Manufacturing process of a part made of composite material
Applying an anti-wetting composition before infiltration addresses surface degradation issues in CMC parts, ensuring smooth surfaces and shape tolerances while maintaining capillary infiltration, thus simplifying and economizing the manufacturing process.
Patent Information
- Application Number
- FR2022005361
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-06-03
- Publication Date
- 2025-07-18
- Estimated Expiration
- 2042-06-03
AI Technical Summary
Existing infiltration methods for ceramic matrix composite materials result in degraded surface conditions, leading to shape tolerance issues and increased manufacturing complexity and costs due to sacrificial excess lengths or post-infiltration machining.
Applying an anti-wetting composition comprising a powder of an anti-wetting agent with a specific particle size distribution before infiltration to prevent surface degradation while maintaining capillary infiltration, using a composition with a mass content between 20% and 80%.
The method ensures a smooth surface condition and adherence to shape tolerances without additional processing steps, reducing material loss and machining costs.
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Abstract
Description
Title of the invention: Method for manufacturing a part made of composite material Technical field
[0001] The invention relates to the field of manufacturing parts made of composite material, and more precisely those formed by a process of infiltration of a composition in the molten state. Prior art
[0002] Ceramic matrix composite (CMC) materials, known for their good mechanical properties which make them suitable for forming structural elements and for retaining these properties at high temperatures, constitute a viable alternative to traditional metal parts. Their reduced mass compared to their metal equivalent makes them parts of choice for addressing the issues of increasing efficiency and reducing polluting emissions from engines in the aeronautical field.
[0003] The parts made of CMC material may comprise a continuous fibrous reinforcement in the form of a woven textile, which is densified by a ceramic matrix. The fibrous reinforcement thus comprises long continuous fibers, the orientation of which may be adapted to the main directions of stress on the part during its use. The preform intended to form the fibrous reinforcement is woven from the continuous fibers to the dimensions of the part using a suitable loom.
[0004] Furthermore, it is known to obtain the matrix of these parts in CMC material by the melt infiltration technique. According to this technique, a molten composition, for example based on molten silicon, can be introduced into the porosity of a fibrous structure comprising silicon carbide particles in order to form a ceramic matrix densifying the fibrous structure. It is desirable in this technique that the molten composition penetrates homogeneously and completely within the porosity of the fibrous structure, so that the part obtained has minimal residual porosity and therefore optimized mechanical properties. Generally, the infiltration of the fibrous preform by the molten silicon is carried out by capillarity, by dipping a small part of the fibrous preform in a bath of liquid silicon.
[0005] However, some of the molten infiltration techniques do not give entirely satisfactory results since the area of the preform brought into contact with the molten silicon bath may have a surface condition which does not allow it to respect the shape tolerances admissible for the part. In addition, a state degraded surface makes any further processing step of the infiltrated part more difficult, for example the deposition of an environmental barrier with which such parts are generally coated.
[0006] To address this problem, several solutions have been proposed. For example, sacrificial excess lengths can be provided, and removed after infiltration to achieve a part with an acceptable surface finish. This first solution complicates the manufacturing process by requiring additional steps, and induces material losses which, multiplied by the number of parts, can represent a significant cost.
[0007] Another advanced solution is machining after infiltration of the part of the part having a surface condition degraded by the infiltration to allow it to return to an acceptable condition and to satisfy the shape tolerances. This machining can be done by sandblasting for example. Such machining is however not desirable because, in addition to being costly and time-consuming, it can lead to local deterioration of the part which can lead to anticipated wear of the part or to mechanical characteristics lower than those expected.
[0008] Another method to overcome the problem mentioned above is to infiltrate the preform without dipping it directly into the molten silicon bath, but by interposing a drain between the bath and the preform.
[0009] It has nevertheless been observed that this solution was not completely satisfactory, at least in that it did not allow a complete response to the problem of the degraded surface condition of the parts thus obtained.
[0010] There therefore remains a need for a solution which makes it possible to impregnate a preform with molten silicon devoid of one or more of the disadvantages described for the solutions of the prior art. Statement of the invention
[0011] To meet this need, the invention proposes a method for manufacturing a part made of ceramic matrix composite material, comprising at least:
[0012] - a step of infiltrating a fibrous structure by soaking a part of said fibrous structure in a bath of the infiltration composition, said infiltration composition comprising at least silicon in the molten state,
[0013] the method being characterized in that it comprises, before the infiltration step, a step of preparing the part of said fibrous structure intended to be dipped in the bath of the infiltration composition, the preparation step comprising at least the application of a layer of an anti-wetting composition, said anti-wetting composition comprising a powder of an anti-wetting agent of the infiltration composition in a mass content of between 20% and 80%, the median particle size distribution of said powder of an anti-wetting agent being between 1.0 pm and 50 pm.
[0014] The treatment of the part of the fibrous structure soaked in the bath of the infiltration composition with an anti-wetting composition makes it possible to prevent the infiltration composition from wetting the external surface of the fibrous structure, and degrading its surface condition.
[0015] However, it is notable that the anti-wetting composition does not harm the capillarity phenomena necessary for the good infiltration of the preform by the infiltration composition.
[0016] Furthermore, the anti-wetting composition does not degrade the thermo-mechanical characteristics of the impregnated preform, and it therefore allows a very advantageous simplification of the manufacturing process of a part made of ceramic matrix composite material.
[0017] In the application, the terms "anti-wetting composition" or "anti-wetting agent" must be understood in the usual sense of physical wetting between a surface and a liquid, the surface here being the surface of the fibrous structure and the liquid the infiltration composition. Wetting can be measured by the contact angle as it is usually defined, that is to say by the tangent to the liquid at the air / liquid / surface interface point. The wetting is all the better when the contact angle is small.
[0018] From the above, and since an anti-wetting agent aims to reduce the wetting of the surface by the liquid, it follows that within the meaning of the invention, an “anti-wetting” agent is defined by its capacity to increase the contact angle between the infiltration composition and the surface of the fibrous structure.
[0019] In one embodiment, the anti-wetting agent may be selected from alumina, boron nitride, yttrium oxide, silica, silicon nitride or a mixture of several compounds selected from the preceding list. Preferably, the anti-wetting agent is boron nitride.
[0020] In one embodiment, the application of the anti-wetting composition may be made by spraying, by dipping the fibrous structure in a bath of anti-wetting composition, or by application with a brush.
[0021] As indicated, the step of applying the anti-wetting composition is carried out on the part of the fibrous structure which is intended to be dipped in the bath of the infiltration composition.
[0022] In one embodiment, the portion of the fibrous structure that is intended to be soaked may be defined as a strip with a width of between 1 mm and 10 mm from one end of the fibrous structure.
[0023] The inventors have found that this choice for the part of the fibrous structure in contact with the infiltration bath makes it possible to ensure that the surface of the fibrous structure immersed in the bath of the infiltration composition ensures good capillary rise of the infiltration composition throughout the fibrous structure.
[0024] In one embodiment, each step of applying the anti-wetting composition may be followed by a drying step.
[0025] For example, such a drying step can be done in air or in an oven.
[0026] For example, the drying step can last between 5 minutes and 30 minutes.
[0027] In one embodiment, the preparation step comprises one or more times the succession of a step of applying a layer of the anti-wetting composition and a drying step.
[0028] The application of several layers of the anti-wetting composition makes it possible to ensure that the entire area of interest, i.e. the part of the fibrous structure soaked in the bath of the infiltration composition, is covered with at least one layer of the anti-wetting composition.
[0029] Indeed, the thickness of anti-wetting composition applied has little influence on obtaining the technical effect, but it is preferable that the entire part of the fibrous structure immersed in the bath of the infiltration composition is covered with at least one layer of anti-wetting composition.
[0030] In one embodiment, the anti-wetting composition comprises a powder of an anti-wetting agent of the alloy in a mass content of between 20% and 40%.
[0031] The inventors have in fact found that reducing the mass content of the anti-wetting agent makes it possible to obtain a good compromise between the effect obtained and the price of the anti-wetting composition.
[0032] In one embodiment, the anti-wetting composition may comprise a powder of a solvent-borne anti-wetting agent. For example, the solvent of the anti-wetting composition may be water, or an alcohol such as ethanol.
[0033] In one embodiment, the median particle size distribution of the powder of an anti-wetting agent is between 1.0 pm and 20 pm.
[0034] The median particle size distribution of the powder is understood in the present application as the number median value, also called d50, around which the diameters of the particles of the powder extend.
[0035] The inventors have found that the proposed particle size distribution makes it possible to further improve the anti-wetting properties of the anti-wetting composition.
[0036] In one embodiment, the infiltration composition may be selected from pure silicon in the molten state, or a silicon alloy in the molten state.
[0037] In one embodiment, the fibrous structure is a fibrous preform of a turbomachine part.
[0038] In one embodiment, such a turbomachine part may for example be a fiber preform of a fixed or mobile turbomachine blade, of a ring sector or of a combustion chamber.
[0039] In one embodiment, the part of the fibrous structure soaked in the bath of the infiltration composition is the part of the fibrous structure intended to form the root of a turbomachine blade.
[0040] The inventors have in fact found that the method of the invention is particularly suitable for turbomachine blades, and even more so when the part intended to form the root of the blade is dipped in the infiltration composition.
[0041] Indeed, the method of the invention allows the effects described above to be obtained for such parts which are most likely to be made by infiltration in the molten state.
[0042] Furthermore, the roots of the turbomachine blades comply with tight tolerances in terms of shape and surface condition, which the method of the invention makes it possible to obtain, thus allowing a simpler and more economical method than the methods of the prior art for obtaining turbomachine blades made of CMC. Indeed, it makes it possible to avoid providing a sacrificial overmaterial, and to avoid the machining steps after infiltration to restore the surface condition. Brief description of the drawings
[0043] [Fig.l] [Fig.l] schematically represents a device allowing the infiltration of a preform via a method according to the invention.
[0044] [Fig.2] [Fig.2] is a photograph of a part obtained by a method according to the invention.
[0045] [Fig.3] [Fig.3] is a photograph of a comparative part obtained by a process outside the invention. Description of the embodiments
[0046] 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 invention.
[0047] [Fig.l] shows a sectional view of a furnace 1 that can be used in the infiltration step of a method for manufacturing a CMC part according to the invention. The furnace 1 comprises a hermetic enclosure 2 inside which are present a crucible 4 having an internal volume containing an infiltration composition 6, and a support tool 100 comprising a plurality of individual supports 300 each loaded with a fibrous structure, here a porous preform 400 of a turbomachine blade shown very schematically, the plurality of individual supports 300 being held in a single cluster 100, the cluster 100 further comprising a holding arm 240.
[0048] The crucible 4 may be made of a ceramic material. The infiltration composition 6 may, for example, be silicon or a silicon alloy. The furnace 1 is here provided with a resistive heating system 10, for example comprising graphite bars. The heating system 10 is arranged around the crucible 4 and the preform 400 in the enclosure 2 of the furnace 1. The heating system further comprises, in a known manner, a generator 16 so as to power the heating system. The furnace 1 may further be provided with a vacuum pump 18 in fluid communication with the interior of the enclosure 2, so as to carry out the vacuum infiltration process. It will be noted that another type of furnace than that illustrated may be used, in particular the furnace may comprise an inductive heating system instead of a resistive system.
[0049] The furnace 1 comprises a device for measuring the mass of the preforms 400 corresponding here to a scale 20 of the weighing scale type. In this example, the scale 20 is located outside the enclosure 2 of the furnace 1, above the enclosure 2. Of course, other mass measuring devices can be used without departing from the scope of the present invention.
[0050] The furnace 1 further comprises a displacement device comprising here a jack 24 having a rod 26 on which the crucible 4 is mounted. In this example, the jack 24 is located outside the enclosure 2 of the furnace 1, below the enclosure 2. In this way, the jack 20 makes it possible to move the crucible 4 with a vertical translation movement inside the enclosure 2 of the furnace 1, in particular in the direction of the porous preforms 400. Thus, the crucible 4 is movable in vertical translation in the enclosure 2. In a variant not illustrated, the crucible can be mounted fixed in the furnace, and the preform can be movable in vertical translation.
[0051] In the example illustrated, the furnace 1 also comprises a control system 28 for controlling the relative position between the preforms and the crucible, which is configured to control the jack 24 as a function of the change in the mass of the preforms 400 as measured by the scale 20 supporting all of the preforms 400 via the holding arm 240. This control system 28 may be, for example, a PLC or a computer equipped with an input / output acquisition card. The control system 28 may receive electrical signals from the scale 20 as input, and send control signals as output to the jack 24.
[0052] The infiltration of the porous preforms 400 is carried out by bringing said preforms 400 into contact with the surface 6a of the infiltration composition 6 which may for example be silicon or a silicon alloy, the infiltration composition 6 infiltrating the porosity of the preforms by capillarity. During the contacting, the lower part of the preforms 400 is directly dipped into the bath of composition infiltration composition 6, which composition is then conveyed into the preforms 400 by capillarity. The bringing or not of the preforms into contact with the infiltration composition 6 and, consequently, the control of the infiltration of the preforms by the infiltration composition 6 is carried out by the control of the jack 24. The infiltration of the preforms 400 by the infiltration composition 6 ends when the balance 20 measures a predetermined mass gain corresponding to the desired level of densification for the preforms 400. Parts are then obtained, made of CMC material comprising a fibrous reinforcement densified by a matrix.
[0053] To carry out a method according to the invention, the lower part of the preforms 400 are covered with an anti-wetting composition, before the infiltration which has just been described.
[0054] For the characterization of the effects of the preparation step of a method according to the invention, two turbomachine blade preforms were infiltrated with molten silicon. One was infiltrated according to a method of the invention and the other according to a method outside the invention which was in all respects identical to the method of the invention except that the second preform did not undergo a preparation step, i.e. it was not covered with anti-wetting composition.
[0055] For this example, the anti-wetting composition is a composition comprising 30% by mass of boron nitride powder whose median particle size is 10 μm, the remainder of the composition being a mixture of acetone, butane, propane and butanone acting as solvent.
[0056] The anti-wetting composition is deposited on the root area of a blade, which root area is then immersed in a bath of molten silicon.
[0057] The two pieces were then visually compared.
[0058] Figures 2 and 3 are photographs of the two parts impregnated according to a method of the invention ([Fig.2]) and according to a method outside the invention ([Fig.3]).
[0059] The frame present in the photographs marks the area of the part having been immersed in the bath of molten silicon.
[0060] It can be noted by comparing figures 2 and 3 that the implementation of the invention makes it possible to obtain a part whose surface condition is much smoother than that of the part infiltrated according to the method outside the invention.
[0061] To ensure that the presence of the anti-wetting composition did not impair the good infiltration of the part by the molten silicon, the densities of the two parts were compared, and are in both cases equal.
[0062] Thus, this example shows that carrying out a method of the invention makes it possible to obtain a part whose surface condition is greatly improved, without harming the good infiltration of the infiltration composition into the part.
Claims
Claims
1. A method of manufacturing a part made of ceramic matrix composite material, comprising at least: - a step of infiltrating a fibrous structure (400) by dipping a portion of said fibrous structure into a bath (6) of the infiltration composition, said infiltration composition comprising at least silicon in the molten state, the method being characterized in that it comprises, before the infiltration step, a step of preparing the portion of said fibrous structure intended to be dipped into the bath of the infiltration composition, said portion of the fibrous structure intended to be dipped into the bath of the infiltration composition being a strip of width between 1 mm and 10 mm from one end of the fibrous structure, the preparation step comprising at least the application of a layer of an anti-wetting composition,said anti-wetting composition comprising a powder of an anti-wetting agent of the infiltration composition in a mass content of between 20% and 80%, the median particle size distribution of said powder of an anti-wetting agent being between 1.0 pm and 50 pm.,
2. A manufacturing method according to claim 1, wherein the anti-wetting agent is selected from alumina, boron nitride, yttrium oxide, silica, silicon nitride or a mixture of several compounds selected from the preceding list.
3. Manufacturing method according to claim 1 or 2, wherein the preparation step comprises one or more times the succession of a step of applying a layer of the anti-wetting composition and a drying step.
4. A manufacturing method according to any one of claims 1 to 3, wherein the application of the anti-wetting composition is made by spraying, by dipping the fibrous structure in a bath of anti-wetting composition, or by application with a brush.
5. A manufacturing method according to any one of claims 1 to 4, wherein the anti-wetting composition comprises a powder of an anti-wetting agent of the infiltration composition in a mass content of between 20% and 40%.
6. A manufacturing method according to any one of claims 1 to 5, wherein the median particle size distribution of the powder of an anti-wetting agent is between 1.0 pm and 20 pm.
7. Manufacturing method according to any one of claims 1 to 6 in which the fibrous structure (400) is a fibrous preform of a turbomachine part.
8. Manufacturing method according to any one of claims 1 to 7 in which the fibrous structure (400) is a fibrous preform of a fixed or mobile turbomachine blade, of a ring sector or of a combustion chamber.
9. Manufacturing method according to claim 8, in which the part of the fibrous structure (400) soaked in the bath (6) of the infiltration composition is a part of the fibrous structure intended to form the root of a turbomachine blade.