JP5592626B2 - Hard film forming method and hard film - Google Patents

Description

  The present invention relates to a hard film that contributes to improved wear resistance of iron-based substrates such as automobile parts and various molding dies and machine parts such as cemented carbide, and a method for producing the same. More specifically, the wear resistance of a component is improved by coating a diamond-like carbon hard film having excellent wear resistance with a thick film with improved adhesion to the substrate surface.

  The hard carbon film is a hard film generally called diamond-like carbon (hereinafter referred to as DLC). In addition, hard carbon has various names such as hard amorphous carbon, amorphous carbon, hard amorphous carbon, i-carbon, diamond-like carbon, etc., but these terms are not clearly distinguished.

  The essence of DLC in which such terms are used is structurally an intermediate structure of both diamond and graphite mixed. The DLC film is as hard as diamond and has excellent wear resistance, solid lubricity, thermal conductivity, chemical stability, etc., so, for example, molds / tools, wear-resistant machine parts, abrasives, It is being used as a protective film for sliding members, magnetic / optical components, and the like. As a method for forming such a DLC film, a physical vapor deposition (hereinafter referred to as PVD) method such as a sputtering method or an ion plating method, a chemical vapor deposition (hereinafter referred to as CVD) method, or the like is employed. For example, a DLC film obtained by a filtered arc method of arc ion plating is known (see Patent Document 1).

  In addition, in order to form a DLC film having excellent adhesion, a film forming method using unbalanced magnetron sputtering (hereinafter referred to as UBMS) has been proposed (see Patent Document 2).

JP 2007-046144 A JP 2002-256415 A

  However, since the DLC film formed by the filtered arc method of Patent Document 1 does not contain hydrogen, the diamond structure is dominant and very hard. Therefore, the adhesion is insufficient, and there is a concern that peeling or cracking occurs. In particular, when an attempt is made to increase the film thickness, the above-described peeling or cracking is likely to occur. In the case of the filtered arc method, since an electromagnetic spatial filter is used, the apparatus is very expensive. In addition, since the ionized carbon atoms have strong straightness, the film formation region is limited, and it is not suitable for processing a large number of large parts and small parts.

  Further, in the case of the UBMS method of Patent Document 2, the main focus is on improving the adhesion of the DLC film to the substrate, and mention is made of a method for increasing the thickness of the DLC film and a method for improving the wear resistance. Not. Patent Document 1 and Patent Document 2 disclose a method of forming a DLC film that has sufficient wear resistance and does not cause peeling or cracking when forming a film on a sliding surface of a sliding member. Absent.

  The present invention has been made in order to cope with such problems, and an object thereof is to provide a hard film capable of improving adhesion and increasing the film thickness and having excellent wear resistance and a film forming method thereof. Do

  A method for forming a hard film according to the present invention is a method for forming a hard film comprising an intermediate layer and a surface layer formed on the surface of a substrate, and the film forming method comprises a metal-based material on the substrate. An intermediate layer forming step for forming an intermediate layer mainly composed of a material, and a surface layer forming step for forming a surface layer mainly composed of DLC on the intermediate layer, and the intermediate layer forming step and the surface layer In the forming step, the intermediate layer and the surface layer use a UBMS apparatus using argon (hereinafter referred to as Ar) gas as a sputtering gas, and the surface layer forming step includes a graphite target and a hydrocarbon as a carbon supply source. The ratio of the introduction amount of the hydrocarbon gas to the introduction amount 100 of the argon gas into the apparatus is 1 to 5, and the degree of vacuum in the apparatus is 0.2 to 0.00. 8 Pa, applied to the substrate It is a step of forming a surface layer mainly composed of DLC by depositing carbon atoms generated from the carbon supply source on the intermediate layer under a condition where a bias voltage is 70 to 150V.

  Note that the bias potential with respect to the substrate is applied so as to be negative with respect to the ground potential, and the bias voltage of 150 V indicates that the bias potential of the substrate is −150 V with respect to the ground potential.

Further, this film forming method is a method for forming a hard film having the following physical properties. The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film is less than 150 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated at a rotational speed of 05 m / s for 30 minutes. In the surface layer forming step, the film thickness of the surface layer formed in a film formation time of 540 minutes is 1.5 μm or more.

  The hydrocarbon gas is methane gas. The amount of Ar gas introduced is 40 to 150 ml / min.

  In the surface layer forming step, a surface layer mainly composed of the diamond-like carbon is formed while increasing a bias voltage applied to the substrate continuously or stepwise.

  The base material is made of a cemented carbide material or an iron-based material. Moreover, before the said intermediate | middle layer formation process, it has the process of giving the nitriding process to the intermediate | middle layer formation surface of the said base material which consists of the said iron-type material, It is characterized by the above-mentioned. The nitriding treatment is a plasma nitriding treatment. Further, the hardness of the intermediate layer forming surface of the base material after the nitriding treatment is Hv 1000 or more in terms of Vickers hardness.

  In the intermediate layer forming step, the intermediate layer is formed using a metal-based material containing at least chromium (hereinafter referred to as Cr) or tungsten (hereinafter referred to as W).

  The hard film of the present invention is formed by the above film forming method. The hard film is used for a sliding surface of a sliding member.

  The method for forming a hard film according to the present invention is a method for forming a hard film comprising an intermediate layer and a surface layer formed on the surface of a base material, wherein the intermediate layer mainly comprises a metal-based material on the base material. And a surface layer forming step of forming a surface layer mainly composed of DLC on the intermediate layer, and the intermediate layer and the surface layer are UBMS using Ar gas as a sputtering gas. Using the apparatus, the surface layer forming step uses a graphite target and a hydrocarbon gas in combination as a carbon supply source, and the ratio of the introduction amount of the hydrocarbon gas to the introduction amount 100 of argon gas into the apparatus is 1 to 1. 5 and the degree of vacuum in the apparatus is 0.2 to 0.8 Pa, and the bias voltage applied to the base material is 70 to 150 V, carbon atoms generated from the carbon source are placed on the intermediate layer. Surface layer mainly composed of DLC Since the step of forming, can be enhanced and thickening of adhesion becomes possible to deposit a hard film having excellent wear resistance.

Since the hard film of the present invention is formed by the film forming method described above, it can be thickened and has excellent wear resistance. Specifically, this hard film has (1) SUJ2 hardened steel with surface roughness Ra: 0.01 μm or less and Vickers hardness Hv: 780, and a load of 0.5 GPa maximum contact surface pressure of Hertz. The specific wear amount is less than 150 × 10 ⁻¹⁰ mm ³ / (N · m) when the mating material is rotated for 30 minutes at a rotational speed of 0.05 m / s when applied and contacted, (2) In the surface layer forming step, the film thickness of the surface layer formed in a film formation time of 540 minutes is 1.5 μm or more. For this reason, the hard film of this invention can be used conveniently for the sliding surface etc. of a sliding member.

It is sectional drawing which shows the structure of the hard film of this invention. It is a figure which shows a friction tester. It is a figure which shows adhesive evaluation criteria. It is a schematic diagram which shows the film-forming principle of UBMS method. It is a schematic diagram of the UBMS apparatus provided with the AIP function.

The hard film in the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the structure of a hard film obtained by the film forming method of the present invention. As shown in FIG. 1, the hard film 1 is composed of an intermediate layer 3 and a surface layer 4 formed on the surface of the substrate 2. The physical properties of the hard film 1 are SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780, and a contact with a load of 0.5 GPa maximum contact surface pressure of Hertz. The specific wear amount of the hard film is preferably less than 150 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 0.05 m / s. Moreover, it is preferable that the dynamic friction coefficient of the hard film 1 is 0.4 or less.

  The film thickness of the surface layer 4 is preferably 1.5 μm or more in a film formation time of 540 minutes. Moreover, it is preferable that it becomes 1.0 micrometer or more in the film-forming time of 180 minutes. If the thickness of the surface layer 4 is less than 1.0 μm, the wear resistance is inferior.

  The film forming method of the present invention is a film forming method for obtaining the hard film 1 having the physical properties as described above. (1) An intermediate layer for forming an intermediate layer 3 mainly composed of a metal-based material on a substrate 2 And (2) a surface layer forming step of forming a surface layer 4 mainly composed of DLC on the intermediate layer 3 under predetermined conditions.

  In the intermediate layer forming step and the surface layer forming step, the intermediate layer 3 and the surface layer 4 are formed using a UBMS apparatus using Ar gas as a sputtering gas. The film forming principle of the UBMS method using the UBMS apparatus will be described with reference to the schematic diagram shown in FIG. As shown in FIG. 4, an inner magnet 14 a and an outer magnet 14 b having different magnetic properties are arranged in the central portion and the peripheral portion of the round target 15, and the magnet 14 a is formed while forming a high-density plasma 19 near the target 15. , 14 b, a part 16 a of the magnetic force lines 16 reaches the vicinity of the base material 12 connected to the bias power source 11. The Ar plasma generated during the sputtering along the magnetic force lines 16a can be diffused to the vicinity of the base material 12. By such an UBMS method, the ion assist effect that Ar ions 17 and electrons reach the base material 12 more than the normal sputtering, along the magnetic field lines 16a reaching the vicinity of the base material 12, due to the ion assist effect. A dense film (layer) 13 can be formed. In the intermediate layer forming step and the surface layer forming step, the target 15 corresponding to each of the intermediate layer and the surface layer is used.

(1) The intermediate layer forming step will be described.
This step is a step of forming an intermediate layer mainly composed of a metal-based material on the base material. As a metallic material, in order to improve the adhesion to the base material 2, when using a cemented carbide material or an iron-based material for the base material 2, Cr, Al, W, which are compatible with the base material 2, are used. It is preferable to include one or more kinds of metals selected from Ta, Mo, Nb, Si, and Ti. More preferred are Cr and W.

  In the intermediate layer forming step, as shown in FIG. 1, the intermediate layer 3 is preferably composed of a layer including a metal layer 3a and a metal-carbon layer 3b. For example, the metal layer 3a mainly composed of Cr is formed on the surface of the substrate 2, and the metal-carbon layer 3b is formed thereon. Although the two-layer structure is illustrated as the intermediate layer 3 in FIG. 1, the intermediate layer 3 may be composed of one layer or three or more layers as necessary.

  The metal-carbon layer 3b is preferably a composition gradient layer that increases the composition ratio of carbon to the surface layer 4 side in order to further improve the adhesion with the surface layer 4. The composition gradient layer can be formed by adjusting the sputter power applied to the target metal and graphite to incline the metal-carbon composition.

  The material of the base material 2 is not specifically limited, For example, a cemented carbide material or an iron-type material can be used. As a cemented carbide material, in addition to a WC-Co alloy having the most excellent mechanical properties, a WC-TiC-Co alloy, a WC-TaC-Co alloy having improved oxidation resistance as a cutting tool, WC-TiC-TaC-Co alloy can be used. Examples of the iron-based material include carbon tool steel, high-speed tool steel, alloy tool steel, stainless steel, bearing steel, and free-cutting steel. In the present invention, even when an inexpensive iron-based material is used as a substrate, a hard film can be formed on the surface.

  In the case of using an iron-based material as the base material 2, in order to improve the adhesion between the base material 2 and the intermediate layer 3, a step of nitriding the intermediate layer forming surface of the base material before the intermediate layer forming step Is preferably incorporated. As the nitriding treatment, it is preferable to perform a plasma nitriding treatment in which an oxide layer that hinders adhesion is hardly generated on the surface of the substrate. Further, the base material 2 having a nitride layer formed on the surface thereof is preferably set to have a Vickers hardness of Hv 1000 or more in order to improve the adhesion with the intermediate layer 3.

(2) The surface layer forming step will be described.
This step is a step of forming a surface layer mainly composed of DLC on the intermediate layer under predetermined conditions. Specifically, a graphite target is used as a carbon supply source. Further, as a carbon supply source, a graphite target and a hydrocarbon-based gas are used together in a predetermined ratio, the degree of vacuum in the UBMS apparatus (in the chamber) is 0.2 to 0.8 Pa, and a bias applied to the substrate 2 This is a step of forming the surface layer 4 mainly composed of DLC by depositing carbon atoms generated from the carbon supply source on the intermediate layer 3 under the condition that the voltage is 70 to 150V. Each condition will be described below.

  The surface layer 4 is a layer mainly composed of DLC, and uses a graphite target and a hydrocarbon-based gas in combination as a carbon supply source during film formation. This combined use can improve the adhesion of the surface layer to the intermediate layer. The hydrocarbon gas is not particularly limited to methane gas, acetylene gas, benzene and the like, but methane gas is preferable from the viewpoint of cost and handling property.

  The ratio of the introduction amount of the hydrocarbon-based gas is 1 to 5 with respect to the introduction amount 100 of Ar gas into the UBMS apparatus (inside the film forming chamber). By setting it in this range, the adhesion can be improved and the film thickness can be increased without deteriorating the wear resistance.

  The introduction amount of Ar gas, which is a sputtering gas, is preferably 40 to 150 ml / min. More preferably, it is 50-150 ml / min. Even more preferably, it is 50-100 ml / min. If the Ar gas flow rate is less than 40 ml / min, Ar plasma is not generated and the DLC film may not be formed. On the other hand, when the Ar gas flow rate is higher than 150 ml / min, the reverse sputtering phenomenon is likely to occur, so that the wear resistance is deteriorated and it is difficult to increase the film thickness. When the amount of Ar gas introduced is large, the collision probability between Ar atoms and carbon atoms increases in the chamber. As a result, the number of Ar atoms reaching the surface of the DLC film decreases, the effect of compacting the DLC film by Ar atoms decreases, and the wear resistance of the film deteriorates.

  The degree of vacuum in the UBMS device (in the chamber) is 0.2 to 0.8 Pa as described above. The degree of vacuum is more preferably 0.24 to 0.45 Pa. If the degree of vacuum is less than 0.2 Pa, Ar plasma is not generated and a DLC film may not be formed. Also, if the degree of vacuum is higher than 0.8 Pa, the reverse sputtering phenomenon is likely to occur, the wear resistance is deteriorated, and it is difficult to increase the film thickness.

  The bias voltage applied to the substrate is 70 to 150 V as described above. The bias voltage is more preferably 100 to 150V. When the bias voltage is less than 70V, densification does not proceed and the wear resistance is extremely deteriorated, which is not preferable. On the other hand, when the bias voltage exceeds 150 V, the reverse sputtering phenomenon easily occurs, the wear resistance is deteriorated, and it is difficult to increase the film thickness.

In the surface layer forming step, the surface layer gradually increases its hardness from the intermediate layer side to the outermost layer side in order to improve the adhesion with the intermediate layer (in FIG. 1, the metal-carbon layer 3b). It is preferable to eliminate an abrupt hardness difference between the intermediate layer and the surface layer. Specifically, the surface layer is a DLC gradient layer obtained by forming a film using a graphite target in the UBMS method while increasing the bias voltage with respect to the substrate continuously or stepwise. The hardness of the DLC gradient layer increases continuously or stepwise because the composition ratio of the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter as the bias voltage increases. Because.

The base material, UBMS apparatus, sputtering gas, and intermediate layer forming conditions used in each example and comparative example are as follows.
(1) Base material: SUS440C or cemented carbide (2) Base material dimensions: mirror surface (Ra = 0.005 μm or so) 30 mm square, thickness 5 mm
(3) UBMS device: manufactured by Kobe Steel; UBMS202 / AIP composite device (4) Sputtering gas: Ar gas (5) Intermediate layer formation conditions Cr layer: vacuumed to about 5 × 10 ⁻³ Pa, and base material with heater Was baked at a predetermined temperature, the substrate surface was etched with Ar plasma, and then a Cr layer was formed with a UBMS apparatus.
WC-C layer: evacuated to about 5 × 10 ⁻³ Pa, baked base material with heater, etched base material surface (or Cr layer surface) with Ar plasma, and then WC with UBMS device The sputter power applied to the graphite was adjusted to incline the composition ratio of WC and C.

  An outline of the UBMS 202 / AIP combined apparatus is shown in FIG. FIG. 5 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 5, the UBMS 202 / AIP combined device instantaneously vaporizes and ionizes the AIP evaporation source material 20 using vacuum arc discharge on the base material 22 arranged on the disk 21, The AIP function for depositing this on the substrate 22 to form a film and the sputter evaporation source materials (targets) 23 and 24 with a non-equilibrium magnetic field increase the plasma density in the vicinity of the substrate 22 to increase the ion assist effect. It is an apparatus having a UBMS function capable of controlling the characteristics of a film deposited on a substrate by increasing the number of films. With this apparatus, a composite film in which an AIP film and a plurality of UBMS films (including a composition gradient) are arbitrarily combined can be formed on a substrate.

Example 1, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 4 to Comparative Example 6
The substrate shown in Table 1 was ultrasonically cleaned with acetone and then dried. After drying, after attaching the base material to the UBMS / AIP composite device (UBMS202 / AIP composite device: manufactured by Kobe Steel), the Cr layer and / or the WC-C layer shown in Table 1 under the above-mentioned intermediate layer formation conditions Formed. A DLC film as a surface layer was formed on the film formation conditions shown in Table 1 to obtain a test piece having a hard film. Note that “degree of vacuum” in Table 1 is the degree of vacuum in the film forming chamber in the above apparatus. The obtained specimens were subjected to the following abrasion test, Rockwell indentation test and film thickness test, and the specific wear amount, dynamic friction coefficient, adhesion and film thickness were measured or evaluated. The results are also shown in Table 1.

<Friction test>
The obtained specimen was subjected to a friction test using a friction tester shown in FIG. 2A is a front view, and FIG. 2B is a side view. A SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 is attached to the rotating shaft 5 as a mating member 7, and the test piece 6 is fixed to the arm portion 8 to give a predetermined load 9 Applied from above, a lubricant is interposed between the test piece 6 and the mating member 7 for 30 minutes at a rotational speed of 0.05 m / s at a maximum contact surface pressure of 0.5 GPa at room temperature (25 ° C.). Without causing the load cell 10 to detect the frictional force generated between the counterpart material 7 and the test piece 6 when the counterpart material 7 is rotated. When the specific wear amount is less than 150 × 10 ⁻¹⁰ mm ³ / (N · m), it is evaluated that the wear resistance is excellent, and “○” mark is 150 × 10 ⁻¹⁰ mm ³ / (N · m) or more. , If it is less than 300 × 10 ⁻¹⁰ mm ³ / (N · m), it is evaluated as being inferior in wear resistance, and “△” mark is exceeded, and if it exceeds 300 × 10 ⁻¹⁰ mm ³ / (N · m), Assume that the wear resistance is extremely inferior, and record “x” marks. Also record the dynamic friction coefficient.

<Rockwell indentation test>
When the diamond indenter was driven into the test piece substrate with a load of 150 kg, the state of occurrence of peeling around the indentation was observed. The adhesion of the test piece was evaluated according to the evaluation criteria shown in FIG. When the amount of peeling generated is small as shown in FIG. 3 (a), it is evaluated that the adhesiveness is excellent, and “◯” mark is shown, and peeling occurs partially as shown in FIG. 3 (b). Is evaluated as having poor adhesion, and “△” mark is recorded, and when peeling occurs all around as shown in FIG. To do.

<Film thickness test>
The film thickness of the obtained test piece was measured by using a surface shape / surface roughness measuring instrument (manufactured by Taylor Hobson Co., Ltd .: Foam Talisurf PGI830). The film thickness was obtained by masking a part of the film forming portion and determining the level difference between the non-film forming portion and the film forming portion.

Example 2, Example 3 and Comparative Example 3
Manufactured by JEOL Ltd .: A substrate (Vickers hardness Hv1000) subjected to the plasma nitrogen treatment shown in Table 1 using a radical nitriding apparatus was ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite device (UBMS202 / AIP composite device: manufactured by Kobe Steel), and then the Cr layer and the WC-C layer shown in Table 1 were formed under the above-mentioned intermediate layer formation conditions. . A DLC film as a surface layer was formed on the film formation conditions shown in Table 1 to obtain a test piece having a hard film. The obtained test piece was subjected to the above-described wear test, Rockwell indentation test, and film thickness test, and the specific wear amount, dynamic friction coefficient, adhesion, and film thickness were measured or evaluated. The results are also shown in Table 1.

  As shown in Table 1, since Examples 1 to 5 were formed under predetermined conditions, a DLC film having excellent wear resistance and adhesion could be obtained. In Comparative Example 1, since the metal layer was not provided in the intermediate layer, the adhesion was insufficient. Since Comparative Example 2 had a high bias voltage, the wear resistance was inferior. Since Comparative Example 3 did not introduce methane gas, the adhesion was inferior. In Comparative Example 4, since the amount of Ar gas introduced was small, Ar plasma could not be generated and no film could be formed. In Comparative Example 5, since the bias voltage was low, the wear resistance was inferior. In Comparative Example 6, since the amount of methane gas introduced was large, the adhesion was good but the wear resistance was inferior.

Example 6, Example 7, Comparative Example 7 to Comparative Example 12
The substrates shown in Table 2 were ultrasonically cleaned with acetone and then dried. After drying, after attaching the base material to the UBMS / AIP composite device (UBMS202 / AIP composite device: manufactured by Kobe Steel), the Cr layer and / or the WC-C layer shown in Table 2 under the above-mentioned intermediate layer formation conditions Formed. A DLC film as a surface layer was formed thereon under the film forming conditions shown in Table 2 to obtain a test piece having a hard film. The obtained test piece was subjected to the above-described wear test, film thickness test, and evaluation of thickening described below, and the specific wear amount, dynamic friction coefficient, and film thickness were measured or evaluated. The results are also shown in Table 2.

<Evaluation of thickening>
When the film thickness is 1.5 μm or more with respect to the test piece having a DLC film forming time of 540 minutes as the surface layer, it is evaluated that the film thickness is excellent, and “◯” is 1.0 to 1. When the thickness is 5 μm, it is evaluated that the film thickness is inferior, and “Δ” is recorded. When the thickness is less than 1 μm, the film thickness is evaluated as being extremely inferior, and “X” is recorded.

Comparative Example 13
Manufactured by JEOL Ltd .: A substrate (Vickers hardness Hv1000) subjected to plasma nitrogen treatment shown in Table 2 using a radical nitriding apparatus was ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite device (UBMS202 / AIP composite device: manufactured by Kobe Steel), and then the Cr layer and the WC-C layer shown in Table 2 were formed under the above-mentioned intermediate layer formation conditions. . A DLC film as a surface layer was formed thereon under the film forming conditions shown in Table 2 to obtain a test piece having a hard film. The obtained test piece was subjected to the above-described wear test, film thickness test, and evaluation of thickening, and the specific wear amount, dynamic friction coefficient, and film thickness were measured or evaluated. The results are also shown in Table 2.

  As shown in Table 2, since Examples 6 and 7 were formed under predetermined conditions, a thick DLC film having excellent wear resistance could be obtained. Comparative Example 7 was excellent in wear resistance, but could not be thickened because of a high bias voltage. In Comparative Example 8, since no metal layer was provided on the intermediate layer, the adhesion was insufficient. In Comparative Example 9, since the bias voltage was high, the wear resistance was inferior and the film thickness could not be increased. Since Comparative Example 10 had a low bias voltage, the wear resistance was inferior. In Comparative Example 11, since the amount of Ar gas introduced was small, Ar plasma could not be generated and no film could be formed. Since the comparative example 12 had much methane gas introduction amount, the abrasion resistance was inferior. In Comparative Example 13, since the amount of Ar gas introduced was large and the bias voltage was too high, the wear resistance was inferior and the film thickness could not be increased.

  The method for forming a hard film of the present invention can improve adhesion and increase the film thickness, and can form a hard film having excellent wear resistance, so that the sliding surface of a sliding member such as a bearing can be formed. It can be suitably used when forming a hard film on the surface.

DESCRIPTION OF SYMBOLS 1 Hard film 2 Base material 3 Intermediate | middle layer 3a Metal layer 3b Metal-carbon layer 4 Surface layer 5 Rotating shaft 6 Test piece 7 Opposite material 8 Arm part 9 Load 10 Load cell 11 Bias power supply 12 Base material 13 Film (layer)
14a Inner magnet 14b Outer magnet 15 Target 16 Magnetic field lines 16a Magnetic field lines reaching the base material 17 Ar ions 18 Ionized target 19 High-density plasma 20 AIP evaporation source material 21 Disk 22 Base material 23, 24 Sputter evaporation source material (target)

Claims (8)

A method for forming a hard film comprising an intermediate layer and a surface layer formed on the surface of a base material made of an iron-based material ,
The film forming method includes an intermediate layer forming step in which an intermediate layer mainly composed of a metal-based material is formed on the base material, and a surface layer formation in which a surface layer mainly composed of diamond-like carbon is formed on the intermediate layer. A process,
In the intermediate layer forming step and the surface layer forming step, the intermediate layer and the surface layer use an unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas, and the argon gas is introduced into the apparatus. Is introduced in an amount of 40 to 150 ml / min,
In the intermediate layer forming step, as the intermediate layer, a Cr layer is formed on the base material using a material containing chromium (Cr), and tungsten carbide (WC) and carbon (C) are formed on the surface of the Cr layer. A WC-C layer that is a composition gradient layer in which the composition ratio of carbon is increased on the surface layer side using a material containing
Prior to the intermediate layer forming step, there is a step of performing plasma nitriding treatment on the intermediate layer forming surface of the base material made of the iron-based material,
The surface layer forming step uses a graphite target and a hydrocarbon gas in combination as a carbon supply source, and the ratio of the introduction amount of the hydrocarbon gas to the introduction amount 100 of the argon gas into the apparatus is 1 to 5. The carbon atoms generated from the carbon supply source under the condition that the degree of vacuum in the apparatus is 0.2 to 0.8 Pa and the bias voltage applied to the substrate is 70 to 150 V, A film forming method comprising: forming a surface layer mainly composed of diamond-like carbon by depositing on a layer. The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s is less than 150 × 10 ⁻¹⁰ mm ³ / (N · m). 2. The film forming method according to 1.   3. The film forming method according to claim 1, wherein in the surface layer forming step, the film thickness of the surface layer formed in a film forming time of 540 minutes is 1.5 μm or more.   4. The film forming method according to claim 1, wherein the hydrocarbon gas is methane gas. In the surface layer forming step, claims 1 to 4 and forming a surface layer composed mainly of the diamond-like carbon while continuously or stepwise raising the bias voltage applied to the substrate The film-forming method as described in any one of these. The hardness of the intermediate layer forming surface of the substrate after nitriding treatment, any film forming method according to one of claims 1 to claim 5, characterized in that at Hv1000 or more in Vickers hardness. Hard film, which is formed by a film forming method of any one of claims 1 to claim 6. The hard film according to claim 7 , wherein the hard film is used for a sliding surface of a sliding member.