US3073761A

US3073761A - Dry lubrication process and bearing surface

Info

Publication number: US3073761A
Application number: US4609A
Authority: US
Inventors: Charles P Covino
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-01-26
Filing date: 1960-01-26
Publication date: 1963-01-15
Anticipated expiration: 1980-01-15

Description

United Staes Patent 3,073,761 DRY LUBRECATIGN PROCESS AND BEARING SURFAQE Charles P. Covino, 31 Woodmont Ave., Upper Montclair, NJ. No'Drawing. Filed Jan. 26, 1960, Ser. No. 4,609 9 Claims. (L 204-68) The present invention relates to a process for bonding dry lubricants to metal surfaces.

In the past it has been found that molybdenum disulphide, molybdenum ditelluride, molybdenum diselenide, tungsten disulphide, titanium disulphide, titanium ditelluride and minerals of equivalent physical structures have certain anti-friction characteristics when applied to bearing surfaces. McCullough in his US. Patent No. 2,622,993 has taught that certain compounds of molybdenum and other metals in its periodic table sequence with sulphur, selenium and tellurium, have unusual lubrication qualities and as such are equivalent to each other under certain circumstances. Such lubricants have proven to be very effective at high temperatures and pressures provide low coefiicients of friction.

Efforts to obtain optimum lubrication and lubrication life had led to efforts to bond these lubricants to metals to lengthen the lubrication life of these dry lubricants and prolong their advantage. McCullough has found one method and Bell, US. Patent No. 2,387,872, both employing a pressure or impact technique for extending and improving the lubricating life of the dry lubricants having the special characteristics of molybdenum disulphide and the related compounds. Bramberry in his US. Patent No. 2,534,408 in another technique taught bonding graphite to bearing surfaces to achieve a more permanent dry lubricating effect by use of resins as a bonding agent as distinguished from impact techniques or pressure techniques taught by McCullough and Bell.

According to the present invention dry lubricants having the characteristics of molybdenum disulphide in resinous vehicles or other carriers are coated and bonded to bearing surfaces in hard, unexpzctably long-lasting coatings capable of resisting high temperatures, great temperature variations and high pressures all with a low or reducing (under pressure) coefficient of friction. Dry lubricants having the characteristics of molybdenum disulphide are bondable in thin layers for long life on a wide variety of metals and alloys.

The object of the presentation provides a new and improved method of bonding dry lubricants having characteristics of molybdenum disulphide in thin anti-frictional coats to various metal and metal alloy surfaces.

Other objects and advantages of this invention residing in the novel features of the steps, and combinations of components, will become more apparent from the description of the specific examples hereinafter following. it will be understood that certain features of the invention may be utilized other than as exactly disclosed.

The invention, however, is not intended to be restricted to any particular step or steps and/or combination of components, or any particular application of such steps and/ or combination of components, or any specific method, or any of. various details thereof, even where specifically set forth and described herein, as the same may be modified in various particulars or may be applied in varied relations without departing from the spirit and scope of the claimed invention, practical examples embodying certain details of the invention being set forth, but only for the purpose of complying with the requirement of the statute for disclosure of operative methods, but without attempting to disclose all of the various ice limits and modifications in which invention might be embodied.

Although such novel features as are believed to be characteristic in the invention are pointed out in the claims, the invention as to its objects and advantages and manner in which they are carried out, may better be understood by reference to the examples and the following information.

The process of the present invention is in particular adapted to .dry lubrication coatings on nickel and nickel alloys, steel and steel alloys, titanium, titanium alloys and zirconium alloys also applies to copper, bronze and other metal customarily used as an antifriction surface.

Example .1

An aircraft part made of a nickel alloy such as In conel X which is a trademark for an alloy containing approximately a minimum of 70 percent nickel, approximately 14 percent chromium and small parts of titanium, columbium, aluminum, silicon, manganese, copper and limited amounts of carbon and sulphur is cleaned by a vapor blast using 120 mesh abrasive grit in water suspension material. The vapor blasted metal part is then rinsed in water, subjected to a 20 percent solution of hydrochloric acid for 30 seconds, rinsed in water, then subjected to an acid solution comprising 10 percent hydrofluoric acid, 30 percent nitric acid in water solution until all over etched, this often takes approximately 30 to 40 seconds. The metal part is then again washed, then given a gold strike, using a direct current of 6 volts at a temperature of F., by dipping in a solution of 5 percent pure gold and 16 ounces potassium cyanide, per gallon for 40 seconds. The part is then gold plated in a solution of one ounce of gold per gallon and 14 ounces of potassium cyanide per gallon in a cold solution; the plating is done at a temperature of 80 F. for 5 minutes, employing 80 milliamps per square inch. The metallic is gold 99 /2 percent pure. Then the part is rinsed in distilled or demineralized water. The next step is to send the metal part through an acetic acid rinse in 10 percent solution of acetic acid. The part is then water rinsed in a hot distilled or demineralized water bath.

The part is then spray-coated with a molybdenum disulphide lubricant whose particles are held in suspension in a vehicle of phenol formaldehyde resin or other resinous vehicle to a depth of .0003 of an inch. The part is then oven-cured for one hour at 350 F. and slow cooled for 4 hours down to room temperature. The same procedure is followed for dry lubricating other nickel alloys such as Hastelloy X which is a trademark for an alloy consisting of approximately 41 percent nickel, 20 percent chromium, 8 percent molybdenum, 17 percent iron and small amounts of cobalt, carbon, silicon and manganese.

' Example 2 A bearing surface of stainless steel to be dry lubricant coated is subjected to vapor blast, rinsed, subjected to a 30 percent nitric acid for 15 minutes at a temperature of F. and rinsed, then treated in the same way as inconel X and Hastelloy X. Commencing with the hydrofiuoric nitric acid bath, steel alloys, titanium alloys and zirconium are treated in the same manner as stainless steel.

Optimum results with various metals have been obtained where in the gold plating step of the gold content is maintained within 10 percent of the one ounce per gallon limit. It has further been found that the best results are obtained in the gold plating step where the potassium cyanide content of the solution is maintained between 14 and 16 ounces per gallon. The plating is best when there is metallic gold in suspension and an anode to cathode ratio of 3 to 1.

Most effective results with the lubricated parts and the greatest success in the lubricant plating have been obtained where the dry lubricant coat is maintained between .0003 and .0005 of an inch.

Slight variations of all steps may be made to accommodate ditferent alloys. A solution of 37 ounces of dry lubricant per gallon in the resinous suspension seems to give the preferred result. Such resins as phenol formaldehyde or silicon resin serve as effective suspension vehicles.

The gold striking has the effect analogous to a primary coat of paint. An infinitesimal amount of gold is deposited but with a very strong bond.

Variations in use of the strong acid solution is generally dependent, upon the metals to be rinsed. The oven curing time of the sprayed dry lubricant varies with the resinous vehicle used, the metal coated and the demands of the use of the part being coated.

Tests of parts dry lubricated in accordance with the teaching of the present invention show unexpected long life of dry lubricant effect under severe loads of torque and friction under high ambient heats of 1000 F.

Further lubricant life under conditions of high heat and stress of heavy load has been found obtainable by the introduction of a silver strike step and silver plate step prior to the gold strike and gold plating of a part to be lubricated.

A diluted bath of silver is used of about one half ounce per gallon of silver salts to a gallon of solution containing 16 to 18 ounces of cyanide per gallon for the silver strike then silver is plated to approximately .0002 an inch. A gold strike is then placed over the silver and gold plate for .0001 of an inch then the dry lubricant is coated from .0003 to .0005 for a final coat. The fixing of the dry lubricant coating to the metal follows as in the prior examples or by other known means depending on the carrier vehicle used for the dry lubricant in the coatmg.

The terms and expressions which are employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. A process for preparing a lubricated metal-bearing surface suitable for high heat and high pressure lubrication comprising cleaning the metal bearing surface, applying a gold strike to said cleaned surface, gold plating said gold strike, and coating said plated surface with a coating comprising a dry lubricant in a resin vehicle, and then curing said resin.

2. The process of claim 1 in which the dry lubricant is a compound of a metallic element.

3. The process of claim 2 in which the gold plate is applied to a thickness of about 0.0001 inch; and in which the dry lubricant is molybdenum disulfide which is applied in a liquid phenol-formaldehyde resin to a thickness in excess of about 0.0003 inch.

4. The process of claim 3 in which the metal-bearing surface utilized is cleaned and abraded prior to the application of gold to said surface; and in which the lubricantphenol formaldehyde resin coating is applied to the said gold plated surface by being sprayed thereon.

5. The process of claim 1 in which a silver plate is applied to the metal-bearing surface prior to the application of the gold plate.

6. The process of claim 1 in which the gold plate is electrodeposited from a gold-containing aqueous cyanide bath.

7. A bearing surface for high heat and high pressure lubrication comprising an inner metal bearing surface, an intermediate gold layer having a thickness of about 0.0001 inch, and an outer surface comprising a cured resinous coating containing a dry lubricant.

8. The bearing of claim 7 in which the outer layer is cured phenol-formaldehyde resin having a thickness of between 0.0003 and 0.0005 inches and containing molybdenum disulfide as the dry lubricant.

9. The bearing of claim 8 having a thin silver layer between the gold layer and the inner metal-bearing surface.

References Cited in the file of this patent UNITED STATES PATENTS