Permeation of fibrous structures comprising liquid silicon reactive layers

Abstract

The invention relates to a method for manufacturing a part made of a ceramic matrix composite material, said method comprising:-infiltrating a pre-densified fibrous structure (10) with a molten infiltrating composition comprising silicon, thereby forming a ceramic matrix in the residual pores of the pre-densified fibrous structure, said pre-densified fibrous structure comprising a pre-densified matrix, the invention relates to a pre-densified substrate comprising a first layer of silicon carbide (13), a reactive layer (14) comprising a reactive material comprising carbon and capable of reacting with silicon in an infiltrating composition, the reactive layer covering the first layer, and a molten silicon wetting layer (15) made of silicon carbide and covering the reactive layer.

Description

Field of the Invention

[0001] The present invention relates to a method for manufacturing a component made of a ceramic matrix composite (CMC), wherein the ceramic matrix is formed by infiltration of a silicon-based composition in a molten state ("Melt-Infiltration"; "MI"). The composite component thus obtained can be used as a hot structural component of a turbine (in particular an aero turbine), such as a turbine component. Background Art

[0002] Ceramic matrix composites can withstand temperatures from 600°C to 1400°C. Since CMCs have higher heat resistance, less cooling is required. Since this cooling traditionally comes from the compressor exhaust, which affects the efficiency of the turbine, CMC materials can improve engine efficiency and thus reduce fuel consumption. In addition, the use of CMCs helps to optimize the performance of the turbine, in particular by reducing the total weight of the turbine, thereby further reducing fuel consumption and significantly reducing pollutant emissions.

[0003] CMC components can be formed by melt infiltration. In this technique, a molten silicon composition can be introduced into the pores of a fiber structure that has been pre-densified by silicon carbide deposits and filled with silicon carbide particles. This method produces a composite material with a fully dense high-modulus Si-SiC matrix and a high linear limit. The resulting composite material has good mechanical properties, but the inventors have observed a certain variability in the elongation at break, which reduces the damage tolerance zone of the material. It is desirable to propose a solution to overcome this drawback. Summary of the Invention

[0004] The present invention precisely meets this need.

[0005] To this end, the present invention proposes a method for manufacturing a component made of a ceramic matrix composite, the method comprising:

[0006] - infiltrating a pre-densified fiber structure with a silicon-containing melt infiltration composition to form a ceramic matrix in the residual pores of the pre-densified fiber structure, the pre-densified fiber structure comprising a pre-densified matrix, the pre-densified matrix comprising a first silicon carbide layer, a reactive layer, and a molten silicon wetting layer, the reactive layer comprising a reactive material containing carbon and capable of reacting with silicon in the infiltration composition, the reactive layer covering the first layer, and the molten silicon wetting layer being made of silicon carbide or carbon and covering the reactive layer.

[0007] In the present application, the term "wetting" should be understood as the physical wetting between a surface and a liquid in the ordinary sense, where the surface refers to the surface of the wetting layer and the liquid refers to the infiltration composition. Wettability can be measured by the contact angle defined commonly, that is, by the tangent of the liquid at the air / liquid / surface interface. The smaller the contact angle, the better the wettability.

[0008] If the contact angle is less than 50°, the layer is said to have "wettability".

[0009] For example, the contact angle used to quantify wettability can be measured by the sessile drop method, the pendant drop method using a goniometer, the Wilhelmy method, or the capillary rise method.

[0010] In the method of the present invention, the special composition of each layer of the pre-densified matrix makes it possible to solve this technical problem.

[0011] This is because liquid silicon first reacts with the molten silicon wetting layer and penetrates through this wetting layer to reach the reactive layer.

[0012] Once reaching the reactive layer, liquid silicon preferentially reacts with this layer, so it will not infiltrate into the first silicon carbide layer.

[0013] Starting from the reactive layer, the molten silicon flow is diverted away from the first layer and the bottom fibers, thus protecting the material.

[0014] The advancing direction of the diverted silicon ensures that the infiltrated liquid silicon does not damage the pre-densified fiber structure as it damages the fiber structures of the prior art. The resulting composite component has less performance variability.

[0015] In one embodiment, the reactive material can be selected from pyrolytic carbon or boron-doped carbon-carbon, such as boron-doped carbon pyrolytic carbon.

[0016] These materials are preferred materials of the present invention because they are easy to deposit by the chemical vapor infiltration process. Therefore, if the rest of the pre-densification of the fiber structure is carried out by the chemical vapor infiltration process, they are good alternative reactive materials.

[0017] In one embodiment, the thickness of the molten silicon wetting layer is greater than or equal to 0.2 μm, for example, 0.2 μm to 10.0 μm, or even 1.0 μm to 10.0 μm.

[0018] In one embodiment, the molten silicon wetting layer has a columnar microstructure.

[0019] This embodiment can be achieved when pre-densifying the fiber structure by chemical vapor infiltration.

[0020] Then, the columnar microstructures are oriented such that the grain boundaries are along a direction transverse to the fiber surface. Since the liquid silicon needs to penetrate between the columns, the columnar microstructures can limit the liquid silicon reaching the reactive material, thus providing good protection even when the reactive material layer is thin.

[0021] Then, the reactive layer changes the erosion direction of the molten silicon and prevents it from continuing to diffuse towards the fibers.

[0022] In one embodiment, the thickness of the reactive layer can be less than or equal to 1000 nm.

[0023] The smallest possible reactive layer ensures that the reactive layer does not affect the mechanical properties of the fiber structure.

[0024] In one embodiment, the thickness of the reactive layer can be greater than or equal to 20 nm.

[0025] A thick enough reactive layer ensures that the liquid silicon cannot pass through the reactive layer during the impregnation process.

[0026] In one embodiment, the thickness of the reactive layer is from 20 nm to 1000 nm, and even from 200 nm to 500 nm.

[0027] This reactive layer thickness represents an optimum value between the above two effects.

[0028] In one embodiment, the ratio of the thickness of the molten silicon wetting layer to the thickness of the first silicon carbide layer is from 40 / 60 to 10 / 90.

[0029] This ratio fixes the position of the reactive layer in the pre-consolidated matrix.

[0030] The ratio between the above values ensures that the thickness of the first silicon carbide layer is sufficient for the pre-consolidated fiber structure to have the desired properties. This ratio also ensures that the reactive layer is far enough from the outer surface of the pre-consolidated matrix (the surface farthest from the fibers) such that the molten silicon wetting layer prevents the liquid silicon from directly reacting with the reactive layer, which reaction is not desired.

[0031] The single reactive layer of the present invention has just been described.

[0032] In other embodiments, in addition to the molten silicon wetting layer, the pre-consolidated matrix can further include one to eight additional protective structures, each additional protective structure including an additional reactive layer and an additional molten silicon wetting layer covering the additional reactive layer, and the additional reactive layer includes a reactive material containing carbon and capable of reacting with the silicon in the infiltration composition.

[0033] If there are multiple additional protective structures, they can be placed in sequence and in contact with each other.

[0034] The result is an alternation of reactive layers and molten silicon wetting layers, thus ensuring that even if the silicon passes through one reactive layer, it will be transferred to the next reactive layer.

[0035] In addition, the alternating structure with multiple reactive layers allows the fibrous structure to better accommodate the heat generated by the chemical reaction between the silicon and one of the reactive layers.

[0036] Then the reaction between the silicon and the reactive layer can occur on multiple reactive layers rather than just on one reactive layer, which ensures a better distribution of the heat generated and thus avoids hot spots that could potentially damage the integrity of the fibrous structure.

[0037] In one embodiment, the pre-densified fibrous structure further includes a boron nitride interfacial phase located between the fiber reinforcement and the pre-densified matrix.

[0038] The presence of the boron nitride interfacial phase advantageously blocks any cracks that may occur in the matrix of the composite component during operation, thus protecting the fiber reinforcement.

[0039] In one embodiment, the fibrous structure includes a pre-densified fiber reinforcement formed by three-dimensional weaving or by multiple two-dimensional fiber layers.

[0040] The choice of a specific weaving structure imparts special mechanical properties to the pre-densified fibrous structure and thus to the resulting component.

[0041] It is noteworthy that this structure is particularly suitable for components used in the aviation industry.

[0042] In an exemplary embodiment, the component is a turbine component. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Figure 1 Schematically shows a pre-densified structure that can be used in the present invention.

[0044] Figure 2 Figure 2 Schematically shows the behavior of molten silicon on the pre-densified structure in the method of the present invention. DETAILED DESCRIPTION

[0045] The present invention will now be described with reference to the drawings, which are for descriptive purposes to illustrate certain embodiments of the present invention and should not be construed as limiting the present invention.

[0046] In addition, for ease of understanding, the drawings use non-realistic scales and should not be construed as the actual scales between the various elements.

[0047] Figure 1 ​​​​Shows a pre-densified fiber structure that can be used to implement the method of the present invention.

[0048] Such a pre-densified structure 10 may include a fiber reinforcement material 11, a boron nitride interface phase 12, a first silicon carbide layer 13, a carbon-containing material reactive layer 14, and a molten silicon wetting layer 15.

[0049] Figure 1 Is a projection on a plane perpendicular to the longest extending direction of the fiber reinforcement material 11 in the structure 10.

[0050] Figure 1 Also shows the thickness e1 of the molten silicon wetting layer 15, the thickness e2 of the reactive layer 14, and the thickness e3 of the first silicon carbide layer 13.

[0051] In one embodiment, the pre-densified fiber structure does not include any other elements except the fiber reinforcement material 11 and the above layers 12, 13, 14, and 15.

[0052] In one embodiment, the interface phase layer 12 contacts the fiber reinforcement material 11 and contacts the first silicon carbide layer 13.

[0053] In one embodiment, the first silicon carbide layer contacts the boron nitride interface phase layer 12 and contacts the reactive layer 14.

[0054] In one embodiment, the reactive layer 14 contacts the first silicon carbide layer 13 and contacts the molten silicon wetting layer 15.

[0055] In one embodiment, the molten silicon wetting layer 15 contacts the reactive layer 14.

[0056] The fiber structure can be formed by one or more textile operations (such as three-dimensional weaving). The fiber structure can be formed from ceramic yarns (such as silicon carbide yarns).

[0057] In one embodiment, the fiber reinforcement material 11 of the pre-densified fiber structure 10 can be made of ceramic yarns (such as silicon carbide yarns). This fiber structure can form the fiber reinforcement material of the composite component to be obtained. Examples of silicon carbide yarns that can be used include yarns under the brand names of "Nicalon", "Hi-Nicalon", or "Hi-Nicalon-S". By atomic percentage, the oxygen content of the ceramic yarns in the fiber structure can be 1% or less. For example, the "Hi-Nicalon-S" yarn has this property.

[0058] The term "three-dimensional weaving" or "3D weaving" should be understood as a weaving method in which at least some warp yarns connect the weft yarns on multiple weft yarn layers. In this specification, the roles of the warp yarns and the weft yarns can be interchanged and should also be considered as included in the claims. The fiber structure can adopt, for example, armure interlock. The term "interlock weaving or fabric" should be understood as a three-dimensional weaving in which each layer of warp yarns connects multiple layers of weft yarns, and all the yarns in the same warp yarn column have the same movement within the weaving plane. It is also possible to start from fiber textures (such as two-dimensional fabrics or unidirectional sheets) and obtain the fiber structure by draping these fiber textures over a model. These textures can optionally be joined together, for example, by stitching or yarn implantation to form the fiber structure.

[0059] In one embodiment, the interfacial phase layer 12 can be formed by chemical vapor infiltration on the fiber reinforcement 11 of the fiber structure. The fiber structure can be placed in a forming tool so that it can form the shape of the component to be obtained while depositing the interfacial phase. The thickness of the interfacial phase can be, for example, from 10 nm to 1000 nm, such as from 10 nm to 100 nm. After the interfacial phase is formed, the fiber structure remains porous, and the initial accessible pores are only filled to a small extent by the interfacial phase. The interfacial phase can be single-layer or multi-layer. The interfacial phase can include at least one of the following: pyrolytic carbon (PyC), boron nitride (BN), silicon-doped boron nitride (BN(Si), where the mass fraction of silicon is 5% to 40% and the rest is boron nitride), or boron-doped carbon (BC, where the atomic fraction of boron is 5% to 20% and the rest is carbon). In this case, the interfacial phase has the function of reducing the brittleness (défragilisation) of the composite material, which promotes the deflection of cracks that may propagate in the matrix and reach the interfacial phase, thereby preventing or delaying the fracture of the fibers due to such cracks. Additionally, it should be noted that the interfacial phase can be formed on the yarns before the fiber structure is formed.

[0060] In one embodiment, the pre-densification of the fiber structure can be carried out by a chemical vapor infiltration process.

[0061] For example, the first silicon carbide layer 13 can be formed from a gas phase containing methyltrichlorosilane (MTS) and hydrogen (H 2 )

[0062] In one embodiment, the thickness e3 of the first silicon carbide layer 13 can be from 0.2 μm to 10 μm.

[0063] For example, the first silicon carbide layer 13 can be obtained through two consecutive chemical vapor infiltration stages.

[0064] For example, in the first stage, the fibrous structure remains in the forming tool, and a first part of the first silicon carbide layer 13 (referred to as the consolidation layer) is deposited on the interface phase 12 and the fiber reinforcement 10. This consolidation layer can be deposited in contact with the interface phase 12. This layer has a sufficient thickness to sufficiently bond the fibers so that the structure can maintain its shape without the aid of clamping tools. This layer protects the interface phase from oxidation and can be formed by a chemically vapor infiltration method known per se, for example from a gas phase containing methyltrichlorosilane (MTS) and hydrogen (H 2 ). For example, the thickness of the consolidation layer can be greater than or equal to 0.1 μm, for example 0.1 μm to 5.0 μm.

[0065] In the second stage, the consolidated fiber structure having the shape of the desired component can be removed from the mold, and a pre-densified matrix is formed by depositing a second part of the first silicon carbide layer 13 on the consolidation layer.

[0066] This first silicon carbide layer contributes significantly to the mechanical properties of the composite material and can prevent molten silicon during subsequent infiltration.

[0067] In one embodiment, according to Figure 1 the variant shown, for a particular deposition, there can be no consolidation layer, and the first silicon carbide layer 13 of the pre-densified matrix can be formed directly on the interface phase 12.

[0068] After the first silicon carbide layer 13 is formed, a reactive layer 14 can be deposited.

[0069] The reactive layer 14 phase can be deposited by chemical vapor infiltration.

[0070] The chemical vapor infiltration can be carried out in the same reactor as for the chemical vapor infiltration for obtaining the first silicon carbide layer 13.

[0071] In particular, this reduces the number of moving operations of the fiber reinforcement to be impregnated.

[0072] For example, the first silicon carbide layer 13 can be deposited by chemical vapor infiltration. For example, a silicon carbide precursor is supplied to the reactor, the temperature of the reactor is maintained between 950 °C and 1080 °C, and the pressure is maintained between 10 and 40 mbar.

[0073] To switch from the deposition of silicon carbide 13 to the deposition of the reactive layer 14, the supply of the silicon carbide precursor is first cut off, the reactor is optionally purged, and then the reactive layer precursor is introduced.

[0074] The pressure and temperature of the reactor can be adjusted or not.

[0075] For example, the reactive layer 14 can be formed of pyrolytic carbon.

[0076] This method avoids the use of boron in the process, optionally except for the interface phase layer 12, thus simplifying the chemical vapor infiltration process.

[0077] The reactive layer can be obtained from a gaseous precursor selected from hydrocarbons (especially methane, propane or a mixture of these two compounds).

[0078] In one embodiment, the reactive layer can be doped with boron.

[0079] The boron in the reactive layer forms a SiBx compound to protect the underlying silicon carbide.

[0080] BCl 3 precursor can be used to dope the boron reactive layer 14 as described above.

[0081] The reactive layer 14 deposited by the chemical vapor infiltration process can form a uniform layer on the fiber reinforcement 11.

[0082] The thickness e2 of the reactive layer can be 20 μm to 1000 μm.

[0083] As Figure 1 shown, the reactive layer 14 can be covered with a molten silicon wetting layer 15.

[0084] For example, the molten silicon wetting layer 15 can be deposited by chemical vapor infiltration, for example, under the same conditions as the first silicon carbide layer 13.

[0085] In one embodiment, in order to switch from the deposition of the reactive layer 14 to the deposition of the molten silicon wetting layer 15, after cutting off the supply of the reactive layer precursor and optionally purging the reactor, the silicon carbide precursor is introduced into the reactor.

[0086] The pressure and temperature of the reactor can be adjusted or not.

[0087] In this way, it is easy to switch from depositing the reactive layer 14 to depositing the molten silicon wetting layer 15.

[0088] The thickness e1 of the molten silicon wetting layer 15 can be 0.2 μm to 10 μm.

[0089] Figure 2 Illustrates the importance of the reactive layer when infiltrating the fiber structure.

[0090] Figure 1 and Figure 2 the same reference numerals in represent the same elements.

[0091] Figure 2 Shows the process of liquid silicon infiltration 21 into the molten silicon wetting layer 15.

[0092] Figure 2 The infiltration process 21 is shown very schematically. However, it should be noted that the advancing direction of silicon in the molten silicon wetting layer 15 is consistent with the transverse direction of the fibers. In addition, as Figure 2 shown, the erosion of liquid silicon may occur at multiple sites on the outer surface of the fibers 10.

[0093] However, the columnar structure of the molten silicon wetting layer 15 restricts the entry of liquid silicon 21 into the reactive layer 14.

[0094] Liquid silicon 22 passes through the molten silicon wetting layer 15 and reaches the reactive layer 14, and then changes direction when reacting with the reactive layer 14.

[0095] The reactive layer 14 hinders the advancement of liquid silicon towards the fiber reinforcement 11 and ensures that the first silicon carbide layer 13, and in particular the interface phase 12 and the fiber reinforcement 11, are protected from the erosion of liquid silicon 21, 22.

Claims

1. A method for manufacturing a ceramic matrix composite component, which comprises: - infiltrating a pre-densified fiber structure (10) with a molten infiltration composition containing silicon, thereby forming a ceramic matrix in the residual pores of the pre-densified fiber structure, the pre-densified fiber structure comprising a pre-densified matrix, the pre-densified matrix comprising a first silicon carbide layer (13), a reactive layer (14) and a molten silicon wetting layer (15), the reactive layer containing a reactive material containing carbon and capable of reacting with silicon in the infiltration composition, the reactive layer covering the first layer, the molten silicon wetting layer (15) being made of silicon carbide and covering the reactive layer, wherein the pre-densified fiber structure (10) comprises a fiber reinforcement (11) formed by three-dimensional weaving.

2. The method according to claim 1, wherein, the reactive material is selected from pyrolytic carbon or boron-doped pyrolytic carbon.

3. The method according to claim 1 or 2, wherein, the thickness of the molten silicon wetting layer (15) is from 0.2 μm to 10.0 μm.

4. The method according to claim 3, wherein, the molten silicon wetting layer (15) has a columnar microstructure.

5. The method according to any one of claims 1 to 4, wherein, the thickness (e2) of the reactive layer (14) is less than or equal to 1000 nm.

6. The method according to any one of claims 1 to 5, wherein, the ratio of the thickness (e1) of the molten silicon wetting layer (15) to the thickness (e3) of the first silicon carbide layer (13) is from 40 / 60 to 10 / 90.

7. The method according to any one of claims 1 to 6, wherein, in addition to the molten silicon wetting layer (15), the pre-densified matrix may further comprise one to eight additional protective structures, each additional protective structure comprising an additional reactive layer and an additional molten silicon wetting layer made of silicon carbide or carbon covering the additional reactive layer, the additional reactive layer comprising a reactive material containing carbon and capable of reacting with silicon in the infiltration composition.

8. The method according to any one of claims 1 to 7, wherein, the pre-densified fiber structure further comprises a boron nitride interface phase (12) located between the fiber reinforcement (11) and the pre-densified matrix (13, 14, 15).

9. The method according to any one of claims 1 to 8, wherein the component is a turbine component.

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