JP6265355B2 - Lubricating oil and lubrication system - Google Patents

Description

  The present invention relates to a lubricating oil, and more particularly to a lubricating oil applied to a metal material having a nanocrystal grain layer on a surface, and a lubricating system using the same.

There is known a method for obtaining a material in which a nanocrystalline structure having a crystal grain size of less than 1 μm is formed by strong processing of a metal material. A metal material having a nanocrystalline structure has very high strength and excellent toughness. Therefore, it is possible to improve the fatigue strength by subjecting the surface of the metal material to strong processing and hardening the surface layer of the metal part or applying compressive residual stress.
Until now, various strong processing methods for obtaining a nanocrystalline structure have been devised, and a method of applying a torsional stress under high pressure, a method of shot peening, a method of sliding friction, and the like are known. For example, as one form of the sliding friction method, a surface layer nanocrystallizing friction processing method is known in which a carbide tip is pressed against the surface of a sample that rotates at high speed to form a nanocrystalline structure on the surface. According to this processing method, it is possible to easily increase the hardness of the metal surface, and the metal material after the processing is excellent in strength, fatigue characteristics, and wear resistance (see Patent Documents 1 and 2). In addition, a metal material having a higher surface hardness by performing a heat treatment on the metal material having a nanocrystal grain layer on such a surface is also known (see Patent Document 3).

JP 2003-39398 A Republished Patent No. 2005-070614 JP 2011-105991 A

  On the other hand, it is difficult for the metal materials described in Patent Documents 1 to 3 to stably obtain good friction characteristics (friction coefficient).

  An object of the present invention is to provide a lubricating oil capable of stably giving good friction characteristics to a metal material having a nanocrystalline layer on the surface, and a lubricating system using the same.

The present inventors diligently examined the initial friction characteristics and the friction characteristics after aging of various lubricants with respect to a metal material having a nanocrystalline layer on the surface. As a result, the present inventors have completed the present invention by finding a lubricating oil having a low friction coefficient from the beginning and having a friction coefficient that does not change significantly even after aging.
That is, the present invention provides the following lubricating oil and lubricating system.
(1) A lubricating oil applied to a metal material having a nanocrystal grain layer on its surface, wherein the lubricating oil is blended with a polar organic compound.
(2) The lubricating oil according to (1) above, wherein the organic compound having the polarity has a polar group containing at least one of a hetero atom and an unsaturated bond.
(3) In the lubricating oil according to (2) above, the polar group is a carbonyl group, a thiocarbonyl group, a sulfonyl group, a sulfinyl group, a phosphoryl group, a thiophosphoryl group, an amino group,
A lubricating oil which is at least one of a hydroxyl group and an alkenyl group.
(4) The lubricating oil according to any one of (1) to (3) above, wherein the organic compound having the polarity is at least one of an ester, an amide, and an α-olefin. And lubricating oil.
(5) A lubricating oil according to any one of the above (1) to (4), wherein at least one of a mineral oil and a synthetic oil is blended as a base oil.
(6) The lubricating oil according to any one of (1) to (5) above, wherein the nanocrystal grain layer has a thickness of 10 nm or more.
(7) The lubricating oil according to any one of (1) to (6) above, wherein the metal material has a hardened structure in an inner layer from the nanocrystal grain layer. .
(8) The lubricating oil according to any one of (1) to (7), wherein the metal material is a material that undergoes a heat-induced phase transformation.
(9) The lubricating oil according to (8) above, wherein the metal material is high carbon chromium steel.
(10) A lubricating system using the lubricating oil according to any one of (1) to (9) above.

  ADVANTAGE OF THE INVENTION According to this invention, the lubricating oil which can provide a favorable favorable friction characteristic stably with respect to the metal material which has a nanocrystal grain layer on the surface, and a lubrication system using the same can be provided.

The figure which shows an example of the method of manufacturing the metal material which has a nanocrystal grain layer on the surface in this invention.

  The present invention is a lubricating oil (hereinafter also referred to as “the present lubricating oil”) applied to a metal material (hereinafter also referred to as “the present metallic material”) having a nanocrystal grain layer on the surface, and having a polarity. It is characterized by blending an organic compound. Hereinafter, the present lubricating oil will be described in detail.

[Metal material having nanocrystal grain layer]
A nanocrystal refers to a crystal having a crystal grain size (length) of 100 nm or less, and a nanocrystal grain layer refers to a structure in which the above-described nanocrystal is contained in at least 50% of the crystal structure. Say. However, the size (length) of the crystal grains of the nanocrystal does not need to be 100 nm or less in any direction, and is intended to be 100 nm or less in at least one direction. That is, the nanocrystal is not necessarily a crystal having a circular cross section, and may be a crystal having a flat cross section.
The nanocrystal grain layer may be a mixed grain structure as long as it contains at least 50% of the above-described nanocrystals, and the remainder other than the nanocrystals is composed of any form of crystals. May be. The size of the nanocrystal grains can be measured by observing with a scanning electron microscope (SEM).

Such a metal material can be produced by the methods disclosed in Japanese Patent Application Laid-Open No. 2003-39398 and Republished Patent Document 2005-070614. For example, using an apparatus as shown in FIG. 1, friction processing may be performed by pressing a hard tool (such as a carbide tip) against the surface of a test material (metal material) that rotates at high speed.
The metal material used as a base is preferably a material that undergoes a heat-induced phase transformation, and more preferably a high carbon chromium steel. A specific method for producing the metal material will be described later.
Note that the present metal material may be further quenched (see JP 2011-105991 A).

[Organic compound having polarity]
Preferred examples of the organic compound having polarity used in the present lubricating oil include those having a polar group containing a hetero atom such as oxygen, sulfur, phosphorus and nitrogen and an unsaturated bond such as a double bond.
This metal material can be obtained by nanocrystallizing the surface layer of a metal material that undergoes a heat-induced phase transformation such as high-carbon chromium steel, but the surface has lattice defects such as dislocations and vacancies, and electron There seems to be a bias. It is presumed that a lubricating oil with low friction and little change in friction coefficient can be obtained by blending the organic compound having the above polarity corresponding to this electron bias.
The blending amount of the organic compound having the above polarity is preferably 0.05% by mass or more, more preferably 0.1% by mass or more based on the total amount of the lubricating oil from the viewpoint of lubricity.

Specific examples of the polar group are preferably a carbonyl group, a thiocarbonyl group, a sulfonyl group, a sulfinyl group, a phosphoryl group, a thiophosphoryl group, an amino group, a hydroxyl group, and an alkenyl group.
By providing such a polar group, the entire compound has polarity. Specific examples of the organic compound having polarity include esters, fatty acids, phosphate esters (phosphate triester, acid phosphate ester (phosphate monoester, phosphate diester), phosphite ester, and acid suboxide. Phosphates, etc.), sulfonates, amines, amides, imides, alcohols, olefins and the like are preferably used.
Further, sulfides (sulfides, disulfides, etc.) and heterocyclic compounds are also suitable. Examples of the heterocyclic compound having sulfur include thiophenes, and examples of the heterocyclic compound having nitrogen include pyridines, quinolines, indoles, and carbazoles.

Esters may be any of monoesters, diesters, aromatics and aliphatics.
Preferred examples of the fatty acid constituting the ester include monocarboxylic acids and dicarboxylic acids having 6 to 60 carbon atoms. Specifically, caproic acid, caprylic acid, nonanoic acid, lauric acid, stearic acid, oleic acid, ricinoleic acid, hydroxy fatty acids (for example, ricinoleic acid, 12-hydroxystearic acid, etc.), arachidic acid, behenic acid, melicic acid , Isononanoic acid, neodecanoic acid, isostearic acid, naphthenic acid, adipic acid, sebacic acid, dodecanedioic acid, mono- or dihydroxyarachidic acid, oleic acid, ricinoleic acid, ricinoleic acid, and hydroxystearic acid.

  The alcohol constituting the ester may be linear or branched, and may be either saturated or unsaturated. Specific examples of saturated alcohols include ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonyl alcohol, decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl. Alcohol, heptadecyl alcohol, and octadecyl alcohol are mentioned. Specific examples of the unsaturated alcohol include ethenyl alcohol, propenyl alcohol, butenyl alcohol, pentynyl alcohol, hexenyl alcohol, peptenyl alcohol, nonenyl alcohol, decenyl alcohol, undecenyl alcohol, and dodecenyl alcohol. , Tridecenyl alcohol, tetradecenyl alcohol, pentadecenyl alcohol, hexadecenyl alcohol, heptadecenyl alcohol, and octadecenyl alcohol.

The above-described ester is not necessarily produced from the above-described carboxylic acid and alcohol, and may be produced by other methods such as a transesterification method.
Specific examples of the ester include butyl stearate, octyl stearate, butyl oleate, hexyl oleate, 2-ethylhexyl oleate, and isodecyl adipate.
In the above, only monoesters and diesters are illustrated, but esters having other structures may be used.
As the fatty acids, those listed as fatty acids constituting the above-mentioned esters are preferably used.

  Among phosphate esters, phosphate triesters include triaryl phosphate, trialkyl phosphate, trialkylaryl phosphate, triarylalkyl phosphate fluoride, trialkenyl phosphate, and the like. Specifically, triphenyl phosphate, trialkyl phosphate, Cresyl phosphate, benzyl diphenyl phosphate, ethyl diphenyl phosphate, tributyl phosphate, ethyl dibutyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, ethyl phenyl diphenyl phosphate, di (ethylphenyl) phenyl phosphate, propylphenyl diphenyl phosphate, di (propyl Phenyl) phenyl phosphate, triethylphenyl phosphate, tripro Ruphenyl phosphate, butylphenyl diphenyl phosphate, di (butylphenyl) phenyl phosphate, tributylphenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, Tristearyl phosphate, trioleyl phosphate and the like can be mentioned.

Acid phosphates include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate, and Examples thereof include isostearyl acid phosphate.
Phosphites include triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tri (nonylphenyl) phosphite, tri (2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl Examples thereof include phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, and trioleyl phosphite.
Examples of the acidic phosphite include dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, and diphenyl hydrogen phosphite.
Among phosphate esters, tricresyl phosphate and triphenyl phosphate are preferable from the viewpoint of lubricity.

  As the sulfonates, alkaline earth metal sulfonates are preferably used. The alkaline earth metal sulfonate is preferably overbased. Specifically, the total base number (TBN) is preferably 100 mgKOH / g or more, and more preferably 300 mgKOH / g or more. As the alkaline earth metal, Ca and Mg are suitable.

  Examples of the amines include butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, laurylamine, stearylamine, oleylamine, benzylamine and the like as examples of monosubstituted amines. Dibutylamine, dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, dibenzylamine, stearyl monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine, benzyl Examples include monoethanolamine, phenyl monoethanolamine, tolyl monopropanolamine, and examples of trisubstituted amines include tributylamine. Tripentylamine, trihexylamine, tricyclohexylamine, trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl monoethanolamine, dilauryl monopropanolamine, dioctyl monoethanolamine, dihexyl Monopropanolamine, dibutyl monopropanolamine, oleyl diethanolamine, stearyl dipropanolamine, lauryl diethanolamine, octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine, phenyl diethanolamine, tolyl dipropanolamine, xylyl Diethanolamine, triethanolamine, tripropanolamine, etc. It can be mentioned.

Examples of amides include those obtained from the above fatty acids and the above amines.
As the imides, mono-type and bis-type alkyl succinimides and alkenyl succinimides are preferably used. Examples of the alkenyl group include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer, and the alkyl group is a hydrogenated form thereof. Suitable alkenyl groups include polybutenyl or polyisobutenyl groups.
As alcohols, those constituting the above-mentioned esters are preferably used.

Examples of olefins include α-olefins. The α-olefin is preferably those having 6 to 18 carbon atoms, more preferably those having 8 to 16 carbon atoms, still more preferably those having 10 to 16 carbon atoms, and most preferably those having 12 to 16 carbon atoms. preferable. As such an α-olefin, a linear one is preferable from the viewpoint of lubricity.
When an α-olefin having 5 or less carbon atoms is used, the components are likely to volatilize. On the other hand, an α-olefin having 19 or more carbon atoms may become a solid when used as a lubricating oil. It is difficult to use.
Specific examples of the α-olefin include 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and mixtures thereof. As these α-olefins, those obtained by various production methods can be used. For example, ethylene oligomers obtained by polymerizing ethylene by usual means can be used.

  In the present invention, a predetermined base oil may be blended as necessary. As the base oil, commonly used mineral oils and synthetic oils are used alone or as a mixture of two or more selected from each. Examples thereof include one or more mineral oils, one or more synthetic oils, a mixed oil of one or more mineral oils and one or more synthetic oils, and the like. As mineral oil, for example, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil can be subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, and hydrogenation. Examples include base oils produced by isomerizing waxes produced by performing one or more treatments such as refining, mineral oil waxes, Fischer-Tropsch processes, etc. . Among the mineral oils, those of API classification group 2 or more are preferred. By using a group 2 or higher mineral oil, the oxidation stability of the lubricating oil can be kept good and good lubricating characteristics can be obtained.

  On the other hand, examples of the synthetic oil include α-olefin polymers (PAO), hydrogenated products thereof, polyol esters, aromatic synthetic oils such as alkylbenzene and alkylnaphthalene, and polyalkylene glycols. Among these synthetic oils, those having polarity also have an effect as the polar compound.

As the PAO, a low molecular weight polymer (oligomer) of α-olefin is preferably used. The number of carbon atoms of the α-olefin as the monomer is preferably 6 to 20 from the viewpoint of viscosity index and evaporability, more preferably 8 to 16, and even more preferably 10 to 14. Specific examples include 1-octene and 1-decene.
Further, as the PAO, an α-olefin trimer is preferable from the viewpoint of low evaporation, but the carbon number of the α-olefin, its blending ratio, and the degree of polymerization may be appropriately adjusted in accordance with the intended properties. As the α-olefin polymerization catalyst, a BF ₃ catalyst, an AlCl ₃ catalyst, a Ziegler type catalyst, a metallocene catalyst, or the like can be used.

The preferable 40 ° C. kinematic viscosity of the lubricating oil is 5 mm ² / s or more and 4000 mm ² / s or less, more preferably 7 mm ² / s or more and 2000 mm ² / s or less, and further preferably 10 mm ² / s or more and 500 mm ² or less. / S or less.

〔Additive〕
Various additives can be blended in the lubricating oil as long as the object of the present invention is not impaired.
These additives include antioxidants, oily agents, extreme pressure agents, cleaning dispersants, rust inhibitors, metal deactivators, viscosity index improvers, pour point depressants, and antifoaming agents. Is possible. These can be used individually by 1 type or in combination of 2 or more types.

As the antioxidant, amine-based antioxidants, phenol-based antioxidants and sulfur-based antioxidants used in conventional hydrocarbon-based synthetic lubricating oils can be used. These antioxidants can be used singly or in combination of two or more.
Examples of the amine antioxidant include monoalkyl diphenylamine compounds such as monooctyl diphenylamine and monononyl diphenylamine, 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine, 4 , 4′-diheptyldiphenylamine, 4,4′-dioctyldiphenylamine, dialkyldiphenylamine compounds such as 4,4′-dinonyldiphenylamine, polyalkyl such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine Diphenylamine compounds, α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-na Ethylamine, hexyl phenyl -α- naphthylamine, heptylphenyl -α- naphthylamine, octylphenyl -α- naphthylamine, and naphthylamine-based compounds such as nonylphenyl -α- naphthylamine.

Examples of the phenolic antioxidant include monophenolic compounds such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol, 4,4 ′ Examples include diphenolic compounds such as -methylenebis (2,6-di-tert-butylphenol) and 2,2'-methylenebis (4-ethyl-6-tert-butylphenol).
Examples of the sulfur-based antioxidant include 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol, phosphorus pentasulfide and Examples thereof include thioterpene compounds such as a reaction product with pinene, and dialkylthiodipropionates such as dilauryl thiodipropionate and distearyl thiodipropionate.
The blending amount of these antioxidants is about 0.01% by mass or more and 10% by mass or less, preferably 0.03% by mass or more and 5% by mass or less, based on the total amount of the lubricating oil.

  Examples of the oily agent include fatty alcohols, fatty acid compounds such as fatty acids and fatty acid metal salts, ester compounds such as polyol esters, sorbitan esters, and glycerides, and amine compounds such as aliphatic amines. The blending amount of the oily agent is about 0.1% by mass or more and 30% by mass or less, preferably 0.5% by mass or more and 10% by mass or less, based on the total amount of the lubricating oil, from the viewpoint of blending effect.

Examples of the extreme pressure agent include a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, an extreme pressure agent containing sulfur and a metal, and an extreme pressure agent containing phosphorus and a metal. These extreme pressure agents can be used singly or in combination of two or more. As the extreme pressure agent, those containing a sulfur atom or a phosphorus atom in the molecule are preferable from the viewpoint of extreme pressure. Examples of extreme pressure agents containing sulfur in the molecule include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, triazine compounds, thioterpene compounds, dialkylthiodipropionate compounds, etc. Can be mentioned.
The blending amount of these extreme pressure agents is about 0.01% by mass or more and 30% by mass or less, more preferably 0.01% by mass or more and 10% by mass or more based on the total amount of the lubricating oil from the viewpoint of blending effect and economy. It is as follows.

Examples of the cleaning dispersant include metal-based cleaning agents and ashless dispersants.
Examples of ashless dispersants include polybutenyl succinimide having a polybutenyl group having a number average molecular weight of 900 to 3,500, polybutenylbenzylamine, polybutenylamine, and derivatives of these boric acid modified products, etc. Is mentioned. These ashless dispersants can be contained singly or in any desired combination, but the preferred blending amount is in the range of 0.1% by mass or more and 20% by mass or less based on the total amount of the lubricating oil.
Examples of metal detergents include sulfonates, phenates, salicylates and naphthenates of alkali metals (sodium (Na), potassium (K), etc.) or alkaline earth metals (calcium (Ca), magnesium (Mg), etc.). Can be mentioned. These can be used alone or in combination of two or more. The total base number and addition amount of these metallic detergents can be arbitrarily selected according to the required performance of the lubricating oil, and the total base number is usually from 0 mgKOH / g to 500 mgKOH / g in the perchloric acid method, Desirably, 20 mgKOH / g or more and 400 mgKOH / g or less, and a preferable blending amount thereof is in a range of 0.1% by mass or more and 10% by mass or less based on the total amount of the lubricating oil.

Examples of the rust inhibitor include metal sulfonates and succinates. The blending amount of these rust preventives is about 0.01% by mass or more and 10% by mass or less, preferably 0.05% by mass or more and 5% by mass or less, based on the total amount of the lubricating oil, from the viewpoint of blending effect.
Examples of the viscosity index improver include non-dispersed polymethacrylates, dispersed polymethacrylates, olefin copolymers (for example, ethylene-propylene copolymers), dispersed olefin copolymers, styrene copolymers. (For example, styrene-diene hydrogenated copolymer). The weight average molecular weight of these viscosity index improvers is preferably 5,000 or more and 1,000,000 or less, and more preferably 100,000 or more and 800,000 or less for dispersed and non-dispersed polymethacrylates, for example. In the case of an olefin copolymer, the number is preferably from 800 to 300,000, more preferably from 10,000 to 200,000. These viscosity index improvers can be blended singly or in any desired combination, but the preferred blending amount is in the range of 0.1% by mass or more and 20% by mass or less based on the total amount of the lubricating oil.

Examples of the pour point depressant include ethylene-vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate,
Examples thereof include polyalkylstyrene, and polymethacrylate is particularly preferably used. A preferable blending amount thereof is in a range of 0.01% by mass to 5% by mass based on the total amount of the lubricating oil.
Examples of the metal deactivator include benzotriazole and thiadiazole. The preferred compounding amount of these metal deactivators is usually about 0.01% by mass or more and 10% by mass or less, preferably 0.01% by mass or more and 1% by mass, based on the total amount of the lubricating oil, from the viewpoint of the blending effect. It is as follows.
Examples of the antifoaming agent include methyl silicone oil, fluorosilicone oil, and polyacrylate. The blending amount of these antifoaming agents is usually about 0.0005% by mass or more and 0.01% by mass or less based on the total amount of the composition from the viewpoint of the blending effect.

  The lubrication system using the lubricating oil of the present invention can stably give good friction characteristics to a metal material having a nanocrystal grain layer on the surface, and is excellent in wear resistance and durability. Therefore, the present invention is extremely excellent as a lubrication system in various bearing parts, engine valve system parts, engine piston ring / liner sliding parts, machine tool sliding parts, large gear parts and the like.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.

[Manufacture of metal materials having nanocrystal grain layers on the surface]
The metal material which has a nanocrystal grain layer uniformly on the surface of a test material was manufactured by pressing the carbide | carbonized_material chip | tip with respect to the test material rotating at high speed using the apparatus shown in FIG. The used test materials, equipment and friction processing conditions are as follows. Structure observation was performed by SEM and TEM, and it was confirmed that the surface layer was a nanocrystal grain layer.
Specimen: SUJ2 steel (HV 7.4 GPa) used as bearing steel
Composition of test material (mass%): C (1.00), Si (0.20), Mn (0.41), P (0.014), S (0.009), Ni (0.08) ), Cr (1.37), Mo (0.03)
Equipment: NC lathe Pushing load F: 500N
Feeding speed V: 0.01mm / rev
Rotational speed ω: 1600 rpm
Holding time: 20s
Lubricating oil: Water-soluble emulsion

[Friction test]
Predetermined lubricating oil was applied to the metal material and raw sample material obtained above, and the coefficient of friction was measured by a pin-on-disk test method. The measurement was carried out for two types of friction coefficient (initial friction coefficient) after 100 minutes from the start of friction and friction coefficient after 600 minutes from the start of friction (time-dependent friction coefficient). The test conditions are as follows.
Load: 200g (1.96N)
Sliding speed: 10mm / s
Sliding radius: 5mm
Pin material: Alumina ball

[Examples 1 to 4, Comparative Examples 1 to 6]
The results of the friction test are shown in Table 1.

Details of the lubricating oil used in Tables 1 and 2 are as follows. Lubricating oils 2, 3, 5, 6, and 7 are lubricating oils of the present invention.
Lubricating oil 1: poly α-olefin (kinematic viscosity at 40 ° C. 17.4 mm ² / s)
Lubricating oil 2: Ester-based lubricating oil mainly composed of isodecyl adipate (40 ° C. kinematic viscosity 20.2 mm ² / s)
Lubricating oil 3: Oil containing 0.3% by mass of tricresyl phosphate in lubricating oil 1 (40 ° C. kinematic viscosity 17.3 mm ² / s)
Lubricating oil 4: mineral oil (40 ° C. kinematic viscosity 17.2 mm ² / s)
Lubricant 5: Lubricant 1 containing 2% by mass of an imide additive (low molecular weight polybutenyl succinimide, neutral) (40 ° C. kinematic viscosity 18.2 mm ² / s)
Lubricant 6: Lubricant 4 containing 2% by mass of an imide additive (low molecular weight polybutenyl succinimide, neutral) (40 ° C. kinematic viscosity 17.9 mm ² / s)
Lubricating oil 7: Lubricating oil 4 containing 0.03% by mass of a sulfur-based additive (sulfides) in terms of sulfur amount (40 ° C. kinematic viscosity 17.4 mm ² / s)

〔Evaluation results〕
In Comparative Example 1, the friction coefficient between an unprocessed specimen (SUJ2 steel: high carbon chromium steel) and a ceramic (alumina ball) was measured (without lubricating oil), but the coefficient of friction with time was 1 It shows a value close to, which is inappropriate for a lubrication system. Further, as in Comparative Example 2, the friction coefficient can be slightly reduced by forming a nanocrystalline layer on the surface of the high carbon chrome steel even if there is no lubricating oil, but the reduction effect is insufficient.
In Comparative Example 3, nonpolar PAO was used as the lubricating oil, but the friction coefficient with respect to the unprocessed high carbon chromium steel was reduced, but the initial friction coefficient was high and stable, although the friction coefficient with time was reduced. Frictional properties cannot be obtained.
As in Comparative Example 4, when a nanocrystalline grain layer is formed on the surface of high carbon chromium steel and lubricated with mineral oil, the coefficient of friction with time decreases, but the initial coefficient of friction is high, which is insufficient as a lubrication system. is there.
Unlike Comparative Example 3, Comparative Example 5 uses non-polar PAO for the friction processed material, but still has a high initial friction coefficient.
In Comparative Example 6, the lubricating oil 7 was used as an unprocessed material, but the initial coefficient of friction was slightly higher.
On the other hand, as shown in Examples 1 to 5, a small initial friction coefficient (less than 0.4) is obtained by forming a nanocrystal grain layer on the surface of high carbon chromium steel and combining it with a predetermined lubricating oil. Moreover, there is no significant change in the coefficient of friction with time.
That is, by forming a nanocrystal grain layer on the surface of a metal material and combining a predetermined lubricating oil, it is possible to realize a lubrication system that can obtain a low coefficient of friction that is stable not only in the initial stage but also for a long period of time.

Claims (6)

A lubricating oil applied to a metal material having a nanograin layer on the surface,
The nanocrystal grain layer is made of the metal material,
The metal material is high carbon chromium steel;
The lubricating oil is blended with a polar organic compound,
A lubricating oil, wherein the organic compound having polarity is at least one of imides and thiophenes. The lubricating oil according to claim 1,
A lubricating oil comprising a mineral oil or a synthetic oil as a base oil. In the lubricating oil according to claim 1 or 2 ,
A lubricating oil, wherein the nanocrystal grain layer has a thickness of 10 nm or more. In the lubricating oil according to any one of claims 1 to 3 ,
The metal material has a quenching structure in an inner layer from the nanocrystal grain layer. In the lubricating oil according to any one of claims 1 to 4 ,
A lubricating oil, wherein the metal material is a material that undergoes a heat-induced phase transformation. A lubricating system according to any one of claims 1 to 5 , wherein the lubricating oil is used.

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