Method for manufacturing a metal part with a doping element by lost-wax casting

Abstract

The invention relates to a method for manufacturing a metal part of a turbine engine by lost-wax casting, the metal part being made of at least one first metal or metal alloy and a second metal or metal alloy, wherein the method comprises the following steps: - pouring the first molten metal into at least one first predetermined region of a moulding cavity in a shell mould; and - pouring the second molten metal into at least one second predetermined region of the moulding cavity, at least one of the first metal and the second metal comprising at least one doping element at a content greater than a normal content of the same doping element in a standard metal, the first metal and the second metal being different according to chemical composition and compatible.

Description

DESCRIPTION TITLE: METHOD FOR MANUFACTURING A METAL PART WITH A DOPING ELEMENT BY LOST-WAX CASTING Technical field of the invention The present invention relates to the field of lost-wax casting for producing lost-wax cast metal parts. Technological background

[0001] Prior art includes documents US-A1-2014 / 363305, US-B2-10239120 and US SA 1-2016 / 288201. The lost-wax casting technique is particularly well-known for manufacturing complex-shaped parts, such as metal components for turbomachinery. The technique involves creating at least one wax model of the metal part to be manufactured and a mold, called a shell mold, which is formed around the wax model. The shell mold is created by successively depositing several layers of ceramic slip, which can have different compositions for each layer. Each slip layer is followed, for example, by draining, sandblasting, and drying. The wax model is then removed, leaving a mold cavity of the corresponding shape inside the shell mold. This mold cavity allows for the flow and filling of molten metal or metal alloy.Before the molten metal is poured, the shell mold undergoes a heat treatment known as sintering to increase its mechanical strength and prevent leaks of the molten metal. After the metal has cooled and solidified, the shell mold is generally destroyed to reveal the raw metal part(s) in the shape of the wax model. Excess material, such as risers, is removed, and each raw part(s) is machined.

[0002] Turbomachine blades, particularly compressor and turbine blades, are examples of highly complex parts to produce despite their simple appearance. These turbomachine blades comprise blades that are swept through a duct by airflows of relatively high temperatures (for example, between 600°C and 1200°C) and platforms at each end that complete the geometries of the surrounding walls.

[0003] These turbomachine blades are made from a metallic material or metal alloy with a complex chemical composition that incorporates several relatively rare and expensive chemical additives to improve the thermomechanical properties of the finished part(s) and to withstand high temperatures, mechanical stresses, and / or corrosion. The chemical composition of the metallic material and the concentration of these chemical additives can vary between the beginning and end of the manufacturing process, depending on the methods used, for example, for solidifying the metallic material.

[0004] Hafnium is an example of an additive chemical element that prevents the propagation of microcracks in turbomachine blades, particularly at the blade attachment point where mechanical stresses are very high. Currently, this additive chemical compound is absorbed by the shell mold during manufacturing, reducing its concentration by up to 50% in the most stressed areas. This represents a significant loss of hafnium, which can lead to non-compliance with chemical composition specifications in certain areas of the part, potentially critical zones, and to damage to the turbomachine blade.

[0005] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0006] The objective of the present invention is to provide a solution for controlling the chemistry of materials in predetermined areas of the mechanical part in order to improve its mechanical, thermal and / or environmental properties.

[0007] We achieve this objective in accordance with the invention by means of a lost-wax casting manufacturing process for a metal turbomachine part, the metal part being made of at least a first metallic material or metal alloy and a second metallic material or metal alloy, the process comprising the following steps: - creation of at least one model in consumable material; - creation of a shell mold in refractory material around the model; - removal of the model in consumable material so as to leave a molding cavity having the shape of the metal part; the process comprising among other steps: - pouring of the first molten metallic material into at least one predetermined area of ​​the mold cavity, and - pouring of the second molten metallic material into at least one second predetermined area of ​​the mold cavity, at least one of the first metallic material and second metallic material comprising at least one doping element at a content higher than a normal content of the same doping element of a standard metallic material, the first metallic material and the second metallic material being different and compatible.

[0008] Thus, this solution achieves the aforementioned objective. In particular, with this improved manufacturing process, the resulting metal part contains, in at least one localized area, a specific doping element to enhance its mechanical, thermal, and / or environmental resistance properties, at least within that localized area. The process allows for precise control of the doping element quantity only in the area requiring it, thereby also reducing the manufacturing costs of the metal part.

[0009] The process also includes one or more of the following features and / or steps, taken alone or in combination: - the first metallic material and second metallic material each comprise a doping element, each having a predetermined content. - the order of pouring the first metallic material and the second metallic material is a function of the position of the first predetermined zone or the second predetermined zone according to a dimension of the molding cavity. - the predetermined content of the doping element of the first metallic material and / or the second metallic material is between 25% and 50% compared to a normal content of the same doping element of a standard metallic material. - the doping element is chosen from at least hafnium, rhenium, aluminium, platinum, chromium, titanium, molybdenum, tungsten and tantalum. - one of the first and second metallic materials is poured rapidly after the other of the first and second metallic materials so as to ensure continuity of pouring between the pouring stages. - the first metallic material and second metallic material are poured in such a way as to obtain an overlap of the pouring stages of the order of a few seconds. - each first metallic material and second metallic material comes from a different power source. - each first metallic material and second metallic material is poured respectively into at least one feed pipe, each feed pipe being supported by a feed bucket allowing the conveyance of the first and second molten metallic materials towards the molding cavity. - each feed pipe rises from a support which is attached and removably fixed to the feed bucket. - each supply pipe is oriented in a direction which has an inclination relative to a central axis of the shell mold. - the process includes a directed solidification step of the first metallic material and second metallic material, in molten form, poured into the molding cavity so as to obtain a compatible or similar crystallographic structure. - the metal part is a turbomachine blade and the first predetermined area corresponds to the foot of the turbomachine blade. - the shell mold making stage includes at least two sub-stages of successive deposits of slip layers comprising a refractory material, each slip deposit sub-stage being followed by sub-stages of draining, sandblasting, and drying of the slip layer. - the first material and / or the second material is poured at a rate which is controlled by a control device. - The casting of metallic materials is gravitational Brief description of the figures

[0010] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the detailed explanatory description that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which: - Figure 1 represents, in an axial and partial section, a turbomachine according to the invention; - Figure 2 is a perspective view of an example of a turbomachine blade according to the invention; - Figure 3 is an example of a flowchart of the steps in the lost-wax manufacturing process of a metal part according to the invention; - Figure 4 is a front view of an example of a shell mold according to the invention; - Figure 5 is a cross-sectional view of an example of a shell mold comprising molding cavities according to the invention; and - Figure 6 schematically represents a step of pouring different metallic materials into a shell mold according to the invention. Detailed description of the invention

[0011] Figure 1 shows an example of a turbomachine 1 comprising an assembly 2 of metal parts that can be manufactured individually or in a sector-like fashion by a lost-wax casting process. The turbomachine 1 is, for example, intended to equip an aircraft (not shown). The aircraft comprises, but is not limited to, a fuselage and at least two wings extending from either side of the fuselage along the fuselage axis. Each wing can carry at least one turbomachine 1.

[0012] Turbomachine assembly 2 is, for example, a turbomachine turbine. The turbine can be a low-pressure turbine or a high-pressure turbine. The high-pressure turbine is advantageously located immediately downstream of the combustion chamber (not shown).

[0013] Assembly 2, here the turbine, includes, for example, rotors 3 which are interconnected and driven in rotation by a shaft 4, such as a low-pressure shaft or a high-pressure shaft. Assembly 2 also includes stators 5 which are attached to one or more stator housings 6 of the turbomachine.

[0014] The assembly 2 advantageously comprises one or more stages 7, each comprising a rotor 3 and a stator 5 arranged and possibly alternating along the longitudinal axis X. Each rotor 3 comprises an annular row of rotor blades 8, or movable blades, and each stator 5 comprises an annular row of stator blades 9, or fixed blades. The rotor blades 8 are movable in rotation about the longitudinal axis X, while the stator blades 9 are fixed in rotation.

[0015] Figure 2 shows an example of a turbomachine blade, and more specifically, a rotor blade 8, in a non-limiting manner. The rotor blade 8 shown includes, for example, a blade 10 extending along a radial axis Z (which is perpendicular to the longitudinal axis X). The rotor blade 8 includes a foot 11, which is provided, for example, at one of the first and second ends of the blade 10. The foot 11 is designed to be mounted in a recess (not shown) located on the periphery of a disk (not shown) of the rotor 3. The foot 11 may be bulbous and include a strut 12. In other words, the foot 11 allows the rotor blade 8 to be attached to the turbomachine disk. The forces transmitted during the rotation of the rotor blade 8 occur at the foot 11.

[0016] Advantageously, but not limitingly, the rotor blade 8 includes a platform 13 which is arranged radially between the strut 12 and the blade 10. The platform 13 includes a radially external surface defining a part of an internal surface of a flow channel in which an airflow flows.

[0017] The rotor blade 8 advantageously, but not exclusively, includes a heel 14 mounted at the opposite end of the first and second ends of the blade 10. The heel 14 includes a radially internal surface that defines a portion of an external surface of the flow channel. The heel 14 generally includes radial swages 15 that cooperate with an abradable material 16 (visible in Figure 1) carried, for example, by the stator housing 6. Of course, the blade 10 may have a free end (i.e., be without a heel).

[0018] As regards the stator blades 9, each of these comprises a blade 17 which extends radially between a radially internal platform 18 and a radially external platform 19.

[0019] Each turbine blade 8, 9 is made of at least one metallic material. The metallic material may be aluminum, steel, a metallic alloy, or a metallic superalloy, etc. Advantageously, but not exclusively, the metallic material is chosen from nickel-based alloys or superalloys. The metallic material may have an equiaxed, columnar, or single-crystal structure. Such materials have the advantage of resisting high temperatures and corrosion, thus enabling the implementation of this type of blade in close proximity, for example, to the combustion chamber where high temperatures prevail.

[0020] In this embodiment example, the turbine blade 8, 9 of the turbomachine is composed of at least two different and compatible metallic materials, hereinafter referred to as the first material and the second material.

[0021] In this description, the term "different" means that slightly different chemical compositions may be found depending on the raw material manufacturers. This difference may affect the concentration of a dopant element such as hafnium, but also the minimum concentration of a basic element in the metallic material, such as carbon, which can play a role in the binding of dopant elements like hafnium.

[0022] In this description, we understand the term "compatible" to mean that metallic materials advantageously share at least one common base of chemical elements but in different proportions.

[0023] For example, a metallic material can be known according to, for example, three shades of directional solidification: - High doping element - Low doping element - Zero doping elements. There may also be a grade of this metallic material without directional solidification, which could have a comparable chemical composition but without the directional solidification. These grades imply the existence, for example, of four different but compatible metallic materials. An example of this metallic material is the one commercially known as DS200, which comes in directional solidification grades of high hafnium, low hafnium, zero hafnium, and a grade without directional solidification called MARM.

[0024] Similarly, at least one of the metallic materials composing the turbine blade 8, 9 is enriched or doped with at least one chemical element or dopant to enhance the mechanical and / or thermal and / or corrosion resistance properties of certain areas of the turbine blade 8, 9.

[0025] The foot 11 of a rotor blade 8 of a turbomachine is one of the predetermined areas which must be able to withstand mechanical breakage and stress and which requires at least one doping element.

[0026] Each doping element can be chosen from at least hafnium, rhenium, aluminium, platinum, chromium, titanium, molybdenum, tungsten and tantalum.

[0027] Advantageously, but not exclusively, one of the metallic materials may contain a high content of a dopant element, for example, in the form of a carbide at the grain boundaries or in the austenitic (or gamma'(y')) phase. These dopant elements contribute to the hardening of the metallic part. Examples of such dopant elements include hafnium, rhenium, tungsten, titanium, molybdenum, and tantalum.

[0028] Advantageously, but not exclusively, one of the doping elements contributes to the protection of the metal part against environmental factors such as oxidation, corrosion, etc. Such doping elements are, for example, aluminum, platinum, or chromium.

[0029] Depending on an advantageous characteristic, but not limited to, the first material and the second material have an identical crystallographic structure. The crystallographic structure is single-crystal, equiaxed, or columnar.

[0030] Figure 3 illustrates, for example, the various stages of a lost-wax casting process 100 for manufacturing a metal part. Advantageously, manufacturing process 100 is implemented in a lost-wax casting installation (not shown). The metal part considered in the subsequent description of process 100 is a turbomachine blade 8, 9, but of course the process can be applied to any other metal part.

[0031] The manufacturing process 100 generally includes: - a production step 110 of at least one model in consumable material; - a step 120 involving the creation of a shell mold made of refractory material around the model made of consumable material; and - a step 130 of the model being removed from the consumable material so as to leave a molding cavity. The molding cavity is intended to be filled with at least one molten metallic material.

[0032] In the present invention, the term "consumable material" refers to a material that is consumed, disappears, or melts at a predetermined temperature. Advantageously, the consumable material is wax or resin. However, the consumable material may be a wax-like material.

[0033] During manufacturing step 110, several models are created from consumable material, each representing the shape of the desired metal part. Each model is advantageously produced in dedicated tooling, such as a mold, and for example, by injection molding the consumable material. The consumable material is then reworked to remove / smooth any imperfections and to ensure that the shape closely matches that of the turbomachine blade 8, 9 to be produced. The consumable material may incorporate sprues and / or risers to facilitate the subsequent casting step. Alternatively, the consumable material can be injected around one or more cores to create an internal cavity in the case of a hollow metal part.

[0034] Advantageously, but not exclusively, each model is attached to a support shaft (not shown) to create a cluster of consumable material models, allowing for the simultaneous production of several metal parts, in this case, turbomachine blades. Optionally, the support shaft is made of a consumable material. Optionally, this shaft can then be covered with a shell mold.

[0035] Step 120 of the shell mold fabrication process may include at least two substeps of successive slip layer deposition, each containing a refractory material. The refractory material is advantageously, but not exclusively, a ceramic. Each slip layer may be produced by dipping the mold cluster into a vat containing the slip or by spraying. Optionally, each slip deposition substep is followed by substeps of draining, sandblasting (or stuccoing), and drying the slip layer. Each slip layer may have a different chemical composition, density, and / or particle size, etc., than the other layers. Similarly, each slip layer may be of a The thickness differs from that of the others. Each sub-stage of stuccoing can be carried out using sand grains applied to the slip layer with a sprinkling machine or a fluidized bed. Sprinkling the sand grains ensures the integrity of the slip layer and creates a thin contact layer.

[0036] Figure 4 illustrates an example of a shell mold 30. In this example, the models that are covered by the shell mold extend in a direction parallel to the central axis A of the shell mold 30 and circumferentially around the central axis A. The direction is vertical here in the plane of Figure 3.

[0037] Preferably, the feet of the turbomachine blade patterns (rotor blades) are arranged in the lower part of the assembly (or shell mold), while the free ends of the patterns are arranged in the upper part of the assembly (relative to the central axis A in the plane of Figure 4). Alternatively, the feet of the patterns are arranged in the upper part of the assembly, while the free ends are arranged in the lower part. In the case of stator blades 9, the radially internal and external platform patterns 18, 19 can be arranged interchangeably. Preferably, the radially external platforms 19 are arranged in the lower part of the shell mold 30, and the radially internal platforms 18 are arranged in the upper part of the shell mold 30. The radially external platform generally allows the stator blade to be attached to a stator housing, for example.

[0038] The removal step 130 of the model(s) in consumable material (known as dewaxing) leaves corresponding molding cavities inside the shell mold 30, each cavity having the shape of the turbine blade 8, 9. As is known, the removal step 130 of the consumable material model is carried out, for example, by heat treatment at a temperature at least equal to the melting temperature of the consumable material. For example, the temperature is between 50°C and 200°C. However, the temperature used must be lower than that of the shell mold material 30. The removal step 130 can take place in an autoclave.

[0039] In Figures 4 and 5, the shell mold 30 (without the patterns) includes, in a known manner, a feed cup 31 which is connected to the mold cavity or cavities 33 via a feed channel 32. The feed cup 31 has a shape of revolution and is centered on the central axis A of the shell mold 30. The molten metal material is poured into the feed cup 31 and then conveyed to the mold cavity or cavities 33. The feed cup 31 is connected to one end 32a of the feed channel 32 which includes various pouring arms 34. which are connected to a vertex 33a of the mold cavity 33 (relative to the central axis). The casting arms 34 are distributed around the central axis A. In other words, the mold cavities 33 are filled from the top along the central axis A of the shell mold 33 shown in Figures 4 and 5.

[0040] Preferably, the casting of metallic materials is gravity-driven (which implies that the shell mold is devoid of conduits connected to a bottom 33b of each molding cavity 33).

[0041] Advantageously, but not limitingly, each molding cavity 33 is elongated and preferably has a height H along the central axis A. The molding cavities 33 are optionally arranged identically in the carapace mold 33.

[0042] Advantageously, but not exclusively, manufacturing process 100 includes a heat treatment step (known as sintering) of the shell mold (with its empty molding cavities). This strengthens the walls of the shell mold. The heat treatment is preferably carried out at a high temperature, for example, between 1000°C and 1700°C.

[0043] The manufacturing process 100 further includes a pouring step 140 of a first molten metallic material into at least one predetermined zone Z1 of the mold cavity 33. The first metallic material includes at least one doping element. Advantageously, but not limitingly, the first metallic material is poured or cast according to the position of the first predetermined zone Z1 along a dimension of the mold cavity 33. Optionally, the dimension corresponds to the height H of the mold cavity 33 in this example.

[0044] The first predetermined zone Z1 preferably corresponds to the foot 11 of the turbine blade 8. Alternatively, the first predetermined zone Z1 may correspond to the radially external platform 19 of the stator blade 9. In this case, the first predetermined zone Z1 is located at the bottom 33b of the mold cavity 33, which, in the example of Figures 4 and 5, corresponds to the foot 11 of the turbine blade 8. The first doped metallic material is poured first so as to fill the bottom 33b of the mold cavity 33. The bottom 33b is oriented along the central axis A to the top 33a of the mold cavity. The first predetermined zone Z1 may extend from the bottom 33b to a predetermined height HP. The predetermined height HP may correspond, for example, to one-third of the height H of the mold cavity 33 measured from the bottom 33b.Alternatively, the predetermined height HP can correspond to the median height of the molding cavity 33 measured from the bottom 33b of the molding cavity or each molding cavity 33.

[0045] The manufacturing process 100 further includes a step 150 of pouring a second molten metal material into the mold cavity or each mold cavity 33. The second molten metal material is poured into at least one second predetermined zone Z2 of the mold cavity or each mold cavity 33.

[0046] In the example of Figure 5, the second predetermined zone Z2 is located at the top 33a of the molding cavity 33. Preferably, the second molten metal material is poured after the first metal material has been poured when the first predetermined zone Z1 is arranged in the lower part (at the bottom 33b) of the molding cavity 33. In this way, the second predetermined zone Z2 corresponds to the remainder of the molding cavity 33 which does not contain, for example, the first molten metal material.

[0047] Of course, the second metallic material is poured into each molding cavity 33 before the first metallic material if the first predetermined area Z1 is arranged in the upper part of the molding cavity 33.

[0048] Advantageously, but not exclusively, the second metallic material differs from the first metallic material in chemical composition in one embodiment. In particular, the second metallic material does not contain a doping element. However, the first and second materials are compatible, meaning they share the same chemical basis.

[0049] The doping element in the first metallic material preferably has a high content that exceeds the normal or standard content of a standard metallic material used in the prior art to manufacture a turbomachine blade. The high content in this description is between 25% and 50% of the normal content of a standard metallic material. A standard metallic material such as DS200, for example, has a normal content of approximately 0.8% of a doping element. The high content of the same doping element in the first material would be between 1% and 2%. We understand that the content of a doping element in a standard metallic material is between 0% and 1%.Thus, even if the carapace mold 30 absorbs part of the doping element from the first metallic material, the final content (after obtaining the final metallic part) is sufficient in the final metallic part and especially in the foot 11 to guarantee thermomechanical and environmental resistance.

[0050] In another embodiment, the second metallic material also comprises a doping element. Advantageously, the doping element of the first metallic material is different from the doping element of the second metallic material. The doping element of the second metallic material can serve to protect the mechanical part from high temperatures while the doping element of the first metallic material can be used to enhance mechanical properties.

[0051] Alternatively, the first and second materials contain the same dopant element but in different concentrations. In this case, if the blade is a rotor blade and the dopant element is, for example, hafnium, the dopant element in the first material has a hafnium content of approximately 1.2%, and the dopant element in the second material has a hafnium content of approximately 0.8%.

[0052] According to another embodiment, the manufacturing process 100 may optionally include further casting steps, for example of a third molten metal material in the mold cavity or each mold cavity 33. The third molten metal material is cast into at least one third predetermined area of ​​the mold cavity or each mold cavity 33. In this embodiment, the first area may correspond to the radially external foot or platform of a blade, the second area may correspond to the blade of the blade and the third area may correspond to the radially internal heel or platform of the blade.

[0053] At least one of the three materials may include a dopant element. Each material may optionally include a different dopant element or the same dopant element in different amounts. According to yet another alternative to the previous embodiment, the turbomachine blade may be made from the first and second materials. The first metallic material may include a dopant element and be poured into the first and third zones of the metallic part, and the second metallic material may be poured into the second zone of the turbomachine blade, or vice versa. One of the first and second materials may include a dopant element. Each of the first and second metallic materials may optionally include a different dopant element or the same dopant element in different amounts.

[0054] Advantageously, but not exclusively, at least one of the first and second metallic materials is poured rapidly after the other to ensure continuous pouring between pouring steps 140 and 150. The term "rapidly" is understood to mean a predetermined period, for example, less than 10 seconds and preferably less than 5 seconds. This is understood to prevent the first material from cooling and to avoid surface problems or loss of mechanical properties.

[0055] An overlap of the casting steps 140 and 150 of a few seconds, for example between one and five seconds, can be considered. This short period between two or more castings or overlaps also prevents the metallic material that will be poured first into the shell mold 30 from cooling or solidifying. Cooling could create an interface or boundary between the different materials and lead to surface problems or loss of mechanical properties, for example.

[0056] Advantageously, but not exclusively, the first material and / or the second material is dispensed at a predetermined rate. Optionally, the predetermined rate is controlled by a molding installation control device.

[0057] Advantageously, but not exclusively, a predetermined quantity of the first metallic material is equal to a predetermined quantity of the second metallic material. The quantities of the first and second metallic materials may be different. Advantageously, but not exclusively, the quantities depend on the volume of the first predetermined zone Z1 and the second predetermined zone Z2.

[0058] According to an advantageous, but not limiting, feature, each first and second metallic material comes from a different feed source 36. The feed source 36 may include a tank containing the molten metallic material. This allows for better control of the different casting stages 140, 150.

[0059] Following an embodiment illustrated in Figure 6, each first and second metallic material is poured into at least one feed channel, designated a "petal" 40. Each petal 40 is advantageously supported by the feed bucket 31. This facilitates a continuous, rapid, and homogeneous pouring of the different metallic materials one after the other. The mixing between the two materials, particularly at their interfaces, is optimized since the molten materials poured rapidly with the aid of the petals 40 remain in a liquid state.

[0060] Each petal 40 rises, for example, from a support 41 which is fixed to the feed cup 31. The support 41 is preferably an added part and is removably fixed. Advantageously, the support 41 has the shape corresponding to the shape of an inlet opening of the feed cup 31 and, for example, in this case, a disc. The support 41 may have dimensions that allow it to cover the inlet opening of the feed cup 31, thus preventing molten material from splashing outside the shell mold.

[0061] Each petal 40, for example, has a cylindrical shape that promotes the flow of molten metallic material towards the feed cup 31.

[0062] Optionally, each petal 40 is oriented along a direction B that is inclined relative to the central axis A. This configuration allows for better pouring of the metallic materials into the feed hopper 31 and potentially controls the flow rate of the metallic materials. The inclination of the petals 40 could prevent obstruction along the central axis A. The angle of inclination can be between 35° and 55°.

[0063] The number of petals 40 can depend on the amount of metallic material to be cast. In the example embodiment, there are two petals 40a, 40b for each mold cavity 33 to be filled. Alternatively, there are two petals 40a, 40b for all the mold cavities 33.

[0064] Of course, more than two petals 40 can be used. If there are more than two petals, the mold's dimensions and / or the pouring method can be adjusted. In particular, when the foot 11 is located at the bottom of the shell mold 30, the first material containing a doping element is poured first, followed by the second material without a doping element. The first and second materials are poured evenly and in a similar manner into the petals. The pouring order is reversed if the foot is located at the top.

[0065] In another embodiment, the metal part can be made of several metallic materials, and each metallic material includes a doping element to enhance its mechanical, thermal, and / or environmental properties in several different areas. Each petal can be used to dispense one of the doped metallic materials. For example, in the case of a metal part made of three metallic materials, each with a different doping element or at different concentrations to reinforce three different areas of the metal part (e.g., the foot, the blade, and the heel), the feed cup has at least three petals 40, each used to dispense a doped metallic material. Advantageously, but not exclusively, the flow rate of the material dispensed into each petal is controlled while allowing continuous feeding of the molding cavity 33.

[0066] The number of petals 40 could also depend on the dimensions of the shell mold and / or the volumes of the molding cavities 33 to be filled. For example, the shell mold 30 has a generally cylindrical shape and a diameter between 250 mm and 500 mm.

[0067] The manufacturing process 100 further includes a directed solidification step 160 of the molten metallic materials poured into the mold cavity or each mold cavity 33. The directed solidification step 160 makes it possible to control and / or promote the nucleation and growth, as well as the direction of the grains in at least one given direction during the transition from the liquid to the solid state and according to thermal gradients so as to obtain a type of crystallographic structure, such as a columnar or single-crystal structure.

[0068] Following an example embodiment, the shell mold can be equipped with at least one conduit (not shown) positioned, for example, below the mold cavity(es). The conduit(s) can be connected to the feed channel 32. The conduit(s) may include, for example, an angled shape. The conduit(s) preferably act as a trap or accessory. This allows the shell mold to be moved slowly for removal from the chamber from below, thus inducing cooling of the shell mold from the bottom up, for example, according to specific descent speed parameters to control the cooling.

[0069] At least the first and second metallic materials advantageously adopt a compatible or similar crystallographic structure. This directed solidification step 160 is carried out, for example, in a furnace (not shown), such as a Bridgman furnace, which comprises a hot section and a cold section. The shell mold 30, comprising the molding cavities 33 filled with molten materials, moves vertically between the hot and cold sections of the furnace to modify the temperature gradient.

[0070] Finally, as is known, manufacturing process 100 includes a step 170 of removing the shell mold 30 in order to reveal the metal part(s) obtained. Removal can be achieved by impact to break the walls of the shell mold 30, by chemical dissolution, or by other means.

[0071] The manufacturing process 100 can finally include a finishing step 180. Each turbomachine blade 8, 9 can then be machined and / or undergo a particular heat or surface treatment in order to obtain the final turbomachine blade.

[0072] We then obtain a turbomachine blade 8, 9 obtained by casting at least two different materials and which includes in certain places a specific chemical composition to reinforce its mechanical properties and / or resistance to corrosion and / or oxidation.

[0073] EXAMPLE 1 Following a first example, a first metallic material comprises a nickel-based superalloy. The first metallic material comprises the following chemical compounds: Chromium (Cr) with a content of approximately 10% by weight relative to the total weight; Carbon (C) with a content of approximately 0.11% by weight relative to the total weight; Titanium (Ti) with a content of approximately 2% by weight relative to the total weight; Aluminium (Al) with a content of approximately 5% by weight relative to the total weight; Tungsten (W) with a content of approximately 12.5% ​​by weight relative to the total weight; Niobium (Nb) with a content of approximately 1% by weight relative to the total weight; Cobalt (Co) with a content of approximately 9% by weight relative to the total weight; Zirconium (Zr) with a content of approximately 0.03% by weight relative to the total weight; and, Boron (B) with a content of approximately 0.015% by weight relative to the total weight.

[0074] The first metallic material has a density of approximately 8.5.

[0075] The first metallic material contains a doping element such as hafnium (Hf) at a concentration of approximately 1.75% by weight relative to the total weight. This hafnium content is very high and exceeds the standard concentration (approximately 0.8%) used in a standard metallic material typically employed for a turbomachine blade, for example. We thus understand that the standard concentration is between 0% and 1%.

[0076] The second metallic material comprises the chemical compounds Cr, C, Ti, Al, T, Al, Nb, Co, Zr, B but lacks the dopant element Hf. Alternatively, the second metallic material can correspond to the standard metallic material used with a hafnium content of 0.8%, which is very low compared to the high content of the dopant element (here hafnium) used in the invention to drastically increase the hafnium content.

[0077] Both the first and second materials contain unavoidable impurities.

[0078] In the case of a molding cavity 33 intended to represent a turbine blade with the foot in the lower part, the first hafnium-doped material is poured first to fill the corresponding area of ​​the foot for example, then the second undoped material is poured quickly in a second step to fill the rest of the molding cavity 33 for example.

[0079] During the solidification step 160, depending on the thermal gradient and the speed of movement of the mold, the same predetermined structure (columnar or single crystal) will be obtained for the two materials which have the same chemical basis and are compatible.

[0080] The resulting metal part will have a foot 11 which will be reinforced in terms of mechanical properties.

[0081] The first material can be DS200Hf and the second material can be DS200.

[0082] EXAMPLE 2 Following a second embodiment, a first metallic material comprises a nickel-based superalloy. The first metallic material comprises the following chemical compounds: Chromium (Cr) with a content of approximately 7% by weight relative to the total weight; Carbon (C) with a content of approximately 0.05% by weight relative to the total weight; Molybdenum (Mo) with a content of approximately 1.5% by weight relative to the total weight; Tantalum (Ta) with a content of approximately 6.5% by weight relative to the total weight; Aluminium (Al) with a content of approximately 6.2% by weight relative to the total weight; Hafnium (Hf) with a content of approximately 0.15% by weight relative to the total weight; Tungsten (W) with a content of approximately 5% by weight relative to the total weight; and, Cobalt (Co) with a content of approximately 9% by weight relative to the total weight.

[0083] The first metallic material has a density of approximately 8.65.

[0084] The first metallic material contains a doping element such as rhenium (Re) at a concentration of approximately 3% by weight relative to the total weight. This first material may be known, for example, by the trade name René N5. The second material has the same chemical base and contains rhenium as a doping element at 1.5%. This second material may be known by the trade name René N515. We thus understand that the standard concentration is between 0% and 1%.

[0085] In the case of a molding cavity 33 intended to represent a turbine blade with the foot in the lower part, the first material doped with a high rhenium content is poured first, then the second material doped with a content lower than that of the doping element (rhenium) of the first material is poured quickly in a second step.

Claims

Demands [1] A method (100) for manufacturing a metal part (8, 9) of a turbomachine by lost-wax casting, the metal part (8, 9) being made of at least one first metallic material or metallic alloy and a second metallic material or metallic alloy, the method (100) comprising the following steps: - production (110) of at least one model in consumable material; - making (120) a shell mold (30) in refractory material around the model; - removal (130) of the model in consumable material so as to leave a molding cavity (33) having the shape of the metal part; - pouring (140) of the first molten metallic material into at least one first predetermined zone (Z1) of the molding cavity (33), and - pouring (150) of the second molten metallic material into at least one second predetermined zone (Z2) of the molding cavity (33), at least one of the first metallic material and second metallic material comprising at least one dopant element, the dopant element being chosen from at least hafnium, rhenium, aluminium, platinum, chromium, titanium, molybdenum, tungsten and tantalum, the first metallic material and the second metallic material being different and compatible with at least one of the same chemical element bases at different contents, characterized in that at least one of the first metallic material and second metallic material is poured after the other of the first and second metallic material after a predetermined period of less than ten seconds so as to ensure continuity of pouring between the pouring steps (140, 150). [2] Method (100) according to claim 1, characterized in that the first metallic material and second metallic material each comprise a doping element each having a predetermined content. [3] Method (100) according to any one of claims 1 and 2, characterized in that the order of casting of the first metallic material and the second metallic material is a function of the position of the first predetermined zone (Z1) or the second predetermined zone (Z2) along a dimension of the molding cavity (33). [4] A method (100) according to any one of claims 1 to 3, characterized in that the content of the doping element in the first metallic material and / or the second metallic material is between 25% and 50% relative to a normal content of the same doping element of a standard metallic material comprising a content of a doping element between 0% and 1%. [5] Method (100) according to any one of claims 1 to 5, characterized in that the first metallic material and second metallic material are poured so as to obtain an overlap of the pouring stages (140, 150) for a duration of between one and five seconds. [6] Method (100) according to any one of the preceding claims, characterized in that each first metallic material and second metallic material is derived from a different feed source. [7] Method (100) according to any one of the preceding claims, characterized in that each first metallic material and second metallic material is poured respectively into at least one feed line (40), each feed line (40) being carried by a feed bucket (31) allowing the first and second molten metallic materials to be conveyed to the molding cavity (33). [8] Method (100) according to the preceding claim, characterized in that each feed pipe (40) rises from a support (41) which is attached and removably fixed to the feed bucket (31). [9] Method (100) according to claim 9 or 10, characterized in that each feed pipe (40) is oriented along a direction (B) which has an inclination with respect to a central axis (A) of the shell mold (30). [10] A method (100) according to any one of the preceding claims, characterized in that it comprises a directed solidification step (160) of at least the first metallic material and second metallic material, in molten form, poured into the molding cavity (33) so as to obtain a compatible or similar crystallographic structure. [11] Method (100) according to any one of the preceding claims, characterized in that the metal part is a turbomachine blade and the first predetermined zone (Z1) corresponds to the foot (11) of the turbomachine blade.

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