Method for manufacturing a turbine engine blade

Abstract

The present invention relates to a method for manufacturing a turbine engine blade, the blade comprising a root (1) connected to a blade extending in a longitudinal direction, the method comprising the following steps: a) providing the root (1); b) providing a mold (2) comprising a first cavity (8) and a second cavity (10) together defining a recess (15), the blade being intended to be formed in the recess, the recess (15) comprising a first space (13) intended to form the blade and a second space (17) intended to form the root (1); c) providing an aluminum strip (20); d) positioning a fiber reinforcement (21); e) arranging the root (1) of the blade in the second space (17); f) injecting a foam comprising aluminum or an aluminum alloy into the first space (13) of the recess (15) of the mold (2) so that the foam impregnates the fiber reinforcement.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bucket for a turbine engine comprising a root made of a titanium-based alloy connected to radial blades based on aluminum. Background Art

[0002] New turbine engine architectures are being sought to meet aviation requirements. These new architectures require compressors capable of withstanding high rotational speeds. This architectural shift introduces additional or new constraints that must be considered in the manufacture of compressor rotors and stator blades.

[0003] Among these, the quality of the rotating blades is particularly challenging. Conventionally, it is known to manufacture blades, including the root and blades, made of titanium to ensure a certain mechanical strength of the assembly. However, blades made of titanium alloys impose significant centrifugal forces, especially on the disks carrying the blades, necessitating the development of new low-density materials.

[0004] Using alloys such as aluminum to reduce the density of the blades is not without consequences. In fact, the blade configuration containing aluminum is subject to mechanical, thermal and environmental stresses. Therefore, it is not possible to use standard aluminum alloys because they will not provide the appropriate structural stiffening.

[0005] Patent WO2019211583 discloses the production of a part in which the cladding is made of a long fiber / metal composite with a foam core. This part type is produced using a liquid metal injection step and a molding process, thereby obtaining a "net-like" part. However, this process has not yet been applied to blades.

[0006] Furthermore, this patent does not address the problem that the root of the blade comprises a titanium alloy, while the blade comprises a base made of another alloy having a density more favorable for reducing mass. Assembling two dissimilar alloys in one blade presents particular problems during production.

[0007] This also presents other problems. Erosion caused by particles drawn in at the air inlet becomes more pronounced as the desired rotational speed increases. Furthermore, it is necessary to ensure that the blades are strong enough to withstand the ingestion of large objects, such as birds. Finally, at these speeds, the risk of icing increases.

[0008] Regarding icing, the easiest way to avoid this problem is to make the surface of the material in question hydrophobic. Therefore, most existing technical solutions involve depositing coatings on the surface of the blades that ensure this function. Nevertheless, erosion caused by inhaled particles can degrade these coatings and their ability to render the surface hydrophobic. Summary of the Invention

[0009] The present invention relates to a method for manufacturing a blade of a turbine engine, said blade comprising a root connected to blades extending according to a longitudinal direction, said method comprising the following steps:

[0010] a) providing a root made of a titanium-based alloy, said root being intended to be assembled on the disk, said root being preferably made by additive manufacturing;

[0011] b) providing a mould comprising a first cavity and a second cavity together defining a recess in which the blade is intended to be formed, said recess comprising a first space intended to form the blade and a second space intended to form the root,

[0012] c) providing an aluminum strip comprising a coating having at least one of a hydrophobic and an anti-erosion function and placing it in contact with:

[0013] o a first cavity in a first space of a recess, and / or

[0014] o a second cavity in the first space of the recess;

[0015] d) placing a fiber reinforcement in the first space of the recess and / or in the second space of the recess and at least partially in contact with the aluminum strip;

[0016] e) arranging the root of the blade in the second space of the recess of the mold;

[0017] f) injecting a compound comprising aluminum into the first space of the recess of the mold such that the compound impregnates the fiber reinforcement.

[0018] Fiber reinforcement enables the surface to withstand different modes of vibration, fatigue stress, and imparts the necessary mechanical properties to the blade. This fiber reinforcement also prevents the propagation of potential cracks, allowing for better tolerance to damaged parts and, consequently, good durability and high reliability of the product. The fiber content should also maintain the necessary ductility to withstand the ingestion of foreign objects, such as birds.

[0019] The use of such a fiber reinforcement will achieve mechanical strength of the blade arrangement and will also allow to withstand erosion caused by the ingestion of foreign particles.

[0020] Furthermore, the enhanced resistivity properties of the aluminum used in the compound and the resulting fiber reinforcement allow for thawing by means of the passage of electrical current and Joule effect heating.

[0021] In step c), carbon nanotubes may be placed over the outer surface of the aluminum strip, preferably by chemical vapor deposition, and include free ends facing the first cavity in the first space of the recess or the second cavity in the first space of the recess.

[0022] The carbon nanotubes have excellent hydrophobicity which limits the formation of ice. Furthermore, they harden the face bearing the aluminum strip, which also helps prevent erosion.

[0023] The aluminum strips may be held in the mold by gluing.

[0024] After the injection of the aluminum-containing compound, the glue holding the aluminum strip is broken, which makes the joining method very versatile and unlimited.

[0025] The fiber reinforcement may comprise a woven structure comprising an arrangement of weft yarns and warp yarns, the warp yarns extending according to a longitudinal direction and the weft yarns extending according to a transverse direction perpendicular to the longitudinal direction.

[0026] The warp threads may have a longitudinal dimension of between 10 and 100% of the longitudinal dimension of the blade to be manufactured, and the weft threads may have a transverse dimension of between 10 and 100% of the transverse dimension of the blade to be manufactured.

[0027] This fiber reinforcement allows reinforcement in the longitudinal and transverse directions of the surface of the blade. These long fibers allow the mechanical properties of the material, once injected, to be made more isotropic.

[0028] The ratio between the number of weft yarns and the number of warp yarns of the fiber reinforcement is between 0 and 0.5.

[0029] The fiber reinforcement may be shaped so as to be present at surface grooves defined between the weft yarns, perpendicular to the longitudinal axis, the width of these grooves being between 10 and 150 μm.

[0030] This characteristic of the fiber reinforcement allows imparting a hydrophobic function on the surface of the blade.

[0031] The grooves perpendicular to the longitudinal axis may be such that the h / s ratio is between 0.1 and 0.6, h being the average amplitude of the grooves perpendicular to the longitudinal axis in μm and s being the spatial period of the grooves perpendicular to the longitudinal axis in μm.

[0032] The surface topography of the blade may have an arithmetic mean roughness parameter Ra between 10 and 200 μm.

[0033] This optimization of the arithmetic mean roughness parameter Ra of the surface topography of the blade forms a method for achieving hydrophobicity and reduced susceptibility to erosion on the blade surface. The higher the roughness to be achieved, the more suitable this method is. The roughness thus achieved allows the aerodynamic properties of the surface to be improved and a texture suitable for boundary layer separation to be obtained.

[0034] The compound may be aluminum foam.

[0035] The low density of the foam allows for a reduced mass of the blade as well as having enhanced resistivity properties.

[0036] The compound may include an aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] [ Figure 1 ] is a schematic diagram showing steps b) to d) of the mold and method according to the present invention;

[0038] [ Figure 2 ] is a schematic diagram showing step e) of the mold and method according to the present invention;

[0039] [ Figure 3 ] is a schematic diagram representing a continuation of step e) of the mold and method according to the present invention;

[0040] [ Figure 4 A] is a schematic diagram showing an aluminum strip according to the present invention;

[0041] [ Figure 4 B] is a schematic diagram showing an aluminum strip with carbon nanotubes according to the present invention;

[0042] [ Figure 4 C] is an image obtained by microscopy of a deposition of carbon nanotubes according to the present invention;

[0043] [ Figure 5 ] is a schematic diagram showing a groove perpendicular to the longitudinal axis according to the present invention. DETAILED DESCRIPTION

[0044] The present invention relates to a blade comprising a root portion 1 made of a titanium-based alloy that is compatible with the material of the disk carrying the blade's root portion. This compatibility allows for direct assembly between the blade and the disk (or shroud), for example by friction welding. The blade further comprises a blade comprising an aluminum alloy.

[0045] like Figure 1 As shown in , a mold 2 is used to manufacture this blade. Finally, the blade to be manufactured matches the geometry of the mold 2. The mold 2 comprises at least a first shell 4 and a second shell 6 that are placed against each other to form the mold 2. The first shell 4 comprises a first inner face that forms a first cavity 8. The second shell 6 comprises a second inner face that forms a second cavity 10. When the first shell 4 and the second shell 6 are assembled against each other, the first cavity 8 and the second cavity 10 together form a recess in which the blade is intended to be formed.

[0046] Each of the first cavity 8 and the second cavity 10 includes a first region 9a, 9b and a second region 11a, 11b. The first region 9a of the first cavity 8 and the first region 9b of the second cavity 10 together define a first space 13 intended to form a recess 15 of the blade. The second region 11a of the first cavity 8 and the second region 11b of the second cavity 10 together define a second space 17 intended to form a recess 15 of the root 1. The first space 13 and the second space 17 of the recess 15 together form an internal recess of the mold 2 intended to form the blade as described above.

[0047] The first shell 4 includes a first internal channel 12, a first end of which opens at the first space 13 of the recess 15, and a second end of which opens outside the mold 2. The second shell 6 includes a second internal channel 14, a first end of which opens at the second space 17 of the recess 15, and a second end of which opens outside the mold 2.

[0048] The first space 13 of the recess 15 defines a space into which the material intended to form the blade is injected. Furthermore, the second space 17 of the recess 15 can in particular receive the root of a blade, preferably made by additive manufacturing.

[0049] According to this invention, a metal strip 20 having a low density between 2 and 5 is used, which is preferably made of aluminum. This metal strip 20 comprises an inner surface and an outer surface. This metal strip 20 can be a strip made of titanium. The outer surface of the aluminum strip comprises a coating capable of producing a hydrophobic and / or anti-erosion function. Figure 4 As shown, carbon nanotubes 16 can also be deposited, preferably by chemical vapor deposition (also known by the abbreviation CVD, which stands for "Chemical Vapor Deposition"), on this outer surface 18 of the aluminum strip 20. The carbon nanotubes 16 are oriented perpendicularly to the outer surface 18 of the aluminum strip 20. The thickness of the deposit of carbon nanotubes 16 is between 20 and 500 μm.

[0050] However, other coatings are also conceivable. These other coatings have the property that they cannot melt in the interval between 600 and 700° C., so as not to contaminate the aluminum or form brittle phases with the aluminum.

[0051] like Figure 2 As shown in , the aluminum strip 20 thus provided with the coating is then cut to the desired size for positioning in the mold. A portion of the aluminum strip is positioned against the first region 9a of the first cavity 8, and / or the aluminum strip is positioned against the first region 9b of the second cavity 10, thereby defining the recess 15. The aluminum strip 20 is held in place by gluing. During the provision of the aluminum strip with carbon nanotubes, these carbon nanotubes include free ends, i.e., ends not bonded to the aluminum strip on the side opposite to the ends bonded to the aluminum strip 20, which face the first region 9a of the first cavity 8 or the first region 9b of the second cavity 10.

[0052] like Figure 1 and 2 As shown in FIG, the fiber reinforcement 21 is placed in the first space 13 of the recess 15 of the mold 2 and is at least partially in contact with the aluminum strip 20. The fiber reinforcement 21 may also be in full contact with the aluminum strip 20.

[0053] In a particular embodiment, only the fiber reinforcement 21 is placed in the first space 13 of the recess 15 of the mold 2 .

[0054] Preferably, this fiber reinforcement 21 comprises a two-dimensional or three-dimensional fabric comprising warp threads and weft threads. The warp threads extend according to a longitudinal direction and the weft threads extend according to a transverse direction perpendicular to the longitudinal direction.

[0055] The weft and warp yarns comprising aluminum include first ends attached to the first region 9a of the first cavity 8 and second ends holding the fiber reinforcement 21 placed in the first space 13 of the recess 15. Similarly, the weft and warp yarns comprising aluminum include first ends attached to the first region 9b of the second cavity 10 and second ends holding the fiber reinforcement 21 placed in the first space 13 of the recess 15.

[0056] The weft and warp threads have lengths imposed by the size of the part. Warp threads oriented in the longitudinal direction have a longitudinal dimension between 10 and 100% of the longitudinal dimension of the blade being manufactured. Weft threads oriented transversely to the longitudinal direction have a transverse dimension between 10 and 100% of the transverse dimension of the blade being manufactured. The volume ratio of weft to warp threads is the same in all areas comprising this fiber reinforcement 21. Thus, this fabric provides reinforcement in both the longitudinal and transverse directions of the blade's surface.

[0057] Regarding the orientation of weft and warp yarns, warp yarns predominate, but weft yarns are also present in the transverse direction perpendicular to the longitudinal direction to reduce anisotropy. The ratio defined by the ratio between the number of weft yarns and the number of warp yarns is between 0 and 0.5.

[0058] In a particular embodiment, the fibers are preferably made of alumina.

[0059] To impart a hydrophobic effect to the blade's surface, the fabric of the fiber reinforcement 21 is patterned. This pattern between the warp and weft threads allows the surface roughness to be adjusted as desired and tailored to the stressed areas of the blade. This pattern of the fabric of the fiber reinforcement 21 results in an arithmetic mean roughness parameter Ra of the blade's surface topography between 10 and 200 μm. This ensures the blade's surface achieves a hydrophobic effect.

[0060] In order to achieve this value of Ra, the arrangement of the weft and warp yarns is optimized. This optimization takes into account the diameter of the yarns. Thus, if Figure 5 As shown in , the fiber reinforcement 21 is formed with objects called ribs defined between the weft yarns at surface grooves perpendicular to the longitudinal axis 24. These grooves perpendicular to the longitudinal axis have a width between 10 and 150 μm, with an h / s ratio between 0.1 and 0.6, where h represents the average amplitude of the grooves perpendicular to the longitudinal axis and s represents the spatial period of the grooves perpendicular to the longitudinal axis.

[0061] The surface roughness of the blade can also be printed on the surface by modifying the first region 9a of the first cavity 8, and / or by optimizing the first region 9b of the second cavity 10, for example, using a laser, to achieve a fine roughness parameter Ra between 500 nm and 100 μm. It is also possible to generate the desired parameter Ra directly on the surface of the blade once demolded. This optimization of the first regions 9a, 9b of the first and second cavities 8, 10 forms a second method for achieving hydrophobicity on the surface of the blade. This second method is more suitable the higher the roughness to be achieved. The roughness achieved in this way allows for improved aerodynamic properties of the surface and a texture suitable for boundary layer separation.

[0062] This fiber reinforcement 21 thus enables the surface to withstand different modes of vibration and fatigue stress. It also prevents the propagation of potential cracks, allowing for better tolerance to damaged parts and, consequently, good durability and high reliability of the product. The fiber content should also allow for the maintenance of some ductility necessary to withstand the ingestion of foreign objects, such as birds.

[0063] The use of fibers made of aluminum oxide allows obtaining neutrality with respect to liquid aluminum.

[0064] The use of this fiber reinforcement 21 will achieve mechanical strength of the blade arrangement and will also allow resistance to erosion caused by the ingestion of foreign particles.

[0065] Then, if Figure 2 and 3 As shown in FIG, the root 1 is placed in the second space 17 of the recess 15 of the mold 2 and retained in this second space 17 of the recess 15, thanks to the precise matching of the geometry of the shell and the root 1. Next, the first cavity 8 and the second cavity 10 of the mold are placed against each other to close the mold.

[0066] The first internal channel 12 of the first cavity 8 of the mold allows the introduction of liquid aluminum, while the second internal channel 14 of the second cavity 10 enables a vacuum to be drawn into the mold. When the foam containing aluminum is injected, the adhesive that holds the aluminum strip is destroyed. Aluminum is injected at the center of the first space 13 of the recess 15 between the fiber reinforcement positioned against the first area 9a of the first cavity 8 and the fiber reinforcement against the first area 9b of the second cavity 10. This allows the fiber reinforcement to be pressed against the first cavity 8 and the second cavity 10 of the mold 2 respectively. The yarn that can hold the fiber reinforcement disappears after injection by merging with the injected aluminum. Therefore, the blade includes a core made of aluminum-based foam to achieve a low density. The conductive properties of aluminum can be thawed by means of the passage of electric current and Joule effect heating. Instead of this aluminum-based foam, the blade may include a core including an aluminum alloy, which may include nano reinforcements of the silicon carbide SiC or aluminum oxide type, for example.

[0067] As for providing the surface of the blade with carbon nanotubes 16, a specific interaction occurs during the injection of liquid aluminum. In fact, during the deposition of the carbon nanotubes 16 over the outer surface 18 of the aluminum strip 20, the carbon nanotubes 16 are connected to the aluminum only at their ends. These carbon nanotubes 16 often consist of several monoatomic carbon sheets wound around each other. When the liquid aluminum infiltrates the substrate of the carbon nanotubes 16, the first sheet of carbon nanotubes 16 interacts with the aluminum, and the carbon of the sheet diffuses into the aluminum. This interdiffusion produces carbides, such as Al4C3, which thus surround the substrate of the carbon nanotubes 16. This corresponds to a metallurgical anchoring of the nanotubes in the aluminum matrix, which allows them to be individually assembled with the surface made of aluminum. These carbides also harden the underlying surface, which also helps to prevent erosion.

Claims

1. A method for manufacturing a turbine engine blade comprising a root (1) connected to a blade extending in a longitudinal direction, the method comprising the following steps: a) providing a root (1) made of a titanium-based alloy, said root (1) being intended to be assembled on a disc; b) providing a mould (2) comprising a first cavity (8) and a second cavity (10) together defining a recess (15) in which the blade is intended to be formed, the recess (15) comprising a first space (13) intended to form the blade and a second space (17) intended to form the root (1), c) providing an aluminum strip (20) comprising a coating having at least one of a hydrophobic and an anti-erosion function and placing it in contact with: o the first cavity (8) in the first space (13) of the recess (15), and / or o a second cavity (10) in the first space (13) of the recess (15); d) placing a fiber reinforcement (21) in the first space (13) of the recess (15) and / or in the second space (17) of the recess and at least partially in contact with the aluminum strip (20); e) arranging the root portion (1) of the blade in the second space (17) of the recess (15) of the mold (2); f) injecting a compound comprising aluminum into the first space (13) of the recess (15) of the mold (2) such that the compound impregnates the fiber reinforcement.

2. The method according to claim 1, characterized in that In step c), a carbon nanotube (16) is placed above the outer surface (18) of the aluminum strip (20), and the carbon nanotube (16) includes a free end (22) facing the first cavity (8) in the first space (13) of the recess (15) or the second cavity (10) in the first space (13) of the recess (15).

3. The method according to claim 1, characterized in that The aluminum strip (20) is held in the mold by gluing.

4. The method according to claim 1, wherein The fiber reinforcement comprises a woven structure including an arrangement of weft yarns and warp yarns, the warp yarns extending according to the longitudinal direction and the weft yarns extending according to a transverse direction perpendicular to the longitudinal direction.

5. The method according to claim 4, characterized in that The warp threads have a longitudinal dimension of between 10 and 100% of the longitudinal dimension of the blade to be manufactured, and the weft threads have a transverse dimension of between 10 and 100% of the transverse dimension of the blade to be manufactured.

6. The method according to claim 4, characterized in that The ratio between the number of weft yarns and the number of warp yarns of the fiber reinforcement (21) is between 0 and 0.

5.

7. The method according to claim 4, characterized in that The fiber reinforcement (21) is shaped so as to be present at the surface grooves defined between the weft yarns, perpendicular to the longitudinal axis (24), the width of these grooves being between 10 and 150 μm.

8. The method according to claim 7, characterized in that The grooves perpendicular to the longitudinal axis (24) are such that the h / s ratio is between 0.1 and 0.6, h being the average amplitude of the grooves perpendicular to the longitudinal axis in μm and s being the spatial period of the grooves perpendicular to the longitudinal axis in μm.

9. The method according to claim 6 or 8, characterized in that The surface of the blade has a topography with an arithmetic mean roughness parameter Ra between 10 and 200 μm.

10. The method according to claim 1, characterized in that The compound is aluminum foam.

11. The method according to claim 1, wherein The compound includes an aluminum alloy.

12. The method according to claim 1, characterized in that The root is produced by additive manufacturing.

13. The method according to claim 2, characterized in that In step c), the carbon nanotubes are deposited by chemical vapor deposition.

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