EP1663554B1 - Method for the production of components of a gas turbine - Google Patents

Abstract

The invention relates to a method for producing components preferably of a gas turbine, particularly an aircraft engine, by means of powder-metallurgical injection molding. In powder-metallurgical injection molding, a powder metal is first mixed with a binding agent so as to obtain a homogeneous mass, whereupon at least one molded body is produced from the homogeneous mass in an injection molding process, and the or each molded body is subsequently subjected to a debinding process. The or each molded body is then compressed by means of sintering to obtain at least one component having desired geometrical properties. According to the invention, several molded bodies are joined together by means of a diffusion process during sintering in order to produce a part. Preferably, the molded bodies that are to be joined together are brought into surface contact, preferably positive surface contact, in sections of the molded bodies, which are to be joined together, at least during sintering, pressure being applied to the molded bodies that are to be joined together during sintering.

Description

The invention relates to a method for producing components of a gas turbine according to the preamble of patent claim 1.

Modern gas turbines, in particular aircraft engines, must meet the highest demands in terms of reliability, weight, performance, economy and service life. In recent decades, aircraft engines have been developed, particularly in the civil sector, which fully meet the above requirements and have achieved a high degree of technical perfection. Among other things, the selection of materials, the search for new, suitable materials and the search for new production processes play a crucial role in the development of aircraft engines.

The most important materials used today for aircraft engines or other gas turbines are titanium alloys, nickel alloys (also called superalloys) and high-strength steels. The high strength steels are used for shaft parts, gear parts, compressor casings and turbine casings. Titanium alloys are typical materials for compressor parts. Nickel alloys are suitable for the hot parts of the aircraft engine.

In the manufacture or production of precision components made of metallic or ceramic powders, the powder metallurgical injection molding has proven itself. Powder metallurgy injection molding is related to plastic injection molding and is also referred to as metal mold injection or metal injection molding (MIM) processes. With the powder metallurgical injection molding components can be produced, which reach almost the full density and about 95% of the static strength of forgings. The reduced dynamic strength compared to forgings can be compensated by suitable choice of material.

In the case of powder metallurgical injection molding, the prior art broadly proceeds in such a way that, in a first process step, a powder, preferably a metal powder, hard metal powder or ceramic powder, is mixed with a binder and optionally a plasticizer to form a homogeneous mass becomes. From this homogeneous mass moldings are manufactured by injection molding. The injection-molded bodies already have the geometric shape of the component to be produced, but their volume is increased by the volume of the binder and plasticizer added. The injection-molded articles are deprived of the binder and plasticizer in a debinding process. Subsequently, during the sintering, the molded body is compressed or shrunk to the finished component. During sintering, the volume of the molded body decreases, wherein it is crucial that the dimensions of the molded part in all three spatial directions must decrease uniformly. The volume shrinkage depends on the binder and plasticizer content between 30% and 60%.

In the prior art, the powder metallurgical injection molding is usually carried out so that each shaped body undergoes the Entbinderungsprozess and is subsequently sintered for themselves. If appropriate, a plurality of components produced by powder metallurgical injection molding are joined together by suitable joining methods only after the actual powder metallurgical injection molding. Accordingly, the production of components having a complex, three-dimensional shape is only possible to a limited extent with the powder-metallurgical injection molding processes known from the prior art.

On this basis, the present invention is based on the problem to propose a novel method for the production of components of a gas turbine.

This problem is solved in that the aforementioned method is further developed by the features of the characterizing part of patent claim 1.

According to the invention, a plurality of molded bodies are connected to one another during the sintering by a diffusion process for producing a component of a gas turbine.

For the purposes of the present invention, it is proposed to produce a component of a gas turbine from a plurality of shaped bodies in that during the sintering, that is to say during the powder metallurgical injection molding, the shaped bodies are connected to one another by a diffusion process. hereby It is possible, by means of powder metallurgy injection molding and components of a gas turbine with a complex, three-dimensional shape quickly and inexpensively.

US 4 813 823 A discloses a method of making drill tools by metallurgical injection molding.

According to an advantageous development of the invention, the moldings to be joined together are brought into surface contact, preferably into a positive surface contact, at least during the sintering of sections of the moldings to be joined, wherein pressure is applied to them during sintering and during the simultaneous diffusion process Molded body is exercised.

The inventive method is used in particular for the production of blades or blade segments from a plurality of blades of an aircraft engine, wherein these blades or blade segments made of a nickel-based alloy or titanium-based alloy.

Preferred embodiments of the invention will become apparent from the dependent subclaims and the following description.

Fig. 1:

ein Blockschaltbild zur Verdeutlichung der einzelnen Verfahrenschritte beim pulvermetallurgischen Spritzgießen;

Fig. 2:

einen Querschnitt durch zwei mit Hilfe des erfindungsgemäßen Verfahrens miteinander zu verbindende Formkörper;

Fig. 3:

einen weiteren Querschnitt durch zwei mit Hilfe des erfindungsgemäßen Verfahrens miteinander zu verbindende Formkörper; und

Fig. 4:

einen weiteren Querschnitt durch zwei mit Hilfe des erfindungsgemäßen Verfahrens miteinander zu verbindende Formkörper.

Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. In the drawing shows:

Fig. 1:

a block diagram illustrating the individual process steps in powder metallurgy injection molding;

Fig. 2:

a cross-section through two by means of the method according to the invention to be joined together molding;

3:

a further cross section through two by means of the method according to the invention to be joined together molding; and

4:

a further cross-section through two with the aid of the inventive method to be joined together molding.

The present invention relates to the production of components of a gas turbine, in particular an aircraft engine, by powder metallurgical injection molding (PM). Powder metallurgy injection molding is also referred to as Metal Injection Molding (MIM).

With reference to Fig. 1, the individual process steps of powder metallurgy injection molding will be explained. In a first step 10, a metal powder, hard metal powder or ceramic powder is provided. In a second step 11, a binder and optionally a plasticizer are provided. The metal powder provided in method step 10 and the binder and plasticizer provided in method step 11 are mixed in method step 12 so that a homogeneous composition is formed. The volume fraction of the metal powder in the homogeneous mass is preferably between 40% and 70%. The proportion of binder and plasticizer on the homogeneous mass thus varies approximately between 30% and 60%.

This homogeneous mass of metal powder, binder and plasticizer is further processed by injection molding in the sense of step 13. In injection molding moldings are made. These moldings already have all the typical features of the components to be produced. In particular, the shaped bodies have the geometric shape of the component to be manufactured. However, they have a volume increased by the binder content and plasticizer content.

In the downstream step 14, the binder and the plasticizer is expelled from the moldings. The method step 14 can also be referred to as the final binding process. The expulsion of binder and plasticizer can be done in different ways. This is usually done by fractional, thermal decomposition or evaporation. Another possibility consists of sucking out the thermally liquefied binding and plasticizing agents by capillary forces, by sublimation or by solvents.

Following the debinding process in the sense of step 14, the shaped bodies are sintered in the sense of step 15. During sintering, the Molded body compacted to the components with the final, geometric properties. During sintering, therefore, the moldings shrink, whereby the dimensions of the moldings must decrease uniformly in all three spatial directions. The linear shrinkage is dependent on the binder content and plasticizer content between 10% and 20%.

After sintering, the finished component is present, which is shown in FIG. 1 by step 16. If necessary, after the sintering (step 15), the component may be subjected to a refining process in the sense of step 17. The refining process is optional. It may already be present immediately after sintering a ready-to-install component.

It is within the meaning of the present invention to produce a component of a gas turbine by means of powder metallurgy injection molding in that the component is formed from a plurality of shaped bodies, wherein the shaped bodies are connected to one another during the powder metallurgical injection molding by a diffusion process. Thus, for example, the component to be produced can be composed of two moldings, wherein the two moldings are joined together during the sintering by the diffusion process. It is also possible to connect a higher number of moldings to a component during sintering.

In order to join the shaped bodies during the production of the component, the shaped bodies are brought into surface contact at portions or surface areas thereof to be joined together. This means that the moldings to be joined touch each other at the sections or surface areas. On the touching moldings or the contacting portions of the moldings, a pressure is exerted during the diffusion process. The surface contact between the moldings to be joined together and the exertion of the pressure on the same takes place at least during the sintering. The diffusion process thus takes place during the sintering.

It is also possible, the surface contact and the pressure on the contacting and to be joined moldings already during a Vorsinterns and / or during the debinding process. The procedure is preferred in that the surface contact is already provided during the debinding process and during the pre-sintering and during the actual sintering, but the pressure is exerted only on the molded bodies during the actual sintering. At this point, for the sake of completeness, it should be noted that the pre-sintering takes place between the debindering process and the actual sintering, wherein during presintering there is still no appreciable shrinkage process of the molded bodies to be joined together.

According to an advantageous development of the method according to the invention, the shaped bodies are brought into a positive surface contact. This will be explained below with reference to FIGS. 2 to 4.

Thus, FIG. 2 shows two moldings 18 and 19 which are to be joined to one another during powder metallurgical injection molding via a diffusion process. The moldings 18 and 19 touch one another at portions or surface regions 20 and 21. As can be seen from FIG. 2, the surface region 20 of FIG Shaped body 18 in cross-section wedge-shaped. This wedge-shaped surface region 20 of the shaped body 18 engages in a form-fitting manner in the correspondingly formed surface area 21 of the shaped body 19. The surface region 21 of the shaped body 19 accordingly forms a wedge-shaped groove in cross-section.

FIG. 3 shows an alternative embodiment of two moldings 22 and 23 to be joined together. Also in the embodiment of FIG. 3, surface regions 24 and 25 to be joined together are in positive contact with the moldings 22 and 23. For this purpose, a cross-sectionally trapezoidal projection is formed on the surface region 25 of the molded body 23, which engages in a correspondingly formed recess in the surface region 24 of the molded body 22.

4. In the exemplary embodiment of FIG. 4, surface regions 28 and 29 of the two shaped bodies 26 and 27 to be joined together are again in positive contact with one another, in contrast to the exemplary embodiment according to FIG. 3 are in the embodiment of FIG. 4, the projection or the recess in the region of the sections or the surface regions 28 and 29 in cross section not trapezoidal, but rather rectangular in cross section. In the embodiments according to FIGS. 2 and 3, the molded bodies 18 and 19 or 22 and 23 to be joined together are arranged side by side, in the case of the embodiment of FIG. 4, the molded bodies 26 and 27 are positioned one above the other.

The positive connection between the moldings to be joined together during the sintering by the diffusion process improves the dimensional stability of the component to be produced.

It should be noted at this point that the shaped bodies to be joined together in the sense of the present invention can be identical both in terms of their material composition and / or in terms of their shrinkage properties, and can also have different properties in this respect. If the material compositions and the shrinkage properties of the moldings to be joined together are identical, then a uniform shrinkage process arises during the sintering for the moldings to be joined together.

However, moldings having different shrinkage properties in the sense of the present invention can also be connected to one another via the diffusion process during sintering. Thus, it is also within the meaning of the present invention to sinter a shaped body having a larger shrinkage circumference during sintering onto a shaped body with a smaller shrinkage circumference. In the exemplary embodiments shown in FIGS. 2 to 4, this would mean that the molded bodies 19, 22 and 26 have a larger shrinkage circumference and thus shrink more strongly than the molded bodies 18, 23 and 27, respectively.

Moldings having different shrinkage properties can be provided by using moldings having different material compositions. Thus, for example, moldings can be used which are formed from different metal powders and thus different metal alloys. Shall shape bodies of different metal powders together be connected, it is important to ensure that the sintering temperature or diffusion temperature of the metal powder is of the same order, so that the shrinkage of the moldings takes place simultaneously. The material composition for providing molded articles having different shrinkage properties can also be changed by variation in the kind and amount of the binder. Different shrinkage properties can furthermore be achieved with the same material composition in that moldings having the same material composition are presintered differently.

Another alternative of the present invention is to compensate for the different shrinkage behavior when using moldings with different shrinkage behavior, that before the actual sintering, the moldings are processed by an upstream presintering process. The different shrinkage behavior of the moldings to be joined together can thus be compensated, so that during the actual sintering, the shrinkage behavior of the moldings is adapted to each other.

According to another alternative of the method according to the invention, the different shrinkage behavior can be compensated by the fact that the moldings, which consist for example of different metal powders, also differ in terms of their binders and optionally plasticizers or in terms of their percentage composition of metal powder, binder and optionally plasticizer. By this means, if, for example, shaped bodies made of different metal powders are to be connected to one another, the different shrinkage behavior can be compensated for. However, it is again important to ensure that the sintering temperature or diffusion temperature of the material compositions of the moldings is of the same order of magnitude, so that the shrinkage of the moldings takes place simultaneously.

By means of the present invention, it is possible to connect powder metallurgical molded bodies directly to each other during sintering. As a result, new design options for powder metallurgy to be produced components are created. Furthermore, the required according to the prior art separate joining or connecting processes after the actual powder metallurgical Injection molding. By eliminating this required according to the prior art, additional process step, the production of components faster and cheaper possible.

To reinforce the diffusion effect during sintering of the moldings to be joined together, the contacting surfaces thereof may have a coating. This coating then forms a so-called sintering aid, which can be applied as a film or as a slip material or slip layer onto the surface areas of the shaped bodies to be brought into surface contact. This diffusion effect-enhancing coating can be applied to at least one of the surface regions or sections to be joined together or also to both or all of the sections to be joined together.

To enhance the diffusion effect during sintering, the sintering may also be carried out under a special gas atmosphere which promotes the diffusion effect.

The inventive method is suitable for the production of components of a gas turbine, in particular an aircraft engine. Thus, it is within the meaning of the present invention, blades or blade segments or rotors with integral blading - so-called Blisks ( Bl aded discs ) or Blings ( Bl aded R ings ) - to produce a gas turbine using the method according to the invention. Furthermore, sealing parts, adjusting levers, securing parts or other components having a complex three-dimensional shape can be produced by the method according to the invention. Such components for a gas turbine consist in particular of a nickel-based alloy or titanium-based alloy.

Claims (5)

1. A method for producing components of a gas turbine, in particular an aircraft engine, by powder-metallurgical injection-moulding, wherein a plurality of shaped bodies are manufactured from powder/binding agent mixtures and each shaped body is subsequently subjected to a binder removal process, wherein subsequently by means of sintering each shaped body is compressed or shrunk to form at least one component with desired geometrical properties, and wherein in order to produce a component a plurality of shaped bodies are connected together during the sintering by means of a diffusion process by bringing the shaped bodies that are to be connected together into surface contact at sections that are to be connected together at least during the sintering, characterised in that during the sintering a pressure is exerted on the shaped bodies that are to be connected together.
2. A method according to claim 1, characterised in that a coating is applied to at least one of the sections of the shaped bodies that are to be connected together in order to assist the diffusion process.
3. A method according to claim 2, characterised in that the or each coating is applied as a film or slip layer.
4. A method according to one of claims 1 to 3, characterised in that when the shaped bodies that are to be connected together have a different shrinkage behaviour during the sintering, the shaped body with the greater shrunken periphery is shrunk onto the shaped body with the smaller shrunken periphery.
5. A method according to one of claims 1 to 4, characterised in that the same is used to produce blades or vanes, or blade/vane segments, in particular guide vanes, guide-vane segments, rotor blades or rotor-blade segments of an aircraft engine, or to produce rotors with integral blading.

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