DE102015207017B4 - Method for producing covered wheels - Google Patents

Abstract

Method for producing covered wheels (1) with the following successive steps: - providing an open impeller (2) with a number of blades (3), the blades (3) being provided with an outer contour, - filling the spaces between the blades (3) by means of cold gas spraying until the formation of a surface (6) flush with the outer contours of the blades (3) to form a support structure (5), - performing a generative manufacturing process for applying a cover layer (4) to the surface (6) , - Remove the support structure (5).

Description

The present application relates to a method for the production of capped wheels, in particular of capped impellers or blisks.

Impellers, especially impellers or blisks, are used in turbomachinery to compress fluids by mechanical work or to perform mechanical work by relaxing fluids. Impellers can be made open, which means that the blades rotate or close tangentially to a stationary casing, with the blades being fixedly connected to a casing. Closed wheels have a higher efficiency compared to open wheels, since here the frictional resistance of the fluid to the stationary housing is lower.

There are several known methods for producing closed impellers. Thus, the flow channels can be produced for example by a casting process. However, no rework is possible in undercut areas. With thin-walled structures dimensional limitations are also limited.

In EP 2 177 298 A1 For example, a machining strategy is described which, using long tools, generates spark erosion or electrochemical ablation starting apertures. Here, however, are set by the geometry of the cutting tool limits in the production of undercut areas.

Furthermore, often the welding of the wheels of two or more parts application. Here, the individual parts of the impeller are conventionally machined and then joined so that the closed impeller is created. A disadvantage of welding processes are the welds themselves, which can prove to be a potential weak point and the distortion on the component, which results from the high thermal energy input.

Another joining method of the wheels is the soldering, whereby the strong distortion of the welding can be prevented. Here, however, the solder joint is always a potential vulnerability.

Furthermore, it is off EP 2 746 589 A2 known to produce additive monolithic, closed impeller, ie the wheels are completely built up, layer by layer with a laser sintering process, or an electron beam welding process, whereby the weak point of the joining process is bypassed. However, no rework is possible in undercut areas. This is especially problematic because the surface quality is limited by the layer height of the method used by the layered structure throughout the flow channel.

In the WO 2009 058336 A2 A powder metallurgical technique for the production of closed impellers is presented: Here, an open impeller is conventionally machined, then the flow channels are filled with a metal powder and encapsulated. Then a first hot isostatic pressing (HIPpen). The capsule is at least partially removed so that one side of the blades is exposed. Then, a second metal powder is applied from the blade material and the component is encapsulated again. Now the second HIP process takes place. After removing the metal powder from the first HIP process, the flow channels are obtained. In the patent, etching with nitric acid or abrasive jetting is proposed for removing the first metal powder. This process is very time-consuming due to the two HIP processes with the intermediate cutting process, since this requires the component to be clamped and unclamped several times. The use of nitric acid to dissolve out the filler is also expensive.

The object of the invention is to provide a method for the production of capped wheels, which has a low production time and provides a defined surface quality in the flow channel. Furthermore, production-related weak points, such as in particular welds or solder joints, should be avoided.

The solution of this object is achieved by the features of the independent claim.

A conventional open impeller is filled with a support structure, so that an edge region of the blades is flush with the support structure. The resulting surface serves as a substrate for an additive manufacturing process. As a result, the short production time and high surface quality in the machining production of open impellers or blisks are combined with the design possibilities of a generative manufacturing process. Furthermore, production-related weaknesses such as welds or solder joints are eliminated. The application of the support structure by means of cold gas spraying. In this case, metallic particles are accelerated with a carrier gas to supersonic speed by the compressed carrier gas, in particular by means of a Laval nozzle, is relaxed and thereby reaches high gas velocities.

The fact that the metallic particles are not melted upon impact with the substrate, the thermal stresses are lower and the distortion of the component smaller.

It has surprisingly been found that the surface, which serves as a substrate for the generative manufacturing process, even with a production by means of cold gas spraying has an excellent quality for performing the generative manufacturing process. Thus, the use of the cold gas spraying on the one hand, a method with little effort available, which is very component gentle due to low thermal stresses, on the other hand, the implementation of generative manufacturing process can be performed directly on the cold gas injected support structure. Thus, in particular an additional, complex step of the surface treatment of the support structure is avoided.

The term generative manufacturing process refers here to a primary molding of products of informal material, such as in particular liquids or powders, or form neutral, in particular band or wire-shaped material by means of chemical and / or physical processes.

With the method according to the invention, the production of closed wheels is no longer limited by the accessibility with cutting tools, since open wheels are easy to produce even with complicated blade shapes with conventional Zerspanmethoden.

The method according to the invention comprises the following steps, which are carried out in the order shown. First, an open impeller with a number of blades, the blades being provided with an outer contour is provided. In a next step, the spaces between the blades are filled up with cold gas spraying until the formation of a surface which is flush with the outer contours of the blades and forms a support structure. Then, the implementation of a generative manufacturing process for applying a cover layer to the surface. Finally, the support structure is removed. Thus, a capped impeller is present, in particular, no production-related weaknesses are present.

The dependent claims have preferred developments of the invention to the content.

The support structure is removed in particular by corrosion.

Furthermore, it is particularly advantageous that the surface is machined before carrying out the generative production process. Thus, in particular, the outer contour of blades of the open impeller is machined. The inventive method thus allows in a simple manner to change the geometry of the open impeller before applying the cover layer.

The open impeller and / or the Deckschickt are advantageously made of metallic materials. Alternatively, the method according to the invention can also be applied to other materials, in particular plastic, so that the open running wheel and / or the cover layer can preferably also be made from these other materials.

In one embodiment of the invention, the generative process is cold gas spraying. Thus, both the application of the support structure and the application of the cover layer by means of the same method, namely the cold gas spraying, are carried out particularly advantageously. In this case, advantageously, the material to be used is different, so that the material of the support structure differs from the material of the cover layer. By using a uniform method, the entire manufacturing process is very simple and inexpensive, since only a mechanical device for carrying out a process has to be kept ready. For further embodiment of the invention, a water-corrodible material is used as a support structure. In particular, thermally sprayed magnesium with steel forms an easily corrodible composite material. This can be quickly washed out with water and is therefore less problematic than the use of nitric acid, and less expensive than abrasive water jets.

An edge region of the blades of the open impeller is advantageously shaped such that a positive force transmission of the cover layer is ensured to the blades. For this purpose, the edge regions of the blades are advantageously provided with a convex contour. Thus, local voltage peaks are avoided within the capped impeller, as already by the positive connection a power transmission is possible.

Furthermore, it is preferably provided that the capped impeller is a capped impeller or a capped blisk.

Finally, it is preferably provided that the open impeller is produced by machining. Thus, particularly preferably, the aforementioned step of providing the open impeller is such as to provide a machined open impeller. Alternatively, it is preferably provided that this step is replaced by the machining production of an open impeller.

The invention will now be described with reference to an embodiment in consideration of attached drawings described in detail. In the drawings:

1 1 is a schematic representation of an open impeller during a first step of the method according to a preferred embodiment of the invention;

2 a schematic representation of an open impeller during a second step of the method according to the preferred embodiment of the invention,

3 a schematic representation of a capped impeller according to a third step of the method according to the preferred embodiment of the invention, and

4 a schematic representation of a capped impeller according to a fourth step of the method according to the preferred embodiment of the invention.

1 shows a first step of the method for producing capped wheels 1 according to a preferred embodiment of the invention. This is an open impeller 2 provided. The open wheel 2 is preferably made by machining and has a plurality of blades 3 on. In the in 1 illustrated embodiment is the open wheel 2 an impeller. Thus, it is provided in the preferred embodiment that a capped impeller is to be produced.

In a second step is on the open wheel 2 a support structure 5 applied. By applying the support structure 5 become spaces of the blades 3 filled. This creates a surface 6 wherein a surface of the support structure 5 flush with the outer contours of the blades 3 is. The outer contours of the blades 3 are provided with a convex contour, leaving a cover layer 4 (see. 3 ) with the blades 3 is positively connected.

The application of the support structure 5 done by means of cold gas spraying. This eliminates a complicated production of containers that are needed in particular for metallic powders. Compared with a hot isostatic pressing the application of the support structure according to the preferred embodiment of the invention is very simple, inexpensive and time-saving possible. In addition, the cold gas spraying allows to reduce thermal stresses and thus a distortion of the open impeller 2 to minimize.

The surface 6 can before the in 3 shown next step of the process to be machined. However, one advantage of cold gas spraying is that the surface finish of the support structure 5 is sufficiently high for performing the next step, so that the machining process is not necessarily required. However, the machining process allows the surface 6 the outer contour of the open impeller 2 and thus the later capped impeller 1 to change.

In 3 a third step of the method is shown, wherein in this third step, a generative manufacturing process is performed. The generative manufacturing process becomes a cover layer 4 on the surface 6 applied. The cover layer 4 in particular by cold gas spraying on the surface 6 applied. Thus, the process is identical to the application of the support structure 5 , where only the material to be used is different. The support structure 5 therefore differs from the topcoat 4 , In particular, it is provided that the cover layer 4 with the blades 3 is connected, wherein this compound may be cohesive or positive nature.

4 finally shows the finished capped impeller 1 , For this purpose, a fourth step of the process is carried out, in which the support structure 5 Will get removed. The support structure 5 is in particular made of a material that is easily corroded. Particularly advantageous is the support structure 5 made of a material that is corrodible with water. Thus, the support structure can be 5 very easy to wash with water. As well corrodible by water material in particular thermally sprayed magnesium with steel is known because both materials give a readily corrodible composite material. Thus, the last step of the inventive method according to the preferred embodiment is very simple and time-saving feasible.

It is thus apparent that the method shown is very time-saving and easy and therefore inexpensive to carry out. Furthermore, thermal loads on the covered impeller 1 minimized, so that this has only a small delay and therefore a long life expectancy.

LIST OF REFERENCE NUMBERS

1

capped impeller

2

open impeller

3

shovel

4

topcoat

5

support structure

6

surface

Claims (9)

Method for producing covered wheels ( 1 ) with the following, temporally successive process steps: - providing an open impeller ( 2 ) with a number of blades ( 3 ), the blades ( 3 ) are provided with an outer contour, - filling the spaces between the blades ( 3 ) by means of cold gas spraying until the formation of a with the outer contours of the blades ( 3 ) flush surface ( 6 ) to form a support structure ( 5 ), - performing an additive manufacturing process for applying a topcoat ( 4 ) on the surface ( 6 ), - removing the support structure ( 5 ). Method according to claim 1, characterized by the step of: - removing the supporting structure ( 5 ) by corrosion. Method according to claim 1 or 2, characterized in that the surface ( 6 ) is machined before the generative manufacturing process is carried out. Method according to one of the preceding claims, characterized in that the open impeller ( 2 ) and / or the cover layer ( 4 ) are made of a metallic material. Method according to one of the preceding claims, characterized in that it is the generative process to cold gas spraying. Method according to one of the preceding claims, characterized in that the support structure is made of a water-corrodible material. Method according to one of the preceding claims, characterized in that an edge region of blades ( 3 ) of the open impeller ( 2 ) is shaped such that a positive power transmission of the cover layer ( 4 ) to the blades ( 3 ) is guaranteed. Method according to one of the preceding claims, characterized in that the covered impeller ( 1 ) is a capped impeller or a capped blisk. Method according to one of the preceding claims, characterized in that the open impeller ( 2 ) is made by machining.

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