Process of depositing a coating by a chemical vapor deposition process.

Abstract

Method for depositing a coating by a chemical vapor deposition process. The invention relates to a method for chemical vapor deposition of a coating on a substrate, comprising at least the following steps: - a step of arranging the substrate (100, 200) in a reaction chamber; - a step of obtaining a first layer (101, 201), by supplying the chamber with a mixture of dihydrogen and methyltrichlorosilane in a first volume ratio H2 / methyltrichlorosilane, the chamber being at a first temperature and at a first pressure;- a step of obtaining a second layer (102, 203), by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane in a second H2 / methyltrichlorosilane volume ratio different from the first ratio, the enclosure being at a second temperature and at a second pressure, at least one of the second volume ratio, the second temperature and / or the second pressure being different respectively from the first volume ratio, the first temperature and / or the first pressure. Figure for the abstract: Fig. 1.;

Description

Title of the invention: Method for depositing a coating by a chemical vapor deposition process. Technical field

[0001] The present disclosure relates to a method of coating a substrate with a coating comprising silicon and carbon. Prior art

[0002] Ceramic matrix composite (CMC) materials withstand temperatures ranging from 600°C to 1400°C. Due to their better resistance to high temperatures, CMCs require less cooling. This cooling traditionally comes from a tap in the compressor which impacts the efficiency of the turbomachine, CMC materials therefore make it possible to improve engine efficiency which reduces fuel consumption.

[0003] Furthermore, the use of ceramic matrix composite materials 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.

[0004] Due to their industrial interest, the manufacturing processes of composite materials have undergone numerous improvements in recent years.

[0005] Among the manufacturing processes for such materials, chemical vapor infiltration processes (or "CVI" for the acronym in English "Chemical Vapor infiltration") are known.

[0006] Such methods can not only be used for the formation of the ceramic matrix of CMC materials but are also used for depositing coatings on parts, in particular CMC parts, for example to allow the subsequent attachment of protective coatings against oxidation or temperature.

[0007] CVI processes require the use of gaseous precursors which, by chemical decomposition under the effect of temperature, allow the desired layer to be formed.

[0008] Although this method is already used industrially, it nevertheless requires complex ovens as soon as the nature of the layers to be deposited is multiple.

[0009] Indeed, it is necessary to be able to introduce predefined precursors into the ovens to obtain the desired layer at the desired time. This complicates the programming of the ovens which must be prepared specifically to allow the introduction of the desired precursors at the right time.

[0010] This is why it is desirable to have CVI processes which would allow the depositing of coatings of several types while using more simpler than the methods of the prior art. Statement of the invention

[0011] The invention aims precisely to respond to the problem stated above.

[0012] According to a first of its aspects, it relates to a process for chemical vapor deposition of a coating on a substrate, comprising at least the following steps: - a step of placing the substrate in a reaction chamber; - a step of obtaining a first layer, by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane in a first volume ratio H2 / methyltrichlorosilane, the enclosure being at a first temperature and at a first pressure, - a step of obtaining a second layer, by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane in a second H2 / methyltrichlorosilane volume ratio different from the first ratio, the enclosure being at a second temperature and at a second pressure, at least one of the second volume ratio, the second temperature and / or the second pressure being different respectively from the first volume ratio, the first temperature and / or the first pressure.

[0013] The proposed method makes it possible to deposit a coating comprising two layers both comprising silicon and carbon, but in different contents and this in a single reaction chamber.

[0014] The expression "in a complementary content" means that the sum of the atomic content of silicon and the carbon content in a layer of the invention accounts for more than 99.5% of the composition of the layers, or even more than 99.9% or even more than 99.95%.

[0015] This definition of a layer is intended to allow for unavoidable impurities to remain for a CVI process, provided that these impurities are present in an atomic content of said impurities of less than 0.5%, or even 0.1%, and even less than or equal to 0.05%.

[0016] In one embodiment, the silicon content of the second layer differs by at least 10% from the silicon content of the first layer.

[0017] The expression "a second content differing by at least X% from the first content" means that the difference between the first and second contents is, in absolute value, at least X%. The first content may be higher or lower than the second content provided that the difference is greater than X% in absolute value.

[0018] In one embodiment, the temperature and pressure retained for a step of obtaining a given layer are understood respectively as the temperature and the pressure prevailing in the enclosure where the deposition process is carried out.

[0019] In one embodiment, a step of obtaining a layer is directly preceded by a preparation step consisting of bringing the enclosure to the temperature and pressure desired for the step of obtaining the layer but during which no precursor is introduced.

[0020] The “H2 / methyltrichlorosilane volume ratio” is understood in the classical sense of the term “ratio”, namely as the volume quantity of dihydrogen present in the precursors divided by the volume quantity of methyltrichlorosilane present in the precursors.

[0021] Preferably, the process does not comprise precursors other than dihydrogen and methyltrichlorosilane.

[0022] However, in one embodiment, the precursors may be dissolved in a carrier gas.

[0023] For the purposes of the present application, a carrier gas is understood to be a gas which does not participate in the reaction and which only serves to dissolve the gaseous precursors, for example to promote their transport or good mixing.

[0024] In one embodiment, one of the layers is a layer comprising a silicon atomic content greater than or equal to 95% and a complementary carbon atomic content, said layer being obtained with a H2 / methyltrichlorosilane volume ratio greater than or equal to 20 at a temperature between 850°C and 920°C at a pressure between 200 mbar and 400 mbar.

[0025] This embodiment makes it possible to deposit a layer of silicon lightly doped with carbon, denoted Si(C).

[0026] In one embodiment, one of the layers is a silicon carbide layer comprising a silicon atomic content of between 45% and 55% and a complementary carbon atomic content, said layer being obtained with an H2 / methyltrichlorosilane volume ratio of between 7 and 10 at a temperature of between 920°C and 1050°C at a pressure of between 100 mbar and 300 mbar.

[0027] This embodiment makes it possible to deposit a layer of silicon carbide denoted SiC.

[0028] In one embodiment, one of the layers is a silicon carbide layer comprising a silicon atomic content of between 49% and 51% and a complementary carbon atomic content, said layer being obtained with an H2 / methyltrichlorosilane volume ratio of between 7 and 10 at a temperature of between 920°C and 1050°C at a pressure of between 100 mbar and 300 mbar.

[0029] In one embodiment, one of the layers is a layer comprising an atomic content of silicon less than or equal to 20% and a complementary atomic content of carbon, said layer being obtained with a volume ratio H2 / methyltrichlorosilane less than or equal to 3 at a temperature between 950°C and 1020°C at a pressure between 50 mbar and 100 mbar.

[0030] This embodiment makes it possible to deposit a layer of carbon doped with silicon denoted C(Si).

[0031] It is to the credit of the inventors to have determined that it was possible to obtain a layer of SiC, C(Si) or Si(C) with the same precursors, and this only by varying one or more deposition parameters chosen from the volume ratio between the precursors, the temperature or the pressure.

[0032] In particular, the embodiments described thus make it possible to solve a problem of the methods of the prior art which is that of having to have particular precursors for the deposition of particular layers.

[0033] It is notable that the Si(C), SiC and C(Si) layers are perfectly compatible with each other. In other words, the method of the invention makes it possible to obtain a coating comprising at least two distinct layers among those above while ensuring excellent resistance to delamination for the whole.

[0034] Thus, thanks to the method described, it becomes possible to deposit a coating comprising two distinct layers without using different precursors for the different layers.

[0035] In one embodiment, the method is not limited to a coating comprising two layers.

[0036] In one embodiment, the method further comprises: - a step of obtaining a third layer, by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane in a third H2 / methyltrichlorosilane volume ratio, at a third temperature and at a third pressure, at least one of the third volume ratio, the third temperature and / or the third pressure being different respectively from the second volume ratio, the second temperature and / or the second pressure.

[0037] This embodiment makes it possible to produce coatings with particularly advantageous compositions, without having to modify the nature of the precursors, and without having to complicate the furnaces for carrying out such processes.

[0038] In one embodiment, the third layer may have a composition close to that of the first layer. In other words, in one embodiment, the third volume ratio, the third temperature and the third pressure may be respectively equal to the first ratio, the first temperature and the first pressure.

[0039] In one embodiment, the coating can be produced on a substrate and said substrate can be a part made of composite material, for example a part made of SiC / SiC composite, or even an aeronautical part made of composite material.

[0040] Indeed, the method of the invention then makes it possible to deposit on the surface of such a SiC / SiC material a coating comprising a first layer of Si(C), a second layer of SiC and a third layer of Si(C).

[0041] Such a coating can be obtained in a simplified manner compared to the methods of the prior art.

[0042] Such a three-layer coating is also an excellent bonding layer, with properties at least equivalent to the bonding layers of the prior art but obtained in a much simpler manner, and in less complex ovens.

[0043] In one embodiment, the thickness of a layer is controlled by the duration of the step of deposition of said layer, i.e. the duration of introduction of the precursors in a given volume ratio, at the desired pressure and temperature.

[0044] For example, the duration of the steps for obtaining one or more of the layers may be between 5 and 15 hours.

[0045] This makes it possible to obtain layers with a thickness between 10 pm and 50 pm.

[0046] In one embodiment, a step of obtaining a given layer is separated from a step of obtaining the following layer by a purging step, during which all the precursors present are removed from the reaction chamber.

[0047] Such a purging step can for example be carried out by filling the reaction chamber with an inert gas, for example nitrogen or argon, so as to evacuate the precursors from the step of obtaining a layer.

[0048] Alternatively or additionally, and in such a case preferably before filling with an inert gas, the purging step may comprise placing the reaction chamber under vacuum.

[0049] Such a purging step allows a clean transition from a step of obtaining a layer to the step of obtaining the next layer.

[0050] This results in a coating in which the layers are then very well defined.

[0051] Furthermore, the vacuum step makes it possible to improve the purging step, which allows an even more straightforward transition from the step of obtaining one layer to the next.

[0052] In another embodiment, the method comprises, between two successive steps of obtaining a layer, a transition step during which the enclosure is supplied with a mixture of dihydrogen and methyltrichlorosilane in a volume ratio H2 / methyltrichlorosilane which varies during the transition step between the ratio of the first of the steps of obtaining a layer and the ratio of the second of the steps of obtaining a layer, the enclosure being at a temperature which varies during the transition step between the temperature of the first of the steps of obtaining a layer and the temperature of the second of the steps of obtaining a layer and at a pressure which varies during the transition step. between the pressure of the first of the stages of obtaining a layer and the pressure of the second of the stages of obtaining a layer.

[0053] This embodiment makes it possible to provide a transition zone in the coating between two successive layers resulting from the process. In such a transition zone, the carbon and silicon contents vary between the contents of the two layers bordering the transition zone.

[0054] This embodiment is particularly important because it ensures even better chemical compatibility between the two successive layers. Indeed, the progressive variation in composition from the first of the two layers to the second ensures mechanical continuity of the deposit so that the assembly offers better resistance to delamination.

[0055] In one embodiment, the transition step can be carried out for a duration of between 0.5 and 2 hours.

[0056] This ensures that the transition zone is of satisfactory thickness to ensure excellent compatibility between the two zones and at the same time keeps the transition zone small enough not to affect the overall weight of the part.

[0057] In an embodiment that includes such a transition step, all the parameters that vary can vary over an identical duration.

[0058] In one embodiment, at least one of the H2 / methyltrichlorosilane volume ratio, the temperature, or respectively the pressure used for the transition step varies during the transition step in an affine manner between the H2 / methyltrichlorosilane volume ratio used for the step of obtaining a layer preceding the transition step and the H2 / methyltrichlorosilane volume ratio used for the step of obtaining a layer following the transition step; between the temperature used for the step of obtaining a layer preceding the transition step and the temperature used for the step of obtaining a layer following the transition step; and / or between the pressure used for the step of obtaining a layer preceding the transition step and the pressure used for the step of obtaining a layer following the transition step.

[0059] An "affine transition" should be understood as a constant variation of the parameter that varies over the entire duration of the variation. In other words, the parameter that varies can be written as an affine function of the time elapsed since the start of the transition step.

[0060] In one embodiment, the substrate may be an aeronautical part made of ceramic matrix composite material.

[0061] In one embodiment, the substrate may be selected from a turbomachine blade, a distributor portion or a ring sector.

[0062] In one embodiment, the substrate may be a fiber, for example a fiber silicon carbide, glass fiber or carbon fiber.

[0063] In such an embodiment, the substrate may also be a fiber indicated coated with a consolidation interphase.

[0064] For example, such a consolidation interphase may comprise a first layer, for example comprising boron nitride BN or pyrocarbon PyC, placed directly in contact with the fiber.

[0065] In one embodiment, the interphase may further comprise a second external layer placed directly in contact with the first layer and allowing it to be protected, which then guarantees the integrity of the consolidation interphase.

[0066] The deposition of the interphase can be done in a manner known as such and the interphase should not be understood as a layer of a coating that the method described here makes it possible to obtain.

[0067] Such an interphase can give the fiber even better properties, particularly in terms of resistance to cracking and oxidation.

[0068] The manufacturing process is thus simplified compared to the processes of the prior art and offers a major advantage for such substrates. Brief description of the drawings

[0069] [Fig-1] [Fig. 1] is an example of a part that can be obtained in one embodiment of the method.

[0070] [Fig.2] [Fig.2] is an example of the evolution of the temperature over time, for carrying out a method in one embodiment.

[0071] [Fig.3] [Fig.3] is an example of the evolution of the precursor ratio over time, for carrying out a method in one embodiment.

[0072] [Fig.4] [Fig.4] is an example of a part that can be obtained in one embodiment of the method.

[0073] [Fig.5] [Fig.5] is an example of the evolution of the temperature over time, for carrying out a method in one embodiment.

[0074] [Fig.6] [Fig.6] is an example of the evolution of the precursor ratio over time, for carrying out a method in one embodiment. Description of the embodiments

[0075] 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.

[0076] In one embodiment, the substrate may be an aeronautical part made of ceramic matrix composite material.

[0077] For example, it may be a turbine blade made of SiC / SiC material, for example a high pressure turbine or a low pressure turbine, a distributor portion made of SiC / SiC material, or even a turbine ring sector.

[0078] On such parts, a so-called environmental barrier layer is generally placed, giving the substrate better resistance to oxidation and corrosion.

[0079] Conventionally, a bonding layer, often composed of silicon, is placed between the substrate and the environmental barrier layer, which allows good chemical compatibility with both the substrate and the environmental barrier layer, so that the assembly has excellent resistance to delamination.

[0080] A coating obtained by the process described above makes it possible to obtain a bonding layer of at least as good quality as those accessible via the processes of the prior art, while being able to be obtained in less complex ovens.

[0081] For example, such a bonding layer may comprise a first and a third layer comprising an atomic silicon content greater than or equal to 95% and a complementary atomic carbon content, denoted Si(C) and a second layer of silicon carbide SiC.

[0082] The insertion of such a layer of silicon carbide SiC in the middle of the coating makes it possible to ensure better resistance to oxidation of the underlying substrate without modifying the adhesion of the Si(C) bonding layer with the substrate.

[0083] It is particularly interesting to use the process described above for the manufacture of such an adhesion layer, because it allows such a coating to be obtained in a single reaction chamber.

[0084] Figures 1 to 3 refer to such an embodiment.

[0085] [Fig.l] very generally illustrates a substrate 100 coated with a first layer 101, a second layer 102 and a third layer 103.

[0086] The third layer 103 is itself coated with an environmental barrier layer 104.

[0087] The environmental barrier 104 is known as such and may in particular comprise a rare earth disilicate, for example yttrium Y2Si2O7 or ytterbium Y 2Si2O7. It will not be described in further detail.

[0088] As described above, the sequence of layers 101, 102 and 103 can be carried out by means of a method of the invention in a single enclosure.

[0089] Indeed, and as indicated, it is to the credit of the inventors to have managed to determine that with the same precursors of dihydrogen H2 and methyltrichlorosilane CH3SiCl3 it is possible to deposit layers of different compositions by varying the H2 / methyltrichlorosilane ratio, the pressure and the temperature during the deposition steps.

[0090] Without wishing to be bound by theory, the inventors have determined that temperatures between 850°C and 920°C do not allow the dehydrogenation of the radical methyl CH3 but nevertheless allow the reduction of silicon from SiCl3, which then makes it possible to have a process for forming a layer comprising an atomic content of silicon greater than or equal to 95% and a complementary atomic content of carbon: Si(C).

[0091] Furthermore, they determined that increasing the H2 / methyltrichlorosilane ratio promoted the hydrogenation of the methyl radical CH3 into methane which prevents carbon from being deposited.

[0092] The inventors have also determined that increasing the temperature, for example between 920°C and 1050°C, allows both the reduction of SiCl3 to silicon and the dehydrogenation of the methyl radical to promote carbon deposition.

[0093] By further adjusting the H2 / methyltrichlorosilane ratio introduced into the reaction chamber, it becomes possible to deposit silicon carbide comprising an atomic silicon content of between 45% and 55%, or even between 49% and 51%, and an additional atomic carbon content SiC.

[0094] Thus, to obtain a coating described in [Fig. 1], it is possible to place oneself in the temperature conditions T illustrated in [Fig.2] and with a supply of the reaction chamber with the ratio R of precursors illustrated in [Fig.3], the precursors being dihydrogen H2 and methyltrichlorosilane CH3SiCl3.

[0095] For the deposition of the layer 101 of Si(C) on the surface of the substrate 100, dihydrogen H2 and methyltrichlorosilane CH3SiCl3 precursors are provided in a ratio greater than or equal to 20, or even 20, as illustrated in [Fig. 3], the reaction chamber being at a temperature between 850°C and 920°C, or even 920°C as illustrated in [Fig. 2].

[0096] The ratio is understood as the volume of dihydrogen supplied divided by the volume of methyltrichlorosilane.

[0097] For example, the pressure may be between 200 mbar and 400 mbar throughout the duration of the process.

[0098] These conditions are maintained for a duration tb duration of the step of obtaining the first Si(C) layer.

[0099] The duration ti can be determined as a function of the desired thickness e for the first layer 101.

[0100] In the embodiment shown in figures 2 and 3, discontinuous variations in temperature and ratio are visible, between two successive stages of obtaining layers, marked by dotted lines.

[0101] These dotted lines may correspond to a step of purging the reaction chamber, for example by filling it with nitrogen or argon, in order to evacuate all the precursors present for the step of obtaining a previous layer.

[0102] As indicated above, the purging step may optionally comprise a step of placing the reaction chamber under vacuum.

[0103] In an embodiment which is that shown, it is possible, after a purging step, to carry out a second step of depositing a layer 102 while maintaining a temperature and a ratio of precursors different from those of the first step for a duration t2, duration of the step of obtaining the second layer 102 of silicon carbide Si.

[0104] In one embodiment, a layer obtained during a given obtaining step may be directly in contact with a layer obtained during the following obtaining step.

[0105] The distinction between the two layers is even clearer if a purging step is performed.

[0106] Preferably, the duration t2 is determined as a function of the thickness e2 desired for the second layer 102.

[0107] For the deposition of the SiC layer 102 on the surface of the first layer 101, dihydrogen H2 and methyltrichlorosilane CH3SiCl3 precursors are provided in a ratio of between 7 and 10, or even 10, as illustrated in [Fig. 3], the reaction chamber being at a temperature of between 920°C and 1050°C or even 1030°C as illustrated in [Fig. 2].

[0108] At the end of duration t2, a new purge step can be carried out, for example represented by the dotted lines.

[0109] After such a purging step, and in one embodiment, a third step of depositing a layer 103 can then be carried out, here under conditions identical to those of the first deposition step and for a duration t3, which is determined as a function of the thickness e3 desired for the third layer 103.

[0110] In the figures, the durations tb t2 and t3 are represented as being identical and the thicknesses eb e2 and e3 also but this is not at all necessary.

[0111] Figures 4 to 6 represent another embodiment of the method of the invention.

[0112] The method makes it possible to obtain a coating on a fiber 200, for example a silicon carbide fiber, a glass fiber or a carbon fiber.

[0113] For example, the fiber 200 may be directly coated with a consolidation interphase 210. For example, such a consolidation interphase 210 may comprise a first layer, for example comprising boron nitride BN or pyrocarbon PyC, placed directly in contact with the fiber 200.

[0114] In one embodiment, the interphase 210 may further comprise a second external layer arranged directly in contact with the first layer and making it possible to protect the latter, which then guarantees the integrity of the consolidation interphase 210.

[0115] The deposition of the interphase 210 can be done in a manner known as such and the interphase 210 should not be understood as a layer of a coating that the method described here makes it possible to obtain. It will be noted that [Fig.4] does not distinguish the first and second layers of the consolidation interphase 210.

[0116] The consolidation interphase 210 makes it possible above all to improve certain properties of the fiber 200, in particular its resistance to oxidation or cracking.

[0117] Such fibers 200 comprising or not an interphase 210 are used in different technological fields and generally require being coated.

[0118] Thus, it will be understood from the following that the coating can be obtained on the interphase 210 or on the fiber 200 and it is illustrated in [Fig.4] the case where an interphase is present.

[0119] The method described makes it possible to obtain thin coatings, allowing a variation in the composition of said coating to allow optimal functionalization of the fiber, while also allowing the use of less complex ovens than those of the prior art.

[0120] The coating comprises in this example a first layer of silicon carbide 201, a layer of carbon comprising an atomic content of silicon less than or equal to 20% C(Si) 203, and a second layer of silicon carbide 205.

[0121] Between the layers 201 and 203, and between the layers 203 and 205, the coating comprises transition zones 202 and 204, the carbon and silicon contents of which vary in the thickness of said transition zones 202, 204 between the compositions of the layers which surround these transition zones 202, 204.

[0122] In other words, the transition zone 202 comprises a carbon and silicon content which evolves from the constituent contents of the layer 201 towards the constituent contents of the layer 203.

[0123] Similarly, the transition zone 204 comprises a carbon and silicon content which evolves from the constituent contents of the layer 203 towards the constituent contents of the layer 205.

[0124] To obtain a coating described in [Fig.4], it is possible to place oneself in the temperature conditions T illustrated in [Fig.5] and with a supply of the reaction chamber with the ratio R of precursors illustrated in [Fig.6], the precursors being dihydrogen H2 and methyltrichlorosilane CH3SiCl3.

[0125] Figures 5 and 6 represent the evolution of the temperature T and the ratio R of precursors over time t.

[0126] In the embodiment shown, the temperature is first fixed for a duration tb duration of the step of obtaining the first layer 201.

[0127] Then the temperature varies in an affine manner to reach the temperature of the step of obtaining the second layer 203.

[0128] Nevertheless, during this transition step the supply of precursors to the reaction chamber is not cut off, as it could have been for example in the embodiment shown in Figures 1 to 3, but the supply is maintained, with a precursor ratio, shown in [Fig.4] and which varies between the ratio R of the step of obtaining a first layer and the ratio R of the step of obtaining a second layer.

[0129] This embodiment makes it possible to form a transition zone 202, between the step of obtaining the first layer 201 and the step of obtaining the second layer 203.

[0130] These transition zones improve the lifetime of the deposited layers, and the maintenance over time of their properties since they ensure “material” continuity of the layer systems, throughout the lifetime of the coating.

[0131] Furthermore, the progressive variation of the carbon and silicon contents in the transition zone 202 ensures excellent chemical compatibility of the layers 201 and 203, giving the assembly better resistance to delamination.

[0132] In the illustrated embodiment, and generally in the embodiments comprising a transition step, a transition zone can be directly in contact with a layer obtained during a production step and the layer obtained during the following production step can be directly in contact with the transition zone.

[0133]

[0134] Further, Figures 5 and 6 illustrate what is meant by an affine variation of a parameter between a first value and a second value.

[0135] Once the desired parameters for the step of obtaining the second layer 203 have been reached, these are maintained for a duration t2.

[0136] Without wishing to be bound by theory, the inventors have determined that temperatures between 920°C and 1050°C allow both the reduction of SiCl3 to silicon and the dehydrogenation of the methyl radical, which promotes a deposition of silicon carbide.

[0137] By further adjusting the H2 / methyltrichlorosilane ratio introduced into the reaction chamber, for example by choosing a ratio between 7 and 10, or even 10 as illustrated, it is possible to deposit stoichiometric silicon carbide SiC.

[0138] The inventors have also determined that for a temperature between 950°C and 1020°C with a reduced H2 / methyltrichlorosilane ratio, and less than or equal to 5, or even less than or equal to 3, it is possible to obtain deposits very rich in carbon.

[0139] Figures 5 and 6 also show a step of obtaining a third layer 205, which is carried out for a duration t3, and with parameters similar to those of the step of obtaining the first layer.

[0140] For the example, a transition step is again presented allowing to form a transition zone 204, during which the temperature and the ratio of precursors varies in an affine manner between the parameters of the step of obtaining the second layer 203 and the third layer 205.

[0141] In one embodiment, it is also possible to vary or not vary the pressure between two steps of obtaining a layer.

[0142] For example, the pressure can follow a similar evolution to that of the other parameters, namely the temperature and the precursor feed ratio, i.e. with a constant value during the stages of obtaining a layer, and a variable value during the transition stages.

[0143] In one embodiment, the pressure may vary between 50 mbar and 400 mbar during the process.

[0144] For example, a step of obtaining a layer comprising a silicon atomic content of between 45% and 55% or even between 49% and 51% and a complementary carbon atomic content or a step of obtaining a layer comprising a silicon atomic content greater than or equal to 95% and a complementary carbon atomic content can be carried out at 300 mbar.

[0145] In other words, the pressure for the process used to obtain a product according to [Fig.l] can be constant and 300 mbar.

[0146] For example, a step of obtaining a C(Si) layer comprising an atomic content of silicon less than or equal to 20% and a complementary atomic content of carbon can be obtained at a pressure of 100 mbar.

[0147] In other words, for the method illustrated in Figures 5 and 6 for obtaining a product according to [Fig.4], the steps of obtaining the first layer 201 and the third layer 205 can be carried out at 300 mbar, the step of obtaining the second layer 203 can be carried out at 100 mbar and the pressure varies in an affine manner between 300 mbar and 100 mbar for the first transition step and varies in an affine manner between 100 mbar and 300 mbar for the second transition step.

[0148] The examples presented in the detailed description are only present to illustrate advantages of the method of the invention, but should not be considered as limiting either the nature of the substrate or the nature of the deposited layers.

[0149] In particular, the figures are not drawn to scale, and equal times or values ​​in the figures should not be interpreted as necessarily being identical in a method of the present application.

[0150] In the present application, the ranges of values ​​described as "between ... and..." must be understood to include the limits, unless otherwise stated.

Claims

Claims

1. A method for chemical vapor deposition of a coating on a substrate, comprising at least the following steps: - a step of placing the substrate (100, 200) in a reaction chamber; - a step of obtaining a first layer (101, 201), by supplying the chamber with a mixture of dihydrogen and methyl-trichlorosilane in a first volume ratio H2 / methyltrichlorosilane, the chamber being at a first temperature and at a first pressure;- a step of obtaining a second layer (102, 203), by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane in a second H2 / methyltrichlorosilane volume ratio different from the first ratio, the enclosure being at a second temperature and at a second pressure, at least one of the second volume ratio, the second temperature and / or the second pressure being different respectively from the first volume ratio, the first temperature and / or the first pressure.;

2. Deposition method according to claim 1, wherein one of the layers (101, 102, 103, 201, 203, 205) is a layer comprising a silicon atomic content greater than or equal to 95% and a complementary carbon atomic content, said layer being obtained with an H2 / methyltrichlorosilane volume ratio greater than or equal to 20 at a temperature between 850°C and 920°C at a pressure between 200 mbar and 400 mbar.

3. A deposition method according to claim 1 or 2, wherein one of the layers (101, 102, 103, 201, 203, 205) is a layer of silicon carbide comprising a silicon atomic content of between 49% and 51% and a complementary carbon atomic content, said layer being obtained with a H2 / methyltrichlorosilane volume ratio of between 7 and 10 at a temperature of between 920°C and 1050°C at a pressure of between 100 mbar and 300 mbar.

4. Deposition method according to any one of claims 1 to 3, in which one of the layers (101, 102, 103, 201, 203, 205) is a layer comprising a silicon atomic content less than or equal to 20% and a complementary carbon atomic content, said layer being obtained with a H2 / methyltrichlorosilane volume ratio less than or equal to 3 at a temperature between 950°C and 1020°C at a pressure between 50 mbar and 100 mbar

5. Deposition method according to one of claims 1 to 4, in which the method further comprises: - a step of obtaining a third layer (103, 205), by supplying the enclosure with a mixture of dihydrogen and methyl-trichlorosilane in a third volume ratio H2 / methyltrichlorosilane, at a third temperature and at a third pressure, at least one of the third volume ratio, the third temperature and / or the third pressure being different respectively from the second volume ratio, the second temperature and / or the second pressure.

6. Deposition method according to one of claims 1 to 5, in which a step of obtaining a given layer (101, 102, 103, 201, 203, 205) is separated from a step of obtaining the following layer by a purging step, during which all the precursors present are removed from the reaction chamber.

7. Deposition method according to one of claims 1 to 6, in which the method comprises between two successive steps of obtaining a layer (101, 102, 103, 201, 203, 205) a transition step during which the enclosure is supplied with a mixture of dihydrogen and methyltrichlorosilane in a volume ratio H2 / methyltrichlorosilane which varies during the transition step between the ratio of the first of the steps of obtaining a layer and the ratio of the second of the steps of obtaining a layer, the enclosure being at a temperature which varies during the transition step between the temperature of the first of the steps of obtaining a layer and the temperature of the second of the steps of obtaining a layer and at a pressure which varies during the transition step between the pressure of the first of the steps of obtaining a layer and the pressure of the second of the steps of obtaining of a layer.

8. Deposition method according to claim 7, in which at least one of the H2 / methyltrichlorosilane volume ratio, the temperature, or respectively the pressure used for the transition step varies during the transition step in an affine manner between the H2 / methyltrichlorosilane volume ratio used for the step of obtaining a layer (101, 102, 103, 201, 203, 205) preceding the transition step and the H2 / methyltrichlorosilane volume ratio used for the step of obtaining a layer following the transition step; between the temperature used for the step of obtaining a layer preceding the transition step and the temperature used for the step of obtaining a layer following the transition step; and / or between the pressure used for the step of obtaining a layer preceding the transition step and the pressure used for the step of obtaining a layer following the transition step.

9. Deposition method according to one of claims 1 to 8, in which the substrate (100, 200) is chosen from a turbomachine blade, a distributor portion, a ring sector, a fiber optionally coated with a consolidation interphase.

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