JP4984206B2 - Diamond-like carbon film-coated member and method for producing the same - Google Patents

Description

  The present invention relates to a diamond-like carbon film-coated member and a method for producing the same, and in particular, a diamond-like carbon film is formed on the outermost surface and used for machine parts, molds, and the like. The present invention relates to a member and a manufacturing method thereof.

  A diamond-like carbon (hereinafter referred to as “DLC”) film is a carbon film having characteristics such as high hardness and electrical insulation similar to diamond synthesized by a vapor phase synthesis method. The structure of the DLC film is usually an amorphous structure, and has a diamond bond or a graphite bond. Since the DLD film is hard (for example, micro Vickers hardness Hv1000 to 5000) and excellent in wear resistance, it is used to coat various mechanical parts in addition to recording media for hard disks and magnetic recording heads. ing. In order to improve the adhesion between the DLC film and the base material, a method in which an intermediate layer composed of a titanium carbide layer is interposed between the base material and the DLC film (see, for example, Patent Document 1), the base material does not contain hydrogen. A method of coating with a second DLC film containing hydrogen on the first DLC film (see, for example, Patent Document 2), a gas containing carbon and silicon on a base material coated with a carbon ion implantation layer A method of forming a DLC film using plasma gas (for example, see Patent Document 3), a method of covering a base material with a DLC multilayer film in which soft films and hard films are alternately laminated (for example, see Patent Document 4), etc. Various methods have been proposed.

International Publication WO92 / 006234 (Page 3) JP 2000-128516 A (paragraph numbers 0004-0005) JP 2000-319784 A (paragraph numbers 0008-0009) JP 2004-269991 A (paragraph numbers 0007-0008)

  However, the DLC film is a hard film, and the hardness and thermal expansion coefficient of the base material made of alloy steel, carbon steel, stainless steel, titanium, titanium alloy, iron such as soft iron and cast iron, aluminum, aluminum alloy, and the DLC film. Therefore, the methods described in Patent Documents 1 to 4 described above may not be able to sufficiently improve the adhesion between the base material and the DLC film.

  Therefore, in view of such conventional problems, an object of the present invention is to provide a diamond-like carbon film-coated member having good adhesion between a base material made of alloy steel and the like and a DLC film, and a method for producing the same. To do.

  As a result of intensive studies to solve the above problems, the present inventors have coated a base material made of alloy steel or the like with a nitrogen-containing chromium film, and then coated the nitrogen-containing chromium film with a DLC film. It has been found that the adhesion between the material and the DLC film can be improved, and the present invention has been completed.

  That is, the diamond-like carbon film covering member according to the present invention is characterized in that a nitrogen-containing chromium film is formed on a base material, and the diamond-like carbon film is formed on the nitrogen-containing chromium film. In the diamond-like carbon film-coated member, a chromium film is preferably formed between the base material and the nitrogen-containing chromium film. In addition, the nitrogen-containing chromium film is a film in which at least one of nitrogen and chromium nitride is dispersed substantially uniformly in the chromium film, or the nitrogen concentration in the central portion in the film thickness direction in the chromium film is higher than the nitrogen concentration on both sides thereof A high film is preferred.

  The method for producing a diamond-like carbon film-coated member according to the present invention is characterized in that after a nitrogen-containing chromium film is formed on a base material, a diamond-like carbon film is formed on the nitrogen-containing chromium film. In this method for producing a diamond-like carbon film-coated member, it is preferable to form a chromium film on the base material before forming the nitrogen-containing chromium film on the base material, and then form the nitrogen-containing chromium film. The nitrogen-containing chromium film is preferably formed by sputtering in an atmosphere containing argon and nitrogen using a chromium target, and the diamond-like carbon film is formed by sputtering using a carbon target. Preferably it is done. In addition, the nitrogen-containing chromium film is a film in which at least one of nitrogen and chromium nitride is dispersed substantially uniformly in the chromium film, or the nitrogen concentration in the central portion in the film thickness direction in the chromium film is higher than the nitrogen concentration on both sides thereof A high film is preferred.

  ADVANTAGE OF THE INVENTION According to this invention, the diamond-like carbon film coating | coated member with favorable adhesiveness of the base material consisting of alloy steel etc. and a DLC film can be manufactured.

  In the embodiment of the diamond-like carbon film-coated member according to the present invention, a nitrogen-containing chromium film is formed on a base material, and a DLC film is formed on the nitrogen-containing chromium film. As the base material, a base material made of alloy steel, carbon steel, stainless steel, titanium, titanium alloy, iron such as soft iron or cast iron, aluminum, aluminum alloy, or the like can be used.

  The embodiment of the diamond-like carbon film-coated member according to the present invention can be manufactured using the processing apparatus 10 shown in FIG. The processing apparatus 10 includes a vacuum processing chamber 12, a vacuum pump 14 for reducing the pressure in the vacuum processing chamber 12 to form a vacuum, and a rotary table 16 disposed at the center of the bottom of the vacuum processing chamber 12. A base material 20 as a member to be processed placed on the turntable 16 via a jig 18; a target 22 as an evaporation source disposed so as to surround the base material 20; and these targets A DC sputtering power supply 24 connected to each of 22, a DC ion bombard and bias power supply 26 connected to the rotary table 16, and a gas introduction pipe for introducing argon gas and nitrogen gas into the vacuum processing chamber 12. 28.

  The base material 20 is coated with a nitrogen-containing chromium film using a chromium target as the target 22 of the processing apparatus 10, and then coated with a DLC film using a carbon target as the target 22. The nitrogen-containing chromium film may be a film in which nitrogen or chromium nitride is substantially uniformly dispersed in the chromium film (hereinafter referred to as “nitrogen-containing chromium film I”), or the nitrogen concentration in the central portion in the film thickness direction of the chromium film is A film higher than the nitrogen concentration on both sides thereof (hereinafter referred to as “nitrogen-containing chromium film II”) may be used. Hereinafter, a method for forming the nitrogen-containing chromium film and the DLC film will be described in detail.

(Method for forming nitrogen-containing chromium film I)
First, a chromium target is used as the target 22 of the processing apparatus 10, the vacuum pump 14 is operated to evacuate the vacuum processing chamber 12, and then argon gas is introduced into the vacuum processing chamber 12 through the gas introduction pipe 28. And nitrogen gas are introduced to create a sputtering atmosphere in the vacuum processing chamber 12. If necessary, it is preferable to activate the surface of the base material 20 by performing ion bombardment before sputtering.

Next, a high voltage of the sputtering power source 22 is applied to the target 22 to generate glow discharge (low temperature plasma) in the vicinity of the target 22. As a result, the argon gas in the discharge region is ionized and collides with the target 22 at a high speed, and this collision expels chromium atoms from the target 22, and these chromium atoms together with nitrogen atoms in the atmosphere in the vacuum processing chamber 12. Struck against the surface of the base material 20, the surface of the base material 20 was dotted with Cr _X N _Y crystals containing 50 to 99 chromium atoms and 50 to 1 nitrogen atoms per 100 atoms as a chromium film containing nitrogen. A film is formed. In this sputtering, in order to make the thickness of the film uniform and to maintain the temperature of the base material 20 below the tempering temperature, the distance between the target 22 and the base material 20 is preferably maintained at 70 mm, for example. .

  Sputtering is performed without introducing nitrogen gas to form a chromium film having a thickness of 3 μm or less, preferably 1 μm or less on the base material 20, and then nitrogen gas is introduced to perform sputtering to form a nitrogen-containing chromium film I. It may be formed. If the nitrogen-containing chromium film is formed through the chromium film in this way, the adhesion between the base material 20 and the DLC film can be further improved.

(Method for forming nitrogen-containing chromium film II)
First, a chromium target is used as the target 22 of the processing apparatus 10, the vacuum pump 14 is operated to evacuate the vacuum processing chamber 12, and then argon gas is introduced into the vacuum processing chamber 12 through the gas introduction pipe 28. Is introduced into the vacuum processing chamber 12 to form a sputtering atmosphere. If necessary, it is preferable to activate the surface of the base material 20 with argon ions by performing ion bombardment in an argon gas atmosphere before performing sputtering.

  Next, a high voltage of the sputtering power source 24 is applied to the target 22 to generate glow discharge (low temperature plasma) in the vicinity of the target 22. Thereby, the argon gas in the discharge region is ionized and collides with the target 22 at a high speed, and chromium atoms are knocked out of the target 22 by this collision.

  When the introduction of nitrogen gas into the vacuum processing chamber 12 via the gas introduction pipe 28 is started after a predetermined time has elapsed from the start of sputtering or from the start of sputtering, the chromium atoms knocked out from the target 22 are When the nitrogen concentration in the atmosphere in the vacuum processing chamber 12 is zero, chromium alone, and after nitrogen gas is introduced into the atmosphere in the vacuum processing chamber 12, the surface of the base material 20 together with the nitrogen atoms in the atmosphere It is struck and deposited.

  This nitrogen-containing chromium coating II has a structure in which nitrogen is dissolved in chromium, a structure in which chromium nitride is dispersed in chromium, or a structure in which nitrogen is dissolved in chromium and chromium nitride is dispersed. However, the adjustment of the structure can be performed by controlling the nitrogen concentration in the atmosphere in the vacuum processing chamber 12 during sputtering. The nitrogen concentration in the atmosphere is controlled by the gas introduction pipe 28. This can be done by controlling the supply amount of nitrogen gas introduced into the vacuum processing chamber 12 via If the supply amount of nitrogen gas is increased to increase the nitrogen concentration in the atmosphere, the amount of nitrogen that combines with the chromium atoms knocked out of the target 22 and deposits on the surface of the base material 20 increases. If the supply amount of nitrogen gas is reduced to lower the nitrogen concentration in the atmosphere, the amount of nitrogen contained in the nitrogen-containing chromium film II is reduced. Therefore, supply of nitrogen gas so that the nitrogen concentration in the atmosphere at the intermediate point of sputtering is higher than the other points and the nitrogen concentration in the atmosphere at the start and end points of sputtering is lower than the nitrogen concentration at the intermediate point. If the amount is controlled, it is possible to form a nitrogen-containing chromium coating II in which the nitrogen concentration in the central portion in the film thickness direction in the chromium coating is higher than the nitrogen concentration in the portions on both sides. Specifically, it is preferable to increase the nitrogen concentration in the atmosphere from the start time of sputtering to the intermediate time point of sputtering, and to decrease the nitrogen concentration in the atmosphere from the intermediate time point of sputtering to the end time of sputtering. Note that the nitrogen gas may not be supplied at the start of sputtering.

  In this way, a nitrogen-containing chromium film II is formed on the base material 20 in which the nitrogen concentration in the central portion in the film thickness direction in the chromium film is higher than the nitrogen concentration in the both sides. The sputtering time can be appropriately set according to the type of the base material 20 and the required film thickness, and can be set to 0.5 to 15 hours, for example.

  Further, in the nitrogen-containing chromium film II, the hardness is highest in the central portion in the film thickness direction due to the difference in nitrogen content in the film thickness direction, for example, Hv 800 to 2000, preferably about Hv 1700, and the base material 20 side and the surface The hardness is low on the side, for example, Hv 500 to 1000, preferably about 500 on the base material 20 side, and Hv 1000 to 1900 on the surface side, preferably about Hv1000. Therefore, it is considered that the toughness of the film is improved by making the hardness of the entire film lower than that of the highest hardness part and suppressing the generation of chromium nitride (CrN) which is a ceramic.

  Furthermore, since the chromium content is higher on the base material 20 side of the nitrogen-containing chromium coating II than the central portion in the film thickness direction, the adhesion between the coating and the base material 20 is improved. When the base material 20 is a metal such as tool steel or low carbon steel used for a machine member, the difference between the thermal expansion coefficient of the interface with the base material 20 of the nitrogen-containing chromium coating II and the thermal expansion coefficient of the base material 20 is calculated. Generation of thermal stress by decreasing, that is, increasing the chromium content at the interface with the base material 20 of the nitrogen-containing chromium film II and gradually increasing the nitrogen content toward the center in the film thickness direction It is considered that the adhesion strength can be increased by reducing the resistance.

  In addition, since the nitrogen-containing chromium film II has good adhesion to the base material 20, the nitrogen concentration is gradually changed during film formation, so that the thermal expansion coefficient at the contact surface with the base material 20 and the thermal expansion inside the film are increased. It is considered that by reducing (relaxing) the stress due to the difference from the rate, the thermal shock resistance can be improved while maintaining the wear resistance.

  Further, in the nitrogen-containing chromium film II, the surface nitrogen content is higher than the nitrogen content in the contact surface with the base material 20, and therefore the hardness on the film surface side is higher than the hardness on the base material 20 side.

For example, the atmosphere is set so that the partial pressure of argon gas in the atmosphere in the vacuum processing chamber 12 is about 1.2 × 10 ⁻³ torr and the partial pressure of nitrogen gas is about 0 to 0.5 × 10 ⁻³ torr. By changing the nitrogen concentration (nitrogen gas supply amount), a layer on the base material 20 side having a nitrogen concentration of 0 to 0.6 atomic% and Hv of 500 to 1000 can be formed at the initial stage of sputtering. In the middle period, a central layer in the film thickness direction having a nitrogen concentration of 0.5 to 3.0 atomic% and Hv 800 to 2000 can be formed, and in the final stage of sputtering, the nitrogen concentration is 0.3 to 0.6 atomic%, A layer on the surface side of Hv 1000 to 1900 can be formed. The nitrogen concentration in the nitrogen-containing chromium film II thus formed can be measured by applying a normal physical analysis method, for example, using glow discharge luminescence surface analysis (GDS). Can do.

  Further, the thickness of the nitrogen-containing chromium film II can be set to about several μm to a maximum of 100 μm including a portion where the nitrogen content is zero. However, if the nitrogen-containing chromium film II is too thick, cracks tend to easily occur in the film due to the stress of the film, so it is actually preferable to set the upper limit of the film thickness to about 30 μm. Within this range, the film thickness may be determined for each type of mechanical member according to the required characteristics of the mechanical member. For example, in the case of a mechanical member with high precision, the film thickness is about 1 to 5 μm, preferably about 3 μm. In the case of a mechanical member that requires good wear resistance, the film thickness is 5 to 30 μm, preferably It is about 10-20 micrometers.

(Formation of DLC film)
As described above, after the base material is coated with the nitrogen-containing chromium film I or II, ion etching is performed. Next, a carbon target is used as the chromium target 22 of the processing apparatus 10, the vacuum pump 14 is operated to evacuate the vacuum processing chamber 12, and then the gas is introduced into the vacuum processing chamber 12 through the gas introduction pipe 28. Argon gas (or argon gas and nitrogen gas) is introduced to make the inside of the vacuum processing chamber 12 a sputtering atmosphere.

  Next, a high voltage of the sputtering power source 22 is applied to the target 22 to generate glow discharge (low temperature plasma) in the vicinity of the target 22. As a result, the argon gas in the discharge region is ionized and collides with the target 22 at a high speed, and carbon atoms are knocked out of the target 22 by this collision, and the carbon atoms are released into the vacuum processing chamber 12 (argon gas and nitrogen gas). Is introduced to the surface of the base material 20 (with nitrogen atoms in the atmosphere) to form a DLC film containing nitrogen on the surface of the base material 20.

  In this way, a diamond-like carbon film-coated member in which the base material 20 is coated with a nitrogen-containing chromium film and the nitrogen-containing chromium film is coated with a DLC film can be produced. It is preferable to adjust the hardness of the DLC film by adjusting the bias voltage so that the hardness of the interface with the nitrogen-containing chromium film is equal to that of the nitrogen-containing chromium film. For example, the hardness of the surface of the nitrogen-containing chromium film is preferably Hv 800 to 1300, and a DLC film of Hv 1000 to 1300 is preferably formed thereon.

  The carbon in the DLC film can be identified by Raman spectroscopy. The micro Vickers hardness of the film can be measured by a usual method after polishing the cross section of the film and pressing an indenter on the cross section. When the film is thin and the hardness of the cross section of the film cannot be measured, the hardness of the cross section of the film having a thickness that can be measured by increasing the film formation time under the same conditions may be measured.

  Examples of the diamond-like carbon film-coated member and the manufacturing method thereof according to the present invention will be described below in detail.

[Example 1]
A base material made of SCM415 (chromoly steel (Cr-Mo steel)) is prepared as the base material 20 made of alloy steel, and the base material 20 is placed in the vacuum processing chamber 12 of the processing apparatus 10 that uses a chromium target as the target 22. The inside of the vacuum processing chamber 12 was placed in an argon gas atmosphere of 2 × 10 ⁻² torr, and ion bombarding was performed at 1250 V × 0.01 mA for about 40 minutes to activate the surface of the base material 20.

Next, after the inside of the vacuum processing chamber 12 of the processing apparatus 10 is evacuated and evacuated, the partial pressure of argon gas in the atmosphere in the vacuum processing chamber 12 is 1.2 × 10 ⁻³ torr, and the bias voltage is −100 V. Then, sputtering was performed for about 7 minutes, and a chromium film having a hardness of about Hv 700 and a thickness of less than 1 μm was formed on the base material 20.

Subsequently, nitrogen gas is introduced into the vacuum processing chamber 12 of the processing apparatus 10 so that the partial pressure of argon gas in the atmosphere in the vacuum processing chamber 12 is 1.2 × 10 ⁻³ torr and the partial pressure of nitrogen gas is reduced. Sputtering was performed for about 93 minutes at 0.2 × 10 ⁻³ torr and a bias voltage of −100 V, and a nitrogen-containing chromium film I having a hardness of about Hv 1700 and a thickness of 15 μm was formed on the chromium film.

After the base material 20 thus formed with the nitrogen-containing chromium film I is placed in the processing apparatus 10 using a carbon target as the target 22, the inside of the vacuum processing chamber 12 is evacuated and depressurized to 8 × 10 ⁻³ Pa. Ion bombarding was performed at −1000 V × 0.1 A for 3 hours.

  Finally, argon gas is introduced into the vacuum processing chamber 12 of the processing apparatus 10 at 30 to 40 sccm and nitrogen gas at 9 sccm, the bias voltage is set to −150 V, and the plasma generated on the target 22 by DC discharge (1.4 kW) is generated. A DLC film having a thickness of 5 μm was formed on the nitrogen-containing chromium film I by performing sputtering treatment for 4 hours.

[Example 2]
After activating the surface of the base material 20 as in Example 1, the inside of the vacuum processing chamber 12 of the processing apparatus 10 that uses a chromium target as the target 22 is evacuated to a vacuum, and then the atmosphere in the vacuum processing chamber 12 Sputtering was performed at a bias voltage of −100 V for about 180 minutes while the partial pressure of argon gas was 1.2 × 10 ⁻³ torr and the partial pressure of nitrogen gas was changed to 0 to 0.5 × 10 ⁻³ torr. Thus, a nitrogen-containing chromium film II having a hardness Hv700 of the base material side layer, a hardness Hv1700 of the intermediate layer, a hardness of the surface side layer of 1000, and a thickness of 15 μm was formed on the base material 20. Thereafter, a DLC film having a thickness of 5 μm was formed on the nitrogen-containing chromium film II by the same method as in Example 1.

[Comparative example]
A DLC film having a thickness of 5 μm was formed on the base material 20 by the same method as in Example 1 except that the nitrogen-containing chromium film I was not formed.

  The adhesion of the diamond-like carbon film-coated members of Examples 1 and 2 and Comparative Example produced as described above was evaluated. This adhesion was evaluated by scratching the film with a diamond indenter (0.2 mmR) at a load rate of 100 N / min and a scratch rate of 10 mm / min using a scratch tester. As a result, in Example 1, there is no peeling of the film from the base material up to 62N, and no film peeling (destruction) around the scratch, and in Example 2, peeling of the film from the base material and turning of the film even at 100N or more. However, in the comparative example, there was peeling of the film from the base material or turning of the film at 56N.

  According to the present invention, the difference in hardness and thermal expansion coefficient between the base material and the DLC film is smaller than the difference in hardness and thermal expansion coefficient between the base material and the DLC film, and nitrogen is contained but basically the metal. After forming the nitrogen-containing chromium film made of the above on the base material made of metal, the adhesion between the base material and the DLC film can be improved by forming the DLC film thereon. In addition, if a chromium film softer than the nitrogen-containing chromium film is formed between the base material and the nitrogen-containing chromium film, the difference in hardness and thermal expansion coefficient between the nitrogen-containing chromium film and the DLC film is small. The adhesion of the DLC film can be further improved. Further, the adhesion between the base material and the DLC film can be further improved by adjusting the nitrogen concentration in the nitrogen-containing chromium film and the hardness of the DLC film.

It is the schematic of the processing apparatus for manufacturing embodiment of the diamond-like carbon film coating | coated member by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Processing apparatus 12 Vacuum processing chamber 14 Vacuum pump 16 Rotary table 18 Jig 20 Base material 22 Target 24 Sputtering power supply 26 Ion bombardment and bias power supply 28 Gas introduction pipe

Claims (10)

A diamond-like carbon film coating characterized in that a chromium film is formed on a base material , a nitrogen-containing chromium film is formed on the chromium film, and a diamond-like carbon film is formed on the nitrogen-containing chromium film. Element. The diamond-like carbon film-coated member according to claim 1 , wherein the nitrogen-containing chromium film is a film in which at least one of nitrogen and chromium nitride is dispersed substantially uniformly in the chromium film. A nitrogen-containing chromium film is formed on the base material, and a diamond-like carbon film is formed on the nitrogen-containing chromium film . The nitrogen-containing chromium film has a nitrogen concentration in the central portion in the film thickness direction in the chromium film. characterized in that it is higher than the nitrogen concentration coating da ear Mondo-like carbon film covering member. The diamond-like carbon film-coated member according to claim 3, wherein a chromium film is formed between the base material and the nitrogen-containing chromium film. Chromium coating formed on the base material, after forming a nitrogen-containing chromium film on the chrome surface, and forming a diamond-like carbon film on the nitrogen-containing chromium film, diamond-like carbon film covering member Manufacturing method. The method for producing a diamond-like carbon film-coated member according to claim 5 , wherein the nitrogen-containing chromium film is formed by sputtering in an atmosphere containing argon and nitrogen using a chromium target. The method for producing a diamond-like carbon film-coated member according to claim 5 or 6 , wherein the diamond-like carbon film is formed by sputtering using a carbon target. Said nitrogen-containing chromium coating, at least one of nitrogen and chromium nitride is characterized by a substantially uniformly dispersed coating in chrome surface, diamond-like carbon film-coated member according to any one of claims 5 to 7 Manufacturing method. The nitrogen gas supply amount is set so that the nitrogen concentration in the atmosphere at the intermediate point of sputtering is higher than other points and the nitrogen concentration in the atmosphere at the start and end points of sputtering is lower than the nitrogen concentration at the intermediate point. By controlling , after forming a nitrogen-containing chromium film on the base material in which the nitrogen concentration in the central part in the film thickness direction in the chromium film is higher than the nitrogen concentration on both sides, diamond-like carbon is formed on this nitrogen-containing chromium film A method for producing a diamond-like carbon film-coated member, comprising forming a film. The diamond according to claim 9, wherein a chromium film is formed on the base material before the nitrogen-containing chromium film is formed on the base material, and then the nitrogen-containing chromium film is formed. A method for producing a like carbon film-coated member.

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