Thermal oxidation protection layer for a composite material part comprising carbon

Abstract

The present invention relates to the use of a layer comprising an apatite compound of the following general formula (I): M10(XO4)6(Y)2 in which M represents a divalent cation selected from among Ca2+, Sr2+, Ba2+, Na2+, Pb2+, Mg2+, Zn2+, Mn2+, Be2+, Co2+, Fe2+, Ni2+ and Cu2+, XO4 represents a trivalent ionic group where X is selected from among P, Si, As and V and Y represents a monovalent anion selected from among Cl-, Br-, I- and OH- to protect a carbon-containing composite material part against thermal oxidation. The invention further relates to a part intended for the aeronautical or aerospace sector, made of a carbon-containing composite material and comprising the thermal oxidation protection layer, as well as to a method for manufacturing the part.

Description

Protective layer against thermal oxidation of a part made of composite material comprising carbon Technical Field

[0001] The present invention relates to the general field of carbon-containing composite materials, i.e. materials comprising a fibrous reinforcement densified by a matrix and in which the fibrous reinforcement and / or the matrix and / or an interphase coating between the fibers of the reinforcement and the matrix is ​​made of carbon or silicon carbide. A particular field of application of the invention is the protection against oxidation of parts made of carbon / carbon (C / C) composite material, in particular brake discs made of C / C composite, and in particular aircraft brake discs. Prior art

[0002] The materials used for aeronautical braking are generally C / C (carbon / carbon) or C / SiC (carbon / silicon carbide) composites. These materials were chosen for this application due to their lightness, their heat absorption capacity and their good tribological properties. However, in an oxidizing environment, the ability of such parts to maintain good mechanical properties at high temperatures is conditioned by the presence of effective protection against carbon oxidation. Indeed, after its preparation, the composite material usually has residual internal porosity which gives the ambient environment access to the core of the material. It is therefore susceptible to oxidization, particularly by atmospheric oxygen, at operating temperatures which are typically above 450°C.This oxidation can also be catalyzed, for example, by de-icing products used in airports, which may contain, for example, potassium acetates or formates. In addition, these composite materials are also exposed to moisture present on the runways, which can amplify the oxidation phenomenon. Several solutions have been developed to extend the lifespan of a composite material comprising carbon exposed to high temperatures in an oxidizing atmosphere. In particular, a two-layer protection solution can be implemented comprising a. internal anticatalytic layer based on aluminum metaphosphate A PCh and an external layer preventing the diffusion of oxygen into the material. Such a solution provides satisfactory protection but it remains desirable to provide new protection solutions that are simpler to implement and that provide at least equivalent protection against thermal, and possibly catalytic, oxidation.

[0003] It is known that C / C composite materials can be coated with a hydroxyapatite (HA) coating in the medical field for products intended for the human body, such as medical implants. The coating acts (in this field) as a layer allowing the proper integration of the composite material in-situ (in the body). However, it has never been described or suggested that such a coating can prevent the oxidation of the carbon present in the composite material and can therefore be used outside the medical field and in particular outside the human body, in a field where biocompatibility is of little importance, such as the aeronautical or aerospace field.

[0004] The inventors discovered that a layer comprising an apatitic compound could provide protection against thermal oxidation of composite materials containing carbon and that such a layer also exhibited better adhesion to carbon than existing protections. Such a layer is therefore simple to implement (since it is a single layer) and can, depending on requirements, penetrate into the pores to form an internal coating or remain on the surface. Statement of the invention

[0005] The present invention therefore relates to the use of a layer comprising an apatitic compound of the following general formula (I): M 10 (XO4)6(Y)2(I) in which M represents a divalent cation chosen from Ca 2+ , Sr 2+ , Ba 2+ , N / A 2+ , Pb 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Be 2+ , Co 2+ , Fe 2+ , Neither 2+ and Cu2+ XO4 represents a trivalent ionic group with X chosen from P, Si, As and V and Y represents a monovalent anion chosen from F', CF, Br', T and OH', advantageously Y represents a monovalent anion chosen from CP, Br', I' and OH' to protect against thermal oxidation a part made of composite material containing carbon, in particular carbon / carbon composite material, carbon / silicon carbide composite material or silicon carbide / silicon carbide composite material, the part being advantageously intended for aeronautics or aerospace.

[0006] In this application, the expressions "between ... and ..." and "from ... to ...", must be understood to include limits unless explicitly stated otherwise.

[0007] In the context of the present invention, the term "composite material containing carbon" means any composite material comprising a fibrous reinforcement densified by a matrix and in which the fibrous reinforcement and / or the matrix and / or an interphase coating between the fibers of the reinforcement and the matrix is ​​made of carbon or silicon carbide. Advantageously, the matrix (i.e. the continuous phase) and / or the fibrous reinforcement (i.e. the discontinuous phase) contain carbon. In particular, the matrix may be a pyrolytic carbon matrix and the fibrous reinforcement may be made of carbon fibers or silicon carbide fibers.

[0008] Thus, advantageously the composite material containing carbon according to the invention is a carbon / carbon (or C / C) or carbon / silicon carbide (or C / SiC) or silicon carbide / silicon carbide (or SiC / SiC) composite material, more advantageously a carbon / carbon composite material.

[0009] The layer comprising an apatitic compound of general formula (I) according to the invention is also called an oxidation protection layer according to the invention in the remainder of the description of the present application.

[0010] The oxidation protection layer according to the invention therefore comprises an apatitic compound of the following general formula (I): M 10 (XO4)6(Y)2(I) in which M represents a divalent cation chosen from Ca 2+ , Sr 2+ , Ba 2+ , N / A 2+ , Pb 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Be 2+ , Co 2+ , Fe 2+ , Neither 2+ and Cu 2+ , especially Ca 2+ ; XO4 represents a trivalent ionic group with X chosen from P, Si, As and V, in particular P and Y represents a monovalent anion chosen from F', CI', Br', I' and OH', advantageously Y represents a monovalent anion chosen from CI', Br', I' and OH', in particular OH'. Y ​​may represent a monovalent anion F' but advantageously it does not represent this monovalent anion.

[0011] Advantageously, the apatitic compound of general formula (I) is a phosphocalcic apatite, i.e. an apatitic compound of general formula (I) in which M = Ca 2+ and XO4= PO4 3 '. Even more advantageously, it is hydroxyapatite (or HA) with the formula Cai0(PO4)6(OH)2.

[0012] In an advantageous embodiment, the oxidation protection layer according to the invention may comprise one or more other compounds, apart from the apatitic compound of general formula (I). This compound may be chosen from transition metals or alkaline earth elements capable of forming a refractory oxide or carbide or boride such as titanium, zirconium, aluminum, a metal boride such as TiB2 or ZrB2, a metal phosphate salt such as monoaluminum phosphate (or MAIP), silicon dioxide (SiCh), a silicate and / or phosphate glass, a metal carbide such as B4C, an alkaline earth carbonate or a transition metal such as Ca(CO3)2 or Zr(CO3)2 and mixtures thereof.In particular, this compound is chosen from titanium, zirconium, aluminum, a metal boride, monoaluminum phosphate, silicon dioxide, silicate and / or phosphate glass, a metal carbide, an alkaline earth carbonate or a transition metal and mixtures thereof. These compounds make it possible to increase the effectiveness of the oxidation protection layer according to the invention at high and low temperatures by trapping possible catalysts which could come from the degradation of the oxidation protection layer according to the invention or from the external environment but also by trapping oxygen. The transition metals may be present in a mass proportion of between 5 and 20%; the metal borides may be present in a mass proportion of between 10 and 60%; the metal carbides may be present in. a mass proportion of between 10 and 60%; and the metal phosphate salts may be present in a mass proportion of between 5 and 80%.

[0013] In another advantageous embodiment, the oxidation protection layer according to the invention consists essentially of the apatitic compound of general formula (I). In particular, it may consist of the apatitic compound of general formula (I) in a mass proportion greater than or equal to 80%. Advantageously, it consists exclusively of the apatitic compound of general formula (I).

[0014] The present invention further relates to a part intended for aeronautics or aerospace made of composite material containing carbon comprising a protective layer against oxidation according to the invention as described above.

[0015] For the purposes of the present invention, the term "part intended for aeronautics or aerospace" means any part made of composite material according to the invention which will be used in these fields, for example in aircraft such as airplanes or helicopters, in particular airplanes. It is therefore not a part for medical use, in particular intended for the human body, more particularly intended to be in contact or implanted in the human body, for example in the form of an implant. It is therefore not a part which must be compatible with the human body, in particular biocompatible.

[0016] In an advantageous embodiment, the part intended for aeronautics or aerospace according to the invention is a friction part, in particular a brake disc, more particularly an aircraft brake disc, in particular an airplane brake disc.

[0017] Advantageously, the oxidation protection layer according to the invention is located inside and / or on the surface of the composite material part. In other words, the oxidation protection layer according to the invention can form an internal and / or external coating.

[0018] In a first particular embodiment, the oxidation protection layer according to the invention is located directly on the surface of the composite material part. It can also form the external surface of the composite material part. In other words, the composite material part can be devoid of any other oxidation protection layer.

[0019] In a second particular embodiment, the composite material part according to the invention is already coated with a first layer of protection against oxidation already known to those skilled in the art and already described in the prior art. In this case, the oxidation protection layer according to the invention is located on the first protective layer and thus constitutes a second protective layer. The oxidation protection layer according to the invention can form the external surface of the composite material part according to the invention.

[0020] In a third particular embodiment, the oxidation protection layer according to the invention is applied to the surface of the composite material part, so as to form a first oxidation protection layer, and a second oxidation protection layer already known to those skilled in the art is applied to the first oxidation protection layer. The second oxidation protection layer can form the external surface of the composite material part according to the invention.

[0021] In the second and third embodiments, the oxidation protection layer already known to those skilled in the art may in particular comprise a metal phosphate salt, for example aluminum phosphate.

[0022] In a fourth particular embodiment, the oxidation protection layer according to the invention forms a coating inside (and therefore in the porosities) of the composite material of the part intended for aeronautics or aerospace according to the invention. The oxidation protection layer according to the invention can, for example, penetrate the porosity of the part to a depth of one millimeter. The protective layer thus forms an internal coating.

[0023] The fourth embodiment, corresponding to the formation of an internal coating, can be combined with the first, second or third embodiment, corresponding to the formation of an external coating.

[0024] The present invention further relates to a method for manufacturing a part intended for aeronautics or aerospace in composite material containing carbon, said part comprising a layer of protection against thermal oxidation according to the invention, said method comprising the following steps: - a) supply of a part intended for aeronautics or aerospace in composite material containing carbon; - b) application to the part of a coating comprising an apatitic compound of the following general formula (I): MIO(X04)6(Y)2(I) in which M represents a divalent cation chosen from Ca 2+ , Sr 2+ , Ba 2+ , N / A 2+ , Pb 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Be 2+ , Co 2+ , Fe 2+ , Neither 2+ and Cu 2+ XO4 represents a trivalent ionic group with X chosen from P, Si, As and V and Y represents a monovalent anion chosen from F', CF, Br', T and OH', advantageously Y represents a monovalent anion chosen from CI', Br', I' and OH'.

[0025] The part intended for aeronautics or aerospace made of composite material containing carbon, said part comprising a layer of protection against thermal oxidation, is therefore recovered at the end of step b) of the process according to the invention.

[0026] The part intended for aeronautics or aerospace made of composite material comprising carbon can be obtained in a manner known per se, for example by densifying a fibrous reinforcement with a carbon matrix phase. This densification can be carried out by liquid means by impregnation and pyrolysis of a polymer precursor or by gaseous means by chemical vapor infiltration. The part obtained has a surface porosity and an internal porosity in communication with the surface porosity and located under the surface of the part.

[0027] This part may possibly have been coated with a first layer of protection against oxidation known to those skilled in the art, such as an undercoat based on a metal phosphate salt, for example aluminum phosphate, by a process well known to those skilled in the art.

[0028] Thus advantageously, the method according to the invention can comprise an intermediate step A), between steps a) and b), of prior deposition of a first layer of protection against oxidation on the part of step a).

[0029] The method according to the invention may also comprise a subsequent step C) of depositing a subsequent layer of protection against oxidation on the part obtained at the end of step b).

[0030] Steps A) and C) are carried out by methods well known to those skilled in the art.

[0031] Step b) of the process according to the invention can be carried out by the dry or wet method.

[0032] In a particular embodiment, step b) of the method according to the invention is carried out by the wet method. Thus, step b) of the method according to the invention may comprise the following successive steps: - cl) providing an aqueous solution or an aqueous suspension comprising the apatitic compound of general formula (I); - dl) possible preparation of the surface of the part in composite material containing carbon; - el) application of the solution or suspension comprising the apatitic compound of general formula (I); -fl) sintering heat treatment of the coated part.

[0033] Thus the method according to the invention can comprise: - steps a), cl), dl), el) and fl) or - steps a), A), cl), el) and fl) or - steps a), cl), dl), el), fl) and C).

[0034] Advantageously, step cl) of the process according to the invention consists of providing an aqueous solution comprising the apatitic compound of general formula (I), the aqueous solution being obtained by dissolving the compound apatitic compound of general formula (I) in an aqueous solution. The apatitic compound may be present in the aqueous solution in a mass content of between 5 and 80%, preferably between 5 and 30%.

[0035] In a particular embodiment, the aqueous solution is an acid solution having a pH of less than 4, advantageously less than 2, the acid being advantageously chosen from nitric acid HNO3, phosphoric acid H3PO4, H4P2O6, boric acid H3BO3 and their mixtures, advantageously it is HNO3.

[0036] In another advantageous embodiment, step c1) of the method according to the invention consists of providing an aqueous suspension comprising the apatitic compound of general formula (I) in the form of particles. The apatitic compound may be present in the aqueous solution in a mass content of between 5 and 30%. The volume average diameter of the particles of the suspension is advantageously less than 1 μm. This average diameter allows the particles to penetrate into the porosities of the composite material. The volume average diameter is for example measured by the dynamic light scattering technique, or "dynamic light scattering" in English, or by microscopy.

[0037] Unless otherwise stated, "average diameter" means the dimension given by the statistical particle size distribution to half of the population, known as D 50 .

[0038] This solution or suspension may also comprise a compound chosen from transition metals or alkaline-earth elements capable of forming a refractory oxide or carbide or boride such as titanium, zirconium, aluminum, a metal boride such as TiB2 or ZrB2, a metal phosphate salt such as monoaluminum phosphate (or MAIP), silicon dioxide (SiO2), a silicate and / or phosphate glass, or a precursor of these glasses (such as nitrates), a metal carbide such as B4C, an alkaline-earth carbonate or a transition metal such as Ca(CO3)2 or Zr(CO3)2 and mixtures thereof. In particular, this compound is chosen from titanium, zirconium, aluminum, a metal boride, monoaluminum phosphate, silicon dioxide, silicate and / or phosphate glass, a metal carbide, an alkaline earth or transition metal carbonate and mixtures thereof.

[0039] Step dl) of the method according to the invention consists of preparing the surface of the carbon-containing composite material part so as to make the surface compatible with an aqueous solution / suspension. This preparation can be carried out by any method known to those skilled in the art, such as by washing with a surfactant solution in an ultrasonic bath. The surfactant can be an ethoxylated acetylenic surfactant such as Surfynol ® or a surfactant from the family of ethoxylated glycerol fatty acid esters such as Levenol ®. It can also be the product marketed by the German company Sasol Gmbh under the name “Marlophen NP9”. The carbon-containing composite material part is then dried, for example by subjecting it to a temperature of between 90 and 100°C for a period of between 2 and 24 hours.

[0040] Step dl) of preparing the surface of the part made of composite material containing carbon is not obligatory if a first protective layer has been applied to the part made of composite material before the application of a coating comprising an apatitic compound of general formula (I), i.e. if step A) is carried out.

[0041] Step el) of the method according to the invention consists of applying the solution or suspension comprising the apatitic compound of general formula (I) to the composite part, optionally prepared in step dl). The solution or suspension comprising the apatitic compound of general formula (I) can be applied using a brush, by spray, by projection (i.e. spraying with a gun) or by any other means well known to those skilled in the art for impregnating the material. The solution or suspension comprising the apatitic compound of general formula (I) according to the invention thus constitutes an impregnation composition. It is typically possible to apply an amount of impregnation composition per unit area of ​​the treated part of between 10 mg / cm 2 and 30 mg / cm 2 .

[0042] Step fl) of the method according to the invention consists of a sintering heat treatment of the coated part obtained in step el).

[0043] In an advantageous embodiment, step fl) of the process according to the invention is carried out at a temperature between 700°C and 1300°C, in particular between 800°C and 1200°C, more particularly between 900°C and 1100°C, for example at 1000°C.

[0044] In another advantageous embodiment, step fl) of the method according to the invention is carried out for a duration of between 0.5 hours and 8 hours, in particular between 1 hour and 5 hours, more particularly between 1.5 hours and 3 hours, for example for 2 hours.

[0045] In yet another advantageous embodiment, step fl) of the method according to the invention is carried out at a pressure between atmospheric pressure and a pressure of 20 mPa, advantageously at 20 mPa.

[0046] The heat treatment allows sintering and therefore densification of the protective layer according to the invention. It can be implemented by all surface heating methods known to those skilled in the art such as induction, flash sintering, laser, IR.

[0047] In another particular embodiment of the process according to the present invention, step b) is carried out by the dry route. Thus, step b) of the process according to the invention may comprise the following successive steps: - c2) preparation of a solid composition comprising the apatitic compound of general formula (I) - d2) deposition of the solid composition by dry method on the part intended for aeronautics or aerospace in composite material containing carbon.

[0048] The method according to the invention can therefore comprise: - steps a), c2) and d2) or - steps a), A), c2) and d2) or - steps a), c2), d2) and C).

[0049] The solid composition of step c2) comprises the apatitic compound of general formula (I) in the form of particles. The volume average diameter of the particles is advantageously less than 1 pm. This average diameter allows the particles to penetrate into the porosities of the composite material.

[0050] The solid composition may consist solely of the apatitic compound. It may also comprise a compound selected from transition metals or alkaline earth elements capable of forming a refractory oxide or carbide or boride such as titanium, zirconium, aluminum, a metal boride such as TiB2 or ZrB2, a metal phosphate salt such as monoaluminum phosphate (or MAIP), silicon dioxide (SiO2), a silicate and / or phosphate glass, or a precursor of these glasses (such as nitrates), a metal carbide such as B4C, an alkaline earth carbonate or a transition metal such as Ca(CÛ3)2 or Zr(COs)2 and mixtures thereof. In particular, this compound is chosen from titanium, zirconium, aluminum, a metal boride, monoaluminum phosphate, silicon dioxide, silicate and / or phosphate glass, a metal carbide, an alkaline earth carbonate or a transition metal and mixtures thereof.

[0051] Step d2) is carried out by methods well known to those skilled in the art such as plasma spray.

[0052] In a particular embodiment, step b) further comprises, before step d2), step dl) of preparing the surface of the part made of composite material containing carbon as described above. Thus, the method according to the invention may comprise steps a), c2), dl) and d2) or a), c2), dl), d2) and C).

[0053] In a particular embodiment, step b) further comprises, after step d2), step f1) of sintering heat treatment as described below. Thus, the method according to the invention may comprise the steps: - a), c2), d2) and fl) or - a), A), c2), d2) and fl) or - a), c2), d2), fl) and C) or - a), c2), dl), d2) and fl) or - a), c2), dl), d2), fl) and C).

[0054] The present invention will be better understood in light of the description of the examples which follow. The examples are given for informational purposes only and are not limiting. EXAMPLES Example 1: Preparation of a C / C composite material coated with the protective layer according to the invention.

[0055] A 10% mass dispersion of hydroxyapatite in water is supplied.

[0056] The surface of a parallelepiped-shaped part measuring 38x38x20 mm made of C / C composite material is prepared by washing with a solution containing Levenol C201B® in an ultrasonic bath. The part is then removed from the bath and dried at a temperature between 90 and 100 °C for a period of 2 hours.

[0057] The hydroxyapatite solution is then applied to the part thus prepared with a brush at a content of 20 mg / cm 2 .

[0058] A heat treatment is then applied at a temperature of 1000°C for 2 hours and at a pressure of 20 mPa.

[0059] The composite material thus obtained is covered by the protective layer, not only on the surface but also in its internal porosities, to a depth of approximately 5 mm. Example 2: Preparation of a C / C composite material coated with the protective layer according to the invention.

[0060] A 10% by mass dispersion of hydroxyapatite in water is supplied. This dispersion is mixed with a 50% by mass solution of aluminum dihydrogen phosphate in water in the following mass proportions: 70% hydroxyapatite dispersion, 30% aluminum dihydrogen phosphate solution. Solution A is thus obtained.

[0061] The surface of a parallelepiped-shaped part with dimensions of 38x38x20 mm made of C / C composite material is prepared by washing with a solution containing Levenol®C201B, in an ultrasonic bath. The part is then removed from the bath and dried at a temperature between 90 and 100°C for a period of 2 hours.

[0062] Solution A is then applied to the part thus prepared with a brush at a content of 20 mg / cm 2 .

[0063] A heat treatment is then applied at a temperature of 1000°C for 2 hours and at a pressure of 20 mPa.

[0064] The composite material thus obtained is covered by the protective layer, not only on the surface but also in its internal porosities, to a depth of approximately 5 mm.

Claims

Claims

1. Use of a layer comprising an apatitic compound of the following general formula (I): MIO(X04)6(Y)2(I) in which M represents a divalent cation chosen from Ca 2+ , Sr 2+ , Ba 2+ , N / A 2+ , Pb 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Be 2+ , Co 2+ , Fe 2+ , Neither 2+ and Cu 2+ XO4 represents a trivalent ionic group with X chosen from P, Si, As and V and Y represents a monovalent anion chosen from CF, Br', T and OH' to protect against thermal oxidation a part made of composite material containing carbon, in particular carbon / carbon composite material, carbon / silicon carbide composite material or silicon carbide / silicon carbide composite material, characterized in that the part is intended for aeronautics or aerospace.

2. Use according to claim 1, characterized in that the compound of general formula (I) is hydroxyapatite.

3. Use according to any one of claims 1 or 2, characterized in that the layer further comprises a compound chosen from titanium, zirconium, aluminum, a metal boride, monoaluminum phosphate, silicon dioxide, silicate and / or phosphate glass, a metal carbide, an alkaline earth carbonate or a transition metal and mixtures thereof.

4. Part intended for aeronautics or aerospace made of composite material containing carbon comprising a layer of protection against thermal oxidation as defined in any one of claims 1 to 3.

5. Part according to claim 4, characterized in that it is a friction part, in particular a brake disc, more particularly an aircraft brake disc.

6. Part according to any one of claims 4 or 5, characterized in that the thermal oxidation protection layer is located inside and / or on the surface of the part.

7. A method of manufacturing a part according to any one of claims 4 to 6, said method comprising the following steps: - a) supply of a part intended for aeronautics or aerospace in composite material containing carbon; - b) application to the part of a coating comprising an apatitic compound of the following general formula (I): MIO(X04)6(Y)2(I) in which M represents a divalent cation chosen from Ca 2+ , Sr 2+ , Ba 2+ , N / A 2+ , Pb 2+, Mg 2+ , Zn 2+ , Mn 2+ , Be 2+ , Co 2+ , Fe 2+ , Neither 2+ and Cu 2+ XO4 represents a trivalent ionic group with X chosen from P, Si, As and V and Y represents a monovalent anion chosen from CF, Br', T and OH'.

8. Method according to claim 7, characterized in that step b) can be carried out by a dry or wet method.

9. Method according to claim 8, characterized in that step b) comprises the following successive steps: - cl) providing an aqueous solution or an aqueous suspension comprising the apatitic compound of general formula (I); - dl) possible preparation of the surface of the part in composite material containing carbon; - el) application of the solution or suspension comprising the apatitic compound of general formula (I); -fl) sintering heat treatment of the coated part.

10. Method according to claim 8, characterized in that step b) comprises the following successive steps: - c2) preparation of a solid composition comprising the apatitic compound of general formula (I) - d2) deposition of the solid composition by dry method on the part intended for aeronautics or aerospace in composite material containing carbon.

11. A method according to any one of claims 7 to 11, characterized in that the method comprises: 10, characterized in that it comprises: - an intermediate step A), between steps a) and b), of prior deposition of a first layer of protection against oxidation on the part of step a) or - a subsequent step C) of depositing a subsequent layer of protection against oxidation on the part obtained at the end of step b).