JP2003293136A - Amorphous hard carbon film and sliding member using the same - Google Patents

Abstract

(57) [Summary] (Modified) [Problem] High Si that has excellent wear resistance but easily wears the mating material
Provided is an amorphous hard carbon film having excellent sliding characteristics with respect to a contained aluminum alloy, and a sliding member. An amorphous hard carbon film containing C and H as main components has an H content of 30 to 5 in the amorphous hard carbon film.
0 at%, C is 90 at% in the remaining composition excluding H
Above, an amorphous hard carbon film containing less than 5 at% of Si and containing silicon carbide. Further, when 0.5 to 2 at% of oxygen is added, the friction coefficient is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous hard carbon which exhibits excellent wear resistance, seizure resistance and adhesion resistance when it is slid with an aluminum alloy containing silicon at a high concentration as a counter material. The present invention relates to a film and a sliding member using the film.

[0002]

2. Description of the Related Art Conventionally, as a surface treatment method for metal materials, metal carbides such as TiC and TiN formed by plating, nitriding, PVD method, CVD method, etc., hard coatings such as metal nitrides, tools, dies The surface of is coated to improve wear resistance and seizure resistance. However,
These coating layers have a high hardness of Hv2000-3000, but have a large coefficient of friction of about 0.2-0.8, which increases the sliding resistance due to friction with the mating material, causing wear of the coating film and mating material. It causes problems such as damage.

An amorphous hard carbon film formed by a CVD method using plasma or an ion beam has an Hv of about 200.
Since it has a high hardness of 0 to 6000, it has been attracting attention as a hard coating material having good wear resistance. The amorphous hard carbon film is also called an amorphous carbon film, a diamond-like carbon film, an i-carbon film, a hydrogenated amorphous carbon film (a-C: H), etc., and is mainly composed of amorphous carbon. It is a film.

The following techniques have been proposed for such an amorphous hard carbon film. In Japanese Patent No. 2971928, the main components are carbon and hydrogen, and the hydrogen content is 30-.
50 at% and the remaining composition is 70 to 90 a in atomic ratio
It is an amorphous thin film containing silicon of t% carbon and the balance siliconaceous material, has a high hardness including pseudo diamond, and has a very low friction coefficient of 0.05 or less when the mating material is SUJ-2. A hard amorphous carbon-hydrogen-silicon thin film having is disclosed. Since silicon and carbon are combined to form hard silicon carbide, it has high hardness and excellent wear resistance, but no mention is made of the case where a soft material such as an aluminum alloy is a mating material.

In the case of a silicon-containing aluminum alloy, the alloy structure changes at the eutectic point of 12.7 wt%.
Hypereutectic Al with high concentration of silicon of 12.7 wt% or more
-Si alloy has a large amount of silicon that is deposited first during melting.
In the case of a hypoeutectic of 2.7 wt% or less, α solid solution similar to pure aluminum is first deposited. Since silicon is extremely hard, the aluminum alloy containing it has the feature that it is excellent in wear resistance due to the precipitated silicon. However, when an aluminum alloy with a high silicon content is used as the counterpart material, an amorphous hard carbon film is used. Will wear out.

In Japanese Patent No. 2889116, an amorphous hard carbon film containing appropriate amounts of silicon and nitrogen has excellent adhesion to a base material, and has excellent wear resistance and sliding characteristics (friction coefficient). It is disclosed that a membrane is obtained. The contents of silicon and nitrogen in this amorphous hard carbon film are determined from the viewpoint of obtaining good adhesion and wear resistance.

Japanese Unexamined Patent Publication (Kokai) No. 61-163273 discloses an abrasion resistant member in which at least one layer is a diamond film containing silicon. It is disclosed that this diamond film can be made into a film of high hardness with good adhesion because SiC is generated by adding silicon.

In Japanese Patent Laid-Open No. 11-166625, Si,
A piston ring excellent in aluminum adhesion resistance is disclosed, which is coated with a diamond-like carbon film containing elements such as Ti, W, Cr, Mo, Nb, and V.

In Japanese Patent Laid-Open No. 2001-280497, Si
A cylinder made of an aluminum alloy having a content of 7 to 20 wt% and carbides of one or more elements selected from the group of Si, Ti, W, Cr, Mo, Nb and V are dispersed, and the content ratio is 5 to 40 at% and the film hardness is
A combination with a piston ring coated with a hard coating made of diamond-like carbon in the range of Hv 700-2000 is disclosed. Here, since the content ratio of Si and the like is an atomic ratio with respect to the entire hard coating, if the elements of the hard coating are divided into hydrogen and components other than hydrogen, the content of Si and the like in the latter is expressed as 5 to 40.
It will be more than at%.

[0010]

Since pure aluminum and aluminum alloys are lightweight, they have the advantage of reducing fuel consumption when used for automobile parts. However, there is a problem that it is apt to stick to the surface and cause seizure. When considering pure aluminum or aluminum alloy as a sliding member, in addition to wear resistance and seizure resistance, adhesion resistance is also important.

It has been conventionally known that when silicon is added to an amorphous hard carbon film containing carbon and hydrogen as main components, hardness increases, abrasion resistance is excellent, and a sliding film having a low friction coefficient is obtained. There is. However, when examining the conventional findings, S
The hardness of the amorphous hard carbon film before addition such as i is as low as Hv800, and not as high as Hv2000 or higher. The inventors of the present invention have studied the amorphous hard carbon film having such a high hardness, and (a) the wear resistance changes greatly depending on the amount of silicon added; (b) the amount of silicon added is 5 at%. If it exceeds, the hardness decreases and the wear resistance deteriorates; such an amorphous hard carbon film containing carbon and hydrogen as main components and a small amount of silicon has poor adhesion to an iron-based substrate. I found a problem. Therefore, the present invention is a non-stick material excellent in adhesion resistance, scuff resistance, and adhesion without impairing the excellent wear resistance of the high hardness amorphous hard carbon coating with aluminum or aluminum alloy as the counterpart material. An object is to provide a crystalline hard carbon film and a sliding member using the same.

[0012]

The present invention has been made to solve the above problems, and an amorphous hard carbon film according to the present invention is an amorphous hard carbon film containing carbon and hydrogen as main components. And the hydrogen content in the amorphous hard carbon coating is 30 to
It is 50 at% and carbon is 9 in the remaining composition except hydrogen.
It is characterized in that it is 0 at% or more, silicon is less than 5 at%, and contains silicon carbide. Further, the sliding member according to the present invention is a substrate, an intermediate layer formed on the surface of the substrate, and an amorphous hard carbon film mainly composed of carbon and hydrogen formed on the intermediate layer. The amorphous hard carbon film has a hydrogen content of 30 to 50 at%, and the remaining composition excluding hydrogen is 90 at% or more of carbon and 5 a of silicon.
and an amorphous hard carbon coating containing silicon carbide.

The amorphous hard carbon coating according to the present invention has excellent adhesion to an iron-based substrate and has both scuff resistance and wear resistance when a silicon-containing aluminum alloy is used as a mating material. . The hydrogen content in the coating is ERDA (Elastic Recoil
Detection Analysis), low friction coefficient,
From the viewpoint of aluminum adhesion resistance, 30 to 50 at% is preferable. The composition and bonding state excluding hydrogen are ESCA (Electro
It can be measured by n Spectroscopy for Chemical Analysis), and silicon is present mainly as carbides such as SiC by combining with carbon, and its content (total components except hydrogen is 10%).
The content of 0, the same below) must be less than 5 at% (excluding 0%) from the viewpoint of achieving both scuff resistance and wear resistance of the silicon-containing aluminum alloy material partner,
It is preferably set to 2 to 4 at%. In addition to C and Si described above, all components except hydrogen are impurities of raw materials or O and Fe which are accompanying elements during film formation.

In order to secure sufficient adhesion to the base material in the sliding member having the above amorphous hard carbon film formed thereon, silicon, chromium, tungsten, titanium and their alloys and their carbides are used. It is preferable to use an intermediate layer selected from the group consisting of Particularly, in the case of an iron-based base material, chromium, titanium and the like are suitable. An iron alloy is usually used as the base material. When the amorphous hard carbon film of the present invention is applied to a compressor vane or the like, a SKH51 material that has been subjected to quenching and tempering heat treatment can be used. Further, in the case of a fuel injection pump plunger or the like, a SKD11 material or SUJ2 material that has been subjected to quenching and tempering heat treatment can be used. Further, when the amorphous hard carbon coating of the present invention is applied to the piston ring, carbon steel, spring steel, SUS440B material or the like can be used as the base material. Further, a material having a nitride layer, a Cr plating film, a film of chromium nitride, titanium nitride or the like formed on the surface of the substrate may be used.

In the amorphous hard carbon film according to the present invention, silicon mainly exists as carbides such as SiC,
It can be confirmed by ESCA analysis that a part of silicon becomes an oxide such as SiOx by adding a slight amount of oxygen during the film formation. The presence of the silicon oxide thus generated has a smaller friction coefficient and becomes stable in sliding with the mating material. When silicon contained in the film is exposed on the surface by sliding, frictional heat reacts with the surrounding atmosphere to generate silicon oxide. The friction coefficient becomes unstable until silicon oxide is formed on the surface, but if the film contains a proper amount of silicon oxide in advance, such unstable behavior of the friction coefficient is reduced. To be done. From this point of view, in order to properly adjust the ratio of silicon carbide and silicon oxide and obtain good sliding characteristics, the amount of oxygen added is 0.5 to 2 at%.
Is preferred.

The thickness of the amorphous hard carbon coating according to the present invention is not particularly limited, and generally 0.5 to 10 μm is preferable.

[0017]

[Function] When the composition of the amorphous hard carbon film is determined,
Its hardness depends on the bonding state of carbon atoms,
It varies in the range of Hv2000 to 6000. If Si is added to the high hardness amorphous hard carbon film in this range in an amount of 5 at% or more,
The properties of the coating are affected by metal carbides, and the hardness is Hv
Reduced to 1500 or less. However, the amount of Si added should be 5
When the content is less than at%, the hardness is slightly reduced, the above hardness range is substantially maintained, and the adhesion resistance, seizure resistance and adhesion are remarkably improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described in more detail below.

FIG. 1 schematically shows a cross section of a sliding member having an amorphous hard carbon film according to the present invention formed on the surface thereof. Silicon, chromium,
A material selected from the group consisting of tungsten, titanium, their alloys, and their carbides is formed as the intermediate layer 2 preferably to a thickness of 0.3 to 1 μm. Furthermore, the main components are carbon and hydrogen, and the hydrogen content is 30-5.
It is 0 at% and carbon is 90 in the remaining composition except hydrogen.
At least at% and less than 5 at% of silicon, the amorphous hard carbon film 3 containing silicon carbide is formed.

SKH51 material is used as the base material 1 and RF
A Cr intermediate layer 2 is formed by a magnetron sputtering method, and then an amorphous hard carbon film 3 having a high hardness and a low friction coefficient and having excellent aluminum adhesion resistance and abrasion resistance is formed by a plasma CVD method. A sample 13 (material SKH51) is placed on a substrate holder 12 with a rotation mechanism (not shown) arranged in the center of the vacuum chamber 11 (FIG. 2).
And a vacuum pump (not shown) connected to the exhaust port 14 inside the vacuum chamber 11 achieves an ultimate vacuum of 9.3E.
Exhaust to -5 Pa (7.0E-7 torr).

Next, a predetermined flow rate of argon gas is introduced from the gas inlet to adjust the pressure in the vacuum chamber 11 to 0.665P.
Adjust to a (5 mtorr). And board holder 1
13.5 from the bias power source 19 connected to 2 to the sample 13
A high frequency power (RF power) of 6 MHz is applied to excite the plasma discharge. The sample 13 is cleaned by the ion bombardment of the argon ions thus excited.

Next, after increasing the flow rate of the argon gas to adjust the pressure to 1.33 Pa, the target bias power source 1 is applied to the chromium target 17 with the shutter 18 closed.
6, RF power is applied to perform pre-sputtering for a predetermined time, the shutter 18 is opened, and the thickness of the surface of the sample 13 is reduced to 0.
A chromium intermediate layer 2 having a thickness of about 3 μm is formed. After forming the chromium intermediate layer 2, the shutter 18 is closed to stop the argon gas.

Next, acetylene (C ₂ H ₂ ) gas and tetramethylsilane (TMS) gas are introduced into the vacuum chamber 11 at a partial pressure ratio of C ₂ H ₂ : TMS = 1: 0 to 1: 1.
Adjust the pressure to 1.33 Pa (10 mtorr). In this state, RF power is applied to the sample 13 from the bias power source 19 through the substrate holder 12 to generate plasma and form an amorphous carbon film by the decomposed ions. At this time, the Si / (Si + C) ratio is adjusted by adjusting the flow rate ratio of acetylene and tetramethylsilane. The hydrogen content of the coating is 36.5-43.5 at% according to ERDA analysis, and the carbon content excluding hydrogen is 90-from ESCA analysis.
It was 98 at%. Further, by introducing a small amount of oxygen at about several sccm in addition to acetylene and tetramethylsilane during film formation, an amorphous hard carbon film containing both silicon carbide and silicon oxide can be obtained.

Table 1 shows the ratio of Si and C in the source gas and ES
It shows the relationship among silicon content, hardness, wear resistance and aluminum adhesion resistance by CA analysis. The wear resistance is measured by the pin-on-disk test (counterpart material-A39
0), the aluminum adhesion resistance was measured by the pin-on-disc test described later.

[0025]

【table 1】

FIG. 2 shows the relationship between the Si / (Si + C) ratio in the raw material gas and the wear volume in the wear test when the material was produced by the RF plasma CVD method using acetylene or tetramethylsilane as the raw material. The friction and wear test is carried out by the pin-on-disc test method. An amorphous hard carbon film is formed on the surface of the pin, which is obtained by gas nitriding a material equivalent to SUS440B, and is mirror-finished with a radius of curvature of 20 mm (cross section 3.5 mm x 5 mm) , A hypereutectic aluminum-silicon-copper alloy A390 material containing a high concentration of silicon (AA standard S
i16.0 to 18.0, Cu4.0 to 5.0, Fe0.
5 or less, Mn 0.5 or less, Mg 0.45 to 0.65, Z
n 0.1 or less, Ti 0.2 or less, other 0.1 or less, total 0.2 or less, balance Al (wt%) disk as a mating material, load 98.1 N, peripheral speed 0.5 m / sec, sliding It was carried out for 240 minutes at a radius of 100 mm. For lubrication, motor oil P20 (base oil) heated to 100 ° C. was used.

From FIG. 2, Si / (Si + according to the first embodiment
C) = around 4%, the wear volume becomes minimal and the film hardness is
It is about Hv 2500. When the Si / (Si + C) ratio is 4% or less, the film hardness is high but the stress is large, so that the wear progresses in a self-destructive manner. Si / (Si + C) ratio of Comparative Example 1 = 10
%, The coating hardness decreases to Hv1500, and the wear volume also increases. Furthermore, in Comparative Example 2, Si / (Si + C)
When the ratio is 15%, the coating hardness further decreases to around Hv1000, and the wear volume further increases.

FIG. 3 shows the results of the scuffing test when the A390 material was used as the mating material. The scuff test is performed by the pin-on-disk test method, and SKH51
The tip of the material pin has a radius of curvature of 20 mm (cross section is 3.5 mm
X 5 mm) to form an amorphous hard carbon film on the mirror-finished surface, using a disc of aluminum alloy material A390 as a mating material, and an initial load of 1 M at a peripheral speed of 8 m / sec.
The pressure was increased from Pa in 0.2 MPa steps (holding for 30 seconds). For lubrication, motor oil P20 (base oil) heated to 100 ° C. was used. In Example 1 in which the silicon content was 4 at%, no increase in the friction coefficient was observed up to around 23 MPa, and scuffing did not occur. In Comparative Example 1 in which the silicon content is 5 at%, the friction coefficient increases and scuffing occurs at around 17 MPa. Furthermore, in Comparative Example 2 in which the silicon content is as high as 25 at%, scuffing occurs around 13 MPa. Therefore, the silicon content is 4 at
It can be seen that the smaller the percentage, the better the wear resistance and scuff resistance.

Comparative Example 3 in FIG. 3 shows the scuffing characteristics of the untreated SKH51 material on which the amorphous hard carbon coating is not formed. The friction coefficient sharply increases at a low surface pressure near 9 MPa, It can be seen that scuffing has occurred. Comparative Example 4 is a CrN film formed by the arc ion plating method, but the scuffing characteristic shown in FIG. 3 has scuffing at around 10 MPa, which is equivalent to Comparative Example 2 having a silicon content of 25 at%. It can be seen that the scuff is generated under the load.

Table 2 shows the influence of the oxygen addition amount when the silicon content is 4 at%. In the case of Example 1 in which oxygen was not added, the friction coefficient in oil was 0.
In the case of Example 2 in which 0.5 at% oxygen was added, the hardness was reduced to about Hv1500 and the wear resistance was slightly deteriorated, but the scuffing load was about 18 MPa and the friction was good. The coefficient also decreases slightly to 0.07.
Further, in Example 3 in which 2 at% of oxygen is added, the wear volume increases, but the scuffing load is about 14 MPa, and the friction coefficient decreases to 0.05. Therefore, 0.5 to 2 at% is applied to the amorphous hard carbon coating containing a proper amount of silicon.
By adding a certain amount of oxygen, a film having excellent wear resistance and scuffing resistance and a small friction coefficient can be formed.

[0031]

[Table 2]

Table 3 shows the results obtained by forming an amorphous hard carbon coating similar to that of the above-mentioned Example 1 on the SKH51 substrate with the intermediate layer and evaluating the adhesion by the critical load value by the scratch test. It can be seen that in Example 4 in which the chromium intermediate layer by sputtering and Example 5 in which the titanium intermediate layer is applied, the critical load value is larger and the adhesion is higher than in Comparative Example 5 without the intermediate layer.

[0033]

[Table 3]

[0034]

EFFECTS OF THE INVENTION A sliding member whose surface is coated with an amorphous hard carbon film in which the amount of silicon added is adjusted to less than 5 at% has a scuffing property when slid against a material such as an aluminum material or a silicon-containing aluminum alloy. The generated load is high, it is difficult to seize, and it has excellent wear resistance. Furthermore, the amorphous hard carbon coating of the present invention has excellent adhesion to iron-based substrates. Further, the coefficient of friction can be reduced by setting the amount of oxygen added to 0.5 to 2 at%. Further, by applying an intermediate layer of chromium and titanium by sputtering, it is possible to improve the adhesion to the iron-based base material.

As described above, the amorphous hard carbon coating according to the present invention makes it possible to achieve both wear resistance and scuff resistance with respect to the mating material of pure aluminum or aluminum alloy. In the examples, the mating material was hypereutectic aluminum-
Although A390 which is a silicon-copper alloy is shown, ADC10, 12 which is a hypoeutectic aluminum-silicon-copper alloy is used.
In such cases, the amorphous hard coating according to the present invention can be expected to have the same effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing the wear resistance of the amorphous hard carbon coating of the present invention.

FIG. 3 is a diagram showing scuff resistance of the amorphous hard carbon coating of the present invention.

FIG. 4 is an apparatus diagram for forming an amorphous hard carbon film of the present invention.

[Explanation of symbols]

1 ... Base material 2 ... Middle layer 3 ... Amorphous hard carbon film 11 ... Vacuum chamber 12 ... Board holder 13 ... Sample 14 ... Exhaust port 15 ... Gas inlet 16 ... Target bias power supply 17 ... Target 18 ... Shutter

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3J011 QA04 SB12 SB13 SB14 SE02                 3J044 AA02 BB19 BB28 BB30 BB33                       BC06                 4K029 AA02 BA02 BA07 BA17 BB02                       BD04 DC39 FA01                 4K030 BA27 BA28 CA02 FA01 HA04                       LA01 LA23

Claims (5)

[Claims] 1. An amorphous hard carbon film containing carbon and hydrogen as main components, wherein the hydrogen content in the amorphous hard carbon film is 30 to 50 at%, and carbon remains in the remaining composition except hydrogen. 90 at% or more, silicon is less than 5 at%,
An amorphous hard carbon film containing silicon carbide. 2. A base material, an intermediate layer formed on the surface of a sliding portion of the base material, and an amorphous hard carbon film mainly composed of carbon and hydrogen formed on the intermediate layer, the amorphous hard carbon film comprising: The hydrogen content in the hard carbon coating is 30 to 50 at%, the remaining composition excluding hydrogen is 90 at% or more of carbon, and the silicon content is 5 a.
A sliding member comprising an amorphous hard carbon film containing less than t% and containing silicon carbide. 3. An amorphous hard carbon film containing carbon and hydrogen as main components, wherein the hydrogen content in the amorphous hard carbon film is 30 to 50 at%, and carbon remains in the remaining composition excluding hydrogen. 90 at% or more, silicon is less than 5 at%, oxygen is 0.5 to 2 at%, and a silicon carbide and a silicon oxide are contained, and an amorphous hard carbon film is characterized. 4. A base material, an intermediate layer formed on the surface of a sliding portion of the base material, and an amorphous hard carbon film mainly composed of carbon and hydrogen formed on the intermediate layer, the amorphous hard carbon film comprising: The hydrogen content in the hard carbon coating is 30 to 50 at%, the remaining composition excluding hydrogen is 90 at% or more of carbon, and the silicon content is 5 a.
A sliding member comprising an amorphous hard carbon film containing less than t%, oxygen of 0.5 to 2 at%, and containing silicon carbide and silicon oxide. 5. The sliding member according to claim 2, wherein the intermediate layer is selected from the group consisting of silicon, chromium, tungsten, titanium, alloys thereof, and carbides thereof.