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

Definitions

• a dry lubricant coating comprising graphite fluoride powder having a lubricating property dispersed in a coating metal is electrophoretically deposited on a substrate simultaneously with the electrolytic deposition of the coating metal.
• the graphite fluoride is produced by reacting carbon or graphite with fluorine at a temperature of lower than 550 C.
• This invention relates to a dry lubricant coating of a self-replenishing type, method of application thereof to the surface of an article, such as a bearing, and a coated article so obtained.
• self-replenishing type refers to the dry lubricant coating which replenishes itself its lubricating surface as it wears away during the use thereof, which will be described in detail hereinafter.
• An object of this invention is to provide a coating composition and a coating technique which allows control of how much lubricant is on the surface at any moment.
• Another object is to provide a novel coating composition which gives a lubrication coating which supplies lubrication as the substrate material Wears.
• Another object is to provide a coated article of superior lubrication properties.
• graphite fluoride With respect to the graphite fluoride referred above, it was in 1934 that Ruff and Bretschneider first discovered that graphite or carbon and fluorine combined without combination at about 420 C. to form a grey-colored solid (Zeitschrift anorg. allgem. Chem). The approximate composition of this solid was (CF where x is nearly equal to 1. They called the compound carbon monofluoride. However, in this invention we call it graphite fluoride because there are many compounds consisting of carbon and fluorine, such as, carbon tetrafiuoride and fluorocarbon polymer, such as, polytetrafluoroethylene (Teflon of E. I. du Pont de Nemours & Co.).
• the dry lubricant coating of the self-replenishing type wherein graphite flu- United States Patent ice oride particles are dispersed in a coating metal is deposited electrophoretically on a substrate simultaneously with the electrolytic deposition of the coating metal by the method which comprises subjecting the substrate to the process of codeposition in a coating bath consistin of a coating metal, graphite fluoride powder, and one or two additives having a good adsorptive activity for graphite fluoride, such as, watersoluble high molecular weight compounds, water-soluble organic solvents, and colloidal oxides.
• the codeposition of graphite fluoride powder and metal can be effected by the use of a coating bath consisting of coating metal, graphite fluoride, and one or two additives having a good adsorptive activity for graphite fluoride selected from the group of water-soluble high molecular weight compounds, water-soluble organic solvents, and colloidal oxides, wherein graphite fluoride is well dispersed in the coating bath, and further, this codeposition can be repeated with good results.
• graphite fluoride is produced by the reaction of carbon or graphite with fluorine, halogen fluoride or a mixture thereof with an inert gas at a temperature of less than 550 C.
• the configuration is as follows: fluorine is introduced between the layer lattice structure of the carbon or graphite and is chemically bonded with one remaining valence electron in the carbon atom in a covalent bond, and the molecular formula may be expressed as (CF),, and the molar ratio of carbon to fluorine is 1:1.
• the compound is a transparent white or grey solid powder.
• Graphite fluoride does not soften, nor burn at a relatively high temperature, and is stable up to the temperature of 550 C. under atmospheric pressure. Besides, it has a specific gravity of 2.00 to 2.70, is resistant to corrosion by aggressive chemicals such as acids and alkalis, and has a high electric resistance. Graphite fluoride will neither be wet with water nor with oil, and its angle of contact with water is so that it has a strong repellence to oil as well as water, and besides, a lubricating property at an elevated temperature.
• graphite fluoride has the stability to chemicals even in such an acidic solution as a plating bath so that its property as a lubricant will never be deteriorated; and it is quite stable to a frictional heat produced at the boundary lubrication and an atmospheric condition.
• graphite fluoride particles can be dispersed in water or a plating solution with one or two additives, such as, water-soluble high molecular weight compound, water-soluble organic solvent, and colloidal oxide.
• graphite fluoride particles are previously immersed in a water-soluble solvent, such as, alcohol, siloxane, dioxane, and ketone in order to substitute adsorptive gases on the surface thereof, and then the treated particles together with a slight amount of a water-soluble high molecular weight compound, such as, polyethylene glycol and polyvinyl alcohol are added into the plating bath; (2) graphite fluoride particles are adsorbed with a slight amount of colloidal oxide, such as, silicic acid anhydride and titania, and then the treated particles are added into the plating bath; and (3) graphite fluoride particles are adsorbed with a water-soluble high molecular weight compound only, and then the treated particles are added into the bath.
• a water-soluble solvent such as, alcohol, siloxane, dioxane, and ketone
• the water-soluble organic solvent includes methyl alcohol, ethyl alcohol, propyl alcohol, glycol, glycerine, siloxane, acetone, and methyl ethyl ketone, etc.
• the water-soluble high molecular weight compound includes polyethylene glycol, polyvinyl alcohol, polyamine, polyvinyl carbazol, and polyacrylamide; and one, two or more of the above compounds can be employed.
• the upper limit of the volume percentage of graphite fluoride particles to be added to the coating solution in order to produce the dry lubricant coating of the self-replenishing type of this invention is preferred to be 80% by volume.
• the codeposition of a large amount of graphite fluoride particles should be obviated so that the amount thereof should be preferred to be less than 5%.
• the amount of graphite fluoride particles to be added to the plating bath should be less than 500 g. per liter, and the preferred concentration thereof should be in the range of 0.0001 to 50 g. per liter. Further, in the practical operation of the process, a mechanical agitation of the bath has proved to be beneficial.
• the particle size of graphite fluoride should be divided as finely as possible, and less than microns. In particular, more than 80% of the particle size of graphite fluoride is preferred to be less than 0.5 micron.
• EXAMPLE 1 A solution was prepared wherein 0.3 g./l. of graphite fluoride particles having the mean particle size, 0.2 micron, in the spherical form were uniformly suspended in methyl or ethyl alcohol, and this uniform suspension is referred to A solution. Then, a nickel coating having the thickness of 25 microns was deposited on a brass sheet having the thickness of 2 mm. by the electrodeposition under the condition specified below in the plating bath of the following composition containing the above A solution:
• Codcposited surface (this Coated surface invention) (prior art) Number of rotation (70 r.p.m.). 10 10 10x10 Amount of abrasion, mg 170.4 230.3 Taber abrasion, mg./1,0fl0 cycle... 1.70 2.30 Depth of abrasion trace, micron. 13 18 Surface hardness, HMV 599 648 It is clearly shown from the above that the nickel coated surface codeposited with a small amount of graphite fluoride in accordance with this invention has increased its lubricity as well as its abrasion resistance to a remarkable degree.
• EXAMPLE 2 An aqueous dispersion of graphite fluoride was prepared by the steps of mixing one part of graphite fluoride particles, 0.25 part of colloidal anhydrous silicic acid, and two parts of polyethylene glycol No. 300 while these components were kneading under a reduced pressure for a period of one to two hours, and then adding the composition thus obtained to 50 parts of water while agitating. This aqueous dispersion is referred to B solution.
• EXAMPLE 3 A suspension solution (referred to C solution) was prepared wherein 2 g. per liter of graphite fluoride powder were dispersed in dioxane. Then, a nickel coating layer, 15 micron thick, was deposited on a steel sheet by the electrodeposition under the condition specified below in the plating bath of the following composition containing the C solution:
• graphite fluoride in a molar ratio of carbon to fluorine of 1:1, said graphite fluoride being obtained by reacting carbon or graphite with fluorine in an inert gas at a temperature lower than 550 C., and one or more dispersion promoting additives for the graphite fluoride selected from (1) a colloidal oxide selected from the group consisting of silicic acid anhydride and titania, (2) a Water-soluble organic solvent selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, glycol, glycerine, siloxane, acetone, and methyl ethyl ketone and (3) a watersoluble high molecular weight compound selected from the group consisting of a polyethylene glycol, a polyvinyl alcohol, a polamine, a polyvinyl carbazol and a polyacrylamide.
• a colloidal oxide selected from the group consisting of silicic acid anhydride and titania
• dispersion promoting additive is selected from the group consisting of silicic acid anhydride and titania.
• dispersion promoting additive is selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, glycol, glycerine, siloxane, acetone and methyl ethyl ketone.
• dispersion promoting additive is selected from the group consisting of a polyethylene glycol, a polyvinyl alcohol, a polyamine, a polyvinyl carbazol and a polyacrylamide.

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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)
• Lubricants (AREA)

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Cited By (15)

• 1970
  • 1970-12-26 JP JP45118726A patent/JPS4920459B1/ja active Pending
• 1971
  • 1971-12-23 US US00211741A patent/US3756925A/en not_active Expired - Lifetime

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