RU2773286C2 - Part protected with surrounding barrier - Google Patents

Abstract

FIELD: engine building.

SUBSTANCE: group of inventions relates to the field of protection of hot parts of gas turbine engines, such as combustion chamber walls or turbine rings, turbine nozzle blades or turbine working blades, for aircraft engines or industrial gas turbine engines. A part of a gas turbine engine contains substrate (20) made of composite material with a ceramic matrix or monolithic ceramic material, at least part of which, adjacent to surface (S) of substrate, is made of material containing silicon; coupling sublayer (30) located on surface (S) of substrate and containing silicon; surrounding barrier (40), which contains outer layer (42) of ceramic, covering coupling sublayer (30). Moreover, specified surrounding barrier (40) additionally contains self-healing inner layer (41) located between coupling sublayer (30) and outer layer (42). In this case, specified inner layer (41) contains a matrix, in which particles forming silicon dioxide are dispersed. Moreover, the specified particles can generate a phase to tighten cracks of the matrix in the presence of oxygen. The inner layer has a volumetric particle content ranging from 20% to 40%. A method for manufacturing the specified part includes stages of: applying coupling sublayer (30) containing silicon to surface (S) of substrate (20); applying inner layer (41) of surrounding barrier (40) to coupling sublayer (30); applying outer layer (42) of surrounding barrier (40) to inner layer (41), while specified outer layer (42) is made of ceramics.

EFFECT: reduction in corrosion of material, which affects the service life.

9 cl, 7 dwg

Description

The field of technology to which the invention belongs

This invention relates to the general field of corrosion protection of ceramic matrix composite (CMC) parts.

A more specific field of application of the invention is the protection of ceramic matrix composite (CMC) parts that are hot parts of gas turbine engines, such as combustion chamber walls or turbine rings, turbine nozzle vanes or turbine rotor blades, for aircraft engines or industrial gas turbine installations.

State of the art

In the case of such gas turbine engines, the desire to increase efficiency and reduce polluting emissions makes it necessary to envisage ever higher temperatures in the combustion chambers.

For this reason, it has been proposed to replace metallic materials with CMC materials, in particular for the walls of combustion chambers or turbine rings. Indeed, as is known, CMC materials simultaneously have good mechanical properties, allowing them to be used for the manufacture of structural elements, and the ability to maintain these properties at high temperatures. CMC materials contain a fibrous reinforcement of heat-resistant fibers, typically carbon or ceramic, which is compacted with a ceramic matrix, such as SiC.

Under the conditions of operation of aircraft turbines, that is, at high temperature in an oxidizing and humid environment, CMC materials are susceptible to the phenomenon of corrosion. The corrosion of the CMC material is a consequence of the oxidation of SiC with the formation of silicon dioxide, which in the presence of water vapor volatilizes in the form of silicon hydroxides Si(OH) ₄ . Corrosion phenomena lead to deterioration of the properties of the CMC material and affect its service life.

In order to limit this degradation during operation, surrounding barrier coatings have been provided on the surface of the CMC materials. Such a known solution is shown in Fig. one.

As shown in FIG. 1, a ceramic matrix composite (CMC) substrate 1 is coated with a bonding layer 2 of silicon, said bonding layer 2 in turn being coated with a surrounding barrier 3, which may be a rare earth metal silicate layer. During operation of the gas turbine engine, a protective layer 2a of silicon dioxide is formed between the bonding layer 2 of silicon and the surrounding barrier 3 .

The bonding layer 2 makes it possible, on the one hand, to improve the adhesion of the surrounding barrier 3 and, on the other hand, to form during operation a protective layer 2a of silicon dioxide, whose low oxygen permeability allows it to participate in the protection of the CMC substrate 1 against oxidation.

With regard to the surrounding barrier 3, it makes it possible to limit the spread of water vapor towards the protective layer 2a of silicon dioxide obtained by oxidizing silicon in the bonding layer 2, and therefore to limit the deterioration of its properties.

However, a problem with this known solution is that the availability of the silica protective layer 2a to water vapor and air locally is very variable.

These differences in local availability are associated, in particular, with local changes in the density of the surrounding barrier 3, the tortuosity of the network of microcracks and pores in the surrounding barrier, which are responsible for the priority passage of oxygen, and with local heterogeneity of the composition or in the crystal lattice of the surrounding barrier 3.

These local accessibility differences can lead to local thickness differences in the silica protective layer 2a, potentially leading to stress buildup and premature failure of the part from delamination.

Therefore, there is a need for a new system for protecting the CMC substrate against corrosion in order to increase the service life of CMC parts during operation.

Disclosure of the essence of the invention

The main objective of the invention is to eliminate the above disadvantages. This problem is solved in a detail containing:

- a substrate, in which at least a part adjacent to the surface of the substrate is made of a material containing silicon;

- adhesion sublayer located on the surface of the substrate and containing silicon,

- a surrounding barrier, which contains an outer layer of ceramic covering the adhesion sublayer,

wherein said surrounding barrier further comprises a self-healing inner layer located between the adhesion sublayer and the outer layer, wherein said inner layer contains a matrix in which particles forming silicon dioxide are dispersed, and these particles can generate a phase for tightening matrix cracks in the presence of oxygen.

The advantage of such an inner layer of the surrounding barrier is that, on the one hand, it reduces the amount of water and air reaching the adhesion sublayer, and, on the other hand, it reduces the heterogeneity in the amount of water and air passing through the surrounding barrier.

Indeed, since the particles are silica-forming particles, that is, they form silicon dioxide (SiO ₂ ) upon their oxidation, said particles dispersed in the matrix of the inner layer react upon contact with oxygen to form a pull-in phase which seals said inner layer. The particles contain silicon.

In addition, this reaction of particles with oxygen consumes some of the water and air passing through the inner layer of the surrounding barrier, which limits the amount of air and water that passes into the adhesion sublayer and reduces heterogeneity.

In addition, the particles of the inner layer may include ceramic particles, preferably particles of silicon carbide or silicon nitride, or MAX phase containing silicon, or a mixture of such particles.

The particles of the inner layer may also include metal particles, or preferably particles of silicon element Si or metal silicide, or a mixture of such particles.

According to a possible feature, the particles of the inner layer have an average size less than or equal to 5 μm and preferably less than or equal to 2 μm.

Under the "average size" should be understood the size given by the statistical particle size distribution for half of the population and called D50.

In addition, the inner layer may have a particle volume content greater than or equal to 5% and less than 50%, and preferably between 20% and 40%.

According to a further feature, the inner layer has a thickness of 10 µm to 300 µm and preferably 100 µm to 200 µm.

In addition, the matrix of the inner layer may be made of silicate, preferably rare earth metal monosilicate or disilicate, or aluminum silicate such as mullite, or cordierite.

According to another feature, the matrix of the inner layer and the outer layer are made of the same material.

The second object of the invention is a method for manufacturing a part according to any of the previous features, comprising the steps:

- applying an adhesion sublayer containing silicon to the surface of the substrate;

- applying the inner layer of the surrounding barrier on the adhesion sublayer;

- applying the outer layer of the surrounding barrier to the inner layer, said outer layer being made of ceramic.

According to a further feature, the deposition of the inner layer is carried out by means of plasma spraying, in which the material to form particles is introduced into the plasma jet as a suspension in a liquid medium.

In addition, the material intended to form the matrix of the inner layer is introduced into the plasma jet in the form of a powder.

According to another feature, the material to form the matrix of the inner layer is introduced into the plasma jet in the form of a suspension in a liquid medium.

Brief description of the drawings

Other features and advantages of the invention will become more apparent from the following description with reference to the accompanying drawings, which illustrate a non-limiting exemplary embodiment. In the figures shown:

in fig. 1 shows a known solution for the implementation of the surrounding barrier;

in fig. 2 shows a detail according to an embodiment of the invention, a sectional view;

in fig. 3 shows the inner layer of the surrounding barrier in detail;

in fig. 4 shows a first possible embodiment of applying the inner layer of the surrounding barrier;

in fig. 5 shows a second possible embodiment for applying an inner layer of a surrounding barrier;

in fig. 6 shows a third possible embodiment of applying an inner layer of the surrounding barrier;

in fig. 7 schematically shows the various steps of the manufacturing method according to an embodiment of the invention.

Implementation of the invention

The following detailed description provides for the formation of a surrounding barrier on a silicon-containing CMC material substrate. However, the invention can be applied to substrates of a monolithic refractory material containing silicon and, in general, to substrates in which at least a portion adjacent to the outer surface of the substrate is made of a refractory material (composite or monolithic). Thus, the invention relates to the protection of heat-resistant materials consisting of heat-resistant ceramics, for example, silicon carbide SiC or silicon nitride Si ₃ N ₄ , and more specifically to the protection of heat-resistant composite materials, such as ceramic matrix composite materials (CMC) containing silicon eg CMC materials with a matrix at least partially of SiC.

As shown in FIG. 2, the claimed member 10 comprises a substrate 20 having a surface S. The substrate 20 contains silicon in at least a portion adjacent to the surface S. The member 10 may be a turbine ring of a gas turbine engine.

The substrate 20 may be made of a CMC material containing silicon, as well as a fibrous reinforcement, which may be made of carbon (C) fibers or ceramic fibers, for example, SiC fibers or fibers mainly formed by SiC, including Si fibers. -C-O or Si-C-O-N, that is, containing also oxygen and possibly nitrogen. Such fibers are manufactured by Nippon Carbon under the name “Nicalon” or Hi-Nicalon”, or “Hi-Nicalon Type-S”, or by Ube Industries under the name “Tyranno-ZMI”. Ceramic fibers can be coated with a thin interfacial layer of pyrolysis carbon (RuC), boron nitride (BN), or boron-doped carbon (BC, at 5-20 atom.% B, the rest is C).

The fibrous reinforcement is densified by a matrix which is formed wholly or at least in its outer phase by a silicon-containing material such as a silicon compound, for example SiC, or a Si-B-C tertiary system. Under the outer phase of the matrix should be understood as the phase of the matrix, formed last and the most remote from the reinforcement fibers. So, the matrix can consist of several phases of different nature, for example, it can be:

a mixed C-SiC matrix (with SiC on the outside), or

a sequential matrix with alternating phases of SiC and matrix phases of less rigidity, for example, from pyrolysis carbon (PyC), boron nitride (BN) or carbon doped with boron (BC), with a terminal matrix phase of SiC, or

self-healing matrix with matrix phases of boron carbide (B ₄ C) or from the tertiary Si-BC system, optionally with free carbon (B ₄ C + C, Si-BC + C) and with a Si-BC or SiC terminal phase.

The matrix can be at least partially obtained by CVI, which is known in itself. In a variant, the matrix can be at least partially obtained by a liquid method (impregnation with resin, which is the starting material of the matrix, and transformation by cross-linking and pyrolysis, while the process can be repeated), or by infiltration of silicon in a molten state ("Melt-Infiltration" method). ). In this latter case, the powder is introduced into the fibrous reinforcement, which may be pre-compacted, which powder may be carbon and possibly ceramic powder, and then infiltrated with a silicon-based metal composition in the molten state to obtain a matrix of the SiC-Si type.

The silicon-containing adhesive sublayer 30 is on the substrate 20. The adhesive sublayer 30 comes into contact with the substrate 20. The adhesive sublayer 30 may be composed of silicon (element Si) or mullite (3Al2O3.2SiO2). During operation, the cohesive sublayer 30 oxidizes and forms a passivation layer of silicon dioxide (SiO ₂ ) (“Thermally Grown Oxide”).

On the adhesion sublayer 30 is a surrounding barrier 40 to protect said adhesion sublayer 30 and the substrate 20. The surrounding barrier 40 comprises a self-healing inner layer 41 located on the adhesion sublayer 30 and an outer ceramic layer 42 located on the inner layer 41. The inner layer 41 is included in contact, on the one hand, with the adhesion sublayer 30 and, on the other hand, with the outer layer 42.

A self-healing material in this case should be understood as a material that forms a glassy composition in the presence of oxygen, which, due to the transition to a pasty or fluid state in a certain temperature range, is able to tighten cracks that appear inside the material.

As shown in FIG. 3, the inner layer 41 contains a matrix 41m in which particles 41p are dispersed. The matrix 41m is made of a material different from that of the particles 41p. In addition, the matrix 41m contains cracks 41f and other pores.

The particles 41p are silica-forming particles, that is, capable of generating the crack-filling phase 41f of the matrix 41m in the presence of oxygen. In particular, the 41p particles can generate a pull-in phase when the temperature exceeds 800°C. The 41p particles contain silicon.

Indeed, during operation, air and water flows 51 pass through the outer layer 42 of the environmental barrier 40 and reach the inner layer 41 of said environmental barrier 40. Since the particles 41p are silica-forming particles, they react with oxygen and form silicon dioxide (SiO ₂ ) . This silica created by the particles 41p forms an entraining phase and fills the cracks 41f and other pores of the matrix 41m due to capillarity, thus sealing the inner layer 41 and restricting the passage of air and water flows 51 through said inner layer 41. Such a self-healing reaction of the internal The layer 41 seals said inner layer 41 in contact with the air and water streams 51, thereby limiting the amount of air and water that reaches the cohesive sublayer 30 through the outlet streams 52.

Moreover, in addition to sealing the inner layer 41 by filling the cracks 41f, this self-healing effect causes some of the water and air to be consumed, which also reduces the amount of air and water in the outflows 52 that reach the adhesion sublayer 30.

In addition, as shown in FIG. 3, the amount of air and water is heterogeneous in the streams 51 that enter the inner layer 41. The fact that part of the water and air is consumed by the reaction of the particles 41p improves the uniformity of the outgoing air and water streams 52 that enter the adhesion sublayer 30. This homogeneity of the exit streams 52 reduces local thickness variations in the protective layer of silicon dioxide formed by the adhesive sublayer 30, which reduces the risk of stress concentration and early failure of the part 10 from delamination.

Moreover, in addition to the oxidation reaction, the 41p particles can corrode in the presence of water and air and form gaseous H _x Si _y O _z . This corrosion reaction of the particles 41p also consumes water and air, which reduces the amount of water and air entering the adhesion sublayer 30 .

The 41p particles may be ceramic particles. Preferably, the particles 41p are silicon carbide (SiC) particles, silicon nitride (Si ₃ N ₄ ) particles or silicon-containing max phase particles, or a mixture of such particles. The most preferred materials include silicon carbide.

The particles 41p can also be metal particles. Preferably, the particles 41p are silicon particles (element Si), metal silicide particles, or a mixture of such particles.

Preferably, the particles 41p have an average size (D50) of less than or equal to 5 µm. Indeed, it is preferred that the particles 41p have an average size of less than or equal to 5 μm, as this allows the inner layer 41 to be more reactive to generate the SiO ₂ entrainment phase and to consume air and water. Indeed, the use of small particles makes it possible to increase the free surface for the oxidation reaction and corrosion of 41p particles. Preferably, the particles 41p have an average size less than or equal to 2 µm, for example, from 0.1 µm to 2 µm, which further enhances the reactivity and efficiency of the inner layer 41.

As will be shown below, the use of particles having an average size of less than 5 μm is ensured, in particular, in the case of application by plasma spraying, where the material intended to obtain particles 41p is injected in a liquid way.

Preferably, the inner layer 41 has a volume content of particles 41p greater than or equal to 5% and less than (strictly) 50%. On the one hand, this ensures a better reactivity of the inner layer 41 for generating the draw-in phase and consuming water and air, and also ensures a sufficient service life of the inner layer 41, and, on the other hand, allows the properties provided by the matrix 41m to be sufficiently preserved. Preferably, the inner layer 41 has a volume content of particles 41p of 20% to 40%.

Preferably, the matrix 41m is made of silicate, and preferably a rare earth metal monosilicate or disilicate, or an aluminosilicate such as mullite, or cordierite. It should be noted that preferably the matrix 41m is not made of barium strontium aluminosilicate (BSAS), since BSAS reacts with silica. In a preferred embodiment, a rare earth metal monosilicate or disilicate matrix 41m is provided. In preferred versions of the embodiment in which the matrix 41m is made of rare earth metal monosilicate or disilicate, a matrix 41m of Y ₂ Si ₂ O ₇ , RE ₂ Si ₂ O ₇ , or RE ₂ SiO ₅ is provided.

The inner layer 41 has a thickness E which may be 10 µm to 300 µm. This thickness allows the inner layer 41 to fulfill its role of protecting the adhesion sublayer 30 . In addition, when the inner layer 41 has a large thickness, for example, 200 μm to 300 μm, it can independently provide the function of sealing the surrounding barrier 40 against water and air, while the upper layer 40 can only serve as an abradable material. In addition, the thickness E of the inner layer 41 is preferably 100 µm to 200 µm.

The outer layer 42 of the surrounding barrier 40 is made of ceramic. The outer layer 42 may be a classic ambient barrier layer. The outer layer 42 may be made of a rare earth metal monosilicate or disilicate, or an aluminosilicate such as mullite, or barium strontium aluminosilicate (BSAS), or cordierite.

Preferably, in order to provide better mechanical and chemical compatibility between the inner layer 41 and the outer layer 42 of the surrounding barrier 40, the matrix 41m of the inner layer 41 and the outer layer 42 are made from the same material. Such a feature is more advantageous when the inner layer 41 and the outer layer 42 come into direct contact with each other. Preferably, the matrix 41m of the inner layer 41 and the outer layer 42 are made of rare earth metal monosilicate or disilicate. In addition, the outer layer 42 may contain a filler of fibers or inclusions, depending on the properties that you want to give the specified outer layer 42.

The surrounding barrier 40 may also include additional layers located on the outer layer 42.

As shown in FIG. 7, according to an exemplary embodiment, the method for manufacturing part 10 comprises the following steps:

- E1: application of an adhesion sublayer 30 containing silicon on the surface S of the substrate 20;

- E2: application of the inner layer 41 of the surrounding barrier 40 on the underlayer 30 adhesion;

- E3: applying the outer layer 42 of the surrounding barrier 40 to the inner layer 41, said outer layer 42 being made of ceramic.

According to a preferred embodiment of the method for manufacturing part 10, the application of the inner layer 41 is carried out by plasma spraying, in which the material intended to form particles 41p dispersed in the inner layer 41 is introduced into the plasma jet in the form of a suspension in a liquid medium.

The introduction of the material intended to form particles 41p into the plasma jet in the form of a suspension in a liquid medium allows the use of 41p particles with a small average size, in particular, with an average size of less than 5 μm. Indeed, if the particles are not introduced into the plasma jet in the form of a suspension in a liquid medium, but for example in the form of a powder, the particles can bounce off the plasma jet due to their too small size, which makes it difficult to control the deposition of the inner layer 41.

In addition, the introduction of a material intended to form 41p particles into the plasma jet in the form of a suspension in a liquid medium provides a wider choice of 41p particles. Indeed, some materials, notably silicon carbide (SiC), can only barely withstand being introduced into the plasma jet and are at risk of sublimation. This makes it difficult to control the deposition of the inner layer 41 with particles 41p of such materials, in particular silicon carbide (SiC). The introduction of particles 41p into the plasma jet in the form of a suspension in a liquid medium makes it possible to protect materials from the plasma jet, and it is also easier to control the deposition of the inner layer 41.

According to the first possible embodiment for applying the inner layer 41 shown in FIG. 4, said inner layer 41 of the surrounding barrier 40 is performed by plasma spraying using a plasma torch 60 which generates a plasma jet 61. Plasma spraying can be performed at atmospheric pressure in air.

The material to form the matrix 41m of the inner layer 41 is injected into the plasma jet 61 by the nozzle 70 in the form of a powder 71. According to an example, the powder 71 may be a Y ₂ Si ₂ O ₇ powder with an average size of 30 µm.

The material to form the particles 41p of the inner layer 41 is injected into the plasma jet 61 by means of a nozzle 80 in the form of a suspension 81 in a liquid medium. According to the example, the suspension 81 may be an aqueous suspension containing 20 wt. % silicon carbide (SiC) particles with an average size of 1 μm.

In the example shown in FIG. 4, on the adhesion sublayer 30, an inner layer 41 is formed containing a matrix 41m of Y ₂ Si ₂ O ₇ and SiC particles. The volume content of particles 41p in this inner layer 41 is 30%, and the thickness E of said inner layer is 150 µm.

According to the second embodiment shown in FIG. 5, the material intended to form the matrix 41m of the inner layer 41 is injected into the plasma jet not in the form of a powder, but in the form of a suspension 91 in a liquid medium containing both the material intended to form the matrix 41m and the material intended to form particles 41p. This suspension 91 is injected into the plasma jet 61 using a single nozzle 90.

According to the example, suspension 91 is an aqueous suspension containing 20 wt. % filler from materials intended to obtain a matrix 41m and particles 41p. The proportion of the two materials in the mixture is calculated so that the volume content of particles 41p in the inner layer 41 is 30%. Suspension 91 contains Y ₂ Si ₂ O ₇ particles with an average size of 30 µm, which are intended to form the matrix 41m (which will therefore consist of Y ₂ Si ₂ O ₇ ), and SiC particles with an average size of 1 µm, which are intended to obtain 41p particles (which would thus be SiC particles). The resulting inner layer 41 has a thickness E of 150 µm.

According to the third embodiment shown in FIG. 6, the material to form the matrix 41m and the material to form the particles 41p are injected into the plasma jet 61 not in the same suspension, but in two different suspensions 101a and 101b.

The first suspension 101a is an aqueous suspension containing 20 wt. % particles of Y ₂ Si ₂ O ₇ to obtain a matrix of 41m, which have an average size of 5 μm. The first suspension 101a is injected into the plasma jet 61 through the first nozzle 100a.

The second suspension 101a is an aqueous suspension containing 20 wt. % SiC particles to obtain particles 41p, and these particles have an average size of 1 μm. The second suspension 101b is injected into the plasma jet 61 through the second nozzle 100b. The resulting inner layer 41 has a thickness E of 150 µm.

The expression "ranges from ... to..." must be understood as "including limits".

Claims (16)

1. Detail (10) of a gas turbine engine, containing: - a substrate (20) made of a composite material with a ceramic matrix or a monolithic ceramic material, at least part of which, adjacent to the surface (S) of the substrate, is made of a material containing silicon, - adhesion sublayer (30) located on the surface (S) of the substrate and containing silicon, - surrounding barrier (40), which contains an outer layer (42) of ceramics, covering the sublayer (30) of adhesion, characterized in that said surrounding barrier (40) further comprises a self-healing inner layer (41) located between the adhesion sublayer (30) and outer layer (42), wherein said inner layer (41) contains a matrix (41m) in which are dispersed particles (41p) forming silicon dioxide, and these particles (41p) can generate a phase for tightening cracks (41f) of the matrix (41m) in the presence of oxygen, while the inner layer has a volume content of particles (41p) ranging from 20% to 40 %. 2. Part (10) according to claim 1, in which the particles (41p) of the inner layer (41) include ceramic particles, preferably particles of silicon carbide or silicon nitride, or phase MAX containing silicon, or a mixture of such particles. 3. Part (10) according to claim 1 or 2, in which the particles (41p) of the inner layer (41) include metal particles, or particles of silicon element Si, or metal silicide, or a mixture of such particles. 4. Item (10) according to any one of paragraphs. 1-3, in which the particles of the inner layer have an average size less than or equal to 5 μm and preferably less than or equal to 2 μm. 5. Item (10) according to any one of paragraphs. 1-4, wherein the inner layer has a thickness of 10 µm to 300 µm and preferably 100 µm to 200 µm. 6. Item (10) according to any one of paragraphs. 1-5, in which the matrix of the inner layer is made of silicate, preferably rare earth metal monosilicate or disilicate, or aluminum silicate such as mullite, or cordierite. 7. Item (10) according to any one of paragraphs. 1-6, in which the matrix of the inner layer and the outer layer are made of the same material. 8. Method for manufacturing parts (10) according to any one of paragraphs. 1-7, including steps: - (E1) applying an adhesion sublayer (30) containing silicon to the surface (S) of the substrate (20); - (E2) applying the inner layer (41) of the surrounding barrier (40) on the sublayer (30) adhesion; - (E3) applying the outer layer (42) of the surrounding barrier (40) to the inner layer (41), while said outer layer (42) is made of ceramic. 9. The method according to claim 8, in which the application of the inner layer (41) is carried out by plasma spraying, in which the material intended to form particles is introduced into the plasma jet in the form of a suspension in a liquid medium.

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