RU2793311C2 - Method for manufacturing a part from composite material with ceramic matrix - Google Patents

Abstract

FIELD: method for manufacturing a ceramic matrix composite (CMC) part.
SUBSTANCE: invention relates to the part with at least one slot, as well as to such a CMC part capable of withstanding high temperatures, which can be used in the field of aircraft engineering, in particular in sectors of a cylindrical element gas turbine engine. According to the invention, the method comprises the following steps of creating a fibrous reinforcement: a cavity is formed in the fibrous reinforcement section, a slurry containing at least one ceramic powder and a solvent is injected, while the slurry is injected so as to impregnate the fibrous reinforcement and fill the fibrous reinforcement cavity. The obtained complex is dried, sealing is carried out by means of impregnation with liquid silicon and due to the hardening of the specified sealing material. By means of machining, at least one slot is made in the resulting rough part inside the volume corresponding to the fibrous reinforcement cavity.

EFFECT: technical result of the invention is the ability to obtain a more even surface condition during machining when cutting the final part, which provides better contact between the element inserted into the slot and this slot and allows to achieve a higher level of tightness.

18 cl, 6 dwg

Description

The field of technology to which the invention belongs

This document proposes a method for manufacturing a CMC part, that is, a ceramic matrix composite material having at least one slot, as well as such a CMC part having at least one slot.

Such a manufacturing method can be used, in particular, in the field of aircraft construction for the manufacture of parts capable of withstanding high temperatures. In particular, we can talk about sectors of the cylindrical element of a gas turbine engine, such as an aircraft turbojet engine, and, in particular, sectors of the turbine ring, although this is just an example.

State of the art

Turbines of a turbojet engine contain a ring that allows you to get an external flow path of the turbine. Classically, this ring is divided into several sectors, butted together to form a complete ring. At the same time, in order to ensure the tightness of the ring, grooves are made on the intermediate sides of each sector, and metal plates are inserted into these grooves, connecting the sectors in pairs.

Given the ultra-high temperatures in these turbines, the ring sectors are made of CMC. As for metal plates, they are usually made of an alloy based on nickel or cobalt or based on other materials that can withstand these high temperatures.

The grooves, typically having a width of 0.4 to 1 mm, are generally machined. However, this method has the disadvantage of exposing the fibers of the fibrous reinforcement present within the CMC sector, leading to corrosion and/or accelerated oxidation of the part exposed to high temperatures.

Due to the great depth of these grooves in relation to their small width, it is difficult and sometimes even impossible to apply a protective coating to their bottom by thermal spraying.

In addition, due to mechanical processing inside the fibrous reinforcement of the ring sector, the surface state of the inner walls of the grooves is rather uneven, in particular, with an arithmetic mean roughness Ra of more than 6 μm, which results in insufficient tightness between the metal plates and ring sectors.

Thus, there is a real need for a method for manufacturing a CMC part, as well as such a CMC part, which at least partially eliminates the disadvantages of the above-mentioned known method.

Disclosure of the essence of the invention

The object of the present invention is a method for manufacturing a CMC part having at least one slot, comprising the following steps, in which:

- supply fiber reinforcement,

- a cavity is formed in the area of fibrous reinforcement,

- a slurry containing at least one ceramic powder and a solvent is injected, wherein the slurry is injected in such a way as to impregnate the fibrous reinforcement and fill the cavity of the fibrous reinforcement,

- drying the resulting complex,

- sealing is carried out by impregnation with a liquid sealing material and by hardening of said sealing material,

- perform by machining at least one slot in the draft part obtained inside the volume corresponding to the cavity of the fibrous reinforcement.

Thus, within the framework of this method, the slurry is injected simultaneously into the fibrous reinforcement and into the volume of the cavity made in the fibrous reinforcement. Therefore, after drying and compacting the whole complex, a blank part is obtained having a first part formed by a fibrous reinforcement immersed in a ceramic matrix and a second part located inside the reinforcement cavity formed by a ceramic matrix and having no reinforcement.

The volume inside the fiber reinforcement cavity is thus completely free of fibers: this second part can be machined easily and stress-free without exposing the fibers of the fiber reinforcement. This reduces the risk of corrosion and/or oxidation of the part, resulting in longer life and less maintenance.

In addition, in the absence of intertwined fibers, the structure of the second part of the rough part is more uniform than the structure of the first part, which makes it possible to obtain a more even surface condition during machining when cutting the final part. This ensures better contact between the element inserted in the groove (metal plate) and the groove and allows for example a higher level of tightness.

In this document, the terms "axial", "radial", "tangential", "internal", "outer" and their derivatives are defined with respect to the main axis of the gas turbine engine; by "axial plane" is meant a plane passing through the main axis of the gas turbine engine, and by "radial plane" is meant a plane perpendicular to this main axis; finally, the terms "inlet" and "outlet" are defined with respect to the direction of air flow in a gas turbine engine.

In some embodiments, the implementation of the fibrous reinforcement is performed by weaving, preferably three-dimensional weaving. Three-dimensional weaving makes it possible, in particular, to obtain fibrous reinforcements that have complex geometries and are monoblock, which ensures a very high strength of the final part.

In some embodiments, the fiber reinforcement comprises SiC fibers, preferably at least 50% SiC fibers, and more preferably at least 95% SiC fibers. However, any type of ceramic fiber can also be used, and in particular carbon fibers.

In some embodiments, during the slurry pumping step, the slurry is pumped in such a way as to also fill the volume located on the surface of the fiber reinforcement portion in which the cavity is formed. This allows you to completely protect the side of the part where the slot is located, including along the edges of the specified slot. In particular, this provides a better seal on the surface of this section of the workpiece.

In some embodiments, the ceramic slurry powder contains SiC, preferably at least 50% SiC, and more preferably at least 95% SiC. However, any type of ceramic powder can also be used, and in particular B, B ₄ C, TiC, ZrC, BN, Si ₃ N ₄ or TiSi ₂ .

In some embodiments, the average particle diameter of the ceramic slurry powder is 0.1 µm to 10 µm, preferably 0.5 µm to 5 µm. Making a part of the green part formed solely by the ceramic matrix, without fiber reinforcement, is difficult due to the high degree of porosity remaining in this part of the green part after removal of the solvent. Thus, before its compaction, this second part of the raw part is very brittle and can easily crumble, crack and even completely separate from the first part having the fiber reinforcement, in particular if this second part is located not only inside the fiber reinforcement cavity, but also on its surface. In order to reduce the risks of the aforementioned damages, various parameters are provided to make it possible to strengthen this second part of the raw part: among them, the particle diameter of the ceramic powder can be specified. Thus, the inventors have found that the diameter values suggested above facilitate the implementation of the present method.

In some embodiments, the ceramic slurry powder particle diameter D50 is between 0.5 and 2 microns. The distribution of powder particles can be unimodal or bimodal.

In some embodiments, the d10 particle diameter of the ceramic slurry powder is greater than 0.1 µm.

In some embodiments, the d90 particle diameter of the ceramic slurry powder is less than 4 microns.

In some embodiments, the slip solvent is an aqueous solvent.

In some embodiments, the slurry contains an organic binder. This binder ensures a higher resistance of the slip and then the second part of the green part obtained after drying the slip: in particular, it makes it easier to separate the green part from the mold and then manipulate this part without damage.

In some embodiments, the implementation of the specified organic binder contains at least one of the following compounds: polyvinyl alcohol (PVA), polyvinylpyrrolidone (PvP), polyethyleneimine and polyethylene glycol (PEG). Indeed, these various compounds greatly increase the strength of the raw part.

In some embodiments, the implementation of the mass concentration of the specified organic binder in relation to the mass of the powder is from 0.5 to 10%, preferably from 1 to 5%. Such concentration values provide a high binder efficiency and, consequently, a high strength of the green part.

In some embodiments, the slurry further comprises a plasticizer and/or a dispersant. In particular, it can be a plasticizer or a binder of the PVA, PEG or PVP type. The plasticizer increases the resistance of the ceramic raw material after injection: it reduces the viscosity of the slurry and makes the raw material soft. With regard to dispersants, we can talk about bases having a pH of 8 to 12, preferably 9 to 11, such as tetraethylammonium hydroxide (TEAH), tetramethylammonium hydroxide (TMAH) or sodium hydroxide (NaOH), or electrosteric systems, for example, the polyesterimide (PEI) type. These dispersants allow particles to be held in suspension by electrostatic dispersion.

In some embodiments, during the slurry pumping step, a consumable is placed in the fibrous reinforcement tool. Such a consumable makes it possible to obtain a predetermined state of the surface in the area of its placement. Various consumables can be used, such as fabrics, elastomers and/or metal foils. The consumable may or may not be porous depending on the area of the tool.

In some embodiments, the drying step includes a lyophilization step. Such a freeze-drying step reduces the risk of cracking of the second part of the green part during the drying step. It also provides good adhesion between the first and second parts of the raw part.

In some embodiments, the drying step includes a temperature controlled evaporation step. This controlled evaporation allows for controlled solvent removal, which reduces the risk of cracking during the drying step.

In some embodiments, the drying step includes a deliquoring type drying step (dewatering step) in which the part is dried using a pressure gradient.

In some embodiments, the slope of the temperature rise curve during the controlled evaporation step is from 1 to 5°C/min.

In some embodiments, the temperature rise in the controlled evaporation step ends at a final temperature of 100 to 140°C, preferably 115 to 125°C.

In some embodiments, the temperature rise in the controlled evaporation step starts from an initial temperature of 30 to 70°C, preferably 45 to 65°C.

In some embodiments, the degree of compaction of the ceramic powder beyond the fiber reinforcement after the drying step is greater than 50%. The degree of compaction corresponds to the content of the material in relation to the volume of the part in question: in particular, it expresses the degree of porosity of the part. This degree of compaction provides sufficient strength to the second part of the raw part.

In some embodiments, the implementation of the sealing material contains Si, preferably at least 50 wt. % Si and more preferably at least 95 wt. % Si.

In some embodiments, the method further comprises the step of annealing and pre-sintering the ceramic powder after the slip injection step and before the densification step. This makes it possible to increase the strength of the raw part by obtaining connections between the particles of the ceramic powder.

In some embodiments, the annealing and presintering step is carried out at a temperature of 1200 to 1600°C, preferably 1300 to 1500°C, for 30 minutes to 2 hours, preferably 45 minutes to 1 hour 30 minutes.

In some embodiments, the annealing and pre-sintering step is carried out under an inert gas atmosphere, such as an argon atmosphere.

In some embodiments, the slot machined into the rough part is a slot. However, it is of course possible to provide any type of slot, and in particular holes, notches, shoulders, cavities, marks, etc. You can make several slots of different types in the same rough part.

In some embodiments, the machined slot in the rough part is less than 1 mm wide.

In some embodiments, the machined groove in the rough part has a depth of at least three times its width.

In some embodiments, the arithmetic mean roughness Ra of the inner walls of a slot machined in a rough part is less than 5 µm, preferably less than 2 µm. This allows the element inserted into the slot to be pressed more tightly against the wall of the slot, which provides a higher level of tightness.

In some embodiments, the machining step is performed by milling, grinding, and/or EDM.

In some embodiments, the method further comprises the step of applying a protective coating to at least one side of the end piece that does not have a slot.

In some embodiments, the machined side of the final part does not have a protective coating. Such a coating is in particular useless if the slurry has also been injected onto the surface of this side of the final reinforcement.

In some embodiments, prior to the slip injection step, the method further comprises an interfacial layer application step for coating the fiber reinforcement fibers with the interfacial layer material.

In some embodiments, the implementation step of applying the interfacial layer is carried out by a gas method.

In some embodiments, the interfacial layer material contains SiC and/or BN, preferably at least 50% SiC, and even more preferably at least 95% SiC.

In some embodiments, the method further comprises a preparation step. In particular, it may be a sandblasting step or any other step that makes it possible to locally increase the surface roughness of the part.

In some embodiments, said CMC part is an aircraft part, such as a combustion chamber or turbine part. In particular, we can talk about the sector of the turbine ring.

The subject of the present invention is also a CMC part having at least one slot and obtained using the method according to any of the previous embodiments.

Furthermore, the subject of the present invention is a turbine comprising a ring having at least two ring sectors, each of which has a groove on each of its tangential end sides, and a sealing plate inserted into the grooves of two consecutive sectors of the ring, while at least one of the ring sectors is a CMC detail according to any of the previous embodiments.

The subject of the present invention is also a gas turbine engine comprising at least one CMC part or a turbine according to any of the previous embodiments.

The above, as well as other distinctive features and advantages will be more apparent from the following detailed description of examples of the proposed method. This detailed description is presented with reference to the accompanying drawings.

Brief description of the drawings

The accompanying drawings are schematic and are primarily intended to illustrate the principles of the invention.

In these drawings, from one figure (Fig.) to another, identical elements (or parts of an element) have the same designations. In addition, elements (or parts of an element) related to different embodiments, but having a similar function, have symbols increased by 100, 200, etc. in the figures.

In FIG. 1 shows a gas turbine engine according to the present invention, a sectional view;

in fig. 2 schematically shows a sectorized turbine ring;

in fig. 3 shows a section of a ring according to the invention, in perspective view;

in fig. 4 shows the sequence of steps according to the first embodiment of the claimed method;

in fig. 5 shows the change in the view of the part during this first example of the method;

in fig. 6 shows the change in the view of the part during the implementation of the second example of the method.

Implementation of the invention

To specify the invention below with reference to the accompanying drawings are examples of the implementation of the methods. It should be noted that the invention is not limited to these examples.

In FIG. 1 shows a section along a vertical plane passing through the main axis A, showing a bypass turbojet engine 1 according to the invention. From the inlet to the outlet in the direction of the air flow, it contains a fan 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6 and a low pressure turbine 7.

In FIG. 2 shows an annulus 60 of the high pressure turbine 6 which forms the outer boundary of the air flow path within the high pressure turbine 6 . This ring 60 is divided into several substantially identical sectors 61 of CMC connected by sealing metal plates 62.

Such a sector 61 is shown in FIG. 3: it comprises a flow path wall 63, an inlet flange 64 and an outlet flange 65. The flow path wall 63, having the shape of a cylinder sector, is designed in such a way that, together with other sectors 61, it forms a cylindrical ring with axis A. The flow path wall has an internal main a side 63p which is to define an air flow path, an inlet end side 63m, an outlet end side 63v and two intermediate side sides 63i.

A groove 66 is formed in each intermediate side 63i. These grooves 66, extending axially along almost the entire length of the wall 63 of the flow path, have in this example a depth of 3 mm and a width of 0.5 mm. The inner walls of the grooves 66 have an arithmetic mean roughness Ra of less than 1.6 µm.

The plate 62, made of a nickel or cobalt base alloy, has a length substantially equal to the length of the slot 66 and a thickness slightly less than this slot so that the plate 62 can be inserted into the slot 66.

In FIG. 4 and 5 show the various steps of an exemplary embodiment of the inventive method to make such an annular sector 61 from CMC, i.e. ceramic matrix composite material. In particular, FIG. 5 is a schematic view without considering the exact shape of the part.

The method starts by weaving E1 a fibrous blank 10 which will act as the fibrous reinforcement of sector 61. Preferably, this blank 10 is weaved in accordance with a known three-dimensional weaving technique, for example with an interlock weave. In this example, the weaving of the workpiece 10 is made with silicon carbide SiC fibers.

After the preform 10 is finished, it is shaped and, in a known step E2, an interfacial layer is applied to it, for example, by a chemical vapor deposition process (also known as CVD from "Chemical Vapor Deposition"). In this example, the applied interfacial material is silicon carbide SiC. Thus, a SiC sheath is formed around the fibers of the preform 10, which makes it possible to strengthen the preform 10 and fix the shape given to it during molding. After this step E2 of applying the interfacial layer, the fibers of the preform 10 are interfacially coated, but the preform 10 is still very porous.

During the machining step E2', a groove 18 is cut in each side 19 of the workpiece 10 corresponding to the intermediate sides 63i of the end sector 61. This results in a hardened and cut workpiece 10'.

Thereafter, the hardened and cut blank 10' is placed in a mold to carry out the step E3 of injecting the ceramic slurry. In this example, the slurry contains a solvent, in this case water, a ceramic powder, in this case silicon carbide SiC, and an organic binder, in this case polyvinyl alcohol.

In this example, the concentration of SiC powder in the slip is about 20% by volume. The binder concentration is 1 wt. % relative to the weight of the SiC powder in the slip.

The mold is designed to follow the shape of the blank 10' while leaving a free volume inside the grooves 18. Thus, when the slurry is injected into the mold, it impregnates, on the one hand, the blank 10' and, on the other hand, fills the free volume inside the grooves 18 of the workpiece 10'.

A drying step E4 is then carried out to remove the slip solvent. This example is a lyophilization step (also known as "freeze-drying" in English) in which the mold is rapidly cooled to sub-zero temperatures to solidify the solvent, then gradually heated at very low pressure to achieve almost sublimation of the solvent. without affecting the surrounding materials, while the solvent in the gas phase is removed, for example, using a cold trap.

Optionally, the drying step E4 may comprise a controlled solvent evaporation step during which the chamber temperature is gradually raised from 50 to 120°C at a heating rate of 1 to 5°C/min, preferably 1°C/min.

Alternatively, the drying step E4 may comprise a deliquoring step carried out at a pressure of 50 to 100 millibars for 1-2 hours.

During this drying step E4 inside the workpiece 10', the slip ceramic particles are separated by decantation and settle on the fibers of the workpiece as the solvent is removed, thus filling the pores of the workpiece 10. In addition, inside the free volume, the ceramic particles agglomerate and bind to each other, in particular, under the action of an organic binder.

Thus, after the drying step E4, a green part 20 is obtained, having a first part 21 with reinforcement formed by the fiber blank 10, and a second part 22 inside the grooves 18, without reinforcement and consisting of agglomerated ceramic powder with a degree of compaction in excess of 50%.

The green part 20 thus obtained is then subjected to an annealing and pre-sintering step E5, which makes it possible to strengthen the bonds between the particles of the ceramic powder and consequently increase the strength of the green part 20, especially in its second part 22.

In this example, annealing takes place in an atmosphere of inert gas, such as argon, at a temperature of 1400° C. for 1 hour.

After completion of this step E5, the green part 20 is separated from the mold and moved to the sealing step E6. During this sealing step E6, a liquid sealing material, in this case silicon Si, is poured onto the green part 20: the sealing material penetrates by capillarity into the inside of the green part 20, both its first part 21 and its second part 22, and fills the residual pores of the raw part 20.

After the sealing material has cooled and solidified, a rough part 30 is obtained which no longer has or practically no pores. Similar to the green part, the rough part 30 has a first part 31 with the reinforcement formed by the fiber blank 10 and immersed in the matrix, and the second part 32, located inside the grooves 18, not having the fiber reinforcement 10 and consisting solely of the matrix.

Thereafter, during a machining step E7, preferably EDM, slots 66 can be made inside the second part 32 without affecting the fiber reinforcement 10 to obtain the end sector 61 of the ring.

Naturally, in the second part 32 of the rough part 30, other types of machining can be performed without exposing the fibers of the fibrous reinforcement 10. In addition, some sides of the sector 61 of the ring, and in particular the main inner side 63p, can be thermally coated. Preferably, the intermediate sides 63i do not have such a thermal coating.

In FIG. 6 shows a second embodiment of the proposed method. Only the differences from the first example will be shown below. In particular, the sequence of the various steps remains the same as in FIG. 3, and only the slurry pumping step E3 is carried out differently.

Thus, the method starts by weaving E1 a fiber blank 110 similar to the first example. It is subjected to the stage E2 of applying the interfacial layer similarly to the first example, then to the stage E2' of machining similarly to the first example, and a hardened and cut blank 110' is obtained with grooves 118 made in each of its sides 119.

Thereafter, the hardened and cut billet 110' is placed in a mold to carry out the ceramic slurry injection step E3. Similar to the previous example, the slip contains a solvent, in this case water, a ceramic powder, in this case silicon carbide SiC, and an organic binder, in this case polyvinyl alcohol, with the same concentration values.

However, the mold used has a shape different from the first example. Indeed, it is provided in such a way as to follow the shape of the workpiece 110', leaving a free volume not only inside the grooves 18, but also on the surface of the sides 119 of the workpiece. Thus, when the slip is injected into the mold, it impregnates the workpiece 110' and also fills the free volume remaining inside the grooves 118 and in front of the sides 119 of the workpiece 110'.

After that, similarly to the first example, the drying step E4 is carried out. Thus, after the drying step E4, a green part 120 is obtained, having a first part 121 with reinforcement formed by the fiber blank 110, and a second part 122 having no fiber reinforcement 110 and consisting of agglomerated ceramic powder with a degree of compaction in excess of 50%. The main surfaces 119 of the workpiece 110 are in this case at the interface between these first and second parts 121, 122 of the raw part 120.

The resulting green part 120 is subjected to an annealing and pre-sintering step E5 similar to the first example. After completion of this step E5, the green part 120 is separated from the mold and moved to the sealing step E6, similar to the first example.

After the sealing material has cooled and solidified, a rough part 130 is obtained which no longer has or practically no pores. Similar to the green part, the rough part 130 has a first part 131 with the reinforcement formed by the fiber blank 110 and immersed in the matrix, and the second part 132 without the fiber reinforcement 110 and consisting solely of the matrix.

In particular, since the main surfaces 119 of the blank 110 are located inside the green part 120, the seal at the level of these side surfaces 119 is complete and uniform, with no edge effect.

Thereafter, during a machining step E7, preferably spark machining, slots 166 can be made within the second portion 132 without affecting the fibrous reinforcement 110 to obtain an end sector 161 of the ring.

In this second example, the layers of non-fiber-reinforced matrix formed on the surface of the sides 119 of the blank 110 provide protection to the intermediate surfaces 163i of the final sector 161, thereby eliminating the need for a special thermal coating on them.

Although the present invention has been described with reference to specific embodiments, of course, various changes can be made to these examples without departing from the general scope of the invention defined by the claims. In particular, individual features of the various embodiments shown/described may be combined in additional embodiments. Therefore, the description and drawings are to be considered illustrative only and not restrictive.

It is also clear that all features described with reference to a method can be transposed singly or in combination to a device, and conversely, all features described with reference to a device can be transposed singly or in combination to a method.

Claims (31)

1. A method for manufacturing a part from a composite material with a ceramic matrix having at least one slot, comprising the following steps, in which: - get (E1) fibrous reinforcement (10, 110), - form (E2') cavity (18, 118) in the area of fibrous reinforcement (10, 110), - slip (E3) is injected containing at least ceramic powder and solvent, while the slip is injected so as to impregnate the fibrous reinforcement (10', 110') and fill the cavity (18, 118) of the fibrous reinforcement (10', 110 '), - dry (E4) the resulting complex, - produce a seal (E6) by impregnation with liquid silicon and due to its hardening, - perform (E7) by machining at least one slot (66) in the obtained draft part (30, 130) inside the volume corresponding to the cavity (18, 118) of the fibrous reinforcement (10, 110). 2. Method according to claim 1, wherein the fibrous reinforcement (10, 110) is carried out by three-dimensional weaving (E1). 3. The method according to claim 1 or 2, wherein during step (E3) of pumping the slurry, the slurry is pumped so as to fill also the volume located on the surface of the area (119) of the fibrous reinforcement (110') in which the cavity (118) is made . 4. The method according to any one of paragraphs. 1-3, in which the slot (66, 166) machined into the rough part (30, 130) is a slot having a width of less than 1 mm. 5. The method according to any one of paragraphs. 1-4, wherein the slot (66, 166) machined into the rough part (30, 130) is a slot having a depth of at least three times its width. 6. The method according to any one of paragraphs. 1-5, in which the arithmetic average roughness Ra of the inner walls of the slot (66, 166) made by machining in the rough part (30, 130) is less than 5 µm. 7. The method according to any one of paragraphs. 1-6, in which step (E7) of machining is carried out by milling, grinding and/or EDM. 8. The method according to any one of paragraphs. 1-7, further comprising the step of applying a protective coating to at least one side (63p, 136p) of the final part (61, 161), on which there is no slot (66, 166), while on the side (63i, 163i) of the final part (61, 161), in which the slot (66, 166) has been machined, there is no protective coating. 9. A method for manufacturing a part from a composite material with a ceramic matrix having at least one slot, comprising the following steps, in which: - get (E1) fibrous reinforcement (10, 110), - form (E2') cavity (18, 118) in the area of fibrous reinforcement (10, 110), - slip (E3) is injected containing at least ceramic powder and solvent, while the slip is injected so as to impregnate the fibrous reinforcement (10', 110') and fill the cavity (18, 118) of the fibrous reinforcement (10', 110 '), - dry (E4) the resulting complex, - produce (E5) pre-sintering at a temperature of 1200-1600°C, - sealing (E6) is carried out by impregnating with a liquid sealing material and by hardening said sealing material, - perform (E7) by machining at least one slot (66) in the obtained draft part (30, 130) inside the volume corresponding to the cavity (18, 118) of the fibrous reinforcement (10, 110). 10. Method according to claim 9, wherein the fibrous reinforcement (10, 110) is performed by three-dimensional weaving (E1). 11. The method according to claim 9 or 10, wherein during step (E3) of pumping the slurry, the slurry is pumped so as to fill also the volume located on the surface of the area (119) of the fibrous reinforcement (110') in which the cavity (118) is made . 12. The method according to any one of paragraphs. 9-11, in which the slot (66, 166) machined into the rough part (30, 130) is a slot having a width of less than 1 mm. 13. The method according to any one of paragraphs. 9-12, wherein the slot (66, 166) machined into the rough part (30, 130) is a slot having a depth of at least three times its width. 14. The method according to any one of paragraphs. 9-13, in which the arithmetic average roughness Ra of the inner walls of the slot (66, 166) made by machining in the rough part (30, 130) is less than 5 µm. 15. The method according to any one of paragraphs. 9-14, in which step (E7) of machining is carried out by milling, grinding and/or EDM. 16. The method according to any one of paragraphs. 9-15, further comprising the step of applying a protective coating to at least one side (63p, 136p) of the final part (61, 161) on which there is no slot (66, 166), while on the side (63i, 163i) of the final part (61, 161), in which the slot (66, 166) has been machined, there is no protective coating. 17. A turbine comprising a ring (60) having at least two sectors (61) of the ring, each of which has a groove (66) on each of its tangential end sides (63i), and a sealing plate (62) inserted into the grooves (66) two consecutive sectors (61) of the ring, while at least one of these sectors (61) of the ring is a part of a composite material with a ceramic matrix, obtained by the method according to one of paragraphs. 1-16. 18. A gas turbine engine containing a turbine according to claim 17.

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