IL32488A - Lubricant producing system - Google Patents

Description

I RICANT PRODUCING S3TSTEM B.I. DU ΡΟΝΪ DE NEMOURS AND COMPANY 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 dis dvantages. 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 assemblies composed of rolling element bearings, seals, sliding vanes, pistons, piston rings, gears, etc. moving against opposing surfaces that will function in the presence of low viscosity organic agents. It is another object to provide an assembly 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 characterised 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 fo designing and constructing devices (engines, pumps, etc.) in which the problems resulting from the conventional use of lubricants are eliminated.

According to the present invention there is provided a lubricant producing system comprising 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 400, preferably the alloy of a) or b) ; the metal-opposing surface of member B comprising an alloy of at least 6, preferably at least 12, atom percent of an element selected from the group consisting of molybdenum and tungsten, at least 10 percent, preferably 20 - 85 percent, by volume *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 elemen (s) presen as a carbide(s) or in a fully hardened solid solution, e.g., the martensite phase of iron. of the alloy being an intermetallic compound of said element preferably in the topologically close packed phase, the Vickers Hardness number of the compound being 550 - 1800, and any matrix containing the compound when present , having a Vickers Hardness number less than that of the compound, the coefficient of dry friction of the opposing surface of member B against the surface of member A being no greater than 0.25; and the fluid being selected from the group consisting of petroleum hydrocarbons having a terminal boiling point no greater than 345°C, aliphatic alcohols of 1 - 12 carbon atoms; and aliphatic aldehydes of 4 - 9 carbon atoms.

Specifically, assemblies of this invention can be formed that meet the criteria set forth in the previous paragraph where one of the relatively movable opposing surfaces comprises an alloy of 6 - 85, preferably 19 - 25 atom percent molybdenum, 4 - 6, preferably 4 - 22 atom percent silicon and the balance essentially 10 - 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 rela-tively 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 comprises an alloy of tungsten, it may be difficult to incorporate more than 25 atom percent of tungsten 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 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: The substantially flat metal-"contacting" surface of the member having the lower Vickers Hardnees number (usually member B) is given a metallographic polish and washed with acetone to insure a smooth clean surface. A 3/16-inch 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 the harder member (usually member A) is cleaned by polishing with 600 grit emery cloth. The test sample of the flat member is mounted on a moving track and passed at a speed of 0.001 cm/sec in contact with the ball of the second member. A load of 1000 grams is imposed on the ball. The frictional drag created by the sample of the flat member moving in contact with the ball is measured by a tangential strain gauge. The value 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) alloy surface; 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 Alloy Surface The important criteria for selecting this 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 percent by volume of an intermetallic compound having molybdenum or tungsten a3 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 0 and l800; and, when present, the matrix containing the intermetallic compound should have a Vickers Hardness number less than that of the intermetallic compound.

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* Specifically, when subjected to 50,000 PV (load in p.s.i. x velocity of 180 ft/rain or greater) in the wear tester shown in Figure 1, the total wear of both lubricant producing allo^r (sample) and mating surface (reference ring) will be less than 4.0 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.

Figure 1 is a schematic representation of the wear tester utilised 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 specimen 12 of member A to be tested is rotated by a DC motor 10. The friction between the ring 11 of member B and the test specimen 12 of member A produces a torque in the shaft 13. The shaft lj5 is constrained from turning by the lever arm 14 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 thruat 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 teflt 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 II., the tester is run at 650 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 l8 to 20 hours. Due to -fluid evaporation, additional fuel must be added every I4. 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.

In the following examples, a series of alloys were tested in the device shown in Figure 1. The results illustrate the importance of the criteria set forth previously for the lubricant producing alloy surface.

EXAMPLES 1 - 10 The tes t spec imens were prepared from the elements set forth in Tables I -A and I -B by mixing, melting and casting them into buttons 1-1/2 inches in diameter and 3/8 inch thick. The buttons were machined to fit the wear tester shown in Figure 1. All except the composit ion of Example 7 were tested us ing "Elastuf i+JLj." steel* composed of 2.1 atom percent carbon, 1 atom percent chromium, 0.3 atom percent molybdenum, O.lj. atom percent silicon, 0, 9 atom percent sulfur and the balance, 93· 6 atom percent, iron as the ring; and liquid gasoline as the fluid. In Example 7» the ring was composed of an alloy of 95.7 atom percent iron and I ..3 atom percent carbon hardened to a Vickers Hardness number of 10.

The results obtained for the examples are shown in Table I -A and, for comparison, the results for 11 controls, Controls A - K, are shown in Table I-B. It should be noted that although the materials used in Controls C - J contain at least 6 atom percent molybdenum with at least one other element, some of which might form intermetallic compounds with molybdenum, these materials did not contain at least volume percent of any intermetallic compound. ttManu actured by Horace T. Potts Co. , Philadelphia, Pa.

(A TABLE I -A Chemical Composit ion Vickera ( atom percent ) Coeff . Hardness No. of of Inter - Dry metallic ♦Examples Mo Co Pe Ni si Friction Compound 1 ¾-$t 6 20 6J+ 10 _ 0.15 900-1200 0.13 2 9 81 - 10 0.25 1100 0.15 3 13 - 75 12 0. 09 1100 0.13 k& 16 23 - 56 0.23 1100 0.12 5b 19 - 65 it 0.10 950-1200 0.11 6 19 77 - k 0.11 1050 0.11 7 22 56 - 22 0.07 1100 0.10 8 2k - 63 13 0.11 1050 0.11 9 63 - - 37 0.22 8oo 0.10 65 15 - - 0.11 1150 0.10 ■K-All materials used in the exaraplea contain at least 10 volume perc metallic compound of molybdenum. -x-afleat treated I . hours at -4.80°C . a Also contained 5 atom percent silver b Also contained 12 atom percent chromium TABLE I-B A 3 97 - 0.19 0. 13 8 B 3 - 97 0. 31 -seiz C 6 - 9k O. I4.6 -seiz D* 6 11 5.1 k9 0. 17 3 E 9 - 91 0.3k ■seiz F 10 90 - 0.12 0.11+ 18 Gb 12 - 6 61 0.25 -seiz H 13 - 87 0. 35 ■seiz I 15 - 5 80 0. 11+ -seiz J 17 83 - 0.15 0.15 5 100 _ 0. 16 0.16 10 ■M-None of the materials used in the controls contained at least 10 vo an intermetallic compound of molybdenum, a Also contained 21.1 atom percent chromium, 3· 6 atom percent titaniu b Also contained 19 atom percent chromium and 2 atom percent tungst EXAMPLES 11 - H4.

In these Examples, tungsten was used in place of molybdenum. The test specimens were prepared and tested following the procedure set forth in Examples 1 - 10. The results obtained are compared to the results obtained with four controls in Table II.

-Ik- TABLE II Chemic al Composition Vickers (atom ; percent) Coeff . Hardness No. Coeff of of Interof Dry metallic Fric¬ ■it-Examples W Co Fe Ni Si Friction Compound tion 11 7 - 82 11 0.23 1000 0.13 12 15 - - 75 lo 0.09 600-900 0.11 13 21 - - 52 27 0.11 600-900 0.10 ih 21 59 20 0.08 800-1150 0.11 Controls La 50 - - - 0.11 250O-26OO O.50 -:H:-M 3 - - 97 0.37 -*-::-N 6 - - 0.23 •K--XO C 8 13 68. _ _ 0.11 «-Α11 materials used in the examples contain at least 10 volume percen metallic compound of tungsten.

**-These materials did not contain at least 10 volume percent of an int compound of tungsten, a Also contained $0 atom percent carbon, i.e., a3 tungsten carbide. b Also contained atom percent chromium, atom percent carbon and 1 c Also contained 5 atom percent chromium, /j. atom percent carbon and 2 Prom the foregoing examples and controls, it will be apparent that the presence of at least 10 volume percent of an internetalllc compound of molybdenum or tungsten in the contacting surface of member B is vital to the operabllity of the present invention. These intermetallic compounds, in most cases, occur as an intermediate or secondary phase within the 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 M0C and M23C type and 3) Mo S±2 type. The presence and amount of intermetallic compounds may be determined by either x-ray diffraction or metallographic analysis. For example, in Example 6 (Co/Mo/Si - 77/19/1+) there is present 20 volume percent Laves phase, an intermetallic compound. Example 9 is a pure intermetallic compound (MoSi2) with no matrix.

If the relatively soft matrix i3 present, it has been observed that this matrix portion wears preferentially leaving the hard intermetallic compound in relief. It is believed that the fluid and lubricant formed collect in the micro-cavities which are sufficiently close to provide superior lubrication at the areas of member B that undergo sliding or rolling action with opposing areas of member A.

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-W-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.

The critical necessity for having the requisite amount of intermetallic compound present may be dramatically shown by comparing Example 2 with Control E. In both alloys, 9 atom percent of molybdenum is present with iron as the major constituent. In the case of an acceptable alloy in Example 2, however, 10 atom percent of silicon is also present. The silicon, which along with vanadium, columbium and tantalum, is a known promoter or stabilizer of intermetallic compounds in metal alloys, forms a ternary intermetallic compound in excess of 10 volume percent. Similarly, the binary iron-molybdenum alloy in the atomic ratios shown in Controls B and C does not have the requisite amount of an intermetallic compound. Comparison of the data obtained shows that the binary alloy of the Controls produces a high dry friction coefficient and seizes against the mating surface in the wear tester, while the ternary compound in Example 2, although containing a like amount of molybdenum, is a satisfactory lubricant producing alloy. Similarly, whereas the molybdenum-cobalt binary alloy (Control J) did not contain at least 10 volume percent of an intermetallic compound, the ternary Mo-Co-Si alloys of Examples 6 and 7 formed intermetallic compounds (Laves phase) in excess of 10 volume percent.

One exception to the foregoing discussion is apparent in Control L of Table II. Tungsten carbide, which is classified as an intermetallic compound by the present definition, does not operate in the present invention. Although this material displays an extremely high wear resistance, it also is characterized by a Vickers Hardness number in excess of 00, This hardness results in excessive wear of the mating material (member A) rather than lubrication.

It should also be noted that Controls G and I, which are Hastelloy B and C, respectively, and Control D are similar in chemical composition to the operable compositions of this invention. However, since Hastelloy B and C are designed for corrosion resistance, and Control D is designed for high temperature operation, the molybdenum and tungsten are maintained in solution in the matrix phase rather than in compounds. As discussed by Streicher in Corrosion, Vol, 19, No, 8 August, 1963, pp. 7 - 81., the formation of molybdenum or tungsten compounds, e.g., Laves or sigma phases, tends to accelerate corrosion and, as discussed by Simms in Journal of Metals, October, 1966, pp. 1119-1130, the formation of these compounds is undesirable for high temperature application. Without the formation of intermetallic compounds, these materials do not function in the present Invention. 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 as Vickers Hardness numbers of 150. 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 lj.00.

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.

In the following examples, a series of mating surfaces were tested in the device shown in Figure 1. The results illustrate the importance of the criteria set forth previously for the mating surface.

EXAMPLES 15 - 20 The test specimens were prepared and tested following the procedure set forth in Examples 1 - 10. As the lubricant producing alloy, the alloy of Example 7 was used; namely, 56 atom percent cobalt, 22 atom percent molybdenum and 22 atom percent silicon. The results obtained are compared to the results obtained with four controls in Table III.

TABLE III Chemical Composition (atom percent) Vickers Coeff.

Hardness of PV Examples Pe c Cr Mo V Number Friction x 1 95.7 _ — _ 510 0.1 120 16 88 k 5 1 2 210 0.1 31 17 88 k 5 1 2 7^0 0.11 135 18 80 6.6 12 ο 1 200 0.1 110 19 80 6.6 12 1 71+0 0.1 165 86.5 13.5 - - - 200 0.1 5 Controls A 100 - - - - 80 0.15 31 Ba 5 - - 15 - 225 0.12 k Cb 63 1 19 2 - 155 DC 66.5 0.5 20 - 155 - -sei Also contained 80 atom percent nickel.

Also contained 11 atom percent nickel and 2 atom percent silicon Also contained 9 atom percent nickel, 2 atom percent silicon and manganese.

EXAMPLES 21 - 23 The test specimens were prepared and tested following the procedure set forth in Examples 1 - 10. As the lubricant producing alloy, the alloy of Example 6 was used; namely, 77 atom percent cobalt, 19 atom percent molybdenum and Ij. atom percent silicon. The results obtained are compared to the results obtained with two controls in Table IV.

TABLE IV Chemical Composition ( atom percent) Vickers Coeff .

Hardness of P Examples Pe c Cr w V Number Friction 21a 93.6 2.1 1.0 _ kko 0.11 22 90.6 1.8 2.9 0.6 320 0.12 23 81+ k 5 6 1.0 5 0 0.11 Controls Eb 68 k 5 8 2 310 0.1+0 Pc 78.5 3.2 17.7 - - 580 Also contained 0.3 atom percent molybdenum, 0o atom percent silic 0.9 atom percent manganese and 1.7 atom percent sulfur.

Also contained 13 atom percent cobalt.

Also contained 0.6 atom percent molybdenum.

Prom the foregoing examples and controls, the necessity for a minimum Vickers Hardness Number of 200 when at least 80 atom percent iron is present in the mating surface will be apparent. Controls B - P, when contrasted to Examples 18 and 19, bring out the importance of the minimum content of iron in the surface. The failure of relatively soft materials is illustrated in Control A. 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 3^5°C.

In Examples 1 - 23, gasoline was used as the environmental medium, gasoline being representative of petroleum hydrocarbons having a terminal boiling point no greater than 3 5°C. In the following examples, Examples 2k - 30, other fluids of lesser commercial interest were tested following the procedure set forth in the previous examples. The combination of alloys used in Examples 7 and 15 were used; namely, 56 atom percent cobalt, 22 atom percent molybdenum and 22 atom percent silicon as the lubricant producing alloy and 95. 7 atom percent iron and k, 3 atom percent carbon as the mating surface alloy. The results obtained are set forth in Table V.

TABLE V Coeff. Total of Wear Environmental FricPV (mils/ Examples Medium tion x 1000 100 hrs. ) 2k methyl alcohol 100* 0. 3 ethyl alcohol k00* 1.1 26 n-butyl alcohol 3OO- 0.5 27 n-octyl alcohol 500* 0 28 butyraldehyde 100* 1.0 29 10 wt.# ethyl 50 0.2 alcohol 90 wt.^trichloro ethylene 10 wt.^n-butyl 60 1 alcohol 90 wt.^trichloro ethylene Control trichloroethylene 0.3 27 ^greater than It should be noted in Examples 29 and 30 that as little as 10 weight percent of a fluid operable in this invention in combination with 90 weight percent of an inoperable fluid (Control) 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 in-vention could permit the use of mixtures or dispersions 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 neces-sary with more viscous fluids.

Although in the examples the fluids have been used in liquid form, the fluids have also been used in 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.

EXAMPLES 31 - 32 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 21 and the bearing to be tested -US* causes a ke Λ yo¾ 23 to rotate when a load 2Ι is applied. The rotation Ke of the yo¾£ applies a force to a torque transducer 5 through lever arm 26. Prom 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, in this case gasoline, is introduced into the bearing system through port 27.

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, The two types of bearings tested were roller bearings (inner and outer races) in Example 31 and journal bearings in Example 32: Example 31 Inner and outer races for roller bearings were made by centrifugally casting an alloy of 77 atom percent cobalt, 19 atom percent molybdenum and \. atom percent silicon to nominal dimensions. The final tolerances were obtained by grinding.

The roller bearing tes t was carried out by using the cast inner and outer races and commercially available rollers of hardened s teel (SAE 52100 )*. The nominal inside diameter of the outer race was 0.901 inch and the outsi de diameter of the inner race was 0, 7U2 inch. The rollers were O. 078 inch in diameter and 0.612 inch long. The results of tests on the roller bearing described above and tes ts on a control using a roller bearing having hardened steel (SAE 521OO ) inner and outer races are given in Table VI . As can be seen from the table, the steel-steel roller bearing system failed at 3600 rpm at a load of 600 lbs ; while the system of Example 31 was still operating efficiently at a load of 1000 lbs. Addit ionally it can be seen, that even at smaller loads, the coefficient of friction in the system of Example 31 is significantly less than that of the steel races .

Example 32 Journal bearings were fabricated by centrifugally casting an alloy of atom percent cobalt, 22 atom percent molybdenum and 22 atom percent silicon. The nominal size of the journal bearings was 0.752 inch and the shaft of hardened steel (SAR 52100 )* was 2 mil3 undersize to give the recommended clearance for this size bearing. The journals were rough machined using carbide tools to within 10 mils of final tolerances and then ground the rest of the way.

Tests using a shaft speed of 1200 rpm were conducted on the cast CoMoSi bearing us ing the bearing tester in the manner described hereinbefore. A journal bearing of the same dimensions was fabricated from bronze SAE 660** and tested as *SAE 5 IOO - 93.2 at. % Pe, I — - at. % C, 1.5 at. % Cr, 0.6 at. Si 0. 3 at. % Mn a control under the same conditions* The performances of the two bearings are described in Table VII, As shown in the table, the bronze bearing seized at the first increment of loading. The cast CoMoSi bearing was loaded to a PV of 100,000 with no seizure, TABLE VI Coefficient of Friction Control Example 31 Load at 3600 rSAE~52ioo) (CoMoSi) rpm in lbs. ( Races ) (Races ) 100 .005 .0014- 200 .010 .003 300 ,011 .003 I4.OO .017 .003 500 .011 .003 600 Failed .OOI4. 700 - .001. 800 - .005 900 - .005 1000 _ .005 TABLE VII Coefficient of Friction PV Control Example 32 (PSI X Ft/Mln. ) (Bronze SAE 660 (Cast CoMoS l ) , 000 Seized , 000 Seized 0.21 50, 000 Seized 0.16 75, 000 Seized 0.16 100, 000 Seized 0.16 EXAMPLE 33 Cast CM 553 * was compared on the wear tes ter of Figure 1 with bearing bronze (SAE 660 )·»* and gray cast iron ( all mated against Elastuff l| )#*# in water containing various concentrations of an emulaifiable petroleum base oil. Operating at 1, 000 r.p.m. and a PV of li 0, 000 the test series was started at a dilution of 200 parts by volume water to one part oil. The bronze se ized at this c oncentration. The gray cast iron began stick-slip at 800 to 1 dilution and seized at 1600 to 1, CM 5535 ran well through 1600 to 1 and seized at 3200 to 1, USES OF THIS INVENTION The assemblies of this invention f ind applicability in all types of engines: 2- and l^-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 #CM 5535 - 56. if at. % Co. 22.1 at. % Mo, 21.5 at. % Si 4HKSAE 660 - 90 at. Cu, at. Sn, at. % Zn, 2 at % Pb *-##Elastuff - 9 .6 at. S Fe 2. 1 at, C 1 at. Cr coated with the alloy of molybdenum or tungsten referred to herein as the member B alloy; 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. In an actual test of such an engine in which the connecting rod bearing had a CM 7028* outer race, a case- hardened shaft of AISI Ε-Ι ΐ5# as the inner race and AISI 1090 -5HH* steel needles hardened to a Rockwell Hardness of over 55, there was no measurable wear.

The assemblies are also useful in fuel pumps and fuel injectors. Thus, in the fuel injectors the member B alloy 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 alloy which makes 'teontactJ' 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 overc ome the side sealing problem. A coating of member B alloy of the present invention has been used on the "contacting" surf ace of the ring seals in the side seal assembly of such a rotary engine while "contacting" end walls composed of member A alloy. It is apparent that the member B alloy ¾CM 7028 - 77 at. Co, 19 at. % Mo, 1+ at. % Si *«AXSI i 6l - 9 at. Pe 1 at Ni 0 at of the assembly of the present Invention would be useful as the 'contacting" surface of all the end face seals while the inner surface of the end walls was composed of the 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 alloy 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. 32488/2 r

Claims (1)

1. CLAIMS 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, aid having a Vickers Hardness number of at least 150, b) an alloy of at least 80 atom percent iron, -ei-/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 of at least 400, the sum of any cobalt and nickel in 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) consisting of chromium, molybdenum, manganese or tungsten, which are present as carbide(s) or in a fully hardened solid solution; the opposing surface of member B consisting essentially 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 el e-ment, the Vickers Hardness number of the compound being 550 - 1800, and any matrix in the alloy containing the compound, when present, having a Vickers Hardness number less than that of the compound, th coefficient of dry friction of the surface of member B against the surface of member A being no greater than 0.25; and the environmental fluid consisting of petroleum hydrocarbons having a terminal boiling point no greater than 345° C, aliphatic aloohols 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· 3e A lubricant producing system according to Claims 1 or 2 wherein the opposing surface of member A is said alloy of at least 80 atom percent iron having a Vickers Hardness number of at least 200. ',, · ' ■■' 1/ 4. A lubricant producing system according to Claims 1 - 3 wherein the opposing surface of member B consists essentially of an alloy of at least 12 atom percent of molybdenum. » A lubricant producing system according to Claims 1 - 3 wherein the opposing surface of member B consists essentially of an alloy of at least 12 atom percent of tungsten, 6. A lubricant producing system according to Claims 1 - 5 wherein the intermetallic compound in the alloy of the opposing surface of member B is 20 - 85 percent by volume of the alloy. 7· A lubricant producing system according to Claim 1 wherein the opposing surface of member B consists essentially of an allo of 6 - 85 atom percent molybdenum, # - 6 atom percent silicon, the balance consisting of iron, cobalt or nickel. 8. A lubricant producing system according to Claim 1 wherein said opposing surface of member B consists essentially of an alloy of 19 - 2 atom percent molybdenum, 4-22 atom percent silicon and 53 - 77 atom percent cobalt. 9. A lubricant producing system according to Claim 1 wherein the environmental fluid is gasolinee 10. A lubricant producing system substantially as hereinbefore J0+00/ £. 11» A process for preparing a lubricant producing system according to Claims 1 - 10 which comprises placing the surfaces of at least two members, members A and B, in opposition, adding a fluid in a manner such that it flows onto the opposing surfaces of members A and B, and moving said opposing surfaces relative to each other whereby said fluid is polymerized to form a lubricating medium, 12. A lubricant producing system according to Claim lwherein oil is added to the environmental fluid. - 55 - 32488/1 13. An assembly for use in a lubricant producing system according to any one of Claims 1-10 and 12 comprising at least two members, members A and B, 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 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 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 alloys b) and c) being less than 5 atom percent, at least one-half of the weight of the remainder of alloys b) and c) consisting of chromium, molybdenum, manganese or tungsten, which are present as carbide (s) or in a fully hardened solid solution; the opposing surface of member B consisting essentially 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 the compound being 55- - l800, and any matrix in the alloy containing the compound, when present, having a Vickers Hardness number less than that of the compound, the coefficient of dry friction of the surface of member B against the. surface of member A being no greater than 0 .25 - 1 . An assembly according to Claim 13 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 . 15. An assembly according to Claims 13 or 14 wherei the o os n sur 32488/1 16 . An assembly according. to any one of Claims 13-15 wherein the opposing surface of member B consists essentially of an alloy of at least 12 atom percent of molybdenum. 17. An assembly according to any one of Claims 13-15 wherein the opposing surface of member B consists essentially of an alloy of at least 12 atom percent of tungsten. 18. An assembly according to any one of Claims 13-17 wherein the interm'etallic compound in the alloy of the opposing surface of member B is 20 - 85 percent b volume of the alloy. 19 - An assembly according to any one of Claims 13-15 wherein the opposing surface of member B consists essentially of. an alloy of 6 - 85 atom percent molybdenum, - 5β atom percent silicon, the balance consisting of iron, cobalt, or nickel. 20. An assembly according to any one of Claims 13-15 wherein said opposing surface of member B consists essentially of a alloy of 19 - 5 atom percent molybdenum, 4 - 22 atom percent silicon, and 53 - 77 atom percent cobalt. For the Applicants