FR3037972A1 - PROCESS SIMPLIFYING THE CORE USED FOR THE MANUFACTURE OF A TURBOMACHINE BLADE - Google Patents

Abstract

The invention relates to a method for producing a turbomachine blade (26) comprising an apex with a closing wall (31) joining the intrados and extrados walls to delimit a bottom (31) of a shape of bath (28), this method comprising a molding step implementing a core defining the bath-shaped (28) and at least one internal channel (27). The core used for molding comprises a main element having a body delimiting the internal channel (27) and having an end extended by an outgrowth delimiting at least a portion of the bath (28), the main core element passing through the bottom ( 31) leaving an opening in this bottom. The method comprises a step of closing this opening (32) with a material-making process such as a metal powder deposition process.

Description

TECHNICAL FIELD The invention relates to the manufacture of a turbine engine type aircraft engine blade, such as for example a turbojet engine or a turboprop engine. STATE OF THE PRIOR ART In such an engine, indicated by 1 in FIG. 1, air is admitted into an inlet sleeve 2 to pass through a fan comprising a series of rotating blades 3 before splitting into a central primary flow. and a secondary stream surrounding the primary stream. The primary flow is compressed by turbines 4 and 6 before reaching a combustion chamber 7, after which it relaxes through turbines 8, before being evacuated by generating a thrust. The secondary flow is propelled directly by the blower to generate a complementary thrust. Each turbine 8 comprises series of blades oriented radially and regularly spaced around a rotation shaft AX, carried by an outer casing 9 surrounding the entire engine. The cooling of the blades is ensured by circulating in each blade air taken upstream of the combustion and admitted at the bottom of the blade, this air being evacuated by holes through the walls of these blades. Such a blade, which is indicated by 11 in FIG. 2, comprises a foot P through which it is fixed to a rotating body, and a blade 12 carried by this foot P, the foot and the blade being separated by a platform 13. The blade 12 has a left twisted shape about an axis EV said span axis which is perpendicular to the axis AX. It comprises a base by which it is connected to the platform 13 and which extends radially to a vertex S which is the free end of this blade. The two main walls of the blade are its intrados wall 14 and its non-visible extrados wall in FIG. 2 which are spaced apart from one another in the current part. The top S of the blade 11 has a closing wall perpendicular to the direction EV, and which connects the walls of the intrados and extrados. This non-visible closure wall in FIG. 2 is recessed towards the axis AX with respect to the free edges of the intrados and extrados walls. It delimits together with these edges a hollow portion open in the opposite direction to the axis AX, called bath, marked by 15 in Figure 2, and located at the head of the blade. Such a blade is made by molding a metallic material, using a core consisting of several cores rigidly secured to each other to delimit particular channels. These channels comprise an upstream channel of the blade, with respect to the direction of flow of the fluid in the engine when the blade is in use, and serving to supply air to its leading edge, a downstream channel relative to the direction of the fluid used to supply air to its trailing edge, and the bathtub which is located at the top of the blade. In general, the manufacture and assembly of these cores is a delicate operation requiring great expertise to build and assemble a larger amount of cores, given the increasing complexity of the internal shapes of the blades .

The object of the invention is to provide a manufacturing method for simplifying the manufacture of cores in the process of manufacturing a blade. SUMMARY OF THE INVENTION The subject of the invention is a method for manufacturing a turbomachine turbine engine blade comprising an intrados wall and an extrados wall spaced apart from one another in the current portion, this dawn comprising a top with a closure wall joining the walls of the suction and suction surface to delimit a bottom of a bathtub shape, this process comprising a molding step using a core delimiting the tub form and the less an internal channel 3037972 3 of the blade for receiving cooling air of this blade, characterized in that the core used for the molding operation comprises a main core member having a body defining the internal channel and having an end extended by an outgrowth defining at least a portion of the tub, this main core member passing through the tub bottom leaving an opening therein when the blade has been molded, and in that it comprises a step of closing this opening with an additive manufacturing process by adding metal material in this opening, in particular by depositing metal powder. The additive manufacturing additive process, which is usually used to form a geometry, is used according to the invention to close or plug an opening in the tub, thereby providing a core element passing through this tub to improve the support of the tub. the core part delimiting the bathtub. Various additive manufacturing processes can be used, such as the Direct Additive Laser Construction method, generally designated by the trademark CLAD, the so-called Laser Metal Deposition process generally referred to by the acronym LMD, the so-called Direct Metal Deposition process generally designated by the acronym DMD, or the so-called method of Direct Laser Metal Deposition generally designated by the acronym DLMD. The invention also relates to a method thus defined, comprising a machining operation of the material deposited for flattening the bottom of the bath in the material supply region, this machining being carried out by means of a method such that a machining process by electro erosion. The invention also relates to a method thus defined, wherein the core used comprises another core element secured to the outgrowth of the main core element to delimit together with this protrusion the entire bath. The invention also relates to a method thus defined, wherein the main core element comprises a connecting portion of the end of the body of the main core element with the protrusion, which is inclined relative to the body of the core. main core element, to constitute a widening chamfer 3037972 4 the mouth of the opening in the bottom of the bath to improve the accessibility of this opening for the implementation of the step of contribution of matter in this opening. The invention also relates to a turbomachine blade obtained with the method thus defined. The invention also relates to a turbomachine comprising a blade thus defined. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 already described is an overall view of a double-flow turbojet engine shown in lateral section; Figure 2 already described is an overview of a reactor blade; Figure 3 is a schematic representation of the elements of a core before assembly according to the method according to the invention; Figure 4 is a schematic representation of the assembled core members in accordance with the invention; Figure 5 is a schematic sectional representation of the cast blade comprising the core according to the invention; Figure 6 is a schematic representation in section of the blade cast according to the invention after removal of the core; Fig. 7 is a schematic representation of the method used in the invention for supplying material to a region of the dawn tub; Figure 8 is a schematic representation of the channel of the blade being closed with the additive manufacturing process by material ratio; Fig. 9 is a schematic representation of the closed vane channel with the additive manufacturing method by material ratio; Figure 10 is a schematic representation of the vane channel closed with the additive manufacturing process in relation to material after machining.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS The basis of the invention is a molding architecture in which a portion of the core element defining the bath of the blade is an integral part of a core element delimiting a channel. feeding another part of the dawn and 5 which thus crosses the bottom of the bath to improve the support of the core portion defining the bath. After molding, the opening left by this core element in the bottom of the bath is closed with an additive manufacturing process involving a contribution of metallic material in this opening. The method is a method used is a method of the type of laser powder metallurgy with deposition in successive layers. Other metal deposition methods can be envisaged. As seen in FIG. 3, the constituent elements of the core 16 according to the invention comprise a first main core element 17, a second complementary core element 18 and a third core element 19. The main core element 17 comprises a elongated body 21 extending in the direction of span EV of the blade, and an end extended by an outgrowth 22. This protrusion is shifted transversely of the body 21 relative to the span direction EV, the body 21 and the protuberance 22 being connected via a connecting portion 23 inclined relative to the span direction EV.

These core elements, which are made of ceramic, are assembled together to form a unit arranged in accordance with FIG. 4. More particularly, the second element 18 is then fixed to the protrusion 22 so as to extend it in accordance with FIG. AX axis which corresponds substantially to the axis of rotation of the blade when in use. The assembly constituted by the second element 18 attached to the protrusion 22 delimits the bottom and the edges of the tub located at the top of the blade to be manufactured, and marked by 28 in FIG. 6. The body 21 of the main element 17 delimits for its part an upstream cooling air supply channel with respect to the direction of flow of the fluid around the dawn in service, allowing for example to cool the leading edge of the dawn . The third core element 19 which also extends in the span direction EV is located downstream of the body 21 of the main element 17, to delimit another cooling air supply channel, to cool for example the region of the trailing edge of dawn when in use. Complementarily, the main element 17 is rigidly connected to the third element 19 by elements of cores not shown in the figures. For the molding operation, the core 16 is installed and held in position in a mold, prior to casting of the metal alloy material 24 constituting the blade 26, as molded, as shown schematically in FIG. Once the blade has been cast and the material has been cooled, the core elements are removed, for example by chemical etching, thereby obtaining the actual blade 26, shown in FIG. This blade 26 comprises a body comprising an upstream channel 27 for cooling its leading edge, a bath 28 at its top, and a downstream channel 29 for cooling its trailing edge. These channels 27 and 29 and this bath 28 are enveloped by the outer wall 20 of the blade 26, not visible in Figure 6, which comprises in particular its intrados wall and its extrados wall. As can be seen in FIG. 8, the bottom 31 of the bath 28 has an opening 32 which corresponds to the connecting portion 23 of the main core element 17 connecting its body 21 to its protrusion 22.

This opening which connects the upstream channel 27 to the bath is not desired because it is not desired that the bath 28 be supplied with cooling air, but that on the contrary all or at least the majority of the air circulating in the upstream channel 27 is dedicated to cooling the leading edge of the blade. According to the invention, this opening is closed by depositing thereon metal material according to an additive manufacturing process, so as to seal it.

One such method which is usually designated by the trademark CLAD, namely the Direct Additive Laser Construction method, consists in using an apparatus 33 for generating a laser beam 34 in order to melt on a substrate which is here the edge of the opening 32, one or more metal powders 36 provided by a nozzle 37, so as to successively constitute deposition layers 38. This nozzle 37 is a coaxial nozzle capable of producing the homogeneous injection of metal powders through a bundle laser. With this process, the laser-fused powders provide a homogeneous and dense deposit on the surface or layer which carries them, which is also fused during the process. Since there is no contact in particular between the nozzle and the substrate, the method is free of wear. The successive deposits or stacks are protected throughout the process by a neutral gas to prevent oxidation problems. This method makes it possible to make deposits by targeting with a certain precision the places where the material is brought. It is also possible to use several metals of different contributions to achieve if necessary an alloy with progressive proportions depending on the height. This makes it possible to optimize various aspects such as the mass, the adhesion with the substrate, that is to say the dilution and the porosity, as well as the properties of abradability, abrasiveness, and expansion. The substrate that constitutes the existing part 20 on which the material is provided makes it possible to start the construction. In general, the deposited material is itself chosen according to the substrate to have a suitable mechanical strength, abradability and compatibility with the substrate that are appropriate in particular for dilution and porosity.

As indicated above, the connecting portion 23 is inclined with respect to the span direction EV, to delimit a chamfered surface 39 which widens the opening 32 at its connecting portion with the bottom 31. This chamfered surface 39 which corresponds to the downstream portion of the wall delimiting the opening 32, makes it possible to constitute an enlargement of the opening 32 at the level of the bottom 31. Thanks to this widening, the apparatus used for the deposition of 3037972 8 material can installed in or in the vicinity of the bath 28 in an orientation enabling it to impact an inner region of the opening 32 which is as close as possible to the bottom level 31 along the span axis EV. This makes it possible to produce a deposit of material 41 having the smallest possible thickness in order to limit the volume of material to be deposited, and hence the mass of material necessary to seal the opening 32. In other words, the chamfer The inclined surface 39 widens the opening 32 so that it is advanced downstream of the bottom 31 of the bath, so that this opening has an enlarged mouth providing the greatest possible latitude for the orientation of the bath. the equipment used for the supply of material. The material 41 is thus deposited first on the wall portion 40 of the opening 32 which is located upstream along the axis AX, and this material, in successive layers is deposited until joining the downstream portion 39 of this wall of the opening. More concretely, a first deposited cord serves as a support for the following and so on. Thanks to the chamfer that constitutes this inclined downstream wall 39, the thickness, counted along the span axis EV, of material 41 which is deposited may be as small as possible, and comparable to that of the bottom 31, as shown. schematically in Figure 9.

Furthermore, as can be seen in FIG. 9, deposition of material by the direct laser manufacturing method can lead to a relatively irregular upper patching surface. This irregularity which is likely to penalize the air flow in the bath can be canceled by machining this upper surface to give it a flat shape 42, as shown in FIG.

This finishing machining can be performed by electro erosion, according to the method known by the acronym EDM stands for Electrical Discharge Machining, that is to say machining by electric discharge. This machining can also be ensured by means of cutting tools of the milling cutter type or the like, which makes it possible to achieve the form finish making it possible to constitute the partition as such.

In a general manner, the invention makes it possible to use the same core element which delimits on the one hand a lower channel of the blade and on the other hand a portion of the bath, so that the part of The core constituting the tub is firmly supported so that it will not move during molding operations.

More concretely, all the core portion defining the bath is supported at least by the connecting portion of the main core element, which provides it with a robust support at least on its front portion. In the downstream portion of this bath, support may be provided by other unrepresented core components, or alternatively by alumina rods connecting the downstream portion of the tub to other core members. The invention has been described with a method of additive manufacturing by laser powder melting in successive layer deposition, but other methods can be used. In particular, the SWET process, which means Superallow Welding at Elevated Temperature, can also be envisaged. 15

Claims (7)

REVENDICATIONS1. A method of manufacturing a turbomachine blade (26) comprising a lower surface wall and an extrados wall spaced apart from each other in the running portion, said blade (26) comprising an apex with a closure wall (31) joining the walls of the lower and upper surfaces to delimit a bottom (31) of a bathtub shape (28), this method comprising a molding step using a core (16) delimiting the shape in tub (28) and at least one internal channel (27) of the blade (26) for receiving cooling air of the blade (26), characterized in that the core (16) used for the molding operation comprises a main core element (17) having a body (21) delimiting the inner channel (27) and having an end extended by an outgrowth (22) delimiting at least a portion of the bath (28), this element main core (17) passing through the bottom (31) of the bathtub leaving an opening (32) when the dawn ( 26) has been molded, and in that it comprises a step of closing this opening (32) with an additive manufacturing process by adding metal material into this opening (32), in particular by deposition of metal powder. 2. Method according to claim 1, comprising a machining operation of the deposited material for flattening the bottom (31) of the bath (28) in the material supply region, this machining being carried out by means of a method such as an electro-erosion machining process. 3. The method of claim 1 or 2, wherein the core (16) used comprises another core element (18) secured to the protrusion (22) of the main core element (17) to delineate together with this protruding (22) the entire bath (28). 4. Method according to one of the preceding claims, wherein the main core element (17) comprises a connecting portion (23) of the end of the body of the main core element (17) with the protrusion (22), which is inclined (39) relative to the body of the main core element (21), to constitute, once the molded vane, a chamfer (39) for enlarging the mouth of the opening (32) in the bottom (31) of the bath to improve the accessibility of this opening 5 (32) for the implementation of the material supplying step in this opening. 5. Method according to one of the preceding claims, wherein the deposition of metal powder is provided with a coaxial nozzle homogeneous injection of powder through a laser beam. 6. Turbomachine blade obtained with the method according to one of claims 1 to 5. 7. A turbomachine comprising a blade according to claim 6.