TW201804017A - Hard coating, hard coating-covered member, and method for producing hard coating - Google Patents

Abstract

This hard coating 20 includes each of the elements Al, Cr, and N. The hard coating 20 has a cubic rock salt-type crystal structure, and comprises the compositional formula AlmCr1-mN1-x-y-zCxByOz (where 0.68 ≤ m ≤ 0.85, and y ≤ 0.10). When H (GPa) represents the hardness of the hard coating 20, and E (GPa) represents the Young's modulus of the hard coating 20, the ratio H/E of the hardness to the Young's modulus is in the range of 0.050-0.120 inclusive, and H is at least 20 GPa.

Description

Hard film, hard film covering member, and manufacturing method of hard film

The present invention relates to a hard film, a hard film covering member including the hard film, and a method for manufacturing a hard film.

In the past, cutting tools, metal molds, and other tools that caused a large temperature rise or abrasion due to sliding between them and hard objects were used. In order to improve wear resistance, a hard film made of ceramic material was used on the surface of the substrate. Countermeasures. For example, the following Patent Documents 1 and 2 and Non-Patent Document 1 disclose that a hard film made of AlCrN is formed on the surface of a substrate such as a cutting tool. The following Patent Document 1 and Non-Patent Document 1 disclose the formation of an AlCrN film containing 70 atomic percent or more of aluminum on a substrate. In addition, the following Patent Document 2 discloses the formation of an AlCrN film containing less than 70 atomic percent of aluminum on a substrate.

The AlCrN film has a crystalline structure of cubic crystals in a quasi-stable state where aluminum is solid-dissolved in the CrN lattice. Here, when the aluminum content is high as in the following Patent Documents 1 and Non-Patent Document 1, the state of solid solution of aluminum in the CrN lattice becomes unstable, and hexagonal AlN in a stable phase is generated. Such a hexagonal crystal structure has poor mechanical properties, and in the following Patent Document 1 and Non-Patent Document 1, a hard film having excellent abrasion resistance cannot be obtained.

On the other hand, a film having a low aluminum content as in the following Patent Document 2 has a crystal structure in which coarse cubic crystals of AlCrN are generated. In this case, the film becomes hard and the Young's coefficient becomes high. Therefore, the deformation energy from the external force becomes scarce and easily develops into cracks, and there is a problem that the wear resistance is inferior.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4475230

[Patent Document 2] Japanese Patent Publication No. 2006-524748

[Non-patent literature]

[Non-Patent Document 1] Surface & Coatings Technology, 200, (2005), 2114-2122

An object of the present invention is to provide a hard film with improved abrasion resistance, a hard film covering member including the hard film, and a method for manufacturing the hard film.

A hard film related to one aspect of the present invention is a hard film containing aluminum, chromium, and nitrogen, and is composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z . In the aforementioned composition formula, m is an atomic ratio of aluminum to aluminum and chromium in total. 1-m is the atomic ratio of chromium to aluminum and chromium in total. 1-xyz is the total atomic ratio of nitrogen to nitrogen, carbon, boron, and oxygen. x is the atomic ratio of carbon to nitrogen, carbon, boron, and oxygen in total. y is the atomic ratio of boron to nitrogen, carbon, boron, and oxygen in total. z is the atomic ratio of oxygen to nitrogen, carbon, boron, and oxygen in total. The relational expressions of 0.68 ≦ m ≦ 0.85 and y ≦ 0.10 are satisfied. With cubic crystal salt crystal structure. When the hardness of the hard film 20 is H (GPa), and when the Young's coefficient of the hard film 20 is E (GPa), the ratio H / E of the ratio of the hardness to the Young's coefficient is 0.050 or more and 0.120 or less, and H is 20 GPa or more.

A hard film covering member according to another aspect of the present invention includes a base material and a hard film formed on a surface of the base material.

The manufacturing method of the hard film related to the other aspects of the present invention is a hard structure having a crystal structure of cubic rock salt type composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z A method for forming a film on the surface of a substrate. In the aforementioned composition formula, m is an atomic ratio of aluminum to aluminum and chromium in total. 1-m is the atomic ratio of chromium to aluminum and chromium in total. 1-xyz is the total atomic ratio of nitrogen to nitrogen, carbon, boron, and oxygen. x is the atomic ratio of carbon to nitrogen, carbon, boron, and oxygen in total. y is the atomic ratio of boron to nitrogen, carbon, boron, and oxygen in total. z is the atomic ratio of oxygen to nitrogen, carbon, boron, and oxygen in total. It satisfies the relational expressions of 0.70 <m ≦ 0.85 and y ≦ 0.10. The method includes a step of setting the substrate on a stage, a step of setting a target having a component composition of the hard film, and a step of forming the hard film on a surface of the substrate by evaporating the target. In the step of forming the hard film, the hard film is formed while applying a bias voltage to the substrate so that the bias voltage V applied to the substrate by the stage satisfies -316 ≦ V ≦ -214.3m + 110.

2‧‧‧ film forming device

10‧‧‧ Insert

11‧‧‧ Substrate

20‧‧‧ Hard film

21‧‧‧vacuum chamber

22‧‧‧Arc Power

22A‧‧‧ target

23‧‧‧Sputtering Power

23A‧‧‧Sputtering evaporation source

24‧‧‧ stage

25‧‧‧ Bias Power

26‧‧‧heater

27‧‧‧ Discharge DC Power Supply

28‧‧‧heating AC power

31‧‧‧dig face

32‧‧‧ escape face

33‧‧‧ cutting edge

100‧‧‧ to be cut

101‧‧‧chips

FIG. 1 is a schematic diagram showing an insert of a hard film covering member related to Embodiment 1 of the present invention.

FIG. 2 is a schematic view showing a shape of a material to be cut by the insert.

FIG. 3 is a schematic diagram showing the configuration of a hard film according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a flow of a method for manufacturing a hard film according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram showing the configuration of a film forming apparatus used for the film formation of the hard film.

FIG. 6 is a schematic diagram showing a magnetic field generated in a direction perpendicular to a target discharge surface.

FIG. 7 is a schematic diagram showing a magnetic field generated in a direction perpendicular to a target discharge surface.

FIG. 8 is a graph showing the relationship between the atomic ratio of aluminum and the bias voltage applied to the substrate.

FIG. 9 is a graph showing the relationship between the atomic ratio of aluminum and the bias voltage applied to the substrate.

FIG. 10 is a schematic diagram showing a metal mold of a hard film covering member according to a second embodiment of the present invention.

(Outline of the embodiment of the present invention)

First, an outline of a method for manufacturing a hard film, a hard film covering member, and a hard film according to an embodiment of the present invention will be described.

A hard film related to one embodiment of the present invention is a hard film containing aluminum, chromium, and nitrogen, and is composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z . With this composition, the relational expressions of 0.68 ≦ m ≦ 0.85 and y ≦ 0.10 are satisfied. This hard film has a crystalline structure of cubic rock salt type. When the hardness of the hard film is H (GPa) and when the Young's coefficient of the hard film is E (GPa), the ratio H / E of the ratio of the hardness to the Young's coefficient is 0.050 or more and 0.120 or less, and H is 20 GPa or more.

In the aforementioned hard film, by adjusting the aluminum content to the range of 0.68 ≦ m ≦ 0.85, and adjusting the hardness H and Young's coefficient E at the same time, it becomes a H / E of 0.050 or more and 0.120 or less and H of 20 GPa or more (H ≧ 20 GPa) range. For a film whose H / E is less than 0.050, the Young's coefficient E becomes too high for the hardness H, and when an external force is applied, the amount of deformation of the film becomes small. For this reason, it is easy to crack, and abrasion resistance falls. On the other hand, a film with a large H / E (over 0.120) causes the Young's coefficient E to become too low, making it difficult to exert its function as a hard film.

In contrast, the aforementioned hard film has a crystalline structure of cubic rock salt type and has a hardness H in a range of 20 GPa or more. By adjusting H / E to a range of 0.050 or more and 0.120 or less, the wear resistance is greatly improved. H / E is preferably 0.0505 or more, more preferably 0.0510 or more, more preferably 0.0515 or more, and more preferably 0.0520 or more. Further, H / E is preferably 0.058 or more, more preferably 0.060 or more, and still more preferably 0.061 or more. In addition, regarding the upper limit, H / E It is preferably 0.10 or less, and more preferably 0.09 or less. In addition, the hardness H is preferably 22 GPa or more, 24 GPa or more is better, 25 GPa or more is better, and 26 GPa or more is better.

The "hardness H (GPa)" and "Young's coefficient E (GPa)" of the hard film were measured by performing a Nano Indentation Test using a superhard test piece formed with a hard film. For measurement by a nano-indenter, "ENT-1100 (manufactured by Elionix)" was used. In addition, in an indentation tester, a triangular pyramid indenter of a geometrical pyramid type (Berkovich) was used.

First, five points of load curves were measured using five kinds of loads of 2, 5, 7, 10, and 20 mN. Then, using the method of compliance and the tip shape of the correction device (J. Mater. Res. Vol. 16, No. 11, 2001, 3084) proposed by SAWA, etc., the data was corrected to calculate the "hardness H (GPa) "and" Young's coefficient E (GPa) ". The value of H / E (-) can be calculated from the measured value.

In addition, the atomic ratios of Al, Cr, N, C, B, and O of the hard film can be measured using an Energy Dispersive X-ray Spectrometer.

In the hard film, when measured by X-ray diffraction using CuKα rays, it is preferable that the half-peak full-amplitude value of the peak of the (111) plane of the cubic crystal salt-type crystal structure is 0.25 ° to 1.00 °.

In the aforementioned hard film, the strain caused by the formation of extremely fine hexagonal crystals in the crystal and the ionic conflict during film formation hinders the growth of cubic crystals, and as a result, the cubic crystal grains become smaller. Therefore, perform X-ray diffraction In the case of measurement, the full width at half maximum of the peak of the (111) plane of the cubic crystal salt-type crystal structure is 0.25 ° or more and 1.00 ° or less. The half-peak full-amplitude value becomes a film in which cubic crystals are refined in this range, and the range of H / E is adjusted to a range of 0.050 to 0.120 as described above. Moreover, the extremely fine cubic crystals in the crystal are of such a magnitude that they cannot be detected by X-ray diffraction measurement.

When the full width of the half-peak value is less than 0.25 °, the grain size of the cubic crystal grows greatly, and the H / E ratio is smaller than the range of 0.050 to 0.120. On the other hand, when the full width of the half-peak value exceeds 1.00 °, the crystal grains of the cubic crystal are too fine, so the crystal grains tend to fall off and the wear resistance is reduced. Therefore, the range of the full width of the half-peak is preferably from 0.25 ° to 1.00 °. In addition, the lower limit of the full width of the half-peak value is more preferably 0.255 ° or more, more preferably 0.26 ° or more, 0.265 ° or more, and even better. Furthermore, the lower limit of the full amplitude at half maximum is preferably 0.32 ° or more, more preferably 0.35 ° or more, more preferably 0.37 ° or more, and more preferably 0.40 ° or more. In addition, the upper limit of the full width of the half-peak value is preferably 0.95 ° or less, more preferably 0.90 ° or less, and 0.85 ° or less.

In addition, as described above, in order to obtain a hard film in which extremely fine hexagonal crystals and finer cubic crystals are mixed, it is also necessary to adjust the aluminum content in the film. When the aluminum content is too low, extremely fine hexagonal crystals are not generated. Therefore, in the aforementioned hard film, the atomic ratio m of aluminum is 0.68 or more, preferably more than 0.70, more preferably more than 0.71, more preferably 0.72 or more, and even more preferably 0.75 or more. On the other hand, when the aluminum content is too high, cubic crystals are not generated. Therefore, in the aforementioned hard film, the atomic ratio m of aluminum is 0.85 or less, preferably 0.82 or less, more preferably 0.80 or less, and even more preferably 0.78 or less.

In the hard film, the atomic ratio x of carbon may satisfy the relational expression of 0.05 ≦ x <0.5. In addition, the atomic ratio of boron may satisfy the relational expression of y ≦ 0.10, and further satisfy the relational expression of 0.01 ≦ y. In addition, the atomic ratio z of oxygen may satisfy the relational expression of 0 <z <0.10.

The hard film is based on a nitride, and may further include elements such as carbon (C), boron (B), and oxygen (O) in order to provide further functions. Carbon increases the hardness of the film by forming carbides in the crystal. In order to obtain such an effect, the atomic ratio x of carbon is preferably 0.05 or more. However, if the carbon content is excessive, the heat resistance of the film is lowered, so the carbon atomic ratio x is preferably less than 0.5.

Boron, by combining with nitrogen in the film to form a solid lubricant nitrogen boride, imparts a lubricating effect to the film. In order to obtain such an effect, the atomic ratio y of boron is preferably 0.01 or more. However, if the boron content is excessive, the hardness of the film decreases. Therefore, the atomic ratio y of boron is preferably 0.10 or less, and more preferably 0.08 or less. In addition, oxygen may be added for the purpose of increasing the hardness of the film by forming alumina Al ₂ O _3. However, if the oxygen content is excessive, the abrasion resistance is reduced. Therefore, the atomic ratio z of oxygen is preferably less than 0.1.

The hard film covering member according to the embodiment includes a base material and a hard film formed on the surface of the base material. The hard film covering member is one in which the hard film excellent in abrasion resistance is formed on a surface of a substrate. Therefore, the aforementioned hard film covering member can be suitably used for a tool that requires high abrasion resistance and is used in an environment where there is a severe sliding between a cutting tool, a metal mold, and a hard object.

The manufacturing method of the hard film according to this embodiment is a hard film having a crystal structure of cubic rock salt type composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z . On the surface of the substrate. With this composition, the relational expressions of 0.70 <m ≦ 0.85 and y ≦ 0.10 are satisfied. The method includes a step of setting the substrate on a stage, a step of setting a target having a component composition of the hard film, and a step of forming the hard film on a surface of the substrate by evaporating the target. In the step of forming the hard film, the hard film is formed while applying a bias voltage to the substrate so that the bias voltage V applied to the substrate by the stage satisfies -316 ≦ V ≦ -214.3m + 110. The lower limit of the bias voltage V is preferably -1666m + 1100.

In the aforementioned method of manufacturing a hard film, a hard film is formed while applying a bias voltage V controlled to the aforementioned range to a substrate. In hard films with a large aluminum content (0.70 <m), hexagonal crystals with stable phases are easily formed. On the other hand, in the aforementioned manufacturing method, by applying a bias voltage V controlled to an appropriate range to the substrate, it is possible to impart energy to the charged particles that are evaporated from the target and made incident on the substrate. Therefore, high-energy charged particles can be sputtered onto the film surface during film formation. Thereby, the energy on the film surface during film formation can be increased, and it can be made into a state of local instability. Therefore, a cubic crystal with a quasi-stable phase can be generated, and at the same time, a film in which the crystal grains of the cubic crystal are refined is formed by extremely fine hexagonal crystals. As a result, the aforementioned hard film excellent in abrasion resistance adjusted to a range of H / E of 0.050 or more and 0.120 or less and a hardness H of 20 GPa or more can be obtained.

When the bias voltage V is higher than the aforementioned range, coarse hexagonal crystals are formed in the film, so that H / E becomes large but the hardness H of the film becomes low. On the other hand, when the bias voltage V is lower than the aforementioned range, The energy of the charged particles is too high, so the effect of the sputtering rate is greater than the film formation rate. Therefore, formation of a hard film becomes difficult. On the other hand, by appropriately controlling the bias voltage V as described above, a hard film excellent in abrasion resistance adjusted to a range of H / E of 0.050 or more and 0.120 or less and hardness H of 20 GPa or more can be formed.

In the method for manufacturing a hard film, in the step of forming a hard film, a magnetic field is generated in a direction perpendicular to a discharge surface of the target.

As described above, in order to obtain a hard film excellent in abrasion resistance in which H / E and hardness H are adjusted to a suitable range, it is important that the film is formed stably and uniformly. On the other hand, the plasma evaporation source forms a magnetic field that is perpendicular to the discharge surface of the target. The discharge becomes stable and continuous, and the fluctuation of the plasma (ions, electrons) generated is reduced and becomes uniform. Furthermore, by the magnetic field lines extending perpendicularly to the discharge surface, the generated plasma becomes easier to reach the target, and stable film growth is possible.

(Details of the embodiment of the present invention)

Hereinafter, a method for manufacturing a hard film, a hard film covering member, and a hard film according to an embodiment of the present invention will be described in detail with reference to the drawings.

<Implementation Mode 1>

[Hard film covering member]

First, an insert 10 of a hard film covering member according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view schematically showing the entire structure of the insert 10. Fig. 2 shows the mode of cutting by insert 10 A diagram of the shape of the material 100 to be cut. In addition, the hard film covering member of the present invention can be applied to cutting tools such as a drill bit for drilling operations such as drill bits, and screw cutting operations such as taps, in addition to cutting tools for rotary processing such as the insert 10 described below. A variety of cutting tools, such as cutting tools for turning processing such as cutting tools and end mills, and cutting tools for cutting processing such as blades.

The insert 10 is a tool for cutting the workpiece 100, and is used by being attached to the tip of a shank (not shown). The insert 10 includes a base material 11 of a base material of the tool, and a hard film 20 coated on the surface of the base material 11.

The base material 11 is made of a hard material such as cemented carbide, diamond, iron-based alloy containing metal carbide, cermet, or high-speed tool steel. The base material 11 has a portion or an excavation surface 31 that bites into the material to be cut 100, and an escape surface 32 of a portion that escapes to avoid contact with the material 100 to be cut. A cutting edge 33 is formed at a portion where the digging surface 31 and the escape surface 32 are connected.

As shown in FIG. 2, by moving the insert 10 such that the cutting edge 33 bites into the surface of the work material 100, the surface of the work material 100 is cut, and the chips 101 generated thereby pass through the digging surface 31. In such a cutting process, the hard film 20 is abraded by intense sliding between the insert 10 and the workpiece 100. On the other hand, in the insert 10 according to the embodiment, the hard film 20 having excellent abrasion resistance is coated on the surface of the substrate 11 to extend the tool life. Hereinafter, the hard film 20 related to this embodiment will be described in detail.

[Hard film]

Next, a hard film 20 according to this embodiment will be described with reference to FIG. 3. FIG. 3 is a partial cross-sectional structure of the insert 10 including the substrate 11 and the hard film 20 in the thickness direction. The hard film 20 is formed as a wear-resistant layer on the surface of the substrate 11 by, for example, physical vapor deposition (PVD) such as arc ion plating (AIP) or sputtering deposition, sputtering etching, sputtering, sputtering, or sputtering. The hard film 20 contains at least aluminum, chromium, and nitrogen elements, and its composition formula is represented by Al _m Cr _1-m N _1-xyz C _x B _y O _z . In this composition formula, "m" is the atomic ratio of aluminum to aluminum and chromium in total. "1-m" is the atomic ratio of chromium to aluminum and chromium in total. "1-xyz" is the total atomic ratio of nitrogen to nitrogen, carbon, boron, and oxygen. "X" is the atomic ratio of carbon to nitrogen, carbon, boron, and oxygen in total. "Y" is the atomic ratio of boron to nitrogen, carbon, boron, and oxygen in total. "Z" is the atomic ratio of oxygen to nitrogen, carbon, boron, and oxygen in total.

The hard film 20 generates extremely fine hexagonal crystals and cubic crystals at the same time. The extremely fine hexagonal crystals hinder the crystal growth of the cubic crystals, thereby making the crystal grains of the cubic crystals finer. In other words, the hard film 20 exists as a mixture of miniaturized cubic crystals and extremely fine cubic crystals. With such a characteristic crystalline structure, when the hardness of the hard film 20 is H (GPa) and the Young's coefficient of the hard film 20 is E (GPa), the ratio of hardness / Young's coefficient H / E is 0.050 or more and 0.120 or less. , And the hardness H is 20 GPa or more.

When H / E is less than 0.050, the Young's coefficient becomes too high for the hardness of the film, and the amount of deformation when an external force is applied to the film becomes small. Therefore, cracking of the film is likely to occur, so that the abrasion resistance is reduced. On the other hand, in the hard film 20, H / E is adjusted to 0.050 or more with a hardness H in a range of 20 GPa or more. The abrasion resistance is dramatically improved. On the other hand, if H / E becomes too large (more than 0.120), the Young's coefficient becomes too low, and it becomes difficult to exert the function of a hard film. Therefore, the H / E of the hard film 20 is adjusted to 0.120 or less. H / E is preferably 0.058 or more.

In this way, the crystal structure in which cubic crystals are made finer by extremely fine hexagonal crystals can be confirmed by X-ray diffraction measurement. The hard film 20 has a crystalline structure of a cubic rock salt type. In the case where the hard film 20 is subjected to X-ray diffraction measurement using CuKα rays, the half-peak full-amplitude value of the peaks around the diffraction angle of 38 ° on the (111) plane of the cubic rock salt crystal structure is 0.25 ° or more and 1.00 ° or less. Moreover, the extremely fine cubic crystals are of such a magnitude that they cannot be detected by X-ray diffraction measurement.

In the X-ray diffraction measurement, when the full amplitude of the half-peak value is less than 0.25 °, the crystal grains of the cubic crystal grow greatly, and the H / E becomes smaller. On the other hand, when the full width of the half-peak value exceeds 1.00 °, the cubic crystal is too fine, so the crystal grains tend to fall off and the wear resistance is reduced. Therefore, by confirming the full width at half maximum of the X-ray diffraction measurement to be 0.25 ° or more and 1.00 ° or less, it is possible to confirm a crystal structure where the cubic crystals are moderately fined in the film. The full width at half maximum is preferably 0.32 ° or more.

In addition, by using X-ray diffraction measurement based on the peak position of the cubic (111) plane and the full width at half maximum, using t = λ / Bcosθ (Scherrer formula), the sub-grain size t ( Å). λ is the wavelength (Å) of the X-ray. B is the full amplitude at half-peak (radians). θ is half the peak position 2θ (radian). The sub-grain size is 400 Å or less, preferably 375 Å or less, and more preferably 360 Å or less. Further preferably, a sub-grain size of 290Å or less may be used. Below 285Å is also possible, and below 280Å. However, if the sub-grains are fined too much, the hardness of the film is reduced. Therefore, the sub-grain size is 40 Å or more, preferably 50 Å or more, and more preferably 70 Å or more.

In addition, in order to obtain a hard film in which such extremely fine hexagonal crystals and finer cubic crystals are mixed, it is necessary to adjust the aluminum content in the film. Therefore, the aluminum content is adjusted to a range of 0.68 ≦ m ≦ 0.85. When the aluminum content is less than 0.68, extremely fine hexagonal crystals are not generated. On the other hand, when the aluminum content exceeds 0.85, cubic crystals do not occur, and the entire film becomes coarse hexagonal crystals. Therefore, the aluminum content is adjusted to a range of 0.68 ≦ m ≦ 0.85. The amount of aluminum is preferably 0.70 <m.

In addition, the hard film 20 may contain only aluminum, chromium, and nitrogen as additional elements, and further may include elements such as carbon, boron, and oxygen. Thereby, various functions can be provided to the hard film 20. Carbon increases the hardness of the film by forming carbides such as AlC or CrC in the crystal. In order to obtain this effect, the atomic ratio x of carbon is adjusted to 0.05 or more in the hard film 20. However, when the carbon content is excessive, the heat resistance of the film is reduced. To prevent this, in the hard film 20, the atomic ratio x of carbon is adjusted to less than 0.5.

Boron combines with nitrogen in the film to form a boron nitride, which is a solid lubricant, and provides a lubricating effect to the hard film 20. In order to obtain this effect, in the hard film 20, the atomic ratio y of boron is adjusted to 0.01 or more. However, if the boron content is excessive, the hardness decreases. To prevent this, in the hard film 20, the atomic ratio y of boron is adjusted to 0.10 or less.

Oxygen combines with aluminum in the film to form hard Al ₂ O ₃ , which increases the hardness of the hard film 20. However, if the oxygen content in the film is excessive, the abrasion resistance of the film is reduced. Therefore, in the hard film 20, the atomic ratio z of oxygen is adjusted to less than 0.1.

In addition, carbon, boron, and oxygen are not essential addition elements to the hard film 20. The hard film 20 may be a film containing only aluminum, chromium, and nitrogen (x, y, z = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, and carbon (y, z = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, and boron (x, z = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, and oxygen (x, y = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, carbon, and boron (z = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, carbon, and oxygen (y = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, boron, and oxygen (x = 0). The hard film 20 may be a film containing aluminum, chromium, nitrogen, carbon, boron, and oxygen.

[Manufacturing method of hard film]

Next, a method for manufacturing the hard film 20 will be described with reference to a flowchart of FIG. 4. FIG. 5 is a schematic plan view of the film forming apparatus 2 used for film formation of the hard film 20 in plan view. First, the configuration of the film forming apparatus 2 will be described mainly with reference to FIG. 5.

The film forming apparatus 2 includes a vacuum chamber 21, a plurality of (2) arc power sources 22 and a sputtering power source 23, a stage 24, a bias power source 25, a plurality of (4) heaters 26, a DC power source 27 for discharge, And an AC power source 28 for filament heating. The vacuum chamber 21 is provided with a gas exhaust port 21A for vacuum exhaust and a gas supply port 21B for supplying gas into the vacuum chamber 21. The negative bias side of the arc power source 22 is connected to an arc evaporation source (target) 22A, and sputtering The negative bias side of the power source 23 is connected to a sputtering evaporation source (target) 23A. The positive bias side of the arc power source 22 and the sputtering power source 23 are connected to the vacuum chamber 21. The stage 24 is configured to be rotatable and has a support surface for supporting the substrate 11 as a film formation target. The bias power source 25 applies a negative bias to the substrate 11 via the stage 24.

In addition, as shown in FIG. 6, the film forming apparatus 2 includes a magnetic field generating member 42 disposed near the target 22A of the cathode. The magnetic field generating member 42 is, for example, an electromagnetic coil or a permanent magnet, and is disposed on the atmosphere side other than the vacuum chamber 21. Thereby, in the direction perpendicular to the discharge surface 22B of the target 22A, a magnetic field M extending from the target 22A toward the substrate 11 can be generated. In addition, as shown in FIG. 7, two magnetic field generating members 42 may be disposed on the substrate 11 side more than the cathode cooling surface 22C so as to sandwich the target 22A. In addition, three or more magnetic field generating members 42 may be arranged.

Next, a manufacturing method of the hard film 20 implemented using the film forming apparatus 2 will be described. First, step S10 is performed in which the substrate 11 is placed on the stage 24. In this step S10, first, the substrate 11 is washed with a washing liquid such as ethanol. Next, the cleaned base material 11 is introduced into the vacuum chamber 21 and set on the stage 24.

Next, step S20 of setting the target 22A is performed. In this step S20, an aluminum chromium (AlCr) target having a component composition (0.70 <m ≦ 0.85) of the hard film 20 to be formed is prepared, and this is used as a cathode to function, and it is connected to the negative bias side of the arc power source 22 . When the boron-containing hard film 20 is formed, an AlCrB target is prepared, and this target is set in the same manner.

In the target 22A, the average particle diameter of chromium is less than 150 μm, which is smaller than It is preferably less than 120 μm, and more preferably less than 100 μm. The average particle diameter of aluminum is less than 120 μm, preferably less than 110 μm, and more preferably less than 100 μm. By reducing the average particle diameters of chromium and aluminum, discharge can be uniformly caused on the discharge surface 22B of the target 22A. Therefore, fluctuations in the concentration of the charged particles reaching the substrate 11 are reduced, and stable crystal growth is possible. On the other hand, if the average particle diameters of chromium and aluminum become too small, intermetallic compounds tend to be generated when the powder is cured. In order to prevent this, the average particle diameters of chromium and aluminum are both 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more.

Next, step S30 of etching the base material 11 is performed. In this step S30, first, the inside of the vacuum chamber 21 is decompressed to a specific pressure through the gas exhaust port 21A, and a vacuum state is obtained. Next, argon gas is introduced into the vacuum chamber 21 through the gas supply port 21B, and the substrate 11 is heated to a specific temperature by the heater 26. Next, the surface of the substrate 11 is etched by argon ions for a specific time. Thereby, the oxide film formed on the surface of the base material 11 is removed. In addition, this step S30 is not an essential step in the method for manufacturing a hard film of the present invention, and may be omitted.

Next, step S40 of forming a hard film 20 is performed. In step S40, nitrogen gas is introduced from the gas supply port 21B, and the inside of the vacuum chamber 21 is adjusted to a specific film forming pressure. Then, the target 22A is evaporated with a specific arc current, and the stage 24 is rotated at a specific rotation speed. Thereby, the evaporated target material is deposited on the surface of the substrate 11, and a hard film 20 is formed on the surface of the substrate 11.

When a hard film 20 containing carbon and oxygen elements is formed, a hydrocarbon gas such as methane or acetylene, an oxygen-containing gas such as oxygen or water vapor is introduced into the vacuum chamber 21, and the film is formed in this state. When the hard film 20 containing boron is formed, when the target 22A does not contain boron, a boron fluoride (BF ₃ ) gas may be introduced into the vacuum chamber.

In this step S40, the hard film 20 is formed in a state where a specific bias voltage V is applied from the stage 24 to the substrate 11 by the bias power source 25. Specifically, the value of the bias voltage V is adjusted so that the bias voltage V applied to the substrate 11 by the stage 24 satisfies the relational expression of -316 ≦ V ≦ -214.3m + 110. The lower limit of the bias voltage V can be -310, -300, -1666m + 1100, -1556m + 1022.6, or -1429m + 940.3. In addition, the upper limit of the bias voltage V may be -267m + 147, or -250m + 132.5. The bias voltage V may be a DC voltage or an AC voltage. In particular, if m exceeds 0.70, cubic crystals exceeding 20 GPa will be formed, so it is necessary to control the bias voltage. This is probably because if m exceeds 0.70, coarse cubic crystals tend to be formed at the initial stage of film formation. From the viewpoint of such bias control, the upper limit formula is defined as (V = -214.3m + 110).

8 and 9 are graphs showing the relationship between the atomic ratio m (horizontal axis) of aluminum of the hard film 20 and the bias voltage V (vertical axis) applied to the substrate 11. In FIG. 8, (1) is a straight line showing the upper limit of the bias voltage V = -214.3m + 110. (1) 'is a straight line of V = -267m + 147. (1) "is a straight line of V = -250m + 132.5. (2) is a straight line of V = -1666m + 1100. (2) 'is a straight line of -1556m + 1022.6. (2)" is V = -1429m + 940.3 Of straight lines.

In FIG. 9, (1) is a straight line of V = -1429m + 940.3. (1) 'is a straight line of V = -1556m + 1022.6. (1) "is a straight line of V = -1600m + 1053.4. (1) '" is a straight line of V = -1665m + 1098.9. (2) is a straight line of V = -316 showing the lower limit of the bias voltage V. (2) ) 'Is a straight line of V = -310. (2) "is V = -300 straight.

In this embodiment, as shown in FIG. 8, the hard film 20 is formed under conditions in a region surrounded by a straight line (1), a straight line (2), a straight line of m = 0.7, and a straight line of m = 0.85. In addition, the conditions in the area enclosed by the straight line (1) ', straight line (2)', a straight line of m = 0.7, and a straight line of m = 0.85 are better. The conditions in the area surrounded by the straight line of m = 0.7 and the straight line of m = 0.85 are even better.

The film forming conditions are not limited to those shown in FIG. 8. In FIG. 9, the film formation of the hard film 20 may be performed under conditions in a region surrounded by the straight line (1), the straight line (2), a straight line of m = 0.7, and a straight line of m = 0.85. In addition, the conditions in the area enclosed by the straight line (1) ', straight line (2)', a straight line of m = 0.7, and a straight line of m = 0.85 may be adopted. The straight line (1) ", straight line (2)" The conditions in the area enclosed by the straight line of m = 0.7 and the straight line of m = 0.845 can also be used. The straight line of m = 0.7 and the straight line of m = 0.84 are used. Conditions in a region surrounded by a straight line are also possible. Thereby, the charged particles which are evaporated by the target 22A and made incident on the substrate 11 can be accelerated by a potential gradient formed near the substrate 11 to impart energy. Such high-energy charged particles collide with the substrate 11, and the energy on the surface of the film is increased by sputtering, so that energy-stable hexagonal crystals are not generated, but fine cubic crystals with a quasi-stable phase are generated. As a result, it is possible to obtain the hard film 20 adjusted to have an H / E of 0.050 or more and 0.120 or less and a hardness H of 20 GPa or more.

In addition, as shown in FIGS. 6 and 7, in this step S40, the magnetic field generating member 42 is formed in a state where a magnetic field M extending from the target 22A toward the substrate 11 is generated in a direction perpendicular to the discharge surface 22B. Hard film 20. Thereby, the discharge becomes stable and continuous, and the fluctuation of the generated plasma (ions, electrons) is reduced and uniformized. Then, the magnetic field M (magnetic field lines) extending perpendicularly to the storefront 22B makes it easy for the generated plasma to reach the substrate 11 and stable film formation is possible. Thereby, the hard film 20 can be formed stably and uniformly, and the hard film 20 having a fine cubic structure can be formed. In particular, as shown in FIG. 7, by arranging the magnetic field generating member 42 (permanent magnet or electromagnetic coil) on the substrate 11 side than the cathode cooling surface 22C, the magnetic field M perpendicular to the discharge surface 22B of the target 22A can be easily generated. .

<Implementation Mode 2>

Next, a metal mold 50 for a hard film covering member according to a second embodiment of the present invention will be described with reference to FIG. 10. FIG. 10 shows a state where the steel plate 60 of the pressed member is set in the metal mold 50.

The metal mold 50 is, for example, a metal mold used for the hot forming of the steel sheet 60, and includes an upper metal mold 51 (first metal mold) and a lower metal mold 52 (second metal mold) which are disposed spaced apart from each other in the upper phase direction. The upper metal mold 51 has a convex portion 53, and a concave portion 54 is formed along the shape of the convex portion 53 in the lower metal mold 52. The upper metal mold 51 and the lower metal mold 52 are configured to be movable in a mutually approaching direction or a mutually spaced direction by a driving force from a driving source (not shown). As shown in FIG. 10, the metal mold 51 is lowered in a state where the heated steel plate 60 is provided on the forming surface of the lower metal mold 52, and the steel plate 60 is pressed along the lower metal by the convex portion 53 to form the steel plate 60 along the lower metal. The shape of the recessed portion 54 of the mold 52. Moreover, it is not limited to the hot-stand forming process, and a cold-stand forming process may be performed.

Each of the upper metal mold 51 and the lower metal mold 52 includes base materials 55 and 58 constituting a main body portion of the metal mold and hard films 56 and 57 on the surfaces of the base materials 55 and 58 by PVD coating. These hard films 56, 57 are composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z (0.68 ≦ m ≦ 0.85), and have cubic crystals as well as the first embodiment. The rock salt type has a crystal structure in which the H / E is 0.050 or more and 0.120 or less and the hardness H is adjusted to 20 GPa or more, which is excellent in wear resistance. Therefore, not only the cutting tool exemplified in the aforementioned embodiment 1 but also a plastic processing tool such as the metal mold 50 can exhibit an excellent abrasion resistance effect. In addition, the metal mold 50 is not limited to the bending type shown in FIG. 10, and may be other pressing metal molds such as a draw type, a twist type, or a compression type.

<Other implementation types>

Next, other embodiments of the present invention will be described.

The hard film covering member of the present invention can be applied to various mechanical parts requiring abrasion resistance in addition to cutting tools or metal molds. For example, the present invention is also applicable to sliding parts such as piston rings and valves.

In the aforementioned embodiment 1, the substrate 11 and the hard film 20 are not directly contacted as shown in FIG. 3, and a primer layer may be formed between the substrate 11 and the hard film 20 to improve the adhesion. Examples of the lower layer include materials such as TiAlN, CrN, or TiN.

In the foregoing embodiments 1, 2, the carbon atomic ratio x may also be outside the range of 0.05 ≦ x <0.5. The atomic ratio y of boron may be less than 0.01. In addition, the atomic ratio z of oxygen may be outside the range of z <0.10.

In the first embodiment, the case where the hard film 20 is formed by arc ion plating has been described, but it is not limited to this. For example, the film may be formed by other physical vapor deposition methods such as sputtering.

[Example]

With respect to the abrasion resistance of the hard film, an experiment was performed to confirm the effect of the present invention.

(Example 1)

[Film formation of hard film]

First, various targets 22A having different aluminum contents (atomic ratios) are prepared, and the bias voltage (substrate bias) V applied to the substrate 11 is changed to form the hard film 20. The conditions for the aluminum atomic ratio m and the substrate bias V of the target 22A are shown in Table 1 (Nos. 1 to 25) below. For the film formation, the film formation apparatus 2 described with reference to FIGS. 5 to 7 was used.

者。 First, as the base material 11, a mirror-like superhard test piece (13 mm × 13 mm × 5 mm thick) was prepared. Next, the base material 11 was ultrasonically cleaned in ethanol, introduced into the vacuum chamber 21, and set on the stage 24. In addition, a target 22A made of AlCr with the composition shown in Table 1 was prepared and connected to the negative side of the arc power source 22. As the target 22A, a target diameter of 100 mm was used

By.

Next, the inside of the vacuum chamber 21 was evacuated to 5 × 10 ^-3 Pa, the substrate 11 was heated to 500 ° C. by the heater 26, and then etching was performed by argon ions for 5 minutes. Thereafter, nitrogen was introduced into the vacuum chamber 21 to 4 Pa. Next, the target 22A is evaporated by a discharge current of 150 A, and the stage 24 is rotated at a rotation speed of 5 rpm to form a hard film 20 on the surface of the substrate 11. At this time, the bias voltage V applied to the substrate 11 by the bias power source 25 is controlled as shown in Table 1 below. As the bias power source 25, a DC power source is used. The thickness of the hard film 20 is 3 μm.

[Determination of hardness / Young's coefficient]

The hardness H (GPa) and the Young's coefficient E (GPa) of the hard film 20 after film formation were measured using a Nano-Indenter to calculate the value of H / E.

The hardness was measured by a nano indentation test using a superhard test piece on which the hard film 20 was formed. According to the measurement by the Nano-Indenter, "ENT-1100 (manufactured by Elionix)" was used, and the indentation tester used a triangular pyramid (Berkovich) type indenter. Firstly, 5 points of load curve were measured under 5 load conditions of 2mN, 5mN, 7mN, 10mN and 20mN. Then, the method of correction (compliance) and the shape of the tip of the indenter (J. Mater. Res. Vol. 16, No. 11, 2001, 3084) proposed by SAWA and others was used to correct the data. In this manner, the value of H / E was calculated from the obtained hardness and Young's coefficient.

[X-ray diffraction measurement]

For each sample, X-ray diffraction (CuKα line, 40kV-40mA, θ-2θ, divergence slit 1 °, divergence longitudinal limit slit 10mm, scattering slit 1 °, light receiving slit 0.15mm, black and white light receiving slit Seam 0.8mm), investigated The crystallinity of the hard film 20 on the substrate 11. According to the peak of the cubic (111) plane of the hard film 20, the diffraction pattern on the X-ray is observed around the diffraction angle (2θ) of 38 ° (36 ~ 39 °). The existence of this peak confirmed the generation of cubic crystals. The full width half maximum (FWHM) of the peak was calculated by calculation. In addition, when the peak of the (110) plane from the hexagonal crystal was confirmed near the diffraction angle of 59 °, it was determined that the film was completely hexagonal crystallized. In Table 1 below, when it is considered to be completely hexagonal crystallized, mark "×" in the column of "hcp (hexagonal close-packed)". In addition, the sub-grain size t (Å) was calculated based on the peak position and full-peak half-amplitude (FWHM) of the cubic (111) plane using the Scherer formula (t = λ / Bcosθ). λ is the wavelength of the X-ray (Å), B is the full amplitude at half-peak (radian), and θ is the peak position 2θ (radian).

[Measurement of erosion rate]

The wear resistance of the hard film 20 was confirmed by an MSE (Micro Slurry-Jet Erosion) test. For each sample in which the hard film 20 was formed on the base material 11 made of cemented carbide, the erosion rate was measured by the MSE test, and the abrasion resistance was evaluated. MSE experiment, using a slurry (3% by mass) of amorphous aluminum oxide particles containing # 8000 (average particle size 1.2 μm), with a projection distance of 10 mm, a projection angle of 90 °, and a projection pressure of 0.390 MPa (within ± 0.002) Come on. Next, the polishing slurry was projected for a certain period of time, and the erosion depth was determined by measuring the projection mark using a stylus type roughness meter, and the erosion rate (μm / min) was calculated. An erosion rate of 3.0 × 10 ^-2 μm / min or less is considered acceptable.

[Inspection]

From the foregoing test results, it can be seen that the erosion rate of the sample with H / E less than 0.050 exceeds 3.0 × 10 ^-2 μm / min. In contrast, the sample with H / E of 0.050 or more and less than 0.058 and hardness H of 20 GPa or more The erosion rate is all below 3.0 × 10 ^-2 μm / min, which shows that the wear resistance is improved.

In addition, in a range where the aluminum content is 0.7 <m ≦ 0.85, the bias (absolute value) is reduced, the erosion rate is increased, and the wear resistance is reduced. This should be because the energy provided to the film surface becomes smaller and hexagonal crystals are produced. On the other hand, when the aluminum content is high (m = 0.87), it becomes a hexagonal film and the hardness decreases, so the wear resistance is poor.

In addition, when the bias voltage exceeds the upper limit (-1429m + 940.3), hexagonal crystals are formed even if the aluminum content is in the range of 0.70 <m ≦ 0.85, and the wear resistance is poor. In addition, when the bias voltage is lower than the lower limit (-316V), the effect of sputtering becomes large, and an evaluable film cannot be formed. In FIG. 9, the circles correspond to the examples of Nos. 1 to 25 in Table 1, and “×” corresponds to the comparative example. From this result, by forming the film with the aluminum content in the range of 0.7 <m ≦ 0.85 and the bias voltage V in the range of -316 ≦ V ≦ -1429m + 940.3, it is possible to adjust the H / E to be 0.050 or more. Hard film 20 having an abrasion resistance of less than 0.058 and a hardness H of 20 GPa or more.

(Example 2)

The conditions of the aluminum atomic ratio m and the substrate bias V of the target 22A were adjusted as shown in the following Tables 2 and 3 (Nos. 1 to 47), and the same tests as in Example 1 were performed.

[Inspection]

From the test results, it can be seen that the sample with an H / E less than 0.058 has an erosion rate of 3.0 × 10 ^-2 μm / min or less and exceeds 2.0 × 10 ^-2 μm / min. In contrast, H / E is 0.058 or more The erosion rate of the samples is less than 2.0 × 10 ^-2 μm / min, and it can be seen that the wear resistance is improved.

In addition, when the aluminum content is low (m = 0.68), the bias voltage is reduced and the erosion rate is reduced. However, compared with the case where the aluminum content is 0.70 <m ≦ 0.85, the wear resistance is more improved. This should be because the Young's coefficient becomes smaller, so that the film becomes less likely to break. On the other hand, when the aluminum content is high (m = 0.87), it becomes a hexagonal film and the hardness decreases, so the wear resistance is poor.

In addition, when the bias voltage exceeds the upper limit (-214.3m + 110), hexagonal crystals are formed even if the aluminum content is in the range of 0.7 <m ≦ 0.85, and the wear resistance is poor. In addition, compared with the case where the bias voltage is made lower than the lower limit (-1666m + 1100), the wear resistance is more improved in the case where the bias voltage is higher than the lower limit. In FIG. 8, “○” corresponds to the examples of Nos. 1 to 47 in Tables 2 and 3, and “×” corresponds to the comparative example. From this result, by forming the film with the aluminum content in the range of 0.7 <m ≦ 0.85 and the bias voltage V in the range of -1666m + 1100 ≦ V ≦ -214.3m + 110, the formation can be adjusted to H / E The hard film 20 having an abrasion resistance of 0.058 or more and 0.120 or less.

(Example 3)

It is the same as the first embodiment except that a hard film 20 containing carbon, boron, and oxygen elements is formed. In Example 1 described above, methane (CH ₄ ) gas and oxygen (O) gas were introduced by nitrogen gas during film formation, and carbon and oxygen were added to the film. In addition, boron (B) was added by adding the target 22A. The aluminum content was 71 at%, and the bias voltage applied to the substrate 11 was -200V. The evaluation methods of the hard film 20 are the same as those in the first embodiment. The test results are shown in Table 4 below. In addition, the results of No. 1 in Table 4 are represented by the circle marks in FIG. 9.

When the carbon content is 0.5 or more (No. 3), and when the carbon content is less than 0.5 (No. 2), the erosion rate is high, and the wear resistance is poor. This should be due to the increase of the Young's coefficient of the film, which makes the film easily break. In addition, if the boron content exceeds 0.1 (No. 5), the fineness of the crystal grains will be excessively exceeded, so the hardness will be lower than that in the case where the boron content is 0.1 or less (No. 4). In addition, the full-peak half-amplitude (FWHM) becomes larger, each grain becomes easier to fall off, and the wear resistance is poor. In addition, in the case where the oxygen content is 0.1 or more (No. 7), the film is too softened, and the abrasion resistance is poor compared with the case where the content is less than 0.10 (No. 6).

(Example 4)

It is the same as the first embodiment except that a hard film 20 containing carbon, boron, and oxygen elements is formed. In Example 1 described above, methane (CH ₄ ) gas and oxygen (O) gas were introduced by nitrogen gas during film formation, and carbon and oxygen were added to the film. In addition, boron (B) is added by adding the target 41. The aluminum content was 77 at%, and the bias voltage applied to the substrate 11 was -100V. The evaluation methods of the hard film 20 are the same as those in the first embodiment. The test results are shown in Table 5 below.

Compared with the case where the carbon content is 0.5 or more (No. 5), the case where the carbon content is less than 0.5 (No. 1 to 4) has a lower erosion rate and improved abrasion resistance. This should be because the hardness of the film and the Young's coefficient both decrease, making the film difficult to break. In addition, if the boron content exceeds 0.1 (No. 8), the fineness of the crystal grains is excessively exceeded, and therefore, the hardness is lower than that in the case where the content is 0.1 or less (No. 6, 7). In addition, the full-peak half-amplitude (FWHM) becomes larger, each grain becomes easier to fall off, and the wear resistance is poor. In addition, when the oxygen content is 0.1 or more (No. 11), the film is softened and the abrasion resistance is poor.

10‧‧‧ Insert

11‧‧‧ Substrate

20‧‧‧ Hard film

Claims (11)

A hard film containing aluminum, chromium, and nitrogen, which is characterized by a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z . In the foregoing composition formula, m is aluminum to aluminum, and chromium is a total Atomic ratio, 1-m is chromium to aluminum, total atomic ratio of chromium, 1-xyz is nitrogen to nitrogen, carbon, boron, oxygen total atomic ratio, x is carbon to nitrogen, carbon, boron, oxygen total atomic ratio Ratio, y is the total atomic ratio of boron to nitrogen, carbon, boron, and oxygen, and z is the total atomic ratio of boron to nitrogen, carbon, boron, and oxygen, satisfying the relationship of 0.68 ≦ m ≦ 0.85, y ≦ 0.10, with cubic Crystalline salt type crystal structure. When the hardness of the hard film 20 is H (GPa) and the Young's coefficient of the hard film 20 is E (GPa), the ratio of hardness / Young's coefficient H / E is 0.050 or more and 0.120 or less. And H is 20 GPa or more. For example, the hard film of the first scope of patent application, in which H / E is above 0.058. For example, the hard film of the scope of patent application No. 1 or 2, in which the X-ray diffraction measurement using CuKα line is used, according to the above-mentioned half-peak full-amplitude value of the peak of the (111) plane of the cubic crystal rock salt type crystal structure is above 0.25 ° Below 1.00 °. For example, the hard film of the third scope of the application for a patent, wherein the full width of the aforementioned half-peak is above 0.32 °. For example, the hard film of the scope of patent application No. 1, 2 or 4, wherein the atomic ratio x of carbon satisfies the relationship of 0.05 ≦ x <0.5. For example, the hard film of the scope of patent application No. 1, 2 or 4, wherein the atomic ratio y of boron satisfies the relationship of 0.01 ≦ y ≦ 0.10. For example, the hard film of the scope of patent application No. 1, 2 or 4, wherein the atomic ratio z of oxygen satisfies the relationship of 0 <z <0.10. A hard film covering member, comprising a base material and a hard film formed on the surface of the base material in the scope of patent applications No. 1, 2 or 4. A method for manufacturing a hard film, characterized in that a hard film having a crystal structure of a cubic rock salt type composed of a composition formula of Al _m Cr _1-m N _1-xyz C _x B _y O _z is formed on a substrate. On the surface, in the foregoing composition formula, m is the atomic ratio of aluminum to aluminum and chromium in total, 1-m is the atomic ratio of chromium to aluminum and chromium to total, and 1-xyz is the atomic ratio of nitrogen to nitrogen, carbon, boron, and oxygen in total , X is the total atomic ratio of carbon to nitrogen, carbon, boron, and oxygen, y is the total atomic ratio of boron to nitrogen, carbon, boron, and oxygen, and z is the total atomic ratio of oxygen to nitrogen, carbon, boron, and oxygen, satisfying The relational expression of 0.70 <m ≦ 0.85 and y ≦ 0.10; including: a step of setting the substrate on a stage; a step of setting a target having the component composition of the hard film; and evaporating the target in the The step of forming the hard film on the surface of the substrate; in the step of forming the hard film, the bias voltage V applied by the stage to the substrate satisfies the relation of -316 ≦ V ≦ -214.3m + 110 In an embodiment, the hard film is formed while applying a bias voltage to the substrate. For example, the method for manufacturing a hard film according to item 9 of the application, wherein the aforementioned bias voltage V satisfies the relationship of -1666m + 1100 ≦ V. For example, the method for manufacturing a hard film according to item 9 or 10 of the scope of patent application, wherein in the aforementioned step of forming a hard film, a magnetic field is generated in a direction perpendicular to the discharge surface of the target.