A method of protecting a composite material part against oxidation

Abstract

The invention provides a method for protecting a carbon-containing composite component against oxidation, the method comprising at least: applying a first coating composition in the form of an aqueous suspension on the outer surface of the component, the first coating composition comprising: a metal phosphate; a powder of a titanium-containing component; and a B4C powder; subjecting the applied first coating composition to a heat treatment to obtain a first coating on the outer surface of the component; applying a second coating composition on the first coating composition, the second coating composition comprising: an aqueous suspension of colloidal silica; a borosilicate glass powder; and a TiB2 powder; and subjecting the applied second coating composition to a second heat treatment to obtain a second coating on the first coating. By the particular selection of the first coating composition and the second coating composition in the order specified by the invention, a coating of increased thickness is obtained, which has good adhesion and imparts excellent oxidation resistance in wet media and at very high temperatures.

Description

[0001] This application is a divisional application. The parent application of this divisional application has the application number 2019101237337, the application date is February 19, 2019, and the invention title is "A method for protecting composite material parts against oxidation". Technical Field

[0002] This invention relates to providing oxidation protection for components made of carbon-containing composite materials (i.e., components comprising fiber reinforcements densified from a matrix), wherein the fiber reinforcements and / or the matrix and / or the interphase coating between the reinforcing fibers and the matrix are made of carbon. A particular application area of ​​this invention is providing oxidation protection for components made of carbon / carbon (C / C) composite materials, particularly C / C composite brake discs, and more specifically aircraft brake discs. Background Technology

[0003] In oxidizing media, the ability of carbon-containing composite components to maintain good mechanical properties at high temperatures depends on the presence of effective protection against carbon oxidation. Specifically, once the composite material is prepared, it typically produces residual internal pores that allow the surrounding medium to penetrate the core of the material.

[0004] To provide this antioxidant protection, internal systems based on metal phosphates are known to be used, which are placed in place by impregnating the residual pores of the composite component with a composition in the form of an aqueous solution. To extend the protection to higher temperatures, external coatings can be used.

[0005] For example, document US 2007 / 0026153 describes a method for protecting carbon-containing composite components, particularly brake discs made of C / C composites. In the first step of this method, internal protection is achieved by impregnation with an aqueous solution of a metal phosphate (such as monoaluminate phosphate) and heat treatment at approximately 700°C under nitrogen (N2). Subsequently, protection is further achieved by applying an aqueous medium containing colloidal silica SiO2, and Pyrex... A liquid composition of borosilicate glass powder and titanium diboride (TiB2) powder forms an external coating. When used in an oxidizing medium, TiB2 oxidizes and forms B2O3, thereby regenerating B2O3 and preserving the healable borosilicate glass phase from a paste-like state at 600°C.

[0006] However, due to the loss of B2O3 and the consumption of TiB2, repeated exposure to humid environments results in a relatively limited protection lifespan. When subjected to very high temperatures and pressures, there is a desire to improve the protection provided by the solution outlined in US 2007 / 0026153. Summary of the Invention

[0007] In a first aspect, the present invention provides a method for protecting carbon-containing composite material components against oxidation, the method comprising at least:

[0008] - Applying a first coating composition in the form of an aqueous suspension to the outer surface of the component, the first coating composition comprising:

[0009] - Metal phosphates;

[0010] - Powder containing titanium; and

[0011] - B4C powder;

[0012] - The applied first coating composition is heat-treated to obtain a first coating on the outer surface of the component;

[0013] - Applying a second coating composition onto the first coating composition, the second coating composition comprising:

[0014] - An aqueous suspension of colloidal silica;

[0015] - Borosilicate glass powder; and

[0016] - TiB2 powder; and

[0017] - The applied second coating composition is subjected to a second heat treatment to obtain a second coating on the first coating.

[0018] To improve the performance of the composition disclosed in US 2007 / 0026153, the inventors tested a first solution that involved increasing the thickness of the coating described in that document. For this purpose, a second layer of the same composition was applied. The increased thickness resulted in reduced adhesion of the resulting bilayer coating. Therefore, this solution did not improve the antioxidant properties.

[0019] The present invention relates to using the above-described first coating composition to provide a first coating constituting an adhesive underlayer for the composition disclosed in document US 2007 / 0026153, which corresponds to the above-described second coating composition.

[0020] By specifically selecting and combining the first and second coating compositions in the order specified in this invention, a coating with increased thickness is obtained, which exhibits good adhesion and imparts excellent oxidation resistance in wet media and at high temperatures. The resulting oxidation resistance is particularly significantly improved compared to the performance obtained using the solution in US 2007 / 0026153 or compared to other coatings with increased thickness.

[0021] In one embodiment, the titanium-containing component is titanium metal.

[0022] In one embodiment, the metal phosphate is aluminum phosphate.

[0023] In one embodiment, the first coating composition comprises, prior to application:

[0024] - Metal phosphates with a content ranging from 27% to 36% by weight;

[0025] - Powders containing titanium in the range of 8% to 18% by weight; and

[0026] - B4C powder with a content ranging from 11.5% to 21% by weight.

[0027] In one embodiment, during the first heat treatment, the first heat treatment temperature is in the range of 330°C to 740°C.

[0028] In one embodiment, the aqueous suspension of colloidal silica is alkaline.

[0029] By using an alkaline suspension, the adhesion of the second coating to the first coating, which is based on an acidic metal phosphate, can be advantageously further improved.

[0030] In one embodiment, the second coating composition comprises, prior to application:

[0031] - An aqueous suspension of colloidal silica with a content of 25% to 50% by weight, wherein the silica content in the suspension is in the range of 20% to 50% by weight;

[0032] - Borosilicate glass powder with a content ranging from 5% to 20% by weight; and

[0033] - TiB2 powder with a content ranging from 30% to 60% by weight.

[0034] - The remainder, if any, is water.

[0035] In one embodiment, during the second heat treatment, the second heat treatment temperature is in the range of 600°C to 800°C. The second treatment temperature may, for example, be in the range of 650°C to 740°C.

[0036] In one embodiment, at least one internal protective layer is formed by impregnating at least a portion of the composite material component with an impregnation composition containing metal phosphates before applying the first coating composition.

[0037] In one embodiment, the component is a friction component. In particular, the friction component may be made of a carbon / carbon composite material. Attached Figure Description

[0038] Other features and advantages of the invention will become apparent from the following description, given in a non-limiting manner and with reference to the accompanying drawings, wherein:

[0039] - Figure 1 These are flowcharts of the successive steps of the exemplary method of the present invention; and

[0040] - Figures 2 to 5 The plot is a curve showing the change in weight of samples made of C / C composite material with different oxidation resistances as a function of oxidation duration. Detailed Implementation

[0041] In the following description, consideration is given to protecting C / C composite material components against oxidation, and more specifically, protecting brake discs, such as aircraft brake discs. More generally, the invention is applicable to providing oxidation-resistant components made of any carbon-containing composite material.

[0042] exist Figure 1 In a particular embodiment of the method, the first stage includes forming an internal protection within an accessible pore in a part of the component or a portion of the component to be protected, the internal protection comprising at least one metal phosphate suitable for providing protection against carbon oxidation.

[0043] This can be performed as described in document US 5853821. The first step involves depositing a wetting agent into the accessible pores of the composite material. For this purpose, an aqueous solution of the wetting agent is used, such as a substance sold by the German supplier Sasol GmbH under the name "Marlophen NP9". After impregnating the composite material with this wetting agent solution and allowing it to dry, an impregnation composition in the form of an aqueous solution containing a metal phosphate is applied to the entire outer surface of the part, or selectively applied to a portion of the outer surface of the part, for example by means of a brush or spray (i.e., with a spray gun) (step 10). For example, an aqueous solution of aluminum hydrogen phosphate Al(H2PO4)3 is used. The metal phosphate can also be zinc phosphate, for example having the following chemical formula: Zn3(PO4)2·xH2O, manganese phosphate, for example having the following chemical formula: Mn(H2PO4)2·2H2O, or actually magnesium phosphate, for example having the following chemical formula: Mg3(PO4)2·8H2O.

[0044] The wetting agent present on the surface of the accessible pores in the composite material helps the impregnating composition penetrate into the accessible pores of the composite material. Drying is then performed, followed by a preheating treatment (step 20) to restrict the entry of oxygen from the air into the pore surface through the internal protection provided by the metal phosphate.

[0045] Preheating is performed by raising the temperature to a range of 200°C to 740°C, for example, in the range of 650°C to 740°C, such as about 700°C. This temperature can be maintained for one to several hours.

[0046] Preheating can be carried out in a non-oxidizing atmosphere, such as nitrogen (N2).

[0047] Subsequently, first and second surface coatings are formed on the composite material component. These coatings are formed in the manner described below.

[0048] First, a first coating is formed using a first coating composition.

[0049] The first coating composition is applied, for example by brushing or spraying, to the outer surface of the component or to a portion of the outer surface, preferably at the same location as the impregnation composition (step 30).

[0050] For brake discs made of carbon-based composite materials, the application of the impregnation composition and the first coating composition may be limited to the non-friction portions of the outer surface, and then the frictional annular surfaces of the end discs in a set of stator and rotor discs or the relative frictional surfaces of the discs located between the end discs shall not be impregnated to avoid damaging their tribological properties.

[0051] Examples of the first coating composition applicable to the context of this invention are described in document US 2015 / 0291805.

[0052] As described above, the first coating composition comprises:

[0053] - Metal phosphates;

[0054] - Powder containing titanium; and

[0055] - B4C powder.

[0056] The metal phosphate of the first coating composition may comprise aluminum phosphate, such as aluminum hydrogen phosphate Al(H2PO4)3. This compound is commercially available in an aqueous solution of 48%-50% by weight. In the same manner as described above, zinc, manganese, or magnesium phosphates may be used as the metal phosphate of the first coating composition.

[0057] Titanium-containing components can be selected from: titanium metal (Ti); titanium diboride (TiB2); titanium carbide (TiC); titanium dioxide (TiO2); and mixtures thereof.

[0058] Specifically, the first coating composition may comprise titanium metal powder and / or titanium diboride powder. Specifically, the titanium-containing component may be titanium metal.

[0059] Powders containing titanium may be in the form of particles with an average size of less than or equal to 150 micrometers (µm). Unless otherwise stated, the term "average size" is used to refer to the size given by the statistical particle size distribution of the half-population, written as D50.

[0060] Boron carbide (B4C) powder can be in the form of particles with an average size of less than or equal to 30 µm, for example, less than or equal to 7.5 µm.

[0061] Additionally, the first coating composition may contain an organic dispersant. The organic dispersant is advantageously used to further improve the adhesion of the first coating to the underlying component.

[0062] Organic dispersants can be water-soluble and nonionic, such as those made from oxyethylene fatty acids, oxyethylene fatty alcohols, oxyethylene alkylphenols, or higher ester polyols. Organic dispersants can also be alkoxyacetylene polyols, such as those marketed by the US supplier Evonik under the name "Surfynol". "Sales. The organic dispersant used can also be supplied by KAO Company under the name "Levenol" "The products sold may be those sold by the supplier Sasol GmbH under the name "Marlophen NP9".

[0063] In addition, the first coating composition may include refractory filler. Prior to application, the refractory filler may be present in the first coating composition at a content of less than or equal to 5% by weight.

[0064] Refractory fillers may include one or more refractory oxides, nitrides, or carbides (except B4C). Refractory fillers may include one or more ceramic compounds. Refractory fillers may be in the form of particles with an average size of less than or equal to 150 µm.

[0065] In one embodiment, the first coating composition may include, prior to application:

[0066] - Metal phosphates with a content ranging from 27% to 36% by weight;

[0067] - B4C powder with a content ranging from 11.5% to 21% by weight;

[0068] - Powder containing titanium in the range of 8% to 18% by weight;

[0069] - Organic dispersants, such as alkoxyacetylene polyols, in a content ranging from 0.1% to 1.5% by weight;

[0070] - Water content ranging from 33% to 50% by weight; and

[0071] - Optionally, refractory filler comprising less than or equal to 5% by weight.

[0072] In one embodiment, prior to application, the first coating composition may substantially, i.e., at least 90% by weight, consist of at least one metal phosphate, titanium metal powder, boron carbide B4C powder, an organic dispersant, and water.

[0073] Once the first coating composition is applied, a first heat treatment is then performed to obtain the first coating (step 40). During the first heat treatment, a first treatment temperature is applied.

[0074] During the first heat treatment, the first treatment temperature can be high enough to achieve association between at least one crystalline metal phosphate phase and at least one amorphous metal phosphate phase within the first coating. The first treatment temperature can be kept low enough to avoid crystallizing all metal phosphates and thus preserve the amorphous metal phosphate phase in the resulting first coating.

[0075] The proportion of amorphous metal phosphates obtained in the first coating can depend on the first treatment temperature and the duration of application. For example, increasing the application duration at the first treatment temperature can lead to a decrease in the proportion of amorphous metal phosphates in the first coating.

[0076] The resulting first coating can be a ratio of [the weight of the amorphous metal phosphate in the first coating] divided by [the sum of the weight of the amorphous metal phosphate in the first coating and the weight of the crystalline metal phosphate in the first coating] greater than or equal to 0.1, for example, greater than or equal to 0.2. In particular, this ratio can be in the range of 0.1 to 0.7, for example, in the range of 0.2 to 0.5.

[0077] The crystalline and amorphous phases of metal phosphates can be detected by (1D and 2D) nuclear magnetic resonance (NMR) spectroscopy of solid nuclei such as 31P and 27Al.

[0078] The first processing temperature can be in the range of 330°C to 740°C, for example, in the range of 650°C to 740°C. This temperature value is specifically used to obtain a first coating comprising a first phase and a second phase, wherein the metal phosphate in the first phase is in crystalline form and the metal phosphate in the second phase is in amorphous form.

[0079] During the first heat treatment, the first treatment temperature can be applied for a duration of 1 hour (h) or more, for example, in the range of 1h to 15h.

[0080] The first heat treatment can be carried out in an oxidizing atmosphere, such as in air. In a variant, the first heat treatment can be carried out in an inert atmosphere, such as in nitrogen.

[0081] The amount of the first coating composition applied can be selected to obtain a first coating with a thickness ranging from 40 µm to 80 µm. Typically, the amount of the first coating composition applied, measured prior to the first heat treatment, can be 16 mg / cm². 2 ) to 23 mg / cm² 2 Within the range of ).

[0082] The above description relates to forming a first coating on the surface of a composite material component. A second coating is then prepared on top of the first coating.

[0083] The second coating is made from a second coating composition, as described below.

[0084] The second coating composition is applied to the previously formed first coating, for example, using a brush or by spraying (step 50). The second coating composition is applied in contact with the first coating.

[0085] Examples of the second coating composition applicable to the context of this invention are described in document US 2007 / 0026153.

[0086] As described above, the second coating composition comprises:

[0087] - An aqueous suspension of colloidal silica;

[0088] - Borosilicate glass powder; and

[0089] - TiB2 powder.

[0090] Borosilicate glass and TiB2 powder are dispersed in an aqueous suspension of colloidal silica.

[0091] The average particle size of silica in the suspension is less than or equal to 200 nanometers (nm), for example, in the range of 5 nm to 100 nm, or in the range of 5 nm to 40 nm.

[0092] Borosilicate glass comprises silicon dioxide and boron oxide (B₂O₃). The sum of the weight contents of silicon dioxide and boron oxide (B₂O₃) in borosilicate glass can be greater than or equal to 80%, for example, greater than or equal to 90%.

[0093] As an example of borosilicate glass, Pyrex glass from the US supplier Corning can be used. "Glass powder, or glass supplied by the UK supplier Barloword Scientific (formerly Bibby Sterilin), which has essentially the following composition (by weight percentage):"

[0094] - SiO2: 80.60%;

[0095] - B2O3: 12.60%;

[0096] - Na2O3: 4.2%;

[0097] - Al2O3: 2.25%;

[0098] - Cl: 0.1%;

[0099] - CaO: 0.1%;

[0100] - MgO: 0.05%;

[0101] - Fe2O3: 0.05%.

[0102] Other types of glass may be used, such as borosilicate glass from the US supplier Ferro with reference numbers 823-01 to -05, or glass sold by the German supplier Schott AG under the names "Duran" (e.g., reference number "8330"), "Suprax" or "Borofloat 40".

[0103] Aqueous suspensions of colloidal silica can be alkaline. This alkalinity can be imparted by additives, which are advantageous for use as stabilizers of colloidal suspensions, such as ammonia (NH3) or sodium oxide (Na2O).

[0104] Prior to application, the second coating composition may include:

[0105] - An aqueous suspension of colloidal silica with a content of 25% to 50% by weight, wherein the silica content of the suspension is in the range of 20% to 50% by weight;

[0106] - Borosilicate glass powder with a content ranging from 5% to 20% by weight;

[0107] - TiB2 powder with a content ranging from 30% to 60% by weight; and

[0108] - The remainder, if any, is water.

[0109] In particular, an aqueous suspension of colloidal silica may be present in the second coating composition at a weight content of 30% to 40% prior to application.

[0110] In particular, borosilicate glass powder may be present in the second coating composition at a weight content of 10% to 15% prior to application.

[0111] Specifically, TiB2 powder may be present in the second coating composition at a weight content ranging from 35% to 50% prior to application.

[0112] Once the second coating composition is applied, a second heat treatment is then performed to obtain a second coating on the first coating (step 60). The resulting second coating comes into contact with the first coating. During the second heat treatment, a second treatment temperature is applied.

[0113] The second treatment temperature applied during the second heat treatment can be in the range of 600°C to 800°C, for example, in the range of 650°C to 740°C.

[0114] During the second heat treatment, the second treatment temperature may be applied for a duration of 3 hours or more, for example, in the range of 3h to 4h. In a variant, the second treatment temperature may be applied for a duration of 10 minutes or less, for example, in the range of 1min to 10min.

[0115] The second heat treatment can be carried out under an inert atmosphere, such as nitrogen.

[0116] The amount of the second coating composition applied can be selected to obtain a second coating with a thickness ranging from 30 µm to 70 µm. Typically, the amount of the second coating composition applied, measured before the second heat treatment, is 14 mg / cm³. 2 Up to 21 mg / cm 2 Within the range.

[0117] Example

[0118] The inventors conducted tests to demonstrate the advantages of this invention in terms of antioxidant protection.

[0119] During these tests, a density of 1.65 grams per cubic centimeter (g / cm³) was used. 3 ) to 1.9 grams per cubic centimeter (g / cm³) 3 Components made of C / C composite materials within the range of approximately 6% to 18% have a residual void volume. These components offer a variety of different antioxidant protections.

[0120] In the following tests, the following preparatory steps were performed before applying all oxidation protection:

[0121] - Impregnate with an aqueous solution of "Marlophen NP9" or Levenol C201-B before drying;

[0122] - Apply a 50% by weight aqueous solution of monoaluminophosphate in water using a brush or by robotic spraying (i.e., using a spray gun); and

[0123] - Heat treatment is performed under a nitrogen (N2) atmosphere by gradually increasing the temperature to 700°C and holding it at that temperature for at least 1 hour.

[0124] To evaluate the protective antioxidant properties tested, various oxidation schemes were used, as described below:

[0125] - P650+: Expose to air at 650°C for 4 hours, repeat 6 times and restore to ambient temperature after each exposure, then soak in water at 20°C for 24 hours, and then expose to air at 650°C for 16 hours;

[0126] - P850+: Expose to air at 850°C for 30 min, repeat 6 times, restore to ambient temperature after each exposure, then soak in water at 20°C for 24 h, and then expose to air at 850°C for 3 h;

[0127] - P1200+: Exposure to 650℃ in air for 4 hours, followed by return to ambient temperature, then exposure to 1200℃ for 15 minutes, followed by return to ambient temperature, then two separate exposures to 650℃ for 4 hours with intervals between return to ambient temperature, then exposure to 1200℃ for 15 minutes, followed by return to ambient temperature, and then exposure to 650℃ for 8 hours; and

[0128] - P1400+: Exposure to 650℃ in air for 4 hours, then return to ambient temperature, then exposure to 1400℃ for 10 minutes, then return to ambient temperature, then exposure to 650℃ for 4 hours twice, then return to ambient temperature, then exposure to 1400℃ for 10 minutes, then return to ambient temperature, then exposure to 650℃ for 8 hours.

[0129] The steps for soaking in water include:

[0130] - Immerse the applied component in softened water at 20°C for 24 hours; and

[0131] - Dry the sample at 90°C for 4 hours.

[0132] Reference protection 1 (not the present invention)

[0133] The first reference protection (“Reference Protection 1”) is provided by applying an aqueous suspension to the C / C composite component, the aqueous suspension comprising:

[0134] - An aqueous solution of aluminum monophosphate with a content of 67% by weight, which contains 50% by weight of aluminum monophosphate;

[0135] - Titanium metal powder with a content of 11% by weight;

[0136] - B4C powder with a content of 16.3% by weight;

[0137] - Water content equal to 4.7% by weight; and

[0138] - 1% Surfynol .

[0139] The applied composition was heat-treated at 660°C for 1 hour under a nitrogen atmosphere to obtain a coating.

[0140] Apply a single-layer composition to form reference protection 1.

[0141] For each test protocol performed, the amounts of composition deposited before and after heat treatment for reference protection 1 are listed in Table 1. The amount of composition per unit area is given.

[0142] Table 1

[0143]

[0144] The coating obtained for reference protection 1 has a thickness of approximately 60 µm.

[0145] Reference protection 2 (not the present invention)

[0146] The second reference protection (“Reference Protection 2”) is provided by applying a composition to the C / C composite component, the composition comprising:

[0147] - An aqueous suspension of colloidal silica with a content of 38% by weight, wherein the silica content in the aqueous suspension is 30% by weight;

[0148] - Pyrex content equal to 13% by weight "Borosilicate glass powder; and"

[0149] - TiB2 powder with a content of 49% by weight.

[0150] Using Pyrex "The glass is supplied by the American supplier Corning and has the following basic components (by weight percentage):"

[0151] - SiO2: 80.60%;

[0152] - B2O3: 12.60%;

[0153] - Na2O3: 4.2%;

[0154] - Al2O3: 2.25%;

[0155] - Cl: 0.1%;

[0156] - CaO: 0.1%;

[0157] - MgO: 0.05%;

[0158] - Fe2O3: 0.05%.

[0159] The applied composition was heat-treated at 700°C for 3 hours under a nitrogen atmosphere to obtain a coating.

[0160] Apply a single-layer composition to form reference protection 2.

[0161] For each test protocol performed, the amounts of composition deposited before and after heat treatment for reference protection 2 are listed in Table 2. The amount of composition per unit area is given.

[0162] Table 2

[0163]

[0164] The coating obtained for reference protection 2 has a thickness of approximately 60 µm.

[0165] Reference protection 3 (not the present invention)

[0166] The third reference protection (“Reference Protection 3”) is prepared by applying an aqueous suspension to a C / C composite component, said aqueous suspension comprising:

[0167] - An aqueous solution of aluminum monophosphate with a content of 67% by weight, which contains 50% aluminum monophosphate by weight;

[0168] - Titanium metal powder with a content of 11% by weight;

[0169] - B4C powder with a content of 16.3% by weight;

[0170] - Water content equal to 4.7% by weight; and

[0171] - 1% Surfynol .

[0172] The first layer of the composition is applied, followed by a first heat treatment at 660°C for 1 hour under a nitrogen atmosphere.

[0173] The second layer of the composition was then applied to the resulting coating. Subsequently, a second heat treatment was performed at 660°C for 1 hour under a nitrogen atmosphere.

[0174] Thus, a double-layer coating is obtained using the above composition.

[0175] For each test protocol performed, the amount of composition deposited for reference protection 3 is listed in Table 3. The amount of composition per unit area is given.

[0176] Table 3

[0177]

[0178] The coating obtained for reference protection 3 has a thickness of approximately 100 µm.

[0179] Protection of this invention

[0180] An exemplary protection of the present invention (“the protection of the present invention”) is prepared by applying a first coating composition in the form of an aqueous suspension to a C / C composite component, the first coating composition comprising:

[0181] - An aqueous solution of aluminum monophosphate with a content of 67% by weight, which contains 50% aluminum monophosphate by weight;

[0182] - Titanium metal powder with a content of 11% by weight;

[0183] - B4C powder with a content of 16.3% by weight;

[0184] - Water content equal to 4.7% by weight; and

[0185] - 1% Surfynol .

[0186] The first layer of the first coating composition is applied, followed by a first heat treatment at 660°C for 1 hour under a nitrogen atmosphere. This yields the first coating.

[0187] Subsequently, a second coating composition is applied to the obtained first coating, the second coating composition comprising:

[0188] - An aqueous suspension of colloidal silica with a content of 38% by weight, wherein the silica content in the aqueous suspension is 30% by weight;

[0189] - Pyrex content equal to 13% by weight "Borosilicate glass powder; and"

[0190] - TiB2 powder with a content of 49% by weight.

[0191] Then, a second heat treatment is performed at 700°C for 3 hours in an inert atmosphere. This yields a second coating on top of the first coating.

[0192] For each test protocol performed, the amount of composition deposited for protection under this invention is listed in Table 4. The amount of composition per unit area is given.

[0193] Table 4

[0194]

[0195] The coating obtained for protection under this invention has a thickness of approximately 100 µm.

[0196] Test results for various oxidation schemes are as follows: Figures 2 to 5 As shown. In each figure:

[0197] - Reference protection 1 marked point;

[0198] - Reference protection 2 marked point;

[0199] - Reference protection 3 marked point; and

[0200] - The protection markings of this invention are point.

[0201] P650+ and P850+ tests ( Figure 2 and 3 The results show that the present invention provides significantly less weight loss compared to references 1 to 3. These tests demonstrate that the present invention offers better antioxidant protection in wet media compared to references 1 to 3.

[0202] P1200+ and P1400+ tests ( Figure 4 and 5 The results show that the present invention provides significantly less weight loss compared to references 1 to 3. These tests also demonstrate that the present invention offers better antioxidant protection at very high temperatures compared to references 1 to 3.

[0203] The inventors also observed that the reference protection 4, consisting of two superimposed reference protections 2, could not be used to improve antioxidant protection, resulting in limited adhesion of the double-layer coating under this solution.

[0204] Adhesion problems were also encountered during testing of Reference Protection 5, which comprises a double coating "reverse" to the protection of the present invention. Therefore, Reference Protection 5 is formed by first applying the second coating composition described above, and then applying the first coating composition described above.

[0205] By specifically selecting and combining the first and second coating compositions in the order specified in this invention, a coating with increased thickness is obtained, exhibiting good adhesion and excellent oxidation resistance in wet media and at very high temperatures. This oxidation resistance is particularly significantly superior to coatings that also have increased thickness but different compositions, in which two layers of the first coating composition are applied sequentially. Figures 2 to 5 Reference protection 3 marks (Points). Therefore, the specific combination of the first and second coating compositions of the present invention provides antioxidant properties, which are particularly effective in wet media and at high temperatures.

[0206] The term “within the range of… to…” should be understood to include the boundary.

Claims

1. A method for protecting carbon-containing composite material components against oxidation, the method comprising at least: - Applying a first coating composition in the form of an aqueous suspension to the outer surface of the component, the first coating composition comprising: - Metal phosphates; - Powder containing titanium; and - B4C powder; - The applied first coating composition is heat-treated to obtain a first coating on the outer surface of the component; - Applying a second coating composition onto the first coating composition, the second coating composition comprising: - An aqueous suspension of colloidal silica; - Borosilicate glass powder; and - TiB2 powder; and - The applied second coating composition is subjected to a second heat treatment to obtain a second coating on the first coating; During the second heat treatment, the treatment temperature is in the range of 600°C to 800°C, and the treatment time is longer than or equal to 3 hours; wherein, before applying the first coating composition, at least a portion of the composite material component is impregnated with an impregnation composition containing metal phosphate to form at least one internal protective layer.

2. The method according to claim 1, wherein the titanium-containing component is titanium metal.

3. The method according to claim 1, wherein the metal phosphate is aluminum phosphate.

4. The method of claim 1, wherein the first coating composition comprises, prior to application: - Metal phosphates with a content ranging from 27% to 36% by weight; - Powders containing titanium in the range of 8% to 18% by weight; and - B4C powder with a content ranging from 11.5% to 21% by weight.

5. The method according to claim 1, wherein during the first heat treatment, the first heat treatment temperature is in the range of 330°C to 740°C.

6. The method according to claim 1, wherein the aqueous suspension of colloidal silica is alkaline.

7. The method of claim 1, wherein the second coating composition comprises, prior to application: - An aqueous suspension of colloidal silica with a content of 25% to 50% by weight, wherein the silica content in the suspension is in the range of 20% to 50% by weight; - Borosilicate glass powder with a content ranging from 5% to 20% by weight; and - TiB2 powder with a content ranging from 30% to 60% by weight.

8. The method according to claim 1, wherein the component is a friction component.

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