Method for manufacturing a part made of ceramic matrix composite material

Abstract

Method for manufacturing a part made of a ceramic matrix composite material. The present invention relates to a method for manufacturing a part made of a ceramic matrix composite material, comprising: - the infiltration (S60) of a pre-densified fibrous structure comprising a powder composition by a molten infiltration composition comprising silicon in order to form a ceramic matrix in a residual porosity of the pre-densified fibrous structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powder composition comprising core-shell particles (1) comprising a core (3) of silicon carbide and a shell comprising at least one layer (5; 51; 52) of carbon or boron-doped carbon with boron in an atomic proportion of between 5% and 20%. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing a part made of ceramic matrix composite material technical field

[0001] The invention relates to the manufacture of a ceramic matrix composite (CMC) part in which the ceramic matrix is ​​formed by infiltration of a molten silicon-based composition (MI). The invention incorporates a functionalized powder composition to protect the pre-densified silicon carbide from attack by the molten silicon. The resulting composite part can be used as a hot section component of a turbomachine, particularly an aeronautical turbomachine, such as a turbine component. Prior art

[0002] Ceramic matrix composite materials (CMCs) withstand temperatures ranging from 600°C to 1400°C. Due to their superior high-temperature resistance, CMCs require less cooling. Since this cooling is traditionally obtained from the compressor, which impacts the turbomachine's efficiency, CMCs improve engine efficiency, thereby reducing fuel consumption. Furthermore, their use helps optimize turbomachine performance, notably by reducing the overall mass of the turbomachine, which further contributes to lower fuel consumption and thus a significant reduction in pollutant emissions.

[0003] CMC parts can be formed by molten infiltration. In this technique, a molten silicon composition can be introduced into the porosity of a fibrous structure pre-densified by a silicon carbide deposit and loaded with silicon carbide particles. This method makes it possible to obtain a fully dense, high-modulus Si-SiC matrix and a high linearity limit composite. The resulting composites exhibit good mechanical properties, but the inventors have observed some variability in the elongation at break, which reduces the material's damage tolerance zone. It is desirable to propose a solution to address this drawback. Description of the invention

[0004] The invention relates to a method for manufacturing a part made of ceramic matrix composite material, comprising: - the infiltration of a pre-densified fibrous structure comprising a powdered composition by a molten infiltration composition comprising silicon in order to form a ceramic matrix in a residual porosity of the pre-densified fibrous structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powder composition comprising core-shell particles comprising a silicon carbide core and a shell comprising at least one layer of carbon or boron-doped carbon with boron in an atomic proportion between 5% and 20%.

[0005] The inventors observed that the variability in fracture behavior was linked to uncontrolled attack on the silicon carbide of the pre-densification matrix by the silicon molten in the prior art solution. This phenomenon can lead to the degradation of the fibrous reinforcement and the interphase, resulting in a reduction of the composite's structural integrity. The invention addresses this drawback by functionalizing the powder composition using core-shell particles, as described above, which reduce the attack on the silicon carbide of the pre-densification matrix. The powder composition is distributed homogeneously within the pre-densified fibrous structure to provide protection throughout its entire volume and along the entire penetration path. This results in composite materials with significantly improved fracture behavior.

[0006] In one embodiment, the process further includes the manufacture of the core-shell particles, prior to infiltration, by forming the shell around the core by chemical vapor deposition in a fluidized bed.

[0007] The shell formation conditions implemented during chemical vapor deposition advantageously allow for the deoxidation of the silicon carbide core surface by reduction without significant growth in crystallite sizes, thus leading to improved wetting by the molten silicon without promoting the attack of the pre-densified silicon carbide. Following the consumption of the shell carbon, capillary rise will not be hindered by inwetting due to the prior deoxidation of the silicon carbide cores.

[0008] In one embodiment, the particle shell comprises a boron-doped carbon layer with boron in an atomic proportion between 5% and 20%.

[0009] This feature makes it possible to further protect the underlying silicon carbide and to provide protection throughout the volume of the pre-densified structure and throughout the infiltration, which further improves the fracture behavior of the resulting composite material.

[0010] In particular, the particle shell may comprise a first layer of boron-doped carbon with boron in an atomic proportion of between 5% and 20%, and a second carbon layer that may cover the first layer. One does not However, it does not fall outside the scope of the invention when the bark is a single layer with a layer of carbon or boron-doped carbon with boron in an atomic proportion between 5% and 20%.

[0011] In one embodiment, the infiltration composition includes boron.

[0012] Such a characteristic advantageously provides even more protection for the underlying silicon carbide.

[0013] In one embodiment, the particle shell has a thickness between 5 nm and 300 nm, for example between 100 nm and 150 nm.

[0014] Such a characteristic makes it possible to obtain a good compromise between effective protection of the pre-densification silicon carbide during infiltration, without penalizing the size of the particles so as not to affect their ability to be introduced into the porosity of the fibrous structure.

[0015] In one embodiment, the pre-densified fibrous structure further comprises a boron nitride interphase between a fibrous reinforcement and the pre-densification matrix.

[0016] The presence of a boron nitride interphase advantageously allows the deflection of cracks that may appear in the matrix of the composite part in operation so as to preserve the fibrous reinforcement.

[0017] In one embodiment, the fibrous structure includes a fibrous reinforcement formed by three-dimensional weaving or from a plurality of two-dimensional fibrous layers.

[0018] In one embodiment, the part is a turbomachine part.

[0019] The part may be a turbine component, for example, an aircraft engine turbine component. The part may, for example, be a turbomachine blade, a turbine ring sector, or a distributor. Brief description of the drawings

[0020] [Fig.1] Fig.1 is a flowchart showing a sequence of steps of an example of a process according to the invention.

[0021] [Fig.2] Fig.2 represents, schematically and partially, a core-shell particle usable within the framework of the invention.

[0022] [Fig.3] Fig.3 provides images obtained by transmission electron microscopy of the particles before and after bark formation.

[0023] [Fig.4] Fig.4 represents, schematically and partially, a variant of core-shell particle usable within the framework of the invention. Description of the implementation methods

[0024] An example of a method for manufacturing a part made of CMC material according to the invention will now be described in relation to the flowchart of [Fig.1].

[0025] A first step S10 of the process may consist of forming the fibrous structure by carrying out one or more textile operations, such as three-dimensional weaving. The fibrous structure may be formed from ceramic yarns, for example, silicon carbide yarns. The fibrous structure may constitute the fibrous reinforcement of the composite part to be obtained. Examples of usable silicon carbide yarns may be "Nicalon," "Hi-Nicalon," "Hi-Nicalon-S," or Tyranno SA3 yarns from UBE Industries. The ceramic yarns of the fibrous structure may have an oxygen content of 1% or less as an atomic percentage. "Hi-Nicalon-S" yarns, for example, have such a characteristic. "Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the warp yarns interlace weft yarns over several weft layers.A reversal of roles between warp and weft is possible in this text and should be considered as also covered by the claims. The fibrous structure may, for example, exhibit an interlock weave. By "interlock weave or fabric," we mean a 3D weave in which each layer of warp yarns connects several layers of weft yarns, with all yarns in the same warp column having the same movement within the plane of the weave. It is also possible to start with fibrous textures such as two-dimensional fabrics or unidirectional sheets, and to obtain the fibrous structure by draping such fibrous textures over a form. These textures may optionally be joined together, for example, by stitching or yarn implantation, to form the fibrous structure.

[0026] In a step S20, a chemical vapor infiltration (CVI) interphase can be formed on the fibers of the fibrous structure. The fibrous structure can be positioned in a shaping tool, allowing it to be molded to the shape of the part to be obtained during the interphase deposition. The thickness of the interphase can, for example, be between 10 nm and 1000 nm, or between 200 nm and 500 nm. After the interphase is formed, the fibrous structure remains porous, with only a small portion of the initial accessible porosity being filled by the interphase. The interphase can be single-layered or multi-layered.The interphase can comprise at least one layer of pyrolytic carbon (PyC), boron nitride (BN), silicon-doped boron nitride (BN(Si), with silicon in a mass proportion of 5% to 40%, the remainder being boron nitride), or boron-doped carbon (BC, with boron in an atomic proportion of 5% to 20%, the remainder being carbon). The interphase here serves to weaken the composite material by deflecting any cracks that may reach the interphase after propagating through the matrix, thus preventing or delaying fiber breakage due to such cracks. Alternatively, it can be noted that the interphase can be formed on the fibers before the structure is formed. fibrous, that is to say before implementation of step S10.

[0027] A step S30 for forming a silicon carbide deposit is then carried out. This step S30 can be divided into two phases. During the first phase, the fibrous structure is still in the forming tooling, and a silicon carbide consolidation layer is deposited on the interphase and the fibrous reinforcement. The consolidation layer can be deposited in contact with the interphase. This layer has sufficient thickness to bind the fibers adequately so that the structure retains its shape without assistance from the holding tooling. This layer provides protection to the interphase against oxidation and can be formed by chemical vapor infiltration in a manner known per se, for example, from a gaseous phase comprising methyltrichlorosilane (MTS) and hydrogen (H2). The thickness of the consolidation layer can be greater than or equal to 0.1 µm, for example, between 0.1 µm and 5 µm.During the second phase, the consolidated and shaped fibrous structure of the desired part can be removed from the tooling, and the pre-densification matrix can be formed by depositing a layer of silicon carbide. This layer can be deposited in contact with the consolidation layer. The thickness of this layer can be greater than the thickness of the consolidation layer. This silicon carbide layer significantly improves the mechanical performance of the composite material and provides protection against the molten silicon used during subsequent infiltration. The thickness of this layer can be greater than or equal to 1 µm, for example, between 1 µm and 20 µm. As with the consolidation layer, the pre-densification matrix layer can be formed by chemical vapor infiltration using a method known per se.According to an unillustrated variant, the consolidation layer could be omitted and the pre-densification matrix could be formed directly on the interphase.

[0028] The volumetric residual porosity rate of the pre-densified fibrous structure obtained following step S30 can be between 20% and 40%, for example between 30% and 35%.

[0029] The process continues by introducing a powder composition into a residual porosity of the pre-densified structure (step S40). This powder composition can be introduced into the fibrous structure by slurry-casting in a manner known per se. The powder composition is notable in that it comprises core-shell particles 1, which will now be described. Particle 1 comprises a silicon carbide core 3 and a shell formed by a layer 5, distinct from the core 3, and surrounding it. The shell 5 is made of carbon, or boron-doped carbon with boron in an atomic proportion of between 5% and 20%. The shell 5 defines an external surface Sext of particle 1. The shell 5 is here single layer. The shell 5 extends from the surface Sext to the core 3 in the illustrated example. The shell 5 completely surrounds the core 3. The particle 1 can have a size less than or equal to 5 pm, for example, less than or equal to 1 pm. The size d of the core 3 of the particles 1 can be between 0.5 pm and 4 pm. The thickness e of the shell 5 can be between 5 nm and 300 nm, for example, between 100 nm and 150 nm. The particle 1 can have a granular shape, for example, a substantially spherical or ellipsoidal shape. Figure 2 illustrates the case of a bimaterial particle 1 where the particle 1 consists essentially of a silicon carbide core 3 and a region 5, in contact with the core 3, made of carbon or boron-doped carbon. As mentioned above, particle 1 can be obtained by formation of the shell 5 on the core 3 by chemical vapor deposition in a fluidized bed.The inventors implemented the operating conditions below to manufacture such particles 1, which are provided by way of example.

[0030] A 250-gram charge of silicon carbide powder was fluidized at 400 mbar with a nitrogen flow rate of 1000 standard cubic centimeters per minute (sccm). The fluidized bed was heated to 1000°C and then exposed to a propane flow rate of 200 standard cubic centimeters per minute for 5 hours. High-resolution TEM analyses (see [Fig. 3]) show that the powder grains are initially coated with a thin, nanometric amorphous layer, presumably silica. After the treatment described above, the SiC grains are individually coated with a thin sp2 carbon deposit. The carbon is in direct contact with the SiC surface, and the amorphous layer has disappeared.

[0031] The volumetric residual porosity rate of the pre-densified fibrous structure loaded by the powder composition can be less than or equal to 25%, for example between 15% and 25%.

[0032] Fig. 2 illustrates a particle 11 with a single-layered shell 5, but alternatively a particle with a two-layered shell can be implemented, comprising for example a first layer 51 of boron-doped carbon surrounding the core 3 and a second layer 52 of carbon surrounding the first layer, as illustrated in Fig. 4.

[0033] Once the powdered composition has been introduced, step S50 is carried out, during which the residual porosity is infiltrated with a molten infiltration composition comprising at least silicon, so as to form a ceramic matrix within the porosity of the fibrous structure. The formation of this ceramic matrix can finalize the densification of the part. This infiltration step corresponds to a molten infiltration step. The infiltration composition can consist of pure molten silicon or, alternatively, be in the form of a molten alloy of silicon and one or more other constituents. The infiltration composition can The composition must be predominantly silicon by mass, meaning it must have a silicon content of 50% or more by mass. For example, the infiltration composition may have a silicon content of 75% or more by mass. The constituent(s) of the silicon alloy may be selected from B, Al, Mo, Ti, Ge, and mixtures thereof. When the powder composition includes carbon particles in addition to the core-shell particles, a chemical reaction may occur between the infiltration composition and these carbon particles during infiltration, resulting in the formation of silicon carbide. A reaction also occurs with the carbon in the shell.

[0034] After step S50, a part made of CMC material is obtained. Such a part made of CMC material can be a static or rotating turbomachine part. Examples of turbomachine parts have been mentioned above. Such a part can also be coated with an environmental or thermal barrier coating before use.

[0035] The expression "between ... and ..." should be understood as including the bounds.

Claims

Demands

1. A method for manufacturing a part of a ceramic matrix composite material, comprising: - the infiltration (S60) of a pre-densified fibrous structure comprising a powder composition by a molten infiltration composition comprising silicon in order to form a ceramic matrix in a residual porosity of the pre-densified fibrous structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powder composition comprising core-shell particles (1; 11) comprising a core (3) of silicon carbide and a shell comprising at least one layer (5; 51; 52) of boron-doped carbon with boron in an atomic proportion of between 5% and 20%.

2. A process according to claim 1, wherein the process further comprises the manufacture of the core-shell particles (1), prior to infiltration, by forming the shell around the core (3) by chemical vapor deposition in a fluidized bed.

3. A method according to claim 1 or 2, wherein the particle shell comprises a first layer (51) of boron-doped carbon with boron in an atomic proportion of between 5% and 20%, and a second layer (52) of carbon covering the first layer.

4. A method according to any one of claims 1 to 3, wherein the infiltration composition comprises boron.

5. A method according to any one of claims 1 to 4, wherein the particle shell has a thickness (e) between 5 nm and 300 nm.

6. A method according to any one of claims 1 to 5, wherein the pre-densified fibrous structure further comprises a boron nitride interphase between a fibrous reinforcement and the pre-densification matrix.

7. A method according to any one of claims 1 to 6, wherein the fibrous structure comprises a fibrous reinforcement formed by three-dimensional weaving or from a plurality of two-dimensional fibrous layers.

8. A method according to any one of claims 1 to 7, wherein the part is a turbomachine part.

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