JP2010120100A - Hard coating film coated tool for turning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coating film coated tool for turning, having high abrasion resistance by high hardness and excellent chipping resistance by high hardness. <P>SOLUTION: In the hard coating film coated tool for turning, a hard coating film is formed by coating a first hard coating film and a second hard coating film from a base surface. The first hard coating film is shown by (Al<SB>a</SB>Me<SB>1-a</SB>)<SB>e</SB>N<SB>f</SB>, where 35≤a≤65, and 0.85≤e/f≤1.25. The second hard coating film is shown by (Ti<SB>1-h</SB>B<SB>h</SB>)<SB>m</SB>N<SB>p</SB>, where 1≤h≤30, and 0.85≤m/p≤1.25. When surface intervals (nm) of (200) surfaces in X-ray diffraction of the first hard coating film and the second hard coating film are taken as d1 and d2, an equation of 1.01≤d2/d1≤1.05 is obtained. The second hard coating film has a columnar structure, and a crystal grain of the columnar structure has a composition modulation structure with a compositional difference in a B component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a turning tool used for processing metal parts and the like. In particular, the present invention relates to a hard coating tool for turning, in which a hard coating is coated on the surface of a tool that requires improved wear resistance and fracture resistance using a physical vapor deposition method (hereinafter referred to as PVD method).

  Patent Documents 1 and 2 disclose the orientation of the (200) plane and the half width of the diffraction peak in X-ray diffraction of a hard coating coated by the PVD method. Patent Document 3 discloses a technique for controlling peak intensity on the (220) plane and the (111) plane. Patent Document 4 discloses a technique for adjusting the constituent ratio of a metal element and a gas component element constituting a hard coating. Patent Document 5 discloses a technique related to improvement in adhesion at a film interface by epitaxial growth.

JP 2003-136302 A JP 2003-145313 A JP 2003-71611 A JP-A-7-188901 JP 2001-181826 A

  The problem to be solved by the present invention is that it is hard for turning with excellent wear resistance due to high hardness and fracture resistance due to high toughness while ensuring reduction of compressive stress and adhesion in a hard film that is thickened. It is to provide a film coating tool.

The present invention relates to a hard film coating tool for turning, in which a hard film having a compressive stress is coated on a substrate with a cemented carbide alloy in a film thickness of 5 to 30 μm. The hard film is a first hard film from the surface of the substrate, The second hard coating is coated, the outermost coating is coated with the second hard coating, and the first hard coating is represented by (Al _a Me _1-a ) _e N _f , where a is atomic%, e and f represent atomic ratios, 35 ≦ a ≦ 65, 0.85 ≦ e / f ≦ 1.25, and Me is one or more selected from the group 4a, 5a, 6a, Si, and B The second hard coating is represented by (Ti _1-h B _h ) _m N _p , where h is atomic%, m, p represents an atomic ratio, 1 ≦ h ≦ 30, 0.85 ≦ m / p ≦ 1.25, and the crystal structure of the first hard coating and the second hard coating is a face-centered cubic structure, and the X-ray rotation of the first hard coating is When the peak intensity of the (111) plane is Ir, the peak intensity of the (200) plane is Is, and the peak intensity of the (220) plane is It, 1.5 ≦ Is / Ir ≦ 15.0,. 6 ≦ It / Ir ≦ 1.5, and when the distance (nm) between the (200) planes in the X-ray diffraction of the first hard coating and the second hard coating is d1 and d2, respectively. 1.01 ≦ d2 / d1 ≦ 1.05, the second hard film has a columnar structure, and the crystal grains of the columnar structure have a composition modulation structure having a composition difference in the B component. This is a hard film coated tool for turning. By adopting the above configuration, while ensuring reduced compression stress and adhesion in hard coatings that have become thicker, for turning with excellent wear resistance due to increased hardness and fracture resistance due to increased toughness The hard film-coated tool can be provided.

  In the hard film-coated tool for turning of the present invention, the N element of the non-metallic component in the first hard film is partially replaced with C element and O element, and the whole non-metallic component is set to 1, atomic%. Where the content of the C element is x and the content of the O element is y, 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, the content of the N element is 1-xy, It is preferable that Further, regarding the Ti element of the metal component in the second hard film, when 1 part thereof is substituted with the Si element and the entire metal component is 1, the content of the Si element in atomic% is k, It is preferable that 0 <k ≦ 20 and the content of Ti element is 1-hk.

  Hard film coated tool for turning with excellent wear resistance due to high hardness and fracture resistance due to high toughness while ensuring reduction of compressive stress and adhesion in hard film thickened by the present invention Could be provided.

The metal component of the first hard coating in the hard film-coated tool of the present invention is excellent in heat resistance and wear resistance when the a value representing the Al content is in the range of 35 ≦ a ≦ 65. On the other hand, if the value a is larger than 65%, the cross-sectional structure of the film becomes finer and the residual compressive stress increases and the adhesiveness deteriorates. Selecting, for example, Ti as the Me component is effective for increasing the hardness of the film. Further, for example, in Si and B, the content range for maintaining the solid solution is from 1% to 20%, so that excellent heat resistance and lubrication characteristics can be obtained. Moreover, containing W, Nb, and Cr is effective in improving the heat resistance and hardness of the coating. It is preferable to cover nitrides containing elements of groups 4a, 5a, 6a having an ionic radius of 0.041 to 0.1 nm, and Si, B having an ionic radius of 0.002 to 0.04 nm.
By setting the ratio e / f value of the metal component and the non-metal component of the first hard coating to 0.85 to 1.25, the compressive stress of the hard coating can be set to an optimum range, and high adhesion is achieved. Can be obtained. Further, the hard film structure can have a columnar crystal structure having high toughness, and excellent chipping and wear resistance can be obtained. When the e / f value is 0.85 or more, the crystal lattice strain of the hard coating can be reduced. However, when the e / f value is less than 0.85, the crystal lattice strain increases and the continuity of crystal lattice fringes is lost. The cross-sectional structure becomes finer and grain boundary defects increase. As a result, the residual compressive stress is increased and the adhesion is deteriorated. For example, in hard coatings for cutting tools, this grain boundary defect leads to a reduction in coating density and inward diffusion of the elements that make up the workpiece into the hard coating, reducing the hardness and fracture resistance of the hard coating. Deteriorate. When the e / f value exceeds 1.25, the hard coating has a columnar crystal structure, but impurities are likely to be taken into the crystal grain boundary. This impurity is a component remaining inside the apparatus that performs the coating process. As a result, the bonding strength between crystal grains deteriorates, and the hard coating is easily broken by an external impact. By controlling the hard coating of the present invention in the range of 0.85 ≦ e / f ≦ 1.25, the residual compressive stress of the coating is in the range of 1.5 to 5.0 GPa. Industrially, it is possible to determine the e / f value and manage the residual compressive stress of the hard coating.

When the second hard coating is a nitride having a face-centered cubic structure containing Ti and B, excellent welding resistance can be realized. The h value indicating the B content in the second hard coating is 1 ≦ h ≦ 30. This is important for making the second hard coating a columnar structure. Moreover, when B element is contained, the wear resistance of the rake face of the tool is improved. In the initial stage of cutting, B is oxidized from the state where the tool edge is still at a low temperature to form a B-containing oxide. This B-containing oxide exhibits the effect of suppressing the diffusion of workpiece components into the hard coating. However, when the h value exceeds 30%, the structure of the film becomes finer. In addition, BN crystals appear, the hardness decreases, the compressive stress of the film increases, and the drawback of decreasing adhesion appears. Even if the h value is about 1%, the effect appears, but if it is less than 1%, it becomes difficult to perform quality control because detection with a general-purpose analysis facility becomes difficult. Therefore, it was set to 1% or more that can be detected by the analyzer.
In addition, by controlling the ratio m / p value of the metal component and the non-metal component of the second hard coating to 0.85 to 1.25, the compressive stress of the coating can be adjusted to an optimum range, and high adhesion Can be obtained. Further, the hard film structure can have a columnar crystal structure having high toughness, and excellent chipping and wear resistance can be obtained. When the first hard film and the second hard film have a face-centered cubic structure, a hard film having high hardness can be obtained. Further, by controlling the film structure to columnar crystals, it is possible to obtain excellent chipping and wear resistance.

In order to control the first hard film in the range of 0.85 ≦ e / f ≦ 1.25, it is important to control the reaction pressure during film formation. In order to obtain a nitride, the reaction pressure of nitrogen is set to 3 Pa to 8 Pa. More preferably, it is controlled in the range of 3.5 Pa to 7 Pa. When the reaction pressure is less than 3 Pa, the kinetic energy of ions incident on the substrate cannot be suppressed, which appears as crystal lattice strain, the residual compressive stress cannot be suppressed, and the e / f value is less than 0.85. When film formation is performed under conditions exceeding 8 Pa, the plasma density decreases, the kinetic energy of incident ions decreases, and the e / f value exceeds 1.25.
As a condition for forming the first hard coating, the pulsed bias voltage application is controlled by amplifying it negatively and positively, and by further orienting strongly in the (200) plane, the compressive stress of the hard coating is reduced. Control can be realized. This can be realized by controlling the bias 20 to 100V to be negative and the positive voltage to 5 to 10V.
In order to set the Is / Ir value of the first hard coating to 1.5 ≦ Is / Ir ≦ 15, it is necessary to control the bias voltage, and it is preferable to apply the pulsed bias voltage. When the bias voltage is less than 20V, the Is / Ir value tends to increase and the compressive stress is reduced, but the hardness of the hard coating is lowered and the wear resistance is deteriorated. Further, by applying the bias voltage in a pulsed manner, it is possible to adjust the kinetic energy when the hard film constituent elements ionized in the plasma at the time of film formation reach the object to be processed. The control of the pulse frequency is particularly important when the bias voltage is pulsed. When the bias voltage is applied in a pulsed manner, the peak intensity of the (111) plane, the (200) plane, and the (220) plane can be changed, particularly by suppressing crystal growth on the (111) plane. , Compressive stress can be suppressed and adhesion can be enhanced.
When the pulse frequency is 5 to 35 kHz, the It / Ir value is 0.6 ≦ It / Ir ≦ 1.5, and the compression stress of the hard coating at this time is controlled within the optimum range of 2.0 to 6.0 GPa. it can. When the pulse frequency is lower than 5 kHz, the It / Ir value exceeds 1.5. On the other hand, if it exceeds 35 kHz, the kinetic energy when ions reach the workpiece cannot be reduced, and the It / Ir value becomes less than 0.6.

When the bias voltage applied during the formation of the second hard film is pulsed in the same manner as the conditions for forming the first hard film, the kinetic energy of B ions reaching the substrate can be kept low. Incorporated into the crystal lattice of TiN, the hard coating has a single crystallized structure containing B.
On the other hand, when the second hard film is formed by applying a DC bias voltage, B is replaced by a lattice having a face-centered cubic structure of TiN, c-BN, h-BN, amorphous BN. Etc. Since ions of B in the plasma are lighter elements than Ti and the like, it is considered that the ions reach the substrate with high kinetic energy and various unstable bonds are generated. When the hard film contains only h-BN, it is expected that the lubrication characteristics are improved and the rake face wear can be suppressed, but it is difficult to contain h-BN alone. Since it comes to coexist with substances having other crystal structures such as c-BN, the compressive stress increases. In particular, when a large amount of c-BN is contained, the hardness of the hard coating can be increased, but the compressive stress increases, which is not preferable.

  In the present invention, it is necessary that the hard film having a face-centered cubic structure be oriented most strongly in the (200) plane. This is because the durability against cutting force from the shear direction in cutting is excellent. On the other hand, when the orientation to the (111) plane becomes strong, the compressive stress becomes high and the adhesion of the hard coating is lowered. As a result, the chipping resistance and wear resistance are lowered, resulting in inconvenience. Therefore, the Is / Ir value of the first hard coating is defined as 1.5 ≦ Is / Ir ≦ 15, and the It / Ir value is defined as 0.6 ≦ It / Ir ≦ 1.5. If the first hard coating is controlled to 1.5 ≦ Is / Ir ≦ 15, excellent wear resistance can be realized, and if it is controlled to 0.6 ≦ It / Ir ≦ 1.5, an appropriate residual can be achieved. It can be controlled within the range of compressive stress. Therefore, it is possible to obtain a high hardness film while the thick film has high adhesion. However, when the Is / Ir value is less than 1.5 and the It / Ir value is less than 0.6, the cross-sectional structure of the hard coating becomes finer and the residual stress increases. Therefore, although abrasion resistance is excellent, film peeling occurs easily. Particularly when the It / Ir value is less than 0.6, the internal defects of the hard coating increase. When the It / Ir value is less than 0.6, the peak intensity of the (111) plane appears greatly even if the Is / Ir value is 1.5 ≦ Is / Ir ≦ 15.0. At this time, the residual compressive stress of the first hard film is about 5.0 GPa, and even though the adhesion between the substrate and the hard film can be ensured, the adhesion strength between the columnar crystal grain boundaries deteriorates and the wear resistance decreases. Therefore, it is defined as 0.6 ≦ It / Ir ≦ 1.5. When the Is / Ir value is larger than 15 and the It / Ir value is larger than 1.5, the residual stress is reduced, but the bonding strength of the grain boundary in the cross-sectional structure of the hard film is lowered and the adhesion is reduced. And wear resistance deteriorate. When the It / Ir value exceeds 1.5, the film has a columnar crystal structure and a low residual compressive stress can be obtained. However, the adhesion strength at the grain boundaries of the columnar crystals decreases, and the film surface Crack fracture in a direction substantially perpendicular to the substrate direction tends to occur. As a result, chipping resistance and wear resistance are not improved. In addition, the workpiece element tends to diffuse into the grain boundary, and the mechanical characteristics are deteriorated.

  For the hard coating of the present invention, the d2 / d1 value is 1.01 ≦ d2 / d1 ≦ 1.05, whereby the adhesion between the first hard coating and the second hard coating is improved, and the wear resistance is improved. Excellent. In order to improve the adhesion between the films, it is necessary to reduce the crystal lattice strain between the films. In order to reduce this strain, high adhesion can be obtained by reducing the difference in the (200) plane spacing between the films to reduce misfit. Therefore, by defining the d2 / d1 value in the range of 1.01 ≦ d2 / d1 ≦ 1.05, a hard coating excellent in wear resistance and fracture resistance can be obtained without impairing adhesion to the substrate. . If the d2 / d1 value is less than 1.01, the residual compressive stress of the entire hard coating increases, and the adhesion to the substrate deteriorates. If it exceeds 1.05, the number of internal defects at the film interface increases, and not only the adhesion between the films is impaired, but also the residual compressive stress of the entire hard film increases and the adhesion with the substrate decreases.

Regarding the hard coating of the present invention, the second hard coating has a columnar structure and is a hard coating in which crystal grains are continuously grown in the boundary region without forming an interface with respect to the crystal grain growth direction. Here, the columnar structure is a vertically grown crystal structure extending in the film thickness direction. The hard coating is a polycrystalline material, but has a form similar to the growth of a single crystal material if it is grasped in units of crystal grains. The crystal grain of the columnar structure has a composition modulation structure having a composition difference in the B component with respect to the crystal grain growth direction. At this time, it is preferable that crystal lattice fringes are continuous at the composition modulation boundary in the composition modulation structure. The second hard film has a B component composition modulation structure, and the mechanical strength of the film is increased by controlling the residual compressive stress. For example, a B layer enriched layer forms a relatively soft layer. When this soft layer is present between other relatively hard layers, a buffering effect is exhibited, and the residual compressive stress is relieved as the entire hard film. Further, a hard film having lubricity can be obtained by the lubrication characteristics of the B component. However, the preferable composition difference of the B component at this time is 10% at the maximum. More preferably, it is controlled within a range of 0.1% to 7%. The composition modulation structure of the B component can be realized by performing film formation while applying a pulse bias using targets having different B contents. A portion where the B content has a composition difference becomes a composition modulation structure, and crystal lattice fringes continuously grow between the layers. This can be confirmed, for example, by observing the columnar crystal grains under the condition of an acceleration voltage of 20 kV using a JEM-2010F type field emission transmission electron microscope (hereinafter referred to as TEM) manufactured by JEOL.
By setting the film thickness of the entire hard coating to 5 μm or more, excellent wear resistance can be obtained. On the other hand, when the thickness is 30 μm or more, the hard coating film has a high compressive stress and deteriorates the adhesion to the substrate. Further, the film thickness of the first hard film is thicker than that of the second hard film, and more preferably, the film thickness of the second hard film is 50% or less with respect to the film thickness of the entire hard film.

For the N element of the non-metallic component in the first hard film, when 1 part thereof is replaced with the C element and the O element, the content of the C element in atomic% is the x value and the content of the O element is the y value. It is preferable that 0 <x ≦ 10, 0 <y ≦ 10, and 0 <x + y ≦ 10. As a result, a hard coating having high hardness, excellent oxidation resistance, adhesion and lubrication can be obtained. When C element and O element are contained, in order to avoid deterioration of the mechanical strength of the film, the sum of the x value and the y value is 10% or less, so that excellent welding resistance and slidability are obtained. The hard film which has is obtained. More preferably, when the C element and the O element are contained alone, the content is made 2% to 10%. However, if the x value and y value exceed 10%, the crystal structure of the film becomes finer, and defects at the grain boundaries increase. As a result, even if the lubrication characteristics of the hard coating are improved, the residual compressive stress increases, so that there is a drawback that the adhesion and fracture resistance are lowered. When C element and O element are contained in the first hard film, it is preferable to use hydrocarbon-based gas or oxygen-containing gas. When film formation is performed by introducing a gas, the total pressure combined with the N ₂ gas is preferably in the range of 3 to 8 Pa. Alternatively, the target evaporation source can contain C element and O element.

  With respect to the Ti element of the metal component in the second hard film, when 1 part of the Ti element is substituted with the Si element and the entire metal component is 1, the content of Si element in atomic% is k, and 0 <k ≦ By setting it to 20, the wear resistance is improved. In order to make the film structure of the second hard film a columnar structure, the k value is preferably controlled to 20% or less. When Si is contained, by controlling so that the single crystalline structure of TiN becomes a solid solution, for example, a hard film having excellent wear resistance on the rake face of the cutting tool can be obtained. On the other hand, if the k value exceeds 20%, the film structure becomes finer, the residual compressive stress increases, and the disadvantage of decreasing the adhesion appears. Further, the film structure includes various structures such as a TiN crystalline structure, a SiN composition crystalline structure, and an amorphous structure. As a result, crystal grain boundaries increase, crystal lattice distortion occurs, and residual compressive stress increases.

The composition of the hard coating of the present invention can be measured, for example, using a JXA8500F type EPMA analyzer manufactured by JEOL. In the vertical section of the hard coating or the inclined section polished by tilting the film cross section at 17 degrees, the hard coating is performed from a position not affected by the substrate, the acceleration voltage is 10 kV, the irradiation current is 1.0 μA, and the probe diameter is about 10 μm. It is possible by setting to. When measuring from the surface of the hard coating, the probe diameter is preferably set to about 50 μm. Moreover, when C element and O element are contained, if it is less than 2%, detection by analysis becomes difficult. The film thickness of the hard coating can be measured from a vertical break using, for example, an S-4200 type electrolytic emission scanning electron microscope manufactured by Hitachi, Ltd.
Measurement of the peak intensity ratio of the (111), (200), (220) planes in the X-ray diffraction of the hard coating is measured by, for example, 2θ-θ scanning method using a RU-200BH X-ray diffractometer manufactured by Rigaku Corporation it can. The range of 2θ (degrees) was 10 to 145 degrees, the X-ray source used was a CuKα1 line having a λ value of 0.15405 nm, and background noise was removed by software built in the apparatus. As a result of the measurement, the detected 2θ peak position substantially coincided with the X-ray diffraction pattern (JCPDS file number 38-1420) of TiN whose crystal structure is a face-centered cubic structure. , (220) peak intensity was measured. For the peak intensity, the maximum value of the peak top of each index surface was used as the peak intensity, and the peak intensity ratio was determined using the peak intensity. Furthermore, the numerical value of the peak position which shows the said (200) plane was applied to the surface space | interval. Similarly, the peak intensity was measured in the case of a hard film based on CrN.
The residual compressive stress in the hard coating of the present invention was calculated by the curvature measurement method shown below. That is, when a test piece obtained by processing a base having a known Young's modulus and Poisson's ratio into a predetermined shape is coated on the surface, the test piece is coated by the residual compressive stress generated in the hard coating. Will bend and deform. The amount of deflection deformation was determined, and the residual compressive stress σ value of the entire hard coating was calculated using Chemical Formula 1.

  Here, the Es value (GPa) is the Young's modulus of the substrate used for the test piece, the D value (mm) is the thickness of the test piece, the δ value (μm) is the amount of deflection of the test piece before and after coating, and the l value ( mm) is the length from the end surface in the longitudinal direction of the test piece where the deflection is caused by the coating to the maximum deflection part, νs value is the Poisson's ratio of the substrate used for the test piece, and d (μm) is coated on the surface of the test piece. It is the film thickness of the hard coating. In addition, as a specimen material, a cemented carbide material is suitable with little variation in measurement values. The shape of the test piece is preferably a strip shape. For example, when a shape having a width of 8 mm, a length of 25 mm, and a thickness of 0.5 to 1.5 mm is used, variation in measured numerical values is small. The upper and lower surfaces having a large area of the test piece are mirror-polished so that the parallelism is ± 0.1 mm, and then heat-treated in a vacuum of 600 to 1000 ° C., and particularly the surface portion of the material used for the test piece. Remove distortion. If this distortion is not removed to some extent, the resulting residual compressive stress varies. After measuring the deflection deformation amount of one mirror-finished surface having a large test piece area before coating, the surface is coated, and the deflection amount of the obtained coated test piece is measured again. Measure the amount of deflection before and after coating, the length from the end surface in the length direction of the test piece where the deflection occurred due to coating, to the maximum deflection, and the thickness of the coated hard coating. For example, even if the composition of the hard coating, the film forming conditions change, or the composition has a modulation structure, the value of the compressive stress can be calculated by this measurement method.

  When the hard coating tool is made of tungsten carbide base cemented carbide, high-speed tool steel substrate, cermet, or the like, the balance between wear resistance and toughness is further optimized. However, when high-speed tool steel is used as the substrate, it is preferable to coat in the range of 500 to 550 ° C. in consideration of its heat treatment characteristics. When the film is formed at such a relatively low temperature, the bias voltage to be applied and the reaction pressure at the time of film formation are appropriately optimized. As a film forming method, a film forming method in which a pulsed bias voltage can be applied and compressive stress is applied is preferable. An ion plating method such as an arc ion plating (hereinafter referred to as AIP) method or a sputtering method is preferred. If appropriate manufacturing conditions are applied, a composite apparatus in which each method is installed in one facility may be used. The present invention will be described in more detail by the following examples.

Example 1 of the present invention was prepared by coating a test piece capable of measuring residual compressive stress and the surface of a cemented carbide substrate having an insert shape for turning with the hard coating of the present invention. Example 1 of the present invention uses an AIP apparatus, the composition of only the metal component is atomic%, the Ti: 50%, Al: 50% (TiAl) N film is 6 μm thick, and then the composition of only the metal component A (TiB) N film of Ti: 90% and B: 10% was formed to a film thickness of 6 μm so that the total film thickness was 12 μm. The deposition temperature was 550 ° C., the reaction pressure was 3.5 Pa, and the initial (TiAl) N film was deposited with a bias voltage of DC 50V to 1 μm, and then a pulsed bias voltage was applied. The pulse frequency was set to 10 kHz, and the positive bias voltage was set to 5V. After the (TiAl) N film was formed, the (TiB) N film was also formed under the same conditions as (TiAl) N. The evaporation source is selected from various alloy targets and used as a nitride, carbonitride, oxynitride, oxycarbonitride alone, or a hydrocarbon gas such as nitrogen, oxygen, acetylene, or It was mixed and introduced during film formation. Invention Examples 2 to 35 and Comparative Examples 36 to 52 in which the film thickness, composition, X-ray diffraction peak intensity, and residual stress of the hard coating were changed using the film forming conditions of Invention Example 1 as a standard were prepared.
Tables 1, 2 and 3 show the details of the prepared samples, the hard coating composition, the manufacturing conditions of the hard coating, the measured values of the residual compressive stress, and the evaluation results of the coated insert cutting test. Further, as a result of TEM film cross-sectional observation, all of the second hard films in the examples of the present invention have a columnar structure, and the crystal grains of the columnar structure have a compositional difference in the B component with respect to the crystal grain growth direction. It was confirmed that it has.

The produced turning insert was attached to a blade-type replaceable cutting tool, and a turning test was performed under the following conditions to confirm the superiority or inferiority of wear resistance, fracture resistance, and adhesion in a hard film having residual compressive stress. The insert used for the cutting evaluation uses a general-purpose CNMG120408 shape, using cemented carbide as a base, and HRA91 corresponding to M20 type in the JIS standard. In turning, a special insert with a chip breaker and a rake angle of 1 degree was used. In the evaluation method, the abrasion generated on the flank and rake face of the hard film-coated insert generated at a cutting distance of 5 m was observed with an optical microscope at a magnification of 50 times. Further, when cutting was continued and a defect including micro chipping of 10 μm or more occurred, or when there was no defect, the tool life was defined as the time when the VBmax value of the flank wear width reached 0.3 mm, and the cutting distance at this time The performance was evaluated by (m). The damage state of the cutting edge during cutting was appropriately observed.
(Test conditions)
Cutting method: Continuous cutting in the longitudinal direction Work material shape: Round bar material with a diameter of 160 mm and a length of 600 mm Work material: S53C, HB260, tempered material Axial depth of cut: 2.0 mm
Cutting speed: 220 m / min Feed rate per rotation: 0.4 mm / rotation Cutting oil: None

Invention Examples 1 to 5 and Comparative Examples 36 and 37 were prepared in order to see the influence of the film thickness of the hard coating. The film thickness was adjusted by the coating time. The ratio between the first hard film and the second hard film was 1: 1, and only the entire film thickness was changed. The residual compressive stress increased as the thickness of the hard coating increased. What the total film thickness shown to this invention examples 1-5 has 5 micrometers or more was excellent in abrasion resistance. In any of the samples, there was no occurrence of welding of the workpiece components to the cutting edge, and (TiB) N of the second hard coating was considered to have a great effect on crater wear and welding resistance. The total film thickness of Invention Example 1 was 12 μm, the residual compressive stress value was 1.6 GPa, and the tool life was 24 m. As a result of confirming the wear state of the blade edge after the cutting time of 5 minutes, the flank wear amount was as small as 0.088 mm and was excellent in wear resistance. When the damaged state of the cutting edge was confirmed during cutting, the hard coating was not dropped, peeled off, chipped, or the like in the vicinity of the cutting edge, and normal wear was exhibited. The example of the present invention in which film formation was performed by applying a pulsed bias voltage had a long tool life and excellent results. On the other hand, the total film thickness of Comparative Example 36 was 40 μm, the residual compressive stress was 6.8 GPa, and the tool life was inferior to Invention Examples 1-5. In Comparative Example 36, fine film breakage was observed at the edge of the blade edge before cutting. When the damage state of the edge part of the cutting edge during the cutting was confirmed, the film breakage expanded to a width of 8 μm or more, and this broken part led to a defect. This is because the residual compressive stress is increased by increasing the film thickness. The total film thickness of Comparative Example 37 was 4 μm and had a low residual compressive stress of 1.6 GPa. However, the tool life was short due to inferior abrasive wear.
Invention Examples 6 and 7 were prepared in order to observe the influence of the film thickness ratio of the first hard film and the second hard film. As shown in Invention Example 6, the tool life was superior to Invention Example 1 by increasing the thickness of the first hard coating. However, in Invention Examples 6 and 7, the second hard coating of (TiB) N was as thin as 1 μm and 3 μm, respectively, and crater wear occurred during cutting. The blade edge strength was lost due to the progress of crater wear, leading to defects. In order to confirm reproducibility, cutting evaluation was also performed on a film having a total film thickness of 12 μm and a second hard film coated to 0.3 μm. Similarly, crater wear mainly proceeded.
Invention Examples 8 to 17 and Comparative Examples 38 and 39 were prepared in order to observe the influence of the composition of the first hard film. It was prepared by changing the composition of the target material for coating. Invention Example 8, which had the best tool life, contained 10% W, and was approximately 1.3 times better than Invention Example 1. When the cutting edge state was confirmed when the cutting distance was 5 m, chipping was not confirmed at the cutting edge part, and the flank wear was 0.034 mm. There was almost no welding of the workpiece at the cutting site, and the life was reached only by the progress of normal wear. The reason why welding did not occur is that the outermost second hard film contains B and has excellent lubrication characteristics. Invention Example 9 contained 10% Nb, and Invention Examples 10 and 11 contained Cr and Si, and thus were superior to Invention Example 1. As shown in Example 12 of the present invention, even when B is contained in the first hard coating, the tool life is excellent, but welding slightly occurs at the portion of the first hard coating exposed after the second hard coating is worn. By containing B in the first hard film, a remarkable effect was expected for welding and crater wear, but the tool life of Example 1 of the present invention was not reached. In Invention Examples 8 to 17, since the first hard film is a hard film of nitride of an element selected from Al, elements 4a, 5a, and 6a, Si, and B, the heat resistance and hardness of the film are remarkably high. Increased. On the other hand, Comparative Example 38 was a film having an Al content of 75%, and the welding phenomenon and the abrasive wear of the tool flank progressed from the beginning of cutting. In the observation of the structure of the cross section of the film, it was miniaturized. For this reason, the residual compressive stress increases, and the adhesiveness is considered to deteriorate. Further, the film hardness was 20 GPa, and it was considered that the decrease in hardness caused early progress of wear. In Comparative Example 39, the structure of the cross section of the film was observed, and the same refinement was confirmed.

Invention Examples 18 to 21 and Comparative Examples 40 and 41 were prepared in order to see the influence of the composition of the second hard coating. It was created by changing the composition of the target material for coating. In Invention Examples 18 and 19, the B content of the second hard coating was 1% and 25%, respectively. Inventive Example 20 had a Si content of 20%, and Inventive Example 21 contained B and Si. When the structures of these film cross-sections were observed, it was confirmed that all were columnar structures. On the other hand, regarding the comparative example 40 in which the B content of the second hard coating is 40% and the comparative example 41 in which the Si content is 30%, the cross-sectional structure of the second hard coating was observed to confirm the refined structure. . When the B and Si contents were increased, peeling of the hard coating and crater wear occurred from the beginning of cutting. It was considered that the difference in the structure morphology brought about superiority or inferiority of the cutting performance.
Invention Examples 22 and 23 and Comparative Examples 42 and 43 were prepared in order to observe the influence of O and C contained in the first hard film. Oxygen and hydrocarbons were used as part of the reaction gas. The tool life of Inventive Examples 22 and 23 was about 10% superior to Inventive Example 1 containing no O or C. Moreover, the damage state of the blade edge at the time of the cutting distance of 15 m tended to be less welded than that of Example 1 of the present invention. In particular, the occurrence of crater wear on the rake face was reduced. Crater wear is caused by a chemical reaction accompanying an increase in cutting temperature, and by adding O and C, the lubrication characteristics are increased and the friction coefficient is reduced. As a result, the cutting temperature when scrapes scrape the rake face is reduced. Suppressed and reduced wear. Furthermore, as a result of observing the structure of the film cross section, a columnar structure was confirmed. For this reason, it was excellent in mechanical strength and the tool life was excellent. On the other hand, in Comparative Examples 42 and 43, since the x value and the y value were 10% or more, peeling of the hard film and occurrence of crater wear from the initial stage of cutting were confirmed. It was. Further, the friction coefficient of the ball-on-disk method was measured for Invention Example 1 containing no C, Invention Example 22 having a C content of 7%, and Comparative Example 42 having a C content of 15%. In this friction coefficient measurement, a SUS304 φ6 mm ball was slid on a coated cemented carbide disk and measured in the air without lubrication. As a result of the measurement, the friction coefficient of Invention Example 1 was 0.8, Invention Example 22 was 0.4, and Comparative Example 42 was 0.7 at a measurement temperature of 650 ° C. Even if the film contains a large amount of C, it has been confirmed that damage such as flank wear and crater wear occurs at the beginning of cutting unless the cross-sectional structure of the film is columnar.

  Invention Examples 24-26 and Comparative Examples 44 and 45 were prepared in order to observe the influence of the reaction pressure on the composition during film formation. In particular, the influence on e / f value and residual compressive stress was investigated. At this time, the reaction pressure was changed and set in a range of 1.6 Pa to 13.5 Pa. Inventive Examples 1, 24 to 26, in which the film was formed at a reaction pressure of 2.2 to 8.1 Pa, all had a tool life of 20 m or more and an excellent tool life. In particular, Invention Example 24 having an e / f value of 1.16 was the most excellent, and unstable elements such as chipping of the film did not occur. In Comparative Example 44 in which the film was formed at the lowest reaction pressure of 1.6 Pa, the residual compressive stress was 6.5 GPa, the e / f value was 0.82, and the tool life was 14 m. This was a lifetime of about 60% as compared with Example 1 of the present invention. The lower the nitrogen pressure, the higher the residual compressive stress, and the e / f value tended to show a lower value. The reason is considered that the residual compressive stress of the film is high. When the residual compressive stress exceeded 6.0 GPa, film damage at the edge portion of the blade edge was confirmed in the damage state of the insert blade edge during cutting. In order to confirm reproducibility, the cutting life was evaluated several times using a new corner of the insert of Comparative Example 44. As a result, the tool life was 9 m and 11 m, and was not stable. In Comparative Example 45, the residual compressive stress was a relatively low value of 0.5 GPa, but the tool life was 8 m. As a result of observing the damage state of the blade edge when the cutting time was 5 m, film peeling from the base and hard film interface at the edge of the blade edge, large wear on the flank, and crater wear occurred. The film hardness also decreased and the wear resistance was inferior. The e / f value was 1.32, and although the film cross-sectional structure had a columnar structure, many defects were generated in the hard film, and adhesion and wear resistance were inferior. The reason for this is that the reaction pressure is 13.5 Pa, so that the kinetic energy when ions enter the substrate is lowered.

Invention Examples 27 to 30 and Comparative Examples 46 and 47 were prepared in order to observe the influence of the Is / Ir value. At this time, the pulse frequency of the pulsing bias was kept constant at 10 kHz, and the bias voltage value was changed and set in the range of 30 to 200V. In Invention Example 1 and Invention Examples 27-30, the Is / Ir value was within the specified range of the present invention, the residual compressive stress was as low as 3.5 GPa or less, and the tool life was excellent. Further, when the bias voltage was changed, the Is / Ir value was changed, and the residual compressive stress was changed accordingly. In Comparative Examples 46 and 47, the residual compressive stress exceeded 7 GPa, and delamination of the hard coating was observed from the beginning of cutting. As the residual stress increased, the tool life was inferior.
Invention Examples 31 to 33 and Comparative Examples 48 to 50 were prepared in order to see the effect of the It / Ir value on the residual compressive stress. At this time, the positive bias value of the pulsed bias voltage was changed from 5 to 40V. When the positive bias voltage is increased, the orientation strength toward the (111) plane tends to be relatively increased, and the It / Ir values of Invention Examples 1, 31 to 33 and Comparative Examples 48 to 50 are 0.3. Changed to ~ 1.1. In Invention Example 1 and Invention Examples 31 to 33, the It / Ir value was within the specified range of the present invention, the residual compressive stress was relatively low, and a satisfactory tool life was obtained. On the other hand, in Comparative Examples 48 to 50, the positive bias voltage exceeded 20 V, the It / Ir value was less than 0.6, and in the blade edge damage state observation when the cutting distance was 5 m, many peeling of the hard coating was observed. Residual compressive stress increased, and the tool life decreased as the hard coating peeled and broken mainly. In addition to controlling the orientation strength of the (111) plane in the X-ray diffraction of the first hard film, in order to improve the adhesion at the interface between the first hard film and the second hard film, a positive pulse voltage is applied. Bias voltage value control is important. This is because application of a bias voltage only in the negative region is insufficient to suppress defects caused by micro arcing during film formation.

  Invention Examples 34 and 35 and Comparative Examples 51 and 52 were prepared in order to observe the influence of the surface spacing of the first hard film and the second hard film. The face spacing was adjusted by changing the pulse frequency of the pulsed bias voltage in the range of 1 to 40 kHz. Examples 34 and 35 of the present invention are cases where the pulse frequencies are 30 kHz and 2 kHz, respectively, but the d2 / d1 value is 1.02, and the residual compressive stress of the entire hard film is controlled to be low, so that the first hard film and the first hard film 2 Excellent adhesiveness of hard coating, and a satisfactory tool life was obtained. On the other hand, in Comparative Example 51 in which film formation was performed at a pulse frequency of 1 kHz, the d2 / d1 value was 1.06, and the adhesion deteriorated due to the gap between the first hard coating and the second hard coating. In Comparative Example 52, peeling of the film occurred and the tool life was short. In this case, damage to the cutting edge during cutting was observed at the interface between the substrate and the first hard coating. This is because the d2 / d1 value was 1.01 because the film was formed at 40 kHz, the residual compressive stress of the entire film increased to 6.6 GPa, and the adhesion to the substrate deteriorated. It was also confirmed that the It / Ir value also changed with the change of the pulse frequency. The relationship between the pulse frequency and the residual compressive stress is considered to be correlated, and the residual compressive stress tends to increase as the pulse frequency increases. This is because when the pulse frequency is increased, the state approaches a state where a DC bias voltage is applied.

Claims (3)

In a hard film coated tool for turning, in which a hard film having a compressive stress is coated on a substrate with a thickness of 5 to 30 μm, the hard film is formed from the surface of the substrate by the first hard film and the second hard film. The outermost coating is coated with the second hard coating, and the first hard coating is represented by (Al _a Me _1-a ) _e N _f , where a is atomic%, e and f are Represents an atomic ratio, 35 ≦ a ≦ 65, 0.85 ≦ e / f ≦ 1.25, Me has one or more selected from 4a, 5a, 6a group, Si, B, The second hard coating is represented by (Ti _1-h B _h ) _m N _p , where h is atomic%, m, p represents an atomic ratio, and 1 ≦ h ≦ 30, 0.85 ≦ m / p ≦ 1.25, and the crystal structure of the first hard coating and the second hard coating is a face-centered cubic structure, and in the X-ray diffraction of the first hard coating ( When the peak intensity of the (111) plane is Ir, the peak intensity of the (200) plane is Is, and the peak intensity of the (220) plane is It, 1.5 ≦ Is / Ir ≦ 15.0, 0.6 ≦ It /Ir≦1.5, and 1.01 when the plane spacing (nm) of the (200) plane in the X-ray diffraction of the first hard coating and the second hard coating is d1 and d2, respectively. ≦ d2 / d1 ≦ 1.05, the second hard film has a columnar structure, and the crystal grains of the columnar structure have a composition modulation structure having a composition difference in the B component. A hard-coated tool for turning. 2. The hard coating tool according to claim 1, wherein one part of the N element in the first hard coating is replaced with C element and O element, the whole nonmetallic component is set to 1, and the C element is contained in atomic%. 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, and the content of N element is 1-xy when the amount is x and the content of O element is y. Hard coating tool for turning. 3. The hard film-coated tool according to claim 1, wherein a part of the Ti element in the second hard film is replaced with an Si element, and when the entire metal component is set to 1, an atom The hard film-coated tool for turning, wherein 0 <k ≦ 20 and the content of Ti element is 1-hk where the content of Si element is k in%.