Dawn with covered louvers

Abstract

Blade with coated blades. The invention relates to a blade for an aeronautical turbomachine made of a ceramic matrix composite material comprising a blade root portion (1), a main blade portion (2) and a blade tip portion (3), the blade tip portion comprising at least one blade (31), intended to rub against an abradable material disposed opposite said blade, the blade being characterized in that the blade comprises, from the inside out, at least the following layers: - a blade body (311) made of a ceramic matrix composite material; - a tack layer (312) comprising silica; - an environmental barrier layer (313); - a silicon layer (314); and - a silicon carbide layer (315). Figure for the abstract: Fig. 1.

Description

Title of the invention: Coated blade Technical field

[0001] The present disclosure relates to the field of blades for aeronautical turbomachines and more precisely to the coatings making it possible to confer particular properties on such blades. Prior art

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

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

[0004] Furthermore, their use contributes to optimizing the performance of 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.

[0005] These advantages explain the industrial interest in developing such ceramic matrix composite materials.

[0006] Among these compounds, carbide-based ceramic matrix composite materials, in particular SiC / SiC composites, make it possible to advantageously replace parts made from nickel-based or cobalt-based superalloys.

[0007] However, the physicochemical environment of an aeronautical turbomachine, and in particular of the hot part of an aeronautical turbomachine, is oxidizing and corrosive.

[0008] Thus, the CMCs considered for such an application are covered with a protective layer called an environmental barrier (or EBC for the English acronym “environmental barrier coating”).

[0009] Such protective layers have been developed and offer satisfactory protection. However, the integrity of these layers then becomes an important imperative for the use of CMC parts because if the protective layer is removed, even locally, the entire part may suffer from the absence of the protective layer.

[0010] For this reason, it is complex to consider the use of CMC parts for moving parts, because the risks of friction for such parts are higher, and the friction risks causing deterioration of the protective layer.

[0011] The low friction resistance of the environmental barrier poses a problem in the manufacture of moving blades made of CMC material.

[0012] Indeed, in a conventional manner, the tip of the moving blades in an aeronautical turbomachine rubs against the casing arranged opposite the moving blades to satisfy aerodynamic needs, in this case to prevent part of the air flow from being able to escape at the tip of the blade.

[0013] This friction is essential to meet aerodynamic needs but is incompatible with the use of a traditional environmental barrier, so there is a need to develop new protective layers for an application of CMC moving blades. Statement of the invention

[0014] The present invention aims precisely to respond to this problem.

[0015] For this, it relates according to one of its aspects to a blade for an aeronautical turbomachine made of ceramic matrix composite material comprising a blade root part, a main blade part and a blade head part, the blade head part comprising at least one wiper, intended to rub against an abradable material arranged opposite said wiper, the blade being characterized in that the wiper comprises from the inside to the outside at least the following layers: - a blade body made of ceramic matrix composite material; - a bonding layer comprising silica; - an environmental barrier layer; - a layer of silicon; and - a layer of silicon carbide.

[0016] The described blade makes it possible to obtain a blade made of composite material for which the parts at risk of wear by friction are reinforced.

[0017] Indeed, the silicon carbide layer is very hard and the underlying silicon layer ensures excellent chemical continuity between the environmental barrier layer and the silicon carbide layer, which allows excellent adhesion of the layers to each other.

[0018] In such a blade, it is the external silicon carbide layer of the wiper which rubs against the abradable material arranged opposite the wiper.

[0019] Thus, not only does the wiper fulfill its role and prevent any air leakage between the tip of the blade and the casing, but also the silicon carbide layer ensures excellent abrasion resistance of the wiper, which thus ensures the integrity of the underlying environmental barrier layer.

[0020] Also, the bonding layer ensures excellent continuity between the blade body and the environmental barrier layer, particularly in terms of thermal expansion coefficients and chemistry.

[0021] Indeed, it is preferable, for reasons of differential expansion during the use of a blade described above, that the thermal expansion coefficients of two successive layers are sufficiently close to avoid delamination of the assembly.

[0022] Similarly, the silicon layer provides excellent continuity between the environmental barrier layer and the silicon carbide layer, particularly in terms of coefficient of thermal expansion and chemistry.

[0023] The stacking of the invention therefore ensures that the layers are firmly bonded together and that the assembly has excellent resistance to delamination.

[0024] In one embodiment, the blade only comprises the silicon and silicon carbide layers on its blade tip portion, or even only on its lip, the remainder of the blade comprising a blade body made of composite material, a bonding layer comprising silica and an environmental barrier layer.

[0025] This embodiment allows excellent integration of the invention into known blade manufacturing processes.

[0026] Indeed, the particular choice of arranging the protection on the tip part of the blade, or even only on the wiper(s) and not on the entire blade, makes it possible to use the blades of the prior art without the risk that the addition of the layers of silicon and silicon carbide will disturb the geometry of the blade for parts fulfilling a very precise aerodynamic role, in particular the main part of the blade, notably the leading edge or the trailing edge.

[0027] Since these parts are not subject to friction, it is not essential that they be coated with the silicon layer and the silicon carbide layer, unlike the wiper.

[0028] In one embodiment, the entire blade root, main blade portion and blade tip comprise from the inside to the outside at least the following layers: - a blade body made of ceramic matrix composite material; - a bonding layer comprising silica; - an environmental barrier layer; - a layer of silicon; and - a layer of silicon carbide.

[0029] This embodiment allows a simplified preparation process for the entire blade because it is simpler to deposit the silicon layer and the silicon carbide layer on the entire blade than to deposit them selectively on the wiper.

[0030] Furthermore, the silicon carbide layer thus protects the entire environmental barrier layer against dissolution by reaction with molten sands (known as "CMAS" for the acronym of their English name "calcium-magnesium aluminosilicate"), because the silicon carbide layer is inert with respect to such species.

[0031] In one embodiment, at least the wiper comprises, without any other layer and from the inside to the outside, the stacking of the following layers: - a blade body made of ceramic matrix composite material; - a bonding layer comprising silica; - an environmental barrier layer; - a layer of silicon; and - a layer of silicon carbide.

[0032] In one embodiment, the blade assembly comprises, without any other layer and from the inside to the outside, the stack of the following layers: - a blade body made of ceramic matrix composite material; - a bonding layer comprising silica; - an environmental barrier layer; - a layer of silicon; and - a layer of silicon carbide.

[0033] In one embodiment, the blade body made of ceramic matrix composite material comprises a fibrous reinforcement comprising silicon carbide fibers whose porosity is filled by a silicon carbide matrix.

[0034] In one embodiment, the environmental barrier layer may comprise a rare earth disilicate RE2Si2O7, where the rare earth RE is selected from yttrium, ytterbium or a mixture of these two compounds.

[0035] In one embodiment, the environmental barrier layer comprises for more than 90% by weight, or even for more than 99% by weight, or even consists of a rare earth disilicate RE2Si2O7, where the rare earth RE is chosen from yttrium, ytterbium or a mixture of these two compounds.

[0036] In one embodiment, the silicon layer has a thickness greater than or equal to 2 μm.

[0037] The inventors found that such a thickness was sufficient to allow the silicon layer to fulfill its role, i.e. to allow excellent adhesion of the silicon carbide layer to the underlying environmental barrier layer.

[0038] In one embodiment, the silicon layer has a thickness of between 2 μm and 20 μm.

[0039] This embodiment makes it possible to ensure, on the one hand, excellent adhesion of the silicon carbide layer to the environmental barrier layer, and on the other hand part of limiting the size of such a layer.

[0040] The “thickness” of a layer is understood in the usual sense of this term for a layer, and represents its dimension in a direction perpendicular to the blade body which it covers.

[0041] In one embodiment, the silicon carbide layer has a thickness greater than or equal to 10 μm.

[0042] The inventors found that such a thickness ensured excellent resistance of the upper silicon carbide layer throughout the lifetime of a turbomachine blade.

[0043] In one embodiment, the silicon carbide layer has a thickness of between 10 μm and 100 μm.

[0044] This embodiment is an optimum between the thickness necessary for the silicon carbide layer to fulfill its role and a limitation of the size of the deposited coating.

[0045] According to another of its aspects, the invention relates to an aeronautical turbomachine comprising a casing and a movable blade arranged in said casing, the movable blade comprising at least one blade as described above, and in which the surface of the casing facing the wiper comprises an abradable material chosen from a metallic material or a ceramic material.

[0046] The particular choice of abradable material can be made depending on the desired operating temperature for the blade.

[0047] In such an embodiment, it is ensured that the surface facing the blade wiper as described is more abradable than the upper layer of the silicon carbide wiper.

[0048] Thus, it is ensured that an aeronautical turbomachine is obtained having the advantages of blades made of ceramic matrix composite material, in particular in terms of lightening and temperature resistance, and further ensuring that the integrity of the blades is assured for its portion which risks experiencing friction. Brief description of the drawings

[0049] [Fig-1] [Fig.l] represents a blade in one embodiment of the invention.

[0050] [Fig.2] [Fig.2] represents a detail of a blade lick in a mode of realization of the invention. Description of the embodiments

[0051] 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.

[0052] [Fig.l] illustrates a turbomachine blade in one embodiment.

[0053] Such a blade comprises a root portion 1, a main blade portion 2 and a blade head portion 3, which comprises a wiper 31.

[0054] For example, the foot part 1 may comprise a platform 11 and a stilt zone 12, allowing the blade to be mounted on a movable ring, not shown.

[0055] The main blade part 2 comprises a leading edge 22 and a trailing edge 21.

[0056] Conventionally, the main part of the blade comprises a lower surface and an upper surface whose curvature is a function of the aerodynamic properties desired for the blade.

[0057] The blade finally comprises a blade head portion 3, which comprises a wiper 31.

[0058] The blade may comprise a plurality of wipers 31, as shown in [Fig.l].

[0059] The wiper 31a is intended to ensure that the tip of the blade is in contact with an abradable material arranged opposite when the blade is arranged in a casing.

[0060] This reduces air leakage at the tip of the blade, which increases the proportion of air in the air stream actually providing work to the blade, thereby increasing the efficiency of the turbomachine.

[0061] As described, the wiper 31 is intended to be in contact with an abradable material, not shown.

[0062] In one embodiment, a material will be said to be “abradable” if it has a hardness lower than that of silicon carbide.

[0063] For example, such an abradable material may be chosen from a metallic material or a ceramic material, for example zirconia ZrO2.

[0064] Indeed, the upper layer of the wiper 31 made of silicon carbide ensures that the rotation of the blade and its friction on said abradable material does not damage the wiper 31, and in particular does not compromise the integrity of the environmental barrier layer arranged below the silicon carbide layer, unlike what has been observed for blades where the environmental barrier layer would rub against the abradable material.

[0065] In one embodiment, the blade comprises an external surface covered with an environmental barrier, except for its wipers where it then comprises an external surface made of silicon carbide.

[0066] Indeed, the thickness introduced by the silicon layer and that of silicon carbide of a described stack can represent an undesired excess thickness for certain parts of the blade and in particular for the main part of the blade 2.

[0067] Indeed, the main part of the blade 2 has a profile which plays a crucial aerodynamic role, and it is very important that its geometry meets precise specifications.

[0068] Further deposition of a layer of silicon 314 and silicon carbide 315 requires redesigning the entire blade and its geometry to ensure that it continues to meet aerodynamic specifications.

[0069] The embodiment where only the wipers are coated then makes it possible to use blades made of ceramic matrix composite material comprising a bonding layer and an environmental barrier layer of the prior art with geometries already known and validated.

[0070] Alternatively, the whole dawn comprises from its heart outwards: - a blade body made of ceramic matrix composite material; - a bonding layer comprising silica; - an environmental barrier layer; - a layer of silicon; and - a layer of silicon carbide.

[0071] This embodiment requires taking into account the thickness of the silicon layer and the silicon carbide layer in the geometric design of the blade but in return ensures better resistance to deterioration by reaction with molten sands.

[0072] [Fig.2] illustrates a stack of layers which can form a lip 31 in one embodiment of the invention.

[0073] As described in [Fig.2], the wiper 31 comprises from its core outwards: - a blade body 311 made of ceramic matrix composite material; - a bonding layer 312 comprising silica; - an environmental barrier layer 313; - a layer of silicon 314; and - a layer of silicon carbide 315.

[0074] In one embodiment, the blade comprises a blade body made of composite material of which both the fiber reinforcement and the matrix are made of silicon carbide.

[0075] Such materials, also called SiC / SiC materials, are known as such.

[0076] For example, the bonding layer is a layer of silica SiO2 called thermally grown oxide (or TGO for the English acronym “thermally grown oxide”).

[0077] Such a layer 312 makes it possible to ensure excellent chemical continuity between the blade body made of ceramic matrix composite material 311 and the environmental barrier layer 313.

[0078] Furthermore, such a layer 312 also ensures good continuity in terms of thermal expansion coefficients, which prevents delamination when the entire blade is exposed to the high temperatures encountered in aeronautical turbomachines.

[0079] The bonding layer 312 also plays a role in protecting the blade body 311 against oxidation and corrosion during use in an aeronautical turbomachine.

[0080] In one embodiment, which is the one shown, the layers described are in direct contact with each other, in the order indicated, and the stack does not comprise any other layer than the layers shown.

[0081] In other words, in one embodiment, the blade body 311 is in contact with the adhesion layer 312 comprising silica, itself in contact with the environmental barrier layer 313, itself in contact with the silicon layer 314 itself in contact with the silicon carbide layer 315.

[0082] In one embodiment, the silicon layer 314 may be obtained by a physical vapor deposition process or a chemical vapor deposition.

[0083] In one embodiment, the silicon carbide layer 315 may be obtained by a physical vapor deposition process or a chemical vapor deposition.

[0084] In one embodiment, the layers of silicon 314 and silicon carbide 315 can be obtained in the same physical vapor deposition or chemical vapor deposition chamber.

[0085] In one embodiment, the bonding layer comprising silica 312 can be obtained by liquid means, according to a method known as such.

[0086] In one embodiment, the environmental barrier layer 313 can be obtained by liquid means, according to a method known as such, for example by a sol-gel method.

Claims

Claims

1. Blade for an aeronautical turbomachine made of ceramic matrix composite material comprising a blade root portion (1), a main blade portion (2) and a blade head portion (3), the blade head portion comprising at least one wiper (31), intended to rub against an abradable material arranged opposite said wiper, the blade being characterized in that the wiper comprises from the inside to the outside at least the following layers: - a blade body (311) made of ceramic matrix composite material; - a bonding layer (312) comprising silica; - an environmental barrier layer (313); - a silicon layer (314); and - a silicon carbide layer (315).

2. A blade according to claim 1, wherein the silicon layer (314) has a thickness greater than or equal to 2 pm.

3. A blade according to claim 1 or 2, wherein the silicon carbide layer (315) has a thickness greater than or equal to 10 pm.

4. A blade according to any one of claims 1 to 3, wherein the environmental barrier layer (315) comprises a rare earth disilicate RE2Si2O7, where the rare earth RE is selected from yttrium, ytterbium or a mixture of these two compounds.

5. A blade according to any one of claims 1 to 4, wherein the assembly of the blade root (1), the main blade part (2) and the blade head (3) comprises from the inside to the outside at least the following layers: - a blade body (311) made of ceramic matrix composite material; - a bonding layer (312) comprising silica; - an environmental barrier layer (313); - a silicon layer (314); and - a silicon carbide layer (315).

6. Aeronautical turbomachine comprising a casing and a movable blade arranged in said casing, the movable blade comprising at least one blade according to any one of claims 1 to 5, and in which the surface of the casing opposite the wiper (31) comprises an abradable material chosen from a metallic material or a ceramic material.

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