PART WITH PROTECTIVE COATING A

GRADUAL COMPOSITION

GENERAL TECHNICAL FIELD AND PRIOR ART

The present invention generally relates to surface treatments applied to mechanical parts, in particular when they are confronted with demanding conditions of use.

The field of application of the invention is in particular that of layers of protective materials deposited on parts made of composite materials with a ceramic matrix used in aircraft engines, and more particularly in combustion chambers, high pressure turbines and engine exhaust components.

The invention is nevertheless applicable to any type of part comprising portions made of a composite material with a ceramic matrix.

Ceramic matrix composites (CMC) are more and more widely used in the aeronautical industry for their excellent structural properties, their low density as well as their excellent resistance to oxidation up to temperatures of the order of 1000 ° vs.

To cope with prolonged exposure to such conditions, for example in the combustion chamber of an aircraft engine, parts made of a ceramic matrix composite material are conventionally covered with a layer of silicon protecting the part against the oxidation, the oxidation producing silica (SiO2).

A layer of Si02 forms on the surface of the silicon layer, the rate of formation of Si02 decreasing as the Si02 layer thickens, thus forming a barrier slowing down oxidation and limiting the consumption of silicon Si present in the matrix of the composite material.

In the case of use in a humid corrosion atmosphere, in the presence of species comprising OH (g) hydroxides, the silica layer volatilizes very quickly from 1100 ° C in the form of acid species

silicas of general formula SiOx (OH) 4 -2x, such as orthosilicic acid Si (OH) 4 (g) or metasilicic acid SiO (OH) 2 (g).

This phenomenon leads to a decrease in the net growth rate of the silica SiO 2, the thickness of which tends towards a limit value and an accelerated recession of the silicon present in the matrix of the composite material.

To respond to this phenomenon, it is known in the prior art to deposit a ceramic layer designed to prevent the diffusion of OH hydroxides accelerating the degradation of the part, which has low thermal conductivity and which resists erosion. caused by solid particles.

However, these solutions encounter limits, in particular in the event of spalling of the surface ceramic layer, cracks due to shocks or to thermal cycles generating stress gradients between materials having too different expansion coefficients.

Thus, the silica layer is again exposed to a humid corrosion atmosphere, leading to an accelerated degradation of its structure and a reduction in the life of the part.

It is also known in the state of the art to produce sub-layers comprising aluminum in the thermal barrier systems of combustion chambers or of high pressure turbine components made of a nickel-based and / or carbon-based superalloy. cobalt.

The oxidation of these sub-layers generates a layer of alumina, which protects the part against a greater oxidation, in particular in a humid corrosive environment thanks to the good chemical stability of the alumina vis-à-vis the vapor of water.

Alumina also exhibits a slower formation rate than silica, which makes it possible to increase the life of the protection thanks to the reduced need for the quantity of material necessary to feed the reaction.

Alumina also has the advantage of good physicochemical compatibility with the ceramic thermal barrier, and also has a coefficient of thermal expansion close to that of the ceramic thermal barrier.

The use of such alumina-generating sublayers for the protection of materials rich in Si such as ceramic matrix composites or silicides (silicon nitride SÏ3N4, molybdenum silicide MoSix, niobium silicide NbSi, etc.) is however contraindicated due to the large difference between the thermal expansion coefficients of the different substrates.

In addition, a phenomenon of cross-diffusion of the composite part with a ceramic matrix rich in Si and the aluminum-rich alumina-generating layer causes the formation of unwanted phases with low ductility, weakening the interface between the protective layer and the part and can lead to chipping of the protective layer, leaving the part vulnerable to corrosion.

Thus, in the current state of the art, there are no effective solutions making it possible to establish the link between materials based on silicides, which are mechanically efficient but not very resistant to oxidation at high temperature, and alumina materials. -formers resistant to oxidation but possessing modest mechanical properties at high temperature. The present invention proposes to remedy this lack.

GENERAL PRESENTATION OF THE INVENTION

An object of the invention is to improve the resistance to corrosion in a humid environment of parts made of composite material with a ceramic matrix.

Another aim is to increase the life of parts made of composite material with a ceramic matrix.

Another aim is to ensure the mechanical and chemical cohesion of a coating mainly comprising an aluminum composite with a part mainly comprising a silicon composite.

The invention makes it possible to meet the following specifications:

• Have a coating that is stable at high temperature (<1100 ° C);

• Have a coating having an expansion coefficient close to that of the silicon carbide SiC / SiC substrate and a ceramic thermal barrier;

• Form alumina on the aluminum rich side;

“Do not interact with the SiC / SiC substrate on the silicon-rich side;

• Do not form fragile intermetallic phases in the aluminum / silicon transition zone.

The invention proposes here to use certain MAX phase materials, the crystal structure of which, the thermophysical properties as well as their resistance to oxidation are compatible with these specifications. The term “MAX phase material” will be understood to mean materials of the general formula M n + iAX n where n is an integer between 1 and 3, M is a transition metal (chosen from selenium, titanium, vanad ium, chromium , zirconiu m, n iobium, molybdenum, hafn ium and tantalum), A is an element of group A, that is to say chosen from alu minium, silicium, phosphorus, gal liu m, germanium, arsenic, cad mium, ind iu m, tin, titanium and lead, and X is an element selected from carbon and nitrogen.

In a first aspect, the invention provides a mechanical part comprising at least partially a composite material with a ceramic matrix, said composite material being covered at least locally with at least one protective layer against environmental degradation, the protective layer comprising a graded composition coating layer, this graded composition layer comprising at least one MAX phase material of silicon and one MAX phase material of aluminum, the graded composition layer extending within the protective layer between a first height relative to the mechanical part and a second height relative to the mechanical part, the composition of the layer with gradual composition at the first height not including aluminum,the composition of the layer with gradual composition at the second height not comprising silicon, an intermediate height situated between the first height and the second height having a composition comprising

aluminum and silicon, the part of aluminum and the part of silicon gradually evolving in the layer with gradual composition depending on the position of the intermediate height, the part of aluminum increasing when the intermediate height approaches the second height.

Such a device is advantageously supplemented by the following various characteristics taken alone or in combination:

- The proportion of aluminum and the proportion of silicon evolve linearly as a function of the intermediate height in the layer with gradual composition;

- The sum of the molar proportions of silicon and aluminum is variable regardless of the position of the intermediate height in the gradual composition layer;

- The gradual composition layer comprises MAX phase materials TÏ3AIC2 and TÏ3SÏC2;

- It may include:

o An underlayer, essentially comprising silicon, the thickness of which may be between 10 pm and 100 pm; o A layer of gradual composition with a thickness between 50 μm and 500 μm, with a substitution of Si by Al moving away from the part at a rate between 0.1 and 0.4 at% / μm;

o A generating layer with a thickness of 10 to 300 μm, composed essentially of TÏ2AIC so as to generate alumina on the surface when it is oxidized, to increase the resistance in a humid environment;

o A layer of alumina;

o An environmental or thermal barrier formed of ceramics, with a thickness between 50 μm to 1000 μm, configured to limit transfers between the external environment and the part;

It may include:

o A sub-layer composed essentially of silicon, the thickness of which may be between 10 pm and 100 pm; o A layer of gradual composition with a thickness between 50 μm and 500 μm, with a substitution of Si by Al moving away from the part at a rate between 0.1 and 0.4 at% / μm;

o A generating layer with a thickness of 50 to 300 μm composed essentially of TÏ2AIC so as to generate alumina at the surface when it is oxidized, to increase resistance in a humid environment;

o A layer of alumina;

- It may include:

o A layer of gradual composition with a thickness between 50 μm and 500 μm, with a substitution of Si by Al moving away from the part at a rate between 0.1 and 0.4 at% / μm;

o A generating layer with a thickness of 50 to 300 μm composed essentially of TÏ3AIC2, configured to generate alumina at the surface when it is oxidized, so as to increase the resistance in a humid environment; o A layer of alumina (7).

According to another aspect, the invention also provides a method for depositing at least one protective layer on a mechanical part, the protective layer comprising at least one layer of gradual composition, the method comprising the following steps:

- Optimization of surface preparation conditions before deposition;

- Production of the layer with gradual composition by thermal spraying of the species composing said layer with gradual composition;

the graded composition layer comprising at least one MAX phase material of silicon and one MAX phase material of aluminum, the MAX phase material of silicon and the MAX phase material of aluminum representing a given proportion of the layer of gradual composition, and the layer with gradual composition is produced by injecting into a thermal spray device on the one hand particles of aluminum MAX phase material and on the other hand particles of MAX phase material of silicon, the MAX phase material aluminum gradually replacing the MAX phase material of silicon depending on the height of the layer produced.

Such a process is advantageously supplemented by the following characteristics taken alone or in combination:

- The particles of aluminum MAX phase material and silicon MAX phase material are powders of TÏ3AIC2 and Ti3SiC2 suspended in a solvent in two separate containers, the suspensions of TÏ3AIC2 and Ti3SiC2 then being injected in a controlled proportion. in a plasma configured to heat and project the particles of the MAX phase material suspensions onto the workpiece, thereby effecting the deposition;

- The solvent is a non-aqueous solvent configured to limit the formation of oxides from the particles of TÏ3AIC2 and Ti3SiC2, so as to limit the presence of oxides in the gradual composition layer.

According to another aspect, the invention also provides a liquid thermal spraying device (called SPS for “Suspension Plasma Spraying” or SPPS for “Suspension Precursor Plasma Spraying”) to implement such a deposition process of at least a layer of material on a part, the device comprising:

- A first tank containing a suspension of particles of MAX phase material of aluminum in a solvent;

- A second tank containing a suspension of particles of MAX phase silicon material in a solvent;

- A first and a second suspension injector, the first suspension injector being linked to the first reservoir via a first pipe, the second suspension injector being linked to the second reservoir via a second pipe, the suspension injectors being configured to control the injection rate of aluminum and silicon particles;

- A plasma torch, configured to generate a plasma in which the particles of MAX phase material of aluminum and of MAX phase material of silicon are injected, the plasma heating and thus projecting the particles injected within it onto the part.

In such a device, the particles of MAX phases of aluminum and silicon can be powders of TÏ3AIC2 and Ti3SiC2.

The term “plasma torch” will be understood to mean any thermal projection device making it possible to accelerate and melt particles in suspension. Mention may be made, by way of example, of HVOF (“High Velocity Oxy Fuel”, for projection by supersonic flame), blown or inductive arc plasma projection (APS for “Atmospheric Plasma Spraying” or plasma projection under atmospheric pressure, IPS for “Inert gas Plasma Spraying” or plasma spraying in a neutral (inert) atmosphere, VPS for “Void Plasma Spraying” or plasma spraying under partial vacuum, ...)

PRESENTATION OF FIGURES

Other characteristics, aim and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and should be read with reference to the appended figures in which:

- Figure la is a schematic representation of a section of a protection device according to the invention, highlighting the different layers of a first embodiment;

- Figure lb is a graph showing the evolution of the silicon and aluminum content of the different layers of a protection device according to the first embodiment of the invention as a function of the height in this layer;

- Figure 2a is a schematic representation of a section of a protection device according to the invention, highlighting the different layers of a second embodiment;

FIG. 2b is a graph showing the evolution of the silicon and aluminum content of the various layers of a protection device according to the second embodiment of the invention as a function of the height in this layer;

- Figure 3a is a schematic representation of a section of a protection device according to the invention, showing the different layers of a third embodiment;

FIG. 3b is a graph showing the evolution of the silicon and aluminum content of the different layers of a protection device according to the third embodiment of the invention as a function of the height in this layer;

- Figure 4 is a schematic representation of a device for manufacturing by plasma suspension spraying (SPS) involving two tanks of MAX phase material suspensions connected to two separate injectors allowing the introduction of particles of material suspensions of MAX phase in a plasma jet in order to heat them and project them onto the surface of the substrate to produce a coating by adding material according to the invention.

DESCRIPTION OF ONE OR MORE MODES OF IMPLEMENTATION AND

OF ACHIEVEMENT

The embodiments described below relate to the case of a mechanical part 1 comprising a substrate 5 made of composite material with a ceramic matrix, at least part of which has been covered with a protection 2 against wear related to its environment. , this protection 2 being composed of successive layers in a direction Y, including a layer having a gradual composition 3, the layers being deposited by a local material addition process. This is however presented for illustrative and non-limiting purposes. It will be noted that the height is zero at the level of the face of the substrate 5 which is opposite the protection.

In this description, the term “height” will be understood to mean the dimension along the Y direction. The thickness of the various layers is expressed along this Y direction.

In what follows, it will be noted that:

the substrate 5 extends between heights hl and h2 (knowing that hl is zero and h2 is greater than hl),

the sub-layer 4 extends between heights h2 and h3 (knowing that h3 is greater than h2),

the gradual composition layer 3 extends between heights h3 and h4 (knowing that h4 is greater than h3),

the alumina-generating layer 5 extends between heights h4 and h5 (knowing that h5 is greater than h4) and

- the alumina layer extends between heights h5 and h6 (knowing that h6 is greater than h5).

These heights h1-h6 will be defined more precisely in the remainder of the description.

Referring to FIG. 1a, an embodiment of a protection 2 against wear produced on the surface of the part 1 comprises several layers superimposed along the Y axis normal to the surface of the part 1.

The protective layer comprises successively, from the substrate 5, an under-layer 4, a layer with gradual composition 3, an alumina-generating layer 6 and an alumina layer 7.

The sublayer 4 is located directly in contact with the substrate 5 making up at least part of the part 1 made of ceramic matrix composite. The sublayer 4 has a thickness which may be between ΙΟμηη and ΙΟΟμη-ι.

The substrate 5 comprising silicon carbides SiC, the sub-layer 4 essentially comprises silicon, so as to ensure continuity between the part 1 and the protection 2 and a protective barrier against oxidation, which ensures adhesion. and the chemical and mechanical compatibility of protection 2 and part 1.

By essentially, it is understood that the level of silicon in the sublayer 4 is greater than 90%.

The gradual composition layer 3 comprises a plurality of chemical species, the proportion of some of the species present being a function of the height observed in the layer from the substrate 5.

Here, the gradual composition layer 3 comprises TÏ3AIC2 and Ti3SiC2, in different proportions depending on the height considered.

The lower part of the gradual composition layer 3, being in contact with the silicon sublayer 4, only contains Ti3SiC2, so as to ensure the mechanical and chemical continuity of the medium between the sublayer 4 and the layer to gradual composition 3.

The proportion of TÏ3AIC2 in the graded composition layer 3 increases as a function of the height, replacing Ti3SiC2, the proportion of which decreases as much as that of TÏ3AIC2 increases.

At the high end of the graded composition layer 3, T13AIC2 has completely supplanted Ti3SiC2.

The variation in the proportion of TÏ3AIC2 in the gradual composition layer 3 can be linear, or have any other profile, for example a polynomial or exponential curve, studied to favor a behavior chosen such as the continuity of the coefficient of thermal expansion or even to favor certain ones. behaviors in some

areas of the layer such as for example the ability to fill in the microcracks appearing in the protection 2 during use, or to respect a compromise between different determined factors.

The ability to fill micro-cracks in this layer is particularly beneficial in increasing the life of the part.

The gradual composition layer 3 has a thickness which may vary from 50μΓη to 500μΓη.

The alumina-generating layer 6 covers the graded composition layer 3.

The alumina-generating layer 6 comprises TI2AIC, thereby exhibiting a coefficient of thermal expansion similar to that of the upper end of the graded composition layer 3 and thus ensuring the mechanical compatibility of these two layers.

The generating layer 6 makes it possible to generate, by oxidizing, the protective alumina layer 7 on its upper surface, thus limiting deeper oxidation, and also having significant chemical stability against water vapor.

The presence of TI2AIC further enables alumina to be formed up to a temperature of 1300 ° C.

This alumina layer 7 protects the layers comprising silicon from reactions with the OH hydroxide species, the generating layer 6 having a thickness of between 10 μm and 300 μm making it possible to constitute an aluminum reservoir supplying the reaction for the formation of alumina.

A thermal barrier 8 covers the alumina layer 7 so as to minimize the thermal transfer between the surrounding medium and the part 1, thereby establishing a thermal gradient between the environment and the part 1, and therefore limits the heating of the multiples. layers of protection.

The thermal barrier 8 is composed of a layer of ceramic with low thermal conductivity, and has a thickness of between 50 μm and 100 μm.

The ceramic is chosen such that its coefficient of expansion is close to that of the generating layer 6 of alumina.

In the exemplary embodiment illustrated in FIG. 1b, the aluminum and silicon content of the various protective layers is represented as a function of the height of the layer concerned.

Between the height h1 and the height h2, corresponding to the substrate layer 5 of the part 1, the silicon content has a first constant value A, however exhibiting a strong increase in the vicinity of the height h2. The aluminum content is zero in this layer.

Between the height h2 and the height h3, corresponding to the sub-layer

4, the silicon content has a second constant value B greater than the first value A. The aluminum content is zero in this layer.

Between the height h3 and the height h4, corresponding to the gradual composition layer 3, the silicon content decreases, going from a second value B to a zero rate at the height h4.

The aluminum content increases, passing from a zero value to a third value C. In the example illustrated, the third value C is equivalent to the second value B, but it is possible that an additional species in the layer to gradual composition 3 can move this third value C and place it at a level lower or higher than the second value B.

For an intermediate height h comprised between Iesh3 and h4, both aluminum and silicon are present in the composition of the layer.

In one embodiment, the sum of the molar fractions of aluminum and of silicon is constant whatever the intermediate height h considered in the layer with gradual composition 3.

In other embodiments, the sum of the molar fractions of aluminum and silicon can also be variable according to the intermediate height h considered in the layer with gradual composition 3.

It is possible to have some MAX phase material species in excess in Graduated Composition Layer 3.

Between the height h4 and the height h5, corresponding to the alumina-generating layer 6, the level of aluminum has a constant fourth value D. This fourth value D may be equivalent to, less than or greater than the third value C.

The silicon content is zero in this layer.

Between the h5 and the h6 height, corresponding to the alumina layer 7, the level of aluminum has a constant fifth value E.

The fifth value E is greater than the fourth value D.

The silicon content is zero in this layer.

In the embodiment illustrated in FIG. 2a, when the part 1 is not subjected to temperatures exceeding 1200 ° C. during operation, it is not necessary to make a thermal barrier 8. The layer of alumina 7 is sufficient to protect part 1 from the reaction effect with OH hydroxide species.

An example of protection 2 comprises, in accordance with the first embodiment, a sub-layer 4 covered by a layer of gradual composition 3, itself covered by a generating layer 6 of alumina, the alumina generated forming a layer of alumina 7 on the generating layer 6 and thus providing chemical protection against the OH hydroxide species.

The difference lies in the fact that the alumina layer 7 is not covered by a thermal barrier 8, the temperatures to which the part is subjected not requiring it.

The sub-layer 4, with a thickness of 10 to 100 μm, essentially comprises silicon.

By essentially, it is understood that the level of silicon in the sublayer is greater than 90%.

The gradual composition layer 3, with a thickness of 50 to 500 μm, comprises TÏ3AIC2 and Ti3SiC2, the proportions of which depend on the height observed in the layer.

Generating layer 6 essentially comprises TIIAIC. By essentially it is meant that the mass fraction of T12AIC in the generator layer 6 is greater than 90%.

Generating layer 6, however, has a thickness of between 50 μm and 300 μm, which is greater than in the first example so as to provide a large chemical reservoir in order to maintain the protective alumina layer 7.

In the exemplary embodiment illustrated in FIG. 2b, the protection 2 comprises an aluminum and silicon presence rate profile similar to that presented previously. Note here that the values ​​of h1-h6 may differ from those in Figure lb.

Between the height h1 and the height h2, corresponding to the substrate layer 5 of part 1, the silicon content has a first constant value A ′, however exhibiting a strong increase in the vicinity of the second height h2. The aluminum content is zero in this layer.

Between the height h2 and the height h3, corresponding to the sub-layer 4, the silicon content has a second constant value B 'greater than the first value A'. The aluminum content is zero in this layer.

Between the height h3 and the height h4, corresponding to the gradual composition layer 3, the silicon content decreases, going from a second value B ′ to a zero rate at the level of the fourth height h4.

The aluminum content increases, passing from a zero value to a third value C. In the example illustrated, the third value C is equivalent to the second value B ', but it is possible that an additional species in the layer with gradual composition 3 can move this third value C and place it at a level lower or higher than the second value B '.

For an intermediate height h comprised between height h3 and height h4, aluminum and silicon are both present in the composition of the layer.

Between the height h4 and the height h5, corresponding to the alumina-generating layer 6, the level of aluminum has a fourth constant value D ′. This fourth value D 'may be equivalent to, less than or greater than the third value C.

The silicon content is zero in this layer.

Between the height h5 and the height h6, corresponding to the alumina layer 7, the level of aluminum has a constant fifth value E '.

The fifth value E 'is greater than the fourth value D'.

The silicon content is zero in this layer.

In the exemplary embodiment illustrated in FIG. 3a, when the part 1 is not subjected to temperatures exceeding 1100 ° C, the stresses generated by the differential thermal expansions are less important, and no longer require the presence of the under -layer 4 of silicon.

The generator layer 6 of TÏ2AIC can also be omitted, in favor of a layer of TÏ3AIC2 present in the gradual composition layer 3, thereby reducing the process for producing the protection 2.

The substrate 5 at the surface of the part 1 is therefore directly covered by the gradual composition layer 3, with a thickness of 50 to 500 μm, comprising TÏ3AIC2 and Ti3SiC2, the proportions of which depend on the height observed in the layer.

The generating layer 6 comprising TÏ3AIC2 here has a thickness of between 50 μm and 300 μm, so as to provide a large chemical reservoir in order to maintain the protective alumina layer 7.

In the exemplary embodiment illustrated in FIG. 3b, the protection 2 comprises a profile of the presence rate of aluminum and silicon different from those presented above. It will be noted here again that the values ​​of hl-h6 may differ from those of figures lb and 2b. Furthermore, this protection 2 does not include a sub-layer 4: the heights h2 and h3 are therefore equal.

Between the height h1 and the height h3, corresponding to the substrate layer 5 of part 1, the level of silicon has a first constant value A ". The level of aluminum is zero in this layer.

Between the height h3 and the height h4, corresponding to the gradual composition layer 3, the silicon content decreases, going from a first value A "to a zero rate at the height h4.

The aluminum content increases, passing from a zero value to a second value C ". In the example illustrated, the second value C" is greater than the first value A ", but it is possible that an additional species in the gradual composition layer 3 can displace this second value C "and place it at a level less than or equal to the first value A".

For an intermediate height h comprised between the height h3 and the height h4, the aluminum and the silicon are both present in the composition of the layer with gradual composition 3.

Between the height h4 and the height h5, corresponding to the alumina-generating layer 6, the level of aluminum has a third constant value D. This third value D "can be equivalent to, lower or higher than the second value C". .

The silicon content is zero in the generator layer 6.

Between the height h5 and the height h6, corresponding to the alumina layer 7, the level of aluminum has a constant fourth value E ".

The fourth value E "is greater than the third value D".

The silicon content is zero in the alumina layer 7.

Referring to Figure 4, the protection 2 is at least partially produced on the part 1 using a method 9 for adding material projecting particles onto the surface of the part 1 so as to produce a layer of protection.

In what follows, the process will be described in relation to the production of a layer with a gradual composition 3. This process can however be applied mutatis mutandis for other layers, such as the alumina-generating layer 6 for example.

The method 9 for producing the gradual composition layer 3 is based on a principle of thermal spraying by plasma 10, particles being injected into the plasma to be heated and projected onto the part 1 so as to form the gradual composition layer 3.

In the present case, the particles of T13AIC2 and Ti3SiC2 are stored separately and suspended in a solvent.

The suspensions of TÏ3AIC2 and Ti3SiC2 are then injected into the plasma 10 at respective flow rates controlled to comply with the desired proportion of Al and Si obtained as a function of the height of the layer produced.

The solvent here is nonaqueous so as to prevent the formation of oxides in the gradual composition layer 3 and thus to guarantee its homogeneity and its mechanical properties.

The spraying can also be carried out in a neutral atmosphere so as to limit the formation of intermetallic phases or oxides originating from the high temperature oxidation of the materials projected by the surrounding oxidizing atmosphere.

Plasma deposition, and therefore at high temperature, also makes it possible to obtain, during cooling to ambient temperature, residual compressive stresses in the deposited coating, which thus limits the overall damage to the system by reinforcing its self-healing nature and therefore its natural tendency to close any cracks.

It is also conceivable to carry out the deposition using different thermal spraying processes such as plasma powder spraying at atmospheric pressure (APS) or under neutral gas (IPS), or a high speed flame spraying process ( HVSFS or similar).

The method 9 is carried out using a thermal projection device 11 comprising a torch 12 generating a plasma 10, a first 13 and a

second 14 injector placed in communication with a first 15 and a second 16 reservoir by means of a first 17 and a second 18 pipe.

The first reservoir 15 contains a suspension of Ti3AIC2 powder in a solvent, the second reservoir 16 containing a suspension of Ti3SiC2 powder in a solvent.

The first injector 13 injects the suspension of Ti3AIC2 into the plasma, which heats up and projects the suspension onto the part 1, thus depositing the particles which will form the protection 2, the second injector 14 injecting the suspension of Ti3SiC2 into the plasma.

The injection rates of the two suspensions are controlled jointly, so as to control the aluminum and silicon content of the protective layer formed, and to vary these proportions so as to produce the layer with gradual composition 3.
CLAIMS

1. Mechanical part (1) comprising at least partially a ceramic matrix composite material, said composite material being covered at least locally with at least one protective layer (2) against environmental degradation, characterized in that the protective layer (2) comprises a graded composition coating layer (3), this graded composition layer (3) comprising at least one MAX phase material of silicon and one MAX phase material of aluminum, the gradual composition layer (3) ) extending within the protective layer (2) between a first height (h3) relative to the mechanical part (1) and a second height (h4) relative to the mechanical part (3), the composition of the gradual composition layer (3) at the first height (h3) not comprising aluminum,the composition of the layer with gradual composition (3) at the second height (h4) not comprising silicon, an intermediate height (h) located between the first height (h3) and the second height (h4) exhibiting a composition comprising aluminum and silicon, the part of aluminum and the part of silicon gradually evolving in the gradual composition layer (3) depending on the position of the intermediate height (h), the part of aluminum increasing when the height intermediate (h) approaches the second height (h4).aluminum and the part of silicon gradually evolving in the gradual composition layer (3) depending on the position of the intermediate height (h), the part of aluminum increasing when the intermediate height (h) approaches the second height ( h4).aluminum and the part of silicon gradually evolving in the gradual composition layer (3) depending on the position of the intermediate height (h), the part of aluminum increasing when the intermediate height (h) approaches the second height ( h4).

2. Mechanical part (1) according to claim 1, characterized in that the part of aluminum and the part of silicon evolve linearly as a function of the intermediate height (h) in the gradual composition layer (3).

3. Mechanical part (1) according to claim 1 or claim 2, characterized in that the sum of the molar proportions of silicon and aluminum is constant regardless of the position of the intermediate height (h) in the composition layer gradual (3).

Mechanical part (1) according to one of the preceding claims, characterized in that the gradual composition layer (3) comprises the MAX phase materials TÏ3AIC2 and Ti3SiC2.

Mechanical part (1) according to one of the preceding claims, characterized in that it comprises:

- An underlayer (4), essentially comprising silicon, the thickness of which may be between 10 pm and 100 pm;

- A layer of gradual composition (3) with a thickness of between 50 μm and 500 μm, with a substitution of Si by Al moving away from the part at a rate of between 0.1 and 0.4 at% / μm;

- A generating layer (6) with a thickness of 10 to 300 μm, composed essentially of TÏ2AIC so as to generate alumina on the surface when it is oxidized, to increase the resistance in a humid environment;

- A layer of alumina (7);

- An environmental barrier (8) formed of ceramic, with a thickness between 50 μm to 1000 μm, configured to limit transfers between the external environment and the part (1).

Mechanical part (1) according to one of claims 1 to 4, characterized in that it comprises:

- An underlayer (4) of silicon, the thickness of which may be between 10 μm and 100 μm;

- A layer of gradual composition (3) with a thickness between 50 μm and 500 μm, with substitution of Si by Al moving away from the part at a rate between 0.1 and 0.4 at% / m;

- A generating layer (6) with a thickness of 50 to 300 μm composed essentially of TÏ2AIC so as to generate alumina at the surface when it is oxidized;

- A layer of alumina (7).

Mechanical part (1) according to one of claims 1 to 4, characterized in that it further comprises:

- A layer of gradual composition (3) with a thickness of between 50 μm and 500 μm, with a substitution of Si by Al moving away from the part at a rate of between 0.1 and 0.4 at% / μm;

- A generating layer (6) with a thickness of 50 to 300 μm composed essentially of TÏ3AIC2, configured to generate alumina at the surface when it is oxidized;

- A layer of alumina (7).

Method of depositing (9) at least one protective layer (2) on a mechanical part (1), the protective layer (2) comprising at least one layer with gradual composition (3), the method (9) comprising the following steps:

Production of the layer with gradual composition (3) by thermal spraying of the species composing said layer (3);

characterized in that the graded composition layer (3) comprises at least one MAX phase material of silicon and one MAX phase material of aluminum, and in that the graded composition layer (3) is made by injecting into a thermal spray device (11) on the one hand particles of aluminum MAX phase material and on the other hand particles of MAX phase material of silicon, the MAX phase material of aluminum gradually replacing the MAX phase material of silicon as a function of the layer height produced.

9. A method of depositing (9) at least one layer of material on a part (1) according to claim 8, characterized in that the particles of MAX phase material of aluminum and of MAX phase material of silicon are powders of TÏ3AIC2 and Ti3SiC2 suspended in a solvent in two respective containers, the suspensions of TÏ3AIC2 and Ti3SiC2 then being injected in a controlled proportion into a plasma (10) configured to heat and project the suspensions of MAX phase material onto part (1), thus making the deposit.

10. A method of depositing (9) at least one layer of material on a part (1) according to claim 9, characterized in that the solvent is an aqueous or non-aqueous solvent configured to limit the oxidation of the particles of TÏ3AIC2 and Ti3SiC2, so as to limit the presence of oxides in the graded composition layer (3).