Method for manufacturing a part made of ceramic matrix composite material

Abstract

Method for manufacturing a part made of ceramic matrix composite material. The present invention relates to a method for manufacturing a part made of 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 structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powder composition comprising silicon carbide particles, the method further comprising, prior to infiltration, the removal (S50) of metallic impurities, comprising aluminum and / or iron, from the silicon carbide particles by dissolution in a solvent. 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 proposes a method for eliminating aluminum and iron metallic species from the silicon carbide powder, which have a catalytic effect on the attack of the pre-densified silicon carbide 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. Previous technique

[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 densified 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. 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 composition powdered by a molten infiltration composition comprising silicon to form a ceramic matrix in a residual porosity of the pre-densified structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powdered composition comprising silicon carbide particles, the process further comprising, prior to infiltration, the removal of metallic impurities, including aluminum and / or iron, of silicon carbide particles by dissolution in a solvent.

[0005] The inventors observed that the variability in fracture behavior was linked to uncontrolled attack of the silicon carbide in the pre-densification matrix by molten silicon 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 character. The inventors detected metallic impurities, present in standard SiC powders, in the area of ​​attacked fibers, demonstrating the role of these impurities in the degradation mechanism. The present invention proposes to decontaminate the SiC powder before infiltration by dissolving the metallic impurities in a solvent. The techniques for removing these metallic species are known per se; the invention is based on the observation that these metallic species, present on the SiC powder, play a role in the degradation mechanism.After this elimination process, composite materials with significantly improved fracture behavior are obtained.

[0006] In one embodiment, the removal of metallic impurities is achieved by bringing the solvent into contact with the silicon carbide particles present in a porosity of the pre-densified fibrous structure.

[0007] Such a characteristic corresponds to the case where the silicon carbide particles were introduced into the porosity of the fibrous structure before removal. This case advantageously avoids any risk that removal might disrupt the introduction of the powder, by making its suspension more difficult due to a modification of the surface chemistry of the particles, and also avoids any risk of re-pollution during the steps following removal.

[0008] In one embodiment, the removal of metallic impurities is carried out by solid / liquid extraction, for example from a solvent in the liquid state obtained by condensation of a vapor phase.

[0009] In particular, metallic impurities can be removed by a Soxhlet extraction technique.

[0010] This technique ensures a progressive extraction of metallic impurities and continuous regeneration of the solvent, and constitutes a "gentle" technique, unlike methods of total immersion of the structure with agitation, and therefore allows for to limit the risk of partial release of the powders due to resuspension.

[0011] In one embodiment, the solvent comprises an acid.

[0012] In particular, the solvent may comprise a strong acid.

[0013] When using a strong acid, this process also allows for partial or total deoxidation of the surface silica layer of the silicon carbide powder grains, which promotes capillary rise. The benefit of performing deoxidation at this stage is, firstly, to achieve complete deoxidation throughout the structures when they are thick (typically greater than approximately 6 mm) and, secondly, to significantly reduce the high-temperature holding time (approximately 1400°C), which is energy-intensive and potentially carries the risk of contributing to a reduction in the fiber potential.

[0014] In one embodiment, the solvent is chosen from hydrochloric acid, aqua regia, hydrofluoric acid, sulfuric acid or mixtures thereof.

[0015] In one embodiment, the solvent comprises a fluid in a supercritical state.

[0016] In particular, the solvent may comprise carbon dioxide or water in a supercritical state. The solvent in a supercritical state may be a supercritical mixture of carbon dioxide and dioxygen, or of water and hydrogen peroxide.

[0017] In one embodiment, the infiltration composition includes boron.

[0018] Such a characteristic advantageously allows for even greater protection of the silicon carbide present in the pre-densification matrix.

[0019] In one embodiment, the pre-densified fibrous structure further comprises a boron nitride interphase between a fibrous reinforcement and the pre-densification matrix.

[0020] The presence of a boron nitride interphase advantageously allows the deflection of cracks which may appear in the matrix of the composite part in operation so as to preserve the fibrous reinforcement, and to provide resistance to oxidation.

[0021] In one embodiment, the fibrous structure comprises a fibrous reinforcement formed by three-dimensional weaving or from a plurality of two-dimensional fibrous layers.

[0022] In one embodiment, the part is a turbomachine part.

[0023] 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

[0024] [Fig.1] Fig.1 is a flowchart showing a sequence of steps of an example of a process according to the invention.

[0025] [Fig. 2] [Fig. 2] schematically and partially represents an example of a device that can be implemented to remove metallic impurities. Description of embodiments

[0026] An example of a method for manufacturing a part in CMC material according to the invention will now be described in relation to the flowchart of [Fig.1] and the device illustrated in [Fig.2].

[0027] 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 10 of the composite part to be obtained. Examples of usable silicon carbide yarns may be yarns marketed under the reference "Nicalon", "Hi-Nicalon", "Hi-Nicalon-S" or Tyranno SA3 from UBE Industries. The ceramic yarns of the fibrous structure may have an oxygen content less than or equal to 1% atomic percentage. "Hi-Nicalon-S" yarns, for example, have such a characteristic. By "three-dimensional weaving" or "3D weaving", it is understood that a weaving method in which at least some of the warp yarns bind 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.

[0028] In a step S20, a chemical vapor infiltration (CVI) interphase 20 can be formed on the fibers of the fibrous structure. The fibrous structure can be positioned in a shaping tool to conform it 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 include at least one layer of pyrolytic carbon. (PyC), boron nitride (BN), silicon-doped boron nitride (BN(Si), with silicon in a mass proportion between 5% and 40%, the remainder being boron nitride), or boron-doped carbon (BC, with boron in an atomic proportion between 5% and 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 should be noted that the interphase can be formed on the fibers before the formation of the fibrous structure, i.e., before the implementation of step S10.

[0029] 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.In 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 silicon carbide pre-densification layer. This pre-densification layer can be deposited in contact with the consolidation layer. The thickness of the pre-densification layer can be greater than the thickness of the consolidation layer. The pre-densification layer significantly contributes to the mechanical performance of the composite material and provides protection against the molten silicon used during subsequent infiltration. The thickness of the pre-densification 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 layer can be formed by chemical vapor infiltration using a method known per se.In general, the pre-densification matrix can be formed by chemical vapor infiltration. According to an unillustrated variant, the consolidation layer could be omitted and the pre-densification layer could be formed directly on the interphase.

[0030] The volumetric residual porosity of the pre-densified fibrous structure obtained following step S30 may be greater than or equal to 20%, for example including between 20% and 40%, for example between 30% and 35%.

[0031] 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 may comprise silicon carbide powder, optionally with carbon powder and / or boron carbide powder. The volumetric percentage of residual porosity in the pre-densified fibrous structure filled with the powder composition may be less than or equal to 25%, for example, between 15% and 25%.

[0032] The metallic impurities, including aluminum and / or iron, are then removed from the silicon carbide particles (step S50). The example illustrated in [Fig. 2] concerns the case where this removal is carried out by a Soxhlet extraction technique, which is known per se. The figure on the left shows the assembly of a Soxhlet extractor, and the figure on the right shows this extractor in operation.

[0033] The Soxhlet extractor 1 comprises a flask 3 containing the solvent 5 for recovering metallic impurities. The neck 6 of the flask 3 cooperates with a positioning portion 8 of a body 7 of the extractor. The body 7 defines a closed treatment volume V in its lower part (located on the side of the flask 3) in which a filter paper cartridge 9 is present. The pre-densified fibrous structure 10 comprising the powdered composition is placed in this cartridge 9. In the present case, the removal is carried out after the powdered composition is introduced into the fibrous structure, but it does not depart from the scope of the invention when a loose powder of silicon carbide particles is placed in the cartridge 9 so as to remove the metallic impurities before introducing these particles into the fibrous structure.The body 7 has in its upper part (located on the side opposite the flask 3) a second positioning portion 12 connected to a condenser 17 via a connecting piece 15. The extractor 1 further includes a tube 11 connected to the body 7 which has an inlet 1a in communication with the flask 3 and an outlet 11b in communication with the condenser 17. The extractor 1 further includes a siphon tube 13, separate from the tube 11 and also connected to the body 7, which has an inlet 13a in communication with the volume V and an outlet 13b in communication with the flask 3.

[0034] During operation, the solvent 5 is brought to a boil and the solvent vapors SV rise from the flask to the condenser 17 through the tube 11. A cooling fluid (arrows F), such as water, circulates through the condenser 17, condensing the vapors SV into liquid solvent SL, which then falls back into volume V, at the level of the cartridge 9 containing the silicon carbide particles. The metallic impurities present on these particles of Silicon carbide particles are then dissolved by the liquid solvent SL. The solvent SL accumulates in the body 7 until it reaches the top of the siphon tube 13, which then causes the return of the solvent SLI containing the metallic impurities into the flask 3. The solvent 5 contained in the flask 3 thus becomes progressively enriched with metallic impurities.

[0035] The invention remains within the scope of action when metallic impurities are removed by a different method, for example, by immersion in an acid bath followed by rinsing and drying, or by dissolution in a supercritical fluid as mentioned above. If removal is carried out while the powdered composition is present in the pre-densified fibrous structure, a person skilled in the art will, of course, take care to choose the solvent and the contact time so as to avoid degradation of the fibrous reinforcement.

[0036] If desired, the silicon carbide powder can be deoxidized before infiltration by applying a temperature greater than or equal to 1350°C for a period of at least 30 minutes under vacuum or a pressure less than or equal to 100 mbar of a neutral gas.

[0037] Once the powder composition has been cleaned of metallic impurities, step S60 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 consist predominantly of silicon by mass, i.e., have a silicon mass content greater than or equal to 50%. The infiltration composition can, for example, have a silicon mass content greater than or equal to 75%.The constituent(s) present within the silicon alloy can be chosen from B, Al, Mo, Ti, Ge and mixtures thereof. When the powder composition includes carbon particles, a chemical reaction can occur between the infiltration composition and these carbon particles during infiltration, resulting in the formation of silicon carbide.

[0038] After step S60, a part made of CMC material is obtained. Such a part made of CMC material can be a static or rotating turbomachine component. Examples of turbomachine components have been mentioned above. Such a part can also be coated with an environmental or thermal barrier coating before use.

[0039] The expression "between ... and ..." should be understood as including the terminals.

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 structure, the pre-densified fibrous structure comprising a pre-densification matrix comprising silicon carbide and the powder composition comprising silicon carbide particles, the method further comprising, prior to infiltration, the removal (S50) of metallic impurities, comprising aluminum and / or iron, of silicon carbide particles by dissolution in a solvent (SL).

2. A method according to claim 1, wherein the removal (S50) of metallic impurities is carried out by contacting the solvent (SL) with the silicon carbide particles present in a porosity of the pre-densified fibrous structure (10).

3. A method according to claim 1 or 2, wherein the removal of metallic impurities is carried out by solid / liquid extraction.

4. A method according to claim 3, wherein the metallic impurities are removed by a Soxhlet extraction technique.

5. A method according to any one of claims 1 to 4, wherein the solvent (SL) comprises an acid.

6. The method according to claim 5, wherein the solvent (SL) comprises a strong acid.

7. A method according to claim 1 or 2, wherein the solvent comprises a fluid in the supercritical state.

8. A method according to any one of claims 1 to 7, wherein the infiltration composition comprises boron.

9. A method according to any one of claims 1 to 8, wherein the pre-densified fibrous structure further comprises a boron nitride interphase between a fibrous reinforcement and the pre-densification matrix.

10. A method according to any one of claims 1 to 9, wherein the fibrous structure comprises a fibrous reinforcement formed by three-dimensional weaving or from a plurality of two-dimensional fibrous layers. sional.

11. A method according to any one of claims 1 to 10, wherein the part is a turbomachine part.

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