Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
  • C23C4/11—Oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
  • C23C28/042—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/134—Plasma spraying

Definitions

• the present invention relates to the manufacture of a nanostructured or finely structured multilayer ceramic coating, intended in particular to cover metal parts or metal alloys such as turbine blades and combustion chamber parts exposed to high temperatures in the engines used. particularly in the aeronautical, space, naval and nuclear industries.
• Some metal parts or metal alloys are intended to be used at high temperature (that is to say up to a temperature of 1300 ° C) and to undergo thermal cycles of large amplitude. This is for example the case of gas turbine components (fixed and mobile blades, turbine rings, etc.).
• thermal back This thermal barrier is generally made based on zirconia stabilized with yttrium (YSZ). Its function is, because of its low thermal conductivity, to limit the surface temperature seen by the structuring superalloy.
• Thermal barriers are currently achieved either by dry thermal spraying or electron beam-assisted physical vapor deposition (EB-PVD for "Electron Beam Physical Vapor Deposition”).
• EB-PVD electron beam-assisted physical vapor deposition
• the technique of dry thermal spray deposition consists of introducing, via a carrier gas, powders of the material to be sprayed into a plasma jet, in which the particles will be melted and accelerated before crashing into the substrate to be covered.
• the powders used for dry thermal spraying have a micrometric particle size or greater.
• the use of nanometric powder is for example only possible in the form of agglomerates of micrometric sizes.
• the deposit by dry thermal spraying in the particular case of ceramic oxide projections, is most often performed at atmospheric pressure: it is called APS deposit (for "Atmospheric Plasma Spraying" in English).
• APS deposit makes it possible to produce thick layers, generally of a thickness of a few tens of micrometers to a few hundreds or even thousands of micrometers, of very varied natures on substrates to be coated all as varied.
• This technique makes it possible to obtain a deposit having a porous lamellar structure, which gives the deposit a low thermal conductivity (of the order of 0.9 to 1.5 Wm-1K 1 in the case of YSZ).
• a structure has a limited thermal fatigue resistance in the case of applications of the thermal barrier type.
• the EB-PVD method allows the formation of layers having a columnar type architecture, which is particularly interesting for forming a thermal barrier, because this type of architecture has the particularity of giving the layers good resistance to thermal fatigue (from its ability to accommodate deformations), as well as an average thermal conductivity (of the order of 1.6 to 2 W.nr 1 .K 1 in the case of YSZ), which is greater than that of thermal barriers performed by APS deposit.
• the columnar structure is sensitive to infiltration by pollutants, leading in the long term to a degradation of the layer.
• the EB-PVD process is relatively expensive to implement compared to the APS process. It is also relatively difficult to coat large parts with EB-PVD.
• CMAS dust particles or sand
• CaO lime
• MgO magnesium oxide
• Al2O3 alumina
• SiO2 silicon oxide
• these particles are sucked by the turbine and can degrade the thermal barrier in two ways:
• CMAS having melting points relatively low compared to the temperatures prevailing in the turbines, they can be melted on the surface of the thermal barrier and then interact with it.
• One possible solution to protect the thermal barrier from the deleterious effect of CMAS is to block the penetration of CMAS inside the latter by the formation of a protective layer.
• the multilayer and multifunctional coating thus obtained makes it possible to increase the performance of the thermal barrier by adding a complementary function of protection against CMAS.
• this protective layer against CMAS many surface treatment processes can be used, such as PVD, CVD, sol-gel treatments, etc. or the APS and EB-PVD treatments mentioned above.
• the inventor therefore set himself the goal of designing a multilayer ceramic coating, as well as its manufacturing process, which meet several criteria for improving the thermal barriers, namely, on the one hand, improving the combined performance resistance to thermal cycling and thermal conductivity of the thermal barrier and, on the other hand, the improvement of the life of the thermal barrier vis-à-vis the CMAS resistance.
• a multilayer ceramic thermal protection coating intended to coat a surface of a substrate, characterized in that it comprises n consecutive ceramic layers, n being an integer greater than or equal to 2 , each of the n layers having a micrometric scale architecture of the columnar, segmented or homogeneous type and having a finely structured or nanostructured microstructure.
• the n layers of the coating object of the invention have a nanostructured or finely structured porosity, having a homogeneous distribution, which has the effect of limiting the conduction of heat.
• the term "size”, applied to particulate elements, particles or pores, refers to the largest dimension of such particulate elements, particles or pores;
• nanoscale means greater than or equal to 1 nanometer and less than or equal to 100 nanometers;
• submicrometer means greater than 100 nanometers and less than 1000 nanometers;
• micrometric means greater than or equal to 1 micrometer and less than 1000 micrometers.
• the term "columnar architecture”, applied to a layer, means that the layer has a structure having, at the micrometric scale, an orientation privileged elementary bricks in the direction of the thickness of the layer, these bricks being organized in the form of columns.
• the average diameter of the columns is of the order of 40 ⁇ and is adjustable according to the projection conditions (heating and driving in step b)).
• the intercolumn space reflects the compactness of the columnar stack and the amplitude of this intercolumn space is also adjustable according to the projection conditions.
• homogeneous architecture applied to a layer means that the layer has a structure formed of elementary bricks that have no characteristic orientation at the micrometric scale. Similarly, the porosity of the layer has no characteristic orientation at the micrometric scale.
• mented architecture applied to a layer means that the layer has a structure with a homogeneous architecture in which microcracks perpendicular to the surface have been generated during the formation of the layer. This architecture is an intermediate architecture between homogeneous architecture and columnar architecture.
• the elementary bricks of the columnar, segmented and homogeneous architectures have a density of about 80% of the theoretical density of the bulk material and consist of particles (semi-melted and solidified) and pores distributed homogeneously.
• microstructure applied to a layer, means that one speaks of its structure at the micrometric scale.
• nanostructured applied to a layer means that the layer has a nanoscale organization of its porosity; the term “finely structured” applied to a layer means that the layer has a submicron scale organization of its porosity.
• nanostructured and “finely structured” apply when at least 50% of the porosity meets these definitions.
• the coating comprises a first columnar type architectural layer and a second homogeneous type architecture layer, the second layer surmounting the first layer.
• the coating comprises a first layer of homogeneous type architecture, a second layer of columnar type architecture, and a third layer of homogeneous type architecture, the second layer overlying the first layer, and the third layer overlying the second layer.
• the first, the second and the optional third layer have a nanostructured microstructure.
• the n consecutive ceramic layers may be of materials selected from oxides of zirconium or hafnium, 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 in a pyrochlore structure.
• the first, the second and the optional third layer are based on zirconia stabilized with yttrium (YSZ).
• the invention also relates to a part comprising a substrate having a surface which is coated with a multilayer coating as defined above.
• the substrate on which the coating is deposited is a metal substrate, that is to say that it is made of a material chosen from a metal or a metal alloy.
• the invention also relates to a method for forming a multilayer coating on a surface of a substrate, the multilayer coating comprising n consecutive ceramic layers, n being an integer greater than or equal to 2.
• the method is characterized in that each N layers are produced by an SPS arc plasma projection method of a suspension of submicron or nanometric particles.
• a suspension comprising nanoscale solid particulate elements makes it possible to obtain a nanostructured layer, while the use of a suspension comprising solid particles of sub-micron sizes makes it possible to obtain a finely structured layer.
• the structure of the layer obtained from this suspension will be mixed and function of the majority proportion of the size of the solid particles in the suspension.
• the n layers are obtained by performing, for each of the n layers, the following operations:
• steps a) and b) being carried out continuously and repeated for each of the n layers by modifying at least one of the following parameters:
• this distance preferably being between 30 and 70 mm;
• n ceramic layers of the multilayer coating therefore differ from each other either by their microstructures (nanostructured or finely structured layer), or by their architectures (columnar, homogeneous or segmented), or by their compositions.
• Steps a) and b) of the process which is the subject of the invention are steps of a deposition technique known as SPS deposition (for "Plasma Suspension”). Spraying "in English).
• SPS deposition for "Plasma Suspension”
• spraying in English
• the particles are injected into an SPS deposit from a suspension of nanometric or submicron sized particles. conveyed in a pressure vector liquid. This makes it possible to penetrate nanometric or submicron particles by inertia effect at the heart of the plasma jet without excessive disturbance of the latter and thus optimize their transport and heating by the plasma jet to obtain a microstructure deposit controlled.
• the multilayer coating according to the invention therefore comprises n different consecutive ceramic layers each having an architecture controlled at the micrometric scale (columnar, homogeneous or segmented), and being nanostructured or finely structured, each layer being preferably produced by the SPS filing technique.
• the continuous realization of the n layers by the technique of a SPS deposit makes it possible to easily modulate the architecture of the coating according to the intended application by continuously assembling several consecutive nanostructured or finely structured microstructure layers of different architectures (from columnar, segmented or homogeneous type) and / or different compositions, while easily varying the thickness of each layer according to the injection parameters (step a)) and projection (step b) heating and training ).
• the thermal protection layer having a columnar or segmented or homogeneous architecture, which will make it possible to reduce the thermal conductivity and increase the resistance to thermal fatigue of the substrate, and a layer of protection against CMAS, having a columnar or segmented or homogeneous architecture, located above the thermal protection layer, which will serve as an environmental barrier by limiting the infiltration of CMAS into the thermal protection layer.
• the thermal protection layer may have a columnar architecture, while the protective layer against CMAS has a homogeneous architecture. If the n layers comprise more than two layers, the additional layer or layers add additional functionality to the thermal protection layer serving as a thermal barrier: it may for example be an additional thermal protection layer, a additional CMAS protection layer, an abradable layer, etc.
• the continuous shaping of the n consecutive ceramic layers of the multilayer coating by the SPS technique is time saving and of great economic interest.
• the injection of the suspension into the plasma jet in step a) is done radially.
• the inclination of the injector relative to the longitudinal axis of the plasma jet can vary from 20 to 160 °, but is preferably 90 °.
• 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 diameter of the injector can vary between 50 ⁇ and 300 ⁇ .
• 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 injection in step a) is carried out by means of an injection system having an injection diameter of between 50 and 300 ⁇ at a pressure injection system injection of between 1 and 7 bars and from a suspension comprising between 1% and 40% by weight of solid particulate elements.
• the method which is the subject of the invention has the advantage of being easily industrializable, since the injection system necessary for carrying out the injection can fit on most thermal spray devices that are used in the industry.
• it can advantageously be carried out at atmospheric pressure and by using a plasma torch with an electrical power of less than 60 kW, this type of torch having the advantage of being available on most of the plasma projection devices used in the industry. , which does not require the purchase of additional expensive equipment.
• the nanostructured layers and the finely structured layers have optimized properties, both mechanical and physicochemical. Indeed, a decrease in the size of the particles makes it possible to greatly increase their specific surface area, the number of inter-particle contacts, as well as the shape, the size and the geometry of the porosities.
• the nanostructured layers and the finely structured layers have a lower thermal conductivity than the layers obtained from micrometric particles.
• the combination of these microstructures with a controlled architecture also makes it possible to improve the thermal cycling life of the layers compared to coatings obtained from micron-sized powders. This is particularly the case of columnar architectures that are much less sensitive to deformations than homogeneous or segmented architectures and which have increased resistance to thermal cycling.
• the coating according to the invention makes it possible, on the one hand, to improve the combined performance of resistance to thermal cycling and thermal conductivity of the thermal barrier by producing, as a layer intended to serve as a thermal barrier, a nanostructured or finely structured microstructure layer with controlled architecture (columnar, homogeneous or segmented) and, on the other hand, to improve the life of the thermal barrier with respect to CMAS resistance by adding an additional layer nanostructured or finely structured surface of the thermal barrier, composition and architecture may be different from that of the thermal barrier.
• the ceramic compounds that can be used in the composition of the n consecutive layers of the coating obtained according to the invention mention may notably be made of:
• oxides such as simple metal oxides (for example, an aluminum oxide or a zirconium oxide) or mixed metal oxides (for example, a metal silicate or a metal zirconate);
• non-oxides such as, for example, carbides, borides and nitrides of metals such as tungsten, magnesium, platinum, silicon, zirconium, hafnium, tantalum and titanium;
• composite ceramics generally defined as being a combination of one or more oxides and one or more non-oxides, such as those mentioned above.
• the n consecutive ceramic layers can thus be zirconium or hafnium oxides stabilized with yttrium oxide or with other rare earth oxides (for example, (La, Gd or Nd ⁇ Z ⁇ O? (La, Gd, Nd) 2Ce 2 O 7)); aluminum silicates, yttrium or rare earths, these silicates being optionally doped with alkaline earth metal oxides; rare earth zirconates, which crystallize according to a pyrochlore structure, etc. (eg perovskite structures such as SrZr0 3 and BaZr0 3 ).
• the continuous production of the n consecutive layers with, for each layer, the use of the injection and projection steps typical of an SPS deposit greatly facilitates the realization of the multilayer coating and makes possible the possible change of architecture and / or composition from one layer to another by varying the parameters of the suspension (particle size, charge rate, solvent, concentration, injection diameter, etc.) and the conditions of the plasma jet. It is furthermore possible to produce an architectural and / or composition gradient within the same layer by changing only at least one of the parameters mentioned above.
• the surface of the substrate prior to the formation of the n consecutive ceramic layers of the coating according to the method which is the subject of the invention, it is possible to treat the surface of the substrate in order to improve the adhesion of the coating to the substrate.
• This treatment is intended to remove impurities, pollutants and other foreign bodies on the surface of the substrate and is to adapt the coefficients of thermal expansion depending on the type of layer to be deposited on the surface of the substrate.
• This pretreatment may for example consist of sanding the surface of the substrate to increase its roughness.
• an alumino-forming layer (so-named because it forms alumina by selective oxidation and also called a bond coat or "bond coat” in English).
• This layer is intended to protect the substrate from oxidation and corrosion.
• This layer may, for example, be of NiPtAI or ⁇ / ⁇ 'composition based on nickel and platinum, thermochemically prepared (activated cementation), or else of MCrAIY, M composition which may be iron, nickel, cobalt or a combination of these elements, deposited by dry thermal spraying.
• a layer of alumina generally between 0.5 and 1 ⁇ thick and called TGO (for "Thermally Grown Oxide” in English), can be obtained by heat treatment in air or in a controlled atmosphere at high temperature. (950-1100 ° C) of the tie layer.
• This layer TGO formed between the bonding layer and the first of the n consecutive layers of ceramic, makes it possible to guarantee the protection of the bonding layer, while improving the bonding of the n ceramic layers.
• FIG. 1 represents, in a schematic manner, the experimental device used to implement the manufacturing method according to the invention.
• Figures 2a to 2c are images obtained by scanning electron microscopy of a layer respectively having a homogeneous architecture (Figure 2a), a segmented architecture ( Figure 2b) and a columnar architecture (Figure 2c).
• FIG. 3 schematically represents, in a sectional view, a first embodiment of a multilayer coating according to the invention.
• FIG. 4 is an image obtained by scanning electron microscopy of the coating made according to the first example, in a sectional view.
• FIG. 5 schematically represents, in a sectional view, a second embodiment of a multilayer coating according to the invention.
• FIG. 6 schematically represents, in a sectional view, a third embodiment of a multilayer coating according to the invention.
• FIG. 7 is an image obtained by scanning electron microscopy of part of the coating made according to the third example, in a sectional view.
• the n consecutive ceramic layers of the multilayer coating according to the invention are preferably produced by thermal spraying of suspension (SPS deposit), that is to say by injecting, in a plasma jet, a liquid suspension comprising particles of nanometric or submicron sizes.
• SPS deposit thermal spraying of suspension
• the multilayer coating may further comprise other layers (tie layer and / or TGO layer), but which are not realized by the SPS technique.
• the suspension plasma projection used to produce the n ceramic layers of the multilayer coating according to the invention is shown diagrammatically in FIG. 1.
• It consists of injecting into a flow with a high thermal and kinetic energy (for example a plasma jet 1 which can be produced by a plasma torch 2 DC), a liquid suspension 3 containing submicron ceramic particles and / or nanoscale material of the layer to be prepared.
• the suspension 3 is injected by means of a mechanical injector 4 radially from a pressurized reservoir 5 and perpendicular to the axis of the jet 1.
• the injection angle can be varied from 20 ° to 160 ° around the middle position at 90 °.
• the injection can be made at the same distance or at different distances from the part to be coated 6.
• the suspension thus injected will fragment in contact with the enthalpic carrier gas.
• the solvent will then evaporate, the particles will be heat-treated and accelerated to the substrate, and thus form a nanostructured or finely structured layer 7.
• the architecture of this nanostructured or finely structured layer will be chosen from a homogeneous (layer 400), segmented (layer 500) or columnar (layer 600) architecture and obtained by controlling the injection parameters, suspension and plasmagenic conditions.
• An image obtained by scanning electron microscopy for each of these three architectures is given in FIGS. 2a to 2c.
• a Sulzer Metco F4VB TM DC plasma torch equipped with an anode having an inside diameter of 6 mm is used to obtain the plasma jet used in the SPS technique for producing the n layers. ceramic.
• the suspensions used for the formation of the n ceramic layers it is possible to use powders such as zirconium or hafnium oxides stabilized with yttrium oxide, other rare earth oxides, aluminum silicates , yttrium or rare earth doped with alkali metal oxides earth. It is thus possible, for example, to obtain zirconium layers of rare earths, which crystallize in a pyrochlore structure such as (La, Gd or Nd ⁇ Z ⁇ O or also (La, Gd, Nd) 2Ce 2 07, or according to Perovskite structures such as SrZrO3 and BaZrO3.
• a pyrochlore structure such as (La, Gd or Nd ⁇ Z ⁇ O or also (La, Gd, Nd) 2Ce 2 07, or according to Perovskite structures such as SrZrO3 and BaZrO3.
• compositions of the layers as well as their architecture (columnar, segmented or homogeneous) according to the functionalities sought for the multilayer coating.
• the particle size of the powder used is greater than or equal to 10 nm and less than 1000 nm.
• the powder is suspended with a filler content greater than 1% by weight in an aqueous or alcoholic solvent, preferentially in water or ethanol, depending on the type of deposit to be obtained (homogeneous or columnar).
• a zirconia powder is used stabilized with 7% by mass of p ytti ⁇ um 0 ur achieve YSZ layers.
• This powder is suspended at 12% by weight in an aqueous or alcoholic solvent depending on the type of deposit to be prepared.
• the suspension is injected, by pressurizing the reservoir with argon, into the plasma jet at the outlet of the torch via a mechanical injector oriented at 90 ° with respect to the axis of the plasma jet and whose diameter varies between 50 and 300 ⁇ according to the projection conditions.
• This set of conditions makes it possible to obtain nanostructured or finely structured coatings.
• the substrate is first cleaned with acetone. It is also sandblasted, then preheated, before depositing the first layer of n layers of the multilayer coating, with the plasma jet at a temperature of about 100 ° C, which improves the adhesion of the deposit.
• the selected projection parameters are adapted according to the type of deposit to be prepared.
• the method that is the subject of the invention makes it possible to easily modulate the architecture of the n ceramic layers of the coating as a function of the intended application and of the desired functionalization, by continuously assembling via the SPS technique n layers that can have a composition. and / or a different architecture, among which a layer having a columnar type architecture, a layer having a homogeneous type architecture and a layer having a segmented type architecture.
• This example illustrates the production of a coating 11 on one side of a substrate 304X stainless steel 50x50 mm 2 and rough machining (R a about 0.5 ⁇ ).
• the coating 11 here comprises two nanostructured YSZ layers: a columnar type layer 12, surmounted by a homogeneous type layer 13 (FIG. 3).
• the coating 11 is here a nanostructured YSZ bilayer.
• the selected projection parameters are:
• the projection is further carried out at atmospheric pressure.
• yttrium having a particle size of between 30 and 60 nm.
• the powder is suspended at 12% by weight in a suitable solvent. Ethanol is chosen as the solvent.
• the carrier gas used to inject the suspension into the plasma jet at the outlet of the torch is argon.
• the suspension is injected via a mechanical injector, oriented at 90 ° with respect to the main axis of the plasma jet.
• the plasma torch is located at a distance of 50 mm from the surface of the substrate to be covered and the nozzle of the mechanical injector is located at a distance of 45 mm from this surface.
• the substrate 10 is pre-cleaned by being immersed in an acetone bath for 30 minutes, then in an ethanol bath in which ultrasound is applied.
• Substrate 10 is then dried, then sandblasted, for example by making crossed passes by projecting on the substrate corundum grains having an average diameter of 79 ⁇ at a pressure of 1.5 bars, until a roughness is obtained. close to about 0.8 ⁇ .
• Substrate 10 is then preheated with the plasma jet at a temperature of about 100 ° C.
• ethanol is used as solvent with an injector having a diameter of 150 ⁇ and the nozzle of the injector is located at a distance (projection distance) of 50 mm from the substrate to be covered.
• the solvent used is water and the injector has a diameter of 250 ⁇ and the projection distance is 60 mm. .
• FIG. 4 An image taken by scanning electron microscopy of the bilayer coating thus obtained is visible in FIG. 4.
• a first columnar type layer 11 having a thickness of about 150 ⁇ is obtained, which allows the accommodation thermomechanical stresses, and a second layer 12 of homogeneous type having a thickness of about 150 ⁇ , which limits the infiltration of CMAS.
• a multilayer coating 21 on one side of an AMI (nickel-based) superalloy substrate 20 the coating comprising a bonding layer 210, a TGO layer 211, a layer 22 having a columnar architecture as a thermal barrier and a layer 23 architecture of homogeneous type serving as protection against CMAS layers 23 and 23 forming a nanostructured YSZ bilayer.
• the various bonding layers are a thermochemically prepared NiPtAI layer, a thermochemically prepared ⁇ / ⁇ 'NiPt layer, and a NiCoCrAlY layer prepared by dry plasma spraying.
• a bonding layer 210 is formed by
• NiPtAI on the AMI superalloy substrate 20.
• the NiPtAI layer is then cleaned with ethanol and acetone, followed by sandblasting to obtain a roughness of approximately 1.6 ⁇ .
• the layer 210 of NiPtAI is then placed for one hour at 1100 ° C. in air, which leads to the formation of a thin layer of alumina 211 (TGO layer) at its surface of approximately 0.9 ⁇ .
• TGO layer alumina 211
• a nanostructured bilayer is deposited in YSZ of homogeneous type using the same operating conditions as in Example 1.
• a ⁇ / ⁇ NiPt bond layer 210 is formed on the AMI superalloy substrate 20.
• the ⁇ / ⁇ NiPt layer is then cleaned with ethanol and acetone, followed by sandblasting to obtain a roughness of approximately 1 ⁇ .
• a YSZ nanostructured bilayer with a homogeneous type architecture is deposited using the same operating conditions as in Example 1.
• a NiCoCrAlY bonding layer 210 is formed on the AMI superalloy substrate 20.
• a NiCoCrAlY layer having a roughness of approximately 7 ⁇ is thus obtained.
• a YSZ nanostructured bilayer with a homogeneous type architecture is deposited using the same operating conditions as in Example 1.
• a multilayer coating 31 on an AMI superalloy substrate 30, comprising a NiPtAI bonding layer 310, an alumina TGO layer 311, and a nanostructured YSZ tricouche comprising a layer 32 to homogeneous type architecture, a layer 33 with a columnar type architecture and a layer 34 with a homogeneous type architecture.
• TGO 311 alumina proceed as indicated for the first coating of Example 2.
• the same injection device (same tank containing the suspension and the same injector) can be used to make the first and third layers.
• FIG. 7 is an image obtained by scanning electron microscopy which has been zoomed on the interfaces between the NiPtAI link layer 310, the TOG layer 311 and the homogeneous first layer 32 of the YSZ trilayer.

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• 2015
  • 2015-11-09 FR FR1560692A patent/FR3043411B1/fr active Active
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