Part coated with a protective composition against CMAS with controlled cracking, and corresponding treatment process

TECHNICAL FIELD OF THE INVENTION

The invention relates to a part of a turbomachine, such as a high pressure turbine blade or a combustion chamber wall.

STATE OF THE ART

In a turbojet, the exhaust gases generated by the combustion chamber can reach high temperatures, greater than 1200 ° C, or even 1600 ° C. The parts of the turbojet, in contact with these exhaust gases, must be able to retain their mechanical properties at these high temperatures. In particular, the components of high pressure turbines, or TuHP, must be protected against an excessive rise in surface temperature, in order to guarantee their functional integrity and to limit oxidation and corrosion.

It is known to manufacture certain parts of the turbojet engine in “superalloy”. Superalloys are a family of high strength metal alloys that can work at temperatures relatively close to their melting points (typically 0.7 to 0.8 times their melting point). It is also known to manufacture parts in composites with a ceramic matrix, or CMC.

It is known practice to cover the surface of parts made of said materials with a coating acting as a thermal barrier, and / or as an environmental barrier.

A thermal or environmental barrier generally comprises a thermally insulating layer, one function of which is to limit the surface temperature of the coated component, and a protective layer making it possible to protect the substrate from oxidation and / or corrosion.

The ceramic layer generally covers the protective layer. By way of example, the thermally insulating layer may be of yttriated zirconia.

A metallic sub-layer can be deposited before the protective layer, and the protective layer can be formed by oxidation of the metal sub-layer. The metallic sublayer provides a bond between the surface of the superalloy substrate and the protective layer: the metallic sublayer is sometimes called a “bonding sublayer”. In addition, the protective layer can be pre-oxidized before the deposition of the thermally insulating layer, in order to form a dense alumina layer usually called Thermally Grown Oxide (TGO) to promote the adhesion of the thermally insulating layer and strengthen the oxidation and corrosion protection function.

It is crucial to ensure a satisfactory life of the thermal and environmental barriers throughout the operating cycles of the turbomachine parts. This service life is particularly conditioned by the resistance of the barrier to thermal cycling on the one hand, and to environmental attacks such as erosion and corrosion on the other hand. The thermal or environmental barrier is liable to deteriorate rapidly in the presence of particles rich in inorganic compounds of silica type, or even, if it is located in an atmosphere rich in compounds commonly called CMAS, including in particular the oxides of calcium, magnesium, aluminum. and silicon. CMAS are liable to infiltrate in the molten state into the thermal or environmental barrier, especially in cracks formed in the internal volume of the layers of the barrier. Once infiltrated, the particles of CMAS compounds can cause partial chemical dissolution of the barrier, or even stiffen within the barrier and lower the mechanical strength properties of the thermal or environmental barrier.

To prevent the penetration of liquid contaminants at high temperature such as CMAS compounds within the coating layers, anti-CMAS deposits are known which promote the formation of a tight barrier layer on the surface of the coated part, by spontaneous chemical reaction. between chemical species of anti-CMAS deposits and CMAS compounds. The tight barrier layer thus formed blocks the progression of the molten CMAS compounds within the part to be protected. Such anti-CMAS deposits can be implemented either directly on the substrate to form a complete thermal or environmental barrier, or in a functionalization layer. The reaction kinetics between the anti-CMAS deposit and the CMAS compounds is then in competition with the infiltration kinetics of the CMAS compounds within the coating,

However, the effectiveness of anti-CMAS deposits is reduced when the part to be protected exhibits transverse cracking. In the following, a “transverse cracking” designates a plurality of cracks having a general orientation substantially orthogonal to the plane tangent to the surface of the coated part. Figures la, lb and appended illustrate the phenomenon of capillary penetration of CMAS compounds from ambient air into a network of cracks within the external surface of a part. In Figure la, the part, which may be a high pressure turbine engine turbine blade, has on its surface a layer 2 of anti-CMAS deposit, of substantially uniform thickness. The anti-CMAS layer comprises a substantially transverse crack 4. This crack 4 is part of a larger transverse cracking network comprising through cracks for layer 2, orthogonal to the surface and little deviated. In Figure 1b, particles of CMAS compounds, melted due to the high surface temperature at the level of the layer 2 during the operation of the vane, form a liquid phase 3 at the surface of the layer 2. This phase liquid 3 is partially infiltrated into crack 4. In Figure le, which represents the system in a state subsequent to that of Figure lb, the chemical species present in the anti-CMAS deposit layer 2 reacted with the infiltrated CMAS compounds to form a blocking phase 5 around the periphery of the crack 4. The blocking phase 5 is shown schematically here by a network of contiguous pentagonal shapes. This blocking phase 5 blocks the infiltration of the CMAS compounds of the liquid phase 3. In addition, a secondary phase 6 may form in places, this secondary phase 6 being represented by the circular shapes shown in FIG. Here, the crack 4 being substantially transverse, the liquid phase 3 infiltrates rapidly over the entire thickness of the anti-CMAS 2 deposition layer, the infiltration kinetics of the molten CMAS compounds outweighing the reaction kinetics. chemical leading to the formation of the blocking phase. Layer 2 is weakened thereby, and the life of the part is reduced. the crack 4 being substantially transverse, the liquid phase 3 infiltrates rapidly over the entire thickness of the anti-CMAS 2 deposit layer, the infiltration kinetics of the molten CMAS compounds outweighing the kinetics of the chemical reaction leading to to the formation of the blocking phase. Layer 2 is weakened, and the life of the part is reduced. the crack 4 being substantially transverse, the liquid phase 3 infiltrates rapidly over the entire thickness of the anti-CMAS 2 deposit layer, the infiltration kinetics of the molten CMAS compounds outweighing the kinetics of the chemical reaction leading to to the formation of the blocking phase. Layer 2 is weakened thereby, and the life of the part is reduced.

There is therefore a need for a surface treatment of a turbomachine part, comprising the application of a thermal and / or environmental barrier, the integrity of which would be guaranteed throughout the life of the part, in an environment loaded with compounds. CMAS. The problem arises in particular of the mechanical strength of anti-CMAS deposition layers arranged on the surface of turbine parts, facing the infiltration of molten CMAS compounds.

GENERAL PRESENTATION OF THE INVENTION

The invention meets the need highlighted above by providing a turbomachine part comprising a substrate made of metallic material, or of composite material, and comprising a protective coating layer against the infiltration of compounds of the oxides type. calcium, magnesium, aluminum or silicon, or CMAS, the coating layer at least partially covering the surface of the substrate,

the protective coating layer comprising a plurality of elementary layers, elementary layers of a first set

with elementary layers being interposed between elementary layers of a second set of elementary layers, each contact zone between an elementary layer of the first set and an elementary layer of the second set forming an interface favoring the propagation of cracks along said interface.

A part according to the invention thus has an anti-CMAS coating layer promoting the deflection of any cracks in a direction substantially parallel to the surface of the part. Capillary penetration of molten CMAS-like compounds during part operation is intended to be minimized. In fact, the liquid phase formed by the molten CMAS compounds, instead of propagating within the cracks in a direction substantially orthogonal to the thickness of the successive layers of coating and quickly reaching the substrate of the part, infiltrates in tortuosities formed by cracks along elementary layer interfaces. The kinetics of the formation reaction

Another advantage provided by the invention is to allow cracking of the anti-CMAS coating layers while ensuring good mechanical strength due to the reduction in the infiltrated CMAS compounds. The presence of cracks within the coating makes it possible to accommodate thermomechanical deformations on the surface of the part, without causing any greater breakage which would adversely affect the performance of the part.

Additional and non-limiting characteristics of a turbomachine part according to the invention are as follows, taken alone or in any of their technically possible combinations:

- the elementary layers of the first set have tenacities which differ by at least 0.7 MPa.m 1/2 compared to the tenacities of the elementary layers of the second set,

the elementary layers of the first set being able for example to have a tenacity of between 0.5 and 1.5 Mpa.m 1/2 and the elementary layers of the second set being able to have a tenacity of between 1.5 and 2.2 Mpa.m 1/2 .

The change in tenacity between two consecutive elementary layers induces preferential cracking in the direction of the interface between the consecutive layers, in particular in operation and possibly at the end of manufacture after cooling;

the elementary layers of the second set comprise a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, or comprise a mixture of several of these materials;

- the elementary layers of the first set include a material taken from the following list: RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, or comprise a mixture of several of these materials;

- the elementary layers of the first set have thermal expansion coefficients which differ by at least 3.5 10 6 K 1 compared to the thermal expansion coefficients of the elementary layers of the second set,

the elementary layers of the first set being able to have a thermal expansion coefficient of between 3.5 and 6.0 10 6 K 1 and the elementary layers of the second set being able to have a thermal expansion coefficient of between 7.0 and 12.0 10 6 K 1 .

The change in coefficient of expansion between two consecutive elementary layers induces preferential cracking in the direction of the interface between the consecutive layers, in particular during operation and possibly at the end of manufacture after cooling;

- the elementary layers of the second set include a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, YAG, or comprise a mixture of several of these materials;

- The elementary layers of the first set comprise RE2SÎ207 or RE2SÎ05 with RE a material of the rare earth family, or include a mixture of these materials;

the ratio of the cumulative thickness of the elementary layers of the first set to the cumulative thickness of the elementary layers of the second set is between 1: 2 and 2: 1;

the total thickness of the protective coating layer is between 20 and 500 μm, preferably between 20 and 300 μm;

the part is a moving turbine blade, or a high pressure turbine distributor, or a high pressure turbine ring, or a combustion chamber wall.

According to a second aspect, the invention relates to a method of treating a turbomachine part comprising steps of depositing by thermal spraying a plurality of elementary layers, on the surface of a substrate of the part, the substrate being formed in metallic material, or in composite material, to produce a protective coating layer against the infiltration of CMAS-type compounds,

the method comprising steps of depositing on the surface of the substrate elementary layers belonging to a first set, said steps being interposed between steps of depositing elementary layers belonging to a second set,

the elementary layers of the first set having tenacities which differ by at least 0.7 MPa.m 1/2 compared to the tenacities of the elementary layers of the second set,

or the elementary layers of the first set having thermal expansion coefficients which differ by at least 3.5 10 6 K 1 with respect to the thermal expansion coefficients of the elementary layers of the second set.

The process can have the following additional and non-limiting characteristics:

- the stages of deposition of elementary layers being carried out according to the technique of thermal suspension plasma spraying, or Suspension Plasma Spraying (SPS), or according to one of the other following techniques: plasma spraying at atmospheric pressure (APS), plasma spraying precursor solutions (SPPS), plasma spraying under an inert atmosphere or reduced pressure (IPS, VPS, VLPPS), PVD and EB-PVD, HVOF and HVOF for suspension (HVSFS), or according to a combination of several of these techniques;

- The method further comprises a step, preliminary to the deposition of elementary layers, of deposition on the surface of the substrate of a coating layer forming a thermal barrier, and / or of depositing a coating layer forming an environmental barrier, and / or or depositing a tie sublayer promoting the bonding of a coating layer;

an elementary layer deposition step is carried out by a torch passage without cooling, and the directly consecutive elementary layer deposition step, or the directly antecedent elementary layer deposition step, is carried out by a torch passage with cooling, the cooling being carried out using compressed air nozzles, or using cryogenic nozzles of liquid carbon dioxide,

the coating layer can then be produced with inter-passes between torch passages without cooling and torch passages with immediately consecutive or previous cooling.

According to another aspect, the invention relates to a method of manufacturing a turbomachine part in which a thermal shock at the level of the surface of the turbomachine part is caused between the deposition of a first elementary layer and the deposition of a second. successive elementary layer, said thermal shock being preferably obtained by passing a torch without cooling after deposition of the first elementary layer, and passing a torch with cooling for the second elementary layer.

This latter process makes it possible to weaken the interface between the first elementary layer and the second elementary layer so as to promote the propagation of cracks within the plane of the interface.

GENERAL PRESENTATION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the following description, which is illustrative and not restrictive, and from the appended figures, including Figures la, lb and le already described above, as well as the other drawings. following:

FIG. 2a schematically represents the surface of a part of a turbomachine according to the invention, exhibiting, within a coating layer, both transverse and horizontal cracking.

Figure 2b schematically shows the part of Figure 2a subjected to an infiltration of molten CMAS compounds.

FIG. 2c schematically represents the advance of the infiltration front of the molten CMAS compounds in a crack of the part of FIGS. 2a and 2b.

Figure 3 is a view of a partially horizontal crack between two elementary layers of different tenacity.

FIG. 4 represents the steps of a manufacturing process according to an embodiment of a process of the invention.

FIG. 5 represents the steps of a manufacturing process according to an alternative embodiment of a process of the invention.

FIG. 6 represents the steps of a manufacturing process according to another alternative embodiment of a process of the invention.

FIG. 7a represents a multilayer stack for protection against CMAS according to a first example.

FIG. 7b represents a multilayer stack for protection against CMAS according to a second example.

FIG. 7c represents a multilayer stack for protection against CMAS according to a third example.

FIG. 7d represents a multilayer stack for protection against CMAS according to a fourth example.

DETAILED DESCRIPTION OF AN EMBODIMENT

There is shown in Figure 2a a turbomachine part 10 according to a possible embodiment of the invention. The part 10 may comprise a substrate 1 made of a metallic material, for example a nickel-based or cobalt-based superalloy such as the known superalloys AMI, CM-NG, CMSX4 and its derivatives or else the Rene superalloy and its derivatives. The part 10 can also comprise a substrate 1 made of ceramic matrix composite (also denoted CMC). The part 10 can be any part of a turbomachine exposed to thermal cycling and exposed to high temperature CMAS compounds. The part 10 can in particular be a moving turbine blade, or a high turbine distributor.

pressure, or a high pressure turbine ring, or a combustion chamber wall.

The substrate 1 can be covered with an alumino-forming bonding layer (not shown in Figure 2a) including for example MCrAIY type alloys (M = Ni, Co, Ni and Co), b- type nickel aluminides. NiAI (modified or not by Pt, Hf, Zr, Y, Si or combinations of these elements), aluminides of g-Ni-y'-Ni3AI alloys (modified or not by Pt, Cr, Hf, Zr , Y, Si or combinations of these elements), the MAX phases (M n + i AX n (n = l, 2,3) where M = Sc, Y, La, Mn, Re, W, Hf, Zr, Ti; A = groups IIIA, IVA, VA, VIA; X = C, N), or any other suitable tie sublayer, as well as mixtures of the compositions mentioned above.

Furthermore, the substrate 1 can be covered (as well as the possible aluminum-forming bonding layer) with a coating layer forming a thermal barrier, or forming an environmental barrier, or even forming a thermal and environmental barrier. Such a coating layer is not shown in Figure 2a.

A thermal barrier may comprise yttriated zirconia, for example exhibiting a level of 7 to 8% Y 2 0 3 by weight. The shaping of such a thermal barrier can be carried out for example by APS (plasma spraying at atmospheric pressure), SPS (plasma spraying of suspension), SPPS (plasma spraying of precursor solutions), HVOF ("High Velocity Oxi- Fuel ”), sol-gel process, HVSFS (“ High-Velocity Suspension Flame Spraying ”), EB-PVD (“ Electron Beam Physical Vapor Deposition ”), or any other known process for shaping thermal barriers.

An environmental barrier is advantageously used to protect a CMC substrate. A thermal and environmental barrier system can include one or more materials from the following group: MoSi 2 , BSAS (Ba0i -x -Sr0 x -AI 2 0 3 -2Si0 2 ), Mullite (3 AI 2 0 3 -2 Si0 2 ) , rare earth mono-and dis-silicates (rare earth = Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), zirconia

totally or partially stabilized or even doped, or any other composition known for an environmental thermal barrier.

According to the invention, the substrate 1 is partially or totally covered (as well as the possible alumino-forming bonding layer, and / or the possible thermal and / or environmental barrier layer) with a coating layer 2 thickness of protection against the infiltration of CMAS-type compounds. The protective layer 2 comprises a plurality of elementary layers. The following will be referred to as an elementary layer, to denote a layer thickness having a substantially homogeneous chemical composition and substantially homogeneous physicochemical characteristics (for example a homogeneous toughness and a homogeneous thermal expansion coefficient). Layer 2 advantageously comprises a number of elementary layers between 3 and 50, and preferably between 3 and 35.

If a coating layer forming a thermal or environmental barrier is present on the substrate, one can speak of a functionalization layer to denote the anti-CMAS protective layer 2. As an alternative, the layer 2 can be implemented directly on the substrate 1. in the absence of any other coating layer forming a thermal or environmental barrier.

Among the elementary layers within layer 2 and according to the embodiment illustrated in FIG. 2a, there are elementary layers 20 of a first set of elementary layers and elementary layers 21 of a second set of elementary layers. The elementary layers 20 are interposed between the elementary layers 21. In the example illustrated, the layer 2 only has an alternation of elementary layers 20 and elementary layers 21. However, according to a variant not illustrated, elementary layers belonging to a third type of layers, or more, could also be present within layer 2, either

interposed with the elementary layers 20 and 21, either above or below a series of elementary layers 20 and 21. The thickness of an elementary layer 20 or 21 is preferably between 0.1 micrometer and 50 micrometers. The three elementary layers 20 and the three first elementary layers 21 closest to the surface are shown in enlarged size, and the remaining consecutive elementary layers with a lesser thickness; however, a part according to the invention does not necessarily have this difference in thickness between the elementary layers, this mode of representation being chosen here to illustrate cracks.

According to the invention, the contact interfaces between an elementary layer 20 and an elementary layer 21 are adapted to promote the propagation of cracks along said interface. With the orientation of FIG. 2, the cracks thus intended to form, along the wear of the part 10 or even during cooling of the part 10 after manufacture, will have a substantially horizontal orientation. Each contact zone between an elementary layer 20 and an elementary layer 21 thus forms a mechanically weakened interface favoring the propagation of cracks. A detailed description of the elementary layers 20 and 21 is given below in relation to Example 1. Due to the presence of mechanically weakened interfaces between the elementary layers 20 and 21, over the course of the wear of the part, a cracking network is intended to develop with a greater tortuosity than for a layer 2 which would consist of a thickness of uniform composition. There is shown in Figure 2a such a network of cracks, comprising cracks 42 oriented in the plane of the interface between two successive layers, and cracks 41 oriented transversely in the direction of the thickness of layer 2. We consider will refer hereinafter to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 thus forms an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. a cracking network is intended to develop with a greater tortuosity than for a layer 2 which would consist of a thickness of uniform composition. There is shown in Figure 2a such a network of cracks, comprising cracks 42 oriented in the plane of the interface between two successive layers, and cracks 41 oriented transversely in the direction of the thickness of the layer 2. We consider will refer hereinafter to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 thus forms an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. a cracking network is intended to develop with a greater tortuosity than for a layer 2 which would consist of a thickness of uniform composition. There is shown in Figure 2a such a network of cracks, comprising cracks 42 oriented in the plane of the interface between two successive layers, and cracks 41 oriented transversely in the direction of the thickness of the layer 2. We consider will refer below to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 thus forms an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. uniform composition thickness. There is shown in Figure 2a such a network of cracks, comprising cracks 42 oriented in the plane of the interface between two successive layers, and cracks 41 oriented transversely in the direction of the thickness of the layer 2. We consider will refer below to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 thus forms an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. uniform composition thickness. There is shown in Figure 2a such a network of cracks, comprising cracks 42 oriented in the plane of the interface between two successive layers, and cracks 41 oriented transversely in the direction of the thickness of the layer 2. We consider will refer below to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 thus forms an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. and cracks 41 oriented transversely in the direction of the thickness of layer 2. Reference will be made below to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 forms thus an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations. and cracks 41 oriented transversely in the direction of the thickness of layer 2. Reference will be made hereinafter to “horizontal” cracks for cracks 42 and to “transverse” cracks for cracks 41. Layer 2 forms thus an anti-CMAS protective layer with controlled cracking. It will easily be understood that the part could also include cracks having other orientations.

The same system is shown schematically in Figure 2b, in an environment where liquid contaminating compounds at high temperature of the CMAS type are present. Due to the high surface temperature at layer 2 during operation of the blade, a liquid phase 3 forms on the surface of layer 2. This liquid phase 3 gradually infiltrates over time. on the thickness of the layer 2, via the cracks 42 and 41. The presence of horizontal cracks 42, in addition to the transverse cracks 41, causes an extension of the infiltration path of the liquid phase 3. During d 'exposure of part 1 to molten CMAS compounds, more time passes before a liquid phase 3 reaches substrate 1.

Figure 2c is a close-up schematic view of the interface between the liquid phase 3 and cracks 42 and 41 near the surface of the part of Figure 2b. During the infiltration of liquid phase 3, there is a competition between the kinetics of progression of said phase 3 within the cracks, and the reaction kinetics of the molten CMAS infiltrated with the anti-CMAS compounds within the elementary layers. 20 and 21 - examples of anti-CMAS chemical compounds being set out below. Said reaction between molten CMAS and anti-CMAS compounds, which may for example be a crystallization reaction, forms a "blocking" phase on the periphery of the infiltration path of the molten CMAS. The blocking phase blocks the progression of molten CMAS compounds. We can also speak of a “waterproof barrier layer”.

Compared to a part obtained by a treatment consisting in filling the cracks, for example with a highly reactive ceramic, the part of Figures 2a to 2c is advantageous because the anti-CMAS deposition layer is not made mechanically rigid. In addition, the

presence of cracks in the anti-CMAS coating makes it possible to accommodate thermomechanical deformations undergone by the part during its operation, in particular caused by thermal cycling. This constitutes an additional advantage of a part of the invention, compared to a part which would have undergone a treatment aimed at filling cracks.

FIG. 3 represents a view under the microscope of a cracked interface between an elementary layer 20 and an elementary layer 21. It is noted that the network of cracks formed during the thermal cycling of the part can be more complex than the simplified shape shown on Figures 2a to 2c. In particular, horizontal cracks 42 may be formed at the level of the interface, shown here in dotted lines around the perimeter of the view under the microscope, but may also be formed at positions offset with respect to said interface.

Manufacturing process of a controlled cracking part - Example 1

A treatment process 40 for obtaining a part with controlled cracking, that is to say favoring the formation of cracks at the level of interfaces between elementary coating layers, according to a first example of implementation, is illustrated in FIG. 4. It is considered that a substrate of the part to be treated is already formed upstream of said process, for example formed of metallic material or of ceramic matrix composite (CMC).

In an optional step 100, an aluminum-forming bonding layer 7 is deposited on the surface of the substrate, to promote the adhesion of the following layer, as described above in relation to FIG. 2a.

In an optional step 200, a layer 8 forming a thermal barrier, or environmental barrier (EBC), or thermal-environmental barrier (TEBC) is formed on the surface of the substrate, or on the surface of the tie layer 7. This layer 8 can in particular be obtained by any technique of deposition by thermal spraying, as described above in relation to FIG. 2a. Step 200 is in particular not essential if the elementary layers deposited subsequently play the role of thermal barrier and / or environmental barrier. A step 300 is then implemented for forming a layer 2 of protective coating against the infiltration of compounds of CMAS type. Step 300 comprises a succession of substeps 300 (1), 300 (2) ... 300 (N), each of these substeps comprising a deposit 301 of

Here, the elementary layers 20 have tenacities different from the elementary layers 21, which creates mechanically weakened interfaces between said layers. Advantageously, the tenacities of the elementary layers 20 differ by at least 0.7 MPa.m 1/2 compared to the tenacities of the elementary layers 21. By way of example, the elementary layers 20 have a tenacity of between 0, 5 and 1.5 Mpa.m 1/2 and the elementary layers 21 have a tenacity of between 1.5 and 2.2 Mpa.m 1/2 . The elementary layers 20 do not necessarily all have the same tenacity, just like the elementary layers 21.

In the example of method 40, the layers 20 are formed from Gd 2 Zr 2 0 7 , with a tenacity of 1.02 Mpa.m 1/2 , and the layers 21 are formed from yttriated zirconia Zr0 2 - 7-8 % mass Y 2 0 3 (YSZ), with a toughness of 2.0 Mpa.m 1/2 .

The layers 20 are formed by plasma spraying of suspensions (“Suspension Plasma Spraying” hereinafter SPS). We use for

steps 301 a “Sinplex Pro” torch with an argon / helium / dihydrogen volumetric flow rate of 80/20/5 standard liters per minute or “slpm” according to the current abbreviation. A YSZ / ethanol suspension is used, with an injection rate of 40 to 50 grams per minute. The deposition rate of the YSZ is 2 micrometers of layer thickness per deposition cycle, one cycle being defined as one round trip of the plasma torch past the workpiece surface to be treated. Three deposition cycles are carried out for the deposition of an elementary layer 20, which thus has a thickness of 6 micrometers.

The layers 21 are formed by SPS using a “Sinplex” torch with an argon / helium / dihydrogen volumetric flow rate of 80/20/5 slpm. A Gd 2 Zr 2 0 7 / ethanol suspension is used , with an injection rate of 40 to 50 grams per minute. The deposition rate of Gd 2 Zr 2 0 7 is 2 micrometers of thickness of layer 21 per deposition cycle. Three deposition cycles are carried out for the deposition of an elementary layer 21, which thus has a thickness of 6 micrometers.

The same suspension injector is used to carry out steps 301 and 302, with two separate suspension reservoirs and open alternately for fluid communication with the suspension injector: a first reservoir is open for steps 301 and a second reservoir is open for steps 302.

The anti-CMAS coating layer 2 is produced by a series of 25 steps 300 (N = 25), for a total thickness of 300 micrometers.

As an alternative, a thickness of the layer 2 can be between 20 and 500 micrometers, preferably between 20 and 300 micrometers.

As an alternative, steps 301 and 302 can be implemented:

- Using a "Triplex Pro" torch with an argon / helium / dihydrogen volumetric flow rate having a value in slpm taken from the following values: 80/20/0, 80/20/5, 80/0/5 ;

- Using a "Sinplex Pro" torch with an argon / helium / dihydrogen volumetric flow rate of value in slpm taken from the following values: 50/0/5, 40/0/5, 80/20/0, 80/20/5, 80/0/5; - Using an "F4" torch with an argon / helium / dihydrogen volumetric flow rate of value in slpm taken from the following values: 45/45/3, 44/10/3, 45/30/5, 40 / 20/0, 30/50/5. These values ​​can also be used for methods 50 and 60 described below.

Alternatively, the layers 20 can be formed from a material taken from: RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, or a mixture of several of these materials.

Alternatively, the layers 21 can be formed of a material taken from: Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, or a mixture of several of these materials.

According to one variant, step 300 could not only include steps for depositing layer 20 and steps for depositing layer 21, and could also include steps for depositing additional varieties of elementary layers.

In addition, a thermal shock can optionally be caused at the surface of the part between the deposition of an elementary layer 20 and the deposition of a successive elementary layer 21, or vice versa, said thermal shock being obtainable by a passage torch without cooling after deposition of the first elementary layer, and a torch passage with cooling for the second elementary layer. This has the effect of further weakening the interface between the elementary layers 20 and 21 to promote horizontal cracking.

Manufacturing process of a controlled cracking part - Example 2

A treatment process 50 to obtain a part with controlled cracking according to a second example is given in FIG. 5.

The optional steps 100 and 200 are similar to the steps of method 40.

A step 400 of forming a layer 2 of protective coating against the infiltration of compounds of CMAS type is then implemented.

Step 400 comprises a succession of substeps 400 (1), 400 (2) ... 400 (N), each of these substeps comprising a deposition 501 of an elementary layer 22, followed by a deposition 402 of an elementary layer 23.

In the example of method 50, the layers 22 are formed in Y 2 Si 2 07, with an expansion coefficient of 3.9 10 6 K 1 , and the layers 23 are formed in yttriated zirconia Zr0 2 - 7-8% mass Y 2 0 3 (YSZ), with an expansion coefficient of 11.5 10 6 K 1 . Layers 22 and 23 are formed by SPS using a “Sinplex Pro” torch with an argon / helium / dihydrogen volumetric flow rate of 40/0/5 slpm. We use a suspension Y 2 Si 2 0 7/ ethanol for layers 22 and YSZ / ethanol for layers 23, with an injection rate of 40 to 50 grams per minute. The deposition rate of the YSZ is 2 micrometers of layer 23 thickness per injection cycle. Three injection cycles are carried out for the deposition of an elementary layer 23, which thus has a thickness of 6 micrometers.

The rate of deposition of Y 2 Si 2 0 7 is 1 micrometers thick of layer 22 per injection cycle. Three injection cycles are carried out for the deposition of an elementary layer 22, which thus has a thickness of 3 micrometers.

The same suspension injector is used to carry out steps 401 and 402, with two separate suspension reservoirs which are open alternately for fluid communication with the suspension injector.

The anti-CMAS coating layer 2 is produced by a series of 34 iterations of steps 400 (N = 34), for a total thickness of approximately 300 micrometers. As for process 40, thermal shocks can be caused to further weaken the interfaces between elementary layers.

As an alternative, the elementary layers 22 comprise RE 2 Si 2 0 7 or RE 2 Si0 5 with RE a material of the rare earth family, or comprise a mixture of these materials.

As an alternative, the elementary layers 23 comprise a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, YAG, or include a mixture of these materials.

Manufacturing process of a controlled cracking part - Example 3

A treatment process 60 to obtain a part with controlled cracking according to a third example is given in FIG. 6.

The optional steps 100 and 200 are similar to the steps of method 40.

A step 500 of forming a layer 2 of anti-CMAS protective coating is then implemented. Step 600 comprises a succession of substeps 500 (1) ... 500 (N) depending on the thickness of layer 2 desired in particular. Each of said substeps comprises a first deposit 501 of elementary layer 24, and a second deposit 502 of elementary layer 24 according to a different protocol from deposit 501. Between a step 501 and a successive step 502, or vice versa, a thermal shock is caused. by passing a torch without cooling at the end of step 501, and a torch passing with cooling at the end of step 502.

The cooling is carried out using compressed air nozzles, for example 6 nozzles at 6 bar of the carp tail type, or using nozzles with cryogenics of liquid carbon dioxide, for example two nozzles at 25 bar.

A deposit 500 is produced here with inter-passes, with a slow deposition kinematics (illumination speed less than 300 millimeters per second) and with a high mass load rate (more than 20% by mass of solid particles in suspension) .

In the particular example of method 60, the layers 24 are formed from YSZ. Steps 501 and 502 are implemented with a torch

“F4 - MB” with an argon / helium / dihydrogen volumetric flow rate of 45/45/6 slpm, with a YSZ / ethanol suspension.

The deposits 501 are made with a mass load rate of 12% and an injection rate of 25 to 30 grams per minute, for a thickness of 10 micrometers (2 micrometers per cycle). The deposits 502 are made with a mass load rate of 20% and an injection rate of 45 to 50 grams per minute, for a thickness of 9 micrometers (3 micrometers per cycle).

Preferably, two separate suspension injectors are used to carry out steps 501 and 502, with two separate suspension reservoirs which are open alternately.

In the example of method 60, N = 16 iterations of steps 500 are carried out, for a total thickness of approximately 300 micrometers for layer 2.

Examples of controlled cracking turbomachine parts

Figures 7a to 7d schematically show several examples of stacking layers implemented for parts of a turbomachine according to the invention.

The anti-CMAS deposition layers 2 shown in FIGS. 7a to 7d are obtained, for example, according to any method described above.

FIG. 7a shows a part comprising a substrate 1 made of a metal alloy covered with a layer 2 of anti-CMAS coating. In this exemplary embodiment, layer 2 can play both the role of a thermal barrier and that of an anti-CMAS deposit.

In FIG. 7b, an alumino-forming tie layer 7 is interposed between the substrate 1 and the anti-CMAS layer 2.

In FIG. 7c, a thermal barrier layer 8 is interposed between the tie layer 7 and the anti-CMAS layer 2. The anti-CMAS deposit 2 can be a functionalization layer which does not play the role of thermal barrier.

In Figure 7d, the substrate 1 is formed of ceramic matrix composite (CMC). The substrate is covered with a bonding layer 7, a thermal and environmental barrier layer 9 (TEBC) and an anti-CMAS deposition layer 2.

The parts of Figures 7a to 7d exhibit, in accordance with the above description, mechanically weakened interfaces promoting cracking in planes substantially parallel to the surface of the part.

CLAIMS

1. Turbomachine part comprising:

5- a substrate in metallic material, or in composite material,

- a protective coating layer against the infiltration of compounds such as oxides of calcium, magnesium, aluminum or silicon, or CMAS, the coating layer at least partially covering the surface of the substrate,

0 the coating layer comprising a plurality of elementary layers,

the part being characterized in that elementary layers of a first set of elementary layers are interposed between elementary layers of a second set of 5 elementary layers, each elementary layer of the first set and each elementary layer of the second set comprising a compound anti-CMAS,

each contact zone between an elementary layer of the first set and an elementary layer of the second set 0 forming an interface favoring the propagation of cracks along said interface.

2. Turbomachine part according to claim 1, wherein each elementary layer of the first set has a toughness which differs by at least 0.7 MPa.m 1/2 with respect to the tenacities of all the elementary layers of the second set.

3. Turbomachine part according to claim 2, wherein the elementary layers of the first set have a tenacity of between 0.5 and 1.5 MPa.m 1/2 and the elementary layers of the second set have a tenacity of between 1 , 5 and 2.2 Mpa.m 1/2 .

4. Part according to one of claims 2 or 3, wherein the elementary layers of the first set comprise a material taken from the following list: RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, or include a mixture of several of these materials.

5. Part according to one of claims 2 to 4, wherein the elementary layers of the second set comprise a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, or comprise a mixture of several of these materials.

6. Turbomachine part according to claim 1, wherein each elementary layer of the first set has a coefficient of thermal expansion which differs by at least 3.5 10 6 K 1 relative to the thermal expansion coefficients of all the elementary layers of the second set.

7. Part according to claim 6, wherein the elementary layers of the first set have a thermal expansion coefficient between 3.5 and 6.0 10 6 K 1 and the elementary layers of the second set have a thermal expansion coefficient between 7.0 and 12.0 10 6 K 1 .

8. Part according to one of claims 6 or 7, wherein the elementary layers of the first set

include RE2SÎ207 or RE2SÎ05 with RE a material of the rare earth family, or include a mixture of these materials.

9. Part according to one of claims 6 or 7, wherein the elementary layers of the second set comprise a material from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, RE2Zr207 with RE a material of the rare earth family, Ba (Mgl / 3Ta2 / 3) 03, La (All / 4Mgl / 2Tal / 4) 03, YAG, or comprise a mixture of several of these materials.

10. Part according to one of claims 1 to 9, wherein the ratio of the cumulative thickness of the elementary layers of the first set to the cumulative thickness of the elementary layers of the second set is between 1: 2 and 2: 1.

11. Part according to one of claims 1 to 10, where the total thickness of the protective coating layer is between 20 and 500 pm, preferably between 20 and 300 pm.

12. Part according to one of claims 1 to 11, forming a moving turbine blade, or a high pressure turbine nozzle, or a high pressure turbine ring, or a combustion chamber wall.

13. A method of treating a turbomachine part comprising steps of deposition by thermal spraying of a plurality of elementary layers, on the surface of a substrate of the part, the substrate being formed of metallic material, or of

composite material, to produce a protective coating layer against the infiltration of CMAS-type compounds,

the method being characterized in that steps of depositing elementary layers belonging to a first set on the surface of the substrate are interposed between steps of depositing elementary layers belonging to a second set,

the elementary layers of the first set having tenacities which differ by at least 0.7 MPa.m 1/2 compared to the tenacities of the elementary layers of the second set,

or the elementary layers of the first set having thermal expansion coefficients which differ by at least 3.5 10 6 K 1 with respect to the thermal expansion coefficients of the elementary layers of the second set.

14. The method of claim 13, wherein a thermal shock at the surface of the turbomachine part is caused between the deposition of a first elementary layer and the deposition of a second successive elementary layer, said thermal shock being of preferably obtained by a torch passage without cooling after deposition of the first elementary layer, and a torch passage with cooling for the second elementary layer.