Method of manufacturing an abradable coating, abradable coating and coated part

Abstract

Method for manufacturing an abradable coating, abradable coating and coated part Method for manufacturing an abradable ceramic composite coating on a substrate, comprising: obtaining (E1) a powder composition (30) comprising a matrix powder and a hydrated ceramic filler precursor powder having a lamellar crystallographic structure, the ceramic filler powder representing 5 to 40% of the combined volume of the matrix powder and the ceramic filler powder, compressing the prepared powder composition at a pressure greater than 150 MPa, and a reactive sintering step (E2) of the obtained powder composition, during which the compression is maintained, at a temperature less than 550°C and the particles of the matrix powder in the sintered powder composition have a form factor greater than or equal to 2. Abradable ceramic coating obtained according to the method.Superalloy part for a turbomachine, for example a turbine, comprising such a coating. Figure for abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing an abradable coating, abradable coating and coated part Technical field

[0001] The present disclosure relates to a method of manufacturing an abradable layer and a substrate coated with this layer.

[0002] Such an abradable layer can in particular be used to equip a rotating machine ring in order to ensure the sealing of the machine at the top of the rotating blades for example. Such an abradable layer is particularly suitable for equipping turbine rings in the aeronautical field, and particularly in aircraft turbojets. Prior art

[0003] Abradable seals are currently used in gas turbines to minimize functional clearance, and therefore leaks, between rotating parts (e.g. rotor blades) and static parts (e.g. ring sectors). In high-pressure turbines, the abradable seals are deposited on the ring sectors, forming a substrate, attached to the casing. When the turbine blades come into contact with the abradable seal, the latter should wear out as a priority, which would allow the aerodynamic performance of the engine to be maintained.

[0004] However, it is also preferable to protect the ring sectors from high temperatures, which can reach 1600°C, and from erosion by the flow of gas emerging at high temperature and pressure. With this in mind, a ceramic or refractory metal-based coating is usually formed by thermal spraying on the ring sectors, to form a thermal barrier type protective coating. However, the coatings thus obtained may not have very high abradability, which can lead to wear of the blade tips during operation, resulting in complex and costly repairs.

[0005] In order to increase the abradable nature of thermal barriers, various solutions have been considered in the state of the art. In this respect, mention may be made of the incorporation of porogenic agents in order to increase the porosity rate of the barrier. These solutions may however not be entirely satisfactory because they may lead to significantly degrading the erosion resistance of the coating and therefore the lifetime of the barrier and the underlying substrate.

[0006] Another solution, presented in patent application FR 3 044 945, uses flash sintering, usually called Spark Plasma Sintering (SPS) in English, in order to generate abradable coatings having gradients of properties, with notably a lower porosity rate at the edges of the coating in order to better resist erosion. However, although offering good results, this solution requires special preparation of the substrate. Generally speaking, this type of sintering involves temperatures above 1000°C. This is called solid-state sintering.

[0007] Yet another solution, presented in patent application FR 3 082 765, uses yttria-containing zirconia powders with different form factors. However, this solution results in relatively high porosity rates, between 30 and 50%, such that even higher erosion resistance is desired for certain particularly demanding applications. Furthermore, this type of solution involves sintering the yttria-containing zirconia at temperatures above 1000°C.

[0008] There is therefore a need to provide an abradable layer as well as a method of manufacturing this layer having both good abradability and good resistance to erosion. Statement of the invention

[0009] The present disclosure relates to a method for manufacturing an abradable ceramic composite coating on a substrate, comprising: obtaining a powder composition comprising a matrix powder and a hydrated ceramic filler precursor powder, the filler content of the mixture being between 5 and 40%, compressing the powder composition obtained at a pressure greater than 150 MPa, and a step of reactive sintering of the powder composition obtained, during which the compression is maintained, at a temperature less than 550°C, and the particles of the matrix powder in the sintered powder composition have a form factor greater than or equal to 2.

[0010] In this disclosure, the term "reactive sintering" refers to sintering in which the sintered material undergoes a chemical reaction. Typically, the sintered material may undergo dehydration.

[0011] In the present disclosure, the form factor corresponds to the number average value of the following ratio R calculated for each particle of a given set of particles, with R denoting the ratio [largest dimension of the particle] / [largest transverse dimension of the particle]. If the particle is a fiber, the form factor can be calculated by the ratio [length of the fiber] / [diameter of the fiber].

[0012] It is understood that the form factor is measured after compression of the powder composition. The form factor is measured from images of the abradable coating obtained by scanning electron microscope.

[0013] In this disclosure, the term "filler rate" is defined as the volume percentage of the ceramic filler precursor powder in its form dehydrated referred to the total combined volume of the matrix powder and the ceramic filler precursor powder in its dehydrated form. In other words, the hydrated ceramic filler powder is added to the mixture in such a way as to obtain a desired loading rate, calculated for a corresponding dehydrated ceramic filler. The hydration rate is taken into account in this calculation to determine the volume of ceramic filler precursor in its dehydrated form, given the volume of the hydrated precursor. The hydration rate of the ceramic filler can be measured by thermogravimetric analysis, for example. Here, the loading rate is between 5 and 40%.

[0014] In the present disclosure, the ceramic filler precursor designates the chemical species which, once sintered, transforms into ceramic filler.

[0015] In the present disclosure, the expression “hydrated precursor powder” designates a powder comprising within it either chemisorbed water molecules (for example hydrates such as LaPO4xH2O), or hydroxyl groups (for example Zr(OH)4).

[0016] The use of the powdery composition as previously described, as well as the use of a pressure sintering technique, advantageously makes it possible to obtain a layer having both good abradability and good resistance to erosion. In addition, the inventors have found that the abradable layers formed by reactive sintering under pressure at a relatively low temperature (for example less than 500°C) have better resistance to erosion compared to the layers formed by solid-state sintering at an equal porosity rate, or even, in certain cases, if the porosity rate is higher. This is then referred to as low-temperature sintering.

[0017] In this disclosure, the erosion of an abradable coating is evaluated according to ASTM G76.

[0018] Furthermore, the use of a hydrated ceramic filler precursor makes it possible to broaden the ranges in which the sintering parameters are acceptable and make it possible to obtain a satisfactory abradable coating. This latitude gained by the operator allows more room for the latter to optimize the abradable coating for precise use.

[0019] In addition, the ceramic filler powder makes it possible to fill part of the macroporosities obtained in the ceramic matrix at the end of the sintering step. This results in a lower porosity rate, which provides better resistance to erosion.

[0020] The present method also has advantages related to the low temperatures it involves, as opposed to the temperatures involved in known methods. Indeed, temperatures below 550°C make it possible, firstly, to reduce the impact of differences in thermal expansion and degradation of one component compared to another, for example. This therefore facilitates the development of coatings for potentially multi-layered, and increases chemical adhesion at the interfaces of such coatings. Secondly, the use of low temperatures has an intrinsic economic interest since it simplifies the implementation of the process while being up to ten times less energy-intensive than with the use of high temperatures.

[0021] In certain embodiments, the sintering step comprises a temperature increase at a rate of between 10°C / min and 100°C / min, followed by a hold during which the temperature is kept constant for 1 to 30 minutes.

[0022] In this configuration, the reactivity of the hydrated precursor is optimized.

[0023] In some embodiments, the hydrated ceramic filler precursor powder comprises hydrated lanthanum phosphate and / or zirconium hydroxide.

[0024] In some embodiments, the matrix powder comprises yttria-stabilized zirconia.

[0025] The use of yttrium-stabilized zirconia (or YSZ) has a double advantage. Indeed, it has good chemical stability at high temperatures and low thermal conduction, which makes YSZ suitable for use as a thermal barrier. On the other hand, YSZ has good mechanical properties and in particular good resistance to erosion.

[0026] In some embodiments, the charge rate is between 10% and 35%.

[0027] Such a charge rate makes it possible, in the case of a lanthanum precursor, to fill the porosity of the matrix while limiting the percolation of the latter, which could unduly increase the microhardness of the final coating. Furthermore, in the case of a zirconium precursor, such a loading rate makes it possible to limit the appearance of possible solid inclusions of the load in the matrix.

[0028] In certain embodiments, the compression of the powdery composition takes place at a pressure of between 200 and 400 MPa.

[0029] This pressure range makes it possible to guarantee satisfactory sintering at low temperature while limiting the breakage of the matrix fibers.

[0030] In some embodiments, the hydrated ceramic filler precursor comprises hydrated lanthanum phosphate and wherein the sintering temperature is less than 500°C.

[0031] Such a sintering temperature makes it possible to limit the crystallization of LaPO4xH2O into anhydrous LaPO4, which gives better properties to the coating obtained.

[0032] In some embodiments, the hydrated ceramic filler precursor comprises zirconium hydroxide and wherein the sintering temperature is less than 400°C.

[0033] Such a temperature makes it possible to limit the rapid crystallization of ZrO2, which gives better properties to the resulting coating.

[0034] In certain embodiments, obtaining the powdery composition comprises mixing the matrix powder and the hydrated ceramic filler precursor powder by dry means, preferably for at least one hour.

[0035] In certain embodiments, the powdered composition undergoes grinding which makes it possible to homogenize the distribution of the fiber sizes contained in the ceramic matrix powder.

[0036] In some embodiments, the sintering step is performed by flash sintering.

[0037] In this configuration, the microstructure of the abradable obtained can be controlled. more precisely.

[0038] The present disclosure further relates to an abradable ceramic coating obtained according to the method of one of the preceding aspects, the coating having a volume rate of open porosity of between 10% and 40%, preferably between 15% and 30%, and a Vickers microhardness of between 0.1 and 3 GPa.

[0039] In this disclosure, porosity is measured according to ISO 5017:2013.

[0040] In some embodiments, the abradable ceramic coating comprises a matrix and ceramic fillers having a lamellar or pyrochlore crystallographic structure.

[0041] The present disclosure also relates to a superalloy part for a turbomachine, for example a turbine, comprising a coating according to the preceding aspect. The substrate, such as a ring sector, may be made of nickel alloy.

[0042] The above-mentioned characteristics and advantages, as well as others, will appear on reading the detailed description which follows, of exemplary embodiments of the proposed device and method. This detailed description refers to the attached drawings. Brief description of the drawings

[0043] The attached drawings are schematic and are intended primarily to illustrate the principles of the disclosure.

[0044] [Fig-1] [Fig.l] illustrates schematically, in section and in perspective, a part of a stator ring according to one embodiment of the invention.

[0045] [Fig.2A-2B] Figures 2A and 2B schematically illustrate the embodiment of an example of a method according to an embodiment of the invention.

[0046] [Fig.3] [Fig.3] schematically illustrates a method according to the embodiment of the invention.

[0047] [Fig.4A-4B] Figures 4A-4B represent an example of pressure evolution compression and temperature during the manufacture of the abradable layer according to the method of the embodiment of the invention.

[0048] [Fig.5] [Fig.5] represents the evolution of porosity and microhardness in function of the loading rate, for a YSZ / LaPO4 composite coating manufactured at a sintering temperature of 350°C.

[0049] [Fig.6] [Fig.6] represents the evolution of porosity and microhardness as a function of the loading rate, for a YSZ / Zr(OH)4 composite coating manufactured at a sintering temperature of 350°C.

[0050] [Fig.7] [Fig.7] represents the evolution of porosity and microhardness as a function of the pressure applied during sintering, for a YSZ / LaPO4 composite coating manufactured at a sintering temperature of 350°C.

[0051] [Fig.8] [Fig.8] represents the evolution of porosity and microhardness as a function of the pressure applied during sintering, for a YSZ / Zr(OH)4 composite coating manufactured at a sintering temperature of 350°C.

[0052] [Fig.9] [Fig.9] represents the evolution of porosity and microhardness as a function of the maximum sintering temperature, for a YSZ / LaPO4 composite coating. Description of the embodiments

[0053] In order to make the disclosure more concrete, an example of a method is described in detail below, with reference to the attached drawings. It is recalled that the invention is not limited to this example.

[0054] [Fig.l] schematically illustrates a stator ring, which is divided into several sectors each comprising a substrate 10 coated with an abradable layer 12.

[0055] An exemplary embodiment of the abradable layer 12 will be described in connection with FIGS. 2A, 2B and 3. FIGS. 2A and 2B schematically illustrate the embodiment of an exemplary method according to the invention, while [Fig. 3] schematically illustrates the progress of this method.

[0056] The method comprises obtaining E1 of a powdery composition 30 and a reactive sintering step E2 of the prepared powdery composition 30.

[0057] The substrate 10 to be coated is placed in the cavity of a mold 20. The powdery composition 30 is then deposited on a surface S of the substrate 10. As shown in FIG. 2B, the mold 20 is then closed, for example by a cover 25. A bearing face of its cover 25 is applied against the layer of powdery composition 30 so as to compress the latter on the substrate 10. The compression pressure applied to the powdery composition 30 may be a uniaxial pressure. The thickness of the layer of powdery composition 30 is thus reduced due to the compression between the substrate 10 and the cover 25: the powdery composition 30 is compacted. The powdery composition 30 undergoing compression is then sintered. For example, a flash sintering technique (“SPS”) can be used to produce the abradable layer 12. The abradable layer 12 is obtained following this sintering step E2.

[0058] In the example illustrated, the abradable layer 12 obtained has a substantially uniform density. Alternatively, abradable layers with variable density could be formed, for example by following the principles described in patent application FR 3 044 945.

[0059] In the present example, it is described that the abradable layer 12 is directly formed on the substrate 10 from the powder composition 30 previously deposited on the substrate 10. In a variant not illustrated, the abradable layer 12 can first be formed on a support separate from the substrate 10 by implementing the pressure sintering method which has been described above. According to this variant, the abradable layer 12 thus formed is then separated from the support to be positioned on the surface S of the substrate 10. This abradable layer 12 thus positioned is then secured to the surface S of the substrate 10 in order to obtain the coated substrate. This securing can be carried out by brazing, sintering or using added elements (bolting for example).

[0060] The abradable layer 12 formed is particularly suitable for equipping high or low pressure turbine rings or compressor rings, for example in the aeronautical field, and particularly in aircraft turbojets.

[0061] Various details relating to the substrate 10, to the powder composition 30 and to the operating parameters which can be imposed during the process will now be described.

[0062] The substrate 10 may be made of metallic material, for example a superalloy. When the substrate 10 is made of metallic material, the latter may for example be formed from one of the following commercial materials: “AMI” alloy, “C263” alloy or “M509” alloy (the trademarks in quotation marks being registered).

[0063] Alternatively, the substrate 10 may be made of ceramic matrix composite (CMC) material. In this case, the substrate 10 may comprise a woven fibrous reinforcement, formed of carbon or silicon carbide fibers, densified by a ceramic matrix, comprising for example silicon carbide.

[0064] To improve the adhesion of the abradable layer 12 to the substrate 10, the substrate 10 may be coated with a bonding layer (not shown) that the abradable layer 12 is intended to coat. In the case of a metal substrate 10, it is possible, for example, to use an MCrAlY bonding layer, for example a CoNiCrAlY bonding layer. In the case of a CMC substrate, it is possible to use a mullite bonding layer, for example.

[0065] Regarding the powdery composition 30, it comprises ceramic particles and an inorganic filler.

[0066] In the present embodiment, the ceramic particles, forming a powder, are made of yttria zirconia (YSZ). This powder is intended, after sintering, to form the coating matrix, which is why we speak of ceramic matrix powder. Other examples of ceramic powder can be used, for example zirconia co-doped with a transition metal or a lanthanide (dysprosium, scandium, hafnium, tantalum, lanthanum, etc.).

[0067] In other examples, these particles are fibrous: they then have variable form factors, between 2 and 30, preferably between 2 and 25.

[0068] The fibrous particles may have an average diameter in the non-agglomerated state (or average width) greater than or equal to 6 μm, for example between 6 μm and 8 μm. The fibrous particles may have an average length greater than or equal to 15 μm, for example between 15 μm and 300 μm, it being understood that the average shape factor of the fibrous particles remains greater than or equal to 2.

[0069] The fibrous particles that can be used in the context of the disclosure may correspond to those described in patent application FR 3 082 765.

[0070] The hydrated precursor of inorganic filler is typically a powder of hydrated lanthanum phosphate LaPO4.xH2O capable of forming, once sintered, an anhydrous lanthanum phosphate filler LaPO4 of lamellar structure or a powder of zirconium hydroxide Zr(OH)4 capable of forming a zirconium oxide filler ZrO2. Such powders are known in themselves and generally marketed directly in a hydrated phase, for example by the companies Alfa-Aesar ® or Merck ®.

[0071] Subsequently, we describe the method for manufacturing the abradable coating by taking the example of lanthanum phosphate as an inorganic filler. However, this description applies mutatis mutandis to any other hydrated inorganic filler, in particular to zirconium hydroxide. Other hydrated precursors may be considered as hydrates or precursors comprising hydroxyl groups. Among the hydrates, the following may be considered: hydrated phosphate, hydrated carbonate or hydrated sulfate.

[0072] The powdery composition 30 is then obtained by mixing the ceramic powder with this hydrated inorganic powder. The inorganic powder loading rate in the powdery composition 30 can theoretically be between 1 and 75%; however, the best results are obtained for a volume content of inorganic powder between 10 and 40%. This is supported by the comparative tests discussed below.

[0073] The powdery composition 30 then undergoes a dry mixing step using a three-dimensional dynamic mixer, for example a mixer marketed under the Turbula brand by the company WAB. The duration of this mixing step may be between 5 minutes and 4 hours, for example between 30 minutes and 2 hours.

[0074] Various details relating to the substrate 10 and to the powdery composition 30 have just been described. We will now describe details relating to the abradable layer 12 which can be obtained as well as to the operating conditions which can be implemented.

[0075] Modifying the temperature imposed during sintering, the duration of sintering and / or the compression pressure applied makes it possible to vary the volume porosity rate of the abradable layer 12 obtained. Generally speaking, increasing the temperature, the duration of sintering and / or the compression pressure thus makes it possible to reduce the volume porosity rate of the abradable layer 12. Thus, the volume porosity rate of the abradable layer 12 may be between 5% and 50%, for example between 15% and 40%, for example between 25% and 35% or even between 25% and 30%.

[0076] Figures 4A-4B show a possible example of the evolution of the compression pressure and the temperature during the manufacture of the abradable layer 12.

[0077] The assembly of the substrate 10 and the powdery composition 30 is initially brought to a first temperature T1, for example between 25 and 50°C. While the assembly is brought to this first temperature T1, the compression pressure increases until it reaches, at a first instant t1, a plateau at a value Pc which corresponds to the compression pressure which will be applied during the sintering of the powdery composition 30.

[0078] The compression pressure Pc imposed on the powder composition 30 during sintering may be between 150 and 600 MPa, for example between 150 MPa and 400 MPa or between 250 MPa and 500 MPa. The compression pressure Pc is maintained throughout the sintering of the powder composition 30.

[0079] From the first instant t1 the temperature imposed on the substrate 10 and on the powder composition 30 is increased up to the sintering temperature Tf. The temperature reaches the sintering temperature Tf at a second instant t2 and is then maintained at this value. The sintering temperature Tf depends on the nature of the powder composition 30 used. This sintering temperature Tf can be between 150°C and 550°C, for example between 100°C and 300°C.

[0080] The sintering temperature Tf and the compression pressure Pc are maintained until the third instant t3. The sintering duration (t3-t2) may be greater than or equal to 1 minute, for example between 1 and 30 minutes. Once the sintering is complete, the compression pressure and the temperature are gradually reduced and the substrate 10 coated with the abradable layer 12 is then recovered and / or created.

[0081] In the illustrated example, a first temperature rise rate is imposed up to the sintering temperature Tf. By way of illustration, the first temperature rise rate may be greater than or equal to 10°C / minute. The temperature rise rate may be constant or variable.

[0082] By way of non-limiting example, the sintering can be carried out by flash sintering with a compression pressure Pc of 400 MPa, a sintering temperature Tf of 350°C, and a duration of 10 minutes.

[0083] Comparative tests - YSZ / LaPCh

[0084] [Fig.5] represents the evolution of porosity and microhardness as a function of the loading rate, for a YSZ / LaPO4 composite coating manufactured at a sintering temperature of 350°C.

[0085] Generally, it is observed that the porosity decreases in a substantially linear manner when the loading rate increases. Furthermore, for a loading rate between 5 and 40%, it is observed that the porosity is between 20 and 30%.

[0086] Generally, it is observed that the microhardness increases when the filler rate increases. A more pronounced increase is noted for a filler rate greater than 30%. Indeed, in the area where the filler rate is less than 30%, the filler only partially fills the macroporosity generated by the matrix. The microhardness of the abradable is then close to the microhardness of the matrix. For a filler rate greater than 30%, the filler particles percolate into the porous network of the matrix, which significantly increases the microhardness. As a result, the resistance to erosion increases.

[0087] [Fig.7] represents the evolution of porosity and microhardness as a function of the pressure applied during sintering, for a YSZ / LaPO4 composite coating at 20% loading rate manufactured at a sintering temperature of 350°C.

[0088] Generally, it is observed that porosity decreases when pressure increases. Conversely, microhardness increases when pressure increases. These changes are explained by a particulate rearrangement of the filler particles to form denser networks when pressure increases.

[0089] [Fig.9] represents the evolution of porosity and microhardness as a function of the sintering stage temperature, for a YSZ / LaPO4 composite coating at 20% loading rate manufactured at a pressure of 400 MPa.

[0090] Generally, it is observed that the porosity is relatively little dependent on the sintering temperature. Conversely, it is observed that the microhardness increases progressively when the sintering temperature increases, and increases sharply above 350°C. This progressive evolution is due to the crystallization of the anhydrous lanthanum phosphate from the hydrated precursor.

[0091] Comparative tests - YSZ / ZrOH4

[0092] [Fig.6] represents the evolution of porosity and microhardness as a function of the loading rate, for a YSZ / Zr(OH)4 composite coating manufactured at a sintering temperature of 350°C.

[0093] Generally, it is observed that the porosity decreases significantly. linear when the loading rate increases. Furthermore, for a loading rate between 5 and 40%, we observe that the porosity is between 20 and 25%.

[0094] Generally, it is observed that the microhardness increases when the filler rate increases. A more pronounced increase is noted for a filler rate between 5% and 10%. Indeed, in this range, the filler partially fills the macroporosity generated by the matrix, which significantly increases the microhardness. As a result, the erosion resistance increases. In other words, the microhardness of the composite is close to the microhardness of the matrix. For a filler rate greater than 10% (and less than 50%), the filler agglomerates form solid inclusions in the matrix, which limit the porosity-filling effect. As a result, the increase in Vickers microhardness is less marked, and may even decrease.

[0095] [Fig.8] represents the evolution of porosity and microhardness as a function of the pressure applied during sintering, for a YSZ / Zr(OH)4 composite coating at 20% loading rate manufactured at a sintering temperature of 350°C.

[0096] Generally, it is observed that porosity decreases when pressure increases. Conversely, microhardness increases when pressure increases. These changes are explained by a particulate rearrangement of the filler particles to form denser networks when pressure increases.

[0097] [Fig.9] represents the evolution of porosity and microhardness as a function of the sintering temperature, for a YSZ / Zr(OH)4 composite coating at 20% load rate manufactured at a pressure of 400 MPa.

[0098] Generally, it is observed that the porosity is relatively little dependent on the sintering temperature. Conversely, it is observed that the microhardness increases when the sintering temperature increases, and increases sharply above 350°C. This behavior above 350°C is due to the crystallization of monoclinic zirconium oxide from amorphous zirconium hydroxide.

[0099] Without being bound by theoretical conditions, the inventors identified three zones delimited by the maximum temperature experienced by the powdery composition during the sintering step, hereinafter called sintering temperature. a. At a sintering temperature below 250°C, a small proportion of zirconium hydroxide gradually dehydrates. The abradable layer formed then comprises a matrix and a partially hydrated amorphous filler. Such an abradable layer has a low microhardness. b. At sintering temperatures between 250°C and 400°C, a large proportion of the amorphous filler Zr(OH)4 crystallizes into the harder monoclinic oxide ZrO2. Consequently, the microhardness increases. c. For a sintering temperature above 400°C, all the amorphous ceramic filler precursor Zr(OH)4 is transformed very quickly into a monoclinic phase ZrO2. A mesoporosity then appears. The appearance of this mesoporosity leads to a slight decrease in the Vickers microhardness despite the crystallization of the ceramic filler ZrO2.

[0100] Other tests show that the abradable layers obtained by the method make it possible to obtain, during an abradability test, almost zero wear of blades placed opposite such abradable layers. Furthermore, the erosion resistance of the abradable layers obtained by the method of the invention is better compared to known abradable layers. Indeed, the abradable layers obtained by the method of the invention have an erosion resistance up to 60 times greater than known abradable layers.

[0101] In these present examples it appears that the charge rate and the sintering parameters can be optimized in order to lower the porosity rates, while maintaining coatings whose microhardness is between 0.1 and 3 GPa. In such a situation, the abradability and the erosion resistance of the coating obtained is improved.

[0102] Although the present invention has been described with reference to specific 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, the description and the drawings should be considered in an illustrative rather than restrictive sense.

[0103] 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. A method of manufacturing an abradable ceramic composite coating on a substrate, comprising: obtaining (E1) a powder composition (30) comprising a matrix powder comprising a zirconia co-doped with a transition metal or a lanthanide and a hydrated precursor powder of a ceramic filler comprising a hydrate or a hydroxyl group, the filler content of the mixture being between 5 and 40%, compressing the powder composition (30) obtained at a pressure greater than 150 MPa, and a reactive sintering step (E2) of the powder composition (30) obtained, during which the compression is maintained, at a temperature less than 550°C, and the particles of the matrix powder in the sintered powder composition have a form factor greater than or equal to 2.

2. A method according to claim 1, wherein the sintering step (E2) comprises a temperature increase at a rate of between 10°C / min and 100°C / min, followed by a plateau during which the temperature is kept constant for 1 to 30 minutes.

3. A method according to either of claims 1 or 2 wherein the hydrated ceramic filler precursor powder comprises hydrated lanthanum phosphate and / or zirconium hydroxide.

4. A method according to one of claims 1 to 3, wherein the matrix powder comprises yttrium oxide stabilized zirconia.

5. Method according to one of claims 1 to 4, in which the charge rate is between 10% and 35%.

6. Method according to one of claims 1 to 5, in which the compression of the powdery composition (30) takes place at a pressure of between 200 and 400 MPa.

7. A method according to any one of claims 1 to 6, wherein the hydrated ceramic filler precursor comprises hydrated lanthanum phosphate and wherein the sintering temperature is less than 500°C.

8. A method according to any one of claims 1 to 7, wherein the hydrated ceramic filler precursor comprises zirconium hydroxide and wherein the sintering temperature is less than 400°C.

9. Method according to one of claims 1 to 8, in which the obtaining (El) of a powdery composition (30) comprises a mixture of the matrix powder and ceramic filler powder by dry method, preferably for at least one hour.

10. Method according to one of claims 1 to 9, in which the sintering step is carried out by flash sintering.

11. Abradable ceramic coating (12) obtained according to the method of one of the preceding claims, the coating (12) having a volume rate of open porosity of between 10% and 40%, preferably between 15% and 30%, and a Vickers microhardness of between 0.1 and 3 GPa.

12. Superalloy part for a turbomachine, for example a turbine, comprising a coating according to claim 11.

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