JP4462077B2 - Combination sliding member - Google Patents

Description

  The present invention relates to a combination sliding member in which two sliding members having a coating made of an amorphous carbon material formed on the sliding surface are combined, and in particular, a combination that improves the sliding characteristics of the sliding surfaces of these members. The present invention relates to a sliding member.

  Conventionally, in a sliding member made of structural steel or steel alloy steel, a hard carbon film or an amorphous carbon (DLC) film is provided on the sliding surface in order to improve wear resistance and obtain low friction characteristics. Coating is well known.

  For example, in a sliding member obtained by combining a sliding member having an amorphous hard carbon (DLC) film on a sliding surface and a sliding member made of ceramics on the sliding surface. A sliding member having a sliding surface with a surface roughness (Ra) equal to or lower than the surface roughness (Ra) of an amorphous hard carbon film is disclosed (see Patent Document 1).

  In addition to this, as an example of a combination of sliding members to obtain the optimum characteristics of the lubricant to be used for the sliding members, both sliding surfaces with steel as the base material have the same surface hardness. A combination sliding member coated with DLC, and a combination sliding member coated with DLC only on one sliding surface are disclosed as experimental examples (see Non-Patent Documents 1 and 2).

JP 2001-280497 A Urban WIKLUND, RUNNING-IN PHENOMENA OF DLC COATINGS, Fukui University International Congress on Tribology Workshop Proceedings, 2002. 157-163 S. Jacobson, S .; Hogmark, On the tribological character of boundary lubricated DLC coated components, 28th Leeds-Lyon Symposium, Abstracts of papers, 2001. 801

  Incidentally, in recent years, automobile engines are required to have high performance by high output and high rotation. For example, in a sliding member in which a cylinder and a piston of a fuel injection part are combined, these members are downsized. On the other hand, the surface pressure acting on the sliding surface in order to achieve such high performance tends to increase. With this increase in surface pressure, oil film breakage occurs on the sliding surfaces of these members, and as a result, both the cylinder and the piston may be significantly worn or seized.

  However, as described above, even if DLC is coated on one of the sliding members to improve the wear resistance and the like, the wear resistance of the sliding member coated with the DLC is improved. It is difficult to comprehensively improve various performances such as reduction of the coefficient of friction and improvement of seizure resistance of the combined sliding members.

  Moreover, in the combination sliding member as described in the said nonpatent literatures 1 and 2, although the coefficient of friction was reduced by using DLC for the sliding surface, DLC was coat | covered on both sliding surfaces. Even in the case where DLC is coated only on one sliding surface, the friction coefficient is almost the same, and if both the sliding surfaces are simply coated with DCL, an innovative combination sliding member can be obtained. The sliding characteristics were not improved.

  The present invention has been made in view of such problems, and the object of the present invention is to reduce wear of both of the sliding members to be combined even under the severe use environment described above, and to combine this combination. An object of the present invention is to provide a combination sliding member capable of improving various characteristics such as seizure characteristics and friction characteristics of the sliding member.

  The inventors have conducted many experiments and researches to solve the above-described problems, so that both sliding surfaces of the combined sliding member are coated with an amorphous carbon material (diamond-like carbon: DLC). In order to improve the sliding characteristics, we obtained the knowledge that it is important to determine the initial surface state of the sliding surface in consideration of the initial familiarity, and as a factor for determining this initial surface state, sliding We focused on surface hardness and surface roughness.

  Then, one surface of these sliding members is made harder than the other surface, the other surface is made rougher than one surface, and the surface hardness and surface roughness of these sliding members are As a result, it has been found that sliding characteristics are improved dramatically when a predetermined numerical relationship is satisfied.

  The present invention is based on the above-mentioned new knowledge obtained by the present inventors. The combined sliding member of the present invention has a surface roughness on the sliding surface with a center line average roughness Ra of 0.05 μm or less. A surface roughness of the first sliding member on which the amorphous carbon material film is formed and the sliding surface sliding with the sliding surface of the first sliding member has a center line average roughness Ra of 0.1 μm or less. A second sliding member formed with a coating of amorphous carbon material, and the coating of the first sliding member has a higher surface hardness than the coating of the second sliding member, and the second sliding member. The film of the moving member is characterized in that the surface roughness is larger than the film of the first sliding member.

  In the combination sliding member having the surface state as in the present invention, the surface of the first sliding member is harder than the second sliding member, so the surface of the first member is not easily worn by the surface of the second sliding member. . The surface of the second sliding member is rougher than that of the first sliding member, but the surface of the second sliding member is worn out because the surface of the first sliding surface is hard and smooth. hard. Furthermore, by relatively roughening one of the surfaces in this manner, the conformability is improved, and the lubricating oil can easily enter between the sliding surfaces, the lubricity of the sliding surfaces is improved, and the wear is further increased. It becomes difficult to do.

  Because of these effects, these combined sliding members have good initial familiarity and are less likely to generate initial wear powder. The wear resistance of the sliding member is improved. Moreover, since the seizure characteristics and the friction characteristics of the combination sliding member are improved, the life of the member can be extended.

  As a method of forming a film of this amorphous carbon material, the film may be formed by physical vapor deposition (PVD) using vacuum deposition, sputtering, ion plating, etc., and plasma electrolytic treatment or the like is used. The film may be formed by chemical vapor deposition (CVD).

  Further, the surface roughness of the coating film of the first sliding member needs to be Ra 0.05 μm or less, and the surface roughness of the coating film of the second sliding member needs to be Ra 0.1 μm or less. Wear powder is generated from one of the sliding surfaces, and wear cannot be reduced. Such surface roughness can be obtained by adjusting the surface roughness of the base material of these sliding members before coating.

  Moreover, it is preferable that the surface hardness of the film of the first sliding member has a surface hardness higher by Hv400 or more than the surface hardness of the film of the second sliding member. When such a hardness difference cannot be obtained, wear of both sliding members is promoted. Furthermore, as a preferable aspect, this hardness difference is Hv500 or more.

  Further, the surface hardness of the coating film of such a sliding member is preferably in the range of Hv1000 to Hv4000. When the hardness is Hv1000 or less, wear occurs from the surface of the low hardness coating film, and the hardness is Hv4000 or more. In this case, the adhesion between the coating and the base material of the sliding member is reduced.

  Therefore, in order to satisfy the surface hardness range and the surface hardness of the coating film of the first sliding member is higher than the surface hardness of the coating film of the second sliding member by Hv400 or more, the first sliding member The surface hardness of the member coating is preferably in the range of Hv1400 to Hv4000, and the surface hardness of the coating of the second sliding member is preferably in the range of Hv1000 to Hv3600. When the hardness difference is Hv500 or more, the surface hardness of the coating on the first sliding member is in the range of Hv1500 to Hv4000, and the surface hardness of the coating on the second sliding member is in the range of Hv1000 to Hv3500.

  Further, the surface hardness of such a film can be adjusted by setting the bias voltage to a predetermined voltage when a film is formed by PVD with a bias voltage applied. it can. In addition, the surface hardness of the coating film can be adjusted by adding an additive element such as Si, Ti, Cr, Mo, Fe, or W into the amorphous carbon material.

  Furthermore, the surface roughness of the coating film of the second sliding member is set to a center line average roughness Ra that is Ra 0.005 μm or more larger than the surface roughness of the coating film of the first sliding member while satisfying the surface hardness condition. It is preferable that the wear can be reduced by providing such a difference in surface roughness.

  Furthermore, in forming this coating on the sliding member, by providing a layer made of chromium (Cr) as an intermediate layer between the base of the sliding member and this coating, the adhesion of this coating can be improved. Can be improved. Further, instead of chromium, titanium (Ti) or tungsten (W) may be used.

  Further, the film thickness of these sliding members is preferably 0.1 μm or more. If the film thickness is smaller than this film thickness, the film is quickly worn away during sliding, and the desired thickness The effect cannot be obtained.

  And when using such a sliding member for the piston ring and cylinder block which comprise an internal combustion engine, the 1st sliding member of the said combination sliding member is on the sliding surface of the piston ring of the said internal combustion engine. It is preferable to use the second sliding member of the combination sliding member on the sliding surface of the cylinder block.

  Furthermore, when using such a sliding member for the piston and cylinder constituting the mechanical device, the first sliding member of the combination sliding member is used for the sliding surface of the piston of the mechanical device, It is preferable to use the second sliding member of the combination sliding member on the sliding surface of the cylinder.

  By applying such a combination sliding member to the piston ring and cylinder block of an internal combustion engine, or the piston and cylinder of a mechanical device, it is possible to reduce wear of both parts and improve sliding characteristics. Therefore, it is possible to extend the life of these devices.

  In addition, the sliding surface of the first sliding member has a higher surface hardness and a lower surface roughness than the sliding surface of the second sliding member, and is difficult to wear. By using the piston ring and the piston whose sliding surface is always in contact with the sliding surface of the mating member, wear of both members can be further suppressed.

  According to the present invention, wear of both of the combined sliding members can be reduced, seizure characteristics, friction characteristics, etc. as the combined sliding members can be improved, and the life of the entire member can be extended. Can do.

  Hereinafter, the present invention will be described by way of examples.

Example 1
As a first sliding member, a 16 mm × 6 mm × 10 mm dice test piece was manufactured from a rod of stainless steel (JIS standard SUS440C, quenched product, surface hardness Hv500). The surface roughness of this dice test piece is adjusted so that the center line average roughness Ra is 0.007 μm, and an unbalanced magnetron sputtering apparatus (manufactured by Kobe Steel) is used. A film made of an amorphous carbon material (DLC) was formed. As a film forming condition of this film, a gas obtained by mixing 5% by volume of methane (CH ₄ ) with argon (Ar) is used as a flow gas, and an atmospheric temperature is set to 100 ° C. and a bias voltage of 100 V is applied to the dice specimen. Then, by making the graphite target into sputtered particles, as shown in Table 1, the DLC film surface hardness: 2000 Hv, and the surface roughness Ra (center line average roughness) 0.01 μm, the particles were tested. A DLC film having a thickness of 1.5 μm was formed.

On the other hand, a cylindrical test piece having an outer diameter of 35 mm, an inner diameter of 30 mm, and a width of 10 mm was manufactured from a rod of stainless steel (JIS standard SUS440C, quenched product, surface hardness Hv500) as the second sliding member. The surface roughness of the dice test piece (base material) was adjusted so that the center line average roughness Ra was 0.015 μm, and a film made of DLC was formed on the surface by plasma CVD. Specifically, film forming raw material gas: acetylene (C ₂ H ₂ ), film forming pressure: 0.5 × 10 ⁻² Torr, high frequency power: 2 kW, applied voltage frequency: 2.5 GHz, power applied electrode As shown in Table 1, a DLC film with a thickness of 1.5 μm is formed so that the surface hardness is 1500 Hv and the surface roughness Ra (centerline average roughness) is 0.016 μm, depending on the film formation conditions of temperature: 500 ° C. did.

  FIG. 1 also shows the difference in surface hardness (hardness difference) and the difference in surface roughness (roughness difference) between the two specimens. The difference in surface hardness is the surface hardness of the dice specimen. Is a value obtained by subtracting the surface hardness of the cylindrical test piece, and the difference in surface roughness is a value obtained by subtracting the surface roughness of the dice test piece from the surface roughness of the cylindrical test piece.

(Example 2)
A first sliding member and a second sliding member were produced in the same manner as in Example 1. The difference from Example 1 is that the bias voltage under the above film formation conditions, the high frequency power, and the surface roughness of the base material of each sliding member before this coating is formed are adjusted as shown in Table 1. The surface hardness of the sliding member (dice test piece) is Hv3000, the surface roughness Ra is 0.02 μm, the surface hardness of the second sliding member (cylindrical test piece) is Hv2000, and the surface roughness Ra is 0.03 μm. The point is that a coating is formed on each sliding member.

  A wear test was performed on the combination sliding members of Examples 1 and 2. Specifically, the 16 mm × 6 mm surface of the DLC-coated dice test piece is brought into contact with the outer peripheral surface of the cylindrical test piece coated with DLC, and lubricating oil (SAE5W-30) is applied to the contacted sliding surface. While supplying oil, a continuous test was performed for 30 minutes under the conditions of a load of 30 kgf and a rotational speed of the cylindrical test piece of 160 rpm. Then, the wear scar depth of the dice test piece and the wear weight of the cylindrical test piece were measured, and these measured values were used as the respective wear amounts. Furthermore, the friction coefficient μ of these combination sliding members at the time of the wear test was also measured at the same time. The test results are shown in FIG.

  As shown in FIG. 1, the wear amount of the dice test pieces of Example 1 and Example 2 is about 0.5 μm, the wear amount of the cylindrical test piece is 0.35 mg, and the friction coefficient is 0.05. There was almost no difference in the results.

(Comparative Example 1)
A first sliding member and a second sliding member were produced in the same manner as in Example 1. The difference from Example 1 is that the high-frequency power, which is the film forming condition of the second sliding member, is set to 2.5 kW, and the surface roughness of the base material of each sliding member before this coating is formed is adjusted. As shown in Table 1, each sliding member was coated with a DLC coating so that the surface hardness of the second sliding member (cylindrical test piece) was Hv2000 and the surface roughness Ra was 0.01 μm.

(Comparative Example 2)
Similar to Example 2, a first sliding member and a second sliding member were produced. The difference from Example 2 is that the surface roughness of the base material of each sliding member before coating the coating is adjusted, and as shown in Table 1, the surface roughness of the second sliding member (cylindrical test piece). The DLC film is formed on the sliding member so that Ra is 0.02 μm.

(Comparative Example 3)
A first sliding member and a second sliding member were produced in the same manner as in Example 1. The difference from Example 1 is that, as shown in Table 1, the second sliding member (cylindrical test piece) is not coated with the DLC film, the surface hardness is Hv500, and the surface roughness Ra is 0.016 μm. This is the point where the surface of this sliding surface is processed.

(Comparative Example 4)
A first sliding member and a second sliding member were produced in the same manner as in Example 1. The difference from Example 1 is that the surface roughness of the base material of each sliding member before forming the coating is adjusted, and as shown in Table 1, the surface roughness Ra0 of the first sliding member (dice test piece). The DLC film is formed on each sliding member so that the surface roughness Ra of the second sliding member (cylindrical test piece) is 0.12 μm.

  These Comparative Examples 1 to 4 were subjected to the same wear test as in Example 1, and the wear amount and friction coefficient of each test piece were obtained. The result is shown in FIG.

  As shown in FIG. 1, both the dice test piece and the cylindrical test piece of Comparative Examples 1 to 4 had a larger amount of wear and a higher friction coefficient than Examples 1 and 2.

(Evaluation 1)
When Example 1 and Comparative Example 1 are compared, as in Comparative Example 1, a dice test piece as in Example 1 is compared to a case in which the surface hardness and surface roughness of the dice test piece and cylindrical test piece are the same. It is considered that the wear amount of the test piece is reduced when a difference (500 Hv) is provided in the surface hardness Hv between the test piece and the cylindrical test piece and a difference (roughness difference Ra 0.006) is provided in the surface roughness Ra. .

  That is, when at least one of the conditions of making one surface of the sliding member harder than the other surface or making the other surface rougher than the one surface is satisfied, Abrasion resistance is thought to improve.

(Evaluation 2)
When Example 2 and Comparative Example 2 are compared, even if a difference (hardness difference 1000 Hv: the same hardness difference as Example 2) is provided in the surface hardness between the dice test piece and the cylindrical test piece as in Comparative Example 2. If there is no difference in the surface roughness between the dice test piece and the cylindrical test piece, it is considered that the wear amount of the test piece is not reduced as in Example 2.

  From the above Evaluation 1 and Evaluation 2, when the two conditions of making one surface of the sliding member harder than the other surface and making the other surface rougher than the other surface are simultaneously satisfied Only the wear resistance of the sliding member is considered to be improved.

(Evaluation 3)
Furthermore, when Example 1 and Comparative Example 4 are compared, as in Comparative Example 4, even if the surface hardness of the dice test piece and the cylindrical test piece is the same as that of Example 1, the absolute value of the dice test piece and the cylindrical test piece is the same. If the surface roughness is too large, a large amount of DLC wear powder is generated due to the abrasive wear, and it is considered that the wear is not reduced.

  Therefore, from Comparative Example 4, the surface roughness of the dice test piece is preferably smaller than Ra 0.06 μm, and the roughness of the cylindrical test piece is preferably smaller than Ra 0.12 μm. Further, it is estimated that the surface roughness of the more preferable dice test piece is Ra 0.05 μm or less, and the roughness of the cylindrical test piece is Ra 0.1 μm or less.

(Evaluation 4)
When Example 1 and Comparative Example 3 are compared, as in Comparative Example 3, even if the surface roughness of the dice test piece and the cylindrical test piece is the same as that of Example 1, the cylindrical test piece that does not form a DLC film is shown. Since the surface hardness is too low (Hv500), it is considered that the wear amount was large.

  From this, it is considered that a surface hardness of Hv1000 to Hv4000 can be obtained by coating the sliding surface with DLC. Therefore, it is considered that a difference in surface hardness should be provided within this hardness range. That is, if the surface hardness is Hv 1000 or less, this low hardness surface is worn, and even if a surface hardness of Hv 4000 or more is obtained by forming a coating, it is generally considered that the adhesion of the coating is deteriorated. ing.

(Evaluation 5)
From such evaluations 1 to 4, the coating of the first sliding member has a higher surface hardness than the coating of the second sliding member, and the coating of the second sliding member is the coating of the first sliding member. It has been found that wear of the sliding member is reduced by increasing the surface roughness. And from the hardness difference of Example 1 and Example 2 as shown in Table 1, the surface hardness of the coating of the first sliding member is higher by about Hv400 or more than the surface hardness of the coating of the second sliding member. It is estimated that the surface hardness is good, and more preferably, the hardness difference is considered to be Hv500 or more.

  Further, it is estimated that the surface roughness of the coating film of the second sliding member should be a large center line average roughness Ra of about Ra0.005 μm or more compared to the surface roughness of the coating film of the first sliding member. More preferably, the roughness difference is considered to be Ra 0.006 μm or more.

  The combination sliding member of this embodiment has a high sliding frequency and a high surface pressure on the sliding surface, such as a combination sliding part consisting of an engine piston ring and a cylinder block, and a combination sliding part consisting of a cylinder and a piston. It is particularly suitable for sliding members used in the environment.

The figure which showed the abrasion test result of the combination sliding member of an Example, and the combination sliding member of a comparative example.

Claims (3)

The sliding surface, a first slide member formed with the amorphous carbon material coating,
The sliding surface of the sliding surface and the sliding of the first sliding member comprises a second slide member formed with the amorphous carbon material coating, and
The coating of the first sliding member has a higher surface hardness than the coating of the second sliding member, and the coating of the second sliding member has a surface that is higher than the coating of the first sliding member. The roughness is large,
The surface hardness of the coating of the first sliding member is in the range of Hv1400 to Hv4000, the surface hardness of the coating of the second sliding member is in the range of Hv1000 to Hv3600, and the coating of the first sliding member surface hardness of the than the surface hardness of the coating of the second sliding member, have a high surface hardness than Hv 400,
The surface roughness of the film of the first sliding member is a center line average roughness Ra of 0.05 μm or less, and the surface roughness of the film of the second sliding member is a center line average roughness Ra of 0.1 μm or less, The surface roughness of the coating of the second sliding member has a center line average roughness Ra that is Ra 0.005 μm or more larger than the surface roughness of the coating of the first sliding member.
A combination sliding member characterized by that. 2. An internal combustion engine using the combination sliding member according to claim 1, wherein a first sliding member of the combination sliding member is used on a sliding surface of a piston ring constituting the internal combustion engine, and a cylinder block. An internal combustion engine characterized in that a second sliding member of the combination sliding member is used on the sliding surface. A mechanical device using the combination sliding member according to claim 1, wherein a first sliding member of the combination sliding member is used on a sliding surface of a piston constituting the mechanical device, and a cylinder sliding member is formed. A mechanical device characterized in that a second sliding member of the combination sliding member is used on a moving surface.

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