Method for depositing a coating by a chemical vapour deposition method

Abstract

The invention relates to a method for chemical vapour 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 methyltrichlorosilane in a first H2 / methyltrichlorosilane volume ratio, the chamber being at a first temperature and at a first pressure; and - a step of obtaining a second layer (102, 203), by supplying the chamber with a mixture of dihydrogen and methyltrichlorosilane in a second H2 / methyltrichlorosilane volume ratio that is different from the first ratio, the chamber 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 from the first volume ratio, the first temperature and / or the first pressure, respectively.

Description

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

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

[0002] Ceramic matrix composites (CMCs) can withstand temperatures ranging from 600°C to 1400°C. Due to their improved resistance to high temperatures, CMCs require less cooling. Since this cooling traditionally comes from a draw in the compressor, which impacts the efficiency of the turbomachine, CMC materials therefore improve engine efficiency, thereby reducing fuel consumption.

[0003] Furthermore, the use of ceramic matrix composite materials helps to optimize the performance of turbomachines, particularly 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, we know of chemical vapor infiltration processes (or "CVI" for the acronym in English "Chemical Vapor Infiltration").

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

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

[0008] Although this method is already used industrially, it requires complex ovens when 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 specifically prepared 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 deposit of coatings of several types while using simpler processes than the processes 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 H 2 / 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 volume ratio H 2 / methyltrichlorosilane 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 process 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 the existence of unavoidable impurities 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 content 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 selected for a step of obtaining a given layer are understood respectively as the temperature and 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 "volume ratio H 2 / methyltrichlorosilane” 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 this 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 volume ratio H 2 / methyltrichlorosilane 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, noted 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 a H^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 noted 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 a H^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 a silicon atomic content less than or equal to 20% and a complementary carbon atomic content, said layer being obtained with a volume ratio H 2 / 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 described process, 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 volume ratio H 2 / 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.

[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 ovens 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 may be carried out on a substrate and said substrate may 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 to obtain one or more of the layers can be between 5 and 15 hours.

[0045] This allows layers to be obtained 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 one 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] In addition, the vacuum stage allows for an improvement in the purging stage, allowing for an even smoother transition from the stage 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 H^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 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 whole offers better resistance to delamination.

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

[0056] This ensures that the transition zone is of a 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 of the parameters that vary may vary over an identical period of time.

[0058] In one embodiment, at least one of the volume ratio H 2 / methyltrichlorosilane, the temperature, or respectively the pressure used for the transition step varies during the transition step in an affine manner between the volume ratio H^methyltrichlorosilane used for the step of obtaining a layer preceding the transition step and the volume ratio H 2 / methyltrichlorosilane 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 varying parameter can be written as an affine function of the time elapsed since the beginning of the transition step.

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

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

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

[0063] In such an embodiment, the substrate may also be a specified fiber 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 disposed directly in contact with the first layer and making it possible to protect the latter, 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 process 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 major interest for such substrates. Brief description of the drawings

[0069] [Fig. 1] Figure 1 is an example of a part obtainable in one embodiment of the method.

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

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

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

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

[0074] [Fig. 6] Figure 6 is an example of the evolution of the precursor ratio over time, for the realization of 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 a 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 portion of a distributor 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 provides 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] Figure 1 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 Y 2 If 2 O 7 or ytterbium Y 2 If 2 O 7 . It will not be described in further detail.

[0088] As described above, the chaining 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 H 2 and methyltrichlorosilane CH 3 SiCI 3 it is possible to deposit layers of different compositions by varying the H ratio 2 / methyltrichlorosilane, pressure and temperature during the deposition steps.

[0090] Without wishing to be bound by theory, the inventors determined that temperatures between 850°C and 920°C do not allow the dehydrogenation of the methyl radical CH 3 but nevertheless allow the reduction of silicon from SiCI 3which then makes it possible to have a process for forming a layer comprising an atomic silicon content greater than or equal to 95% and a complementary atomic carbon content: Si(C).

[0091] Additionally, they determined that increasing the H ratio 2 / methyltrichlorosilane promoted the hydrogenation of the methyl radical CH 3 into methane which prevents carbon from being deposited.

[0092] The inventors also determined that increasing the temperature, for example between 920°C and 1050°C allows both the reduction of SiCI 3 in silicon and dehydrogenation of the methyl radical to promote carbon deposition.

[0093] By further adjusting the H ratio 2 / methyltrichlorosilane brought into the reaction chamber it becomes possible to deposit silicon carbide comprising an atomic content of silicon between 45% and 55%, or even between 49% and 51%, and an atomic content of complementary carbon SiC.

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

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

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

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

[0098] These conditions are maintained for a duration t 1; duration of the step of obtaining the first Si(C) layer.

[0099] The duration tt can be determined according to the thickness ei desired 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 include 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 t 2 , 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 t 2 is determined as a function of the thickness e 2 desired for the second layer 102.

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

[0108] At the end of duration t 2, 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 t 3 , which is determined as a function of the thickness e 3 desired for the third layer 103.

[0110] In the figures, the durations t 1; t 2 and t 3 are represented as being identical and the thicknesses ei, e 2 summer 3 also but this is not necessary at all.

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

[0112] The method allows a coating to be obtained 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 disposed 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 Figure 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] Likewise, 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 figure 4, it is possible to place oneself in the temperature conditions T illustrated in figure 5 and with a supply of the reaction chamber with the ratio R of precursors illustrated in figure 6, the precursors being dihydrogen H 2 and methyltrichlorosilane CH 3 SiCI 3 .

[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 ti, 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] However, 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 figure 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 lifespan of the deposited layers, and the maintenance over time of their properties since they ensure “material” continuity of the layer systems, throughout the lifespan 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 embodiments comprising a transition step, a transition zone may be in direct contact with a layer obtained during a production step and the layer obtained during the following production step may be in direct contact with the transition zone.

[0133]

[0134] Furthermore, 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 t 2 .

[0136] Without wishing to be bound by theory, the inventors determined that temperatures between 920°C and 1050°C allow both the reduction of SiCI 3 in silicon and the dehydrogenation of the methyl radical which promotes a deposit of silicon carbide.

[0137] By further adjusting the H ratio 2 / methyltrichlorosilane brought 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 also determined that for a temperature between 950°C and 1020°C with a ratio H 2 / methyltrichlorosilane decreased, 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 t 3 , and with similar parameters to those of the step of obtaining the first layer.

[0140] For the example, a transition step is again presented making it possible to form a transition zone 204, during which the temperature and the ratio of the precursors vary 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 stages of obtaining a layer.

[0142] For example, the pressure can follow a similar evolution to that of the other parameters such as temperature and 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 Figure 1 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 process illustrated in Figures 5 and 6 for obtaining a product according to Figure 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 stage and varies in an affine manner between 100 mbar and 300 mbar for the second transition stage.

[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 construed as necessarily being identical in a method of the present application.

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

Claims

Claims

1. A method of 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 enclosure with a mixture of dihydrogen and methyltrichlorosilane; - a step of obtaining a second layer (102, 203), by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane; - a step of obtaining a third layer (103, 205), by supplying the enclosure with a mixture of dihydrogen and methyltrichlorosilane; the first layer and the third layer being a layer comprising an atomic content of silicon greater than or equal to 95% and a complementary atomic content of carbon, said layers being obtained with a volume ratio H 2 / methyltrichlorosilane greater than or equal to 20 at a temperature between 850°C and 920°C at a pressure between 200 mbar and 400 mbar and the second layer being a layer of silicon carbide comprising an atomic content of silicon between 49% and 51% and a complementary atomic content of carbon, said layer being obtained with a volume ratio H 2 / methyltrichlorosilane between 7 and 10 at a temperature between 920 °C and 1050 °C at a pressure between 100 mbar and 300 mbar

2. Deposition method according to claim 1, 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.

3. Deposition method according to one of claims 1 or 2, 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 H 2 / methyltrichlorosilane which varies during the transition step between the ratio of the first of the layer-forming steps and the ratio of the second of the layer-forming steps, the enclosure being at a temperature which varies during the transition step between the temperature of the first of the layer-forming steps and the temperature of the second of the layer-forming steps and at a pressure which varies during the transition step between the pressure of the first of the layer-forming steps and the pressure of the second of the layer-forming steps.

4. A deposition method according to claim 3, wherein at least one of the volume ratio H 2 / methyltrichlorosilane, the temperature, or respectively the pressure used for the transition step varies during the transition step in an affine manner between the volume ratio H 2 / methyltrichlorosilane used for the step of obtaining a layer (101, 102, 103, 201, 203, 205) preceding the transition step and the volume ratio H 2 / methyltrichlorosilane 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.

5. Deposition method according to one of claims 1 to 4, 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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