Core for the production of ceramic matrix composite distributors
The core with fluidic passages addresses the issue of uneven deposition in CMC manufacturing by ensuring uniform boron nitride and silicon carbide distribution, enhancing mechanical and thermal performance.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN CERAMICS SA
- Filing Date
- 2021-11-26
- Publication Date
- 2026-04-17
AI Technical Summary
Conventional cores with solid structures in CMC manufacturing obstruct gas flow, leading to uneven boron nitride deposition and subsequent mechanical weakness, which compromises the mechanical and thermal performance of the ceramic matrix composite parts.
A core with fluidic passages along its transverse thickness allows gas circulation, ensuring homogeneous boron nitride and silicon carbide deposition, maintaining appropriate thicknesses to enhance mechanical and thermal performance.
The solution achieves uniform deposition and sufficient mechanical strength, preventing mechanical weakness and degradation, while improving thermal performance and resistance to oxidation at high temperatures.
Smart Images
Figure 00000009_0000 
Figure 00000009_0001 
Figure 00000009_0002
Abstract
Description
Title of the invention: Core for the production of a ceramic matrix composite distributor. Technical field of the invention
[0001] This document relates to ceramic matrix composite distributors and more particularly to cores for obtaining such distributors. Prior art
[0002] This document relates to the field of distributors made of ceramic matrix composite (CMC). Patent application WO2019068987A1 describes the steps of a process for obtaining parts made of CMC. The main steps of such a process are outlined below.
[0003] As illustrated in [Fig. 1], the method for manufacturing distributors comprises a first step of positioning a fibrous preform around a core 2 made of an oxidizable material, the core ensuring a three-dimensional conformation of a cavity within the fibrous preform. The core 2 is made of carbon, graphite, or another carbon-derived material. The fibrous preform is obtained by weaving warp and weft yarns in a manner well known to those skilled in the art.
[0004] The fibrous preform and the core 2 inserted in a hollow area of the fibrous preform are then placed in a shaping tool in order to achieve a three-dimensional shaping of the fibrous preform corresponding to the final shape of the distributor.
[0005] The fibrous preform is densified during a gaseous deposition step of boron nitride (BN). This step is called "Chemical Vapor Infiltration" (CVI), and several cycles are performed. The gaseous phase includes precursors such as boron trichloride (BC13) and ammonia (NH3). Boron nitride is used because it is resistant to oxidation and has good mechanical properties. This boron nitride acts as a mechanical "fuse" and has a high capacity to withstand high temperatures (1400°C). This CVI step is very important because it allows the dimensions of the CMC part to be fixed. This step will give the part its mechanical properties: the quality of the deposition during the different CVI cycles determines the mechanical strength of the final part. In the conformer, a silicon carbide (SiC) deposit is made using CH3SiCl3 and H2 gases.This silicon carbide (SiC) deposit is configured to protect the boron nitride (BN) from air. The part is removed from the former and exposed to air.
[0006] In a third step, the core 2 is removed from the part to obtain a fibrous preform having a hollow area. Then, a second deposit of silicon carbide SiC The process begins with CH3SiCl3 gas. This second silicon carbide deposit protects the part from the liquid silicon injected later. The part is then infiltrated with silicon carbide powder using a slurry designed to fill large pores. Finally, the resulting distributor receives a liquid silicon metal infiltration to further fill the material's porosity. This densification step is carried out at a temperature between 1400°C and 1450°C.
[0007] In this process, the core provides the structure and resists CVI cycles which involve high temperatures and a harsh atmosphere.
[0008] During CVI cycles, gases circulate within the part to be deposited onto the fibrous preform. However, as illustrated in [Fig. 1], the conventional 2 cores used have a solid structure: they are solid with a continuous surface and completely fill the cavity. This configuration blocks the passage of gases that do not pass through the core completely. This consequently disrupts the deposition of the BN, particularly by limiting deposition in hard-to-reach areas.
[0009] From this configuration, it follows that on all faces in contact with the core, a diffusion gradient forms from each extrados face to each intrados face of said core faces, along a transverse direction. The closer one gets to core 2, the thinner the deposited BN layer is, such that a thickness less than that required in the manufacturing specifications can be obtained. If the BN thickness is less than the specification, when the part is subjected to mechanical stresses, the BN thickness will not be sufficient to transfer the mechanical load onto the fibers. Consequently, the part will have insufficient mechanical properties that will not meet the correct specification.
[0010] This also impacts subsequent process steps. For example, during the infiltration step with silicon carbide powder via the slurry, the slurry thickness is insufficient. Consequently, the liquid silicon diffuses through the SiC layer and attacks the BN. The part then loses its mechanical properties.
[0011] The present invention aims to remedy these drawbacks in a simple, reliable and inexpensive way. Summary of the invention
[0012] The present invention relates to a core for manufacturing a blade by molding a fibrous preform around said core, the core extending along a longitudinal direction (L) between a foot and a tip and comprising a first face and a second face connected to each other at a first longitudinal edge and at a second longitudinal edge, characterized in that it comprises fluidic passages in a transverse thickness of the core, these fluidic passages being capable of allowing fluid to pass from the first face to the second face and vice versa.
[0013] It is understood that the core includes fluidic passages which open at the level of the first face and the second face.
[0014] The fluid passages at the level of the core allow the circulation of gases within the cavity to increase and ultimately to obtain a homogeneous deposit of BN and SiC on the distributor.
[0015] This consequently eliminates the gradient that was present when the core was solid, as in the prior art. Such a core improves the mechanical performance of the ceramic matrix composite part. Under these conditions, there is an appropriate amount of interphase, allowing for sufficient tensile strength. Furthermore, this prevents areas of mechanical weakness from extending and causing a drop in modulus. These positive factors are achieved thanks to a BN thickness that is appropriate, neither too thin nor too thick.
[0016] Thanks to this device, it is possible to obtain a suitable SiC thickness, that is, neither too thick nor too thin. Thus, the SiC can act as a barrier to the liquid silicon during the densification stage, preventing attack on the BN by the silicon and degradation of the mechanical performance of the ceramic matrix composite part. Furthermore, thanks to the suitable SiC thickness obtained, the part is well filled, particularly during the densification stage, which improves the thermal performance of the ceramic matrix composite part. Good resistance to oxidation and thinning is thus achieved at high temperatures.
[0017] Said fluidic passages of the core may include substantially straight orifices.
[0018] Outlets of the orifices of the core can form a unitary square pattern arrangement.
[0019] The total surface area of the outlets of the fluidic passages at the level of each of the first face and the second face can correspond to at least 5% of the surface of said face considered.
[0020] At least one of the first face and the second face may include connecting channels for at least some of the outlets of the fluidic passages.
[0021] The fluidic passages may have a polygonal shape, for example hexagonal.
[0022] The core may comprise a foam structure, said fluidic passages being formed by open cells of said foam.
[0023] This document relates to an assembly of the aforementioned type comprising: - a kernel as described above; and - a conformer surrounding the fibrous preform and the core housed in the fibrous preform in order to achieve a predetermined three-dimensional conformation of the fibrous preform.
[0024] The conformer may include walls in contact with the fibrous preform, these walls including fluidic passages connected to means for supplying fluid from the inside of the conformer.
[0025] The fluid passages at the level of the conformer also make it possible to improve the circulation of gases around the conformer and towards the fibrous preform.
[0026] The outlets of the fluidic passages of the walls of the former can be connected by junction channels. Brief description of the figures
[0027] The invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which is given by way of non-limiting reference with reference to the figures in which: [Fig.l] already described previously, is a core according to the prior art;
[0028] [Fig.2] illustrates a nucleus according to a first embodiment, this figure includes a part A showing a first face of the nucleus and a part B showing a second opposite face of the nucleus;
[0029] [Fig.3] illustrates a nucleus according to a second embodiment, this figure includes a part A showing a first face of the nucleus and a part B showing a second opposite face of the nucleus;
[0030] [Fig.4] illustrates a cross-sectional view of a core surrounded by a fibrous preform and a core;
[0031] [Fig.5] illustrates a nucleus and an associated conformer, according to the invention; Detailed description of the invention
[0032] As illustrated in [Fig.2], the present document relates to a core 2 extending along a longitudinal direction L between a foot 4 and a head 6. It comprises a first face 8 and a second face 10 opposed to each other along a transverse direction T to the longitudinal direction. As illustrated in [Fig. 4], the first face 8 of the core 2 is a face intended to come into contact with a fibrous preform 12, this first face allowing the delimitation of a first face 14 of the preform opposite that forming an extrados face 16. The second face 10 of the core is a face intended to come into contact with the fibrous preform 12, this second face 10 allowing the delimitation of a second face 18 of the preform opposite that forming an intrados face 20. The first face 8 and the second face 10 of the core are connected to each other at a first longitudinal edge 22 and at a second longitudinal edge 24.
[0033] The core 2 comprises fluid passages 26 in a transverse thickness of the core 2. These fluid passages 26 are adapted to allow fluid to pass from the first face 8 of the core 2 to the second face 10 of the core 2 and vice versa. These fluid passages 26 include substantially straight orifices 28. These orifices 28 have a diameter between 1 and 6 mm, preferably 5 mm. The total surface area of the outlets of the fluid passages 26 at each of the first face 8 and the second face 18 of the core comprises at least 5% of the surface area of said face.
[0034] These cores 2 further include connecting channels 30 at the ends of the outlets of the fluid passages 26. These connecting channels 30 are present on the surface of the first face 8 and the second face 10 of the core. The connecting channels 30 link the fluid passages 26. The outlets of the orifices 32 form a square unit pattern arrangement. Diagonals and edges of this square pattern are formed by the connecting channels 30. Each fluid passage 26 thus comprises eight connecting channels 30 extending from it. The part is homogeneous insofar as the number of fluid passages 26 and connecting channels 30 are quantitatively identical regardless of the height of the part. The surface area occupied by the fluid passages 26 is calculated to be as large as possible, limited only by the mechanical strength of the material used.
[0035] The core 2 has a gap 34 at the first longitudinal edge 22 and at the second longitudinal edge 24. This gap 34, having no fluid passage 26 or junction channel 30, follows the geometry of the core and opens downwards. The thickness of the first longitudinal edge 22 and the second longitudinal edge 24 varies as it opens towards the base 4 of the core.
[0036] According to a particular embodiment, the core 2 comprises fluidic passages 26 having a polygonal shape, preferably hexagonal. Each fluidic passage 26 is delimited by a boundary. This cell boundary defines a spacing between each fluidic passage.
[0037] According to another particular embodiment, the core 2 comprises a foam structure including open cells as fluidic passages 26. These cells include pores which communicate with each other from one face to another.
[0038] As illustrated in [Fig. 4] and 5, the core 2 is housed in a fibrous preform 12 surrounded by a conformer 36. A conformer 36 is a mold that holds the fibrous preform 12 in the desired shape. This conformer 36 is then positioned in a reactor that performs CVI cycles to deposit the BN. This conformer 36 has fluidic passages 38 on its walls in contact with the fibrous preform 12. These passages The fluid passages 38 of the former are connected to means for supplying fluid to the interior of the former 36. The former includes, on its walls connecting the fluid passages 38, connecting channels 40 through which gases flow to supply the external faces of the fibrous preform 12. The fluid passages 38 of the former have a diameter between 1 and 6 mm, preferably 5 mm. There is thus a synergy between the former 36 and the core 2 used.
[0039] The fluidic passages 26 and the junction channels 30 at the core 2 allow the circulation of gases within the cavity to be increased and a homogeneous deposit of BN and SiC slip to be obtained on the fibrous preform of the distributor.
[0040] This consequently eliminates the gradient present on a solid core of the prior art. Such a core 2 improves the mechanical performance of the ceramic matrix composite part. Under these conditions, there is an appropriate amount of interphase, allowing for sufficient tensile strength. Furthermore, this prevents areas of mechanical weakness from extending and causing a drop in modulus. These positive factors are achieved thanks to a BN thickness that is appropriate, neither too thin nor too thick.
[0041] Thanks to this device, it is possible to obtain a suitable SiC thickness, that is, neither too thick nor too thin. Thus, the SiC can act as a barrier to the liquid silicon during the densification stage, preventing attack on the BN by the silicon and degradation of the mechanical performance of the ceramic matrix composite part. Furthermore, thanks to the suitable SiC thickness obtained, the part is well filled, particularly during the densification stage, which improves the thermal performance of the ceramic matrix composite part. Good resistance to oxidation and thinning is thus achieved at high temperatures.
[0042] The homogeneity of the positioning of the fluidic passages 26 and the junction channels 30 of the core over the entire height of the part makes it possible to avoid inhomogeneity of the part.
[0043] Furthermore, in such a configuration, a contact surface between the part and the core is sufficient for the mechanical function of the part to be fulfilled.
[0044] In the direction of the leading edge and the trailing edge on the core, the forbidden bands make it possible to protect these fragile areas.
[0045] The fluid passages 38 and the junction channels 40 of the conformer also make it possible to improve the circulation of gases around the conformer and towards the fibrous preform.
Claims
Demands
1. Core (2) for manufacturing a blade by molding a fibrous preform (12) around said core (2), the core (2) extending along a longitudinal direction (L) between a foot (4) and a head (6) and comprising a first face (8) and a second face (10) connected to each other at a first longitudinal edge (22) and at a second longitudinal edge (24), characterized in that it comprises fluidic passages (26) in a transverse thickness of the core (2), these fluidic passages (26) being capable of allowing a passage of fluid from the first face (8) to the second face (10) and vice versa; the total surface area of the outlets of the fluidic passages (26) at each of the first face (8) and the second face (10) of the core (2) comprising at least 5% of the surface area of said face considered;and at least one of the first face (8) and of the second face (10) comprising connecting channels of at least some of the outlets of the fluidic passages (26).;
2. Core according to claim 1, wherein said fluidic passages (26) of the core comprise substantially straight orifices (32).
3. Core according to claim 1 or 2, wherein outlets of the orifices (32) of the core (2) form a square unit pattern arrangement.
4. Core according to any one of the preceding claims, wherein the fluidic passages (26) have a polygonal shape, for example hexagonal.
5. Core according to any one of the preceding claims, wherein the core (2) comprises a foam structure, said fluidic passages (26) being formed by open cells of said foam.
6. Assembly comprising: - a core (2) according to any one of the preceding claims; and - a conformer (36) surrounding a fibrous preform (12) and the core housed in the fibrous preform (12) in order to achieve a predetermined three-dimensional conformation of the fibrous preform (12).
7. Assembly according to claim 6, wherein the conformer (36) comprises walls in contact with the fibrous preform (12), these walls comprising fluidic passages (38) connected to means for supplying the interior of the conformer (36) with fluid.
8. Assembly according to claim 6 or claim 7, wherein the outlets of the fluidic passages (38) of the walls of the former are connected by junction channels (40).