EP3529395A1

EP3529395A1 - Method for coating a surface of a solid substrate with a layer comprising a ceramic compound, and coated substrate thus obtained

Info

Publication number: EP3529395A1
Application number: EP17797677.6A
Authority: EP
Inventors: Benjamin Bernard; Aurélie QUET; Emmanuel HERVE; Luc Bianchi; Aurélien JOULIA; André MALIE
Original assignee: Commissariat a lEnergie Atomique CEA; Safran SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Safran SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2016-10-18
Filing date: 2017-10-18
Publication date: 2019-08-28
Also published as: RU2761397C2; BR112019007670A2; CN109874330A; RU2019115140A3; WO2018073538A1; CA3040347A1; US20190242001A1; FR3057580A1; RU2019115140A; CN109874330B; BR112019007670B1; JP2019533090A; JP7271429B2

Abstract

The invention relates to a method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a suspension plasma spraying (SPS) technique, in which at least one suspension of solid particles of at least one ceramic compound is injected into a plasma jet, and then the thermal jet that contains the solid particle suspension is sprayed onto the surface of the substrate, by means of which the layer comprising at least one ceramic compound is formed on the surface of the substrate; method characterised in that, in the suspension, at least 90 vol% of the solid particles have a larger dimension (referred to as d₉₀), such as a diameter, smaller than 15 µm, preferably smaller than 10 µm, and at least 50 vol% of the solid particles have a larger dimension, such as a diameter (referred to as d₅₀), no smaller than 1 µm. The invention also relates to a substrate coated with at least one layer that can be obtained by said method. The invention also relates to a part comprising said coated substrate. The invention further relates to the use of said layer in order to protect a solid substrate against degradations caused by contaminants such as CMAS.

Description

METHOD FOR COATING A SURFACE OF A SOLID SUBSTRATE WITH A LAYER COMPRISING A CERAMIC COMPOUND, AND A COATED SUBSTRATE THUS OBTAINED

DESCRIPTION

TECHNICAL AREA

The present invention relates to a method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound.

This layer is in particular a layer able to withstand infiltration and degradation at high temperature due to contaminants, in particular contaminants in the form of solid particles such as dust, sand, or ash. These contaminants may be in particular constituted by a mixture of oxides generally comprising lime (CaO), magnesium oxide (MgO), alumina (Al2O3) and silicon oxide (S102). These contaminants are usually called CMAS.

The invention further relates to the solid substrate coated with a layer obtainable by the coating method according to the invention.

The invention also relates to a part comprising said solid substrate. More particularly, the layer prepared by the process according to the invention is intended to be integrated within multilayer coatings protecting a solid substrate made of metal alloy or metal superalloy or ceramic matrix composite (CMC), optionally coated with a layer. connection, itself optionally also coated with a thermally insulating ceramic layer, and / or an anti-oxidation layer, and / or an anti-corrosion layer.

The technical field of the invention can be broadly defined as that of anti-CMAS coatings.

The invention finds particular application in gas turbines or propulsion systems used in particular in the aeronautical, space, naval and land, for the protection of parts exposed to high temperatures such as, for example, turbine parts such as stationary and moving vanes, distributors, turbine rings, parts of the combustion chamber or the nozzle. STATE OF THE PRIOR ART

To increase the efficiency of gas turbines, their operating temperature must be higher and higher. The parts that constitute them are then subjected to increasingly severe environments in terms of skin temperature, thermomechanical stresses, or chemical aggression.

Thus, over the years, the increase in operating temperatures of gas turbines has required the use of thermal barrier systems comprising a thermally insulating layer of ceramic oxide, most often made of YSZ ("Yttria-Stabilized"). Zirconia "), that is to say zirconia stabilized with yttrine (yttrium oxide Y2O3), typically containing from 7 to 8% by weight of yttrium oxide Y2O3.

A thermal barrier system is a multilayer system composed of at least one thermally insulating layer making it possible to reduce the surface temperature of the structuring material, namely the surface temperature of the material constituting the part such as a gas turbine part. that we want to protect thermally.

In industry, two technologies are currently used to prepare the YSZ insulating ceramic layer. These technologies are the dry plasma projection under atmospheric pressure ("APS" for "Atmospheric Plasma Spraying"), and the electron beam-assisted physical vapor deposition method ("EB- PVD "for" Electron Beam - Physical Vapor Deposition ").

Plasma sputtering leads to lamellar microstructures with low thermal conductivity but limited life during thermal cycling [1].

For parts that are strongly thermomechanically stressed, the EB-PVD process is preferred because of the resulting columnar microstructures which, despite less advantageous thermal conductivities, ensure accommodation of thermomechanical stresses, and ensure long service life. The EB-PVD process is also preferred to the APS process for its ability to maintain aeration vents allowing for increased operating temperatures [1].

Ceramic coatings with improved thermal insulation properties have recently been obtained using specific materials or processes.

Particularly noteworthy is the production of YSZ deposits by solution plasma projection methods ("SPPS" or "Solution Precursor Plasma Spraying") or suspensions ("SPS", "Suspension Plasma Spraying"). The deposits obtained by these processes have varied microstructures that increase the thermal insulation of the coating while ensuring a significant thermal cycling resistance. The microstructures can be homogeneous (that is, the pores or particles that make up the layer have no characteristic orientation at the micrometric scale), porous, vertically cracked, or columnar (ie that is, the layer has a structure having, at the micrometric scale, a preferred orientation in the direction of the thickness of the layer, with an organization in the form of columnar domains and, between the columnar domains, empty spaces or spaces inter-columnar that reflect the compactness of the columnar stack and the amplitude of which is scalable), with or without inter passes (resulting from the presence of unmelted particles (unmelted) or partially melted within the deposit. may also have combinations of the various morphologies described above Examples of these microstructures are presented in documents [2] and [3].

Document [4] shows that the SPS process makes it possible to successfully prepare thermal barrier coatings on aeronautical parts of the turbine blade type while allowing the preservation of vent holes.

However, other problems have emerged, requiring new features to thermal barrier systems. Thus, the increase in operating temperatures of gas turbines induces significant damage in the hot parts of the turbines due to the contaminants, generally in the form of dust, present in the environment of the parts of these turbines. These contaminants may, for example, in the case of a turbojet engine, be oxides, in the form of particles, originating either from the outside or from ablated elements on the parts situated in the colder zones. These contaminants are usually called CMAS and are most often composed of a mixture of oxides generally comprising lime (CaO), magnesium oxide (MgO), alumina (Al2O3) and oxide. of silicon (S1O2). From temperatures of the order of 1150 ° C, melted CMAS infiltrate within the thermal barrier system and can lead, during thermal cycling, stiffening, cracking and, ultimately, delamination of the thermal barrier system. Furthermore, a chemical interaction is observed between the CMAS and the layers of the system, leading to the dissolution of the yttria zirconia and the precipitation of new, less stable phases. These two phenomena can lead to a loss of integrity of the thermal barriers and constitute a brake on the increase of the operating temperature of the turbojets.

In addition to thermal barrier systems, environmental barrier systems may also experience this type of degradation by CMAS particles.

An environmental barrier system is a multilayer system, typically applied to metal surfaces or ceramic matrix composites. This environmental barrier system is composed of at least one layer resistant to corrosive environments.

Various ways have been explored to propose so-called "anti-CMAS" materials that react with CMAS contaminants, to form stable phases at high temperature that will stop and / or limit infiltration at the core of the coating.

In particular, apatite and / or anorthite phase formation appears to be able to stop CMAS infiltration. Different materials have been identified for their ability to form these phases. The documents [5] and [6] notably present materials making it possible to limit and / or stop the infiltration of CMAS. We will mention for example, rare earth zirconates of formula RE ₂ Zr ₂ 0 ₇ (where RE = Se, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, Lu), composite materials composed of Y ₂ O 3 and ZrO ₂ and / or Al ₂ O 3 and / or TiO ₂ , hexa-aluminates, and rare earth mono- and di-silicates (the rare earth being Y or Yb), and mixtures of these materials.

The chemical incompatibility with other elements of the thermal barrier system and / or the low mechanical properties of the anti-CMAS compositions led to the development of systems, architectures, comprising a first layer of YSZ and then a second layer of protection against CMAS, made of a material that can have an anti-CMAS effect. Documents [7], [8], [9] and [10] deal with such systems.

For the formation of this protective layer against CMAS, many deposition processes can be used, such as the APS, SPS, SPPS, EB-PVD processes, already mentioned above, the physical vapor deposition process ("PVD "Physical Vapor Deposition"), the Chemical Vapor Deposition ("CVD") process, the sol-gel process, etc.

The realization of EB-PVD bilayer architectures, comprising a columnar microstructure thermal insulating layer protected by an anti-CMAS layer, induces the presence of inter-columnar spaces which, after infiltration of the CMAS and cooling, stiffen the system which can then delaminate.

Anti-CMAS coatings made by APS lead to non-columnar lamellar microstructures, with lamellae with large surfaces able to react with CMAS to form more stable phases. However, it is complicated to apply these layers on high pressure turbine parts, as this may obstruct the vent holes.

The SPS and SPPS processes, which provide nanostructured layers or finely structured layers, may be solutions for forming anti-CMAS layers having homogeneous microstructures without obstructing the vent holes.

The anti-CMAS layers obtained by SPS are currently produced with suspensions containing particles having sizes smaller than 1 μm (documents [9] and [10]). However, it has been found that in the anti-CMAS layers obtained by SPS there are infiltration points of the CMAS contaminants through the layer, thus making the infiltration of CMAS contaminants very important at the core of the coating, under the anti-CMAS layer, unlike, for example, a deposit made by the APS technique.

There is therefore, with regard to the foregoing, a need for a process, in particular for an SPS process, which makes it possible to prepare on a solid substrate a ceramic layer, more specifically an anti-CMAS layer, in particular having an increased resistance. infiltration by CMAS contaminants and not obstructing the vent holes.

The solid substrate may be constituted simply by a simple support which is in the form of a solid support or in the form of a layer, or the solid substrate may be constituted by a support on which there is a layer or a coating multilayer for example a multilayer thermal protection coating namely a thermal barrier system or a multilayer coating for protection against corrosive environments, namely an environmental barrier system.

This method must allow the preparation of this layer on all types of substrates, whatever the geometry of this substrate, whatever the material constituting this substrate (that is to say more exactly the material constituting the support or the layer on which is deposited the layer prepared by the process), regardless of the structure, in particular the microstructure of the substrate (support or layer), and whatever the method by which this substrate (support or layer) was prepared.

In particular, the method according to the invention must allow the preparation of a ceramic layer, more specifically an effective anti-CMAS layer, on a substrate (support or layer) prepared by a technique chosen from EB techniques. -PVD, APS, SPS, SPPS, PVD, CVD, gel sol, and all combinations of these techniques.

In particular, the method according to the invention must allow the preparation of a ceramic layer, more specifically of an effective anti-CMAS layer, on a substrate (support or layer) having a microstructure chosen from a structure columnar, columnar and porous structure, compact and porous columnar structure, homogeneous structure, homogeneous and porous structure, dense structure, dense and vertically fissured structure, porous and vertically fissured structure, and all combinations of these techniques .

There is in particular a need for such a process which ensures the operation of turbojets at lower temperatures, without degradation of the system by the CMASs.

The object of the invention is, inter alia, to provide a method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound, which meets these needs, among others, and which does not does not present the disadvantages, defects, limitations and disadvantages of the prior art processes, including prior art SPS methods, and which solves the problems of the prior art methods. STATEMENT OF THE INVENTION

This and other objects are achieved according to the invention by a method of coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a plasma projection of "SPS" suspensions, in which at least one suspension of solid particles of at least one ceramic compound is injected into a plasma jet and then the thermal jet which contains the suspension of solid particles is sprayed onto the surface of the substrate, whereby the layer comprising at least one ceramic compound is formed on the surface of the substrate; characterized in that in the suspension, at least 90% by volume of the solid particles have a larger dimension (called dgo), such as a diameter, less than 15 μιη, preferably less than 10 μιη, and at least 50 % by volume of the solid particles have a larger dimension (called dso) such that a diameter greater than or equal to 1 μιη; a method further characterized in that the ceramic compound is selected from the so-called anti-CMAS compounds, preferably the ceramic compound is selected from the rare earth zirconates of the formula RE ₂ Zr ₂ 0 ₇ , where RE is Se, Y , La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, or Lu, the composites Y2O3 with Zr0 ₂ and / or Al2O3 and / or Ti0 ₂ , hexa-aluminates, aluminum silicates, yttrium silicates or other rare earth silicates, these silicates being dopable by one or more metal oxides alkaline earths, and mixtures thereof; more preferably, the ceramic compound is Gd ₂ Zr ₂ 07.

Advantageously, in the suspension, at least 90% by volume of the solid particles have a larger dimension (called dgo), such as a diameter, less than 8 μιη, preferably less than 5 μιη.

Advantageously, in the suspension, at least 50% by volume of the solid particles have a larger dimension (called dso) such that a diameter greater than or equal to 2 μιη, preferably greater than or equal to 3 μιη, more preferably greater than or equal to 4 μιη, better still greater than or equal to 5 μιη.

For example, dso may be equal to 1 μιη, 1.01 μιη, 3 μιη, 5 μιη, or 5.5 μιη.

For example, dgo can be equal to 7 μιη, 4 μιη, 4,95 μιη, 5 μιη, 12 μιη, 13 μιη or 13,2 μιη.

The invention covers all possible combinations of dgo and dso values mentioned above.

The analysis of the particle size of the suspension is carried out by laser diffraction granulometry according to the ISO 24235 standard.

The dgo and the dso can be determined from the ISO 9276 standard.

In the following, the term "lamellar", applied to a layer, means that the layer has a structure having, at the micrometric scale, elementary bricks having a preferred orientation in the direction perpendicular to the thickness of the layer.

The term "columnar", applied to a layer, means that the layer has a structure having, at the micrometric scale, a preferred orientation of elementary bricks in the direction of the thickness of the layer, these bricks being organized in the form of of columns.

The term "homogeneous" applied to a layer means that the layer has a structure formed of elementary bricks that have no characteristic orientation to the micrometric scale. Similarly, the porosity of the layer has no characteristic orientation at the micrometric scale.

The method according to the invention is fundamentally different from the processes of the prior art in that it implements a specific deposition technique, namely a suspension plasma projection technique (SPS) and in that the suspension contains particles which have a very specific particle size, namely a particle size defined by the fact that at least 90% by volume of the solid particles have a larger dimension (called dgo), such as a diameter, of less than 15 μιη, preferably less than 10 μιη, and at least 50% by volume of the solid particles have a larger dimension such that a diameter (called dso) greater than or equal to 1 μιη.

Such granulometry of the suspension particles is neither described nor suggested in the prior art, where the SPS methods used to prepare, for example, anti-CMAS layers use suspensions containing "small" particles having different sizes. less than 1 μιη, that is to say with a dso less than 1 μιη, in particular a dso and / or a nanometric dgo, that is to say greater than or equal to 1 nanometer and less than or equal to 100 nanometers , or a dso and / or submicrometer dgo, that is to say greater than 100 nanometers and less than 1000 nanometers.

In the prior art, the use of small particles promotes the appearance of infiltration points of the contaminants, for example CMAS through the layer and thus makes the infiltration of contaminants, for example CMAS, more important at the heart of the coating. This behavior of the anti-CMAS layers obtained by SPS in the prior art can be attributed to the low tortuosity of the porous network of the layers obtained from fine particles.

On the contrary, the layer obtained by the process according to the invention has a much greater tortuosity, because of the use of much larger particles. This significant tortuosity makes it possible to slow the infiltration, for example liquid CMAS in the thickness of the layer. In contrast to the APS technique in which the injection of the particles is carried out using a carrier gas, the injection of the particles in the SPS technique carried out according to the invention is carried out on the basis of a suspension of particles carried in a pressurized liquid vector. This makes it possible to penetrate the particles having a dgo less than 15 μιη, preferably less than 10 μιη, by inertia effect at the heart of the plasma jet without undue disturbance of the latter and thus optimize their transport and heating by the plasma jet.

The process according to the invention does not have the disadvantages of the processes of the prior art and provides a solution to the problems of the processes of the prior art.

Advantageously, the layer obtained by the process according to the invention has a lamellar microstructure and a tortuous porous network.

Advantageously, the layer obtained by the process according to the invention comprises at the same time:

slats resulting from the melting of the solid particles of the suspension,

solid particles resulting from the partial melting of the solid particles of the suspension, and

solid particles of the unmelted suspension.

The layer obtained by the process according to the invention may optionally have cracks, but it is non-columnar and non-homogeneous, whatever the microstructure of the surface to be coated.

The layer obtained by the process according to the invention thus has a microstructure which is particularly adapted to its anti-CMAS function. It allows the formation on its surface, with a limited infiltration of its porous network, stable phases, reaction products between the material of the layer and liquid CMAS. These stable phases block the infiltration of CMAS deep into the coating.

Due to the specific size of the initial particles used in the suspension, the layer according to the invention has a stack of molten lamellae (resulting from the melting of the solid particles of the suspension), partially melted (solid particles resulting from the partial melting of the solid particles of the suspension) and unmelted particles (solid particles of the unmelted suspension which have retained their initial shape, by example of sphere). The layer thus has a tortuous porous network making it difficult to access contaminants, its infiltration by contaminants, such as liquid CMAS.

Unlike the layers obtained by the SPS technique implementing the suspensions traditionally used in this technique, whose particles have a dso of less than 1 μιη, in particular a dso and / or a nanometric dgo, that is to say higher or equal to 1 nanometer and less than or equal to 100 nanometers, or submicrometer, that is to say greater than 100 nanometers and less than 1000 nanometers, the microstructure of the layer according to the invention is lamellar. It is neither columnar nor homogeneous.

The lamellar microstructure of the layer obtained by the process according to the invention assures an increased resistance with respect to the particulate mechanical erosion, in particular the resistance with respect to the particulate mechanical erosion is greater than a microstructure. homogeneous or columnar obtained by an SPS technique using the suspensions traditionally used in this technique with "small" particles.

In addition, advantageously, the layer according to the invention is characterized in that it does not obstruct the vent holes. Indeed, the particle size distribution of the initial particles of the suspension is sufficiently fine to lead to more finely structured layers when compared to layers prepared by an APS technique.

The method according to the invention by using suspended particles having a dgo less than or equal to 10 μιη and a dso greater than or equal to 1 μιη, makes it possible to prepare layers with microstructures that are close to the microstructures obtained by the APS technique without presenting the defects of these microstructures, that is to say by not obstructing the vent holes. Finally, the use according to the process of the invention of suspended particles having a dgo less than 15 μιη, preferably less than 10 μιη, and a dso greater than or equal to 1 μιη, makes it possible to obtain a layer with a microstructure lamellar to increase chemical resistance to contaminants such as CMAS and mechanical resistance to particle erosion, while not obstructing vent holes.

Advantageously, the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume.

Advantageously, the layer has a thickness of 10 μιη to 1000 μιη, preferably from 10 to 300 μιη.

There is no limitation on the substrate which can be coated with a layer by the method according to the invention.

The method according to the invention ensures the preparation of a layer having the advantageous properties exposed herein on all types of substrates, whatever the geometry of this substrate, whatever the material constituting this substrate (ie to say more exactly the material constituting the support or the layer on which the layer prepared by the process is deposited, regardless of the structure, in particular the microstructure of the substrate (support or layer), whatever the morphology of this substrate, and whatever the method by which this substrate (support or layer) was prepared.

In particular, the process according to the invention makes it possible to prepare a ceramic layer, more specifically an effective anti-CMAS layer, on a substrate (support or layer) prepared by a technique chosen from EB-techniques. PVD, APS, SPS, SPPS, PVD, CVD, gel sol, and all combinations of these techniques.

The solid substrate may be constituted simply by a simple solid support, which is for example in the form of a solid support or in the form of a layer, and is deposited, by the method according to the invention, the layer comprising at least one ceramic compound directly on at least one surface of said support.

Or, the solid substrate may be constituted by a solid support on which there is a single layer (different from the layer of at least one compound ceramic prepared by the process according to the invention), or a stack of several layers (different from the layer of at least one ceramic compound prepared by the process according to the invention), and the layer comprising at least one ceramic compound is deposited on at least one surface of said single layer or on at least one surface of the upper layer of said stack of layers.

Said support may be made of a material chosen from materials that are susceptible to infiltration and / or attack by contaminants such as CMASs.

Said support can be in particular a material chosen from metals, metal alloys, such as superalloys such as superalloys AMI, René, and CMSX ^® -4, ceramic matrix composites (CMC), such as matrix composites SiC, C-SiC mixed matrix composites, and combinations and / or mixtures of the aforementioned materials.

Superalloys are metal alloys characterized by mechanical strength and resistance to oxidation and corrosion at high temperatures.

In the context of the invention, it is preferably monocrystalline superalloys.

Such a superalloy, commonly used, is for example the superalloy called AMI, which is a nickel base superalloy, having a mass composition of 5 to 8% Co, 6.5 to 10% Cr, 0.5 to 2.5% Mo, 5 to 9% W, 6 to 9% Ta, 4.5 to 5.8% Al, 1 to 2% Ti, 0 to 1.5% Nb, and C, Zr, B each less than 0.01. %.

The AMI superalloy is described in US-A-4,639,280.

The family of superalloys called René was developed by

General Electric ^® .

CMSX ^® -4 superalloy is a trademark of Cannon-Muskegon ^® .

The layer of the invention can be applied to parts formed by these superalloys.

Advantageously, the single layer or said stack of layers which is on the support forms on the support a monolayer or multilayer thermal protection coating, namely a thermal barrier system, and / or a coating. monolayer or multilayer protection against corrosive environments, namely an environmental barrier system.

Advantageously, the single layer may be chosen from the binding layers, and the thermal or environmental barrier layers, such as the layers, in particular the ceramic layers, thermally insulating, the layers, in particular the ceramic layers, the anti-oxidation layers, and the layers including ceramic layers anti-corrosion.

Advantageously, the stack of several layers that is on the support can comprise, from the support:

a tie layer which covers the support;

one or more layers chosen from among the thermal barrier layers and the environmental barrier layers, such as the layers, in particular the ceramic layers, thermally insulating, the layers, in particular the ceramic, anti-oxidation layers, and the layers, in particular anti-corrosion ceramic layers;

or the multilayer stack on the support includes:

a plurality of layers chosen from among the thermal barrier layers and the environmental barrier layers, such as the layers, in particular the ceramic layers, thermally insulating, the layers, in particular the ceramic, anti-oxidation layers, and the layers, in particular the ceramic layers, anti corrosion.

Advantageously, the thermal barrier layers and the environmental barrier layers, such as the layers, in particular the ceramic layers, thermally insulating, the layers, in particular the ceramic layers, anti-oxidation, and the layers, in particular the ceramic, anti-corrosion layers can be layers prepared by a technique selected from EB-PVD, APS, SPS, SPPS, sol-gel, PVD, CVD, and combinations of these techniques.

Advantageously, the thermal barrier layers are made of a material chosen from zirconium or hafnium oxides, stabilized with yttrium oxide. or other rare earth oxides, aluminum silicates, yttrium silicates or other rare earths, these silicates being doped with alkaline earth metal oxides, and rare earth zirconates, which crystallize according to a pyrochlore structure, and combinations and / or mixtures of the aforementioned materials.

Preferably, the thermal barrier layers are yttria stabilized zirconia (YSZ).

Advantageously, the environmental barrier layers are made of a material chosen from aluminum silicates, optionally doped with alkaline earth elements, rare earth silicates, and combinations and / or mixtures of the abovementioned materials.

Advantageously, the bonding layer may be of a material selected from metals, metal alloys such as metal alloys β-ΝϊΑΙ, modified or otherwise by Pt, Hf, Zr, Y, Si or combinations thereof, metal alloys γ-Νί-γ'-ΝΪ3ΑΙ modified or not with Pt, Cr, Hf, Zr, Y, Si or combinations thereof, alloys MCrAIY where M is Ni, Co, NiCo, Si, SiC, SiO ₂ , mullite, BSAS, and combinations and / or mixtures of the aforementioned materials.

According to one embodiment, the substrate may consist of a support of a metal alloy such as a superalloy, preferably monocrystalline, or of a ceramic matrix composite (CMC), coated with a metal bonding layer itself. coated with a layer, such as a ceramic layer selected from the thermal barrier layers and the environmental barrier layers.

According to another embodiment, the substrate is constituted by a support of a metal alloy such as a superalloy or a ceramic matrix composite (CMC), coated with a metal bonding layer itself coated with a layer zirconia thermal barrier ceramic (Zr0 ₂ ) stabilized with yttrine (Y ₂ O 3).

According to yet another embodiment, the substrate may consist of a support of a metal alloy such as a superalloy or a ceramic matrix composite (CMC), coated with a metal bonding layer itself coated with a ceramic layer of thermal and / or environmental barrier performed by a technique selected from the techniques of APS, EB-PVD, SPS, SPPS, sol-gel, CVD, and combinations of these techniques.

The plasma projection technique of a suspension is used to produce the layer according to the invention. It consists in injecting into a flow with high thermal and kinetic energy (for example a plasma jet which can be produced by a plasma DC torch), a liquid suspension containing particles of the material of the layer to be prepared.

Generally, the suspension contains from 1 to 40% by weight, preferably from 8 to 15% by weight of solid particles, for example 12% by weight of solid particles.

The solvent of the suspension may be selected from water, alcohols such as aliphatic alcohols 1 to 5C such as ethanol and mixtures thereof.

The suspension is injected using a mechanical injector, from a pressurized tank.

In the process according to the invention, the injection of the suspension into the plasma jet is generally radial. The inclination of the injector relative to the longitudinal axis of the plasma jet can vary from 20 to 160 °, but is preferably 90 °. In a manner known to those skilled in the art, the orientation of the injector makes it possible to optimize the injection of the suspension into the plasma jet, and thus to promote the formation of a layer of good quality on the surface of the plasma jet. substrate.

The injector can be moved in the longitudinal direction of the plasma jet. The closer the injector is to the surface of the substrate to be coated, the shorter the residence time of the particles in the plasma jet, thus making it possible to control the thermokinetic treatment imposed on the particles.

The diameter of the injector can vary between 50 μιη and 300 μιη.

The injection device may be provided with one or more injectors, for example according to the amount of suspension and / or the number of different suspensions to be injected. The suspension thus injected will fragment in contact with the plasma jet. The solvent will then evaporate, the particles will be heat-treated and accelerated to the substrate, and thus form a layer.

The plasma jet can be generated from a plasmagene gas advantageously chosen from argon, helium, dihydrogen, dinitrogen, the binary mixtures of the four gases mentioned, the ternary mixtures of the four gases mentioned.

The plasma jet generation technique is chosen from an arc plasma, blown or not, an inductive plasma or radiofrequency plasma. The generated plasma can operate at atmospheric pressure or at lower pressure. In the case of an arc plasma, the latter can be extended by the stack of neutrodes between the cathode and the anode between which the arc is generated.

According to a preferred embodiment of the method which is the subject of the invention, the injection is carried out by means of an injection system having an injection diameter of between 50 and 300 μιη at an injection pressure of the injection system. injection between 1 and 7 bar and from a suspension comprising between 1% and 40% by weight of solid particulate elements.

The invention further relates to the substrate coated with at least one layer obtainable by the method according to the invention, as described above.

Advantageously, the layer has a lamellar microstructure and a tortuous porous network.

Advantageously, the layer comprises at the same time:

lamellae resulting from the melting of the solid particles of suspension,

solid particles of the unmelted suspension.

Advantageously, the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume. Advantageously, the layer has a thickness of 10 μιη to 1000 μιη, preferably from 10 μιη to 300 μιη.

The invention also relates to a part comprising said coated substrate.

This part may be a part of a turbine, such as a turbine blade, a distributor, a turbine ring, or a part of a combustion chamber, or a part of a nozzle, or more generally any part subjected to aggression by liquid and / or solid contaminants such as CMAS.

This turbine may be for example an aeronautical turbine or a land turbine.

The invention also relates to the use of the layer obtainable by the method according to the invention, for protecting a solid substrate against degradation caused by contaminants such as CMAS.

The invention finds particular application in gas turbines or propulsion systems used in particular in the aviation, space, naval and land, for the protection of parts exposed to high temperatures such as, for example, parts of the turbine like stationary and moving vanes, distributors, turbine rings, parts of the combustion chamber or the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side sectional view showing a multilayer system whose upper layer is an "anti-CMAS" layer 1, according to the invention, obtained by the method according to the invention implementing the SPS technique with initial particles having a dgo less than 10 μιη and a dso greater than or equal to 1 μιη.

FIG. 2 is a schematic sectional side view which shows in a simplified manner the multilayer system represented in FIG. 1, the upper layer of which is an "anti-CMAS" layer 1, according to the invention, obtained by the method according to the invention implementing the SPS technique with initial particles having a dgo less than 15 μιη, preferably less than 10 μιη, and a dso greater than or equal to 1 μιη. FIG. 3 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in Example 1 which comprises an anti-CMAS layer obtained by SPS with initial particles having a dgo less than 10 μιη and a dso greater than or equal to 1 μιη made on the surface of a porous columnar YSZ layer 6 obtained by SPS.

The scale shown in FIG. 3 represents 100 μιη.

FIG. 4 is a scanning electron micrograph (SEM) in backscattered electrons of a polished section of the sample prepared in Example 2, which comprises an anti-CMAS layer 1 obtained by SPS with initial particles having a dgo less than 10 μιη and a dso greater than or equal to 1 μιη, and produced on the surface of a porous compact columnar YSZ layer 7 obtained by SPS.

The scale shown in FIG. 4 represents 100 μιη.

Figure 5 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in Example 3, which comprises an anti-CMAS layer obtained by SPS with initial particles having a dgo less than 10 μιη and a dso greater than or equal to 1 μιη, and produced on the surface of a columnar YSZ layer 8 obtained by EB-PVD.

The scale shown in FIG. 5 represents 100 μιη.

FIG. 6 is a backscattered microscopic electron microscopy (M EB) micrograph of a polished section of SPS-derived CMAS layer 1 in Example 3 at the surface of a columnar YSZ layer 8 obtained by EB-PVD.

The observation is performed after CMAS infiltration.

The scale shown in FIG. 6 represents 5 μιη.

FIG. 7A is a scanning electron micrograph (SEM) in backscattered electrons, and FIG. 7B is an EDS ("Energy Dispersive Spectroscopy") analysis of the silicon of a polished section of layer 1 (FIG. analogous to SPS anti-CMAS layer 13 of Figure 9A) in Example 4 at the surface of an APS-obtained YSZ layer 11. The observation is performed after CMAS infiltration. The scale shown in FIGS. 7A and 7B represents 25 μιη.

Figure 8A is another scanning electron micrograph (SEM) of backscattered electrons, and Figure 8B is an EDS analysis of silicon of a polished section of layer 1 (similar to layer 13 of Figure 9A). ) anti-CMAS according to the invention, obtained by SPS in Example 4 on the surface of a YSZ layer 11 obtained by APS.

The observation is performed in an area with a crack 12 after CMAS infiltration.

The scale shown in FIGS. 8A and 8B represents 25 μιη.

FIG. 9A is yet another scanning electron micrograph (SEM) in backscattered electrons and an analysis in EDS of the silicon of a polished section of an anti-CMAS layer of Gd ₂ Zr ₂ 07 obtained in FIG. Example 4, by SPS, with initial particles having a dgo of 7 μιη and a dso of 3 μιη. This layer is made on the surface of a YSZ layer 11 obtained by APS.

The scale shown in FIG. 9A represents 25 μιη.

The observation is performed in an area with crack after CMAS infiltration.

FIG. 9B is a backscattered electron microscopy (SEM) micrograph (left) and a silicon EDS analysis (right) of a polished section of an anti-CMAS layer of Gd2Zr ₂ 07 according to the invention, obtained in Example 5, by SPS, with initial particles having a diameter of 4.95 μιη and a dso of 1.01 μιη, on the surface of a layer 11 YSZ obtained by APS.

The observation is carried out in a zone exhibiting cracking after CMAS infiltration.

The scale shown in FIG. 9B represents 25 μιη.

FIG. 9C is a backscattered electron microscopy (SEM) micrograph and an EDS analysis of silicon of a polished section of the anti-CMAS layer of Gd ₂ Zr ₂ 07 obtained in Example 6, not according to the invention by SPS, with initial particles having a dgo of 0.89 μιη and a dso of 0.41 μιη. This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is performed in an area with crack after CMAS infiltration.

The scale shown in FIG. 9C represents 25 μιη.

FIG. 10 is a diffractogram obtained by CMAS infiltration X-ray diffraction of the anti-CMAS layer 13 obtained in Example 4.

Figure 11 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in Example 11. This sample comprises an anti-CMAS layer 21 made of Gd2Zr ₂ 07 prepared at the surface of a YSZ layer 8, columnar, obtained by an EB-PVD process. The anti-CMAS layer is prepared according to the invention by an SPS method using a suspension containing initial particles having a dgo of 13.2 μιη and a dso greater than or equal to 1 μιη, namely 5.5 μιη. .

The scale shown in FIG. 11 represents 100 μιη.

FIG. 12 is a scanning electron micrograph (SEM) in backscattered electrons of a polished section of the anti-CMAS layer 21 obtained by SPS in example 12 on a self-supporting substrate 11 made of stabilized zirconia stabilized in a phase t 'and obtained by APS.

The observation is performed after CMAS infiltration (Example 13).

The scale shown in FIG. 12 represents 100 μιη.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 shows an embodiment of the method according to the invention, in which the layer according to the invention prepared by the process according to the invention, 1, is deposited on the surface of a system comprising the layers 2 , 3, 4, shown in Figure 1.

The various layers of the stack 2, 3, 4 may represent, by way of example and not exclusively, the layers of a thermal barrier system applied to aeronautical parts superalloy.

Advantageously, the layer 2 can be made of a material chosen from the materials of thermal barrier systems and / or barrier systems such as for example zirconia (Zr0 ₂ ) and / or yttrine (Y2O3) for stabilizing the phase t ', and all other suitable materials, as well as combinations and / or mixtures of these materials.

In addition, advantageously, the layer 2 can be produced by a method, a deposition technique, chosen from the EB-PVD, APS, SPS, SPPS, sol-gel and CVD processes, and all the other processes capable of carrying out this process. layer, as well as combinations of these processes.

Advantageously, the layer 2 has a microstructure characteristic of the deposition technique used. This layer may, for example, non-exclusively present a columnar microstructure, a columnar and porous microstructure, a compact and porous columnar microstructure, a homogeneous microstructure, a homogeneous and porous microstructructure, a dense microstructure, a dense and vertically cracked microstructructure, a porous and vertically cracked microstructructure.

According to a first embodiment, the layer 1 according to the invention can be applied to a layer 2 having a porous columnar microstructure obtained by SPS (layer 6 in FIG. 3).

According to a second embodiment, the layer 1 according to the invention can be applied to a layer 2 having a porous compact columnar microstructure obtained by SPS (layer 7 in FIG. 4).

According to a third embodiment, the layer 1 according to the invention can be applied to a layer 2 having a columnar microstructure obtained by EB-PVD (layer 8 in FIG. 5).

Advantageously, the layer 2 has a function of thermal barrier and / or environmental barrier. It also allows, but not exclusively, to ensure good performance in terms of life and thermal insulation or protection against oxidation and wet corrosion.

Advantageously, the layer 3 acts as a link layer.

The layer 3 can be made of a material chosen from metals, metal alloys such as metal alloys β-NiAI (modified or not by Pt, Hf, Zr, Y, Si or combinations of these elements), γ-Νί-γ'-ΝΪ3ΑΙ alloy aluminides (modified or otherwise by Pt, Cr, Hf, Zr, Y, Si or combinations thereof), MCrAIY alloys ( where M = Ni, Co, NiCo), Si, SiC, SiO ₂ , mullite, BSAS, and all other suitable materials, as well as combinations and / or mixtures of these materials.

Advantageously, the layer 3 may comprise an oxide layer obtained by oxidation of the elements of the layer 3, as described above. For example, but not exclusively, layer 3 may be an aluminoform layer, i.e., oxidation of layer 3 may advantageously produce a layer of α-alumina.

Advantageously, the layer 4 is part of a part or element of a part made of a material chosen from metal alloys, such as metal superalloys, ceramic matrix composites (CMC), and combinations and / or mixtures of these materials. This material of the layer 4 may in particular be chosen from superalloys AMI, René, and CMSX ^® -4.

In Figure 2, the layer 1, and the system comprising the layers 2, 3, 4, shown in Figure 1 are simplified to two elements, namely:

an anti-CMAS layer 1 according to the invention obtained by the process according to the invention implementing the SPS technique with particles of the injected suspension having a dgo less than 10 μιη and a dso greater than or equal to 1 μιη;

a layer 5 that can accurately describe the layer system

2, 3, 4 of Figure 1, or one or more layers of the system of layers 2, 3, 4 of Figure 1, or one or more combinations of layers of the system of layers 2, 3, 4 of Figure 1. This system is coated with an anti-CMAS layer 1 obtained by SPS with injected particles having a dia less than 15 μιη, preferably less than 10 μιη, and a dso greater than or equal to 1 μιη.

Thus, advantageously, the layer 1 according to the invention may be applied to the surface of a layer 5. This layer 5 may include independently and / or combined the layers 2, 3, 4. Advantageously, the layers 2 and 3 and / or the layer 5 allow, but not exclusively, to provide a thermal and / or environmental barrier function. They also allow, but not exclusively, to ensure good performance in terms of service life and thermal insulation or protection against oxidation and wet corrosion. Advantageously, the addition of the layer 1 according to the invention does not degrade the performance of the systems, described in Figures 1 and 2, on which it is applied.

Advantageously, the microstructure of the layer 1 has a homogeneous and / or cracked morphology, but not exclusively, whether it is carried out on the layer 2 or the layer 5 and whatever the microstructure and / or the composition of the layer 2 or layer 5.

Advantageously, the layer 1 according to the invention reacts with CMAS at high temperature, more precisely at a temperature above the melting temperature of CMAS, to form a reactive zone 9 (FIG. 6) beyond which CMAS penetration within layer 1 is stopped and / or limited.

Finally, the solidified CMASs 10 are thus observed on the surface of the coating (see examples, FIG. 6).

Advantageously, zone 9 is composed of reaction products between CMAS and layer 1 including, but not exclusively, apatite and / or anorthite and / or zirconia phases and / or other reaction products and or combinations thereof. and / or mixtures of these phases.

For example, no CMAS infiltration within the layer 1 deposited on a layer 11 obtained by APS is observed after a CMAS infiltration test beyond the reaction zone 9 (FIGS. 7A and 7B). Advantageously, the layer 11 obtained by APS is included in the description of the layer 2 described in FIG.

Similarly, no CMAS infiltration within layer 1 deposited on APS layer 11 was observed after a CMAS infiltration test beyond reaction zone 9 (Figures 8A and 8B). The crack 12 observed in layer 1 deposited on a layer 11 obtained by APS, is rapidly blocked by reaction products similar to those comprising zone 9 (FIGS. 8A and 8B). In a way Advantageously, the layer 11 obtained by APS is included in the description of the layer 2 described in FIG.

It should be noted that, when a layer 1 according to the invention is produced by the process according to the invention, it is possible before coating the substrate (including layers 2 to 4 of FIG. 1 and / or layer 5 of Figure 2) by the layer 1, prepare and / or clean the surface to be coated in order to eliminate residues and / or contaminants (inorganic and / or organic) which could prevent the deposition and / or degrade the adhesion and / or affect the microstructure. The surface preparation may be the formation of a surface roughness by sanding, the oxidation of the substrate to generate a thin oxide layer and / or a combination of these methods of preparation.

The invention will now be described with reference to the following examples, given by way of illustration and not limitation.

To prepare the anti-CMAS layers, suspensions of ceramic particles in ethanol are first prepared by placing ceramic particles in suspension in ethanol to obtain suspensions having a ceramic concentration of 12%. in mass.

The suspensions thus prepared are then injected into a blown arc plasma using an assembly consisting of:

Oerlikon-Metco ^® Oerlikon-Metco ^® and / or Oerlikon-Metco ^® F4-VB DC plasma torch;

a robotic device on which is placed the torch and which allows its displacement;

a device for fixing the surface to be coated at a defined distance from the torch. The combination of the movement authorized by this device and that of the preceding device makes it possible to coat the surface of a sample;

a suspension injection device.

In Examples 1, 2, 3 and 4, the layer is made with an Oerlikon-Metco ^® Triplex Pro200 torch, with a distance between the torch outlet and the substrate of 70 mm, using a mixture of plasma gas consisting of 80% by volume of argon and 20% by volume of helium.

In Example 5, the layer is made with an Oerlikon-Metco ^® triplex Pro200 torch, with a distance between the torch outlet and the 60 mm substrate, using a mixture of plasma gas consisting of 80% by volume. of argon and 20% by volume of helium.

In Example 6, the layer is made with an Oerlikon-Metco ^® type F4-VB torch, with a distance between the torch outlet and the substrate of 50 mm, using a mixture of plasma gas consisting of % by volume of argon and 38% by volume of helium.

EXAMPLES

Example 1

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention (see FIG. 3).

The anti-CMAS layer 1, consisting of Gd ₂ Zr ₂ O 7, is prepared on the surface of a columnar YSZ layer 6, porous, obtained by an SPS process. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a dgo less than 10 μιη, namely a dgo of 7 μιη, and a dso greater than or equal to 1 μιη, namely 3 μιη.

The thus prepared sample constituted by the anti-CMAS layer on the substrate falls within the scope of the system shown in FIGS. 1 and 2.

Figure 3 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in this example.

Example 2

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention. The anti-CMAS layer 1 consisting of Gd ₂ Zr ₂ 07 is prepared on the surface of a columnar, compact, porous YSZ layer 7 obtained by an SPS process. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a dgo less than 10 μιη, namely a dgo of 7 μιη, and a dso greater than or equal to 1 μιη, namely 3 μιη.

Figure 4 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in this example.

Example 3

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention.

The anti-CMAS layer 1 consisting of ₂ Gd2Zr 07 is prepared on the surface of a layer 8 of YSZ, columnar shape, obtained by an EB-PVD process. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a dgo less than 10 μιη, namely a dgo of 7 μιη, and a dso greater than or equal to 1 μιη, namely 3 μιη.

Figure 5 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in this example.

Example 4

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention (see FIG. 9A after infiltration by CMAS).

The layer 13 anti-CMAS consisting of Gd ₂ Zr ₂ 07, is obtained by SPS using a suspension containing particles of Gd ₂ Zr ₂ 07 having a dgo of 7 μιη and a dso of 3 μιη. The layer is made on a free-standing substrate 11 of stabilized zirconia stabilized in a phase t 'and obtained by APS.

Example 5

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention (see FIG. 9B after infiltration by CMAS).

The layer 14 has nti-CMAS consists of Gd2Zr _{February 07,} is obtained by SPS using a suspension containing particles of Gd2Zr _{February 07} having a dgo 4.95 μιη and a dso 1.01 μιη. The layer is made on a free-standing substrate 11 of stabilized zirconia stabilized in a phase t 'and obtained by APS.

Example 6 (Comparative).

In this example, an anti-CMAS layer not according to the invention is prepared by a process which is not in accordance with the invention (see FIG. 9C after infiltration by CMAS).

The layer 15 has nti-CMAS consists of Gd2Zr20 _7, is obtained by SPS using a non-suspension according to the invention, containing Gd2Zr2Û ₇ particles having a dgo 0.89 μιη and a dso 0.41 μιη. The layer is made on a free-standing substrate 11 of stabilized zirconia stabilized in a phase t 'and obtained by APS.

In Examples 7 to 10 below, CMAS infiltration tests are carried out on the samples prepared in Examples 3 to 6.

In each of Examples 7 to 10, the CMAS (23.5% CaO - 15.0% Al ₂ O ₃ - 61.5% SiO 2 - 0% MgO (in mass%)) is deposited on the surface of each of the samples ( 30 mg / cm ² ). The sample is heated at 1250 ° C for 1 hour.

At the end of the tests, each of the anti-CMAS layers reacted and showed a drop of CMAS solidified on the surface of the sample.

At the end of the tests, a scanning electron microscope (M EB) observation is carried out in backscattered electrons of a polished section of each of the samples. Also, for most samples, an energy dispersive spectroscopy (EDS) of the silicon of a polished section of the sample is carried out. Example 7

In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 3, and the sample is observed after infiltration.

FIG. 6 is a scanning electron micrograph (M EB) of backscattered electrons of a polished section of the anti-CMAS layer obtained by SPS in Example 3 at the surface of a columnar YSZ layer 8 obtained by EB-PVD.

The observation made after infiltration by the CMAS reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1.

Example 8.

In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 4, and the sample is observed after infiltration of CMAS.

Figure 7A is a scanning electron micrograph (M EB) of backscattered electrons, and Figure 7B is an EDS ("Energy Dispersive Spectroscopy") analysis of the silicon of a polished section of layer 1 (13). ) Anti-CMAS obtained by SPS in Example 4 on the surface of a YSZ layer 11 obtained by APS.

The observation is made here in an uncracked area, without crack, in which there was no infiltration.

The observation made after infiltration of CMAS reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1. The lighter zone on the EDS plate corresponds to either the solidified CMAS 10 either at reaction zone 9. Figure 8A is another scanning electron micrograph (SEM) of backscattered electrons, and Figure 8B is another DHS analysis of silicon of a polished section of the SPS-derived CMAS layer 1 in the Example 4 on the surface of a YSZ layer 11 obtained by APS.

The observation is made here in a zone having a crack 12 after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1 (13). The lighter zone on the EDS plate corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the crack of the CMAS or of the reaction products between the CMAS and the layer 1.

Figure 9A is yet another Scanning electron microscope (SEM) micrograph in backscattered electrons (left) and an EDS analysis of silicon (right) of a polished section of an anti-CMAS layer of Gd ₂ Zr ₂ 07 obtained in Example 4, by SPS, with initial particles having a dgo of 7 μιη and a dso of 3 μιη. This layer is made on the surface of a YSZ layer 11 obtained by APS.

The observation is carried out in a zone having a fissure after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 13. The lighter zone on the EDS plate corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the CMAS crack or the reaction products between the CMAS and the layer 13.

FIG. 10 is a diffractogram obtained by X-ray diffraction after CMAS infiltration of the anti-CMAS 13 layer. The analysis shows the presence of the initial material Gd2Zr ₂ 07, an apatite phase Ca ₂ Gd 8 (SiO ₄ ) 60 ₂ of an anorthite phase CaAl ₂ (SiO ₄ ) ₂ and zirconia.

Example 9.

In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 5, and the sample is observed after infiltration. FIG. 9B is a backscattered electron microscopy (SEM) micrograph (left) and an EDS analysis of silicon (right) of a polished section of an anti-CMAS layer of Gd ₂ Zr ₂ 07 obtained in Example 5, by SPS with initial particles having a diameter of 4.95 μιη and a dso of 1.01 μιη.

This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is carried out in a zone having cracking after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 14. The lighter zone on the EDS plate corresponds either to the solidified CMAS 10 or to the reaction zone 9 or to the degree of penetration within the CMAS crack or the reaction products between the CMAS and the layer 14.

Example 10 (Comparative).

In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample not according to the invention prepared in Example 6, and the sample is observed after infiltration.

Figure 9C is a micrograph made with a scanning electron microscope (SEM) backscattered electron (left) and analysis by EDS silicon (right) of a polished section of the 15 anti-CMAS layer Gd2Zr _{February 07} obtained in the example

6, by SPS, with initial particles having a dgo of 0.89 μιη and a dso of 0.41 μιη.

This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is carried out in a zone having a fissure after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 15. The lighter zone on the EDS plate corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within CMAS cracking or the reaction products between the CMAS and the layer 15. Conclusion of Examples 1 to 10.

Between the CMASs and the anti-CMAS layer, a reactive zone 9 composed of blocking phases is observed (FIGS. 6, 7A, 7B, 8A, 8B, 9A, 9B, 9C).

The visualization of the CMASs and the reactive zone is also illustrated by the EDS images shown in Figures 9A, 9B and 9C.

The phases in the presence analyzed by X-ray diffraction comprise the initial material Gd ₂ Zr ₂ 07, an apatite phase Ca ₂ Gd 8 (SiO ₄ ) 60 ₂ , an anorthite phase CaAl ₂ (SiO ₄ ) ₂ and zirconia (FIG. ).

Whether it is through the porosity of the coating or cracks, the reactive zone 9 as well as the CMAS penetration within the anti-CMAS layer is more important, more severe, as the particle sizes decrease. .

In particular, the layer 15 of Example 6 (FIG. 9C), not in accordance with the invention, has a much larger infiltration, which is harsher than the layers 13 and 14 according to the invention (FIGS. 9A and 9B).

The size of the particles of anti-CMAS material injected into the plasma jet generates a difference in the morphology of the porosity. In fact, the smaller particles will notably offer the liquid CMAS a greater number of entry points, and more numerous and direct propagation paths in the thickness of the layer. Thus, in Example 6, not in accordance with the invention, "small particles" are used in the suspension, and there is then an infiltration of the coating by the CMAS in the thickness of the coating.

The kinetics of penetration within the coating is in competition with the kinetics of reaction allowing the formation of effective blocking phases.

In the layers prepared by the process according to the invention, the reaction kinetics of CMAS with the material of the layers is faster than the kinetics of infiltration, penetration, CMAS in the porosity of the layers. Indeed, the layers according to the invention, because they are prepared with suspensions which have a "large" particle size therefore have a high tortuosity, which slows down the kinetics of penetration, infiltration CMAS. The kinetics of CMAS penetration in the layers prepared by the process according to the invention is much slower than the reaction kinetics of CMAS with the layer material which allows the formation of effective blocking phases.

The kinetics of penetration of the anti-CMAS layer by CMAS at high temperature is slowed down for initial particles having sizes according to the invention. In this case, the anti-CMAS layer makes it possible, by the strong tortuosity generated, to form the blocking phase and / or the blocking phases at the surface and / or at a shallow depth within the anti-CMAS layer.

The lowest degree of infiltration, at the level of the cracks or at the level of the uncracked zones, is observed for the layer 13 of Example 4 according to the invention.

Example 11

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention. The anti-CMAS layer 21 consisting of Gd ₂ Zr ₂ 07 is prepared on the surface of a columnar YSZ layer 8 obtained by an EB-PVD process.

The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a dgo of 13.2 μιη and a dso greater than or equal to 1 μιη, namely 5.5 μιη.

The YSZ layer 8 is the same as the YSZ layer 8 of Example 3 but the layer 21 has a different particle size.

Figure 11 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the sample prepared in this example.

Example 12.

In this example, an anti-CMAS layer according to the invention is prepared by the process according to the invention (see FIG. 12 after infiltration by CMAS). The anti-CMAS layer 21 consisting of Gd ₂ Zr ₂ O 07 is obtained by SPS using a suspension containing particles of Gd2Zr ₂ 07 having a dgo of 13.2 μιη and a dso of 5.5 μιη. The layer is made on a free-standing substrate 11 of yttria stabilized zirconia in a phase t 'and obtained by APS. Example 13

In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 12, and the sample is observed after infiltration.

Figure 12 is a scanning electron micrograph (SEM) of backscattered electrons of a polished section of the anti-CMAS layer obtained by SPS.

The observation is performed after infiltration by the CMAS, and reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 21.

REFERENCES

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Claims

A method of coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a "SPS" plasma spraying technique in which at least one suspension of solid particles is injected of at least one ceramic compound in a plasma jet and then projecting the thermal jet which contains the suspension of solid particles onto the surface of the substrate, whereby the layer comprising at least one ceramic compound is formed on the surface of the substrate; characterized in that in the suspension, at least 90% by volume of the solid particles have a larger dimension (called dgo), such as a diameter, less than 15 μm, preferably less than 10 μm, and at least 50% by volume of the solid particles have a larger dimension (called dso) such that a diameter greater than or equal to 1 μιη; a method further characterized in that the ceramic compound is selected from compounds known as anti-CMAS compounds, preferably the ceramic compound is selected from the earth zirconates of formula RE ₂ Zr ₂ O ₇ , where RE is Se, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, or Lu, the composites of Y ₂ O 3 with Zr0 ₂ and / or Al ₂ O 3 and / or TiO ₂ , hexaluminates, aluminum silicates, yttrium silicates or other rare earth silicates, which silicates may be doped with one or more alkaline earth metal oxides, and mixtures thereof; more preferably, the ceramic compound is Gd ₂ Zr ₂ 0 ₇ .

2. Method according to claim 1, in which the layer has a lamellar microstructure and a tortuous porous network.

The method of claim 2, wherein the layer comprises both:

lamellae resulting from the melting of the solid particles of the suspension,

solid particles resulting from the partial melting of the solid particles of the suspension, and solid particles of the unmelted suspension.

4. A process according to any one of the preceding claims, wherein the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume.

5. Method according to any one of the preceding claims, wherein the layer has a thickness of 10 μιη to 1000 μιη, preferably 10 μιη to 300 μιη.

6. Method according to any one of the preceding claims, wherein the solid substrate is constituted by a solid support, which is for example in the form of a solid support or in the form of a layer, and is deposited layer comprising at least one ceramic compound directly on at least one surface of said support.

7. Method according to any one of claims 1 to 5, wherein the solid substrate is constituted by a solid support on which is a single layer or a stack of several layers, and is deposited the layer comprising at least one ceramic compound on at least one surface of said single layer or on at least one surface of the upper layer of said stack of layers.

The method of claim 6 or 7, wherein the support is of a material selected from materials susceptible to infiltration and / or attack by contaminants such as CMAS; in particular the support is made of a material chosen from metals, metal alloys such as superalloys, preferably monocrystalline superalloys, ceramic matrix composites (CMC) such as SiC matrix composites, mixed matrix composites C- SiC, and combinations and mixtures of the aforesaid materials.

9. The method of claim 7, wherein the single layer or said stack of layers on the support forms on the support a monolayer or multilayer thermal protection coating, namely a thermal barrier system, and / or a coating. monolayer or multilayer protection against corrosive environments, namely an environmental barrier system.

10. The method of claim 7, wherein the single layer is selected from the bonding layers, and the thermal or environmental barrier layers, such as layers, including ceramic layers, thermally insulating layers, including ceramic layers. , anti-oxidation, and the layers, especially the ceramic layers, anti-corrosion.

The method of claim 7, wherein the stack of multiple layers on the carrier comprises, from the carrier:

a tie layer which covers the support;

one or more layers chosen from among the thermal barrier layers and the environmental barrier layers, such as the layers, in particular the ceramic layers, thermally insulating, the layers, in particular the ceramic, anti-oxidation layers, and the layers, in particular the ceramic layers, anti-corrosion;

or the multilayer stack on the support includes:

12. The method of claim 10 or 11, wherein the thermal barrier layers and the environmental barrier layers, such as layers, in particular the ceramic layers, thermally insulating layers, including the ceramic layers, anti-oxidation, and the layers, in particular the ceramic layers, anti-corrosion are layers prepared by a technique chosen from EB-PVD, APS, SPS, SPPS, sol-gel, PVD, CVD, and the combinations of these techniques.

13. Process according to any one of claims 10 to 12, in which the thermal barrier layers are made of a material chosen from zirconium or hafnium oxides, stabilized with yttrium oxide or with other oxides. rare earths, aluminum silicates, yttrium or other rare earth silicates, these silicates being doped with alkaline earth metal oxides, and rare earth zirconates, which crystallize in a pyrochlore structure, and the combinations and / or blends of the above materials, preferably, the thermal barrier layers are yttrium stabilized zirconia (YSZ); and the environmental barrier layers are of a material selected from aluminum silicates, optionally doped with alkaline earth elements, rare earth silicates, and combinations and / or mixtures of the aforementioned materials.

14. Method according to any one of claims 10 to 13, wherein the bonding layer is a material selected from metals, metal alloys such as metal alloys β-ΝϊΑΙ, modified or not with Pt, Hf, Zr, Y, Si or combinations of these elements, metal alloys γ-Νί-γ'-ΝΪ3ΑΙ modified or not by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements, the alloys MCrAIY where M is Ni, Co, NiCo, Si, SiC, SiO ₂ , mullite, BSAS, and combinations and / or mixtures of the aforementioned materials.

15. The method as claimed in any one of the preceding claims, in which the substrate consists of a support made of a metal alloy such as a superalloy or a ceramic matrix composite (CMC), coated with a metal bonding layer. - Even coated with a layer, such as a ceramic layer selected from the thermal barrier layers and the environmental barrier layers.

16. The method as claimed in any one of the preceding claims, in which the substrate consists of a support made of a metal alloy such as a superalloy or a ceramic matrix composite (CMC) coated with a metal bonding layer. - even coated with a yttrine stabilized zirconia (ZrO ₂ ) thermal barrier ceramic layer (Y2O3).

17. A method according to any one of the preceding claims, wherein the substrate is constituted by a support of a metal alloy such as a superalloy or a ceramic matrix composite (CMC), coated with a metal bonding layer it - Even coated with a ceramic layer of thermal and / or environmental barrier made by a technique selected from the techniques of APS, EB-PVD, SPS, SPPS, sol-gel, CVD, and combinations of these techniques.

18. Substrate coated with at least one layer obtainable by the method according to any one of claims 1 to 17.

The substrate of claim 18, wherein the layer has a lamellar microstructure and a tortuous porous network.

The substrate of any of claims 18 and 19, wherein the layer comprises both:

lamellae resulting from the melting of the solid particles of the suspension,

solid particles of the unmelted suspension.

The substrate of any one of claims 18 to 20, wherein the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume.

22. Substrate according to any one of claims 18 to 21, wherein the layer has a thickness of 10 μιη to 1000 μιη, preferably 10 μιη to 300 μιη.

23. Part comprising the coated substrate according to any one of claims 19 to 22.

24. Part according to claim 23 which is a part of a turbine, such as a turbine blade, a distributor, a turbine ring, or a part of a combustion chamber, or a part of a nozzle, or more generally any part subjected to aggression by liquid and / or solid contaminants such as CMAS.

25. Use of the layer obtainable by the method according to any one of claims 1 to 17, for protecting a solid substrate against degradation caused by contaminants such as CMAS.