Method for manufacturing a cmc part

Abstract

The invention relates to a method for manufacturing a part made of ceramic matrix composite material, the part comprising at least one cavity, the method comprising the following steps: - filling (S1) a cavity (102) in the fibre preform (101) of a part to be obtained with a silicon non-wetting particle powder (202); then - a step of infiltrating (S2) the fibre preform with a liquid infiltration composition (212), wherein the infiltration composition comprises at least silicon; then - a step of cooling (S3) the infiltrated preform (301), the cavity of which is filled with the particle powder; then - removing (S4) the silicon non-wetting particle powder from the cavity in the densified preform.

Description

Description Title of the invention: Method for manufacturing a CMC part Technical Field

[0001] This disclosure relates to a method for manufacturing a part made of ceramic matrix composite material. Prior art

[0002] Ceramic matrix composites (CMC) materials withstand temperatures ranging from 600°C to 1400°C.

[0003] Due to their better resistance to high temperatures, CMCs require less cooling. Since this cooling traditionally comes from a draw in the compressor, which impacts the efficiency of the turbomachine, CMC materials therefore improve engine efficiency, which reduces fuel consumption.

[0004] Furthermore, their use contributes to optimizing the performance of turbomachines, in particular by reducing the overall mass of the turbomachine, which further contributes to a reduction in fuel consumption and therefore to a significant reduction in polluting emissions.

[0005] These advantages explain the industrial interest in developing such ceramic matrix composite materials.

[0006] A known method for manufacturing such a part is infiltration with molten silicon, often called "MI" for the English acronym "Melt Infiltration".

[0007] In such a method, a fiber preform is impregnated with an infiltration composition generally comprising molten silicon to form the matrix of the CMC material in the porosity of the fiber preform. Generally, to carry out the infiltration, one end of the preform is dipped into a bath of infiltration composition, so that the latter fills the porosity of the preform by capillarity.

[0008] Such a method is satisfactory industrially, but improvements remain desirable.

[0009] In particular, silicon being denser in the solid state than in the liquid state, its cooling and solidification causes part of the liquid silicon to escape in the form of drops solidifying on the surface of the part, thus forming nodules of solid silicon. These nodules then cause significant difficulties since they modify the dimensions of the part beyond tolerances and degrade the adhesion of any surface coating subsequently deposited. In addition, the subsequent removal of these nodules by sandblasting or machining is slow, laborious, and therefore expensive; it can also affect the material health of the final part.

[0010] Consequently, in order to combat the appearance of such nodules, certain solutions have been considered. One of these aims to modify the composition of the densification material or ceramic slip, for example by adding diamond particles, sources of carbon that will consume the excess silicon to form SiC. However, it is not always possible or desirable to modify the composition of the slip in this way.

[0011] Another option is to provide a sacrificial layer of ceramic slip all around the intermediate part in order to protect the final part, and in particular its reinforcement, during sandblasting or machining of the nodules. However, naturally, such an option results in a significant overconsumption of raw materials and requires complete machining of the final part, which is long and tedious.

[0012] Alternatively, it is possible to add thermal masses to the locations where nodules are desired to form. However, this alternative does not allow for complete control over where nodules appear, and is not applicable to all part geometries.

[0013] There is therefore a real need for a method of manufacturing a CMC part which allows better control of the densification stage of the part and which is free, at least in part, from the drawbacks inherent in the aforementioned known methods. Statement of the invention

[0014] This presentation aims precisely to meet this need.

[0015] For this purpose, the invention relates, according to a first of its aspects, to a method for manufacturing a part made of ceramic matrix composite material, the part comprising at least one cavity, the method comprising the following steps: - filling a cavity of the fiber preform of a part to be obtained with a powder of anti-wetting particles of silicon; then - a step of infiltrating the fiber preform with a liquid infiltration composition, said infiltration composition comprising at least silicon; then - a step of cooling the infiltrated preform whose cavity is filled with the particle powder; then - removal of the silicon anti-wetting particle powder from the cavity of the densified preform.

[0016] The use of anti-wetting particle powder protects the interior of the cavity from excess silicon. Indeed, if the infiltration composition comprising silicon leaves the preform towards the interior of the cavity, rather than forming nodules there, it will be trapped in a network of particles with the surface of which the infiltration composition has no affinity. It will then form small clusters in this network of particles dispersed like oil bubbles in water. In this way, it will not be able to adhere to the internal surface of the preform and the formation of silicon nodules is therefore prevented.

[0017] Thus, a relatively simple means is provided for protecting the internal cavity of a fiber preform from the appearance of silicon nodules during the infiltration step by an infiltration composition comprising molten silicon.

[0018] Indeed, it is in such an internal cavity of a part that silicon nodules are generally observed, in particular since cooling is slower there than the external surfaces of the preform.

[0019] Also, on the surface of an internal cavity it is very complicated to consider subsequent machining steps to eliminate the nodules once they have formed and this is why the proposed process ensures an excellent surface condition, achieved via a simplified process.

[0020] In one embodiment, the particles of the silicon anti-wetting particle powder may comprise particles selected from: boron nitride particles, alumina particles, yttrium oxide particles, silica particles, silicon nitride particles or a mixture of two or more such particles.

[0021] In the application, the term "anti-wetting" must be understood in the usual sense of physical wetting between a surface and a liquid, the surface here being the surface of the particles and the liquid being silicon.

[0022] Wetting can be measured by the contact angle between the liquid and the surface as it is usually defined, that is, by the tangent to the liquid at the air / liquid / surface interface point. The smaller the contact angle, the better the wetting.

[0023] From the above, and since the purpose of an anti-wetting particle is precisely to have poor wetting with the liquid, it follows that within the meaning of the invention an “anti-wetting” particle is defined by its capacity to have a contact angle with the liquid silicon, a contact angle greater than or equal to 60°, or even greater than or equal to 90°, better still greater than or equal to 120°.

[0024] In one embodiment, the particles of the particle powder may comprise for more than 90% by mass, or even for more than 95% by mass, or even for more than 99% by mass particles chosen from: boron nitride particles, alumina particles, yttrium oxide particles, silica particles, silicon nitride particles or a mixture of two or more of such particles.

[0025] In one embodiment, the particle powder may comprise particles having a size between 0.1 pm and 1000 pm, for example between 1 pm and 1000 pm.

[0026] The "size" of a particle can be defined as the largest dimension of extension of the particle, i.e. the diameter of the smallest sphere in which the particle fits.

[0027] In one embodiment, the particle powder may comprise particles whose sizes are distributed such that the median size d50 of the particle powder is between 100 pm and 1.0 mm.

[0028] The median size d50 of a particle distribution can be determined in a conventional manner in the field of powdery materials, by using a granulometer, for example a granulometer using the Mie method.

[0029] In a known manner that is not explained in detail here, such a measurement is based on the detection of the refraction angles of a laser beam sent onto a sample.

[0030] In one embodiment, the fiber preform may be chosen from a preform of an aeronautical part, for example a preform of a turbine blade or a preform of a distributor portion.

[0031] Indeed, the preforms of such parts generally include cavities intended to form complex cooling circuits, for which it is advantageous to be able to have an improved surface finish.

[0032] In one embodiment, the fibrous preform has a three-dimensional weave.

[0033] By "three-dimensional weaving" or "3D weaving" is meant here a method of weaving the preform by which at least some of the warp threads bind weft threads over several weft layers, such as for example an "interlock weave".

[0034] By "interlock weave" is meant here a 3D weave weave where each warp layer links several weft layers with all the yarns in the same warp column having the same movement in the plane of the weave.

[0035] In one embodiment, the preform may comprise silicon carbide fibers and / or carbon fibers.

[0036] Indeed, it is for such preforms that it is particularly advantageous to use infiltration processes using molten silicon.

[0037] In one embodiment, the step of infiltrating the fibrous preform may be carried out by dipping a portion of the preform into a bath of the infiltration composition.

[0038] In one embodiment, the step of infiltrating the fibrous preform can be carried out by interposing a drain between the infiltration composition and the preform.

[0039] This embodiment avoids direct contact between the infiltration composition and the fiber preform, which ensures a better surface condition for the preform. This reduces the risk that a machining step on the densified preform is necessary after infiltration to improve its surface condition, which may be necessary if the preform is dipped in the bath of the infiltration composition.

[0040] In one embodiment, the infiltration composition may comprise pure silicon, or a silicon alloy.

[0041] Since the infiltration composition comprises molten silicon, or is a molten silicon alloy or is made of molten silicon, anti-wetting particles of the molten silicon will have similar behavior, i.e. anti-wetting, with the infiltration composition.

[0042] In one embodiment, the filling of the internal cavity of the fibrous preform can be carried out by dry filling of the cavity with the powder.

[0043] By "dry deposition" is meant that the method of the invention does not require the use of a third-party carrier fluid when depositing the particle powder in the cavity of the preform, unlike, for example, methods of the prior art which use slips.

[0044] In a dry deposition process, the solid composition can nevertheless be sprayed in a liquid, solid or pasty form, without a third-party carrier liquid, and it forms a solid deposit once its deposition is complete.

[0045] For example, the powder can be compacted once in the cavity by placing the preform on a vibrating table.

[0046] In one embodiment, the filling of the cavity may be carried out by means of a slip, the slip being made up of anti-wetting particles of silicon, said particles being dispersed in a liquid solution.

[0047] In one embodiment, the liquid solution may comprise distilled or reverse osmosis water, ethanol, or a mixture of two of these species.

[0048] For example, the silicon anti-wetting particles for forming the particle powder may be dispersed in a liquid solution to form a slip, then the preform cavity is filled with said slip, and finally the liquid solution is removed, for example by evaporation. Brief description of the drawings

[0049] [Fig. 1] Figure 1 shows a flowchart showing a method in one embodiment.

[0050] [Fig. 2] Figure 2 is a schematic representation of a preform to illustrate one step of a process.

[0051] [Fig. 3] Figure 3 is a schematic representation of a filled preform to illustrate one embodiment of a step of a process.

[0052] [Fig. 4] Figure 4 is a schematic representation of an infiltration step to illustrate one embodiment of a step of a method.

[0053] [Fig. 5] Figure 5 is a schematic representation of an impregnated preform to illustrate one embodiment of a step of a process.

[0054] [Fig. 6] Figure 6 is a schematic representation of an impregnated preform to illustrate a part obtained in one embodiment of the invention. Description of the embodiments

[0055] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0056] Figure 1 shows a flowchart illustrating the steps of a method in one embodiment.

[0057] The process of Figure 1 includes four steps numbered S1 to S4: - the SI filling of a cavity of the fiber preform of a part to be obtained with a powder of anti-wetting particles of silicon; then - a step S2 of infiltration of the fiber preform with a liquid infiltration composition, said infiltration composition comprising at least silicon; then - a cooling step S3 of the infiltrated preform whose cavity is filled with the particle powder; then - the removal S4 of the silicon anti-wetting particle powder from the cavity of the densified preform.

[0058] Figure 2 shows a preform 101 in one embodiment of the method.

[0059] Such a preform 101 may be a preform of an aeronautical part, for example a preform of a turbomachine blade or a preform of a portion of a distributor.

[0060] The fiber preform 101 has a cavity 102.

[0061] The cavity 102 is furthermore open in the sense that the interior of the cavity is in fluid communication with the exterior of the cavity.

[0062] In one embodiment, the fibers making up the fiber preform 101 are chosen from silicon carbide SiC fibers and / or carbon fibers.

[0063] The loading of the cavity 102 can be done by dry means, that is to say without using a vector fluid to supply the particles 202 into the cavity 102.

[0064] Alternatively, the cavity 102 can be filled via a slip, consisting of a liquid solution in which the particles are dispersed.

[0065] The slip is introduced into the cavity 102, then the liquid solution is removed, for example by exposing the entire preform 101 and the slip to a temperature greater than or equal to the evaporation temperature of the liquid solution.

[0066] For example, cavity filling can be done by plugging one end of the cavity and loading it from the other end.

[0067] Figure 3 illustrates the preform 101 after step SI, that is to say after its cavity 102 has been filled with the powder of anti-wetting particles 202 of the silicon.

[0068] Figure 4 illustrates the performance of an infiltration step S2 of the preform 101 by a liquid infiltration composition 212.

[0069] In one embodiment, as illustrated in FIG. 4, the preform 101 can be placed directly in contact with the infiltration solution 212, which is placed here in a crucible 210.

[0070] In an embodiment not shown, the preform 101 may be separated from the infiltration composition 212 by a drain. Such a drain makes it possible to prevent a portion of the preform from being in direct contact with the infiltration composition. Such an embodiment makes it possible to improve the surface condition of the preform after infiltration.

[0071] The method of infiltration by the infiltration composition in the liquid state 212 is not described here in more detail because the advantages described for the method are not specific to the parameters chosen for the step of infiltration of the preform by the infiltration composition.

[0072] For example, the assembly of the preform 101, the particles 202, the crucible 210 and the infiltration composition 212 which it comprises are arranged in an enclosure heated to a temperature greater than or equal to the melting temperature of the infiltration composition 212.

[0073] The porosity of the preform 101 is sufficient for the infiltration composition 212 to be subjected to capillary phenomena and for it to impregnate the preform 101 when the latter is placed in contact with it.

[0074] In one embodiment, the infiltration composition 212 may be selected from a silicon or silicon alloy composition.

[0075] Preferably, the infiltration composition 212 comprises more than 90% by mass or even more than 95% by mass of silicon.

[0076] When the infiltration composition 212 is a silicon alloy, the anti-wetting behavior of the silicon particles nevertheless makes it possible to obtain the desired technical effect described below.

[0077] Figure 5 illustrates the infiltrated preform 301, that is to say the preform 101 at the end of the infiltration step S3, during which the infiltration composition 212 has impregnated its porosity, preferably by capillarity.

[0078] Furthermore, the infiltration composition present in the porosity of the preform may, after cooling, have overflowed from the preform 101 into the cavity 102.

[0079] However, unlike prior art methods, rather than thus forming a silicon nodule on the surface of the cavity 102 of the preform 101, the infiltration composition 212 forms an anti-wetting contact with the particles 202 of the silicon anti-wetting powder present in the cavity 102.

[0080] As shown in Figure 5, due to the poor wetting between the particles 202 of the powder and the infiltration composition 212, the infiltration composition leaving the preform 101 is trapped in the network of particles 202 and forms small clusters 310 there.

[0081] Due to the non-wetting nature of the contact between the infiltration composition and the particles 202, the infiltration composition does not adhere to the internal surface of the cavity 102 as it would have in the absence of the powder.

[0082] It is then possible to get rid of the clumps 310 of the infiltration composition thus formed in the particles 202 during the step S4 of removing the particles from the cavity 102 of the infiltrated preform 301, while ensuring that the infiltration composition has not been able to form nodules.

[0083] This results in a greatly improved surface condition of the surface of the cavity 102 of the part 301 obtained after infiltration of the composition 212 into the preform, because this surface is then free of nodules.

[0084] Figure 6 represents the composite material part 301 at the end of step S4, that is to say after the removal of the particle powder 202 from the cavity 102.

[0085] The now infiltrated preform 101 forms a part 301 made of composite material whose fiber preform is formed by the preform 101 and whose matrix is formed by the infiltration composition 212.

[0086] It will be noted in particular that the cluster 310 formed during the cooling of the infiltration composition was removed during the removal of the particles 202.

[0087] In one embodiment, the method may comprise a subsequent final machining step, for example allowing the part to be given its final dimensions for integration into a turbomachine.

[0088] For example, such final machining may include a machining, contouring, drilling or any other step aimed at correcting the dimensions of the part.

[0089] As illustrated by means of the figures, the method allows the densification of a preform 101, while jointly ensuring that the cavities 102 of such a preform have an excellent surface condition at the end of the method and this without complicating the step of densification of the fiber preform, nor requiring machining of the internal surface of the cavities.

Claims

Claims

1. Method for manufacturing a part (301) made of ceramic matrix composite material, the part comprising at least one cavity, the method comprising the following steps: - filling (SI) a cavity (102) of the fibrous preform (101) of a part to be obtained with a powder of anti-wetting particles (202) of silicon; then - a step of infiltration (S2) of the fiber preform with a liquid infiltration composition (212), said infiltration composition comprising at least silicon; then - a cooling step (S3) of the infiltrated preform (301) whose cavity is filled with the particle powder; then - removing (S4) the silicon anti-wetting particle powder from the cavity of the densified preform.

2. The method of claim 1, wherein the particles (202) of the silicon anti-wetting particle powder comprise particles selected from: boron nitride particles, alumina particles, yttrium oxide particles, silica particles, silicon nitride particles, or a mixture of two or more such particles.

3. The method of claim 2, wherein the particles (202) of the silicon anti-wetting particle powder comprise more than 90% by mass of particles selected from particles selected from boron nitride particles, alumina particles, yttrium oxide particles, silica particles, silicon nitride particles, or a mixture of two or more such particles.

4. A method according to one of claims 1 to 3, wherein the particle powder comprises particles (202) having a size between 0.1 pm and 1000 pm.

5. Method according to one of claims 1 to 4, in which the preform (101) comprises silicon carbide fibers and / or carbon fibers.

6. Method according to one of claims 1 to 5, in which the infiltration composition (212) may comprise pure silicon or a silicon alloy.

7. Method according to one of claims 1 to 6, in which the step of filling the internal cavity (102) of the preform (101) is carried out by means of a slip, the slip being made up of the anti-wetting particles of silicon (202) dispersed in a liquid solution.

8. Method according to one of claims 1 to 7, in which the fibrous preform (101) is chosen from a preform of an aeronautical part, for example a preform of a turbine blade or a preform of a distributor portion.

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