DE1621793B2 - A method of manufacturing an article coated with a metal and a solid lubricant and using the article as a dry-lubricated body - Google Patents

Description

The invention relates to a method for making one with a metal and a solid Lubricant-coated object by electrolytic deposition of positively charged metal ions and electrophoretic deposition of solid lubricant particles from a positive metal ion and bath containing solid lubricant particles on the object and use of such an object as a dry-lubricated body.

From "Materials and Corrosion" (1958), p. 292, polytetrafluoroethylene dispersions are known which can also be filled with metal powder, among other things. Such metal-containing polytetrafluoroethylene dispersions can be sprayed onto metal surfaces. After spraying on, the dispersing medium, z. B. by heating, which is cumbersome and time consuming. Further the adhesive properties of the coating cannot be as good as can be achieved by spraying on electrolytic application of the metal to the

"i object is the case.

From BE-PS 622338 a method for application is known from polytetrafluoroethylene on a substrate, with a porous on the substrate Interlayer is applied, which subsequently

ι »is coated with polytetrafluoroethylene. This intermediate layer can also be a powdered metal, among other things. A similar procedure is out the GB-PS 833332 known, according to which a zirconium suspension in a metal surface first

ι · ") vaporizable medium is applied. Then the medium evaporates and the metal surface is heated, causing the zirconium particles to adhere to the Metal surface can be bound as a porous layer. A polytetrafluoroethylene dispersion is then applied to this layer applied in water, the water is evaporated and the coated surface is heated. These methods have the disadvantage that an intermediate layer must first be applied to the object in a cumbersome manner

r> and that only then is a polytetrafluoroethylene dispersion applied to this intermediate layer can.

From DT-PS 957677 it is known, together with positively charged metal ions on a negative

jo cathode lubricant particles, such as graphite and molybdenum disulfide, to be deposited. According to GB-PS 953 506, together with positively charged metal ions Mica particles are deposited as lubricant particles on a negative cathode.

Γ) The present invention is based on the object a simple and economical method of making one with a metal and a solid To create lubricant coated object.

This object is achieved in a method of the type mentioned in that the electrolytic Deposition of the positive metal ions and for electrophoretic deposition of the negative charged lubricant particles with a diameter of 0.05 to 0.5 μm have the polarity of the electric current flowing through the bath is periodically reversed.

The inventive method enables the simple and economical production of one-

■ -, coated with a metal and a solid lubricant Objects with excellent lubricating properties.

From BE-PS 656670 it is already known, electrolytically metal ions and simultaneously from a metal also to separate polytetrafluoroethylene lubricant particles. This is done in that on the Metal connected as cathode electrolytically discharges dissolved metal ions contained in the electrolyte and deposited in the form of the metal. To-

bo together with the positively charged metal ions that under the influence of the electric current flowing through the electrolyte to the negative cathode migrate and are discharged there, solid lubricant particles also migrate to the negative cathode.

_b5 These lubricant particles are precipitated together with the metal ions and stored in the metal layer that is being formed.

From this patent it can only be seen that

the lubricant particles through a passive migration mechanism not described in detail Get cathode. This assumption is justified by the fact that nowhere in the patent it is mentioned that the lubricant particles under "» the influence of electrical Charges migrate according to an active migration mechanism.

In the aforementioned patent it is disclosed that the metal is electrolytic and the lubricating "' central articles would be deposited "electrophoretically". With this separation of the lubricant particles But it is not a real electrophoretic process, at least not one Process as it is referred to in the present patent application with the term "electrophoresis" will. According to the teaching of the present patent application, negatively charged lubricant particles are under the influence of these charges and the electric current on the - '» deposited as an anode to be coated object. After changing polarity the electrical current flowing through the electrolyte, d. H. after the object to be coated was connected as a cathode, is applied to the 2 "> layer of separate, solid lubricant particles electrolytically deposited a metal layer. By repeating this process, the invention becomes achieved layered arrangement of the coating achieved. - It can therefore be assumed, jo that from BE-PS 656670 only the passive migration neutral lubricant particles along with the migration of positive metal ions towards on a negative cathode is known. Presumably, some of the lubricant particles are carried by the π Migration movement of the positive metal ions to the negative cathode is also drawn towards this or carried away. The process must be imagined as the embedding of impurities in electrodeposited coatings. That the above evaluation of the so-called "electrophoresis" according to BE-PS 656670 is applicable, also emerges from the corresponding GB-PS 1032 899, in which the term "electrophoretic" is not used; this is done, for example, on page 1, lines -n 43 to 46 and lines 71 to 76 are referred where disclosed is that the lubricant particles coincide with the "electro-deposition" of the metal to the substrate migrate or that the lead is applied electrolytically and the lead and the polytetrafluoroethylene serving as a lubricant are applied simultaneously.

In the process according to the invention, metals such as copper, gold, silver or nickel are electrophoresed knocked down on an object. After reversing the polarity of the counter- ■> ■> negatively charged lubricant particles are deposited electrophoretically. So if the Object is designed as a cathode, the metal is deposited first; after reversing the polarity, if the object is connected as an anode, t> o the negatively charged lubricant particles are precipitated. The periodic reversal of the polarity of the The object is continued until a layer of the desired thickness is obtained.

The lubricant particles with a diameter 6 -, from 0.05 to 0.5 microns are deposited as a thin layer of discrete particles, and that Metal is deposited as a continuous thin layer over the particles and partly around the particles, so that the ultimate result of a multilayered precipitate is an essentially one is homogeneous dispersion of lubricant particles in metal.

In order to avoid removing one precipitate before making the next, the electrodeposition is carried out at a higher current density and for a longer time than the electrodeposition. The electrolytic precipitate can e.g. B. proceed at a current density of 10 A per 9.29 dm ² , while the electrophoretic deposition takes place at a 5 to 80% lower current density. Likewise, the control time can be 2 to 30 seconds for the cathode electrolytic deposition, while only 1 to 5 seconds are used for the deposition when the polarity is reversed.

The power source can be a direct current source, e.g. B. a battery or a rectifier, the corresponding Relays, reversing switches and resistors are provided by a timing device be regulated to reverse the current at certain times and convert its value into Conformity with the requirements of the object to be coated and the coating bath to change, taking care that, as mentioned above, the electrolytic precipitation at a Current density and time occurs since / prevents substantial removal of a precipitate before the next precipitation is carried out. The electrical potential does not need to be above the Value at which the electrolysis of the water takes place, but is preferably below this value. Corresponding devices and electrical controls are known, for. B. the electric Controls according to "Electroplating Engineering Handbook", Reinhold Publishing Co., 1955, pages 578 to 580.

The lubricant particles can consist of any material with lubricating properties. The. most of these materials in aqueous dispersions normally have or can have a negative charge be provided with a negative charge. Suitable materials are molybdenum disulfide, copper oxide, other oxides and sulfides as well as other compounds, metal compounds and also plastics and resins with lubricating properties. Particularly satisfactory results are obtained with particles of the Fluorocarbon polymers have been obtained. Specific examples of such compounds are polytetrafluoroethylene, Polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, Vinylidene fluoride-hexafluoropropylene copolymer, polyhexafluoropropylene, Poly-1,1,1 -trifluoropropylmethyldichlorosilane, fluorosilicone elastomers, polyfluoroaniline and Copolymers of tetrafluoroethylene and trifluoronitrosomethane. The preferred fluorocarbon polymers are those which are completely fluorinated, and of these is from the point of view of low Coefficient of friction polytetrafluoroethylene the best. This material is called negatively charged particles commercially available in an aqueous solution. The lubricant particles are preferably in the Electrolytes used in colloidally dispersed form.

The lubricants can be applied to any surface

ι υ ζ. ι / ζι ^ j

ehe, ζ. B. made of ceramic and metal, are applied.

The treated surfaces can be used as bearings, including clock bearings, electrical contacts, hard-coated counter surfaces and for dry lubrication of housings "» sen are used for military and aerospace purposes. The treated parts show a slight Friction and a prolonged wear time.

In the case of electrical contacts with low electrical resistance, the coatings result in constant insertion and withdrawal forces, and the contacts exhibit increased wear time.

The coverings can be of any thickness, but results in a total thickness of the applied composite Layer of approximately 0.00025 cm '"> satisfying results.

The example illustrates the invention.

Polished brass plates (10 cm × 6.3 cm) with an area of 63 cm ² or steel plates, after a 0.0005 cm thick copper layer had been applied to them, are used as a base.

The base was freed from foreign materials, dirt, grease and oxides before the treatment. A water-breaking open area is a good indication of adequate cleaning. The fol- 2-> The following procedures were used to clean the brass plates:

a) Degreasing in perchlorethylene steam for two minutes long, followed by ultrasonic cleaning in perchlorethylene for 5 minutes. i <>

b) Soak cleaning for 5 minutes at room temperature in a solution of sodium carbonate (44.8 g / l), sodium cyanide (3.7 g / l) and preferably 1 percent of a wetting agent, followed by a Rinse with cold running water. r>

c) Electric cleaning in a solution of sodium carbonate (22.4 g / l), trisodium phosphate (14.9 g / l), sodium cyanide (7.5 g / l) and sodium hydroxide (3.7 g / l) at 71 ° C 40 seconds and 5 seconds in reverse polarity at 6 V, followed by two rinses of cold running water for 30 seconds while the rake holding the plate is briskly up and down and in a whirling motion by hand. 4 ^r )

d) To neutralize, immerse in 5% H ₂ SO ₄ solution by hand whirling the workpiece for 10 seconds, followed by rinsing with running water for 30 seconds each time.

e) treatment in a cyanide copper solution of the following composition at 15 to 20 ASF and 52 ° C for one minute with manual movement of the workpiece maintained

^: will.

Copper cyanide
Sodium cyanide
sodium
Rochelle salt
free NaCN

26.17 g / l 34.40 g / l 29.91 g / l 44.87 g / l 5.6-7.47 g / l

This is followed by two rinses and a neutralization bath in 5% H-, SO ₄ -LOSUHg, followed by another rinse. The workpiece (copper plate) is then transferred to the plating tank.

The bath for electrophoretic and electrolytic precipitation is prepared in the following way:

_{680 g of CuSO 4} 5 H ₂ O and 198.4 g of H ₂ SO _{4 are} added to distilled or deionized water, so that 7.57 l of solution are obtained. This is treated with 5 g of activated charcoal per liter for 10 hours at room temperature, after which the solution is filtered. The filtrate is transferred to a glass tank with a capacity of 7.57 liters, surrounded by a jacket through which water flows. The glass tank has a heating device and the temperature of the bath is kept between 38 and 54 ° C. An aqueous polytetrafluoroethylene suspension (0.5% by weight of negatively charged colloidal particles of polytetrafluoroethylene, dispersed in water and acidified with citric acid to an electrometrically measured pH value of 4) is added to the electrolyte in an amount of 5 ecm per liter while stirring added to ensure uniform dispersion. Before and after the addition of polytetrafluoroethylene, the bath has a Baume degree of 10 ° Be. Its specific conductivity without the addition is 96000 S / cm and with the addition 94000 S / cm.

The brass plate is attached to a cathode rod stirrer located in the bath reciprocated at a speed of 28 strokes per minute.

A direct current of 10 to 40 A per 9.29 dm ² is supplied during the first two minutes.

In the case of the electrolytic deposit, the anode consists of copper plates.

The energy source is then connected to a periodic reversal system with the following cycles:

Direct cycle (electrolytic precipitation) 16 lake.

Reverse cycle (electrolytic precipitation) 3 sec.

The current density of the reverse cycle was set to 50% of the current density in the forward or direct Cycle set by means of a rheostat connected in series with the reverse cycle.

The process is suitable for both rake and drum plating.

Claims (5)

ib 21 / yj claims: 1. A method of manufacturing a coated with a metal and a solid lubricant Object by electrolytic deposition of positively charged metal ions and electrophoretic deposition of solid lubricant particles from a positive metal ion and bath containing solid lubricant particles on the object, characterized in that that for the electrolytic deposition of the positively charged metal ions and for the electrophoretic deposition of the negatively charged lubricant particles with a diameter of 0.05 to 0.5 μm The polarity of the electric current flowing through the bath is periodically reversed. 2. The method according to claim 1, characterized in that the electrophoretic Deposition performs at a 5 to 80% lower current density than the electrolytic Precipitation and that the time for electrophoretic deposition is much shorter selects as the time for electrolytic deposition. 3. The method according to claim 2, characterized in that the electrophoretic Deposition for 1 to 5 seconds and the electrolytic deposition for 2 to 30 seconds. 4. The method according to at least one of claims 1 to 3, characterized in that one the method with lubricant particles substantially colloidally dispersed in the electrolyte performs. 5. The method according to at least one of claims 1 to 4, characterized in that one a fluorocarbon polymer is used as the lubricant particle. o. The method according to claim 5, characterized in that that one is called fluorocarbon polyitrisat Polytetrafluoroethylene uses. J. Use of the article produced according to at least one of claims 1 to 6 as a dry-lubricated body.