JP2011246792A - Slide part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide part having more satisfactory low friction and high abrasiveness than in a conventional technology in a sliding environment where there is a lubricant containing abrasion adjustor coexists.SOLUTION: The slide part 1 is used in an environment where there is a lubricant containing a molybdenum compound and has a hard protective layer 20 formed on an outermost surface of a base material 3 composing the slide part, and having the surface hardness of 1,800 or larger in Vickers hardness, wherein the hard protective layer includes mainly carbon, nitrogen and a metal element, and the hard protective layer is composed of a complex of an amorphous carbon body containing nitrogen and a compound crystal of the metal element, and the compound crystal is composed of at least one of a metal carbide, a metal nitride, and a metal carbonitride.

Description

  The present invention relates to a sliding component used in an environment where lubricating oil coexists, and more particularly to a sliding component having an amorphous carbon film formed on a sliding surface.

  A sliding part having an amorphous carbon film formed on the sliding surface has been energetically researched and developed for the main purpose of reducing friction at sliding parts, mainly automobile parts. As the amorphous carbon material, a thin film material called DLC (diamond-like carbon), i-C (eye carbon), hard carbon or the like is usually used.

  Since the amorphous carbon film is an amorphous structure having no grain boundary (not having a clear crystal structure), the amorphous carbon film has a feature of achieving both high hardness and high toughness and low friction characteristics. For this reason, it is said that the amorphous carbon film is superior in durability against mechanical wear as compared with a crystalline hard film such as TiN or CrN. Therefore, a sliding component having an amorphous carbon film formed on the sliding surface is expected to contribute to a reduction in fuel consumption and a longer life of the component.

  The amorphous carbon film is generally a hard film composed of carbon atoms and hydrogen atoms, but a plurality of amorphous carbon films to which a third element is added have been proposed. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-23356) describes amorphous carbon containing carbon as a main component, hydrogen of more than 30 at% and less than 50 at%, and silicon of 1.5 at% to 20 at%. A sliding layer is disclosed. According to Patent Document 1, the friction of the sliding member can be reduced by the self-smoothness of the sliding layer and the silanol formed on the sliding surface.

  Patent Document 2 (WO 03/029685) discloses an amorphous hard carbon film containing at least one of silicon and nitrogen in the range of 1 to 50 at%. According to Patent Document 2, it has a stable high friction coefficient and good friction coefficient-speed-dependent characteristics under wet sliding conditions using a drive system lubricant, and is excellent in wear resistance and has a high attack resistance. It is said that a low high friction sliding member is obtained.

  In Patent Document 3 (Japanese Patent Laid-Open No. 2001-316686), in a sliding member in which a hard carbon film is formed on a base material and used in lubricating oil, elements IIb, III, IV, Va of the Periodic Table of Elements are used. , A sliding member is disclosed in which a hard carbon film to which 5 to 70 at% of at least one metal element selected from Group Via, VIIa and VIII is added is formed on at least the surface layer. According to Patent Document 3, a lubricating oil additive film is easily formed on the surface of a hard carbon film in a lubricating oil environment to which Mo-DTC (molybdenum dialkyldithiocarbamate) and Zn-DTP (zinc dithiophosphate) are added. It is said that it exhibits excellent low friction characteristics.

  In Patent Document 4 (Japanese Patent Application Laid-Open No. 2006-2221), a chromium-containing diamond-like carbon film containing chromium and carbon as main components and having a chromium content of 5 to 16 at% is coated on the outermost surface of the material to be coated. A sliding member is disclosed. According to Patent Document 5, it is said that the chromium-containing diamond-like carbon film can obtain good sliding characteristics with low friction even under non-lubrication and poor lubrication.

  Patent Document 5 (Japanese Patent Laid-Open No. 2008-195903) discloses a sliding structure in an environment in which a lubricating oil containing at least an organic molybdenum compound such as Mo-DTC exists, and at least one of a pair of sliding members slides. An amorphous carbon coating containing a hydrogen element is formed on the surface, and the amorphous carbon coating has a sliding structure containing a suppressing element for suppressing the generation of molybdenum trioxide from the organomolybdenum compound. Proposed. Specifically, for example, an amorphous carbon film to which at least one element of sulfur, magnesium, titanium, or calcium is added as the suppression element is formed, and the suppression is performed by wear powder generated during sliding. It is disclosed that an element is supplied (intervened) in a lubricating oil.

  Shinyoshi et al. In Non-Patent Document 2 and Jia et al. In Non-Patent Document 3 report a study on the wear of an amorphous carbon film in a lubricating oil containing Mo-DTC. According to these documents, Mo-DTC in lubricating oil is thermally decomposed in a sliding environment to produce molybdenum disulfide and molybdenum oxide, and among these, molybdenum trioxide is particularly resistant to abrasion of amorphous carbon films. It is said to be involved. However, views regarding the wear mechanism differ between the documents. In Non-Patent Document 2, an oxidation-reduction reaction occurs between molybdenum trioxide and an amorphous carbon film, and the amorphous carbon film is worn by being changed to carbon dioxide gas. On the other hand, in Non-Patent Document 3, the amorphous carbon film is mechanically worn by molybdenum trioxide having a hard and sharp shape.

JP 2007-23356 A WO03 / 029685 JP 2001-316686 A JP 2006-2221 A JP 2008-195903 A

T. Shinyoshi, Y. Fuwa, and Yoshinori Ozaki: “Wear Analysis of DLC Coating in Oil Containing Mo-DTC”, SAE 2007 Trans. Journal of Fuels and Lubricants 116 2007-01-1969. Z. Jia, P. Wang, Y. Xia, H. Zhang, X. Pang, and B. Li: “Tribological behaviors of diamond-like carbon coatings on plasma nitrided steel using three BN-containing lubricants”, Applied Surface Science 255 (2009) 6666-6674.

  In general, an amorphous carbon film is known as a film having high hardness and low friction, and also having high wear resistance. However, as reported in Non-Patent Documents 1 and 2 and Patent Document 5, it contains molybdenum compounds such as Mo-DTC (molybdenum dialkyldithiocarbamate) and Mo-DTP (molybdenum dithiophosphate) which are known as friction modifiers. In the case of the sliding environment in which the lubricating oil coexisted, the wear of the amorphous carbon film may be remarkably increased, which is a problem. Here, as can be inferred from the difference in views in Non-Patent Documents 1 and 2, the wear theory has not yet been established academically at this stage.

  On the other hand, demands for environmental protection and energy saving have increased in recent years, and further improvement of low friction and wear resistance in various sliding parts represented by automobile parts is a very important issue. In addition, the invention described in Patent Document 5 is an attempt to solve the problem from the standpoint of a wear mechanism close to the view of Non-Patent Document 1, but in the confirmation experiment of the present inventors, the effect is completely It was not enough. This was thought to be due to the fact that the wear mechanism itself was unclear. In other words, in order to solve the above-mentioned problems, it was thought that the point was to elucidate the wear mechanism.

  Therefore, the object of the present invention is to elucidate the wear mechanism of the amorphous carbon film in order to overcome the above-mentioned problems, and in a sliding environment where a lubricating oil containing a friction modifier coexists, it is better than the conventional technique. An object of the present invention is to provide a sliding part having both friction and high wear resistance.

  The present inventors systematically conduct a sliding test in an environment where a lubricating oil containing a molybdenum compound as a friction modifier coexists, investigate the test pieces and the lubricating oil in detail after the sliding test, and The wear mechanism of the amorphous carbon film was clarified by conducting thermal analysis and structural analysis (details will be described later). The present invention has been completed based on the important and novel findings.

One aspect of the present invention has the following features in order to achieve the above object.
The sliding component according to the present invention is a sliding component used in an environment in which a lubricant containing a molybdenum compound coexists, and a hard protective layer is formed on the outermost surface of the base material constituting the sliding component. Sliding parts,
The hard protective layer is mainly composed of carbon, nitrogen and a metal element, and is composed of a composite of a carbon amorphous body containing nitrogen and a compound crystal of the metal element, and the compound crystal is a metal carbide , At least one of metal nitride and metal carbonitride, and the surface hardness of the hard protective layer is Vickers hardness of 1800 or more.

Another aspect of the present invention has the following characteristics in order to achieve the above object.
The method for manufacturing a sliding component according to the present invention is a sliding component that is used in an environment in which a lubricating oil containing a molybdenum compound coexists, and has a hard protective layer formed on the outermost surface thereof, The hard protective layer is composed of a composite of a carbon amorphous body containing carbon, nitrogen, and a metal element as a main component and the nitrogen-containing carbon amorphous body and a compound crystal body of the metal element, and the compound crystal body is a metal carbide. A method for producing a sliding component, which is at least one of a metal nitride and a metal carbonitride, wherein the hard protective layer has a Vickers hardness of 1800 or more,
The hard protective layer is formed by a reactive sputtering method using a non-equilibrium magnetron sputtering apparatus. The target material is a graphite target and a target containing one or more metal elements selected from chromium, titanium, and tungsten. Used, hydrocarbon gas and nitrogen gas are used as reaction gas.

  ADVANTAGE OF THE INVENTION According to this invention, the sliding component which has the low friction property better than the prior art, and high abrasion resistance in the sliding environment where the lubricating oil containing a friction modifier coexisted can be provided.

It is a cross-sectional schematic diagram of an example of a sliding member according to the present invention and an image diagram of a composition distribution in the cross-section. It is a cross-sectional schematic diagram of another example of the sliding member which concerns on this invention, and an image figure of the composition distribution in this cross section. It is a bright-field image of the cross section of the hard protective layer observed with the transmission electron microscope in Example 1, Example 8, Comparative Example 1, and Comparative Example 7. 2 is a high-resolution observation image of Example 1. 7 is an X-ray photoelectron spectroscopy spectrum in Example 5. It is a schematic diagram which shows the method of a reciprocating sliding test. It is a surface observation image of the hard film (Example 1 and Comparative Examples 1, 5, 9, and 10) after a reciprocating sliding test. It is the figure which compared the length (abrasion width) which the base material exposed by abrasion in the reciprocating sliding test. It is a graph which shows the change of the friction coefficient in a reciprocating sliding test (number of times of reciprocating:-6x10 ⁵ times). It is an observation image around the Rockwell impression when a Rockwell indenter is pushed into the hard coating surface of a strip-shaped test piece (Example 1 and Comparative Examples 1, 4 to 7, 10). It is a schematic diagram which shows the sliding environment of the sliding member which concerns on this invention.

[Elucidation of wear mechanism]
As described above, the present inventors conducted a sliding test in an environment in which a lubricating oil (specifically, engine oil) containing a molybdenum compound (specifically, Mo-DTC) as a friction modifier coexists. The wear mechanism of the amorphous carbon film was elucidated by conducting detailed investigations of the specimens and lubricants after the sliding test and conducting various thermal and structural analyses. The experiment and investigation will be described below.

  Conventionally, the wear mechanism of the amorphous carbon film includes (1) weakening of the film surface due to frictional heat, (2) weakening of the film surface due to chemical reaction, (3) mechanical wear of the weakened part due to sliding, And (4) mechanical wear of weak spots due to hard inclusions. Non-Patent Document 1 reports the mechanisms (1) to (3), and Non-Patent Document 2 reports the mechanisms (1) and (4). In a sliding environment that does not include the process (2) or (4) (for example, in a lubricating oil environment that does not contain a molybdenum compound friction modifier, or in a sliding environment that does not use the lubricating oil itself) It is known that there is no factor that promotes wear by mechanical and mechanical action, and the amorphous carbon film exhibits high wear resistance.

  First, we experimented and investigated the weakening of the coating surface due to frictional heat. When an amorphous carbon film (such as a DLC film) is heat-treated at a temperature of 350 ° C. or higher, the amorphous carbon film undergoes a structural change that increases the D-Peak intensity in the Raman scattering spectrum. It is known to change to a stable but mechanically fragile microstructure. In fact, when the heat-treated DLC film was subjected to microstructure observation using a transmission electron microscope and analysis using Raman scattering spectroscopy, the bond between carbon atoms changed from a diamond-like sp3 bond to a graphite-like sp2 bond. It was confirmed that graphite clusters having a particle size of 0.1 to 100 nm were formed.

  There is a concern that the surface of the amorphous carbon film is heated and weakened by frictional heat during sliding. Therefore, a sliding test was performed using engine oil that does not contain Mo-DTC. As a result of a detailed investigation of the engine oil collected after the sliding test, the abrasion powder of the amorphous carbon film (the absolute amount of abrasion powder is small) discharged into the oil is the same as the coating component itself (DLC) before the test. It was confirmed that the carbon solid was composed of a graphite-like structure. From this investigation result, it was considered that the wear mechanisms (1) and (3) exist at least.

  Next, the effect of Mo-DTC, which is usually added as a friction modifier, was examined and investigated. It is known that chemically active and hard molybdenum compounds are produced in sliding using engine oil containing Mo-DTC. Molybdenum sulfide and molybdenum oxide, which are sliding products of Mo-DTC, are present in the oil collected after the sliding test using engine oil containing Mo-DTC and on the surface of the test piece. Was confirmed.

  Therefore, in order to confirm the influence of molybdenum sulfide and molybdenum oxide, the following additional test was performed. First, an amorphous carbon film with the addition of aluminum (Al), which has higher oxidation reactivity than carbon and does not easily form carbides, was prepared, and a sliding test was conducted using Mo-DTC-containing engine oil. . If the wear mechanism of (2) above (that is, the wear promoting action by the chemical reaction (oxidation-reduction reaction) with the molybdenum compound) is strongly influenced, the Al component in the amorphous carbon film causes the sacrificial oxidation reaction. This is because it was thought that the wear of the amorphous carbon film should be suppressed. However, as a result of the test, the wear of the Al-added amorphous carbon film was sufficiently large, and a remarkable wear suppression effect due to sacrificial oxidation of Al was not confirmed.

  Next, while using engine oil containing no Mo-DTC, a sliding test was performed by mixing hard alumina particles having high chemical stability and hard into the engine oil. This is an experiment for verifying the wear mechanism of (4) (that is, the wear-promoting action by hard inclusions), and does not depend on a chemical reaction (redox reaction) by using chemically stable alumina particles. This is because the wear of the amorphous carbon film was considered to be observed. As a result, the wear of the amorphous carbon film showed much larger wear than the sliding test in oil without hard particles, but more than the sliding test in oil containing Mo-DTC. There was little wear. Further, when the abrasion powder of the amorphous carbon film discharged into the oil was investigated, it was confirmed that the carbon solid was composed of a graphite structure.

  The above results suggest that the influence of the hard inclusion reported in Non-Patent Document 2 is greater than the wear due to the oxidation-reduction reaction reported in Non-Patent Document 1. In addition, the wear by the molybdenum compound having a hardness lower than that of the alumina particles was greater, so it was considered that there was a considerable amount of wear promoting action by the oxidation-reduction reaction. Furthermore, since the wear powder had a graphite structure, it was considered that the change from a diamond structure to a graphite structure was the beginning of wear. By combining the above experimental and investigation results, it was considered that the wear mechanism of the amorphous carbon film was “chemical mechanical wear” in which all the mechanisms (1) to (4) were combined.

  In addition to low friction characteristics, high hardness characteristics, and high toughness in lubricating oil, in addition to low friction characteristics, high hardness characteristics, and high toughness in lubricating oil, in a sliding environment where lubricating oil coexists, such as automobile parts, A hard film having durability against chemical mechanical wear (wear resistance) and a sliding part on which the hard film is formed are strongly desired.

  Here, the friction reduction effect by the molybdenum compound in the sliding part between metals is remarkable, and the friction modifier is added to many kinds of lubricating oils and is actively used at present. In such a situation, it is not realistic to use a lubricating oil that does not contain a friction modifier only to suppress the wear of the amorphous carbon film. That is, it is necessary to take an essential measure against the amorphous carbon film after understanding the wear mechanism as described above. The inventors of the present invention have focused on the fact that a change from a diamond-like structure to a graphite-like structure in the structure of an amorphous carbon film (bonding between carbon atoms) is an initial process of wear. The starting point of the present invention was to stabilize the structure of the carbon film.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments taken up here, and can be appropriately combined and improved without departing from the scope of the invention.

As described above, the sliding component according to the present invention is a sliding component that is used in an environment in which a lubricant containing a molybdenum (Mo) compound coexists, and the most base material that constitutes the sliding component. A sliding component having a hard protective layer formed on the surface,
The hard protective layer is composed of a composite of carbon (C), nitrogen (N) and a metal element as a main component, and a carbon amorphous body containing nitrogen and a compound crystal of the metal element, The compound crystal is at least one of metal carbide, metal nitride, and metal carbonitride, and the hard protective layer has a Vickers hardness (Hv) of 1800 or more.

Moreover, the present invention can add the following improvements and changes to the sliding component according to the above invention.
(I) The hard protective layer has an atomic ratio in which the total of carbon, nitrogen, and the metal elements is 100 atomic%, carbon is 59 atomic% or more, and nitrogen is 0.1 atomic% or more and 35 atomic% or less. The metal element is 0.05 atomic% or more and 38 atomic% or less, and the total of nitrogen and the metal element is 5 atomic% or more.
(Ii) The hard protective layer further includes 25 atomic% or less of hydrogen (H), 18 atomic% or less of oxygen (O), and 5 atomic% or less of argon (Ar).
(Iii) The metal element is at least one of chromium (Cr), titanium (Ti), and tungsten (W).
(Iv) The composite is formed by dispersing the compound crystal body having a particle size of 0.1 nm or more and 100 nm or less in a matrix phase of the carbon amorphous body, and the compound crystal in the hard protective layer. The volume fraction of the body is 0.08 vol% or more and 76 vol% or less, and the number density of the compound crystal is 10 ^-6 · µm ^-3 or more and 10 ¹² · µm ^-3 or less.
(V) The composite is configured by alternately laminating the carbon amorphous layer and the compound crystal layer, and the volume fraction of the compound crystal in the hard protective layer is 30. The thickness of the compound crystal body is 1 nm to 50 nm and the thickness of the carbon amorphous body layer is 0.3 nm to 100 nm.
(Vi) In the sliding component, a plurality of intermediate layers are interposed between the hard protective layer and the base material, and the plurality of intermediate layers are formed on the base material and made of the metal element. A first intermediate layer; a second intermediate layer formed immediately above the first intermediate layer and made of the metal element and the metal carbide; and formed immediately above the second intermediate layer and the metal carbide and the carbon amorphous. A third intermediate layer comprising a body.
(Vii) The sliding parts are provided in a valve lifter, adjusting shim, cam, camshaft, rocker arm, tappet, piston, piston pin, piston ring, timing gear, timing chain, and oil pump disposed in the internal combustion engine. Drive gear, driven gear, rotor, vane, or cam.
(Viii) The lubricating oil is engine oil, and the molybdenum compound is molybdenum dialkyldithiocarbamate (Mo-DTC) or molybdenum dithiophosphate (Mo-DTP).

[Configuration of hard coating]
The hard protective layer of the present invention is a composite mainly composed of amorphous carbon having high hardness and high toughness, and a microstructure added to suppress the weakening of the amorphous carbon. This shows excellent durability against the above-mentioned chemical mechanical wear. At the same time, the hard protective layer of the present invention activates the interaction with oily additives, extreme pressure additives, friction reducing agents and the like by adding an appropriate amount of metal element, and a lubricating oil containing these additives. Excellent low-friction properties even when used inside.

  The structural change of the amorphous carbon film caused by frictional heat is due to a change in the bond between carbon atoms, and the effect of making structural change difficult to occur by substituting some of the carbon atoms with nitrogen atoms. is there. In addition, the metal carbide, metal nitride and metal carbonitride compound crystals formed in the carbon amorphous body have higher thermochemical stability than the carbon amorphous body, and the entire composite (hard protective layer) Effective in improving heat resistance. Among these, metal nitrides have high thermochemical stability and are highly effective. As a result of these effects acting in combination, chemical mechanical wear of the hard protective layer can be suppressed. Further, by controlling the amounts of nitrogen and metal elements added to the hard protective layer, it is possible to ensure a Vickers hardness of 1800 or more desired as a hard film.

  Addition of nitrogen is most effective in suppressing chemical mechanical wear of the amorphous carbon film, but adding more than 35 atomic% of nitrogen is not preferable because the hardness of the amorphous carbon film is lowered. Moreover, the effect is insufficient when nitrogen is added in an amount of less than 0.1 atomic%. Note that the addition of only nitrogen tends to lower the hardness of the amorphous carbon film and easily cause mechanical wear, and tends to increase the coefficient of friction in the lubricating oil.

  On the other hand, regarding the addition of a metal element, adding more than 38 atomic% is not preferable because high toughness peculiar to an amorphous carbon film deteriorates. In addition, when a metal element of less than 0.05 atomic% is added, the amount of the compound crystal formed is too small, and the above effect is insufficient. The metal element is preferably at least one of chromium, titanium, and tungsten that forms hard carbide, nitride, and carbonitride. In addition, when only a metal element is added, since the effect of suppressing the structural change of the amorphous carbon film is small, the effect of suppressing chemical mechanical wear is insufficient, and the toughness tends to be deteriorated.

  Amorphous carbon film (hard protective layer) has an atomic ratio when the total of carbon, nitrogen and metal elements is 100 atom%. Carbon is 59 atom% or more, and nitrogen is 0.1 atom% or more and 35 atom%. Preferably, the metal element is 0.05 atomic% or more and 38 atomic% or less, and the total of nitrogen and the metal element is 5 atomic% or more. By controlling to such a composition range, a preferable microstructure can be formed and the surface hardness of the hard protective layer can be set to a Vickers hardness of 1800 or more. If the hardness of the hard protective layer is less than this, the amount of deformation of the base material tends to increase during sliding, which is not preferable because it causes interface peeling.

  As in the present invention, the amorphous carbon film (hard protective layer) in which nitrogen and metal elements are added in combination is a metal nitridation with higher thermochemical stability in addition to nitrogen substitution structure and metal carbide crystal formation. And metal carbonitrides can be produced and simultaneously satisfy the low friction characteristics, high hardness characteristics, high toughness, and chemical mechanical wear deterrence in the lubricating oil. Further, the metal element in the hard protective layer can obtain excellent low friction characteristics due to the interaction with the molybdenum compound in the lubricating oil.

  FIG. 11 is a schematic diagram showing a sliding environment of the sliding member according to the present invention. As shown in FIG. 11, the sliding member 1 according to the present invention has a hard coating 2 formed on the sliding surface of the base material 3, and is connected to the mating member 9 via a lubricating oil 8 containing a molybdenum compound. It slides. In addition, as a material of the base material 3, a steel material is preferably used, but is not limited thereto.

  FIG. 1 is a schematic cross-sectional view of an example of a sliding member according to the present invention and an image diagram of a composition distribution in the cross-section. As shown in FIG. 1, the hard protective layer 20 which is the outermost surface layer of the hard coating 2 is composed of metal carbide, metal nitride and metal carbonitride in the matrix phase of the carbon amorphous body 4 containing nitrogen. Among these, a composite body in which particles 5a of at least one compound crystal body are finely dispersed. The hard coating 2 of the present invention may be a single-layer film of the hard protective layer 20, but in addition to the hard protective layer 20, it is more excellent if it has a multilayer structure provided with intermediate layers 21 to 23 whose composition changes in a gradient manner. It exhibits characteristics (details will be described later).

  In order to maintain the high toughness inherent in the carbon amorphous body 4, it is desirable to reduce the size of the dispersed compound crystal particles 5a. Due to the strengthening mechanism similar to the Hall-Petch equation known in metal crystallography, the smaller the particle diameter, the higher the toughness. Furthermore, from the viewpoint of preventing the brittle process in which the amorphous carbon 4 changes and grows from a diamond structure to a graphite structure cluster, the size of these compound crystal particles 5a is about 0.1 to 100 nm, the same size as the graphite cluster. It is preferable to control within the range.

When the compound crystal particles 5a are finely dispersed in the hard protective layer 20, the volume ratio of the compound crystal particles 5a is preferably 0.08 to 76% by volume, and the number density is 10 ⁻⁶ to 10 ¹² particles / μm. ^-3 is preferred. When the volume fraction of the compound crystal is larger than the specified value, the toughness of the hard protective layer 20 is lowered. In the present invention, the compound crystal particles 5a formed on the hard protective layer 20 can be reduced to the nanoscale, and the size of the compound crystal particles 5a within the above-described composition range is 0.1 to By controlling in the range of 100 nm, the volume ratio and number density can be controlled in a suitable range. These microstructures can be analyzed by cross-sectional observation using a transmission electron microscope, surface analysis using an X-ray diffraction method or X-ray photoelectron spectroscopy.

  As described above, it is preferable to have a multilayer structure in which the intermediate layers 21 to 23 are provided between the hard protective layer 20 and the substrate 3. At this time, the first intermediate layer 21 made of only metal is formed immediately above the base material 3, the second intermediate layer 22 made of metal and metal carbide is formed immediately above the first intermediate layer 21, and the second intermediate layer 22 is formed. A third intermediate layer 23 made of a metal carbide and amorphous carbon is formed immediately above the substrate, and the composition profile in the thickness direction of the intermediate layers 21 to 23 extends from the interface with the substrate 3 to the interface with the hard protective layer 20. It is desirable to change continuously (refer FIG. 1). In other words, each intermediate layer has a composition closer to the next layer as it goes upward. By forming such a multilayer structure, the internal stress of the hard coating 2 is relieved and the adhesion to the base material 3 is improved, so that the interfacial peeling can be suppressed and the durability can be further improved.

  FIG. 2 is a schematic cross-sectional view of another example of the sliding member according to the present invention and an image diagram of the composition distribution in the cross-section. As shown in FIG. 2, the hard protective layer 20 ′, which is the outermost surface layer of the hard coating 2 ′, includes a layer of a carbon amorphous body 4 containing nitrogen, a metal carbide, a metal nitride, and a metal carbonitride. Among these, a composite body in which at least one compound crystal layer 5b is alternately laminated. The hard coating 2 ′ of the present invention may be a single layer film of the hard protective layer 20 ′, but in addition to the hard protective layer 20 ′, intermediate layers 21 to 23 whose composition is changed in a gradient manner as described above are provided. When a multilayer structure is used, more excellent characteristics are exhibited.

  When the layers of the carbon amorphous body 4 and the compound crystal layer 5b are alternately laminated, the volume ratio of the compound crystal layer 5b is preferably 30 to 76% by volume, and the thickness of the layer 5b is 1 ˜50 nm is preferable, and the distance between the layers 5b (the thickness of the carbon amorphous body 4) is preferably 0.3 to 100 nm. When the volume ratio of the compound crystal layer 5b is less than 30% by volume, it becomes difficult to form a layered microstructure. Regarding the thickness of the layer 5b, the smaller the thickness, the greater the followability to the deformation of the base material 3 and the interfacial peeling can be suppressed, but if it is 50 nm or less, which is smaller than 1/10 of the thickness of the hard protective layer 20 ′. Fully functional. These microstructures can also be analyzed by cross-sectional observation using a transmission electron microscope, surface analysis using X-ray diffraction or X-ray photoelectron spectroscopy, and the like.

  As described above, the hard protective layer has good characteristics in any microstructure in which the compound crystal is distributed in the form of fine particles or layers. In the case of fine particles, since both the carbon amorphous body and the compound crystal body exist on the outermost surface of the hard protective layer, good durability against chemical mechanical wear is exhibited. Even in the case of a layered structure, since the thickness of each layer (carbon amorphous layer and compound crystal layer) is sufficiently thin and alternately laminated, the hard protective layer as a whole is in the form of fine particles Has the same effect as Also, for example, at the time of local wear, both the carbon amorphous body and the compound crystal body exist on the outermost surface of the hard protective layer. In FIG. 2, the carbon amorphous layer and the compound crystal layer are drawn in parallel to the outermost surface. And may be formed obliquely. In that case, both the carbon amorphous body and the compound crystal body are present on the outermost surface of the hard protective layer from the beginning.

  Various additives are usually added to the lubricating oil. For example, oil additives such as fatty acids, alcohols and esters, extreme pressure additives such as sulfur and phosphorus, and friction reducing additives such as molybdenum dialkyldithiocarbamate (Mo-DTC) Compound additives such as zinc dialkyldithiophosphate (Zn-DTP) having multiple effects are widely used. Conventionally, low friction by activating these additives has been studied.

In particular, friction reducing additives such as Mo-DTC and Mo-DTP are molybdenum compounds that generate MoS ₂ and MoO ₃ by frictional heat during sliding, etc. It is known that it can be rubbed. Further, this production reaction is affected by the material of the sliding part, and it is known that the reaction is accelerated particularly when a metal element belonging to IVa group, Va group and VIa group is present. However, the conventional hard coating (amorphous carbon coating) has a problem that the wear progresses conversely due to MoS ₂ or MoO ₃ generated to reduce friction.

On the other hand, the hard protective layer of the present invention has high durability (wear resistance) against chemical mechanical wear due to MoS ₂ or MoO ₃ by adopting the above-mentioned microstructure. In addition, since the hard protective layer of the present invention contains a sufficient amount of at least one of chromium, titanium, and tungsten as metal elements, it is possible to increase the generation efficiency of MoS ₂ , MoO _3, etc. It is possible to exhibit friction characteristics. Although any metal element can provide excellent low friction characteristics, in particular, addition of chromium, which is an element belonging to the same group as molybdenum, easily adsorbs various molybdenum compounds on the surface, and has the greatest friction reduction effect.

  On the other hand, in the case of a sliding environment where the surface pressure is very large or a sliding environment where the lubricating oil does not reach sufficiently, the content of the metal element in the hard protective layer is about half of the specified maximum amount (for example, 0.05 to It is preferable to control (in the range of 17 atomic%). In addition, when priority is given to low friction properties, a metal element that enhances the generation efficiency of the molybdenum compound is sufficiently contained, and the nitrogen content is controlled to be small (for example, in the range of 0.1 to 2 atomic%). Is preferred.

  The sliding component according to the present invention is suitable for sliding components for automobiles and the like, particularly those used in a sliding environment using a lubricating oil containing a molybdenum compound. For example, sliding parts of an internal combustion engine include valve lifters, adjusting shims, cams, camshafts, rocker arms, tappets, pistons, piston pins, piston rings, timing gears, timing chains, and the like. Moreover, examples of the sliding parts in the oil pump include a drive gear, a driven gear, a rotor, a vane, and a cam. However, the present invention is not limited to these, and can be widely applied as sliding parts for other purposes.

[Production method]
As a manufacturing method of the hard film of the present invention, an existing method such as a sputtering method, a plasma CVD method, or an ion plating method can be used, but a reactive sputtering method is used as a manufacturing method of the hard protective layer. Is particularly preferred. The reactive sputtering method is a film forming method that can easily produce a hard film in which a film surface can be produced smoothly and a metal element, nitrogen and carbon are combined. Moreover, a harder film can be produced by carrying out reactive sputtering using a hydrocarbon gas in order to supply carbon that is difficult to ionize.

  In carrying out the reactive sputtering method, it is preferable to use a non-equilibrium magnetron sputtering apparatus. When a conventional sputtering apparatus is used, plasma is excited mainly in the vicinity of the target, and it is difficult to maintain a high excitation state in the vicinity of the base material that is the film forming material. On the other hand, in the reactive sputtering method using a non-equilibrium magnetron sputtering apparatus, it is possible to increase the plasma density on the substrate side.

  A graphite target and a target containing one or more metal elements selected from chromium, titanium, and tungsten are used as the target material, and a hydrocarbon gas and a nitrogen gas are used as the reaction gas. In addition, argon gas is used to control the plasma. Nitrogen gas is once excited in the vicinity of the target to form nitrogen plasma, and then delivered to the substrate while maintaining its high excited state. At the same time, ionized carbon and atoms excited from each target are delivered to the substrate while maintaining a high excited state. As a result, the nitrogen component can be efficiently taken into the amorphous carbon film, and metal nitride, metal carbonitride, and metal carbide can be efficiently generated.

  When a hard protective layer is formed by the above manufacturing method, hydrogen and argon are inevitably mixed. Even in that case, it is preferable to control hydrogen to 25 atomic% or less and argon to 5 atomic% or less. Exceeding the specified range is not preferable because the hard protective layer becomes brittle. Further, when the formed hard protective layer is exposed to the atmosphere, oxygen may enter the hard protective layer due to surface oxidation or the like. Even in that case, it is preferable that oxygen is 18 atomic% or less. If the amount of oxygen on the outermost surface of the hard protective layer is suppressed to 18 atomic% or less, it can be suppressed to 2 atomic% or less at a position about 0.1 μm deep from the surface. If it is this range, it will not have a bad influence on the characteristic of a hard protective film. Each numerical value of “atomic%” is an atomic ratio when the total of carbon, nitrogen, and metal elements is 100 atomic% as described above.

  In the sputtering method, in general, a crater due to adhesion of foreign matter (particles) or abnormal discharge may be formed. If a large defect portion (particle, crater, etc.) having a diameter of 10 μm or more is present on the surface of the hard protective layer, interfacial peeling may occur from the defect portion during sliding, which is not preferable. Therefore, it is necessary to control the film forming process so that a defect portion having a diameter of 10 μm or more is not formed on the surface of the hard protective layer.

  Further, in the hard protective layer of the present invention which is a composite of an amorphous body and a crystalline body, the amorphous body hardly forms a grain shape, and the crystalline body is in the form of fine particles or Distributed in any layered microstructure. At this time, it is easy to form a microstructure of a layered structure when the volume of the crystalline body and that of the amorphous body are about the same. It can also be controlled by the material bias voltage.

  Hereinafter, specific examples of the present invention will be described in detail by way of examples. In addition, this invention is not limited to a following example.

  First, a test piece was prepared in which a hard protective layer having a crater having a diameter of 10 μm or more was intentionally formed using a non-equilibrium magnetron sputtering apparatus. When the test piece was subjected to a reciprocating sliding test using an engine oil (viscosity index: 5W-30) not containing Mo-DTC, interface peeling starting from the crater occurred and the base material was greatly exposed. . In response to this result, all the test pieces of sliding members by reactive sputtering described in Tables 1 to 3 below (Examples 1 to 24 and Comparative Examples 1 to 9, 11 to 16, 19, and 21) Was fabricated under process conditions that do not generate craters with a diameter of 10 μm or more.

(Production of Example 1)
The manufacturing method of the sliding member sample of Example 1 is as follows. A steel substrate, metal target, and graphite target were set in a non-equilibrium magnetron sputtering device, and a hard protective layer was formed on the surface of the steel substrate by reactive sputtering while introducing argon gas, hydrocarbon gas, and nitrogen gas. .

  First, argon gas was introduced and electric power was supplied to the metal target to form the first intermediate layer 21 made of only metal. Next, argon gas and hydrocarbon gas are introduced to continuously change the input power of the metal target and the graphite target, and the second intermediate layer 22 made of metal and metal carbide, and made of metal carbide and amorphous carbon. A third intermediate layer 23 was formed. Finally, argon gas, hydrocarbon gas, and nitrogen gas were introduced, and power was supplied to the metal target and graphite target to form a hard protective layer.

  In Example 1, as raw materials, a titanium target with a purity of 99.9% by mass or more, a graphite target containing carbon with a purity of 99.9% by mass or more, an argon gas with a purity of 99.999% by mass or more, and a nitrogen gas with a purity of 99.999% by mass or more Using methane gas with a purity of 99.999 mass or more. In addition, the hard protective layer deposition process conditions were as follows: the target input power ratio of “graphite to titanium” was 100: 3, the gas flow ratio of “argon to nitrogen to methane” was 100: 40: 5, and the film thickness was The film formation time was adjusted to be 1.9 μm. When the composition analysis of the hard protective layer produced using X-ray photoelectron spectroscopy was performed, the atomic ratio of “metal element: nitrogen: carbon” was 17:18:65.

(Production of Examples 2 to 16 and Comparative Examples 1 to 9 and 11 to 16)
Samples of Examples 2 to 16 and Comparative Examples 1 to 9 and 11 to 16 were produced by the same procedure as that of Example 1. At this time, the metal type of the target, the target input power, the gas flow rate, and the film formation time were adjusted to form hard protective layers having different compositions and film thicknesses (see Tables 1 and 2 described later).

  Examples 2, 3, and 4 are examples manufactured by changing the film thickness. Example 5 was prepared by decreasing the titanium concentration. In contrast to Example 1 in which titanium was used as the metal target, in Example 6, chromium (purity of 99.99% by mass or more) was used as the metal target. Example 7 is an example in which the nitrogen concentration was decreased. Examples 8, 9, and 10 are examples produced by changing the chromium concentration. In Example 11, tungsten (purity 99.999 mass% or more) was used for the metal target.

  Further, Comparative Example 1 is an example prepared without containing a metal element and nitrogen. Comparative Example 2 and Comparative Example 3 were prepared without adding nitrogen, although titanium was added. Comparative Example 4 and Comparative Example 5 were prepared without adding nitrogen, although chromium was added. Comparative Example 6 was prepared by adding tungsten but not containing nitrogen. In Comparative Example 7, aluminum (purity 99.999% by mass or more) was used as a metal target and nitrogen was not included. Comparative Example 8 is an example in which the total addition amount of the metal element and nitrogen deviates from the definition of the present invention. Comparative Example 9 was prepared as an example (Hv = 1600) in which the film hardness was decreased by adding more metal element than specified in the present invention.

(Production of Comparative Examples 10, 17 and 18)
Comparative Examples 10, 17 and 18 are examples in which a graphite target was placed in an arc ion plating apparatus and a hard protective layer was formed on the surface of the steel substrate. First, electric power was turned on using a graphite target as a cathode to cause arc discharge to form an amorphous single layer film. Next, in order to remove the droplets (carbon lump generated from the target) adhering to the film surface during film formation, a lapping process was performed on the test piece taken out from the arc ion plating apparatus. The obtained hard protective layer was a film (carbon 100 atomic%) containing only hydrogen and not containing hydrogen and argon, and the film hardness was Hv = 8000.

[Observation and measurement of sample]
Various observations / analysis / measurements were performed on the samples prepared in Examples 1 to 16 and Comparative Examples 1 to 18. Microstructure, chemical bonding morphology and composition were analyzed by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. However, in the X-ray photoelectron spectroscopy, the composition measurement accuracy is several atomic% due to the energy resolution. Therefore, the composition of a sample having an additive element content of 1 atomic% or less was analyzed by using both X-ray photoelectron spectroscopy and wavelength dispersive characteristic X-ray spectroscopy or fluorescent X-ray spectroscopy. The presence or absence of hydrogen was analyzed by Rutherford backscattering analysis equipped with an elastic recoil particle detector. Furthermore, a reciprocating sliding test was conducted in engine oil with Mo-DTC added or engine oil without Mo-DTC (both viscosity index: 0W-20). Each result list is shown in Tables 1 and 2.

(Tissue observation)
The films (Examples 1 to 16 and Comparative Examples 1 to 9 and 11 to 16) formed by the reactive sputtering method were all smooth surfaces having no crater on the film surface. On the other hand, craters having a diameter of 1 μm or more exist at a number density on the order of 10 ⁶ / mm ^{2 on} the film surfaces of Comparative Examples 10, 17, and 18 formed by the arc ion plating method, and have a diameter of 10 μm or more. Large craters existed at a number density on the order of 10 ³ pieces / mm ² . These were considered to be traces of removing the droplets adhering during film formation as craters.

FIG. 3 is a bright-field image of a cross section of the hard protective layer observed with a transmission electron microscope in Example 1, Example 8, Comparative Example 1, and Comparative Example 7. FIG. 4 is a high-resolution observation image of Example 1. When the high-resolution image of Example 1 is viewed (see FIG. 4), moire fringes indicating crystalline can be observed in an unclear contrast indicating amorphous. Since the average diameter of the compound crystal particles of Example 1 separately measured by the X-ray diffraction method was about 3 nm, the size of the crystal particles observed by a transmission electron microscope and the crystals measured by the X-ray diffraction method It was confirmed that the size of the particles almost coincided. Example 1 has a microstructure in which compound crystal particles are dispersed in an amorphous body on the order of a number density of 10 ⁷ particles / μm ³ , and the volume fraction of the compound crystal is about 35% by volume. It was. In Example 8, a microstructure in which a compound crystal layer having a thickness of 2.0 nm and an amorphous layer having a thickness of 2.3 nm were alternately laminated was observed, and the volume ratio of the compound crystal was 46.5 volumes. %Met. On the other hand, in Comparative Example 1 in which no metal element or nitrogen was added and in Comparative Example 7 in which aluminum was added, only a homogeneous amorphous body was formed.

  FIG. 5 is an X-ray photoelectron spectroscopy spectrum in Example 5. Example 5 is a sample with a small amount of metal element added (see Table 1). As a result of analyzing the bonding form of atoms by X-ray photoelectron spectroscopy, only metal nitride was detected as a compound crystal, and metal carbide was Almost no detection. In other words, it can be said that the manufacturing method according to the present invention is a manufacturing method in which a metal nitride is easily generated in a hard protective layer in preference to a metal carbide. In addition to Example 5, in Examples 2 to 4, 9, 10 and Comparative Example 8 in which the amount of addition of the metal element is small, formation of metal nitride was confirmed, and formation of metal carbide was not confirmed (see Table 1). ). In addition, in the sample in which the amount of metal element added was relatively large and nitrogen was added in combination, formation of metal carbide and / or metal carbonitride was confirmed in addition to metal nitride. On the other hand, among Comparative Examples 2 to 7 to which only nitrogen was added without adding nitrogen, Comparative Examples 2 to 6 to which titanium, chromium or tungsten was added respectively produced hard metal carbides. On the other hand, in Comparative Example 7 to which aluminum was added, a cluster structure was formed by entering between the atoms of amorphous carbon without forming carbides. Further, in the sample to which nitrogen was added, nitrogen substitution of amorphous carbon was confirmed.

(Reciprocating sliding test)
The reciprocating sliding test was performed by the following method. FIG. 6 is a schematic diagram showing a method of a reciprocating sliding test. A hard protective layer 2 is formed on the surface of a strip-shaped steel substrate 3 '(material: Cr-Mo alloy steel, shape: 50 mm x 15 mm x 5 mm ^t ) with a surface roughness of Ra = 0.02 µm Thus, a strip-shaped test piece 1 ′ was produced. In the reciprocating sliding test, the side surface of the cylindrical specimen 6 (material: cast iron, shape: 4 mmφ x 11 mm) and the surface of the strip specimen 1 'are line-contacted, and the engine with Mo-DTC added to the contact surface The strip-shaped test piece 1 ′ was slid back and forth while dropping oil from the metal tube 7 at a rate of 1.0 ml / sec. The sliding conditions were a surface pressure of 822 MPa (load 784 N), a sliding speed of 0 to 1.6 m / sec, a sliding width of 30 mm, and a sliding start temperature of 110 ° C. The temperature of the strip-shaped test piece was set so that the initial temperature was 110 ° C. by heating before the test, and it increased to about 150 ° C. due to frictional heat during sliding. A sliding test was conducted with the number of reciprocations of 1.8 × 10 ⁶ times, and it was judged that the specimen had sufficient durability (○ wear resistance) when no peeled area with a size of 0.1 mm or more was found on the hard coating surface. . In Comparative Examples 11 to 14, 16, and 18, engine oil without addition of Mo-DTC was used.

  FIG. 7 is a surface observation image of the hard coating (Example 1 and Comparative Examples 1, 5, 9, and 10) after the reciprocating sliding test. As shown in FIG. 7, from the observation of the surface of the hard coating, the wear phenomenon in the engine oil with Mo-DTC added is the wear of the film thickness gradually decreasing (Comparative Example 1) and the area of interface peeling. It was confirmed that there are linear wear (Comparative Examples 5 and 9) that linearly expands along the sliding direction and speckle wear (Comparative Example 10) in which local interface peeling exists in the form of spots. . Wear occurs when the chemical mechanical wear phenomenon cannot be suppressed, linear wear occurs when the hardness or toughness of the hard coating is insufficient, and spotted wear has defects such as craters in the hard coating. It was thought to occur when

  FIG. 8 is a diagram comparing lengths (abrasion width) at which the base material is exposed by abrasion in a reciprocating sliding test. The results of Comparative Example 1 were set as a reference value “100”, and other Examples and Comparative Examples were expressed as relative values. In the amorphous carbon film (Comparative Example 1) prepared without using a reactive sputtering method without containing a metal element and nitrogen, the surface of the substrate was greatly exposed by abrasion. On the other hand, when the results of Comparative Examples 2 to 7 in which only the metal element was added were seen, the abrasion width was improved in Comparative Examples 2 and 4, but the effect was insufficient. In Comparative Examples 3, 5, and 6 having a high metal element concentration, the surface exposure due to abrasion was almost eliminated, but linear wear occurred.

  In Comparative Example 7 to which aluminum was added, the wear width increased. Aluminum is an element that is expected to have a sacrificial oxidation reaction effect due to its low free energy for oxide formation, but the effect of the sacrificial reaction on the chemical mechanical wear of the amorphous carbon film that was elucidated in the present invention. It turns out not to show.

  Further, in Comparative Example 8 in which the total addition amount of the metal element and nitrogen deviated from the definition of the present invention, the abrasion width was improved as compared with Comparative Example 1, but the effect was insufficient. In Comparative Example 9 in which more metal element was added than specified in the present invention, the surface exposure due to abrasion was almost eliminated, but linear wear occurred. On the other hand, in Examples 1 to 10 according to the present invention, the surface of the base material was not exposed (no wear and no linear wear) and showed good wear resistance. Moreover, since Example 3 and Example 4 have the outstanding abrasion resistance, it can be said that it is applicable in the range of at least 0.4-8 micrometers regarding a film thickness (refer Table 1).

  The amorphous carbon film not containing hydrogen (Comparative Example 10) produced by the arc ion plating method has high hardness characteristics similar to diamond, and the wear width is about 1/10 of that of Comparative Example 1. . However, the surface of the sample of Comparative Example 10 has a crater that is a trace from which droplets have been removed, and therefore, interfacial delamination starting from the crater occurred in spots (see FIG. 7).

FIG. 9 is a graph showing changes in the coefficient of friction during the reciprocating sliding test (number of reciprocations: ˜6 × 10 ⁵ times). As the lubricating oil, Mo-DTC-added engine oil (viscosity index: 0W-20) is used. In Example 1, Example 9, Comparative Example 3, Comparative Example 5, and Comparative Example 7 to which the metal element was added, the friction coefficient was lower than those of Comparative Example 1 and Comparative Example 10 to which the metal element was not added. This suggests that the addition of metal elements is effective for reducing friction. In particular, Example 7 and Comparative Example 4 to which chromium, which is an element belonging to the same group as molybdenum, was added showed the lowest friction coefficient, and Example 1 and Comparative Example 3 to which titanium was added showed a low friction coefficient corresponding thereto. These metal elements are considered to have the effect of activating the molybdenum disulfide self-lubricating film by adsorbing molybdenum compounds.

  Similarly, a reciprocating sliding test was performed on Examples 12 to 15 and Comparative Examples 11 to 18. Here, comparison was made between engine oil with Mo-DTC added and engine oil without Mo-DTC added. As a result, as shown in Table 2, it was demonstrated that the hard protective layer according to the present invention is highly effective in reducing friction and has excellent wear resistance especially in engine oil added with Mo-DTC. It was.

(Rockwell indentation test)
FIG. 10 is an observation image around the Rockwell indentation when the Rockwell indenter is pushed into the hard coating surface of the strip-shaped test piece (Example 1 and Comparative Examples 1, 4 to 7, 10). In the Rockwell indentation test, when a film having poor adhesion to the base material is tested, interfacial peeling is generally observed around the indentation, but due to adhesion in Examples 1 to 11 and Comparative Examples 1 to 10 Interfacial debonding, which seems to be, was not confirmed. However, some cracks were observed around the indentation as a starting point of peeling, which was judged to be due to low toughness.

  As shown in FIG. 10, the hard film according to the present invention (Example 1), the hard film containing no metal element and nitrogen (Comparative Example 1), and the aluminum-added hard film in which compound crystal particles were not formed ( Comparative Example 7) was considered to have high toughness without occurrence of cracks. On the other hand, clear cracks were observed in samples (Comparative Examples 5 and 6), which were hard coatings in which only metal elements were added and metal carbide particles were produced, and the amount added was relatively large. Since the metal carbide is a hard crystal (that is, a brittle crystal), it was considered that the microstructure in which only the metal carbide was dispersed impaired the toughness of the hard coating. This result is consistent with the results of FIGS. 7 and 8 (the wear width was reduced, but interface peeling (linear wear) occurred).

  On the other hand, the sample of Comparative Example 10 had high toughness that did not generate cracks around the Rockwell indentation. However, there were many craters that seemed to be traces of removing the droplets. These craters were considered to be the origin of interfacial delamination, and the cause of spotted wear in the reciprocating sliding test (see FIG. 7).

(Production and Evaluation of Examples 17-24 and Comparative Examples 19-22)
Examples 17 to 24 and Comparative Examples 19 to 22 were produced by forming a hard film on the surface of an actual automobile part by the same production method as described above. In Examples 17 to 20 and Comparative Examples 19 and 20, a hard coating is formed on the valve lifter crown surface in a motoring engine simulating a direct acting valve system. In Examples 21 to 24 and Comparative Examples 21 and 22, a hard film was formed on the vane surface of the vane type oil pump. Using engine oil containing Mo-DTC as a lubricating oil (viscosity index: 0W-20), an actual machine durability test was conducted to evaluate the durability. The results are shown in Table 3.

  In the actual machine endurance test of the valve lifter (Examples 17 to 20 and Comparative Examples 19 and 20), an accelerated test was performed in which the load was increased to twice that of the actual machine, and the wear state of the hard coating after the test was investigated. As a result, in Comparative Example 19, wear of the film was observed on the entire surface of the valve lifter crown surface, and in Comparative Example 20, significant wear was observed at the center of the crown surface where the sliding speed was maximum. On the other hand, it was demonstrated that Examples 17-20 showed the outstanding durability.

  In the vane actual machine durability test (Examples 21 to 24 and Comparative Examples 21 and 22), the durability test was performed at a speed corresponding to the actual machine, and the wear state of the hard coating after the test was investigated. As a result, in Comparative Examples 21 and 22, significant film wear was observed at the vane tip portion sliding with the cam and the vane side surface portion sliding with the edge portion of the rotor. In contrast, Examples 21, 22, and 24 were proved to exhibit excellent durability.

  However, micro peeling was observed on the surface of Example 22 containing 38 atomic% of chromium. This was thought to be due to the occurrence of cracks originating from the interface between the metal crystal and the amorphous material due to the local surface pressure becoming extremely large. For this reason, it is more preferable to suppress the content of the metal element in the hard coating to about half of the specified maximum amount for a sliding component in which the surface pressure is locally increased (a load is locally applied). (For example, see 0.05 to 17 atomic%, see Examples 21, 22, and 24).

1 ... sliding parts, 1 '... strip-shaped specimens, 2, 2' ... hard coating,
20, 20 '... hard protective layer, 21 ... first intermediate layer, 22 ... second intermediate layer, 23 ... third intermediate layer,
3 ... Base material, 3 '... Steel base material,
4 ... Amorphous carbon, 5a ... Compound crystal particles, 5b ... Compound crystal layer,
6 ... cylindrical test piece, 7 ... metal tube, 8 ... lubricating oil, 9 ... counter member.

Claims (10)

A sliding component used in an environment in which a lubricating oil containing a molybdenum compound coexists, and a sliding component in which a hard protective layer is formed on the outermost surface of a base material constituting the sliding component,
The hard protective layer is mainly composed of carbon, nitrogen and a metal element, and is composed of a composite of a carbon amorphous body containing nitrogen and a compound crystal of the metal element,
The compound crystal is at least one of metal carbide, metal nitride, and metal carbonitride,
A sliding component, wherein the hard protective layer has a Vickers hardness of 1800 or more. The sliding component according to claim 1,
The hard protective layer has an atomic ratio in which the total of carbon, nitrogen and the metal element is 100 atomic%, carbon is 59 atomic% or more, nitrogen is 0.1 to 35 atomic%, and the metal element is A sliding component characterized in that it is 0.05 to 38 atomic%, and the total of nitrogen and the metal element is 5 atomic% or more. In the sliding component according to claim 2,
The sliding component according to claim 1, wherein the hard protective layer further contains 25 atomic% or less of hydrogen, 18 atomic% or less of oxygen, and 5 atomic% or less of argon. In the sliding component according to any one of claims 1 to 3,
A sliding component, wherein the metal element is at least one of chromium, titanium, and tungsten. In the sliding component according to any one of claims 1 to 4,
The composite is configured by dispersing the compound crystal having a particle size of 0.1 to 100 nm in the matrix of the amorphous carbon.
A sliding component characterized in that the volume fraction of the compound crystal body in the hard protective layer is 0.08 to 76% by volume, and the number density of the compound crystal body is 10 ⁻⁶ to 10 ¹² pieces / μm ^−3. . In the sliding component according to any one of claims 1 to 4,
The composite is configured by alternately laminating the carbon amorphous layer and the compound crystal layer,
The volume ratio of the compound crystal in the hard protective layer is 30 to 76% by volume, the thickness of the compound crystal is 1 to 50 nm, and the thickness of the amorphous carbon layer is Sliding parts characterized by being 0.3 to 100 nm. In the sliding component according to any one of claims 1 to 6,
The sliding component has a plurality of intermediate layers interposed between the hard protective layer and the base material,
The plurality of intermediate layers are formed directly on the substrate and made of the metal element, and formed on the first intermediate layer and made of the metal element and the metal carbide. And a third intermediate layer formed immediately above the second intermediate layer and made of the metal carbide and the amorphous carbon. The sliding component according to any one of claims 1 to 7,
The sliding parts are arranged in a valve lifter, adjusting shim, cam, camshaft, rocker arm, tappet, piston, piston pin, piston ring, timing gear, timing chain, and oil pump arranged in the internal combustion engine. A sliding part characterized by being a drive gear, driven gear, rotor, vane, or cam. The sliding component according to any one of claims 1 to 8,
The sliding component, wherein the lubricating oil is engine oil and the molybdenum compound is molybdenum dialkyldithiocarbamate or molybdenum dithiophosphate. It is a sliding part used in an environment where a lubricant containing a molybdenum compound coexists, and a hard protective layer is formed on the outermost surface thereof, and the hard protective layer contains carbon, nitrogen and metal elements. It is composed of a composite of a carbon amorphous body containing nitrogen and the compound crystal of the metal element, the compound crystal being a metal carbide, metal nitride, or metal carbonitride. A method for producing a sliding component, wherein the hard protective layer has a Vickers hardness of 1800 or more,
The hard protective layer is formed by a reactive sputtering method using a non-equilibrium magnetron sputtering apparatus. The target material is a graphite target and a target containing one or more metal elements selected from chromium, titanium, and tungsten. A method for producing a sliding component, comprising using hydrocarbon gas and nitrogen gas as reaction gases.

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