MELTSAND-RESISTANT AEROSPACE PART

Description

FIELD OF THE INVENTION

[0001] The invention relates to an aeronautical part, such as a turbine blade or a distributor vane for example, used in aeronautics. STATE OF THE ART

[0002] In a turbojet engine, the exhaust gases generated by the combustion chamber can reach high temperatures, above 1200°C, or even 1600°C. A part of the turbojet engine, in contact with these exhaust gases, such as a turbine blade for example, must therefore be able to maintain its mechanical properties at these high temperatures. In addition, corrosion and / or oxidation of the part's substrate is encouraged by these high temperatures.

[0003] For this purpose, it is known to protect the part against excessively high temperatures, oxidation and / or corrosion, by covering it with an environmental barrier.

[0004] There figure 1schematically illustrates a section of a known turbine part 1, for example a turbine blade 6 or a nozzle vane. The part 1 comprises a substrate 2, for example made of a single-crystal metal superalloy. The substrate 2 is covered with a coating, for example an environmental barrier 3.

[0005] There figure 2schematically illustrates a section of the known turbine part 1. The part 1 comprises the substrate 2 covered with the environmental barrier 3. The environmental barrier 3 typically comprises a sub-layer 4, a protective layer 5 and a thermally insulating layer 7. The sub-layer 4 covers the substrate 2. The sub-layer 4 is covered by the protective layer 5, formed for example by oxidation of the sub-layer 4. The protective layer 5 makes it possible to protect the substrate 2 from corrosion and / or oxidation. The thermally insulating layer 7 covers the protective layer 5. The thermally insulating layer 7 may be made of ceramic, for example yttria-containing zirconia.

[0006] The environmental barrier 3 degrades particularly when exposed to sand particles (for example inorganic compounds such as silica) or more generally to oxides of calcium, magnesium, aluminum and / or silicon, the acronym of which is CMAS. The CMAS have a lower melting temperature than the materials of the environmental barrier 3, and can thus infiltrate in a molten state into the environmental barrier 3 during use of the part 1, particularly in the interstices of the environmental barrier 3. The infiltration of the CMAS into the environmental barrier 3 causes the environmental barrier 3 to stiffen, which can lead to its mechanical rupture under the conditions of use of the turbine. The infiltration of the CMAS also leads to a dissolution of the thermally insulating layer 7 by chemical reaction between the CMAS(s) and the thermally insulating layer 7.

[0007] In reference to the figure 3 and to the figure 4 , one or more CMAS 8 compounds may infiltrate into the interstices of the thermally insulating layer 7, causing the thermally insulating layer 7 to stiffen.

[0008] In reference to the Figure 5 and to the figure 6 , the thermally insulating layer 7 can be chipped and broken by an insertion of CMAS compounds 8 during the use of the part 1, and for example be detached from the underlayer 4.

[0009] Levi et al.(Levi, CG, Hutchinson, JW, Vidal-Sétif, MH, & Johnson, CA (2012). Environmental degradation of thermal-barrier coatings by molten deposits. MRS bulletin, 37(10), 932-941) describes the use of a part 1 coated with rare earth zirconate, such as Gd 2 Zr 2 O 7 (GZO). Upon contact with CMAS, the rare earth zirconate is dissolved, and precipitates on the one hand into a fluorite phase Zr(Gd,Ca)O x and on the other hand into a very stable apatite phase Ca 2 Gd 8 (SiO 4 ) 6 O 2 . These precipitations cause the interstices between the different columns of GZO and / or the thermally insulating layer 7 to be blocked and a diffusion barrier to be formed, making it possible to slow down the dissolution rate of the columns of GZO and / or the thermally insulating layer 7.

[0010] In contrast, the precipitation of molten CMAS, described by Levi et al.,clogs the gaps when the CMAS has entered the gaps of the GZO and / or the thermally insulating layer 7, resulting in deterioration of the mechanical properties of the environmental layer 3.

[0011] For example, a reactive layer of lanthanum zirconate (La 2 Zr 2 O 7 ) can also be deposited on a turbine part. When the reactive layer comes into contact with molten CMAS, part of the reactive layer is dissolved, and the reaction between the reactive layer and the CMAS produces an apatite phase of Ca 2 La 8 (SiO 4 ) 6 O 2 . Cracks appear in the reactive layer, resulting in areas of the part that are not protected from the CMAS.

[0012] US 2016 / 011589 describes a reactive layer comprising an anti-CMAS coating comprising an oxide having an orthorhombic lattice structure, making it possible to prevent the infiltration of molten CMAS into the environmental barrier.

[0013] US2017 / 022113A1 and EP3178799A1 disclose the use of an oxide of formula RE2TiO5 (RE= Y, Yb) in thermal protection coatings intended for turbine parts. STATEMENT OF THE INVENTION

[0014] One aim of the invention is to increase the resistance of an aeronautical part to CMAS compounds.

[0015] Another aim of the invention is to propose a coating allowing an aeronautical part to resist CMAS compounds different from a coating known from the prior art.

[0016] Another aim of the invention is to propose a coating enabling an aeronautical part to resist CMAS compounds and having adjustable mechanical and / or chemical properties.

[0017] These aims are achieved within the framework of the present invention thanks to an aeronautical part, comprising: a substrate, an environmental barrier comprising at least one layer chosen from a thermally insulating layer, an underlayer adapted to promote adhesion between the substrate and a thermally insulating layer and a protective layer adapted to protect the substrate from oxidation and / or corrosion, the environmental barrier at least partially covering the substrate, at least one reactive layer adapted to react with at least one CMAS compound chosen from a calcium oxide, a magnesium oxide, an aluminum oxide and a silicon oxide, the reactive layer covering at least part of the environmental barrier, characterized in that the material of the reactive layer comprises at least one oxide of formula A' 4-x HAS" x B' 2-y B" y O 11-δ , A' being chosen from a rare earth, yttrium and scandium, A" being chosen from a rare earth, yttrium, scandium and aluminum, B' being chosen from tantalum and niobium, B" being chosen from tantalum, niobium, zirconium, hafnium, aluminum and caesium, x and y being real numbers between 0 and 2 and δ being a real number between -1 and 2, and preferably between -1 and 1.

[0018] The invention is advantageously supplemented by the following characteristics, taken individually or in any of their technically possible combinations: the oxide has a predominantly cubic lattice by volume, the oxide has a rare earth atomic fraction of between 18% and 24%, A' and A" are the same element, A' and A" being chosen from a rare earth, scandium and yttrium and preferably, A' and A" are an element chosen from the lanthanides, B' and B" are the same element, B' and B" being chosen from tantalum and niobium, the oxide is suitable for forming at least one precipitate comprising apatite and / or anorthite in contact with a CMAS compound chosen from a calcium oxide, a magnesium oxide, an aluminum oxide and a silicon oxide, the oxide has a predominantly cubic crystal lattice, the oxide has a predominantly crystal lattice having a space group of type [Math. 1] Fm3m, the reactive layer directly covers a layer chosen from the thermally insulating layer and the protective layer, the reactive layer has a thickness of between 5 µm and 500 µm, the oxide is adapted to form a product during a first reaction with the CMAS compound, said product being adapted to form an apatite phase during a second reaction with the CMAS compound and / or with another product of the first reaction, the reactive layer also comprises at least one complementary oxide chosen from yttria-containing zirconia, Al 2 O 3 , Y 2 O 3 -ZrO 2 -Ta 2 O 5 and an oxide of formula C 2 D 2 0 7 , in which C is chosen from a rare earth and yttrium, and D is chosen from zirconia and silicon, the average volume fraction of said oxide in the reactive layer varies as one moves away from the substrate, the reactive layer comprises at least 50% by volume of said oxide.

[0019] The invention also relates to a method for protecting an aeronautical part, for example a turbine part, comprising a step of depositing, on the part, a reactive layer adapted to react with at least one CMAS compound chosen from a calcium oxide, a magnesium oxide, an aluminum oxide and a silicon oxide, characterized in that the material of the reactive layer comprises an oxide of formula A' 4-x A" x B' 2-y B" y O 11-δ , A' being chosen from a rare earth and yttrium, A'' being chosen from a rare earth, yttrium, aluminum and scandium, B' being chosen from tantalum and niobium, B" being chosen from tantalum, niobium, zirconium, hafnium and cesium, x and y being real numbers between 0 and 2 and δ being a real number between -1 and 2, and preferably between -1 and 1.

[0020] The method is advantageously supplemented by the following characteristics, taken individually or in any of their technically possible combinations: the part comprises a substrate, an environmental barrier comprising at least one layer selected from a thermally insulating layer, an underlayer adapted to promote adhesion between the substrate and the thermally insulating layer and a protective layer adapted to protect the substrate from oxidation and / or corrosion, the environmental barrier at least partially covering the substrate, the deposited reactive layer at least partially covering the environmental barrier, the reactive layer being deposited on the environmental barrier, the reactive layer is deposited by a method selected from atmospheric pressure plasma spraying, suspension plasma spraying, solution plasma spraying, high-speed flame spraying in powder mode, electron beam evaporation, vapor deposition, sol-gel and electrophoresis. DESCRIPTION OF FIGURES

[0021] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which: [ Fig. 1 ] - there figure 1 schematically illustrates a section of a turbine part, for example a turbine blade or a nozzle vane, [ Fig. 2 ] - there figure 2 is a microphotograph illustrating a section of substrate covered with an environmental barrier, [ Fig. 3 ] - there figure 3 is a microphotograph, illustrating the insertion of molten CMAS compounds into the environmental barrier, [ Fig. 4 ] - there figure 4 is a microphotograph, illustrating the insertion of molten CMAS compounds into the environmental barrier, [ Fig. 5 ] - there Figure 5 is a microphotograph illustrating the rupture of an environmental barrier, [ Fig. 6 ] - there figure 6a microphotograph illustrating the rupture of an environmental barrier, [ Fig. 7 ] - there figure 7 schematically illustrates a turbine part comprising a coating according to the invention, [ Fig. 8 ] - there figure 8 schematically illustrates a turbine part comprising a coating according to the invention, in contact with CMAS compounds, [ Fig. 9 ] - there figure 9 schematically illustrates a turbine part comprising a coating according to the invention.

[0022] Throughout the figures, similar elements have identical references. DEFINITIONS

[0023] The term "superalloy" refers to an alloy that exhibits, at high temperature and high pressure, very good resistance to oxidation, corrosion, creep and cyclic stresses (particularly mechanical or thermal). Superalloys find particular application in the manufacture of parts used in aeronautics, for example turbine blades, because they constitute a family of high-strength alloys that can work at temperatures relatively close to their melting points (typically 0.7 to 0.8 times their melting temperatures).

[0024] A superalloy may have a two-phase microstructure comprising a first phase (called the "γ phase") forming a matrix, and a second phase (called the "γ' phase") forming precipitates that harden in the matrix. The coexistence of these two phases is referred to as the γ-γ' phase.

[0025] The "base" of the superalloy refers to the main metallic component of the matrix. In most cases, superalloys include an iron, cobalt, or nickel base, but sometimes also a titanium or aluminum base. The base of the superalloy is preferably a nickel base.

[0026] Nickel-based superalloys have the advantage of offering a good compromise between resistance to oxidation, resistance to fracture at high temperatures and weight, which justifies their use in the hottest parts of turbojets.

[0027] Nickel-based superalloys consist of a γ phase (or matrix) of the austenitic face-centered cubic γ-Ni type, possibly containing α-substitution solid solution additives (Co, Cr, W, Mo), and a γ' phase (or precipitates) of the γ'-Ni 3 X type, with X = Al, Ti or Ta. The γ' phase has an ordered L12 structure, derived from the face-centered cubic structure, consistent with the matrix, i.e. having an atomic mesh very close to it.

[0028] The term "volume fraction" refers to the ratio of the volume of an element or group of elements to the total volume.

[0029] The "space group" of a crystal refers to the set of symmetries of a crystal structure, that is, the set of affine isometries that leave the structure invariant. It is a group in the mathematical sense of the term. DETAILED DESCRIPTION OF THE INVENTION

[0030] In reference to the figure 7, a part 1 comprises a substrate 2. The substrate 2 may preferably be a superalloy substrate, and preferably a nickel-based superalloy as described above. The substrate 2 is covered, at least in part, with an environmental barrier 3. The environmental barrier 3 may comprise, in a known manner, and as illustrated in figure 1, a sub-layer 4 extending between the substrate 2 and the other layers of the environmental barrier 3, directly covering the substrate 2, adapted to promote adhesion between the substrate 2 and the other layers of the environmental barrier 3. The environmental barrier 3 may also comprise a protective layer 5, adapted to protect the substrate 2 from oxidation and / or corrosion, and directly covering the sub-layer 4. The protective layer 5 is for example formed by oxidation of the sub-layer 4. It may for example be made of alumina. The environmental barrier 3 may also comprise a thermally insulating layer 7, directly covering the protective layer 5.

[0031] The part 1 also comprises a reactive layer 9 adapted to react with at least one CMAS compound 8. The CMAS compound 8 may be a calcium oxide, a magnesium oxide, an aluminum oxide and / or a silicon oxide. The reactive layer 9 at least partially covers the environmental barrier 3. It may directly cover at least one of the layers of the environmental barrier 3, chosen from the protective layer 5 and the thermally insulating layer 7. Different reactive layers 9 may also cover different layers of the environmental barrier 3. The embodiment illustrated in the figure 1 comprises at least one reactive layer 9 covering all the layers of the environmental barrier 3. The reactive layer 9 may have a thickness of between 5 µm and 500 µm, so as to allow the formation of an apatite phase in contact with a CMAS compound 8.

[0032] The material of the reactive layer 9 comprises an oxide of formula A' 4 ,A",B' 2 . y B'' y O 11-δ , A' being chosen from a rare earth and yttrium, A'' being chosen from a rare earth, yttrium, aluminum and scandium, B' being chosen from tantalum and niobium, B" being chosen from tantalum, niobium, zirconium, hafnium, aluminum and cesium, x and y being real numbers between 0 and 2 and δ being a real number between -1 and 2, and preferably between -1 and 1. This formula allows the oxide of the reactive layer 9 (hereinafter "the oxide") to have a predominantly cubic mesh in volume. Thus, the material of the reactive layer 9 comprises a volume fraction of rare earth and / or Yttrium high enough to allow rapid precipitation of the molten CMAS compound(s), and to avoid their introduction into interstices presented in the environmental barrier 3.At the same time, the oxide, due to its composition, has a predominantly cubic mesh in volume, which allows it to have a high atomic fraction of rare earths and / or yttrium. Table 1 includes the different elements A', A", B' and B" which can be chosen for the oxide. [Table 1] A' A" B' B" Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al Ta, Nb Ta, Nb, Zr, Hf, Al, Ce

[0033] Thus, the oxide material may have a rare earth and / or yttrium atomic fraction of between 18% and 24%. This range of rare earth and / or yttrium atomic fraction, higher than that of Gd 2 Zr 2 O 7 for example, allows the material of the reactive layer 9 to have reaction kinetics with the CMAS 8 compound(s) faster than that of the materials described in the prior art (for example Gd 2 Zr 2 O 7 ). Thus, the molten CMAS 8 compound(s) in contact with the reactive layer 9 are immobilized more quickly, or slowed down by the production of an apatite phase, thickening and / or solidifying the CMAS 8 reactive compound at the interface with the environmental barrier 3, and avoiding contact between the CMAS 8 compound(s) and other parts of the environmental barrier 3.

[0034] Advantageously, the elements A' and A" may be different. Thus, the reactivity of the oxide with respect to one or more CMAS 8 may be increased by the formation of different phases, including at least one apatite phase, for example of general formula Ca 2 RE 8 (SiO 4 ) 6 0 2 , RE being a rare earth or yttrium. Y 2 Gd 2 Ta 2 O 11 and Y 2 Yb 2 Ta 2 O 11 are examples of compositions used for the oxide, in which A' and A" are different elements.

[0035] Advantageously, the elements B' and B" can be different. Thus, the mechanical properties of the oxide can be adjusted. For example, the mechanical strength can be higher. Gd 4 Ta 1.5 Zr 0.5 O 10.75 , Gd 4 Nb 1.5 Zr 0.5 O 10.75 , La 4 Ta 1.5 Hf 0.5 O 10.75 are examples of compositions used for the oxide, in which B' and B" are different elements.

[0036] Advantageously, the elements A', A'', B' and B" are chosen so as to allow the formation of an apatite phase and an anorthite phase when the oxide and a CMAS 8 compound are in contact. The apatite phase and the anorthite phase are then blocking or sealing with respect to the CMAS 8 compounds. In addition, the reactivity of the oxide with respect to the CMAS 8 compounds can be increased. Preferably, A' and / or B' are aluminum. Due to the volume fraction of aluminum in the reactive layer 9, the CMAS 8 compound can be locally enriched in aluminum oxide, and be more easily crystallizable. 3 AlTaAlO 10 , Gd 3.1 Al 0.9 Ta 1.7 Ti 0.3 O 10.85 (not according to the invention) are examples of compositions making it possible to form both an apatite phase and a phase anorthite in contact with a CMAS 8 compound.

[0037] Advantageously, the elements A', A'', B' and B" are chosen so as to allow the formation of a secondary oxide, resulting from the reaction between the oxide and the CMAS 8 compound(s). The secondary oxide formed is reactive with secondary products of the reaction between the oxide and the CMAS 8 compound(s), such as for example Ta 2 O 5 or Nb 2 O 5 , ZrO 2 , CaO, MgO, HfO 2 , CaTiO 3 and MgTiO 3 , and adapted to form an apatite phase during the reaction with these secondary products. For example, an oxide of general formula A 4 B 2 O 11-δ (A being chosen from Y, La and Lu, and B being chosen from Ta and Nb) is adapted to form a secondary oxide of general formula A 6 B 4 O 19 . The atomic fraction of reactive cations (i.e. compound A) in the oxide secondary is approximately equal to 20.69%.

[0038] The elements A' and A" can be the same element A: the oxide of the reactive layer 9 can be described by the formula A 4 B' 2-y B" y O 11-δ . The elements of the oxide are chosen from the elements described in Table 2. [Table 2] A B' B" Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Ta, Nb Ta, Nb, Zr, Hf, Al, Ce

[0039] Thus, the atomic fraction of rare earth and / or yttrium and / or scandium and / or aluminum can be increased compared to known oxides, due to the structure of the oxide.

[0040] The elements B' and B" can also be the same element B, chosen from Ta and Nb. In this case, the general formula of the oxide is A' 4-x A" x B 2 O 11-δ .

[0041] Advantageously, and to simplify the manufacture of the reactive layer 9, the same elements can be chosen on the one hand for A' and A" and on the other hand for B' and B". In this case, the oxide can be described by the formula A 4 B 2 O 11 .

[0042] The reactive layer 9 may also comprise at least one complementary oxide chosen from yttria-containing zirconia, Al 2 O 3 , Y 2 O 3 -ZrO 2 -Ta 2 O 5 and an oxide of formula C 2 D 2 0 7 , in which C is chosen from a rare earth and yttrium and D is chosen from zirconia and silicon. The complementary oxide(s) are known to have properties that make it possible to increase the lifetime of parts exposed to CMAS compounds. The complementary oxide(s) have properties that are different from the oxide, such as the reaction kinetics with the CMAS compound and / or the reaction products with the CMAS compound. The properties of the oxide and the complementary oxide may thus be combined in the reactive layer 9.

[0043] The reactive layer 9 may also have an average oxide volume fraction that varies with distance from the substrate 2. Thus, the reactive layer 9 has a gradient in oxide volume fraction. A reactive layer 9 having an oxide gradient may, for example, be manufactured by depositing a succession of reactive sub-layers, each sub-layer having a different oxide volume fraction.

[0044] Another aspect of the invention is a method for protecting a part with molten sand(s). The method comprises a step of depositing the reactive layer 9 as described above, on a part 1. After deposition, the part 1 comprises the reactive layer 9. The reactive layer 9 can be deposited directly on the substrate 2 of the part 1, for example a superalloy substrate 2, or on one or more layers of an environmental barrier 3. The deposition of the reactive layer 9 can be carried out on at least one of the layers forming the environmental barrier 3, and preferably on the thermally insulating layer 7.Thus, and unlike known parts, the part 1 comprising the reactive layer 9 deposited on the thermally insulating layer 7 has sufficient reactivity with the CMAS compound(s) 8 to produce at least one apatite phase before the insertion of the molten CMAS compound(s) 8 into the interstices of the thermally insulating layer 7, and thus avoid or limit this insertion. In this way, the CMAS compound(s) 8 can more difficultly access the surface of the environmental barrier 3, and their effect on the rupture of the environmental barrier 3 is limited. Examples Example 1: reaction between a liquid CMAS and a reactive layer of Gd 4 Nb 1.5 Zr 0.5 O 10.75

[0045] In reference to the figure 8 , a reactive layer 9 comprising the oxide Gd 4 Nb 1.5 Zr 0.5 O 10.75 is subjected to chemical attack by a molten CMAS 8. The reactive layer 9 is deposited by high-speed flame spraying in the powder process (SPS, English acronym for Spark Plasma Sintering ) .

[0046] In reference to the figure 9 , after a reaction time for example greater than 5 min, preferably greater than 1 minute, a part of the reactive layer 9 is dissolved by the CMAS 8 compound, and an apatite phase Ca 2 Gd 8 (SiO 4 ) 6 O 2 impermeable to the molten CMAS 8 is formed between the reactive layer 9 and the molten CMAS 8. The layer of Ca 2 Gd 8 (SiO 4 ) 6 O 2 is also impermeable to the other reaction products (secondary products) between the reactive layer 9 and the CMAS 8 compounds. The layer of Ca 2 Gd 8 (SiO 4 ) 6 O 2 also makes it possible to produce secondary phases, making it possible to protect the reactive layer 9. The environmental barrier 3 does not have any cracks. Indeed, the reservoir of compound cations A, that is to say A' and A" when A' and A" are the same element, makes it possible to form a tight layer and therefore to limit the depth of penetration, compared to the use of a known reactive layer such as La 2 Zr 2 O 7 . Example 2: reaction between a liquid CMAS and a reactive layer of Y 2 Gd 2 Ta 2 O 11

[0047] In reference to the figure 8 , a reactive layer 9 comprising the oxide Y 2 Gd 2 Ta 2 O 11 is subjected to chemical attack by a molten CMAS 8. The reactive layer 9 is deposited by high-speed flame spraying in the powder process (SPS, English acronym for Plasma Spraying Suspension ) .

[0048] With reference to Figure 8b, after a reaction time for example greater than 5 min, preferably greater than 1 minute, a part of the reactive layer 9 is dissolved by the CMAS 8 compound, and two apatite phases Ca 2 Gd 8 (SiO 4 ) 6 O 2 and Ca 2 Y 6 (SiO 4 ) 6 O 2 impermeable to the molten CMAS 8 are formed between the reactive layer 9 and the molten CMAS 8. The environmental barrier 3 does not have any cracks. Indeed, the reservoir of Y and Gd cations makes it possible to form two impermeable layers in large quantities and therefore to limit the penetration depth, compared to the use of a known reactive layer such as La 2 Zr 2 O 7 . Indeed, six Y 3+< cations are sufficient to preferentially form the apatite Ca 4 Y 6 (SiO 4 ) 6 O while eight Gd 3+< cations are necessary for the formation of the apatite with a more complex crystallographic structure Ca 2 Gd 8 (SiO 4 ) 6 O 2 .Furthermore, the formation of two different layers as a product of the reaction between the reactive layer 9 and the CMAS 8 increases the kinetics of this reaction. Example 3: reaction between a liquid CMAS and a reactive layer of Gd 3.1 Al 0.9 Ta 1.7 Ti 0.5 O 10.85 (not according to the invention)

[0049] In reference to the figure 9 , a reactive layer 9 comprising the oxide Gd 3.1 Al 0.9 Ta 1.7 Ti 0.5 O 10.85 is subjected to chemical attack by a molten CMAS 8. The reactive layer 9 is deposited by high-speed flame spraying in the powder process (SPS, English acronym for Suspension Plasma Spraying ) .With reference to Figure 8b, after a reaction time for example greater than 5 min, preferably greater than 1 min, a part of the reactive layer 9 is dissolved by the CMAS 8 compound, and a phase 10 of apatite Ca 2 Gd 8 (SiO 4 ) 6 O 2 impermeable to the molten CMAS 8 is formed between the reactive layer 9 and the molten CMAS 8. In addition, an anorthite phase CaAl 2 Si 2 O 8 has also been produced. This phase is suspended in the molten CMAS 8. The environmental barrier 3 does not have any cracks. Indeed, the cation reservoir makes it possible to form two impermeable layers in large quantities and therefore to limit the penetration depth, compared to the use of a known reactive layer such as La 2 Zr 2 O 7 . The modification of the mobility of CMAS 8 by production of the secondary anorthite phase and the apatite phase thus limits the possibility for the liquid to penetrate the still healthy Gd 3.1 Al 0.9 Ta 1.7 Ti 0.50 O 10.85 layer.

Claims

1. An aeronautical part (1), comprising: - a substrate (2), - an environmental barrier (3) comprising at least one layer selected from a thermally insulating layer (7), a sublayer (4) suitable for promoting adhesion between the substrate (2) and a thermally insulating layer (7) and a protective layer (5) suitable for protecting the substrate from oxidation and / or corrosion, the environmental barrier (3) at least partially covering the substrate (2) - at least one reactive layer (9) suitable for reacting with at least one CMAS compound (8) selected from a calcium oxide, a magnesium oxide, an aluminum oxide and a silicon oxide, the reactive layer (9) at least partially covering environmental barrier (3), characterized in that the material of the reactive layer (9) comprises at least one oxide of formula A'4-xA"xB'2-yB"yO11-δ, A' being selected from a rare earth, yttrium and scandium, A" being selected from a rare earth, yttrium, scandium and aluminum, B' being selected from tantalum and niobium, B" being selected from tantalum, niobium, zirconium, hafnium, aluminum and cesium, x and y being real numbers between 0 and 2 and δ being a real number between -1 and 1.

2. The part (1) as claimed in claim 1, wherein the oxide predominantly has a cubic lattice in volume.

3. The part (1) as claimed in claim 1 or 2, wherein the oxide has a rare-earth atomic fraction of between 18% and 24%.

4. The part (1) as claimed in one of claims 1 to 3, wherein A' and A" are the same element, A' and A" being selected from a rare earth, scandium and yttrium.

5. The part (1) as claimed in one of claims 1 to 4, wherein B' and B" are the same element, B' and B" being selected from tantalum and niobium.

6. The part (1) as claimed in one of claims 1 to 5, wherein the reactive layer (9) directly overlies a layer selected from the thermally insulating layer (7) and the protective layer (5).

7. The part (1) as claimed in one of claims 1 to 6, wherein the reactive layer (9) has a thickness of between 5 µm and 500 µm.

8. The part (1) as claimed in one of claims 1 to 7, wherein the reactive layer (9) comprises at least 50% by volume of said oxide.

9. The part (1) as claimed in one of claims 1 to 8, wherein the reactive layer (9) also comprises at least one complementary oxide selected from yttriated zirconia, Al2O3, Y2O3-ZrO2-Ta2O5 and an oxide of formula C2D2O7, wherein C is selected from a rare earth and yttrium and D is selected from zirconia and silicon.

10. The part (1) as claimed in one of claims 1 to 9, wherein the average volume fraction of said oxide in the reactive layer (9) varies with increasing distance from the substrate (2).