Installation for silicification

Abstract

Installation for silicification The invention relates to an installation for the silicification of a fibrous preform comprising: - an upper chamber (10) including a holding support (12) for holding said preform (13); - a lower chamber (20) including a bath support (23) adapted to support a container (21) adapted to contain a bath of an infiltration composition (25) comprising molten silicon; - heating means (22); and - a displacement member (26) for putting the holding support (12) and the bath support (23) into relative motion;the installation further comprising a closing device (40) disposed between the lower chamber (20) and the upper chamber (10) and allowing the installation to be moved from an open position, where the upper chamber and the lower chamber are in fluidic communication, to a separation position, where the lower and upper chambers are hermetically separated from each other. Figure for the abbreviation: Fig. 1.;

Description

Title of the invention: Installation for siliciding Technical field

[0001] The present disclosure relates to an installation allowing the siliciding of fibrous reinforcements as well as a method that this installation allows to be implemented. Prior art

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

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

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

[0005] Among the CMC materials, there are in particular materials comprising a silicon carbide fiber reinforcement and a silicon carbide matrix.

[0006] Such materials are called SiC / SiC and are generally obtained by infiltration of molten silicon into a fibrous reinforcement formed by silicon carbide fibers.

[0007] During such infiltration, a silicon bath is generally used which also comprises boron, in known proportions, the boron making it possible to protect the fibers from corrosion which could be caused by molten silicon in the absence of boron.

[0008] Nevertheless, it is generally observed that after infiltration of the preform produced, the remaining siliciding bath no longer has the same proportions between boron and silicon.

[0009] The remaining bath cannot be reused for a subsequent infiltration process and the remainder of the bath is then completely replaced by a new siliciding bath.

[0010] However, the loss of unused infiltration bath represents a significant cost, which could be avoided if the infiltration bath could be recycled.

[0011] Such recycling is neither possible nor envisaged in existing installations and this is why there remains a need for an installation which would allow the recycling of the silicon bath, without compromising on the performance of said installation for the siliciding step of the fiber preforms. Statement of the invention

[0012] The present disclosure aims precisely to propose an installation meeting the needs stated above.

[0013] The invention therefore relates to an installation for the siliciding of at least one fiber preform comprising: - an upper chamber comprising a holding support for holding said preform; - a lower chamber comprising a bath support capable of supporting a container capable of containing a bath of an infiltration composition comprising molten silicon; - means for heating at least said lower chamber; and - a movement member allowing the holding support and the bath support to be moved relative to each other; the installation further comprising a closing member arranged between the lower chamber and the upper chamber and making it possible to move the installation from an open position, where the upper chamber and the lower chamber are in fluid communication, to a separation position, where the lower and upper chambers are hermetically separated from each other.

[0014] The installation according to the invention advantageously makes it possible to carry out a step of recycling the infiltration composition in the same installation as that used for siliciding.

[0015] Recycling ensures a reduction in raw material losses and therefore a significant economic gain for the process as a whole.

[0016] Furthermore, in an installation described above, recycling can be carried out directly after siliciding thanks to the closing member making it possible to isolate the lower chamber in which the support capable of containing the infiltration composition is located.

[0017] Since recycling the infiltration composition generally requires an increase in temperature, the configuration proposed for the installation makes it possible to take advantage of the temperature already prevailing in the lower chamber at the end of siliciding, without requiring the used infiltration composition bath to be conveyed out of the installation, which minimizes heat losses and reduces heating requirements.

[0018] An infiltration bath will be said to be “used” when it has participated in the performance of a siliciding step of one or more fiber preforms.

[0019] The displacement member makes it possible to bring the fibrous preform(s) held by the holding support into contact with the bath of infiltration composition.

[0020] A relative movement of the holding support and the bath support is described, since it it is sufficient that one of the two supports is mobile relative to the other.

[0021] In one embodiment, the moving member allows the bath support to be moved from the lower chamber to the upper chamber.

[0022] This embodiment may be achieved with an elevating bath support that allows the bath of infiltration composition to be moved from the lower chamber to the upper chamber, and thus to bring at least a portion of the fiber preform(s) into contact with the bath of infiltration composition.

[0023] In an alternative embodiment, the displacement member makes it possible to move the holding support from the upper chamber to the lower chamber.

[0024] In an alternative embodiment, the installation comprises two displacement members, one allowing the holding support to be lowered and the other allowing the bath support to be raised.

[0025] In one embodiment, the installation further comprises a gas source connected to the lower chamber. Optionally, a humidifier may also be connected to the lower chamber.

[0026] The gas source and, where appropriate, the humidifier advantageously make it possible to carry out a process for recycling the used infiltration composition.

[0027] Indeed, the inventors have found that bringing the bath of used infiltration composition into contact with a treatment atmosphere makes it possible to recycle the infiltration composition.

[0028] More specifically, the infiltration composition preferably comprises silicon and boron, in known proportions, all the other species present in the infiltration composition being present in a content less than or equal to 100 ppm. Preferably, the sum of the mass contents for the species other than silicon or boron is less than or equal to 100 ppm.

[0029] Such infiltration compositions ensure on the one hand infiltration into the porosity of the fibrous preforms of molten silicon, and on the other hand the boron makes it possible to protect the preforms against the corrosion that the molten silicon would cause in its absence.

[0030] However, after infiltration of the preforms by the infiltration composition, it was found that the proportions of boron and silicon in the remainder of the bath were no longer the same as those of the initial composition, which made the used infiltration composition unsuitable for reuse as is.

[0031] In order to allow the reuse of the infiltration composition, it is proposed by the inventors to remove the boron from the used infiltration composition to obtain a treated used infiltration composition comprising only silicon and possibly other elements including boron in a content less than or equal to 500 ppm.

[0032] It will then be sufficient to determine the quantity of used infiltration composition thus obtained and then to add boron in a known quantity to produce a new infiltration composition.

[0033] The gas sources of the proposed installation make it possible to impose on the lower chamber of the installation a treatment atmosphere capable of eliminating boron from the used infiltration composition.

[0034] For example, the gas sources may be an argon source and / or a dihydrogen source.

[0035] Without wishing to be bound by theory, the inventors consider that such an atmosphere can react with the used infiltration composition to form a volatile species of boron monohydride HBO, which then escapes from the bath of used infiltration composition which thus becomes depleted in boron.

[0036] The proposed installation makes it possible on the one hand to carry out the step of recycling the used infiltration composition and on the other hand to limit the quantity of reagents used for this. Indeed, since the lower chamber can be hermetically separated from the upper chamber, this greatly reduces the volume of the chamber in which such a step can be carried out.

[0037] In one embodiment, the holding support further comprises a weighing member.

[0038] This embodiment makes it possible to ensure excellent monitoring of the siliciding step of the fiber preforms.

[0039] Indeed, when the preforms are placed in contact with the bath of infiltration composition, the latter become loaded by capillarity with infiltration composition.

[0040] Monitoring the mass of the preforms makes it possible to easily control the progress of the siliciding of the preforms.

[0041] In one embodiment, the heating means are induction heating means.

[0042] In one embodiment, the heating means are resistive means.

[0043] In one embodiment, the means for heating the upper chamber and the heating means of the lower chamber are separate.

[0044] In such an embodiment, it is possible to heat one, the other or both chambers, which in particular ensures excellent thermal homogeneity of the chamber in an open position.

[0045] However, this embodiment advantageously makes it possible to heat only the lower chamber in a separation position, which ensures substantial energy savings, given the volumes considered.

[0046] According to another of its aspects, the invention also relates to a method for siliciding a fiber preform, carried out in an installation which has just been described, the method comprising at least: - a siliciding step during which the installation is in a position opening and in which the fibrous preform is in contact with the infiltration composition bath; and - a step of recycling the infiltration composition, carried out in the lower chamber and during which the installation is in a separation position.

[0047] Such a method makes it possible to take advantage of the advantages already described for the installation and thus to have a siliciding process in which the used infiltration composition can be reprocessed.

[0048] The method ensures that the siliciding step, carried out by infiltration of the infiltration composition into the fiber preforms, can be carried out under conditions similar to those of the prior art.

[0049] The recycling step can be carried out in the lower chamber only, which is smaller than the entire enclosure. This step ensures, on the one hand, better use of the raw material by recycling the treated used infiltration composition, and on the other hand, does not require any handling of said treated used infiltration composition because the latter is already in the installation.

[0050] What is more, the installation is already at a high temperature, necessary for the siliciding step, which allows energy savings since the recycling step does not require heating from ambient temperature.

[0051] In one embodiment, the recycling step is carried out by introducing a treatment atmosphere into the lower chamber.

[0052] Such an embodiment of the recycling step has been described above, in connection with the gas sources possibly connected to the lower chamber.

[0053] In one embodiment, the recycling step may be carried out by a treatment atmosphere comprising, or even consisting of, a partial pressure of argon of between 1.0 bar and 5.0 bar, a partial pressure of dihydrogen of between 0.0 bar and 1.0 bar and a partial pressure of water vapor of between 0.0 bar and 1.0 bar.

[0054] In an alternative embodiment, the treatment atmosphere may comprise, or even consist of, a partial pressure of dihydrogen of between 1.0 bar and 5.0 bar, and a partial pressure of water vapor of between 0.0 bar and 1.0 bar.

[0055] In the present application, the partial pressure of a gas takes its usual meaning in the field of thermodynamics of ideal gases, and is intended to represent the pressure which would be exerted by the molecules of this gas if it alone occupied the volume offered to the mixture, at the temperature of said mixture.

[0056] In one embodiment, the treatment atmosphere may be supplied to the lower chamber by bubbling in the spent infiltration composition.

[0057] In one embodiment, the temperature of the upper chamber during the siliciding step is between 1400°C and 1500°C, and the temperature of the lower chamber during the recycling stage is between 1400°C and 1600°C.

[0058] As described above, the installation described makes it possible to reuse for the recycling step a large part of the heat already used for the siliciding step, which reduces the energy requirement of the entire process.

[0059] In one embodiment, the recycling step can be carried out for a period of between 1 hour and 10 hours. Brief description of the drawings

[0060] [Fig-1] [Fig.l] shows an installation in one embodiment of the invention in an open position.

[0061] [Fig.2] [Fig.2] shows an installation in one embodiment of the invention in a separation position. Description of the embodiments

[0062] 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.

[0063] [Fig.l] illustrates an embodiment of the invention in which the installation is in an open position.

[0064] Such an installation comprises an upper chamber 10 and a lower chamber 20.

[0065] The upper chamber here comprises a holding support 12 from which fiber preforms 13 are suspended, here 4 in number.

[0066] The number of fiber preforms 13 is in no way limiting of the installation. In particular, a single fiber preform 13 could be suspended from the holding support 12.

[0067] In the embodiment shown, the installation further comprises heating means 11 and 22.

[0068] Here the heating means 11 of the upper chamber 10 are distinct from the heating means 22 of the lower chamber 20.

[0069] This is not at all necessary, even if it is preferable that the heating means 11 of the upper chamber 10 be separated from the heating means 22 of the lower chamber 20 in order to be able to selectively heat one or the other of the chambers 10 or 20, according to the needs of the methods of the invention.

[0070] Each of the two heaters 11 and 22 can be inductive or resistive depending on the particular choices for the design of the installation.

[0071] In [Fig.l], the installation is shown in a position where the two chambers 10 and 20 are in fluid communication.

[0072] Indeed, the closing member 40, which will be described in more detail with the embodiment illustrated by [Fig.2], is open.

[0073] Furthermore, the installation comprises a bath support 23, supporting a container 21, which contains a bath of the infiltration composition 25.

[0074] In [Fig. 1], the bath of infiltration composition 25 is in contact with the lower end of the fibrous preforms 13, in order to allow infiltration into the latter of the infiltration composition 25, by capillarity.

[0075] In one embodiment, the preforms comprise or are made of silicon carbide.

[0076] In addition to what has been described above, the installation comprises a displacement member 26 which makes it possible to raise the bath support 23, and thus bring it closer to the fiber preforms 13.

[0077] The installation finally comprises a scale 24 which makes it possible to quantify the quantity of infiltration composition present in the container 21.

[0078] In one embodiment, not illustrated here, the holding support 12 may also comprise a weighing member which then makes it possible to precisely determine the mass gain of the fiber preforms 13, and thus to quantify the progress of the siliciding step.

[0079] Elements 31, 32, 33 and 34 will be described in more detail with [Fig.2] and are for [Fig.l] identical to what will be described below.

[0080] [Fig.2] illustrates an installation of the invention in a separation position, also called a closing position.

[0081] [Fig.2] illustrates elements common to those already described for [Fig.l], which common elements then bear the same numerical legends.

[0082] In the closed position shown, the lower chamber 20 is hermetically isolated from the upper chamber 10.

[0083] This closed position is achieved here by interposition between the two chambers of the closing member 40, here a sliding door.

[0084] It is understood that a closure is “hermetic” when it ensures that gases cannot pass through said closure either to enter the lower chamber 20 or to exit it.

[0085] Furthermore, in the closed position, the lower chamber accommodates the bath support 23, the container 21 comprising the infiltration composition 25, as well as the scale 24.

[0086] The presence of these elements in the lower chamber 20 is ensured by the rest position of the displacement member 26.

[0087] In a similar but not shown embodiment, the displacement member can allow the displacement of the holding support 12, and then allows in a opening position of the installation, to lower the fiber preforms 13 towards the bath 25, rather than raising the bath 25 towards the preforms 13 as shown in [Fig.l].

[0088] In the closing configuration it is understood that the closing member 40 makes it possible to hermetically isolate the lower chamber 20 from the upper chamber 10, in other words, the gases from the chamber 10 cannot go into the chamber 20 and vice versa.

[0089] The installation further comprises, in the embodiment shown, two gas sources 31 and 32, as well as a humidifier 33 and a gas injection pipe 34.

[0090] The sources 31 and 32 may for example be respectively an argon source and a dihydrogen source.

[0091] These sources 31, 32 as well as the humidifier 33 make it possible, in coordination with the injection pipe 34, to deliver a treatment atmosphere into the lower chamber 20 and into a closed position of the installation.

[0092] [Fig. 2] illustrates that recycling of the used infiltration composition can take place, without requiring conveying of this composition. In addition, the closed position of the installation ensures a smaller volume for the lower chamber than in the absence of the closing member 40, which reduces the need for reactive gases.

[0093] Finally, the installation described allows recycling to be carried out directly in the same installation as that where the siliciding takes place.

[0094] This makes it possible, as indicated above, to limit thermal losses between the siliciding step and the recycling step, which reduces the costs of the process by lowering its heating requirements.

[0095] Furthermore, if it is necessary to provide heat for the recycling step, the only means 22 for heating the lower chamber 20 can then be used, and the gain achieved thanks to the independence of the heating means 22 and 11 will then be noted.

[0096] Moreover, the installation may, in an embodiment not shown, comprise only the heating means 22, which are then sufficient to heat the entire installation, i.e. the lower 20 and upper 10 chambers, in the open position.

[0097] Throughout the present application, the expression "between ... and..." must be understood inclusively.

Claims

Claims

1. Installation for the siliciding of at least one fibrous preform comprising: - an upper chamber (10) comprising a holding support (12) for holding said preform (13); - a lower chamber (20) comprising a bath support (23) capable of supporting a container (21) capable of containing a bath of an infiltration composition (25) comprising molten silicon; - heating means (22) of at least said lower chamber; and - a displacement member (26) for setting the holding support (12) and the bath support (23) into relative movement;the installation further comprising a closing member (40) arranged between the lower chamber (20) and the upper chamber (10) and making it possible to move the installation from an open position, where the upper chamber and the lower chamber are in fluid communication, to a separation position, where the lower and upper chambers are hermetically separated from each other.;

2. Installation according to claim 1, in which the displacement member (26) makes it possible to move the bath support (23) from the lower chamber (20) to the upper chamber (10).

3. An installation according to claim 1 or 2, wherein the installation further comprises a gas source (31, 32) and optionally a humidifier (33) connected to the lower chamber (20).

4. Installation according to any one of claims 1 to 3, in which the holding support (12) further comprises a weighing member.

5. Installation according to any one of claims 1 to 4, in which the heating means (11, 22) are induction heating means.

6. A method of siliciding a fiber preform, carried out in an installation according to one of claims 1 to 5, the method comprising at least: - a siliciding step during which the installation is in an open position and in which the fiber preform (13) is in contact with the infiltration composition bath (25); and - a step of recycling the infiltration composition, carried out in the lower chamber (20) and during which the installation is in a closed position.

7. A siliciding method according to claim 6, wherein the recycling step is carried out by introducing a treatment atmosphere into the lower chamber (20).

8. A siliciding process according to claim 6 or 7 wherein the temperature of the upper chamber during the siliciding step is between 1400°C and 1500°C, and the temperature of the lower chamber during the recycling step is between 1400°C and 1600°C.

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