Fluidized bed filament coating process

Abstract

Filament Coating Method in Fluidized Bed The present invention relates to a filament coating method, comprising: - the deposition of a coating onto elongated filaments (11) in a treatment zone (TZ) of a reactor (3) by chemical vapor deposition in a fluidized bed from a gaseous phase introduced into the reactor, the method further comprising (i) monitoring of filament fluidization, and (ii) one or more corrective filament fluidization actions, each triggered if a lack of filament fluidization is detected during monitoring and each comprising a temporary modification of the flow rate of a dispersion gas during which an increased flow rate is imposed, at least three times the nominal flow rate imposed during deposition, this increased flow rate being imposed for at least 3 seconds. Figure for the abstract: Fig. 1.

Description

Title of the invention: Fluidized bed filament coating method technical field

[0001] The present disclosure relates to a process for coating filaments by chemical vapor deposition in a fluidized bed, associated processes for manufacturing a part in composite material and a device for implementing this coating process. Previous technique

[0002] Ceramic matrix composite materials (CMCs) possess good thermostructural properties, that is, high mechanical properties that make them suitable for structural components, and the ability to retain these properties at high temperatures. CMCs may include a textile reinforcement made of long, continuous fibers woven along the stress directions of the final composite part. The weaving step is costly, and the use of a woven fiber reinforcement may present limitations in the case of parts with complex or small geometries. Indeed, the minimum weave pitch may prove too coarse for producing a small geometric detail.

[0003] To solve this problem, it was considered using a reinforcement made not of continuous long fibers but of fibrous elements dispersed within the matrix. However, it is well known that the performance of a CMC material requires specific management of the interfacial bonds between the fibers and the matrix in order to achieve the damage-prone nature of the final composite. This modulation of the interfaces is conventionally achieved by interposing an interphase between the fiber and the matrix.

[0004] When seeking to coat dispersed fibrous elements, it is desirable to avoid the formation of agglomerates and to obtain a homogeneous and uniform coating of these elements in order to achieve the desired protective effect. However, the fluidization of filaments with a high aspect ratio, greater than or equal to 5, poses a particular problem because it falls outside any existing classification. Indeed, the available classification, called the Geldart classification, is established for powders with an aspect ratio of 1.

[0005] However, solutions have been proposed in the prior art to address this problem. In this regard, WO 2022 / 003269 proposes adding spacer particles separate from the reinforcement to be coated. This solution provides Satisfactory results but requires a final step of separating the added particles from the coated reinforcement of interest.

[0006] It is therefore desirable to provide new techniques that make it possible to do away with such a final separation step while making it possible to obtain a homogeneous and unitary coating of filaments having a high aspect ratio. Description of the invention

[0007] The present description relates to a filament coating process, comprising: - the deposition of a coating on filaments in a treatment zone of a reactor by chemical vapor deposition in a fluidized bed from a gaseous phase introduced into the reactor, the filaments having a shape factor greater than or equal to 5, for example greater than or equal to 10, and being made of ceramic material or carbon, the process further comprising (i) control of the fluidization of the filaments during deposition, and (ii) one or more corrective actions for filament fluidization, each being triggered if a lack of filament fluidization is detected during the control and each comprising a temporary modification of the flow rate of a dispersion gas, forming part of the gaseous phase, introduced into the reactor during which an increased flow rate is imposed, at least equal to three times a nominal flow rate imposed during deposition.This increased data rate is imposed for at least 3 seconds.

[0008] The present invention proposes a method for coating filaments using a fluidized bed chemical vapor deposition technique. It is notable in that it provides control over filament fluidization and, when necessary, corrective fluidization action. During this corrective action, the flow rate of at least one constituent gas of the gas phase, referred to as the dispersion gas, is temporarily increased relative to its predetermined nominal flow rate and adjusted to achieve the deposition in order to obtain, maintain, or restore filament fluidization if it has been lost. The quality of the fluidization can be assessed by monitoring the pressure difference across the treatment zone, i.e., the pressure drop produced by the filaments, as will be detailed below.However, those skilled in the art will recognize that other techniques for controlling filament fluidization, known in themselves, can be implemented, such as measuring the temperature at different points in the treatment area. Generally, the dispersion gas can be the diluent gas of the gas phase, in particular an inert gas such as nitrogen or argon. Alternatively, the dispersion gas can be a reactive gas involved in coating formation, such as dihydrogen, which can notably be used to deposit silicon carbide. As will be discussed below, it is possible to temporarily modify only the flow rate of the diluent gas or only that of the reactive gas, in the proportions and for the durations indicated, to carry out each corrective action. It should also be noted that we do not depart from the scope of the invention if we temporarily modify both the flow rates of the reactant gas and the diluent gas.

[0009] The invention makes it possible, in particular, to maintain fluidization throughout the deposition process, which can take several hours, and thus to obtain uniformly and homogeneously coated filaments, providing optimal performance. Furthermore, the present invention has the advantage of avoiding the need for third-party components such as spacer particles or devices for vibrating or stirring the reactor, thereby considerably simplifying implementation.

[0010] The filaments can result from grinding offcuts from textile operations, such as three-dimensional weaving, or from cutting continuous strands or cables wound into spools. The length variation of filaments obtained by such techniques can vary significantly from one batch to another, which necessitates experimentally adjusting the temporary increase in the dispersion gas flow rate within the ranges provided above to ensure the fluidization of a given batch of filaments. The characteristics relating to the temporary increase in the dispersion gas flow rate provided below are merely preferred and are not essential depending on the batch of filaments being processed.

[0011] In one embodiment, the increased flow rate is at least five times the nominal flow rate, in particular at least ten times the nominal flow rate.

[0012] Such a characteristic advantageously facilitates the fluidization of filaments.

[0013] In particular, if we denote the nominal flow rate DN and the increased flow rate DA, DA can be between 3 DN and 25 DN, for example between 3 DN and 20 DN. DA can be between 5 DN and 25 DN, for example between 5 DN and 20 DN. DA can be between 10 DN and 25 DN, for example between 10 DN and 20 DN.

[0014] In one embodiment, the increased flow rate is imposed for at least 8 seconds, for example for at least 10 seconds.

[0015] In particular, the increased flow rate can be imposed for a duration of between 3 and 30 seconds, for example, between 3 and 20 seconds. This duration can be between 8 and 30 seconds, for example, between 8 and 20 seconds. This duration can also be between 10 and 30 seconds, for example, between 10 and 20 seconds.

[0016] In one embodiment, the temporary change in flow rate relates only to an inert diluent gas of the gaseous phase.

[0017] In this case, the characteristics described above relating to the intensity of the flow rate increase and the duration for which this increased flow rate is imposed apply only to the diluent gas. Such a characteristic allows advantageously avoid any risk of altering the deposit made during corrective fluidization actions.

[0018] Alternatively, the temporary modification of the flow rate relates to both an inert diluent gas of the gaseous phase and a reactive precursor gas of the coating to be deposited.

[0019] In this case, the characteristics described above relating to the intensity of the flow rate increase and the duration for which this increased flow rate is imposed apply to each of the diluent and reactive gases. In the case of this combined modification of the flow rates, the ratio of the reactive gas and diluent gas flow rates can be substantially equal to the nominal ratio imposed for the deposit. However, particularly in the case of short-duration corrective actions, a variation in this ratio during the corrective actions can be permitted without significantly affecting the deposit obtained, such that this variation does not fall outside the scope of the present invention.

[0020] In one embodiment, the coating deposited on the filaments is made of pyrolytic carbon, silicon carbide, boron nitride, silicon-doped boron nitride, silicon nitride or boron-doped carbon.

[0021] In one embodiment, the process further includes, before the coating is deposited, a pre-treatment of the filaments by covering them with a thin layer of pyrocarbon of thickness less than or equal to 5000 nm, for example between 5 nm and 5000 nm.

[0022] Unless otherwise stated, the thickness can be measured using a scanning electron microscope (SEM).

[0023] The inventors have found that this preliminary and fine deposit of pyrocarbon makes it possible to facilitate the fluidization of the filaments.

[0024] In particular, this thin layer of pyrocarbon can be produced in the reactor by chemical vapor deposition in a fluidized bed. More specifically, filament fluidization control can be applied during pretreatment, and one or more corrective actions as described above can be implemented if necessary.

[0025] The present description also relates to a method for manufacturing a part made of composite material, comprising at least: - the implementation of a process such as the one described above in order to obtain coated filaments, - shaping the coated filaments to form a porous preform of the part to be obtained, and - the formation of a matrix in the porosity of the preform in order to obtain the part in composite material.

[0026] In one embodiment, the matrix is ​​formed by infiltrating a molten silicon composition or a molten silicon alloy into the porosity of the preform.

[0027] The present description also relates to a method for manufacturing a part made of composite material, comprising at least: - the implementation of a process such as the one described above in order to obtain coated filaments, - the mixing of the coated filaments with the matrix material or with a matrix precursor, and - the introduction of the mixture thus obtained into a mold and the heat treatment of the introduced mixture in order to obtain the part in composite material.

[0028] Generally speaking, the part can be a turbomachine part, for example an aeronautical turbomachine part or an industrial turbomachine part.

[0029] The present disclosure also relates to a device for chemical vapor deposition in a fluidized bed for implementing a process as described above, comprising: - the reactor defining the treatment zone in which the fluidized bed chemical vapor deposition is intended to be carried out on the filaments from the gaseous phase, - a tank containing the dispersion gas in communication with the treatment area, - a means of modulating the flow rate of the dispersion gas configured to perform each corrective action, and - a control and command unit configured to detect filament fluidization or the absence of such fluidization, and to actuate the flow modulation means according to the result of this detection.

[0030] This object implements an automated triggering of the corrective action(s), thus further simplifying the implementation of the process for the user. It should be noted that the invention is not limited to this case and that each corrective action can be triggered by the user after a lack of fluidization has been observed.

[0031] In one embodiment, the device further comprises a differential pressure sensor configured to measure the pressure difference across the treatment zone, the modulation means being configured to perform each corrective action based on the measurement result provided by the differential pressure sensor, and the control unit being configured to compare the pressure difference measured by the differential pressure sensor to a value predetermined corresponding to a fluidization of the filaments, and to actuate the flow modulation means according to the result of this comparison.

[0032] This embodiment relates to fluidization control by differential pressure measurement, but alternatively, fluidization control could be implemented by a different technique, for example by temperature measurement, as mentioned above. Brief description of the drawings [Fig.1] Fig.1 illustrates, schematically and partially, a device for implementing a chemical vapor deposition process in a fluidized bed according to the invention. [Fig.2] Fig.2 represents in isolation a filament intended to be processed within the framework of the invention. [Fig.3] Fig.3 represents an example of modulation of the dispersion gas flow rate that can be implemented within the framework of the invention. [Fig.4] Fig.4 illustrates, schematically and partially, the fluidization of the filaments obtained within the framework of the invention. [Fig.5] Fig.5 provides photographs obtained by scanning electron microscopy of coated filaments by implementing an example of a process according to the invention. [Fig.6] Fig.6 provides photographs obtained by scanning electron microscopy of coated filaments by implementation of another example of a process according to the invention. [Fig.7] Fig.7 illustrates possible sequences of steps to obtain a part made of composite material according to the invention. Description of the implementation methods

[0033] The invention is now described by means of figures, which are present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0034] We will describe, in relation to [Fig.1], the structure of a device 1 useful for implementing a coating process according to the invention.

[0035] The device 1 comprises a reactor 3 defined by a wall which may be made of quartz, Inconel®, or alumina. The reactor 3 comprises an inlet 5 in communication with a gas source 6 through which the gaseous phase comprising the precursor of the coating to be formed is intended to be introduced. The reactor 3 further comprises an outlet 7 in communication with a pumping system 8 to ensure a vacuum is created in the reactor 3. The device 1 includes a heating system 9 capable of heating the interior of reactor 3 to enable the formation of the coating from the precursor introduced by chemical vapor deposition. To stabilize the temperature of reactor 3 during coating, reactor 3 can be fitted at the inlet 5 with a thermal insulating element.

[0036] The filaments 11 to be coated are present inside the reactor 3 in a treatment zone ZT. The ZT zone is located above the inlet 5. The filaments 11 may have distinct lengths 1 and, for example, have an average length 1, corresponding to their size D50, less than or equal to 5 mm, for example, less than or equal to 1 mm, for example, less than or equal to 500 µm. The average length of the filaments 11 may be between 50 µm and 5 mm, for example, between 50 µm and 1 mm, for example, between 50 µm and 500 µm. The filaments 11 may have an average diameter, corresponding to the diameter D50, less than or equal to 20 µm, for example, between 5 µm and 20 µm, or even between 8 µm and 14 µm.The shape factor of the filaments 11, corresponding to the ratio between their length and their diameter, can be greater than or equal to 5, for example greater than or equal to 10, for example greater than or equal to 50, or even between 5 and 100, or between 10 and 100 or between 50 and 100. The filaments 11 can be obtained from long fibers by mechanical cutting, grinding or by laser cutting.

[0037] The filaments 11 are made of ceramic or carbon material. The filaments 11 may be made of carbide, nitride, or oxide ceramic material. In particular, silicon carbide filaments 11 may be used, having, for example, an oxygen content of 1% or less as an atomic percentage. Such filaments 11 may be Hi-Nicalon type S fibers marketed by NGS. The filaments 11 may constitute the only material to be coated in the treatment zone; in this case, in particular, there is an absence of third-party particles having a granular or spherical shape.

[0038] The gaseous phase introduced into reactor 3 for the production of the coating depends on the nature of the coating to be obtained and it is up to the general knowledge of the person skilled in the art to choose it and to determine the associated deposition conditions, in terms of temperature, pressure and nominal flow rate of each of the gases used.

[0039] A person skilled in the art shall ensure, during implementation of the invention, that a fluidization phenomenon of the filaments 11 is achieved. To enable monitoring of the fluidization, the device 1 considered here includes a differential pressure sensor 4, allowing measurement of the pressure drop across the ZT zone (or across the filament bed 11). A person skilled in the art may advantageously aim to maintain this pressure drop at a value equal, to within 20%, to the ratio between the weight of the bed and the cross-section of the reactor 3, which corresponds to a state where the filaments are considered fluidized. This ratio is denoted RA. If the pressure drop is below this range, the filaments 11 are not fluidized. A person skilled in the art can also ensure relative temperature homogeneity within the bed. This thermal property, characteristic of optimally functioning fluidized beds, is achieved by the presence of bubbles that ensure excellent filament agitation. Heat transfer within the bed is thus greatly enhanced. Thermocouples 17 located inside a sheath 15 centered at reactor 3 are positioned at different locations within the fluidized bed (at different heights in the ZT zone) and allow for monitoring the bed's isothermal properties. The quality of the fluidization can also be assessed from the maximum temperature difference displayed by the thermocouples.For example, a skilled person can perform the application with a maximum temperature difference of less than or equal to 20°C, for high-temperature applications (above 800°C).

[0040] The invention is remarkable in that it proposes a particular solution for fluidizing filaments by temporarily increasing the flow rate of at least one gas constituting the gaseous phase if a pressure drop that is too low is detected by the sensor 4.

[0041] In the illustrated example, the gas source 6 comprises a first source 61 of the precursor intended to form the deposit in the ZT zone, and a second source 62 of a diluent gas, distinct from the precursor, and intended to be mixed with the latter to form the gas phase. Each of the sources 61, 62 is associated with a respective modulation means MD1, MD2 for the flow rate of the gas in question so as to obtain the desired proportions in the gas phase introduced into the reactor 3. In the illustrated example, the diluent gas is inert and constitutes the dispersion gas; its flow rate will be temporarily increased so as to fluidize the filaments. The diluent gas can be nitrogen or argon. The invention also applies to the case where the flow rate of the reactive gas participating in the deposition is increased, or where the flow rates of the reactive gas and the diluent gas are jointly increased to obtain, maintain, or restore the fluidization of the filaments.

[0042] Figure 3 illustrates an example of modulation of the dispersion gas flow rate as a function of time which can be implemented within the framework of the invention.

[0043] As indicated above, the gases used and the associated conditions, in terms of temperature, pressure and nominal flow rate of each of the gases used, are first determined by the person skilled in the art according to the deposit to be made.

[0044] The filaments are introduced into the ZT zone, and then reactor 3 is brought to the predetermined deposition temperature during a temperature ramp-up EM step, during which the diluent gas, from source 62, is introduced into reactor 3 at its predetermined nominal flow rate DN. The deposition ED step begins when this The temperature is reached to coat the filaments with the precursor, from source 61, introduced into reactor 3. This precursor can also be introduced into reactor 3 at its predetermined nominal flow rate during this EM step, or this introduction can be initiated only when the deposition temperature is reached. The pressure is regulated to a predetermined value compatible with the deposition to be carried out during the EM and ED steps. In the specific case of pyrocarbon deposition, the precursor gas can be a hydrocarbon such as propane, methane, or a mixture of these two gases. The diluent gas can be an inert gas such as nitrogen or argon. In the case of silicon carbide deposition, the precursor gas can be methyltrichlorosilane (CH3SiCl3 or MTS) and the dispersion gas can be dihydrogen.

[0045] In the example of [Fig. 3], an insufficient pressure drop was detected by the differential pressure sensor 4 at several points during step ED, which triggered the execution of several corrective actions AC for filament fluidization. In the case where a device according to [Fig. 1] is implemented, the signal from sensor 4 is transmitted to a control unit U, which acts on the means MD2 to significantly increase the flow rate of the dispersion gas from the second source 62 in order to perform each corrective action AC. During each AC action, the dispersion gas is introduced into reactor 3 at an increased flow rate DA, which is at least three times greater than the nominal flow rate DN, as indicated above. The duration T of application of the increased flow rate DA can be greater than or equal to 3 seconds, as described above.A pressure drop reflecting fluidization of the filaments 11 can be obtained after a single AC action, or after a succession of such AC actions, each spaced a predetermined distance apart, for example, at least one minute. Following each AC action, the MD2 device is activated again to return the dispersion gas flow rate to the nominal flow rate DN. Generally, the dispersion gas can be introduced into reactor 3 at its nominal flow rate DN throughout the entire deposition process, except during the AC action(s). For example, the flow rate of the precursor gas, separate from the diluent gas, may remain unchanged during deposition, with only the diluent gas flow rate being modified during each AC action. It should be noted that a temporary change in the ratio of the reactive gas to the diluent gas flow rates can be tolerated without significantly affecting the deposition.Furthermore, as indicated above, the invention remains within the scope of action if the flow rate of the reactive gas and the flow rate of the diluent gas are jointly increased during corrective actions. Unit U may include a computer equipped with software configured to act on the means MD2 based on a comparison of the pressure difference measured by sensor 4 to a predetermined value corresponding to a state of filament fluidization. Thus, if the... When the pressure difference measured by sensor 4 decreases to less than 0.8 * RA (RA being the ratio defined above), unit U can actuate means MD2 to increase the flow rate of the dispersion gas introduced into reactor 3 from the nominal flow rate DN to the increased flow rate DA. When the pressure difference measured by sensor 4 increases to greater than or equal to 0.8 * RA, unit U can actuate means MD2 to decrease the flow rate of the dispersion gas introduced into reactor 3 from the increased flow rate DA to the nominal flow rate DN.

[0046] The example illustrated in [Fig. 3] shows the execution of several AC actions, each with the same duration T, but this does not depart from the scope of the invention if only one AC action is performed, or if the AC actions have different durations. The number and duration of the AC actions depend on the fluidization requirement of the filaments 11 observed in the experiment under consideration. Generally, the duration or number of these AC actions can be limited to the minimum quantity sufficient to achieve filament fluidization, by stopping the corrective action (reduction of the dispersion gas flow rate to the nominal flow rate DN) as soon as this fluidization is achieved, or for example, at the latest 5 seconds after this fluidization is achieved.

[0047] In the specific case where the filaments are not fluidized after the EM step, the inventors observed that applying a thin layer of pyrocarbon could disperse the filaments while avoiding any bonds that would prevent their fluidization. One or more AC actions are then performed during the deposition as described above to maintain fluidization.

[0048] The example just described concerns automated control of the dispersion gas flow rate, but it should be noted that we do not depart from the scope of the invention when this is not the case and when the measurement provided by the sensor 4 is monitored by a user who acts, according to it, on the means MD2 to adjust the dispersion gas flow rate (absence of a control unit U).

[0049] The paragraphs below detail experiments carried out by the inventors to deposit pyrocarbon on filaments 11 within the framework of the invention.

[0050] First experiment

[0051] Reactor 3 was first filled with a few centimeters of 0.5 mm diameter zirconia beads positioned on a diffuser. The filaments 11 were introduced into the CVD fluidized bed reactor above the zirconia beads. The reactor pressure was regulated to reach 200 mbar, and then a flow of diluent (nitrogen) and precursor (propane) gas was introduced.

[0052] A mass of approximately 250g of filaments 11 was loaded into reactor 3. This mass alone theoretically generates a pressure drop of 10.2 mbar. Three Thermocouples were placed at the core of the bed, respectively at the bottom, top, and a few centimeters above the fixed load. For this entire experiment, a minimum fluidization velocity Umf of the filaments was calculated and was approximately 55 cm / min.

[0053] The diluent gas (here nitrogen) and precursor gas (here propane) were injected into reactor 3. The flow rates were selected so that the gas velocity was equal to 15 x Umf. No fluidization of the feed was observed at ambient temperature. The temperature ramp was carried out to reach a temperature close to 900°C. As the temperature increases, the gas velocity also increases. The pressure drop (AP) also increases but still does not reach the desired theoretical pressure drop value, an indicator of fluidization.

[0054] From 800°C, the precursor gas began to decompose and the pressure drop AP remained low, a sign of bridging (agglomeration) of the filaments 11.

[0055] At the set temperature, numerous injections of diluent gas (nitrogen) were carried out in the bed at intervals of a few minutes. Propane was always injected at a constant flow rate. After several series of nitrogen injections at different rates, the pressure drop in the AP bed reached a value representative of good fluidization. Furthermore, fluidization was confirmed by the fact that the temperatures measured by the different thermocouples were similar.

[0056] After approximately 30 minutes, the experiment was stopped. The coated fibers were observed under SEM (see [Fig. 5]). The fine coating is very clearly visible when the fibers are lightly crushed. The inventors also observed that all of the filaments were coated, indicating fluidization achieved during the deposition process.

[0057] Of course, the duration of the ED step is adjusted according to the desired thickness of the deposit and further corrective actions can be carried out if a drop in pressure loss is detected.

[0058] Second experiment

[0059] In the second experiment, a thicker deposit is considered on the filaments obtained from the first experiment described above, which had a thin PyC deposit. The aim here is to validate the feasibility of a thicker PyC ex-C3H8 deposit on particles with a high aspect ratio. This deposition was carried out under the same conditions as before, only the temperature was modified to reach 1000°C at the center of the bed.

[0060] At ambient temperature and during the temperature rise, the pressure drop is low, less than expected: fluidization is not achieved. At 800°C, the decomposition temperature of the precursor gas, the temperatures within the bed are similar, indicating good thermal homogeneity in the middle of the bed. At the same time, AP increases spontaneously to reach a value indicative of effective and stable fluidization.

[0061] During deposition, corrective actions (CA) are performed in case of a drop in pressure drop to restart fluidization. After several hours of deposition, the supply of precursor gas is stopped and the heating is switched off. An increased nitrogen flow rate can also be used to accelerate cooling. The coated filaments obtained are illustrated in [Fig. 6].

[0062] Fig. 7, which will now be described, illustrates a series of steps that can be implemented to prepare a part made of composite material after obtaining the coated filaments by implementing a process as described above (step E10).

[0063] A mixture comprising a binder and coated filaments can be prepared. The binder may, for example, comprise a polymer, such as a thermoplastic or thermosetting resin, or a plasticizer. It may be advantageous to heat the mixture to make the binder more fluid, thus facilitating mixing and allowing for better homogenization. A porous preform of the part to be manufactured is then formed by shaping (step E20) the prepared mixture, for example, by injecting the mixture into the cavity of a mold followed by the removal of the binder. The binder removal can be carried out by pyrolysis so as to leave a consolidating phase that improves the shape retention of the porous preform. The porous preform is not woven.

[0064] The matrix is ​​then formed within the porosity of this porous preform (step E30). The matrix coats the filaments. The matrix can be formed by molten infiltration of the porosity of the porous preform with a molten composition comprising molten silicon, in order to obtain the part. The molten composition can consist of pure molten silicon or, alternatively, be in the form of a molten alloy of silicon and one or more other constituents. A part made of CMC material is then obtained. Alternatively, another type of matrix, such as an organic or carbon matrix, can be formed. Various matrix formation techniques are possible, such as chemical vapor infiltration or processes involving the infiltration and pyrolysis of matrix precursors in the liquid state. Alternatively, the coated filaments can be mixed with the matrix material or a matrix precursor (step E21), and then this mixture can be introduced into a mold.The part can then be obtained by heat treatment (step E31) of the mixture introduced into the mold, for example to crosslink the matrix material or pyrolyze the precursor.

[0065] The resulting part may be a turbomachine component, for example, an aeronautical or industrial turbomachine component. The resulting part may be a turbine component. The resulting part may be a turbomachine blade, for example, a turbine blade. Alternatively, the resulting part may be a turbine ring sector.

[0066] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A filament coating process comprising: - the deposition (E10) of a coating on filaments (11) in a treatment zone (ZT) of a reactor (3) by chemical vapor deposition in a fluidized bed from a gaseous phase introduced into the reactor, the filaments having a form factor greater than or equal to 5 and being made of ceramic material or carbon, the process further comprising (i) control of filament fluidization during deposition, and (ii) one or more corrective actions (CA) of filament fluidization, each being triggered if a lack of filament fluidization is detected during control and each comprising a temporary modification of the flow rate of a dispersion gas, forming part of the gaseous phase, introduced into the reactor during which an increased flow rate (DA) is imposed at least equal to three times a nominal flow rate (DN) imposed during deposition, this increased flow rate being imposed for at least 3 seconds.

2. Method according to claim 1, wherein the increased flow rate (DA) is at least equal to five times the nominal flow rate (DN).

3. Method according to claim 1 or 2, wherein the increased flow rate (DA) is imposed for at least 8 seconds.

4. A method according to any one of claims 1 to 3, wherein the temporary change in flow rate relates only to an inert diluent gas of the gaseous phase.

5. A method according to any one of claims 1 to 3, wherein the temporary change in flow rate relates both to an inert diluent gas of the gaseous phase and to a reactive precursor gas of the coating to be deposited.

6. A method according to any one of claims 1 to 5, wherein the coating deposited on the filaments (11) is pyrolytic carbon, silicon carbide, boron nitride, silicon-doped boron nitride, silicon nitride or boron-doped carbon.

7. A method according to any one of claims 1 to 6, wherein the method further comprises, prior to coating deposition, a pretreatment of the filaments by coating them with a thin layer of pyrocarbon of thickness less than or equal to 5000 nm.

8. A method for manufacturing a part made of composite material, comprising at least: - the implementation of a process according to any one of claims 1 to 7 in order to obtain coated filaments, - the shaping (E20) of the coated filaments so as to form a porous preform of the part to be obtained, and - the formation of a matrix (E30) in the porosity of the preform in order to obtain the part in composite material.

9. A method according to claim 8, wherein the matrix is ​​formed by infiltrating a molten silicon composition or a molten silicon alloy into the porosity of the preform.

10. A method for manufacturing a part made of composite material, comprising at least: - carrying out a process according to any one of claims 1 to 7 in order to obtain coated filaments, - mixing (E21) the coated filaments with the matrix material or with a matrix precursor, and - introducing the mixture thus obtained into a mold and heat treating (E31) the introduced mixture in order to obtain the part made of composite material.

11. Device (1) for chemical vapor deposition in a fluidized bed for carrying out a process according to any one of claims 1 to 7, comprising: - the reactor (3) defining the treatment zone (TZ) in which chemical vapor deposition in a fluidized bed is intended to be carried out on the filaments (11) from the gaseous phase, - a reservoir (3) containing the dispersion gas in communication with the treatment zone, - a means for modulating (MD2) the flow rate of the dispersion gas configured to perform each corrective action (AC), and - a control and command unit (U) configured to detect fluidization of the filaments or the absence of such fluidization, and to actuate the flow rate modulation means according to the result of this detection.

12. A device according to claim 11, wherein the device (1) further comprises a differential pressure sensor (4) configured to measure the pressure difference across the treatment zone (TZ), the modulation means (MD2) being configured to perform each corrective action (CA) according to of the measurement result provided by the differential pressure sensor, and the control and command unit (U) being configured to compare the pressure difference measured by the differential pressure sensor to a predetermined value corresponding to a fluidization of the filaments, and to actuate the flow modulation means according to the result of this comparison.

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