PART COATED WITH A COMPOSITION FOR PROTECTION AGAINST CMAS WITH CONTROLLED CRACKING AND CORRESPONDING TREATMENT METHOD

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a turbomachine part, such as a high-pressure turbine blade or a combustion chamber wall. STATE OF THE ART

[0002] In a turbojet engine, the exhaust gases generated by the combustion chamber can reach high temperatures, exceeding 1200°C or even 1600°C. The turbojet engine parts in contact with these exhaust gases must be able to maintain their mechanical properties at these high temperatures. In particular, the components of high-pressure turbines, or HPTs, must be protected against excessively high surface temperatures in order to ensure their functional integrity and limit oxidation and corrosion.

[0003] It is known to manufacture certain turbojet parts from "superalloys". 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 temperatures). It is also known to manufacture parts from ceramic matrix composites, or CMCs.

[0004] It is known to cover the surface of parts made of said materials with a coating acting as a thermal barrier, and / or as an environmental barrier.

[0005] A thermal or environmental barrier generally comprises a thermally insulating layer whose function is to limit the surface temperature of the coated component, and a protective layer to protect the substrate from oxidation and / or corrosion.

[0006] The ceramic layer usually covers the protective layer. For example, the thermally insulating layer can be made of yttria-containing zirconia. A metallic underlayer can be deposited before the protective layer, and the protective layer can be formed by oxidation of the metallic underlayer. The metallic underlayer provides a bond between the surface of the superalloy substrate and the protective layer: the metallic underlayer is sometimes called a "bonding underlayer". 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 reinforce the protection function against oxidation and corrosion.

[0007] It is crucial to ensure a satisfactory service life of thermal and environmental barriers throughout the operating cycles of turbomachine parts. This service life is notably conditioned by the resistance of the barrier to thermal cycling on the one hand, and to environmental aggressions such as erosion and corrosion on the other hand. The thermal or environmental barrier is likely to degrade rapidly in the presence of particles rich in inorganic compounds of the silica type, or if it is located in an atmosphere rich in compounds commonly called CMAS, including in particular calcium, magnesium, aluminum and silicon oxides. CMAS are likely to infiltrate in the molten state into the thermal or environmental barrier, in particular in cracks formed in the internal volume of the barrier layers.Once infiltrated, CMAS compound particles 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.

[0008] To prevent the penetration of high-temperature liquid contaminants such as CMAS compounds into the coating layers, anti-CMAS deposits are known that promote the formation of a tight barrier layer on the surface of the coated part, by spontaneous chemical reaction between chemical species of the anti-CMAS deposits and the CMAS compounds. The tight barrier layer thus formed blocks the progression of the molten CMAS compounds into 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 then compete with the infiltration kinetics of the CMAS compounds into the coating, and in particular into cracks in the coating.

[0009] However, the effectiveness of anti-CMAS deposits is reduced when the part to be protected has transverse cracking. Throughout the following, "transverse cracking" means a plurality of cracks having a general orientation substantially orthogonal to the plane tangent to the surface of the coated part. Figures 1a, 1b And 1c attached illustrate the phenomenon of capillary penetration of CMAS compounds from ambient air into a network of cracks within the external surface of a part. la Figure 1a , the part, which may be a high-pressure turbine blade of a turbomachine, 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 network of transverse cracking comprising through cracks for layer 2, orthogonal to the surface and slightly deviated. On the Figure 1b, particles of CMAS compounds, melted due to the high surface temperature at layer 2 during operation of the blade, form a liquid phase 3 on the surface of layer 2. This liquid phase 3 is partially infiltrated into crack 4. On the Figure 1c , which represents the system at a state subsequent to that of the Figure 1b , 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 edge of the crack 4. The blocking phase 5 is represented here by a network of contiguous pentagonal shapes. This blocking phase 5 blocks the infiltration of the CMAS compounds from the liquid phase 3. In addition, a secondary phase 6 can form in places, this secondary phase 6 being represented by the circular shapes shown on the Figure 1c. Here, crack 4 being substantially transverse, the liquid phase 3 infiltrates rapidly over the entire thickness of the anti-CMAS deposit layer 2, the infiltration kinetics of the molten CMAS compounds prevailing over the kinetics of the chemical reaction leading to the formation of the blocking phase. Layer 2 is weakened, and the service life of the part is reduced.

[0010] There is therefore a need for a surface treatment of a turbomachine part, comprising the application of a thermal and / or environmental barrier whose integrity would be guaranteed throughout the life of the part, in an environment loaded with CMAS compounds. In particular, there is the problem of the mechanical resistance of anti-CMAS deposit layers placed on the surface of the turbine parts, in the face of the infiltration of molten CMAS compounds. A turbomachine part according to the prior art is disclosed in WO2011 / 123432. GENERAL PRESENTATION OF THE INVENTION

[0011] The invention meets the need highlighted above by providing a turbomachine part according to claim 1

[0012] A part according to the invention thus has an anti-CMAS coating layer promoting the deflection of possible cracks in a direction substantially parallel to the surface of the part. The capillary penetration of the molten CMAS-type compounds during operation of the part is intended to be minimized. Indeed, 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 coating layers and quickly reaching the substrate of the part, infiltrates into tortuosities formed by the cracks along interfaces of elementary layers. The kinetics of the reaction for the formation of a blocking phase involving chemical compounds of the coating is favored compared to the kinetics of infiltration of the molten CMAS compounds.

[0013] Another advantage provided by the invention is to allow the cracking of the anti-CMAS coating layers while ensuring good mechanical strength due to the reduction of 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 a more significant breakage which would harm the strength of the part.

[0014] 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 may, for example, have a toughness of between 0.5 and 1.5 Mpa.m 1 / 2< and the elementary layers of the second set may have a toughness of between 1.5 and 2.2 Mpa.m 1 / 2<.

[0015] The change in toughness between two consecutive elementary layers induces preferential cracking in the direction of the interface between the consecutive layers, particularly during operation and possibly at the end of manufacturing after cooling; the elementary layers of the second set comprise a material taken from the following list: YSZ, Y2O3-ZrO2-Ta2O5, BaZrO3, CaZrO3, SrZrO3, or comprise a mixture of several of these materials; the elementary layers of the first set comprise a material taken from the following list: RE2Zr2O7 with RE a material from the rare earth family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, or comprise a mixture of several of these materials; the elementary layers of the first set being able to have a coefficient of thermal expansion between 3.5 and 6.0 10 -6 K -1 and the elementary layers of the second set which may have a coefficient of thermal expansion between 7.0 and 12.0 10 -6 K -1 .

[0016] The change in expansion coefficient between two consecutive elementary layers induces preferential cracking in the direction of the interface between the consecutive layers, particularly during operation and possibly at the end of manufacturing after cooling; the elementary layers of the second set comprise a material taken from the following list: YSZ, Y2O3-ZrO2-Ta2O5, BaZrO3, CaZrO3, SrZrO3, RE2Zr2O7 with RE a material from the rare earth family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, YAG, or comprise a mixture of several of these materials; the elementary layers of the first set comprise RE2Si2O7 or RE2SiO5 with RE a material from the rare earth family, or comprise 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 nozzle, or a high-pressure turbine ring, or a combustion chamber wall.

[0017] According to a second aspect, the invention relates to a method for 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 from metallic material, or from 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 intercalated between steps of depositing elementary layers belonging to a second set, the elementary layers of the first set having toughnesses which differ by at least 0.7 Mpa.m 1 / 2< compared to the toughnesses of the elementary layers of the second set, or the elementary layers of the first set having coefficients of thermal expansion which differ by at least 3.5 10 -6< K -1< compared to the coefficients of thermal expansion of the elementary layers of the second set.

[0018] The method may have the following additional and non-limiting characteristics: the steps of depositing elementary layers being carried out according to the technique of suspension plasma thermal projection, or Suspension Plasma Spraying (SPS), or according to one of the other following techniques: atmospheric pressure plasma projection (APS), plasma projection of precursor solutions (SPPS), plasma projection under inert atmosphere or reduced pressure (IPS, VPS, VLPPS), PVD and EB-PVD, HVOF and suspension HVOF (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 depositing on the surface of the substrate a coating layer forming a thermal barrier, and / or of depositing a coating layer forming an environmental barrier, and / or of depositing a bonding sub-layer promoting the adhesion of a coating layer;an elementary layer deposition step is carried out by a torch pass without cooling, and the directly consecutive elementary layer deposition step, or the directly preceding elementary layer deposition step, is carried out by a torch pass with cooling, the cooling being carried out using compressed air nozzles, or using liquid carbon dioxide cryogenic nozzles, the coating layer then being able to be produced with inter-passes between torch passes without cooling and torch passes with cooling immediately consecutive or preceding.;

[0019] The treatment method may further comprise a step in which 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 preferably being obtained by a torch pass without cooling after deposition of the first elementary layer, and a torch pass with cooling for the second elementary layer.

[0020] This last step 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 interface plane. GENERAL PRESENTATION OF THE FIGURES

[0021] Other characteristics, aims and advantages of the invention will emerge from the following description, which is illustrative and not limiting, and from the appended figures among which the Figures 1a, 1b And 1calready described above, as well as the following other drawings: There Figure 2a schematically represents the surface of a turbomachine part according to the invention, presenting within a coating layer both transverse and horizontal cracking. The Figure 2b schematically represents the part of the Figure 2a subjected to infiltration of molten CMAS compounds. The Figure 2c schematically represents the advance of the infiltration front of the molten CMAS compounds in a crack of the part of the Figures 2a And 2b . There Figure 3 is a view of a partially horizontal crack between two elementary layers of different toughness. The Figure 4 represents the steps of a manufacturing method according to an embodiment of a method of the invention. The Figure 5 represents the steps of a manufacturing process according to an alternative embodiment of a process of the invention. The Figure 6represents the steps of a manufacturing method according to another alternative embodiment of a method of the invention. The Figure 7a represents a multi-layer stack of protection against CMAS according to a first example. The Figure 7b represents a multi-layer stack of protection against CMAS according to a second example. The Figure 7c represents a multi-layer stack of protection against CMAS according to a third example. The Figure 7d represents a multi-layer stack of protection against CMAS according to a fourth example. DETAILED DESCRIPTION OF AN EMBODIMENT

[0022] We represented in Figure 2aa turbomachine part 10 according to a possible embodiment of the invention. The part 10 may comprise a substrate 1 made of metallic material, for example a nickel-based or cobalt-based superalloy such as the known superalloys AM1, CM-NG, CMSX4 and its derivatives or the René superalloy and its derivatives. The part 10 may also comprise a substrate 1 made of ceramic matrix composite (also noted CMC). The part 10 may be any turbomachine part exposed to thermal cycling and exposed to CMAS compounds at high temperature. The part 10 may in particular be a moving turbine blade, or a high-pressure turbine nozzle, or a high-pressure turbine ring, or a combustion chamber wall.

[0023] The substrate 1 may be covered with an alumino-forming bonding layer (not shown in the Figure 2a) including for example MCrAlY type alloys (M = Ni, Co, Ni and Co), β-NiAl type nickel aluminides (modified or not by Pt, Hf, Zr, Y, Si or combinations of these elements), γ-Ni- γ'-Ni3Al alloy aluminides (modified or not by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements), MAX phases (M n+1 AX n (n=1,2,3) where M = Sc, Y, La, Mn, Re, W, Hf, Zr, Ti; A = groups IIIA, IVA, VA, VIA; X = C,N), or any other suitable bonding sub-layer, as well as mixtures of the compositions mentioned above. Furthermore, the substrate 1 may be covered (as well as the possible alumino-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 the Figure 2a .

[0024] A thermal barrier may comprise yttria-containing zirconia, for example, having a content of 7 to 8% Y 2 O 3 by mass. The shaping of such a thermal barrier may be carried out, for example, by APS (atmospheric pressure plasma spraying), SPS (suspension plasma spraying), SPPS (precursor solution plasma spraying), 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 forming thermal barriers.

[0025] An environmental barrier is advantageously used to protect a CMC substrate. A thermal and environmental barrier system may comprise one or more materials from the following group: MoSi 2 , BSAS (BaO 1-x -SrO x -Al 2 O 3 -2SiO 2 ), Mullite (3 Al 2 O 3 -2 SiO 2 ), rare earth mono- and di-silicates (rare earth = Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), fully or partially stabilized or doped zirconia, or any other composition known for an environmental thermal barrier.

[0026] According to the invention, the substrate 1 is partially or totally covered (as well as the optional alumino-forming bonding layer, and / or the optional thermal and / or environmental barrier layer) with a layer thickness 2 of protective coating against the infiltration of CMAS type compounds. The protective layer 2 comprises a plurality of elementary layers. In the following, we will speak of an elementary layer, to designate a layer thickness having a substantially homogeneous chemical composition and substantially homogeneous physicochemical characteristics (for example a homogeneous toughness and a homogeneous coefficient of thermal expansion). The layer 2 advantageously comprises a number of elementary layers of between 3 and 50, and preferably between 3 and 35. A total thickness of the layer 2 is advantageously between 20 and 500 micrometers, preferably between 20 and 300 micrometers.

[0027] If a coating layer forming a thermal or environmental barrier is present on the substrate, we can speak of a functionalization layer to designate the anti-CMAS protection layer 2. Alternatively, layer 2 can be implemented directly on the substrate 1 in the absence of another coating layer forming a thermal or environmental barrier.

[0028] Among the elementary layers within layer 2 and according to the embodiment illustrated in Figure 2a, elementary layers 20 of a first set of elementary layers and elementary layers 21 of a second set of elementary layers are distinguished. The elementary layers 20 are intercalated between the elementary layers 21. In the illustrated example, 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 intercalated with the elementary layers 20 and 21, or 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 first three 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.

[0029] 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 the Figure 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 promoting the propagation of cracks. A detailed description of the elementary layers 20 and 21 appears below in relation to Example 1.

[0030] Due to the presence of mechanically weakened interfaces between the elementary layers 20 and 21, as the part wears, a cracking network is intended to develop with greater tortuosity than for a layer 2 which would be made up of a uniform thickness of composition. Figure 2asuch 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. Reference will be made 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 be easily understood that the part could also comprise cracks having other orientations.

[0031] The same system is shown schematically on the Figure 2b ,in an environment where high-temperature liquid contaminant compounds 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 through the thickness of layer 2, via cracks 42 and 41. The presence of horizontal cracks 42, in addition to transverse cracks 41, causes an elongation of the infiltration path of the liquid phase 3. During exposure of the part 1 to molten CMAS compounds, more time elapses before a liquid phase 3 reaches the substrate 1.

[0032] There Figure 2c is a close-up schematic view of the interface between liquid phase 3 and cracks 42 and 41 close to the surface of the part of the Figure 2b. During the infiltration of the liquid phase 3, there is a competition between the progression kinetics of said phase 3 within the cracks, and the reaction kinetics of the infiltrated molten CMAS 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 5 around the periphery of the infiltration path of the molten CMAS. The blocking phase 5 blocks the progression of the molten CMAS compounds. We can also speak of a “watertight barrier layer”. A secondary phase 6 can also be formed around the periphery of the cracks.

[0033] Compared to a part obtained by a treatment consisting of filling cracks, for example with a highly reactive ceramic, the part of the Figures 2a to 2cis advantageous because the anti-CMAS deposit layer is not made mechanically rigid. In addition, the presence of cracks within 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 has undergone a treatment aimed at filling the cracks.

[0034] There Figure 3 represents a microscope view of a cracked interface between an elementary layer 20 and an elementary layer 21. It can be seen that the network of cracks formed during the thermal cycling of the part can be more complex than the simplified form represented on the Figures 2a to 2c. In particular, horizontal cracks 42 may be formed at the interface, shown here as dotted lines around the perimeter of the microscope view, but may also be formed at positions offset from said interface. Manufacturing process for a part with controlled cracking - Example 1

[0035] A treatment method 40 for obtaining a part with controlled cracking, i.e. promoting the formation of cracks at interfaces between elementary coating layers, according to a first example of implementation, is illustrated in Figure 4 . It is considered that a substrate of the part to be treated is already formed upstream of said process, for example formed in metallic material or in ceramic matrix composite (CMC).

[0036] In an optional step 100, an alumino-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 the Figure 2a .

[0037] 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 bonding layer 7. This layer 8 can in particular be obtained by any thermal spray deposition technique, as described above in relation to the Figure 2a Step 200 is notably non-essential if the elementary layers deposited subsequently act as a thermal barrier and / or an environmental barrier.

[0038] A step 300 of forming a layer 2 of protective coating against the infiltration of CMAS type compounds is then implemented. Step 300 comprises a succession of sub-steps 300(1), 300(2) ... 300(N), each of these sub-steps comprising a deposition 301 of an elementary layer 20, followed by a deposition 302 of an elementary layer 21. The deposits 301 and 302 are preferably carried out by thermal spraying techniques, for example, by APS, SPS, SPPS, HVOF, sol-gel process, HVSFS, EB-PVD, plasma spraying under inert atmosphere or under reduced pressure (IPS or "Inert Plasma Spraying", VPS or "Vacuum Plasma Spraying", VLPPS or " Very Low Pressure Plasma Spraying").

[0039] Here, the elementary layers 20 have different toughnesses than the elementary layers 21, which creates mechanically weakened interfaces between said layers. Advantageously, the toughnesses of the elementary layers 20 differ by at least 0.7 Mpa.m 1 / 2< compared to the toughnesses of the elementary layers 21. For example, the elementary layers 20 have a toughness of between 0.5 and 1.5 Mpa.m 1 / 2< and the elementary layers 21 have a toughness of between 1.5 and 2.2 Mpa.m 1 / 2<. The elementary layers 20 do not necessarily all have the same toughness, just like the elementary layers 21.

[0040] In the example of method 40, the layers 20 are formed in Gd 2 Zr 2 O 7 , with a toughness of 1.02 Mpa.m 1 / 2,< and the layers 21 are formed in yttria zirconia ZrO 2 - 7-8%massY 2 O 3 (YSZ), with a toughness of 2.0 Mpa.m 1 / 2< .

[0041] Layers 20 are formed by plasma spraying of suspensions (“Plasma Spraying Suspension » hereinafter SPS). For steps 301, a “Sinplex Pro” torch is used 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 YSZ deposition rate is 2 micrometers of layer thickness 20 per deposition cycle, a cycle being defined as a round trip of the plasma torch in front of the surface to be treated of the part. Three deposition cycles are carried out for the deposition of an elementary layer 20, which thus has a thickness of 6 micrometers.

[0042] The 21 layers 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 O 7 / ethanol suspension is used, with an injection rate of 40 to 50 grams per minute. The deposition rate of Gd 2 Zr 2 O 7 is 2 micrometers of layer 21 thickness 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.

[0043] The same suspension injector is used to carry out steps 301 and 302, with two separate suspension reservoirs opened 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.

[0044] Layer 2 of anti-CMAS coating is produced by a sequence of 25 steps 300 (N = 25), for a total thickness of 300 micrometers. Alternatively, a thickness of layer 2 can be between 20 and 500 micrometers, preferably between 20 and 300 micrometers.

[0045] Alternatively, steps 301 and 302 may 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 a 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 a value in slpm taken from the following values: 45 / 45 / 3, 44 / 10 / 3, 45 / 30 / 5, 40 / 20 / 0, 30 / 50 / 5.

[0046] These values ​​can also be used for the 50 and 60 processes described below.

[0047] Alternatively, the layers 20 may be formed from a material taken from: RE2Zr2O7 with RE a material from the rare earth family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, or a mixture of several of these materials.

[0048] Alternatively, the layers 21 may be formed from a material selected from: Y2O3-ZrO2-Ta2O5, BaZrO3, CaZrO3, SrZrO3, or a mixture of several of these materials.

[0049] According to a variant, step 300 could not only comprise steps of depositing layer 20 and steps of depositing layer 21, and could also comprise steps of depositing additional varieties of elementary layers.

[0050] In addition, a thermal shock may 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 able to be obtained by a torch pass without cooling after deposition of the first elementary layer, and a torch pass 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 for a part with controlled cracking - Example 2

[0051] A treatment method 50 for obtaining a part with controlled cracking according to a second example is given in Figure 5 .

[0052] Optional steps 100 and 200 are similar to the steps of method 40.

[0053] A step 400 of forming a layer 2 of protective coating against the infiltration of CMAS type compounds is then implemented. Step 400 comprises a succession of sub-steps 400(1), 400(2) ... 400(N), each of these sub-steps comprising a deposition 501 of an elementary layer 22, followed by a deposition 402 of an elementary layer 23.

[0054] In the example of process 50, layers 22 are formed in Y 2 Si 2 O 7 , with an expansion coefficient of 3.9 10 -6 < K -1 < , and layers 23 are formed in yttria-containing zirconia ZrO 2 - 7-8%massY 2 O 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. A Y 2 Si 2 O 7 / ethanol suspension is used for layers 22 and YSZ / ethanol for layers 23, with an injection rate of 40 to 50 grams per minute. The deposition rate of YSZ is 2 micrometers of layer thickness 23 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.

[0055] The deposition rate of Y 2 Si 2 O 7 is 1 micrometer of layer thickness 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.

[0056] The same suspension injector is used to carry out steps 401 and 402, with two separate suspension reservoirs opened alternately for fluid communication with the suspension injector.

[0057] Layer 2 of anti-CMAS coating is produced by a series of 34 iterations of 400 steps (N = 34), for a total thickness of approximately 300 micrometers. As with process 40, thermal shocks can be induced to further weaken the interfaces between elementary layers.

[0058] Alternatively, the elementary layers 22 comprise RE 2 Si 2 O 7 or RE 2 SiO 5 with RE a material from the rare earth family, or comprise a mixture of these materials.

[0059] Alternatively, the elementary layers 23 comprise a material taken from the following list: YSZ, Y2O3-ZrO2-Ta2O5, BaZrO3, CaZrO3, SrZrO3, RE2Zr2O7 with RE a material from the rare earth family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, YAG, or comprise a mixture of these materials. Manufacturing process for a part with controlled cracking - Example 3

[0060] A treatment method 60 for obtaining a part with controlled cracking according to a third example is given in Figure 6 .

[0061] Optional steps 100 and 200 are similar to the steps of method 40.

[0062] A step 500 of forming a layer 2 of anti-CMAS protective coating is then implemented. Step 600 comprises a succession of sub-steps 500(1) ... 500(N) depending on the desired thickness of layer 2 in particular. Each of said sub-steps comprises a first deposition 501 of elementary layer 24, and a second deposition 502 of elementary layer 24 according to a protocol different from the deposition 501.

[0063] Between a step 501 and a successive step 502, or vice versa, a thermal shock is caused by passing the torch without cooling at the end of step 501, and a passing the torch with cooling at the end of step 502.

[0064] Cooling is carried out using compressed air nozzles, for example 6 nozzles at 6 bar of the carp tail type, or using liquid carbon dioxide cryogenic nozzles, for example two nozzles at 25 bar.

[0065] Here we carry out a 500 deposition with inter-passes, with slow deposition kinematics (illumination speed less than 300 millimeters per second) and with a high mass loading rate (more than 20% by mass of suspended solid particles).

[0066] In the particular example of method 60, layers 24 are formed from YSZ. Steps 501 and 502 are implemented with an “F4 - MB” torch with an argon / helium / dihydrogen volumetric flow rate of 45 / 45 / 6 slpm, with a YSZ / ethanol suspension.

[0067] 501 deposits are made with a mass loading rate of 12% and an injection rate of 25 to 30 grams per minute, for a thickness of 10 micrometers (2 micrometers per cycle). 502 deposits are made with a mass loading rate of 20% and an injection rate of 45 to 50 grams per minute, for a thickness of 9 micrometers (3 micrometers per cycle).

[0068] Two separate suspension injectors are preferably used to carry out steps 501 and 502, with two separate suspension reservoirs opened alternately.

[0069] 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 turbomachine parts with controlled cracking

[0070] THE Figures 7a to 7d schematically represent several examples of stacks of layers implemented for turbomachine parts according to the invention.

[0071] The 2 layers of anti-CMAS deposit shown on the Figures 7a to 7d are obtained for example according to any process described previously.

[0072] There Figure 7arepresents a part comprising a substrate 1 made of metal alloy covered with a layer 2 of anti-CMAS coating. In this exemplary embodiment, layer 2 can play the role of both a thermal barrier and an anti-CMAS deposit.

[0073] On the Figure 7b , an alumino-forming bond layer 7 is interposed between the substrate 1 and the anti-CMAS layer 2.

[0074] On the Figure 7c , a thermal barrier layer 8 is interposed between the bonding layer 7 and the anti-CMAS layer 2. The anti-CMAS deposit 2 may be a functionalization layer not acting as a thermal barrier.

[0075] On the Figure 7d , substrate 1 is formed from ceramic matrix composite (CMC). The substrate is covered with a bonding layer 7, a thermal and environmental barrier (TEBC) layer 9 and an anti-CMAS deposition layer 2.

[0076] The parts of the Figures 7a to 7d present, in accordance with the description above, mechanically weakened interfaces promoting cracking in planes substantially parallel to the surface of the part. of a layer 9 of thermal and environmental barrier (TEBC) and a layer 2 of anti-CMAS deposit.

[0077] The parts of the Figures 7a to 7d present, in accordance with the description above, mechanically weakened interfaces promoting cracking in planes substantially parallel to the surface of the part.

Claims

1. Turbomachine part comprising : - a substrate of metallic or composite material, - a coating layer to protect against the infiltration of compounds such as calcium, magnesium, aluminium or silicon oxides, or CMAS, the coating layer at least partially covering the surface of the substrate, the coating layer comprising a plurality of elementary layers, each elementary layer having a substantially homogeneous chemical composition and substantially homogeneous physicochemical characteristics, elemental layers of a first set of elemental layers being sandwiched between elemental layers of a second set of elemental layers, each elemental layer of the first set and each elemental layer of the second set comprising an anti-CMAS compound, the part being characterised in that each elementary layer of the first assembly has a tenacity which differs by at least 0.7 Mpa.m1 / 2, or a coefficient of thermal expansion which differs by at least 3.5 10-6K-1, respectively with respect to the tenacities or the coefficients of thermal expansion of all the elementary layers of the second assembly, each zone of contact between an elementary layer of the first assembly and an elementary layer of the second assembly forming an interface which encourages the propagation of cracks along said interface.

2. A turbomachine part as claimed in claim 1, in which the elementary layers of the first assembly have a toughness of between 0.5 and 1.5 Mpa.m1 / 2 and the elementary layers of the second assembly have a toughness of between 1.5 and 2.2 Mpa.m1 / 2.

3. Part according to one of claims 1 or 2, in which the elementary layers of the first assembly comprise a material taken from the following list : RE2Zr207 with RE a material from the rare earths family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, or comprise a mixture of several of these materials.

4. Part according to one of claims 1 to 3, in which the elementary layers of the second assembly comprise a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZr03, or comprise a mixture of several of these materials.

5. A part according to claim 1, wherein the elemental layers of the first assembly have a coefficient of thermal expansion of between 3.5 and 6.0 10-6 K-1 and the elemental layers of the second assembly have a coefficient of thermal expansion of between 7.0 and 12.0 10-6 K-1.

6. A part according to one of claims 1 or 5, in which the elementary layers of the first assembly comprise RE2Si207 or RE2SiO5 with RE a material from the rare earth family, or comprise a mixture of these materials.

7. Part according to one of claims 1 or 5, in which the elementary layers of the second assembly comprise a material taken from the following list: YSZ, Y203-Zr02-Ta205, BaZr03, CaZr03, SrZrO3, RE2Zr2O7 with RE a material from the rare earths family, Ba(Mg1 / 3Ta2 / 3)O3, La(Al1 / 4Mg1 / 2Ta1 / 4)O3, YAG, or comprise a mixture of several of these materials.

8. Part according to one of claims 1 to 7, wherein the ratio of the cumulative thickness of the elementary layers of the first assembly to the cumulative thickness of the elementary layers of the second assembly is between 1:2 and 2:1.

9. Part according to any of claims 1 to 8, wherein the total thickness of the protective coating layer is between 20 and 500 µm, preferably between 20 and 300 µm.

10. Part according to one of claims 1 to 9, forming a turbine moving blade, or a high-pressure turbine nozzle, or a high-pressure turbine ring, or a combustion chamber wall.

11. A method of treating a turbomachine part, comprising the steps of depositing a plurality of elementary layers on the surface of a substrate of the part by thermal spraying, the substrate being formed from a metallic material or a composite material , in order to produce a protective coating layer against the infiltration of compounds of the CMAS type, in which steps for depositing elementary layers belonging to a first set on the surface of the substrate are interposed between steps for depositing elementary layers belonging to a second set, the process being characterised in that the elementary layers of the first set tenacities which differ by at least 0.7 Mpa.m1 / 2 from the tenacities of the elementary layers of the second set, or the elementary layers of the first assembly coefficients of thermal expansion which differ by at least 3.5 10-6 K-1 from the coefficients of thermal expansion of the elementary layers of the second assembly.

12. Method according to claim 11, in which a thermal shock at the surface of the turbomachine part is caused between the deposition of a first elemental layer and the deposition of a second successive elemental layer, the thermal shock preferably being obtained by a torch pass without cooling after deposition of the first elemental layer, and a torch pass with cooling for the second elemental layer.