Patent Application
20240376018
The invention relates to the field of carbon/carbon composite material parts, and more specifically to methods for protecting such parts from oxidation.
The invention relates to the protection from oxidation of carbon/carbon composite material parts, i.e., 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 from oxidation of C/C composite brake discs, and, in particular, of brake discs for aircraft, for example airplanes, or of brake discs for land vehicles.
In an oxidizing environment, the ability of such parts to maintain good mechanical properties at high temperatures is subject to the presence of effective protection from carbon oxidation. Indeed, after its creation, the composite material usually has residual internal porosity which provides the ambient environment with access to the core of the material.
Additionally, in some applications, oxidation protection must maintain its effectiveness in the presence of moisture and/or carbon oxidation catalysts. This is particularly the case for C/C composite aircraft brake discs which can be exposed to moisture present on runways and come into contact with carbon oxidation catalysts introduced, for example, by potassium acetates or formates present in de-icing products commonly used on runways.
Protection from oxidation of such parts is generally provided by coatings deposited on the carbon/carbon composite material parts. However, such external coatings are sensitive to mechanical degradation caused by the friction, impact and vibrations inevitable for such parts.
Introducing a layer of oxidation protection into the internal porosity of the composite material parts has also been considered to overcome such disadvantages. For example, documents FR 2,726,554 and EP 3,072,866 describe methods for protecting a carbon/carbon composite material part from oxidation obtained using aqueous compositions making it possible to form, after a heat treatment, protection from oxidation in the internal porosity of the part.
However, it is desirable to improve the resistance to oxidation of such parts in order to increase their lifespan.
The inventors have noted 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 carbon/carbon composite material parts.
For this, the inventors propose a method for protecting a carbon/carbon composite material part from oxidation, the method comprising at least the following steps:
The inventors have noted that such a protection method allows the formation of a barrier against oxidation in the internal porosity of the part. It is advantageous for the protection to be present in the internal porosity since it is thus not subject to the impacts or friction that the part may undergo.
Furthermore, unlike the protection methods considered in the prior art, the solid composition of a protective glass is deposited dry.
It is understood by “dry deposition” that the method of the invention does not require the use of a third carrier liquid during the deposition of the solid composition and its infiltration into the internal porosity, unlike the deposition methods of the prior art which use slurries.
The choice of the dry method for deposition of the solid composition makes it possible to obtain, after an impregnation heat treatment, an oxidation-resistant glass directly in the internal porosity of the part with an increased deposition yield compared to the deposit methods of the prior art. In addition, the glass obtained is more homogeneous than with methods requiring carrier liquids for the solid composition.
In a dry deposition method, the solid composition can be sprayed in a liquid, solid or pasty form, without a third carrier liquid, and it forms a solid deposit once its deposition is completed.
For example, the dry deposition of the solid composition is carried out by electrostatic spraying, by thermal spraying of powder 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 should be understood as a deep impregnation of the internal porosity, i.e., that the oxidation-resistant glass is not only formed on the surface of the part, but extends from the surface deep into the part into its internal porosity.
For example, impregnation heat treatment allows the formation of an oxidation-resistant glass to a depth greater than or equal to 0.5 mm, measured from the external surface of the part.
In one embodiment, the oxidation-resistant glass can be formed in the internal porosity of the part and throughout its thickness.
In one embodiment, the method may comprise a preliminary heat treatment step at a temperature comprised between 680° C. and 740° C., carried out after the impregnation composition application step and before the solid composition deposition step.
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 oxidation-resistant glass.
The preliminary heat treatment allows the impregnation composition to further impregnate the internal porosity of the part and to form a layer therein for trapping carbon oxidation catalysts, and thus improves the oxidation resistance of the part. In addition, the presence of the impregnation composition allows better impregnation of the internal porosity of the preform by the solid composition.
This preliminary heat treatment is not necessary, however, and the application of the impregnation composition can be followed directly by the dry deposition of the solid composition. 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 a single step of impregnating the internal porosity of the part with the impregnation composition and forming there the oxidation-resistant glass and a layer for trapping carbon oxidation catalysts.
For example, the solid composition can be a glass powder composed of a plurality of particles, the mean size of which is less than or equal to 10 μm. Unless otherwise stated, “mean size” refers to the dimension given by the statistical particle size distribution at half of the population, called D50.
The duration and temperature of the heat treatment which make 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 an oxidation-resistant glass 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 phosphate or silicate glass powder, the impregnation heat treatment is carried out at a temperature comprised between 680° C. and 1100° C., and, for example, for a duration comprised between 1 minute and 2 hours.
For example, the heat treatment can be carried out by 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:
These additional steps make it possible to further improve the resistance to oxidation of the parts obtained, not only compared to those obtained with the methods of the prior art, but also compared to those obtained after the deposition of a single solid composition.
In one embodiment, the solid composition is the same for the first and second dry deposition steps. In another embodiment, the first and second solid compositions may be different.
The choice of identical or different solid compositions makes it possible to further improve the oxidation resistance properties of the parts obtained and to adapt them 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:
In this embodiment, the first, second and third compositions may be identical or different. It is also possible that two of the three compositions are identical, and the other is different.
An embodiment comprising three steps 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 steps rather than in a single step 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 onto at least a portion of the external surface of the part during the dry deposition step or steps can be greater than or equal to 3 mg/cm2, or even greater than or equal to 5 mg/cm2.
Such quantities of solid composition make it possible to obtain resistance to oxidation greater than that of parts obtained by the methods of the prior art.
In one embodiment, the solid oxidation-resistant glass composition(s) can be chosen from phosphate or silicate glass powders.
In one embodiment, the solid oxidation-resistant glass composition may comprise, in mass percentages:
In one embodiment, the solid oxidation-resistant glass composition may comprise, in mass percentages:
In one embodiment, the carbon/carbon composite material part is a friction part, for example, an aircraft brake disc.
The invention will now be described by means of figures illustrating particular embodiments of the invention which are present only for illustrative purposes in order to better understand the invention, and which should not be interpreted as limiting the invention.
Such a method comprises a first step 10 of application onto at least a portion of the external surface of the part of an impregnation composition comprising at least one metal phosphate.
In one example of embodiment, the metal phosphate is an aluminium phosphate. As a variant, a manganese, zinc, calcium or magnesium phosphate could be used, with or without phosphoric acid. In one embodiment, the metal phosphate is mono-aluminium phosphate Al(H2PO4)3.
In other embodiments, complex phosphates may also be used, for example, complex aluminium and calcium phosphates.
The impregnation composition makes it possible, after impregnation in the internal porosity, to form a layer for trapping carbon oxidation catalysts therein, and thus to improve the resistance to oxidation.
Indeed, it is known that phosphates make it possible to oppose the effect of catalytic agents of carbon oxidation, and in particular of alkaline or alkaline earth elements.
The impregnation composition can be applied by brush, by atomisation or by spraying onto an external surface of the part.
In one embodiment, the quantity of impregnation composition deposited during step 10 may be greater than or equal to 6.0 mg/cm2, or even greater than or equal to 8.0 mg/cm2.
The quantity of impregnation composition deposited is expressed as a function of the surface area of the part covered in order to be able to compare the oxidation resistance properties observed for parts with different surfaces. The same will be done for the quantities of solid compositions described below.
As indicated in
Such a preliminary heat treatment step 20 allows the impregnation composition to impregnate the internal porosity of the part and to form a layer therein for trapping carbon oxidation catalysts, and thus improves the oxidation resistance of the part.
However, 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 oxidation-resistant glass composition.
Whether the preliminary heat treatment 20 is carried out or not, the method then comprises a step of dry deposition of a solid oxidation-resistant glass composition 30 followed by an impregnation heat treatment step 40.
The combination of steps 30 and 40 allows both the impregnation of the internal porosity of the part with the softened or melted protective glass composition, and the formation in the internal porosity of the part of an oxidation-resistant glass.
The oxidation-resistant glass 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 composite material part.
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, capillary 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 by means of the impregnation composition and the softened or melted protective glass composition makes it possible to produce, directly in the internal porosity of the part, an oxidation protection coating combining the role of a trap for carbon oxidation catalysts and an oxygen diffusion barrier.
This method comprises steps 10, 20, 30 and 40 identical to those described previously.
In particular, and as described above, step 20 is optional in the method illustrated in
The method described in
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 may be identical to the impregnation heat treatment 40. However, when the solid compositions of steps 30 and 31 are different, the durations and/or temperatures of the heat treatments 40 and 41 may be different.
The method of
The solid composition deposited by dry method during step 32 may be identical or different to that of step 30 and/or that of step 31.
The method described in
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 impregnation composition 10, possibly a preliminary heat treatment 20, the dry deposition of a solid oxidation-resistant glass composition 30, an impregnation heat treatment 40, the dry deposition of a second solid oxidation-resistant glass composition 31 and a second heat treatment 41; these steps can each be carried out as described above.
In carrying out the methods of the invention, the quantity of total solid composition deposited may be greater than or equal to 3.0 mg/cm2, or even greater than or equal to 6.0 mg/cm2.
In embodiments comprising the dry deposition of a single solid composition, the quantity of solid composition deposited may be comprised between 2.0 and 10.0 mg/cm2, or even between 3.0 and 8.0 mg/cm2.
The effect of a protective coating obtained by a method of the invention is now described by means of particular examples, which should not be considered as limiting the invention.
Carbon/carbon composite material parts protected from oxidation were prepared from a carbon/carbon composite material part by a method comprising a step of depositing a metal phosphate impregnation composition. The impregnation composition is an aqueous solution of aluminium 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 method onto a surface of the sample, a heat treatment being applied after each dry deposition step. The heat treatment is carried out at a temperature of 700° C. for 1 hour and 30 minutes.
The solid composition called P1 comprises:
The solid composition called P2 comprises:
Table 1 describes the nature and quantity of the various solid compositions deposited onto each of the samples.
The resistance to oxidation is then determined by weighing the samples after:
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 prior art methods.
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 U.S. Pat. No. 9,758,678 (reference 2) which differ from the invention.
Reference 1 is obtained by impregnating a carbon/carbon composite material part with an aqueous solution of aluminium dihydrogen phosphate Al(H2PO4)3 concentrated at 50% by weight applied by brush. The impregnation is followed by a heat treatment at 700° C. for 5 hours.
Reference 2 is obtained by impregnating a carbon/carbon composite material part in a manner similar to that of reference 1 above. This treatment provides an internal layer of protection. The part is then coated with an external layer obtained by applying with a brush or by thermal spraying a composition comprising, in mass:
The oxidation resistance is then determined by weighing the samples after the same steps as those described for samples A to G.
Table 2 and
3%
As can be observed in
In Table 1, the symbol “---” indicates that the layer is less efficient than the reference, in the sense that the mass loss is greater. For example, samples A and D have greater mass losses than reference 2. They nevertheless have better oxidation resistance 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 steps rather than in a single step in order to obtain better resistance to oxidation.
In addition, sample G shows that the use of two different solid compositions makes it possible to obtain oxidation resistance properties better than according to the prior art, and comparable to those obtained for samples where two identical solid compositions have been deposited.
Furthermore, sample G shows that the oxidation resistance properties are improved by the second composition, even if this composition is deposited in a lower quantity than the first.
Finally, excellent penetration of the solid composition is observed during the heat treatment steps, for all samples, even those comprising three stages of deposition of a solid composition.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2109171 | Sep 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/051621 | 8/29/2022 | WO |
