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

Abstract

A process for manufacturing a part in SiC / SiC composite material. A process for manufacturing a part in SiC / SiC composite material comprising: - the production of a fibrous preform (20) from refractory material fibers; - a first densification step by chemical infiltration in the gas phase; - a second densification step by chemical deposition in the gas phase so as to obtain an intermediate part comprising the fibrous preform (20) densified throughout by the first matrix phase with a surface coating constituted by the second matrix phase; - 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.Figure for the summary: Fig. 2.

Description

Title of the invention: Simplified manufacturing process for a part made of ceramic matrix composite material. Technical field

[0001] The invention relates to the manufacture of parts in ceramic matrix composite material (CMC). Previous technique

[0002] One field of application of the invention is the production of parts intended to be exposed in service to high temperatures, in particular in aeronautical and space fields, in particular 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.

[0003] CMC composite materials possess good thermo-structural properties, that is to say high mechanical properties which make them suitable for forming structural parts and the ability to retain these properties at high temperatures.

[0004] 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.

[0005] In the field of aircraft engines, composite materials contribute to optimizing turbomachinery performance, particularly 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 allow for higher operating temperatures, thereby improving engine efficiency and further reducing fuel consumption.

[0006] A well-known process for manufacturing parts from CMC material comprises the following steps:

[0007] - creation of a fibrous texture from carbon or carbide fibers silicon (SiC),

[0008] - consolidation and possibly pre-densification of the fibrous texture put in form by chemical gas infiltration (CVI),

[0009] - trimming of the consolidated preform,

[0010] - injection of a SiC powder slurry into the fibrous preform ("Slurry Cast") or "Slurry Transfer Molding") and filtration of the slip to deposit the solid SiC particles into the preform by sedimentation,

[0011] - smoothing of the surface of the infiltrated preform,

[0012] - infiltration of the preform with a molten silicon-based composition of in order to form a ceramic matrix, a densification process known as the MI process ("Melt Infiltration").

[0013] Such a process is described in particular in document US 2019 / 337859.

[0014] In this case, the preform is first loaded into a first installation (furnace) for the CVI consolidation treatment. It is then unloaded from the installation and placed in a mold for the injection / filtration of the slip. The infiltrated preform is then removed from the mold and loaded into a second installation (furnace) to carry out the MI process.

[0015] Such a manufacturing process is not optimal because it increases the cycle time for manufacturing a part. In addition, the various operations involved represent a significant cost in terms of human resources (operators) and economic resources (molds, consumables, etc.).

[0016] There is, therefore, a need to manufacture parts in CMC material with a determined surface finish, and this with a rationalized manufacturing process. Description of the invention

[0017] To this end, the invention proposes a method for manufacturing a part made of ceramic matrix composite material comprising:

[0018] - the production of a fibrous preform from refractory material fibers;

[0019] - the consolidation of the fibrous preform by deposition of an interphase on the fibers of said fibrous preform;

[0020] - a first densification step comprising the deposition of a first phase of ceramic matrix at the core in the fibrous preform by chemical infiltration in the gas phase;

[0021] - 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 gas phase so as to obtain an intermediate part comprising the fibrous preform densified at its core by the first matrix phase with a surface coating consisting of the second matrix phase;

[0022] - the formation in the coating formed by chemical vapor deposition of a or several access openings to the porosity of the fibrous preform,

[0023] - a third densification step comprising the impregnation of the preform fibrous with an impregnation composition containing at least silicon so as to obtain a part in ceramic matrix composite material.

[0024] The process of the invention eliminates the slip injection / filtration step. Without this step, post-injection / filtration surface smoothing is no longer necessary. The method of the invention is, therefore, faster, simpler and more economical than the method of the prior art.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] According to another particular feature of the process of the invention, 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.

[0029] 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.

[0030] 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.

[0031] According to another particular feature of the process of the invention, 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.

[0032] The manufacturing process of a part made of CMC composite material of the invention can in particular be applied to the manufacture of a blade, a distributor, a turbine ring or a gas turbine combustion chamber. Brief description of the drawings

[0033] [Fig.1] Fig.1 is a flowchart showing successive steps of an embodiment of a process according to the invention,

[0034] [Fig.2] Fig.2 is a schematic cross-sectional view of a gas-phase chemical infiltration treatment plant used for implementing a process according to the invention.

[0035] [Fig.3] Fig.3 is a schematic view of an intermediate piece obtained after the first and second densification steps of the process according to the invention,

[0036] [Fig.4] [Fig.4] is a schematic view of the intermediate part of [Fig.3] after machining.

[0037] [Fig.5] Fig.5 is a schematic cross-sectional view of a furnace for infiltration treatment of a molten silicon-based composition used for implementing a process according to the invention,

[0038] [Fig.6] The [Fig.6] is a schematic view of a part made of ceramic matrix composite material obtained after processing in respectively the installation of [Fig.2] and the furnace of [Fig.5]. Description of the implementation methods

[0039] 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.

[0040] Fig. 1 shows successive steps of an implementation method of a process according to the invention for manufacturing a part in ceramic matrix composite material.

[0041] 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.

[0042] The fibrous structure is preferably obtained by three-dimensional weaving or by multilayer weaving.

[0043] By "three-dimensional weaving" or "3D weaving," we mean a weaving method in which at least some of the warp yarns interlock with weft yarns over several weft layers, such as an "interlock weave." "Interlock weaving" here refers to a 3D weave structure in which each warp layer interlocks with several weft layers, with all yarns in the same warp column having the same movement within the plane of the weave.

[0044] By "multilayer weave" is meant here a 3D weave with several layers of weft, the basic weave of each layer being equivalent to a classic 2D fabric weave, such as a plain weave, satin or twill weave, but with certain points of the weave which link the weft layers together.

[0045] The realization 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 of the part in composite material obtained, in a single textile operation.

[0046] 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 intended to form 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 three-dimensional woven fibrous preform used to form a complete CMC ring for use in a gas turbine.

[0047] The fibrous structure can also be achieved by stacking two-dimensional layers or folds of SiC fibers.

[0048] In step 20, the fibrous structure is shaped and held in its shape by means of a shaping tool, to obtain a fibrous preform having 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.

[0049] The preform held in its shaping tooling is consolidated by deposition of an interphase, for example of graphite, formed in a known manner by chemical infiltration in the gas phase or CVI onto the fibers of the preform, this interphase being in particular based on boron nitride (BN) (step 30). The thickness of the interphase is preferably between 10 nm and 1000 nm.

[0050] In the case of SiC fibers, a surface treatment of these prior to the formation of the interphase coating may optionally be carried out to remove the sizing and a surface layer of oxide such as silica SiO2 if they are present on the fibers.

[0051] In step 40, a first densification step of the fibrous preform is carried out, comprising 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) with a ceramic matrix precursor.

[0052] CVI treatment is a well-known process for densifying fibrous preforms to produce parts made of CMC composite material. 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 The constituent material of the matrix is ​​introduced into the reaction chamber. The temperature and pressure in the installation are set to allow the reactive gas to diffuse within the porosity of the preforms and to form a deposit of the constituent material of the matrix by decomposition of one or more constituents of the reactive gas or by reaction between several constituents, these constituents forming the precursor of the matrix.

[0053] As illustrated in [Fig. 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. The treatment installation may of course include several gas inlets.

[0054] In the example described here, the gas exhaust outlet 130 includes a gas phase depletion module having vents 131 connected to a gas exhaust line (not shown in [Fig.2]) connected to the enclosure 110 of the installation.

[0055] Still in the example described here, only one fibrous preform 20 is present in the reaction chamber 120 of the installation. However, it is possible to place several fibrous preforms 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.

[0056] The processing unit 100 also includes heating means. In the example described here, the unit 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 unit 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 processing unit 100 is heated by warming 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 an electric current in the susceptor 1110 which causes by Joule effect heating of the latter, the fibrous preform(s) present inside enclosure 110 being heated by radiation.

[0057] 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.

[0058] 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.

[0059] The first ceramic matrix phase deposited in the core of the fibrous preform may, in particular, 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, yielding SiC upon decomposition, may be used, for example. 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 may 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 (BC13).

[0060] 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.

[0061] By way of non-limiting example, 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 for a duration between 15 hours and 50 hours, by supplying the CVI treatment installation with a gaseous phase comprising at least one of the precursors mentioned above.

[0062] 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%.

[0063] If necessary, subsequent densification steps can be carried out without shaping tooling or support because the fibrous preform is self-supporting at this stage of the manufacturing process.

[0064] 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, made up of a second ceramic matrix phase. This second densification step is performed by chemical vapor deposition (CVD). As is known, the CVD deposition process is similar to that of CVI infiltration 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. However, the pressure and temperature conditions of the CVI and CVD treatments are different.Indeed, in the case of CVI infiltration into the core of the preform, the temperature and pressure in the reaction chamber are defined to promote the infiltration of the gaseous phase into the core of the preform before its decomposition to form a matrix deposit. Conversely, in the case of CVD deposition on the surface of the preform, the temperature and pressure in the reaction chamber are defined to promote the decomposition of the gaseous phase upon contact with the external surface of the preform in order to form a layer or coating anchored to said external surface of the preform.

[0065] 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 a CVI infiltration than for a CVD deposition.

[0066] The second densification step, comprising the CVD deposition of a second matrix phase onto the external surface of the fibrous preform, can be carried out in the processing installation 100 described above. The CVD deposition can, for example, 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.

[0067] By way of non-limiting example, 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 for a duration between 2 and 10 hours, by supplying the CVI treatment unit with a gas phase comprising at least one of the aforementioned precursors, namely 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 nature.Conversely, it is possible to use for CVD deposition a gaseous phase comprising 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 that of the second ceramic matrix phase constituting the surface coating of the preform.

[0068] 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.

[0069] As illustrated in [Fig.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.

[0070] The next step (step 60) of the manufacturing process of the invention consists of making 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.

[0071] In the example described here and as illustrated in [Fig.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.

[0072] 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.

[0073] During or after the making of the access opening(s) in the surface coating 21, the latter is rectified in order to give it its final thickness and the desired surface condition (step 70).

[0074] 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 "MI" (for "Melt Infiltration") process. This step can also be described as the "silicilation" step. More specifically, 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, greatly facilitating its penetration into the preform's pores by capillary action.

[0075] 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 hermetically sealed chamber 210 inside which is a crucible 204 having an internal volume containing a molten silicon-based composition 206. Hereinafter, "silicon-based composition" means a composition comprising silicon in a minimum mass content of 85%. The silicon-based composition may, in particular, comprise a silicon alloy. It may comprise boron in a mass content of between 1% and 15%. The crucible 204 may be made of a ceramic material. The furnace 200 is here 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 enclosure 210 of the furnace.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.

[0076] The furnace 200 further includes a displacement device comprising here 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. In this way, the cylinder 224 allows the crucible 204 to be moved with a vertical translational movement inside the furnace chamber 210, in particular in the direction of an intermediate piece 30. Thus, the crucible 204 is movable in vertical translation within the chamber 210. In an alternative embodiment not shown, the crucible can be fixed in the furnace, and the intermediate piece can be movable in vertical translation. According to yet another alternative embodiment not shown, the intermediate piece can be cold-loaded into the furnace with a drain present between the piece and the crucible which are fixed in position, the infiltration of the intermediate piece with the molten silicon-based composition being achieved by capillary action via the drain.

[0077] 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 mass of the intermediate part 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.

[0078] Infiltration is achieved by bringing the intermediate piece 30 into contact with the molten silicon composition 206, which infiltrates the porosity of the piece by capillary action. The contact can be direct, i.e., the intermediate piece is directly immersed in the bath of the molten silicon composition, or indirect, by bringing the intermediate piece into contact with one or more drains (not shown in [Fig. 5]) which are themselves in contact with the bath of the molten silicon composition, which is then conveyed to the piece by capillary action. In the case of direct contact, preferably at least a portion of the intermediate piece with an access opening is immersed in the bath of the molten silicon composition. As in the example illustrated in [Fig.4] and 5, the intermediate piece preferably includes a second opening in the surface coating present on a part of the piece opposite that having the first opening through which the molten silicon-based composition is infiltrated in order to facilitate capillary circulation throughout the porosity of the fibrous preform 20. .

[0079] The contact or non-contact of the intermediate piece with the molten silicon-based composition and, consequently, the control of the infiltration of the preform by the molten metal are carried out by the control of the cylinder 224. The infiltration of the intermediate piece 30 by the molten silicon-based composition 206 ends when the balance 220 measures a predetermined mass gain corresponding to the desired level of densification.

[0080] 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 [Fig.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.

[0081] The process of the invention finds advantageous application in the manufacture of composite material parts of which only one or more parts 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 of which is subjected to high thermomechanical loads because it is located in the flow path, while the root portion is exposed to lower temperatures. In this case, the first part of the porous preform corresponds to a preform portion of the blade of a turbomachine blade, and the second part of the porous preform corresponds to a root portion of the turbomachine blade. The process of the invention can, of course, be applied to the manufacture of other types of composite material parts, such as turbine ring sectors that have an annular base or tub thicker than its flanges or mounting lugs, or distributor sectors that have blade portions thinner than the inner and outer platforms.

Claims

Demands

1. A method for manufacturing a part made of a ceramic matrix composite material (40) comprising: - the creation 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 made of 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 process according to claim 2, wherein the gas-phase chemical infiltration of the first densification step is carried out with a ceramic matrix precursor selected from one of the following precursors: Methyltrichlorosilane, Monomethylsilane, Vinyltrichlorosilane, Dimethylidichlorosilane.

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 for a duration 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, Dimethylidichlorosilane.

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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