Aspects about chemisorptions and molecular antifriction treatment at friction couple of piston-segments-cylinder.

Ungur, Petru ; Pop, Adrian Petru ; Veres, Eugen Mircea 等

Abstract: The paper has presented aspects about structural changes of cutting surfaces of workpieces by environmental due to forming of oil film with gas by absorption, chemisorptions and chemical reactions. The anti-friction molecular treatment with self-lubricates solid additives of friction couple of piston-segments-cylinder by get in composition of motor oils created a special film with improving antifriction properties which due to enhance age of engine with spark ignition.

Key words: couple, chemisorptions, film, molecular treatment.

1. INTRODUCTION

The operating characteristics and work age of engine with spark ignition is dependent by quality execution of cylinder shirt (inner wall of cylinder) from block engine. The main technical machining required of inner cylinder surface of cylinder shirts by pearlite lamellar or nodular cast iron [Schrader,2000] are: higher tolerances for fit diameter, roundness of (0.015-0.03)mm per all length of shirt, circular runout less 0.03mm, higher quality of mirror surface obtained by honing, material hardness of (300-350)HB.

The condition of inner cylinder shirt, micro-geometry and hardness is influenced during working by temperature, impurities of oil lubricate, friction, oil lubricate, combustion composite, undergoing essential alters with consequence in depth material.

The surfaces of inner cylinder shirts are location of real transformations which are dependent by nature of base material, lubricate medium, fuel, frictions, temperature, physics-chemical processes, adhesion, absorption which due to forming of nano-metric organ-metallic film with tribology properties at interference segments-cylinder [Kragelsky,1978].

2. STRUCTURAL CHANGES OF CUTTING WORKPIECE SURFACES

After [Kragelsky,1978;Schrader,2000] the state of surfaces realized by mechanical machining are distribution in four characteristics areas. The textures of machining surfaces (Fig.1) had formed by areas: 1-absorber layer, 2-amorphous layer, 3layer with distortion crystalline structure, 4-layer with complete crystalline structure.

In first layer has a depth of (0.2-8)nm is action Van der Walls force field, which is dependent of material and extern medium. The second layer is an amorphous structure and has destroyed crystalline structure on a depth of (0.1-5)[micro]m.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

The third layer has a deformed crystalline structure on a stain hardness depth of (10-15)[micro]m with o greater hardness as base material. The fourth layer with a depth of (20-50)[micro]m has a non-attack crystalline structure.

The lubrication-EH is going in special on surface of second layer. The first and second layer both roughness and waveness is influenced the lubrication process. The finishing surfaces are made in presence of one cooling lubricate liquid. In case of finishing cylinder shirts by honing is used gas.

On metallic surface of cutting workpiece is adhesion an oil film with gases encouraged by structural non-homogenous by absorption, chemisorptions and chemical reaction [Marcu, 1979].

Absorption: gas molecules from atmosphere are absorption on clean surfaces each degassing and are formed monomolecular layer of oxidants agents as Oxygen and Nitrogen. The layer thickness is (0.2-0.3)nm, and molecules of absorb gas is holding by Van der Walls forces with bound energy of 0.05eV (Fig.2).

Chemisorptions: molecules of oxygen had dissociated in atoms and then in ions by caption of free electrons which appeared at metal surface. The oxygen is suffered a chemisorptions with a bound energy of (1-8)eV. The layer thickness is (1-2)nm and is forming in some minutes (Fig.3). Chemical reaction: metallic ions, which had lost one electron is get in chemical reaction with gas ions, which are captured one electron. In film has migration, both gas ions and metallic ions. The chemical reaction is done slow, the surface of workpiece, in our case cylinder shirt from cast iron, is getting a film of [Fe.sub.2][O.sub.3] with thickness of 10nm (Fig.4).

The chemical process of oxidation has realized in two phases, in first phase is formed FeO, which at smaller temperature is passing in [Fe.sub.2][O.sub.3]:

FeO + 1/[20.sub.2] [right arrow] [Fe.sub.2][O.sub.3] (1)

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

The atoms of oxygen absorbed at metallic surface is arise at electrical dipoles behind of partial ionization process of oxygen atoms with metallic electrons [Marcu, 1979] (fig.5).

3. PHYSIC-CHEMICAL TRANSFER PROCESSES

The most important tribo-technical system of spark ignition engine is composed from: piston-segments-shirt of cylinder, engine block. All the elements of this system are engaged in a permanent mechanical, thermal and chemical interaction [Balasiu,1990]. Mechanical stress and thermal action, physic-chemical effects can destroy or rebuild microstructure of surface layers on surface of cylinder shirt of engine. Inside of shirt cylinders is raise a disintegration process of ones molecules oil and fuel following by dissolution of heterogeneous film of organ-metallic adhesions on metallic surface. By reducer process of iron's oxides ([Fe.sub.2][O.sub.3]) on inner surface of cylinders at small temperatures and carbureted of FeO, following by removing from friction is formed very fine metallic powders [Marcu,1979]. These reactions are:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)

In addition, by dissociation of aromatics hydrocarbons fractions are formed radicals with change of atoms:

C[H.sub.4] [right arrow] C[H.sub.3] + H RH + C[H.sub.3] [right arrow] R + C[H.sub.4] RH + H [right arrow] R + [H.sub.2] (3)

By active resulted hydrogen actions from decomposition under pressure and explosion of fuel in mixture with air about iron oxides resulting:

FeO + [H.sub.2] [right arrow] Fe + [H.sub.2]O [Fe.sub.2][O.sub.3] + 3[H.sub.2] [right arrow] 2Fe + 3[H.sub.2]O (4)

removing by friction in segments-cylinder couple, characteristic by higher speeds-(8-12)m/s, temperatures of (200-250)oC at superior part of cylinder shirt, random grease with alter of friction mode along stroke, mixed-limited friction on superior part of shirt, stopped lubricate at start of cold (fig.6).

For improving antifriction molecular treatment of inner surface of cylinder at spark ignition engine, the lubricated oils are additive with addition of solid lubricates under micropowder form as: polyethylene terephthalate (PETE), colloidal graphite, bisulfate of molybdenum (Mo[S.sub.2]), which compacted heterogeneous antifriction film, reducing coefficient of sliding friction in piston-cylinder couple (fig.7) [Ungur,2007].

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

The colloidal graphite has presented under particle form less of 5im granulation, which has mixed in composition of engine oils in small quantity, being in suspension as its little density and remaining in stability until a temperature of 4000C.

The bisulfate of molybdenum (Mo[S.sub.2]), under microgranules has natural antifriction properties, being stable in air until at 3800C. The chemical composition of Mo[S.sub.2] [Catalog Mo[S.sub.2]] is: Mo-min 58.8%, S-min 38.5%, Si[O.sub.2]-max 0.1%, Femax 0.2%, Cu-max 0.1%, Pb-max 0.1% and Zn-max 0.1%.

For enhance adhesion of micro-particle of graphite or Mo[S.sub.2] by metallic surface of cylinder shirt is required a chemical treatment with tension-active solutions on base of amines and sulfur, which is other objective research of authors.

4. CONCLUSIONS

For improving the properties of: adhesion, greasy, stretching and covering of asperity surface going in relative moving from each other, is required chemical treatment of solid lubricates with micro-powder of polar tension-active substance.

Antifriction molecular treatment of system piston-segments-cylinder, by addition of engine oil solid additives lubricates, bisulfate of molybdenum (Mo[S.sub.2]), colloidal graphite, polyethylene terephthalate (PETE) has positive technoeconomic effects. These effects are: reducing of power lost of spark ignition engines, decreasing friction at warm and cold of surfaces in relative motion, reducing of fuel consumption with 2-3% and of oil consumption, enhance compression capacity of engines, warn reducer of segments and cylinder shirts, improving age spark ignition engines.

Antifriction molecular treatments of system pistonsegmentscylinder have positive effects for environment by: reducer emission of HC combustion in environment at a normal operating of spark ignition engines, reducing the environment pollution by reducer of fuel and lubricates consumption.

5. REFERENCES

Balasiu, D. (1990). Techniques of Investigation for Deterioration Processes, Technical Editor, Bucharest

Kragelsky, I.V. & al. (1978). Friction Wear Lubrification, Vol. I-II, Tribology Handbook, Mir Publishers, Moscow Marcu, G. (1979), Chemical of Metals, Didactical & Pedagogical Editor, Bucharest.

Schrader, G.F., Elshennawy, A.K. (2000). Manufacturing Processes & Materials, SME Editor, ISBN-087263-517-1, Dearborn, Michigan, USA

Ungur, P.; Pop, P.A.; Gordan, M., Caraban,A. (2007), Industrial Wastes Using For Green Cleaning Of Lubricant Oils of Exhausted Motor, Proceeding of Inter. Scientific Conference microCAD 2007, pp.155-160, ISBN 978-963661-742-4 O, ISBN 978-963-661-744-8, Innov. & Tech. Transfer Center and University of Miskolc Publisher.

***. Catalog of Produces on Base of Bisulfate of Molybdenum, Romanian Minister of Industry and Commerce, CNCAF MINVEST Deva, Branch of Stei, Romania.