JP5640942B2 - Sliding member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sliding member coated with an amorphous carbon coating, and more particularly to a sliding member excellent in wear resistance.

  Conventionally, sliding members are used in various devices such as engines and transmissions in automobiles. There, various research and developments are underway to reduce the sliding resistance of the sliding member to reduce energy loss and to meet future fuel efficiency regulations for protecting the global environment.

  For example, one such research and development is a technique for coating the sliding surface in order to improve the wear resistance of a sliding member made of structural steel or high alloy steel and to obtain low friction characteristics. is there. In recent years, amorphous carbon materials such as nanodiamond particle-like carbon (DLC) have attracted attention as this coating material. The film on which the amorphous carbon material is formed (amorphous carbon film) is a hard film mainly composed of carbon, and since the carbon of the hard film also acts as a solid lubricant, it has a low sliding property. It is a coating that can achieve both dynamic resistance and high wear resistance.

  For example, as such a technique, a sliding member in which an amorphous carbon film contains a metal such as Ag, Mg, In, or Sn has been proposed (see, for example, Patent Document 1). As another technique, a combination of a first sliding member coated with an amorphous carbon film and a second sliding member made of an iron-based metal has been proposed (see, for example, Patent Document 2).

JP 2007-177313 A JP 2004-176848 A

  However, when the sliding member described in Patent Document 1 is repeatedly slid with respect to the mating member in the lubricating oil, significant wear may occur on the sliding surface. In particular, when applied to a cylinder bore and piston ring for an internal combustion engine, a cylinder and a piston constituting a fuel injection valve, etc., these members are smaller and have higher surface pressure than other members. Due to the use of various fuels and the like, the oil film is easily cut between the sliding member and the counterpart member, and as a result, significant wear may occur on both sides.

  In recent years, the performance of automobile engine parts has been greatly improved due to higher output and higher rotation. In the sliding member used in the above-described engine, the surface of the base material of the sliding member is disclosed in Patent Document 2, for example. In addition, sufficient sliding characteristics may not be obtained by simply coating an amorphous carbon film.

  In view of such a point, the present invention aims to cover the surface of the base material with an amorphous carbon coating, which is used as a sliding member with high surface pressure and high sliding frequency. An object of the present invention is to provide a sliding member that can suppress wear of the amorphous carbon film on the surface even if it is used.

  As a result of intensive studies, the inventors have obtained the following knowledge. Specifically, in the technique described in Patent Document 1, metals such as Ag, Mg, In, and Sn are added to the amorphous carbon film. However, in this technique, these metals are added to the sliding member. This is because it is difficult to be compatible with commonly used metal materials. As a result, adhesion is less likely to occur when the amorphous carbon coating containing these metal elements and the mating member slide. That is, when these metals are used, adhesion wear with the mating member can be suppressed.

  However, as described above, when a higher load than before is applied to the sliding surface, such characteristics alone are not sufficient, and the inventor has determined that the amorphous carbon coating and the mating member It was considered desirable to increase the surface slipperiness and the strength of the amorphous carbon coating. Therefore, the inventor has focused on Bi (bismuth) as an element that is more ductile and malleable than the above-described metal and that suppresses a decrease in strength of the coating even when contained in an amorphous carbon coating. Then, this Bi is clustered and contained in the amorphous carbon coating, so that the strength of the amorphous carbon coating is kept to the same level as before, and when sliding, this Bi becomes the amorphous carbon coating. The new knowledge that it extended to the surface and can improve the abrasion resistance of a sliding member epoch-making by this was acquired.

  The present invention is based on the inventor's new knowledge, and the sliding member according to the present invention is a sliding member in which an amorphous carbon film is formed on the surface of a substrate, In the carbonaceous film, Bi clusters are dispersed.

  According to the present invention, since the cluster (that is, particles) made of Bi is dispersed in the amorphous carbon coating, the surface on which the amorphous carbon coating is formed is used as a sliding surface, and the relative member Is slid, a Bi thin film having low shearing properties is formed on the surface of the amorphous carbon coating. With this Bi thin film, the shear resistance between the sliding member and the mating member can be reduced, the wear resistance of the sliding member can be improved, and the friction coefficient can be lowered.

  In this way, when the coating made of Bi is formed on the surface of the amorphous carbon coating so as to improve the wear resistance during sliding and further reduce the friction coefficient, Bi is particularly preferable. The content of is not limited. However, it is more preferable that Bi is contained in an amount of 0.5 to 20 at% (atomic%) with respect to the amorphous carbon film.

  According to the present invention, by containing Bi so as to be in such a range, a Bi thin film is formed on the surface of the amorphous carbon coating during sliding, and more reliably wear resistance of the sliding member. The friction coefficient can be lowered.

  That is, when the Bi content exceeds 20 at%, the hardness of the amorphous carbon coating film may be lowered, and thereby the sliding characteristics of the sliding member are lowered. On the other hand, when the Bi content is less than 0.5 at%, the improvement of the sliding characteristics by Bi may not be sufficient.

  According to the present invention, even if the surface of the base material is coated with an amorphous carbon coating, and this is used as a sliding member with a high surface pressure and a high sliding frequency, Wear can be suppressed.

The typical conceptual diagram of the sliding member which concerns on embodiment of this invention. The figure which showed the result of the abrasion test of the sliding member which concerns on Example 1, the comparative example 1, and the comparative example 2. FIG.

  The following embodiments of the present invention will be described. FIG. 1 is a schematic conceptual view of a sliding member according to an embodiment of the present invention.

  First, as shown in FIG. 1, a base member 10 of a sliding member is prepared. Examples of the base material 10 include carbon steel (JIS: S45C, S30C, etc.), alloy steel such as chromium steel, chromium molybdenum steel (JIS standard: SCr, SCM, etc.), alloy tool steel (JIS standards: SKS, SKD, etc.). ), Special purpose steels such as stainless steel, bearing steel, and spring steel (JIS standards: SUS, SUJ, SUP, etc.), or iron-based substrates of cast iron. However, it is not limited to these metal materials as long as the adhesion with the amorphous carbon film 20 to be described later can be secured, and for example, an aluminum alloy containing aluminum, Cu, Mg, Zn or the like , Copper, or a metal material such as a copper alloy containing Zn, Al, Sn, or the like.

  Next, an amorphous carbon coating 20 is coated on the surface of the substrate 10. Specifically, the substrate 10 is formed by physical vapor deposition (PVD) using sputtering, vacuum vapor deposition, ionized vapor deposition, ion plating, or the like.

  More specifically, as an example of film formation by a sputtering method, a carbon target and a Bi target are prepared, and an inert gas such as argon is simultaneously accelerated and irradiated to these targets.

  Thereby, the atoms or molecules on the surfaces of the carbon target and the Bi target are discharged, and these are vaporized by a physical action, whereby the amorphous carbon film 20 is formed on the surface of the substrate 10. In this way, it is possible to obtain the sliding member 1 in which the surface of the base material 10 is coated with the amorphous carbon coating 20 in which Bi clusters 21, that is, Bi particles are dispersed.

  Since the cluster (Bi particles) 21 made of Bi are dispersed in the amorphous carbon coating 20 of the sliding member 1, the surface on which the amorphous carbon coating 20 is formed is used as a sliding surface. When the mating member is slid, a Bi thin film having low shearing properties is formed on the surface of the amorphous carbon coating 20. With this Bi thin film, the shear resistance between the sliding member 1 and the mating member can be reduced, the wear resistance of the sliding member 1 can be improved, and the friction coefficient can be lowered.

  In the present embodiment, Bi is contained in an amount of 0.5 to 20 at% (atomic%) in a cluster state with respect to the amorphous carbon film 20. In the case of forming a film by sputtering, Bi can be contained in such a range by adjusting the target power (voltage × current) with respect to the Bi target.

  And by containing Bi with respect to the amorphous carbon film 20 so that it may become the range of 0.5-20 at%, the Bi thin film is formed in the surface of the amorphous carbon film 20 at the time of sliding, and more Certainly, the wear resistance of the sliding member can be improved and the friction coefficient can be lowered.

  That is, when the Bi content exceeds 20 at%, the hardness of the amorphous carbon coating 20 may be lowered, and thereby the sliding characteristics of the sliding member 1 are lowered. On the other hand, when the Bi content is less than 0.5 at%, the improvement of the sliding characteristics of the sliding member 1 by Bi may not be sufficient. It is more preferable that Bi is 1.0 at% or more in a cluster state with respect to the amorphous carbon film 20.

  The size of the cluster made of Bi is preferably 200 nm or less. When it exceeds 200 nm, the hardness of the amorphous carbon coating 20 is lowered, and as a result, this strength is lowered.

  Further, when the amorphous carbon film 20 is formed, together with the inert gas described above, for example, a hydrocarbon gas such as methane gas or acetylene gas is introduced, and the hydrocarbon gas is decomposed by discharge to contain hydrogen. An amorphous carbon film 20 may be formed.

  Thereby, in addition to the cluster 21 which consists of Bi, the amorphous carbon film 20 contains a hydrogen atom, Therefore The obtained sliding member can express the further low friction characteristic. Here, the hydrogen content with respect to the amorphous carbon coating 20 is preferably more than 0 at% and not more than 35 at%. When the hydrogen content exceeds 35 at%, the amorphous carbon film 20 is amorphous carbon. There exists a possibility that the intensity | strength of the film 20 may fall.

  Therefore, in order to express such an effect more efficiently, the hydrogen content in the amorphous carbon coating 20 is more preferably 5 to 25 at%. By containing hydrogen in such a range, it is possible to exhibit further low friction characteristics of the sliding member and to secure the strength of the amorphous carbon coating.

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

Example 1
As a base material of the sliding member, a 16 mm × 6 mm × 10 mm dice test piece (surface roughness Ra 0.1 μm) was prepared from a rod of stainless steel (JIS standard: SUS440C, hardened product, surface hardness Hv500). . Next, an amorphous carbon film in which clusters of Bi were dispersed was formed on the surface constituting 16 mm × 6 mm of this dice test piece by an unbalanced magnetron sputtering method.

Specifically, using a graphite target and a Bi target, a base material (dice test piece) was placed in the processing chamber, and the base material temperature was set to 100 ° C. Next, a gas containing 5% by volume of CH ₄ (methane) in Ar as a reaction gas was allowed to flow into the processing chamber, a bias voltage on the graphite target side was applied by 100 V, and a bias voltage on the Bi target side was applied by 80 V.

  As a result, the surface of the substrate was coated with an amorphous carbon film having a thickness of 1.5 μm, and a sliding member corresponding to the present invention was obtained. The surface roughness of the obtained amorphous carbon film is Ra 0.12 μm, the surface hardness is Hv2000, the Bi content is 5 at%, the size of the cluster composed of Bi is 50 nm, and the hydrogen content is 10 at%.

(Comparative Example 1)
A sliding member was produced in the same manner as in Example 1. The difference from the first embodiment is that no Bi target is used. That is, in the case of the comparative example 1, it is carried out on the surface constituting a 16 mm × 6 mm × 10 mm dice test piece (JIS standard: SUS440C, quenched product, surface hardness Hv500, surface roughness Ra 0.1 μm). Under the same conditions as in Example 1, an amorphous carbon film not containing Bi was coated by using an unbalanced magnetron sputtering method using only a carbon target.

  Thereby, the sliding member which coat | covered the amorphous carbon film with a film thickness of 1.5 micrometers on the base-material surface was obtained. The obtained amorphous carbon coating had a surface roughness Ra of 0.12 μm, a surface hardness of Hv2100, and a hydrogen content of 10 at%.

(Comparative Example 2)
A sliding member was produced in the same manner as in Example 1. The difference from the first embodiment is that an Au target is used instead of the Bi target. That is, in the case of the comparative example 2, it is carried out on the surface constituting a 16 mm × 6 mm × 10 mm dice test piece (JIS standard: SUS440C, quenched product, surface hardness Hv500, surface roughness Ra 0.1 μm). Under the same conditions as in Example 1, an amorphous carbon film containing Au in the form of clusters was coated with a carbon target and an Au target by an unbalanced magnetron sputtering method.

  Thereby, the sliding member which coat | covered the amorphous carbon film with a film thickness of 1.5 micrometers on the base-material surface was obtained. The surface roughness of the obtained amorphous carbon film was Ra 0.12 μm, the Au content was 5 at%, the size of the cluster made of Au was 80 nm, and the hydrogen content was 15 at%.

<Abrasion test>
A cylindrical test piece having an outer diameter of 35 mm, an inner diameter of 30 mm, and a width of 10 mm was produced using stainless steel (JIS standard: SUS440C) as a counterpart member of the sliding members of Example 1, Comparative Example 1, and Comparative Example 1. The surface roughness of the peripheral surface of the obtained cylindrical test piece was Ra 0.20 μm, and the surface hardness was Hv380.

  Then, the surface of 16 mm × 6 mm (that is, the surface coated with the amorphous carbon film) of the sliding member (dice test piece) of each of Examples, Comparative Example 1 and Comparative Example 2, and the cylindrical test piece An abrasion test was performed in which a cylindrical test piece was rotated for 30 minutes under the conditions of a load of 60 kgf and a rotation speed of 160 rpm while contacting the outer peripheral surface and supplying lubricating oil (SAE5W-30). The result is shown in FIG. The wear amount of the dice test piece corresponding to the sliding member shown in FIG. 2 is the wear scar depth, and the wear amount of the cylindrical test piece is the wear weight.

[Result 1 and discussion]
As shown in FIG. 2, in the case of Example 1, the amount of wear of each of the dice test piece (sliding member) and the cylindrical test piece (counter member) was less than that of Comparative Example 1. This result is considered to be because the sliding member of Example 1 contained a cluster of Bi dispersed in the amorphous carbon film. That is, in the case of Example 1, since the cluster (Bi particle | grains) which consists of Bi is disperse | distributing in the amorphous carbon film, on the surface of an amorphous carbon film at the time of sliding, it is very thin low shear property A Bi thin film having the structure was formed. Thereby, it is considered that the shear resistance between the sliding member and the mating member was reduced, the wear resistance as compared with Comparative Example 1 was improved, and the friction coefficient was reduced.

  Further, the amount of wear of the dice test piece (sliding member) of Example 1 was less than that of Comparative Example 2. The result is that the sliding member of Comparative Example 2 contains a cluster of Au dispersed in the amorphous carbon coating, but when Au is used, Bi is used. The surface hardness of the amorphous carbon coating is lower than when used. As a result, the sliding member of Comparative Example 2 is considered to have increased the amount of wear compared to that of Example 1. From the above, it is considered that Bi is optimal as an element to be included as a cluster in the amorphous carbon coating in order to improve the sliding characteristics of the sliding member.

(Example 2)
A sliding member was produced in the same manner as in Example 1. The difference from Example 1 is that the amount of Bi contained in the amorphous carbon coating was changed as shown in Table 1 below. Specifically, the Bi content was changed by changing the voltage applied to the Bi target when the amorphous carbon film was formed. And the abrasion test was done like Example 1. FIG. The results are shown in Table 1. In addition, the value of the friction coefficient shown in Table 1 is the value of the friction coefficient immediately after 30 minutes from the start of the wear test. Table 1 also shows the results of a friction test of a sliding member (a sliding member corresponding to Comparative Example 1) that does not contain Bi clusters (Bi content: 0 at%).

(Comparative Example 3)
A sliding member was produced in the same manner as in Example 2. The difference from Example 2 is that the Au target was used as in Comparative Example 2, and the amount of Au contained in the amorphous carbon coating was changed as shown in Table 1 below. It is. Specifically, when the amorphous carbon film was formed, the voltage applied to the Au target was changed to change the Au content. And the abrasion test was done like Example 2. FIG. The results are shown in Table 1. Table 1 also shows the results of a friction test of a sliding member (a sliding member corresponding to Comparative Example 1) that does not contain Au clusters (Au content: 0 at%).

[Result 2 and discussion]
As shown in Table 1, it was found that the dice test piece (sliding member) of Example 2 had a smaller amount of wear and a lower friction coefficient than those of Comparative Example 3. This is considered to be the same reason as shown in the discussion of result 1. Further, it can be seen that by containing Bi in a cluster state in the amorphous carbon coating, the wear amount of the dice test piece and the wear amount of the cylindrical test piece are reduced, and the friction coefficient is also lowered.

  As is apparent from Table 1, when Bi is contained in an amount of 0.5 to 20 at% in a cluster state with respect to the amorphous carbon coating, the wear amount of the dice test piece and the cylindrical test piece It is considered that the amount of wear is further reduced and the friction coefficient is further reduced.

  This is presumably because when the Bi content exceeds 20 at%, the hardness of the amorphous carbon coating is lowered, thereby increasing the wear amount of the die test piece. As a result, the wear amount of the cylindrical test piece which is the counterpart member also increased, and as a result, the friction coefficient is considered to have increased.

  On the other hand, when the content of Bi is less than 0.5 at%, the Bi coating may not be sufficiently formed due to the Bi cluster. It is thought that the amount of wear of the specimen increased. As a result, the friction coefficient is considered to have increased.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed.

1: sliding member, 10: base material, 20: amorphous carbon coating, 21: cluster

Claims (1)

A sliding member having an amorphous carbon film formed on the surface of a substrate,
In the amorphous carbon film, clusters of Bi are dispersed ,
A sliding member comprising 0.5 to 20 at% Bi relative to the amorphous carbon coating .

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