WO2017179233A1 - Hard coating and cutting tool - Google Patents

Abstract

A hard coating that is formed on a substrate, wherein the hard coating comprises a bilayer structure layer made by laminating, in order from the substrate side, a lower layer and an upper layer. When the lower surface of the lower layer that is located on the substrate side of the bilayer structure layer and configures the lower end face is a first interface, the interface between the upper surface of the lower layer and the lower surface of the upper layer is a second interface, the upper surface of the upper layer that configures the upper end face opposite to the lower end face of the bilayer structure layer is a third interface, and a cross-section of the bilayer structure layer that is parallel to the thickness direction thereof is viewed, the average grain diameter G₁ of crystal grains at a distance of 100 nm from the first interface toward the second interface, the average grain diameter G₂ of crystal grains at a distance of 100 nm from the second interface toward the first interface, the average grain diameter G₃ of crystal grains at a distance of 100 nm from the second interface toward the third interface, and the average grain diameter G₄ of crystal grains at the third interface satisfy the relational expression G₂>G₃>G₄>G₁.

Description

Hard coating and cutting tool

The present invention relates to a hard coating and a cutting tool. This application claims priority based on Japanese Patent Application No. 2016-081127, which is a Japanese patent application filed on April 14, 2016. All the descriptions described in the Japanese patent application are incorporated herein by reference.

As a cutting tool having excellent cutting performance, there is a cutting tool in which a hard coating such as TiAlN is provided on the surface of a base material. One method for forming such a hard coating is an arc ion plating (AIP) method. For example, Japanese Patent Laid-Open No. 2002-160107 (Patent Document 1) discloses a technique for reducing the occurrence of droplets, which is a problem of hard coatings produced by the AIP method, by appropriately controlling various conditions of arc discharge. Is disclosed.

Another method for forming a hard coating is a chemical vapor deposition (CVD) method. For example, Japanese Patent Laid-Open No. 2013-212575 (Patent Document 2) discloses that a hard film and a hard film can be obtained by reducing the grain size of crystal grains located in the vicinity of the interface with the base material among the crystal grains constituting the hard film. A technique for improving the adhesion to a substrate is disclosed. Japanese Patent Application Laid-Open No. 2014-061588 (Patent Document 3) discloses that a hard film in which an A layer composed of a fine grained structure and a B layer composed of a columnar structure are alternately laminated is provided on a base material, whereby Techniques for improving chipping and wear resistance are disclosed.

JP 2002-160107 A JP 2013-212575 A JP 2014-061588 A

The hard film according to one embodiment of the present disclosure is a hard film formed on a base material, and the hard film includes a two-layer structure layer in which a lower layer and an upper layer are laminated in order from the base material side. The lower surface of the lower layer constituting the lower end surface located on the substrate side of the two-layer structure layer is defined as a first interface, and the interface between the upper surface of the lower layer and the lower surface of the upper layer is defined as a second interface. When the upper surface of the upper layer constituting the upper end surface opposite to the lower end surface is the third interface and a cross section parallel to the thickness direction is observed in the two-layer structure layer, the first interface is moved to the second interface side. The average grain diameter G ₁ of the crystal grains at a position 100 nm away from the second interface, the average grain diameter G ₂ of the crystal grains at a position 100 nm away from the second interface toward the first interface side, and from the second interface to the third interface side. Contact to 100nm crystal grains having an average grain size of G ₃ at a position away and third interface, towards That the average particle size G ₄ of the crystal grains satisfies the _{G 2> G 3> G 4} > G 1 relationship.

The cutting tool which concerns on 1 aspect of this indication is equipped with a base material and said hard film which coat | covers the surface of this base material.

FIG. 1 is a schematic cross-sectional view showing an example of a configuration in which a hard coating according to the first embodiment is provided on a substrate. FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the two-layer structure layer according to the first embodiment. FIG. 3 is a schematic diagram showing an arrangement state of the base material in the chamber of the HiPIMS apparatus when the two-layer structure layer is manufactured. FIG. 4 is a schematic plan view showing an example of a cutting tool according to the third embodiment. 5 is a cross-sectional view taken along the line XX shown in FIG. FIG. 6 is a schematic diagram for explaining how to obtain the ratio Tf / Tm. FIG. 7 is a schematic perspective view showing an example of a cutting tool according to the fourth embodiment. FIG. 8 is a cross-sectional perspective view showing a Y region in the hatched portion of FIG. 7, and is a view showing an aspect in which the cutting edge has a sharp edge shape. FIG. 9 is a diagram showing an aspect in which honing is applied to the cutting edge in the cross-sectional perspective view shown in FIG. 7. FIG. 10 is a diagram showing an aspect in which the negative cutting is applied to the cutting edge in the cross-sectional perspective view shown in FIG. 7.

[Problems to be solved by this disclosure]
However, the technique of Patent Document 1 cannot sufficiently solve the problem of droplets. Further, the hard coating disclosed in Patent Document 2 has insufficient fracture toughness due to the large crystal grain size on the surface of the hard coating. Further, in the hard coating disclosed in Patent Document 3, the crystal grains constituting the columnar structure are likely to fall off due to the structure of the B layer. As described above, since there is an insufficient point in the characteristics of any hard coating, it is a fact that the tool having the hard coating has an insufficient life.

In view of the above problems, an object of the present disclosure is to provide a hard coating capable of extending the tool life and a cutting tool including the hard coating.
[Effects of the present disclosure]
Based on the above, it is possible to provide a hard coating and a cutting tool capable of extending the tool life.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

The present inventors consider that there is a limit to the performance of the hard coating produced by the conventional AIP method and CVD method, and instead of these methods, J. Mater. Res., Vol. 27, No. 5 (2012), 780-792 (Non-patent Document 1), focusing on the High Power Impulse Magnetron Sputtering (HiPIMS) method. As a result of intensive investigations on the production of a hard film using the HiPIMS method, it is possible to produce a hard film containing crystal grains having a specific shape by changing the bias voltage applied to the substrate in two stages. The hard film which concerns on this indication was completed by discovering that it was possible and progressing further examination.

[1] The hard coating according to one embodiment of the present disclosure is a hard coating formed on a base material, and the hard coating is a two-layer structure in which a lower layer and an upper layer are laminated in order from the base material side. The lower surface of the lower layer constituting the lower end surface located on the substrate side of the two-layer structure layer is the first interface, and the interface between the upper surface of the lower layer and the lower surface of the upper layer is the second interface, When the upper surface of the upper layer constituting the upper end surface opposite to the lower end surface of the layer structure layer is the third interface, and the cross section parallel to the thickness direction of the two-layer structure layer is observed, Average grain size G ₁ of crystal grains at a position 100 nm away from the interface side, average grain diameter G ₂ of crystal grains at a position 100 nm away from the second interface toward the first interface side, third from the second interface the average particle diameter G ₃ of crystal grains in the 100nm away toward the interface side, and a third field The average particle diameter G ₄ of crystal grains in satisfies _{G 2> G 3> G 4} > G 1 relationship.

According to the two-layer structure layer included in the hard coating, since the average particle diameter of G ₁ in the first interface side is small, it exhibits high adhesion to the others to form the first interface. Meanwhile, since the average particle diameter G ₄ in the third interface side is small, it can exhibit high fracture toughness at the surface of the hard coating.

Here, if the two-layer structure layer is simply composed of fine particles having a small average particle diameter, the two-layer structure layer has a high compressive residual stress due to the film forming environment. In this case, the two-layer structure layer is easily peeled off, and there is a concern about the occurrence of abnormal wear. Further, if the two-layer structure layer is a normal columnar crystal, that is, a columnar crystal having a uniform average grain size in the growth direction, there is a concern that the chipping resistance may be reduced due to dropping of the columnar crystal. On the other hand, in the two-layer structure layer, as is clear from the above relational expression, the average grain size of the crystal grains contained in the two-layer structure layer varies specifically in the thickness direction. Thereby, occurrence of abnormal wear as described above (decrease in wear resistance) and reduction in fracture resistance are suppressed. Therefore, the hard coating of this embodiment can exhibit high adhesion and high fracture toughness while suppressing a decrease in wear resistance, fracture resistance, and the like by having the above two-layer structure layer. . For this reason, according to the hard film of this embodiment, the tool life can be prolonged.

[2] In the hard coating, preferably, the lower layer includes crystal grains having an average particle diameter increasing from the first interface side toward the second interface, and the upper layer is directed from the second interface toward the third interface side. Crystal grains whose average grain size decreases. Thereby, it can further be excellent in the above-mentioned effect.

[3] In the preferred above hard coating, the average particle size wherein G ₁ is a 50nm or less, the average particle size G ₂ is is a 200nm or 600nm or less, the average particle size G ₃ are is at 300nm inclusive 75 nm, average particle size G ₄ is 150 nm or less. Thereby, it can further be excellent in the above-mentioned effect.

[4] In the hard coating, the ratio Tt / Tb of the upper layer thickness Tt and the lower layer thickness Tb is preferably 0.2 or more and 0.75 or less. Thereby, it can further be excellent in the above-mentioned effect.

[5] Preferably, in the hard coating, the two-layer structure layer includes one or more first elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al and Si in the periodic table; , C, N, and O. The composition is composed of one or more second elements selected from the group consisting of C, N, and O. As a result, the hardness of the hard coating can be improved, and thus the wear resistance can be improved.

[6] Preferably, in the hard coating, the two-layer structure layer has two or more kinds of first elements in its composition, and the concentrations of the two or more kinds of first elements are each periodically in the thickness direction of the upper layer. To change. As a result, strain is accumulated in the crystal grains located between the second interface and the third interface, so that the hardness of the two-layer structure layer can be increased.

[7] In the hard coating, preferably, the upper surface of the upper layer has an arithmetic average roughness Ra of 0.07 μm or less and a maximum height Rz of 0.50 μm or less. In this case, the hard coating can have excellent surface smoothness.

[8] The hard coating preferably has less than 10 irregularities having a height difference of 1 μm or more in a range of 100 μm × 100 μm on the upper surface of the upper layer of the two-layer structure layer. In this case, the hard coating can have excellent surface smoothness.

[9] A cutting tool according to one embodiment of the present disclosure includes a base material and a hard coating that covers a surface of the base material, and the hard coating is the hard coating. According to the cutting tool, the tool life can be extended and the cutting performance can be stabilized.

[10] Preferably, the cutting tool preferably has a ratio Tf / Tm of a hard coating thickness Tf covering the groove and a hard coating thickness Tm covering the margin of 0.8 to 1.5. Thereby, the tool life of the cutting tool can be further extended.

[Details of the embodiment of the present invention]
Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present embodiment is not limited thereto. Also, in this specification, those having no particular atomic ratio in chemical formulas such as “TiAlN”, “TiN”, “TiCN” do not indicate that the atomic ratio of each element is only “1”. Any conventionally known atomic ratio is not necessarily limited to the stoichiometric range.

[First Embodiment]
<Hard coating>
FIG. 1 is a schematic cross-sectional view showing an example of a configuration in which a hard coating according to the first embodiment is provided on a substrate. The cross section shown in FIG. 1 is a cross section parallel to the thickness direction of the hard coating (the vertical direction in the figure).

Referring to FIG. 1, the hard coating 100 is formed on the substrate 200. In the present embodiment, the hard coating 100 has a configuration in which the base layer 20, the two-layer structure layer 10, and the surface layer 30 are laminated on the base material 200 in this order from the base material 200 side. The hard coating 100 may not have the base layer 20 and / or the surface layer 30. The hard coating 100 may cover the entire surface of the substrate 200 or may cover only a part (for example, a region that greatly contributes to cutting performance).

As the substrate 200 on which the hard coating 100 is provided, a conventionally known substrate known as a tool substrate can be used without any particular limitation. Examples thereof include tungsten carbide (WC) based cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, and the like. In addition, the base material 200 may be integrally formed, and may be a combination of a plurality of parts.

The shape of the substrate 200 is not particularly limited, and a drill, an end mill, a drill tip changeable cutting tip, an end mill tip replacement insert, a milling throwaway tip, a turning throwaway tip, a metal saw, a gear cutting tool, Any base material used for a reamer, tap, cutting tool, wear-resistant tool, friction stir welding tool, or the like may be used. 4 and 5 illustrate the case where a drill is used as a base material.

Referring back to FIG. 1, the thickness of the hard coating 100 can be set to, for example, 0.3 to 15 μm (0.3 μm to 15 μm). When the thickness is less than 0.3 μm, it is difficult to exhibit the characteristics resulting from having the hard coating 100, and when it exceeds 15 μm, the adhesion between the substrate 200 and the hard coating 100 tends to be reduced.

The thickness of the hard coating 100 is obtained as follows. First, a measurement sample including a cross section of the hard coating 100 is prepared. This measurement sample is obtained, for example, by cutting the substrate 200 provided with the hard coating 100 along the thickness direction of the hard coating 100 (so that a cross section substantially perpendicular to the hard coating 100 is obtained). If necessary, the cross section of the hard coating 100 is polished and smoothed. Next, the cross section is observed with a scanning electron microscope (SEM), and the magnification is adjusted (for example, about 15000 times) so that the entire area of the hard coating 100 in the thickness direction is included in the observed image. And the thickness is measured at five or more points, and the calculated average value is taken as the thickness. In addition, the thickness of each layer mentioned later is calculated | required similarly.

<Double layer structure layer>
FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the two-layer structure layer according to the first embodiment. The cross section shown in FIG. 2 is a cross section parallel to the thickness direction of the hard coating (the vertical direction in the figure).

Referring to FIG. 2, the two-layer structure layer 10 has a two-layer structure in which a lower layer 1 and an upper layer 2 are laminated in order from the substrate 200 side. This two-layer structure layer is a layer produced by the characteristic HiPIMS method described later.

The two-layer structure layer 10 has three interfaces (first interface to third interface). In this specification, the lower surface (position A in FIG. 2) of the lower layer 1 constituting the lower end surface (the surface in contact with the base layer 20 in FIG. 1) located on the substrate 200 side in the two-layer structure layer 10. , The first interface. The interface (position B in FIG. 2) between the upper surface of the lower layer 1 and the lower surface of the upper layer 2 is the second interface. The upper surface (position C in FIG. 2) of the upper layer 2 constituting the upper end surface opposite to the lower end surface (the surface in contact with the surface layer 30 in FIG. 1) of the two-layer structure layer 10 is the third interface.

As can be seen from FIG. 2, the first interface is an interface formed by contact between the base layer 20 (the base material 200 when the base layer 20 is not provided) and the lower layer 1, and the third interface is the surface. This is an interface formed by contacting the upper layer 2 with the layer 30 (the air layer or the outside when the surface layer 30 is not provided). That is, the first interface and the third interface coincide with the surface of the two-layer structure layer 10. On the other hand, the second interface is an interface existing inside the two-layer structure layer 10. The position of each interface can be confirmed by observing the cross section of the two-layer structure layer 10 using TEM or SEM. In addition, when using SEM, it is preferable to carry out the ion milling process for the cross section for accurate observation. In addition, it is desirable to observe with an acceleration voltage as low as about 5 kV.

The two-layer structure layer 10 includes a plurality of crystal grains. That is, the two-layer structure layer 10 has a polycrystalline structure. In particular, when a cross section parallel to the thickness direction of the two-layer structure layer 10 is observed, the average grain size G ₁ of the crystal grains at a position 100 nm away from the first interface toward the second interface side, The average grain size G ₂ of crystal grains at a position 100 nm away from one interface side, the average grain size G ₃ of crystal grains at a position 100 nm away from the second interface toward the third interface side, and the third interface The average grain size G ₄ of the crystal grains satisfies the relational expression of G ₂ > G ₃ > G ₄ > G ₁ .

The average particle diameters G ₁ to G ₄ are determined as follows. First, a measurement sample including a cross section of the two-layer structure layer 10 is prepared. This measurement sample is obtained, for example, by cutting the base material 200 provided with the hard coating 100 along the thickness direction of the hard coating 100 (so that a cross section substantially perpendicular to the two-layer structure layer 10 is obtained). . If necessary, the cross section of the two-layer structure layer 10 is polished and smoothed. Next, the cross-section is observed with a TEM, and the magnification is adjusted so that at least the entire region of the two-layer structure layer 10 is included in the observation image (for example, about 20000 to 50000 times), and the first interface, the second interface, and the third interface are adjusted. The interface (positions A to C in FIG. 2) is specified.

Subsequently, by adjusting the magnification of the TEM (for example, about 200,000 to 500,000 times), a BF (Bright Field) image including a position P ₁ 100 nm away from the first interface toward the second interface side, from the second interface A BF image including a position P ₂ separated by 100 nm toward the first interface side, a BF image including a position P ₃ separated by 100 nm from the second interface toward the third interface side, and a BF including a third interface Take multiple images of each. From these photographed BF images, the widths of all the crystal grains that were clearly confirmed to be one crystal grain at each of the positions P ₁ to P ₃ and the third interface were measured, The grain size of the crystal grains.

Finally, the average value of the measured crystal grain sizes is calculated for each of the positions P ₁ to P ₃ and the third interface, and is set as the average grain size G ₁ to G ₄ .

The hard coating 100 of the present embodiment can extend the tool life by having the above-described two-layer structure layer 10. The reason for this will be described below, including inferences based on the research of the present inventors.

When the cross-section parallel to the thickness direction of the two-layer structure layer 10 is observed, the average particle diameters G ₁ to G ₄ at the position P ₁ , position P ₂ , position P ₃ and the third interface are G ₂ > G The relational expression ₃ > G ₄ > G ₁ is satisfied. That is, the two-layer structure layer 10 has a relatively small average particle size in the vicinity of the first interface and the third interface, and has a relatively large average particle size in the vicinity of the second interface. Since the grain structure at the first interface in contact with the underlayer 20 is dense, the adhesion between the two-layer structure layer 10 and the underlayer 20 is improved. Further, the third interface is the outermost surface of the two-layer structure layer 10 and is the portion that is most loaded during cutting in the two-layer structure layer 10, but the two-layer structure is formed by the dense grain structure on this surface. The fracture toughness of the structural layer 10 is improved.

Here, if the third interface side of the two-layer structure layer 10 is simply composed of fine granular crystals having a uniform and small particle size, the two-layer structure is caused due to the film forming environment for forming such a layer. The layer will have a high compressive residual stress. In this case, the two-layer structure layer is easily peeled off, and there is a concern about the occurrence of abnormal wear. Also, if the two-layer structure layer is simply composed of uniform and large granular crystals, there is a concern that the adhesion on the first interface side and the fracture toughness on the third interface side will be reduced. Further, if the two-layer structure layer is a normal columnar crystal, that is, a columnar crystal having a uniform grain size in the growth direction, there is a concern that the chipping resistance may be reduced due to dropping of the columnar crystal.

On the other hand, the two-layer structure layer 10 is different from any of the above-described structures, and the average grain sizes G ₁ to G _{4 of the} crystal grains contained therein are such that G ₂ > G ₃ > G ₄ > G ₁ . It has a characteristic configuration that satisfies the relational expression. Due to such a change in average grain size, in addition to excellent adhesion on the first interface side and excellent fracture toughness and smoothness on the third interface side, dropout of crystal grains is suppressed by a mechanical action.

Therefore, the hard coating 100 including the two-layer structure layer 10 can exhibit high adhesion and high fracture toughness while suppressing a decrease in wear resistance and fracture resistance. For this reason, according to the hard coating 100 of this embodiment, the tool life can be prolonged.

In the present embodiment, as shown in FIG. 2, the lower layer 1 includes crystal grains 3 whose average grain size increases from the first interface side toward the second interface side, and the upper layer 2 includes the second layer 2. It is preferable to include crystal grains 4 whose average particle diameter decreases from the interface toward the third interface. Thereby, since said mechanical effect | action is exhibited suitably, higher adhesiveness and higher fracture toughness can be exhibited.

In the present embodiment, the average particle diameters G ₁ to G ₄ preferably satisfy the following. In this case, the hard coating 100 can be further excellent in the above-described effects.
Average particle diameter G ₁ : 50 nm or less Average particle diameter G ₂ : 200 to 600 nm
Average particle size G ₃ : 75 to 300 nm
Average particle size G ₄ : 150 nm or less.

The average particle diameter G ₁ is more preferably 40 nm or less, further preferably 30 nm or less, and still more preferably 20 nm or less. The average particle size G ₂ is more preferably 230 to 400 nm, further preferably 260 to 340 nm, and still more preferably 280 to 300 nm. The average particle size G ₃ is more preferably 100 to 200 nm, still more preferably 120 to 160 nm. The average particle size G ₄ is more preferably 85 nm or less, and even more preferably 60 nm or less.

The lower limit of the average particle size G ₁ is not particularly limited, but when the particle size is very small, it becomes difficult to maintain the denseness of the interface, and is particularly preferably 5 nm from the viewpoint of production quality. Is 10 nm, more preferably 15 nm. The lower limit of the average particle size G ₄ is not particularly limited, but is preferably 20 nm, and more preferably 30 nm. Thereby, the fall of the abrasion resistance in a 3rd interface can be suppressed.

In the present embodiment, the thickness of the two-layer structure layer 10 is preferably 0.3 μm or more. If it is less than 0.3 μm, the tool life tends to be insufficient. This is considered to be because if the thickness is too small, it is difficult to bring about the change in the average particle diameter as described above in the two-layer structure layer 10. The thickness of the two-layer structure layer 10 is preferably 10 μm or less. When exceeding 10 micrometers, there exists a tendency for the chipping resistance of the two-layer structure layer 10 to fall. This is presumably because if the thickness of the two-layer structure layer 10 is too large, the compressive residual stress in the layer becomes too large, and the adhesion between the underlayer or base material and the two-layer structure layer 10 is reduced. . The thickness of the two-layer structure layer 10 is more preferably 0.45 to 9.0 μm, further preferably 0.9 to 8.8 μm, and particularly preferably 1 to 7 μm.

In this embodiment, the ratio Tt / Tb between the thickness Tt of the upper layer 2 and the thickness Tb of the lower layer 1 is preferably 0.2 to 0.75. As a result of studies by the present inventors, it has been confirmed that when the ratio Tt / Tb satisfies this ratio, the above-described effects can be appropriately exhibited. One of the reasons is as follows.

In the manufacturing method described later, the lower layer 1 and the upper layer 2 tend to have compressive residual stress, and the compressive residual stress in the lower layer 1 tends to be smaller than the compressive residual stress in the upper layer 2. If the compressive residual stress in the entire two-layer structure layer 10 is too large, peeling of the two-layer structure layer 10 is a concern, but if the ratio Tt / Tb satisfies the above range, an excessive increase in compressive residual stress is suppressed. Therefore, the occurrence of peeling can be suppressed. The ratio Tt / Tb is more preferably 0.2 to 0.5.

Note that “compressive residual stress” is a kind of internal stress (strain energy) existing in a layer, and is represented by a numerical value of “−” (minus). For this reason, the concept that the compressive residual stress is large means that the absolute value of the numerical value is large, and the concept that the compressive residual stress is small means that the absolute value of the numerical value is small.

In this embodiment, the upper surface of the upper layer 2 preferably has an arithmetic average roughness Ra of 0.07 μm or less and a maximum height Rz of 0.50 μm or less. For example, when such a smooth surface constitutes the outermost surface of the hard coating 100 (a surface that contacts the work material), the cutting resistance can be remarkably suppressed, so that abnormal wear can be suppressed. Thus, the tool life can be stabilized. In particular, when such a hard coating 100 is used for a rotary tool such as a drill and an end mill, the chip discharging property can be improved.

The above Ra and Rz are defined in JIS B 0601 (2001) and ISO 4287 (1997). These values can be obtained by measuring the surface of the two-layer structure layer 10 under the following measurement conditions using a shape measurement laser microscope (“VK-X110”, manufactured by Keyence Corporation). Note that it is preferable to perform image processing with a tilt correction function before measurement.

(Measurement conditions)
Magnification: 100 times Function used: Multi-line roughness Multi-line setting: 10 surroundings, 20 thinning cut-off λs: 2.5 μm
Cut-off λc: 0.25 mm
Stylus mode: On-stylus tip angle: 60 °
Stylus tip radius: 2 μm
Noise filter: None.

The Ra and the Rz are more preferably 0.061 μm or less and 0.47 μm or less, respectively, and more preferably 0.05 μm or less and 0.40 μm or less. For example, two layers having such a highly smooth surface (upper surface of the upper layer 2) can be obtained by performing various processes such as increasing the frequency of blasting of each part of the apparatus used for manufacturing the two-layer structure layer 10. The structural layer 10 can be manufactured. The Ra and Rz values can also be reduced by controlling the average particle size G ₄ at the third interface to be small.

In addition, it is difficult to manufacture a hard film with high surface smoothness as described above by the AIP method. This is because droplets exist in the hard coating formed by the AIP method. Surface smoothness can be improved to some extent by performing post-treatment such as polishing on the surface of the hard film formed by the AIP method, but in this case as well, the above high smoothness is imparted. It is difficult. In other words, according to the two-layer structure layer 10 of the present embodiment, excellent smoothness can be exhibited without performing post-treatment such as polishing.

Further, with respect to the upper surface of the upper layer 2 of the two-layer structure layer 10, the number of irregularities (total number of concave portions and convex portions) having a height difference of 1 μm or more in the range of 100 μm × 100 μm is preferably less than ten. For example, when such a smooth surface constitutes the outermost surface of the hard coating 100 (a surface in contact with the work material), the cutting resistance during cutting can be remarkably suppressed, so abnormal wear is prevented. Therefore, the tool life can be stabilized. It is the same as described above that it is particularly suitable for rotary tools such as drills and end mills.

The number of irregularities can be obtained as follows. First, the surface (100 μm × 100 μm) of the two-layer structure layer 10 is observed at a magnification of 100 times by using a shape measurement laser microscope (“VK-X110”, manufactured by Keyence Corporation) and using the concavo-convex portion function. At this time, image processing of the observed image is performed using the tilt correction function, the height threshold is set to the size of “distribution average ± unevenness having a height difference to be measured”, and the number of target unevennesses is measured. To do. For example, in order to measure unevenness with a height difference of 1 μm or more, first, the convex mode is selected and the height threshold is set to “average value + 1 μm”, then the concave threshold mode is changed and the height threshold is set to “average” Set the value to “-1 μm” and measure. Thereby, the number of irregularities having a height difference of 1 μm or more is required. Note that a minute region of 100 pixels or less is set not to be measured.

The number of the irregularities is more preferably 5 or less, further preferably 3 or less, and particularly preferably 0. For example, the two-layer structure layer 10 having such a highly smooth surface is manufactured by performing various processes such as increasing the frequency of the blast process of each part of the apparatus used for manufacturing the two-layer structure layer 10. Can do. As described above, it is difficult to produce such a hard film with high surface smoothness by the AIP method.

Further, with respect to the upper surface of the two-layer structure layer 10, the number of irregularities having a height difference of 0.5 μm or more in the range of 100 μm × 100 μm is preferably 10 or less, more preferably 2 or less, and still more preferably Is 1 or less, particularly preferably 0. Similarly, the number of irregularities having a height difference of 0.3 μm or more is preferably 10 or less, more preferably 5 or less, further preferably 2 or less, and particularly preferably 0. . The number of these irregularities can also be determined according to the above method.

In the present embodiment, the two-layer structure layer 10 includes a group 4 element (Ti, Zr, Hf, etc.), a group 5 element (V, Nb, Ta, etc.), a group 6 element (Cr, Mo, W, etc.) of the periodic table. ), One or more first elements selected from the group consisting of Al and Si, and one or more second elements selected from the group consisting of B, C, N and O.

Specific examples of the composition of the two-layer structure layer 10 include TiAlN, TiCrN, TiAlCrN, TiN, CrN, AlCrN, AlCrSiN, TiSiN, and TiCN. Especially, it is preferable that the two-layer structure layer 10 has a composition which used Ti and Al as the 1st element. This is because it can be particularly excellent in oxidation resistance and hardness.

In particular, the composition of the two-layer structure layer 10 is preferably Ti _1-x Al _x N (0.45 ≦ x ≦ 0.7). This is because it has an excellent balance between hardness at high temperature and oxidation resistance, and therefore has high versatility. Furthermore, the two-layer structure layer 10 having a composition satisfying Ti _1-x Al _x N (0.45 ≦ x ≦ 0.7) has at least one selected from the group consisting of Si, Nb, W, B, and O. It is preferable that seed elements (however, the concentration of each element in the two-layer structure layer 10 is 1 to 5 atomic%) are added. By adding such an element, it is possible to improve the wear resistance by further improving the hardness. The composition of the two-layer structure layer 10 can be confirmed by observing the cross section of the two-layer structure layer 10 with EDS.

<Underlayer and surface layer>
As each of the foundation layer 20 and the surface layer 30, a known layer can be used without particular limitation as a layer provided on the base material surface of a conventional tool.

<Method for producing hard coating>
When the hard coating 100 has the base layer 20 and / or the surface layer 30, these layers can be manufactured by a conventionally well-known manufacturing method. Hereinafter, a manufacturing method of the two-layer structure layer 10 that can be manufactured for the first time by a characteristic manufacturing method using the HiPIMS method will be described with reference to FIG. Here, the case where the two-layer structure layer 10 made of TiAlN is formed on the surface of the substrate 200 will be described as an example.

FIG. 3 is a schematic diagram showing an arrangement state of the base material in the chamber of the HiPIMS apparatus when the two-layer structure layer is manufactured. The HiPIMS apparatus is a HiPIMS apparatus capable of performing the HiPIMS method. Referring to FIG. 3, a target 50 serving as a raw material for the two-layer structure layer 10 is disposed in a chamber (not shown). 3 shows two targets 50, the number of targets 50 is not particularly limited.

A table 51 that is rotatable in the direction of the arrow in the figure is arranged between the plurality of targets 50 arranged in the chamber. The table 51 is supported on the table 51 by a rotating shaft 52 and is indicated by the arrow in the figure. A plurality of substrate holders 53 that can rotate in the direction are arranged. A plurality of base materials 200 are placed on the base material holder 53. The substrate 200 can also be rotated by itself. The number of rotating shafts 52 and the number of substrate holders 53 are not limited to those shown in FIG. Further, a heater (not shown) that can heat the substrate 200 is disposed in the chamber.

The target 50 is connected to a negative electrode of a pulse power source for supplying pulse power. The positive electrode of the short pulse power supply is grounded (not shown). The table 51 is electrically connected to a negative electrode of a bias power source (not shown) for applying a bias voltage. The positive electrode of the bias power source is grounded (not shown). As the bias power source, DC (direct current), pulse DC, RF (high frequency), MF (medium wave number), HiPIMS, or the like can be used.

When manufacturing the two-layer structure layer 10, first, as shown in FIG. 3, the base material 200 is arranged in the chamber and the target 50 is arranged. Each target 50 has the same composition. For example, as the target 50, a polycrystal having a composition of Ti _0.5 Al _0.5 can be used. Then, the chamber is evacuated and inert gas (Ar) and nitrogen gas are introduced. In addition, a bias voltage is applied to the table 51 via a bias power source, and pulse power is supplied to the target 50 via a pulse power source to perform the film forming operation of the HiPIMS apparatus (first step). The film forming conditions in the first step are as follows.

(Film forming conditions for the first step)
Bias voltage: 0 to 50 (-V)
Pulse power: 30-60kW
Average power: 6-8kW (per target)
Pulse width: 10 to 150 μs
Power density: 170-340 W / cm ² (per target)
Ar partial pressure: 1 Pa or less N ₂ partial pressure: Control to form a film in a transition mode.

Thereby, plasma 60 is generated in the chamber, and ions collide with the target 50, whereby metal atoms and / or metal ions are released from the target 50 and adhere to the surface of the substrate 200 together with nitrogen atoms. By this first step, the lower layer 1 is formed.

Next, the film forming operation of the HiPIMS apparatus is performed under the following film forming conditions (second step). By this second step, the upper layer 2 is formed. From the viewpoint of manufacturing cost, cleanliness of the two-layer structure layer 10 and the like, it is preferable that the first step and the second step are performed continuously.

(Deposition conditions for the second step)
Bias voltage: 100 to 200 (-V)
Pulse power: 30-60kW
Average power: 3-5 kW (per target)
Pulse width: 100 to 500 μs
Power density: 170-340 W / cm ² (per target)
Ar partial pressure: 1 Pa or less N ₂ partial pressure: Control to form a film in a transition mode.

As described above, the two-layer structure layer 10 made of the lower layer 1 and the upper layer 2 and having the composition TiAlN is manufactured. In each film forming condition, “power density” is a value obtained by dividing the maximum value of pulse power by the total area of the surface on which the target is sputtered.

As is clear from the comparison between the film forming conditions in the first step and the film forming conditions in the second step, the characteristic point in the above manufacturing method is that the pulse power in both steps is optimized and then the first step. The pulse width, average power, and bias voltage are different from the pulse width, average power, and bias voltage in the second step. Thereby, the two-layer structure layer 10 having the above-described characteristics is formed. Although the reason is not clear, it is guessed as follows based on examination of the present inventors.

Under the film forming conditions in the first step, the amount of ions and / or atoms reaching the substrate 200 is relatively large, 2.7 to 4.0 pieces · cm ⁻² · s ^−1. The pulse power and average power are adjusted. The appropriate values of the pulse power and the average power vary depending on the material. For this reason, the generation density of crystal nuclei on the surface of the substrate 200 is increased. However, at this time, if the bombardment to the growth surface (energy given to the growth surface due to ion bombardment) is large, the crystal nuclei coalesce and the crystal nuclei that become the basis of crystal growth become large. . For this reason, the average grain size in the vicinity of the position A (FIG. 2) becomes large, and as a result, it becomes difficult to form a dense crystal grain structure having an appropriate adhesion force in the vicinity of the position A.

However, the bias voltage in the first step is as small as 0 to 50 (-V). In this case, the bombardment by ions and / or atoms with respect to the surface of the substrate 200 is reduced. For this reason, the average grain size in the vicinity of the position A can be reduced, and as a result, a dense crystal grain structure having excellent adhesion in the vicinity of the position A can be formed.

Also, since the bombardment in the first step is small, the compressive residual stress in the crystal grain structure is small. Further, the compressive residual stress in the crystal grain structure is relieved at the timing when the pulse power is not supplied to the target 50. Due to these synergistic effects, the compressive residual stress applied in the first step becomes sufficiently small, so that the fine crystal grains grow competitively. For this reason, the average grain size of crystal grains increases from position A to position B (FIG. 2).

On the other hand, in the second step, the amount of ions and / or atoms reaching the substrate 200 decreases, the pulse width increases, and the bias voltage increases to 100 to 200 (−V). In this case, the bombardment with respect to the growth surface in the vicinity of the position B becomes large. For this reason, the crystal grains growing from the position B grow while being exposed to etching by ion bombardment. Thereby, the growth rate of the crystal grains in the second step becomes smaller than the growth rate of the crystal grains in the first step, and the average grain size gradually decreases. For this reason, the average grain diameter of crystal grains decreases from position B to position C. Further, by optimizing the amount of ions and / or atoms that reach the substrate 200, the crystal grain structure can be made dense in the vicinity of the position C, and in addition, a synergistic effect by light etching can be used. It is also possible to improve the smoothness of the surface shape.

Regarding the film forming conditions in the first step and the second step, more preferable values are as follows. The range described on the left side (the former) is a more preferable range, and the range described on the right side (the rear) is a more preferable range.
Bias voltage (first step): 10 to 40, 20 to 30 (-V)
Bias voltage (second step): 100 to 175, 100 to 140 (-V)
Pulse power (first step): 40 to 55, 45 to 50 kW
Pulse power (second process): 45-60, 50-60 kW
Pulse width (first step): 50 to 150, 75 to 120 μs
Pulse width (second step): 200 to 400, 250 to 350 μs
Power density (first step): 226 to 311, 255 to 283 W / cm ²
Power density (second step): 255 to 340, 283 to 340 W / cm ²
Average power (first step): 6.5 to 8.0, 7.0 to 8.0 kW Average power (second step): 3.5 to 4.5, 3.5 to 4.0 kW.

As mentioned above, although the manufacturing method of the two-layer structure layer 10 was explained in full detail, even if it uses methods other than HiPIMS method, it is difficult to manufacture the two-layer structure layer 10. For example, when the AIP method is used, there is no timing at which power is not supplied to the target, and hence the above-described relaxation of the residual compressive stress does not occur. Also, the amount of ions and / or atoms that reach the substrate tends to be significantly greater than in the HiPIMS method. For this reason, when a film is formed with a small bias voltage, crystal nuclei in the initial stage of film formation cannot be reduced. Further, when the film is formed with a large bias voltage so as to obtain a dense film, the average particle diameter of the crystal grains cannot be gradually increased because the bombardment is too large.

Also, when the sputtering method is used, the ionization rate necessary for adjusting the bombardment cannot be achieved. In addition, when a film is formed with a small bias voltage, crystal nuclei at the initial stage of film formation cannot be reduced. When the film is formed with a small bias voltage, it is difficult to maintain the denseness.

In addition, when the CVD method is used, a tensile residual stress is applied to the layer to be deposited, so that a crystal grain whose average grain size decreases from position B to position C is intentionally grown. It is thought that it cannot be made.

[Second Embodiment]
<Hard coating>
The hard coating of this embodiment is the same as the hard coating of the first embodiment except that the composition of the upper layer of the two-layer structure layer changes periodically. Hereinafter, differences from the first embodiment will be described in detail.

Referring to FIG. 2, the two-layer structure layer 10 included in the hard coating 100 of the present embodiment has two or more first elements in its composition. Then, in the thickness direction of the upper layer 2, the concentrations of the two or more first elements periodically change. Such periodic changes in composition (types of constituent elements and constituent ratios of constituent elements) can be confirmed using TEM or TEM-attached EDS.

Here, “periodically changing” means that when the increase and decrease of the concentration of the first element, which is continuous in the growth direction (vertical direction in the figure) of the two-layer structure layer 10, is one set of periods, It means that there are at least one set of periods in the thickness direction of the layer 2. For example, when the composition of the entire two-layer structure layer 10 is Ti _1-x Al _x N, the concentration of Al, which is the first element, continuously increases and decreases in the thickness direction of the upper layer 2. As the Al concentration changes, the concentration of Ti, which is another first element, also continuously increases and decreases. The concentration of the first element can periodically change so as to draw a shape such as a sine wave when the vertical axis is the concentration and the thickness direction of the upper layer 2 is the vertical direction in the drawing.

When it has a structure in which the concentration of the first element periodically changes in the thickness direction of the upper layer 2, moderate strain is accumulated in the crystal grains of the upper layer 2. For this reason, such a crystal grain can have higher hardness compared with the case where there is no periodic change of a composition.

The upper layer 2 having such a feature can be obtained by appropriately adjusting the bias voltage, the pulse power, and the average power among the various film forming conditions in the second step described above. By adjusting these conditions as appropriate, one of the reasons why the upper layer 2 has the above structure is presumed.

The upper layer 2 is a region that grows while being exposed to etching by ion bombardment as described above. In the chamber of the HiPIMS apparatus, the distance between the target 50 and the base material 200 changes periodically as the table 51 rotates. For this reason, in the second step, there are periodically a timing at which the upper layer 2 grown on the base material 200 is easily etched (a timing when it is difficult to grow) and a timing at which it is difficult to etch (a timing when it is easy to grow). It becomes. For example, when the upper layer 2 made of TiAlN is grown, Ti and Al are easily etched, and Al is more easily etched. That is, at the timing at which etching is easy, both Ti and Al are etched, but Al is etched more.

Therefore, in the upper layer 2, the Al concentration is low in a region formed at a timing that is easily etched (Ti concentration is high), and the Al concentration is high in a region that is formed at a timing that is difficult to etch. (Ti concentration decreases). Therefore, as a result, the concentrations of Ti and Al in the growing crystal grains change periodically.

The upper layer 2 of the present embodiment formed in this way has higher adhesion between the layers than a conventional super multi-layer structure manufactured using two types of targets having different compositions. For this reason, delamination does not occur easily in the upper layer 2, and therefore it can have higher fracture toughness than the conventional super multi-layer structure.

In the two-layer structure layer 10 of the present embodiment described in detail above, the thickness of the period (one set) in the upper layer 2 is preferably 1 to 10 nm. In this case, since the magnitude of strain accumulated in the crystal grains of the upper layer 2 is suitable, the two-layer structure layer 10 is further excellent in hardness. The thickness of the period is more preferably 4 to 8 nm.

Cycle thickness is measured as follows. First, a cross-sectional sample of the two-layer structure layer 10 is obtained, and the cross-section is analyzed using a TEM-attached energy dispersive X-ray analysis (EDX) apparatus. Thereby, the atomic ratio of the first element in the cross section can be calculated. And the distance of the position where the density | concentration of arbitrary 1st elements becomes the maximum and the position where it becomes the minimum is measured in 10 places, and let this average value be the thickness of a period.

Further, when the total atomic ratio of two or more first elements constituting the composition of the two-layer structure layer 10 is 1, the ratio of at least one first element in the thickness direction of the upper layer 2 is 0. It is preferable that the fluctuation periodically occurs in the range of 2 to 0.7, and the difference between the maximum value and the minimum value of the first element is 0.2 to 0.5. In this case, the above-described distortion can be accumulated while maintaining excellent adhesion, and thus the hardness (abrasion resistance) is excellent. Among these, when Ti and Al are contained in two or more kinds of first elements constituting the two-layer structure layer 10, this effect becomes remarkable.

In particular, when the composition of the two-layer structure layer 10 is TiAlN, the composition in the thickness direction of the upper layer 2 changes from Ti _1-x Al _x N (0.4 <x ≦ 0.7) to Ti _{1− y} Al _y N (0.2 ≦ y ≦ 0.4) is continuously changed, and the difference between the maximum value of Al and the minimum value of Al is 0.2 to 0.4. Preferably there is. In this case, the fracture resistance (fracture toughness) is remarkably excellent. In this case, the composition of the lower layer 1 is preferably Ti _1-z Al _z N (0.45 ≦ z ≦ 0.7). It is because it is excellent in abrasion resistance and oxidation resistance.

[Third Embodiment]
<Cutting tools>
FIG. 4 is a schematic plan view showing an example of a cutting tool according to the third embodiment. 5 is a cross-sectional view taken along the line XX shown in FIG. In the present embodiment, a two-blade drill is exemplified.

Referring to FIG. 4, the cutting tool 70 has a structure composed of a body 71 and a shank 72. The body 71 has an outer peripheral blade portion 73 and a groove portion 74. Referring to FIG. 5, outer peripheral blade portion 73 has a margin 73a. The cutting tool 70 includes a base material 81 and a hard coating 82 that covers the surface of the base material 81. The entire surface of the substrate 81 may be covered with the hard coating 82, or a part of the substrate 81 may be covered.

In the present embodiment, a drill is exemplified as the cutting tool 70 which is one of the rotary tools, but an end mill can be used in addition to the drill. That is, the rotary tool includes a base material 81 having a margin 73a with no clearance angle with respect to the work material, a groove portion 74 for flowing out chips, and a hard coating 82. A suitable cutting tool 70 is a drill.

The base material 81 is the base material 200 described above, and the hard coating 82 is at least one of the hard coating 100 according to the first embodiment and the hard coating 100 according to the second embodiment. For this reason, the cutting tool 70 can exhibit the effect of the hard coating 100, and can thus have a long tool life. In the cutting tool 70, it is preferable that the hard coating 100 is provided at least on the surface of the margin 73a. This is because the effect of the hard coating 100 is appropriately exhibited. In particular, as shown in FIG. 5, it is preferable that a hard coating 100 is provided on the entire surface of the body 71.

In addition, it can confirm that the cutting tool 70 has the hard film 100 as follows. First, a cross section of the cutting tool 70 (for example, the cross section shown in FIG. 5) is prepared, and the cutting tool 70 is embedded in resin so that the cross section is exposed on the surface. Next, after polishing the exposed cross section as necessary, the cross section is observed using an SEM.

In the cutting tool 70 of the present embodiment, the ratio Tf / Tm between the thickness Tf of the hard coating 100 covering the groove 74 and the thickness Tm of the hard coating 100 covering the margin 73a is 0.8 to 1.5. It is preferable. The reason is as follows.

Conventionally, when a hard coating is provided on the surface of the substrate 81 by the AIP method or the like, the smoothness of the surface has not been sufficient due to the presence of drop red. For this reason, in order to reduce cutting resistance, there also exists an example which grind | polishes with respect to the surface of the formed hard film. However, these post-treatments remove more of the hard coating 100 on the margin 73a than the hard coating 100 on the groove 74 due to the nature of the treatment.

For this reason, in the cutting tool after the post-treatment, the thickness Tf of the hard coating 100 that covers the groove 74 and the thickness Tm of the hard coating 100 that covers the margin 73a are compared with the cutting tool before the post-processing. There was a tendency for the ratio Tf / Tm to increase. The hard coating 100 on the margin 73a is greatly related to the cutting performance, and is particularly a portion where damage such as wear and chipping is likely to occur. For this reason, if the thickness Tm of the hard coating 100 in this portion is too small compared to the thickness Tf, the tool life and the tool performance are lowered.

On the other hand, since the two-layer structure layer 10 can have a smooth surface as described above, the hard coating 100 can also have a smooth outermost surface. Therefore, when such a hard coating 100 is provided on the surface of the base material 81, it is not necessary to perform the post-treatment as described above, and therefore the ratio Tf / Tm in the cutting tool obtained as the final product is relatively high. Can be small.

That is, the hard coating 100 according to the present embodiment is difficult to manufacture by the AIP method in which the ratio Tf / Tm is relatively small, 0.8 to 1.5, and the surface smoothness is sufficiently high. It can have the mode which was. The hard coating 100 having such an aspect synergistically combines the characteristics of a long tool life due to a relatively small ratio Tf / Tm and a reduction in cutting resistance due to a smooth surface. It can be demonstrated.

Tf and Tm are determined as follows. In FIG. 6, a circle S is a virtual circle that includes a cross section of the body 71 and is drawn by connecting the leading ends 73aa of the margin 73a, and the diameter thereof is D. The circle S1 is a virtual circle whose center point is the contact point between the tip 73aa of the margin 73a and the circle S and whose radius D1 is 1 / 10D. The line L1 is a virtual line connecting the tip 73aa and the center point P of the circle S. The line L2 is a virtual line that connects the back end 73b of the land width and the center point P of the circle S. The line L3 is a virtual line that equally divides the angle 2α formed by the line L1 and the line L2. The circle S2 is a virtual circle whose center point is the contact point between the line L3 and the outer periphery of the body 71 and whose radius D2 is 1 / 10D.

The thickness Tm of the hard coating 100 covering the margin 73a is the thickness of the hard coating 100 on the margin 73a located in the circle S1, and is an average value of measured values at at least five arbitrary points. The thickness Tf of the hard coating 100 covering the groove 74 is the thickness of the hard coating 100 on the groove 74 located in the circle S2, and is an average value of measured values at at least five arbitrary points.

[Fourth Embodiment]
<Cutting tools>
FIG. 7 is a schematic perspective view showing an example of a cutting tool according to the fourth embodiment. FIG. 8 is a diagram showing a hatched portion in FIG. 7, and is a cross-sectional perspective view showing a Y region. In this embodiment, a throw-away tip is exemplified.

Referring to FIG. 7, the cutting tool 90 has a surface including an upper surface, a lower surface, and four side surfaces, and has a rectangular column shape that is slightly thin in the vertical direction as a whole. Further, the cutting tool 90 is formed with a through-hole penetrating the upper and lower surfaces, and in the boundary portion of the four side surfaces of the cutting tool 90, adjacent side surfaces are connected by an arc surface.

In the cutting tool 90 of the present embodiment, the upper surface and the lower surface form a rake face 91, and the four side faces (and the arc surface connecting them) form a flank face 92. Further, the boundary portion between the rake face 91 and the flank face 92 functions as the cutting edge 93. In other words, the cutting tool 90 of the present embodiment has a surface (upper surface, lower surface, four side surfaces, an arc surface connecting these side surfaces, and an inner peripheral surface of the through hole), and the surface is a rake surface 91 and a clearance. The rake face 91 and a part (boundary portion) of the flank face 92 including the face 92 form a cutting edge 93.

Referring to FIG. 8, the cutting tool 90 includes a base 94 and a hard coating 95 that covers the surface of the base 94. The entire surface of the substrate 94 may be covered with the hard coating 95, or a part of the substrate 94 may be covered.

The substrate 94 is the above-described substrate 200, and the hard coating 95 is at least one of the hard coating 100 according to the first embodiment and the hard coating 100 according to the second embodiment. For this reason, the cutting tool 90 can exhibit the effect of the hard coating 100, and can thus have a long tool life. In the cutting tool 90, it is preferable that the hard coating 100 is provided at least in a portion that contacts the work material and a portion that contacts the chips.

Here, the cutting edge 93 is the “boundary portion of the rake face 91 and the flank 92” as described above, which is “the ridge line that forms the boundary between the rake face 91 and the flank 92, the rake face 91 and the flank face”. The part which combined the part which becomes a ridgeline part in 92 "is meant. The region of the cutting edge 93 defined in this way is determined by the shape of the cutting edge 93 of the cutting tool 90. The area of the cutting edge 93 of each shape is shown in FIGS.

FIG. 8 shows a cutting tool 90 having a sharp edge shape. In such a sharp edge-shaped cutting tool 90, “the ridge line forming the boundary between the rake face 91 and the flank 92” corresponds to the ridge line E in the drawing. Further, “the portion of the rake face 91 and the flank 92 near the ridge line E” is an area where the distance (straight line distance) D from the ridge line E is 100 μm or less (in FIG. 8, a region where point hatching is performed). Defined. Therefore, for example, the cutting edge 93 located on the flank 92 side in the cutting tool 90 having a sharp edge shape is a portion corresponding to a region that is located on the flank 92 side in FIG.

FIG. 9 shows a cutting tool 90 having a honing shape. In FIG. 9, in addition to each part of the cutting tool 90, a virtual plane R including a rake face 91, a virtual plane F including a flank 92, a virtual ridge line EE formed by intersecting the virtual plane R and the virtual plane F, and a rake face A virtual boundary line ER serving as a boundary of the divergence between 91 and the virtual plane R and a virtual boundary line EF serving as a boundary between the flank 92 and the virtual plane F are illustrated. In the honing-shaped cutting tool 90, the “ridge line E” is read as “virtual ridge line EE”.

In such a honing-shaped cutting tool 90, “the portion of the rake face 91 and the flank 92 near the virtual ridge line EE” is a region sandwiched between the virtual boundary line ER and the virtual boundary line EF (in FIG. The area to be hatched). Therefore, referring to FIG. 9, the cutting edge 93 in the honing-shaped cutting tool 90 is located on the flank 92 side and is subjected to the point hatching, the rake face 91 side, and the point hatching. This is a region that is combined with the region to which is applied.

FIG. 10 shows a negative land-shaped cutting tool 90. Also in FIG. 10, the virtual plane R including the rake face 91, the virtual plane F including the flank 92, the virtual ridge line EE formed by the intersection of the virtual plane R and the virtual plane F, and the divergence between the rake face 91 and the virtual plane R. A virtual boundary line ER serving as a boundary of the virtual boundary line EF and a virtual boundary line EF serving as a boundary between the flank 92 and the virtual plane F are illustrated. In the negative land-shaped cutting tool 90, the “ridge line E” is read as “virtual edge line EE”.

In such a negative-land-shaped cutting tool 90, “the portion of the rake face 91 and the flank 92 that is in the vicinity of the virtual ridge line EE” is an area between the virtual boundary line ER and the virtual boundary line EF (in FIG. The area to be hatched). Accordingly, referring to FIG. 10, the cutting edge 93 in the negative land-shaped cutting tool 90 is located on the flank 92 side, is located on the rake face 91 side, and is located on the rake face 91 side. This is a region that is combined with the region to which is applied.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Study 1]
<Example 1>
As a base material, a drill (diameter: 1.0 mm, 2-flute, L / D = 15) which is a cemented carbide of ISO K30 grade was prepared. Next, this base material was placed on a table in the chamber of the HiPIMS apparatus. A plurality of targets made of an alloy of titanium and aluminum were placed in the chamber.

After that, vacuuming is performed so that the pressure in the chamber becomes 0.005 Pa or less, and argon gas is introduced, and 150 (−V) is applied to the substrate while maintaining the pressure in the chamber at 0.7 to 0.9 Pa. A glow discharge was generated in argon by applying a voltage of ˜600 (−V) and passing a current through the etching filament. As a result, the substrate surface was cleaned with argon ions for 15 to 120 minutes. After the cleaning process, the argon gas was exhausted from the chamber.

Then, while introducing argon gas (0.43 Pa) and nitrogen gas (0.14 to 0.19 Pa, adjusted so that the film can be formed in the transition mode), the first step and the first step were performed under the film formation conditions shown in Table 1. Two steps were sequentially performed to form a hard film on the substrate. In each column relating to the film formation conditions in Table 1, the description on the left side separated by a slash is the condition for the first step, and the description on the right side is the condition for the second step. The pressure in the chamber in each process was set to 0.57 to 0.62 Pa.

<Examples 2 to 21, Comparative Examples 1 and 2>
The film formation conditions were changed as shown in Table 1, and a hard film was formed on the substrate in the same manner as in Example 1 except that the target and gas suitable for the composition of each target film were used. Carried out.

<Comparative Examples 3 to 5>
In Comparative Examples 3 to 5, a film forming process was performed on the substrate using an arc discharge device instead of the HiPIMS device. In Comparative Examples 3 to 5, the arc current was 150 A, and the nitrogen pressure was 5.3 Pa. In Comparative Example 4 and Comparative Example 5, post-treatment was performed by a conventionally known method.

<Confirmation of composition and structure of hard coating>
The surface-coated carbide drills of Examples 1 to 21 and Comparative Examples 1 to 5 were cut using a cutting machine equipped with a diamond rotary blade, and the measurements were made including the cross section of the hard coating located at the margin of the surface-coated carbide drill. Samples were prepared. Then, the first to third interfaces were identified by cross-sectional observation with TEM, and the respective compositions of the upper layer and the lower layer and the thicknesses (Tt and Tb) of each layer were confirmed. When the composition of the upper layer was periodically changed in the thickness direction, the thickness of 10 sets of the cycle was measured, and the average value was calculated.

For each example and each comparative example, the average particle diameters G ₁ to G ₄ specified according to the above-described method were calculated. Furthermore, regarding the surface of the hard coating, Ra and Rz were calculated according to the method described above. Further, the surface of the hard coating has a height difference of 1 μm or more, a number of unevennesses of 0.5 μm or more, and a height difference of 0.3 μm or more in the range of 100 μm × 100 μm. The number of irregularities was calculated according to the method described above. The results are shown in Tables 1 and 2.

With reference to Table 1 and Table 2, in Examples 1 to 21, the average particle diameter continuously increases from the first interface toward the second interface, and continuously from the second interface toward the third interface. The two-layer structure layer satisfying the relational expression of G ₂ > G ₃ > G ₄ > G ₁ was formed. On the other hand, in Comparative Examples 1 to 5, a bilayer structure layer having such a change in average particle diameter was not formed.

In Table 1, those in which two compositions are described in the column of “upper layer” are those in which periodic fluctuations in the composition are observed in the upper layer. For example, in the upper layer of Example 2, the thickness of Ti continuously increases from Ti _0.55 Al _0.45 N to Ti _0.75 Al _0.25 N, and then the thickness of Ti decreases continuously to Ti _0.55 Al _0.45 N. An 8 nm period (one set) was observed.

<Calculation of ratio Tf / Tm>
In the surface-coated carbide drills of Examples 1 to 6 and Comparative Examples 1 to 5, the thickness Tm of the hard coating on the margin and the thickness Tf of the hard coating on the groove are measured, and the ratio Tf / Tm is calculated. did. The results are shown in Table 3.

<Cutting test>
Using the surface-coated carbide drills of Examples 1 to 21 and Comparative Examples 1 to 5, a drilling test was performed under the following conditions, and cutting was continued until the surface-coated carbide drill was broken. Table 3 shows the number of holes that have been drilled until they are missing.

(Cutting conditions)
Work material: SUS420
Cutting speed: 40 m / min
Feed amount: 0.03 mm / rev.
Hole depth: 15mm
Cutting oil: Yes (internal lubrication).

Referring to Table 3, according to the surface-coated carbide drills of Examples 1 to 21, it was possible to drill more holes than the surface-coated carbide drills of Comparative Examples 1 to 5. Therefore, in the surface-coated carbide drills of Examples 1 to 21, the tool life can be extended.

[Study 2]
<Example 22 and Comparative Example 6>
Implementation was performed except that a throwaway tip having a material of ISO P20 grade cermet made by Sumitomo Electric Industries and having a shape of “ISO: TNGG160404” was prepared and the film forming conditions were changed as shown in Table 4. In the same manner as in Example 1, a hard film was formed on the substrate.

<Example 23 and Comparative Example 7>
As a base material, a throwaway tip having a material made of cemented carbide and a sintered body of ISO H20 grade cubic boron nitride and having a shape of “4NU-DNGA150408” manufactured by Sumitomo Electric Industries, Ltd. was prepared. A hard film was formed on the substrate in the same manner as in Example 1 except that the film formation conditions were changed as shown in Table 4.

<Confirmation of composition and structure of hard coating>
In the same manner as in Example 1, the composition and structure of the hard coating were confirmed. Each result is shown in Table 4 and Table 5.

<Cutting test>
Using the throw-away tip of Example 22 and Comparative Example 6, a cermet turning test was performed for 10 minutes under the following conditions, and the surface roughness Ra of the work material after turning was measured according to JIS B 0601 (2001). . Further, the gloss of the work material surface was visually confirmed. The results are shown in Table 6.

(Cermet turning conditions)
Work material: SCM415
Cutting speed: 230 m / min.
Feed amount: 0.2 mm / rev.
Cutting depth: 1.0mm
Cutting oil: Yes.

Further, using the cutting tools of Example 23 and Comparative Example 7, a cBN turning test was performed so that the cutting distance was 5 km under the following conditions, and the surface roughness Rz of the work material after turning was set to JIS B 0601 (2001). ). Further, the flank wear amount Vb of the cutting tool was measured. The results are shown in Table 6.

(CBN turning conditions)
Work material: SCM415 (HRC = 60)
Cutting speed: 200 m / min.
Feed amount: 0.1 mm / rev.
Cutting depth: 0.1 mm
Cutting oil: None.

Referring to Table 6, in comparison with Comparative Example 6, Example 22 had a smooth surface shape of the work material after cutting and was excellent in surface appearance. In addition, Example 23 had higher wear resistance and lower maximum height Rz than Comparative Example 7.

It should be considered that the embodiments and examples disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is shown not by the above-described embodiments and examples but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

1 lower layer, 2 upper layer, 3, 4 crystal grain, 5 grain size, 10 two-layer structure layer, 20 underlayer, 30 surface layer, 50 target, 51 table, 52 rotating shaft, 53 substrate holder, 60 plasma, 70, 90 cutting tool, 71 body, 72 shank, 73 outer peripheral edge, 73a margin, 73aa tip, 73b land width back tip, 74 groove, 81, 94, 200 substrate, 82, 95, 100 hard coating, 91 Rake face, 92 flank face, 93 cutting edge.

Claims (10)

1. A hard coating formed on a substrate,
   The hard coating includes a two-layer structure layer in which a lower layer and an upper layer are laminated in order from the base material side,
   Of the two-layer structure layer, the lower surface of the lower layer constituting the lower end surface located on the substrate side is a first interface, and the interface between the upper surface of the lower layer and the lower surface of the upper layer is a second interface, When the upper surface of the upper layer constituting the upper end surface opposite to the lower end surface of the two-layer structure layer is a third interface, and the cross-section parallel to the thickness direction is observed in the two-layer structure layer,
   Average grain size G ₁ of crystal grains at a position 100 nm away from the first interface toward the second interface side, Average grain size of crystal grains at a position 100 nm away from the second interface toward the first interface side The diameter G ₂ , the average grain size G ₃ of the crystal grains at a position 100 nm away from the second interface toward the third interface side, and the average grain size G ₄ of the crystal grains at the third interface are G ₂ > A hard coating satisfying the relational expression of G ₃ > G ₄ > G ₁ .
2. The lower layer includes crystal grains whose average grain size increases from the first interface side toward the second interface, and the upper layer has an average grain size from the second interface toward the third interface side. The hard coating according to claim 1, wherein the hard coating contains crystal grains that decrease in size.
3. The average particle size G ₁ is 50 nm or less,
   The average particle size G ₂ is 200 nm or more and 600 nm or less,
   The average particle size G ₃ are is at 300nm inclusive 75 nm,
   The hard coating film according to claim 1, wherein the average particle size G ₄ is 150 nm or less.
4. The hard coating film according to any one of claims 1 to 3, wherein a ratio Tt / Tb between a thickness Tt of the upper layer and a thickness Tb of the lower layer is 0.2 or more and 0.75 or less.
5. The two-layer structure layer includes one or more first elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al and Si in the periodic table, and a group consisting of B, C, N, and O The hard film according to any one of claims 1 to 4, having a composition comprising one or more second elements selected from the above.
6. The two-layer structure layer has two or more kinds of first elements in its composition, and the concentration of the two or more kinds of first elements changes periodically in the thickness direction of the upper layer. Hard coating as described in 4.
7. The hard film according to any one of claims 1 to 6, wherein an upper surface of the upper layer has an arithmetic average roughness Ra of 0.07 µm or less and a maximum height Rz of 0.50 µm or less.
8. The number of unevenness | corrugations which have a height difference of 1 micrometer or more is less than ten in the range of 100 micrometers x 100 micrometers of the upper surface of the upper layer of the two-layer structure layer. Hard coating.
9. A cutting tool comprising: a base material; and the hard coating film according to any one of claims 1 to 8, which covers a surface of the base material.
10. The cutting tool has a groove and a margin,
    10. The cutting tool according to claim 9, wherein a ratio Tf / Tm of a thickness Tf of the hard coating covering the groove and a thickness Tm of the hard coating covering the margin is 0.8 or more and 1.5 or less.

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