A component comprising a substrate and an environmental barrier, and associated processes

Abstract

Component comprising a substrate and an environmental barrier and associated methods. The invention relates to a component (1) comprising a substrate (3), at least a portion of which, adjacent to a surface of the substrate, is made of a silicon-containing material, and an environmental barrier (2) formed on the surface of the substrate (3), the environmental barrier (2) comprising at least three superimposed regions (7, 9, 11) each comprising a distinct rare-earth silicate and rare-earth oxide, each rare-earth oxide being capable of producing a distinct color upon irradiation by light of a predetermined wavelength. Figure for the abstract: Fig. 1

Description

Title of the invention: Part comprising a substrate and an environmental barrier and associated processes. Technical field

[0001] The present invention relates to the protection of a substrate, at least a portion of which is adjacent to a substrate surface and is made of a silicon-containing material, during use at high temperatures in an oxidizing environment, by implementing an environmental barrier on the substrate surface. The invention particularly proposes an environmental barrier whose state can be easily monitored, so as to provide reliable information on the remaining thickness of the protective material.

[0002] A particular field of application of the invention is the protection of ceramic matrix composite (CMC) material parts forming hot parts of gas turbines, such as combustion chamber walls, or turbine rings, turbine distributors or turbine blades, for aeronautical engines or industrial turbines. Previous technique

[0003] For such gas turbines, the concern to improve efficiency and reduce pollutant emissions leads to considering ever higher temperatures in the combustion chambers.

[0004] It has therefore been proposed to replace metallic materials with CMC materials, particularly for combustion chamber walls or turbine rings. Indeed, CMC materials are known to possess both good mechanical properties, allowing their use for structural elements, and the ability to retain these properties at high temperatures. CMC materials comprise a fibrous reinforcement of refractory fibers, typically carbon or ceramic, which is densified by a ceramic matrix, for example, silicon carbide (SiC).

[0005] Under the operating conditions of aircraft turbines, i.e., at high temperature in an oxidizing and humid atmosphere, CMC materials are susceptible to corrosion. CMC corrosion results from the oxidation of SiC to silica, which, in the presence of water vapor, volatilizes as silicon hydroxide, Si(OH)4. Corrosion causes the CMC to shrink and affects its service life. To limit this degradation during operation, it has been considered to form environmental barrier coatings on the surface of the CMC materials. Such coatings may include a a silicon bonding layer and one or more rare-earth silicate layers positioned on the bonding layer. These coatings are, for example, known from WO 2018 / 127664.

[0006] The bonding layer serves, on the one hand, to improve the adhesion of the rare-earth silicate layer and, on the other hand, to form a protective silica layer, whose low oxygen permeability contributes to protecting the CMC against oxidation. The rare-earth silicate layer, in turn, limits the diffusion of water vapor towards the silica layer formed by silicon oxidation and consequently limits its recession. However, the rare-earth silicate layer itself can be susceptible to recession and can evaporate during operation. It can also undergo erosion or be damaged by thermomechanical effects.

[0007] Environmental barriers are regularly inspected during their manufacture, assembly, or maintenance to verify whether the part can be used as is. However, this inspection can be relatively difficult to perform, particularly in the case of environmental barriers deposited by electrophoresis, which have relatively thin thicknesses that can be difficult to measure in their aged state, or even in their new state.

[0008] It is therefore desirable to provide an environmental barrier whose condition can be easily monitored, in particular to provide reliable information on the remaining thickness of protective material. Description of the invention

[0009] According to a first aspect thereof, the invention proposes a part comprising a substrate, at least a portion of which adjacent to a surface of the substrate is made of a material containing silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier comprising at least three superimposed regions which each comprise a distinct rare earth silicate and a distinct rare earth oxide, each rare earth oxide being capable of producing a distinct color upon irradiation by light radiation of a predefined wavelength.

[0010] The invention provides a component whose environmental barrier state can be easily monitored by observing the color(s) following irradiation by light radiation. The light radiation can be ultraviolet (wavelength between 100 nm and 400 nm) or visible (wavelength between 400 nm and 800 nm). The color of all or part of the rare-earth oxides can result from a luminescence phenomenon, for example, phosphorescence or fluorescence.

[0011] Using at least three environmental barrier regions, each producing a different color, allows for obtaining relatively precise information on the remaining environmental barrier thickness. Indeed, if we consider an environmental barrier with three regions, having a first region located on the substrate side, a second region overlapping the first region, and a third region overlapping the first and second regions and located on the opposite side from the substrate, observing the color of the rare earth oxide in the third region, within the control zone, allows us to deduce that the thickness of the first and second regions has not been consumed and that at least a fraction of the thickness of the third region remains.Observation of the color of the rare earth oxide in the second region allows us to conclude that the third region has disappeared, at least locally, and observation of the color of the rare earth oxide in the first region allows us to conclude that the second and third regions have disappeared, at least locally.

[0012] According to a particular characteristic, the distinct rare earth oxides are each chosen from: erbium oxide, neodymium oxide, praseodymium oxide, dysprosium oxide, samarium oxide, or europium oxide.

[0013] Such a configuration makes it easier to control the color through the use of rare-earth oxides that produce distinct colors. For example, erbium oxide is pinkish, neodymium oxide is blue-gray, and praseodymium oxide is green. Dysprosium, samarium, and europium oxides can produce phosphorescent colors.

[0014] According to a particular characteristic, each rare earth oxide is present in a mass content of between 1% and 5% in the corresponding environmental barrier region.

[0015] Such a mass content of rare earth oxide makes it easier to detect without affecting the barrier effect to oxidizing species.

[0016] According to a particular characteristic, each rare earth silicate is an yttrium silicate, an ytterbium silicate, or a mixture of yttrium silicate and ytterbium silicate.

[0017] According to a particular feature, each superimposed region has a thickness less than or equal to 20 pm, for example less than or equal to 10 pm. Each superimposed region may have a thickness between 5 pm and 20 pm or between 5 pm and 10 pm.

[0018] The invention is of particular interest in the case of such relatively thin regions for which a direct thickness measurement can be tricky as indicated above.

[0019] According to a particular feature, the part further comprises a bonding zone containing silicon, the bonding zone being intercalated between the substrate and the environmental barrier.

[0020] Such a bonding zone facilitates the adhesion of the stack of superimposed regions to the substrate and makes it possible to create an additional region of protection of the substrate against oxidation.

[0021] According to another aspect, the invention proposes a method for manufacturing a part according to the invention, comprising: - the deposition of a precursor from each of the regions onto the substrate by electrophoresis, and - the joint sintering of the precursors thus deposited in order to obtain the environmental barrier.

[0022] Such a manufacturing process makes it possible to obtain a homogeneous layer and avoids the formation of interfaces. Consequently, it is possible to limit the risk of spalling of the final part. Furthermore, performing a single step of joint sintering the precursors of each of the superimposed regions makes the process more economical and faster than those of the prior art. The use of electrophoresis in the process makes it possible to obtain superimposed regions with a controlled thickness on the micrometer scale.

[0023] According to a particular feature, the substrate can be coated with a bonding zone containing silicon, on which the precursor of each of the regions is deposited by electrophoresis.

[0024] According to another aspect, the invention proposes a method for monitoring the state of an environmental barrier of a part according to the invention, comprising: - irradiating the environmental barrier with light radiation of a predefined wavelength such that at least one of the rare earth oxides produces a color, and - observation of the colour(s) produced in order to control the state of the environmental barrier.

[0025] Thus, it is possible to determine in a simple and quick way the protective capacity of the environmental barrier.

[0026] According to another aspect, the invention proposes a method for repairing a part according to the invention whose environmental barrier has at least one damaged area that exhibits a lack of material, comprising: - the deposition of a precursor of at least one of the three superimposed regions on the substrate by electrophoresis so as to fill said at least one damaged area, and - sintering the precursor thus deposited with the rest of the environmental barrier so as to obtain the repaired environmental barrier.

[0027] Such a process allows for rapid and targeted repair of the damaged region or regions of the environmental barrier.

[0028] According to a particular feature, the process may further comprise the deposition of a conductive layer in said at least one damaged area, and in which the precursor of at least one of the three superimposed regions is deposited by electrophoresis on the conductive layer.

[0029] The repair described above can be implemented after carrying out the barrier condition check described above if a damaged area is identified following observation of the color(s) produced during irradiation. Brief description of the drawings

[0030] Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate an example of an embodiment without any limiting character.

[0031] [Fig-1] [Fig.1] illustrates, schematically, a part according to a first mode of the realization of the invention,

[0032] [Fig.2] Fig.2 is a flowchart showing the steps implemented to to make the part illustrated in [Fig.1],

[0033] [Fig.3] [Fig.3] illustrates, schematically, the part of [Fig.1] after a damage to the environmental barrier,

[0034] [Fig.4] Fig.4 is a flowchart showing the steps implemented to to control the state of the environmental barrier of a room according to the invention,

[0035] [Fig.5] Fig.5 is a flowchart showing the steps implemented to repair the part in [Fig.3],

[0036] [Fig. A] [Fig. A] illustrates, schematically, the implementation of step E30 of the process of [Fig. 5],

[0037] [Fig.ôB] [Fig.ôB] illustrates, schematically, the part obtained before the execution of step E40 of the process of [Fig.5]. Detailed description of the implementation methods

[0038] In the detailed description that follows, the formation of an environmental barrier on a silicon-containing CMC material substrate is considered. However, the invention is applicable to substrates made of monolithic refractory material containing silicon and, more generally, to substrates in which at least a portion adjacent to an external surface of the substrate is made of a refractory material (composite or monolithic) containing silicon. Thus, the invention is particularly aimed at protecting refractory materials made of monolithic ceramics, for example silicon carbide (SiC) or silicon nitride (Si3N4), but more particularly at protecting refractory composite materials such as silicon-containing ceramic matrix composites (CMCs), for example CMCs with a matrix at least partially composed of SiC.

[0039] Figure 1 shows a part 1 formed of a substrate 3 provided with an environmental barrier 2 according to a first embodiment of the invention. The surface S of the substrate 3 is formed of a refractory material containing silicon.

[0040] The silicon-containing CMC material substrate 3 comprises a fibrous reinforcement which may be made of carbon fibers (C) or ceramic fibers, for example, SiC fibers or fibers essentially composed of SiC, including Si-C-0 or Si-CON fibers, i.e., also containing oxygen and possibly nitrogen. Such fibers are produced by Nippon Carbon under the reference "Nicalon" or "Hi-Nicalon" or "Hi-Nicalon Type-S", or by Ube Industries under the reference "Tyranno-ZMI". The ceramic fibers may be coated with a thin interphase layer of pyrolytic carbon (PyC), boron nitride (BN), or boron-doped carbon (BC, with 5 at.% to 20 at.% B, the remainder being C).

[0041] The fibrous reinforcement is densified by a matrix which is formed, in its entirety or at least in an external phase thereof, by a silicon-containing material, such as a silicon compound, for example SiC or a Si-BC ternary system. By external matrix phase, we mean a matrix phase formed last, furthest from the reinforcement fibers. Thus, the matrix can be formed of several phases of different natures, and can, for example, be: - a mixed C-SiC matrix (with the SiC on the outer side), or - a sequenced matrix with alternating SiC phases and lower rigidity matrix phases, for example pyrolytic carbon (PyC), boron nitride (BN) or boron-doped carbon (BC), with a terminal SiC matrix phase, or - a self-healing matrix with boron carbide (B4C) matrix phases or in a Si-BC ternary system, possibly with free carbon (B4C + C, Si-BC + C), and with a Si-BC or SiC terminal phase.

[0042] The matrix can be at least partially formed by CVI in a manner known per se. Alternatively, the matrix can be at least partially formed by liquid process (impregnation with a matrix precursor resin and transformation by crosslinking and pyrolysis, the process being repeatable) or by molten silicon infiltration (the "Melt-Infiltration" process). In the latter case, a powder is introduced into the possibly partially densified fibrous reinforcement; this powder may be carbon powder and possibly ceramic powder, and a molten silicon-based metallic composition is then infiltrated to form a SiC-Si type matrix.

[0043] The environmental barrier 2 is formed over the entire external surface S of the substrate 3 or over only a part of this surface S, for example when only a part of the surface S needs to be protected. In the example illustrated in [Fig. 1], the environmental barrier 2 comprises a first region 7, a second region 9, a third region 11, and a bonding zone 5. The bonding zone 5 is present between the substrate 3 and the first region 7. In the illustrated example, the bonding zone 5 is present in contact with the external surface S of the substrate 3. Furthermore, in this example, the first region 7 is in contact with the bonding zone 5.

[0044] The first region 7 comprises a first rare-earth silicate and a first rare-earth oxide. The first region 7 may comprise the first rare-earth silicate in a mass content of between 95% and 99%, and the first rare-earth oxide in a mass content of between 1% and 5%. The first rare-earth oxide may be present as a dopant in the first region 7.

[0045] In particular, and with the inevitable impurities excepted, the first region 7 comprises only the first rare earth silicate and the first rare earth oxide.

[0046] The first rare earth silicate can be a rare earth disilicate of general formula REa2Si2O7 or a rare earth monosilicate of general formula REa2SiO5, where REa is a rare earth element, advantageously it is a rare earth disilicate.

[0047] The first rare earth silicate may be an yttrium silicate, an ytterbium silicate, or a mixture of yttrium silicate and ytterbium silicate.

[0048] The first rare-earth oxide may have the general formula REb2O3, where REb is a rare-earth element. REb may be different from REa. REb may be chosen from erbium Er, neodymium Nd, praseodymium Pr, dysprosium Dy, samarium Sm, and europium Eu.

[0049] The first rare earth oxide is capable of producing a first color when irradiated by light radiation of predefined wavelength.

[0050] The thickness ei of the first region 7 can for example be less than or equal to 20pm.

[0051] The second region 9 covers the first region 7. The second region 9 may be in contact with the first region 7.

[0052] The second region 9 comprises a second rare-earth silicate and a second rare-earth oxide. The second region 9 may comprise the second rare-earth silicate in a mass content of between 95% and 99%, and the second rare-earth oxide in a mass content of between 1% and 5%.

[0053] The second rare earth silicate may be identical or different from the first rare earth silicate.

[0054] The second rare earth oxide is different from the first rare earth oxide.

[0055] The second rare earth oxide may be present as a dopant in the second region 9. In particular and with the inevitable impurities aside, the second region 9 comprises only the second rare earth silicate and the second rare earth oxide.

[0056] The second rare-earth silicate may be a rare-earth disilicate of general formula REc2Si2O7 or a rare-earth monosilicate of general formula REc2SiO5, where REC is a rare-earth element, advantageously a rare-earth disilicate. REc may be the same as or different from REa.

[0057] The second rare earth silicate may be an yttrium silicate, an ytterbium silicate, or a mixture of yttrium silicate and ytterbium silicate.

[0058] The second rare-earth oxide may have the general formula REd2O3, where REd is a rare-earth element. REd may be different from REC. REd is different from REb.

[0059] REd can be selected from erbium Er, neodymium Nd, praseodymium Pr, dysprosium Dy, samarium Sm and europium Eu.

[0060] The second rare earth oxide is capable of producing a second color when irradiated by light of a predefined wavelength. The second color is distinct from the first color.

[0061] The thickness e2 of the second region 9 can for example be less than or equal to 20pm.

[0062] The third region 11 covers the second region 9. The third region 11 may be in contact with the second region 9. The second region 9 may be intercalated between the first region 7 and the third region 11.

[0063] The third region 11 comprises a third rare-earth silicate and a third rare-earth oxide. The third region 11 may comprise the third rare-earth silicate in a mass content of between 95% and 99%, and the third rare-earth oxide in a mass content of between 1% and 5%.

[0064] The third rare earth silicate may be identical or different from the first rare earth silicate and / or the second silicate.

[0065] The third rare earth oxide is different from the first rare earth oxide and the second rare earth oxide.

[0066] The third rare earth oxide may be present as a dopant in the third region 11. In particular, and with the inevitable impurities aside, the third region 11 comprises only the third rare earth silicate and the third rare earth oxide.

[0067] The third rare-earth silicate may be a rare-earth disilicate of general formula REe2Si2O7 or a rare-earth monosilicate of general formula REe2SiO5, where REe is a rare-earth element, advantageously a rare-earth disilicate. REe may be the same as or different from REa and / or REC.

[0068] The third rare earth silicate may be an yttrium silicate, an ytterbium silicate, or a mixture of yttrium silicate and ytterbium silicate.

[0069] The third rare-earth oxide may have the general formula REf2O3, where REf is a rare-earth element. REf may be different from REe. REf is different from REb and REd.

[0070] REf can be selected from erbium Er, neodymium Nd, praseodymium Pr, dysprosium Dy, samarium Sm and europium Eu.

[0071] The third rare-earth oxide is capable of producing a third color when irradiated by light of a predefined wavelength. The third color is distinct from the first and second colors.

[0072] The thickness e3 of the third region 11 can for example be less than or equal to 20pm.

[0073] The number of regions is not a limitation of the invention. In an embodiment other than the one illustrated, the number of regions may be greater than three.

[0074] The bonding zone 5 comprises silicon and may, for example, be made of silicon, mullite (3Al2O3.2SiO2), or a silicon-containing alloy such as a metallic silicide like yttrium silicide. The bonding zone 5 can, in a manner known per se, form a protective, passivating layer of silica during operation ("Thermally Grown Oxide"). The bonding zone 5 facilitates the adhesion of regions 7, 9, and 11 to the substrate 3. An electrically conductive bonding zone 5 is preferred if the environmental barrier is formed by electrophoresis, but this region 5 may be insulating, for example made of mullite, if the barrier is formed by another technique such as thermal spraying.

[0075] The presence of the bonding zone 5 is not limiting to the invention. In an embodiment other than the one illustrated, the part 1 may be devoid of a bonding zone 5. This is particularly the case when the external surface S of the substrate 3 is electrically conductive (if it includes, for example, free silicon).

[0076] Figure 2 illustrates an example of an embodiment of the method according to the invention for manufacture part 1.

[0077] The process may include in a first step En of the formation of a bonding zone 5 which here constitutes an adhesion layer, as illustrated in [Fig.1].

[0078] The presence of step En is not limiting to the invention. In an embodiment other than the one illustrated, the process does not include step En-

[0079] The process includes in a second step Eb the deposition of a precursor of the first region 7 of the environmental barrier 2. For this, the substrate is introduced into a first bath comprising the material constituting the precursor of the first region 7.

[0080] Next, the process is followed by a third step E2 of depositing a precursor of the second region 9 of the environmental barrier 2 onto the precursor of the first region 7. The substrate obtained in step Eb is then introduced into a second bath comprising the constituent material of the precursor of the second region 9.

[0081] The process is then followed by a fourth step E3 of depositing a precursor of the third region 11 of the environmental barrier 2 onto the precursors of the first 7 and second 9 regions. For this, the substrate obtained in step E2 is introduced into a third bath comprising the constituent material of the precursor of the third region IL

[0082] Each of the deposits made during steps Eb E2 and E3 can be carried out by electrophoresis. In this case, the deposition of a precursor from each of the regions 7, 9, 11 can be performed on an electrically conductive surface defined by the external surface S of the substrate 3 or can be performed on an electrically conductive surface defined by a bonding zone 5 containing silicon present on the substrate 3. The kinetics of the electrophoretic deposition decrease as the thickness of the precursor increases. The insulating character of the barrier is only obtained after sintering, which allows the sequential deposition of the precursor from each of the regions 7, 9, 11 by electrophoresis.

[0083] This allows control over the thickness of the deposited layers. Indeed, electrophoresis has the advantage of allowing the deposition of very thin layers, namely layers of a few tens of micrometers.

[0084] In the example illustrated in [Fig.1], the bonding zone 5 facilitates the adhesion of the stack of superimposed regions and conducts electricity during electrophoretic deposition.

[0085] The precursors of regions 7, 9 and 11 can be deposited in powder form.

[0086] The sequence of steps EB E2 and E3 allows the barrier to be manufactured environmental in a simple and quick way.

[0087] Once the precursors of the three regions of the environmental barrier have been deposited, part 1 is subjected to a joint sintering step E4. This step allows the transformation of the precursors of each of the regions respectively into the first, second and third regions 7, 9 and 11. In addition, this helps to limit the risk of spalling of each region of the environmental barrier 2.

[0088] By way of example, sintering can be carried out at a temperature between 1250 °C and 1350 °C and for a duration between 5 hours and 50 hours.

[0089] Sintering can be carried out under ambient air.

[0090] The preceding description relates to the case where the regions are formed by electrophoresis followed by joint sintering, but a person skilled in the art will recognize that other deposition techniques can be used to obtain the environmental barrier to at least three regions as described above.

[0091] Each of the first, second, and third regions 7, 9, and 11 of the fabricated environmental barrier 2 comprises a rare earth oxide that produces a distinct color when exposed to light of a predefined wavelength. In other words, when the surface of the first region 7 is irradiated, the first rare earth oxide in that region will produce a first color. When the surface of the second region 9 is irradiated, the second rare earth oxide in that region will produce a second color. When the surface of the third region 11 is irradiated, the third rare earth oxide in that region will produce a third color. The first, second, and third colors are distinct from one another. This allows, as explained above, for control of damage to the environmental barrier.

[0092] Once manufactured, the part can be used at a temperature greater than or equal to 800°C in an oxidizing and humid atmosphere.

[0093] The part thus manufactured may be a part for an aeronautical or aerospace application. The part may be a hot section component of a gas turbine in an aeronautical or aerospace engine or of an industrial turbine. The part may be a turbomachine component. The part may constitute at least part of a distributor, at least part of a nozzle or a heat protection coating, a combustion chamber wall, a turbine ring sector, or a turbomachine blade.

[0094] Figure 3 shows a part 1 comprising a damaged environmental barrier 2.

[0095] The environmental barrier 2 has a damaged area 8. The damaged area 8 may have at least one adjacent undamaged area. In the example shown in [Fig. 2], the damaged area 8 is located between two adjacent undamaged areas 10a and 10b. The damaged area 8 is generated here by the absence of the third region 11 in said area. In other words, in the damaged area 8, part 1 lacks the third region 11 of the environmental barrier 2.

[0096] An example of an embodiment has been shown where the damaged environmental barrier 2 has a single damaged area 8 to be repaired, but it does not fall outside the scope of the present invention if the damaged environmental barrier has a plurality of damaged areas.

[0097] The damage was detected by implementing a method for checking the condition of an environmental barrier of part 1 shown schematically in [Fig.4].

[0098] The process comprises, in a first step Ei00, irradiating the environmental barrier 2 with light radiation having a predefined wavelength. The light radiation may be ultraviolet or a visible radiation. The first irradiation stage EiOo can be carried out on all or part of the surface of part 1.

[0099] The process is continued by a second step of observing the color or colors E2oo, produced by the rare earth oxides present in the regions of part 1. The E2Oo observation step can be carried out with the naked eye or with the aid of a colorimeter.

[0100] The observation of at least one color during the second step E2Oo may be due to a luminescence phenomenon. Indeed, during the first irradiation step EiOo, the rare-earth oxide present on the surface of the irradiated region is electronically excited. After irradiation, the rare-earth oxide transitions from the excited state to its ground state. The energy loss associated with this transition is emitted in the form of a photon, observable at a predefined wavelength.

[0101] When the environmental barrier 2 of part 1 is not damaged or when at least a fraction of the thickness e3 of the third region 11 remains, only the color of the rare earth oxide present in the third region is observed during the E2Oo step.

[0102] When the environmental barrier 2 of part 1 is damaged, as illustrated for example in [Fig.3], the color of several rare earths can be detected.

[0103] When the surfaces S10 of the undamaged areas 10a and 10b are irradiated during the first step Ei00, the color of the rare earth oxide present in the third region 11 is observed at the second step E2Oo.

[0104] When the surface S 8 of the damaged area 8 is irradiated in the first step En”, the color of the rare earth oxide of the second region 9 is observed in the second step E200. This is due to the disappearance of the third region 11 of the environmental barrier 2, in the damaged area 8.

[0105] This makes it possible to determine the damaged areas in the environmental barrier 2 so that they can be repaired. Furthermore, it makes it possible to identify the depth of the damaged area, in order to determine the number of deposits required to repair it.

[0106] Figure 5 shows an example of the implementation of a repair process for part 1.

[0107] The process includes a step of depositing a precursor of the third region E30 in the damaged area 8. The E30 step may be preceded by a step of depositing an electrically conductive layer, such as a thin platinum layer. This is particularly the case when the step of depositing a precursor of the third region E30 is carried out by electrophoresis.

[0108] The process is then followed by a sintering step E40. Sintering makes it possible to obtain the third repaired region.

[0109] When part 1 lacks the second region 9 in the damaged area, the step of deposition of the precursor of the third region E30 is preceded by a step of deposition of a precursor of the second region E20, and joint sintering can then be carried out to obtain the repaired second and third regions. The E20 step may be preceded by a step of deposition of an electrically conductive layer, such as a thin platinum layer. This is particularly the case when the step of deposition of a precursor of the second region E20 is carried out by electrophoresis.

[0110] When part 1 lacks the first region 7, in the damaged area 8, the process further includes a step of depositing a precursor of the first region Ei0, and joint sintering can then be carried out to obtain the repaired regions. The Ei0 step precedes steps E20 and E30. In this case, the deposition of a precursor of each of the regions 7, 9, 11 can be carried out on an electrically conductive surface defined by the external surface S of the substrate 3 or can be carried out on an electrically conductive surface defined by a silicon-containing bonding zone 5 present on the substrate 3.

[0111] According to an embodiment not shown, when the part 1 lacks the second region 9 and / or the third region 11, the process may include a step of thermally or mechanically stripping the remaining region(s), namely the third region or the second and third regions. The stripping step then precedes the deposition steps E10, E20, and E30. The deposition of a precursor of each of the regions 7, 9, 11 may be carried out on an electrically conductive surface defined by the external surface S of the substrate 3 or may be carried out on an electrically conductive surface defined by a silicon-containing bonding zone 5 present on the substrate 3.

[0112] Each step of deposition of a precursor Ei0, E20, E30 can be carried out by electrophoresis. The sintering step can be as described above.

[0113] Figure [Fig. A] shows the implementation of step E30 of deposition of a precursor of the third region 11 in the damaged area 8. As illustrated, the part 1 bearing the damaged thermal barrier 2 is present in an electrolyte 20 comprising a suspension of particles 21 of the material constituting the third region in a liquid medium.

[0114] The part 1 coated with the damaged thermal barrier 2 constitutes an electrode of the electrophoresis system opposite which is present a counter electrode 30.

[0115] During the deposition step of the precursor of the third region E30, in the damaged area 8, a generator G imposes a potential difference between the part 1 and the counter electrode 30. The generator G is either direct current or pulsed. The part 1 is polarized to a charge opposite to that of the particles 21. Due to the application of an electric field between the part 1 and the counter electrode 30, the particles 21 move and are deposited on the part 1 to form a coating comprising the precursor of the third region 11. In this example, the E30 step is preceded by a step of deposition of an electrically conductive layer, such as a thin platinum film (not shown).

[0116] As illustrated in [Fig. B], during step E30, the precursor 22 of the third region 11 is deposited only in the damaged area 8. The thickness of the deposit made during this step corresponds to the thickness e3 of the third region 11.

[0117] The deposition of the precursor of the third region 11 in the damaged area 8 induces a progressive decrease in the electrical conductivity of this area over time.

[0118] When the process includes steps Ei0 and E20, these are carried out in a similar manner.

[0119] An example of an embodiment is shown where the damaged environmental barrier 2 has a single damaged area 8 to be repaired, but this does not depart from the scope of the present invention if the damaged environmental barrier has a plurality of damaged areas to be repaired. In this case, each of the damaged areas to be repaired is electrically conductive.

Claims

Demands

1. Part (1) comprising a substrate (3), at least a portion of which adjacent to a surface of the substrate is made of a silicon-containing material, and an environmental barrier (2) formed on the surface of the substrate (3), the environmental barrier (2) comprising at least three overlapping regions (7, 9, 11) each comprising a distinct rare earth silicate and rare earth oxide, each rare earth oxide being capable of producing a distinct color upon irradiation by light of a predetermined wavelength.

2. A piece according to claim 1, wherein the distinct earth oxides are each selected from: erbium oxide, neodymium oxide, praseodymium oxide, dysprosium oxide, samarium oxide, or europium oxide.

3. Part according to claims 1 or 2, wherein each rare earth oxide is present in a mass content of between 1% and 5% in the corresponding environmental barrier region.

4. A component according to any one of claims 1 to 3, wherein each rare earth silicate is yttrium silicate, ytterbium silicate, or a mixture of yttrium silicate and ytterbium silicate.

5. Part according to any one of claims 1 to 4, wherein each overlapping region (7, 9, 11) has a thickness (eb e2, e3) less than or equal to 20pm.

6. Part according to any one of claims 1 to 5, further comprising a bonding zone (5) containing silicon, the bonding zone (5) being intercalated between the substrate (3) and the environmental barrier (2).

7. A method for manufacturing a part according to any one of claims 1 to 6, comprising: - the deposition of a precursor from each of the regions (7, 9, 11) onto the substrate (3) by electrophoresis, and - the joint sintering of the precursors thus deposited in order to obtain the environmental barrier (2).

8. A method according to claim 7, wherein the substrate (3) is coated with a bonding zone (5) containing silicon, on which the precursor of each of the regions (7, 9, 11) is deposited by electrophoresis.

9. A method for checking the condition of an environmental barrier (2) of a part (1) according to any one of claims 1 to 6, comprising: - irradiating the environmental barrier (2) with light of predefined wavelength so that at least one of the rare earth oxides produces a color, and - observing the color or colors produced in order to check the condition of the environmental barrier (2).

10. A method for repairing a part according to any one of claims 1 to 6 having an environmental barrier (2) having at least one damaged area (8) which has a lack of material, comprising: - the deposition of a precursor of at least one of the three superimposed regions (7, 9, 11) on the substrate by electrophoresis so as to fill said at least one damaged area (8), and - the sintering of the precursor thus deposited with the remainder of the environmental barrier (2) so as to obtain the repaired environmental barrier.

11. A method according to claim 10, wherein the method further comprises the deposition of a conductive layer in said at least one damaged area (8), and wherein the precursor of at least one of the three superimposed regions (7, 9, 11) is deposited by electrophoresis on the conductive layer.

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