JP5938321B2 - Hard film and film forming method thereof, hard film forming body and manufacturing method thereof - Google Patents

Description

  The present invention relates to a hard film excellent in wear resistance and peeling resistance formed on a member made of an iron-based base material or a super hard material such as an automobile part or various molding dies.

  The hard carbon film is a hard film generally called diamond-like carbon (hereinafter referred to as DLC. A film / layer mainly composed of DLC is also referred to as a DLC film / layer). In addition, hard carbon has various names such as hard amorphous carbon, amorphous carbon, hard amorphous carbon, i-carbon, diamond-like carbon, and 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. It is as hard as diamond and has excellent wear resistance, solid lubricity, thermal conductivity, chemical stability, and corrosion resistance. For this reason, for example, it is being used as a protective film for molds / tools (including dimension measuring jigs), wear-resistant mechanical parts, abrasives, sliding members, magnetic / optical parts, and the like. As a method for forming such a DLC film, physical vapor deposition (hereinafter referred to as PVD) such as sputtering or ion plating, chemical vapor deposition (hereinafter referred to as CVD), unbalanced magnetron sputtering ( Hereinafter, a method such as UBMS) is employed.

While having such excellent characteristics, the DLC film generates extremely large internal stress during film formation, and has high hardness and Young's modulus, but its deformability is extremely small, so its adhesion is weak and it peels off. Has disadvantages such as easy. As a technique for improving the adhesion, for example, a technique that exhibits excellent adhesion even when formed relatively thick is known (see Patent Document 1). In this technique, a film mainly composed of DLC is used as the outermost surface layer, and further includes an intermediate layer and a base material. It has a four-layer structure.
(1) First layer composed of a Cr and / or Al metal layer (2) Mixed layer of Cr and / or Al metal and one or more metals selected from the group consisting of W, Ta, Mo and Nb The second layer (3) consisting of W, Ta, Mo and Nb. The third layer (4) consisting of one or more metal layers selected from the group consisting of W, Ta, Mo and Nb. A fourth layer comprising an amorphous layer containing one or more metals and carbon

  In order to improve adhesion, a technique is known in which a DLC film is formed by a UBMS method under a predetermined condition using a graphite target and a hydrocarbon-based gas in combination as a carbon supply source (Patent Document 2). reference).

JP 2003-171758 A JP 2011-68941 A

  However, even when the technique of Patent Document 1 is used, depending on the film structure and film formation conditions, the adhesion to the substrate is poor, and there is a possibility that the film may be easily peeled off due to residual stress after film formation. When the DLC film is peeled off, the original excellent characteristics of the DLC film cannot be exhibited. In particular, in the case where the hard film is formed in a portion that receives a high contact stress over a long period of time, not only static adhesion and mechanical properties but also fatigue properties are important in order to improve the peel resistance. In the technique of Patent Document 2, the adhesion is improved. However, in order to use it in a site used under more severe conditions as described above, further improvement of the film structure and the like is desired. Yes.

  The present invention has been made to cope with such problems, and has a hard film that has high wear resistance, is excellent in peel resistance, and can prevent peeling over a long period of time, and the hard film is formed. It aims at providing a hard film formation object.

  The hard film of the present invention is a hard film formed on the surface of a substrate, and the hard film is formed of chromium (hereinafter referred to as Cr) and tungsten car directly formed on the surface of the substrate. A first mixed layer mainly composed of a cutting tool (hereinafter referred to as WC), a second mixed layer mainly composed of WC and DLC formed on the first mixed layer, and the second mixed layer The first mixed layer is formed continuously or stepwise from the base material side to the second mixed layer side. The content ratio of Cr in the first mixed layer is reduced and the content ratio of WC in the first mixed layer is increased. The second mixed layer is from the first mixed layer side. The content ratio of the WC in the second mixed layer decreases continuously or stepwise toward the surface layer side, and the top in the second mixed layer is reduced. A layer DLC of content increases, the hydrogen content in the second mixed layer, characterized in that 10 to 45 atomic%.

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 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s. The hard film is characterized in that the sum of the average value of the indentation hardness and the standard deviation value is 25 to 45 GPa. The hard film has a critical peel load in a scratch test of 50 N or more.

  The surface layer is a layer formed using a UBMS apparatus using argon (hereinafter referred to as Ar) gas as a sputtering gas, and a graphite target and a hydrocarbon-based gas are used in combination as a carbon supply source. The ratio of the introduction amount of the hydrocarbon-based gas to the introduction amount 100 of Ar gas into the device is 1 to 5, the degree of vacuum in the device is 0.2 to 0.8 Pa, The film is formed by depositing carbon atoms generated from the carbon supply source on the second mixed layer under a condition in which a bias voltage to be applied is 70 to 150 V. Further, the hydrocarbon gas is methane gas.

  Note that the bias potential with respect to the base material is applied so as to be negative with respect to the ground potential. For example, the bias voltage of 150 V means that the bias potential of the base material is −150 V with respect to the ground potential. Show.

  The surface layer has a relaxation layer portion adjacent to the second mixed layer, and the relaxation layer portion includes a ratio of the introduction amount of the hydrocarbon-based gas, a degree of vacuum in the apparatus, and the base material. It is a part formed by changing at least one of the bias voltages applied to the battery continuously or stepwise.

  The hard film has a thickness of 0.5 to 3 μm, and the ratio of the thickness of the surface layer to the thickness of the hard film is 0.7 or less.

  The hard film forming body of the present invention is a hard film forming body comprising a base material and a hard film formed on the surface of the base material, and the hard film is the hard film of the present invention. It is characterized by. The base material is made of a cemented carbide material or an iron-based material. In particular, the base material is made of an iron-based material, and the iron-based material is high carbon chromium steel, carbon steel, tool steel, or martensitic stainless steel.

  The surface roughness of the substrate is 0.05 μmRa or less. Further, the hardness of the surface of the substrate is Hv650 or more in terms of Vickers hardness.

  A nitride layer is formed on the surface of the base material by nitriding before the hard film is formed. The nitriding treatment is a plasma nitriding treatment, and the surface hardness after the nitriding treatment is a Vickers hardness of Hv1000 or more.

  As described above, the hard film of the present invention comprises (1) the first mixed layer of Cr / WC (composition gradient), (2) the second mixed layer of WC / DLC (composition gradient), (3) It is a hard film having a structure composed of a DLC surface layer. The first mixed layer directly formed on the base material contains Cr and thus has good compatibility with iron-based materials and the like, and has excellent adhesion compared to Al and W. In the above structure, since WC has intermediate hardness and elastic modulus between Cr and DLC, both the first mixed layer and the second mixed layer have a gradient composition containing WC, so Residual stress concentration is unlikely to occur. Further, since the first mixed layer and the second mixed layer have a gradient composition, they have a structure in which different materials are physically combined. Furthermore, since the hydrogen content in the second mixed layer is 10 to 45 atomic%, even when the second mixed layer is formed in a portion that receives high contact stress, it can be prevented from peeling for a long period of time.

  With the above structure, even when the hard film is formed in a part that receives high contact stress, it has excellent peeling resistance and can exhibit the original characteristics of the DLC film. As a result, the hard film formed body of the present invention can be used for various applications as a member having excellent wear resistance, corrosion resistance, fretting resistance and the like.

It is a schematic cross section which shows the structure of the hard film of this invention. 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. It is a figure which shows a friction tester. It is a figure which shows a thrust type | mold rolling fatigue testing machine. It is a figure which shows an example of a GDS analysis result. It is an enlarged view of the 2nd mixed layer (WC / DLC layer) part in FIG. It is a figure which shows the relationship (calibration curve) of the hydrogen amount output value in GDS analysis, and the hydrogen amount measured by ERDA analysis. It is a figure which shows a fine abrasion tester.

  The structure of the hard film of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the structure of a hard film 1 formed on the substrate surface. As shown in FIG. 1, the hard film 1 includes (1) a first mixed layer 1a mainly composed of Cr and WC directly formed on the surface 2a of the substrate 2, and (2) a first mixture. A second mixed layer 1b mainly composed of WC and DLC formed on the layer 1a, and (3) a surface layer 1c mainly composed of DLC formed on the second mixed layer 1b. It has a three-layer structure. A hard film has a residual stress in the film, and the residual stress varies greatly depending on the film structure and film formation conditions. In the present invention, the film structure of the hard film is a three-layer structure as described above, so that sudden changes in physical properties (hardness, elastic modulus, etc.) are avoided.

  The first mixed layer 1a is an underlayer formed directly on the substrate surface. Since the first mixed layer 1a contains Cr, the first mixed layer 1a has good compatibility with a base material made of a cemented carbide material or an iron-based material, and has better adhesion to the base material than when W, Ti, Si, Al, or the like is used. Excellent. Moreover, WC used for the first mixed layer 1a has intermediate hardness and elastic modulus between Cr and DLC, and concentration of residual stress after film formation hardly occurs.

  In addition, since the first mixed layer 1a has a gradient composition in which the Cr content is small and the WC content is high from the base material 2 side toward the second mixed layer 1b side, 2 Adhesiveness on both sides with the mixed layer 1b is excellent. In addition, Cr and WC are physically bonded in the mixed layer, and damage in the mixed layer can be prevented. Furthermore, since the WC content is increased on the second mixed layer 1b side, the adhesion between the first mixed layer 1a and the second mixed layer 1b is excellent.

  The second mixed layer 1b becomes an intermediate layer interposed between the base layer and the surface layer. As described above, the WC used for the second mixed layer 1b has intermediate hardness and elastic modulus between Cr and DLC, and residual stress concentration after film formation hardly occurs. Since the second mixed layer 1b has a gradient composition in which the WC content decreases from the first mixed layer 1a side to the surface layer 1c side and the DLC content increases, the first mixed layer 1a and the surface Excellent adhesion on both sides with the layer 1c. In addition, WC and DLC are physically coupled in the mixed layer, and damage in the mixed layer can be prevented. Furthermore, since the DLC content is increased on the surface layer 1c side, the adhesion between the surface layer 1c and the second mixed layer 1b is excellent.

  The second mixed layer 1b is a layer that bonds non-adhesive DLC to the first mixed layer 1a side by WC with an anchor effect, and exhibits high adhesion even under severe conditions with fatigue due to high surface pressure. It is considered that the mechanical properties and fatigue properties of both DLC and WC in this layer are important. Therefore, the present inventors conducted experiments to optimize the film formation conditions of the second mixed layer (WC / DLC), and as a result, the hydrogen content in the second mixed layer was changed to the general sputtering conditions. It has been found that by increasing the number extremely, the peeling life can be remarkably improved in an environment with fatigue due to high contact stress such as rolling contact.

  The hydrogen content in the second mixed layer is 10 to 45 atomic%. It is more preferable to set it as 15-45 atomic%. When the hydrogen content in the second mixed layer is less than 10 atomic%, the mechanical properties are sufficient and the static adhesion is high, but the fatigue properties are inferior, so that they are easily peeled off under rolling contact. On the other hand, if the hydrogen content exceeds 45 atomic%, the mechanical properties become insufficient, the hard film deforms greatly without being able to withstand high surface pressure such as rolling contact, and stress concentrates on adjacent layers. Long life is difficult to develop.

  Here, the “hydrogen content in the second mixed layer” in the present invention is the hydrogen content (atomic%) obtained by GDS analysis (glow discharge emission spectroscopic analysis). The GDS analysis is an analysis capable of examining the relationship between the depth direction and the element amount, and can be quantified by preparing a calibration curve for each element. The hydrogen calibration curve was created using ERDA analysis (elastic recoil particle detection method) capable of measuring the absolute amount of hydrogen. Further, calibration curves for constituent elements other than hydrogen were prepared using EDX analysis. Details are shown below.

  FIG. 6 shows an example of the GDS analysis result, and FIG. 7 shows an enlarged view of the second mixed layer (WC / DLC layer) portion in FIG. The sputter time on the horizontal axis represents the depth from the surface. The WC / DLC layer is a range in which the C peak and the W peak coexist, and the maximum value (atomic%) of the hydrogen peak within this coexistence range is defined as “hydrogen content in the second mixed layer” in the present invention. Yes. “Atom%” on the vertical axis is calculated from the hydrogen output value (V) in the GDS analysis by the following method.

  Since the hydrogen output value (V) in GDS analysis differs depending on the test piece material, it is necessary to create a hydrogen calibration curve for each of DLC and WC constituting the second mixed layer (WC / DLC layer). is there. Therefore, for each of the DLC single-layer film test piece and the WC single-layer film test piece, test pieces having different hydrogen contents were prepared by adjusting the amount of methane gas introduced under conditions matching the film formation conditions of the WC / DLC layer. ERDA analysis and GDS analysis were performed. An example of the relationship (calibration curve) between the hydrogen output value (V) in the GDS analysis and the hydrogen amount (atomic%) measured in the ERDA analysis is shown in FIG. It can be seen that the hydrogen output value in the GDS analysis has a linear relationship with the hydrogen content. Since the hydrogen content obtained with the DLC hydrogen calibration curve is different from the hydrogen content obtained with the WC hydrogen calibration curve, it can be arbitrarily determined by taking the average of the hydrogen content obtained with both calibration curves. The hydrogen content (atomic%) corresponding to the hydrogen output value (V) can be calculated.

The surface layer 1c is a film mainly composed of DLC. The surface layer 1c preferably has a relaxing layer portion 1d on the side adjacent to the second mixed layer 1b. This is because when the film formation condition parameters (hydrocarbon gas introduction amount, vacuum degree, bias voltage) are different between the second mixed layer 1b and the surface layer 1c, in order to avoid abrupt changes in these parameters, It is a relaxation layer portion obtained by changing at least one continuously or stepwise. More specifically, the film formation condition parameters at the time of forming the outermost layer of the second mixed layer 1b are set as the start point, and the final film formation condition parameters of the surface layer 1c are set as the end points. Change. Thereby, the difference in the abrupt physical properties (hardness, elastic modulus, etc.) between the second mixed layer 1b and the surface layer 1c is eliminated, and the adhesion between the second mixed layer 1b and the surface layer 1c is further improved. By increasing the bias voltage continuously or stepwise, the composition ratio of the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter, and the hardness is inclined (increased). .

  The thickness of the hard film 1 (total of three layers) is preferably 0.5 to 3.0 μm. If the film thickness is less than 0.5 μm, the abrasion resistance and mechanical strength may be inferior, and if it exceeds 3.0 μm, the film is easily peeled off. Furthermore, the ratio of the thickness of the surface layer 1c to the thickness of the hard film 1 is preferably 0.7 or less. When this ratio exceeds 0.7, the inclined structure for physically bonding WC and DLC in the second mixed layer 1b tends to be a discontinuous structure, and the adhesiveness is likely to deteriorate.

  By making the hard film 1 into a three-layer structure including the first mixed layer 1a, the second mixed layer 1b, and the surface layer 1c having the above composition, the peel resistance is excellent.

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 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 0.05 m / s. If the specific wear amount is less than 200 × 10 ⁻¹⁰ mm ³ / (N · m) in the test, the wear resistance is excellent and the generation of wear powder can be prevented.

  Moreover, it is preferable that the sum total of the average value of indentation hardness and a standard deviation value is 25-45 GPa. Within this range, when a hard film is formed on the sliding surface, a high effect is exhibited even in abrasive wear that occurs when a hard foreign object intervenes on the sliding surface.

  Moreover, it is preferable that the critical peeling load in a scratch test is 50 N or more. The method for measuring the critical peel load in the scratch test is as shown in the examples described later. When the critical peel load is less than 50N, the hard film is likely to peel when used under high load conditions. Even if the critical peeling load is 50 N or more, the film may be easily peeled off depending on the case unless it is a film structure as in the present invention.

  Hereinafter, a method for forming the hard film will be described. The hard film is obtained by forming the base layer 1a, the mixed layer 1b, and the surface layer 1c in this order on the substrate surface.

  The surface layer 1c is preferably 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. In the figure, the base material 12 is a base material to be formed. As shown in FIG. 2, an inner magnet 14 a and an outer magnet 14 b having different magnetic characteristics 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. In such a UBMS method, an ion assist effect that causes Ar ions 17 and electrons to reach the base material 12 in a larger amount than the ordinary 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.

  Using this apparatus, the surface layer 1c uses a graphite target and a hydrocarbon gas in combination as a carbon supply source, and the amount of introduction of the hydrocarbon gas relative to the amount of introduction 100 of the Ar gas into the apparatus is as follows. The carbon atoms generated from the carbon supply source under the conditions that the ratio is 1 to 5, 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, The film is preferably deposited on the second mixed layer 1b. This preferable condition will be described below.

  By using a graphite target and a hydrocarbon-based gas in combination as a carbon supply source, the adhesion with the second mixed layer 1b can be improved. As the hydrocarbon-based gas, methane gas, acetylene gas, benzene and the like can be used, and are not particularly limited. However, methane gas is preferable from the viewpoint of cost and handleability.

  By setting the ratio of the introduction amount of the hydrocarbon-based gas to 1 to 5 (volume part) with respect to 100 introduction (volume part) of Ar gas into the UBMS apparatus (in the film formation chamber), the surface layer The adhesion with the second mixed layer 1b can be improved without deteriorating the wear resistance of 1c.

  The degree of vacuum in the UBMS apparatus (inside the film forming chamber) is preferably 0.2 to 0.8 Pa as described above. More preferably, it is 0.25 to 0.8 Pa. If the degree of vacuum is less than 0.2 Pa, the amount of Ar gas in the chamber is small, so that Ar plasma is not generated and film formation may not be possible. On the other hand, if the degree of vacuum is higher than 0.8 Pa, the reverse sputtering phenomenon tends to occur and the wear resistance may be deteriorated.

  The bias voltage applied to the substrate is preferably 70 to 150 V as described above. More preferably, it is 100-150V. 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, reverse sputtering tends to occur, and the wear resistance may be deteriorated. On the other hand, if the bias voltage is too high, the surface layer becomes too hard and may be easily peeled off during use.

  Moreover, it is preferable that the introduction amount of Ar gas which is sputtering gas is 40-150 ml / min. More preferably, it is 50-150 ml / min. When the Ar gas flow rate is less than 40 ml / min, Ar plasma is not generated and film formation may not be possible. On the other hand, if the Ar gas flow rate is higher than 150 ml / min, the reverse sputtering phenomenon tends to occur, so that the wear resistance may be deteriorated. When the amount of Ar gas introduced is large, the collision probability between Ar atoms and carbon atoms increases in the film forming chamber. As a result, the number of Ar atoms reaching the film surface is reduced, the effect of compacting the film by Ar atoms is reduced, and the wear resistance of the film is deteriorated.

  It is preferable that the first mixed layer 1a and the second mixed layer 1b are also formed using a UBMS apparatus using Ar gas as the sputtering gas. When forming the first mixed layer 1 a, a Cr target and a WC target are used in combination as the target 15. In forming the second mixed layer 1b, (1) a WC target, and (2) a graphite target and a hydrocarbon-based gas are used. The target used for each layer is sequentially replaced every time the layers are formed.

  The first mixed layer 1a is formed continuously or stepwise while increasing the sputtering power applied to the WC target and decreasing the power applied to the Cr target. Thereby, it can be set as the layer of the gradient composition which the content rate of Cr is small toward the 2nd mixed layer 1b side, and the content rate of WC becomes high.

  The second mixed layer 1b is formed continuously or stepwise while increasing the sputtering power applied to the graphite target serving as the carbon supply source and decreasing the power applied to the WC target. Thereby, it can be set as the layer of the gradient composition which the content rate of WC becomes small toward the surface layer 1c side, and the content rate of DLC becomes high.

  In order to set the hydrogen content in the second mixed layer 1b within the above range (10 to 45 atomic%), a graphite target and a hydrocarbon gas are used in combination as a carbon supply source, and the ratio of the introduction amount of the hydrocarbon gas. Is increased in comparison with normal sputtering conditions. For example, the ratio of the introduction amount of the hydrocarbon-based gas is 5 to 40, more preferably 10 to 40 (volume part) with respect to the introduction amount 100 (volume part) of Ar gas into the UBMS apparatus (deposition chamber). ). Other conditions such as the degree of vacuum in the apparatus and the bias voltage during the formation of the second mixed layer are the same as the preferred film formation conditions for the surface layer described above.

  The hard film forming body of the present invention comprises a base material and a hard film formed on the surface of the base material. This hard film is the hard film of the present invention described above.

  Although it does not specifically limit as a material of a base material, A cemented carbide material or an iron-type material can be used. As the cemented carbide material, in addition to the WC-Co alloy having the most excellent mechanical properties, the WC-TiC-Co alloy, WC-TaC-Co alloy, WC-TiC- with improved oxidation resistance Examples include TaC-Co alloys. Examples of the iron-based material include high carbon chromium steel, carbon steel, tool steel, martensitic stainless steel, and the like.

  In these substrates, the hardness of the substrate surface on which the hard film is formed is preferably Hv650 or higher in terms of Vickers hardness. By setting it as Hv650 or more, a hardness difference with a hard film (1st mixed layer) can be decreased, and adhesiveness can be improved.

  On the surface of the base material on which the hard film is formed, it is preferable that a nitride layer is formed by nitriding before forming the hard film. 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. Moreover, it is preferable that the hardness of the surface after nitriding is Hv1000 or more in terms of Vickers hardness in order to further improve the adhesion to the hard film (first mixed layer).

  The surface roughness Ra of the substrate surface on which the hard film is formed is preferably 0.05 μm or less. When the surface roughness Ra exceeds 0.05 μm, it is difficult to form a hard film at the tip of the projection having the roughness, and the film thickness is locally reduced.

  The hard film forming body of the present invention can be used in sliding members, molds / tools, abrasives, magnetic / optical parts, and other parts that require high wear resistance and peel resistance.

  The hard film of the present invention was formed on a predetermined substrate, and the physical properties of the hard film were evaluated. These will be described below as examples, comparative examples, and reference examples.

The base material, UBMS apparatus, and sputtering gas used for evaluation of the hard film are as follows.
(1) Base material: Base material shown in each table (2) Base material dimensions, etc .: Surface roughness disks shown in each table (φ48 mm × φ8 mm × 7 mm, film formation on a plane)
(3) UBMS equipment: manufactured by Kobe Steel; UBMS202 / AIP composite equipment (4) Sputtering gas: Ar gas

The conditions for forming the first mixed layer (underlayer) will be described below. The inside of the deposition chamber is evacuated to about 5 × 10 ⁻³ Pa, the substrate is baked with a heater, the surface of the substrate is etched with Ar plasma, and the sputtering power applied to the Cr target and the WC target is adjusted. , A layer in which the composition ratio of Cr and WC was inclined was formed. The bias voltage applied to the substrate is 150V. This layer is a layer having a small Cr content and a high WC content from the base material side toward the second mixed layer side. In addition, when using it as mixed layers other than Cr / WC, it formed on the same conditions except using a corresponding target.

The conditions for forming the second mixed layer (intermediate layer) will be described below. The inside of the film forming chamber is evacuated to about 5 × 10 ⁻³ Pa, and after etching the substrate surface (or the surface of the underlayer) with Ar plasma, while supplying methane gas, which is a hydrocarbon-based gas, The sputtering power applied to the graphite target was adjusted to form a layer in which the composition ratio of WC and DLC was inclined. The bias voltage applied to the substrate is 150V. This layer is a layer in which the content ratio of WC decreases and the content ratio of DLC increases from the first mixed layer side toward the surface layer side. The hydrogen content (atomic%) in the second mixed layer was determined by the above-described method by GDS analysis (glow discharge emission spectroscopic analysis). The methane gas introduction ratio is as shown in each table.

  The conditions for forming the surface layer are as shown in each table.

  An outline of the UBMS 202 / AIP combined apparatus is shown in FIG. FIG. 3 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 3, the UBMS 202 / AIP combined device instantaneously vaporizes and ionizes the AIP evaporation source material 21 by using vacuum arc discharge to the base material 23 arranged on the disk 22. This is deposited on the base material 23 to increase the plasma density in the vicinity of the base material 23 and increase the ion assist effect by the non-equilibrium magnetic field of the sputtering evaporation source material (target) 24. (See FIG. 2), this is an apparatus having a UBMS function capable of controlling the characteristics of the film deposited on the substrate. By 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. In this embodiment, the first mixed layer, the second mixed layer, and the surface layer are formed on the base material as a UBMS film.

Examples 1-10, 12, Comparative Examples 1-7, Reference Examples 1-9
The substrates shown in Tables 1 to 3 were ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite apparatus, and the first mixed layer and the second mixed layer having the materials shown in each table were formed under the above-described formation conditions. On top of that, a DLC film as a surface layer was formed under the film forming conditions shown in each table to obtain a test piece having a hard film. Note that “degree of vacuum” in each table is the degree of vacuum in the film forming chamber in the above apparatus. The obtained specimens were subjected to the following frictional wear test, film thickness test, hardness test, scratch test, and thrust type rolling fatigue test (other than the reference example). The results are shown in each table. The following 1) to 7) in Table 1 are the same in Table 2 to Table 4.

Example 11
Manufactured by JEOL Ltd .: A substrate (Vickers hardness Hv1000) subjected to plasma nitrogen treatment using a radical nitriding apparatus was ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite apparatus, and the first mixed layer (Cr / WC) and the second mixed layer (WC / DLC) having the materials shown in Table 1 were formed under the above-described formation conditions. A DLC film, which is a surface layer, was formed on the film formation conditions shown in Table 1 to obtain a test piece having a hard film. About the obtained test piece, it uses for the test similar to Example 1, and the result is written together in Table 1. FIG.

<Friction and wear test>
The obtained specimen was subjected to a friction test using a friction tester shown in FIG. 4A shows a front view, and FIG. 4B shows a side view. 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 as a mating member 32, the test piece 31 is fixed to the arm portion 33, and a predetermined load 34 is applied to the upper part of the drawing. And a lubricant is interposed between the test piece 31 and the mating member 32 for 30 minutes at a rotation speed of 0.05 m / s under a maximum contact surface pressure of 0.5 GPa at room temperature (25 ° C.). Instead, the load cell 35 detected the frictional force generated between the counterpart material 32 and the test piece 31 when the counterpart material 32 was rotated. From this, the specific wear amount was calculated.

<Film thickness test>
The film thickness of the hard film of the obtained test piece was measured using a surface shape / surface roughness measuring instrument (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.

<Hardness test>
The indentation hardness of the obtained test piece was measured using a nanoindenter (G200) manufactured by Agilent Technologies. In addition, the measured value has shown the average value of the depth (location where hardness is stabilized) which is not influenced by surface roughness, and is measuring 10 each test piece.

<Scratch test>
The obtained test piece was subjected to a scratch test using Nanotech: Level Test RST, and the critical peel load was measured. Specifically, the obtained test piece was tested with a diamond indenter with a tip radius of 200 μm at a scratch speed of 10 mm / min and a load load speed of 10 N / mm (continuously increasing the load), and judged on the testing machine screen. Then, the load at which the area of the exposed base material reached 50% with respect to the frictional trace on the screen (length in the friction direction 375 μm, width about 100 μm) was measured as the critical peel load.

<Thrust type rolling fatigue test>
About the obtained test piece (φ48 mm × φ8 mm × 7 mm), as a thrust type rolling fatigue test using the testing machine shown in FIG. 5, “low lambda condition” assuming that the lubrication state of the bearing is severe, Two conditions, “high lambda conditions”, assuming a good lubrication state, were tested to evaluate the rolling fatigue characteristics of the hard film. Since “low lambda condition” is boundary lubrication, damage due to contact is affected in addition to pure repeated rolling fatigue. Therefore, the wear resistance and adhesion of the hard film are required. Each condition is shown below.

[Low lambda condition]
Lubricating oil: VG2
Lambda: 0.6
Maximum contact surface pressure: 2 GPa
Rotational speed: 1000r / min
Orbit diameter: φ20mm
Rolling element: size 7/32 ", number 3, material SUJ2, hardness Hv750, surface roughness 0.005μmRa
Oil temperature: 70 ° C
Censoring time: None (1111h at 8th load)

[High lambda condition]
Lubricating oil: VG32
Lambda: 9.2
Maximum contact surface pressure: 3.5 GPa
Rotation speed: 4500r / min
Orbit diameter: φ20mm
Rolling element: size 7/32 ", number 3, material SUJ2, hardness Hv750, surface roughness 0.005μmRa
Oil temperature: 70 ° C
Abort time: 300h
(The load count is 8th power at 247h)

  As shown in FIG. 5, the testing machine has a configuration in which the rolling element 42 rolls between a disk-shaped test piece 41 and a raceway (51201) 45, and the test piece 41 has an alignment ball 43. Is supported through. In the figure, 44 is a rotary ball spline for preloading, 46 is a heater, and 47 is a thermocouple. This testing machine has a structure in which the rolling trace does not shift even when the test piece 41 is reattached. In the evaluation method, the test piece is removed every 20 h of test time, and the presence or absence of peeling of the hard film from the test piece is confirmed by observation with an optical microscope. For example, if it peels at the time of 20h confirmation, a lifetime will be 20h. If it is not peeled off at the time of confirmation for 20 hours, the test piece is attached again and the test is continued. The lifetime is shown in Table 1 and Table 2 together. In addition, as a life determination, under low lambda conditions, those having a life of 1500 h or more are recorded as “◯”, and those having a life less than 1500 h are recorded as “x”. Under the high lambda condition, “O” is recorded when the lifetime is 300 h or more, and “X” is recorded when the lifetime is less than 300 h.

  As shown in Table 1, it can be seen that the hard film of each example is excellent in wear resistance and peel resistance. On the other hand, Comparative Examples 1 to 5 having different film structures resulted in inferior peel resistance and the like. Moreover, although the film structure (three-layer structure) is equivalent, in Comparative Examples 6 and 7 in which the hydrogen content in the second mixed layer is not within the scope of the present invention, the result was inferior in peeling resistance under high lambda conditions. .

Examples 13-18, Comparative Examples 8-10
The hard film of the present invention was subjected to the following fine wear test to evaluate its resistance to fretting wear. Test pieces (φ48 mm × φ8 mm × 7 mm, film-formed on a plane) were produced under the conditions shown in Table 4. Each layer was formed under the same conditions as in Example 1 except for the conditions shown in Table 4.

<Fine wear test>
FIG. 9 is a diagram showing a fine wear tester. As shown in FIG. 9, a fine ball wear tester 51 is used to place a steel ball 53 loaded with a radial load 54 on a test piece 52 coated with grease 55 and reciprocate in the horizontal direction AB under the following conditions. The wear depth and specific wear amount of the test piece 52 and the wear amount of the steel ball 53 were measured.

[Measurement condition]
Grease: Calcium / lithium soap / mineral oil grease Radial load: 10kgf
Maximum contact surface pressure: 2.5 GPa
Frequency: 30Hz
Reciprocating amplitude: 0.47mm
Test time: 4 hours

  As shown in Table 4, it can be seen that the hard film of each example is excellent in fretting resistance. Moreover, the wear of the steel ball as the counterpart material could be suppressed. On the other hand, in Comparative Example 8 where the hydrogen content in the second mixed layer is not within the scope of the present invention and Comparative Examples 9 and 10 having different film structures, the fretting resistance is inferior and the wear amount of the steel ball as the counterpart material is large. As a result.

  The hard film of the present invention can be suitably used as a film formed on sliding members, molds / tools, abrasives, magnetic / optical components, and other parts that require high wear resistance and peeling resistance.

DESCRIPTION OF SYMBOLS 1 Hard film | membrane 1a 1st mixed layer 1b 2nd mixed layer 1c Surface layer 1d Relaxation layer part 2 Base material 11 Bias power supply 12 Base material 13 Film | membrane (layer)
DESCRIPTION OF SYMBOLS 15 Target 16 Magnetic field line 17 Ar ion 18 Ionized target 19 High density plasma 21 AIP evaporation source material 22 Disc 23 Base material 24 Sputter evaporation source material (target)
31 Test piece 32 Counterpart 33 Arm part 34 Load 35 Load cell 41 Test piece 42 Rolling body 43 Alignment ball 44 Rotary ball spline 45 Bearing disc 46 Heater 47 Thermocouple 51 Fine movement test machine 52 Test piece 53 Steel ball 54 Radial load 55 Grease

Claims (15)

A hard film formed on the surface of the substrate,
The hard film includes a first mixed layer mainly composed of chromium and tungsten carbide formed directly on the surface of the substrate, and tungsten carbide and diamond formed on the first mixed layer. A film having a structure composed of a second mixed layer mainly composed of like carbon and a surface layer mainly composed of diamond-like carbon formed on the second mixed layer;
In the first mixed layer, the chromium content in the first mixed layer decreases continuously or stepwise from the base material side to the second mixed layer side, and the first mixed layer Is a layer in which the content of the tungsten carbide is high,
In the second mixed layer, the content of the tungsten carbide in the second mixed layer decreases continuously or stepwise from the first mixed layer side to the surface layer side, and the second mixed layer A layer in which the content of the diamond-like carbon in the layer is high,
A hard film, wherein a hydrogen content in the second mixed layer is 10 to 45 atomic%. 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 200 × 10 ⁻¹⁰ mm ³ / (N · m). 1. The hard film according to 1.   The hard film according to claim 2, wherein the hard film has a sum of an average value of indentation hardness and a standard deviation value of 25 to 45 GPa.   The hard film according to claim 2 or 3, wherein the hard film has a critical peel load in a scratch test of 50 N or more. The film thickness of the hard film is 0.5 to 3 µm, and the ratio of the thickness of the surface layer to the film thickness of the hard film is 0.7 or less. 5. The hard film according to any one of 4 above. A method for forming a hard film according to any one of claims 1 to 5,
Said surface layer, using the unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas, a combination of a graphite target as a carbon source and hydrocarbon gas, into the apparatus of the argon gas The ratio of the introduction amount of the hydrocarbon-based gas to the introduction amount 100 is 1 to 5, 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. under conditions at a carbon atom which results from the carbon source, the method of forming the hard film, which is deposited by depositing on the second mixed layer. The surface layer has a relaxation layer portion adjacent to the second mixed layer, and the relaxation layer portion includes a ratio of the introduction amount of the hydrocarbon-based gas, a degree of vacuum in the apparatus, and the base material 7. The method of forming a hard film according to claim 6 , wherein at least one of the bias voltages applied to is a portion formed by changing continuously or stepwise. The hydrocarbon gas is, according to claim 6 or claim 7 method of forming the hard film according to, characterized in that methane gas. A hard film forming body comprising a base material and a hard film formed on the surface of the base material,
The hard film forming body, wherein the hard film is the hard film according to any one of claims 1 to 5 .   The hard film forming body according to claim 9, wherein the substrate is made of a cemented carbide material or an iron-based material.   The hard film forming body according to claim 10, wherein the base material is made of the iron-based material, and the iron-based material is high carbon chromium steel, carbon steel, tool steel, or martensitic stainless steel. .   The hard film forming body according to claim 9, wherein the surface roughness of the substrate is 0.05 μmRa or less.   The hardness of the surface of the said base material is Hv650 or more by Vickers hardness, The hard film formation body of any one of Claim 9 thru | or 12 characterized by the above-mentioned. It is a manufacturing method of the hard film formation object according to any one of claims 9 to 13,
A method for producing a hard film forming body, wherein a nitride layer is formed on the surface of the base material by nitriding before forming the hard film. The method of manufacturing a hard film forming body according to claim 14, wherein the nitriding treatment is a plasma nitriding treatment, and the hardness of the surface after the nitriding treatment is Hv 1000 or more in terms of Vickers hardness.