Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F5/00—Electrolytic stripping of metallic layers or coatings
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F7/00—Constructional parts, or assemblies thereof, of cells for electrolytic removal of material from objects; Servicing or operating

Definitions

• the invention relates to a process for the local removal of a metallic layer from a component made of an alloy.
• the invention relates further to a device of the type disclosed in the pre- characterizing clause of Patent Claim 13 for the local removal of at least one metallic layer from a component made of an alloy.
• the device which is used for the local removal of at least one metallic layer from a component made of an alloy for an aircraft engine, comprises an electrolyte bath, which is filled with an electrolyte fluid.
• the component being processed is immersed in the electrolyte bath, held in said bath by means of a holding device and coupled to an electrode.
• a direct current is applied between the electrode and a counter electrode arranged at a distance from the layer to be removed and the layer is removed electrochemically.
• the electrolyte fluid in this case makes the charge transport possible between the electrode and the counter electrode and transports the anodically removed layer material away.
• the layer to be removed and the component are, as a rule, made of different materials.
• the object of the present invention is creating a process as well as a device of the type mentioned at the outset which makes improved local decoating of a component possible.
• the process according to the invention makes an improved local decoating of the component possible, because the component need no longer be completely immersed in an electrolyte bath. This makes it possible to reliably prevent the entire component from functioning as the electrode during polarization when applying the voltage. Instead, an electric current can flow between the counter electrode and the component connected as the electrode via the electrolyte fluid current only on the region to be decoated. As a result, the layer is removed only within the local electrochemical cell that is generated in the process. Since this is a local decoating process, a covering or protective layer for the component regions that are not supposed to be decoated is not required in contrast to the prior art, thereby making it possible to carry out the process in a considerably quicker and simpler way.
• the electrolyte fluid can be collected as needed and be used, for example, in a cyclic process and/or be recycled.
• the process is suitable as a rule for the local removal of a layer made of a material other than that of the alloy of the component, for example for removal of a dimensional correction layer.
• the process may also be used to remove a layer of the alloy of the component, for example in the course of a precision machining step.
• An advantageous embodiment of the invention provides that the electrode be connected as an anode and/or the counter electrode be connected as a cathode. This allows an especially reliable local decoating of the component to be performed, wherein most layer/component material pairings may be processed in this manner.
• Step e the level of the voltage in Step e) is set between 4 V and 14 V, in particular between 6 V and 12 V and/or set in such a way that the electrochemical removal of component material is limited essentially to the region of the layer to be removed. This ensures an especially precise and reliable removal of the layer without impairing adjacent component regions and without undesired modification of the component.
• a further advantageous embodiment of the invention provides that the counter electrode in Step b) and/or the electrolyte feed channel in Step c) be arranged at a distance of between 100 ⁇ and 1.5 mm from the layer to be removed.
• the component moves relative to the counter electrode before and/or during Step e), in particular rotates around a component axis.
• the component may basically be provided that the component be moved with respect to the stationary counter electrode, that the counter electrode be moved with respect to the stationary component and/or that both the component as well as the counter electrode be moved.
• the electrolyte feed channel is preferably moved along with the counter electrode.
• a counter electrode which is configured to be one piece with the electrolyte feed channel in Step b).
• a counter electrode is used which is configured to be one piece with the electrolyte feed channel in Step b).
• components with challenging geometries or inside surfaces may also be decoated reliably and simply.
• this ensures an especially process-safe contacting between the component and the counter electrode via the electrolyte fluid.
• arranging and moving the counter electrode are simplified, because the electrolyte feed channel is automatically moved along with it and is therefore always positioned optimally.
• another embodiment provides that a chemical composition of the electrolyte fluid and/or a relative position of the counter electrode with respect to the component are selected such that the electrochemical removal of the component material is limited, at least essentially, to the region of the layer to be removed. Adjusting the cited process parameters in such a way simply and reliably prevents an undesired modification of component regions that are not supposed to be decoated.
• an integrally bladed rotor of an aircraft engine in particular a blisk and/or a bling, and/or a component made of a high-temperature-resistant alloy, in particular a titanium-based, nickel-based and/or cobalt- based alloy, is used as a component and/or a layer made of a nickel-based alloy, in particular of a NiCrAI alloy, is locally removed.
• an electrolyte fluid comprised of an inorganic acid, in particular nitric acid, and/or an electrolyte fluid comprised of a base, in particular an inorganic lye are used in Step d).
• an electrolyte fluid comprised of an inorganic acid, in particular nitric acid, and/or an electrolyte fluid comprised of a base, in particular an inorganic lye are used in Step d).
• inorganic acids e.g., sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, silicic acid or boric acid.
• the electrolyte fluid may be comprised of a base.
• all compounds which are in a position to form hydroxide ions in an aqueous solution should be understood as a base.
• the use of an electrolyte fluid comprising a base is, for example, advantageous in the processing of nickel-based materials.
• the inorganic acid and/or the base can be present in this case in a concentrated and/or diluted form. In this case, it may also be provided that the electrolyte fluid is comprised exclusively of an inorganic acid or exclusively of a base.
• a further advantageous embodiment of the invention provides that at least two counter electrodes and/or at least two electrolyte feed channels are used for the local removal of a layer and/or of at least two layers. This allows a further acceleration of the process to be achieved.
• at least two counter electrodes they may, for example, be assigned different voltage amplitudes, whereby two or more layers made of different materials may be easily taken into consideration and may be removed simultaneously.
• the two or more counter electrodes may be used for especially quick removal of large layers.
• the two or more electrolyte feed channels make simultaneous removal of two or more layers and/or of large layers possible.
• different electrolyte fluids may be introduced simultaneously using the at least two electrolyte feed channels, whereby different material properties of different layers may be taken in consideration in an optimal manner.
• the at least two counter electrodes and/or the at least two electrolyte feed channels are moved relative to each other during the process.
• the counter electrodes and/or electrolyte feed channels may each differ in this case with respect to their geometry and/or their material, whereby there is an optimum adaptability to different components, to different layers to be removed and to different electrolyte fluids.
• different materials may be provided for the counter electrodes and/or the electrolyte feed channels, if it is not possible to produce different geometries with a single material.
• a further aspect of the invention relates to a device for the local removal of at least one metallic layer from a component made of an alloy, in particular a component for an aircraft engine, wherein an improved local decoating of the component is rendered possible according to the invention in that the device comprises an electrolyte feed channel, which is arranged in the region of a counter electrode of the device and the layer to be removed, and via which an electrolyte fluid can be introduced into the gap via the electrolyte feed channel for generating an electrolyte fluid current in a gap between the counter electrode and the component.
• the device according to the invention renders an improved local decoating of the component possible because the component need no longer be completely immersed in an electrolyte bath.
• the device removes the layer only within the local electrochemical cell that is generated in this process. Because the device makes local decoating possible, a covering or protective layer for the component regions that are not supposed to be decoated is also not required in contrast to the prior art. Consequently, no coverings or protective layers must be removed after decoating either, thereby making a substantial acceleration and price reduction of the production process possible.
• the electrolyte fluid may be collected as needed and be used, for example, in a cyclic process and/or be recycled.
• the process is suitable as a rule for the local removal of a layer made of a material other than that of the alloy of the component, for example for removal of a dimensional correction layer.
• the process may also be suitable for the removal of a layer of the alloy of the component, for example in the course of a precision machining step.
• An advantageous embodiment of the invention provides that the counter electrode and the electrolyte feed channel be configured as one piece. Because of this, the counter electrode and the electrolyte feed channel have an especially low requirement for space, so that even components with challenging geometries or inside surfaces may be decoated reliably and simply. In addition, this makes an especially process-safe contacting possible between the component and the counter electrode via the electrolyte fluid. In addition, arranging and moving the counter electrode are simplified, because the electrolyte feed channel is automatically moved along with it and therefore always positioned optimally.
• the electrolyte feed channel containing a preferably removable nozzle by means of which the electrolyte fluid current can be guided.
• the nozzle may basically be configured for focusing, for fanning out and/or for spraying the electrolyte fluid. It may also be provided that the nozzle possesses a modifiable geometry. By configuring the nozzle to be removable, it is possible to make different nozzles available and for them to be replaced and mounted correspondingly quickly and simply. As a result, a nozzle that is optimally adapted to the respective intended use may always be used.
• the counter electrode be made of a metal alloy, in particular a titanium alloy and/or a high-grade steel.
• the counter electrode features a particularly high mechanical and chemical resistance with simultaneously low manufacturing costs.
• An analogous situation applies to the electrolyte feed channel, if the counter electrode and the electrolyte feed channel are configured to be one piece.
• a titanium alloy, a stainless steel or the like may be used as the metal alloy.
• the holding device By designing the holding device to move the component relative to the counter electrode, in particular to rotate around a component axis, layers with any geometric design may be locally removed.
• the component may basically be provided that the component be moved with respect to the stationary counter electrode, that the counter electrode be moved with respect to the stationary component, and/or that the component as well as the counter electrode can be moved independently of each other.
• the electrolyte feed channel is able to move along with the counter electrode. Because it is possible to rotate the component around a component axis, a rotationally symmetrical layer in particular may be removed especially quickly and simply.
• the electrolyte feed channel is configured to be flexible and/or rigid and/or be bordered by a wall made of a metallic and/or non-metallic material. This allows for a high level of structural flexibility of the device and a simple adaptability of the electrolyte feed channel to different use profiles.
• a preferably removable splashguard device is arranged in the region of the electrolyte feed channel to limit the electrolyte fluid current.
• the electrolyte fluid may be used especially efficiently, because even with higher flow rates, there are no material losses due to lateral splashing in particular.
• an undesired modification of regions of the component that are not to be decoated is particularly reliably prevented and industrial safety is further improved.
• the splashguard device is configured to be removable, it can be mounted on or removed from the device quickly and simply so that a splashguard device that is optimally adapted to the geometric circumstances and/or to the electrolyte fluid being used may always be used. In this case, it may be provided that the splashguard device be arranged in an end region of the electrolyte feed channel or in the region of a nozzle on the electrolyte feed channel.
• FIG. 1 A schematic diagram of a device for the local removal of a metallic layer from a component for an aircraft engine
• FIG. 2 An enlarged representation of Detail II shown in Fig. 1 ;
• FIG. 3 A schematic diagram of an alternative embodiment of a counter electrode and of an electrolyte feed channel of the device, wherein a splashguard device is also provided;
• FIG. 4 A part of a schematic diagram of an alternative embodiment of the device for removing a large layer
• FIG. 5 A part of a schematic diagram of the device shown in Fig. 4, wherein two layers are removed simultaneously from one component.
• Fig. 1 shows a schematic diagram of a device 10 for the local removal of a metallic layer 12 from a component 14, which is configured here as a blisk (bladed disk) that is known per se for an aircraft engine.
• Fig. 1 will be explained in the following together with Fig. 2, in which an enlarged representation of Detail II depicted in Fig. 1 is illustrated.
• the metallic layer 12 is a dimensional correction layer made of a NiCrAl alloy.
• the component 14 is made of a titanium alloy (Ti-834: Ti-5,8 Al-4 Sn-3,5 Zr-0,7 Nb-0,5 Mo-0,35 Si-0,06 C), which is nonmagnetic and has a high tensile strength and creep resistance up to approx. 600°C along with a very good fatigue strength.
• the layer 12 in this case runs annularly along an inside circumference of the component 14.
• the device 10 features a holding device 16, which is used to hold the component 14 and according to Arrow I can be rotated around a component axis A.
• the device 10 includes an electrode 18 coupled to the component 14, which is connected here as an anode via a control and/or regulating unit (not shown) of the device 10.
• a counter electrode 20 Arranged at a distance from the layer to be removed 12 is a counter electrode 20, which is connected via the control and/or regulating unit as a cathode.
• the device 10 includes an electrolyte feed channel 22, which is configured as one piece with the counter electrode 20 in the depicted exemplary embodiment and by means of which electrolyte fluid 24 can be introduced for generating an electrolyte fluid current in a gap S between the counter electrode 20 and the component 14.
• the electrolyte feed channel 22 or the counter electrode 20 configured as one piece with said electrode feed channel has a nozzle 26, by means of which the electrolyte fluid current can be focused.
• the counter electrode 20 functions simultaneously as a discharge nozzle for the electrolyte fluid 24.
• concentrated and/or diluted nitric acid is used as the electrolyte fluid 24. This thereby ensures that the regions of the component 14 that are not supposed to be removed are not harmed, because titanium or the titanium alloy Ti-834 used behaves electrochemically passively in nitric acid.
• the counter electrode 20, which simultaneously forms the wall bordering the electrolyte feed channel 22, is also made of a titanium alloy and is therefore also not affected by the nitric acid.
• the component 14 is first of all fastened to the holding device 16 and coupled to the electrode 18. Then the counter electrode 20 and the electrolyte feed channel 22 configured as one piece with said counter electrode are arranged at a distance of between approx. 100 ⁇ and approx. 1.5 mm from the layer to be removed 12, thereby forming the gap S. After positioning, the component 14 is put into a slow rotation around the component axis A via the holding device 16. Thereupon, the electrolyte fluid 24 is continuously introduced into the gap S via the electrolyte feed channel 22, whereby the electrolyte fluid current electrically connecting the counter electrode 20 to the component 14 or the electrode 18 is generated.
• an electric voltage is generated between the electrode 18 and the counter electrode 20 by means of the control and/or regulating unit, thereby locally anodically dissolving and removing the layer 12 over the entire circumference of the component 14 due to the rotational movement.
• the level or the amplitude of the voltage in this case is set in such a way that the resulting current is sufficient to locally remove the layer 12.
• a voltage between 4 V and 14 V, in particular between 6 V and 12 V has proven to be suitable.
• a contact closure takes place only at those points at which the electrolyte fluid 24 encounters the component 14.
• the layer 12 is removed only within the "local electrochemical cell" formed hereby.
• the level of voltage is varied as a function of the time and/or of the decoating progress.
• the spatial location or the distance between the counter electrode 20 and the component 14 may be varied as a function of the time and/or of the decoating progress.
• Fig. 3 shows a schematic diagram of an alternative embodiment of a counter electrode 20 and an electrolyte feed channel 22 of the device 10 that is again configured to be one piece with said counter electrode.
• a splashguard device 30 for limiting the electrolyte fluid current is arranged in the region of the electrolyte feed channel 22 or the nozzle 26. Electrolyte fluid 24 splashing off the component 14 is collected in this case with the aid of the splashguard device 30 so that no undesired fluid losses occur, an undesired modification of regions of the component 14 that are not supposed to be decoated is avoided in a particularly reliable manner and in addition, industrial safety is improved.
• the splashguard device 30 in this case can be removed from the electrolyte feed channel 22 or the counter electrode 20 and thus may be replaced quickly and simply for an alternative splashguard device 30 in order to make an optimum adaptation to different component types and component geometries possible.
• Fig. 4 shows part of a schematic diagram of an alternative embodiment of the device 10 for the removal of a large layer 12 from a component 14.
• the device 10 shown here includes two counter electrodes 20a, 20b and two electrolyte feed channels 22a, 22b.
• the counter electrode 20a and the electrolyte feed channel 22a as well as the counter electrode 20b and the electrolyte feed channel 22b are respectively configured as one piece and arranged side by side.
• Nozzles 26a, 26b are attached to the end regions of the electrolyte feed channels 22a, 22b respectively, by means of which the currents of the electrolyte fluids 24a, 24b may be guided.
• the comparably large layer 12 may be locally removed in the above-described manner in one process step, thereby yielding advantages in terms of time and cost.
• Fig. 5 shows part of a schematic diagram of the device 10 depicted in Fig. 4, wherein two geometrically different layers 12a, 12b that are spatially separated from one another are simultaneously removed from a component 14.
• two geometrically different counter electrodes 20a, 20b and two geometrically different electrolyte feed channels 22a, 22b are used.
• the counter electrode 20a and the electrolyte feed channel 22a as well as the counter electrode 20b and the electrolyte feed channel 22b are again respectively configured as one piece and arranged at a distance from one another.
• the counter electrodes 20a, 20b and the electrolyte feed channels 22a, 22b can be moved relative to each other so that different relative distances or spatial alignments may be adjusted before or during the process.
• gaps S of different sizes may be adjusted between the electrolyte feed channels 22a, 22b and the layers 12a, 12b.
• Geometrically different nozzles 26a, 26b are attached to the end regions of the electrolyte feed channels 22a, 22b, by means of which the electrolyte fluid currents 24a, 24b may be guided to the respective layer 12a, 12b in a targeted manner.
• at least one of the nozzles 26a, 26b features a modifiable geometry in order to make a particularly precise adjustment of the electrolyte fluid current to the respective layer 12a or 12b possible.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Electroplating Methods And Accessories (AREA)

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• 2009
  • 2009-09-09 DE DE102009040862A patent/DE102009040862A1/de not_active Withdrawn
• 2010
  • 2010-09-06 WO PCT/IB2010/002210 patent/WO2011030201A1/en active Application Filing
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