JP2007046103A - Hard film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard film having improved fusion resistance and lubricity in particular, without sacrificing the adhesiveness, toughness and high-temperature oxidation resistance of the hard film. <P>SOLUTION: The hard film comprises one or more metallic elements selected from elements in the groups 4a, 5a and 6a, Al, B and Si; and one or more nonmetallic elements which include O and are selected from C and N; and has a columnar structure. In the columnar structure, crystal grains form a multilayer structure that comprises a plurality of layers having respectively different O contents, and has a region which forms contiguous crystal lattice fringe at least in the vicinity of a boundary between the layers. The respective layers have such a thickness T(nm) as to satisfy 0.1≤T≤100. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hard coating having excellent welding resistance and lubricity.

  Patent Document 1 discloses a technique related to an abrasion-resistant hard film in which a compound layer and a composition modulation layer are periodically laminated and a crystal lattice is continuous between the layers.

JP-A-8-127863

  The object of the present invention is not to sacrifice the adhesion, toughness, and high-temperature oxidation resistance of the hard coating, but to improve the welding resistance and lubricity of the hard coating. For example, it is to provide a hard coating that can cope with dry processing, high speed, and high feed in cutting and the like.

  The hard coating of the present invention is composed of one or more metal elements selected from the group 4a, 5a, 6a, Al, B, and Si and one or more non-metal elements selected from C and N containing O. The hard coating has a columnar structure, and the crystal grains in the columnar structure have a multilayer structure composed of a plurality of layers having a difference in O content, and at least in the boundary region between the layers, crystal lattice stripes are continuous. The hard film is characterized in that there is a region where the thickness T (nm) of each layer is 0.1 ≦ T ≦ 100. By containing O in the hard film which is this structure, it has extremely excellent welding resistance and lubricity. In this case, it is possible to provide a hard film with improved characteristics without sacrificing the adhesion, toughness and high-temperature oxidation resistance of the hard film. The hard coating of the present invention preferably has a bond between a metal element and O (hereinafter referred to as a metal-O bond). Furthermore, the surface of the hard coating is preferably smoothed by machining.

  The hard film of the present invention has excellent welding resistance and lubricity. Furthermore, the hard film with improved characteristics can be provided without sacrificing the adhesion, toughness and high-temperature oxidation resistance of the hard film. When the hard coating of the present invention is applied to, for example, a cutting tool or the like, excellent stability and a long tool life can be obtained even in a severe interrupted cutting environment at the time of mold processing, including dry high-efficiency cutting. It is extremely effective for improving productivity in processing.

(1) Composition of coating The composition of the hard coating of the present invention is composed of one or more metal elements selected from groups 4a, 5a, 6a, Al, B, and Si of the periodic table, O, C, and N. Having one or more non-metallic elements selected. When the hard coating of the present invention contains O, a metal-O bond state is formed. For example, when this is applied to a cutting tool, the oxide formed by the heat generated during cutting suppresses the diffusion of the Fe element contained in the work material into the hard film. As a result, welding at the cutting edge of the tool is suppressed and welding resistance is improved. When the O content is 0.1% to 15% in atomic percent of only nonmetallic elements, it is preferable for the lubricity effect. If the O content exceeds 15%, the fracture surface structure of the hard coating changes from a columnar structure to a fine granular structure. When a fine grain structure is formed, the hardness decreases and sufficient mechanical strength cannot be obtained, so that scraping wear tends to occur. If it is less than 0.1%, the lubricity effect of the hard coating cannot be obtained. Furthermore, the difference in the O content of each layer in the multilayer structure is desirably 10% or less. Since the hard coating of the present invention contains the O element and the oxide significantly improves the lubricity, the hard coating preferably has a metal-O bond.
On the other hand, it is preferable that the hard coating of the present invention contains B because it has the effect of increasing the hardness and lubricity of the hard coating. For example, when a hard film containing B is coated on a cutting tool, the tool life is extended. The improvement in hardness is due to the c-BN phase, and the improvement in lubricity is due to the h-BN phase. By optimizing the ratio of B and N, hardness and lubricity can be improved at the same time. The ratio between the c-BN phase and the h-BN phase can be controlled by a bias voltage applied during film formation.
Moreover, when Al is contained in the metal composition of the hard film of the present invention, Al2O3 is formed on the surface layer, and the static heat resistance of the hard film is improved. However, in cutting, Fe or the like in the work material diffuses into the hard film. Therefore, the Al content is preferably 50% or less in terms of atomic% of only the metal element. A more preferable Al content is 40% to 20%. If it is less than 20%, the wear resistance and oxidation resistance of the hard coating may be inferior.
In the composition of the hard coating, when the total amount of metal elements is m and the total amount of nonmetallic elements is n, the atomic ratio (n / m) is preferably more than 1.0, and is 1.02 or more. Is more preferable. The upper limit of n / m is preferably 1.7.

(2) Structure and characteristics of film When the cross section of the hard film is observed with a transmission electron microscope (hereinafter referred to as TEM), it is found that the cross-sectional structure of the hard film of the present invention has a plurality of layers showing light and dark. These layers consist of a layer having a relatively high O content (hereinafter referred to as A layer) and a layer having a relatively low O content (hereinafter referred to as B layer). B layers are laminated alternately without an interface. As a result of composition analysis by energy dispersive X-ray spectroscopy (hereinafter referred to as EDX) attached to the TEM, the difference between the average value of the O content in the A layer and the average value of the O content in the B layer is 15 % Or less, more preferably in the range of 0.2 to 10%. When the difference in O content is in the range of 0.2 to 10%, the hard coating has high toughness. By providing a difference in O content between the A layer and the B layer, a hard coating with improved toughness and reduced residual compressive stress can be obtained while maintaining excellent lubricity.
The hard film of the present invention has a columnar structure, and the columnar crystal grains have a plurality of layers having a difference in O content without having a clear interface, and crystal lattice fringes are continuous in the boundary region between the layers. . The columnar structure is a crystal structure that grows vertically in the film thickness direction. The hard coating is polycrystalline, but each crystal grain has a form similar to a single crystal. In addition, the columnar crystal grains have a multilayer structure having a plurality of layers having different O contents in the growth direction, and crystal lattice fringes are continuous in the boundary region between the layers. Here, the continuity of the crystal lattice stripes does not have to be in all the interlayer boundary regions, and it is sufficient if there is an interlayer boundary region in which the crystal lattice stripes are substantially continuous when observed by TEM. Since the columnar crystal grains have a multilayer structure composed of a plurality of layers having a difference in O content, the hard coating as a whole has toughness.
The thickness T of each layer of the hard coating is 0.1 to 100 nm. When T exceeds 100 nm, distortion occurs in the boundary region between the layers, the lattice stripes in the crystal grains become discontinuous, and the mechanical strength of the hard coating is lowered. For example, when a hard film is formed on a cutting tool, laminar fracture occurs in the hard film due to a cutting impact in the initial stage of cutting. Avoiding the occurrence of strain in the boundary region between layers is effective in improving the adhesion between the hard film and the substrate. On the other hand, the lower limit of T was set to 0.1 nm, which is the minimum thickness at which the layer structure can be confirmed by an X-ray diffractometer or TEM. Moreover, when a multilayer hard film is formed with a lamination period of less than 0.1 nm, the film characteristics vary.
The hard coating of the present invention preferably has a metal-O bond. In particular, due to the presence of metal-O bonds on the surface, the hard coating exhibits excellent welding resistance. For example, when applied to a coated cutting tool, intense welding at the initial stage of cutting can be suppressed. The metal-O bond can be confirmed by X-ray photoelectron spectroscopy (hereinafter referred to as XPS). For example, the Si—O bond has a peak in the range of 100 to 105 eV. In addition, Al-O bonds have peaks in the range of 70 to 77 eV, Ti-O bonds have a peak in the range of 455 to 465 eV, and Nb-O bonds have a peak in the range of 202 to 212 eV. Evaluation by XPS was performed using an X-ray source of AlKα and an analysis region having a diameter of 100 μm and using an electron neutralizing gun.

(3) Method for producing film It is effective to use physical vapor deposition methods having different plasma densities to produce the multilayer hard film of the present invention. Specifically, in order to continuously grow crystal grains having no interface, an arc discharge ion plating (hereinafter referred to as AIP) method having a high plasma density in a plasma reaction gas and a low plasma density are used. Magnetron sputtering (hereinafter referred to as MS) is performed simultaneously. Thereby, the crystal grains themselves in the hard coating have a large mechanical strength. On the other hand, when the AIP method and the MS method are performed sequentially or intermittently, a clear interface is formed between the layers of the hard coating, and the strength of the hard coating is reduced there.
Since the plasma density generated by the AIP method is very high, energy generated when ions generated in the plasma are incident on the substrate is large, and although a good hard film is formed, it is difficult to suppress the residual compressive stress. In addition, it is difficult to give a difference in the content of the specific element between the layers of the hard film having a multilayer structure. Therefore, a combination of the AIP method and the MS method is a preferable mode because it can impart excellent welding resistance and lubricity to a high hardness hard film.
Specifically, it is preferable to use a vacuum apparatus having an AIP target and an MS target and a reactive gas suitable for both the AIP method and the MS method. In the vacuum processing chamber, at least one pair of evaporation sources capable of at least the AIP method and the MS method are installed, and the specification is such that they can be discharged simultaneously. However, the evaporation source of the AIP method and the evaporation source of the MS method are not necessarily paired, and one or more evaporation sources of both types are installed in the same vacuum processing chamber as long as simultaneous discharge is possible. . The O element contained in the hard film is supplied from the reaction gas. Supplying form or when using a mixed gas of N2, there is a case of O ₂ added alone, better to use a mixed gas of N ₂ is preferable. This is because it is difficult to adjust the balance with other introduced gases when O ₂ alone is introduced into the vacuum apparatus. Furthermore, considering mass productivity, it is desirable to make N: O at about 8: 2. The composition of each target is not limited. However, it is desirable to use a system containing Si as a target material for the MS method. Accordingly, Si can be contained in the hard coating without any safety problem in the environment of the plasma-assisted chemical vapor deposition method in which the reaction containing Si uses sulfur.
In order to obtain the multilayer structure of the present invention, although it depends on the target species to be used, it is preferable to set the arc current in the range of 100 to 150 A and the discharge output by the MS method to 4.5 kW or less. In consideration of lubricity, the hard coating that comes into contact with the workpiece is preferably an oxide coating described in ASTM from the viewpoint of heat resistance and welding resistance. Oxidation of the substrate itself by treatment in an oxidizing atmosphere is a major issue and is not realistic for mass production. In the present invention, an O element is added to a hard film mainly composed of nitride and the like within a range where problems such as insulation do not occur, and the chemical bonding state between the constituent metal elements and O is discharged simultaneously by the AIP method and the MS method. This is an unprecedented technique that significantly improves lubricity.
In the present invention, the effect cannot be obtained unless all the metal elements constituting the hard coating and the metal-O bond are obtained. In particular, since W, Nb, Ta, Cr, and the like added as a means for improving the heat resistance in recent years have high heat resistance, a metal-O bond can be obtained by simply introducing O into a physical vapor deposition apparatus. It is not possible. When O is added, for example, (TiAlSi) N is easy to obtain Si-O from the difference in oxide formation energy, but in order to obtain Al-O and Ti-O, the Si content is reduced. We must reduce it as much as possible. In the case of (TiAlNb) N, Al—O is easily obtained, but it is difficult to obtain Nb—O. In the present invention, by keeping the film formation temperature at 600 ° C. and simultaneously discharging the AIP method and the MS method, all the metal elements and metal-O bonds that form the hard coating can be obtained.
The metal-O bond is taken into the main layer formed by the MS discharge. This can be achieved when the coating method of the present invention is applied, that is, when a coating method in which a plasma density difference is generated during discharge is applied. The hard film formed by this method significantly improved the lubricating properties of the hard film by containing a uniform oxide throughout. Furthermore, without sacrificing the decrease in hardness due to the presence of oxides, adhesion, toughness and high-temperature oxidation resistance can be maintained, and further improvements can be made. O element can be added by AIP method alone or MS method alone, and it is possible to obtain a certain level of lubricating characteristics. However, there is no effect of improving the toughness of the hard coating in a use environment with impact. Moreover, when O element was added by the application of AIP method alone or MS method alone, it was confirmed that the hard coating was easily softened and deteriorated the wear resistance. The effectiveness of the hard film to which the O element of the present invention is added is confirmed only by a hard film obtained by discharging the AIP method and the MS method at the same time, and exhibits excellent characteristics. When the AIP method and the MS method of the present invention are used at the same time, by reducing the plasma generated from the MS evaporation source, that is, by setting the discharge output to 4.5 kW or less, the added O element constitutes a hard film. The state of the metal element and the metal-O bond is created. When the discharge output exceeds 4.5 kW, the plasma density increases and the reaction with N and O, which are introduced gas elements, is promoted. For this reason, a large amount of O is taken into the hard coating, and as a result, the phenomenon that the hard coating softens, the cross-sectional structure becomes finer, and the mechanical strength in the shearing direction decreases. In order to carry out the method of the present invention, an apparatus having a vacuum processing chamber capable of physical vapor deposition is required, but considering the facilities, environment and cost, at least the AIP method and the MS method are operated in the processing chamber. One or more pairs of possible evaporation sources are preferably installed and can be achieved by discharging simultaneously.
The AIP target may be a single alloy target or a target of a plurality of metals or alloys having different compositions. When the AIP method and the MS method are simultaneously performed while the substrate is alternately approaching both targets in a state where the reaction gas is turned into plasma, ions having different valences reach the substrate at the same time. When the substrate approaches an AIP evaporation source with a high plasma density, a hard layer is formed, and then when a substrate approaches an MS evaporation source with a low plasma density, a soft layer is formed. The hard layer includes a relatively hard crystalline phase, while the soft layer includes a relatively soft crystalline phase rather than a relatively hard crystalline phase. As a result, distortion occurs in the entire film, and the film is hardened by internal stress. At this time, there is no clear interface between the hard layer and the soft layer. Further, the composition in the interface region gradually changes with a slope. Thus, since the soft layer is sandwiched between the hard layers through the region where the composition gradually changes, the toughness and impact resistance are maintained at a high level while maintaining the high hardness of the entire hard film due to the cushion effect.
In addition, by simultaneously discharging the AIP method and the MS method, the structure of the crystal grains in the hard film having a multilayer structure grows continuously without being divided, and the multilayer structure exists in the same crystal grain. It is possible to make it. As a result, it is possible to improve mechanical strength such as toughness of the hard coating. The reason for this is that even when films having different compositions are laminated, there is no clear lamination interface, and therefore peeling and destruction from the lamination interface are difficult to occur. Furthermore, by simultaneously discharging the AIP method and the MS method, it is possible to add a high melting point material or a highly lubricating material, which was difficult to generate plasma by the AIP method, to the hard coating film. When performing the AIP method and the MS method at the same time, the arrangement of each deposition source comprising an AIP deposition source that generates a high-density plasma and an MS deposition source that generates a low-density plasma and the coated substrate is as follows. It is preferable to arrange them so that the films are laminated alternately. For example, when TiSi material is used for the AIP vapor deposition source and Si material is used for the MS vapor deposition source, discharge is simultaneously performed in a nitrogen atmosphere, and coating with both is performed alternately to form (TiSi) N, thereby improving toughness.
When simultaneously discharging the AIP method and the MS method with different plasma densities, it is desirable to optimize the setting of the necessary reaction gas pressure. In the AIP method, a relatively high reaction gas pressure is used, and a range of about 1 Pa to about 8 Pa can be stably coated. On the other hand, since the plasma density is low, the MS method is performed at a reaction gas pressure of less than 0.5 Pa in order to increase the deposition rate. Therefore, the reactive gas pressure conditions that can form plasma at the same time with the AIP method and the MS method, and can maintain and improve the high hardness and toughness, which are the physical properties of the formed hard film, are studied. did. As a result, when the reaction gas pressure P1 (Pa) was 0.5 ≦ P1 ≦ 8.0, a hard coating satisfying the characteristics was obtained. If it is less than 0.5 Pa, it is difficult to discharge by the AIP method. In the AIP method, it is important to suppress the generation of macro particles. As a suppression measure, a magnetic field region acts on the periphery of the target. However, many macro particles are generated under the condition of less than 0.5 Pa. This macro particle is not preferable because it increases the number of defects inside the hard film. On the other hand, if it exceeds 8.0 Pa, it is difficult to discharge in the MS method, and it is difficult to generate uniform plasma. As a result, the toughness of the hard coating is inferior, which is not preferable.
Regarding the film forming conditions, the current value of the AIP method is preferably set in the range of 100 to 150A. The discharge output of the MS method is preferably set to 6.5 kW or less. It is suitable for controlling the thickness T of each layer of the multilayer hard coating having a columnar structure to be 100 nm or less and making lattice fringes continuous in each crystal grain. Thereby, it is possible to secure a strong adhesion and to form a hard film having high hardness and high toughness.

When the hard coating of the present invention is formed on a cutting tool, it has excellent welding resistance and lubricity, so that an effect of avoiding welding of the work material can be obtained. Further, the hard coating also has strong adhesion and wear resistance, and can suppress welding and diffusion of the work material element in dry cutting where the cutting edge is at a high temperature. The cutting tool coated with the hard coating corresponds to dry, high speed, and high feed cutting. High feed cutting means, for example, cutting in which the feed amount per blade exceeds 0.3 mm / tooth. By smoothing the surface of the hard coating of the present invention by machining, the friction resistance is stabilized, and the variation in the cutting life of the tool is reduced.
When an intermediate layer made of Ti nitride, carbonitride or boronitride, TiAl alloy, Cr, W, or the like is provided on the surface of the substrate, the adhesion between the substrate and the hard coating increases, and the peel resistance of the hard coating and Improved fracture resistance. The cutting tool coated with the hard coating of the present invention is suitable for dry cutting, but can also be used for wet cutting. In either case, the presence of the intermediate layer can prevent the hard film from being broken due to repeated fatigue.
The material of the cutting tool that forms the hard coating of the present invention is not limited. Any of cemented carbide, high speed steel, die steel, etc. may be used. The hard coating of the present invention can be formed not only on cutting tools but also on heat resistant members such as dies, bearings, rolls, piston rings, sliding members, wear resistant members and internal combustion engine parts that require high hardness. . The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

For the coating of the hard coating of the present invention, a cemented carbide insert serving as a substrate was coated using a device in which an AIP evaporation source and an MS evaporation source were provided in a small vacuum apparatus. Each evaporation source uses various alloy targets, and the reaction gas is selected from N ₂ gas, CH ₄ gas, and Ar / O ₂ mixed gas so that the desired film can be obtained. A reaction pressure capable of generating plasma was selected. As other coating conditions, a substrate temperature of 450 ° C. and a bias voltage of −40V to −150V were applied. In the coating step, it is desirable to perform film formation by the AIP method before performing simultaneous discharge, and to perform simultaneous discharge by the AIP method and the MS method after ensuring adhesion. Using the obtained hard coating-coated insert, a cutting test was performed under the following cutting conditions. The work material used in the cutting test was prepared by drilling holes on the surface in advance at equal intervals. By cutting the surface of the work material under high-efficiency machining conditions, intermittent cutting was assumed, and the possible cutting length until the insert was impacted and damaged was evaluated.
(Cutting conditions)
Tool: Face mill Insert shape: SDE53 type special shape Cutting method: Center cut method Workpiece shape: width 100mm x length 250mm
Work material: SCM440, Hardness HB280, There are many Φ10 drill holes on the surface. Cutting depth: 2.0mm
Cutting speed: 180 m / min
1 blade feed amount: 1.5 mm / blade Cutting oil: None, dry cutting The evaluation method is an evaluation in an intermittent environment in which a strong impact can be applied to the insert blade edge, and whether the insert blade edge part is damaged, Alternatively, machining was performed until the tool became uncuttable due to wear of the hard coating or the like, and the cuttable distance at that time was defined as the tool life. Tables 1 and 2 show the details of the hard coating and the results of the cutting test for the invention examples, comparative examples, and conventional examples.

Table 2 shows the evaluation results of Invention Examples 1 to 14, Comparative Examples 15 to 28, and Conventional Examples 29 to 33. As shown in Examples 1 to 14 of the present invention, the cutting performance varied greatly depending on the presence or absence of the metal-O bond constituting the hard coating near the hard coating surface. In addition, the difference in cutting performance was clearly shown depending on the amount of O content when O element was added to the hard film using two or more kinds of physical evaporation sources. In particular, as shown in Example 9 of the present invention, the hard film to which the O element was added and the Si element was further added by NbSi ₂ showed the best result in this evaluation. The coating of Invention Example 9 was treated at 600 ° C. As a result of investigating the hard coating in detail for Example 9 of the present invention, as shown in FIGS. 1 to 4, in the XPS analysis, Si—O bonds are in the range of 100 to 105 eV, Al—O bonds are in the range of 70 to 77 eV, 455 eV to Ti—O bonds were confirmed in the range of 465 eV, and Nb—O bonds were confirmed in the range of 202 to 212 eV. Due to the presence of the metal-O bonds constituting these hard films, intense welding at the initial stage of cutting was suppressed. In the vicinity of the hard coating surface of Example 9 of the present invention, a dense oxide having excellent lubricating properties is present, and a remarkable effect was exhibited in the processing of a metal in which welding is severely generated. The added amount of O was 4.8 atomic%, which was within the range of the proper amount of added O of the present invention.
Furthermore, the fracture surface structure of the hard film was observed with a scanning electron microscope (hereinafter referred to as SEM) at a magnification of 15000 times. The result is shown in FIG. From FIG. 5, the fracture surface structure of the hard coating was a columnar structure. The hard film-coated insert having such a composition and structure has also obtained mechanical strength in the shearing direction in cutting with high impact such as high feed processing. Further detailed investigation was conducted. FIG. 6 shows the result of observing the fractured surface structure with a TEM at a magnification of 20,000 times. Each crystal grain having the columnar structure of the hard film had a multilayer structure. FIG. 7 shows the result of magnifying and observing the crystal grains of FIG. 6 with a TEM at a magnification of 200,000 times. The crystal grains had a multi-layered structure in which a plurality of black layers and gray layers having different brightnesses were alternately laminated. This observation confirmed that each crystal grain was grown in almost the same direction so as to be perpendicular to the substrate surface. From the striped pattern shown in FIG. 7, it can be seen that the thickness of each layer is about 3 to 4 nm. Since the magnification is different between FIG. 6 and FIG. 7, the number of stripe patterns in both does not match. FIG. 8 shows the result of further magnifying the portion in the field of view of FIG. 7 and confirming the continuity of the lattice fringes of each layer in the multilayer portion at a magnification of 2 million times. The observation region in FIG. 8 is enlarged while confirming the positions of the black layer and the gray layer seen in FIG. 7, and the black layer and the gray layer in FIG. 8 correspond to those in FIG. The two lines drawn in FIG. 8 separate the areas corresponding to the black layer and the gray layer, respectively. FIG. 9 is a schematic diagram corresponding to the photograph of FIG. However, the spacing of the checkered pattern is enlarged for clarity of explanation. It can be seen from FIG. 8 that crystal lattice fringes are continuous in the boundary region between layers in the multilayer structure. The continuity of the crystal fringes need not be established in all the boundary regions, and it is sufficient if there is a region in the TEM photograph where the continuity of the lattice fringes is recognized. Although there is a black region on the left side of FIG. 8, this is not related to the black layer shown in FIG. An electron diffraction image of a region surrounded by a circle in FIG. 9 is shown in FIG. 10, and a schematic diagram of FIG. 10 is shown in FIG. As is clear from FIGS. 10 and 11, the electron diffraction image of the black layer indicated by the star mark and the electron diffraction image of the gray layer indicated by the circle mark substantially coincide with each other. As a result, the checkered pattern is continuous. Thus, it can be seen that the columnar crystal grains having a multi-layer structure are in the form of a single crystal. As the composition of the black layer and the gray layer in the multilayer columnar crystal grain of Example 9 of the present invention, the composition of point P (black layer) and point Q (gray layer) in FIG. 8 was analyzed by EDX attached to the TEM. Table 3 shows the composition of the black and gray layers.

As a result of the analysis, a difference in the added O content was confirmed. When the O content exceeds 15% in atomic%, the crystal structure becomes finer, so the compositional difference must be controlled within 15% at the maximum. In Invention Example 9, since the discharge output of NbSi ₂ to be discharged was set to 4.5 kW, the difference in content was 5.2%.
FIG. 12 shows the measurement results of the friction coefficients of Invention Examples 6 and 9 and Conventional Examples 29 and 31. For the measurement, a friction and wear tester using a ball-on-disk system was used, and the measurement was performed in a high temperature environment of 600 ° C. in the atmosphere. From the measurement results, it was confirmed that the lubrication characteristics were significantly improved by adding O to the hard coating. Invention Example 6 containing O gave a cutting performance three times that of Comparative Example 20. By applying the addition of O of the present invention, the friction coefficient of the coating having (TiAl) N as a basic composition was also greatly reduced.

  In Invention Example 9, in addition to the above-described cutting conditions, processing of intermittent portions such as fixing hole processing as seen in die processing was also performed. Here too, due to the improvement in the toughness of the hard coating, stable cutting could be performed without loss even under severe impact. The hard coating of the present invention was applied to drills, end mills, punches, dies, etc., and was effective for application in an intermittent environment.

  Comparative examples 15 to 28 in Table 2 will be described. Except for Comparative Examples 17, 23, 26, and 27, the O content was large, and Comparative Examples 19, 20, 24, 25, and 28 were 30% or more. In particular, Comparative Example 20 had a metal-O bond, and the thickness of one layer in the multilayer structure was within an appropriate range, but the added O content was as large as 34%. As a result of confirming the structure of the film fracture surface, an amorphous microstructure as shown in FIG. 13 was obtained. Hard film hardness tended to soften. If the O content is not properly controlled, the mechanical strength sufficient to withstand harsh use conditions cannot be obtained. In Comparative Example 17, metal-O bonds were confirmed, and the O content was an appropriate range of 9.1%. However, the thickness of one layer of the multilayer structure of the hard coating obtained by simultaneously discharging the AIP method and the MS method has exceeded 134.5 nm. Therefore, the cutting test result was short life due to early wear. The reason for this is that since the discharge output of the CrSi2 target by the MS method, which is the condition at the time of film formation, is 4.6 kW, the layer mainly composed of the MS method is miniaturized and the sectional structure of the entire hard coating is divided. This is because the lattice becomes discontinuous by generating strain in the lattice of each layer in the multilayer structure. In Comparative Example 23, no metal-O bond was confirmed, and the O content of the hard coating was in an appropriate range of 7 atomic%. The treatment temperature during film formation was 400 ° C. The reaction gas used was 10% oxygen added to nitrogen. As a result, the thickness of one layer of the multilayer structure obtained by simultaneous discharge with sputtering was 30.6 nm. In the evaluation, the work piece started to adhere from the middle and reached the early life. This is because the O element taken into the hard coating did not bind to the hard coating constituent metal element Nb because the treatment was performed at a relatively low temperature. For this reason, the effect of increasing hardness and toughness by simultaneously discharging the AIP method and the MS method can be processed to a certain extent, but suppression of welding that occurs at the beginning of cutting, which is affected by the lubricating properties of the hard coating, is suppressed. It was not enough. This was the same tendency in Comparative Example 16. In Comparative Examples 21 and 22, it was impossible to confirm the state of the metal-O bond even when using an analyzer such as XPS. The thickness of one layer in the multilayer structure was 0.2 and 0.8 nm, which are close to the confirmation limit. Therefore, intense welding occurred at the initial stage of cutting. In particular, in Comparative Example 22, a spark occurred and the evaluation was stopped. This is because the discharge output of WSi and NbSi used in the film formation was 0.5 kW, so the amount of O added, the chemical state, and the thickness of one layer of the stack were small.

  In Conventional Example 32, peeling easily occurred, and when it was continuously used thereafter, adhesion of the work piece occurred from the Al 2 O 3 peeling portion, reaching the life. This is because even when Al2O3 is coated on the outermost layer of the hard coating, the adhesion between Al2O3 and the hard coating immediately below the Al2O3 is not improved.

FIG. 1 shows the XPS analysis result of Example 9 of the present invention. FIG. 2 shows the XPS analysis result of Example 9 of the present invention. FIG. 3 shows the XPS analysis result of Example 9 of the present invention. FIG. 4 shows the XPS analysis result of Example 9 of the present invention. FIG. 5 shows a cross-sectional structure of the hard film of Example 9 of the present invention. FIG. 6 shows a transmission electron microscope observation result of the hard coating of Example 9 of the present invention. FIG. 7 shows the enlarged observation result of FIG. FIG. 8 shows an enlarged observation result of FIG. FIG. 9 shows a schematic diagram of FIG. FIG. 10 shows the electron diffraction results of Example 9 of the present invention. FIG. 11 shows a schematic diagram of FIG. FIG. 12 shows the measurement results of the friction coefficient. FIG. 13 shows a cross-sectional structure of the hard film of Comparative Example 20.

Claims (3)

The hard coating is composed of one or more metal elements selected from Group 4a, 5a, 6a, Al, B, and Si, and one or more non-metal elements selected from C and N including O, and the hard film The film has a columnar structure, and the crystal grains in the columnar structure have a multilayer structure composed of a plurality of layers having a difference in O content, and at least a region where crystal lattice stripes are continuous in a boundary region between the layers. A hard coating film that is present and has a thickness T (nm) of each layer of 0.1 ≦ T ≦ 100. The hard film according to claim 1, wherein the hard film has a bond between the metal element and O. The hard film according to claim 1, wherein the surface of the hard film is smoothed by machining.