EP4021663B1 - Improved method for manufacturing a ceramic core for manufacturing turbomachine vanes and ceramic core - Google Patents

Improved method for manufacturing a ceramic core for manufacturing turbomachine vanes and ceramic core Download PDF

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Publication number
EP4021663B1
EP4021663B1 EP20775042.3A EP20775042A EP4021663B1 EP 4021663 B1 EP4021663 B1 EP 4021663B1 EP 20775042 A EP20775042 A EP 20775042A EP 4021663 B1 EP4021663 B1 EP 4021663B1
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EP
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Prior art keywords
orifice
ceramic
manufacturing
core
ceramic core
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German (de)
French (fr)
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EP4021663A1 (en
Inventor
Adrien Bernard Vincent ROLLINGER
Alice Marie Lydie AGIER
Gaël Philippe François BATTISTONI
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Safran SA
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Safran SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • B22C9/103—Multipart cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C21/00—Flasks; Accessories therefor
    • B22C21/12—Accessories
    • B22C21/14—Accessories for reinforcing or securing moulding materials or cores, e.g. gaggers, chaplets, pins, bars
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
    • B22C7/02—Lost patterns

Definitions

  • This presentation concerns the field of the manufacture of turbomachine blades using the lost-wax casting technique, in particular the manufacture of the ceramic cores used for the manufacture of these blades using this technique.
  • the present disclosure relates to a process for the manufacture of such a ceramic core, intended for the manufacture of hollow turbine engine blades according to the lost wax casting technique.
  • the blades present in turbomachines in particular turbine blades, for example low pressure, generally comprise internal cavities necessary for cooling these blades.
  • these cavities are formed, before the formation of the wax mold, by means of ceramic cores, the shape of which corresponds to the desired shape of the cavities in the final piece.
  • a portion of such a core 10 is shown schematically in the figure 1 .
  • These ceramic cores generally comprise a first part 20, the first part 20 being a functional part corresponding to the future cavities of the blade and having the shape thereof (only the upper end of the first part, corresponding to the tip, or head of dawn, is visible on the figure 1 ), and a second part 30, called for example a dome, serving as a region for holding the core 10.
  • the core 10 is held in a fixed position with respect to the ceramic mold via a non-functional portion of this second part 30.
  • the second part 30 also comprises a functional portion, at its lower end, serving in particular to form the contour of the bathtub from dawn to the end of the process of making it.
  • the first part 20 must be spaced from the second part 30, while being integral with the latter and maintained by the latter.
  • thin rods 40 are placed between these two parts, and hold these parts integral with each other and fixed relative to each other, while leaving a space S between these two parts.
  • the cast metal penetrating into this space S between these two parts will correspond to the bottom wall of the top bath of the blade, at the end of the manufacturing process of the blade.
  • Such an example kernel is disclosed in the document FR2889088 .
  • the rods 40 are directly placed in a mold and a ceramic paste is injected around.
  • the complexity of certain ceramic cores requires appropriate manufacturing techniques, such as additive manufacturing.
  • This technique in which the core is built layer by layer, does not allow the insertion of the rods during manufacture. It is therefore necessary to provide orifices in the core during the additive manufacturing of the latter, in order to be able to insert the rods therein a posteriori. Nevertheless, the insertion of these rods first requires cleaning, that is to say emptying the holes provided for this purpose, of the excess ceramic material which is deposited there during the printing of the core.
  • junction portion is formed at the same time as the first part and the second part during additive manufacturing, and therefore comprises the same material as these parts.
  • the junction portion may be a 3D printed manufacturing device, called a “printing medium”, forming a junction portion between these two parts during printing.
  • the junction portion makes it possible to maintain these two parts secured to each other and fixed relative to each other temporarily, before the insertion of the rods.
  • the contact between the junction portion and the first and second parts may be discontinuous.
  • the junction portion may comprise a plurality of studs or spikes interposed between these two parts. This configuration facilitates subsequent removal of this junction portion, after positioning the positioning rods.
  • the manufacture of the blank by additive manufacturing is carried out such that the blank thus obtained comprises the first part, the second part, and the junction portion.
  • this manufacture provides for the presence of at least one through hole.
  • through or “opening”, it is understood that the orifice opens on either side of the blank, as opposed to a blind hole comprising a bottom.
  • the orifice passes through the second part, the junction portion and the first part, opening out at each of its ends into a region outside the blank of the core, around the latter.
  • the configuration of the present disclosure makes it possible to easily expel these residues through an open end of the orifice, by applying pressure, for example by injecting a mixture of solvent and pulsed air, at the other open end of the orifice. 'orifice. It is thus possible to carry out the cleaning of the orifice effectively, by dispensing with the use of unsuitable tools such as drill bits, thus limiting the scrap rate of the cores.
  • the junction portion comprises a passage putting the through-orifice in fluid communication with a space outside the core blank.
  • This passage facilitates the cleaning of the through hole. Indeed, when the orifice is cleaned by injecting a solvent, for example, at the two ends of the orifice, the ceramic paste residues dissolved in the solvent can be evacuated through this passage.
  • the through hole comprises a first rectilinear portion extending from the first end, and a second rectilinear portion presenting an angle less than 180° with respect to the first rectilinear portion, and extending from the second end.
  • the first rectilinear portion extends through the second part from the first end to the junction portion, through the junction portion and part of the first part.
  • the second rectilinear portion extends in the first part between the end of the first portion rectilinear located in the first part, and the second end.
  • the first rectilinear portion and the second rectilinear portion form between them a bend having an angle of less than 180°, this bend preferably being arranged in the first part.
  • the length of the first rectilinear portion can be determined according to the length of the positioning rod to be inserted. The presence of this bend makes it possible to shorten the length of the second rectilinear portion of the orifice, and in particular makes it possible to reach the outside of the core.
  • the angle between the first and the second rectilinear portion is greater than or equal to 100°, preferably comprised between 110° and 120°.
  • the diameter of the first rectilinear portion of the through hole is between 0.15 and 0.3 mm.
  • the diameter of the first rectilinear portion can be determined according to the diameter of the positioning rod to be inserted. Preferably, a clearance must exist between the positioning rod and the orifice.
  • the diameter of the second rectilinear portion of the through hole is between 0.4 and 0.6 mm.
  • the through hole may have a circular section.
  • unsolidified residues of ceramic paste remain in the orifice. Cleaning removes these residues to allow insertion of the positioning rod. Furthermore, the elimination of the junction portion can be carried out by sintering the ceramic using a suitable tool, for example a high precision grinding wheel making it possible to release the space between the first part and the second part. .
  • the cleaning of the through hole is carried out by injecting pulsed air and/or a solvent into at least one end of the hole.
  • the pulsed air and/or the solvent injected at one end of the orifice is evacuated, carrying away the ceramic paste residues, through the other end of the orifice and/or through the passage in the portion of junction.
  • the pulsed air and/or the solvent injected at the two ends of the orifice, simultaneously or not, is evacuated, carrying the ceramic paste residues, through the passage in the junction portion.
  • through hole cleaning is accomplished by mechanically inserting a cleaning means into at least one end of the hole.
  • This technique of mechanical insertion of a cleaning means can be carried out alone, or in addition to the pulsed air and/or the solvent.
  • the cleaning step and the insertion step are performed simultaneously.
  • the fact of inserting the rod at one end of the through orifice makes it possible to push the ceramic residues, these residues being able to escape through the other end of the orifice.
  • the rod thus acts itself as a mechanical cleaning means.
  • the positioning rods are alumina rods.
  • the alumina rods are a ceramic material with the advantage of being resistant to the same thermal stresses as the rest of the part and having the same chemical properties on shakeout. They also allow a high tensile/compressive strength to ensure the dimensional stability of the bottom thickness of the tub, as well as a solid grip between the first and the second part.
  • rods comprising molybdenum can be used.
  • the plugging of the through hole is carried out by applying a ceramic paste to the two ends of said hole.
  • the filling of the two ends of the orifice makes it possible, on the one hand, to avoid an undesired infiltration of the wax during the manufacture of the wax mold, and on the other hand, to obtain a uniform surface state of the ceramic core. , especially on the first part. This ensures that the final piece does not have any irregularities.
  • the method comprises, after the filling, a hardening step making it possible to harden the ceramic paste.
  • the hardening step comprises, for example, exposure under a UV lamp to harden the ceramic paste used for filling. This makes it possible to improve the overall rigidity of the ceramic core, when its manufacture is finished.
  • the positioning rods are coated with ceramic glue.
  • This presentation also relates to a use of a ceramic core obtained by the method according to any one of the embodiments of this presentation, for the manufacture of hollow turbine blades for a turbomachine using the lost-wax casting technique. .
  • FIGS. 2A and 2B schematically represent samples of a ceramic core, in the form of test specimens, making it possible to illustrate the cleaning of an orifice of this core.
  • FIG 2A schematically represents a technique for cleaning an orifice 50 according to the prior art. Orifice 50 is blind.
  • the hatched part represents the ceramic core, more precisely, the polymerized paste forming the ceramic core.
  • the latter comprises a first part 20, a second part 30, and a junction portion 60.
  • the shaded part represents the unpolymerized ceramic paste remaining in the orifice 50 after the printing of the blank of the core.
  • the core blank is produced layer by layer, starting with the first part 20 for example, then the junction portion 60, then the second part 30, providing for the presence of the orifice(s) 50.
  • the junction portion 60 has a serrated shape, limiting the contact surface between the junction portion 60 and the first part 20 and/or the second part 30.
  • the junction portion 60 can thus comprise a plurality of teeth 61, under the form of pins or studs, interposed between these two parts.
  • the orifice 50 is blind and comprises a bottom 51.
  • the orifice cleaning operation is carried out, for example, by means of a drill bit 70, the passage of which through the orifice 50 makes it possible to evacuate the dough. Such a technique leads to the deterioration or breakage of many ceramic cores.
  • the orifice 50 comprises a first rectilinear portion 50a extending through the second part 30, the junction portion 60 and the first part 20, and a second rectilinear portion 50b extending through the first part 20 from the end of the first rectilinear portion 50a, and opening onto an outer face of the first part 20.
  • the first rectilinear portion 50a is preferably longer than the second rectilinear portion 50b, and is intended to receive a positioning rod.
  • the angle ⁇ between the first and the second rectilinear portion 50a, 50b is less than 180°, and greater than or equal to 100°, preferably between 110° and 120°.
  • a passage 62 is provided in the junction portion 60.
  • This passage 62 may be an orifice, or a local absence of teeth 61, making it possible to place the orifice 50 in fluid communication with a region external to the core. ceramic, and surrounding it.
  • This passage 62 makes it possible to facilitate the operation of cleaning the orifice 50. Indeed, at the end of the additive manufacturing, the cleaning of the orifice 50 can be carried out by injecting pulsed air at one or at the two ends of the orifice 50. The pressure exerted at the ends of the orifice 50 allows the evacuation of the unpolymerized paste present in the orifice, through the passage 62 of the junction portion 60 (cf. arrows on there figure 2A ).
  • a solvent can be injected, or a mixture of air and solvent.
  • a cylindrical tool of suitable diameter can be used to push the paste, in addition or instead of air and/or solvent.
  • FIG. 3 represents a schematic view of a part of a ceramic core 10 according to the present description, made by additive manufacturing, comprising a first part 20, a second part 30, and a junction portion 60.
  • the first part 20 has the shape of the desired cavities obtain at the end of the manufacture of the turbine blade.
  • On the picture 3 only the upper end of the first part 20, corresponding to the upper end, or top, of the blade, is visible.
  • the second part 30, or dome allows the maintenance of the ceramic core 10 during the production of the wax model, and during the casting of the metal in a ceramic shell mould.
  • the first part 20 and the second part 30 are spaced apart by a distance S of between 0.4 and 1.4 mm.
  • three through holes 50 extend through the second part 30, the junction portion 60 and the first part 20.
  • Each of these holes 50 comprises a first rectilinear portion 50a opening onto an outer face of the second part 30 , and a second rectilinear portion 50b (only one of which is visible on the picture 3 ) opening an outer face of the first part 20.
  • a positioning rod 40 is inserted into each of these holes 50.
  • These positioning rods 40 can be alumina rods, and can have a length of 13 mm and a diameter of 0.6mm. Nevertheless, these dimensions are not limiting, and can be modified according to the considered geometry of the core.
  • a first step in the manufacture of a ceramic core 10 comprises the manufacture of a blank of the core by additive manufacturing (step S1).
  • the blank comprises the first part 20, the junction portion 60 and the second part 30.
  • Additive manufacturing provides for the presence of the through holes 50, and of the passage(s) 62 in the junction portion 60.
  • the orifices 50 are cleaned, that is to say emptied of the residues of unpolymerized ceramic paste remaining in the orifices 50 (step S2).
  • pulsed air and/or solvent for example, is injected at the ends of the orifices 50.
  • the residual paste is thus evacuated through the passage 62 of the junction portion 60.
  • a positioning rod 40 is then inserted into each through hole 50 (step S3). More specifically, a positioning rod 40 is inserted into the first rectilinear portion 50a of each through hole.
  • the rods 40 are inserted from the top, that is to say from the end of the orifice 50 opening onto an external face of the second part 30, and pushed into the orifice 50 so as to extend to both in the second part 30 and in the first part 20.
  • the rods 40 can be coated beforehand with ceramic glue. This glue solidifies during the heat treatment described below, and allows optimal coating of the rod.
  • step S4 After the placement of the positioning rods 40 in the orifices 50, the latter are sealed (step S4).
  • This filling is carried out using a ceramic paste, so as to obtain a smooth surface state, on the external faces of the first and second parts 20 and 30. This makes it possible to avoid surface irregularities later on the model. in wax, and on the final piece.
  • Filling is followed by a step of hardening the ceramic paste, making it possible to solidify the paste added in step S4 (step S5).
  • This step can be carried out depending on the properties of the paste, depending on whether it is, for example, photosensitive or thermosensitive, by means in particular of a source of UV light or a source of heat.
  • the curing step is carried out by exposure to UV light.
  • the core 10 can also follow a heat treatment step, comprising debinding and sintering.
  • the method finally includes removing the junction portion 60 (step S6).
  • This elimination is facilitated by the serrated shape of the junction part 60, and can be carried out by any suitable tool, which can be inserted between the first part and the second part.
  • the first part 20 and the second part 30 are held together, and positioned relative to each other, by the positioning rods 40 only.
  • the ceramic core 10 thus obtained can then be used in the manufacture of hollow turbine engine blades using the lost wax casting technique.
  • the ceramic core 10 can be placed in a wax mould, being held by the second part 30, to form the wax model having the shape of the final piece, with the cavities formed by the first part 20 of the core.
  • the wax model is then dipped several times in a slip to form the ceramic mould.
  • the molten metal is poured into the ceramic mold and around the ceramic core, the latter being again held in a fixed position by means of the second part 30.
  • the ceramic mold and the ceramic core 10 are then eliminated, for example by shake-out, in order to obtain the final part.
  • the elimination of the ceramic also includes the elimination of the positioning alumina rods 40, removed during shake-out, then leaving small orifices through the bath at the top of the blade, at the place where found these rods. These orifices serve in particular as holes for removing dust or for evacuating the air present in the cavities of the blade.

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  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
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Description

Domaine TechniqueTechnical area

Le présent exposé concerne le domaine de la fabrication des aubes de turbomachine selon la technique de la fonderie à la cire perdue, notamment la fabrication des noyaux céramiques utilisés pour la fabrication de ces aubes selon cette technique. En particulier, le présent exposé concerne un procédé de fabrication d'un tel noyau céramique, destiné à la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue.This presentation concerns the field of the manufacture of turbomachine blades using the lost-wax casting technique, in particular the manufacture of the ceramic cores used for the manufacture of these blades using this technique. In particular, the present disclosure relates to a process for the manufacture of such a ceramic core, intended for the manufacture of hollow turbine engine blades according to the lost wax casting technique.

Technique antérieurePrior technique

Les aubes présentes dans les turbomachines, notamment les aubes de turbine, par exemple basse pression, comportent généralement des cavités internes nécessaires au refroidissement de ces aubes. Lors de la fabrication des aubes selon la technique de la fonderie à la cire perdue, ces cavités sont formées, avant la formation du moule en cire, par l'intermédiaire de noyaux en céramique, dont la forme correspond à la forme souhaitée des cavités dans la pièce finale. Une portion d'un tel noyau 10 est représentée schématiquement sur la figure 1. Ces noyaux céramiques comprennent généralement une première partie 20, la première partie 20 étant une partie fonctionnelle correspondant aux futures cavités de l'aube et ayant la forme de celles-ci (seule l'extrémité supérieure de la première partie, correspondant au sommet, ou tête de l'aube, est visible sur la figure 1), et une deuxième partie 30, appelée par exemple dôme, servant de région de maintien du noyau 10. Plus précisément, lors de la coulée de la cire autour du noyau 10, ou l'évacuation de la cire, le noyau 10 est maintenu en position fixe par rapport au moule céramique par l'intermédiaire d'une portion non fonctionnelle de cette deuxième partie 30. La deuxième partie 30 comprend également une portion fonctionnelle, au niveau de son extrémité inférieure, servant notamment à former le contour de la baignoire de l'aube à la fin du processus de fabrication de celle-ci.The blades present in turbomachines, in particular turbine blades, for example low pressure, generally comprise internal cavities necessary for cooling these blades. During the manufacture of the blades according to the technique of lost wax casting, these cavities are formed, before the formation of the wax mold, by means of ceramic cores, the shape of which corresponds to the desired shape of the cavities in the final piece. A portion of such a core 10 is shown schematically in the figure 1 . These ceramic cores generally comprise a first part 20, the first part 20 being a functional part corresponding to the future cavities of the blade and having the shape thereof (only the upper end of the first part, corresponding to the tip, or head of dawn, is visible on the figure 1 ), and a second part 30, called for example a dome, serving as a region for holding the core 10. More specifically, during the casting of the wax around the core 10, or the evacuation of the wax, the core 10 is held in a fixed position with respect to the ceramic mold via a non-functional portion of this second part 30. The second part 30 also comprises a functional portion, at its lower end, serving in particular to form the contour of the bathtub from dawn to the end of the process of making it.

Pour que le métal puisse être coulé autour du noyau, notamment autour de la portion supérieure de la première partie 20 du noyau 10 visible sur la figure 1, pour former les cavités de l'aube, la première partie 20 doit être espacée de la deuxième partie 30, tout en étant solidaire de cette dernière et maintenue par cette dernière. Pour ce faire, de fines tiges 40 sont disposées entre ces deux parties, et maintiennent ces parties solidaires l'une de l'autre et fixes l'une par rapport à l'autre, tout en laissant un espace S entre ces deux parties. Ainsi, le métal coulé pénétrant dans cet espace S entre ces deux parties correspondra à la paroi de fond de la baignoire de sommet de l'aube, à la fin du processus de fabrication de l'aube. Un tel exemple de noyau est divulgué dans le document FR2889088 .So that the metal can be cast around the core, in particular around the upper portion of the first part 20 of the core 10 visible on the figure 1 , to form the cavities of the blade, the first part 20 must be spaced from the second part 30, while being integral with the latter and maintained by the latter. To do this, thin rods 40 are placed between these two parts, and hold these parts integral with each other and fixed relative to each other, while leaving a space S between these two parts. Thus, the cast metal penetrating into this space S between these two parts will correspond to the bottom wall of the top bath of the blade, at the end of the manufacturing process of the blade. Such an example kernel is disclosed in the document FR2889088 .

Dans les techniques d'injection classiques, les tiges 40 sont directement placées dans un moule et une pâte céramique est injectée autour. Cependant, la complexité de certains noyaux céramiques nécessite des techniques adaptées de fabrication, telles que la fabrication additive. Cette technique, dans laquelle le noyau est construit couche par couche, ne permet pas l'insertion des tiges pendant la fabrication. Il est donc nécessaire de prévoir des orifices dans le noyau lors de la fabrication additive de ce dernier, afin de pouvoir y insérer les tiges a posteriori. Néanmoins, l'insertion de ces tiges nécessite d'abord de nettoyer, c'est-à-dire vider les trous prévus à cet effet, de l'excédent de matière céramique qui s'y dépose pendant l'impression du noyau.In conventional injection techniques, the rods 40 are directly placed in a mold and a ceramic paste is injected around. However, the complexity of certain ceramic cores requires appropriate manufacturing techniques, such as additive manufacturing. This technique, in which the core is built layer by layer, does not allow the insertion of the rods during manufacture. It is therefore necessary to provide orifices in the core during the additive manufacturing of the latter, in order to be able to insert the rods therein a posteriori. Nevertheless, the insertion of these rods first requires cleaning, that is to say emptying the holes provided for this purpose, of the excess ceramic material which is deposited there during the printing of the core.

Cependant, le vidage de ces orifices est complexe du fait du petit diamètre et de la longueur importante de ces derniers. Cette étape de nettoyage des orifices mène de plus à des détériorations fréquentes des noyaux, et à de nombreux rebuts de ces noyaux. Les outils et les techniques actuels ne permettent pas de réaliser cette opération de manière efficace.However, the emptying of these orifices is complex due to the small diameter and the considerable length of the latter. This step of cleaning the orifices also leads to frequent deterioration of the cores, and to numerous rejects of these cores. Current tools and techniques do not allow this operation to be carried out efficiently.

Exposé de l'inventionDisclosure of Invention

Afin de pallier au moins en partie aux inconvénients mentionnés cidessus, le présent exposé concerne un procédé de fabrication d'une ébauche d'un noyau céramique destiné à la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue, l'ébauche étant fabriquée par fabrication additive et comprenant :

  • au moins une première partie destinée à former les cavités des aubes creuses,
  • au moins une deuxième partie configurée pour permettre le positionnement du noyau dans un moule à cire, la deuxième partie et la première partie étant positionnées et maintenues l'une par rapport à l'autre par l'intermédiaire d'une portion de jonction intercalée entre la première partie et la deuxième partie,
  • au moins un orifice traversant s'étendant à travers la deuxième partie, la portion de jonction et la première partie, une première extrémité de l'orifice traversant débouchant sur une face externe de la deuxième partie, et une deuxième extrémité de l'orifice traversant débouchant sur une face externe de la première partie.
In order to overcome at least in part the drawbacks mentioned above, this presentation relates to a process for manufacturing a blank of a ceramic core intended for the manufacture of hollow turbomachine blades according to the technique of lost wax casting, the blank being manufactured by additive manufacturing and comprising:
  • at least a first part intended to form the cavities of the hollow blades,
  • at least a second part configured to allow the positioning of the core in a wax mould, the second part and the first part being positioned and maintained relative to each other via a junction portion interposed between the first part and the second part,
  • at least one through hole extending through the second part, the junction portion and the first part, a first end of the through hole opening onto an outer face of the second part, and a second end of the through hole leading to an outer face of the first part.

On comprend que la portion de jonction est formée en même temps que la première partie et la deuxième partie au cours de la fabrication additive, et comprend donc le même matériau que ces parties. La portion de jonction peut être un artifice de fabrication imprimé en 3D, appelé « support d'impression », formant une portion de jonction entre ces deux parties pendant l'impression. En particulier, la portion de jonction permet de maintenir ces deux parties solidaires l'une de l'autre et fixes l'une par rapport à l'autre de manière temporaire, avant l'insertion des tiges. Le contact entre la portion de jonction et les première et deuxième parties peut être discontinu. Par exemple, la portion de jonction peut comporter une pluralité de plots ou de picots intercalés entre ces deux parties. Cette configuration permet de faciliter le retrait ultérieur de cette portion de jonction, après la mise en place des tiges de positionnement.It is understood that the junction portion is formed at the same time as the first part and the second part during additive manufacturing, and therefore comprises the same material as these parts. The junction portion may be a 3D printed manufacturing device, called a “printing medium”, forming a junction portion between these two parts during printing. In particular, the junction portion makes it possible to maintain these two parts secured to each other and fixed relative to each other temporarily, before the insertion of the rods. The contact between the junction portion and the first and second parts may be discontinuous. For example, the junction portion may comprise a plurality of studs or spikes interposed between these two parts. This configuration facilitates subsequent removal of this junction portion, after positioning the positioning rods.

Par « ébauche », on comprend qu'il s'agit d'un état intermédiaire du noyau au cours de sa fabrication, notamment avant l'insertion des tiges. La fabrication de l'ébauche par fabrication additive est réalisée de telle sorte que l'ébauche ainsi obtenue comprenne la première partie, la deuxième partie, et la portion de jonction. En outre, cette fabrication prévoit la présence d'au moins un orifice traversant. Par « traversant », ou « débouchant », on comprend que l'orifice débouche de part et d'autre de l'ébauche, par opposition à un trou borgne comprenant un fond. En particulier, l'orifice traverse la deuxième partie, la portion de jonction et la première partie, en débouchant à chacune de ses extrémités sur une région extérieure à l'ébauche du noyau, autour de ce dernier.By "draft", it is understood that it is an intermediate state of the core during its manufacture, in particular before the insertion of the rods. The manufacture of the blank by additive manufacturing is carried out such that the blank thus obtained comprises the first part, the second part, and the junction portion. In addition, this manufacture provides for the presence of at least one through hole. By “through” or “opening”, it is understood that the orifice opens on either side of the blank, as opposed to a blind hole comprising a bottom. In particular, the orifice passes through the second part, the junction portion and the first part, opening out at each of its ends into a region outside the blank of the core, around the latter.

Cette configuration permet de faciliter le nettoyage de l'orifice traversant. En effet, à la fin de la fabrication de l'ébauche par fabrication additive, des résidus non solidifiés de pâte céramique restent dans l'orifice, en raison notamment de la viscosité importante de cette pâte.This configuration makes it easier to clean the through hole. Indeed, at the end of the manufacturing of the blank by additive manufacturing, non-solidified residues of ceramic paste remain in the orifice, in particular because of the high viscosity of this paste.

Le nettoyage permet d'enlever ces résidus, afin de permettre l'insertion de la tige de positionnement. Or, la configuration du présent exposé permet d'expulser facilement ces résidus par une extrémité débouchante de l'orifice, en appliquant une pression, par exemple en injectant un mélange de solvant et d'air pulsé, à l'autre extrémité débouchante de l'orifice. Il est ainsi possible de réaliser efficacement le nettoyage de l'orifice, en s'affranchissant de l'utilisation d'outils non adaptés tels que des forets, limitant ainsi le taux de rebuts des noyaux.Cleaning removes these residues to allow insertion of the positioning pin. However, the configuration of the present disclosure makes it possible to easily expel these residues through an open end of the orifice, by applying pressure, for example by injecting a mixture of solvent and pulsed air, at the other open end of the orifice. 'orifice. It is thus possible to carry out the cleaning of the orifice effectively, by dispensing with the use of unsuitable tools such as drill bits, thus limiting the scrap rate of the cores.

Par ailleurs, selon l'art antérieur, la portion de l'orifice traversant la deuxième partie présentant une longueur importante, la longueur des forets ne permettaient pas de déboucher/nettoyer cette portion de l'orifice en une seule étape. Il était alors nécessaire d'imprimer cette deuxième partie en deux parties, afin de nettoyer l'orifice en deux étapes, puis de recoller les deux parties ensemble. La présence d'un orifice traversant selon le présent exposé permet de s'affranchir de cet inconvénient, simplifiant ainsi le processus de fabrication du noyau.Furthermore, according to the prior art, the portion of the orifice passing through the second part having a significant length, the length of the drill bits did not allow this portion of the orifice to be unblocked/cleaned in a single step. It was then necessary to print this second part in two parts, in order to clean the orifice in two stages, then to glue the two parts together. The presence of a through orifice according to the present description makes it possible to overcome this drawback, thus simplifying the manufacturing process of the core.

Dans certains modes de réalisation, la portion de jonction comprend un passage mettant en communication fluidique l'orifice traversant et un espace extérieur à l'ébauche de noyau.In certain embodiments, the junction portion comprises a passage putting the through-orifice in fluid communication with a space outside the core blank.

Ce passage permet de faciliter le nettoyage de l'orifice traversant. En effet, lorsque le nettoyage de l'orifice est effectué en injectant un solvant, par exemple, aux deux extrémités de l'orifice, les résidus de pâte céramique dissouts dans le solvant peuvent être évacués par ce passage.This passage facilitates the cleaning of the through hole. Indeed, when the orifice is cleaned by injecting a solvent, for example, at the two ends of the orifice, the ceramic paste residues dissolved in the solvent can be evacuated through this passage.

Dans certains modes de réalisation, l'orifice traversant comprend une première portion rectiligne s'étendant depuis la première extrémité, et une deuxième portion rectiligne présentant un angle inférieur à 180° par rapport à la première portion rectiligne, et s'étendant depuis la deuxième extrémité.In certain embodiments, the through hole comprises a first rectilinear portion extending from the first end, and a second rectilinear portion presenting an angle less than 180° with respect to the first rectilinear portion, and extending from the second end.

De préférence, la première portion rectiligne s'étend à travers la deuxième partie depuis la première extrémité jusqu'à la portion de jonction, à travers la portion de jonction et une partie de la première partie. La deuxième portion rectiligne s'étend dans la première partie entre l'extrémité de la première portion rectiligne située dans la première partie, et la deuxième extrémité. En d'autres termes, la première portion rectiligne et la deuxième portion rectiligne forment entre elles un coude présentant un angle inférieur à 180°, ce coude étant de préférence disposé dans la première partie. La longueur de la première portion rectiligne peut être déterminée en fonction de la longueur de la tige de positionnement devant être insérée. La présence de ce coude permet de raccourcir la longueur de la deuxième portion rectiligne de l'orifice, et permet notamment d'atteindre l'extérieur du noyau.Preferably, the first rectilinear portion extends through the second part from the first end to the junction portion, through the junction portion and part of the first part. The second rectilinear portion extends in the first part between the end of the first portion rectilinear located in the first part, and the second end. In other words, the first rectilinear portion and the second rectilinear portion form between them a bend having an angle of less than 180°, this bend preferably being arranged in the first part. The length of the first rectilinear portion can be determined according to the length of the positioning rod to be inserted. The presence of this bend makes it possible to shorten the length of the second rectilinear portion of the orifice, and in particular makes it possible to reach the outside of the core.

Dans certains modes de réalisation, l'angle entre la première et la deuxième portion rectiligne est supérieur ou égal à 100°, de préférence compris entre 110° et 120°.In certain embodiments, the angle between the first and the second rectilinear portion is greater than or equal to 100°, preferably comprised between 110° and 120°.

Ces valeurs permettent de limiter le risque, lors de l'étape de nettoyage, que des résidus de pâte céramique restent bloquées dans la partie coudée de l'orifice, si l'angle entre la première et la deuxième portion rectiligne était trop petit. Ces valeurs permettent également de limiter le volume de l'orifice traversant. Ainsi, ces valeurs d'angles entre la première et la deuxième portion rectiligne permettent de faciliter l'opération de nettoyage de l'orifice.These values make it possible to limit the risk, during the cleaning step, of ceramic paste residues remaining blocked in the bent part of the orifice, if the angle between the first and the second rectilinear portion were too small. These values also make it possible to limit the volume of the through hole. Thus, these angle values between the first and the second rectilinear portion make it possible to facilitate the operation of cleaning the orifice.

Dans certains modes de réalisation, le diamètre de la première portion rectiligne de l'orifice traversant est compris entre 0,15 et 0,3 mm. In some embodiments, the diameter of the first rectilinear portion of the through hole is between 0.15 and 0.3 mm.

Le diamètre de la première portion rectiligne peut être déterminé en fonction du diamètre de la tige de positionnement devant être insérée. De préférence, un jeu doit exister entre la tige de positionnement et l'orifice.The diameter of the first rectilinear portion can be determined according to the diameter of the positioning rod to be inserted. Preferably, a clearance must exist between the positioning rod and the orifice.

Dans certains modes de réalisation, le diamètre de la deuxième portion rectiligne de l'orifice traversant est compris entre 0,4 et 0,6 mm.In some embodiments, the diameter of the second rectilinear portion of the through hole is between 0.4 and 0.6 mm.

L'orifice traversant peut avoir une section circulaire. Ces valeurs permettent de faciliter l'insertion des tiges de positionnement et le nettoyage des orifices. En effet, des diamètres trop importants ne seraient pas adaptés aux techniques de nettoyage telles que l'injection d'air pulsé et/ou de solvant, et rendraient cette injection inefficace. L'opération de rebouchage des orifices serait également plus longue, plus complexe, et demanderait une quantité importante de pâte céramique pour reboucher ces orifices. De plus, des diamètres trop importants nuiraient aux propriétés mécaniques du noyau et ne permettraient pas un positionnement précis des tiges de positionnement. A l'inverse, des diamètres trop faibles empêcheraient l'insertion des tiges de positionnement.The through hole may have a circular section. These values facilitate the insertion of the positioning rods and the cleaning of the orifices. Indeed, excessively large diameters would not be suitable for cleaning techniques such as the injection of pulsed air and/or solvent, and would render this injection ineffective. The orifice filling operation would also be longer, more complex, and would require a large quantity of ceramic paste to fill these orifices. In addition, excessively large diameters would harm the mechanical properties of the core and would not allow precise positioning of the positioning rods. Conversely, diameters that are too small would prevent the insertion of the positioning rods.

Le présent exposé concerne également un procédé de fabrication d'un noyau céramique destiné à la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue, le procédé comprenant une étape de fabrication d'une ébauche par le procédé selon l'un quelconque des modes de réalisation précédents, et comprenant également, après la fabrication de l'ébauche :

  • le nettoyage de l'orifice traversant,
  • l'insertion d'au moins une tige de positionnement dans l'orifice traversant,
  • le rebouchage de l'orifice traversant,
  • l'élimination de la portion de jonction.
This disclosure also relates to a process for manufacturing a ceramic core intended for the manufacture of hollow turbomachine blades according to the lost-wax casting technique, the process comprising a step of manufacturing a blank by the process according to any of the preceding embodiments, and also comprising, after manufacture of the blank:
  • cleaning the through hole,
  • inserting at least one positioning rod into the through hole,
  • the filling of the through hole,
  • the elimination of the junction portion.

A la fin de la fabrication de l'ébauche par fabrication additive, des résidus non solidifiés de pâte céramique restent dans l'orifice. Le nettoyage permet d'enlever ces résidus, afin de permettre l'insertion de la tige de positionnement. Par ailleurs, l'élimination de la portion de jonction peut être effectuée par frittage de la céramique à l'aide d'un outil adapté, par exemple une meule de précision élevée permettant de libérer l'espace entre la première partie et la deuxième partie.At the end of the manufacture of the blank by additive manufacturing, unsolidified residues of ceramic paste remain in the orifice. Cleaning removes these residues to allow insertion of the positioning rod. Furthermore, the elimination of the junction portion can be carried out by sintering the ceramic using a suitable tool, for example a high precision grinding wheel making it possible to release the space between the first part and the second part. .

Dans certains modes de réalisation, le nettoyage de l'orifice traversant est réalisé par une injection d'air pulsé et/ou d'un solvant dans au moins une extrémité de l'orifice.In certain embodiments, the cleaning of the through hole is carried out by injecting pulsed air and/or a solvent into at least one end of the hole.

De l'air pulsé seul, un solvant seul, ou un mélange des deux peuvent être utilisés pour le nettoyage de l'orifice. L'air pulsé et/ou le solvant injecté à l'une des extrémités de l'orifice est évacué, en emportant les résidus de pâte céramique, par l'autre extrémité de l'orifice et/ou par le passage dans la portion de jonction. L'air pulsé et/ou le solvant injecté aux deux extrémités de l'orifice, simultanément ou non, est évacué, en emportant les résidus de pâte céramique, par le passage dans la portion de jonction. Ces techniques de nettoyage présentent l'avantage d'être facile à mettre en oeuvre, peu coûteuse, et limite considérablement le risque de casser les noyaux céramiques lors du nettoyage des orifices. Cette technique présente en outre l'avantage d'être rapide, et n'ajoute pas d'étape supplémentaire, contrairement à l'utilisation d'un foret pour nettoyer les orifices selon l'art antérieur. En effet, le nettoyage des orifices par air pulsé et/ou solvant pouvant être réalisé en même temps que le nettoyage du noyau.Forced air alone, solvent alone, or a mixture of the two can be used for orifice cleaning. The pulsed air and/or the solvent injected at one end of the orifice is evacuated, carrying away the ceramic paste residues, through the other end of the orifice and/or through the passage in the portion of junction. The pulsed air and/or the solvent injected at the two ends of the orifice, simultaneously or not, is evacuated, carrying the ceramic paste residues, through the passage in the junction portion. These cleaning techniques have the advantage of being easy to implement, inexpensive, and considerably limiting the risk of breaking the ceramic cores when cleaning the orifices. This technique also has the advantage of being fast, and does not add an extra step, unlike the use of a drill to clean the orifices according to the prior art. Indeed, the cleaning of the orifices by pulsed air and/or solvent can be carried out at the same time as the cleaning of the core.

Dans certains modes de réalisation, le nettoyage de l'orifice traversant est réalisé en insérant mécaniquement un moyen de nettoyage dans au moins une extrémité de l'orifice.In some embodiments, through hole cleaning is accomplished by mechanically inserting a cleaning means into at least one end of the hole.

Cette technique d'insertion mécanique d'un moyen de nettoyage peut être réalisée seule, ou en plus de l'air pulsé et/ou du solvant.This technique of mechanical insertion of a cleaning means can be carried out alone, or in addition to the pulsed air and/or the solvent.

Dans certains modes de réalisation, l'étape de nettoyage et l'étape d'insertion sont réalisées simultanément.In some embodiments, the cleaning step and the insertion step are performed simultaneously.

Selon ce mode de réalisation, le fait d'insérer la tige à une extrémité de l'orifice traversant permet de pousser les résidus de céramique, ces résidus pouvant s'échapper par l'autre extrémité de l'orifice. La tige agit ainsi elle-même comme moyen de nettoyage mécanique.According to this embodiment, the fact of inserting the rod at one end of the through orifice makes it possible to push the ceramic residues, these residues being able to escape through the other end of the orifice. The rod thus acts itself as a mechanical cleaning means.

Dans certains modes de réalisation, les tiges de positionnement sont des tiges d'alumine.In some embodiments, the positioning rods are alumina rods.

Les tiges d'alumine sont un matériau céramique présentant l'avantage d'être résistant aux mêmes contraintes thermiques que le reste de la pièce et ayant les mêmes propriétés chimiques au décochage. Elles permettent également une grande résistance en traction/compression pour assurer la stabilité dimensionnelle de l'épaisseur de fond de baignoire, ainsi qu'une accroche solide entre la première et la deuxième partie. De manière alternative, des tiges comprenant du molybdène peuvent être utilisées.The alumina rods are a ceramic material with the advantage of being resistant to the same thermal stresses as the rest of the part and having the same chemical properties on shakeout. They also allow a high tensile/compressive strength to ensure the dimensional stability of the bottom thickness of the tub, as well as a solid grip between the first and the second part. Alternatively, rods comprising molybdenum can be used.

Dans certains modes de réalisation, le rebouchage de l'orifice traversant est réalisé en appliquant une pâte céramique aux deux extrémités dudit orifice.In certain embodiments, the plugging of the through hole is carried out by applying a ceramic paste to the two ends of said hole.

Le rebouchage des deux extrémités de l'orifice permet d'éviter d'une part une infiltration non souhaitée de la cire lors de la fabrication du moule en cire, et d'autre part, d'obtenir un état de surface uniforme du noyau céramique, en particulier sur la première partie. Cela permet de s'assurer que la pièce finale ne présente pas d'irrégularités.The filling of the two ends of the orifice makes it possible, on the one hand, to avoid an undesired infiltration of the wax during the manufacture of the wax mold, and on the other hand, to obtain a uniform surface state of the ceramic core. , especially on the first part. This ensures that the final piece does not have any irregularities.

Dans certains modes de réalisation, le procédé comprend, après le rebouchage, une étape de durcissement permettant de faire durcir la pâte céramique.In certain embodiments, the method comprises, after the filling, a hardening step making it possible to harden the ceramic paste.

L'étape de durcissement comprend par exemple une exposition sous une lampe UV permet de faire durcir la pâte céramique utilisée pour le rebouchage. Cela permet d'améliorer la rigidité globale du noyau céramique, lorsque sa fabrication est terminée.The hardening step comprises, for example, exposure under a UV lamp to harden the ceramic paste used for filling. This makes it possible to improve the overall rigidity of the ceramic core, when its manufacture is finished.

Dans certains modes de réalisation, avant leur insertion, les tiges de positionnement sont enduites de colle céramique.In certain embodiments, before their insertion, the positioning rods are coated with ceramic glue.

Selon ce mode de réalisation, l'insertionAccording to this embodiment, the insertion

Le présent exposé concerne également une ébauche de noyau céramique destiné à la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue, et comprenant :

  • au moins une première partie destinée à former les cavités des aubes creuses,
  • au moins une deuxième partie configurée pour permettre le positionnement du noyau dans un moule à cire, la deuxième partie et la première partie étant positionnées et maintenues l'une par rapport à l'autre par l'intermédiaire d'une portion de jonction intercalée entre la première partie et la deuxième partie,
  • au moins un orifice traversant s'étendant à travers la deuxième partie, la portion de jonction et la première partie, une première extrémité de l'orifice traversant débouchant sur une face externe de la deuxième partie, et une deuxième extrémité de l'orifice traversant débouchant sur une face externe de la première partie.
This presentation also relates to a ceramic core blank intended for the manufacture of hollow turbine engine blades using the lost wax casting technique, and comprising:
  • at least a first part intended to form the cavities of the hollow blades,
  • at least a second part configured to allow the positioning of the core in a wax mould, the second part and the first part being positioned and maintained relative to each other via a junction portion interposed between the first part and the second part,
  • at least one through hole extending through the second part, the junction portion and the first part, a first end of the through hole opening onto an outer face of the second part, and a second end of the through hole leading to an outer face of the first part.

Le présent exposé concerne également une utilisation d'un noyau céramique obtenu par le procédé selon l'un quelconque des modes de réalisation du présent exposé, pour la fabrication d'aube de turbine creuse de turbomachine selon la technique de la fonderie à la cire perdue.This presentation also relates to a use of a ceramic core obtained by the method according to any one of the embodiments of this presentation, for the manufacture of hollow turbine blades for a turbomachine using the lost-wax casting technique. .

Brève description des dessinsBrief description of the drawings

L'invention et ses avantages seront mieux compris à la lecture de la description détaillée faite ci-après de différents modes de réalisation de l'invention donnés à titre d'exemples non limitatifs. Cette description fait référence aux pages de figures annexées, sur lesquelles :

  • [Fig. 1] La figure 1 représente schématiquement une vue en plan d'une portion d'un noyau céramique destiné à être utilisé pour la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue,
  • [Fig. 2A-2B] La figure 2A représente schématiquement une technique de nettoyage d'un orifice selon l'art antérieur, et la figure 2B représente schématiquement une technique de nettoyage d'un orifice selon le présent exposé,
  • [Fig. 3]La figure 3 représente une vue schématique en transparence d'une portion d'un noyau céramique du présent exposé,
  • [Fig. 4] La figure 4 est un diagramme représentant le procédé de fabrication d'un noyau céramique selon le présent exposé.
The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended figures, on which:
  • [ Fig. 1 ] There figure 1 schematically represents a plan view of a portion of a ceramic core intended to be used for the manufacture of hollow turbine engine blades using the lost wax casting technique,
  • [ Fig. 2A-2B ] There figure 2A schematically represents a technique for cleaning an orifice according to the prior art, and the figure 2B schematically represents a technique for cleaning an orifice according to the present description,
  • [ Fig. 3 ]There picture 3 represents a schematic view in transparency of a portion of a ceramic core of the present disclosure,
  • [ Fig. 4 ] There figure 4 is a diagram representing the method of manufacturing a ceramic core according to the present disclosure.

Description des modes de réalisationDescription of embodiments

Les figures 2A et 2B représentent schématiquement des échantillons d'un noyau céramique, sous la forme d'éprouvettes, permettant d'illustrer le nettoyage d'un orifice de ce noyau. La figure 2A représente schématiquement une technique de nettoyage d'un orifice 50 selon l'art antérieur. L'orifice 50 est non débouchant. La partie hachurée représente le noyau céramique, plus précisément, la pâte polymérisée formant le noyau céramique. Ce dernier comprend une première partie 20, une deuxième partie 30, et une portion de jonction 60. La partie en grisée représente la pâte céramique non polymérisée restant dans l'orifice 50 après l'impression de l'ébauche du noyau.THE figures 2A and 2B schematically represent samples of a ceramic core, in the form of test specimens, making it possible to illustrate the cleaning of an orifice of this core. There figure 2A schematically represents a technique for cleaning an orifice 50 according to the prior art. Orifice 50 is blind. The hatched part represents the ceramic core, more precisely, the polymerized paste forming the ceramic core. The latter comprises a first part 20, a second part 30, and a junction portion 60. The shaded part represents the unpolymerized ceramic paste remaining in the orifice 50 after the printing of the blank of the core.

Lors de la fabrication additive, l'ébauche de noyau est réalisée couche par couche, en commençant par la première partie 20 par exemple, puis la portion de jonction 60, puis la deuxième partie 30, en prévoyant la présence du ou des orifices 50. La portion de jonction 60 présente une forme dentelée, limitant la surface de contact entre la portion de jonction 60 et la première partie 20 et/ou la deuxième partie 30. La portion de jonction 60 peut ainsi comprendre une pluralité de dents 61, sous la forme de picots ou de plots, intercalés entre ces deux parties.During additive manufacturing, the core blank is produced layer by layer, starting with the first part 20 for example, then the junction portion 60, then the second part 30, providing for the presence of the orifice(s) 50. The junction portion 60 has a serrated shape, limiting the contact surface between the junction portion 60 and the first part 20 and/or the second part 30. The junction portion 60 can thus comprise a plurality of teeth 61, under the form of pins or studs, interposed between these two parts.

Selon le cas de figure illustré sur la figure 2A, l'orifice 50 est non débouchant et comprend un fond 51. L'opération de nettoyage de l'orifice s'effectue, par exemple, par l'intermédiaire d'un foret 70, dont le passage dans l'orifice 50 permet d'évacuer la pâte. Une telle technique entraîne la détérioration ou la casse de nombreux noyaux céramiques.Depending on the scenario illustrated in the figure 2A , the orifice 50 is blind and comprises a bottom 51. The orifice cleaning operation is carried out, for example, by means of a drill bit 70, the passage of which through the orifice 50 makes it possible to evacuate the dough. Such a technique leads to the deterioration or breakage of many ceramic cores.

La figure 2B représente schématiquement une technique de nettoyage d'un orifice 50 selon le présent exposé. Contrairement au cas de figure selon l'art antérieur, l'orifice 50 est débouchant. Plus précisément, l'orifice 50 comprend une première portion rectiligne 50a s'étendant à travers la deuxième partie 30, la portion de jonction 60 et la première partie 20, et une deuxième portion rectiligne 50b s'étendant à travers la première partie 20 depuis l'extrémité de la première portion rectiligne 50a, et débouchant sur une face externe de la première partie 20. La première portion rectiligne 50a est de préférence plus longue que la deuxième portion rectiligne 50b, et est destinée à recevoir une tige de positionnement. L'angle β entre la première et la deuxième portion rectiligne 50a, 50b est inférieur à 180°, et supérieur ou égal à 100°, de préférence compris entre 110° et 120°.There figure 2B schematically represents a technique for cleaning an orifice 50 according to the present description. Contrary to the scenario according to the prior art, the orifice 50 emerges. More specifically, the orifice 50 comprises a first rectilinear portion 50a extending through the second part 30, the junction portion 60 and the first part 20, and a second rectilinear portion 50b extending through the first part 20 from the end of the first rectilinear portion 50a, and opening onto an outer face of the first part 20. The first rectilinear portion 50a is preferably longer than the second rectilinear portion 50b, and is intended to receive a positioning rod. The angle β between the first and the second rectilinear portion 50a, 50b is less than 180°, and greater than or equal to 100°, preferably between 110° and 120°.

Lors de la fabrication additive, un passage 62 est prévu dans la portion de jonction 60. Ce passage 62 peut être un orifice, ou une absence locale de dents 61, permettant de mettre l'orifice 50 en communication fluidique avec une région externe au noyau céramique, et entourant celui-ci. Ce passage 62 permet de faciliter l'opération de nettoyage de l'orifice 50. En effet, à la fin de la fabrication additive, le nettoyage de l'orifice 50 peut s'effectuer en injectant de l'air pulsé à l'une ou aux deux extrémités de l'orifice 50. La pression exercée aux extrémités de l'orifice 50 permet l'évacuation de la pâte non polymérisée présente dans l'orifice, par le passage 62 de la portion de jonction 60 (cf. flèches sur la figure 2A). A la place de l'air pulsé, un solvant peut être injecté, ou un mélange d'air et de solvant. De manière alternative, un outil cylindrique de diamètre adapté peut être utilisé pour pousser la pâte, en plus ou la place de l'air et/ou du solvant.During additive manufacturing, a passage 62 is provided in the junction portion 60. This passage 62 may be an orifice, or a local absence of teeth 61, making it possible to place the orifice 50 in fluid communication with a region external to the core. ceramic, and surrounding it. This passage 62 makes it possible to facilitate the operation of cleaning the orifice 50. Indeed, at the end of the additive manufacturing, the cleaning of the orifice 50 can be carried out by injecting pulsed air at one or at the two ends of the orifice 50. The pressure exerted at the ends of the orifice 50 allows the evacuation of the unpolymerized paste present in the orifice, through the passage 62 of the junction portion 60 (cf. arrows on there figure 2A ). Instead of forced air, a solvent can be injected, or a mixture of air and solvent. Alternatively, a cylindrical tool of suitable diameter can be used to push the paste, in addition or instead of air and/or solvent.

La figure 3 représente une vue schématique d'une partie d'un noyau céramique 10 selon le présent exposé, réalisé par fabrication additive, comprenant une première partie 20, une deuxième partie 30, et une portion de jonction 60. La première partie 20 présente la forme des cavités que l'on souhaite obtenir à la fin de la fabrication de l'aube de turbine. Sur la figure 3, seule l'extrémité supérieure de la première partie 20, correspondant à l'extrémité supérieure, ou sommet, de l'aube, est visible. La deuxième partie 30, ou dôme, permet le maintien du noyau céramique 10 lors de la réalisation du modèle en cire, et lors de la coulée du métal dans un moule carapace céramique. La première partie 20 et la deuxième partie 30 sont espacées l'une de l'autre d'une distance S comprise entre 0,4 et 1,4 mm. Cet espacement, et ce positionnement de la première partie 20 par rapport à la deuxième partie 30 sont assurés, à la fin de la fabrication de l'ébauche de noyau, par la portion de jonction 60. Après l'élimination de la portion de jonction 60, l'espace S demeurant entre ces deux parties permet la formation de la baignoire au sommet de l'aube, lors de la coulée du métal s'infiltrant dans cet espace.There picture 3 represents a schematic view of a part of a ceramic core 10 according to the present description, made by additive manufacturing, comprising a first part 20, a second part 30, and a junction portion 60. The first part 20 has the shape of the desired cavities obtain at the end of the manufacture of the turbine blade. On the picture 3 , only the upper end of the first part 20, corresponding to the upper end, or top, of the blade, is visible. The second part 30, or dome, allows the maintenance of the ceramic core 10 during the production of the wax model, and during the casting of the metal in a ceramic shell mould. The first part 20 and the second part 30 are spaced apart by a distance S of between 0.4 and 1.4 mm. This spacing, and this positioning of the first part 20 with respect to the second part 30 are ensured, at the end of the manufacture of the core blank, by the junction portion 60. After the elimination of the junction portion 60, the space S remaining between these two parts allows the formation of the tub at the top of the blade, during the casting of the metal infiltrating into this space.

Dans cet exemple, trois orifices traversants 50 s'étendent à travers la deuxième partie 30, la portion de jonction 60 et la première partie 20. Chacun de ces orifices 50 comprend une première portion rectiligne 50a débouchant sur une face externe de la deuxième partie 30, et une deuxième portion rectiligne 50b (dont une seule est visible sur la figure 3) débouchant une face externe de la première partie 20. Une tige de positionnement 40 est insérée dans chacun de ces orifices 50. Ces tiges de positionnement 40 peuvent être des tiges d'alumine, et peuvent présenter une longueur de 13 mm et un diamètre de 0,6 mm. Néanmoins, ces dimensions ne sont pas limitatives, et peuvent être modifiées en fonction de la géométrie considérée du noyau.In this example, three through holes 50 extend through the second part 30, the junction portion 60 and the first part 20. Each of these holes 50 comprises a first rectilinear portion 50a opening onto an outer face of the second part 30 , and a second rectilinear portion 50b (only one of which is visible on the picture 3 ) opening an outer face of the first part 20. A positioning rod 40 is inserted into each of these holes 50. These positioning rods 40 can be alumina rods, and can have a length of 13 mm and a diameter of 0.6mm. Nevertheless, these dimensions are not limiting, and can be modified according to the considered geometry of the core.

La suite de la description décrit un procédé de fabrication d'un noyau céramique 10 selon le présent exposé, en référence à la figure 4.The rest of the description describes a method for manufacturing a ceramic core 10 according to the present disclosure, with reference to the figure 4 .

Une première étape de la fabrication d'un noyau céramique 10 comprend la fabrication d'une ébauche du noyau par fabrication additive (étape S1). L'ébauche comprend la première partie 20, la portion de jonction 60 et la deuxième partie 30. La fabrication additive prévoit la présence des orifices traversants 50, et du ou des passage(s) 62 dans la portion de jonction 60.A first step in the manufacture of a ceramic core 10 comprises the manufacture of a blank of the core by additive manufacturing (step S1). The blank comprises the first part 20, the junction portion 60 and the second part 30. Additive manufacturing provides for the presence of the through holes 50, and of the passage(s) 62 in the junction portion 60.

A la fin de la fabrication de l'ébauche, les orifices 50 sont nettoyés, c'est-à-dire vidées des résidus de pâte céramique non polymérisée demeurant dans les orifices 50 (étape S2). Pour ce faire, de l'air pulsé et/ou du solvant, par exemple, est injecté aux extrémités des orifices 50. La pâte résiduelle est ainsi évacuée par le passage 62 de la portion de jonction 60.At the end of the manufacture of the blank, the orifices 50 are cleaned, that is to say emptied of the residues of unpolymerized ceramic paste remaining in the orifices 50 (step S2). To do this, pulsed air and/or solvent, for example, is injected at the ends of the orifices 50. The residual paste is thus evacuated through the passage 62 of the junction portion 60.

Une tige de positionnement 40 est ensuite insérée dans chaque orifice traversant 50 (étape S3). Plus précisément, une tige de positionnement 40 est insérée dans la première portion rectiligne 50a de chaque orifice traversant. Les tiges 40 sont insérées par le haut, c'est-à-dire par l'extrémité de l'orifice 50 débouchant sur une face externe de la deuxième partie 30, et enfoncées dans l'orifice 50 de manière à s'étendre à la fois dans la deuxième partie 30 et dans la première partie 20. Les tiges 40 peuvent être préalablement enduites de colle céramique. Cette colle se solidifie lors du traitement thermique décrit ci-dessous, et permet un enrobage optimal de la tige.A positioning rod 40 is then inserted into each through hole 50 (step S3). More specifically, a positioning rod 40 is inserted into the first rectilinear portion 50a of each through hole. The rods 40 are inserted from the top, that is to say from the end of the orifice 50 opening onto an external face of the second part 30, and pushed into the orifice 50 so as to extend to both in the second part 30 and in the first part 20. The rods 40 can be coated beforehand with ceramic glue. This glue solidifies during the heat treatment described below, and allows optimal coating of the rod.

Après la mise en place des tiges de positionnement 40 dans les orifices 50, ces derniers sont rebouchés (étape S4). Ce rebouchage est effectué à l'aide d'une pâte céramique, de manière à obtenir un état de surface lisse, sur les faces externes des première et deuxième parties 20 et 30. Cela permet d'éviter des irrégularités de surface ultérieurement sur le modèle en cire, et sur la pièce finale. Le rebouchage est suivi d'une étape de durcissement de la pâte céramique, permettant de solidifier la pâte ajoutée à l'étape S4 (étape S5). Cette étape peut être réalisée en fonction des propriétés de la pâte, selon qu'elle soit, par exemple, photosensible ou thermosensible, par l'intermédiaire notamment d'une source de lumière UV ou une source de chaleur. Selon ce mode de réalisation, l'étape de durcissement est réalisée par une exposition à la lumière UV. On notera qu'après solidification de la pâte céramique, le noyau 10 peut également suivre une étape de traitement thermique, comprenant le déliantage et le frittage.After the placement of the positioning rods 40 in the orifices 50, the latter are sealed (step S4). This filling is carried out using a ceramic paste, so as to obtain a smooth surface state, on the external faces of the first and second parts 20 and 30. This makes it possible to avoid surface irregularities later on the model. in wax, and on the final piece. Filling is followed by a step of hardening the ceramic paste, making it possible to solidify the paste added in step S4 (step S5). This step can be carried out depending on the properties of the paste, depending on whether it is, for example, photosensitive or thermosensitive, by means in particular of a source of UV light or a source of heat. According to this embodiment, the curing step is carried out by exposure to UV light. It will be noted that after solidification of the ceramic paste, the core 10 can also follow a heat treatment step, comprising debinding and sintering.

Le procédé comprend enfin l'élimination de la portion de jonction 60 (étape S6). Cette élimination est facilitée par la forme dentelée de la partie de jonction 60, et peut être réalisée par n'importe quel outil adapté, pouvant s'insérer entre la première partie et la deuxième partie. A la fin de cette étape, la première partie 20 et la deuxième partie 30 sont maintenues l'une à l'autre, et positionnées l'une par rapport à l'autre, par les tiges de positionnement 40 uniquement.The method finally includes removing the junction portion 60 (step S6). This elimination is facilitated by the serrated shape of the junction part 60, and can be carried out by any suitable tool, which can be inserted between the first part and the second part. At the end of this step, the first part 20 and the second part 30 are held together, and positioned relative to each other, by the positioning rods 40 only.

Le noyau céramique 10 ainsi obtenu peut être ensuite utilisé dans la fabrication d'aubes creuses de turbomachine selon la technique de la fonderie à la cire perdue. En particulier, le noyau céramique 10 peut être disposé dans un moule à cire, en étant maintenu par la deuxième partie 30, pour former la modèle en cire présentant la forme de la pièce finale, avec les cavités formées par la première partie 20 du noyau céramique 10. Le modèle en cire est ensuite plongé à plusieurs reprises dans une barbotine afin de former le moule céramique. Après élimination de la cire, le métal fondu est coulé dans le moule céramique et autour du noyau céramique, ce dernier étant à nouveau maintenu en position fixe par l'intermédiaire de la deuxième partie 30. Enfin, le moule céramique et le noyau céramique 10 sont ensuite éliminés, par exemple par décochage, afin d'obtenir la pièce finale. On notera que l'élimination de la céramique comprend également l'élimination des tiges 40 d'alumine de positionnement, retirées pendant le décochage, laissant alors de petits orifices à travers la baignoire au sommet de l'aube, à l'endroit où se trouvaient ces tiges. Ces orifices servent notamment de trous de dépoussiérage ou d'évacuation de l'air présent dans les cavités de l'aube.The ceramic core 10 thus obtained can then be used in the manufacture of hollow turbine engine blades using the lost wax casting technique. In particular, the ceramic core 10 can be placed in a wax mould, being held by the second part 30, to form the wax model having the shape of the final piece, with the cavities formed by the first part 20 of the core. ceramic 10. The wax model is then dipped several times in a slip to form the ceramic mould. After removal of the wax, the molten metal is poured into the ceramic mold and around the ceramic core, the latter being again held in a fixed position by means of the second part 30. Finally, the ceramic mold and the ceramic core 10 are then eliminated, for example by shake-out, in order to obtain the final part. It will be noted that the elimination of the ceramic also includes the elimination of the positioning alumina rods 40, removed during shake-out, then leaving small orifices through the bath at the top of the blade, at the place where found these rods. These orifices serve in particular as holes for removing dust or for evacuating the air present in the cavities of the blade.

Bien que la présente invention ait été décrite en se référant à des exemples de réalisation spécifiques, il est évident que des modifications et des changements peuvent être effectués sur ces exemples sans sortir de la portée générale de l'invention telle que définie par les revendications. En particulier, des caractéristiques individuelles des différents modes de réalisation illustrés/mentionnés peuvent être combinées dans des modes de réalisation additionnels. Par conséquent, la description et les dessins doivent être considérés dans un sens illustratif plutôt que restrictif.Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different illustrated/mentioned embodiments can be combined in additional embodiments. Accordingly, the description and the drawings should be considered in an illustrative rather than restrictive sense.

Il est également évident que toutes les caractéristiques décrites en référence à un procédé sont transposables, seules ou en combinaison, à un dispositif, et inversement, toutes les caractéristiques décrites en référence à un dispositif sont transposables, seules ou en combinaison, à un procédé.It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a method.

Claims (13)

  1. A method for manufacturing a ceramic core blank (10) for the manufacture of hollow turbomachine blades using the technique of lost wax casting, the blank being manufactured by additive manufacturing and comprising:
    - at least one first part (20) for forming the cavities of the hollow blades,
    - at least one second part (30) configured to allow the positioning of the core (10) in a wax mold, the second part (30) and the first part (20) being positioned and held with respect to one another by means of a temporary junction portion (60) interposed between the first part (20) and the second part (30),
    - at least one through orifice (50) extending through the second part (30), the temporary junction portion (60) and the first part (20), a first end of the through orifice (50) opening to an outer face of the second part (30), and a second end of the through orifice (50) opening to an outer face of the first part (20).
  2. The method according to claim 1, wherein the temporary junction portion (60) comprises a passage (62) putting into fluid communication the through orifice (50) and a space outside the core blank.
  3. The method according to claim 1 or 2, wherein the through orifice (50) comprises a first rectilinear portion (50a) extending from the first end, and a second rectilinear portion (50b) having an angle (β) less than 180° with respect to the first rectilinear portion (50a), and extending from the second end.
  4. The method according to claim 3, wherein the angle (β) between the first and the second rectilinear portion (50a, 50b) is greater than or equal to 100°, preferably comprised between 110° and 120°.
  5. The method according to any one of claims 1 to 4, wherein the diameter of the first rectilinear portion (50a) of the through orifice (50) is comprised between 0.15 and 0.3 mm.
  6. A method for manufacturing a ceramic core (10) for the manufacture of hollow turbomachine blades using the technique of lost wax casting, the method comprising a step of manufacturing a blank by the method according to any one of claims 1 to 5, and also comprising, after the manufacture of the blank:
    - cleaning the through orifice (50),
    - inserting at least one positioning rod (40) into the through orifice (50),
    - capping the through orifice (50),
    - eliminating the temporary junction portion (60).
  7. The method according to claim 6, wherein the cleaning of the through orifice (50) is accomplished by an injection of pulsed air and/or a solvent into at least one end of the orifice (50).
  8. The method according to claim 6 or 7, wherein the positioning rods (40) are rods of alumina.
  9. The method according to any one of claims 6 to 8, wherein the capping of the through orifice (50) is accomplished by applying a ceramic paste to the two ends of said orifice (50).
  10. The method according to any one of claims 6 to 9, comprising, after capping, a hardening step allowing hardening the ceramic paste used for capping the orifice (50).
  11. The method according to any one of claims 6 to 10, wherein, prior to their insertion, the positioning rods (40) are coated with ceramic adhesive.
  12. A ceramic core blank for the manufacture of hollow turbomachine blades using the technique of lost wax casting, comprising:
    - at least one first part (20) for forming the cavities of the hollow blades,
    - at least one second part (30) configured to allow the positioning of the core in a wax mold, the second part (30) and the first part (20) being positioned and held with respect to one another by means of a temporary junction portion (60) interposed between the first part (20) and the second part (30),
    - at least one through orifice (50) extending through the second part (30), the temporary junction portion (60) and the first part (20), a first end of the through orifice (50) opening to an outer face of the second part (30) and a second end of the through orifice (50) opening to an outer face of the first part (20).
  13. A method for manufacturing a hollow turbomachine blade using the technique of lost wax casting, comprising:
    - manufacturing a ceramic core (10) by a method according to any one of claims 6 to 11,
    - manufacturing a wax model having the shape of the final part by arranging the ceramic core (10) obtained in the preceding step in a wax mold,
    - manufacturing a ceramic mold by plunging the wax model obtained in the preceding step several times into a slurry,
    - pouring, after the elimination of the wax, molten metal into the ceramic mold and around the ceramic core,
    - elimination of the ceramic mold and of the ceramic core (10).
EP20775042.3A 2019-08-30 2020-08-27 Improved method for manufacturing a ceramic core for manufacturing turbomachine vanes and ceramic core Active EP4021663B1 (en)

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FR1909534A FR3100143B1 (en) 2019-08-30 2019-08-30 Improved method of manufacturing a ceramic core for the manufacture of turbine engine blades
PCT/FR2020/051507 WO2021038174A1 (en) 2019-08-30 2020-08-27 Improved method for manufacturing a ceramic core for manufacturing turbomachine vanes

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FR3121372B1 (en) * 2021-03-30 2023-03-31 Safran System for inserting rods into a ceramic core blank for the manufacture of turbomachine blades

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US11745255B2 (en) 2023-09-05
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