METHOD FOR PROTECTING A CARBON/CARBON COMPOSITE MATERIAL PART FROM OXIDATION

Abstract

A method for protecting a carbon-carbon composite material part from oxidation, the method including applying an impregnation composition comprising at least one metal phosphate to at least one portion of the outer surface of the part; depositing, by 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 in order to soften or melt the solid composition deposited by 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.

Claims

1. A method for protecting a carbon/carbon composite material part from oxidation, the method comprising: applying onto at least a portion of an external surface of the part an impregnation composition comprising at least one metal phosphate; the dry depositing, after application of the impregnation composition, onto at least a portion of the external surface of the part a solid oxidation-resistant glass composition; and performing an impregnation heat treatment in order to soften or melt the dry deposited solid composition, to allow the impregnation of the internal porosity of the part by the composition thus softened or melted, and to form an oxidation-resistant glass in the internal porosity of the part.

2. The method according to claim 1, wherein 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.

3. The method according to claim 1, further comprising 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.

4. The method according to claim 1, which comprises, after the impregnation heat treatment step: dry depositing onto at least a portion of the external surface of the part a second solid oxidation-resistant glass composition, identical or different to the solid composition; then performing a second impregnation heat treatment in order to soften or melt the second dry deposited solid composition, to allow the impregnation of the internal porosity of the part by the second composition thus softened or melted, and to form a second oxidation-resistant glass in the internal porosity of the part.

5. The method according to claim 4, further comprising, after the second impregnation heat treatment step: dry depositing onto at least a portion of the external surface of the part of a third solid oxidation-resistant glass composition, identical or different to the solid composition; then performing a third impregnation heat treatment in order to soften or melt the third dry deposited solid composition, to allow the impregnation of the internal porosity of the part by the third composition thus softened or melted, and to form a third oxidation-resistant glass in the internal porosity of the part

6. The method according to claim 1, wherein a 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 of a solid composition is greater than or equal to 3 mg/cm.sup.2.

7. A protection method according to claim 1, wherein the solid composition(s) are chosen from: a composition comprising, in mass percentages: 42 to 47% phosphorus pentoxide P.sub.2O.sub.5; 8 to 11% potassium oxide K.sub.2O; 14 to 18% sodium oxide Na.sub.2O; 14 to 18% aluminum oxide Al.sub.2O.sub.3; 7 to 10% boron sesquioxide B.sub.2O.sub.3; and a composition comprising, in mass percentages: 37 to 41% phosphorus pentoxide P.sub.2O.sub.5; 16 to 20% potassium oxide K.sub.2O; 10 to 13% sodium oxide Na.sub.2O; 16 to 19% aluminum oxide Al.sub.2O.sub.3; 7.5 to 10.5% boron sesquioxide B.sub.2O.sub.3.

8. The method according to claim 1 wherein the carbon/carbon composite material part is a friction part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 schematically represents a method in a first embodiment.

[0059] FIG. 2 schematically represents a method in a second embodiment.

[0060] FIG. 3 represents the results obtained for the evolution of the mass loss as a function of time of the samples prepared according to the example.

DESCRIPTION OF THE EMBODIMENTS

[0061] 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.

[0062] FIG. 1 represents a diagram of a method of carrying out the invention.

[0063] 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.

[0064] 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(H.sub.2PO.sub.4).sub.3.

[0065] In other embodiments, complex phosphates may also be used, for example, complex aluminium and calcium phosphates.

[0066] 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.

[0067] 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.

[0068] The impregnation composition can be applied by brush, by atomisation or by spraying onto an external surface of the part.

[0069] In one embodiment, the quantity of impregnation composition deposited during step 10 may be greater than or equal to 6.0 mg/cm.sup.2, or even greater than or equal to 8.0 mg/cm.sup.2.

[0070] 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.

[0071] As indicated in FIG. 1, step 10 of applying the impregnation composition can be followed by a preliminary heat treatment step 20 preferably carried out under an inert atmosphere, for example at a temperature comprised between 680 C. and 740 C.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The heat treatment 40 can be carried out under vacuum or under pressure.

[0078] 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.

[0079] 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.

[0080] FIG. 2 illustrates a method according to another embodiment.

[0081] This method comprises steps 10, 20, 30 and 40 identical to those described previously.

[0082] In particular, and as described above, step 20 is optional in the method illustrated in FIG. 2.

[0083] The method described in FIG. 2 further comprises a step 31 of depositing a second solid composition, identical or different to the solid composition deposited during step 30.

[0084] 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.

[0085] 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.

[0086] The method of FIG. 2 then comprises a step of dry deposition of a third solid composition 32.

[0087] 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.

[0088] The method described in FIG. 2 then comprises a third heat treatment step 42 making it possible to obtain the softening or melting of the third solid composition, its impregnation into the internal porosity of the part and the formation of a third oxidation-resistant glass.

[0089] 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.

[0090] 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/cm.sup.2, or even greater than or equal to 6.0 mg/cm.sup.2.

[0091] 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/cm.sup.2, or even between 3.0 and 8.0 mg/cm.sup.2.

EXAMPLE

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The solid composition called P1 comprises: [0096] 42 to 47% phosphorus pentoxide P.sub.2O.sub.5; [0097] 8 to 11% potassium oxide K.sub.2O; [0098] 14 to 18% sodium oxide Na.sub.2O; [0099] 14 to 18% aluminium oxide Al.sub.2O.sub.3; [0100] 7 to 10% boron sesquioxide B.sub.2O.sub.3.

[0101] The solid composition called P2 comprises: [0102] 37 to 41% phosphorus pentoxide P.sub.2O.sub.5; [0103] 16 to 20% potassium oxide K.sub.2O; [0104] 10 to 13% sodium oxide Na.sub.2O; [0105] 16 to 19% aluminium oxide Al.sub.2O.sub.3; [0106] 7.5 to 10.5% boron sesquioxide B.sub.2O.sub.3.

[0107] Table 1 describes the nature and quantity of the various solid compositions deposited onto each of the samples.

TABLE-US-00001 TABLES 1 Metal phosphate impregnation First solid Second solid Third solid Sample composition composition composition composition A 8.2 mg/cm.sup.2 P1 6.1 mg/cm.sup.2 B 8.1 mg/cm.sup.2 P1 3.1 mg/cm.sup.2 P1 7.9 mg/cm.sup.2 C 8.2 mg/cm.sup.2 P1 2.1 mg/cm.sup.2 P1 2.1 mg/cm.sup.2 P1 1.6 mg/cm.sup.2 D 8.2 mg/cm.sup.2 P2 6.2 mg/cm.sup.2 E 8.0 mg/cm.sup.2 P2 3.7 mg/cm.sup.2 P2 4.8 mg/cm.sup.2 F 8.2 mg/cm.sup.2 P2 2.4 mg/cm.sup.2 P2 2.1 mg/cm.sup.2 P2 1.6 mg/cm.sup.2 G 8.0 mg/cm.sup.2 P1 2.8 mg/cm.sup.2 P2 0.4 mg/cm.sup.2

[0108] The resistance to oxidation is then determined by weighing the samples after: [0109] 8 hours at 650 C. in air, then [0110] 3 hours at 850 C. in air, then [0111] 5 min at 1000 C. in air, then [0112] 2 hours at 650 C. in air.

[0113] 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.

[0114] 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.

[0115] Reference 1 is obtained by impregnating a carbon/carbon composite material part with an aqueous solution of aluminium dihydrogen phosphate Al(H.sub.2PO.sub.4).sub.3 concentrated at 50% by weight applied by brush. The impregnation is followed by a heat treatment at 700 C. for 5 hours.

[0116] 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: [0117] 67% of aqueous solution of mono-aluminium phosphate at 50% by weight of water; [0118] 16.3% of B.sub.4 C powder with at most 2% of impurities, the particles of the powder having a size less than 7.5 m; [0119] 11% dry titanium powder with a particle size comprised between 150 m and 20 m; [0120] 4.7% water; [0121] 1% of a solution with the commercial name Surfynol 440.

[0122] The oxidation resistance is then determined by weighing the samples after the same steps as those described for samples A to G.

[0123] Table 2 and FIG. 3 describe the oxidation resistance results obtained for samples A to G according to the invention, compared to reference samples 1 and 2.

TABLE-US-00002 TABLES 2 Sample Mass Gain compared Gain compared (curve FIG. 3) loss to reference 1 to reference 2 reference 1 (201) 15.8% reference 2 (202) 4.1% 74% A (203) 7.7% 23% B (204) 3.7% 63% 10% C (205) 1.8% 82% 55% D (206) 4.2% 58% E (207) 2.4% 76% 42% F (208) 1.6% 84% 60% G (209) .sup.3% 70% 26%

[0124] As can be observed in FIG. 3 and in Table 2, the method 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.n

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.