Method of depositing an abrasive coating on an aircraft turbine blade tip

Abstract

Method for depositing an abrasive coating on an aircraft turbine blade tip The invention relates to a method for depositing an abrasive coating on an aircraft turbine blade tip (1), the blade tip being made of metal or ceramic. The method comprises: - a step of positioning a sintering mold on the blade tip (1), - a step of covering a surface of the blade tip (2) delimited by the sintering mold with an abrasive outer layer (5) comprising a metal-based or ceramic-based matrix (6) and abrasive particles (7), and - a high-temperature sintering step carried out on the abrasive outer layer (5) to form a blade tip (1) covered with the abrasive coating. Figure for abstract: Fig. 1.

Description

Title of the invention: Method for depositing an abrasive coating on the tip of an aircraft turbine blade Technical field

[0001] The invention relates to the general field of aeronautics and more particularly to a method of depositing an abrasive coating on a high-pressure turbine blade tip of an aircraft turbomachine. Prior art

[0002] It is known to provide abrasive particles embedded in a matrix at the top of a high-pressure turbine blade of aeronautical engines.

[0003] In the event of contact between the rotor and the stator in the turbine, the blade tip strikes the surface of a ring made of a material designed to be sacrificed because it is softer than the abrasive particles. In this way, it is possible to create, by the abrasive action of the particles on the ring, a very small space between the tip and the ring, thus minimizing gas losses. The recirculation gas flow rates at the blade tips and the radial clearances between fixed parts and moving parts forming labyrinths are reduced.

[0004] This makes it possible to improve the efficiency of the compressor or high-pressure turbine of a turbomachine and to reduce the specific consumption. For example, reducing the clearance by 25 pm between the tip of the blade and the ring results in a reduction in specific consumption estimated at 0.1%.

[0005] Document US005702574A discloses an abrasive coating based on inclusions of non-oxide c-BN particles in an MCrAlY matrix (M = Ni / Co), with a thickness of between 125 μm and 150 μm, by an electrodeposition process applied to the tip of compressor stage or high pressure stage blades of a turbomachine composed mainly of nickel and cobalt.

[0006] This abrasive coating has the desired abrasive property but the abrasive material based on non-oxide particles (c-BN) used gradually sublimes at the target operating temperatures (temperature above 900°C). This abrasive coating thus has limited resistance to oxidation (900°C) and its abrasive (or cutting) efficiency will be limited during its aging at temperature.

[0007] Other methods are also known for producing abrasive coatings on blade tips made by a detonation sputtering process of the matrix, for example.

[0008] However, no prior art method makes it possible to provide an abrasive coating on a blade tip having excellent resistance to oxidation at high temperature and therefore constant abrasive efficiency over time. Presentation of the invention

[0009] The objective of the present invention is to provide a high-pressure turbine blade of a turbomachine comprising blade tips covered with an abrasive coating having excellent resistance to oxidation at high temperature and constant abrasive efficiency over time.

[0010] The present invention relates to a method for depositing an abrasive coating on an aircraft turbine blade tip. The blade tip is made of metal or ceramic.

[0011] The deposition process comprises: - a step of positioning a sintering mold on the blade tip, - a step of covering a surface of the blade tip delimited by the sintering mold by an abrasive outer layer comprising a metal or ceramic based matrix and abrasive particles, and - a sintering step carried out on the abrasive outer layer to form a blade tip covered by the abrasive coating.

[0012] The invention thus provides a high-pressure turbine blade of a turbomachine comprising blade tips covered with an abrasive coating having excellent resistance to oxidation at high temperature and constant abrasive efficiency over time.

[0013] The invention makes it possible to increase the durability of the high-pressure turbine blade tips, to improve and maintain the efficiency of the high-pressure turbine over time while maintaining a reduced clearance between the abrasive coating deposited on the blade tips and the abradable coating deposited on the turbine ring.

[0014] The matrix of the abrasive coating exhibits structural stability at high temperature with respect to the chemical composition of the abrasive particles.

[0015] Alternatively, the abrasive outer layer is obtained by a first deposition of a layer of metal-based or ceramic powder to form a matrix in the form of a layer of powder and a second deposition of a layer of abrasive particle powder on the matrix.

[0016] This method makes it possible to obtain an abrasive coating comprising abrasive particles on the surface of the matrix in a simple manner.

[0017] Alternatively, the abrasive outer layer is obtained by a first deposition of a layer of metal-based or ceramic powder encapsulated in a polymer binder-based matrix by a fused wire deposition process to form a matrix in the form of encapsulated powder and a second deposition of a layer of abrasive particles encapsulated in a polymer binder-based matrix on the matrix by a fused deposition process.

[0018] This method also makes it possible to obtain an abrasive coating comprising abrasive particles on the surface of the matrix.

[0019] The fused wire deposition manufacturing method avoids the scrapping of damaged or worn parts by allowing them to be repaired by adding material locally, thus helping to reduce the environmental impact linked to the repair of parts.

[0020] Alternatively, the abrasive outer layer is obtained by a first deposition by printing a metal or ceramic-based layer to form a printed matrix and a second deposition by printing abrasive particles on the printed matrix.

[0021] This method also makes it possible to obtain an abrasive coating comprising abrasive particles on the surface of the matrix.

[0022] Alternatively, the abrasive outer layer is obtained by mixing a powder of abrasive particles with a matrix of a metal or ceramic-based powder.

[0023] This method makes it possible to obtain an abrasive coating comprising inclusions of abrasive particles in volume and on the surface, that is to say inside and on the surface of the matrix.

[0024] Alternatively, the abrasive outer layer is directly deposited on the surface of the blade tip or on a metal or ceramic based bonding sub-layer previously deposited on the surface of the blade tip or on a metal or ceramic based intermediate layer deposited between the bonding sub-layer and the abrasive outer layer.

[0025] Alternatively, the manufacturing method comprises, before the step of covering a surface of the blade tip with the abrasive outer layer, a step of depositing the abrasive outer layer in a preforming mold, a preliminary flash sintering step performed on the abrasive outer layer to form a preformed abrasive outer layer and a step of depositing the preformed abrasive outer layer in the sintering mold. The sintering step is performed on the preformed abrasive outer layer.

[0026] Alternatively, the ratio between the median diameter of the abrasive particles and the thickness of the matrix is between 0.6 and 0.9. The abrasive outer layer has a thickness between 3 μm and 400 μm.

[0027] Alternatively, the ratio between the median diameter of the particles of the matrix and the median diameter of the abrasive particles is between 0.002 and 0.4.

[0028] Alternatively, the sintering step is a flash sintering step. When the matrix is metallic and the blade tip surface is nickel-based, the temperature of the furnace in which the flash sintering step is carried out is between 700°C and 1000°C, preferably between 800°C and 900°C. The pressure inside the furnace is between 25 MPa and 125 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes. The temperature of the furnace corresponds to the temperature to which the blade tip is subjected. Similarly, the pressure inside the furnace corresponds to the pressure applied to the blade tip.

[0029] Alternatively, the sintering step is a flash sintering step. When the matrix is made of a ceramic matrix and the surface of the blade tip is nickel-based, the temperature of the furnace in which the flash sintering step is carried out is between 900°C and 1300°C, preferably between 1000°C and 1100°C. The pressure inside the furnace is between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes.

[0030] Alternatively, the sintering step is a flash sintering step. When the matrix and the surface of the blade tip are made of ceramic, the temperature of the furnace in which the flash sintering step is carried out is between 900°C and 1500°C, preferably between 1200°C and 1400°C. The pressure inside the furnace is between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes.

[0031] The present invention also relates to an aircraft turbine blade comprising at least one blade tip comprising an abrasive coating obtained by the manufacturing method as defined above. Brief description of the drawings

[0032] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the figures, in which:

[0033] [Fig.l] [Fig.l] schematically represents a blade tip surface covered with an abrasive coating, according to an embodiment of the invention,

[0034] [Fig.2] [Fig.2] schematically represents a blade tip surface covered with an abrasive coating, according to another embodiment of the invention,

[0035] [Fig.3] [Fig.3] schematically represents a blade tip surface covered with an abrasive coating, according to another embodiment of the invention. Description of the embodiments

[0036] High pressure turbine blades of aeronautical engines, made of metal or ceramic, comprise a blade tip 1 covered with an abrasive coating comprising abrasive particles 7 embedded in a metal or ceramic-based matrix 6.

[0037] In the event of contact between the rotor and the stator in the turbine, the blade tip 1 strikes the surface of a ring made of a material designed to be sacrificed because it is softer than the abrasive particles 7. In this way, it is possible to create, by the abrasive action of the particles on the ring, a very small space between the tip and the ring, thus minimizing gas losses.

[0038] The invention relates to a method for depositing the abrasive coating on the tip of a high-pressure turbine blade 1.

[0039] Generally, the deposition process comprises: - a step of positioning a sintering mold on the tip of blade 1, - a step of covering a surface of the blade tip 2 delimited by the sintering mold by an abrasive external layer 5 formed from a matrix 6 with a metallic or ceramic base comprising abrasive particles 7, and - a step of sintering the abrasive outer layer 5 to form a blade tip 1 covered by the abrasive coating.

[0040] Preferably, the deposition process is carried out on all the blade tips 2.

[0041] Preferably, the sintering step is a flash sintering step carried out at high temperature (above 900°C).

[0042] Flash sintering or SPS (from the English "Spark Plasma Sintering") also called FAST sintering (from the English "Field Assisted Sintering Technology") is a powder metallurgy method. This technique is related to HP hot pressing (from the English "Hot Pressing") but what differentiates it is the heating method of the tools containing the material to be sintered. Indeed, in SPS sintering, a pulsed direct current, having a waveform that varies depending on the manufacturer, is applied via electrodes to the tool (die + pistons) containing the material to be densified. This makes it possible to heat the material by Joule effect with temperature rise rates that can reach several hundred degrees C / min.The application of pressure (up to several hundred Mega Pascals under the action of a hydraulic press on the pistons) and ultra-rapid heating thus make it possible to lower sintering temperatures (compared to conventional sintering techniques), to limit reactions / diffusions at the interfaces between materials and to control the microstructures of the materials. In most cases, the tools used are made of graphite and sintering is carried out under an inert atmosphere or under vacuum.

[0043] The surface of the blade tip 2 forms a substrate on which the abrasive outer layer 5 can be deposited directly on the blade tip 1 if the blade tip 1 and the matrix 6 of the abrasive outer layer 5 are made of metal.

[0044] This solution consists of shaping, in a single step, by the flash sintering process, a coating with a multi-layer and functional architecture having an abrasive property due to the inclusions of abrasive particles on the surface or in volume, structural stability and high durability in cyclic oxidation at temperature on a tip of a high-pressure turbine blade composed of a superalloy.

[0045] Alternatively, the deposition method may comprise an initial step of deposition of a metal-based or ceramic-based bonding sub-layer 4 on the surface of the blade tip 2, whether it is made of metal or ceramic.

[0046] The bonding sub-layer 4 is positioned between the surface of the blade tip 2 and the abrasive outer layer 5. Flash sintering is carried out on the entire blade and therefore on the bonding sub-layer 4 and the abrasive outer layer 5.

[0047] If the bonding sub-layer 4 is metallic, the matrix 6 of the abrasive outer layer 5 may be metallic or ceramic.

[0048] If the bonding sub-layer 4 is made of ceramic, the matrix 6 of the abrasive outer layer 5 may be made of ceramic.

[0049] The bonding sub-layer 4, called the bonding sub-layer, can be deposited on the surface of the blade tip 2 by thermal spraying, physical vapor deposition, vapor aluminization, flash sintering, slip deposition followed by a consolidation heat treatment or any other compatible deposition process.

[0050] The thickness of the bonding sub-layer 4 is between 1 μm and 200 μm, preferably between 25 μm and 150 μm.

[0051] The bonding sub-layer 4 allows good adhesion of the upper layers to the surface of the blade tip 2.

[0052] Alternatively, the deposition method comprises at least one step of deposition of an intermediate ceramic layer 3 between the bonding sub-layer 4 and the abrasive external layer 5. The intermediate layer 3 is deposited on the bonding sub-layer 4.

[0053] The intermediate layer 3 also makes it possible to ensure good performance in terms of lifetime in cyclic oxidation and thermal shock.

[0054] The intermediate layer 3 can be deposited by thermal spraying, physical vapor deposition, vapor aluminization, flash sintering, slip deposition followed by a consolidation heat treatment or any other compatible deposition process.

[0055] The intermediate layer 3 has a thickness of between 1 μm and 250 μm, preferably between 50 μm and 150 μm.

[0056] The abrasive particles 7 comprise oxides chosen from a-Al2O3, ZrO2- 4.5 mol% < RE2O3 with RE = Sc, Y, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dyn Ho, Er, Tm and Tb, Y2O3-ZrO2-Ta2O5, Y2O3-ZrO2-Nb2O5, ZrO2-Al2O3, MgAl2 O4 and HfO2- 4.5 mol% < RE2O3with RE = Sc, Y, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dyn Ho, Er, Tm and Tb.

[0057] Alternatively, the abrasive particles 7 comprise non-oxide elements chosen from SiC, Si3N4, ZrC, B4C or a mixture of oxides and non-oxide components.

[0058] The abrasive particles 7 have an acicular (angular and angular) morphological or shape.

[0059] According to one embodiment, the matrix 6 and the abrasive particles 7 are deposited in powder form before flash sintering.

[0060] A first deposition of a powder comprising metal-based or ceramic-based compounds is carried out to form a matrix 6 in the form of a bed or layer of powder and a second deposition of abrasive particle powder 7 is carried out on the layer of powder forming the matrix 6.

[0061] According to one embodiment, the abrasive external layer 5 in powder form is directly deposited in the sintering mold, on the surface of the blade tip 2 delimited by the sintering mold. The sintering mold has dimensions and a geometry adapted to the tip of the turbine blade to be functionalized. The turbine blade is fixed in the sintering mold.

[0062] The beds or layers of powder are deposited successively, in a homogeneous manner in the sintering mold by gravity deposition of the particles using a sieve, manually or automatically, for example.

[0063] The abrasive particles 7 are deposited on the surface of the matrix 6 in the form of a thin layer of oxide having a thickness strictly less than 2 μm in order to maintain chemical and structural stability with the matrix 6 during temperature aging.

[0064] Inclusions of abrasive particles 7 are obtained on the surface of the abrasive outer layer 5.

[0065] The median diameter of the abrasive particles 7 is between 0.1 pm and 400 pm, preferably between 0.1 pm and 250 pm.

[0066] Whatever the nature of the matrix 6 (ceramic or metallic) of the abrasive external layer 5, the powder used must have a fine and tight granulometry in order to promote the embedding and adhesion of the abrasive particles 7 on the surface and in volume.

[0067] The median diameter of the particles of the matrix 6 (ceramic or metallic) is between 0.1 pm and 20 pm, preferably between 0.5 pm and 10 pm.

[0068] The choice of the median diameter of the matrix particles is made taking into account that the ratio between the median diameter of the matrix particles and the median diameter of the abrasive particles must be between 0.002 and 0.4.

[0069] This makes it possible to increase the embedding and adhesion of the abrasive particles 7 in the matrix 6. The use of fine and angular particles further increases the embedding and adhesion.

[0070] The thickness of the matrix 6 containing the inclusions of abrasive particles 7 is selected as a function of the size of the abrasive particles 7 used, more precisely as a function of the median diameter of the abrasive particles 7.

[0071] For the choice of the thickness of the matrix 6, the ratio between the median diameter of the abrasive particles 7 and the thickness of the matrix 6 is taken into account, which must be between 0.6 and 0.9.

[0072] The abrasive outer layer 5 has a thickness of between 3 μm and 400 μm.

[0073] This makes it possible to adapt the thickness of the matrix 6 according to the median diameter of the abrasive particles 7 in order to obtain good durability of the abrasive coating while retaining good abrasive properties.

[0074] According to one embodiment, the abrasive outer layer 5 is obtained by a first deposition of a layer of metal-based or ceramic powder encapsulated in a polymer binder-based matrix by a fused wire deposition process, forming a matrix 6 in the form of a layer of encapsulated powder, and a second deposition of a layer of abrasive particles 7 encapsulated in a polymer binder-based matrix on the matrix 6 in the form of a layer of encapsulated powder by a fused wire deposition process.

[0075] The powders are dispersed and encapsulated in a polymer binder-based matrix which decomposes during heat treatment, during flash sintering, thus releasing the encapsulated particles. This method allows better control of the thickness of the deposited material layer.

[0076] According to another embodiment, the abrasive external layer 5 is obtained by a first deposition by printing of a metal or ceramic-based layer and a second deposition by printing of abrasive particles 7 on the metal or ceramic-based layer.

[0077] The surface coverage rate of the abrasive particles 7 is greater than or equal to 70% of the surface area of the abrasive outer layer 5, greater than or equal to 80% of the surface area of the abrasive outer layer 5, greater than or equal to 90% of the surface area of the abrasive outer layer 5 and even more preferably 100%, after consolidation by the flash sintering process.

[0078] The densification of the surface of the abrasive external layer 5 is greater than 95%, preferably greater than 98%.

[0079] According to another embodiment, the abrasive external layer 5 is obtained by mixing a powder comprising metal-based or ceramic-based compounds intended to form the matrix 6 with a powder of abrasive particles 7 to obtain inclusions of abrasive particles 7 in volume, that is to say inside and on the surface of the matrix 6.

[0080] The mixing of the powders can be carried out by a three-dimensional agitator, such as that of the Turbula® brand, for example.

[0081] The mass loading rate of abrasive particles 7 in the matrix 6 is between 20% and 90% of the total mass, advantageously between 30% and 70% of the total mass.

[0082] The powder mixture is deposited homogeneously in the sintering mold by gravity deposition of the particles using a sieve, manually or automatically, for example.

[0083] Alternatively, the powder mixture is dispersed and encapsulated in a binder / polymer-based matrix and then deposited by a fused deposition process in the sintering mold either directly onto the surface of the blade tip 2 or onto the bonding sub-layer 4.

[0084] The binder / polymer matrix of the abrasive outer layer 5 decomposes during heat treatment during flash sintering, thus releasing the encapsulated particles.

[0085] According to another embodiment, the abrasive external layer 5 is obtained by deposition by printing of a mixture of metal-based or ceramic powder and abrasive particle powder 7 directly onto the surface of the blade tip 2 or onto the bonding sub-layer 4.

[0086] The surface coverage rate of the abrasive particles 7 is greater than or equal to 70% of the abrasive external layer 5 after consolidation by the flash sintering process.

[0087] The densification of the layer having the volume inclusions of abrasive particles is greater than 95%, preferably greater than 98%.

[0088] In the case of a metallic matrix 6 with the inclusions of particles 7, a surface finish by mechanical action (sandblasting) or by chemical attack (dissolution) can be applied in order to bring out the abrasive particles 7 on the surface.

[0089] According to one embodiment, the blade tip is made of metal and composed of a superalloy selected from Ni- or Co-based superalloys, for example. The blade tip may be composed of a low-sulfur AMI superalloy, MC-NG, CMSX4 and derivatives or René and derivatives, for example.

[0090] As stated later, one or more intermediate layers 3 may be deposited on the bonding sub-layer 4.

[0091] Alternatively, the intermediate layers 3 and the bonding sub-layer 4 may be deposited in powder form. A sintering step is preferably carried out for each layer.

[0092] The n intermediate layers 3 may be of the same chemical composition as the bonding sub-layer 4.

[0093] The intermediate layer(s) 3 and the bonding sub-layer 4 may be of metallic type such as an MCrAlY alloy (M=Ni, Co, Ni / Co), a nickel aluminide doped or not with a ternary element (e.g. Pt), a nickel aluminide type [3-NiAl (modified or not with Pt, Hf, Zr, Y, Si or combinations of these elements), an aluminide of y-Ni-y'-NhAl alloys (modified or not with Pt, Cr, Hf, Zr, Y, Si or combinations of these elements), with MAX phases (Mn+iAXn (n=1,2,3) where M = Sc, Y, La, Mn, Re, W, Hf, Zr, Ti; A = groups IIIA, IVA, VA, VIA; X = C,N), for example.

[0094] A first intermediate layer 3 directly covering the bonding sub-layer 4 may comprise a ceramic matrix selected from partially stabilized yttria zirconia, zirconia partially stabilized by one or more rare earths (La->Yb), hafnium partially stabilized by one or more rare earths (La->Yb), yttria zirconia doped with tantalum or niobium.

[0095] The first intermediate layer 3 also makes it possible to ensure good performance in terms of lifetime in cyclic oxidation and thermal shock. The first intermediate layer 3 has a thickness of 1 μm to 1000 μm, preferably of 1 μm to 100 μm.

[0096] The additional intermediate layers with ceramic matrix deposited on the first intermediate layer 3 may be either of the same chemical composition as the first intermediate layer 3, or of different chemical compositions allowing environmental protection against CMAS type oxide deposits (CaO-MgO-Al2O3-SiO2).

[0097] Additional intermediate layers forming environmental protection layers comprise compounds selected from rare earth zirconates RE2Zr2O7 (RE= Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, Lu), partially / fully stabilized and optionally doped zirconias, delta phases A4B30i2 (A = Y —> Lu and B = Zr, Hf), spinels MgAl2O4, composites including Y2O3 with ZrO2 and / or A12O3 and / or TiO2, hexa-aluminates, complex perovskites, spinels, mono- and di-silicates of rare earths (rare earth = Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), as well as any other composition anti-CMAS and mixtures of all of these.

[0098] The flash sintering step is carried out on the entire blade and therefore on the stack of layers formed by the bonding sub-layer 4, the intermediate layer 3 and the abrasive external layer 5.

[0099] In the case of a metal matrix 6 of the MCrAlY type when the surface of the blade tip 2 is nickel-based, the temperature of the furnace in which the flash sintering step is carried out is between 700°C and 1000°C, preferably between 800°C and 900°C. The pressure inside the furnace is between 25 MPa and 125 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes. For this example and the others that follow, the temperature of the furnace corresponds to the temperature to which the blade tip 1 is subjected. Similarly, the pressure inside the furnace corresponds to the pressure applied to the blade tip 1.

[0100] In the case of a ceramic matrix 6 and a blade tip surface 2 based on nickel, the temperature of the furnace in which the flash sintering step is carried out is between 900°C and 1300°C, preferably between 1000°C and 1100°C. The pressure in the furnace is between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes.

[0101] The flash sintering process makes it possible to functionalize the blade tip 2 by the coating with abrasive properties with a very short cycle time (less than 60 minutes) without altering the initial microstructure of the monocrystalline superalloy of the blade tip 2. Examples of embodiments are given below.

[0102] [Fig.l] shows an example of a two-layer stack with a metal matrix based on NiCoCrAlY produced on a blade tip surface 2 made of monocrystalline superalloy AMI BS.

[0103] A bonding sub-layer 4, called an adhesion sub-layer, based on NiCoCrAlY is deposited on the blade tip surface 2 and has a thickness of 80 μm.

[0104] The bonding sub-layer 4 may be deposited by thermal spraying, vapor deposition or flash sintering, for example.

[0105] A matrix 6 based on NiCoCrAlY in powder form and intended to form the abrasive external layer 5 is deposited on the bonding sub-layer 4, by gravity.

[0106] A layer of abrasive particles 7 of Al2O3 in powder form is deposited on the matrix 6 based on NiCoCrAlY, by gravity. The ratio between the median diameter of the abrasive particles 7 and the thickness of the matrix 6 is 0.82, i.e. a thickness of matrix 6 of 192 μm for a median diameter of abrasive particles of 160 μm. The ratio between the median diameter of the particles of the matrix 6 and the median diameter of the abrasive particles 7 is 3.125 x 103.

[0107] An abrasive outer layer 5 is obtained in the form of a stack of powder beds on the blade tip surface 2.

[0108] The flash sintering process is then applied to this stack to form an abrasive external layer 5 comprising surface inclusions of alumina A12O3, as abrasive particles 7.

[0109] [Fig.2] shows an example of a multi-layer stack produced on a blade tip surface 2 made of AMI BS monocrystalline superalloy.

[0110] The multilayer stack comprises a bonding sub-layer 4 based on NiCoCrAlY having a thickness of 80 μm, covered with an intermediate layer 3 made of partially stabilized yttria zirconia having a thickness of 50 μm.

[0111] The bonding sub-layer 4 and the intermediate layer 3 may be deposited by thermal spraying, vapor deposition or flash sintering, for example.

[0112] The multi-layer stack comprises an abrasive outer layer 5 covering the intermediate layer 3. The abrasive outer layer 5 comprises a ceramic matrix 6 based on partially stabilized yttria zirconia (8YPSZ) comprising inclusions of abrasive particles 7 ZrO2-Al2O3 in volume.

[0113] The ceramic matrix 6 based on yttria-containing zirconia in powder form is mixed with the abrasive particles 7 ZrO2-Al2O3 according to the method described above.

[0114] The ratio between the median diameter of the abrasive particles 7 and the thickness of the matrix 6 is 0.77 corresponding to a thickness of matrix 6 of 195 μm for a median diameter of abrasive particles 7 of 150 μm. The ratio between the median diameter of the matrix 6 and the median diameter of the abrasive particles 7 is 4.67.103.

[0115] The flash sintering process is then applied to this stack of layers to form an abrasive outer layer 5 comprising volume inclusions of abrasive particles 7 of ZrO2-Al2O3.

[0116] A thin layer of alumina 8 (e « 0.5 pm) grows between the bonding sub-layer 4 and the intermediate layer 3 of yttria-containing zirconia during the flash sintering process by oxidation of the bonding sub-layer 4.

[0117] [Fig.3] shows another example of a multi-layer stack produced on a blade tip surface 2 made of AMI BS monocrystalline superalloy.

[0118] The multilayer stack comprises a bonding sub-layer 4 based on NiAIPt produced by vapor phase aluminization having a thickness of 30 μm.

[0119] The bonding sub-layer 4 is covered with an intermediate layer 3 of partially stabilized yttria zirconia having a thickness of 146 μm.

[0120] A ceramic matrix 6 based on partially stabilized yttria zirconia (8YPSZ) in powder form and intended to form the abrasive external layer 5 is deposited on the bonding sub-layer 4, by gravity.

[0121] A layer of abrasive particles 7 of SiC in powder form is deposited on the matrix 6, by gravity. The ratio between the median diameter of the abrasive particles and the thickness of the matrix 6 is 0.6 corresponding to a thickness of matrix 6 of 4 μm for a median diameter of abrasive particles 7 of 2.5 μm. The ratio between the median diameter of the particles of the matrix 6 and the median diameter of the abrasive particles 7 is 0.28.

[0122] The flash sintering process is then applied to this stack of layers to form an abrasive outer layer 5 comprising surface inclusions of abrasive particles 7 of SiC.

[0123] A thin alumina layer (e ~ 0.5 pm) grows between the bonding sublayer 4 and the intermediate layer 3 during the flash sintering process by oxidation of the bonding sublayer 4.

[0124] Alternatively, the deposition method can be applied to functionalize turbine blade tips 1 made of CMC ceramic matrix composite (Ceramic Matrix Composite) by coatings with abrasive properties produced by flash sintering.

[0125] The stack of layers comprises a bonding sub-layer 4 which is based on silicon, boron-doped silicon, silicon doped with hafnium oxide or rare earths ((RE = Y, Yb, Gd)) with additions of dopants (Zr, Hf, Ta, N, Al), SiAlON and Si-HfB2, SiC-HfO2 or SiC-HfO2-HfB2.

[0126] The bonding sub-layer 4 is shaped, for example, by physical vapor deposition PVD (Physical Vapor Deposition), atmospheric plasma spraying APS (Atmospheric Plasma Solutions), supersonic flame spraying HVOF (High Velocity Oxygen Fuel), low pressure plasma spraying LPPS (Low Pressure Plasma Spraying) or derivatives, inert atmosphere plasma spraying IPS (Inert Plasma Spraying), chemical vapor deposition CVD (Chemical Vapor Deposition), vapor phase aluminization APVS, electrolytic deposition, slip deposition, sol-gel deposition, flash sintering and any other suitable shaping process.

[0127] The stack of layers comprises one or more intermediate layers 3 called environmental protection layers, deposited on the bonding sub-layer 4, is chosen from rare earth disilicates Re2Si2O7, (Re = RE= Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, Lu) and co-doped, rare earth silicates Re2SiO5 and co-doped, barium and strontium aluminosilicate (BSAS, (BaO)x. (SrO)i_x.Al2O3.2SiO2with 0 < x < 1), hafnium-doped rare earth silicates, rare earth-doped hafnium, mullite, MgAl2O4 spinels, garnets (Y3A150i2), partially / fully stabilized and optionally doped zirconias, A4B3O12 delta phases (A = Y —> Lu and B = Zr, Hf), composites including Y2O3 with ZrO2 and / or A12O3 and / or TiO2, hexa-aluminates, complex perovskites as well as any other environmental barrier composition and mixtures thereof. The latter is made by flash sintering or any other deposition process identical to those used for the bonding sub-layer 4, as described previously.

[0128] The intermediate layer 3 has a thickness of between 1 μm and 1000 μm.

[0129] The stack of layers comprises an abrasive outer layer 5 comprising a matrix 6 and abrasive particles 7 included in the matrix 6 on the surface and / or in volume.

[0130] Flash sintering is applied to the abrasive outer layer 5 to obtain an abrasive coating having a thickness of between 3 μm and 400 μm.

[0131] The ceramic matrix 6 integrating the abrasive particles 7 is based on particles described previously for the case of a tip of the blade 2 made of metal.

[0132] The abrasive particles 7 are identical to those described for the tips of the metal blade 1.

[0133] The different methods of application (in the form of powder, encapsulated powder or printing layer) and of production of this functional abrasive external layer 5 in terms of matrix thickness 6, size of abrasive particles 7, chemical compositions of abrasive particles 7, inclusions of particles 7, among others, are identical to those described previously in the case of application to tips of metallic blades 1.

[0134] For consolidation by flash sintering, the temperature of the furnace into which the blade is introduced with its blade tips 1 covered with the stacks of layers, is between 900°C and 1500°C, preferably between 1200°C and 1400°C. The pressure in the furnace is between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa. The cycle time is between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes.

[0135] The various preceding variants describe examples in which the abrasive external layers 5 are directly deposited on the surface of the blade tip 2 or on a bonding sub-layer 4 with a metallic or ceramic base previously deposited on the surface of the blade tip 2 or an intermediate layer 3. A single flash sintering step is carried out on the stack of layers comprising the abrasive external layer 5.

[0136] Alternatively, the abrasive outer layer 5 is preformed in a preforming mold.

[0137] The deposition method then comprises a step of depositing a metal-based or ceramic-based matrix 6 in a preforming mold and a step of depositing a layer of abrasive particles 7 for inclusion of the abrasive particles 7 on the surface of the matrix 6. The preforming mold is adapted to the dimensions and geometry of the tip of the blade 2 to be functionalized.

[0138] Alternatively, the powder constituting the matrix 6 and the powder of abrasive particles 7 can be mixed and deposited in the preforming mold for inclusion of the abrasive particles 7 in volume, inside the surface of the matrix 6.

[0139] The matrix 6 and the layer of abrasive particles 7 may be in the form of powder or powder encapsulated in a polymer binder-based matrix by a fused deposition process or be formed from printed layers.

[0140] A preliminary flash sintering step is performed on the abrasive outer layer 5 in the preforming mold to obtain a preformed abrasive outer layer.

[0141] The preformed abrasive outer layer is then deposited in the sintering mold, on the surface of the blade tip 2, before the flash sintering step of the preformed abrasive outer layer.

[0142] As in the previous examples, the surface of the blade tip 2 may be covered by a metal-based or ceramic-based bonding sub-layer 4 previously deposited on the surface of the blade tip 2 and as described previously. The bonding sub-layer 4 may also be covered by an intermediate layer 3.

[0143] The preformed abrasive outer layer and the other layers possibly deposited on the surface of the blade tip 2 undergo a second flash sintering during the flash sintering step to form the final abrasive coating.

[0144] Alternatively, when the blade tip 1 is metallic, the abrasive outer layer 5 can be preformed on a bed of nickel-based superalloy powder of the same chemical composition as the blade tip 1.

[0145] The superalloy powder bed is then previously deposited in the preforming mold before the deposition of the abrasive external layer 5 by the different methods and in the different forms previously described. The thickness of the nickel-based superalloy powder bed is between 0.5 mm and 5 mm.

[0146] The preliminary flash sintering step is applied to the superalloy powder bed and the abrasive outer layer 5 to obtain a preformed coating comprising a superalloy-based layer covered by a preformed abrasive outer layer.

[0147] The preformed coating is deposited on the surface of the blade tip 2 and undergoes a second flash sintering during the flash sintering step to form the final abrasive coating.

[0148] Alternatively, the abrasive outer layer 5 may be preformed by a first flash sintering on a nickel-based superalloy substrate of the same chemical composition as the superalloy of the blade tip 1 in a preforming mold adapted to the dimensions and geometry of the blade tip 1 to be functionalized.

[0149] The superalloy substrate is machined to the dimensions and geometry of the blade tip 1 to be functionalized. The minimum thickness of the superalloy substrate is between 0.5 mm and 5 mm.

[0150] When the blade tip 1 is made of ceramic, the substrate is made of ceramic and is machined to the dimensions and geometry of the blade tip 1 to be functionalized. The minimum thickness of the ceramic substrate is between 0.5 mm and 5 mm.

[0151] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0152] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

Claims

1. Method for depositing an abrasive coating on a blade tip (1) of an aircraft turbine, the blade tip being made of metal or ceramic, characterized in that it comprises: - a step of positioning a sintering mold on the blade tip (1), - a step of covering a surface of the blade tip (2) delimited by the sintering mold with an abrasive external layer (5) comprising a matrix (6) based on metal or ceramic and abrasive particles (7), and - a sintering step carried out on the abrasive external layer (5) to form a blade tip (1) covered by the abrasive coating.

2. Method according to claim 1, characterized in that the abrasive outer layer (5) is obtained by a first deposition of a layer of powder based on metal or ceramic to form a matrix (6) in the form of a layer of powder and a second deposition of a layer of powder of abrasive particles (7) on the matrix (6).

3. Method according to claim 1, characterized in that the abrasive outer layer (5) is obtained by a first deposition of a layer of metal or ceramic based powder encapsulated in a polymer binder based matrix by a fused wire deposition process to form a matrix (6) in the form of encapsulated powder and a second deposition of a layer of abrasive particles (7) encapsulated in a polymer binder based matrix on the matrix (6) by a fused wire deposition process.

4. Method according to claim 1, characterized in that the abrasive external layer (5) is obtained by a first deposition by printing of a metal or ceramic-based layer to form a printed matrix (6) and a second deposition by printing of abrasive particles (7) on the printed matrix (6).

5. Method according to claim 1, characterized in that the abrasive outer layer (5) is obtained by mixing a powder of abrasive particles (7) with a matrix (6) of a metal or ceramic-based powder.

6. Method according to any one of claims 1 to 5, characterized in that the abrasive external layer (5) is directly deposited on the surface of the blade tip (2) or on a bonding sub-layer (4) with a metallic or ceramic base previously deposited on the surface of the blade tip (2) or on an intermediate layer (3) with a metallic or ceramic base deposited between the bonding sub-layer (4) and the abrasive external layer (5).

7. Method according to any one of claims 1 to 5, characterized in that it comprises before the step of covering a surface of the blade tip (2) with the abrasive outer layer (5), a step of depositing the abrasive outer layer (5) in a preforming mold, a preliminary flash sintering step carried out on the abrasive outer layer (5) to form a preformed abrasive outer layer and a step of depositing the preformed abrasive outer layer in the sintering mold, the sintering step being carried out on the preformed abrasive outer layer.

8. Method according to any one of claims 1 to 7, characterized in that the ratio between the median diameter of the abrasive particles (7) and the thickness of the matrix (6) is between 0.6 and 0.9, the abrasive external layer (5) having a thickness between 3 pm and 400 pm.

9. Method according to any one of claims 1 to 8, characterized in that the ratio between the median diameter of the particles of the matrix (6) and the median diameter of the abrasive particles (7) is between 0.002 and 0.

4.

10. Method according to any one of claims 1 to 9, characterized in that the sintering step is a flash sintering step, when the matrix (6) is metallic and the surface of the blade tip (2) is nickel-based, the temperature of the furnace in which the flash sintering step is carried out is between 700°C and 1000°C, preferably between 800°C and 900°C, the pressure inside the furnace being between 25 MPa and 125 MPa, preferably between 50 MPa and 100 MPa, the cycle time being between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes.

11. Method according to any one of claims 1 to 9, characterized in that the sintering step is a flash sintering step, when the matrix (6) is made of ceramic matrix (6) and the surface of the blade tip (2) is nickel-based, the temperature of the furnace in which the flash sintering step is carried out is between 900°C and

12.

13. 1300°C, preferably between 1000°C and 1100°C, the pressure in the furnace being between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa, the cycle time being between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes. Method according to any one of claims 1 to 9, characterized in that the sintering step is a flash sintering step, when the matrix (6) and the surface of the blade tip (2) are made of ceramic, the temperature of the furnace in which the flash sintering step is carried out is between 900°C and 1500°C, preferably between 1200°C and 1400°C, the pressure in the furnace being between 25 MPa and 150 MPa, preferably between 50 MPa and 100 MPa, the cycle time being between 1 minute and 60 minutes, preferably between 5 minutes and 10 minutes. Aircraft turbine blade comprising at least one blade tip (1), characterized in that the blade tip (1) comprises an abrasive coating obtained by the method as defined according to any one of claims 1 to 12.

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