EP4396153A1

EP4396153A1 - Method for protecting a carbon-carbon composite material part from oxidation

Info

Publication number: EP4396153A1
Application number: EP22773288.0A
Authority: EP
Inventors: Julien Sniezewski; Fanny ALOUSQUE; Véronique FONTARNOU
Original assignee: Safran Landing Systems SAS
Current assignee: Safran Landing Systems SAS
Filing date: 2022-08-29
Publication date: 2024-07-10

Abstract

The invention relates to a method for protecting a carbon-carbon composite material part from oxidation, the method comprising the steps of: - applying (10) an impregnation composition comprising at least one metal phosphate to at least one portion of the outer surface of the part; - depositing (30), by means of a dry deposition process, a solid composition of an oxidation-resistant glass on at least one portion of the outer surface of the part, once the impregnation composition has been applied; and - conducting an impregnation heat treatment (40) in order to soften or melt the solid composition deposited by means of a dry deposition process, to allow the internal porosity of the part to be impregnated with the thus-softened or thus-melted composition, and to form an oxidation-resistant glass in the internal porosity of the part.

Description

Title of the invention: METHOD FOR PROTECTION AGAINST OXIDATION OF A PART MADE OF CARBON/CARBON COMPOSITE MATERIAL.

Technical area

The invention relates to the field of parts made of carbon/carbon composite material and more specifically to processes for protecting such parts against oxidation.

Prior technique

The invention relates to the protection against oxidation of parts made of carbon/carbon composite material, that is to say a material comprising a fibrous reinforcement densified by a matrix in which the fibrous reinforcement and the matrix comprise carbon. A particular field of application of the invention is the protection against oxidation of C/C composite brake discs, and in particular brake discs of aircraft, for example airplanes, or brake discs of land vehicles.

In an oxidizing environment, the ability of such parts to retain good mechanical properties at high temperatures depends on the presence of effective protection against carbon oxidation. Indeed, after its development, the composite material usually has a residual internal porosity which offers the ambient medium access to the heart of the material.

Additionally, in some applications, oxidation protection must retain its effectiveness in the presence of moisture and/or carbon oxidation catalysts. This is particularly the case for aircraft brake discs made of C/C composite which may be exposed to the humidity present on the runways and come into contact with carbon oxidation catalysts provided, for example, by potassium acetates or formates present in de-icing products commonly used on runways.

The protection against oxidation of such parts is generally ensured by coatings deposited on the parts made of carbon/carbon composite material. Nevertheless, such external coatings are sensitive to mechanical degradation. caused by the friction, shocks and vibrations that are inevitable for such parts.

It is also considered to introduce a layer of protection against oxidation in the internal porosity of the parts made of composite material to overcome such drawbacks. For example, documents FR 2 726 554 and EP 3 072 866 describe processes for protecting a part made of carbon/carbon composite material against oxidation, obtained by means of aqueous compositions making it possible to form, after a heat treatment, a protection against oxidation in the internal porosity of the part.

It is however desirable to improve the resistance to oxidation of such parts in order to increase their service life.

Disclosure of Invention

The inventors have found that it is possible to improve the homogeneity of the protective layer formed in the porosity of the part, while increasing the deposition yields and further improving the oxidation resistance properties of parts made of carbon/carbon composite material.

For this, the inventors propose a process for protecting a part made of carbon/carbon composite material against oxidation, the process comprising at least the following steps:

- the application to at least part of the outer surface of the part of an impregnating composition comprising at least one metal phosphate;

- the deposition by dry process, after the application of the impregnating composition, on at least part of the external surface of the part of a solid composition of a glass for protection against oxidation; And

- an impregnation heat treatment in order to soften or melt the solid composition deposited by the dry process, to allow the impregnation of the internal porosity of the part by the composition thus softened or melted, and to form a protective glass against oxidation in the internal porosity of the part.

The inventors have observed that such a protection method allows the formation of a barrier against oxidation in the internal porosity of the part. He is advantageous that the protection is present in the internal porosity since thus, it is not subject to the shocks or the frictions which the part can undergo.

Moreover, unlike the protection methods considered in the prior art, the solid composition of a protective glass is deposited by a dry process.

It is understood by "dry deposition" that the method of the invention does not require the use of a third-party vector liquid during the deposition of the solid composition and its infiltration into the internal porosity, unlike the methods of the prior art which use slips.

The choice of the dry process for the deposition of the solid composition makes it possible to obtain, after a thermal impregnation treatment, a protective glass against oxidation directly in the internal porosity of the part with an increased deposition yield compared to to the deposit methods of the prior art. Also, the glass obtained is more homogeneous than with processes requiring carrier liquids for the solid composition.

In a dry deposition process, the solid composition can be sprayed in a liquid, solid or pasty form, without a third-party vector liquid, and it forms a solid deposit once its deposition is complete.

For example, the dry deposition of the solid composition is carried out by electrostatic spraying, by thermal powder spraying at high speed or even by cold spraying.

It is understood within the meaning of the invention that the impregnation of the internal porosity of the part must be understood as a deep impregnation of the internal porosity, that is to say that the protective glass against oxidation is not only formed on the surface of the part, but that it extends from the surface to the depth of the part in its internal porosity.

For example, the impregnation heat treatment allows the formation of a protective glass against oxidation to a depth greater than or equal to 0.5 mm, measured from the external surface of the part. In one embodiment, the protective glass against oxidation can be formed in the internal porosity of the part and in the entire thickness of the latter.

In one embodiment, the method may comprise a preliminary heat treatment step at a temperature of between 680° C. and 740° C., carried out after the step of applying the impregnating composition and before the step of depositing of the solid composition.

Such a preliminary heat treatment makes it possible to increase the impregnation of the internal porosity of the part by the impregnation composition before the formation of the protective glass against oxidation.

The preliminary heat treatment allows the impregnating composition to further impregnate the internal porosity of the part and to form therein a layer for trapping carbon oxidation catalysts, and thus improves the resistance to oxidation of the part. piece. In addition, the presence of the impregnation composition allows better impregnation of the internal pores of the preform by the solid composition.

This preliminary heat treatment is however not necessary, and the application of the impregnating composition can be followed directly by the deposition of the solid composition by the dry route. If this is the case, the impregnation composition and the solid composition are then both present, and possibly mixed, in the porosity of the part, and the impregnation heat treatment carried out after the deposition of the solid composition will allow in one single step of impregnating the internal porosity of the part both with the impregnating composition and of forming therein the protective glass against oxidation and a layer for trapping catalysts for the oxidation of carbon.

For example, the solid composition can be a glass powder made up of a plurality of particles, the average size of which is less than or equal to 10 μm. Unless otherwise stated, the term "average size" denotes the dimension given by the statistical particle size distribution to half of the population, called D50. The duration and the temperature of the heat treatment making it possible to soften or melt the solid composition are chosen according to the physicochemical nature of the solid composition. In particular, the impregnation heat treatment must allow the solid composition of a glass for protection against oxidation to become sufficiently soft or even melt so that it can impregnate the internal porosity of the part.

In a particular embodiment where the solid composition comprises a powder of phosphate or silicate glass, the thermal impregnation treatment is carried out at a temperature of between 680° C. and 1100° C., and for example for a period of between 1 minute and 2 hours.

For example, the heat treatment can be carried out by a flash heat treatment, or by introduction into an oven.

In one embodiment, the method may comprise, after the impregnation heat treatment step, at least the following steps:

- the deposition by dry process on at least part of the outer surface of the part of a second solid composition of a protective glass against oxidation identical to or different from the solid composition; Then

- a second impregnation heat treatment in order to soften or melt the second solid composition deposited by the dry process, to allow the impregnation of the internal porosity of the part by the second composition thus softened or melted, and to form a second glass protection against oxidation in the internal porosity of the part.

These additional steps make it possible to further improve the resistance to oxidation of the parts obtained not only with respect to those obtained with the methods of the prior art but also with respect to those obtained after the deposition of a single solid composition.

In one embodiment, the solid composition is the same for the first and the second dry deposition step. In another embodiment, the first and the second solid composition can be different. The choice of identical or different solid compositions makes it possible to further improve the properties of resistance to oxidation of the parts obtained and to adapt them most particularly to the external conditions encountered by the part during its final use.

In one embodiment, the method comprises, after the second impregnation heat treatment step, at least the following steps:

- the deposition by dry process on at least part of the outer surface of the part of a third solid composition of a protective glass against oxidation identical to or different from the first and/or the second solid composition; Then

- a third impregnation heat treatment in order to soften or melt the third solid composition deposited by the dry process, to allow the impregnation of the internal porosity of the part by the third composition thus softened or melted, and to form a third glass protection against oxidation in the internal porosity of the part.

In this embodiment, the first, second and third compositions can be identical or different. It is also possible that two of the three compositions are identical and the other different.

An embodiment comprising three stages of deposition of a solid composition makes it possible to further improve the resistance to oxidation of parts obtained by the method described.

In particular, it is observed that a quantity of solid composition deposited and impregnated in two or three successive stages rather than in a single stage makes it possible to obtain a final part whose resistance to oxidation is even better.

In one embodiment, the total quantity of solid composition deposited on at least part of the outer surface of the part during the dry deposition step or steps may be greater than or equal to 3 mg/cm ² , or even greater than or equal to 5 mg/cm ² .

Such amounts of solid composition make it possible to obtain a higher resistance to oxidation than that of parts obtained by methods of the prior art. In one embodiment, the solid composition(s) solid composition of a glass for protection against oxidation can be chosen from powders of phosphate or silicate glasses.

In one embodiment, the solid composition of a glass for protection against oxidation may comprise, in mass percentages:

- 42 to 47% of phosphorus pentoxide P ₂ O ₅ ;

- 8 to 11% potassium oxide K ₂ O;

- 14 to 18% sodium oxide Na ₂ O;

- 14 to 18% aluminum oxide Al ₂ O ₃ ;

- 7 to 10% boron sesquioxide B ₂ O ₃ .

- 37 to 41% of phosphorus pentoxide P ₂ O ₅ ;

- 16 to 20% potassium oxide K ₂ O;

- 10 to 13% sodium oxide Na ₂ O;

- 16 to 19% aluminum oxide Al ₂ O ₃ ;

- 7.5 to 10.5% boron sesquioxide B ₂ O ₃ .

In one embodiment, the part made of carbon/carbon composite material is a friction part, for example a brake disc for an aircraft.

Brief description of the drawings

[Fig. 1] Figure 1 schematically represents a method in a first embodiment.

[Fig. 2] Figure 2 schematically represents a method in a second embodiment.

[Fig. 3] FIG. 3 represents the results obtained for the evolution of the loss of mass as a function of time of the samples prepared according to the example.

Description of embodiments

The invention is now described by means of figures illustrating particular embodiments of the invention which are present for illustrative purposes only in order to better understand the invention, and which should not be construed as limiting the invention.

FIG. 1 represents a diagram of a method for producing the invention.

Such a method comprises a first step 10 of applying to at least a portion of the outer surface of the part an impregnating composition comprising at least one metal phosphate.

In an exemplary embodiment, the metal phosphate is an aluminum phosphate. One could, as a variant, use a phosphate of manganese, zinc, calcium, magnesium, with or without added phosphoric acid. In one embodiment, the metal phosphate is mono-aluminum phosphate Al(H ₂ PO ₄ ) ₃ .

In other embodiments, complex phosphates can also be used, for example complex aluminum and calcium phosphates. The impregnation composition makes it possible, after impregnation in the internal porosity, to form therein a layer for trapping carbon oxidation catalysts, and thus to improve the resistance to oxidation.

Indeed, it is known that phosphates make it possible to oppose the effect of catalytic agents for the oxidation of carbon, and in particular alkaline or alkaline-earth elements.

The impregnating composition can be applied by brush, by spraying or by projection onto an external surface of the part.

In one embodiment, the amount of impregnating composition deposited during step 10 may be greater than or equal to 6.0 mg/cm ² , or even greater than or equal to 8.0 mg/cm ² .

The amount of impregnating composition deposited is expressed as a function of the surface of the part covered in order to be able to compare the properties of resistance to oxidation observed for parts with different surfaces. The same will be done for the quantities of solid compositions described below.

As shown in Figure 1, step 10 of applying the impregnating composition may be followed by a preliminary heat treatment step 20 preferably carried out under an inert atmosphere, for example at a temperature between 680°C and 740°C.

Such a preliminary heat treatment step 20 allows the impregnating composition to impregnate the internal porosity of the part and to form therein a layer for trapping carbon oxidation catalysts, and thus improves the resistance to oxidation of the part.

Nevertheless, step 20 is not necessary, because the impregnation heat treatment 40 which will be described below makes it possible, in the case where step 20 is not carried out, to obtain in a single heat treatment both the impregnation of the internal porosity of the part by the impregnation composition and by the composition of a protective glass against oxidation.

Whether the preliminary heat treatment 20 is carried out or not, the method then comprises a step of dry deposition of a solid composition of a protective glass against oxidation 30 followed by a step of impregnation heat treatment 40 .

The combination of steps 30 and 40 allows both the impregnation of the internal porosity of the part by the softened or molten composition of a protective glass, and the formation in the internal porosity of the part of a glass of protection against oxidation.

The protective glass against oxidation thus formed in the internal porosity of the part acts as an oxygen diffusion barrier and therefore makes it possible to limit the oxidation of the part made of composite material.

The heat treatment 40 can be carried out under vacuum or under pressure.

In one embodiment where the impregnation heat treatment 40 allows the solid composition to melt, capillarity phenomena make it possible to further improve the impregnation of the internal porosity of the part by the molten composition.

The combination of the layer obtained thanks to the impregnation composition and the softened or molten composition of a protective glass makes it possible to produce, directly in the internal porosity of the part, a protective coating against oxidation combining a trap role for carbon oxidation catalysts and an oxygen diffusion barrier.

Figure 2 illustrates a method according to another embodiment.

This method comprises steps 10, 20, 30 and 40 identical to those described above.

In particular, and as described above, step 20 is optional in the method illustrated in figure 2.

The method described in FIG. 2 further comprises a step 31 of depositing a second solid composition, identical to or different from the solid composition deposited during step 30.

The method then comprises a second heat treatment step 41 making it possible to obtain the same effects as the impregnation heat treatment, for the second solid composition deposited during step 31.

For example, if the solid composition used for step 31 is the same as for step 30, the second impregnation heat treatment 41 can be identical to the impregnation heat treatment 40. However, when the solid compositions of the steps 30 and 31 are different, the durations and/or temperatures of the heat treatments 40 and 41 may be different.

The method of FIG. 2 then comprises a step of dry deposition of a third solid composition 32.

The solid composition deposited by the dry route during step 32 may be identical to or different from that of step 30 and/or from that of step 31.

The method described in FIG. 2 then comprises a step of third heat treatment 42 making it possible to obtain the softening or melting of the third solid composition, its impregnation in the internal porosity of the part and the formation of a third protective glass against oxidation.

The third heat treatment makes it possible to obtain the same effects as the impregnation heat treatment 40 described above, but for the third solid composition.

It is also possible, according to an embodiment not illustrated, that a method comprises a step of applying an impregnating composition 10, optionally a preliminary heat treatment 20, the dry deposition of a solid composition of a protective glass against oxidation 30, an impregnation heat treatment 40, the dry deposition of a second solid composition of a protective glass against oxidation 31 and a second heat treatment 41, these steps each being able to be carried out as described above.

In carrying out the processes of the invention, the amount of total solid composition deposited may be greater than or equal to 3.0 mg/cm ² , or even greater than or equal to 6.0 mg/cm ² .

In embodiments comprising the dry deposition of a single solid composition, the amount of solid composition deposited may be between 2.0 and 10.0 mg/cm ² , or even between 3.0 and 8.0 mg /cm ² .

Example

The effect of a protective coating obtained by a method of the invention is now described by means of specific examples, which should not be considered as limiting the invention.

Parts made of carbon/carbon composite material protected against oxidation were prepared from a part made of carbon/carbon composite material by a method comprising a step of depositing a metal phosphate impregnating composition. The impregnation composition is an aqueous solution of aluminum dihydrogen phosphate concentrated at 50% by weight. This solution is for example available under the trade name “aluminum dihydrogen phosphate 50%” from the company Alfa.

One or more solid compositions of composition P1 or P2 were then deposited by dry process on a surface of the sample, a heat treatment being applied after each step of deposition by dry process. The heat treatment is carried out at a temperature of 700° C. for 1 hour 30 minutes.

The solid composition called PI comprises:

42 to 47% phosphorus pentoxide P ₂ O ₅

8 to 11% potassium oxide K ₂ O; - 14 to 18% sodium oxide Na ₂ O;

- 14 to 18% aluminum oxide Al ₂ O ₃ ;

- 7 to 10% boron sesquioxide B ₂ O ₃ .

The so-called P2 solid composition comprises: - 37 to 41% of phosphorus pentoxide P ₂ O ₅ ;

- 16 to 20% potassium oxide K ₂ O;

- 10 to 13% sodium oxide Na ₂ O;

- 16 to 19% aluminum oxide Al ₂ O ₃ ;

- 7.5 to 10.5% boron sesquioxide B ₂ O ₃ . Table 1 describes the nature and the quantity of the various solid compositions deposited on each of the various samples. - 8 hours at 650°C in air, then

- 3 hours at 850°C in air, then

- 5 min at 1000°C in air, then

- 2 hours at 650°C in air. The resistance to oxidation of samples A to G obtained according to the invention is compared between the samples and also with parts obtained by methods of the prior art.

For this, a sample was obtained according to the method described in document FR 2 726 554 (reference 1) and another according to the method described in document US 9 758 678 (reference 2) which differ from the invention.

Reference 1 is obtained by impregnating a part made of carbon/carbon composite material with an aqueous solution of aluminum dihydrogen phosphate Al(H ₂ PO ₄ ) 3 concentrated at 50% by weight applied with a brush. The impregnation is followed by a heat treatment at 700° C. for 5 hours.

Reference 2 is obtained by impregnating a part of carbon/carbon composite material in a manner similar to that of reference 1 above. This treatment provides an internal protective layer. The part is then coated with an outer layer obtained by applying with a brush or by thermal spraying a composition comprising, by mass:

- 67% aqueous solution of mono-aluminum phosphate at 50% by mass of water;

- 16.3% of B ₄ C powder with at most 2% impurities, the grains of the powder having a size of less than 7.5 μm;

- 11% of dry titanium powder, the particle size of which is between 150 μm and 20 μm;

- 4.7% water;

- 1% of a solution with the trade name "Surfynol® 440".

The resistance to oxidation is then determined by weighing the samples after the same steps as those described for samples A to G.

Table 2 and Figure 3 describe the oxidation resistance results obtained for samples A to G according to the invention, compared to reference samples 1 and 2.

[Tables 2]

As can be observed in Figure 3 and in Table 2, the process of the invention makes it possible to increase the resistance to oxidation of the parts compared to reference 1 even when a single solid composition is deposited. . In table 1, the symbol "—" indicates that the layer is less efficient than the reference, in the sense that the mass loss of mass is greater. For example, samples A and D exhibit greater mass losses than reference 2. They nevertheless exhibit better resistance to oxidation than reference 1. Furthermore, the comparison of samples A and C or D and F shows that it is advantageous to deposit a given quantity of solid composition in several stages rather than in a single one in order to obtain better resistance to oxidation.

Also, sample G shows that the use of two different solid compositions makes it possible to obtain better oxidation resistance properties than according to the prior art, and comparable to those obtained for samples where two identical solid compositions have been filed. Furthermore, sample G shows that the properties of resistance to oxidation are improved by the second composition, even if the latter is deposited in a smaller quantity than the first.

Finally, excellent penetration of the solid composition is observed during the heat treatment steps, for all the samples, even those comprising three steps of deposition of a solid composition.

Claims

[Claim 1] Process for protecting a part made of carbon/carbon composite material against oxidation, the process comprising at least the following steps:

- the application (10) on at least part of the outer surface of the part of an impregnating composition comprising at least one metal phosphate;

- the deposition (30) by dry process, after the application of the impregnating composition, on at least part of the external surface of the part of a solid composition of a glass for protection against oxidation; And

- an impregnation heat treatment (40) in order to soften or melt the solid composition deposited by the dry process, to allow the impregnation of the internal porosity of the part by the composition thus softened or melted, and to form a glass of protection against oxidation in the internal porosity of the part.

[Claim 2] Protection process according to claim 1, in which the dry deposition (30) of the solid composition is carried out by electrostatic spraying, by high-speed thermal powder spraying or by cold spraying.

[Claim 3] Method of protection according to claim 1 or 2, further comprising a step of preliminary heat treatment (20) at a temperature between 680°C and 740°C, carried out after the step of applying the impregnation composition (10) and before the step of depositing the solid composition (30).

[Claim 4] Protection method according to any one of claims 1 to 3, which comprises, after the impregnation heat treatment step (40), at least the following steps:

- the deposition (31) by dry process on at least part of the outer surface of the part of a second solid composition of a protective glass against oxidation identical to or different from the solid composition; Then

- a second impregnation heat treatment (41) in order to soften or melt the second solid composition deposited by the dry process, to allow the internal porosity of the part to be impregnated by the second composition as well softened or molten, and to form a second protective glass against oxidation in the internal porosity of the part.

[Claim 5] Protection method according to claim 4, which comprises, after the step of second impregnation heat treatment (41), at least the following steps:

- the deposition (32) by dry process on at least part of the outer surface of the part of a third solid composition of a protective glass against oxidation identical to or different from the first and/or the second composition solid ; Then

- a third impregnation heat treatment (42) in order to soften or melt the third solid composition deposited by the dry process, to allow the impregnation of the internal porosity of the part by the third composition thus softened or melted, and to form a third protective glass against oxidation in the internal porosity of the part.

[Claim 6] Protection method according to any one of claims 1 to 5, in which the total quantity of solid composition deposited on at least part of the external surface of the part during the step or steps of depositing by dry route of a solid composition (30, 31, 32) is greater than or equal to 3 mg/cm ² .

[Claim 7] Protection process according to any one of Claims 1 to 6, in which the solid composition or compositions are chosen from: a composition comprising, in percentages by weight:

- 42 to 47% phosphorus pentoxide P2O5;

- 8 to 11% potassium oxide K ₂ O;

- 14 to 18% sodium oxide Na ₂ O;

- 14 to 18% aluminum oxide Al ₂ O ₂ ;

- 7 to 10% of boron sesquioxide B ₂ O3; and a composition comprising, in mass percentages:

- 37 to 41% of phosphorus pentoxide P ₂ O ₅ ;

- 16 to 20% potassium oxide K ₂ O;

- 10 to 13% sodium oxide Na ₂ O; - 16 to 19% aluminum oxide AI2O3;

- 7.5 to 10.5% boron sesquioxide B ₂ O ₃ .

[Claim 8] Method of protection according to any one of the claims

1 to 7 in which the part made of carbon/carbon composite material is a friction part.