DEVICE AND METHOD FOR MANUFACTURING A CERAMIC CORE FOR A BLADE

Abstract

Method (100) for manufacturing a core (40) using a device comprising a mold (51) which includes a cavity having a first zone (54) and a second zone (56) intended respectively to form a first part (42) and a second part (44) of the core (40), and a connecting channel (58) connecting the first zone (54) to the second zone (56), the method comprising the steps: placing, in the mold (51), a rod (48) intended to connect the first part (42) to the second part (44) of the core (40); injecting a slip (60) into the cavity; cutting an injection appendage (46) formed by solidification of the slip (60) in the connecting channel (58); demolding the core (40) obtained; to remove a binder from the solidified slip (60) and / or to consolidate the ceramic particles of the solidified slip (60). Figure from the abstract: Figure 6

Description

Description Title of the invention: DEVICE AND METHOD FOR MANUFACTURED A CERAMIC CORE FOR A BLADE technical field

[0001] — The present description relates to a device and method for manufacturing a cast ceramic core intended to form at least part of a circuit of cooling of a turbomachine blade. Previous technique

[0002] A turbomachine conventionally extends along an axis and comprises, from upstream to downstream in the direction of gas flow within the turbomachine, a blower, a com- low-pressure press, high-pressure compressor, combustion chamber, a high-pressure turbine, a low-pressure turbine, and an ejection nozzle. The The high-pressure turbine is coupled in rotation to the high-pressure compressor, by via a high-pressure shaft, so as to form a high-pressure body. The low-pressure turbine is rotationally coupled to the low-pressure compressor, by via a low-pressure shaft, so as to form a low-pressure body. The blower is connected to the low-pressure shaft, either directly or via via a speed reducer.

[0003] The blades of the low-pressure and high-pressure turbines of a turbomachine are subjected to the very high temperatures of the combustion chamber gases, which can lead to premature degradation of said blades and limit their lifespan.

[0004] In order to control the temperature of these blades, they include circuits internal cooling. Air coming, for example, from the low-pressure compressor, is sent into the cooling circuits of the blades, in order to limit the temperature pérature.

[0005] In the following description, the terms axial, radial and circumferential are used with reference to the axis of the turbomachine.

[0006] Figure 1 illustrates a high-pressure turbine blade 10 of a turbomachine. awl 10 comprises, radially from the inside out, a foot 12, a plate- shape 18 and a blade 16. The blade 16 has intrados surfaces 20 and extrados surfaces 22 connected upstream by a leading edge 24 and downstream by a trailing edge 26.

[0007] — The radially external end 14 or tip of the blade 16 comprises a part hollow in the shape of a bathtub 30. The latter is delimited by a bottom transverse to the blade 16 and by a peripheral wall forming its edge in the pro- length of the wall of blade 16. Blade 16 further comprises a plurality of internal cavities communicating with a cooling air inlet located at level of the foot 12 of the blade 10 and opening at the level of perforations 28 distributed on the blade 16. The perforations 28 are located at the level of the intrados 20 and extrados 22 surfaces of the blade 16 and at the level of the leading 24 and trailing 26 edges of the blade 16. The perforations 28 at the edge of the trailing edge 26 have the shape of slits, the other perforations 28 have generally circular or oval shapes. Such blades 10 are manufactured by molding a metallic material. These molds 51 have a cavity, that is, a hollow shape defining, in particular, the blade 10 to be produced. One or more ceramic cores 40 can be mounted in the mold 51, at the cavity, so as to form hollow areas in the part to be manufactured, especially when it has a complex geometry. The cores 40 are notably intended to define the cavities defining the cooling circuits as well as the tub 30 at the apex 14 of the blade 16. Figure 2 illustrates a core 40 known for the fabrication of a turbine blade 10. This core extends along a first direction X and comprises a first part 42 and a second part 44 separated from each other along the first direction X. The first part 42 and the second part 44 are connected to each other by at least one rod 48, here two rods 48. The first part 42 forms, during the subsequent molding process of the blade 10, cavities or channels intended to form at least part of the cooling circuit of the blade 10. During the subsequent molding process of the blade 10, the second part 44 is intended in particular to form the tub 30 of the blade 10. The ceramic cores 40 are themselves manufactured by molding a ceramic paste, also called slip 60, into a mold 51. This paste is mainly composed of ceramic powder and a binder. The mold 51 is further composed of two shells 52 joined together at a parting line. Each of the two shells 52 defines a portion of the cavity of the core 40 to be produced. As illustrated in Figures 3 to 5, the imprint extends along a first direction coinciding with the direction of the core 40. The imprint comprises a first zone 54 and a second zone 56 separated from each other along the first direction. The first zone 54 of the imprint is intended to form the first part 42 of the core 40. The second zone 56 of the imprint is intended to form the second part 44 of the core 40. The first zone 54 and the second zone 56 are also linked to each other by means of a link channel 58. During the manufacturing of the core 40, the rod 48 is inserted into the housing of the mold 51 is then filled with slip 60. Slip 60 enters the mold 51. Specifically, slip 60 enters the first zone 54 of the cavity. This first zone 54 is thus progressively filled with slip 60, as illustrated in [Fig. 3]. After the first zone 54 of the cavity is filled ([Fig. 4]), slip 60 enters the second zone 56 of the cavity through the connecting channel 58 ([Fig. 5]). The resulting core 40 is then demolded and subjected to heat treatment to remove the binder and consolidate the ceramic particles. The temperature increase causes the rod 48 to expand and the ceramic-based material to contract. This generates significant stresses at the bond between the first and second parts 42, 44 of the core 40 and the rod 48, leading to defects, such as cracks, in the first part 42 and the second part 44 of the core 40 and / or breakage of the rod 48. This description aims to address these drawbacks. Summary A method is proposed for manufacturing a ceramic core for a turbomachine blade using a device comprising a mold, the mold comprising at least one cavity, the cavity comprising a first zone intended to form a first part of the core and a second zone intended to form a second part of the core, said zones of the cavity being separated from each other in a first direction, the cavity further comprising a connecting channel linking the first zone to the second zone, the method comprising the following steps: - to have, in the mold, at least one rod extending between the first zone and the second zone, said at least one rod being intended to connect the first part of the core to the second part of the core after manufacturing, - to pour or inject a slip or paste made from ceramic particles into the mold, - to proceed with the solidification of the slip, - cut an injection appendage formed by solidification of the slip inside the bonding channel, - to unmold the core obtained by solidifying the slip, the core comprising the first part and the second part connected by the stem, - to proceed with the removal of a binder from the solidified slurry of the core and / or to consolidate the ceramic particles of the solidified slurry of the core. Removing the injection appendage reduces the stresses induced in the first part of the core, the second part of the core, and the stem during the demolding and core debinding and / or consolidation stages. Core debinding involves removing the binder from the solidified core slip. The consumption- Core binding corresponds to the consolidation of the ceramic particles of the solidified slurry of the core. Thus, the risks of damage to the first and second parts of the core (formation of cracks, for example) and the risks of breakage of the stem during the demolding and debinding and / or core consolidation stages are reduced, or even prevented. The blade can extend, in a configuration installed in a turbomachine, in a radial direction between a blade root and a blade tip. The first direction can coincide with the radial direction of the blade. The connecting channel can open onto each of the first and second zones of the footprint. The connecting channel can extend in the first direction. The slip or paste based on ceramic particles can be mainly composed of a ceramic powder and a binder, the latter being made of organic or plastic material. The rod can help to hold the first part of the core together with the second part of the core. The rod can be made of a ceramic or metallic material. In particular, the rod can be made of alumina. The rod can extend in the first direction. The mold may include a recess to receive the rod. The first part of the core can be a functional part. The term "functional" when referring to the core indicates whether the part thus qualified contributes to the final geometry of the blade. A non-functional part, on the other hand, refers to an area of ​​a core element that does not affect the final geometry of the blade. The first part of the core can be a core body. The second part of the core can be a non-functional part. The second part of the core can be a part intended to form a blade tub. The slip can be solidified by firing. The binder can be removed from the solidified slip of the core by heat treatment. The ceramic particles of the solidified slip of the core can be consolidated by firing and / or sintering. The device may include at least one blade received in a slot of the mold, the blade being movable in translation in a second direction transverse to the first direction, the cutting step of the injection appendage being carried out by translation of the blade in the second direction inside the slot. A first rod and a second rod can be arranged in the mold extending between the first zone and the second zone, the first rod and the second rod being arranged on either side of the connecting channel, and separated from each other in a third direction transverse to the first direction, and in which A portion of the blade's tip has a dimension, along the third direction, that is smaller than the distance between the rods along the third direction. Thus, the tip portion of the blade has a dimension suitable for cutting the injection appendage without damaging the rods. The first stem and the second stem can be parallel. The tip of the blade may be pointed. The blade may include a base. The tip of the blade may be a ridge extending from the base of the blade. The device may include heating means suitable for heating the blade, the blade being preheated prior to the cutting step of the injection tip. The blade may be heated to a temperature between 50°C and 100°C. This characteristic facilitates the cutting of the injection tip. The heating means may include at least one electrical resistance element. The device may include means for driving the blade in the second direction and a control element for the drive means, the cutting of the injection appendage being achieved by translating the blade in the second direction using the drive means. Thus, the cutting step of the injection appendage is performed automatically. This feature reduces the core manufacturing time. This feature also ensures repeatability of the cutting step, decreasing the scrap rate of the cores thus manufactured. The blade translation can be performed according to predetermined translation parameters, which may include the blade stroke in the second direction, the blade speed, or the blade acceleration. Specifically, the blade stroke can be between 0 mm and 20 mm, the blade speed between 0.5 m / s and 5 m / s, and / or the blade acceleration between 0 m / s² and 4.5 m / s². The translation parameters can be determined based on the dimensions of the core to be manufactured, the composition of the slurry used, the temperature of the solidified core slurry, the core solidification rate, the blade temperature, or the shape of the injection nozzle. The translation parameters can be stored in or calculated by the control unit. The drive means may include a motor, a crank driven in rotation by the motor, a connecting rod connected at one end to the crank and a slide connected at a second end of the connecting rod, the slide being able to slide in the second direction and being fixed to the blade. The cutting step of the injection appendage can be initiated after a predetermined solidification time. The solidification time can be determined from the start of the injection or the pouring of the slip into the mold. Alternatively, the Solidification time can be determined from a slip compaction phase during which the pressure inside the mold increases. In particular, solidification time can range from 0 s to 360 s. The mold may consist of a first shell and a second shell, each defining a portion of the mold cavity. The first and second shells are designed to be fitted together at a parting line, and the core is demolded by separating the first and second shells. This feature facilitates core demolding. The slit can be formed through the first shell or the second shell. In another respect, a device is proposed for the implementation of the process as described above. Brief description of the drawings Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: [Fig.1] is a perspective view of a turbine blade from the prior art; [Fig.2] is a perspective view of an earlier art core for the manufacture of the dawn of the [Fig.1]; [Fig.3], [Fig.4] and [Fig.5] illustrate a manufacturing step of the core of [Fig.2]; [Fig.6] is a perspective view of a device for manufacturing a core according to the present description; [Fig.7] is a larger scale view of a detail of the mold of [Fig.6]; [Fig.8] is a functional diagram of a manufacturing process for a blade core according to the present description. Description of the implementation methods Reference is now made to Figures 6 and 7, which depict a device 50 for manufacturing two ceramic cores 40 for turbomachine blades 10 as described above. Alternatively, it could be a device 50 for manufacturing two sub-assemblies of a single core 40 for a turbomachine blade 10. The device 50 comprises, firstly, a mold 51. The mold 51 has a first shell 52 and a second shell 52. The first shell 52 and the second shell 52 are adapted to be pressed together at a parting line. The mold 51 here comprises two cavities, each associated with one of the cores 40. Each of the first shell 52 and the second shell 52 delimits a portion of one of the cavities of the mold 51. Each cavity comprises a first zone 54 intended to form a first portion 42 of the respective core 40 and a second zone 56 intended to form a second portion 44 of the respective core 40. Here, the first portion 42 of each core 40 is a functional part of the core 40, in particular a core body 40. The second part 44 of each core 40 is a non-functional part of the core 40, in particular a part intended to form a blade bath 10. The first zone 54 and the second zone 56 of each imprint are separated from each other along a first direction dl. In the following, this first direction dl refers to a principal extension direction of the core 40. The first direction d1 therefore corresponds to a direction between a foot 12 and a tip 14 of the blade 10 manufactured from the core 40. This is also the radial direction of the blade 10 in a configuration installed in a turbomachine. The second direction d2 is transverse to the first direction dl. In the example shown, the second direction d2 is perpendicular to the first direction dl. The second direction d2 is normal to the parting line of the mold 51. Finally, the third direction d3 is transverse to the first direction dl and the second direction d2. In particular, the third direction d3 is perpendicular to the first direction d1 and the second direction d2. Each footprint also includes a connecting channel 58 linking the first zone 54 to the second zone 56. In other words, the connecting channel 58 opens into each of the first zone 54 and the second zone 56 of the respective footprint. Each connecting channel 58 extends here in the first direction dl. The mold 51 is adapted to receive a first rod 48 and a second rod 48 extending between the first zone 54 and the second zone 56 of each cavity. In other words, each rod 48 can be positioned in the mold 51 so as to have one end at the first zone 54 and a second end at the second zone 56 of the respective cavity. To achieve this, the mold 51 can include, for each rod 48, a plurality of recesses, each receiving one of the rods 48, between the first zone 54 and the second zone 56 of the respective cavity. Each rod 48 is intended to connect the first part 42 to the second part 44 of the respective core 40 after the core 40 has been manufactured. Thus, each rod 48 contributes to maintaining the first part 42 with the second part 44 of the respective core 40. The first rod 48 and the second rod 48 are arranged on either side of the connecting channel 58 of their respective cavity, and separated from each other in the third direction d3. Each rod 48 extends in a direction comprising at least one component along the first direction di. Each rod 48 can, for example, extend in the first direction dl. Thus, each first rod 48 and second rod 48 are parallel in pairs. Each rod 48 can be made of alumina or a ceramic material, The first shell 52 of mold 51 also features a pair of slits extending each in the second direction d2. Remarkably, each slot is open-ended with one of the cavities of the mold 51, in particular at the level of the connecting channel 58 of the respective cavity. The device 50 also includes a pair of blades 62. Each blade 62 is received in one of the slots. Each blade 62 is translationally movable in the second direction d2 within its associated slot. The blade 62 can be movable between a retracted position in which it is entirely received in the slot and an extended position in which a portion of the blade 62 protrudes from the slot into the respective impression, specifically at the level of the connecting channel 58 of the respective impression. Each blade 62 can be made of a metallic or ceramic material. As can be seen in [Fig. 7], an end portion of each blade 62 has a dimension, along the third direction d3, that is smaller than the distance between one of the first rods 48 and the respective second rod 48, along the third direction d3. Thus, the end portion of the blade 62 has a dimension suitable for passing between the first rod 48 and the second rod 48 without damaging them. To achieve this, each blade 62 includes a base 62a from which a lug 62b extends in the second direction d2. Alternatively, the end portion of the blade 62 in the second direction d2 may have a pointed shape. The device 50 also includes drive means 64 for each blade 62 in the second direction d2. The translation can be carried out according to predetermined translation parameters such as the stroke of the blade 62 in the second direction d2, the speed of movement of the blade 62, or the acceleration of the blade 62. According to a particular embodiment, each blade 62 can be driven in translation in the second direction d2 independently of the other blade 62. The device 50 may include a control element for the drive means 64. In particular, the translation parameters can be stored in, or calculated by, the control element.For example, the drive means 64 may include a motor, a crank driven in rotation by the motor, a connecting rod connected at one end to the crank and a slide connected to a second end of the connecting rod, the slide being able to slide along the second direction d2 and being integral with the blade 62. The device 50 may further include heating means suitable for heating the blade 62. The heating means may include, for example, at least one electrical resistance. Figure [Fig.8] represents a functional diagram of a manufacturing process 100 of a ceramic core 40 for a turbomachine blade 10 using the device 50 as described above. The process 100 comprises a first step 110 consisting of placing, for each cavity of the mold 51, the first rod 48 and the second rod 48 between the first zone 54 and the second zone 56 of the respective cavity. The first step 110 can be carried out with the mold 51 in an open configuration, i.e., with the first shell 52 separated from the second shell 52. For this purpose, each rod 48 can be placed in its respective associated recess. The process 100 includes a second step 120 consisting of pouring or injecting a slip 60, or paste based on ceramic particles, into the first zone 54 of each cavity, the slip 60 being propagated to the second zone 56 of the respective cavity by flow through the connecting channel 58. Alternatively, the slip can be injected into the second zone 56 of the cavity and propagated to the first zone of the cavity 54 by flow through the connecting channel 58. The slip 60 can be mainly composed of a ceramic powder and a binder, the latter being made of an organic or plastic material. The first shell 52 and the second shell 52 of the mold S1 can be pressed together at the parting line prior to injecting the slip 60 into each cavity. Process 100 includes a third step 130 consisting of solidifying the slip 60. The solidification of the slip 60 can be achieved by firing. The process 100 includes a fourth step 140 consisting of cutting an injection appendage 46 formed by the solidification of the slip 60 inside the bonding channel 58 of each cavity. The cutting of each injection appendage 46 is carried out by translating the respective blade 62 in the second direction d2 inside the slot. In particular, the cutting of each injection appendage 46 is achieved here by translating the respective blade 62 using the drive means 64. Thus, the cutting of the injection appendages is carried out automatically. This feature reduces the manufacturing time of the cores 40. This feature also ensures repeatability of the cutting step, decreasing the scrap rate of the cores 40 thus manufactured.Furthermore, the translation parameters of each blade 62 can be determined according to the dimensions of the core 40 to be manufactured, the composition of the slip 60 used, the temperature of the solidified slip 60 of the core 40, the solidification rate of the core 40, or the temperature of the blade 62. The cutting of each injection appendage 46 can be initiated after a predetermined solidification time. The solidification time can be determined from the start of the injection or pouring of the slip 60 into each cavity of the mold 51. According to a particular embodiment, the injection appendages can be cut at different times. Each blade 62 can be heated prior to cutting the injection appendage 46. This feature facilitates cutting the injection appendage 46. The process 100 includes a fifth step 150 consisting of demolding the core 40 obtained by solidification of the slip 60. The demolding of the core 40 is achieved by separating the first shell 52 and the second shell 52. Such a characteristic makes it easier to demold the core 40. Each core 40 thus comprises the first part 42 and the second part 44 connected by the first rod 48 and the second rod 48. Process 100 includes a sixth step 160 consisting of removing the binder from the solidified slip 60 of each core 40 and / or consolidating the ceramic particles of the solidified slip 60 of each core 40. Removing the binder from the solidified slip 60 of one of the cores 40 is also called debinding. Removing the binder from the solidified slip 60 of each core 40 can be carried out by heat treatment. Consolidating each core 40 corresponds to consolidating the ceramic particles of the solidified slip 60 of the core 40. Consolidating the ceramic particles of the solidified slip 60 of each core 40 can be carried out by firing and / or sintering. Removing the injection appendage 46 reduces the stresses induced in the first part 42, the second part 44 and the rods 48 of each core 40 during the demolding and unbinding and / or consolidation steps of the core 40. Thus, the risks of damage to the first part 42 and the second part 44 of each core 40 (formation of cracks, for example) and the risks of breakage of the rods 48 during the demolding and unbinding and / or consolidation steps of each core 40 are reduced, or even prevented.

Claims

Demands

1. Method (100) of manufacturing a ceramic core (40) for aubc (10) of turbomachine using a device comprising a mold (51), the mold (51) comprising at least one cavity, the cavity comprising a first zone (54) intended to form a first part of the core (42) and a second zone (56) intended to form a second part (44) of the core (40), said zones (54, 56) of the footprint being separated from each other along a first direction (d1), the footprint further comprising a link channel (8) connecting the first zone (54) to second zone (56), the process (100) comprising the steps: - to place, in the mold (51), at least one rod (48) extending between the first zone (54) and second zone (56), said at least one stem (48) being intended to connect the first part (42) of the nucleus (40) to the second part (44) of the core (40) after fabrication, - inject a slip (60) into the impression, - proceed to solidify the slip (60), - cut out an injection appendage (46) formed by solidification of the slip (60) inside the connecting channel (58), - unmold the core (40) obtained by solidification of the slip (60), the core (40) comprising the first part (54) and the second part (56) connected by the stem (48), - proceed to remove a binder from the solidified slip (60) of the core (40) and / or to a consolidation of the ceramic particles of the solidified slip (60) from the core (40).

2. A method (100) according to the preceding claim, wherein the device (50) includes at least one blade (62) received in a slot of the mold (51), the blade (62) being movable in translation within a second direction (d2) transverse to the first direction (d1), the step cutting of the injection appendage (46) being carried out by translation of the blade (62) in the second direction (d2) inside the slot.

3. Method (100) according to claim 2, wherein a first rod (48) and a second rod (48) are arranged in the mold (51) in extending between the first zone (54) and the second zone (56), the first rod (48) and second rod (48) being arranged on either side and on the other side of the connecting channel (46), and spaced apart from each other in a third direction (d3) transverse to the first direction (dl), and in which a portion of the end of the blade (62) has a dimension, along the third direction (d3), which is less than the distance between the rods (48) along the third direction (d3).

4. Method (100) according to claim 2 or 3, wherein the device (51) includes heating means suitable for heating the blade (62), the blade (62) being heated prior to the cutting step the injection appendix (46).

5. Method (100) according to any one of claims 2 to 4, in which device (51) includes training means (64) for the blade (62) in the second direction (d2) and a control member training methods (64), cutting of the injection appendage (46) being obtained by translation of the blade (62) in the second direction (d2) using the training means (64).

6. Method (100) according to any one of the preceding claims, in which the cutting step of the injection appendage (46) is initiated after a predetermined solidification time.

7. Method (100) according to any one of the preceding claims, in which the mold (51) comprises a first shell (52) and a second shell (52) each delimiting a part of the imprint of the mold (51), the first shell (52) and the second shell (52) being adapted to be placed one on top of the other at a joint plane, the The demolding of the core is achieved by separating the first shell (52) and the second shell (52).

8. Method (100) according to the preceding claim, claim 2 applying, the slit being formed through the first shell (52) or the second shell (52).

9. Device (50) for carrying out the method (100) according to one any of the preceding claims.