Manufacturing process for a bi-material aeronautical part

Abstract

A method for manufacturing a bi-material aeronautical part, as well as a blade obtained by such a method, the method comprising a step of producing a first part including the formation of a pattern of the first part, the formation of a first shell mold, then the formation of the first part (12) in a first metal alloy, a step of producing a second part including the formation of a pattern of the second part, transferred onto the first part (12), the formation of a second shell mold (60), then the formation of the second part (14) in a second metal alloy, in which the formation of the second part (14) takes place in a directed crystal growth furnace (90) comprising a relatively hot chamber (91) and a relatively cold chamber (92) separated by a mask (93), and in which, at least at the beginning of the formation of the second part (14),The first part (12) is placed in the cold chamber (92) of the oven (90) with its interface surface (12a) positioned at the boundary between the hot chamber (91) and the cold chamber (92). Fig. 7.

Description

Title of the invention: Method for manufacturing a bi-material aeronautical part Technical field

[0001] The present disclosure relates to a method for manufacturing a bi-material aeronautical part as well as a blade obtained by such a method. Such a method is particularly useful for manufacturing certain turbomachine parts and in particular aircraft or helicopter engines. Prior art

[0002] Methods for manufacturing single-crystal high-pressure turbine blades by lost-wax casting are known.

[0003] These methods include forming a blade pattern from wax or resin, then forming a ceramic shell mold around this blade pattern by successive dipping and drying. The wax or resin is then removed during a dewaxing step, and then the shell mold is sintered, finally leaving the shell mold hollow. A single crystal seed is placed in the shell mold and liquid metal is poured into the shell mold. The shell mold gradually descends out of the hot chamber in which it is placed, which causes the directed solidification of the liquid metal from the single crystal seed. Thus, a single crystal blade is formed.

[0004] In order to ensure good performance, the choice of material is an important criterion. Indeed, a monocrystalline blade must meet specific finishing constraints while remaining as light as possible. The finishing constraints include the mechanical constraints and the temperature constraints which are imposed on the blade arranged in a turbomachine in operation and which the material must withstand. Furthermore, cost optimization is an issue also affecting the choice of material.

[0005] More particularly, single-crystal blades obtained by conventional processes only allow the manufacture of single-piece, single-material blades. Generally speaking, the blades comprise a blade and a root. The characteristics of the material are therefore imposed by the strictest conditions experienced by the finalized blade arranged in the turbomachine in operation. For example, the stresses experienced by the blade of a turbomachine blade in operation are greater than the stresses experienced by the blade root. The material that makes up the blade, and therefore the blade, must therefore comply with restrictive specifications meeting these constraints, which generally makes it more expensive and / or heavier than a material that must meet less significant constraints.

[0006] Therefore, there is a balance to be found between material performance and blade cost. Alloys have been developed to optimize the specifications of single-crystal blades, but there is still room for improvement.

[0007] In this regard, certain foundry processes have been proposed to achieve the manufacturing of bi-material blades so as to adjust the material of each part of the part, typically the blade of the blade on the one hand and its root on the other hand, to the thermal and mechanical stresses that it actually encounters. However, these processes encounter a certain number of difficulties, in particular in controlling the position and composition of the interface between the two materials.

[0008] There is therefore a real need for a method of manufacturing a bi-material aeronautical part which is free, at least in part, from the drawbacks inherent in the aforementioned known methods. Statement of the invention

[0009] The present disclosure relates to a method for manufacturing an aeronautical part comprising a first part and a second part, the method comprising a step of producing the first part comprising the formation of a model of the first part in a removable material, then the formation of a first shell mold from the model of the first part, then the formation of the first part in a first metal alloy in the first shell mold from a grain selector, a step of producing the second part comprising the formation of a model of the second part in a removable material, attached to the first part, then the formation of a second shell mold from the first part and the model of the second part, then the formation of the second part in a second metal alloy, different from the first alloy, in the second shell mold from an interface surface of the first part,wherein the formation of the second part takes place in a directed crystal growth furnace comprising a relatively hot chamber and a relatively cold chamber separated by a mask projecting into the cavity of the furnace, and wherein, at least at the start of the formation of the second part, the first part is disposed in the cold chamber of the furnace with its interface surface disposed at the boundary between the hot chamber and the cold chamber.

[0010] Thanks to such a process, it is possible to obtain a bi-material part in which each part is made using an alloy adapted to the thermal and mechanical constraints actually encountered by the part in question. This avoids oversizing certain parts of the part or its environment, which helps to reduce the mass of the whole. Savings are also made when one of the two alloys is more expensive than the other.

[0011] Furthermore, by using such an oven equipped with such a mask and by placing the first part in the cold chamber with its interface surface placed at the boundary between the cold chamber and the hot chamber, it is possible to avoid exposing the already formed first part to a temperature high enough to cause an undesired modification of the microstructure of the first part.

[0012] In particular, thanks to this arrangement, only the interface surface of the first part reaches the melting temperature of the first alloy, which leads to satisfactory conditions for ensuring the interface between the two alloys in a controlled manner, in particular for allowing epitaxy and therefore the transmission of at least certain parameters of the crystalline structure of the first part to the second part.

[0013] We therefore obtain a bi-material part whose interface between the two materials is well controlled, in terms of position, composition and microstructure.

[0014] In some embodiments, the aeronautical part is a blade, preferably a turbine blade. It may be a low-pressure (LP) or high-pressure (HP) turbine blade. It may be a fixed blade or a moving blade. It may be a helicopter engine blade or an aircraft engine blade.

[0015] In some embodiments, the first portion is a blade and the second portion is a root.

[0016] In some embodiments, the first and second alloys are nickel-based alloys. In the present disclosure, a nickel-based alloy is an alloy in which nickel is the element having the majority mass fraction, preferably greater than 40%.

[0017] In some embodiments, the first alloy has a higher temperature resistance than the second alloy and the second alloy has a higher mechanical resistance, at the operating temperature, than the first alloy.

[0018] In some embodiments, the first alloy has a higher density than the second alloy.

[0019] In some embodiments, the first alloy has a density greater than 8.5 g / cc and the second alloy has a density less than 8.5 g / cc.

[0020] In some embodiments, the second alloy is devoid of any of the following heavy elements: Mo, Ta, W, Re or Ru.

[0021] In certain embodiments, the first part is monocrystalline or columnar. It is preferably monocrystalline to ensure the best properties, in particular resistance to fining, for the first part of the part.

[0022] In certain embodiments, the first alloy is of the CMSX4, CMSX4+ type. or CMSX10.

[0023] In certain embodiments, the second part is monocrystalline, columnar or equiaxial polycrystalline. The second part is in fact designed to meet less demanding constraints than the first part. It is understood that when the second part is polycrystalline, its growth is not directed. The polycrystalline parts can therefore comprise a plurality of grains directed randomly in all directions.

[0024] In certain embodiments, the second alloy is monocrystalline, of the CMSX6 or RR200 type.

[0025] In certain embodiments, the second alloy is polycrystalline, of the In100, René77 or In713 type.

[0026] In some embodiments, the crystal structure of the second part is determined by the crystal structure of the first part. In other words, epitaxy is ensured between the second part and the first part. The coherence and integrity of the part are thus improved.

[0027] In some embodiments, the directed crystal growth furnace is a Bridgman-type vacuum furnace.

[0028] In some embodiments, the cold chamber is located below the hot chamber in the directed crystal growth furnace.

[0029] In some embodiments, during formation of the second portion, the temperature of the hot chamber is greater than the melting temperature of the second alloy, preferably greater than 1450°C.

[0030] In some embodiments, during the formation of the second part, the temperature of the cold chamber is lower than the melting temperature of the two alloys, preferably lower than 500°C.

[0031] In some embodiments, the hot chamber comprises at least two sections, preferably at least three sections, the temperature of which is independently adjustable. This makes it possible to achieve a temperature gradient within the hot chamber and, thus, to better control the directed solidification as well as the interface between the two alloys.

[0032] In some embodiments, the first part is disposed in the cold chamber of the furnace throughout the step of forming the second part.

[0033] In certain embodiments, the interface surface is arranged at the boundary between the cold chamber and the hot chamber throughout the step of filling the second shell mold.

[0034] In certain embodiments, after filling, the second shell mold is gradually pulled towards the cold chamber to accompany the directed solidification of the second part.

[0035] In certain embodiments, the mask has a geometry adapted to that of the contour of the second shell mold at the interface surface of the first part. It is understood here that the mask does not have a standard geometry, with a contour having rectilinear segments for example, but a particular geometry based on the geometry of the contour of the interface surface or at least of the second shell mold at the interface surface. The mask may for example comprise convex portions at the concave portions of the contour of the second shell mold and concave portions at the convex portions of the second shell mold. This reduces the heat transmission from the hot chamber to the cold chamber.

[0036] In certain embodiments, at least at the start of the formation of the second part, and preferably during the formation of the second part, a clearance of less than 5 mm is left between the mask and the second shell mold. This clearance may be constant or variable, in which case it is at all points less than this limit. The contour of the mask may in particular follow the contour of the second shell mold.

[0037] In certain embodiments, the mask comprises at least two movable panels. Since the panels are movable, it is possible to give them a geometry very close to that of the second shell mold without hindering its installation or removal from the oven.

[0038] In some embodiments, the removable material is wax or resin.

[0039] In some embodiments, the first part model is based on the geometry of the first part, without taking into account the geometry of the second part. This results in savings in raw materials.

[0040] In some embodiments, the method comprises at least one heat treatment step after the step of forming the first part. This heat treatment step may allow the microstructure of the first part to be refined.

[0041] In certain embodiments, the method comprises, after the step of forming the first part, a step of protecting the interface surface of the first part. More broadly, the entire first part may, if necessary, be protected in this way. The interface surface being the surface from which the second part will be formed and, in particular, from which the crystal growth of the second part will begin, it is preferable to preserve the interface surface from any alteration, in particular during the formation of the second shell mold.

[0042] In some embodiments, the protecting step comprises placing an oxidation protective coating on the interface surface of the first part. This protective coating may comprise platinum. It is preferably a layer of pure platinum. It should be noted that this protective layer does not prevent epitaxy between the first part and the second part because it liquefies and dissolves in the second alloy when the second alloy is cast.

[0043] In some embodiments, the protective coating has a thickness of between 3 and 10 μm.

[0044] In some embodiments, the step of forming the second part comprises an equiaxial cooling step.

[0045] In some embodiments, the method comprises at least one heat treatment step after the step of forming the second part. This heat treatment step may allow the microstructure of the first part to be refined.

[0046] The present disclosure further relates to a blade, obtained by a method according to any of the preceding embodiments. All the advantages mentioned above obtained by the method are therefore directly transposed to this blade.

[0047] The present disclosure also relates to a turbomachine, comprising a blade according to any one of the preceding embodiments.

[0048] The above-mentioned characteristics and advantages, as well as others, will appear on reading the detailed description which follows, of examples of embodiments of the method and of the proposed blade. This detailed description refers to the attached drawings. Brief description of the drawings

[0049] The attached drawings are schematic and are intended primarily to illustrate the principles of the disclosure.

[0050] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0051] [Fig-1] [Fig. 1] is a perspective view of an example of a blade.

[0052] [Fig.2] [Fig.2] schematically illustrates an example of a manufacturing process.

[0053] [Fig.3] [Fig.3] illustrates the first part model in this example process.

[0054] [Fig.4] [Fig.4] illustrates the step of forming the first part in this example of process.

[0055] [Fig.5] [Fig.5] illustrates the first part in this example process.

[0056] [Fig.6] [Fig.6] illustrates the second part model in this example process.

[0057] [Fig.7] [Fig.7] illustrates the step of forming the second part in this example of process.

[0058] [Fig.8] [Fig.8] illustrates the part obtained by this example process. Description of the embodiments

[0059] In order to make the disclosure more concrete, an example of a manufacturing method is described in detail below, with reference to the attached drawings. It is recalled that the invention is not limited to this example.

[0060] [Fig.l] represents a blade 10 comprising a blade 12 and a root 14. The blade 12 and the foot 14 are formed from different metal alloys. By way of non-limiting example, the blade 12 and the foot 14 are formed from nickel-based alloys. In particular, the blade 12 may be monocrystalline while the foot 14 may be monocrystalline or polycrystalline, in an alloy that is lighter and / or less expensive than the alloy of the blade 12. In a particular example, the first alloy could be of the CMSX4 type and the second could be of the In713 type if polycrystalline or of the RR200 type if monocrystalline.

[0061] In this example, a first part corresponds to the blade 12 and a second part corresponds to the root 14. However, it is possible to subdivide the blade in another way, with a first part and a second part which do not necessarily correspond to the blade 12 and the root 14. In particular, the level of thermomechanical loading of the blade to be formed as well as its associated manufacturing process conditions the interface positioning.

[0062] Furthermore, the blade 10 may comprise a platform which corresponds to a flat part extending at the level of the contact between the root 14 and the blade 12. Thus, depending on the requirements, it is possible to include the platform in the first part or in the second part. It is also possible to provide a part of the platform on the first part of the blade 10 and a second part of the platform on the second part of the blade 10.

[0063] This blade 10 is obtained by a method as shown diagrammatically in [Fig.2], comprising a step of producing the blade (or step of producing the first part) E1, in which the monocrystalline blade 12 is produced, followed by a step of producing the second part E2 in which the root 14 is produced.

[0064] The step of producing the blade E1 comprises a step of forming a blade model 20 made of removable material E1. As shown in [Fig. 3], this first model 20 comprises a main portion 21, having the desired geometry for the blade 12, as well as an upper portion 22, intended to form a funnel 32, and a lower portion 23, intended to form a grain selector 33.

[0065] The step of producing the blade E1 then comprises a step of forming a first shell mold E12 in which a first shell mold 30 is formed using the blade model 20 by successive dipping and drying, then the first shell mold 30 is dewaxed and sintered.

[0066] The blade production step E1 then comprises a blade formation step E13, shown schematically in [Fig. 4], during which the first shell mold 30 is first placed in a Bridgman type furnace 90 comprising a hot chamber 91 and a cold chamber 92 separated by a mask 93 projecting into the cavity of the furnace 90. The hot chamber 91 is located above the cold chamber 92 and comprises three sections 91a, 91b and 91c whose temperatures can be adjusted independently. In this respect, [Fig.4] is simplified, particularly with regard to the structure of the oven 90 and that of the shell mold 30, the latter being represented by a simple line, without taking into account its true thickness.

[0067] Liquid metal 41, intended to form the first metal alloy, is then poured into the first shell mold 30, then placed in the hot chamber 91 of the furnace 90, through its funnel 32.

[0068] Finally, directed solidification is conducted in the hot chamber 92 of the furnace 90, by slowly removing the first shell mold 30 from the hot chamber 91 to the cold chamber 92 to form the monocrystalline blade 12 from the grain selector 33.

[0069] In other examples, the blade 12 could be formed in a columnar manner. In such a configuration, the blade 12 is composed of grains whose crystallization is directed in a preferential direction, from the preferential direction of the grains of the grain selector. The blade 12 can then undergo a heat treatment to homogenize the chemistry between dendrite and interdendrites. This also allows the distribution of precipitates in the blade 12 to be controlled.

[0070] The step of producing the first part E1 finally comprises a finishing step E14, which may in particular comprise a machining step, during which the portions corresponding to the funnel 32 and the grain selector 33 are removed, and a heat treatment step. The blade of [Fig.5] is then obtained.

[0071] In this example, the finishing step E14 further comprises a step of protecting the interface surface 12a of the blade 12 on which the second part of the part, i.e. the root 14, will be attached. This protection step here comprises the formation of a platinum layer 49 on the interface surface 12a, the thickness of the platinum layer being between 3 and 10 μm.

[0072] The step of producing the second part E2 then begins with a step of forming a blade model E21 made of removable material in which a root model 51 is formed on the blade 12 obtained during the blade production step EL. The root model 51 made of removable material and the blade 12 therefore form a blade model 50, shown in [Fig. 6]. The blade model 50 further comprises, made of removable material, an upper portion 52 intended to form a funnel 62.

[0073] The step of forming a blade model E21 is followed by a step of forming a second shell mold E22 in which a second shell mold 60 is formed using the blade model 50 by successive dipping and drying, then the second shell mold 60 is dewaxed and sintered. The blade 12 is held in place in the second shell mold 60 during these steps.

[0074] The step of producing the foot E2 then comprises a step of forming the foot E23, shown schematically in [Fig.7], during which the second shell mold 60 is first placed in a Bridgman type furnace 90 comprising a hot chamber 91 and a cold chamber 92 separated by a mask 93 projecting into the cavity of the furnace 90. This furnace 90 may be of the same type as the furnace 90 used during the blade formation step E13. In this respect, [Fig.7] includes simplifications of the same nature as [Fig.4].

[0075] More precisely, the second shell mold 60 is placed in place such that the blade 12 is positioned in the cold chamber 92 of the furnace 90 while the cavity 61 of the shell mold 60 corresponding to the foot 14 is positioned in the hot chamber 91 of the furnace 90. The interface surface 12a of the blade 12 is thus positioned at the boundary between the hot chamber 91 and the cold chamber 92, that is to say at the level of the mask 93.

[0076] In order to minimize the transfer of heat from the hot chamber 91 to the cold chamber 92, the mask 93 has a contour adjusted to that of the shell mold 60 at the interface surface 12a. A maximum clearance of 5 mm is thus provided between the mask 93 and the shell mold 60. In order to allow the shell mold 60 to be put in place and then removed, the mask 93 comprises several movable panels, which can be moved back or even completely retracted to allow the shell mold 60 to pass through.

[0077] Liquid metal 71, intended to form the second metal alloy, is then poured into the second shell mold 60 through its funnel 62.

[0078] Finally, solidification is conducted in the hot chamber 91 of the furnace 90. In the present example, this solidification is directed by slowly removing the second shell mold 60 from the hot chamber 91 to the cold chamber 92 to form the foot 14 in a monocrystalline or columnar manner. However, it is also possible to completely and quickly remove the shell mold 60 from the hot chamber 91 so as to cause equiaxial cooling resulting in an equiaxial polycrystalline structure.

[0079] In either case, the positioning of the interface surface 12a at the boundary between the hot chamber 91 and the cold chamber 92 makes it possible to obtain the melting of only a thin film of first alloy during the casting of the second metal 71 and promotes epitaxy between the blade 12 and the root 14.

[0080] The step of producing the second part E2 finally comprises a finishing step E24, which may in particular comprise a machining step, during which the portion corresponding to the funnel 62 is removed, and a heat treatment step. The final blade 10 is then obtained, shown in [Fig. 8], in which the blade 12 is made from the first alloy, the root 14 is made from the second alloy, a coherent interphase 13 being formed at the interface between the blade 12 and the root 14.

[0081] This finish may also include heat treatment and / or the deposition of additional layers, such as an anti-oxidation layer or an abrasive coating at the blade tip.

[0082] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0083] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

Claims

1. A method of manufacturing an aeronautical part (10) comprising a first part (12) and a second part (14), the method comprising a step of producing the first part (El) comprising the formation (El 1) of a first part model (20) made of a removable material, then the formation (El2) of a first shell mold (30) from the first part model (20), then the formation (E13) of the first part (12) in a first metal alloy in the first shell mold (30) from a grain selector (33), a step of producing the second part (E2) comprising the formation (E21) of a second part model (51) made of a removable material, attached to the first part (12), then the formation (E22) of a second shell mold (60) from the first part (12) and the second part model (51), then the formation (E23) of the second part (14) in a second metal alloy, different from the first alloy,in the second shell mold (60) from an interface surface (12a) of the first part (12), wherein the formation of the second part (E23) takes place in a directional crystal growth furnace (90) comprising a relatively hot chamber (91) and a relatively cold chamber (92) separated by a mask (93) projecting into the cavity of the furnace (90), the mask (93) comprising at least two movable panels, and wherein, at least at the start of the formation of the second part (23), the first part (12) is arranged in the cold chamber (92) of the furnace (90) with its interface surface (12a) arranged at the boundary between the hot chamber (91) and the cold chamber (92).,

2. A method according to claim 1, wherein the aeronautical part is a blade (10), preferably a turbine blade, and wherein the first part is a blade (12) and the second part is a root (14).

3. A method according to claim 1 or 2, wherein the first alloy has a higher temperature resistance than the second alloy and the second alloy has, at the operating temperature, a higher mechanical resistance than the first alloy, and wherein the first alloy has a higher density than the second alloy.

4. A method according to any one of claims 1 to 3, wherein the first part (12) is monocrystalline or columnar, and wherein the second part (14) is monocrystalline, columnar or equiaxial polycrystalline.

5. A method according to any one of claims 1 to 4, wherein the crystal structure of the second part (14) is determined by the crystal structure of the first part (12).

6. A method according to any one of claims 1 to 5, wherein, during the formation of the second part (E23), the temperature of the hot chamber (91) is higher than the melting temperature of the second alloy, preferably higher than 1450°C, and wherein, during the formation of the second part (E23), the temperature of the cold chamber (92) is lower than the melting temperature of the two alloys, preferably lower than 500°C.

7. Method according to any one of claims 1 to 6, in which the mask (93) has a geometry adapted to that of the contour of the second shell mold (60) at the interface surface (12a) of the first part (12), and in which, at least at the start of the formation of the second part (E23), a clearance of less than 5 mm is left between the mask (93) and the second shell mold (60).

8. A method according to any one of claims 1 to 7, comprising, after the step of forming the first part (E13), a step of protecting (E14) the interface surface (12a) of the first part (12), and wherein the protection step (E14) comprises placing an oxidation protection coating (49) on the interface surface (12a) of the first part (12).

9. Dawn, obtained by a method according to any one of claims 1 to 8.

10. Turbomachine, comprising a blade according to claim 9.

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