JP2011167838A - Hard-film coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend a service life of a hard-film coated cutting tool by suppressing the propagation of a crack caused by residual compression stress in a hard film layer 1, thickening a hard film layer 2 by reducing the residual compression stress, and improving adhesion strength with a base material, in the hard film layers 1, 2 forming a double layer structure. <P>SOLUTION: In the hard-film coated cutting tool including cemented carbide as a base material and coated with a hard film, the front surface side is coated with the hard film layer 1 and the base material side is coated with the hard film layer 2. The hard film layer 1 is composed of (Al<SB>a</SB>Cr<SB>1-a</SB>)N<SB>x</SB>where 0.5≤a≤0.75 and 0.9≤x≤1.1, and the hard film layer 2 is composed of (Ti<SB>b</SB>Al<SB>1-b</SB>)N<SB>y</SB>where 0.4≤b≤0.6 and 0.9≤y≤1.1. When a lattice constant of a plane (111) of the hard film layer 1 in the X-ray diffraction is a1 (nm), and a lattice constant of a plane (200) of the hard film layer 2 is a2 (nm), 0.990≤a1/a2≤0.999 is satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hard film-coated cutting tool that is used for processing metal parts, molds, and the like and that requires improvement in wear resistance and fracture resistance.

  Patent Document 1 discloses a multilayer film composed of a (TiAl) N film and an (AlCr) N film (see sample number 2 in Table 1).

  Patent Document 2 discloses an (AlCr) N-based hard coating having a predetermined composition, in which the half width of 2θ of the X-ray diffraction peak of either the (111) plane or the (200) plane is 0.5 to 2 degrees. (Refer to claim 1, Table 1, etc.) and the X-ray diffraction intensity ratio I (200) / (111) between the (200) plane and the (111) plane is 0.3 <I (200) / (111) <12 (see claim 3, Table 1).

  In Patent Document 3, a first coating layer and a second coating layer having different crystal orientations are laminated and coated on a base material, and both layers are nitrides and carbonitrides of titanium and aluminum, It consists of one or two or more layers of nitride oxide, carbonate, or oxynitride, and the first coating layer has an X-ray diffraction peak intensity having a maximum height on the (200) plane, It is disclosed that the X-ray diffraction peak intensity of the coating layer has a maximum height in the (111) plane (see claim 1).

  In Patent Document 4, a (TiAl) N layer having a predetermined composition having an average layer thickness of 0.05 to 0.5 μm on a substrate, the highest peak of X-ray diffraction appears on the (111) plane, and A (TiAl) N layer having a predetermined composition having an average layer thickness of 2 to 10 μm, and a (111) plane of X-ray diffraction. A surface-coated cemented carbide cutting tool is disclosed in which the highest peak appears and the half-width of the highest peak is 2θ and 0.8 degrees or less, and is physically vapor-deposited (claim 1, claim 2). (See Table 3).

JP 2008-93760 A Japanese Patent Laying-Open No. 2005-126736 JP-A-10-330914 JP 2003-117705 A

  However, in any of Patent Documents 1 to 4, a (TiAl) N coating layer having a composition, an X-ray diffraction pattern and a lattice constant adjusted to a specific appropriate range on a cemented carbide substrate by physical vapor deposition. There is no description or suggestion that a high performance hard coating coated cutting tool can be obtained by laminating the (AlCr) N coating layer with a total film thickness of 5 μm or more.

  The present invention relates to a hard film coated cutting tool having a hard film formed by physical vapor deposition and thickened to 5 μm or more, wherein the hard film is composed of new high performance hard film layers 1 and 2. By having the structure, the hard coating layer 1 can suppress propagation of cracks generated during cutting due to the residual compressive stress, and the hard coating layer 2 can be made thicker by reducing the residual compressive stress. An object of the present invention is to provide a new high-performance hard coating-coated cutting tool capable of realizing a longer life than conventional hard coating-coated cutting tools by improving the adhesion strength.

The hard film-coated cutting tool of the present invention is a hard film-coated cutting tool in which a hard film is coated on a cutting tool based on a cemented carbide, and the hard film has a two-layer structure formed by physical vapor deposition. The two-layer structure has a hard coating layer 1 coated on the surface side and a hard coating layer 2 coated on the substrate side, and the composition of the hard coating layer 1 is (Al _a Cr _{1-1 a} ) _1-x N _x (wherein the content of each element is an atomic ratio, and 0.5 ≦ a ≦ 0.75 and 0.45 ≦ x ≦ 0.55), When the half width of the (111) plane in the X-ray diffraction of the hard coating layer 1 is W ₁ (degrees), 0.7 ≦ W ₁ ≦ 1.1, and the peak intensity Ir of the (111) plane, When the peak intensity Is of the (200) plane and the peak intensity It of the (220) plane are 0.3 ≦ Is / Ir <1, and A .3 ≦ It / Ir <1, the composition of the hard coating layer _2, the content of _{(Ti b Al 1-b)} 1-y N y ( where each element is the atomic ratio of 0. 4 ≦ b ≦ 0.6 and 0.45 ≦ y ≦ 0.55), and the half width of the (200) plane in the X-ray diffraction of the hard coating layer 2 is expressed as W ₂ (degrees). Where 0.4 ≦ W ₂ ≦ 0.6, and (111) plane peak intensity Iu, (200) plane peak intensity Iv, and (220) plane peak intensity Iw, 5 ≦ Iv / Iu ≦ 15 and 2 ≦ Iw / Iu ≦ 4, the lattice constant of the (111) plane of the hard coating layer 1 in X-ray diffraction is a1 (nm) and the (111) plane of the hard coating layer 2 When the lattice constant of a2 is a2 (nm), 0.990 ≦ a1 / a2 ≦ 0.999, and the film thickness of the hard coating layer 1 is T1. [mu] m), and when the film thickness of the hard coating layer 2 was T2 (μm), characterized in that 5 ≦ T1 + T2 ≦ 12, T1 <T2, a.
According to the present invention, the propagation of cracks in the hard film layer 1 in the hard film thickened to a thickness of 5 μm or more by physical vapor deposition, the increase in the thickness of the hard film layer 2 and the adhesion strength with the substrate Improvements can be made. Reflecting the characteristics of the hard coating layers 1 and 2 having the two-layer structure, the life of the hard coating-coated cutting tool can be extended compared to the conventional one.

  In the hard film-coated cutting tool of the present invention, from the viewpoint of practicality, the hard film has columnar crystal grains whose longitudinal direction is the longitudinal direction so that the hard film has high adhesion, It is preferable to have columnar crystal grains that cross the hard coating layer 2 and the hard coating layer 1 at the interface with the hard coating layer 1.

In the hard film-coated cutting tool of the present invention, from the viewpoint of practicality, at least one element of Al and Cr of the hard film layer 1 is Si, B, V, Substitution with at least one element selected from Nb and W is preferred.
In the hard film-coated cutting tool of the present invention, from the viewpoint of practicality, at least one element of Ti and Al of the hard film layer 2 is Si, B, Substitution with at least one element selected from V, Nb and W is preferred.

  According to the present invention, in a hard film having a new and high-performance two-layer structure formed by physical vapor deposition and thickened to 5 μm or more, crack propagation in the upper hard film layer 1 is suppressed, and the lower layer The thickness of the hard coating layer 2 on the side can be increased, and the adhesion strength with the substrate can be improved. With the hard coating layers 1 and 2 having the two-layer structure, it is possible to achieve a longer life of the hard coating-coated cutting tool as compared with the conventional one.

It is a figure which illustrates typically the hard coat coat cutting tool of the present invention. The fracture surface photograph of the film of example 1 of the present invention is shown. The enlarged photograph of the A section of FIG. 2 is shown.

In the hard coating coated cutting tool, the wear resistance of the hard coating is an important factor, and further improvement is desired. As means for improving the wear resistance of the hard film, roughly two kinds of means are conceivable. One is to increase the thickness of the hard film, and the other is to increase the hardness of the hard film.
Although it is possible to improve the wear resistance regardless of the constituent elements by increasing the thickness of the hard coating, it is necessary to mitigate the residual stress generated when the thickness is increased. Increasing the hardness of the hard coating greatly depends on the constituent elements of the hard coating and the film forming conditions.
In the hard film-coated cutting tool coated with a hard film by a physical vapor deposition (hereinafter sometimes referred to as PVD) method, the present invention aims to increase the thickness of the hard film layer 2 on the lower layer side in contact with the substrate. In addition, in the hard coating layer 1 on the upper layer side, high hardness and crack propagation suppression were realized. If the hard coating film has a residual compressive stress exceeding 2 GPa, the hard coating layer tends to self-destruct. Therefore, the residual compressive stress when the hard coating layer 2 is thickened is reduced to 2 GPa or less. Furthermore, the improvement of the adhesion between the hard coating layers having a two-layer structure was also realized.

The hard film layer 1 constituting the hard film employed by the present invention is a nitride film containing Al and Cr as metal components, is excellent in lubricity, and exhibits an effect of suppressing dropout and chipping caused by welding.
Therefore, in order to maintain the hard coating layer 1 at high hardness, the composition (Al _a Cr _1-a ) _1-x N _x was defined as follows. When the Al content is a> 0.75, AlN having a hexagonal close-packed structure (hereinafter referred to as an hcp structure) is likely to be generated, which not only deteriorates the adhesion strength but also decreases the hardness. Also, when the Cr content is higher than the Al content, the residual compressive stress increases and the adhesion strength tends to decrease. From the above, it was defined as 0.5 ≦ a ≦ 0.75. More preferably, 0.6 ≦ a ≦ 0.7.

Next, regarding the composition ratio between the metal component and the non-metal component of the hard coating layer 1, the residual compressive stress is controlled in the range of 1 GPa to 2 GPa by controlling in the range of 0.45 ≦ x ≦ 0.55. Can do. On the other hand, in the case of x <0.45, the ratio of bonding of (Al _a Cr _1-a ) elements in the crystal lattice increases and the strain of the crystal lattice increases. Therefore, the cross-sectional structure of the hard coating layer 1 becomes finer, grain boundary defects increase, residual compressive stress increases, and the adhesion between the substrate and the hard coating deteriorates. For example, in a hard film for a cutting tool, a grain boundary defect causes a decrease in density or inward diffusion of elements constituting the workpiece, thereby reducing mechanical properties, hardness, and fracture resistance. Therefore, the x value must be controlled to 0.45 or more in order to reduce grain boundary defects. On the other hand, when x> 0.55, the crystal structure of the hard coating layer 1 has a columnar structure, but impurities are easily taken into the grain boundary part. This impurity is derived from an internal residue of the film forming apparatus. As a result, the bonding strength at the crystal grain boundary deteriorates, and the hard coating layer 1 is easily broken by an external impact. The x value greatly depends on the gas pressure during film formation. Regarding the optimum control of the x value, when the gas pressure of the film forming apparatus is adjusted to 1 to 7 Pa, the residual compressive stress of the hard film can be controlled to 1 to 2 GPa.

When the W ₁ value of the hard coating layer 1 is in the range of 0.7 ≦ W ₁ ≦ 1.1, the crystal structure forms fine grains. Generally, from the Hall Petch's law, the smaller the crystal grain size, the higher the hardness. Therefore, in the hard film layer 1 having the W ₁ value within the above range, a hard film having a high hardness can be obtained. In the case of W ₁ <0.7, the crystal structure forms columnar crystals, and cracks generated during the cutting process propagate through the grain boundary, so that the cracks can easily reach the base material and the cutting tool can be damaged. High nature. Further, when W ₁ > 1.1, the film structure is likely to become amorphous, leading to a decrease in film hardness. In order to control the W ₁ value, it is necessary to optimize the film formation temperature, and it is necessary to form a film in the range of 300 to 550 ° C. in addition to the bias voltage application condition and the reaction gas pressure condition. Is less than 300 ° C., _{W 1} value exceeds 1.1, the weight, the less than 0.7 550 ° C..

In order to improve the wear resistance of the hard coating layer 1, it is preferable to increase the hardness of the coating. Here, in the face-centered cubic structure, the (111) plane is a close-packed plane of atoms, so when the strongest peak in the X-ray diffraction of the hard coating is the (111) plane, the density is increased and the hardness is easily increased. By increasing the hardness of this hard coating, it was possible to suppress the propagation of cracks that occur during cutting. By setting 0.3 ≦ Is / Ir <1 and 0.3 ≦ It / Ir <1, the strongest peak of the hard coating layer 1 measured by X-ray diffraction is on the (111) plane and the hardness is increased. Therefore, it is excellent in wear resistance and crack propagation suppression.
On the other hand, when Is / Ir <0.3 and It / Ir <0.3, the crystal grain boundary increases and the residual compressive stress increases excessively, leading to self-destruction of the hard coating. Furthermore, when Is / Ir ≧ 1 and It / Ir ≧ 1, a thick columnar crystal structure is formed, cracks easily propagate through the grain boundary and reach the substrate, leading to chipping and chipping of the cutting tool. Cheap. The control of the Is / Ir value and the It / Ir value can be realized by setting the reaction gas pressure during film formation to 1.5 Pa or more and 3.5 Pa or less. If it is less than 1.5 Pa, it becomes difficult to control the crystal orientation. Moreover, when it exceeds 3.5 Pa, film hardness will fall.

The hard coating layer 2 constituting the hard coating employed in the present invention is a nitride coating containing Ti and Al as metal components, and is excellent in wear resistance and adhesion strength, and is effective in improving the life as a cutting tool. . Generally, the higher the film hardness, the greater the wear resistance. Therefore, in order to maintain the hard coating layer 2 at a high hardness, the Ti content of the composition (Ti _b Al _1-b ) _1-y N _y is defined as 0.4 ≦ b ≦ 0.6. When b> 0.6, sufficient wear resistance and oxidation resistance cannot be obtained. When b <0.4, (TiAl) N having a crystal structure of face-centered cubic crystal contains AlN having an hcp structure, and the film hardness is lowered and the wear resistance is deteriorated. More preferably, 0.45 ≦ b ≦ 0.55.

  Next, regarding the composition ratio between the metal component and the non-metal component of the hard coating layer 2, the residual compressive stress is controlled within the range of 0.5 to 2 GPa by controlling within the range of 0.45 ≦ y ≦ 0.55. can do. The reason for defining the numerical range is the same as in the case of the hard coating layer 1. The y value can be controlled within the range of 0.45 ≦ y ≦ 0.55 by setting the reaction gas pressure during film formation to 2.5 Pa or more and 7 Pa or less. If it is less than 2.5 Pa, the y value is less than 0.45, and if it exceeds 7 Pa, it exceeds 0.55.

The W ₂ value of the hard coating layer 2 was defined in the range of 0.4 ≦ W ₂ ≦ 0.6. This is because the hard coating layer 2 ensures the bond strength and toughness at the grain boundaries and exhibits wear resistance during cutting. When W ₂ <0.4, the crystal structure increases the crystallinity of the columnar crystal, but the hardness decreases. In the case of W ₂ > 0.6, the crystal structure forms a refined structure to increase the hardness, while the film toughness is insufficient to induce chipping during cutting. Moreover, since the residual compressive stress increases, the adhesion strength deteriorates. In order to control the W ₂ value, it is necessary to optimize the film formation temperature, and it is necessary to form the film in the range of 400 to 650 ° C. in addition to the bias voltage application condition and the reaction gas pressure condition. If it is less than 400 ° C., the W ₂ value exceeds 0.6, and if it exceeds 650 ° C., it becomes less than 0.4.

  Since the residual compressive stress of the hard coating layer 2 has a correlation with the Iv / Iu value and the Iw / Iu value, the Iv / Iu value and the Iw / Iu value should be controlled in order to reduce the residual compressive stress value. Is possible. The strongest peak surface is preferably the (200) plane, and when the orientation to the (111) plane becomes strong, the residual compressive stress increases and the adhesion tends to decrease. Therefore, by defining 5 ≦ Iv / Iu ≦ 15 and 2 ≦ Iw / Iu ≦ 4, the residual compressive stress is controlled in the optimum range, and a thick hard film having high adhesion strength can be realized. On the other hand, in the case of Iv / Iu <5, in the case of Iw / Iu <2, since the orientation to the (111) plane having a high atomic density is strong, the residual compressive stress becomes high. Moreover, the cross-sectional structure of the hard coating layer 2 becomes finer, and the number of crystal grain boundaries increases and a lot of defects are included, and the residual compressive stress increases. Further, in the case of Iv / Iu> 15, in the case of Iw / Iu> 4, the residual compressive stress is reduced, but the film hardness is reduced and the wear resistance is inhibited. The adhesion strength of the grain boundaries in the cross-sectional structure decreases, and the hard coating surface easily breaks or peels off against external impacts. The control of the Iv / Iu value and the Iw / Iu value can be realized by setting the reaction gas pressure during film formation to 2 Pa or more and 7 Pa or less. If it is less than 2 Pa or more than 7 Pa, it becomes difficult to control the crystal orientation.

In the present invention, in order to suppress film breakage from the film interface of the hard film layer 1 and the hard film layer 2 and to exhibit excellent wear resistance as a cutting tool, improvement in adhesion strength at the interface was realized. Both hard coating layers 1 and 2 have a face-centered cubic structure, and in order to improve the wear resistance as a cutting tool, the hard coating layer 1 is strongly oriented in the (111) plane where the hardness can be increased. The film forming conditions were selected. On the other hand, for the hard coating layer 2, film forming conditions were selected so as to be strongly oriented in the (200) plane where residual compressive stress can be reduced.
Furthermore, in order to ensure the adhesion strength at the interface between the hard coating layer 1 and the hard coating layer 2, studies were made to match each lattice constant. That is, by approximating the lattice constants of the hard coating layers 1 and 2, the crystal growth at the interface between the hard coating layers 1 and 2 can be made continuous. However, in the present invention, since the compositions of the hard coating layers 1 and 2 are different, it is difficult to match the lattice constants of the two. The reason is that the hard coating layer 1 contains Cr and the hard coating layer 2 is a hard coating containing Ti, and the ionic radii are different from each other. For example, if the amount of Al contained in the hard coating layers 1 and 2 according to the present invention is increased beyond 70 atomic%, the lattice constants of both can be perfectly matched. However, when the Al content exceeds 70 atomic%, since an AlN crystal having an hcp structure is included, the hardness is lowered and the wear resistance is extremely deteriorated.
In the present invention, since the orientations of the hard coating layers 1 and 2 are different, it is difficult to perform epitaxial growth at the hard coating layer interface. Therefore, in order to ensure the adhesion at the hard coating layer interface, examination was made to approximate the lattice constant calculated from the (111) plane of the hard coating layers 1 and 2. As described above, the lattice constant calculated from the (111) plane was generally a1 <a2 due to the difference in the composition of the hard coating layers 1 and 2. Therefore, for the hard coating layer 1, the bias voltage value was increased as a film forming condition for increasing the lattice constant. By increasing the bias voltage, the kinetic energy when the element ionized in the plasma reaches the substrate is increased, and the film is formed while distorting the hard film, so that the lattice constant increases. For the hard coating layer 2, the bias voltage was set to be low and the conditions were selected so that the lattice constant would not increase as much as possible.

  In forming the hard coating layers 1 and 2, the bias voltage was applied in the form of pulses (intermittent). Here, pulsing of the bias voltage will be described. Generally, the bias voltage is applied to the substrate as a negative DC voltage. In this case, the residual compressive stress increases as the film thickness increases. In particular, in the film thickness range (5 ≦ T1 + T2 ≦ 12) as defined in the present invention, the residual compressive stress becomes excessive, leading to self-destruction of the hard coating. Therefore, by pulsing the bias voltage, it becomes difficult to generate lattice strain at the moment when the bias voltage is low, leading to a reduction in residual compressive stress.

  Further, the frequency at which the bias voltage is pulsed is important for controlling the residual compressive stress. As a result of intensive studies by the inventors, when the pulse frequency is 5 to 30 kHz, in the hard coating layer 1, the peak intensity ratio between the (220) plane and the (111) plane is 0.30 ≦ It / Ir ≦ 1. 0, and in the hard coating layer 2, the peak intensity ratio between the (220) plane and the (111) plane is 2.0 ≦ Iw / Iu ≦ 4.0, and the residual compressive stress of the hard coating is 0.50 to 2.0 GPa. We found that it was possible to control within the optimum range. When the pulse frequency is lower than 5 kHz, It / Ir exceeds 1.0 and the Iw / Iu value exceeds 4.0. At this time, a hard film having a low compressive stress composed of a columnar structure is obtained, but the adhesion strength between the columnar structures is low, and the fracture resistance is not increased. On the other hand, if the pulse frequency exceeds 30 kHz, the kinetic energy when the film-forming substance reaches the substrate cannot be reduced, It / Ir is less than 0.3, and Iw / Iu is less than 2.0. As a result, the residual compressive stress exceeds 2.0 GPa.

  Further, a bias voltage pulsing method will be described. The pulsing method is roughly divided into a unipolar method and a bipolar method. The unipolar method is a method in which a bias voltage is pulsed and applied in a negative or zero range. At this time, as described above, lattice strain is hardly generated at the moment when the bias voltage is low, which leads to reduction in residual compressive stress. On the other hand, the bipolar method is a method of applying a pulsed bias voltage within a positive range. At this time, since a part of the lattice strain is relieved at the moment when the positive bias voltage is applied, it is possible to further reduce the residual compressive stress.

  From the above, in order to improve the adhesion at the interface between the hard coating layers 1 and 2, the hard coating layer 1 is set to a high bias voltage, and a film is formed by applying a bias voltage pulsed by the bipolar method. went. In the hard coating layer 2, the bias voltage value was set low, and a film was formed by applying a bias voltage pulsed by a unipolar method. That is, the adhesion strength between the hard coating layer 1 and the hard coating layer 2 was increased by controlling 0.990 ≦ a1 / a2 ≦ 0.999. The lattice constants of the hard coating layer 1 and the hard coating layer 2 can be approximated by the film forming conditions.

  The reason why T1 <T2 will be described. From the viewpoint of constituent elements, the residual compressive stress of the hard coating layer 1 tends to be higher than that of the hard coating layer 2. When the T1 value exceeds 2 μm and is thick, self-destruction of the coating tends to occur at the edge of the cutting edge of the tool. Moreover, in order to obtain the lubricity of the hard coating layer 1, it is preferable that it is 0.1 micrometer or more. More preferably, 0.3 μm ≦ T1 ≦ 2 μm. Further, the hard coating layer 2 is excellent in wear resistance, but when T2 <4 μm, the wear resistance is not exhibited. As the T2 value increases, the residual compressive stress tends to gradually increase. When T2> 10 μm, the residual compressive stress becomes excessive, the adhesion strength at the interface between the base material and the hard coating is reduced, and the hard coating is peeled off. It becomes easy to do. More preferably, 5 μm ≦ T2 ≦ 8 μm. Therefore, in order to achieve both the lubricity and fracture resistance of the hard coating layer 1 and the wear resistance of the hard coating layer 2 in the present invention, the residual compressive stress of the entire hard coating layer is suppressed as T1 <T2. is required.

  The hard coating has crystal grains that cross at least the hard coating layer 1 and the hard coating layer 2, and in this case, the adhesion strength at the interface between the hard coating layers 1 and 2 in the same crystal grain is improved. Therefore, the hard coating of the present invention is effective in suppressing delamination during cutting.

  Al and Cr of the hard coating layer 1 and Ti and Al of the hard coating layer 2 have sufficient function of the hard coating by substituting at least one element of their respective metal components in a range of 10 atomic% or less. It is effective for making it exhibit. Addition of at least one element selected from Si, B, V, Nb, and W causes lattice distortion due to element substitution in the crystal structure, thereby increasing the hardness of the coating. However, since the residual compressive stress tends to increase with the addition of the element, the substitution ratio is preferably 10 atomic% or less. Addition of Si is effective in increasing the hardness of the film and improving the oxidation resistance. Similarly, addition of Nb or W is also effective for improving heat resistance. Furthermore, the addition of V or B is effective and preferable for improving the lubricity of the film. It is possible to withstand severe cutting conditions such as high speed and high feed.

<Film formation conditions>
In the present invention, the crystal structure of the hard coating layers 1 and 2 can be controlled within the above range by optimizing the bias voltage, reaction pressure, and film formation temperature during film formation, and the hard coating that is thickened is optimal. The residual compressive stress is inherent and high hardness can be maintained.
For example, the residual compressive stress tends to increase as the bias voltage value increases. Here, it is important to crystallize the film at a relatively slow film formation rate of 1 μm / hour or less. At this time, the range of the optimized residual compressive stress value is 0.5 to 2 GPa. If the residual compressive stress value is less than 0.5 GPa, the wear resistance can be ensured, but the fracture resistance is insufficient, and if it exceeds 2 GPa, chipping of the hard coating tends to occur.

Further, by controlling the bias voltage at the time of forming the hard coating layer 1 to a negative value of 30 to 200 V, the Is / Ir value can be controlled to 0.3 or more, and the bias at the time of forming the hard coating layer 2 is increased. By controlling the voltage to 30 to 100 V, the Iv / Iu value can be controlled to 5 or more. The lower the bias voltage is in the range of 200V or less, the larger the Is / Ir value is. The lower the bias voltage is in the range of 100V or less, the larger the Iv / Iu value is, but at a voltage lower than 30V, the residual compressive stress is reduced. Although the adhesion is increased, the film hardness is lowered and the wear resistance is deteriorated. In the hard coating layer 1 having a face-centered cubic structure, the coating density becomes higher and the hardness is increased when oriented to the (111) plane which is the closest packed surface of atoms. Furthermore, the compressive stress remaining in the hard coating layer 1 is increased, and the effect of suppressing crack propagation during cutting is exhibited. Therefore, it is important to control the bias voltage during film formation within the above range.
Furthermore, the It / Ir value can be controlled by applying a pulsed bias voltage during film formation. At this time, it is possible to suppress an increase in residual compressive stress that becomes noticeable when the hard coating layer is thickened, and to improve the wear resistance by thickening the hard coating layer.

By using a bipolar or unipolar pulse wave as the bias voltage application method, the peak intensity of the (220) plane changes, in particular, as compared with the case where a film is formed with a DC bias voltage. This is presumably because the crystal structure changes because there is room for movement when an element ionized in plasma reaches the object to be processed during film formation.
Furthermore, in the present invention, in order to control the residual compressive stress generated when the hard coating layers 1 and 2 are thickened for improving the wear resistance, it is necessary to pulse the bias voltage and control the pulse frequency. In the present invention, the pulse frequency is set to 25 kHz. As a result, 0.3 ≦ It / Ir <1 and 2 ≦ Iw / Iu ≦ 4, and the residual compressive stress value can be controlled within the optimum range of 0.5 to 2 GPa. When the pulse frequency is less than 5 kHz, the Iw / Iu value exceeds 4. As the cross-sectional structure of the film at this time, a columnar structure having a low residual compressive stress is obtained, but the adhesion strength between the grain boundaries in the columnar structure is low, and cracks generated during the cutting process easily propagate through the grain boundaries. Therefore, the tool is lost. On the other hand, if it exceeds 30 kHz, the kinetic energy when ions reach the workpiece cannot be reduced, so the Iw / Iu value is less than 2. Even when the Iv / Iu value exceeds 15 and the residual compressive stress of the hard coating layer 2 exceeds 2 GPa, the adhesion is remarkably lowered. More preferably, it is 15-30 kHz.

The higher the bias voltage, the higher the energy of ions that reach the substrate during film formation, and the easier it is to (111) orientation, and the film is formed while distortion occurs between the lattices, and the lattice constant increases. That is, the lattice constant of the hard coating layer can be controlled by adjusting the bias voltage. Therefore, in the present invention, studies were made to match the lattice constant difference between the hard coating layer 1 and the hard coating layer 2. When the lattice constants of the hard coating layer 1 and the hard coating layer 2 defined in the present invention were measured, it was generally a1 <a2. This seems to be due to the difference in the content of Al, which is a relatively small atom among the metal atoms constituting the hard coating layer. Therefore, for the hard coating layer 1, the bias voltage value was increased as a film forming condition for increasing the lattice constant. Further, in order to prevent the residual compressive stress from becoming excessive due to the increased bias voltage, it was applied to the substrate as a bias voltage pulsed by a bipolar method. On the other hand, a bias voltage was applied to the hard coating layer 2 with a unipolar pulse wave to suppress an excessive residual compressive stress when the film was thickened.
Hereinafter, the present invention will be described in detail by the following examples, but the present invention is not limited to the following examples.

[1] Film Forming Apparatus As a film forming apparatus for physical vapor deposition, an arc ion plating (AIP) apparatus, a filter-type arc ion plating apparatus, a sputtering apparatus, or the like is suitable. From this, the manufacturing method of the hard film | membrane used for this invention example 1 is demonstrated below.
The apparatus used for the coating was an AIP apparatus, and in the AIP apparatus, there was a rotating jig for mounting a substrate (planetary system), an arc cathode 2 for forming a lower layer and its shutter, and an arc cathode 1 for forming an upper layer. And a shutter, a reaction gas supply port, a bias power source for applying a bias voltage to the substrate, and a decompression vessel. The arc cathode 1 had a composition of atomic% and Al: 60% and Cr: 40% targets, and the arc cathode 2 had Ti: 50% and Al: 50% targets. A cemented carbide insert tool was mounted on the substrate mounting rotating jig for cutting evaluation.

[2] Manufacturing Method (A) Cleaning of Substrate First, the substrate was heated to 600 ° C. while maintaining the inside of the AIP apparatus at a reduced pressure of 2 Pa or less. Subsequently, the Ar gas flow rate was introduced at 100 sccm, and the substrate surface was etched with Ar ions while applying a bias voltage of 200 V at a negative voltage to the substrate while maintaining a vacuum of about 2.5 Pa inside the AIP apparatus. Went.

(B) Formation of Hard Film Layer 2 (1) Film Formation Temperature of Hard Film Layer 2 The film formation temperature of the hard film layer 2 in Invention Example 1 was set to 600 ° C. In order to control the W ₂ value, it is necessary to optimize the film formation temperature, and it is necessary to form a film in the range of 400 to 650 ° C. This is because the W ₂ value exceeds 0.6 when the temperature is less than 400 ° C., and becomes less than 0.4 when the temperature exceeds 650 ° C.

(2) Pressure in the film forming atmosphere of the hard coating layer 2 In the hard coating layer 2 in the present invention example 1, nitrogen gas was introduced and the pressure was set to 3 Pa. At this time, the flow rate of nitrogen gas was set to 750 sccm, and the pressure in the decompression vessel was controlled by the opening ratio of the main valve of the vacuum exhaust system while keeping it constant. The y value of the hard coating layer 2 can be controlled within the range of 0.45 ≦ y ≦ 0.55 by setting the reaction gas pressure during film formation to 2.5 Pa or more and 7 Pa or less. If it is less than 2.5 Pa, y value will be less than 0.45, and if it exceeds 7 Pa, it will exceed 0.55. The control of the Iv / Iu value and the Iw / Iu value can be realized by setting the reaction gas pressure during film formation to 2 Pa or more and 7 Pa or less. On the other hand, if it is less than 2 Pa or more than 7 Pa, it becomes difficult to control the crystal orientation. A preferable nitrogen gas pressure is 3 Pa or more and 4 Pa or less.

(3) Bias voltage of hard coating layer 2 The bias voltage of the hard coating layer 2 in Invention Example 1 was set to 50 V as a negative voltage. The hard coating layer 2 was formed by applying a bias voltage pulsed by a unipolar method with a low bias voltage value. This is to prevent the lattice constant from becoming as large as possible by setting the bias voltage low. The Iv / Iu value can be controlled to 5 or more by controlling the bias voltage during film formation to 30 to 100V. The Iv / Iu value increases as the bias voltage is lower than 100 V. However, at a voltage lower than 30 V, the residual compressive stress is reduced and the adhesion is increased, but the film hardness is lowered and the wear resistance is deteriorated. End up.

(4) Pulse frequency of hard coating layer 2 In forming the hard coating layer 2 in Example 1 of the present invention, the bias voltage was applied in a pulsed (intermittent) manner. The bias voltage in the hard coating layer 2 was applied to the substrate with a periodic amplitude between a negative voltage of 50V and 0V. A bias voltage was applied with this unipolar pulse wave, and the pulse frequency was set to 25 kHz. Accordingly, 2 ≦ Iw / Iu ≦ 4 is established, and the residual compressive stress value can be controlled within an optimum range of 0.5 to 2 GPa. Therefore, it is possible to suppress the residual compressive stress from being excessive when the film is thickened. If the pulse frequency exceeds 30 kHz, the kinetic energy when the film-forming substance reaches the substrate cannot be reduced, and Iw / Iu is less than 2.0. As a result, the residual compressive stress exceeds 2.0 GPa. When the pulse frequency is less than 5 kHz, the Iw / Iu value exceeds 4. More preferably, the pulse frequency is 15-30 kHz.

(5) Arc current of the hard coating layer 2 In forming the hard coating layer 2 in Example 1 of the present invention, a current of 150 A was passed through the arc cathode 2 to generate an arc discharge until the T2 value reached 5.8 μm. A film was formed.

(C) Formation of the hard coating layer 1 (1) Film formation temperature of the hard coating layer 1 The transition period from the end of film formation of the hard coating layer 2 to the start of film formation of the hard coating layer 1 is a lattice at the interface between the two layers. In order to control the ratio of the constants within a specified numerical range and to grow a continuous columnar crystal, precise control is required. Therefore, in controlling the film formation temperature, the set temperature was changed from 600 ° C. to 500 ° C. simultaneously with the completion of the film formation of the hard coating layer 2. The actual temperature drop was set to the set temperature of 500 ° C. within 2 minutes by heater control.
The stationary phase in the formation of the hard coating layer 1 was also set to 500 ° C. The film formation temperature of the hard coating layer 1 needs to be formed in the range of 300 to 550 ° C. This is because if it is less than 300 ° C., the W ₁ value exceeds 1.1 and if it exceeds 550 ° C., it is less than 0.7.

(2) Pressure in Hard Film Layer 1 Film Forming Atmosphere Transition from the end of hard film layer 2 film formation to the start of hard film layer 1 film formation is performed simultaneously with the end of hard film layer 2 film formation. The gas flow rate was changed from 750 sccm to 800 sccm, but the pressure was adjusted to 3 Pa by controlling the opening ratio of the vacuum exhaust system main valve.
The stationary phase of the hard coating layer 1 was also set to 800 sccm, and the pressure was maintained at 3 Pa. Regarding the optimum control of the x value of the hard coating layer 1, when the gas pressure of the film forming apparatus is adjusted to 1 to 7 Pa, the residual compressive stress of the hard coating can be controlled to 1 to 2 GPa. The control of the Is / Ir value and the It / Ir value can be realized by setting the reaction gas pressure during film formation to 1.5 Pa or more and 3.5 Pa or less. If it is less than 1.5 Pa, it becomes difficult to control the crystal orientation. Moreover, when it exceeds 3.5 Pa, film hardness will fall.

(3) Bias voltage of hard coating layer 1 The transition period from the end of film formation of hard coating layer 2 to the start of film formation of hard coating layer 1 improves the adhesion at the interface of hard coating layers 1 and 2 Therefore, the negative bias voltage value of the hard coating layer 1 was set higher than the conditions of the hard coating layer 2, and the film was formed by applying a bias voltage pulsed by the bipolar method. Here, increasing the negative bias voltage value means that the absolute value of the voltage value is large. However, as the bias voltage value increases, the residual compressive stress tends to increase. This is because the higher the bias voltage value, the higher the energy of ions that reach the substrate during film formation, and the easier (111) orientation occurs, and the film is formed while distortion occurs between the lattices. In addition, there is an effect that the lattice constant is increased. Therefore, in Example 1 of the present invention, a bias voltage pulsed by a bipolar method was applied. In this setting, the negative voltage was 150 V, the positive voltage was 10 V, and the amplitude was periodically applied to the substrate.
The bias voltage was applied in a pulsed manner during the stationary phase of the hard coating layer 1 as well. By controlling the negative bias voltage during film formation to 30 to 200 V, the Is / Ir value can be controlled to 0.3 or more. The lower the bias voltage is in the range of 200 V or less, the larger the Is / Ir value becomes. At a voltage lower than 30 V, the residual compressive stress is reduced and the adhesion is increased, but the film hardness is lowered and the wear resistance is deteriorated.

(4) Pulse frequency of hard coating layer 1 The transition period from the end of film formation of hard coating layer 2 to the start of film formation of hard coating layer 1 is from a unipolar system to a bipolar system within a short time. And switching operation.
In the film formation of the hard coating layer 1 in Invention Example 1, the pulse frequency was set to 25 kHz. Thereby, it becomes 0.3 <= It / Ir <1, and it can control a residual compressive stress value to the optimal range of 0.5-2GPa.
When the pulse frequency is 5 to 30 kHz, the peak intensity ratio between the (220) plane and the (111) plane of the hard coating layer 1 is 0.30 ≦ It / Ir <1.0, and when the pulse frequency is lower than 5 kHz, It / Ir exceeds 1.0. When the pulse frequency exceeds 30 kHz, the kinetic energy when the film-forming substance reaches the substrate cannot be reduced, and It / Ir is less than 0.3, and as a result, the residual compressive stress exceeds 2.0 GPa. .

(5) Arc current of the hard coating layer 1 The transition period from the end of the film formation of the hard coating layer 2 to the start of the film formation of the hard coating layer 1 is within the specified numerical range of the ratio of lattice constants at the interface between both layers. In order to control the growth rate and to grow a continuous columnar crystal, precise control is required, but control of the film formation rate is particularly important. Therefore, in order to complete the formation of the hard coating layer 2, the arc cathode 1 is also operated 30 seconds before the arc cathode 2 is closed by the shutter operation of the arc cathode 2, and a current of 150 A is passed while the shutter is kept closed. I started. At the same time that the arc cathode 2 was closed by the shutter operation, the arc cathode 1 was opened by the shutter operation. These series of operations are preferably completed within 5 seconds. Thereafter, the current of the arc cathode 2 may be stopped.
Here, the reason why the current values of the arc cathodes 1 and 2 are set to 150 A is that it is important to grow columnar crystals of the coatings of both layers by obtaining an optimum film formation rate of about 1 (μm / hour). It is. At this time, at the interface between the hard coating layer 2 and the hard coating layer 1, continuous columnar crystals can be grown from the orientation of the (200) plane of the hard coating layer 2 to the orientation of the (111) plane of the hard coating layer. Become. Also, the residual compressive stress value is optimized, and the range is 0.5-2 GPa. However, at 120 A or less, the film formation speed is slow, so the film formation time becomes long and inefficient. On the other hand, at 180A or higher, high energy is locally supplied to the target surface by the arc spot as the film forming speed increases, and therefore, large particles (drops) are formed at the interface between the hard coating layer 2 and the hard coating layer 1. (Let)) will increase. Due to the influence, it becomes difficult to grow columnar crystals from the orientation of the (200) plane to the orientation of the (111) plane.
During the stationary phase of the formation of the hard coating layer 1, a current of 150 A was applied to the arc cathode 1 while applying a bipolar pulse bias voltage until the T1 value reached 1.6 μm.
Invention Example 1 was produced by the above coating process.

  Further, in Examples 2 to 10 of the present invention and Comparative Examples 11 to 20, the conditions other than the setting of the target composition of each arc cathode 1 and 2, each bias voltage value, and each bias voltage application method are the same as the coating process of Example 1 of the present invention. Compliant with. The film forming conditions are shown in Table 1.

Table 1 (continued)

Table 1 (continued)

Table 1 (continued)

The composition of hard coating layer 1 and hard coating layer 2 of the obtained hard coating, X-ray diffraction peak intensity ratio, lattice constant on (200) plane, (111) plane, coating hardness, and residual compressive stress value were measured. . The measurement method is described below.
The composition of the hard coating is measured by grinding and polishing the cross section of the test piece for each sample to a flat surface, and using an EPMA (for example, JXA-8500R type, manufactured by JEOL Ltd.), an acceleration voltage of 10 kV. The sample current was analyzed at 1 μA. The film thickness was measured by observing with a field emission scanning electron microscope (for example, S-4200 manufactured by Hitachi, Ltd.) by cutting a test piece for each sample in the vertical direction. The X-ray diffraction peak intensity ratio of the hard coating, and the lattice constants of the (200) plane and (111) plane are measured using an X-ray diffractometer (Ru-200BH type, manufactured by Rigaku Corporation) with a thin film measurement method. 2θ was measured in the range of 30 to 70 degrees by thin film setting with an angle fixed at 1 degree (θ = 5 degrees as a standard, and measurement was performed even if θ = 1 degree as necessary). A CuKα ray having a λ of 0.1541 nm was used as the X-ray source, and background noise was removed by software built in the apparatus.
In the measurement results of the lattice constant calculated from the (111) plane in the hard coating layer 1 of Invention Examples 1 to 36, the a1 value is 0.410 ≦ a1 ≦ 0.413, and the (111) in the hard coating layer 2 In the measurement result of the lattice constant calculated from the surface, the a2 value was within the range of 0.413 ≦ a2 ≦ 0.416. The residual compressive stress of the hard coating was measured by a curvature measurement method, and a test piece for residual stress measurement was used. This was prepared by mirror polishing the upper and lower surfaces of a base material made of a fine cemented carbide having a length of 10 mm, a width of 25 mm, and a thickness of 1 mm, and the amount of warpage (δ ₀ ) of the mirror surface portion was measured. The test piece was attached to a film forming apparatus so that only one side of the test piece was covered with the hard film, and the film was formed. After film formation, the amount of warpage (δ ₁ ) was measured in the same manner, and the test piece thickness (D) and the fracture surface thickness (d) were measured. From these numerical values, the residual stress value was calculated by (Equation 1). In (Equation 1), the Es value is 518 GPa as the Young's modulus of the substrate, the νs value is 0.238 as the Poisson's ratio of the substrate, and the l value is 12.5 mm of the substrate length up to the maximum deflection. The measurement results are shown in Table 2.

  In Examples 1 to 36 of the present invention, columnar crystal grains traversing the hard coating layer 1 and the hard coating layer 2 are obtained as a result of cross-sectional observation of the hard coating with a magnification of 50 k using a scanning electron microscope (hereinafter referred to as SEM). Confirmed that it exists. The columnar crystal grains had a shape in which the film thickness direction was the longitudinal direction. For example, FIG. 2 shows a fractured cross-sectional photograph of the coating film of Example 1 of the present invention, and FIG. 3 shows an enlarged photograph of part A of FIG. In FIG. 3, the outlines of the two columnar crystal grains crossing the interface between the hard coating layers 1 and 2 are indicated by dotted lines. Moreover, it was confirmed by observation that an interface between the hard coating layers 1 and 2 exists in the columnar crystal grains.

Table 2 (continued)

Table 2 (continued)

Table 2 (continued)

Next, the cutting performance of the obtained hard coating-coated insert was evaluated using the following test conditions. The tool life evaluation method was a processing time until the maximum wear width on the insert flank surface reached 0.3 mm in an intermittent environment in which chipping is likely to occur during cutting. Damage that occurred in the cutting evaluation was also confirmed. Notable damages were wear (width), hard film peeling, hard film breakage, and chipping.
(Test conditions)
Cutting method: Intermittent processing work material: SKD11, two 50 mm × 250 mm plate materials (arranged parallel to the processing direction)
Cutting speed: 200 m / min
Single-blade feed amount: 0.35 mm / blade cutting depth: 1.0 mm
Cutting oil: None, dry cutting

  In Inventive Example 1 and Comparative Examples 37 and 38, the effect of residual compressive stress on cutting performance was investigated. In Comparative Example 37, the residual compressive stress was 4.2 GPa, and in Comparative Example 38, the residual compressive stress was 3.4 GPa. In all of these, chipping at the edge of the cutting edge was confirmed at the initial stage of machining (5 minutes), and the tool life was short. On the other hand, in Example 1 of the present invention, the residual compressive stress was reduced to 1.7 GPa. Therefore, an appropriate residual compressive stress was applied during the cutting process, and crack propagation and chipping of the film were suppressed, so that the tool life was extended. Furthermore, as a result of elemental mapping of the cutting edge surface in the middle of cutting (10 minutes) by EPMA, for example, the amount of Fe element detected compared to the case where a (TiAl) N film as in Conventional Example 73 is present on the hard coating layer surface, for example. There were few. That is, it is considered that the welding of the work material is suppressed from the composition of the hard coating layer 1 and the chipping accompanying the welding of the hard coating layer is prevented.

In Invention Examples 2 and 3 and Comparative Examples 39 and 40, the influence of the composition ratio of the hard coating layer 1 on the cutting performance was confirmed. In Comparative Example 39, the Al content was relatively large, and the presence of AlN having an hcp structure was partially confirmed. AlN having an hcp structure has a low film hardness, flank wear during cutting significantly progresses, and has a short life. In Comparative Example 40, the Cr content was relatively high, and the residual compressive stress was high, so that the adhesion with the hard coating layer 2 was deteriorated. Therefore, flank wear during cutting progressed and the tool life was shortened.
On the other hand, in Example 2 of the present invention, AlN having an hcp structure was not confirmed, and sufficient hardness as the hard coating layer 1 was maintained. In Example 3 of the present invention, the residual compressive stress was controlled within an appropriate range. Therefore, these tool lifetimes were longer than in the comparative examples.

In Invention Examples 4 and 5 and Comparative Examples 41 and 42, the gas (nitrogen) pressure for the film formation of the hard coating layer 1 was examined. In Comparative Example 41, the gas pressure was set to 7 Pa. At this time, since the x value was 0.59, the hard coating layer 1 was softened and the wear resistance was lowered. In Comparative Example 42, the gas pressure was set to 1 Pa. At this time, the x value was 0.42, and although the hard coating layer 1 was hardened, the residual compressive stress was excessively increased, so that there was much chipping from the beginning of cutting and the life was short.
On the other hand, in Invention Example 4, the gas pressure was set to 3.5 Pa. In Example 5 of the present invention, the gas pressure was set to 1.5 GPa. In any case, the residual compressive stress of the hard coating layer 1 was appropriately controlled, and the tool life was prolonged.

In Invention Examples 6 and 7 and Comparative Example 43, the relationship between the film thickness of the hard coating layer 1 and the cutting performance was investigated. In Comparative Example 43, the hard coating layer 1 was 5.9 μm, the hard coating layer 2 was 5.6 μm, and the residual compressive stress was 2.7 GPa. From the viewpoint of the constituent elements, the residual compressive stress of the hard coating layer 1 was higher than that of the hard coating layer 2. Therefore, chipping from the beginning of cutting was conspicuous and the tool life was short.
In Example 6 of the present invention, the film thickness of the hard coating layer 1 was thicker than that of Example 1 of the present invention, but the residual compressive stress was reduced to 1.9 GPa, and the tool life was extended due to the effect of suppressing crack propagation. On the other hand, in Example 7 of the present invention, the thickness of the hard coating layer 1 was 0.3 μm, which was thinner than that of Example 1 of the present invention, but the lubricity as the hard coating layer 1 functioned sufficiently.
Therefore, in order to achieve both the lubricity and fracture resistance of the hard coating layer 1 and the wear resistance of the hard coating layer 2 to be described later, the balance of residual compressive stress is important. It has been found that the thickness of the hard coating layer 1 having a high stress is set to be thinner than that of the hard coating layer 2, that is, T1 <T2.

In Invention Examples 8 and 9 and Comparative Examples 44 and 45, the influence of the magnitude of the bias voltage applied in the hard coating layer 1 on the cutting performance was investigated. In Comparative Example 44, since the bias voltage was too high, the bias voltage was pulsed by the bipolar method, but the residual compressive stress could not be reduced to 2 GPa or less, and chipping during cutting was increased, resulting in tool life. Was short. In Comparative Example 45, although the bias voltage was low, the residual compressive stress was reduced and the adhesion was increased, the film hardness was lowered and the wear resistance was deteriorated. Therefore, the tool life was short.
On the other hand, in Examples 8 and 9 of the present invention, the residual compressive stress was controlled within an appropriate range, and the tool life was increased. In particular, in Example 8 of the present invention, in terms of film formation conditions, the lattice constant ratio a1 / a2 was 0.999, which was the closest among the examples of the present invention, and the adhesion at the interface between the hard coating layers 1 and 2 was considered to have increased. The tool life was also long.

In Examples 10 and 11 of the present invention and Comparative Examples 46 and 47, the influence of the pulse wave application method and the voltage setting value at the pulse portion when a bias voltage was applied to the hard coating layer 1 on the cutting performance was investigated. In Comparative Example 46, although the residual compressive stress was reduced to 0.8 GPa, the bipolar film was pulsed to a positive voltage (+40 V), so that the crystallinity of the hard film layer 1 was lost and the film hardness was reduced. Led to. Further, in Comparative Example 47, since the unipolar pulse was applied to a negative voltage (−50 V), the residual compressive stress was not reduced, chipping occurred during cutting, and the life was short.
On the other hand, in Examples 10 and 11 of the present invention, the residual compressive stress was controlled within an appropriate range, the excellent fracture resistance of the hard coating layer 1 was exhibited, and the life was extended.

In Examples 12 and 13 of the present invention and Comparative Examples 48 and 49, the influence of the frequency when the bias voltage was pulsed was investigated. In Comparative Example 48, since the frequency of the pulse wave was set as high as 50 kHz, the kinetic energy when the film-forming substance reached the substrate was extremely reduced, leading to softening of the hard coating. In Comparative Example 49, since the frequency of the pulse wave was set as low as 5 kHz, the kinetic energy when the film-forming substance reached the base material could not be reduced, and the residual compressive stress increased. Adhesion at the two interfaces deteriorated and the tool life was short.
On the other hand, in the inventive examples 12 and 13, the kinetic energy when the film-forming substance reaches the substrate is appropriately controlled and the residual compressive stress is reduced to 2 GPa or less, so that the chipping of the hard coating layer 1 is suppressed, and the tool Lifespan has been extended.
The In / Ir values in Invention Examples 12 and 13 both satisfied 0.3 ≦ It / Ir ≦ 1.0. In Comparative Example 48, It / Ir <0.3, and in Comparative Example 49, It / Ir <0.3. / Ir> 1. Therefore, it was found that it is important to control the It / Ir value when applying a pulse wave to the bias voltage.

In Invention Examples 15 to 19 and Comparative Examples 50 to 54, the influence of additive elements on the hard coating layer 1 was investigated. In Examples 15 to 19 of the present invention, the amount of the additive element is 10 atomic% or less, and the additive element enters or substitutes into the (AlCr) N crystal lattice constituting the hard coating layer 1 so that an appropriate strain is obtained. It is assumed that the hardness of the film was increased, the wear resistance was increased, and the tool life was extended. Also, by adding B, V, and Si elements to the hard coating layer, it has been confirmed that the welding component of the work material generated on the cutting edge during cutting is reduced, which is effective in improving welding resistance. Met. Furthermore, the addition of Nb and W improved the oxidation resistance of the hard coating layer, and was effective in improving the tool life.
However, when the amount of added elements exceeded 10 atomic% as in Comparative Examples 50 to 54, the tool life was reduced. This is because the additive element is incorporated into the (AlCr) N or (TiAl) N film crystal structure in an intrusion type or a substitution type, but because of the large amount of additive element, the crystal of the (AlCr) N or (TiAl) N film This seems to be because the structure collapses, leading to a reduction in the hardness of the film. Moreover, when there was much Si element like the comparative example 50, the film | membrane structure | tissue became amorphous easily and the film | membrane softened simultaneously.

In Examples 20 and 21 of the present invention and Comparative Examples 55 and 56, the influence of the composition ratio of the hard coating layer 2 on the cutting performance was confirmed. In Comparative Example 55, the Al content was relatively large, and the presence of AlN having an hcp structure was partially confirmed. AlN having an hcp structure has a low film hardness, flank wear during cutting significantly progresses, and has a short life. Further, in Comparative Example 56, although the Ti content was relatively large and the residual compressive stress was reduced, columnar crystals grew from the base material in the film thickness direction of the hard coating layer 1, but the grain boundary strength of the columnar crystals was high. It was weak, a lot of chipping was confirmed, and the tool life was shortened.
On the other hand, in Example 20 of the present invention, AlN having an hcp structure was not confirmed, and sufficient hardness as the hard coating layer 1 was maintained. In Inventive Example 21, the residual compressive stress was controlled in an appropriate range, and the adhesion with the base material was increased, so that the tool life was extended.

  In Invention Examples 22 and 23 and Comparative Examples 57 and 58, the gas (nitrogen) pressure for the film formation of the hard coating layer 2 was examined. These tend to be the same as in the case of the hard coating layer 1.

In Inventive Examples 24 and 25 and Comparative Examples 59 and 60, the relationship between the film thickness of the hard coating layer 2 and the cutting performance was investigated. In Comparative Example 59, the hard coating layer 2 was thickened to 12.2 μm. At this time, it was shown that although the residual compressive stress of the hard coating layer 2 is relatively low in the (TiAl) N composition, it is invalidated if the film thickness is excessively increased. In Comparative Example 60, the hard coating layer 2 was thinned to 1.3 μm. This was thinner than 1.6 μm of the hard coating layer 1. In this case, although the residual compressive stress was reduced and the adhesion to the substrate was increased, the flank wear progressed rapidly and the life was short.
On the other hand, in Example 24 of the present invention, the film thickness of the hard coating layer 2 was 10.1 μm. At this time, although the residual compressive stress was reduced to 2 GPa or less, the wear resistance was not significantly improved as compared with Example 1 of the present invention. This is probably because the thicker the hard coating layer 2 is, the more the residual compressive stress is increased, which inhibits the adhesion with the substrate. In consideration of industrial productivity, it is important to control the film thickness range of the hard coating layer suitable for use as a cutting tool. The film thickness of the hard coating layer 2 of Invention Example 25 was 3.5 μm, which was thinner than the film thickness of 5.8 μm of the hard coating layer 2 of Invention Example 1. At this time, although the residual compressive stress was reduced to 1.2 GPa and the adhesion with the base material was improved, the wear resistance was lowered as compared with Example 1 of the present invention. Therefore, it was suggested that the tool life can be improved by increasing the film thickness after controlling the residual compressive stress within an appropriate range.

  In inventive examples 26 and 27 and comparative examples 61 and 62, the influence of the magnitude of the bias voltage applied in the hard coating layer 2 on the cutting performance was investigated. These tend to be the same as in the case of the hard coating layer 1.

  In Invention Examples 28 and 29 and Comparative Examples 63 and 64, the influence of the pulse wave application method and the voltage setting value at the pulse portion on the cutting performance when a bias voltage was applied to the hard coating layer 2 was investigated. These tend to be the same as in the case of the hard coating layer 1.

  In the inventive examples 30 and 31, and the comparative examples 65 and 66, the influence of the frequency when the bias voltage was pulsed was investigated. These tend to be the same as in the case of the hard coating layer 1.

  In Invention Examples 32-36 and Comparative Examples 67-71, the influence of additive elements on the hard coating layer 1 was investigated. These were the same as in the case of the hard coating layer 1.

  In the conventional examples 72 and 73, film formation was performed under a DC bias voltage condition, and the film thickness was about 3 μm, so the tool life was short. Although the film thickness has a great influence on the tool life, it was confirmed that if the physical properties of the hard coating could not be controlled within an appropriate range, no industrial advantage could be obtained.

  The hard film coated cutting tool of the present invention is suitable for applications such as processing of metal parts and dies, for example, and has extremely severe wear resistance and resistance such as high feed cutting and high feed high speed cutting. It can be used for applications that require deficiency.

1 Hard coating layer 1
2 Hard coating layer 2
3 Base material

Claims (4)

In a hard film coated cutting tool in which a hard film is coated on a cutting tool based on cemented carbide, the hard film has a two-layer structure formed by physical vapor deposition, and the two-layer structure is formed on the surface side. The hard coating layer 1 is coated, and the hard coating layer 2 is coated on the substrate side. The composition of the hard coating layer 1 is (Al _a Cr _1-a ) _1-x N _x (however, The content of each element is an atomic ratio, and 0.5 ≦ a ≦ 0.75 and 0.45 ≦ x ≦ 0.55)), and the X-ray diffraction of the hard coating layer 1 When the half width of the (111) plane at W ₁ (degrees) is 0.7 ≦ W ₁ ≦ 1.1, the peak intensity Ir of the (111) plane, the peak intensity Is of the (200) plane, And (220) plane peak intensity It, 0.3 ≦ Is / Ir <1, and 0.3 ≦ It / Ir <1, The composition of the hard coating layer _{2, (Ti b Al 1-b} ) 1-y N y ( where the content of the element each is an atomic ratio, 0.4 ≦ b ≦ 0.6 and 0.45, ≦ y ≦ 0.55), and when the half width of the (200) plane in the X-ray diffraction of the hard coating layer 2 is W ₂ (degrees), 0.4 ≦ W ₂ ≦ 0 .6, 5 ≦ Iv / Iu ≦ 15, and 2 ≦ Iw / Iu, where (111) plane peak intensity Iu, (200) plane peak intensity Iv, and (220) plane peak intensity Iw ≦ 4, when the lattice constant of the (111) plane of the hard coating layer 1 in X-ray diffraction is a1 (nm) and the lattice constant of the (111) plane of the hard coating layer 2 is a2 (nm), 0.990 ≦ a1 / a2 ≦ 0.999, the thickness of the hard coating layer 1 is T1 (μm), and the film of the hard coating layer 2 A hard film-coated cutting tool, wherein 5 ≦ T1 + T2 ≦ 12 and T1 <T2 when the thickness is T2 (μm).   2. The hard coating-coated cutting tool according to claim 1, wherein the hard coating has columnar crystal grains whose film thickness direction is a longitudinal direction, and the hard coating is formed at an interface between the hard coating layer 2 and the hard coating layer 1. A hard film-coated cutting tool characterized by having columnar crystal grains traversing the film layer 2 and the hard film layer 1.   2. The hard film-coated cutting tool according to claim 1, wherein at least one element of Al and Cr of the hard film layer 1 is Si, B, V, Nb, and W within a range of 10 atomic% or less, respectively. A hard film-coated cutting tool characterized by being substituted with at least one element selected from the above.   2. The hard film-coated cutting tool according to claim 1, wherein at least one element of Ti and Al of the hard film layer 2 is Si, B, V, Nb, and W within a range of 10 atomic% or less, respectively. A hard film-coated cutting tool characterized by being substituted with at least one element selected from the above.