Method for manufacturing a metal reinforcement for a turbomachine blade

Abstract

The invention relates to a method for manufacturing a metal reinforcement (3) for a turbomachine blade, in particular for an aircraft, wherein the metal reinforcement (3) is intended to extend along an edge of the blade and comprises two lateral fins (32, 34) and a nose (36) connecting the two lateral fins (32, 34) to one another, and wherein the method comprises the steps of: (a) producing at least one intermediate preform (30) of the metal reinforcement (3) by additive manufacturing, wherein the intermediate preform (30) has at least one excess thickness; and (c) forging the intermediate preform (30) so as to eliminate the at least one excess thickness.

Description

[0001]DESCRIPTION TITLE: METHOD FOR MANUFACTURING A METAL REINFORCEMENT FOR A TURBOMACHINE BLADE Field of the invention The present invention relates to a method for manufacturing a metal reinforcement for a turbomachine blade, in particular an aircraft blade. The present invention also relates to a metal reinforcement obtained by such a method, a turbomachine blade comprising this metal reinforcement and a turbomachine, in particular an aircraft blade, comprising such a blade. Technical background The state of the art includes in particular documents US-A1- 2017 / 081752, US-A1-2022 / 193770, US-A1-2016 / 001407 and CN-A- 114535598. It is known that a turbomachine, in particular an aircraft,comprises blades each having an aerodynamic profile. The blade comprises a lower surface and an upper surface connected to each other by a leading edge and a trailing edge. The leading edge corresponds to an upstream part (in the direction of airflow in the turbomachine) which faces an airflow and divides the flow of the airflow into an intrados airflow and an extrados airflow. The trailing edge corresponds to the downstream part of the aerodynamic profile where the intrados and extrados airflows meet. Turbomachine blades, such as blades of a fan or a turbomachine rectifier, can be subjected to significant mechanical stresses linked in particular to the rotation speed,and must be able to meet strict weight and size requirements. One of the options being considered to lighten the blades is the use of composite materials for their manufacture. It is known to equip turbomachine blades with a metal reinforcement extending along the leading edge of the blade. Such a metal reinforcement protects the blade during an impact from a foreign body (such as a bird, hail or stones). In the case of blades made of composite material, the metal reinforcement also protects the leading edge by avoiding the risk of delamination, breakage of the fibers of the composite material or damage by decohesion between the fibers and the matrix making up the composite material. The metal reinforcement generally comprises two lateral fins connected to each other by a joined intermediate portion, called a nose. The metal reinforcement is generally bonded to the leading edge of the blade,for example over the entire height of the leading edge and a lengthwise portion of the intrados and extrados of the blade. The metal reinforcement may be produced entirely by forging from a block of metal material (such as a bar or a thick sheet) by making several compression passes (for example between three and five passes). Figure 1 illustrates an example of production of the metal reinforcement 1 by forging which may comprise the following steps: (1a) providing a metal bar 40 extending along a longitudinal axis A, (1b) making several forging passes of the metal bar 40 to obtain a twisted metal bar 40 for example with a double camber in first C and second B directions by means of a press, the second direction B is perpendicular to the axes A and C,(1c) performing a forging by spinning the twisted metal bar 40 of step (1b) so as to obtain an intermediate part 400 substantially U-shaped or V-shaped in cross-section to form the two lateral fins 32, 34 located on either side of a solid part 402 (intended to form the nose 36 of the metal reinforcement 3) and the pins 404 at the ends of the intermediate part 400 to allow handling, (1d) performing a shaping of the intermediate part 400 in a shaping tool having the final shape of the metal reinforcement 2, and (1e) performing a finishing machining step to remove in particular the pins 404 and polishing in order to obtain the required surface condition of the metal reinforcement 3. The metal reinforcement obtained according to the method of FIG. 1 requires at least approximately five forging passes with different tools for each pass. With reference to FIG. 2,the metal reinforcement 3 can be produced by diffusion welding which can comprise the following steps: (2a) providing two metal sheets 50 having a flat shape, (2b) performing hot forming on each of the two metal sheets 50 to curve them, (2c) performing diffusion welding to assemble the two preformed metal sheets 500 together with another O-shaped tool so as to obtain the final shape of the metal reinforcement 3, and (2d) performing a finishing and polishing step in order to obtain the required surface condition of the metal reinforcement 3. However, the metal reinforcement is a complex part to produce, requiring numerous rework operations and complex tools involving significant production costs. Furthermore,the aerodynamic profile (i.e. with a twisted three-dimensional geometry and a thickness that can be scalable between the nose and the side fins) can be complex to produce by forging or diffusion welding. The metal reinforcement can be produced by additive manufacturing, such as powder bed additive manufacturing using a high-energy laser beam (LBM process, acronym for Laser Beam Melting). The LBM process allows selective consolidation of powder layers in order to constitute, layer by layer, a three-dimensional part, such as the metal reinforcement. However, additive manufacturing can generate a so-called degraded surface condition (or otherwise said to be granular, rough and non-smooth) of the metal reinforcement. Figure 3 illustrates an example of the surface condition of the metal reinforcement obtained by additive manufacturing which has so-called degraded zones Z, Dwhich are identified by arrows in this figure 3. This metal reinforcement generally has a surface roughness Ra between 5 and 50 μm. This degraded surface condition does not allow the formation of a sufficiently smooth aerodynamic profile suitable for use with the turbomachine blade. Following the LBM process, the outer surface of the metal reinforcement can be treated, for example, by chemical polishing to reduce its degraded surface condition. Figure 4 illustrates an example of the surface condition of the metal reinforcement after a surface treatment by chemical polishing which still has degraded areas Z D. Thus, this surface treatment does not allow the roughness of the outer surface of the metal reinforcement to be sufficiently reduced. In addition, the surface treatment can be complex to implement on the metal reinforcement which has a changing thickness (in particular between the nose and the lateral fins). In this context, the invention aims to solve the problems mentioned above, by proposing a method for producing a metal reinforcement for a turbomachine blade, in particular an aircraft blade, making it possible to simplify and optimize the manufacturing range of such a metal reinforcement, and to significantly reduce manufacturing costs. Summary of the invention The invention proposes a simple, effective and economical solution to the aforementioned drawbacks of the prior art. To this end, the invention proposes a method for manufacturing a metal reinforcement for a turbomachine blade, in particular an aircraft blade,the metal reinforcement being intended to extend along an edge of the blade and comprising two lateral fins and a nose connecting the two lateral fins together, the method comprising the steps of: (a) producing at least one intermediate preform of the metal reinforcement by additive manufacturing, said intermediate preform having at least one excess thickness and a portion without excess thickness, and (c) forging said intermediate preform so as to remove said at least one excess thickness. Thus, this solution makes it possible to achieve the aforementioned objective. In general, the method according to the invention makes it possible to simplify and optimize the production of the metal reinforcement. For this, the metal reinforcement is initially produced with an excess thickness by additive manufacturing, then this excess thickness is removed by forging. In particular,the metal reinforcement is made by integrating both an overthickened part and a part without overthickness. Additive manufacturing makes it possible to form the metal reinforcement with the overthickness in one piece, to maintain continuity of material between the lateral fins and the nose of the metal reinforcement, and to easily produce the twisted shape and evolving thickness of the metal reinforcement. The overthickness can thus be localized on at least one predetermined area of ​​the intermediate preform. The overthickness makes it possible to reduce possible deformations due to the low thickness of the metal reinforcement which can occur during its handling, for example when cutting parts from the manufacturing plate. Forging (or otherwise known as forging) is the set of techniques used to obtain a mechanical part by cold or hot plastic deformation by applying a significant force to a metal part,in order to force it to fit the desired shape. It is therefore understood that the force applied during forging makes it possible to remove the aforementioned excess thickness by constraining the material. Forging also makes it possible to carry out work hardening on the surface of the material which makes it possible to optimize the optimal mechanical properties of the metal reinforcement. Advantageously, the forging step can be carried out in a single pass. This makes it possible to provide the part with these final properties (such as a surface condition, mechanical property and the removal of the excess thickness). More particularly, forging has the following advantages: - significantly improves the surface condition of the metal reinforcement (in particular with a surface that is as smooth as possible, homogeneous and continuous so as to adapt to the aerodynamic profile of the blade), - reduce or eliminate all indications of porosity or lack of fusion from additive manufacturing (in particular obtaining a porosity rate of less than 0.1%),- improve the microstructure of the metal reinforcement, - improve the impact strength of the metal reinforcement, - re-conform the metal reinforcement with the desired final dimensions, and - obtain the final dimensioning according to a predetermined tolerance of the metal reinforcement. The method according to the invention can also facilitate the mass production of the metal reinforcement (for example at least one series of between two and ten or more than ten). Furthermore, the use of a more efficient method for producing the metal reinforcement according to the invention is also advantageous for reducing the environmental footprint. Indeed, it makes it possible to increase and optimize the manufacturing, production and / or repair capacity and, consequently, to significantly reduce the associated greenhouse gas emissions. This optimization also makes it possible to extend the service life of the metal reinforcement and, consequently,to reduce the number of replacements of new parts, and to significantly reduce the number of discarded parts that may be difficult to recycle. The manufacturing method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: -- said at least one excess thickness is located on a portion of the intermediate preform; - said at least one excess thickness is located on at least one of the lateral flanks intended to form the lateral fins of the metal reinforcement; - said at least one excess thickness is located on an end intended to form the nose of the metal reinforcement; - the method comprises, between steps (a) and (c), a step (b) of heat treatment of at least one portion of the intermediate preform; the heat treatment step (b) is carried out at a temperature of between 700°C and 800°C, for example approximately 730°C,and with a duration of between 100 and 150 minutes, for example approximately 120 minutes; - said excess thickness is between 0.2 and 1 mm, for example between 0.2 and 0.5 mm; - the intermediate preform in step (a) has a surface roughness Ra, aminimum of approximately 3 μm, for example between 3 and 50 μm; - the metal reinforcement in step (c) has a surface roughness Rac of less than 1.6 μm, for example between 0.6 and 1.6 μm; the additive manufacturing of step (a) is carried out by laser powder bed fusion (LBM), laser powder deposition by laser fusion (LDM), fused wire deposition (FFF), extrusion (EAM), pellet extrusion (FGF) or injection of a binder onto a powder bed; - the forging of step (c) is carried out by die-forging the intermediate preform; - the method comprises, after step (c), a final step (d) of polishing the metal reinforcement; - step (a) comprises producing a plurality of intermediate preforms joined together, and in that the method further comprises a step of cutting said plurality of intermediate preforms so as to separate and form individual pieces of intermediate preforms; -- the plurality of preformsintermediate preforms produced in step (a) comprises between two and ten intermediate preforms or more than ten intermediate preforms; -- the cutting step is carried out before step (c); -- the cutting step is carried out before step (b); -- the metal reinforcement is made of a metallic material, such as titanium, a titanium-based alloy (for example TA6V type), a steel (for example stainless steel) or a nickel and cobalt alloy (NiCo); -- the metal reinforcement extending along a leading edge and / or a trailing edge of the blade. The invention also relates to a metal reinforcement for a turbomachine blade, in particular an aircraft blade, obtained by a manufacturing method according to one of the features of the invention. The metal reinforcement comprises at least one portion work-hardened by forging and a portion not work-hardened by forging. More particularly, the work-hardened portion is formed by removing the excess thickness by forging. In particular, theForging differs from rolling in the present application, in that the mechanical properties (such as surface condition, roughness, etc.) of a portion work-hardened by forging are different from those of a portion work-hardened by rolling. The metal reinforcement and in particular its work-hardened portion may have a surface roughness Rac of less than 1.6 μm, for example between 0.6 and 1.6 μm. The invention also relates to a turbomachine blade, in particular an aircraft blade, comprising a metal reinforcement according to the invention. The blade comprises a lower surface and an upper surface connected together by a leading edge and a trailing edge of the blade, the metal reinforcement extending along the leading edge or the trailing edge. The invention further relates to a turbomachine, in particular an aircraft blade, comprising at least one blade according to the invention. Brief Description of the Figures The invention will be better understood and other details, features and advantages of the invention will become apparentmore clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which: Figure 1 schematically represents a first example of a method for manufacturing a metal reinforcement according to the prior art, Figure 2 schematically represents a second example of a method for manufacturing a metal reinforcement according to the prior art, Figure 3 represents a surface condition of a metal reinforcement obtained by additive manufacturing of the LBM type according to the prior art, Figure 4 represents a surface condition after surface treatment of the metal reinforcement of Figure 3, Figure 5 is a half axial sectional view schematically representing an aircraft turbomachine, Figure 6 is a schematic profile view of a rotor-type blade of an aircraft turbomachine comprising a metal reinforcement according to the invention, Figure 7 is a schematic profile view of a stator-type blade of a turbomachineof an aircraft comprising a metal reinforcement according to the invention, Figure 8 is a partial schematic sectional view of Figure 6 or 7 along the section plane BB, Figure 9 schematically represents a method of manufacturing the metal reinforcement according to the invention, Figure 10 is a schematic axial sectional view of the intermediate preform of the metal reinforcement with an excess thickness according to a first example not covered by the present application, Figure 11 is a schematic axial sectional view of the intermediate preform of the metal reinforcement with an excess thickness according to a second example, Figure 12 is a schematic axial sectional view of the intermediate preform of the metal reinforcement with an excess thickness according to a third example. The elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention By convention, in the description below, the terms "longitudinal" and "axial" describe the orientation of structural elements extending in the direction of a longitudinal axis (such as that of a turbomachine). The terms "radial" or "vertical" describe an orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner" and "outer", and "internal" and "external" are used with reference to a positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an inner face facing the longitudinal axis and an outer surface, opposite its inner surface. Figures 1 to 4 have been described in the technical background of the present application and illustrate examples of manufacturing a metal reinforcement according to the prior art and its surface condition. The invention can be applied in a non-limiting manner to a turbomachine 10, in particular an aircraft. The turbomachine 10 can be streamlined which is byexample shown in Figure 5. The turbomachine 10 may be a turbojet, turboshaft or turboprop. The turbomachine 10 extends around a longitudinal axis X. It comprises from upstream to downstream in the direction of flow of the gases F along the longitudinal axis X, a fan 2a, at least one compressor (such as a low pressure compressor 1a and / or a high pressure compressor 1b), a combustion chamber 1c, at least one turbine 1d (such as a high pressure turbine and / or a low pressure turbine) and a nozzle (not shown). The turbomachine 10 further comprises a rectifier 2b. The rectifier 2a may comprise at least one annular row of blades 2 (in particular fixed ones), called OGV blades extending around the axis X. The OGV blades make it possible to straighten the flow at the outlet of a rotor located upstream in order to provide maximum thrust at the outlet of the turbomachine 10. In the particular example of FIG. 1, the rectifier 2b is located downstream of thefan 2a and allows a secondary flow F2 to be straightened. The fan 2a comprises an annular row of blades 2 (in particular mobile blades), called fan blades extending around the axis X. The fan 2a allows the suction of an air flow dividing into a primary flow F1 and a secondary flow F2. The primary flow F1 passes through a primary vein of the turbomachine 10 while the secondary flow F2 is directed towards a secondary vein surrounding the primary vein. The primary flow F1 is compressed within the low-pressure compressor 1a then the high-pressure compressor 1b. The compressed air is then mixed with a fuel and burned within the combustion chamber 1c. The gases formed by the combustion pass through the turbine 1d. The gases finally escape through the nozzle, the section of which allows the acceleration of these gases to generate propulsion. The secondary flow F2 passes through the rectifier 2b which accelerates the circulation speed of the secondary flow F2 to generatepropulsion. The fan 2a, the low pressure compressor 1a, the high pressure compressor 1b, the turbine 1d (high pressure and / or low pressure), and the rectifier 2a each comprise blades 2. The blades 2 may be movable (for example the fan blade of Figure 6) in rotation around the longitudinal axis X, or fixed (the blade 2 OGV of the rectifier 2b of Figure 7) relative to the axis X. The blades 2 extend radially relative to the axis X. In the following description, the invention will be described in the context of its application in a non-limiting manner to the blade 2 with reference to Figures 5 to 8. This blade 2 may be movable from the fan 2a (Figure 6) or fixed from the rectifier 2b (Figure 7). The invention is however not limited to a moving fan or rectifier blade of a shrouded turbomachine, and can be applied generally to other types of blades, such as: - fixed and / or moving blades of low pressure compressors 1a and highpressure 1b, high pressure and low pressure turbines of the turbomachine 10, and / or - fixed and / or moving blades of an unducted turbomachine. With reference to Figures 6 and 7, the blade 2 extends, on the one hand, along an elongation axis A (substantially vertical in Figures 5 and 7), and on the other hand, along a longitudinal axis B (substantially horizontal in Figures 6 and 7). This axis A is substantially perpendicular to the axis B. The axis A is substantially perpendicular or inclined to the axis X of the turbomachine 10. The blade 2 may comprise an intrados face 21 (hereinafter referred to as intrados) and an extrados face 22 (hereinafter referred to as extrados). The intrados 21 and the extrados 22 extend transversely between a leading edge 23 and a trailing edge 24 of the blade 2. The blade 2 may comprise a blade 20. In the present application, the blade 20 may be likened to the blade 2. The blade 20 may have an aerodynamic profile to form the aerodynamic part of the blade 2. Forthis, the blade 20 can have a curved profile of variable thickness between the leading edge 23 and its trailing edge 24 of the blade 2. In the examples of Figures 6 and 7, the blade 20 extends along the axis A between a first end and a second end opposite the first end. In the case of the movable blades 2 of Figure 6, these blades 2 can each further comprise a root 26. The root 26 is in particular connected to the second end of the blade 20. It is intended to be fixed to a disk (not shown) for example movable in rotation around the axis X. The second end is free and configured to form a tip 25 (or a head) of blade 2. In the case of the fixed blades 2 of the shrouded turbomachine of Figure 7, these blades 2 can each further comprise a first platform 27a and a second platform 27b opposite. The first platform 27a is secured to the first end of the blade 20 and the second platform 27b is secured to thesecond end. As a variant (not shown), of the fixed blades of an unducted turbomachine, the second end of these blades comprises the second platform 27b and the first end is free. The blade 2 may be made of a composite material. Preferably, the blade 2 may be formed by a fiber preform embedded in a resin (organic matrix composite material). Furthermore, the blade 2 may also comprise a metal reinforcement 3 (or in other words a metal shield, a metal foil). This metal reinforcement makes it possible to protect the blade against external impacts (gravel from a takeoff / landing runway, hailstones, birds, etc.) and against erosion of the blade or delamination of the blade. The metal reinforcement 3 can extend along the leading edge 23 and / or the trailing edge 24 of the blade 2. Advantageously, the metal reinforcement 3 can extend in height (relative to the axis A) and over a portion in length (relative to the axis B) ofthe intrados 21 and the extrados 22 from the leading edge 23 or the trailing edge 24. The metal reinforcement 3 can be fixed to the leading edge 23 and / or to the trailing edge 24 by gluing. With reference to FIG. 8, the metal reinforcement 3 can have a general shape, in cross section relative to the axis A, in “V” or “U”. The metal reinforcement 3 can comprise two lateral fins, respectively, intrados 32 and extrados 34. The intrados lateral fin 32 is connected to the extrados lateral fin 34 by an intermediate portion called “nose” 36. The lateral fins 32, 34 and the nose 36 are monobloc (i.e. made in one piece). The side fins 32, 34 and the nose 34 may define between them a cavity in which the leading edge 23 or the trailing edge 24 is arranged. The side fins 32, 34 may be tapered in the opposite direction to the nose 36. The metallic material of the metallic reinforcement 3 may be titanium, a titanium-based alloy (e.g.example of type TA6V), a steel (for example a stainless steel) or a nickel and cobalt alloy (NiCo). One of the particularities of the invention is that the metal reinforcement 3 may comprise at least one work-hardened or forged portion. The metal reinforcement 3 may have a surface roughness Rac of less than 1.6 μm, for example between 0.6 and 1.6 μm. The present application will now describe a method of manufacturing the metal reinforcement 3 as described below (in particular with reference to FIGS. 5 to 8). FIGS. 9 to 11 illustrate in a non-limiting manner at least one of the steps of the method of the invention. In general, the method according to the invention comprises the steps of: (a) producing at least one intermediate preform 30 of the metal reinforcement 3 by additive manufacturing, this intermediate preform 30 having at least one excess thickness 300 and a part without excess thickness 300, and (c) forging the intermediate preform 30 so as toremove the at least one excess thickness 300. The intermediate preform 300 produced in step (a) may comprise first 320 and second 340 lateral flanks intended to form, respectively, the intrados 32 and extrados 34 lateral fins of the metal reinforcement 3 to be produced. This intermediate preform 300 may comprise an end 360 intended to form the nose 36 of the metal reinforcement 3 to be produced. The end 360 may connect the lateral flanks 320, 340 together. According to an embodiment not covered by the present application, in step (a), the excess thickness 300 may be located over the entirety of the intermediate preform 30. Figure 10 illustrates in a non-limiting manner the excess thickness 300 formed over the entirety of an internal surface of the intermediate preform 30. As a variant, this excess thickness 300 may extend over the entirety of an external surface of the intermediate preform 30. According to another embodiment of the present application, the excess thickness 300 may be locatedon at least one predetermined area (or a predetermined part) of the intermediate preform 30. The excess thickness 300 can therefore be located either on at least one of the lateral flanks 320, 340, or on the end 360 of the intermediate preform 30. Figure 11 illustrates in a non-limiting manner an example of the intermediate preform 30 in which the excess thickness 300 is located only on the lateral flanks 320, 340 (in particular on the internal surface of these lateral flanks), thus the excess thickness 300 is not present on the end 360. Figure 12 illustrates in a non-limiting manner an example of the intermediate preform 30 in which the excess thickness 300 can be located only on the end 36 and absent from at least one of the lateral flanks 320, 340. The excess thickness 300 can be between 0.2 and 1 mm. For example, the excess thickness can be between 0.2 and 0.5 mm. This allows forging to be carried out to obtain the metal reinforcement 3 with the dimensions anddesired final mechanical properties. In addition, this extra thickness makes it easier to handle the intermediate preform 30 without deforming it, for example when cutting the intermediate preform 30 from a manufacturing plate (visible in FIG. 9). The dimension and position of the extra thickness 300 on the metal reinforcement 3 may be variable depending on the manufacturing parameters and / or the desired final shape for the metal reinforcement 3. Step (a) may comprise producing a plurality of intermediate preforms (30) joined together. The method may further comprise a step of cutting this plurality of intermediate preforms (30) so as to separate and form individual pieces of intermediate preforms (30). This cutting step may be carried out before step (c). The cutting step may be carried out before a chemical treatment step (b) described below. The plurality of preformsintermediate preforms 30 produced in step (a) may comprise between two and ten intermediate preforms 30 or more than ten intermediate preforms 30. Figure 9 illustrates in a non-limiting manner the production of several intermediate preforms 30 joined by additive manufacturing on a manufacturing plate P. Before carrying out step (c), and possibly before step (b), the method may therefore comprise the step of cutting the intermediate preforms 30 to separate them from each other and from the plate P. In step (a), the additive manufacturing may be carried out by laser powder bed fusion (LBM), laser direct manufacturing (LDM), fused filament fabrication (FFF), extrusion (EAM), extrusion of granules (FGF) or injection of a binder onto a powder bed.(also known as binder jetting). Additive manufacturing allows the production of parts with complex shapes, such as U- or V-shaped cross-sections and varying thicknesses of the metal reinforcement 3. LBM additive manufacturing allows the selective consolidation of powder layers to form, layer by layer, the metal reinforcement 3 with the excess thickness 300 in three dimensions. FFF additive manufacturing allows the successive deposition of layers of materials using a filament of molten polymer material or a resin filament. EAM additive manufacturing allows the deposition of a continuous filament of composite or thermoplastic material to build the metal reinforcement 3 with the excess thickness 300 in three dimensions layer by layer. FGF additive manufacturing allows the deposition of granules of molten composite or thermoplastic material layer by layer to form the metal reinforcement 3 with the excess thickness 300 in three dimensions.dimensions. The intermediate preform 30 in step (a) may have a surface roughness Ra a minimum of about 3 μm. For example, this roughness Ra a can be between 3 and 50 μm. The surface condition of the intermediate preform 30 can substantially correspond to that illustrated in FIG. 3. In step (c), the forging thus makes it possible to form the work-hardened portion of the metal reinforcement 3. Furthermore, the forging also makes it possible to reduce to a single forging pass of the intermediate preform 30 to form the metal reinforcement 3. The metal reinforcement 3 at this step (c) can have a surface roughness Ra c less than 1.6 μm. This roughness Ra ccan be more particularly between 0.6 and 1.6 μm. This makes it possible to form a sufficiently smooth, homogeneous and continuous surface so as to adapt to the aerodynamic profile of the blade. In step (c), the forging (or in other words the work hardening) can be carried out by die-forging under a press of the intermediate preform 30, in particular of the excess thickness 300. For example, the intermediate preform 30 can be deformed (or in other words work hardened) by forging with a press, for example an isothermal press brought to a temperature of between 700°C and 940°C to have good deformation properties, in particular of titanium at low forging speed. According to another variant, the forging of step (c) can be carried out using a screw press and a punch / die tool. Forging makes it possible in particular to twist and give the final or near-final shape to the metal reinforcement 3. Advantageously, the forging step can be carried out in a single pass.This makes it possible to provide the part with these final properties (such as a surface condition, mechanical property and the elimination of excess thickness). In the event of material burr after forging, step (c) may comprise a step of machining this burr. The method of the invention may comprise, between steps (a) and (c), a step (b) of heat treatment of at least a portion of the intermediate preform 30. This makes it possible to reduce or even eliminate the residual stresses and thus limit the deformations of the intermediate preform 30 at the end of the additive manufacturing step (a). This heat treatment step (b) may be carried out at a temperature of between 700°C and 800°C and for a duration of between 100 and 150 minutes. For example, step (b) may be carried out at a temperature of about 730°C (with a possible temperature variation of about + / - 10°C) for about 120 minutes (with a possible duration variation of about + / - 10%).The method of the invention may comprise, after step (c), a final step (d) of polishing the metal reinforcement (3). This makes it possible to obtain the final shape and dimensions of the metal reinforcement 3 which is ready to be installed on the blade 2. Furthermore, the method according to the invention may make it possible to facilitate the mass production of the metal reinforcements 3 (for example at least one series of between two and ten or more than ten). For this, the intermediate preforms 30 may be formed in step (a) in a manner linked to each other to form the desired series of metal reinforcements. As an example, FIG. 9 illustrates approximately five intermediate preforms 30 formed in a single step (a). Then, the method may comprise a cutting step to form individual pieces of the intermediate preforms 30 (and consequently of the metal reinforcements 3).Each of these individual intermediate preforms 30 may be forged in step (c), and / or heat treated in step (b), and / or polished in step (d). This cutting step may be performed after the additive manufacturing step (a) or after the forging step (c).

Claims

CLAIMS 1. Method for manufacturing a metal reinforcement (3) for a turbomachine blade (2), in particular an aircraft blade, the metal reinforcement (3) being intended to extend along an edge (23, 24) of the blade (2) and comprising two lateral fins (32, 34) and a nose (36) connecting the two lateral fins (32, 34) together, the method comprising the steps of: (a) producing at least one intermediate preform (30) of the metal reinforcement (3) by additive manufacturing, said intermediate preform (30) having at least one excess thickness (300) and a portion without excess thickness (300), and (c) forging said intermediate preform (30) so as to remove said at least one excess thickness (300).Manufacturing method according to claim 1, characterized in that said at least one excess thickness (300) is located either on at least one of the lateral flanks (320, 340) intended to form the lateral fins (32, 34) of the metal reinforcement (3), or on an end (360) intended to form the nose (36) of the metal reinforcement (3).

3. Manufacturing method according to any one of the preceding claims, characterized in that it comprises, between steps (a) and (c), a step (b) of heat treatment of at least a portion of the intermediate preform (30).

4. Manufacturing method according to claim 3, characterized in that the step (b) of heat treatment is carried out at a temperature of between 700°C and 800°C, for example approximately 730°C, and with a duration of between 100 and 150 minutes, for example approximately 120 minutes. 5.Manufacturing method according to any one of the preceding claims, characterized in that said excess thickness is between 0.2 and 1 mm, for example between 0.2 and 0.5 mm.

6. Manufacturing method according to any one of the preceding claims, characterized in that the intermediate preform (30) in step. (a) has a surface roughness Ra a minimum of approximately 3 μm, for example between 3 and 50 μm.

7. Manufacturing method according to any one of the preceding claims, characterized in that the metal reinforcement (3) in step (c) has a surface roughness Ra cless than 1.6 μm, for example between 0.6 and 1.6 μm.

8. Manufacturing method according to any one of the preceding claims, characterized in that the additive manufacturing of step (a) is carried out by laser powder bed fusion (LBM), laser powder deposition by laser fusion (LDM), fused wire deposition (FFF), extrusion (EAM), pellet extrusion (FGF) or injection of a binder onto a powder bed.

9. Manufacturing method according to any one of the preceding claims, characterized in that the forging of step (c) is carried out by die-forging the intermediate preform (30).

10. Manufacturing method according to any one of the preceding claims, characterized in that it comprises, after step (c), a final step (d) of polishing the metal reinforcement (3). 11.Manufacturing method according to any one of the preceding claims, characterized in that step (a) comprises the production of a plurality of intermediate preforms (30) joined to one another, and in that the method further comprises a step of cutting said plurality of intermediate preforms (30) so as to separate and form individual pieces of intermediate preforms (30).

12. Metal reinforcement (3) for a blade (2) of a turbomachine, in particular of an aircraft, obtained by a manufacturing method according to any one of the preceding claims, and characterized in that the metal reinforcement comprises at least one portion hardened by forging and one portion not hardened by forging.

13. Metal reinforcement according to the preceding claim, characterized in that said hardened portion has a surface roughness Ra. c less than 1.6 μm, for example between 0.6 and 1.6 μm.

14. Turbomachine blade (2), in particular for an aircraft, comprising a metal reinforcement (3) according to claim 12 or 13, the blade (2) comprising a lower surface (21) and an upper surface (22) connected to each other by a leading edge (23) and a trailing edge (24) of the blade, the metal reinforcement (3) extending along the leading edge (23) or the trailing edge (24).

15. Turbomachine (10), in particular for an aircraft, comprising at least one blade (2) according to claim 14.

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