WO2009109849A1

WO2009109849A1 - Antifriction, antiwear compound

Info

Publication number: WO2009109849A1
Application number: PCT/IB2009/000447
Authority: WO
Inventors: Franco Coccollone
Original assignee: Nanotek S.R.L.
Priority date: 2008-03-06
Filing date: 2009-03-06
Publication date: 2009-09-11
Also published as: EP2250243A1; ITTO20080172A1

Abstract

An antifriction and wear-resistant compound for mechanical groups, such as speed gears, differential groups and the like, comprising a solid phase and a liquid phase wherein said solid phase is in suspension and is characterised in that it comprises at least one from among the following elements: silicon, silica, silicon nitride, graphite, diamond, copper, nickel, zinc, aluminium and alumina, all present in nanopowder form.

Description

Antifriction, antiwear compound

DESCRIPTION

The subject of the present invention is an antifriction and wear- resistant compound for mechanical groups in general, such as gears, differentials and the like.

As is known, friction and wear are very important problems in mechanics in general. Tribology was developed for studying these phenomena, a multidisciplinary science which deals with the problems of friction and wear, as well as consequently aspects tied to the lubrification of the mechanical members. The reduction of the friction and wear of the components in internal combustion engines, gears, bearings and kinematic mechanisms in general are typical examples of tribology problems. Starting in the 1980s, dozens of additives for lubricants appeared on the market: viscosity correctors, sliding promoters, antioxidants, anticorrosive agents, antifoaming agents, detergents, dispersing agents, which were moreover already present in a certain percentage in every lubricating oil. For several years, another generation of additives based on molybdenum disulfide (MoS₂), graphite, polytetrafluoroethylene or Teflon (P.T.F.E.) and fullerene has been on the market, both as solid lubricants and wear regenerators. In reality, while their good performances as solid lubricants are not disputed, such products do not have (except temporarily) regenerating qualities for worn parts in internal combustion engines: indeed, fullerene (C 60) is a friction modifier, from sliding into rolling friction, and exhausts its limited action with the substitution of the lubricant. The other products become chemically unstable and are oxidised, respectively, at 440⁰C (MoS₂), at 310⁰C (graphite) and at 295⁰C (P.T.F.E.), temperatures well below the 900⁰C which are reached in the high friction zones in internal combustion heat engines. The big disadvantage of the already known applications also consists of the fact that said substances, while consisting of particles of several micron size, are still excessively large. This is very much against the trend of vehicle manufacturer requirements, since in modern lubrication systems filtration occurs by means of filters with 5-15 micron windows. For several years, research has therefore been aimed for developing permanent wear-resistant products that are resistant to high temperatures.

The most recent research known at the state of the art has led to the achievement of tribotechnical substances, also called nanopowders, which are entirely of mineral and metallic origin; such substances are dispersed in an oil-based compound compatible with any type of lubricating oil or grease, capable of being uniformly distributed over the entire oil volume and on the metal surfaces subjected to friction. Said substances protect and restore the worn metallic mechanisms and locks of any industrial component and motor vehicle and prevent the wear of new engines. In addition, they remove the heavy metals present inside the worn lubricating oil, preventing their subsequent release; they remove friction and thus prevent overheating and combustion of the lubricating oil itself, with consequent diminution of the polluting emissions deriving therefrom.

Recently, the undersigned company filed a patent application (TO2007A000132) having as subject a substance composed of very small particles, comparable to atomic size, effective against wear phenomena in very limited quantities and not contaminating the lubricant. Said substance comprises at least one reagent selected from among silica, graphite, diamond, aluminium, copper and nickel, and is obtained by means of a very strong grinding such to obtain particles with size not greater than 15 nm. The results obtained with such additive were very promising and encouraged the undersigned company to carry out further research projects on the matter.

Object of the present finding is an antifriction and wear-resistant compound which constitutes an improvement of the preceding invention and increases the fields of application, and whose characteristics are specified in claim 1. This is an additive with high lubricating power, with high heat conductivity, and is permanent even after the substitution of the lubricant. It is the product of nanotechnology and is composed of nanoparticles of mineral and metallic origin which fill the empty spaces and pores of the metals and treat the regions subjected to osmosis and wear with a permanent membrane, with low friction coefficient and high heat resistance. The compound remains chemically stable up to over 1100⁰C, abundantly exceeding the performances required in the internal combustion heat engines. In addition, it is characterised in that it can be carried in lubricants of any type (oils or greases) and, interposed between metal surfaces in relative motion, it forms a compound called nitriding, "table Ia", or iron silicate, copper silicate or nickel silicate, "table 2", with low friction coefficient and high heat conductivity nearly equal to that of silver.

According to another object, the present compound also carries out an exceptional action as solid lubricant, during cold ignition, a time when the danger of wear is greater; here, in the first revolutions, the lubricating liquid has not yet come into circulation, and the contact between the surfaces generate strong resistance and causes deep abrasions.

These and other advantages will be clearer during the following detailed description of the invention, which will make reference to several absolutely non-limiting embodiments. The subject of the present finding is a tribotechnical substance, i.e. a compound with friction reduction properties, as well as a regenerator of the worn parts, and is carried by any lubricant (oil or grease). It comprises at least one from among the following reagents: silicon - as a pure element, in the form of an oxide, or silica, and as silicon nitride -, copper, nickel, zinc, aluminium or alumina - all present in nanopowder form. It also comprises an oily liquid phase in which said nanopowders are in suspension. The reagents can be separately used, in pure form, or in a mixture thereof, as a function of the desired performances. For example, silicon, in oxidised form or nitride form, can be used in pure form. By using silicon nitride in high percentages, up to 100%, a compound is obtained with excellent qualities, applicable in new engines or in those in optimal wear condition. The nanotechnique applied in the present invention makes use of polymers of fossil and synthetic nature, minerals and metals ground into extremely small particles, on the order of several millionths of a millimetre - due to the size and polarisation the particles are oriented by the electric field, incorporate the heavy metals present in the oil (residue of the wear effect) and prevent their subsequent release; in the friction zones, the heat developed by the mechanical pressing process forms microfusions between the particles which, by filling the free space give rise to the new compound. A film is thus created over all the surfaces subjected to friction: in the case of gears, the sliding is improved between the toothing and also in the rolling axis, in the case of bearings, the noise and the vibrations are reduced, as these are passive effects of the friction. Moreover, in the case of internal combustion engines, in addition to the sliding of the rings in the cylinders, the seal is increased during the compression and combustion phases, the pressure losses are limited, the discharge of harmful gases and particulate is reduced, the actual compression is brought to nominal values and the heat dispersion is reduced, since a new adiabatic barrier is formed. Several preferred embodiments of the present finding are presented below, all of them of course exemplifying. According to a first embodiment suitable for new engines or those in optimal wear condition, the composition of the solid phase is reported in table Ia.

Table Ia

In the composition, the silicon nanoparticles, if present, by means of mechanical pressure, temperature and plasticity of the metals, penetrate by expelling carbon in the friction points up to a depth of 100 - 300 nm; this depends on the mechanical pressure and hardness and porosity of the metals. This element, in addition to being used in pure form, can also be used as a carrier of other elements, for example the nitrogen in the Si₃N₄ Indeed, using silicon nitride (S1₃N₄), the carrier deeply bears the nitrogen, creating a film, i.e. an adiabatic barrier of silicon nitride of extreme hardness, with low friction coefficient and high heat shock resistance. It also can be applied in ballistics, modifying the atomic surface of the metals of the barrels and increasing the speed of the exiting projectile due to the reduction of the friction, the lower heat dispersion and the greater seal of the pressure. An alternative embodiment of the compound, equally suitable for new engines, in which it is possible to forgo the effect of lapping by reducing the size of the particles is represented by the following:

Table Ib

A further embodiment of the finding, suitable in the case of considerably worn mechanisms, if a protective film is required with high thickness comprised between 0.2 and 3 micron, is represented by the following:

Table 2

The silicon nitride (Si₃N₄) penetrates via mechanical pressure; the liquid copper subject to friction penetrates via osmosis of the metals, while the nickel, having very high hardness, is bonded to the copper at very high temperatures. Finally, the zinc at high temperatures creates very strong bonds between iron-carbon and the compound, generating a silicon nitride - copper - nickel film. According to a particular embodiment suitable for medium wear engines, the composition of the solid phase is reported in table 3:

Table 3

Finally, in case of recovery from wear of main bearings, rod bearings, camshaft bearings and the like, a separate treatment is preferable with only aluminium particles in pure form. Aluminium is inserted in the compound in order to restore the antifriction film of the bearings, in particular those of the crankshaft, both main and rod bearings. The temperature of the motor oil (180⁰C) and the mechanical pressure act as catalyst, creating the aggregation condition of the material.

The liquid phase is composed, for all of the above-presented - compositions, of mineral oil in a volumetric percentage of 80%, synthetic oil ( 15%) and triol (5%).

The differences with the preceding compound are various and have a very important impact. If on one hand all the performances attained by the old product and referred to in the previous patent application are also attained by the new compound, the latter achieves further, fundamental advantages (increased hardness and heat shock resistance) Several results are reported below of the tests carried out by the Centro Nazionale Ricerche sulle Nanostrutture dell'Universita di Modena-Reggio Emilia (National Nanostructure Research Centre at the University of Modena-Reggio Emilia) on a four- stroke diesel engine of a Fiat Punto, with 300,000 kilometres, highly worn and close to seizure. Reference will be made to the figures of the tables 1/3 - 3/3 and in particular: • Fig. 1 is an optical microscope comparison at various magnifications of a plate treated with the compound of the present invention (Fig. Ia), a plate which operated with a normal lubricant (Fig. Ib) and a plate that was not operated (Fig. Ic). Inside the red squares, the scraped zones are highlighted following cam-plate contact; • Fig. 2, still taken from an electron microscope analysis, shows two strips extracted from a single cylinder which operated with lubricant added with the present compound; the cylinder is close to seizure and is strongly ovaled; the two elements were extracted from two zones at 90° angular distance from each other, in particular: Fig. 2a is an extraction from a zone at which the segment-cylinder contact is maximum, Fig. 2b is an extract from a zone at which the contact is only piston-cylinder and the segments are involved only to a limited extent; • Fig. 3, with increasing magnification, reports the images processed from scanning electron microscope (SEM) analysis of the plate of Fig. 1 treated with the compound of the present invention;

• Fig. 4 reports the same images of Fig. 3, which are however referred to the plate of Fig. 1 treated with a normal lubricant.

With reference to Fig. 1 , the optical microscope analyses of the tappet plates first of all show a clear difference (even visible to the naked eye) between the plates which operated with the present compound (Fig. Ia) and the plates which operated with the normal lubricant (Fig. Ib). The difference is not so much linked to the fairly substantial presence of scrapes on the surface from the cam-plate contact, which are present on all the plates, as it is to the morphology of the metallic submatrix. In the plates which did not see the use of the lubricant added with the present compound, the surface clearly appears rougher and thus more similar to the original component (never used inside the engine). In particular, it is observed in Fig. 1 how both the plates which operated in the engine were scraped at the macroscopic level (5X magnification), while by increasing the magnification one observes how beyond the macroscopic scrapes there is a clear surface roughness difference. With reference to fig. 2, the analysis at^' the optical microscope carried out on the samples drawn from the cylinder strips shows results analogous to those observed on the plates. In particular, Fig. 2a presents various affected zones, linked to the segment-cylinder contact. There is a first zone, between points 1 and 6, in which the contact occurs between the segments and the surface of the cylinder, while beyond point 6 there is no type of contact (at point 6, there is the end stop of the last segment and between 6 and 7 there is the scraper ring contact). It should be observed how between 1 and 3, the surface is mainly cleaned, with various grinding scratches from the lubricant recirculation and some marks from the segment locking on the cylinder surface; beyond point 3, the surface is dirtier but the submatrix is entirely analogous. Beyond point 7, on the other hand, it is interesting to note how the situation completely changes - indeed, in this zone there are many grinding marks, with macroscopic scrapes and also a submatrix with more microscopic scratches. This submatrix completely disappears in the zones which operated with the present compound (between points 1 and 6). Regarding Fig. 2b, it is noted how there are no actual transition zones, basically linked with the contact between the segments (which travel a limited path) and the inner wall of the cylinder. In this case, the segments are not practically in function and the contact occurs almost exclusively between the piston and the cylinder. For this reason, the system operates nearly in the same manner over the entire length of the cylinder, not creating very different morphological zones along its travel. The only zone with some particular features is the lower one, zone 8-9, in which there are no segments and probably the contact between the cylinder piston is very strong, creating deep scrapes in axial direction. In all of the zones analysed in this sample, one notes a decrease of the roughness of the sample with the disappearance of the grinding marks submatrix; the most pronounced marks obviously remain, but locally the roughness appears much improved. The purely morphological analysis of the tappet points at the SEM electron microscope confirms that which was observed at the optical microscope level. As can be seen in the different magnifications of figures 3-4, there is indeed a clear difference in roughness between the plate treated with the present compound and the plate not-treated with the additive. In Fig. 3, one observes how the surface is clearly smoother, apart from several grinding scratches, above all in the grain of the material, while in Fig. 4 it is possible to note how the surface has a poor surface finishing with many imperfections in the grain of the material (the surface has a very accentuated porosity).

The preferred applications of the finding are internal combustion engines, gears, differentials, reducers, bearings and all the members subjected to friction, lubricated with oil or grease. The fields of use, therefore, extend to the entire transportation sector (automobile, naval, railway, aircraft), fixed industrial plants and ballistics. The preferred metering, per square meter of surface subjected to friction, is equal to 0.7 grams (+/- 30%) of powder in suspension in the oily liquid phase. The ready-for-use compound is contained in syringes, diluted in percentage by about 0.14 g per ml in the aforesaid liquid. Advantageously, the contents of a syringe will be equal to 5 ml, this amount being suitable, for example, for the treatment of an engine, gear or differential lubricated with 5 1 of oil.

Claims

C L A I M S

1) Antifriction and wear-resistant compound for mechanical groups, such as speed gears, differential groups and the like, comprising a solid phase and a liquid phase wherein said solid phase is in suspension and is characterised in that it comprises at least one from among the following elements: silicon, silica, silicon nitride, graphite, diamond, copper, nickel, zinc, aluminium and alumina, all present in nanopowder form.

2) Compound according to claim 1, characterised in that said elements in nanopowder form can be used separately, in pure form, or in a mixture thereof.

3) Compound according to claim 2, wherein its composition is reported in the following table:

4) Compound according to claim 2, wherein its composition is reported in the following table:

5) Compound according to claim 2, wherein its composition is reported in the following table:

6) Compound according to claim 2, wherein its composition is reported in the following table:

7) Compound according to claim 2, wherein its composition consists of only aluminium nanopowder in pure form.

8) Compound according to claim 2, wherein its composition consists of a silica-silicon mixture.

9) Compound according to claim 2, where its composition consists of silicon nitride (Si₃N₄).

10) Compound according to one of the preceding claims, characterised in that the liquid phase consists of mineral oil in a volumetric percentage of 80%, synthetic oil (15%) and triol (5%).

11) Compound according to one of the preceding claims, characterised in that it can be carried in any one lubricant, such as oil, grease or the like.

12) Compound according to one of the preceding claims, characterised by a metering on the order of 0.7 g ( +/- 30%) of powders in suspension in the oily liquid phase per square meter of surface subjected to friction.

13) Compound according to one of the preceding claims, characterised in that it is used by means of syringes with a dilution in lubricating oil equal to 0.14 g per ml.

14) Compound according to claim 12, wherein the syringe content is equal to 5 ml, suitable for the treatment of an engine, gear or differential lubricated with 5 1 of oil.

15) Use of an additive as described in claims 1 - 13 for all the mechanical applications with bodies in relative motion, i.e. internal combustion engines, gears, differentials, reducers, bearings and all the members subjected to friction, lubricated with oil or grease.

16) Use of an additive as described in claims 1-13 for the entire transportation field, for fixed industrial plants and ballistics.