EP0574727B1 - Method for the production of a high temperature-resistant element from two different materials - Google Patents

Description

TECHNICAL AREA

The invention is based on a component for high Temperatures, in particular from a turbine blade, according to the introductory part of claim 1.

STATE OF THE ART

Such a component and a method for producing a such a component are described in DE 28 13 892 A1. The Component described is designed as a turbine impeller, which is achieved by hot pressing metal powders with different Particle structures and different chemical Compositions has been made. With this turbine impeller was mechanical as a starting material for the blades pretreated powder of a nickel base superalloy, such as for example the alloy IN 792, with particles in the form flattened beads used. As starting material for the Impeller was a mechanically not pretreated powder another nickel-based superalloy, such as of alloy IN 100, used with spherical particles. Due to the structure and chemical composition of the The powder is characterized by a good starting powder Corrosion resistance at high temperatures the impeller disc has high tensile strength and good Fatigue resistance. As starting materials for the Turbine impellers are, however, only suitable alloys that like the very related nickel-based superalloys without Changing their structure and thus their properties exposed to high temperatures during hot isostatic pressing can be. Therefore, when making this Alloys are not used for the turbine impeller excellent properties for different ones Have tasks, but only if they differ considerably deviating temperatures can be hot compressed.

SUMMARY OF THE INVENTION

The invention as specified in claims 1 and 5 is based on the task of a component, in particular to specify a turbine blade of the type mentioned at the outset, which operate when used in a high temperature Device, such as in particular a gas turbine is characterized by a long service life and at the same time a way to point, which makes it possible to simplify such a component and to be suitable for mass production.

The component according to the invention is distinguished from comparable Components according to the state of the art by long service life. On the one hand, this is due to the fact that differently stressed parts of the component from different specified alloys exist, which correspond to the different stresses on the parts of the component are adjusted. Secondly, these alloys are selected that when hot compacting it becomes a bimetallic Composite material form a boundary layer of high strength. The Component according to the invention can therefore with great certainty absorb high thermal and mechanical loads, as they do for example when operating a gas turbine or a compressor Turbocharger occur.

The one used to manufacture the components according to the invention The process is characterized in that the hot compression is carried out at temperatures at which the for desired physical or chemical properties desired structure of the alloys even with a large one Certainty is present if the ones that form the starting powder Alloys are very different chemical Have compositions.

BRIEF DESCRIPTION OF THE DRAWING

Fig.1

eine Aufsicht auf einen in Längsrichtung geführten Schnitt durch eine erste Variante eines als Turbinenschaufel ausgeführten erfindungsgemässen Bauteils nach Beendigung eines beim Herstellverfahren ausgeführten heiss-isostatischen Pressvorganges,

Fig.2

eine Aufsicht auf einen in Längsrichtung geführten Schnitt durch eine zweite Variante eines als Turbinenschaufel ausgeführten erfindungsgemässen Bauteils nach Beendigung eines beim Herstellen ausgeführten heiss-isostatischen Pressvorganges, und

Fig.3

ein Schliffbild des umrandet angegebenen Bereichs der zweiten Variante des erfindungsgemässen Bauteils.

Preferred exemplary embodiments of the invention and the advantages which can be achieved thereby are explained in more detail below with reference to drawings. Here shows:

Fig. 1

1 shows a plan view of a longitudinal section through a first variant of a component according to the invention designed as a turbine blade after completion of a hot isostatic pressing process carried out during the manufacturing process,

Fig. 2

a top view of a longitudinal section through a second variant of a component according to the invention designed as a turbine blade after completion of a hot isostatic pressing process carried out during manufacture, and

Fig. 3

a micrograph of the outlined area of the second variant of the component according to the invention.

WAYS OF CARRYING OUT THE INVENTION

The shown in Figures 1 and 2 and each as Turbine blade 1 designed components each contain one elongated airfoil 2 and one at one end of the Blade 2 molded blade root 3. With the Reference numeral 4 denotes a press can. This Press can encloses the in the embodiment according to Fig.1 Blade root 3 and has one filled by the blade 2 Opening 5, which is preferably by welding or Soldering the press can 4 to the airfoil 2 gas-tight is completed. In the embodiment according to Fig. 2 the press can 4 encloses the entire turbine blade 1.

The turbine blade 1 shown in FIG. 1 is produced as follows:
A cast body designed as an airfoil 2 is guided with its one end through the opening 5 into the press can 4. The press can 4, which is preferably made of steel, is soldered or welded to the cast body in a gas-tight manner in the region of the opening 5. Through a further opening of the press can 4, which is not shown, a cavity of the press can, which accommodates the blade root of the turbine blade 1, is filled with alloy powder. The press can 4 is then evacuated and sealed gas-tight.

Doped gamma titanium aluminides are used as the material for the cast body and for the powder alloys based on Titanium or nickel used. The one that forms the cast body Alloy is advantageously a gamma titanium aluminide with one Proportion of at least 0.5 and at most 8 atomic percent Dopant, such as one or more of the elements B, C, Co, Cr, Ge, Hf, Mn, Mo, Nb, Pd, Si, Ta, V, Y, W and Zr. For example, a typical alloy is 48 Atomic percent Al, 2 to 4 atomic percent chromium and the rest besides has unavoidable impurities Ti. Especially An alloy with the following value has proven itself Composition in percent by weight 33.2 Al - 3.9 Cr - Impurities less than 0.5 - balance Ti. Gamma titanium aluminides are characterized by a low density and good mechanical resistance at temperatures up to 800 ° C out. However, their ductility is comparatively low (<4%).

Contains the titanium base alloy used in the form of powder in addition to the titanium aluminum and a share of up to 20 Atomic percent of one or more additional elements, such as especially V and / or Nb. Typical alloys included in addition to unavoidable impurities and Ti either 6 Atomic percent Al and 4 atomic percent V or 24 atomic percent Al and 11 atomic percent Nb.

The nickel-based alloy used in the form of powder can for example the alloy IN 792 (composition in Weight percent Ni -0.12 C - 12.4 Cr - 9.0 Co - 1.9 Mo - 3.8 W - 3.9 Ta - 3.1 Al - 4.5 Ti - 0.2 B - 0.1 Zr).

The size of the powder particles is for all powders used less than 500 µm. Such titanium and nickel-based alloys are characterized by good ductility (> 10%) Room temperature. The mechanical resistance of the titanium base alloys however, this is not the case at high temperatures as high as that of gamma titanium aluminides. Nickel based alloys however, have a much higher density than gamma titanium aluminides.

The finished by gas-tight closing of the press jug 4 Sample was placed in a press and at Use of a titanium base alloy at temperatures between 900 and 980 ° C hot isostatically compressed. A typical one Pressing process at approx. 950 ° C lasted at a pressure of approx. 200 MPa about 3 hours. Here, the two alloys were under Formation of a boundary layer 6 pore-free to a bimetallic Composite material compressed.

This already has the shape of the turbine blade Composite material was removed after removing the deformed press can 4 then typically at temperatures of approx. 700 ° C heat treated for about 4 hours. Subsequent was by minor processing, such as grinding, Polishing and / or electrochemical treatment, the Turbine blade according to the invention completed.

In the manufacture of the turbine blade shown in FIG. 2 1 was extended in the longitudinal direction and the entire turbine blade 1 receiving press can 4 used. The bucket blade 2 was first inserted into this press can 4 forming castings entered and subsequently according to the previously described embodiment, the alloy powder filled. The press can 4 was then evacuated and gas-tight locked. The test specimen thus produced was according to the previously described embodiment treated. The alloys used were the same Composition on as described above Embodiment.

The structure and the are from the micrograph according to FIG Microstructure of a part of the frame indicated in Fig. 2 To remove turbine blade according to the invention. From this is it can be seen that the alloy forming the airfoil 2 a coarse-grained alloy that forms the blade root 3 has a fine-grained microstructure and that the boundary layer 6 connecting both alloys is almost unstructured and according to chemical analysis in the essentially of a binary TiAl alloy with a proportion of approximately 25 atomic percent Al is formed.

Material tests have shown the following properties for the bimetallic composite material on which the turbine blade 1 according to the invention is based:
The alloy forming the airfoil 2 has a ductility of approximately 0.5 to 1% at room temperature, while the alloy forming the airfoil 3 has a ductility of 18 to 20%. At a temperature of approximately 700 ° C., the airfoil 2 has a creep resistance which is considerably higher than the creep resistance of the nickel-base superalloys usually used in this temperature range. The turbine blade 1 shows a ductility of 0.5 to 1% corresponding to the material of the blade leaf 2, which means that the ductility of the blade is not negatively influenced by the boundary layer 6. The turbine blade 1 according to the invention is therefore characterized by a blade root 3 with high ductility and an airfoil 2 which is brittle at room temperature but has a high creep resistance at high temperatures. The strength of the boundary layer 6 is sufficient to ensure safe operation of the turbine blade 1 at high temperatures.

This can increase the strength of the boundary layer 6 can be achieved that the two alloys - as in Fig. 2 shown - at least partially in the area of the boundary layer 6 or are fully interlocked. This can happen before the introduction of the cast body into the press can 4 in simple Instruction by grinding or sandblasting the cast body its end receiving the blade root 3 up to one Roughness of up to 0.1 mm can be effected.

Instead of a cast body forming the airfoil 2 in the press can 4 also a body made of a hot isostatic compacted powder are introduced. In another alternative embodiment of the invention were approximately 100 g an alloy powder with 48 atom percent Al, 3 atom percent Cr, balance Ti and small amounts of impurities Temperatures between 1050 and 1300 ° C and a pressure of approx. 250 MPa hot isostatically compressed for approx. 3 hours. The compacted powder was then at temperatures heat treated between 1300 and 1400 ° C for a few hours. Of the resulting body was then shown in Figure 2 Press can 4 brought and at those described there Conditions together with that forming the blade root 3 Powder is hot isostatically compressed. The according to that Heat treatment and corresponding post-processing resulting turbine blade pointed towards the Turbine blade according to Figure 2 with consistently good Creep resistance increased ductility by approx. 50% Blade 2 at room temperature.

In a further variant of the invention, the Gamma titanium aluminide existing blade one blade root 3 molded from a nickel-based alloy. To this end was in the or already containing the airfoil alternatively in the welded to the airfoil Press jug filled with 4 powders of the nickel-based alloy. The Press can 4 was evacuated and sealed gas-tight. By hot isostatic pressing for approx. 3 hours at approx. 1000 up to 1250 ° C and a pressure of approx. 250 MPa pore-free bimetallic composite material made from after removing the press can 4, after heat treatment approx. 700 ° to 800 ° C and post-processing to remove material a turbine blade was manufactured according to the invention. At this turbine blade showed the boundary layer 6 in particular good strength.

In a further variant of the invention, it is possible to Place a press can 4 as a form for receiving the alloys to use a sintered mold, and compacting to Achieve turbine blade in a sintering process.

The invention is not limited to turbine blades. she also refers to others mechanically at high temperatures heavily loaded components, such as integrally formed Turbocharger turbine wheels.

LIST OF DESIGNATIONS

1

Turbine blade

2nd

Airfoil

3rd

Blade root

4th

press jug

5

opening

6

Boundary layer

Claims (9)

1. Component, in particular a turbine bucket (1), which can be exposed to high temperatures, having a component body comprising at least one first section (bucket footing 3) and at least one second section (bucket blade 2), in which component the first section (3) is formed by a ductile material and the second section (2) comprises a material which is brittle compared with the ductile material, and each of the two materials comprises one of two alloys of different chemical composition which have been hot-compacted with the formation of a boundary layer (6) joining the first (3) and the second section (2) to produce a bimetallic composite material, a first of the two alloys which forms the first section predominantly comprising titanium and/or nickel, and in that [sic] a second of the two alloys which forms the second section is a gamma-titanium aluminide and contains a proportion of at least 0.5 and at most 8 atomic per cent of dopant.
2. Component according to Claim 1, wherein the second alloy comprises one or more of the elements B, C, Co, Cr, Ge, Hf, Mn, Mo, Nb, Pd, Si, Ta, V, Y, W and Zr as dopant.
3. Component according to either of Claims 1 or 2, wherein the first alloy also comprises aluminum and vanadium or aluminum and niobium in addition to titanium.
4. Component according to any of Claims 1 to 3, wherein the first and the second section are keyed into one another in the region of the boundary layer (6).
5. Method of producing the component according to Claim 1, wherein, prior to the hot compacting, at least one end of a body cast from the second alloy or hot-compacted from powder of the second alloy is introduced into a mould constructed as pressing can (4) and in that the first alloy is poured into the pressing can as a powder and is brought into contact with the end of the body situated in the pressing can (4).
6. Method according to Claim 5, wherein the pressing can (4) has an opening (5) which is filled by the body introduced and which is preferably sealed off by welding or soldering the pressing can (4) to the body.
7. Method according to either of Claims 5 or 6, wherein the hot compacting is performed at temperatures of between 900 and 980°C if a first alloy based on titanium is used.
8. Method according to either of Claims 5 or 6, wherein the hot compacting is performed at temperatures of between 1100 and 1250°C if a first alloy based on nickel is used.
9. Method according to either of Claims 7 or 8, wherein the composite material produced by hot compacting is heat-treated at temperatures between 700 and 800°C.

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