Patent Application
20170087669
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 102015218477.3, filed Sep. 25, 2015, and German Patent Application No. 102015223189.5, filed Nov. 24, 2015. The entire disclosures of the priority applications are expressly incorporated by reference herein.
1. Field of the Invention
The invention relates to a method for producing and/or repairing in particular rotationally symmetrical components. The invention further relates to a corresponding apparatus according for carrying out the method.
2. Discussion of Background Information
It is known to cast or to forge components from titanium aluminide (γ-TiAl). However, the components are becoming ever more complex and larger, with the wall thicknesses of the components becoming ever smaller for weight reasons. If TiAl components of this nature are required in very small quantities, conventional production will be uneconomical or is no longer possible on account of the increasing complexity.
Thus, generative production by means of powder presents itself. In virtual terms, the component to be produced is split into a plurality of mutually parallel layers. In this case, a laser is used to sinter or melt the metal powder onto those sites which correspond to the current component layer of the virtual model. The component located on a platform is lowered slightly. Fresh metal powder is applied to the surface. Then, the next layer is heated in accordance with the virtual data. This is repeated until all the layers have been produced.
In the case of such methods based on a powder bed, however, there is a serious risk of the formation of pores, impurities and bonding errors.
In view of the foregoing, it would be advantageous to have available a method and a corresponding apparatus which make the cost-effective production of TiAl components in small quantities possible.
The present invention provides a method for producing and/or repairing in particular rotationally symmetrical components. The method comprises:
The specific temperature in (c), which will usually be in the range from about 500° C. to about 850° C., ranges from about 300° C. below to about 50° C. above the brittle-ductile transition temperature of the material of the component.
In one aspect of the method, (c) and/or (d) may be carried out in vacuo, in particular at a pressure of less than about 10−3 mbar.
In another aspect, the preheating in (c) may be carried out with at least one of a radiation furnace, a laser, and an electron source.
In yet another aspect of the method, in (c) the heating power may be from about 400 W to about 1200 W.
In a still further aspect of the method, in (d) the energy source may be a laser and/or an electron source.
In another aspect, the diameter of the wire-shaped and/or rod-shaped filler additive material may be from 0.3 mm to 2 mm.
In another aspect, in (c) and/or in (d) the component and/or the starting platform may be turned, in particular continuously.
The present invention also provides a component which has been produced by the method set forth above (including the various aspects thereof).
In one aspect of the component, the component may be made of titanium aluminide and/or the component may be a guide ring, a housing part in a compressor and/or turbine, an outlet guide wheel, a stator segment and/or a sealing ring.
The present invention also provides an apparatus for producing and/or repairing in particular rotationally symmetrical components. The apparatus comprises:
In one aspect, the apparatus may further comprise a storage vessel and/or a conveying unit for a filler additive material, which is or are arranged in the process chamber.
In another aspect of the apparatus, the heating source may comprise at least one of a laser, an electron source, a radiation furnace.
In yet another aspect, an individual segment of the heating source may comprise at least one luminaire and/or at least one, in particular water-cooled, metal block. For example, the luminaire may be arranged in the, in particular mirrored, metal block and/or the spacing between the luminaire and the component and/or starting platform may be from 1 cm to 30 cm.
In a still further aspect of the apparatus, the energy source may comprise a laser and/or an electron source.
As set forth above, the invention relates to a method for producing and/or repairing in particular rotationally symmetrical components. The method comprises the following steps. In step (a), a component and/or a starting platform are provided. This starting platform can be produced from a high-temperature-resistant alloy. These include, for example, Ni-based, Co-based, Fe-based and/or Mo-based alloys. In step (b), the component or the starting platform is placed on a sample table. Then, in step (c), the component or the starting platform is preheated to a specific temperature by means of a heating source. Then, in step (d), a wire-shaped or rod-shaped filler additive material comprising TiAl is applied to the component or to the starting platform by means of build-up welding. In this case, the TiAl of the filler additive material can have a composition which takes into account, or even partially or entirely prevents, the evaporation of aluminum from the filler additive material during step (d). In this case, an energy source causes the filler additive material to melt. According to the present invention, the specific temperature during preheating in step (c) lies in the range from about 300° C. below to about 50° C. above the brittle-ductile transition temperature of the component material. In particular, the temperature can lie in the range from about 500° C. to about 850° C. This method has the advantage that the production times are low and a high yield of material is achieved. Furthermore, the production can be effected near net shape. Even very complex shapes are now possible in this way.
In one advantageous configuration of the invention, step (c) and/or step (d) is carried out in vacuo, in particular at a pressure of less than about 10−3 mbar. The vacuum affords the advantage that there are very low heat losses via the heat conduction.
In a further advantageous configuration of the invention, the preheating in step (c) takes place by means of a radiation furnace, a laser and/or an electron source. The heating power is preferably in the range from about 400 W to about 1200 W. This has the advantage that even complex and large components can be preheated uniformly.
In a further advantageous configuration of the invention, in step (d) the energy source used is at least one laser and/or at least one electron source. These energy sources can advantageously be redirected very quickly in all spatial directions. By using the electron beam, it is possible to achieve higher deposition rates than when a laser beam is used, since more energy can be introduced per unit of time and the deflection is quicker (electrical coils) than in the case of the laser (mechanical lenses). The economic viability of the electron beam method is increased as a result. By contrast, the laser is less susceptible to interference by an electrical field from a radiation furnace. If it is not possible to compensate for the diversion of the electron beam as energy source by the interfering fields of the radiation furnace, it is possible to preheat the entire component only by means of the electron beam as heating source. It is also conceivable to heat the entire component only by means of a laser as heating source, but this would be realized via a separate second laser or a plurality of further lasers. In addition, the temperature can be controlled and/or regulated by way of a temperature sensor, such as a pyrometer and/or thermocouple.
In a further advantageous configuration of the invention, the diameter of the wire-shaped and/or rod-shaped filler metal is from 0.3 mm to 2 mm. This allows for a continuous feed, and therefore the microstructure of the filler additive material is reproducible after the melting.
In a further advantageous configuration of the invention, in step (c) and/or in step (d) the component and/or the starting platform is turned, in particular continuously. This has the advantage that in particular large rotationally symmetrical components can also be preheated uniformly in vacuo in the construction sector, such that no microcracks form during the wire build-up welding of TiAl material.
In a further advantageous configuration of the invention, the component is a guide ring, a housing part in the compressor and/or turbine, an outlet guide wheel, a stator segment and/or a sealing ring. Components of this type are particularly large and rotationally symmetrical. It is often the case that components of this type have small and different wall thicknesses, such that induction heating, for example, causes scarcely any induction current or induction current of a differing level to flow in the component wall. These components can be produced from TiAl.
The invention further relates to an apparatus for producing and/or repairing in particular rotationally symmetrical components. The apparatus comprises a process chamber, a sample table movable in rotation and/or translation, an annular heating source, which is arranged around a heating region arranged over the sample table, and a sample head having at least one energy source for melting a filler additive material and having a feed unit for the in particular wire-shaped or rod-shaped filler additive material, which preferably comprises TiAl. The feed unit can thus be a wire nozzle.
In this case, the heating source is preferably made up of a plurality of individual segments. By way of example, at least two individual segments can be arranged alongside one another. This affords the advantage that the number of individual segments can be adapted to the diameter of the component. It is thereby possible to ensure that the heating source can be arranged sufficiently close to the component to be produced or to the component to be repaired. In particular, the spacing between the component and the heating source should be in the range from 1 cm to 30 cm. The process chamber can preferably have a strong rotary vacuum pump water-cooled at the flange on the housing wall of the process chamber. Gas which has been sucked up from the operation of pre-cleaning and flushing with noble gas (Ar, He) can be purified and reused.
In a further advantageous configuration of the invention, the apparatus comprises a storage vessel and/or a conveying unit for a filler additive material, which is or are arranged in the process chamber. Thus, the storage vessel can be a roller with coiled TiAl wire, for example. The conveying unit can be a drive roller, which can feed the wire. The filler additive material can be stored in the apparatus in vacuo, as wire material on a roller and as rod material in a cylindrical rod feed conveyor. Material can be refilled via a separate lock. The rods can be guided to the sample head without welding, edge-to-edge, or as welded-together wire.
In a further advantageous configuration of the invention, the heating source comprises a laser, an electron source and/or a radiation furnace.
In a further advantageous configuration of the invention, the individual segment comprises at least one luminaire and/or at least one, in particular water-cooled, metal block. The luminaire is preferably arranged in the, in particular mirrored, metal block. This has the advantage that the heat radiation of the at least one luminaire can be exploited better. Furthermore, the heat generated by the luminaire can be transported away better owing to the thermal conductivity of the metal block.
In a further advantageous configuration of the invention, the energy source comprises a laser and/or an electron source. On the one hand, higher deposition rates can be produced with an electron source than with a laser. However, the electron beams are more susceptible than laser beams to electrical interference fields, for example from a radiant heating system.
Further advantageous configurations of the invention are specified in the dependent claims.
Hereinbelow, preferred exemplary embodiments of the invention will be described in more detail on the basis of the schematic drawings, in which:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description in combination with the drawings making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.
In the upper region of
The two partial rings 30 and 38 leave a first gap 40 and a second gap 42 free on the left and on the right in
A laser 46, shown on the left in
A sample head 54, shown on the right in
In combination therewith or as an alternative thereto, a further sample head 54′ having an energy source 56′ and a feed unit 57′ can be arranged above the component (see
The electron source 56 affords the possibility to split the beam thereof into a plurality of beams, such that, as is visible in
The heating source 20, formed as a radiation furnace, ensures that there is a uniform temperature of the entire component 18 located in the heating region. In this respect, this heating source 20 shown in
Firstly, in step S1, the process chamber 4 is cleaned. In this process, the process chamber 4 is evacuated down to a negative pressure of about 10−5 mbar. Then, the process chamber 4 is flooded with an inert gas (Ar and/or He). The process chamber is evacuated again after the flooding. The flushing can be repeated a number of times here as required.
In step S2, the starting platform 16 or the component 18 to be repaired is then preheated to a temperature of about 500° C. to about 850° C. by means of the heating source 20 in the form of a radiation furnace, and the sample table 6 is turned. At the same time, the wire 60 and the first electron beam 58 impinge on the weld point 61.
In step S3, the component is slowly cooled after the end of the construction job.
Then, in step S4, any supporting structures present are removed.
Finally, in step S5, the component 18 is mechanically reworked. Here, the necessary contact surfaces of the component 18 shown here are machined, for example by grinding or milling, in order to obtain planar surfaces. Further surfaces of the component at which high stresses arise are likewise mechanically reworked.
It is thereby possible to produce large, approximately rotationally symmetrical components made of TiAl for aero engine applications at from room temperature to about 900° C. It is thereby possible to cost-effectively produce a few large, complex parts per aero engine in low quantities.
By means of electron beam build-up welding, it is thereby possible to use an additive production method which makes it possible to achieve relatively short construction times, a high material yield, near-net-shape and complex shaping and therefore components and structures which to date have not been able to be produced from TiAl.
Although the present invention has been described in detail with the aid of the exemplary embodiments, it is clear to the person skilled in the art that the invention is not restricted to these exemplary embodiments, but rather that variants are possible in that individual features may be omitted or other combinations of features may be implemented, so long as the protective scope of the appended claims is not departed from. The present disclosure also includes all combinations of the individual features proposed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015218477.3 | Sep 2015 | DE | national |
| 102015223189.5 | Nov 2015 | DE | national |
