JP2010208007A - Hard film-coated tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard film-coated tool having excellent wear resistance by highly hardening, while securing reduction of compressive stress and close contactness in a thickened hard film. <P>SOLUTION: In this hard film coated tool, the hard film is coated with a first hard film and a second hard film from a surface of a substrate. The first hard film is shown by (Al<SB>a</SB>Me<SB>100-a</SB>)<SB>e</SB>N<SB>f</SB>, where 35≤a≤65 and 0.85≤e/f≤1.25 are satisfied. The second hard film is shown by (Ti<SB>100-h</SB>B<SB>h</SB>)<SB>m</SB>N<SB>p</SB>, where 1≤h≤30 and 0.85≤m/p≤1.25 are satisfied. When plane spacings (nm) of (111) planes in X-ray diffraction of the first hard film and the second hard film are defined as d1 and d2, respectively, 1.01≤d2/d1≤1.05 is satisfied. The second hard film has a columnar structure where crystal grains have composition-modulated structures having composition differences in B component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

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

JP 2006-281363 A JP 2003-71611 A JP-A-7-188901 JP 2001-181826 A

  The problem to be solved by the present invention is to provide a hard film coated tool excellent in wear resistance by increasing the hardness while ensuring a reduction in compressive stress and adhesion in a hard film having increased thickness.

The present invention relates to a hard film coated tool in which a hard film having a compressive stress is coated on a substrate with a film 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 _100-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 _100-h B _h ) _m N _p , where h is atomic%, m, p represents an atomic ratio, 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, 0.2 ≦ Is / Ir ≦ 1.4, 0.6 ≦ It / Ir ≦ 1.5, and when the distance (nm) between the (111) planes in the X-ray diffraction of the first hard film and the second hard film is d1 and d2, respectively. Hard film, wherein 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 It is a coated tool. By adopting the above-described configuration, it is possible to provide a hard film-coated tool that is excellent in wear resistance due to high hardness while ensuring a reduction in compressive stress and adhesion in a hard film that has been thickened.

  In the hard film-coated tool of the present invention, a part of the nonmetallic component nitrogen (N) element in the first hard coating is replaced with carbon (C) element and oxygen (O) element, and the entire nonmetallic component is 100, the content of C element in atomic% is x, and the content of O element is y, 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, and the content of N element is 100 -Xy is preferable. Further, regarding the Ti element of the metal component in the second hard film, when one part thereof is replaced with silicon (Si) element and the total of the metal component is 100, the content of Si element in atomic% is k, Then, it is preferable that 0 <k ≦ 20 and the content of Ti element is 100-hk. It is more preferable that the hard film having a compressive stress has a thickness of 10 μm to 30 μm.

  According to the present invention, it is possible to provide a hard film coated tool having excellent wear resistance due to high hardness while ensuring a reduction in compression stress and adhesion in a thick hard film.

The first hard film in the hard film-coated tool of the present invention is represented by (Al _a Me _100-a ) _e N _f as _a composition, and the a value representing the aluminum (Al) content is in the range of 35 ≦ a ≦ 65. When heat resistance and wear resistance are excellent. If the a value exceeds 65%, the first film cross-sectional structure becomes finer, the compressive stress increases, and the inconvenience that the adhesion to the substrate deteriorates occurs. If the a value is less than 35%, there is a disadvantage that the wear resistance is poor. The Me component collectively referred to as the element Me includes elements 4a, 5a, and 6a having an ionic radius of 0.041 to 0.1 nm, silicon (Si) having an ionic radius of 0.002 to 0.04 nm, It is preferable to coat as a nitride containing boron (B) or the like. This is because there is a difference between the ionic radius of the Me component, silicon or boron, and the ionic radius of the aluminum element, and stress acts on the crystal structure, which is convenient for increasing the hardness of the film. By selecting, for example, titanium (Ti) as the Me component, it is effective for increasing the hardness of the first hard coating. For example, when Me is silicon (Si) or boron (B), the content range for maintaining a solid solution is 1% to 20%, and excellent heat resistance and lubrication characteristics can be obtained. Moreover, containing W, Nb, and Cr as Me is effective in improving the heat resistance and hardness of the first hard coating.

  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, when the e / f value is 0.85 to 1.25, the structure of the first hard film can be a columnar 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 first hard film 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 of the first hard coating becomes finer and grain boundary defects increase. As a result, the compressive stress is increased and the adhesion is deteriorated. For example, in hard coatings for cutting tools, this grain boundary defect causes a decrease in the density of the hard coating and inward diffusion of the elements constituting the workpiece into the hard coating. Deteriorate. When the e / f value exceeds 1.25, the first hard film has a columnar structure, but it is easy to incorporate impurities 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 the crystal grains deteriorates, and the first hard coating is easily broken by an external impact. By setting the first hard coating of the present invention in the range of 0.85 ≦ e / f ≦ 1.25, the compressive stress of the first hard coating is in the range of 1.5 to 5.0 GPa. Industrially, by setting the e / f value within the range of the present invention, it is possible to manage the first hard coating within a range where the compressive stress is not excessive while having the compressive stress.

  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 (atomic%) indicating the B content in the second hard coating is h ≦ 30. This range of h values 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 diffusion of the workpiece component into the second hard coating. However, when the h value exceeds 30%, the structure of the second hard coating becomes finer. In addition, boron nitride (BN) crystals appear and the hardness is lowered, and the compressive stress of the second hard film is increased, resulting in a drawback that adhesion is lowered. An effect appears even if the h value is about 1%.

  Moreover, by setting the ratio m / p value of the metal component and the nitrogen component of the second hard coating to 0.85 to 1.25, the compressive stress of the second hard coating can be set to an optimum range, and high adhesion can be achieved. Sex can be obtained. Further, when the m / p value is 0.85 to 1.25, the second hard film can be a columnar structure having high toughness, and both excellent chipping properties and wear resistance can be achieved. When the first hard film and the second hard film have a face-centered cubic structure, a hard film having high hardness and excellent wear resistance as a whole can be obtained.

Below, the manufacturing conditions for achieving the composition and structure conditions of the present invention will be described. In the first hard coating (Al _a Me _100-a ) _e N _f , it is important to control the reaction pressure during film formation in order to make the range 0.85 ≦ e / f ≦ 1.25. It is. In order to obtain a nitride, the reaction pressure of nitrogen is set to 3 Pa to 8 Pa. More preferably, it is good to set it as the range of 3.5 Pa-7Pa. 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, and the 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 negatively and positively amplituded and strongly oriented in the (111) plane, thereby suppressing the compression stress of the first hard coating and increasing the level. Hardness can be realized. For this purpose, the bias voltage application can be realized by making an amplitude between a negative voltage of 100 to 200V and a positive voltage of 5 to 10V.

  In order to make the Is / Ir value of the first hard film 0.2 ≦ Is / Ir ≦ 1.4, it is necessary to control the bias voltage, and it is preferable to apply the bias voltage in a pulsed manner. When the bias voltage is less than minus 100 V, the Is / Ir value tends to increase and the compressive stress is reduced, but the hardness of the first hard film is lowered and the wear resistance is deteriorated. When film formation is performed by applying a relatively high negative bias voltage up to minus 200 V, the kinetic energy of ions attracted to the substrate increases. That leads to an increase in compressive stress. The compressive stress is also affected by the film thickness of the first hard coating. That is, the thicker the film, the more the compressive stress tends to increase. The first hard film having a face-centered cubic structure according to the present invention was strongly oriented to the (111) plane that is the most filled surface of atoms to form a thick film. However, when the thickness of the first hard coating is increased, the compressive stress is remarkably increased and high adhesion to the substrate cannot be obtained. Therefore, it is necessary to adjust the kinetic energy when the element constituting the first hard film ionized in the plasma at the time of film formation reaches the substrate by applying a pulsed bias voltage. 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 (200) plane. In addition, the compressive stress can be suppressed and the adhesion can be improved, and further excellent wear resistance can be obtained. It is considered that the structure of the first hard coating slips on the (111) plane and the compressive stress is relieved. The slip surface becomes a grain boundary in the structure, which is considered to improve the wear resistance.

  When the pulse frequency is 5 to 35 kHz, the It / Is value is 0.6 ≦ It / Is ≦ 1.5, and the compressive stress of the first hard coating at this time is in an optimal range of 2.0 to 6.0 GPa. Can be. When the pulse frequency is lower than 5 kHz, the It / Is value exceeds 1.5. If it exceeds 35 kHz, the kinetic energy when ions reach the substrate cannot be adjusted, so the It / Is value is less than 0.6.

  If the bias voltage applied when forming the second hard film is pulsed in the same manner as the conditions for forming the first hard film, the kinetic energy of boron (B) ions reaching the substrate can be adjusted. Incorporated into the crystal lattice of titanium nitride (typically referred to as TiN), the second 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 of TiN face-centered cubic structure, cubic boron nitride (c-BN), hexagonal crystal In many cases, the second hard film contains boron nitride (h-BN), amorphous BN, or the like. 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 only the h-BN is included in the second hard coating, 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 compounds having other crystal structures such as c-BN, the compressive stress increases. In particular, when a large amount of c-BN is contained, although it is possible to increase the hardness of the second hard coating, it is not preferable because the compressive stress increases and the adhesion deteriorates.

  Next, an important (111) plane peak intensity condition among the constituent features of the present invention will be described. A major feature of the present invention is that the first hard film having a face-centered cubic structure is most strongly oriented in the (111) plane when evaluated by X-ray diffraction. Due to this feature, in the present invention, the first hard film has a high hardness, and the durability against the cutting force from the shear direction in cutting is excellent.

  Generally speaking, the hard coating is destroyed (hereinafter referred to as a crack) in response to an external impact caused by cutting. The crack propagates through the grain boundary of the structure in the hard film in a direction perpendicular to the base, reaches the base, and causes cracks and wear. Therefore, when the orientation to the (200) plane in the first hard film in contact with the base becomes strong, the compressive stress is reduced and the adhesion of the first hard film is increased. However, a strong orientation to the (200) plane causes a problem that cracks are easily propagated due to deterioration of wear resistance due to a decrease in hardness and an increase in the size of the columnar structure, resulting in a disadvantage that the fracture resistance is lowered.

  As in the present invention, by strongly orienting the first hard film on the (111) plane, the propagation of cracks generated in the direction perpendicular to the substrate is reduced, and the wear resistance is increased. Therefore, in the present invention, in the X-ray diffraction of the first hard film, 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, The Is / Ir value of the hard coating is defined as 0.2 ≦ Is / Ir ≦ 1.4, and the It / Is value is defined as 0.6 ≦ It / Is ≦ 1.5. If the first hard coating is 0.2 ≦ Is / Ir ≦ 1.4, excellent wear resistance can be realized, and if 0.6 ≦ It / Is ≦ 1.5, proper compression is achieved. A range of stress can be obtained. Accordingly, the first hard film having high hardness can be obtained while the thick film has high adhesion. However, when the Is / Ir value is less than 0.2 and the It / Is value is less than 0.6, the cross-sectional structure of the first hard coating is remarkably refined and the compressive stress increases. Therefore, although abrasion resistance is excellent, film peeling occurs easily. In particular, when the It / Is value is less than 0.6, the internal defects of the first hard coating increase. When the It / Is value is less than 0.6, the compressive stress of the first hard film can be controlled even if the Is / Ir value is 0.2 ≦ Is / Ir ≦ 1.4. It becomes difficult. At this time, the compressive stress of the first hard film is about 6.5 GPa, and the adhesion between the substrate and the first hard film is remarkably deteriorated. Therefore, it is defined as 0.6 ≦ It / Is ≦ 1.5. When the Is / Ir value is larger than 1.4 and the It / Is value is larger than 1.5, the compressive stress is reduced and the adhesion is increased. However, on the other hand, the hardness is significantly reduced and the wear resistance is poor. Moreover, the joint strength at the grain boundaries in the cross-sectional structure of the hard coating is reduced, and the fracture resistance is deteriorated.

  In the hard coating according to the present invention, 1.01 ≦ d2 / d1 when the distance (nm) between the (111) planes in the X-ray diffraction of the first hard coating and the second hard coating is d1 and d2, respectively. ≦ 1.05 and by setting d2 / d1 value to 1.01 ≦ d2 / d1 ≦ 1.05, the adhesion between the first hard film and the second hard film is improved, and the wear resistance is improved. Excellent. In order to improve the adhesion between the hard films, it is necessary to reduce the crystal lattice strain. In order to reduce this distortion, high adhesion can be obtained by reducing the difference in (111) plane spacing between hard coatings to reduce misfit. Therefore, by defining the d2 / d1 value in a range of 1.01 ≦ d2 / d1 ≦ 1.05, a hard coating having excellent wear resistance can be obtained without impairing adhesion to the substrate. If the d2 / d1 value is less than 1.01, the 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 is impaired, but also the compressive stress increases and the adhesion with the substrate decreases. As an example of the film forming condition, the method of setting the range of 1.01 ≦ d2 / d1 ≦ 1.05 is to use the pulse frequency in bias application as the film forming condition in the range of 2 kHz to 30 kHz.

  Regarding the hard film according to the present invention, the second hard film has a columnar structure, and the crystal grains are continuously grown in the boundary region between the crystal grains 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 second hard film is a polycrystalline material, but has a form similar to the growth of a single crystal material when grasped in units of crystal grains. As a feature of the present invention, the crystal grains of the columnar structure have 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 is increased by controlling the compressive stress. For example, a B layer enriched layer forms a relatively soft layer. When this soft layer exists between layers with other relatively hard layers, a buffer effect is exhibited, and the compressive stress is relieved as the second hard film as a whole. Furthermore, the 2nd hard film | membrane which has lubricity can be obtained with the lubrication characteristic of B component. However, the preferable composition difference of the B component at this time is 10% at the maximum. More preferably, it is in the range of 0.1% or more and 7% or less.

  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. The second hard coating according to the present invention can be realized by applying a high bias voltage by a pulse bias. Therefore, in particular, in the second hard coating, since B having an ion radius smaller than that of Ti is contained in the crystal lattice of the face-centered cubic structure TiN, it is necessary to control the kinetic energy of ions by applying a pulse bias. This is because it becomes difficult to contain B in the second hard film when a high DC bias voltage is applied. By applying a pulse bias, a portion where the B content in the columnar structure has a composition difference becomes a composition-modulated structure, and crystal lattice fringes continuously grow between the layers. The composition modulation structure in which the crystal lattice fringes between the layers are continuously grown has an acceleration voltage of 20 kV using, for example, a JEM-2010F type field emission transmission electron microscope (hereinafter referred to as TEM) manufactured by JEOL Ltd. This can be confirmed by observing the columnar structure under conditions.

  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, if it exceeds 30 μm, the hard coating film has a high compressive stress and deteriorates the adhesion to the substrate, so that it is preferably 30 μm or less. 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. More preferably, the hard film has a thickness of 10 μm to 30 μm, whereby excellent wear resistance can be obtained.

Regarding the nitrogen element of the non-metallic component in the first hard film, when a part of the nitrogen element is replaced with a carbon element and an oxygen element, the content of the carbon element is x value and the oxygen element content is y value in atomic%. It is preferable that 0 <x ≦ 10, 0 <y ≦ 10, and 0 <x + y ≦ 10. Thereby, the 1st hard film which has high hardness, the outstanding oxidation-resistant characteristic, adhesiveness, and a lubrication characteristic is obtained. When carbon element and oxygen element are contained, in order to avoid mechanical strength deterioration, the sum of x value and y value is made 10% or less, so that excellent welding resistance and sliding property are obtained. More preferably, when the carbon element is contained alone, the content is 2% to 10%. However, when the x value and y value exceed 10%, the crystal structure becomes finer, and defects at the grain boundaries increase. As a result, even if the lubrication characteristics of the first hard coating are improved, the compressive stress increases, and thus a defect that adhesion and fracture resistance are lowered appears. When the carbon element and the oxygen element are contained in the first hard film, it is preferable to use a hydrocarbon-based gas or an oxygen-containing gas. When film formation is performed by introducing gas, the total pressure combined with nitrogen gas is preferably in the range of 3 to 8 Pa. When film formation is performed by introducing a gas in the addition of carbon element, it is easier to control using nitrogen (N ₂ ) and methane (CH ₄ ) or ethylene (C ₂ H ₆ ). In the case of introducing a hydrocarbon gas, up to about 20% of the nitrogen flow rate is a range in which film formation can be performed stably. In the case of introducing oxygen gas, it is preferable to perform film formation by introducing nitrogen gas and oxygen gas, or nitrogen gas, oxygen gas, and argon. Alternatively, the target evaporation source can be contained as a compound containing carbon element and oxygen 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 second hard film a columnar structure, the k value is preferably 20% or less. When Si is contained, the second hard film having excellent wear resistance on the rake face of the cutting tool can be obtained, for example, by forming a single crystal of TiN into a solid solution. On the other hand, if the k value exceeds 20%, the structure becomes finer, the compressive stress increases, and the disadvantage of decreasing the adhesion appears. In addition, the second hard coating includes various structures in the form of TiN crystalline, SiN composition crystalline, or amorphous. As a result, crystal grain boundaries increase, crystal lattice distortion occurs, and compressive stress increases.

  The composition of the hard film of the present invention can be measured, for example, using a JXA8500F type EPMA analyzer manufactured by JEOL. Specifically, in the vertical cross section of the hard film or the inclined cross section obtained by inclining the film cross section at an angle of 17 degrees, the hard film is applied from a position not affected by the substrate, the acceleration voltage is 10 kV, the irradiation current is 1.0 μA, the probe diameter. The composition can be specified by setting the value to about 10 μm. When measuring from the surface of the hard coating, the probe diameter is preferably set to about 50 μm. Further, when carbon or oxygen is contained, if it is less than 2%, detection by analysis becomes difficult. The film thickness of the hard coating can be measured, for example, by observing the fracture surface in the vertical direction at a magnification of 25,000 times, for example, using an S-4200 type electrolytic emission scanning electron microscope manufactured by Hitachi, Ltd.

  The measurement of the peak intensity ratio of the (111), (200), (220) plane in the X-ray diffraction of the first hard coating is, for example, 2θ-θ using a RU-200BH type X-ray diffractometer manufactured by Rigaku Corporation. It can be measured by the scanning method. In the embodiment of the present invention, the range of 2θ (degrees) is 10 to 145 degrees, the X-ray source is a CuKαl line having a λ value of 0.15405 nm, and background noise is 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 on each index plane was taken 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 (111) plane was applied to the surface space | interval. Further, the peak intensity was measured in the same manner for the first hard coating based on CrN.

  The compressive stress in the hard film according to the present invention can be calculated by the following curvature measurement method. That is, when a test piece obtained by processing a substrate having a known Young's modulus and Poisson's ratio into a predetermined shape is coated on the surface, the coated test piece is caused by the compressive stress generated in the hard film. Deforms and deforms. The amount of deflection deformation is obtained, and the numerical value 1 is used to calculate the compressive stress σ value of the entire hard coating. In Examples and the like described later, numerical values calculated by this method are described.

  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, 1 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 material for forming the test piece, a cemented carbide material is suitable with little variation in measured numerical 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. It is important to remove the distortion. Unless this strain is removed to some extent, the resulting compressive stress values will vary. 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 face in the length direction of the test piece where the deflection occurred to the maximum deflection, and the film thickness of the coated hard coating. For example, it is possible to calculate the value of the compressive stress even if the composition of the hard film and the film forming conditions are changed or the composition has a modulation structure.

  When the hard coating tool is made of tungsten carbide base cemented carbide, high speed tool steel, cermet or the like as the substrate, 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 by physical vapor deposition 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, but the present invention is not limited thereby.

  A hard coating according to the present invention was coated on a surface of a cemented carbide substrate having a test piece capable of measuring compressive stress and a turning insert shape, thereby producing a sample of the present invention example 1. In Example 1 of the present invention, an AIP apparatus is used so that the composition of only the metal component is atomic% and a Ti: 50%, Al: 50% (TiAl) N film is used as the first hard film so as to have a film thickness of 6 μm. A film was formed. Thereafter, a (TiB) N film having a composition of only metal components of Ti: 90% and B: 10% was formed as a second hard film with a film thickness of 6 μm so that the total film thickness was 12 μm. It is. The deposition temperature is 550 ° C., the reaction pressure is 3.5 Pa, and the (TiAl) N film, which is the first hard film, is formed by forming a 1 μm film with a bias voltage of DC 150 V and then applying a pulsed bias voltage. . 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 as the second hard film was also formed under the same conditions as (TiAl) N. The evaporation source is selected from various alloy targets according to the present invention and the comparative example, and in order to obtain nitrides, carbonitrides, oxynitrides, oxycarbonitrides, nitrogen, oxygen, methane, etc. A hydrocarbon-based gas was produced either alone or mixed and introduced during film formation. Inventive Examples 2 to 35 and Comparative Examples 36 to 52 were prepared in which the film thickness, composition, X-ray diffraction peak intensity, and compressive stress of the hard coating were changed using the film forming conditions of Inventive Example 1 as a standard. .

  Tables 1, 2 and 3 show details of the prepared samples, hard coating composition, manufacturing conditions of the hard coating, measured values of compressive stress, and evaluation results of the cutting test of the coated insert. Further, as a result of observation of the film cross-section by TEM, the second hard film in the example of the present invention all has a columnar structure, and the crystal grains of this 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 superiority or inferiority of wear resistance, fracture resistance, and adhesion. 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.

(Cutting 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: 300 m / min Feed rate per rotation: 0.4 mm / rotation Cutting oil: None

  Invention Examples 1 to 5 and Comparative Examples 39 and 40 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 film thickness ratio of the first hard film and the second hard film was the same as 1: 1, and only the entire film thickness was changed. The compressive stress tended to increase as the thickness of the hard coating increased. Those having a total film thickness of 5 μm or more shown in Invention Examples 1 to 5 were excellent in wear resistance such as flank wear and crater wear. In any of the samples, there was no occurrence of welding of the workpiece component to the cutting edge in the initial 5 m of cutting. It was considered that having the second hard film specified in the present invention has a great effect on crater wear and welding resistance. In Example 1 of the present invention, the total film thickness was 10 μm, the compressive stress value was 1.4 GPa, and the tool life was 18 m. As a result of confirming the damaged state of the cutting edge when the cutting distance is 5 m, the flank wear amount is 0.068 mm, which is superior to the thin film thickness examples 4 and 5 of the present invention and further compared to the comparative example 40. It was much better. 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.

  The total film thickness of Comparative Example 39 was 40 μm, the compressive stress was 7.1 GPa, and the tool life was inferior to Invention Examples 1-5. In Comparative Example 39, 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 9 μm, and the breakage part led to a defect. This is because the compressive stress is increased by increasing the total film thickness to 40 μm. The total film thickness of Comparative Example 40 was 4 μm and had a low compressive stress of 1.3 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 Inventive Example 6, the tool life was superior to Inventive Example 1 by increasing the thickness of the first hard coating. This was considered to be because progress of flank wear was suppressed. However, in Invention Examples 6 and 7, the second hard film 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 for a film having a total film thickness of 12 μm and a second hard film coated to 0.3 μm, but the progress of flank wear was suppressed, but crater wear was the main component. Progressed to life.

  Invention Examples 8 to 20 and Comparative Examples 41 and 42 were prepared in order to see the influence of the composition of the first hard coating. It was produced by changing the composition of the target material for coating. Invention Example 10, which has the best tool life, contained 10% tungsten (W), and was about 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 0.029 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. It is considered that the reason why the flank wear is excellent is that the hardness is increased by containing W. The hardness of the first hard coating in Invention Example 1 was 28 GPa, and Invention Example 10 was 32 GPa. Furthermore, since the oxidation resistance has increased, it is considered that the progress of flank wear was suppressed. In particular, when the oxidation resistance is increased, damage at the tool boundary where the cutting heat is highest tends to be reduced. Further, the reason why welding did not occur is that boron (B) was contained in the second hard film of the outermost film and the lubrication characteristics were excellent. Invention Example 12 contains 10% of niobium (Nb), and Invention Examples 13 and 14 contain chromium (Cr) and silicon (Si), so that the mechanical properties of the first hard coating are enhanced, and Invention Example 1 Excellent compared to As shown in Invention Example 15, the tool life was excellent even when B was contained in the first hard coating. Welding was also suppressed at the portion of the first hard film exposed after the second hard film was worn. Even when B was contained in the first hard film, a remarkable effect was obtained with respect to welding and crater wear. In Invention Examples 8 to 20, since the first hard film is a nitride of an element selected from Al, Group 4a, 5a, and 6a elements, Si, and B, heat resistance and hardness are remarkably improved.

  In Comparative Example 41, the Al content of the first hard coating was 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 first hard film cross section, the structure was refined. For this reason, compressive stress increases and adhesion deterioration can be considered. Further, the hardness of the first hard film was 20 GPa, and the decrease in hardness caused early progress of wear. As a result of performing X-ray diffraction on Comparative Example 41, a hexagonal structure peak appeared in addition to the face-centered cubic structure peak. As a result of the investigation, it was confirmed that the peak was attributed to the AlN compound. Thereby, it is considered that the wear resistance is remarkably deteriorated. In Comparative Example 42, the same phenomenon was confirmed.

  Invention Examples 21 to 24 and Comparative Examples 43 and 44 were prepared in order to observe the influence of the composition of the second hard film. It was produced by changing the composition of the target material for coating. In inventive examples 21 and 22, the B content of the second hard coating was 1% and 25%, respectively. Inventive Example 23 had a Si content of 20%, and Inventive Example 24 contained B and Si. When the structures of the cross sections of these second hard coatings were observed, it was confirmed that all of them were columnar structures. On the other hand, regarding Comparative Example 43 in which the B content of the second hard film is 40% and Comparative Example 44 in which the Si content is 30%, the cross-sectional structure of the second hard film is observed, and both are fine structures. It was confirmed. When the B and Si contents were increased, peeling of the hard coating and crater wear occurred from the beginning of cutting. The difference in the film structure resulted in superiority or inferior cutting performance. In particular, in Comparative Example 44 in which the Si content was 30%, many deposits were observed on the surface of the second hard film from the middle of cutting.

  Invention Examples 25 and 26 and Comparative Examples 45 and 46 were prepared in order to observe the influence of oxygen and carbon contained in the first hard film. Oxygen and hydrocarbon gas were used as part of the reaction gas. In Invention Example 26 and Comparative Example 46 containing oxygen, nitrogen, argon (Ar), and oxygen were simultaneously introduced during film formation. In all cases, the total pressure was set to 3.0 Pa. In the case of Invention Example 26, the gas was introduced at a gas flow ratio of 88% nitrogen: 10% argon: 2% oxygen. This is because, when a large amount of oxygen was introduced, the arc discharge generated during film formation became small and stable, and therefore the inert gas Ar was introduced to adjust the total pressure. Although discharge is possible without using Ar gas, Ar gas was introduced for further stabilization. In Comparative Example 46, in order to increase the oxygen content, the amount of nitrogen was decreased and the amounts of Ar gas and oxygen gas were increased. The tool life of Inventive Examples 25 and 26 was about 1.2 times better than Inventive Example 1 that did not contain oxygen and carbon elements. Moreover, the damage state of the blade edge at the time of the cutting distance of 5 m tended to be less welded and flank wear than the first example of the present invention. Furthermore, the occurrence of crater wear on the rake face was reduced. Crater wear occurs due to a chemical reaction accompanying an increase in cutting temperature, so that the inclusion of oxygen and carbon elements increases the lubrication characteristics and reduces the friction coefficient. As a result, it is considered that the cutting temperature at which the chips scrape the rake face is suppressed, and wear is reduced.

  In Comparative Examples 45 and 46, since the x value and y value of the first hard film were 10% or more, peeling of the hard film and occurrence of crater wear were confirmed from the beginning of cutting, and the structure observation of the cross section of the first hard film was similarly performed. As a result, it was miniaturized. With respect to Invention Example 1 containing no carbon element, Invention Example 25 having a carbon content of 7%, and Comparative Example 45 having a carbon content of 15%, a sample of only the first hard film was prepared and the coefficient of friction was measured. The coefficient of friction was measured by a ball-on-disk method, and a SUJ2 φ6 mm ball was slid on a coated cemented carbide disc and measured without lubrication in the atmosphere. The wear resistance and welding resistance of the hard film at a measurement temperature of 600 ° C. were investigated. The friction coefficient of Invention Example 1 was 0.8, Invention Example 25 was 0.5, and Comparative Example 45 was 0.8. Even if the first hard coating contains a large amount of carbon element, it is confirmed that damage such as flank wear, crater wear and welding of the work piece to the tool edge will occur from the beginning of cutting if the structure of the cross section of the coating becomes finer. It was done. The same tendency was observed when oxygen was contained.

  Invention Examples 27 to 29 and Comparative Examples 47 and 48 were prepared in order to observe the influence of the reaction pressure on the composition during film formation. In particular, the influence of the e / f value on the compressive stress was investigated. At this time, the reaction pressure was changed and set in the range of 1.6 Pa to 13.5 Pa. In the case of Inventive Examples 1 and 27 to 29 in which the film was formed at a reaction pressure of 2.2 to 8.1 Pa, the tool life was excellent on the high pressure side as compared with Inventive Example 1. Inventive Example 29, which is on the lower pressure side than Inventive Example 1, has a far superior tool life as compared with Comparative Examples 47 and 48, but extremely fine chipping occurred at the beginning of cutting. In particular, Invention Example 27 having an e / f value of 1.16 was the most excellent, and unstable elements such as chipping of the first hard coating did not occur. In Comparative Example 47 in which the film was formed at the lowest reaction pressure of 1.6 Pa, the compressive stress was 6.9 GPa, the e / f value was 0.82, and the tool life was 8 m. This was a short life of about 60% compared to Example 1 of the present invention. The lower the nitrogen pressure, the greater the compressive stress and the lower the e / f value. This reason is considered to be because the compressive stress of the first hard coating is high. When the compressive stress exceeded 6.0 GPa, it was confirmed that the first hard coating was broken at the edge of the blade edge in the damage state of the insert blade edge during cutting. In order to confirm reproducibility, as a result of cutting evaluation of several degrees using a new corner of the insert of Comparative Example 47, the tool life varied from 2 m to 0.2 m and was not stable.

  In Comparative Example 48, the compressive stress was a relatively low value of 0.3 GPa, but the tool life was 4 m. Since the damage state of the cutting edge at the cutting distance of 5 m could not be observed, the damage at the initial cutting distance of 1 m was confirmed using a new corner, and as a result, the film from the substrate and the first hard coating interface at the edge of the cutting edge A large amount of welding occurred at the site where peeling and the first hard coating were removed. In addition, large wear on the flank and crater wear occurred. This was thought to be due to a decrease in the hardness of the first hard coating. The e / f value was 1.32. Although the cross-sectional structure of the first hard film had a columnar structure, many defects were generated in the first hard film, and the adhesion and wear resistance were poor. The reason for this is considered to be that the kinetic energy when ions are incident on the substrate is lowered by performing the reaction pressure at 13.5 Pa.

  Invention Examples 30 to 37 and Comparative Examples 49 and 50 were prepared in order to observe the influence of the Is / Ir value. During film formation, the pulse frequency of the pulse bias was kept constant at 10 kHz, and the bias voltage value was changed and set in the range of 100 to 300V. Invention Example 1 and Invention Examples 30 to 33 have an Is / Ir value within the specified range of the present invention, a compressive stress of 4 GPa or less, and an excellent tool life. Further, when the bias voltage was changed, the Is / Ir value was changed, and the compressive stress was changed accordingly. In Comparative Examples 49 and 50, the compressive stress exceeded 8 GPa, and peeling of the hard film was observed from the beginning of cutting. When the compressive stress was increased, the tool life was inferior.

  Invention Examples 34 to 36 and Comparative Examples 51 to 53 were prepared in order to see the effect of the It / Is value on the compressive stress. At this time, the positive bias value of the pulse bias voltage was changed from 5 to 40V. When the positive bias voltage increases, the orientation strength toward the (200) plane tends to be relatively strong, and the It / Is values of Invention Examples 1, 34 to 36, and Comparative Examples 51 to 53 are 0.2. Changed to ~ 1.5. In Invention Example 1 and Invention Examples 34 to 36, the It / Is value was within the specified range of the present invention, the compressive stress was relatively low, and a satisfactory tool life was obtained. On the other hand, in Comparative Examples 51 to 53, the positive bias voltage exceeded 20 V, the It / Ir value was less than 0.6, and in the blade edge damage state observation at a cutting distance of 5 m, many peelings of the first hard film were observed. . Since the compressive stress increased and exceeded 6 GPa, not only peeling from the interface between the substrate and the first hard coating but also many shell-like fractures were observed, which resulted in a decrease in tool life. In order to improve the adhesion at the interface between the first hard film and the second hard film, the positive bias voltage value in the pulse bias voltage is controlled to be low, and the orientation strength of the (200) plane of the first hard film is lowered. This is very important. This is because application of a bias voltage having only a negative value is insufficient for suppressing defects caused by micro arcing during film formation.

  Invention Examples 37 and 38 and Comparative Examples 54 and 55 were prepared in order to observe the influence of the (111) plane spacing in the X-ray diffraction of the first hard film and the second hard film. The surface spacing was adjusted by changing the pulse frequency of the pulse bias voltage in the range of 1 to 40 kHz. Inventive Examples 37 and 38 are cases where the pulse frequency is 30 kHz and 2 kHz, respectively, and the d2 / d1 value is 1.01 to 1.02, and the compressive stress of the entire hard film is lowered, and the first hard film is reduced. And excellent adhesion of the second hard film, and a satisfactory tool life was obtained. On the other hand, in Comparative Example 54 in which the film was formed at a pulse frequency of 1 kHz, the d2 / d1 value was 1.07, and the adhesion deteriorated due to the gap between the first hard film and the second hard film. In Comparative Example 55, more peeling was observed at the interface between the first hard film and the second hard film than at the initial stage of cutting than between the base and the hard film. This was the cause of the short tool life. The reason for this is that since the film was formed at 40 kHz, the d2 / d1 value was 0.99, the compressive stress of the entire hard film increased to 6.9 GPa, and in addition to the adhesion to the substrate, the first hard film and the first hard film This is because the adhesiveness deteriorated due to misfit of the spacing between the two hard coatings. It was also confirmed that the It / Is value changed with the change of the pulse frequency. The relationship between the pulse frequency and the compressive stress is considered to be correlated, and the compressive stress tends to increase as the pulse frequency increases. This is considered to be due to the fact that the DC bias voltage is applied as the pulse frequency increases.

  The hard film-coated tool of the present invention can be applied to, for example, general tools for metal processing that require wear resistance.

Claims (4)

In a hard film coated tool 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 coated with the first hard film and the second hard film from the surface of the substrate, The outermost coating is coated with the second hard coating, and the first hard coating is represented by (Al _a Me _100-a ) _e N _f , where a represents atomic%, and e and f represent atomic ratios. 35 ≦ a ≦ 65, 0.85 ≦ e / f ≦ 1.25, Al is aluminum, Me is one or more elements selected from Group 4a, 5a, 6a, Si, B, N is It is nitrogen, and the second hard coating is represented by (Ti _100-h B _h ) _m N _p , where h is atomic%, m, p represents an atomic ratio, h ≦ 30, 0.85 ≦ m / p ≦ 1.25, Ti is titanium, B is boron, N is nitrogen, the first hard coating, the second hard coating The crystal structure of the porous film is a face-centered cubic structure, and in the X-ray diffraction of the first hard film, 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 0.2 ≦ Is / Ir ≦ 1.4, 0.6 ≦ It / Is ≦ 1.5, and in the X-ray diffraction of the first hard coating and the second hard coating. When the interplanar spacing (nm) of the (111) plane is d1 and d2, 1.01 ≦ d2 / d1 ≦ 1.05, and the second hard film has a columnar structure, and the columnar structure The hard film-coated tool, wherein the crystal grains have a composition modulation structure having a composition difference in the B component.   The hard film-coated tool according to claim 1, wherein one part of nitrogen in the first hard film is substituted with carbon and oxygen, the whole nonmetallic component is 100, and the content of carbon element in atomic% is x, Hard film coating characterized by 0 <x ≦ 10, 0 <y ≦ 10, 0 <x + y ≦ 10, and nitrogen content 100−xy, where oxygen content is y tool.   3. The hard film-coated tool according to claim 1, wherein a part of the titanium in the second hard film is replaced with silicon, and when the total metal component is 100, the silicon content is expressed in atomic%. k, where 0 <k ≦ 20, and the titanium content is 100−h−k.   4. The hard film-coated tool according to claim 1, wherein the hard film having a compressive stress has a total film thickness of 10 to 30 [mu] m.