WO2009089840A1

WO2009089840A1 - Method and device for controlled edm machining

Info

Publication number: WO2009089840A1
Application number: PCT/EP2008/000207
Authority: WO
Inventors: Ulrich Laudien
Original assignee: Siemens Aktiengesellschaft
Priority date: 2008-01-11
Filing date: 2008-01-11
Publication date: 2009-07-23

Abstract

According to the prior art, during EDM machining a constant current is set. When changing the effective electrode surface, this results in slower machining of the substrate (4). According to the invention, the effective electrode surface is measured and the relevant machining parameters are adjusted accordingly.

Description

Method and device for controlled EDM processing

The invention relates to a method for the controlled EDM machining of a component according to claim 1 and a corresponding apparatus according to claim 12.

Metallic components can be processed in various ways. One possibility is the EDM machining (spark erosion).

The object of the invention is to further improve the effectiveness of EDM processing.

The object is achieved by a method according to claim 1 and a device according to claim 12.

In the subclaims further advantageous measures are listed, which can be combined with each other in an advantageous manner in an advantageous manner.

Show it:

1, 2 schematically show the course of an EDM processing, FIG. 3 shows a gas turbine,

FIG. 4 is a perspective view of a turbine blade, FIG. 5 is a perspective view of a combustion chamber, and FIG. 6 is a list of superalloys.

The figures and the description show only embodiments of the invention. FIG. 1 shows a device 1 for EDM processing of a substrate 4 of a component.

The component may be a turbine blade 120, 130 (FIGS. 3, 4), a combustor portion 155 (FIG. 5) of a turbine, in particular a gas turbine 100 (FIG. 3).

The material of the substrate 4 is preferably a cobalt, nickel or iron based superalloy. In particular, a superalloy according to FIG. 6 is used.

The substrate 4 with the surface 7 is processed by means of an EDM electrode 10 in order to produce a specific structure in the substrate 4 or in the component 120, 130, 155. The EDM electrode 10 is preferably partially conical, which is not known in the prior art, so that the EDM processing parameters are not known. In particular, the conicity is present at the tip 28 of the EDM electrode 10 and the remainder is preferably round or rectangular in cross-section.

In this case, a generator 19, which is electrically connected by means of lines 13, 22 to the substrate 4 and the EDM electrode 10, generates a voltage which leads to the generation of a spark rollover between the tip of the electrode 10 and the substrate 4.

According to the state of the art, there is no change in the machining parameters; in particular, a constant current is set for the entire machining period at the beginning of the machining.

This is in the creation of a cylindrical hole, the z. B. generated perpendicular to a planar surface, also the optimal setting.

However, as shown only by way of example in FIG. 1, the machining parameters are no longer optimal if the hole to be produced, no matter in which form, extends obliquely to a surface 7 and the effective electrode surface is located changes, so when the area of the electrode changes, which contributes to the processing.

The hole 25 is just one example of a structure to be fabricated in the substrate.

In FIG. 1, in the sectional drawing, there is a length Al and Bl corresponding to a newly created area Y in the substrate 4, which was generated at the beginning of processing with initial values of the EDM processing parameters.

In an advanced stage of EDM machining in accordance with Figure 2, the length Al has increased to the length A2 and the length Bl has increased to the length B2 and accordingly, the surface newly created strat Y ¹ (Y '> Y) in the sub- 4th

According to the invention, this progress of the processing of the substrate 4 is measured. The measurement can be checked continuously or in predetermined small steps (discontinuous).

By means of a measuring device 11, a progress parameter, for. Example, the generated area (Y, Y ¹ ) or an effective electrode surface, between which a sparkover occurs between the EDM electrode 10 and the substrate 4, are determined.

Other parameters, such. B. penetration depth d of the EDM electrode 10, can also be measured as a measure of the effective electrode surface area.

The end ring depth d can be determined over the length of the EDM electrode 10, which still protrudes from the substrate 4, and the penetration angle.

According to these measured progress parameters, the performance of the EDM processing can be increased or decreased accordingly. According to Figure 2, the generator power would be increased to make the EDM machining efficient. Likewise, the feed rate can be changed. Likewise, the power and the feed speed can be adjusted simultaneously or alternately. In this case, the device 1 has a control of the feed rate and / or power control (not shown), which drives the EDM electrode 10 faster or slower or varies the power. Likewise, there may be no need for adjustment throughout EDM processing, even as the progress of EDM processing is measured.

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 101, which is also referred to as a turbine runner. Along the rotor 103 successively follow an intake housing 104, a compressor 105, for example, a torus-like

Combustion chamber 110, in particular annular combustion chamber, with a plurality of coaxially arranged burners 107, a turbine 108 and the exhaust housing 109. The annular combustion chamber 110 communicates with an example annular hot gas channel 111. There, for example, four successively connected turbine stages 112 form the turbine 108th

Each turbine stage 112 is formed, for example, from two blade rings. As seen in the direction of flow of a working medium 113, in the hot gas channel 111 of a row of guide vanes 115, a series 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 113 flows along the hot gas channel 111 past the guide vanes 130 and the rotor blades 120. On the rotor blades 120, the working medium 113 expands in a pulse-transmitting manner, so that the rotor blades 120 drive the rotor 103 and drive 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 earths 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 present a thermal barrier coating, and consists for example of ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , 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 guide blade 130 has a guide blade root facing the inner housing 138 of the turbine 108 (not shown here) and a guide blade foot opposite

Guide vane head on. 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, a fastening area 400, an adjacent blade platform 403 and an airfoil 406 and a blade tip 415.

As a guide blade 130, the blade 130 may have another platform at its blade tip 415 (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 Christmas tree or Schwalbenschwanzfuß 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, solid 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 produced 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, for example, by directed solidification from the melt. These are casting methods in which the liquid metallic alloy solidifies into a monocrystalline structure, ie a single-crystal workpiece, or directionally. 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, in common parlance, referred to as directionally solidified) or a monocrystalline structure, ie the whole Workpiece consists of a single crystal. In these procedures must one avoids the transition to globulitic (polycrystalline) solidification, because by non-directional growth necessarily transverse and longitudinal grain boundaries form, 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.

A protective aluminum oxide layer (TGO = thermal grown oxide layer) is formed on the MCrAlX layer (as an intermediate layer or as the outermost layer).

Preferably, the layer composition comprises Co-30Ni-28Cr-8A1-0, 6Y-0, 7Si or Co-28Ni-24Cr-10Al-0, 6Y. In addition to 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-1OA1-O, 4Y-1 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 ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , ie it is not, partially or completely stabilized by yttria and / or calcium oxide and / or magnesium oxide.

The thermal barrier coating covers the entire MCrAlX layer. 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, 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 film cooling holes 418 (indicated by dashed lines) on.

FIG. 5 shows a combustion chamber 110 of a gas turbine. The combustion chamber 110 is designed, for example, as a so-called annular combustion chamber, in which a multiplicity of burners 107 arranged in the circumferential direction about an axis of rotation 102 open into a common combustion chamber space 154 which generates flames 156. For this purpose, the combustion chamber 110 is in their entirety designed as an annular structure which is positioned around the rotation axis 102 around.

To achieve a relatively high efficiency, the combustion chamber 110 is designed for a relatively high temperature of the working medium M of approximately 1000 ⁰ C to 1600 ° C. 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 fluid 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 can 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, for example, a ceramic thermal barrier coating may be present and consists for example of ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , ie it is not, partially or completely stabilized by yttria 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 thermal barrier coating 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

1. A method for controlled EDM processing of a substrate (4), in which a progress parameter of the structure to be produced in the substrate to be processed (4) is measured during the EDM processing, which represents a measure of the progress of the EDM processing, and which is used to adapt an EDM processing parameter of the EDM processing equipment, and wherein the EDM processing parameter is at least selected from the group: power, voltage, current of the EDM processing equipment.

2. The method of claim 1, wherein the progress parameter is continuously measured or determined.

3. The method of claim 1, wherein the progress parameter is measured or determined discontinuously.

A method according to claim 1, 2 or 3, wherein the progress parameter is a surface (Y, Y ¹ ) facing an EDM electrode (10) within the substrate (4).

5. The method of claim 1, 2 or 3 wherein the progress parameter is the penetration depth (d) of an EDM electrode (10) into the substrate (4).

6. The method of claim 1, wherein a hole (25) is produced, which represents the structure to be produced.

7. The method of claim 1 or 6, wherein a layer system is processed.

8. The method of claim 1, wherein as the EDM processing parameters only the power changed, in particular increased.

9. The method of claim 1, wherein as the EDM machining parameters, only the voltage is changed, in particular is increased.

10. The method of claim 1, wherein only the current is changed as EDM processing parameters, in particular increased.

11. The method of claim 1, wherein an at least partially conical EDM electrode (10) is used, which is in particular conically formed on the tip (28).

12. A device (1) for controlled EDM processing of a substrate (4), comprising means for measuring a progress parameter of a structure to be fabricated in a substrate to be processed (4) and means for controlling an EDM processing parameter in dependence on the measured progress parameter having .

13. The apparatus of claim 12, comprising a power control of an EDM electrode (10).

14. The apparatus of claim 12 or 13, having a regulation of the voltage of an EDM electrode (10).

15. The apparatus of claim 12, comprising a control of the current of an EDM electrode (10).

16. The device according to claim 12, which has an at least partially conically shaped EDM electrode (10) which is conical, in particular at the tip (28).