Solutions for manufacturing one-piece blade disks

Abstract

The present invention relates to a method for manufacturing an integrated blade disk of a turbine, the method comprising the following steps: (El): manufacturing a plurality of blades, wherein the blades include a root and a special-shaped portion; the method is characterized in that the method comprises the following steps: (E2): rapidly sintering the blades with metal powder, wherein the blades are distributed at an angle on the contour of an annular rapid sintering mold, the root of the blades is embedded in the metal powder, and the special-shaped portion of the blades protrudes radially outward from the metal powder.

Description

Technical Field

[0001] The present invention relates to the general field of manufacturing integrally formed bladed disks for turbomachines.

[0002] The invention has particularly advantageous application in the production of turbine disks, in particular high-pressure turbine disks. Prior art

[0003] The turbine blade disk of a turbine is usually produced by producing a central hub on the one hand and a plurality of blades on the other hand, on the periphery of which units are produced in order to fasten them to the central hub.

[0004] However, this solution may encounter the following difficulties:

[0005] - In order to avoid malfunctions during the machining of the center hub unit, the center hub is dimensioned by increasing the amount of material at the unit level, which results in an increased mass of the disc;

[0006] - premature wear of the blade root may occur due to friction (wear) between the blade root and the central hub unit;

[0007] - A compromise must be found so that the blade disk can resist creep on the one hand and traction forces on the other hand;

[0008] - The geometry of the blade root has to be chosen to allow insertion into the cell, thus limiting the possible geometries.

[0009] The manufacture of integrally formed bladed disks allows meeting some of these limitations, in particular by eliminating the blade root portion. These integrally formed bladed disks are usually manufactured by machining in a large mass of forged raw material, or by welding the blades constituting the blades to a forged disk.

[0010] However, this solution may encounter some difficulties.

[0011] For example, for high-volume machining, the choice of the constituent material of the blade is determined by the material chosen for the disk, thus preventing the material of the blade from being adapted to its specific stresses.

[0012] In the case of disc / blade assemblies, assembly areas are often located in critical areas, which can result in oversizing of the components to accommodate the thermomechanical stresses. These methods also typically involve steps where material melting occurs, which has a negative impact on the material.

[0013] Additionally, for high volume processing or for disk / paddle assemblies, the use of single crystal or directionally solidified paddles is prohibited. Summary of the invention

[0014] The object of the present invention is therefore to propose a solution allowing the manufacture of bladed disks which solves the above-mentioned problems.

[0015] According to a first aspect, the invention provides a method for manufacturing an integrally formed blade disk of a turbine, the method comprising the following steps:

[0016] - manufacturing a plurality of blades comprising, on the one hand, a root portion and, on the other hand, a profiled portion;

[0017] Characterized in that the method comprises the following steps:

[0018] - Spark plasma sintering of blades from metal powder, the blades being angularly distributed on the contour of an annular spark plasma sintering mould, the roots of the blades being embedded in the metal powder and the profiled parts of the blades protruding radially outwards from the metal powder.

[0019] According to one possible feature, the blade is a single crystal.

[0020] According to one possible feature, the method comprises the following steps:

[0021] - placing the blades in a first spark plasma sintering mould comprising a first metal powder;

[0022] - spark plasma sintering the blades with a first metal powder to form an intermediate disk;

[0023] - placing the intermediate disk in a second spark plasma sintering mold comprising a second metal powder;

[0024] - Spark plasma sintering of the intermediate disk with a second metal powder.

[0025] According to a possible characteristic, the intermediate disk formed by spark plasma sintering of the blades with a first metal powder comprises a porosity between 30% and 10%.

[0026] According to one possible feature, the method comprises the following steps:

[0027] - placing the blades in a spark plasma sintering mould comprising a first metal powder and a second metal powder, the root of the blade being embedded in the first metal powder so that the first metal powder forms the outer part of the central hub of the blade disk to be manufactured, and the second metal powder being surrounded by the first metal powder so that the second metal powder forms the inner part of the central hub of the blade disk to be manufactured;

[0028] - Spark plasma sintering of the blades using the first metal powder and the second metal powder.

[0029] According to one possible feature, the metal of the first metal powder has a higher creep resistance than the metal of the second metal powder.

[0030] According to one possible feature, the metal of the second metal powder has a higher tensile strength than the metal of the first metal powder.

[0031] According to one possible feature, the method comprises the following steps:

[0032] - Heat treatment of blade disks formed by spark plasma sintering of blades from metal powder.

[0033] According to a second aspect, the invention proposes an integrally formed turbine blade disk obtained by a method according to any one of the preceding features.

[0034] According to a possible feature, the bladed disk comprises a plurality of single-crystal blades and a polycrystalline central hub.

[0035] According to a third aspect, the invention proposes a turbomachine comprising an integrally formed bladed disk according to any one of the preceding features. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Other characteristics and advantages of the invention will become apparent from the description given below, with reference to the accompanying drawing, which illustrates an exemplary embodiment without any limiting character.

[0037] Figure 1 A blade disk of a turbine is schematically represented.

[0038] Figure 2 The steps of a method for producing a turbine blade disk are schematically represented.

[0039] Figure 3 The steps of a method for manufacturing a turbine disk according to a first possible variant are schematically represented.

[0040] Figure 4 The steps of a method for manufacturing a turbine disk according to a second possible variant are schematically represented.

[0041] Figure 5 A cross-sectional view schematically illustrates spark plasma sintering of a plurality of blades using a first metal powder.

[0042] Figure 6 Schematic representation of a cross-section of spark plasma sintering of an intermediate disk using a second metal powder. DETAILED DESCRIPTION

[0043] The present invention relates to the production of an integrally formed turbine blade disk 1 , in particular an integrally formed turbine blade disk 1 .

[0044] The bladed disk may be a high pressure turbine disk, ie a turbine located directly downstream of the combustion chamber, or a low pressure turbine disk, ie a turbine located downstream of the high pressure turbine. The invention is particularly suitable for manufacturing high pressure turbine bladed disks comprising uncooled solid blades, ie blades without internal cooling channels.

[0045] The blade disk 1 is made of metal. For example, it can be made of a titanium-based alloy or a nickel-based alloy, which is determined according to the use conditions of the blade disk 1. In particular, in the case of a high-pressure turbine disk, a nickel-based alloy is very advantageous.

[0046] The turbomachine is an aircraft turbomachine, such as an airplane turbomachine, or a helicopter turbomachine. The invention is particularly suitable for manufacturing high-pressure turbine blade disks of helicopter engines.

[0047] like Figure 1 As shown, the blade disk 1 is an annular component with an axis θ, which comprises a plurality of blades 2, which are angularly distributed on the contour of a central hub 3. The blade disk 1 is integrally formed, and the blades 2 and the central hub 3 are made in one piece.

[0048] like Figure 1 and 5 It can be seen that these blades 2 each comprise, on the one hand, a profiled portion 21 with inner and outer arcs and, on the other hand, a root 22 fixed to the central hub 3, the profiled portion 21 and the root 22 being separated by a platform 23 defining an airflow path.

[0049] like Figure 2 As shown, the manufacturing method of the blade disk 1 includes the following steps:

[0050] - E1: The blades 2 are manufactured, for example, by lost wax casting. The blades 2 are manufactured according to their final shape, that is to say they comprise a profiled portion 21, a root 22 and a platform 23. The blades 2 are metal blades.

[0051] - E2: These blades 2 are then sintered from metal powder according to spark plasma sintering in a spark plasma sintering mold having the shape of the blade disk 1 to be produced. In order to give the blade disk 1 its shape, the blades 2 are distributed at an angle to the contour of the mold, such as Figure 5 6. The root 22 of the blade 2 is embedded in the metal powder so that the blade 2 is thus fixed to the central hub 3 which will be formed by the metal powder 2 at the end of the sintering step. The profiled portion 21 of the blade 2 itself is directed radially outwards and is located outside the metal powder and therefore protrudes. The metal powder can be, for example, a titanium-based alloy or a nickel-based alloy, the composition of which is selected according to the properties required for manufacturing the blade disk 1.

[0052] The fact that the blade disk 1 is manufactured by spark plasma sintering the blades 2 from the metal powder forming the central hub 3 makes it possible to form an integrally formed blade disk 1, thus avoiding wear caused by friction between the blades 2 and the central hub 3.

[0053] Furthermore, the fact that the sintering is spark plasma sintering allows to avoid destabilizing the metallurgical structure of the different alloys used to form the blades 2 and the central hub 3. In particular, when the blades 2 manufactured are single crystal, the use of spark plasma sintering allows to avoid recrystallization of the blades 2. Thus, the blade disk 1 can comprise single crystal blades 2 and a polycrystalline central hub 3, while being an integrally formed blade disk. This is in particular due to the very short spark plasma sintering densification cycle, for example lasting less than 15 minutes.

[0054] Furthermore, the shape of the root 22 of the blade 2 is no longer affected by the stresses inserted into the unit machined in the central hub 3 , so that a geometry of the blade root 22 can be used which ensures better rigidity in fixing to the central hub 3 .

[0055] Advantageously too, the central hub 3 does not need to be machined in order to form a unit intended to receive the root 22 of the blade 2 .

[0056] Spark plasma sintering is performed by compacting the metal powder and the blade 2 and by applying an electric current through the metal powder and the root 22 of the blade 2. Therefore, the spark plasma sintering mold is configured to eject and allow electric current to pass on the one hand and to apply pressure on the other hand.

[0057] At the end of the step E2 of spark plasma sintering of the blades 2 from metal powder, a blade disk 1 is formed comprising blades 2 distributed angularly around a central hub 3 .

[0058] like Figure 1 As shown, after the spark plasma sintering of the blades 2 from the metal powder, the blade disk 1 can be heat treated. This heat treatment step E3 is particularly advantageous in order to give the central hub 3 the desired properties. This heat treatment step E3 can be carried out directly in the spark plasma sintering mold or in a separate tool. The heat treatment is adapted to the alloy used to manufacture the blade disk 1. In addition, in the case where the blades 2 are single crystals, the heat treatment is adapted to avoid recrystallization of said blades 2.

[0059] Furthermore, a step of machining the blade disk 1 into the finished product can be carried out at the end of the manufacturing method, for example to adapt the surface conditions of the disk. This machining step can be carried out in particular after the heat treatment step E3.

[0060] like Figure 3 , 4 , 5 and 6, several variations can be achieved Figure 1 The manufacturing method shown.

[0061] according to Figure 3 , 5 In a first possible variant, shown in FIG. 6 , the central hub 3 is manufactured in a plurality of spark plasma sintering steps, while according to Figure 4 In the second variant shown, the central hub 3 is manufactured in a single spark plasma sintering step.

[0062] According to a first variant, after manufacturing the blade 2, the method comprises the following steps:

[0063] - E21: The blade 2 is placed in a first spark plasma sintering mold 51, inside which the first metal powder 41 is also positioned. In a similar manner to step E2, the root 22 of the blade 2 is embedded in the first metal powder 41, while the profiled portion 21 protrudes radially outwards from the first metal powder. The first metal powder 41 is intended to form an outer portion 31 of a central hub 3 positioned at the level of the root 22 of the blade 2.

[0064] - E22: The blades 2 and the first metal powder 41 are sintered according to spark plasma sintering. The intermediate disk 6 is formed only by these blades 2 and by the outer part 31 of the central hub 3, the intermediate disk 6 therefore comprising a hole in its center. The pressure applied by the first spark plasma sintering mold 51 can be adapted so that the densification of the intermediate disk is only local. For example, the porosity of the intermediate disk 6 can be between 30% and 10%. The porosity can be, for example, between 25% and 15%. Porosity is here understood to mean the volume of porosity divided by the total volume of the component. Such a porosity allows the intermediate disk to be handled without risk of cracking.

[0065] - E23: The intermediate disk 6 is placed in a second spark plasma sintering mold 52, and the second metal powder 42 is also arranged in said second mold 42. The second metal powder 42 is arranged in a hole formed in the center of the intermediate disk 6 and is intended to form the inner part 32 of the central hub 3 surrounded by the outer part 31.

[0066] - E24: The intermediate disk 6 and the second metal powder 42 are sintered according to spark plasma sintering, so that the blade disk 1 can be obtained.

[0067] Figure 4 The second variant shown is Figure 3 The first variant differs in that the central hub 3 is manufactured in a single step by spark plasma sintering the blade 2 simultaneously with the first metal powder 41 and the second metal powder 42. Figure 4 In the second variant shown, the method comprises the following steps:

[0068] - E25: The blade 2 is placed in a spark plasma sintering mold, inside which a first metal powder 41 and a second metal powder 42 are arranged. The first metal powder 41 is intended to form the outer portion 31 of the central hub 3, and the second metal powder 42 is intended to form the inner portion 32 of the central hub 3. The first metal powder 41 is arranged in the mold to cover the root 22 of the blade 2 and to form a ring around the second metal powder 42.

[0069] - E26: Sintering the blade 2, the first metal powder 41 and the second metal powder 42 according to spark plasma sintering.

[0070] In the previously described variant, the second metal powder 42 is different from the first metal powder 41. That is, the composition of the two metal powders is different, thus making the central hub 3 a multi-material hub. The multi-material central hub 3 allows the mechanical properties of the central hub 3 to be locally adapted according to the stresses encountered. Thus, advantageously, the outer part 31 of the central hub 3 is adapted to be more resistant to creep, while the inner part 32 is adapted to be more resistant to traction. The metal of the first metal powder 41 has a higher creep resistance than the metal of the second metal powder 42. In addition, the metal of the second metal powder 42 has a higher tensile strength than the metal of the first metal powder 41. According to a possible example, the first metal powder is made of a nickel-based high-temperature alloy N19 and the second metal powder is made of a nickel-based high-temperature alloy N18.

[0071] According to a possible variant, the central hub 3 may be made of a single material and manufactured in a step of spark plasma sintering of the blades 2 from a single metal powder.

[0072] More than two metal powders with different compositions may be used, for example, three or four metal powders with different compositions, so that other local adaptations of the mechanical properties of the central hub 3 can be made.

Claims

1. A method for manufacturing an integrally formed blade disk of a turbomachine, the method comprising the following steps: - manufacturing a plurality of blades, said blades comprising a root portion and a profiled portion; - placing the blades in a first annular spark plasma sintering mold containing a first metal powder, the blades being angularly distributed on the contour of the annular spark plasma sintering mold, the roots of the blades being embedded in the metal powder, and the profiled portions of the blades protruding radially outwards from the metal powder; - spark plasma sintering the blade with the first metal powder to form an intermediate disk; - placing the intermediate disk in a second spark plasma sintering mould containing a second metal powder; - spark plasma sintering of said intermediate disk with said second metal powder, said blade being single crystalline both before and after the spark plasma sintering step, Wherein, the intermediate disk formed by spark plasma sintering the blade with the first metal powder comprises a porosity between 25% and 15%.

2. The method according to claim 1, wherein: The metal of the first metal powder has a higher creep resistance than the metal of the second metal powder.

3. The method according to claim 1, wherein: The metal of the second metal powder has a higher tensile strength than the metal of the first metal powder.

4. The method according to claim 1, wherein: The method further includes the step of heat treating the blade disk formed by spark plasma sintering the blades from the metal powder.

5. An integrally formed turbine blade disk obtained by the method according to claim 1.

6. The turbine blade disk according to claim 5, wherein: The blade disk includes single crystal blades and a polycrystalline central hub.

7. A turbine comprising the turbine blade disk according to claim 5.

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