IL32490A - Lubricant producing system - Google Patents

Description

Lubricant producing aytstem DU PONT DB NEMOURS AND C MPANY BACKGROUND OP THE INVENTION This invention is in the field of functional systems producing lubrication.

Ideally, a lubricant for the interface of relatively movable (sliding, rubbing, rolling, etc.) opposing surfaces should serve to completely separate those surfaces. This condition is known as full-film or hydrodynamic lubrication.

Pull-film lubrication physically separates the two sliding surfaces by a relatively thick continuous film of self-pressurized lubricant with no metal-to-metal contact. Technologically, this is the preferred kind of lubrication since it offers the lowest coefficient of friction and the smallest amount of wear.

When the two sliding surfaces are being rubbed together in the presence of an extremely thin film of lubricant which adheres to both surfaces, this condition is known as complete boundary lubrication. Unless the lubricant is renewed periodically, the thin film is eventually destroyed and intimate metal-to-metal contact results (dry operation) with the result being scoring and galling of the metals, and eventually seizure.

A transitional zone known as mixed-film lubrication is a combination of hydrodynamic and boundary lubrication.

Under this condition, part of the total load applied to an opposing metal surface is supported by individual load-carrying areas of self-pressurized lubricant and the remaining part by the very thin film associated with boundary lubrication.

Under full-film conditions, the coefficient of fluid friction is approximately proportional to viscosity and speed and inversely proportional to load. Where true boundary lubrication exists, the coefficient of friction is independent of viscosity and rubbing speed. Thus for small values of ZN/p, where Z is the viscosity of the input fluid, N is rotational speed and p is bearing pressure (load), the coefficient of friction remains essentially constant.

Between the boundary and full-film zones of lubrication is the zone where, with reduction of ZN/p, the coefficient of friction increases sharply. Evidence indicates that in this zone a combination of fluid friction and boundary lubrication exists, i.e., mixed-film lubrication.

When the speed (N) and viscosity (Z) are low, the load, which can be applied to surfaces without attaining unduly high coefficients of friction and the resultant catastrophic effects thereof, must necessarily be very low. Hence, the use of low viscosity fluids as lubricants is precluded in most industrial applications since their use places a severe restriction on the load bearing capacity.

Lubrication of the opposing surfaces of seals, gears, bearings and pistons, therefore, has required the use of more viscous materials such as hydrocarbon oils, synthetic oils and greases. These lubricants, in addition to being incapable of being tolerated in certain applications because of process contamination, possess other disadvantages. When these lubricants are used continuously over extended periods at high pressures and elevated temperatures, they tend to deteriorate. Sludges tend to form in the lubricants as a result of oxidation, polymerization, or other causes. These sludges reduce the lubricating qualities of the lubricant and often cause sticking of relatively moving parts. In addition, organic acids tend to form in the lubricant during use thereof, apparently because of oxidation of the oil at the elevated temperatures to which the oil is exposed, and organic acids cause corrosion.

Additional disadvantages exist where the operation of engines require mixing oil with the fuel as in the 2-cycle engine and the epitrochoidal rotary engines. Smoke, fouling of the spark plugs, sticking of piston rings, and carbon deposits result from the use of such mixtures.

It is apparent that great advantages could be obtained if the process fluid, e.g., gasoline in internal combustion engines, could itself be used for lubricating the opposing parts. Besides eliminating the need for auxiliary systems for handling lubricant, the use of the process fluid for lubrication could lead to Improved reliability and reduction in the size, weight and cost of the apparatus. Additionally, since these fluids are being continuously used up in the operation of the particular process, contamination by such things as sludge formation would be minimized.

It is, therefore, the object of this invention to provide a lubricant producing system comprising assemblies composed of sleeve bearings, seals, sliding vanes, pistons, piston rings, etc. moving against opposing surfaces that will function in the presence of low viscosity organic agents. It is another object to provide a system capable of converting in situ a low viscosity organic fluid, e.g., gasoline vapor or liquid, unsuitable as a lubricant in its unpolymerized state to a more viscous polymeric material characterized by its ability to maintain a state of boundary lubrication or full-film lubrication during periods of operation. It is a further object to provide lubricant-producing assemblies for designing and constructing devices (engines, pumps, etc. ) in which the problems resulting from the conventional use of lubricants are eliminated.

SUMMARY OP INVENTION According to the presen invention, the lubricant producing system comprises an assembly of at least two .members having relatively movable opposing surfaces, members A and B, and a fluid capable of polymerizing to form a lubricant during operation of the assembly (a lubricant precursor); the metal-opposing surface of member A comprising an alloy selected from the group consisting of a) an alloy of 11 - 15 atom percent carbon, 1.5 - 3 atom percent silicon and the balance being substantially all iron, and having a Vickers Hardness number of at least 150, b)# an alloy of at least 80 atom percent iron and having a Vickers Hardness number of at least 200, and c)« an alloy of at least $0 atom percent ( 50 - 79 atom percent) iron and having a Vickers Hardness number of at least 1+00, preferably the alloy of a) or b); the metal-opposing surface of member B comprising a mixture of 10 - 90, preferably 25 - 60, percent by volume of an alloy of at least 6, preferably at least 12, atom percent of an element selected from the group *Also containing at least 1 atom percent carbon, the sum of any cobalt and nickel being less than 6 atom percent and wherein at least one-half of the weight of the remainder of the alloy is composed of at least one element selected from the group consisting of chromium, manganese, molybdenum and tungsten, said element s) resent as a carbide(s) or in a full hardened consis ting of molybdenum and tungsten, at least 10 percent, preferably 20 - 85 percent, by volume of the alloy being an intermetallic compound of s aid element preferably in the topologically close packed phase, the Vickers Hardness number of the compound being 5 0 - 1800, the coefficient of dry friction of the alloy of member B against the surf ace of member A being no greater than 0.25, and, correspondingly, 90 -10 (preferably 75 - ij-0 ) percent by volume of a material having a Vickers Hardness number less than that of the alloy, the strength and adhes ive properties of said materi al being sufficient to support said alloy therein; and the fluid being selected from the group consisting of petroleum hydrocarbons having a terminal boiling point no greater than 3li.5°C . , aliphatic alcohols of 1 - 12 carbon atoms ; and aliphatic aldehydes of I . - 9 carbon atoms.

It should be understood that the mixture constituting the opposing surface of member B may take the form of particles of the molybdenum or tungsten alloy embedded in a matrix of the softer material to form a compos ite. The size of the molybdenum or tungsten alloy particles will range from minus I .O mesh to plus lj.00 mesh.

Specifically, assemblies of this invention can be formed that meet the criteria set forth in the previous paragraphs where one of the relatively movable opposing surfaces comprises a mixture of copper and an alloy of 6 - 85, preferably 19 - 25 atom percent molybdenum, I . - 56, preferably I . - 22 atom percent silicon and the balance essentially - 90 atom percent of an element selected from the group consisting of iron, cobalt and nickel, preferably 53 - 77 atom percent cobalt; the other of the relatively movable opposing surfaces comprising an alloy of 1 - 7 atom percent carbon, up to 13 atom percent chromium and the balance essentially 80 - 98 atom percent iron; and the fluid selected from the previously stated group but being preferably gasoline.

Where the first-mentioned relatively movable opposing surface contains an alloy of tungsten, it may be difficult to incorporate more than 2 atom percent into the alloy because of the high melting point of tungsten.

It should be understood that in addition to molybdenum and tungsten in the one opposing surface and iron in the other opposing surface, amounts of elements other than those specified above may be used in both surfaces provided that the criteria regarding the Vickers Hardness numbers, inter-metallic compound and coefficient of dry friction are met as set forth above. It is also possible to include minor amounts of refractory metal oxides in the alloys used such as those disclosed in U. S. Patent 3, 317, 285. In using the system of this invention for sliding elements, performance can be further improved by optimizing the topography, the grooving and the clearance of both surfaces of the sliding couple.

"Coefficient of dry friction", as used in the Summary Of The Invention, is measured in air, as follows: A test sample of the alloy containing the inter-metallic compound used in member B is given a metaliographic polish and washed with acetone to insure a smooth clean surface. A 3/16-in.ch ball or, alternatively, an object having a spherical surface (radius of 3/32-inch) near its point of contact with the flat surface, composed of the material of member A ia cleaned by polishing with 600 grit emery cloth. The test sample of the alloy is mounted on a moving track and passed at a speed of 0.001 cm/sec in contact with the ball of the member A. A load of 1000 grams is imposed on the ball. The frictional drag created by the sample of the alloy moving in contact with the ball is measured by a tangential strain gauge. The coefficient of dry friction is the tangential force required to move the test sample divided by the normal force, which in this case is 1000 grams.

For purposes of simplicity and clarity in illustrating the critical features of this invention, the discussion will be divided into three segments: 1. Metal-"contacting" or opposing surface of member B, also referred to as the lubricant producing (LP) sur-face; 2. Metal-"contacting" or opposing surface of member A, also referred to as the mating surface; and 3. Environmental Medium, also referred to as the process fluid, carrier fluid or simply, the fluid. 1. Lubricant Producing Surface This surface is a composite of a relatively soft material and the molybdenum or tungsten alloy.

The relatively soft materials may be selected from any of the following four groups. Group (a) includes the metals copper, nickel, aluminum, lead, tin, cadmium and iron. Group (b) includes alloys of the metals of group (a); lead base alloys such as Babbitt (71+· 5 lead, 10 tin, 15 antimony, 0.5 copper)*-, tin base alloys such as Babbitt (91.2 tin, 1 . 5 copper, ij. antimony, 0. 3 lead)*, cadmium base alloys (97.5 cadmium, 1 nickel, 1 silver, 0.5 copper)*, copper base alloys such as tin bronze (88 copper, 10 tin, 2 zinc)*, leaded tin bronze (80 copper, 10 lead, 10 tin)*, and copper-lead (70 copper, 30 lead)*, aluminum base alloys such as (91 aluminum, 7 tin, 1 copper, 1 silicon)*, nickel base alloys such as Monel (66 nickel, 31.5 copper, 1.3 iron, 0.9 manganese, 0.1 carbon)*. Group (c) includes the metals chromium and molybdenum. Group (d) includes phenolic resins and essentially linear resins having a second order transition temperature (as determined by plots of flexural modulus versus tempera-ture) of at least 250°C. and a room temperature modulus of at least 300,000 psi, e.g., phenol-formaldehyde resins, aromatic polyimides, aromatic polyamides, aromatic polyketones, aromatic polythiazoles and polybenzotriazoles.

The important criteria for selecting the molybdenum or tungsten alloy are in three distinct areas: chemical composition; physical structure; and physical characteristics.

As for chemical composition, the alloy should contain at least 6 atom percent of molybdenum or tungsten. As for physical structure, it should be composed of at least 10 per-cent by volume of an interraetallic compound having molybdenum or tungsten as a component. The physical characteristics should be such that the alloy has a coefficient of dry friction when contacted against the mating surface of no greater than 0.25; the intermetallic compound of the alloy has a Vickers Hardness number ranging between 5 0 and l800; and the relatively soft material matrix containing the intermetallic compound should have a Vickers Hardness number less than that of the intermetallic compound. *parts by weight When used in the present invention, the aforementioned alloys will be capable of producing lubricant when subjected to sliding action in the presence of a fluid capable of being converted into a material having lubricating properties. It is believed that the soft matrix permits particles of the aforementioned alloy to accommodate to any misalignment between surfaces, e.g., shaft and bearing, etc. Thus, superior compatibility and superior results are obtained using the composite. Specifically, when subjected to 50,000 PV (load in p.s.i. x velocity of l80 ft/min or greater) in the wear tester shown in Figure 1, the total wear of both lubricant producing surface (sample) and mating surface (reference ring) will be less than l+.O mils/100 hrs. as measured by micrometer or weight measurements; and the coefficient of friction will be less than 0.2. The test procedure, as set forth hereinafter, was designed so that operating conditions would lead to a state of lubrication below that of the full-fluid range, thus obtaining metal-to-metal interaction. In this way, the compatibility and ability of the metal combinations to produce lubricant can be measured. It is believed that the lubricant is not produced continuously in the system of the invention. Instead, additional lubricant is only produced after that originally formed is used.

It is also observed that the softer matrix, e.g., copper, wears away preferentially, thereby creating cavities at the sliding interface. It is believed that these cavities become filled with the environmental fluid and the lubricant formed. On a micro scale the same phenomenon occurs within the molybdenum or tungsten alloy in that the softer matrix portion is worn preferentially leaving the hard intermetallic compound in relief. It is believed that the environmental fluid and the lubricant formed collect in the micro-cavities which are close enough to provide superior lubrication at the contact points undergoing sliding action.

Figure 1 is a schematic representation of the wear tester utilized in determining wear performance. It is representative of end thrust type bearings and is useful as a screening device for determining systems of the present invention. The speciraen^of member A to be tested ~ . is rotated by a DC motor 10. The friction between the ring^of 12 member B and the test specimen/of member A ~ . produces a torque in the shaft 13. The shaft 13 is constrained from turning by the lever arm 11+ connected to a strain gauge 15. The strain gauge voltage is continuously monitored on a recorder. This voltage is converted into pounds pull by previous calibration. Prom the geometry of the system, the tangential force on the specimen is calculated. The coefficient of friction equals the tangential force divided by the normal thrust of load pushing the specimen and wear ring together. Wear rates are determined from weight loss and also by micrometer measurements. Tests are carried out by rotating the test specimen at a speed of l80 ft/min and at varying loads. The PV is determined by multiplying the load in p.s.i. based upon actual contact area by the speed in ft/min.

Specifically, the specimen 12 and the ring 11 are machine ground to obtain parallel faces and then hand lapped on I.OO grit paper; vacuum dried at 100°C. for at least 1 hour and then weighed to 0.0001 gram and measured to 0.0001 inch.

They are then mounted in the tester as shown in Figure 1 and the cup 16 filled with gasoline or other fluid 17. The cup 16 is lined with cooling coils to minimize evaporation. Using only the weight of the shaft 13 and lever ll+, the tester is run at 50 rpm (to provide l80 ft/min) for 1 to 2 minutes.

After this period, the preselected test load is applied and the test is run continuously for 18 to 20 hours. Due to fluid evaporation, additional sga®$ must be added every I to 6 hours. After 18 to 20 hours, the specimen 12 and the ring 11 are again vacuum dried; weighed; and measured. Alternatively, the tester may be loaded in increments of 20 lbs. while being run at the previously disclosed speed. The tester may be run 30 minutes at each weight increment until failure occurs.

The presence of at least 10 volume percent of an intermetallic compound of molybdenum or tungsten in the contacting surface of member B is vital to the operability of the present invention. These intermetallic compounds, in most cases, occur as an intermediate or secondary phase within a solid solution or matrix phase. They vary in amount and size and are of diverse types. The amount and type is determined by such factors as the particular chemistry of the metals being alloyed, the length of time at which the alloy is subjected to specific temperature conditions, and the cooling rate. Intermetallic compounds found in the alloys operable in this invention include 1) the topological close packed (TCP) structures including the sigma, Chi, Mu and Laves phases, 2) the semi-carbides of the M^C and M23C6 type and 3) Mo Si2 type. The presence and amount of intermetallic compounds may be determined by either x-ray diffraction or metallographic analysis.

Of primary interest for this invention are the intermetallic compounds of Laves phase structures characterized by the ternary phase systems, Co-Mo-Si, Ni-Mo-Si, Co-W-Si and Ni- -Si. These alloys are disclosed in U.S. Patent 3, 257, 178 to Severns and Smith and represent the most desirable alloys for use as the metal-opposing surface of member B. Specifically, these alloys are defined in this patent as consisting essentially of a substantial amount of at least one metal A and a substantial amount of at least one metal B, and silicon, metal A being selected from the group consisting of molybdenum and tungsten and metal B being selected from the group consisting of cobalt and nickel; the sum of the amounts of metals A and B being at least 60 atom percent of the alloy; the amount of silicon and the relative amounts of metals A and B being such as to provide 30 - 85 volume percent of said alloy in the Laves phase; the Laves phase being distributed in a relatively soft matrix of the remaining 70 - 15 volume percent of said alloy. 2. Mating Surface The important criteria for selecting the material for the mating surface of member A are in two distinct areas: chemical composition and physical characteristics. The particular materials may be divided into three groups, the first two being preferred.

The first group embraces the cast irons containing graphite. They are the gray cast irons and malleable cast irons. Carbon content varies from 11 to 15 atom percent, and silicon content from 1.5 to 3 atom percent with the balance being iron and trace amounts of other metals. Hardnesses can be as low aa Vickers Hardness number of 1$0, It is believed that the presence of the carbon as graphite offsets the effect of softness. These alloys are useful as piston rings, cylinder walls and in other applications having poor lubrication.

The second group consists of iron alloys containing at least 80 atom percent iron, at least 1 atom percent carbon and having Vickers Hardness numbers of at least 200. This group embraces the white cast irons, carbon steels, most of the tool steels and the bottom of the range of martensitic stainless steels. It is preferred that the Vickers Hardness number of the steels in this group be over 270.

The third group consists of iron-base alloys containing 50 - 79 atom percent iron, at least 1 atom percent carbon and having Vickers Hardness numbers of at least I.OO.

Also undesirable are the ferritic stainless steels and most of the austenitic stainless steels. However, it may be possible to use work hardened low nickel alloys of austenitic stainless steels.

The major alloying elements for the second and third groups are chromium, manganese, molybdenum and tungsten. These elements should represent at least one-half of the weight of the remaining alloying elements (besides iron and carbon) and should be present primarily as carbide precipitates or in a fully hardened solid solution, e.g., the martensite phase of iron. Nickel and cobalt are undesirable and their sum in the alloy should be less than 6 atom percent. 3. Environmental Medium The most impressive feature of the system of this invention is its ability to polymerize certain fluids to form lubricants in situ, thereby obviating the necessity of using an extraneous (non-essential to the function of the system) material such as heavy petroleum products (e.g., motor oils, lubes, and greases). Because of their commercial interest, the invention is concerned primarily with systems involving petroleum hydrocarbon fuels as the environmental medium. Thus, gasoline in automotive, marine, and aircraft engines; kerosene and jet fuels in modern jet aircraft; and diesel fuels in diesel type engines are particularly useful in this invention. These fluids may be classified as petroleum hydrocarbons whose terminal boiling points are no greater than 3l$°C, The fluids may be used in liquid or vapor form. One method to achieve the results of the present invention is to spray gasoline vapor into the chamber containing the relatively movable opposing surfaces.

It should be noted that as little as 10 weight percent of a fluid operable in this invention in combination with 90 weight percent of an inoperable fluid will operate successfully as part of the system of this invention. It should also be pointed out the systems of this invention will operate in the presence of conventional lubricants (solid or fluid) and hydraulic fluids and will thus make possible the use of lesser quantities of such added lubricant. Furthermore, the systems of this invention could permit the use of mixtures or disper-sions of the specified hydrocarbons, alcohols and aldehydes with such fluids as trichloroethylene, water, etc, which are not usually considered lubricants. The use of the systems of this invention make it possible to use hydraulic fluids of relatively low viscosity* During operation, the viscosity of the lubricants produced from these fluids is high enough to perform a lubricating function. In cold weather operation, the viscosity of the hydraulic fluid is low enough so that no heating is required to maintain fluidity as is usually necessary with more viscous fluids.

USES OP THIS INVENTION The assemblies of this invention find applicability in all types of engines: 2- and l4.-cycle reciprocating engines 2- and l.-cycle rotary engines including the epitrochoidal, elliptical, wedge and vane piston types; free piston gas generating engines; turbo-jet engines; standard jet engines; and gas turbine engines. Thus, in a 2-cycle reciprocating engine, the bearing surfaces and seals can be composed of or coated w th a composite of copper and the alloy of molybdenum or tungsten referred to herein &a member B; while the opposing surfaces including the crankshaft, the piston cylinder wall, etc. can be composed of the alloy of iron referred to herein as the member A alloy.

The assemblies are also useful in fuel pumps and fuel injectors. Thus, in the fuel injectors the member B composite can be used as a surface coating for the plunger which slides through a chamber made of member A, or member B can be used as a coating for the cylinder chamber through which a plunger made of or coated with member A slides. In a fuel pump, the vanes can be coated with or composed of the member B composite which makes "contact" with a chamber of member A, or visa versa. This permits operation with low viscosity fuels such as gasoline or kerosene. This opens up the possibility of operating diesel engines with less viscous fuels than are now used.

A particularly interesting application of the present invention is in the rotary internal combustion engine described in U.S. Patent 3,359,953. This patent describes special techniques to overcome the side sealing problem. The member B composite of the present invention has been used on the "contacting" surface of the end face seals while the inner surfaces of the end walls were composed of member A alloy.

Another interesting application of the present invention is as a solution to the problem of increasing the load bearing capacity of oil impregnated porous bearings, i.e., self-lubricating bearings. Relatively large pores are needed in these bearings to transmit the relatively viscous lubricant, thereby reducing load bearing capacity. By using a low viscosity precursor that forms a high viscosity lubricant in situ on the bearing surface, smaller pores would be used.

This, in turn, increases the load bearing capacity of the bearing. By using the member B composite in the bearing along with the environmental media set forth for this invention, greases having greater viscosity than conventional oils are produced with an accompanying increase in load bearing capacity.

To summarize, the assemblies of this invention will be useful in a multitude of situations involving the use of bearings, gears, seals and pistons, the members of the assemblies being used either to form the parts or as coatings for such parts. The following listing of uses is not intended to be limitative but intended to apprise those skilled in the art of useful applications of this invention.

LISTING OP END USES General Bearings A. Journal Bearings B. Thrust Bearings 1. Bushings 1. Plat-land 2. Wick-Oil 2. Tapered land 3. Oval-ring 3. Pivoted shoe . Pressure-fed h. Step . Circumferential 5. Externally groove pressurized 6. Cylindrical Pocket 7. Cylindrical Standardized overshot bushings 8. Pressure Slewing rings 9. Multiple-groove . Elliptical 11. Three-lobe 12. Pivoted shoe 13. Partial I . Externally pressurized Specific Bearings 1. Internal combustion engines reciprocating 2. Internal combustion engines rotary (epitrochoidal, elliptical, wedge, vane piston) Liquid handling pumps, stirrers, and other chemical processing equipment.

Hydraulic equipment 8. Refrigerating equipment Vacuum pumps 9. Stirling cycle (heat) engine Turbine engines . Gas compressors Jet engines III . Specific Gears 1. Transmis sions - automotive, farm machinery 2. Milling machinery 8. Splines 3. Lathes 9. Cams l Differentials 10. Worms . Gear reducers 11. Chain drives 6. Planetary 12. High speed slides 7. High speed quills IV. Se als V. Pistons 1. Rotary engines 1. Internal combus tion engines 2. Pis ton rings - Internal combustion engines 2. Hydraulic equipment 3· Chemical pumps 3. Fuel Injectors I .. Fuel pumps and pumps I4.. Pos itive displacement type fuel pumps It should be noted that in using this system for sliding elements, e.g. , seals, journal bearings, etc. , performance can be improved by optimizing the topography, the grooving and the clearance of both opposing surfaces of the sliding couple.

The present invention is further illustrated by the following examples .

EXAMPLE 1 A composite was prepared by mixing -100 mesh copper powder with -100 + 200 mesh alloys of cobalt, molybdenum and s ilicon in the ratio of $0/$0 percent by volume. The mixture was plasma sprayed onto an aluminum substrate. The composite #56 atom percent cobalt, 22 atom percent molybdenum and 22 atom percent silicon was then tested in the wear tester shown in Figure 1 against 1095 steel* hardened to a Vickers Hardness number of $10.

A PV of I-4.0, 000 was applied to the test specimen and the tester was run for 6 hours in an environment of gasoline. The gasoline was introduced into the tester in the form of a spray at a flow rate of 0.i|2 ml/min. The coefficient of friction was measured and found to be 0.08. At the end of the 6-hour run, the test specimen and the mating surface were examined. Not only was there substantially little or no wear evidenced, but also an amber colored product resembling grease was found to be present at the interface of contacting surfaces. The average cryoscopic molecular weight of this reaction product was found to be 1+20, contrasting with an average molecular weight of 107 for the gasoline initially introduced.

The lubricity of the reaction product was then measured and compared with that of commercially available grease. A small amount of the reaction product was rubbed on a specimen made from 1020 cold rolled steel**. This specimen was then placed in the wear tester and brought into contact with a reference ring of 1095 steel (Vickers Hardness number = 510 ) . The combination of 1095 steel against 1020 steel would normally seize immediately in a gasoline environment. In the presence of the reaction product, however, which was smeared on the surface interface between the two steels, the tester ran smoothly at a PV of 200, 000; the wear rate was low; and the coefficient of friction was 0.036, identical to that obtained when a commercial grade lubricating grease was employed. #95.7 atom percent iron, I4..3 atom percent carbon ■5H5-0.9 atom percent carbon, 0.5 atom percent manganese, 93.6 atom percent iron (all nominal) In contrast, when vaseline, a less effective lubricant was substituted, the coefficient of friction increased to 0.08 at a PV of only 55*000. The measured wear rate was correspondingly high, EXAMPLES 2 - 8 A series of iron alloys as member A and composites of various matrix materials and alloys of molybdenum or tungsten as member B was prepared and tested in the wear tester shown in Figure 1 following substantially the procedure set forth in Example 9. Gasoline was used as the environmental medium in Examples 2 - 6; n-octane, in Example 7 an hexanol, in Example 8.

The alloy used as member A and its Vickers Hardness number (V.H.) and the composite used as member B are shown in Table I-A and the results are shown in Table I-B.

TABLE I-A Member B alloy - matrix material Example Member A (volume percent) 2 1095 steela 20 CM 5535b - 60 copper, 20 3 Elastuff kk.c I±0 CM 5535 - 60 nickel * Elastuf hk 2£ CM 5535 - 75 polyimided 1095 steel 20 NW kSk e - 80 copper 6 C 6l0f 35 CM 5535 - 65 copper 7 1095 steel 35 NW 51+0 - 6 copper 8 Elastuf IJ. 35 CM 5535 - 65 copper a 95.7 a . o Pe, 1+.3 at.% C (V.H. 516) b 56,1+ at.% Co, 22.1 at.% Mo, 21.5 a.t.% Si c 93.6 at.% Pe, 2.1 at.% C, 1.7 at.% S, 1 at.% Cr, 0.9 at.% Mn, 0.1+ at.% Si, 0.3 at.% Mo (V.H. 1+314-) d polymer of 1+, l+l-oxydi aniline and pyromellitic dianhydride e 50.7 at.% Ni, 11+.5 at.% W, 3^.8 at.% Si f 80 at.% Pe, 12 at.% Cr, 6.6 at.% C, 1 at.% V, 0.1+ at.% Mo (V.H. 720) TABLE I-B Total Wear PV Coefficient (mils/100 hrs. ) Example x 1000 of Friction Mem. A Mem. B 2 161+ 0.11 0. 0 0.2 3 57 0.17 0.0 0.0 k 57 o.o 0.0 0.0 100 0.05 0.1 0.5 6 90 0.16 0. 0 0. 7 7 55 0.1 0.0 0 8 70 0.07 0.0 0.0 EXAMPLE 9 Figure 2 illustrates a device utilized to test the efficiency of certain type bearings intended for commercial applications. Referring to this schematic sketch, friction between shaft 61 and the bearing to be tested 62 causes a yoke -yolk 63 to rotate when a load 61+ is applied. The rotation yoke of the yeik applies a force to a torque transducer 65 through lever arm 66. From the torque which is recorded on a chart recorder, not shown, the tangential force acting at the bearing shaft interface is calculated. This divided by the load applied gives the coefficient of friction. The transducer is calibrated before each test. The process fluid, is introduced into the bearing system through port 67.

The test procedure involves increasing the flow of gasoline to 1 lb. per hour at no load and then increasing the "rpm" of the shaft to the desired level. The load is applied in increments of 20 lb. and the apparatus allowed to run from 30 minutes to an hour at each step.

A composite was prepared by pressing -100 mesh copper powder with 28 volume percent of an alloy consisting of 56 atom percent cobalt, 22 atom percent molybdenum and 22 atom percent silicon ( -100 mesh + 200 mesh). After heating the com-5 posite to 850°C. in hydrogen, billets were forged in air to a diameter of 1-1/]+ inches. After heat treatment at 850°C. in hydrogen for 3 - k hours to promote bonding between copper and the alloy, Journals were rough machined using carbide tools to within 10 mils of final tolerances and then ground 0 to the final diameter of the journal bearings, 0.750 inch.

As Control A, the journal bearings were fabricated by casting the above-mentioned cobalt-molybdenum-silicon alloy alone, As Control B, journal bearings were fabricated from 5 bronze SAE 66 CM , The bearings were all tested in the device shown in Figure 2 using gasoline as the fluid and a shaft of hardened steel, SAE 52100## and a shaft speed of 1200 revolutions per minute. The results at various loadings are shown in the 0 following table: TABLE II Coefficient of Friction at Various Loadings (PV) PV (psi x ft/min) ιο, οοο 25, 000 50, 000 75, οοο 100, 000 Example 9 — O.OOI+ 0.006 0.007 0.001+ Control A -- 0.21 0.16 0.16 0.16 Control B seized seized seized seized seized #90 atom percent copper, I4. atom percent tin, 1+ atom percent zinc, and 2 atom percent lead *H*93.2 atom percent iron, I..I. atom percent carbon, 1.5 atom percent chromium, 0.6 atom percent silicon, 0.3 atom percent manganese EXAMPLE 10 A 2-cycle engine was modified as shown in Figure 3 to permit operation without addition of oil to the fuel system. The original engine was a 2-cycle, 2-1/2 horsepower engine Model D-I.O2 manufactured by the Outboard Marine Corp., Gales-burg, 111. The clearances after modifications of the bearings, piston, and piston rings were the maximum allowable falling within the specifications of the manufacturer. In addition, the sleeve bearings were grooved to direct the gasoline to the bearing interfaces.

The sleeve bearings 21 and 22 used as magneto plate-bearings and shaft bearings were made from composites of copper and 28 percent by volume of the alloy* used in Example 1.

These bearings were sealed at both ends to prevent gasoline from passing directly into the aluminum crankcase. A hardened low alloy steel within the definition of member A of the invention was used as the crankshaft 21j.. The piston 29 was coated with a mixture of copper and 25 percent by volume of the alloy of Example 1 by plasma spraying to a thickness of .OOI.-5 inch. The particular size used in these coatings was -100 mesh and 200 mesh. A band of thi3 coating was put at the top and bottom of the piston, although it is preferable to coat the entire piston. Ths piston rings 28 which slide against the cast iron cylinder walls were the manufacturers cast iron rings coated with the alloy of Example 1 by plasma spraying.

Although the fuel pump was electrically operated, it may be operated as a positive displacement diaphragm-type fuel pump as shown in Figure 3. The flow of fuel (gasoline) #5° atom percent cobalt, 22 atom percent molybdenum and 22 atom ercent silicon Is designated by the dotted lines. Fuel from the tank 31 s sucked into the fuel pump 30. Prom here, it is pumped into bearing 22, removed from a port on the opposite side, and passed into the cast-iron cylinder 32 through port 33 and other similar orthogonal ports not shown. The fuel flowing into port 33 lubricates bearings 26 and 27 in the following manner. Hollow wrist pin 5 is blocked at one end to prevent fuel from passing through it and out the exhaust port 3k- When the wrist pin 25 passes over the port 33» gasoline is ejected into it and flows towards the exhaust end. Since this end is blocked and bearings 26 and 7 are provided with openings, this gasoline flows into these bearings for lubrication. Not shown in Figure 3 are the openings in the bottom of bearing 27 and in the top of bearing 26 to allow gasoline vapor in the crankcase 36 to provide additional lubrication to bearings 26 and 27.

Fuel may also be pumped from pump 30 into bearing 21. It then flows down this bearing as indicated and through an opening 35 in the crankshaft 2L|. to lubricate bearing 23. Bearing 23 is a roller bearing having an outer race of an alloy ( 77 atom percent cobalt, 19 atom percent molybdenum and I . atom percent silicon). The crankshaft eerved as an inner race and the manufacturer's needles (52100 steel}* were used as rolling elements.

The fuel is ejected from bearing 23 into the crankcase chamber 36. Fuel is also pumped into the carburetor 37. The reed valve 38 on the carburetor closes when the crankcase 36 is under compression and opens when the crankcase is under «•93.2 at.# Fe, I .. I . at.# C, 1.5 at.# Cr, 0.6 &t, Si, 0.3 at.# Mn a low pressure, i.e., when the piston 39 is in its highest position. Although not shown on the figure, there are por*ts for channeling the gasoline - air mixture into the combustion chamber I4.O, Plow of fuel through the carburetor 37 is controlled by the amount of air sucked into the engine. This amount of air, in turn, is controlled by a governor.

It was found that for smooth engine operation it was desirable that at least $0 percent of the fuel passed through the normal combustion route, i.e., through the carburetor and into the combustion chamber on the upstroke of the piston. The control of the amount of flow of gasoline through the carburetor 37 and to bearings 21, 22 and 23 is accomplished by needle valves.

In the test run, the pump 30 was started to admit fuel to all bearing surfaces just prior to starting the engine. Thus, the bearings were not operated in the dry condition.

The engine was then run for 50 hours using commercially available premium gasoline containing no oil. The fuel was introduced into the engine at a rate of 2.1 lbs. /hr. The air flow was 19 lbs. hr. giving an air-fuel ratio of about 9 to 1. The engine speed was 2, 1+50 rpm. No load was placed on the engine. During operation, there was no visible smoke in the exhaust as occured during operation of the unmodified 2-cycle engine run on the fuel-oil mixture recommended by the manufacturer. Other than a thin sooty deposit that covered the piston and cylinder walls, there were no engine deposits. The dimensions of the essential friction wear parts were measured before and after the test to determine the amount of wear. The results are tabulated in Table III.

TABLE III DIMENSIONS OP ESSENTIAL FRICTION WEAR PARTS BEFORE AND AFTER 50 HOUR ENGINE TEST Dimensions Before After Total Testing Testing Wear Wear Part ( Inches ) ( Inches ) ( Inches ) Magneto Plate -Bearing 22 0.8772 0.8772 0.0000 Lower Bear ing 21 0.8771 0.8771 0.0000 Shaft Magneto Bearing 22 0.871+ 0.8742 0.0002 Shaf Lower Bearing 21 0.87 3 0.8741 0.0002 Piston 29 2.3710 2.3710 0.0000 Cylinder 3 2.3770 2.3770 0.0000 Where engine designs are such that oil must be present to insure lubrication of certain surfaces, it is pos sible by use of the lubricant -producing surfaces of this invention to greatly reduce the amount of oil that must be supplied. For example, the 2-cycle engine described above has been run, without introduc ing fuel through the cylinder wall, by using instead of the pure gasoline a mixture of 1 part of SAE 30 oil in 500 parts of gasoline. With the usual sliding surfaces in the combustion chamber a ratio of 1 part of standard oil in 16 parts of gasoline is required.

When a completely unmodified 2-cycle engine of a similar design was run on a gasoline-oil ( 16 - 1 ratio ) mixture for 3 hours, the exhaust ports were almost completely clogged with heavy deposits of carbon. Further running of this engine would require disassembly and cleaning of ports, piston and cylinder.

EXAMPLE 11 One of the most promising potent ial end uses for the present invention would appear to be as seals in rotary engines . A sequence of tests to evaluate the performance of the system of this invention aa seals in the engine described in U, S. Patent 3, 359, 953 ( the Wankel engine ) was initiated. For this, a Gast air motor was used, as illus trated in Figure I .. Normally, this engine would be powered by compressed air injected through the inlet. For these experiments, however, the motor was driven by means of the bearing tester described f or use in Figure 2. The motor of the bearing tester was attached to the rotary shaft of the air motor by a coupling c ausing the air motor to rotate.

In the first test, vanes $1 made from a composite of copper and 30 percent by volume of the alloy of Example 1 were compared to hard chromium plated vanes . The test was run at room temperature. The motor was driven at 1200 rpm while 0.1 lb, per hour of commercially available premium grade gasoline was flushed through it with 1 lb. per hour of nitrogen. This low amount of gasoline was used to more closely simulate the amount of unburned fuel in an engine. In a 3.5 hour run the chromium plated vanes ruined the cast-iron hous ing and generated enough wear debris to plug the outlet port. In the s ame period, no wear of the vanes or hous ing could be measured when the vanes were made from the composite described in Example 9. Next, the test on the vanes of this composite was repeated except that the housing was heated to 150°C , the highest surface temperature reached in the Wankel engine*. Again, no wear of the composite vanes or housing could be measured. After the test all interior surfaces were coated with a substance corresponding in viscos ity to SAE 20 -30 grade commerc ial oil, indicating formation of a lubricant in situ when in continuous contact with gasoline.

EXAMPLE 12 To demonstrate a gasoline pump using the system of this invention, the vanes in a Gast air motor were replaced with vanes prepared from the composite set forth in Example 11. The motor was operated a3 a pump by driving it with the bearing tester of Figure 2 at 1200 rpm. Gasoline was pumped at a rate of 30 gal hr. in a closed loop with a one gallon reservoir for 5.25 hours. No wear on the vanes could be measured and the weight loss per vane averaged one milligram.

Claims (22)

Claims for Foreign Filing

1. A lubricant producing system comprising an assembly of at least two members, members A and B, having relatively movable opposing surfaces and an environmental fluid capable of forming a lubricating medium for the opposing surfaces during operation of the assembly; the opposing surface of member A consisting essentially of a) an alloy of 11 - 15 atom percent carbon 1.5 - 3 atom percent silicon and the balance being substantially all iron, and having a Vickers Hardness number of at least 150, b) an alloy of at least 80 atom percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of at least 200, or c) an alloy of 50 - 79 atom percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of at least ^00, the sum of any cobalt and nickel in said alloys b) and c) being less than 6 atom percent, at least one-half of the weight of the remainder of alloys b) and c) being elements consisting of chromium, molybdenum, manganese and tungsten, which are present as carbide(s) or in a fully hardened solid solution; the opposing surface of member B consisting essentially of a mixture of 10 - 90 volume percent of an alloy of at least 6 atom percent of an element consisting of molybdenum or tungsten, at least 10 percent by volume of the alloy being an intermetallic compound of the element, the Vickers Hardness number of said compound being 550 - 1800, the coefficient of dry friction of the alloy of member B against the surface of member A being no greater than 0.25, and, correspondingly, 90 - 10 percent by volume of a material having a Vickers Hardness number less than that of the alloy of member B, the strength and adhesive properties of the material being sufficient to support the alloy therein; and the environmental fluid consisting of petroleum hydrocarbons having a terminal boiling point no greater than 345°C, aliphatic alcohols of 1 - 12 carbon atoms or aliphatic aldehydes of 4 - 9 carbon atoms.

2. A lubricant producing system according to Claim 1 wherein the opposing surface of member A is an alloy of 11 - 15 atom percent carbon, 1.5 - 3 atom percent silicon, the balance being substantially all iron, having a Vickers Hardness number of at least 150.

3. A lubricant producing system according to Claims 1 or 2 wherein the opposing surface of member A is the alloy of at least 80 atom percent iron having a Vickers Hardness number of at least 200.

4. A lubricant producing system according to Claims 1 - 3 wherein the alloy of the mixture in the opposing surface of member B is an alloy of at least 12 atom percent of molybdenum.

5. A lubricant producing system according to Claims 1 - 3 wherein the alloy of the mixture in the opposing surface of member B is an alloy of at least 12 atom percent of tungsten.

6. A lubricant producing system according to Claims 1 - 3 wherein the alloy of the mixture in the opposing surface of member B consists essentially of 6 - 85 atom percent molybdenum, 4 - 6 atom percent silicon, the balance being selected from the group consisting of iron, cobalt and nickel.

7. A lubricant producing system according to Claims 1 - 3 wherein the alloy of the mixture in the opposing surface of member B consists essentially of 19 - 25 atom percent molybdenum, 4 - 22 atom percent silicon and 53 - 77 atom percent cobalt.

8. A lubricant producing system according to Claims 1 - 7 wherein the intermetallic compound in the alloy of said opposing surface of member B is 20 - 85 percent by volume of the alloy. - . ···· - .-, L_J.- .- L_J L, . ·.;_ j — 32490/2 .'

9. A lubricant producing system according to Claim 1 · wherein the environmental fluid is a. petroleum hydrocarbon having a terminal boiling point no greater than 3 5°C. such as gasoline.

10. A lubricant producing system according to Claims 1 -9 wherein oil is added to said environmental fluid. -

11. A lubricant producing system according to Claims 1 - 10 wherein said material in the mixture having a ' ■'· ■ Vickers Hardness number less than that of the alloy of member B consists of a) copper, nickel, aluminum, lead, tin, cadmium or iron, b) alloys of the metals of group (a), c) chromium and molybdenum, or d) polyimides, aromatic polyamides, aromatic polyketones, polybenzimidazoles, aromatic polyimines, polybenzotriazoles, aromatic polythiazoles, or phenol-formaldehyde resins. .

12. A. lubricant producing system according to Claim 11 wherein the. material is copper. . ..

13. A lubricant producing system according to Claim 11 wherein the material is a copper alloy.

14. A lubricant producing system according to Claim 11 wherein the material is nickel.

15. A lubricant producing system according to Claim 11 wherein the material is a polyimide of pyromellitic dianhydride and 4,4 ' oxydianiline. . l6..

A lubricant producing system substantially as . \ hereinbefore described.

17. An assembly for use in a lubricant producing system, according to any one of Claims l-l6 comprising at least two members, members A and having relatively movable opposing surfaces, the opposing surface of member A consisting essentially of a) ' an alloy of 11 - 15 atom percent carbon, 1.5 -' 3 atom percent silicon and the balance being substantially all iron, and having a Vickers Hardness number of at least 150, b) an alloy of a least 80 atom percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of :.;at least 200, or c) an alloy of 0 - 79 atom * percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of at least 400, the sum of any' cobalt and nickel in said alloys b) and c) being less than δ atom percent, at least one-half, of the weight of the remainder of alloys b) and c) being elements consisting of chromium, molybdenum, manganese and tungsten, which are present as carbide(s) or in a fully hardened solid solution; the opposing surface of member B consisting essentially of a mixture of 10 - 90 volume percent of an alloy of at least δ atom percent of an element consisting of molybdenum or tungsten, at least 10 percent by volume of the alloy being an intermetallic compound of the element, the Vickers Hardness number of said compound being 550 - l800, the coefficient of dry friction of the alloy of member B against the surface of member A being no greater than Ο.25, and, correspondingly, 90 - 10 percent by volume, of a material having a Vickers Hardness number less than that of the ^ alloy of member B, the strength and adhesive properties of the material being sufficient to support the alloy therein.

18. An assembly according to Claim 17 wherein the ; opposing surface of member A is an alloy of 11 - 15 atom percent carbon, 1.5 - 3 atom percent silicon, the balance ^eing substantially all iron, having a Vickers Hardness number of at least 150. 32490/1

19. An assembly according to Claims 17 or l8 wherein the opposing surface of member A is the alloy of at least 80 atom percent iron having a Vickers Hardness number of at least 200.

20 . An assembly according to any one of Claims 17-19 wherein the alloy of the mixture in the opposing surface of member B is an alloy of at least 12 atom percent of molybdenum.

21. An assembly according to any one of Claims 17-19 wherein the alloy of the mixture in the opposing surface of member B is an alloy of at least 12 atom percent of tungsten.

22 . An assembly according to any one of Claims 17-19 wherein the alloy of the mixture in the opposing surface of member B consists essentially of δ - 85 atom percent molybdenum, 4 -5δ atom percent silicon, the balance being selected from the group consisting of iron, cobalt, and nickel. 23 · An assembly according to any one of Claims 17-19 wherein the alloy of the mixture in the opposing surface of member B consists essentially of 19 - 25 atom percent molybdenum, 4 - 22 atom percent silicon, and 53 - 77 atom percent cobalt.

24. An assembly according to any one of Claims 17-23 wherein the intermetallic compound in the alloy of said opposing surface of member B is 20 - 85 percent by volume of the alloy. 25 · An assembly according to any one of Claims 17-24 wherein the material in the, mixture having a Vickers Hardness number less than that of the alloy of member B consists of a) copper, nickel, aluminum, lead, tin, cadmium, or iron^ b) alloys of the metals of group (a), c) chromium and molybdenum, or d) polyimides, aromatic polyamides, aromatic polyketones, polybenzi-midazoles, aromatic polyimines, polybenzotriazoles, aromatic 32490/1

25. An assembly according to Claim 25 wherein the material is copper. 27- An assembly according to Claim 25 wherein the material is a copper alloy.

28. An assembly according to Claim 25 wherein the material is nickel. 29· An assembly according to Claim 25 wherein the material is a polyimide of pyromellitic dianhydride and ,4'oxydi-aniline .

30. Process for preparing lubricant producing systems according to Claims 1 - 15 which comprises placing the surfaces of at least two members, members A and B, in opposition, the opposing surface of member A consisting essentially of a) an alloy of 11 - 15 atom percent carbon, 1.5 - 3 atom percent silicon and the balance being substantially all iron, and having a Vickers Hardness number of at least 150, b) an alloy of at least 8o atom percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of at least 200, or c) an alloy of 50 - 79 atom percent iron, at least 1 atom percent carbon, and having a Vickers Hardness number of at least 400, the sum of any cobalt and nickel in said alloys b) and c) being less than 6 atom percent, at least one-half of the weight of the remainder of alloys b) and c) being elements consisting of chromium, molybdenum, manganese or tungsten, which are present as carbide (s) or in a fully hardened solid solution; and the opposing surface of member B consisting essentially of a mixture of 10 - 90 volume percent of an alloy of at least 6 atom percent of an element consisting of molybdenum or tungsten, at least 10 percent by volume of the alloy being an intermetallic compound of the element, the Vickers Hardness number of said compound being 550 - l800, the coefficient of dry friction of the alloy of member B against the surface of member A being no greater than 0.25, and, correspondingly, 90- 10 percent by volume of a material having a Vickers Hardness number less than that of the alloy of member B, the strength and adhesive properties of the material being sufficient to support the alloy thereinjadding a fluid in a manner such it flows onto the opposing surfaces of members A and B, the fluid consisting of petroleum hydrocarbons having a terminal boiling point no greater than 3^5°C, aliphatic alcohols of 1 - 12 carbon atoms or aliphatic aldehydes of 4 - 9 carbon atoms; and moving the opposing surfaces relative to each other whereby the fluid is polymerized to form a lubricating medium. 32490/2

31. Process according to Claim 30, wherein an oil is added with the fluid.

32. Process for producing lubricant producing systems according to the methods described in any of Examples 1 - 12.

33. Lubricant producing system whenever prepared according to the methods set forth i any of the foregoing Claims 30 - 32. . . . PAHfiJERS PC/rb