FR2962483A1 - Method for realizing hollow metal reinforcement of e.g. leading edge of fan blade of turbomachine, involves chemically attacking fugitive insert to form internal cavity in massive part to obtain reinforcement of leading or trailing edge - Google Patents

Abstract

The method involves weaving a three-dimensional fibrous structure (300) by weaving wires and/or metal strands (301). A fugitive insert (50) is incorporated in the fibrous structure. An assembly formed by the fibrous structure and by the fugitive insert causing agglomeration of metal wires of the fibrous structure is isostatic hot-pressed around the fugitive insert so as to obtain a massive part. The fugitive insert is chemically attacked so as to break the insert and to form an internal cavity in the massive part to obtain a hollow metal reinforcement of leading edge or trailing edge.

Description

PROCESS FOR PRODUCING A HOLLOW METAL REINFORCEMENT OF TURBOMACHINE BLADE.

The present invention relates to a method for producing a hollow metallic reinforcement of composite blade or metal turbomachine. More particularly, the invention relates to a method for producing a hollow metal reinforcement of turbomachine blade leading edge. The field of the invention is that of turbomachines and more particularly that of the fan blades, made of composite or metallic material, of a turbomachine and whose leading edge comprises a hollow metal structural reinforcement. However, the invention is also applicable to the production of a metal reinforcement intended to reinforce a blade trailing edge of any type of turbomachine, terrestrial or aeronautical, and in particular a helicopter turbine engine or an aircraft turbojet engine but also propellers such as propellers of double blowers contrarotative unducted ("open rotor" in English). It is recalled that the leading edge corresponds to the front part of an airfoil which faces the airflow and which divides the airflow into an intrados airflow and a flow of air. extrados air. The trailing edge corresponds to the posterior part of an aerodynamic profile where the intrados and extrados flows meet. The turbomachine blades, and in particular the fan blades, undergo significant mechanical stress, particularly related to the speed of rotation, and must meet strict conditions of weight and bulk. As a result, blades made of composite materials are used which are lighter and have better heat resistance. It is known to equip the fan blades of a turbomachine, made of composite materials, with a metallic structural reinforcement extending over the entire height of the blade and beyond their leading edge as mentioned in EP1908919. Such a reinforcement makes it possible to protect the composite blading during an impact of a foreign body on the blower, such as, for example, a bird, hail or pebbles.

In particular, the metallic structural reinforcement protects the leading edge of the composite blade by avoiding risks of delamination, fiber breakage or damage by fiber / matrix decohesion. In a conventional manner, a turbomachine blade has an aerodynamic surface extending, in a first direction, between a leading edge and a trailing edge and, in a second direction substantially perpendicular to the first direction, between a foot and a dawn summit. The metallic structural reinforcement follows the shape of the leading edge of the aerodynamic surface of the blade and extends in the first direction beyond the leading edge of the aerodynamic surface of the blade to match the profile of the blade. the intrados and the upper surface of the dawn and in the second direction between the foot and the top of the dawn. In known manner, the metallic structural reinforcement is a metal part made entirely by milling from a block of material. However, the metal reinforcement of a blade leading edge is a complex piece to achieve, requiring many rework operations and complex tools involving significant realization costs. In addition, when the metal reinforcement of the leading edge is hollow, that is to say that it comprises recesses so as to improve the mass criterion, the realization by milling from a block of material becomes very difficult to achieve. In this context, the invention aims to solve the above-mentioned problems by proposing a method for producing a leading edge metal reinforcement or turbomachine blade trailing edge making it possible to simplify the manufacturing range of the machine. hollow complex piece such as a leading edge metal reinforcement while reducing the costs of production. To this end, the invention proposes a method for producing a hollow metal reinforcement of leading edge or trailing edge of turbine engine blade comprising successively: a step of weaving a three-dimensional fibrous structure by weaving wires and / or metal strands: a step of incorporating at least one fugitive insert into said fibrous structure; a step of hot isostatic pressing of the assembly formed by said fibrous structure and by said at least one incorporated fugitive insert causing the agglomeration of the metal threads of said fibrous structure around said at least one fugitive insert, so as to obtain a massive piece; a step of etching said at least one fugitive insert so as to dissolve said insert and to form an internal cavity in said solid part, so as to obtain said hollow metal reinforcement of leading edge or trailing edge.

The term "fugitive insert" means an insert which is not intended to be permanent and which is only necessary for the realization of the leading edge hollow metal reinforcement. The fugitive insert is not present in the metal reinforcement in its final state and does not participate in any mechanical characteristics of the metal reinforcement.

Thanks to the invention, the hollow metal structural reinforcement is produced in a simple and fast manner from a weave of a fibrous structure forming a preform of the metal reinforcement and a pressing process or hot isostatic compaction (HIP for Hot Isostatic Pressing in English) to obtain a compact piece without porosity by the combination of plastic deformation, creep and diffusion welding. The incorporation of a fugitive insert into the fibrous structure creates a defined area in which the metal material of the fibrous structure can not flow during the hot isostatic pressing step. This insert, made of a material different from the fibrous structure, is then dissolved by a chemical attack so as to create an internal cavity in the metal reinforcement and thus to obtain a lightened piece. This production method thus makes it possible to dispense with the complex implementation of reinforcement by machining in the mass, such as milling, broaching, from flats requiring large volume of processing material and consequently significant costs in terms of supply. of raw material and makes it possible to easily achieve metal reinforcements meeting strict requirements of mass and / or geometric. The method for producing a hollow turbine engine blade metal reinforcement according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: - prior to said isostatic pressing step at hot, said method comprises a step of placing said set in a tool; at the same time said installation of said assembly and a shaping of said assembly in said tooling; said method comprises a prior step of pre-deformation of the assembly by means of a deformation tool; prior to said hot isostatic pressing step, said method comprises a step of degreasing said assembly; said etching step is carried out by dipping said massive piece, obtained during the hot-pressing step, in a bath of chemical agent; said step of incorporating said at least one fugitive insert is carried out by placing said at least one fugitive insert between two independent preforms forming said fibrous structure produced during the weaving step; said step of incorporating said at least one fugitive insert is carried out by winding a monolayer preform, forming said fibrous structure produced during the weaving step, around said fugitive insert; said step of incorporating said at least one fugitive insert is carried out by placing said at least one fugitive insert in a cavity via a slot previously formed in a monolayer preform forming said fibrous structure during said step of weaving said structure fibrous; said solid piece is a hollow metal reinforcement of the leading edge or trailing edge of a turbine engine or propeller fan blade. Other characteristics and advantages of the invention will emerge more clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended figures, in which: FIG. 1 is a side view of a blade comprising a hollow metal structural reinforcement of the leading edge obtained by means of the embodiment method according to the invention; - Figure 2 is a partial sectional view of Figure 1 along a cutting plane AA; - Figure 3 is a block diagram showing the main steps of providing a hollow metal structural reinforcement turbomachine blade leading edge of the embodiment of the invention; FIG. 4 illustrates a partial cross-sectional view of the turbomachine blade leading edge hollow metal reinforcement during the first step of the process illustrated in FIG. 3; FIG. 5 illustrates a partial cross-sectional view of the turbomachine blade leading edge hollow metal reinforcement during the second step of the process illustrated in FIG. 3; FIG. 6 illustrates a partial view of the turbomachine blade leading edge hollow metal reinforcement during the third step of the process illustrated in FIG. 3; FIG. 7 illustrates a partial view of the turbomachine blade leading edge hollow metal reinforcement during the fourth step of the process illustrated in FIG. 3; FIG. 8 illustrates a partial view of the turbomachine blade leading edge hollow metal reinforcement during the fifth step of the process illustrated in FIG. 3. In all the figures, the common elements bear the same reference numerals unless specifically opposite.

In the following description, the hollow metal reinforcement of leading edge or trailing edge will be indifferently named metal reinforcement or reinforcement. FIG. 1 is a side view of a blade comprising a leading edge hollow metal structural reinforcement obtained by means of the embodiment method according to the invention. The blade 10 illustrated is for example a mobile blade of a fan of a turbomachine (not shown). The blade 10 has an aerodynamic surface 12 extending in a first axial direction 14 between a leading edge 16 and a trailing edge 18 and in a second radial direction 20 substantially perpendicular to the first direction 14 between a foot 22 and a top 24. The aerodynamic surface 12 forms the extrados face 13 and intrados 11 of the blade 10, only the extrados face 13 of the blade 10 is shown in Figure 1. The intrados 11 and the extrados 13 form the lateral faces of the blade 10 which connect the leading edge 16 to the trailing edge 18 of the blade 10. In this embodiment, the blade 10 is a composite blade obtained typically by draping or shaping. a woven fibrous texture. By way of example, the composite material used may be composed of an assembly of woven carbon fibers and a resinous matrix, the assembly being formed by molding using an RTM-type resin injection process ( for "Resin Transfer Molding"). The blade 10 has a metal structural reinforcement 30 bonded at its leading edge 16 and which extends both in the first direction 14 beyond the leading edge 16 of the aerodynamic surface 12 of the blade. dawn 10 and in the second direction 20 between the foot 22 and the apex 24 of the dawn. As represented in FIG. 2, the structural reinforcement 30 matches the shape of the leading edge 16 of the aerodynamic surface 12 of the blade 10 that it extends to form a leading edge 31, said leading edge of the reinforcement . Conventionally, the structural reinforcement 30 is a one-piece piece comprising a substantially V-shaped section having a base 39 forming the leading edge 31 and extended by two lateral flanks 35 and 37 respectively fitting the intrados 11 and extrados 13 of the aerodynamic surface 12 of the dawn. Flanks 35, 37 have a tapered or thinned profile towards the trailing edge of the blade. The base 39 has a rounded internal profile 33 capable of conforming to the rounded shape of the leading edge 16 of the blade 10. The base 39 of the structural reinforcement 30 also comprises an internal cavity 40 extending over the height of the structural reinforcement 30 , from the foot to the top of dawn. The structural reinforcement 30 is metallic and preferably based on titanium. This material has indeed a high energy absorption capacity due to shocks. The reinforcement is glued on the blade 10 by means of adhesive known to those skilled in the art, such as a cyanoacrylic or epoxy glue. This type of metal structural reinforcement 30 used for the turbomachine composite blade reinforcement is more particularly described in particular in the patent application EP1908919. The method according to the invention makes it possible to produce a structural reinforcement comprising an internal cavity as illustrated in FIG. 2, FIG. 2 illustrating the reinforcement 30 in its final state. FIG. 3 is a block diagram illustrating the main steps of a method of making a blade leading edge metal structural reinforcement 200 as illustrated in FIGS. 1 and 2. The first step 210 of FIG. Embodiment 200 is a step of weaving a three-dimensional fibrous structure 300 by weaving metal wires. This first step 210 makes it possible to produce at least one preform 310, 320 of metal wires 301, 302 woven in three dimensions so as to form a fibrous structure making it possible to form the preform of the final piece by itself. In a first embodiment illustrated in FIG. 4, the fibrous structure 300 is a multilayer structure formed by a first preform 310 forming the inner flank of the fibrous structure 300 and by a second preform 320 forming the upper flank of the fibrous structure. 300. Inner flank means the portion of the fibrous structure 300 intended to form the inner part of the metal reinforcement in contact with the surface 12 of the blade (FIG. 2) and by the upper flank the portion of the fibrous structure. 300 which is intended to form the outer portion of the metal reinforcement 30. The weaving patterns of the fibrous structure 300 are conventionally weaving patterns used, for example, in the field of weaving composite fibers such as, for example, the weaving patterns described in FIG. patent application EP1526285. As such, the fibrous structure 300 includes a plurality of warp yarns 301 is a plurality of weft yarns 302.

The title of the wire, the warp 301 and / or the weft wire 302, of the fibrous structure may vary depending on the user's needs, the stiffness and the material thickness of the metal reinforcement required. The metal wires used for weaving the fibrous structure 300 are mainly titanium yarns. However, it is possible to incorporate in the weaving of titanium son son based on silicon carbide and titanium (SiC-Ti), son coated boron (SiC-Bore), or silicon carbide (SiC -SiC). According to another embodiment, the fibrous structure 300 may be formed by a plurality of woven strands acting as "warp yarn" and "weft yarn". The diameter of the metal strands may vary depending on the needs of the user, and the material thickness necessary for the realization of the piece. The determination of the diameter of the strand is carried out according to a compromise between flexibility of the fibrous structure and material thickness necessary in the tooling. The diameter of the strands and the nature of the strands constituents may also vary especially between the strands capable of forming the warp son and the strands capable of forming the weft son. The metal strands are formed from a plurality of wire strands twisted, braided or helically wound about the longitudinal axis of the strand. Advantageously, each metal strand forming the strand has a diameter less than 0.1 mm. The principle of making the metal strands is advantageously the principle of making braided metal cables from twisted metal strands. By way of example, the metal strand comprises between 20 and 30 coiled strands. The use of metal strands formed by a plurality of coiled metal strands thus makes it possible to obtain a flexible and manually deformable strand. By making metal strands with a diameter greater than 0.5 mm, and even a few millimeters, the metal strands remain flexible enough to allow their manipulation, their manual deformation. The metal strands used for producing the strands are mainly titanium-based strands. However, it is possible to incorporate in the weaving strands based on silicon carbide and titanium (SiC-Ti), boron-coated strands (SiC-Bore) or silicon carbide (SiC-SiC) . According to a second embodiment of the invention, the fibrous structure 300 is a monolayer structure formed by a single preform. The second step 220 of the production method 200 is a step of incorporating an insert 50 into the fibrous structure 300 as illustrated in FIG. 5. When the fibrous structure 300 is formed by two independent preforms 310, 320, the insert 50 is positioned between the two preforms forming two weaving layers. In this case, it may be necessary during this second step 220 to assemble the independent preforms 310, 320 so as to maintain the insert 50 in position. The assembly of the two independent preforms 310, 320 can be made by threads so as to form a seam between the two independent preforms, by spot welding of different strand strands or by a weaving geometry specific to one or several preforms, for example to form a local extra thickness able to form a stop and hold the insert in position. According to another embodiment, the fugitive insert can also be hooked onto one or more preforms using, for example, spikes coming into the independent preforms 310, 320. Finally, the fugitive insert can simply be maintained. in the tooling without the independent preforms 310, 320 being assembled. When the fibrous structure is formed by a monolayer structure formed by a single preform, the insert may be incorporated by winding the monolayer structure around the insert or by sliding the insert into a cavity previously made by means of a slot provided in the monolayer structure during the weaving step. The insert 50 is made of a material different from the material of the metal wires used for weaving the fibrous structure 300. The insert 50 is made of a material capable of withstanding a high temperature, of the order of 900 ° C. a high pressure, of the order of 1000 bar, which is compatible with the materials of the weaving threads so as not to create impurities or oxidation on the fibrous structure 300.

The material of the insert 50 must also be chemically etchable by dissolution using a chemical agent. Advantageously, the insert 50 is made of copper or quartz or silica. The shape of the insert 50 incorporated in the fibrous structure 300 is identical to the shape of the final internal cavity 40 shown in Figure 2 and may include any kind of profile. The insert 50 is obtained indifferently by a forging process, machining, or by casting. According to another embodiment, several inserts 50 are incorporated inside the fibrous structure 300. The third step 230 of the production method 200 is a step of setting up and shaping the formed fibrous assembly 500 by the fibrous structure 300 and the insert 50 in a tool 400. This step 230 is illustrated particularly in Figure 6. The tool 400 comprises a cavity 410 (matrix) corresponding to the final external shape of the metal reinforcement 30 and against imprint 420 (punch) corresponding to the final internal shape of the leading edge metal reinforcement. The production method 200 may comprise, prior to the third step of placing the fibrous assembly in the tool, a step 225 of pre-deformation in a specific tool. This pre-deformation step of the fibrous assembly can be useful in particular when using metal wires of large diameter. When the weaving of the fibrous structure is carried out by means of flexible strands, step 225 of pre-deformation is not necessary. Indeed, the use of strands eliminates the problems of significant springback related to the rigidity of titanium-based son diameter greater than 0.4 mm. The fourth step 240 of the embodiment method 200 is a Hot Isostatic Pressing (HIP) step of the fibrous assembly 500 in the tooling 400, illustrated in FIG. 7. Hot isostatic pressing is a widely used manufacturing process known to reduce the porosity of metals and affect the density of many metals, such as ceramics. The isostatic pressing process also makes it possible to improve the mechanical properties and the exploitability of the materials. Isostatic pressing is carried out at high temperature (conventionally between 400 ° C. and 1400 ° C., and of the order of 1000 ° C. for titanium) and at isostatic pressure.

Thus, the application of the heat combined with the internal pressure eliminates the voids of the fibrous structure 300, as well as the microporosities by means of a combination of plastic deformation, creep, and diffusion welding to form a part The solid piece 430 resulting from the isostatic pressing step comprises the internal and external profiles of the metal reinforcement 30. The solid piece 430 is then demolded from the tool 400. The isostatic pressing step is carried out under vacuum, advantageously under secondary vacuum is in a welded tool in which the secondary vacuum is made or in autoclave bag, the choice of the method depending on the number of part to be produced. The secondary vacuum makes it possible to avoid the presence of oxygen in the tooling and at the level of the fibrous structure, during the titanium isostatic pressing step. Tooling 400 is made of a mechanical alloy called superalloy or high performance alloy. The isostatic pressing step 240 may previously comprise a step 235 for cleaning, degreasing and / or chemical etching of the fibrous assembly 500 so as to eliminate the residual impurities of the fibrous structure 300.

Advantageously, the impurity cleaning step is carried out by dipping the fibrous assembly in a bath of cleaning agent or chemical agent. The fifth step 250 of the production method 200 is a chemical etching step of the insert 50 incorporated into the material of the solid piece 430 by means of a chemical agent capable of etching the material in which the insert 50 is made. . This step is illustrated in FIG. 8. Chemical etching of the insert 50 dissolves the insert 50 so that the space released by the dissolved insert 50 forms the internal cavity 40 of the metal reinforcement 30 illustrated in FIG. figure 2.

Advantageously, the etching step 250 is carried out by dipping the solid piece 430 in a bath comprising the chemical agent capable of dissolving the insert 50. The chemical agent is, for example, an acid or a base. Advantageously, the chemical agent is capable of dissolving copper, quartz or silica. In association with these main production steps, the method according to the invention may also comprise a finishing step and machining of the hollow solid piece obtained at the output of the tool so as to obtain the reinforcement 30. This step recovery comprises: - a step of recovery of the profile of the base 39 of the reinforcement 30 so as to refine it and in particular the aerodynamic profile of the leading edge 31; a step of recovery of the flanks 35, 37; this step consisting in particular of trimming the flanks 35, 37 and the thinning of the intrados and extrados flanks; - A finishing step to obtain the required surface condition. In association with these main production steps, the method according to the invention may also comprise non-destructive testing steps of the reinforcement 30 making it possible to ensure the geometrical and metallurgical conformity of the assembly obtained. By way of example, non-destructive inspections may be carried out by an X-ray method. The invention has been particularly described for producing a metallic reinforcement of a composite turbomachine blade; however, the invention is also applicable for producing a metal reinforcement of a turbomachine metal blade. The invention has been particularly described for producing a metal reinforcement of a turbomachine blade leading edge; however, the invention is also applicable to the production of a metal reinforcement of a trailing edge of a turbomachine blade or to the production of a metallic helical reinforcement composite or metal. The other advantages of the invention are in particular the following: reduction of implementation costs; - reduction of the production time; - simplification of the manufacturing range;

Claims (10)

REVENDICATIONS1. Method for producing (200) a hollow metal reinforcement (30) of a turbomachine blade comprising successively: a step (210) of weaving a three-dimensional fibrous structure (300) by weaving wires and / or metal strands (301, 302): a step (220) of incorporating at least one fugitive insert (50) into said fibrous structure (300); a step (240) of hot isostatic pressing of the assembly (500) formed by said fibrous structure (300) and by said at least one incorporated fugitive insert (50) causing the agglomeration of the metal wires of said fibrous structure ( 300) around said fugitive insert (50), so as to obtain a solid piece (430); a step (250) of etching said at least one fugitive insert (50) so as to dissolve said at least one insert (50) and to form an internal cavity (40) in said solid piece (430), so as to obtaining said hollow metal reinforcement (30) of leading edge or trailing edge. 2. Method of producing (200) a metal reinforcement (30) turbomachine blade according to claim 1 characterized in that prior to said step (240) of hot isostatic pressing, said method comprises a step (230) placing said assembly (500) in a tool (400). 3. A method of producing (200) a metal reinforcement (30) turbomachine blade according to claim 2 characterized in that simultaneously carries out said establishment (230) of said assembly (500) and formatting said assembly (500) in said tool (400). 4. Method of producing (200) a metal reinforcement (30) turbomachine blade according to one of claims 1 to 3 characterized in that said method (200) comprises a prior step (225) of pre-deformation of the assembly (500) by means of deformation tools. 5. A method of producing (200) a metal reinforcement (30) turbomachine blade according to one of claims 1 to 4 characterized in that prior to said step (240) of hot isostatic pressing, said method ( 200) comprises a step of degreasing (235) said assembly (500). 6. A method of producing a metal reinforcement (30) turbomachine blade according to one of claims 1 to 5 characterized in that said step (250) etching is performed by soaking said massive piece (430). ), obtained during the hot pressing step (240), in a chemical agent bath. 7. A method of producing a metal reinforcement (30) turbomachine blade according to one of claims 1 to 6 characterized in that said step (220) of incorporating said at least one fugitive insert (50) is performed by placing said at least one fugitive insert (50) between two independent preforms (310, 320) forming said fibrous structure (300) produced during the weaving step. 8. A method of producing a metal reinforcement (30) turbomachine blade according to one of claims 1 to 6 characterized in that said step (220) of incorporating said at least one fugitive insert (50) is performed by winding a monolayer preform, forming said fibrous structure (300) made during the weaving step, around said fugitive insert (50). 9. Process for producing a turbine engine blade reinforcement (30) according to one of claims 1 to 6, characterized in that said step (220) for incorporating said at least one fugitive insert (50) is carried out. by placing said at least one fugitive insert (50) in a cavity via a slot previously formed in a monolayer preform forming said fibrous structure (300) during said step (210) of weaving said fibrous structure (300). 10. Production method according to one of claims 1 to 9 characterized in that said solid part is a hollow metal reinforcement (30) of leading edge or trailing edge of turbine engine fan blade or propeller. 20