Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D15/00—Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
  • C25D15/02—Combined electrolytic and electrophoretic processes with charged materials
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12486—Laterally noncoextensive components [e.g., embedded, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12944—Ni-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31678—Of metal
  • Y10T428/31703—Next to cellulosic

Definitions

• Composite material consisting of a metallic matrix and talc
• the invention relates to a composite material, its use as a lubricating metallic coating, and a process for its preparation.
• a so-called “electroless” codeposition process on a substrate is a process consisting in incorporating particles during the process of growth of a metal or an alloy by catalyzed redox.
• An electrochemical codeposition process consists in incorporating particles during the growth process of a metal or an alloy on a substrate to be coated, from an electrolyte in an electrolysis cell.
• a lubricating coating of PTFE in a metallic matrix based on nickel by an "electroless” process from a suspension of PTFE in a solution of nickel precursor is known by X.
• NiP-B 4 C lubricant coatings can also be deposited [Cf. JP Ge, et al., Plating and surface finishing, October 1998].
• Ni-BN h coatings are described by M.
• the object of the present invention is to provide a material which has the hardness and wear resistance properties conventionally required for mechanical parts in contact and in displacement with respect to each other in a mechanical assembly, and stable lubricating properties at high temperatures, for example of the order of 800 ° C. This is why the present invention relates to a composite material, its use as a self-lubricating coating of a substrate, as well as a process for its preparation.
• the composite material according to the invention consists of a metal matrix within which are distributed talc particles in sheets,. It is characterized in that the talc particles carry on their surface a compound derived from cellulose, fixed by replacement of all or part of the hydroxyl groups.
• the metal matrix can be constituted by a metal chosen from Fe, Co, Ni, Mn, Cr, Cu, W, Mo, Zn, Au, Ag, Pb, Sn, by an intermetallic compound or an alloy of several metals chosen from aforementioned metals, or by an alloy of one or more of said metals with a metalloid.
• Composite materials whose matrix is nickel, a metal alloy of nickel with other metals, or a nickel alloy with a metalloid (for example NiP) are particularly interesting.
• Unmodified talc is a magnesium silicate corresponding to the formula Mg 3 Si 4 O ⁇ 0 (OH) 2 which is part of the family of phyllosilicates and is in the form of a stack of sheets. The elementary sheet has a thickness of 0.9 nm. It loses its water of constitution around 800 ° C and decomposes around 950 ° C. The properties it gives to a composite material are therefore stable up to 950 ° C.
• the presence of modified talc particles in the composite material according to the invention can be determined using various analysis techniques. Scanning Electron Microscopy (SEM) images show that the talc treated has on the surface groups derived from celulose of micrometric size. The analyzes by electron microscopy with scanning by dispersion of energy of X photons (SEM-EDX) after metallization by Au, by low voltage SEM, or by electron spectroscopy for chemical analysis (ESCA) give quantities of C, which show the presence of an organic compound on the surface.
• SEM-EDX dispersion of energy of X photons
• ESA electron spectroscopy for chemical analysis
• X-ray diffraction confirms the existence of cellulose derivatives on the surface of the talc particles, the spot size and the size of the groups of cellulose derivatives on the talc being substantially identical.
• the Fourier Transform Infrared spectrometry in diffuse reflectance shows the presence of vibration bands specific to talc as well as vibration bands specific to the groups linked to the carbon of the cellulose derivative, the positions of the respective vibration bands being different.
• RAMAN point laser
• the coating of talc particles with a cellulose derivative in the composite material of the invention can also be demonstrated by the icro-PIXE technique (particle-induced X-ray emission) which allows a chemical analysis of the micrometer order, and by the EXAFS technique (X-ray absorption by the fine structure) which allows the determination of the ligands of the probed atom and the inter-atomic distances around the ligand up to 6 nm.
• icro-PIXE technique particle-induced X-ray emission
• EXAFS technique X-ray absorption by the fine structure
• talc which is a relatively soft material, into the metallic matrix, does not modify the hardness and abrasion resistance properties inherent in the material constituting said matrix.
• the composite material according to the invention can advantageously be used as a coating on a substrate.
• a coating consisting of a composite material according to the invention can be deposited electrolytically on the substrate to be treated.
• the method of depositing on a substrate a coating consisting of the composite material according to the invention consists in carrying out an electrolytic deposition using a solution of precursors of the metal matrix of the coating. It is characterized in that the precursor solution also contains talc particles in suspension, said talc particles having been previously modified on the surface by irreversible adsorption of a cellulose derivative compound by replacement of all or part of the hydroxyl groups .
• the deposition process is implemented chemically, by bringing the surface of the substrate to be coated into contact with the solution containing the precursors of the metal matrix, the modified talc particles, as well as a compound acting as a catalyst for the oxidation-reduction of the precursors of the metallic matrix of the coating.
• the deposition process is carried out electrochemically in an electrochemical cell in which said substrate to be coated constitutes the cathode and the electrolyte is a solution of precursors of the metallic matrix of the coating further containing the modified talc particles.
• CMC carboxymethylcellulose
• guar a compound derived from cellulose
• CMC is a cellulose ether resulting from the reaction of alkali cellulose and sodium monoacetate. Part of the hydroxyl groups of the cellulose are replaced by sodium carboxymethyl groups (-CH 2 COONa).
• -CH 2 COONa sodium carboxymethyl groups
• CMC may have different degrees of substitution.
• the degree of substitution DS is 3 in theory. In practice, the DS is much lower than 3.
• the commercial CMCs have DS ranging from 0.6 to 0.95.
• the dissolution of CMC in water causes ionization of the carboxymethylcellulose groups, which gives the CMC macromolecule a negative charge.
• an aqueous solution contains a weakly substituted, more hydrophobic CMC, it has a thixotropic nature.
• an aqueous solution contains a highly substituted CMC, it has a pseudoplastic character.
• the viscosity of the aqueous medium in which the CMC is dissolved depends on the length of the CMC macromolecule, that is to say on the number of units of anhydroglucose and on the critical micellar concentration.
• Commercial CMCs cover a fairly wide viscosity range (10 to 9000 mPa.s) depending on the chain length and the concentration.
• a guar is a cellulosic compound in which certain hydroxyl groups (-OH) of a cellulosic cycle are substituted by hydroxyglucose groups. In this case the possibility of substitution on a given chain length is much lower than in the case of CMC. The degrees of substitution of the guar are close to 0.1.
• the formula for the guar recurring unit is shown below.
• the process for treating talc particles with the cellulose-derived compound (CDC) comprises the following steps:
• the inventors have finally found that the preliminary modification of the talc particles using a a cellulosic compound in which at least part of the OH groups are substituted made it possible to remedy these problems.
• the talc particles preferably have an average size of less than 15 ⁇ m.
• the metal matrix precursors are chosen from ionic compounds, complexed or not, reducible in solution by chemical means or by the addition of electrons.
• salts such as chlorides, sulfates, sulfamates, as well as complexes such as citrates and acetates.
• the precursor solution also contains one or more compounds making it possible to adjust the pH to the desired value, as well as the particles of modified talc.
• the electrolyte is a solution containing at least one nickel salt chosen from nickel sulphate and nickel chloride, a pH regulating agent and a support electrolyte.
• a particularly preferred pH regulator is boric acid; at pH 4.5, it forms a complex with nickel, releasing an H + and thus balances the reduction of H + ions at the cathode.
• a support electrolyte mention may, for example, be made of sodium sulfate, magnesium sulfate and sodium bromide.
• an electrolyte containing at least one nickel salt chosen from nickel sulfate and chloride may be used, a pH-regulating agent, a phosphorus precursor and a support electrolyte.
• H 3 PO 3 is advantageously chosen as a phosphorus precursor.
• the pH regulator can be chosen from H 3 PO 4 and H 3 BO 3 , H 3 PO 4 being particularly preferred.
• a support electrolyte mention may, for example, be made of sodium sulfate, magnesium sulfate and sodium bromide.
• a coating comprising a zinc-nickel matrix When a coating comprising a zinc-nickel matrix is deposited electrochemically, basic or acidic electrolytes containing at least one can be used.
• nickel salt chosen from nickel sulfate and chloride, at least one zinc oxide or a zinc salt such as zinc chloride, a complexing agent of the amine type, and a support electrolyte such as for example KC1.
• the process is carried out under the usual conditions of electrochemical deposition. The duration of the electrolysis depends in particular on the thickness desired for the coating.
• the temperature in the electrochemical cell is advantageously between 0 ° C and 90 ° C and the current density applied to the cell is between 0.1 and 10 A. dm -2 .
• An electrochemical cell is preferably used in which the anode is of the soluble anode type, constituted by the metal to be deposited.
• the substrate may consist of an intrinsically conductive material (for example a metal or an alloy) used in the solid state or in the form of a coating on any support.
• the substrate can also consist of an insulating or semiconducting material (for example a polymer or a ceramic), the surface to be treated has been made conductive by a preliminary metallization step.
• the mechanical properties of the composite coatings have been tested with a pawn-disc tribometer in which the pawn (which constitutes the opposing body) is a 100C6 steel ball which has a hardness of 1000 Hv.
• the pawn which constitutes the opposing body
• the adhesion of nickel to steel is manifested by a high coefficient of friction and a high rate of wear of the steel ball.
• the disc used is made of a nickel-talc composite material according to the invention, the coefficient of friction and the rate of wear are greatly reduced.
• Example 1 The present invention is described in more detail by the following examples, to which it is not however limited.
• Example 1 The present invention is described in more detail by the following examples, to which it is not however limited.
• Talc particles modified were prepared using 3 samples of carboxymethylcellulose (CMC), the characteristics of which (degree of substitution which causes the charge, and viscosity which depends on the chain length) are given in the table below. below.
• CMC carboxymethylcellulose
• the treatment was carried out under the following conditions: preparation of an aqueous mother solution of CMC at 50 g / 1 preparation of a paste by dispersing 100 g of talc in 100 ml of a solution obtained by addition of 5 g of CMC with demineralized water, and homogenization by mechanical stirring for 15 min complete evaporation of the aqueous phase of the dough in an oven at 80 ° C until a dehydrated solid is obtained - deagglomeration of the dehydrated solid in order to obtain treated talc particles with a particle size identical to that of the initial powder.
• first cycle comprising washing with demineralized water, centrifugation to separate the talc particles, evaporation of the water in an oven at 80 ° C. and deagglomeration 6.
• second washing / centrifugation / evaporation / deagglomeration cycle under the same conditions
• Example 2 Nickel / talc composite coating.
• the coating was prepared in an electrochemical cell consisting of a 4 cm 2 nickel anode and a 1.762 cm 2 copper cathode on which the deposition is carried out.
• the electrochemical cell contains an electrolyte having a pH of 4.5 and the following composition:
• the deposition is carried out by maintaining the electrolyte at a temperature of 55 ° C. under a current density of 2.5 A. dm "2 , for a duration of 1.5 hours.
• SEM scanning electron microscopy
• Qualitative chemical analysis by EDX of the surface of the composite coating reveals the characteristic peaks of the carbon present on the particles.
• An analysis by infrared spectrometry in diffuse reflection highlights the vibration bands of the cellulosic groupings of the CMC and the bands specific to talc.
• the deposition is carried out by maintaining the electrolyte at a temperature of 80 ° C., for a period of 45 min.
• the SEM analysis of the coating obtained shows the presence of talc sheets incorporated into the metallic matrix, the qualitative chemical analysis by EDX of the surface of the composite coating appear the characteristic peaks of the carbon present on the particles.
• the presence of the latter in the form of cellulosic groups characteristic of CMC is confirmed by analysis by infrared spectrometry in diffuse reflection.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)
• Electroplating Methods And Accessories (AREA)
• Laminated Bodies (AREA)
• Glass Compositions (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Sliding-Contact Bearings (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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