Simplified method for manufacturing a part made of ceramic matrix composite material

Abstract

The invention relates to a method for manufacturing a part made of SiC / SiC composite material, comprising: - producing a fibrous preform (20) from fibres made of refractory material; - a first step of densification by chemical vapour infiltration; - a second step of densification by chemical vapour deposition so as to obtain an intermediate part comprising the fibrous preform (20) densified at the core by the first matrix phase and having a surface coating consisting of the second matrix phase; - forming one or more openings for access to the porosity of the fibrous preform in the coating formed by chemical vapour deposition, - a third densification step comprising impregnating the fibrous preform with an impregnation composition containing at least silicon so as to obtain a part made of ceramic matrix composite material.

Description

[0001] Description

[0002] Title of the invention: Simplified manufacturing method for a part made of ceramic matrix composite material

[0003] Technical Field

[0004] The invention relates to the manufacture of parts made of ceramic matrix composite (CMC).

[0005] Previous technique

[0006] One area of ​​application of the invention is the production of parts intended to be exposed in service to high temperatures, particularly in aeronautical and space fields, especially hot parts of aeronautical turbomachinery, it being noted that the invention can be applied in other fields, for example the field of industrial gas turbines.

[0007] CMC composite materials possess good thermostructural properties, that is, high mechanical properties which make them suitable for structural parts and the ability to retain these properties at high temperatures.

[0008] The use of CMC materials instead of metallic materials for parts exposed in service to high temperatures has therefore been recommended, especially since CMC materials have a significantly lower density than the metallic materials they replace.

[0009] In the field of aircraft engines, composite materials help optimize turbomachinery performance, notably by reducing the overall mass of the turbomachine, which contributes to lower fuel consumption and therefore a significant reduction in pollutant emissions. Furthermore, when made of CMC material, the parts can withstand higher operating temperatures, improving engine efficiency and further reducing fuel consumption. A well-known process for manufacturing parts from CMC material includes the following steps:

[0010] - creation of a fibrous texture from carbon fibers or silicon carbide (SiC),

[0011] - consolidation and possibly pre-densification of the fibrous texture shaped by chemical infiltration in gas phase (CVI),

[0012] - trimming of the consolidated preform,

[0013] - injection of a SiC powder slurry into the fibrous preform ("Slurry Cast" or "Slurry Transfer Molding" >>) and filtration of the slurry in order to deposit the solid SiC particles into the preform by sedimentation,

[0014] - smoothing of the surface of the infiltrated preform,

[0015] - infiltration of the preform with a molten silicon-based composition to form a ceramic matrix, a densification process known as the Ml process ("Melt Infiltration").

[0016] Such a process is described in particular in document US 2019 / 337859.

[0017] In this case, the preform is first loaded into a primary installation (furnace) for the CVI consolidation treatment. It is then unloaded from the installation and placed in a mold for slip injection / filtration. The infiltrated preform is then removed from the mold and loaded into a secondary installation (furnace) to implement the Ml process.

[0018] This manufacturing process is not optimal because it increases the cycle time for manufacturing a part. Furthermore, the various operations involved represent a significant cost in terms of human resources (operators) and economic resources (molds, consumables, etc.).

[0019] There is, therefore, a need to manufacture parts from CMC material with a determined surface finish, and this with a streamlined manufacturing process.

[0020] Description of the invention

[0021] To this end, the invention proposes a method for manufacturing a part in ceramic matrix composite material comprising: the production of a fibrous preform from refractory material fibers; the consolidation of the fibrous preform by depositing an interphase on the fibers of said fibrous preform; a first densification step comprising the deposition of a first phase of ceramic matrix in the core of the fibrous preform by chemical infiltration in the gas phase; a second densification step comprising the deposition of a second phase of ceramic matrix on the surface of the fibrous preform by chemical deposition in the gas phase so as to obtain an intermediate part comprising the fibrous preform densified in the core by the first phase of matrix with a surface coating constituted by the second phase of matrix;the formation in the coating formed by chemical vapor deposition of one or more access openings to the porosity of the fibrous preform, a third densification step comprising the impregnation of the fibrous preform with an impregnation composition containing at least silicon so as to obtain a part in ceramic matrix composite material.;

[0022] The process of the invention eliminates the need for the slip injection / filtration step. Without this step, post-injection / filtration surface smoothing is no longer necessary. The process of the invention is therefore faster, simpler, and more economical than the prior art process.

[0023] Furthermore, the process of the invention makes it possible to manufacture CMC parts which have a free silicon content similar to that obtained with prior art manufacturing processes.

[0024] According to a particular feature of the process of the invention, the chemical infiltration in the gas phase of the first densification step is carried out at a temperature between 900°C and 1000°C, with a pressure between 50 millibars and 100 millibars and over a period of between 15 hours and 50 hours.

[0025] According to another particular feature of the process of the invention, the gas-phase chemical infiltration of the first densification step is carried out with a ceramic matrix precursor chosen from one of the following precursors: Methyltrichlorosilane, MonomethylSilane, VinylTriChlorosilane and dimethyldichlorosilane.

[0026] According to another particular feature of the process of the invention, the gas-phase chemical deposition of the second densification stage is carried out at a temperature between 1200°C and 1400°C, with a pressure between 300 millibars and 400 millibars and over a period of between 2 hours and 10 hours.

[0027] According to another particular feature of the process of the invention, the gas-phase chemical deposition of the second densification step is carried out with a ceramic matrix precursor chosen from one of the following precursors: Methyltrichlorosilane, MonomethylSilane, VinylTriChlorosilane and dimethyldichlorosilane.

[0028] According to another particular feature of the process of the invention, the fibrous preform is produced by three-dimensional weaving between a plurality of warp yarn layers and a plurality of weft yarn layers.

[0029] According to another particular feature of the process of the invention, the warp yarns of the plurality of layers of warp yarns and the weft yarns of the plurality of layers of weft yarns are made of silicon carbide fibers.

[0030] The manufacturing process for a part made of CMC composite material of the invention can be applied in particular to the manufacture of a blade, a distributor, a turbine ring or a gas turbine combustion chamber.

[0031] Brief description of the drawings

[0032] [Fig. 1] Figure 1 is a flowchart showing successive steps of an embodiment of a process according to the invention,

[0033] [Fig. 2] Figure 2 is a schematic cross-sectional view of a gas-phase chemical infiltration treatment plant used for implementing a process according to the invention,

[0034] [Fig. 3] Figure 3 is a schematic view of an intermediate part obtained after the first and second densification steps of the process according to the invention, [Fig. 4] Figure 4 is a schematic view of the intermediate part of Figure 3 after machining,

[0035] [Fig. 5] Figure 5 is a schematic cross-sectional view of a molten silicon-based composition infiltration treatment furnace used to implement a process according to the invention,

[0036] [Fig. 6] Figure 6 is a schematic view of a ceramic matrix composite material part obtained after processing in the installation of Figure 2 and the furnace of Figure 5 respectively.

[0037] Description of the implementation methods

[0038] The invention applies generally to the manufacture of parts in carbide-based ceramic matrix composite (CMC) material such as SiC / SiC, SiC / SiBC or SiC / SiC-SiBC material.

[0039] Figure 1 shows successive steps of an implementation method of a process according to the invention for manufacturing a part in ceramic matrix composite material.

[0040] In step 10, a fibrous structure intended to form the fibrous reinforcement is made from refractory fibers, here high-performance silicon carbide (SiC) fibers such as the fibers supplied by the Japanese company Nippon Carbon under the reference "Hi-Nicalon" or, preferably, under the reference "Hi-Nicalon Type-S" having a high elastic elongation limit.

[0041] The fibrous structure is preferably obtained by three-dimensional weaving or by multi-layer weaving.

[0042] "Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the warp threads interlock with weft threads across multiple weft layers, such as in an "interlock weave." An "interlock weave" is a 3D weave structure where each warp layer interlocks with multiple weft layers, with all threads in the same warp column having the same movement within the plane of the weave.

[0043] By "multilayer weaving" we mean here a 3D weave with several layers of weft where the basic weave of each layer is equivalent to a classic 2D fabric weave, such as a plain weave, satin or twill weave, but with certain points of the weave that link the weft layers together.

[0044] The creation of the fibrous structure by 3D or multilayer weaving makes it possible to obtain a bond between the layers, thus having good mechanical strength of the fibrous structure and the part made of composite material obtained, in a single textile operation.

[0045] The fibrous structure can be produced in a known manner using a Jacquard-type loom on which a bundle of warp yarns is arranged in a plurality of layers, the warp yarns being bonded by layers of weft yarns also arranged in a plurality of layers. A detailed example of the production of a fibrous preform for forming the fibrous reinforcement of an aircraft engine blade from a 3D woven fibrous blank is described in detail in US patents 7,101,154, 7,241,112, and WO 2010 / 061140. US patent 2010 / 111678 discloses the production of a 3D woven fibrous preform used to form a complete CMC ring for use in a gas turbine.

[0046] The fibrous structure can also be achieved by stacking two-dimensional layers or folds of SiC fibers.

[0047] In step 20, the fibrous structure is shaped and held in its form using a shaping tool to obtain a fibrous preform with a shape close to that of the part to be manufactured. Examples of shaping fibrous preforms from a fibrous structure can be found, in particular, in US patent application 2011 / 0293828.

[0048] The preform, held in its forming tool, is consolidated by deposition of an interphase, for example graphite, formed in a known manner by chemical infiltration in the gas phase or CVI onto the fibers of the preform, this interphase being notably based on boron nitride (BN) (step 30). The thickness of the interphase is preferably between 10 nm and 1000 nm.

[0049] In the case of SiC fibers, a surface treatment prior to the formation of the interphase coating may be performed to remove sizing and a surface layer of oxide, such as silica (SiO2), if present on the fibers. In step 40, a first densification step of the fibrous preform is carried out, involving the deposition of a first ceramic matrix phase within the core of the fibrous preform. This first densification step is performed by chemical vapor infiltration (CVI), also known as gas-phase chemical infiltration, using a ceramic matrix precursor.

[0050] CVI treatment is a well-known process for densifying fibrous preforms to produce CMC composite parts. The preform(s) to be densified are placed in a reaction chamber of a processing plant where they are heated. A reactive gas containing one or more gaseous precursors of the matrix material is introduced into the reaction chamber. The temperature and pressure in the plant are adjusted to allow the reactive gas to diffuse within the porosity of the preforms and form a deposit of the matrix material through the decomposition of one or more components of the reactive gas or through reactions between several components, these components forming the matrix precursor.

[0051] As illustrated in Figure 2, a fibrous preform 20 produced as described above is placed in a processing unit or furnace 100 delimited by an enclosure 110 comprising a cylindrical side wall 111, a bottom wall 112, and a top wall 113. The processing unit 100 includes a gas inlet 101 located at one end of the unit, a preheating chamber 150, a reaction chamber 120, and a gas outlet 130. The gas inlet 101 includes a port 102 connected to a reactive gas line 140. The preheating chamber 150 includes several multi-perforated trays 151, 152, and 153 and is located between the gas inlet 101 and one end 121 of the reaction chamber 120. The gas outlet 130 is located at a second end 122. of the installation opposite the first end.

[0052] The treatment facility may of course include several gas inlets.

[0053] In the example described here, the gas vent outlet 130 includes a gas phase depletion module with vents 131 connected to a gas vent line (not shown in Figure 2) connected to the enclosure 110 of the installation. Also in this example, only one fibrous preform 20 is present in the reaction chamber 120 of the installation. However, it is known that several fibrous preforms can be placed in the reaction chamber. In this case, a load of several preforms is prepared in advance and placed in the reaction chamber of the installation.

[0054] The treatment plant 100 also includes heating means. In the example described here, the plant is heated by induction. More specifically, the cylindrical side wall 111 of the enclosure 110 includes an armature, or susceptor 1110, for example made of graphite, which is coupled to an inductor 1112 located outside the plant and consisting of at least one induction coil. An insulator 1111 is interposed between the inductor 1112 and the susceptor 1110. As is well known, the heating of the treatment plant 100 is achieved by heating the susceptor 1110 when the inductor 1112 is supplied with an alternating voltage. For this purpose, the inductor coil(s) are connected to an alternating voltage generator (not shown).The magnetic field created by the inductor 1112 induces in the susceptor 1110 an electric current which causes by Joule effect heating of the latter, the fibrous preform(s) present inside the enclosure 110 being heated by radiation.

[0055] The heating of the treatment installation 100 can be ensured by other means such as electric heating means consisting for example of free heating resistors (behind the graphite susceptor) or embedded in the side wall of the enclosure.

[0056] A gas stream 11, containing a gaseous ceramic precursor, in particular a carbide that yields a ceramic material by decomposition, is admitted into the reaction chamber 120 through the reactive gas line 140 and the injection port 102. The gas stream 11 is preheated during its circulation in the preheating chamber 150 before its introduction into the reaction chamber 120. The gas stream 11 flows from the preheating chamber 110 to the gas outlet 130. During its passage through the reaction chamber 120, the gas stream 11 penetrates the internal porosity of the fibrous preform 20, which is accessible (i.e., open) to the surface 21a of the fibrous preform 20. The gas stream 11 thus diffuses to the core of the preform, where it decomposes to form the first matrix phase. The by-products 12 resulting from the decomposition of the gas stream 10 are discharged through the gas outlet 130.The CVI treatment temperature imposed in the reaction chamber 120 is maintained for a determined duration corresponding to the level of CVI densification that is to be achieved in the fibrous preform 20, this duration being generally calculated according to the deposition kinetics and a target porosity rate.

[0057] The first ceramic matrix phase deposited within the fibrous preform can correspond to a silicon carbide (SiC) matrix, a Si-BC ternary system (SiBC), or a combination of the two (SiC / SiBC). For the deposition of a SiC matrix phase by CVI, monomethylsilane (MMS), methyltrichlorosilane (MTS), vinyltrichlorosilane, or dimethyldichlorosilane, which yields SiC upon decomposition, can be used. For the deposition of a SiBC phase by CVI, the gaseous phase consists of a mixture of precursors of the elements Si, B, and C, to which a reducing element such as hydrogen (H2) is added. The carbon and silicon elements can be generated by precursors belonging respectively to the hydrocarbon and silane or chlorosilane families. The boron element is generated by a borane or a halide, such as boron trichloride (BCl3).

[0058] This first densification step is carried out under CVI conditions allowing the fibrous preform to be densified at its core, namely by depositing a first matrix phase in the internal porosity of the preform.

[0059] As a non-limiting example, the gas-phase chemical infiltration of the first densification stage is carried out at a temperature between 900°C and 1000°C, with a pressure between 50 millibars and 100 millibars and over a period of between 15 hours and 50 hours, by supplying the CVI treatment plant with a gas phase comprising at least one of the precursors mentioned above.

[0060] The duration of the chemical infiltration in the gas phase is determined so as to reduce the core porosity rate of the fibrous preform to a value between 15% and 25% and more preferably to a value of about 20%.

[0061] If necessary, subsequent densification steps can be performed without shaping tools or supports, as the fibrous preform is self-supporting at this stage of the manufacturing process. According to the invention, a second densification step of the preform (step 50) is then carried out, consisting of forming a coating ("seal-coat") on the external surface of the fibrous preform, composed of a second ceramic matrix phase. This second densification step is performed by chemical vapor deposition (CVD). As is known, CVD deposition is similar to CVI deposition in that, in both cases, the matrix is ​​deposited by decomposition of one or more components of the reactive gas or by reaction between several components, these components forming the matrix precursor.In contrast, the pressure and temperature conditions for CVI and CVD treatments differ. In CVI infiltration into the core of the preform, the temperature and pressure in the reaction chamber are set to promote the infiltration of the gaseous phase into the preform's core before its decomposition to form a matrix deposit. Conversely, in CVD deposition on the preform's surface, the temperature and pressure in the reaction chamber are set to promote the decomposition of the gaseous phase upon contact with the preform's external surface, thus forming a layer or coating bonded to that external surface.

[0062] In other words, for the same gaseous phase, the temperature and pressure conditions are defined differently in order to obtain a slower deposition kinetics for CVI infiltration than for CVD deposition.

[0063] The second densification step, which involves CVD deposition of a second matrix phase onto the external surface of the fibrous preform, can be carried out in the processing plant 100 described previously. For example, CVD deposition can advantageously be performed consecutively with the CVI infiltration of the first densification step, thus avoiding any handling of the preform during these two steps and consequently reducing manufacturing time and cost.

[0064] By way of non-limiting example, the gas-phase chemical deposition of the second densification stage is carried out at a temperature between 1200°C and 1400°C, with a pressure between 300 millibars and 400 millibars, and for a duration of between 2 and 10 hours. This is achieved by supplying the CVI treatment system with a gas phase containing at least one of the aforementioned precursors: monomethylsilane (MMS), methyltrichlorosilane (MTS), vinyltrichlorosilane, or dimethyldichlorosilane, which yields SiC by decomposition. The ceramic precursor(s) present in the gas phase may be identical to those present in the gas phase used for CVI infiltration. In this case, the first and second ceramic matrix phases are of the same type.Conversely, it is possible to use a gaseous phase for CVD deposition containing ceramic matrix precursors different from those present in the gaseous phase used for CVI infiltration. In this case, the preform is densified throughout with a first ceramic matrix phase of a different nature than the second ceramic matrix phase that constitutes the surface coating of the preform.

[0065] The duration of the CVD deposition is determined so as to form a ceramic coating on the surface of the fibrous preform having a thickness of at least 50.

[0066] As illustrated in Figure 3, an intermediate part 30 is obtained comprising the fibrous preform 20 densified throughout by the first matrix phase with a surface coating 21 constituted by the second matrix phase.

[0067] The next step (step 60) of the manufacturing process of the invention consists of creating one or more openings in the surface coating 21 in order to locally reopen the internal porosity of the fibrous preform 20 and allow access to the porosity of the preform by the molten silicon during the third densification step. In other words, one or more portions of the surface coating 21 are removed to expose the external surface 20a of the preform 20.

[0068] In the example described here and as illustrated in Figure 4, the surface coating 21 is removed at the lower and upper ends of the intermediate piece 30 so as to locally expose the external surface 20a of the fibrous preform 20.

[0069] The formation of one or more access openings to the porosity of the fibrous preform in the surface coating 21 can be achieved by machining during a trimming or deburring operation of the preform.

[0070] During or after the creation of the access opening(s) in the surface coating 21, the latter is rectified to achieve its final thickness and the desired surface finish (step 70). In step 80, the third densification step of the fibrous preform is carried out by impregnating it with a molten silicon or silicon-based composition, corresponding to the well-known "Ml" (for "Melt Infiltration") process. This step can also be described as the "silicidation" step. More precisely, the preform is heated while in contact with a source of molten metallic silicon or a molten silicon alloy. The molten silicon readily wets the ceramic material(s) present in the preform, which greatly facilitates its penetration into the pores of the preform by capillary action.

[0071] Figure 5 shows a cross-sectional view of a furnace 200 that can be used to infiltrate the intermediate piece 30 with a molten silicon-based composition. The furnace 200 comprises a sealed chamber 210 inside which is a crucible 204 having an internal volume containing a molten silicon-based composition 206. Here, "silicon-based composition" is understood to mean a composition comprising silicon in a minimum mass content of 85%. The silicon-based composition may, in particular, include a silicon alloy. It may include boron in a mass content of between 1% and 15%. The crucible 204 may be made of a ceramic material. The furnace 200 is equipped with an induction heating system 240 comprising an induction coil 242 and a susceptor 244, which are arranged around the crucible 204 and the second part 22 of the porous preform 20 in the furnace chamber 210.The heating system further includes, as is known, a high-frequency generator 236 connected to the coil 242 so as to generate a variable magnetic field using the coil. The susceptor 244 can, for example, be a graphite cylinder. The furnace 200 can also be equipped with a vacuum pump 238 in fluidic communication with the interior of the chamber 210, so as to achieve vacuum infiltration. It should be noted that a different type of furnace than the one illustrated can be used; in particular, the furnace can include a resistive heating system instead of an inductive system, which could, for example, use graphite bars that alternately heat the load, here the intermediate part 30, by radiation. The furnace 200 includes a device for measuring the mass of the intermediate part 30, corresponding here to a balance 220 of the spring type, from which the intermediate part 30 is suspended by means of the interface rod 221.The furnace 200 further includes a displacement device comprising, in this case, a cylinder 224 having a rod 226 on which the crucible 204 is mounted. In this example, the cylinder 224 is located outside the furnace chamber 210, below the chamber 210. Thus, the cylinder 224 allows the crucible 204 to be moved vertically within the furnace chamber 210, specifically towards the intermediate piece 30. Therefore, the crucible 204 is mobile in vertical translation within the chamber 210. In a variant not shown, the crucible can be fixed within the furnace, and the intermediate piece can be mobile in vertical translation.According to yet another variant not illustrated, the intermediate piece can be cold-loaded into the furnace with a drain present between the piece and the crucible which are here fixed in position, the infiltration of the intermediate piece with the molten silicon-based composition being achieved by capillary action via the drain.

[0072] In the illustrated example, the furnace 200 also includes a control system 228 for the relative position between the preform and the crucible, which is configured to control the cylinder 224 according to the evolution of the intermediate part mass 30 as measured by the scale 220. The control system 228 can receive electrical signals as input from the scale 220, and send control signals as output to the cylinder 224.

[0073] Infiltration is achieved by bringing the intermediate part 30 into contact with the molten silicon composition 206, which infiltrates the part's porosity by capillary action. Contact can be direct, meaning the intermediate part is directly immersed in the molten silicon composition bath, or indirect, by placing the intermediate part in contact with one or more drains (not shown in Figure 5) which are themselves in contact with the molten silicon composition bath, which is then conveyed to the part by capillary action. In the case of direct contact, preferably at least a portion of the intermediate part with an access opening is immersed in the molten silicon composition bath.As in the example illustrated in Figures 4 and 5, the intermediate piece preferably includes a second opening in the surface coating located on a portion of the piece opposite the portion containing the first opening. The molten silicon-based composition is infiltrated through this opening to facilitate capillary circulation throughout the porosity of the fibrous preform 20. Contact between the intermediate piece and the molten silicon-based composition, and consequently the control of the infiltration of the preform by the molten metal, is achieved by controlling the actuator 224. The infiltration of the intermediate piece 30 by the molten silicon-based composition 206 is complete when the scale 220 measures a predetermined mass gain corresponding to the desired level of densification.

[0074] After infiltration of the intermediate piece 30 with the molten silicon-based composition, a piece 40 made of composite material is obtained, as illustrated in Figure 6, comprising a CMC core 41 formed by the fibrous preform 20 (fibrous reinforcement of the piece) densified by the first matrix phase and the silicon-based composition, the core 41 being provided with a surface coating 42 corresponding to the second matrix phase.

[0075] The process of the invention finds advantageous application in the manufacture of composite material parts, only one or more of which are intended to be subjected to high temperatures, typically exceeding 1300°C, as is the case, for example, with a turbomachine turbine blade. The blade portion is subjected to high thermomechanical loads because it is located in the turbine runner, while the root portion is exposed to lower temperatures. In this case, the first part of the porous preform corresponds to a portion of the blade preform of a turbomachine turbine, and the second part of the porous preform corresponds to a portion of the root of the turbomachine turbine blade.The process of the invention can of course be applied to the manufacture of other types of parts in composite material such as turbine ring sectors which have an annular base or tub thicker than its flanges or fixing lugs or distributor sectors which have blade portions thinner than the internal and external platforms.

Claims

Demands

1. A method for manufacturing a part made of ceramic matrix composite material (40) comprising: the production of a fibrous preform (20) from refractory material fibers; the consolidation of the fibrous preform (20) by depositing an interphase on the fibers of said fibrous preform; a first densification step comprising the deposition of a first phase of ceramic matrix in the core of the fibrous preform by chemical infiltration in the gas phase; a second densification step comprising the deposition of a second phase of ceramic matrix on the surface of the fibrous preform by chemical deposition in the gas phase so as to obtain an intermediate part (30) comprising the fibrous preform (20) densified in the core by the first matrix phase with a surface coating (21) constituted by the second matrix phase;the formation in the coating (21) formed by chemical vapor deposition of one or more access openings to the porosity of the fibrous preform (20), a third densification step comprising the impregnation of the fibrous preform with an impregnation composition (206) containing at least silicon so as to obtain a part in ceramic matrix composite material.;

2. A process according to claim 1, wherein the gas-phase chemical infiltration of the first densification step is carried out at a temperature between 900°C and 1000°C, with a pressure between 50 millibars and 100 millibars and over a period of between 15 hours and 50 hours.

3. A method according to claim 2, wherein the gas-phase chemical infiltration of the first densification step is carried out with a ceramic matrix precursor chosen from one of the following precursors: Methyltrichlorosilane, MonomethylSilane, VinylTriChlorosilane, dimethyldichlorosilane.

4. A method according to any one of claims 1 to 3, wherein the gas-phase chemical deposition of the second densification step is carried out at a temperature between 1200°C and 1400°C, with a pressure between 300 millibars and 400 millibars and over a period of between 2 hours and 10 hours.

5. The process according to claim 4, in the gas-phase chemical deposition of the second densification step is carried out with a ceramic matrix precursor chosen from one of the following precursors: Methyltrichlorosilane, MonomethylSilane, VinylTriChlorosilane, dimethyldichlorosilane.

6. A method according to any one of claims 1 to 5, wherein the fibrous preform (20) is produced by three-dimensional weaving between a plurality of warp yarn layers and a plurality of weft yarn layers.

7. A method according to claim 6, wherein the warp yarns of the plurality of warp yarn layers and the weft yarns of the plurality of weft yarn layers are made of silicon carbide fibers.

8. Application of the method according to any one of claims 1 to 7 to the manufacture of a blade, distributor, turbine ring or gas turbine combustion chamber.

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