JP2014098184A - Slide member having multilayer dlc film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide member having a multilayer DLC film excellent in both characteristics of adhesion and abrasion resistance.SOLUTION: In a slide member, a multilayer diamond-like carbon (DLC) film composed of a ground layer comprising Cr, a gradient layer containing Cr and carbon, and a Cr-DLC monolayer or a Cr-DLC laminate containing Cr and DLC is formed on the surface of a metal substrate, and the gradient layer has a gradient composition in which the Cr content rate is gradually reduced and the carbon content rate is gradually increased in proportion to the distance from the surface of the metal substrate.

Description

  The present invention relates to a sliding member having a multi-layer diamond-like carbon film on the sliding surface, which is particularly suitable for protecting the surface of a member that requires wear resistance.

Diamond-like carbon (hereinafter referred to as DLC) is an amorphous hard film mainly composed of carbon and hydrogen, and has excellent hardness characteristics, wear resistance, solid lubricity, thermal conductivity and chemical stability. Since it has the characteristic of having a low friction coefficient, it has a great effect on the surface modification of various members that require such a characteristic. Therefore, DLC is used as a surface layer of various members such as sliding members, wear-resistant machine parts, cutting tools, and the like.
However, DLC has a problem that peeling easily occurs at an interface with a metal serving as a base material, and various techniques for improving adhesion with the base material have been proposed.
For example, in Patent Document 1, as a technique for improving adhesion to a base material, a first layer made of a Cr and / or Al metal, a Cr and / or Al metal, and carbon are formed on an iron base material. There has been proposed a hard multilayer film forming body in which an intermediate layer having a two-layer structure including a second layer including an amorphous layer is provided and a DLC film is formed thereon as an outermost surface layer.

JP 2002-256415 A

  As described above, DLC has excellent properties such as high hardness and a low friction coefficient, but adhesion with a base material is weak in film formation by an existing process, and even in the technique proposed in Patent Document 1, it is a high surface. It cannot be said that the wear resistance is always realized under the reduction, and the DLC film forming technique having both high adhesion and wear resistance is still required for the sliding member to which the DLC film is applied.

  This invention is made | formed in view of such a condition, Comprising: It aims at providing the sliding member which has the multilayer DLC film excellent in the characteristic of both adhesiveness and abrasion resistance.

  As a result of intensive studies in order to achieve the above object, the present inventors provided a Cr metal layer (underlying layer), an inclined layer containing Cr and carbon on the surface of the metal substrate, By providing a Cr-DLC single layer or the Cr-DLC laminated layer as a layer made of Cr and diamond-like carbon on the uppermost layer portion that becomes the contact surface of this, a slide having a multilayer DLC film excellent in both adhesion and wear resistance is provided. As a result, the present invention has been completed.

That is, the present invention provides a surface of a metal substrate.
An underlayer made of Cr, a graded layer containing Cr and carbon, and a Cr-DLC single layer containing Cr and diamond-like carbon (DLC) and the Cr content does not vary substantially over the thickness of the layer A multilayer DLC film, or
Forming a multi-layer DLC film composed of a Cr-DLC laminate in which an underlayer made of Cr, a gradient layer containing Cr and carbon, and a Cr layer made of Cr and a DLC layer made of DLC are alternately stacked;
The gradient layer relates to a sliding member having a gradient composition in which the Cr content gradually decreases and the carbon content gradually increases as the distance from the surface of the metal substrate increases.

  The sliding member of the present invention is a low-hardness DLC layer having a hardness of less than 20 GPa between the gradient layer and the Cr-DLC single layer or the Cr-DLC laminate, as measured by a nanoindenter measurement method. May be further formed.

Moreover, the sliding member of this invention WHEREIN: It is preferable that the said Cr-DLC single layer or the said Cr-DLC lamination | stacking has Cr content rate of 2-12 atomic%.
Furthermore, it is preferable that the Cr-DLC stack has a thickness of 6 nm or more and 8 nm or less per cycle of the Cr layer-DLC layer.
And it is more preferable that the said Cr-DLC single layer or the said Cr-DLC lamination | stacking has a surface hardness of 20 GPa or more by the measurement according to a nanoindenter measurement method.

  ADVANTAGE OF THE INVENTION According to this invention, the sliding member in which the multilayer DLC film which was excellent in the adhesiveness with a metal base material and satisfy | filled the characteristics of both hardness and abrasion simultaneously was formed can be provided.

FIG. 1 is a conceptual diagram showing the structure of a multilayer DLC film according to the present invention, in which the uppermost layer portion is a Cr-DLC single layer (FIG. 1A), and the uppermost layer portion is a Cr-DLC laminate. It is a figure which shows a thing (FIG.1 (b)). FIG. 2 is a conceptual diagram showing the structure of a multilayer DLC film including a low-hardness DLC layer according to the present invention, in which the uppermost layer portion is a Cr-DLC single layer (FIG. 2 (c)), and the uppermost layer portion is It is a figure which shows what is a Cr-DLC lamination | stacking (FIG.2 (d)). FIG. 3 is a conceptual diagram of a magnetron sputtering apparatus that can be used in the present invention. FIG. 4 is a view showing a scanning electron microscope (SEM) photograph of the Cr-DLC stack in Comparative Example 1 (the stack cycle of the DLC layer—Cr layer in the uppermost layer is set to 12 nm) (magnification of 300,000 times). . FIG. 5 is a view showing a scanning electron microscope (SEM) photograph of a Cr-DLC single layer in Example 3 (the DLC layer-Cr layer stacking period in the uppermost layer is set to 2 nm) (magnification of 300,000 times) ). FIG. 6 shows carbons by etching depth (□) from the outermost surface of the Cr-DLC stack toward the inside (base material side) in Example 4 (the DLC layer-Cr layer stacking period in the uppermost layer is set to 6 nm). It is a figure which shows the content rate of Cr) (). FIG. 7 shows the etching depth according to the etching depth from the outermost surface of the Cr-DLC single layer to the inside (base material side) in Example 2 (the DLC layer-Cr layer stacking period in the uppermost layer is set to 0.6 nm). It is a figure which shows the content rate of carbon (□) and Cr (▲). FIG. 8 is a graph showing the surface hardness of the sliding member with respect to the lamination period (nm) of the DLC layer-Cr layer in the uppermost layer portion in Examples 1 to 4 and Comparative Example 1. FIG. 9 is a graph showing the specific wear amount at a surface pressure of 1.3 GPa with respect to the lamination cycle of the DLC layer-Cr layer in the uppermost layer in Examples 1 to 8 and Comparative Examples 1 to 3 and Comparative Example 5. It is. FIG. 10 shows the specific wear at a surface pressure of 1.3 GPa with respect to the lamination period of the DLC layer-Cr layer in the uppermost layer in Examples 1 to 8 and Comparative Examples 1 to 3 and Comparative Example 5. It is a graph (what changed the scale of the vertical axis | shaft of FIG. 9) which shows quantity.

Examples of the sliding member targeted by the present invention include a sliding bearing, a rolling bearing, a roller, a pulley, and a linear guide. The sliding member has not only a sliding surface by sliding but also a rolling sliding surface with rolling and sliding. Members are also included.
Such sliding members are made of metal materials usually used for machine parts such as iron-based materials such as carbon steel, bearing steel and stainless steel, copper alloys, aluminum alloys and titanium alloys. When a DLC layer having a high hardness is formed on the sliding surface of the moving member, specifically, when a DLC layer having a hardness of 20 GPa or more according to the nanoindenter measurement method (ISO 14577) is formed, the metal material and the DLC The problem of poor adhesion with the layer arises. On the other hand, when a low hardness DLC layer having a hardness of less than 20 GPa is formed, the adhesion is improved, but the problem is that the amount of wear increases.
In consideration of these problems, the present inventors have devised a structure of a sliding member having a multilayer DLC film that achieves both good wear characteristics and good adhesion as follows.
Hereinafter, the present invention will be described in more detail.

The present invention is a sliding member provided with a multi-layer DLC film on the surface of a metal substrate, the multi-layer DLC film comprises a base layer made of Cr from the metal substrate side, a gradient layer containing Cr and carbon, Then, as the uppermost layer portion that becomes the contact surface with the sliding member, a Cr-DLC single layer containing Cr and diamond-like carbon (DLC) and having a Cr content that does not substantially change over the thickness of the layer. Or a Cr layer made of Cr as an uppermost layer portion that becomes a contact surface with the sliding member, and an underlayer made of Cr from the metal substrate side, an inclined layer containing Cr and carbon, It is characterized by comprising a Cr-DLC stack in which DLC layers made of DLC are alternately stacked.
The gradient layer has a gradient composition in which the Cr content gradually decreases and the carbon content gradually increases as the distance from the surface of the metal substrate increases.

1 and 2 are conceptual diagrams showing the structure of a multilayer DLC film according to the present invention.
As shown to Fig.1 (a), the structure of the said multilayer DLC film | membrane forms the base layer, inclination layer, and Cr-DLC single layer which consist of Cr100% in order on a metal base material. Further, as shown in FIG. 1B, a base layer, an inclined layer, and a Cr-DLC stack in which a DLC layer and a Cr layer are alternately stacked may be formed.
A low-hardness DLC layer can be formed between the gradient layer and the Cr-DLC single layer or the Cr-DLC stack (FIGS. 2C and 2D).

  The metal substrate is not particularly limited, and materials usually used for machine parts, such as iron-based materials such as carbon steel, bearing steel, and stainless steel, copper alloys, aluminum alloys, and titanium alloys can be used. .

The gradient layer is composed of Cr and carbon, and the Cr content is stepped from the lower metal substrate side (underlayer side) toward the uppermost Cr-DLC single layer or Cr-DLC laminate. Or continuously decreasing, i.e. Cr atomic percent decreases from 100% to 0%, while carbon content decreases stepwise or continuously, i.e. carbon atomic percent decreases from 0% to 100%. With a gradient composition.
By adopting such a composition of graded composition, the mechanical properties of the multilayer DLC film can be changed stepwise or continuously from the metal substrate side to the uppermost layer (Cr-DLC single layer or Cr-DLC laminate) side. Thus, peeling due to local stress concentration due to thermal shock or the like can be prevented. The thickness of the inclined layer is not particularly limited, but can be selected from, for example, 100 nm to 300 nm.

The uppermost layer serving as the contact surface with the sliding member is composed of Cr and DLC, and the Cr-DLC single layer (FIG. 1A), in which the Cr content does not substantially change over the thickness of the layer. 2 (c)), or a Cr-DLC stack (FIG. 1 (b), FIG. 2 (d)) formed by alternately stacking a Cr layer made of Cr and a DLC layer made of DLC. In the case of a Cr-DLC stack, as shown in FIGS. 1B and 2D, a DLC layer is formed as the uppermost layer.
The Cr content in the uppermost layer is preferably 2 to 12 atomic%, more preferably 10 to 12 atomic%, regardless of the form of the Cr-DLC single layer / Cr-DLC laminate.
The thickness of the uppermost layer is not particularly limited, but can be selected from, for example, 500 nm to 800 nm.

The uppermost layer portion is formed by alternately laminating Cr layers and DLC layers using a sputtering apparatus to be described later. Here, the Cr content is different depending on the difference in thickness per cycle between the Cr layer and the DLC layer. It is determined whether it is in the form of a Cr-DLC single layer that does not substantially change or in the form of a Cr-DLC stack.
Specifically, when the layer is formed with the thickness per cycle of the Cr layer-DLC layer set to less than 6 nm, a so-called laminated structure in which the Cr layer and the DLC layer are alternately formed is not formed. And DLC are mixed to form a layer, and a Cr-DLC single layer is formed in which the Cr content does not substantially change.
On the other hand, when a layer is formed with the thickness per period set to 6 nm or more, a laminated structure in which Cr layers and DLC layers are alternately formed is formed.
However, in the present invention, if the thickness per cycle of the Cr layer-DLC layer is more than 8 nm, it is not desirable because the wear resistance is lowered.

  Moreover, it is preferable that the uppermost layer part (Cr-DLC single layer or Cr-DLC lamination | stacking) has a surface hardness of 20 GPa or more by the measurement according to the nanoindenter measuring method based on ISO14577. However, a surface hardness of 38 GPa or higher is not desirable because it leads to a decrease in wear resistance.

When a low-hardness DLC layer is formed between the inclined layer and the uppermost layer (Cr-DLC single layer or Cr-DLC laminate), the hardness of the low-hardness DLC layer follows a nanoindenter measurement method based on ISO 14577 In the measurement, the hardness is set to be lower than that of the uppermost layer, specifically, less than 20 GPa.
The low hardness DLC layer can be obtained by forming a DLC film with zero bias voltage applied to the metal substrate, that is, without bias, in a film forming process using a sputtering apparatus described later. By forming a film without a bias, the DLC obtained has a hardness of less than 20 GPa by the nanoindenter measurement method, and this layer is lower than the uppermost layer portion that becomes a high hardness DLC having a hardness of, for example, 20 GPa or more. Since the adhesion to the formation is excellent, peeling of the layer is more effectively prevented.
The thickness of the low hardness DLC layer can be selected from, for example, 50 nm to 300 nm.

  In the present invention, the thickness of the low-hardness DLC layer is approximately 50 nm to 300 nm as described above, whereas the uppermost layer portion is a Cr-DLC laminate in which a Cr layer and a DLC layer are alternately laminated. Since the thickness of the DLC layer is several nm, the low-hardness DLC layer can be distinguished from the DLC layer in the stacked portion.

The structure of the multilayer DLC film according to the present invention shown in FIGS. 1 and 2 is formed using a magnetron sputtering apparatus shown in FIG.
A specific film forming process is as follows.
First, a metal substrate whose surface has been cleaned by cleaning is set on a drum, and the drum is moved into a vacuum chamber CH1, which is a preparation chamber. After evacuating the vacuum chamber CH1 to a substantial vacuum state, Ar gas is introduced to make an Ar gas atmosphere. Here, the metal substrate is subjected to an ion bombardment treatment with Ar plasma by applying a bias voltage by a high-frequency power source RF in the vacuum chamber CH1 before film formation. By this treatment, the substrate surface is etched and cleaned. By performing such a cleaning process using a high-frequency bias before film formation, impurities on the substrate surface are removed, the substrate surface is activated, and an effect of improving the adhesion of the thin film to the substrate surface is obtained.

Next, the drum is moved into the vacuum chamber CH2, which is a film formation chamber, and film formation is performed in an Ar gas atmosphere. In the vacuum chamber CH2, a carbon material and a Cr material for forming a Cr metal layer (underlayer, Cr layer in the Cr-DLC stack), an inclined layer, a Cr-DLC single layer, a DLC layer in the Cr-DLC stack, and the like Attach targets (C target, Cr target).
The Ar gas pressure is set to a pressure suitable for sputtering, the drum is rotated, a negative bias voltage is applied to the metal substrate by a DC pulse power source, and an AC power source (not shown) is applied to the C target or Cr target side. When sputtering power is supplied, glow discharge occurs and film formation starts.
Here, the type, thickness and hardness of the layers constituting the coating are controlled by adjusting the Ar gas pressure, bias voltage, sputtering power, drum rotation speed, film formation time, and the like. Further, the ratio of the thickness of the Cr layer to the DLC layer and the stacking cycle in the uppermost layer are also controlled in the same manner.
Standard conditions at the time of film formation are an Ar gas pressure of about 1 to 5 Pa, a bias voltage of 0 to −200 V, a sputtering power of 0.4 to 10 kW, and a drum rotation speed of 1 to 100 rpm.
Each layer is formed in order, and when the predetermined film thickness is reached, the sputtering power supply is stopped to finish the film formation process, the drum is moved from the vacuum chamber CH2 to the vacuum chamber CH1 and the outside, the substrate is taken out, and the multilayer DLC is removed. A base material (sliding member) having a film structure is obtained.

  In the sliding member according to the present invention, the total film thickness of the multilayer DLC film formed on the surface of the metal substrate can be about 0.5 to 3 μm.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to this.

[Example 1 to Example 8 to Comparative Example 1 and Comparative Example 2]
A sliding member having the multilayer DLC film structure shown in FIGS. 1 and 2 was produced by the following procedure. Examples 1 to 3 are shown in FIG. 1 (a), Example 4 and Comparative Example 1 are shown in FIG. 1 (b), Examples 6 to 7 are shown in FIG. 2 (c), Example 8 and Comparative Example 2 is a sliding member having a multilayer DLC film structure shown in FIG.

As the metal substrate, martensitic stainless steel [mirror surface (Ra <0.1 μm), φ20 mm square, thickness 3 mm] was used, which was ultrasonically cleaned in an alkali bath and a pure water bath and then dried. After the metal substrate subjected to the cleaning treatment is mounted in the magnetron sputtering apparatus of FIG. 3, it is evacuated to 2 × 10 ⁻⁵ Torr (2.6 × 10 ⁻³ Pa) and baked with a heater. Ion bombardment treatment was performed with Ar plasma, and the substrate surface was cleaned by etching.

The Ar gas pressure, bias voltage, sputtering power, and drum rotation speed are adjusted as appropriate to satisfy the conditions such as film thickness in the order of the following 1) to 4) according to the above-described film forming process for the substrate after cleaning. Layer formation.
1) Underlayer: formed with a Cr content of 100% and a film thickness of about 250 nm.
2) Gradient layer: formed with a film thickness of 70 nm to 90 nm while changing the Cr content from 100% to 0% (that is, the carbon content from 0% to 100%) stepwise. Note that the power applied to the C and Cr targets is determined so that the desired Cr / carbon mixing ratio is obtained, the mixing ratio is adjusted by sequentially changing the power of each target, and the drum is rotated so as not to have a laminated structure. The speed was adjusted accordingly.
3) Low-hardness DLC layer: In Examples 5 to 8 and Comparative Example 2, the DLC layer is formed in a film thickness of 70 nm to 125 nm continuously to the inclined layer. By setting the bias voltage applied to the metal substrate to zero, the hardness is set to 15 GPa in the measurement according to the nanoindenter measurement method based on ISO 015777.
4) Uppermost layer portion: In Examples 1 to 3 and Examples 5 to 6, the lamination period of the Cr layer and the DLC layer is 0.06 nm, 0.6 nm, 2 nm, Examples 4 and 8 Is 6 nm, Comparative Example 1 and Comparative Example 2 are 12 nm, and the film thickness is about 600 nm to 700 nm. In addition, while adjusting the applied electric power of C and Cr target so that it might become a predetermined | prescribed lamination | stacking period (film thickness of a Cr layer and a DLC layer), the rotational speed of the drum was adjusted suitably.
Table 1 shows the film thickness of the low-hardness DLC layer, the stacking cycle (presence / absence of stacking), the film thickness, hardness, Cr content, and bias voltage applied to the metal substrate during film formation. In addition, the Cr content rate of Table 1 is a measured value by X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy).

[Comparative Examples 3 to 6]
The procedure described above, except that a low-hardness DLC layer (hardness 15 GPa) or a high-hardness DLC layer (hardness 38 GPa) is formed as a single layer instead of the top layer (Cr-DLC single layer or Cr-DLC laminate) Accordingly, the sliding members of Comparative Examples 3 to 6 were formed.
In Comparative Examples 3 and 4, a DLC single layer was formed on the gradient layer, and in Comparative Examples 5 and 6, a low-hardness DLC layer was formed on the gradient layer, and then a DLC single layer was formed. .
Table 2 shows the film thickness of the low hardness DLC layer, the hardness of the DLC single layer, the film thickness, the bias voltage applied to the metal substrate during the DLC single layer deposition, and the Ar gas pressure during the DLC single layer deposition.

  In the magnetron sputtering apparatus shown in FIG. 3, a Cr layer is formed when the substrate faces the Cr target side as the drum rotates, and a DLC layer is formed when the substrate faces the C target side. Further, when the bias voltage is made constant, the film formation rate can be changed depending on the strength of the sputtering power. When sputtering power is simultaneously applied to both the Cr target and the C target, the Cr layer and the DLC layer are alternately laminated every time the drum makes a full turn. Moreover, the content rate of Cr and carbon or the film thickness of each layer changes with the electric power supplied to a Cr target and a C target. Therefore, it is possible to control the lamination period and the ratio of Cr and carbon by controlling the drum rotation speed and the sputtering power.

As shown in Table 1, in Examples 1 to 8, when the uppermost layer portion was formed, the deposition period was set to 0.06 nm to 6 nm. Moreover, in Comparative Example 1 and Comparative Example 2, the stacking cycle was set to 12 nm and film formation was performed.
FIG. 4 is a scanning electron microscope (SEM) photograph of the uppermost layer portion (DLC-Cr laminate) in Comparative Example 1, and FIG. 5 is a scanning electron image of the uppermost layer portion (DLC-Cr single layer) in Example 3. A microscope (SEM) photograph is shown respectively.
Also, in FIG. 6, the coating is gradually etched away from the outermost surface of the uppermost layer (DLC-Cr laminate) in Example 4 toward the inside (base material side), and carbon and Cr at different etching depths are removed. The results obtained by measuring the content by XPS are shown in FIG. 7, and the results in Example 2 (DLC-Cr single layer) are also shown.

As shown in FIG. 4, in Comparative Example 1 in which the DLC layer-Cr layer stacking period was set to 12 nm, a multilayer structure in which the DCL layer and the Cr layer overlapped alternately was obtained. Note that the same multilayer structure is obtained in Example 4 and Example 8 in which the stacking period is set to 6 nm, and the stacked structure in which the Cr layer and the DLC layer are alternately formed by setting the stacking period to 6 nm or more. It was confirmed that
On the other hand, in Example 3 in which the lamination period was set to less than 6 nm, for example, 2 nm, no multilayer structure was seen as shown in FIG. This is because when the stacking period is set to less than 6 nm, the period is too small, so the Cr layer and the DLC layer are not formed as separate layers, and the Cr and DLC are mixed to form a layer, and the Cr content is substantially It is thought that it became the Cr-DLC single layer which does not change automatically.

Further, as shown in FIG. 7, in Example 2 where the set lamination period is 0.6 nm, the carbon and Cr contents are kept constant at about 90 atomic% and about 10 atomic%, respectively, regardless of the etching depth. The result that it was kept was obtained. This was a result showing that Cr and DLC were mixed to form a Cr-DLC single layer.
On the other hand, as shown in FIG. 6, in Example 4 in which the set lamination period is 6 nm, the carbon content is between 88 and 98 atomic% and the Cr content is between 2 and 12 atomic% depending on the etching depth. In both cases, the results showed that they change periodically. In addition, when the carbon content takes the maximum value, the Cr content takes the minimum value, and when the carbon content takes the minimum value, the Cr content takes the maximum value. That is, also in this result, it was confirmed that the uppermost layer portion has a laminated structure in which Cr layers and DLC layers are alternately formed by setting the lamination period to 6 nm or more.

  FIG. 8 shows the DLC layer-Cr layer stacking cycle and the surface hardness of the sliding member (the hardness of the multilayer DLC film) set in forming the uppermost layer in Examples 1 to 4 and Comparative Example 1. It is a graph which shows a relationship. As shown in FIG. 8, the maximum hardness is obtained in the vicinity of the stacking period of 6 nm, and it is desirable to set the stacking period of the DLC layer-Cr layer in the range of 0.6 nm to 10 nm in view of only the hardness. As a result. In particular, by setting the lamination period in the range of 2 to 8 nm, a hardness of 20 to 23 GPa can be obtained, and a sliding member having excellent wear resistance can be obtained. It is desirable to set the stacking period.

The wear resistance characteristics of the multilayer DLC films on the sliding members of Examples 1 to 8 and Comparative Examples 1 to 6 were evaluated by a ball-on-disk device.
The test conditions were set to a surface pressure of 1.3 GPa assuming a high load load, and the ball was a φ6 mm silicon nitride ball, unlubricated, and a rotational speed of 480 rpm. In addition, martensitic stainless steel was adopted as the metal base material of the sliding member.
The obtained results are shown in Table 3. Moreover, the figure which made the result of Table 3 into a graph is shown in FIG.9 and FIG.10 (what changed the scale of the vertical axis | shaft of FIG. 9).

In Comparative Example 4 and Comparative Example 6, as shown in Table 2, the hardness of the DLC single layer is 38 GPa, and the sliding member of Example (19 to 23 GPa, see Table 1) and the sliding member of other comparative examples Although the hardness was the highest in comparison, as shown in Table 3, the specific wear amount was the largest. As described above, even if the DLC single layer itself has a high hardness, the result shows that the DLC single layer does not necessarily exhibit good wear resistance under a high surface pressure.
On the other hand, each of Examples 1 to 8 shows a specific wear amount that is an order of magnitude smaller than that of the comparative example. For example, Example 4 and Example 8 (lamination period: 6 nm) are Comparative Examples 1 and Comparative Example. 2
The specific wear amount was about 3,000 times that of (lamination cycle: 12 nm).
As a result, in consideration of wear characteristics, it is preferable to set the stacking period of the DLC layer-Cr layer as the uppermost layer in a range of 0.06 nm to 8 nm, and it is particularly preferable to set the stacking period to 0.6 to 6 nm. The result was particularly suitable.
Further, when comparing the wear characteristics with and without the low-hardness DLC layer, Examples 6 to 8 in which the low-hardness DLC layer is continuously formed on the inclined layer are examples in which the low-hardness DLC layer is not provided. As compared with Examples 1 to 4, the specific wear amount was small, and the superiority of providing a low hardness DLC layer between the inclined layer and the uppermost layer was confirmed.

  When the multilayer DLC film according to the present invention is formed on a sliding surface, a sliding member that has excellent adhesion to a metal substrate and has little wear and can achieve a long life can be obtained. Moreover, since the multilayer DLC film concerning this invention is formed by sputtering, regardless of the kind of metal base material to coat | cover, steel, such as carbon steel, bearing steel, stainless steel, copper alloy, aluminum alloy, titanium alloy, for example The sliding member can be formed using a wide range of materials usually used for machine parts.

Claims (5)

On the surface of the metal substrate,
An underlayer made of Cr, a graded layer containing Cr and carbon, and a Cr-DLC single layer containing Cr and diamond-like carbon (DLC) and the Cr content does not vary substantially over the thickness of the layer A multilayer DLC film, or
Forming a multi-layer DLC film composed of a Cr-DLC laminate in which an underlayer made of Cr, a gradient layer containing Cr and carbon, and a Cr layer made of Cr and a DLC layer made of DLC are alternately stacked;
The gradient layer has a gradient composition in which the Cr content gradually decreases and the carbon content gradually increases as the distance from the surface of the metal substrate increases. A low-hardness DLC layer having a hardness of less than 20 GPa is further formed between the gradient layer and the Cr-DLC single layer or the Cr-DLC laminate by measurement according to a nanoindenter measurement method. The sliding member according to claim 1, wherein the sliding member is characterized. The sliding member according to claim 1 or 2, wherein the Cr-DLC single layer or the Cr-DLC laminate has a Cr content of 2 to 12 atomic%. The sliding member according to any one of claims 1 to 3, wherein the Cr-DLC stack has a thickness of 6 nm or more and 8 nm or less per one period of the Cr layer-DLC layer. The said Cr-DLC single layer or the said Cr-DLC lamination | stacking has the surface hardness of 20 GPa or more by the measurement according to a nanoindenter measurement method, It is any one of Claims 1 thru | or 4 characterized by the above-mentioned. The sliding member.