce stalk-shaped grains in the thermal barrier coating.

Other coating methods are conceivable, e.g. atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier coating may have porous, micro- or macro-cracked grains for better thermal shock resistance. The thermal barrier coating is therefore preferably more porous than the MCrAlX layer.

Refurbishment means that components 120, 130 may need to be deprotected after use (e.g., by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. Optionally, even cracks in the component 120, 130 are repaired. This is followed by a re-coating of the component 120, 130 and a renewed use of the component 120, 130.

The blade 120, 130 may be hollow or solid.

If the blade 120, 130 is to be cooled, it is hollow and may still have film cooling holes 418 (indicated by dashed lines).

FIG. 5 shows a combustion chamber 110 of a gas turbine.

The combustion chamber 110 is configured, for example, as a so-called annular combustion chamber, in which a multiplicity of burners 107 arranged in the circumferential direction about a rotation axis 102 open into a common combustion chamber space 154, which generate flames 156. For this purpose, the combustion chamber 110 is configured in its entirety as an annular structure, which is positioned around the axis of rotation 102 around.

To achieve a comparatively high efficiency, the combustion chamber 110 is for a comparatively high temperature the working medium M of about 1000 ⁰ C to 1600 ⁰ C designed. In order to enable a comparatively long service life for these operating parameters, which are unfavorable for the materials, the combustion chamber wall 153 is provided on its side facing the working medium M with an inner lining formed from heat shield elements 155.

Each heat shield element 155 made of an alloy is equipped on the working medium side with a particularly heat-resistant protective layer (MCrAlX layer and / or ceramic coating) or is made of high-temperature-resistant material (solid ceramic blocks).

These protective layers may be similar to the turbine blades, so for example MCrAlX means: M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare earths, or hafnium (Hf). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 Bl, EP 0 412 397 B1 or EP 1 306 454 A1.

On the MCrAlX may still be present, for example, a ceramic thermal barrier coating and consists for example of ZrC> 2, Y2Ü3 Zrθ2, ie it is not, partially or fully ^¬ dig stabilized by yttrium and / or calcium oxide and / or magnesium oxide.

By suitable coating methods, e.g. Electron beam evaporation (EB-PVD) produces stalk-shaped grains in the thermal barrier coating.

Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The heat-insulating layer may have porous, micro- or macro-cracked grains for better thermal shock resistance. Refurbishment means that heat shield elements 155 may have to be freed of protective layers after their use (eg by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. If necessary, cracks in the heat shield element 155 are also repaired. This is followed by a recoating of the heat shield elements 155 and a renewed use of the heat shield elements 155.

Due to the high temperatures inside the combustion chamber 110 may also be provided for the heat shield elements 155 and for their holding elements, a cooling system. The heat shield elements 155 are then, for example, hollow and possibly still have cooling holes (not shown) which open into the combustion chamber space 154.

Claims

claims A method of reflowing a curved surface (7) of a substrate (4) by means of an energy beam (13), wherein the energy beam (13) and / or the substrate (4) are moved against each other to reflow the curved surface (7) . characterized in that the orientation of the energy beam (13) to the curved surface (7) is varied during the process. 2. The method according to claim 1, characterized in that An angle (γ) between a normal (n) of the curved surface (7) and the energy beam (13) is kept constant. 3. The method according to claim 1, characterized in that the orientation of the energy source (16) of the energy beam (13) to the curved surface (7) is changed quasi-continuously, in particular at least three times. 4. The method according to claim 1, 2 or 3, characterized in that the reorientation of the energy beam (13) to the curved surface (7) is achieved only by rotation of the energy source (16) of the energy beam (13). 5. The method according to claim 1, 2 or 3, characterized in that the reorientation of the energy beam (13) to the curved surface (7) of the substrate (4) is achieved only by rotation of the substrate (4). 6. The method according to claim 1, 2 or 3, characterized in that the reorientation of the energy beam (13) to the curved surface (7) of the substrate (4) is achieved both by rotation of the energy source (16) of the energy beam (13) and by rotation of the substrate (4). 7. The method of claim 1, 2, 3, 4, 5 or 6, characterized in that the distance between the energy source (16) of the energy beam (13) and the curved surface (7) of the substrate (4) is kept constant. 8. The method of claim 1, 2, 3, 4, 5, 6 or 7, characterized in that an angle (γ) between 8 ° to 12 °, in particular 10 °, between the energy beam (13) and the normal (s) of the curved surface (7) is set. 9. The method according to one or more of the preceding claims 1, 3 to 8, characterized in that the energy source (16) of the energy beam (13) is moved with respect to the curved surface (7) so that the angle (γ) between the normal (n) of the curved surface (7) and the energy beam (13) of the energy source ( 16) and that from an angle change between the energy beam (13) and the normal (n) of 3 °, in particular of 1 °, in particular of 0.5 °, the orientation of the energy source (16) and energy beam (13) is adjusted. 10. Method according to one or more of the preceding Claims, characterized in that the energy beam (13) represents a laser beam. 11. The method of claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, characterized in that Welded material of the curved surface (7) is supplied. 12. The method of claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, characterized in that the surface (7) of the substrate (4) is only remelted. 13. The method of claim 1, 5, 6, 7, 11 or 12, characterized in that a molten portion of the substrate (4) or weld metal is allowed to solidify columnar (DS) or monocrystalline (SX). 14. The method of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 11 or 12, characterized in that the curved surface (7) is U-shaped. 15. A device for melting a curved surface (7), which can receive a substrate (4) having a welding device (16), and Having means by which an angle (γ) between the energy beams (13) of the welding device (16) and a normal (s) of the curved surface (7) can be varied, and Moving means by which the substrate (4) and the welding device (16) can move relative to each other.