METHOD FOR COATING A COMPOSITE SUBSTRATE

Abstract

A method for coating a composite substrate characterized includes a—preparing a sol-gel composition by mixing in an aqueous medium: 1—of at least one metal alkoxide of formula (I) M(OR.sup.1), 2—in the presence of at least one organo alkoxysilane of formula (II) R.sup.3mSi(OR.sup.2).sub.4-m, 3—and in the presence of optional oxide or metal particles, 4—by mixing the composition in order to allow condensation of the organic-inorganic hybrid networks, b—depositing at least one underlayer of the sol-gel composition obtained in step a) on the composite substrate; c—depositing at least one subsequent coating layer on the coated composite substrate obtained in step b).

Claims

1. A method for coating a composite substrate, comprising the following steps: a—preparing a sol-gel composition by mixing in an aqueous medium: 1—of at least one metal alkoxide of formula (I) M(OR.sup.1).sub.x wherein R.sup.1 represents a C.sub.1-C.sub.4 alkyl group, M represents a metal chosen from the group consisting of transition metals, lanthanides, phosphorus, magnesium, tin, zinc, aluminum and antimony and x is an integer representing the metal valence, 2—in the presence of at least one organo alkoxysilane of formula (II) R.sup.3.sub.mSi(OR.sup.2).sub.4-m, wherein R.sup.2 represents a C.sub.1-C.sub.4 alkyl group, m represents an integer chosen between 1, 2 and 3, and each R.sup.3 represents, independently of one another, a non-hydrolysable group chosen from polydimethylsiloxane, a C.sub.1-C.sub.18 alkyl group, C.sub.2-C.sub.4 alkenyl group, C.sub.2-C.sub.4 alkynyl group, C.sub.6-C.sub.10 aryl group, methacryl, methacryl (C.sub.1-C.sub.10 alkyl) or methacryloxy(C.sub.1-C.sub.10 alkyl), epoxylakyl or epoxyalkoxyalkyl wherein the alkyl group is linear, branched or cyclic C.sub.1-C.sub.10 alkyl and the alkoxy group is a C.sub.1-C.sub.10 alkoxy group, C.sub.2-C.sub.10 haloalkyl, C.sub.2-C.sub.10 perhaloalkyl, C.sub.2-C.sub.10 mercaptoalkyl, C.sub.2-C.sub.10 aminoalkyl (C.sub.2-C.sub.10 aminoalkyl)amino(C.sub.2-C.sub.10 alkyl), di(C.sub.2-C.sub.10 alkylene)triamino(C.sub.2-C.sub.10 alkyl), imidazolyl-(C.sub.2-C.sub.10 alkyl) and C.sub.2-C.sub.10 imidoalkyl, 3—and in the presence of optional oxide or metal particles, 4—by mixing the composition in order to allow condensation of the organic-inorganic hybrid networks; b—depositing at least one underlayer of the sol-gel composition obtained in step a) on a composite substrate, and c—depositing at least one subsequent coating layer on the composite substrate coated with the underlayer obtained in step b).

2. The method according to claim 1, wherein the metal M is chosen in the group consisting of Cu, Mn, Sn, Fe, Mg, Zn, Al, P, Sb, Zr, Ti, Hf, Ce, Nb, V and Ta.

3. The method according to claim 1, wherein the Si/M molar ratio in the sol-gel composition obtained in step a) is comprised between 0.1 and 0.5.

4. The method according to claim 1, wherein a content of oxide or metal particles of the sol-gel composition obtained in step a) is 0-50% by mass relative to the total mass of the composition.

5. The method according to claim 1, wherein thickness of the sublayer obtained in step b) is comprised between 5 μm and 200 μm.

6. The method according to claim 1, wherein the subsequent coating layer of step c) is a layer of metal, ceramic, cermet or reinforced or unreinforced polymer or a mixture.

7. The method according to claim 1, wherein step c) is a thermal spraying step.

8. The method according to claim 1, wherein the substrate is an organic matrix composite.

9. The method according to claim 1, further comprising a prior step alpha) of preparing the surface of the composite substrate before step b) of depositing the sol-gel underlayer.

10. The method according to claim 1, further comprising an intermediate step b1), between steps b) and c), of heat treating the coated composite substrate obtained in step b), at a maximum temperature of 200° C., step c) being implemented on the substrate obtained in step b1).

11. The method according to claim 1, further comprising an intermediate step b2), between steps b) and c) or between optional step b1) and c), of increasing the roughness of the coated composite substrate surface obtained in step b) or step b1), step c) being implemented on the substrate obtained in step b2).

12. The method according to claim 1, wherein fusible particles are added to the sol-gel composition of step a) and wherein the method further comprises, between steps b) and c), the intermediate step b3) of thermal treatment or chemical etching to free the porosity of the substrate obtained in step b), step c) being implemented on the substrate obtained in step b3).

13. The method according to claim 1, wherein the sol-gel composition obtained in step a) has a controlled state of gelation and wherein the particles deposited during step c) penetrate into the sol-gel underlayer thus creating a concentration gradient of particles embedded in the underlayer.

14. The method according to claim 1, further comprising an intermediate step b4), between steps b) and c) or between optional step b1) and step c), of coating the composite substrate obtained in step b) or optional step b1) by an additional underlayer of sol-gel composition obtained by mixture in an aqueous medium: 1—of at least one metal alkoxide of formula (I) M(OR).sub.x, 2—in the presence of at least one organo alkoxysilane of formula (II) R.sup.3.sub.mSi(OR.sup.2).sub.4-m, 3—and in the presence of optional oxide or metal particles, 4—by mixing the composition in order to allow condensation of the organic-inorganic hybrid networks, the sol-gel composition having a controlled state of gelation and in that step c) is implemented on the substrate obtained in step b4) so that the particles deposited during step c) penetrate into the additional sol-gel underlayer thus creating a concentration gradient of particles embedded in the additional underlayer.

15. The method according to claim 1, wherein the composite substrate is an engine or nacelle part.

16. A coated composite substrate obtainable by the method according to claim 1, wherein a thickness of the sol-gel underlayer of the substrate is comprised between 5 μm and 200 μm.

17. (canceled)

18. The method according to claim 4, wherein the content of oxide or metal particles of the sol-gel composition obtained in step a) is 5-15% by mass relative to the total mass of the composition.

19. The method according to claim 6, wherein the subsequent coating layer of step c) is a layer of metal.

20. The method according to claim 1, wherein the metal M is chosen in the group consisting of Zn, Ti and Al.

21. The method according to claim 15, wherein the composite substrate is a fan blade, a fan casing or an outlet guide vane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0123] FIG. 1 is a representative diagram in vertical section of a composite substrate (1) coated with a sol-gel underlayer (2) and with a subsequent coating layer (3) obtained by the method of the invention.

[0124] FIG. 2 is a representative diagram in vertical section of a composite substrate (1) coated with a sol-gel underlayer having a controlled state of gelation containing a gradient of particles (4) and with a subsequent coating layer (3) obtained by a variant of the method of the invention.

EXAMPLE 1: SI—ZR SOL-GEL UNDERLAYER AND ZRO.SUB.2 .PARTICLE BEFORE DEPOSITION BY THERMAL SPRAYING

[0125] The following compounds are added to a beaker in order and with magnetic stirring: a 70% by mass zirconium (IV) propoxide solution and glacial acetic acid, such that Zr/H.sup.+=2. After homogenization, distilled H.sub.2O is added with stirring such that Zr/H.sub.2O=15.

[0126] The solution is held with stirring approximately 1 hour until a homogeneous and clear solution is obtained.

[0127] To this solution is added (3-glycidoxypropyl)trimethoxysilane with stirring, such that Si/Zr=0.3. The stirring is maintained for approximately 1 hour until a homogeneous and clear solution is obtained. 5% by mass of ZrO.sub.2 particles (mean diameter 50 nm) is added to this mixture with stirring and/or ultrasound.

[0128] Then an organic matrix composite (OMC) substrate is prepared, said OMC being made up of an epoxy matrix composite reinforced by carbon fibres, according to a methodology known to the skilled person, such as sanding or sand-blasting, followed by cleaning in order to remove any dust from the surface.

[0129] The formulation of the underlayer is then deposited on the OMC substrate by spray coating or dip coating so as t completely cover the surface, then within a time of a few minutes to one hour, the substrate thus coated is placed in the oven at 110° C. for 1 h.

[0130] The resulting substrate is then coated with a metal aluminium layer obtained by a low-pressure cold spray method.

EXAMPLE 2: SI—TI SOL-GEL UNDERLAYER AND TIO.SUB.2 .PARTICLE BEFORE DEPOSITION BY THERMAL SPRAYING

[0131] The following compounds are added to a beaker in order and with magnetic stirring: titanium (IV) butoxide and glacial acetic acid, such that Ti/H.sup.+=2 and then distilled H.sub.2O is added with stirring such that Ti/H.sub.2O=8.

[0132] The solution is held with stirring for approximately 30 minutes, before adding 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) and aminopropryltriethoxysilane (APTES) still with stirring, such that Si/Ti=0.2 and γ-MPS/APTES=3. Stirring is maintained for approximately 1 hour. 5% by mass of TiO.sub.2 particles (mean diameter 20 nm) is added to this mixture with stirring and/or ultrasound.

[0133] Then an organic matrix composite (OMC) substrate is prepared, said OMC being made up of an epoxy matrix composite reinforced by carbon fibres, according to a methodology known to the skilled person, such as sanding or sand-blasting, followed by cleaning in order to remove any dust from the surface.

[0134] The formulation of the underlayer is then deposited on the OMC substrate by spray coating or dip coating so as to completely cover the surface, then within a time of a few minutes to one hour, the substrate thus coated is placed in the oven at 110° C. for 1 h.

[0135] The resulting substrate is then coated by a metal titanium layer obtained by a low-pressure cold spray method.

EXAMPLE 3: SI—AL UNDERLAYER BEFORE ALUMINIUM SPRAYING

[0136] The aluminum (III) isopropoxide precursor is mixed with distilled water (such that the H.sub.2O/Al molar ratio=10). The mixture is held with stirring at 80° C. for 1 h.

[0137] The pH is adjusted to 3 by addition of concentrated nitric acid (68%) in order to form the oxide network. After 1 h of vigorous stirring at 80° C., a clear, blue and stable sol is obtained. The solution is left to return to ambient temperature and (3-glycidoxypropyl)trimethoxysilane is added thereto, such that Si/Al=0.3. The solution is held with stirring for 2 h.

[0138] Then an organic matrix composite (OMC) substrate is prepared, said OMC being made up of an epoxy matrix composite reinforced by carbon fibres, according to a methodology known to the skilled person, such as sanding or sand-blasting, followed by cleaning in order to remove any dust from the surface.

[0139] The formulation of the underlayer is then deposited on the OMC substrate by spray coating or dip coating so as t completely cover the surface, then within a time of a few minutes to one hour, the substrate thus coated is placed in the oven at 110° C. for 1 h.

[0140] The resulting substrate is then coated with a metal aluminium layer obtained by a low-pressure cold spray method.

EXAMPLE 4: SI—TI SOL-GEL UNDERLAYER AND FUSIBLE POLYSTYRENE PARTICLES BEFORE DEPOSITION BY THERMAL SPRAYING

[0141] The following compounds are added to a beaker in order and with magnetic stirring: titanium (IV) butoxide and glacial acetic acid, such that Ti/H.sup.+=2 and then distilled H.sub.2O is added with stirring such that Ti/H.sub.2O=8.

[0142] The solution is held with stirring for approximately 30 minutes, before adding (3-glycidoxypropyl)trimethoxysilane (GPTMS) and aminopropryltriethoxysilane (APTES) still with stirring, such that Si/Ti=0.2 and GPTMS/APTES=5. Stirring is maintained for approximately 2 hours. 5% by mass of polystyrene particles (mean diameter 5 nm) is added to the mixture with stirring and/or ultrasound.

[0143] Then an organic matrix composite (OMC) substrate is prepared, said OMC being made up of an epoxy matrix composite reinforced by carbon fibres, according to a methodology known to the skilled person, such as sanding or sand-blasting, followed by cleaning in order to remove any dust from the surface.

[0144] The formulation of the underlayer is then deposited on the OMC substrate by spray coating or dip coating so as t completely cover the surface, then within a time of a few minutes to one hour, the substrate thus coated is placed in the oven at 110° C. for 1 h, then at 170° C. for 30 min in order to free the porosity of the polystyrene particles on the surface.

[0145] The resulting substrate is then coated by a metal titanium layer obtained by a low-pressure cold spray method.

EXAMPLE 5: DOUBLE SI—TI SOL-GEL UNDERLAYER AND TIO.SUB.2 .PARTICLE THEN SI—AL UNDERLAYER BEFORE DEPOSITION BY THERMAL SPRAYING OF AN ALUMINIUM LAYER

[0146] 1.sup.st Underlayer:

[0147] The following compounds are added to a beaker in order and with magnetic stirring: titanium (IV) butoxide and glacial acetic acid, such that Ti/H.sup.+=2 and then distilled H.sub.2O is added with stirring such that Ti/H.sub.2O=8. The solution is held with stirring for approximately 30 minutes, before adding 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) and aminopropryltriethoxysilane (APTES) still with stirring, such that Si/Ti=0.2 and γ-MPS/APTES=3. Stirring is maintained for approximately 1 hour. 5% by mass of TiO.sub.2 particles (mean diameter 20 nm) is added to this mixture with stirring and/or ultrasound.

[0148] Then an organic matrix composite (OMC) substrate is prepared, said OMC being made up of an epoxy matrix composite reinforced by carbon fibres, according to a methodology known to the skilled person, such as sanding or sand-blasting, followed by cleaning in order to remove any dust from the surface.

[0149] The formulation of the underlayer is then deposited on the OMC substrate by spray coating or dip coating so as to completely cover the surface, then within a time of a few minutes to one hour, the substrate thus coated is placed in the oven at 80° C. for 45 min.

[0150] 2.sup.Nd Underlayer:

[0151] Further, the aluminum (III) isopropoxide mixture is prepared with distilled water (such that the H.sub.2O/AI molar ratio=10). The mixture is held with stirring at 80° C. for 1 h.

[0152] The pH is adjusted to 3 by addition of concentrated nitric acid (68%) in order to form the oxide network. After 1 h of vigorous stirring at 80° C., a clear, blue and stable solution is obtained. The solution is left to return to ambient temperature and (3-glycidoxypropyl)trimethoxysilane is added thereto, such that Si/Al=0.3. The solution is held with stirring for 2 h.

[0153] The formulation of this underlayer is then deposited on the OMC substrate covered with the preceding underlayer, by spray coating so as to completely cover the surface, then the substrate thus coated is placed in the oven at 110° C. for 1 h.

[0154] The resulting substrate is then coated with a metal aluminium layer obtained by a low-pressure cold spray method.