JP6296295B2 - Surface coated cutting tool with excellent wear resistance - Google Patents

Description

  The present invention relates to a surface-coated cutting tool having a hard coating layer with excellent wear resistance. More specifically, even when subjected to high-speed cutting such as carbon steel or alloy steel, chipping, chipping, peeling, etc. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance over a long period of time without causing abnormal damage.

In general, coated tools are used for turning and planing of work materials such as various types of steel and cast iron, inserts that can be used detachably attached to the tip of a cutting tool, drilling processing of work materials, etc. There are drills, miniature drills, solid type end mills used for chamfering, grooving, shoulder processing, etc. of the work material, etc. Also, inserts are detachably attached and cutting is performed in the same way as solid type end mills An insert type end mill is known.
Conventionally, as a coated tool, for example, a coated tool in which a WC-based cemented carbide, a TiCN-based cermet, and a cBN sintered body are used as a tool base and a hard coating layer is formed on the tool base is known. Various proposals have been made for the purpose.

  For example, Patent Document 1 discloses a hard coating made of, for example, a (Ti, Al) N layer on the surface of a tool substrate in order to improve the adhesion between the tool substrate and the hard coating layer and to achieve both toughness and wear resistance. Forming a layer, and the layer includes a fine structure region and a coarse structure region, and the fine structure region has an average crystal grain size of a compound constituting the layer of 10 to 200 nm, and from the surface side of the layer It occupies a range of 50% or more with respect to the total thickness of the layer, and has an average compressive stress that is a stress in a range of −4 GPa or more and −2 GPa or less. A coated tool which has a stress distribution and has two or more maximum values or minimum values in the stress distribution, and those maximum values or minimum values are located closer to the surface in the thickness direction, and a higher compressive stress is formed. Has been proposed.

  Patent Document 2 discloses that a tool substrate is provided with a hard coating layer having excellent high-temperature hardness and high-temperature strength, thereby preventing chipping, chipping, peeling, and the like, and improving wear resistance. In the coated tool in which a hard coating layer made of (Ti, Al) N is vapor-deposited on the surface, the hard coating layer is divided into a thin layer A made of granular crystals (Ti, Al) N and columnar crystals (Ti, Al). It is configured as an alternating laminated structure of thin layers B made of N, each of the thin layers A and B has a layer thickness of 0.05 to 2 μm, and the crystal grain size of the granular crystals is 30 nm or less, and the columnar shape A coated tool having a crystal grain size of 50 to 500 nm has been proposed.

Furthermore, in Patent Document 3, in order to improve the chipping resistance of the hard coating layer in high-speed intermittent cutting with high heat generation and impact load acting on the cutting edge, Ti _1-x Al _x ) (C _y N _1-y ) represents an alternate stacked structure composed of a region A layer and a region B layer, and the region A layer has 0.70 ≦ x ≦ 0.80. 0.0005 ≦ y ≦ 0.005, the average particle width W is 0.1 μm or less, and the average particle length L is 0.1 μm or less, while the region B layer has 0.85 ≦ x ≦ 0.95, 0.0005 ≦ y ≦ 0.005, a coated tool with an average particle width W of 0.1 to 2.0 μm and an average particle length L of 0.5 to 5.0 μm is proposed Has been.

JP2011-67883A JP2011-224715A JP 2014-61588 A

The hard coating layer with a controlled crystal structure composed of nitrides and carbonitrides of Ti and Al proposed in the prior art can be expected to have excellent wear resistance as well as hardness and heat resistance. Thus, under the cutting conditions in which a high load acts on the cutting edge, the conventional coated tool has not been able to exhibit a sufficiently satisfactory wear resistance.
Therefore, there is a need for a coated tool that exhibits stable wear resistance over a long period of time even when subjected to high-speed cutting.

  Therefore, the present inventors diligently studied about the structure of the hard coating layer in order to solve the above problems, and obtained the following knowledge.

When a hard coating layer is vapor-deposited on the surface of a tool base using, for example, an arc ion plating apparatus, a Ti and Al nitride having a fine granular crystal structure (hereinafter referred to as “(Ti, Al) N”) may be used. A hard coating layer is formed as a laminated structure of an A layer composed of (A) and a B layer composed of (Ti, Al) N having a columnar crystal structure, and a wide column shape is formed from the vicinity of the interface between the A layer and the B layer. It has been found that the wear resistance of the hard coating layer can be improved by growing the crystal grains in a direction perpendicular to the surface of the tool substrate and further forming the columnar crystal structure of the B layer as crystal grains having a specific shape. .
In addition, by controlling the deposition conditions of the A layer and the B layer, by aligning the crystal orientation of the A layer and the B layer, by improving the interlayer adhesion strength between the A layer and the B layer, chipping, It has been found that the wear resistance can be improved without causing abnormal damage such as defects and peeling.

The present invention has been made based on the above knowledge,
In a surface-coated cutting tool in which a hard coating layer in which an A layer and a B layer are laminated is formed on the surface of a tool base made of any of WC cemented carbide, TiCN-based cermet, and cubic boron nitride sintered body. ,
(A) The A layer is
Compositional formula: (Ti _1-x Al _x ) N (where x is an atomic ratio, 0.45 ≦ x ≦ 0.65), and has a rock salt cubic crystal structure, 0.1 to 1 A fine grained Ti and Al nitride layer having an average layer thickness of 0.0 μm and an average width of 0.01-0.1 μm crystal grains;
(B) The B layer is
Compositional formula: (Ti _1-y Al _y ) N (where y is an atomic ratio, 0.4 ≦ y ≦ 0.65) and has a rock salt cubic crystal structure, 0.5-3 A nitride layer of Ti and Al with a columnar crystal structure having an average layer thickness of 0.0 μm;
(C) When the columnar crystal grains of the B layer are observed in a longitudinal section perpendicular to the tool base surface, the maximum crystal grain length L in the direction perpendicular to the tool base surface is 60% or more of the average layer thickness of the B layer. In addition, the approximate width of the columnar crystal grains is 0.1 to 1.5 μm, the aspect ratio is 1.4 or more, and 0.2 L, 0 from the tool base side of the maximum crystal grain length L The columnar crystal grains having a difference between the columnar crystal grain widths W _0.2 and W _0.8 measured at the height of 0.8 L and the approximate width of the columnar crystal grains within 20% respectively are formed on the tool base surface. Occupies an area ratio of 50% or more of the vertical cross-sectional area of the vertical B layer,
(D) When the diffraction peak intensity on the (200) plane was determined as I (200) and the diffraction peak intensity on the (111) plane was determined as I (111) by X-ray diffraction for the A layer and the entire hard coating layer, (200) / I (111) is 7-20, The surface coating cutting tool characterized by the above-mentioned. "
It is characterized by.
It should be noted that the present invention is characterized in that the hard coating layer composed of a laminate of the A layer and the B layer has the greatest feature. However, as a surface layer on the hard coating layer of the present invention, wear resistance and lubrication are provided. It does not prevent further providing other layers such as nitride and carbonitride having excellent properties. Examples of the surface layer include a TiN layer, a CrN layer, a TiCN layer, a TiSiN layer, an AlCrN layer, and an AlTiSiN layer.

  Here, the coated tool of the present invention will be described in more detail.

A layer:
As shown in the schematic diagram of FIG. 1, the A layer satisfies the composition formula: (Ti _1-x Al _x ) N (where x is an atomic ratio, 0.45 ≦ x ≦ 0.65). Although it is configured as a (Ti, Al) N layer having an average layer thickness of 1 to 1.0 μm, the content of the Al component in the A layer is 0.45 (provided that the atomic component accounts for the total amount with the Ti component). If the ratio is less than 0.65 (provided that the atomic ratio) exceeds the proportion of the total amount of Ti component, the crystal structure of a part of the structure is derived from the rock salt type crystal structure. Since it changed to a hexagonal crystal structure and the hardness decreased, the content ratio x of the Al component in the total amount with the Ti component in the A layer was determined to be 0.45 ≦ a ≦ 0.65. A more preferable composition range is 0.55 ≦ x ≦ 0.65.
Further, if the average layer thickness of the A layer is less than 0.1 μm, the effect of suppressing the occurrence and development of cracks is not sufficient, while if the average layer thickness of the A layer exceeds 1.0 μm, crystal grains Since it becomes easy to coarsen and the effect of improving chipping resistance cannot be obtained, the average layer thickness of the A layer is determined to be 0.1 to 1.0 μm.

The A layer is configured as a fine granular crystal structure having an average width of 0.01 to 0.1 μm crystal grains, but when the average width of the (Ti, Al) N crystal grains constituting the A layer is less than 0.01 μm The number of crystal grain boundaries becomes excessive. On the other hand, when the average width exceeds 0.1 μm, the crystal grain boundaries decrease, and therefore, the effect of dispersing the crack propagation paths cannot be obtained sufficiently. The average width of (Ti, Al) N crystal grains constituting the fine grain structure is 0.01 to 0.1 μm. A preferable average width is 0.01 to 0.05 μm.
The “approximate width” and “average width” of the crystal grains referred to in the present invention are the longitudinal section images obtained by section observation using a scanning electron microscope (SEM) having a longitudinal section perpendicular to the surface of the tool substrate. The shape of each particle forming the layer is determined by electron backscatter diffraction (EBSD), and the maximum crystal grain length L in the direction perpendicular to the tool substrate surface is determined for each crystal particle. Taking the maximum crystal grain length L as a reference, the shape of the particle is approximated to a rectangle so that the cross-sectional areas in the vertical cross section perpendicular to the tool substrate surface are equivalent, and the length orthogonal to the calculated maximum crystal grain length L Is referred to as “approximate width”, and a value obtained by averaging the “approximate width” of all particles in the longitudinal cross-sectional image is referred to as “average width”.
Here, the surface of the tool base is a reference line of the interface roughness between the base and the hard coating layer in an observation image of a cross section perpendicular to the surface direction of the surface in contact with the hard coating layer of the base.
Further, although there is no special provision for the aspect ratio of the crystal grains of the A layer (maximum crystal grain length L / approximate width of crystal grains), from the viewpoint of dispersing crack propagation paths and reducing abnormal damage The average aspect ratio of each particle is desirably 1.0 to 1.5.

B layer:
As shown in the schematic diagram of FIG. 1, the B layer _{satisfies the} composition formula: (Ti _1-y Al _y ) N (where y is an atomic ratio and 0.4 ≦ y ≦ 0.65). A (Ti, Al) N layer having a columnar grain structure having an average layer thickness of 5 to 3.0 μm is formed, but the content of the Al component in the B layer is 0. 0 in the total amount with the Ti component. If it is less than 4 (however, the atomic ratio), sufficient wear resistance cannot be obtained. On the other hand, if the content ratio of the Al component in the total amount with the Ti component exceeds 0.65 (however, the atomic ratio), A As in the case of the layer, since the crystal structure of a part of the structure changes from a rock salt type crystal structure to a hexagonal crystal structure and the hardness decreases, the content ratio of the Al component in the total amount with the Ti component in the B layer y was determined to be 0.4 ≦ a ≦ 0.65.
Further, if the average layer thickness of the B layer is less than 0.5 μm, sufficient wear resistance cannot be obtained, while if it exceeds 3.0 μm, the film tends to be self-destructed. Was determined to be 0.5 to 3.0 μm.
Note that the average composition and average layer thickness of the A layer and the B layer are as follows: Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Energy Dispersive X-ray Spectroscopy (Energy) It can be measured by cross-sectional measurement using Dispersive X-ray Spectroscopy (EDS). Here, the layer thickness of each layer is the thickness of the layer in the direction perpendicular to the tool base surface.

The (Ti, Al) N crystal grains constituting the B layer are composed of a columnar crystal structure having the following shape.
First, if the approximate width of the (Ti, Al) N crystal grains constituting the B layer is less than 0.1 μm, sufficient wear resistance cannot be exhibited, whereas if the approximate width exceeds 1.5 μm, the B layer Therefore, the approximate width of the (Ti, Al) N crystal grains constituting the B layer is set to 0.1 to 1.5 μm.
Even if the crystal grains have the approximate width, the maximum crystal grain length L in the direction perpendicular to the tool base surface is less than 60% of the average layer thickness of the B layer, or the aspect ratio of the crystal grains If (the maximum crystal grain length L / approximate width of crystal grains) is less than 1.4, sufficient wear resistance cannot be obtained, so the B layer is formed (Ti, Al). The maximum crystal grain length L in the direction perpendicular to the tool substrate surface of N crystal grains is 60% or more of the average layer thickness of the B layer, and the aspect ratio (maximum crystal grain length L of crystal grains / approximation of crystal grains) The width is set to 1.4 or more.
Further, even for crystal grains having the approximate width, maximum crystal grain length L, and aspect ratio, 0.2 L and 0.8 L from the tool base side of the maximum crystal grain length L in the direction perpendicular to the tool base surface. When the widths W _0.2 and W _0.8 of the columnar crystal grains in the direction parallel to the surface of the tool base at the height positions are measured, the measured widths W _0.2 and W _{0.8 of} the columnar crystal grains are When the difference from the approximate width of the columnar crystal grains exceeds 20%, or the columnar crystal grains whose difference between the approximate widths of W _0.2 and W _0.8 and the columnar crystal grains is within 20% When there is only an area ratio of less than 50% of the vertical cross-sectional area of the B layer perpendicular to the surface, the B layer cannot exhibit sufficient wear resistance over a long period of use.
Therefore, the (Ti, Al) N crystal grains constituting the B layer have the approximate width, the maximum crystal grain length L, the aspect ratio, and the tool having the maximum crystal grain length L in the direction perpendicular to the tool base surface. A rectangle in which the difference between the widths W _0.2 and W _0.8 of the columnar crystal grains measured at heights of _0.2 L and 0.8 L from the substrate side and the approximate width of the columnar crystal grains is within 20% The crystal grains having such a columnar crystal structure must occupy an area ratio of 50% or more of the longitudinal sectional area of the B layer perpendicular to the surface of the tool base.
Note that the composition and average layer thickness of the A layer, the B layer, the average width of the crystal grains of the A layer, the shape of the crystal grains constituting the B layer, and the longitudinal direction of the hard coating layer perpendicular to the surface of the tool substrate are scanned. Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), Transmission Electron Microscope (TEM), Energy Dispersive Electron Microscope (TEM), Energy Dispersive Electron Microscopy (TEM) : Can be measured by cross-sectional measurement using EDS).

In order for the (Ti, Al) N crystal grains constituting the B layer to form the columnar crystal structure described above, it is important to align the orientation of the A layer and the B layer.
That is, in the present invention, the hard coating layer composed of the A layer and the B layer is formed by using, for example, the arc ion plating apparatus shown in FIG. By controlling the nitrogen gas partial pressure and the film formation rate, and slowly growing the (200) plane with a lower surface energy than the (111) plane in the rock salt cubic structure, the orientation of the A and B layers is aligned. In addition, a columnar crystal structure having a wide crystal grain width can be formed from the interface between the A layer and the B layer.
Then, X-ray diffraction is performed on the entire A layer and the hard coating layer, and when the diffraction peak intensity on the (200) plane is I (200) and the diffraction peak intensity on the (111) plane is I (111), I (200 ) / I (111) is less than 7, it is difficult to grow a columnar crystal having a wide crystal width from the interface between the A layer and the B layer, while I (200) / I (111) When the value exceeds 20, the columnar crystal grains of the B layer are likely to be coarsened, the crystal grain boundaries are reduced, and the chipping resistance and chipping resistance during high-load cutting are reduced. Therefore, the peak intensity ratio I (200) / I (111) is 7-20.

  Here, the peak intensity ratio I (200) / I (111) for the entire hard coating layer is a diffraction peak in which the A layer and the B layer overlap each other as one diffraction peak, and the (200) plane overlap. This is the value of I (200) / I (111) calculated with the peak intensity as I (200) and the diffraction peak intensity with the (111) plane overlapped as I (111). The diffraction peak intensity of the A layer is measured, for example, by processing and removing the B layer by a method such as a focused ion beam (FIB) method and then using the X-ray diffraction method described above. Can do.

  The coated tool of the present invention is formed by laminating an A layer made of (Ti, Al) N having a fine granular crystal structure and a B layer made of (Ti, Al) N having a columnar crystal structure on the surface of the tool base. In particular, the (Ti, Al) N crystal grains of the columnar crystal structure in the B layer have a predetermined approximate width, maximum crystal grain length L, aspect ratio, and a shape close to a rectangle. In addition, the crystal grains of such a columnar crystal structure occupy an area ratio of 50% or more of the vertical cross-sectional area of the B layer perpendicular to the tool base surface. Further, the X-rays of the A layer and the entire hard coating layer By setting the diffraction peak intensity ratio I (200) / I (111) to 7 to 20, high-speed cutting of carbon steel, alloy steel, etc. does not cause abnormal damage such as chipping, chipping, peeling, etc. Excellent wear resistance throughout use It is to volatilization.

The cross-sectional schematic diagram of the hard coating layer of this invention coated tool is shown. In addition, the “characteristic columnar crystal grains” of the B layer shown in the figure means that the maximum crystal grain length L in the direction perpendicular to the surface of the tool base is 60% or more of the average layer thickness of the B layer, and The approximate width of the columnar crystal grains is 0.1 to 1.5 μm, the average aspect ratio is 1.4 or more, and the width of the columnar crystal grains at heights of 0.2 L and 0.8 L from the tool base side. This refers to columnar crystal grains in which the difference between W _0.2 and W _0.8 and the approximate width of the columnar crystal grains is 20% or less, respectively. It is the schematic of the arc ion plating apparatus for carrying out vapor deposition formation of a hard coating layer, (a) is a front view, (b) shows a side view.

Next, the coated tool of the present invention will be specifically described with reference to examples.
As a specific explanation, a coated tool made of a cBN substrate and a coated tool made of a cemented carbide substrate will be described, but the same applies to a coated tool using a TiCN-based cermet as a tool substrate.

Tool substrate production:
As raw material powder, cBN particles having an average particle size of 1 to 4 μm are used as raw material powder for forming a hard phase, and TiN powder, TiC powder, TiCN powder, Al powder, AlN powder, and Al ₂ O ₃ powder are used for forming a binder phase. Prepare as raw powder.
Among these, the blending ratio shown in Table 1 is blended so that the content ratio of cBN particles is 50% by volume when the total amount of some raw material powder and cBN powder is 100% by volume.
Next, the raw material powder was wet-mixed for 72 hours in a ball mill, dried, and then press-molded at a molding pressure of 100 MPa to a size of diameter: 50 mm × thickness: 1.5 mm. In a vacuum atmosphere, it is preliminarily sintered while being held at a predetermined temperature in the range of 900 to 1300 ° C., and then charged into an ultra-high pressure sintering apparatus, pressure: 5 GPa, temperature: in the range of 1200 to 1400 ° C. A cBN-based sintered body is prepared by sintering at a predetermined temperature.
This sintered body is cut into a predetermined size with a wire electric discharge machine, Co: 5% by mass, TaC: 5% by mass, WC: remaining composition and insert made of WC-based cemented carbide with ISO standard CNGA120408 insert shape Brazing to the brazing part (corner part) of the main body using an Ag-based brazing material having a composition consisting of Cu: 26%, Ti: 5%, and Ag: the rest, and polishing the upper and lower surfaces and outer periphery, By performing the honing process, cBN tool bases 1 to 3 having an insert shape of ISO standard CNGA120408 were manufactured.

Formation of hard coating layer:
A hard coating layer was formed on the tool bases 1 to 3 using an arc ion plating apparatus shown in FIG.
As the Ti—Al alloy target in FIG. 2, a plurality of Ti—Al alloy targets having different compositions are arranged in the apparatus according to the target (Ti, Al) N layer.
(A) The tool bases 1 to 3 are ultrasonically cleaned in acetone and dried. Then, the tool bases 1 to 3 are arranged along the outer periphery at a predetermined distance in the radial direction from the central axis on the rotary table in the arc ion plating apparatus. Install. Further, a Ti—Al alloy target having a predetermined composition is disposed as a cathode electrode (evaporation source).
(B) First, the interior of the apparatus was evacuated and kept at a vacuum of 10 ⁻² Pa or less, and the interior of the apparatus was heated to 500 ° C. with a heater, and then set to an Ar gas atmosphere of 0.5 to 2.0 Pa. A DC bias voltage of −200 to −1000 V is applied to the tool base that rotates while rotating on the rotary table, and the tool base surface is bombarded with argon ions for 5 to 30 minutes.
(C) Next, the A layer is formed as follows.
Nitrogen gas is introduced into the apparatus as a reaction gas to obtain a predetermined reaction atmosphere of 0.5 to 4 Pa shown in Table 2, while maintaining the apparatus internal temperature similarly shown in Table 2, while rotating on the rotary table. A predetermined DC bias voltage of −25 to 100 V shown in Table 2 is applied to the rotating tool base, and a surface between the cathode electrode (evaporation source) and the anode electrode made of the Ti—Al alloy target having the predetermined composition is applied. A predetermined current of 110 to 200 A shown in FIG. 2 is caused to flow simultaneously for a predetermined time to generate an arc discharge, and a (Ti, Al) N layer having a target composition and a target average layer thickness shown in Table 4 is formed on the surface of the tool base. A layer was formed by vapor deposition.
(D) Next, the B layer is formed as follows.
First, nitrogen gas is introduced into the apparatus as a reaction gas so as to obtain a predetermined reaction atmosphere within the range of 2 to 10 Pa shown in Table 2, and the apparatus is also maintained at the apparatus temperature shown in Table 2 on the rotary table. A predetermined DC bias voltage within a range of −25 to −75 V shown in Table 2 is applied to a tool base that rotates while rotating, and a cathode electrode (evaporation source) and an anode electrode made of the Ti—Al alloy target A predetermined current in the range of 80 to 120 A shown in Table 2 is caused to flow to cause arc discharge, and the target composition and target average layer thickness (Ti, Al) shown in Table 4 are formed on the surface of the A layer. A B layer composed of an N layer was formed by vapor deposition.
According to the above (a) to (d), the coated tools of the present invention (hereinafter referred to as “the present invention tool”) 1 to 6 shown in Table 4 in which the hard coating layer composed of the laminate of the A layer and the B layer was formed by vapor deposition were used. Produced.

For comparison, by coating the lower layer and the upper layer on the tool bases 1 to 3 under the conditions shown in Table 3, a coated tool of a comparative example shown in Table 5 (hereinafter referred to as “comparative tool”). 1-6 were produced.
In addition, since the lower layer and the upper layer of the comparative example tool are layers corresponding to the A layer and the B layer of the present invention, respectively, in the following, the lower layer and the upper layer of the comparative example tool are respectively referred to for convenience. Specifically, they are referred to as A layer and B layer.

  About the longitudinal section of the hard coating layer perpendicular to the tool base surface of the present invention tools 1 to 6 and Comparative Examples tools 1 to 6 produced above, the width in the direction parallel to the tool base surface is 10 μm. For the field of view set to include all the thickness regions, cross-sectional measurement using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS) was performed. The composition of the layer and the layer thickness were measured at a plurality of locations and averaged to calculate the average composition and average layer thickness.

In addition, the approximate width and aspect ratio of the crystal grains of the A layer and the B layer are determined by cross-sectional observation using a scanning electron microscope (SEM), electron beam backscatter diffraction (EBSD), and transmission electron microscope (TEM). The value of all crystal grains in the field of view was measured, and the approximate width and aspect ratio were calculated.
Specifically, by processing using a focused ion beam (FIB), the tool base surface of the hard coating layer is positioned at a position of 100 μm in the direction of the flank from the ridge line formed by the honing surface and the flank of the tool base. Measurement by EBSD under the condition of a step interval of 0.02 μm in a visual field set so that a vertical longitudinal section is formed, the width in the direction parallel to the substrate surface is 10 μm, and the entire thickness region of the hard coating layer is included. Analysis was performed, and a boundary where crystal orientations differ by 2 ° or more at adjacent points among the measurement points was determined as a crystal grain boundary, and crystal shapes of the A layer and the B layer were determined. For crystal grains of 0.02 μm or less, the crystal grain shape was directly observed with a transmission electron microscope (TEM), and the crystal grain boundaries were determined from the contrast of the image. In addition, in the same image field as the field of view where the EBSD measurement was performed, the crystal shape of the crystal grain shape of 0.02 μm or more was confirmed by measurement using a transmission electron microscope (TEM). It is confirmed that it can be obtained. For the tool substrate surface, element mapping using EDS is performed in a longitudinal section perpendicular to the tool substrate surface of the hard coating layer to define the interface between the A layer and the tool substrate. As for the roughness curve of the interface, an average line was obtained arithmetically and used as the tool base surface.
Next, for each crystal grain shape of the A layer and B layer determined by the above procedure, the length perpendicular to the tool base surface was determined, and the maximum crystal grain length L was determined. Using this maximum crystal grain length L as a reference, a rectangle that has an area equivalent to the area of the crystal grain in the cross-sectional image is determined, and the length in the direction parallel to the rectangular tool base surface is obtained. The approximate width was obtained, and the maximum crystal grain length L was divided by the approximate width to obtain the aspect ratio of each crystal grain. For the A layer, the above operation was performed on all particles in the cross-sectional image, and the approximate width and aspect ratio thereof were averaged to obtain the average width and average aspect ratio of the crystal grains forming the hard coating layer. Further, regarding the shape of each crystal grain of the B layer obtained from EBSD, the tool base surface at a height of 0.2 L and 0.8 L from the tool base side of the maximum crystal grain length L in the direction perpendicular to the tool base surface. The widths W _0.2 and W _0.8 of the columnar crystal grains in the direction parallel to the horizontal axis are obtained, and among the crystal grains of the B layer, the maximum crystal grain length L is 60% or more of the average layer thickness of the B layer, A tool at an approximate width of 0.1 to 1.5 μm, an aspect ratio of 1.4 or more, and a height of 0.2 L and 0.8 L from the tool base side with the maximum crystal grain length L. The columnar crystal grains in which the widths W _0.2 and W _0.8 of the columnar crystal grains in the direction parallel to the substrate surface are within 20% of the approximate width were determined. Further, the columnar crystal grains defined in the present application can be obtained by summing up the vertical cross-sectional areas of such columnar crystal grains in the field of view of the observation image and dividing by the vertical cross-sectional area of the B layer in the observation image. The area ratio in the vertical sectional area of the B layer perpendicular to the substrate surface was calculated.

Next, the diffraction peak intensity ratio I (200) / I (111) of the entire hard coating layer is the diffraction peak intensity of the (200) plane where the A layer and the B layer overlap by X-ray diffraction using a Cr tube. It was measured as I (200), and the diffraction peak intensity of the (111) plane where the A layer and B layer overlapped was measured as I (111), and obtained from I (200) / I (111).
Further, the diffraction peak intensity of the A layer is measured by processing and removing the upper layer B by a method such as a focused ion beam (FIB) method after film formation, and then using the X-ray diffraction method described above. Then, I (200) / I (111) was determined from the diffraction peak intensity I (200) of the (200) plane and the diffraction peak intensity I (111) of the (111) plane.

  Tables 4 and 5 show the various values obtained above.

Then, about this invention tools 1-6 and comparative example tools 1-6,
Cutting condition A:
Work material: JIS / SCr420 carburized quenching material (HRC60) round bar,
Cutting speed: 260 m / min. ,
Cutting depth: 0.15 mm,
Feed: 0.15 mm,
A cutting test was performed under the dry continuous cutting conditions, cutting to a cutting length of 910 m, and flank wear width was measured.
Table 6 shows the results.

Tool substrate production ::
As raw material powder, Co powder, VC powder, Cr ₃ C ₂ powder, TiC powder, TaC powder, NbC powder, WC powder are prepared, and these raw material powders are blended into the blending composition shown in Table 7, and wax is further added. In addition, it is wet-mixed for 72 hours in a ball mill, dried under reduced pressure, press-molded at a pressure of 100 MPa, these green compacts are sintered, processed to a predetermined size, and an ISO standard SEEN1203AFTN1 insert shape. WC-based cemented carbide tool bases 11 to 13 having the above were manufactured.

Film formation process:
Using the arc ion plating apparatus as shown in FIG. 2 for the WC-base cemented carbide tool bases 11 to 13, the hard coating layer was subjected to the conditions shown in Table 8 in the same manner as in Example 1. The present coated tools (referred to as “the present invention tool”) 11 to 16 having the A layer and the B layer shown in Table 10 were produced.

  For comparison, the A and B layers shown in Table 11 are formed on the tool bases 11 to 13 by vapor-depositing a hard coating layer under the conditions shown in Table 9, similarly to Comparative Tools 1 to 6. Comparative example-coated tools (referred to as “comparative example tools”) 11 to 16 were prepared.

About this invention tool 11-16 produced above and the comparative example tools 11-16, it carried out similarly to Example 1, and computed the average composition and average layer thickness of A layer and B layer.
In addition, the maximum crystal grain length L, the approximate width, the aspect ratio, and the maximum crystal grain length L of the B layer crystal grains in the direction perpendicular to the tool base surface of the A layer and B layer crystal grains are 0 from the tool base side. Width of columnar crystal grains W _0.2 and W _0.8 at heights of 2 L and 0.8 L, and the area ratio of such columnar grains to the vertical sectional area of layer B perpendicular to the tool base surface Was calculated by cross-sectional observation using a scanning electron microscope (SEM), electron beam backscatter diffraction (EBSD), and transmission electron microscope (TEM).
Furthermore, the diffraction peak intensity ratio I (200) / I (111) of the entire A layer and the hard coating layer was determined by X-ray diffraction using a Cr tube.
Tables 10 and 11 show the various values obtained above.

Next, for the inventive tools 11 to 16 and the comparative tools 11 to 16, a single-blade high-speed face milling test was carried out under the following cutting conditions B using a cutter of SE445R0506E.
Cutting condition B:
Work material: JIS / S45C block material (width 60 mm x length 250 mm),
Cutting speed: 260 m / min. ,
Rotational speed: 662 rev / min,
Cutting depth: 1.5 mm,
Feed: 0.15 mm / tooth,
Cutting width: 60 mm
Under these conditions, the cutting length was cut to 1300 m, and the flank wear width was measured.
Table 12 shows the results.

According to the results of Table 6, the average flank wear width of the inventive tools 1 to 6 is about 0.09 mm, and according to the results of Table 12, the average flank wear width of the inventive tools 11 to 16 Was about 0.14 mm, but comparative tools 1-6, 11-16 were subject to flank wear, and some of them had a short life due to chipping.
From this result, it can be seen that the tool of the present invention is superior in both wear resistance as well as abnormal damage properties such as chipping resistance, chipping resistance, and peel resistance as compared with the comparative example tool.

The surface-coated cutting tool of the present invention is not only for cutting under normal cutting conditions such as various types of steel, but also carbon steel, alloy steel, etc. that particularly involve high heat generation and a heavy load on the cutting edge. Even in high-speed cutting, it exhibits excellent abnormal damage resistance and wear resistance, and exhibits excellent cutting performance over a long period of time. And it can cope with energy saving and cost reduction sufficiently satisfactorily.

Claims (1)

In a surface-coated cutting tool in which a hard coating layer in which an A layer and a B layer are laminated is vapor-deposited on the surface of a tool substrate made of any of WC cemented carbide, TiCN-based cermet, and cubic boron nitride sintered body,
(A) The A layer is
Compositional formula: (Ti _1-x Al _x ) N (where x is an atomic ratio, 0.45 ≦ x ≦ 0.65), and has a rock salt cubic crystal structure, 0.1 to 1 A fine grained Ti and Al nitride layer having an average layer thickness of 0.0 μm and an average width of 0.01-0.1 μm crystal grains;
(B) The B layer is
Compositional formula: (Ti _1-y Al _y ) N (where y is an atomic ratio, 0.4 ≦ y ≦ 0.65) and has a rock salt cubic crystal structure, 0.5-3 A nitride layer of Ti and Al with a columnar crystal structure having an average layer thickness of 0.0 μm;
(C) When the columnar crystal grains of the B layer are observed in a longitudinal section perpendicular to the tool base surface, the maximum crystal grain length L in the direction perpendicular to the tool base surface is 60% or more of the average layer thickness of the B layer. In addition, the approximate width of the columnar crystal grains is 0.1 to 1.5 μm, the aspect ratio is 1.4 or more, and 0.2 L, 0 from the tool base side of the maximum crystal grain length L The columnar crystal grains having a difference between the columnar crystal grain widths W _0.2 and W _0.8 measured at the height of 0.8 L and the approximate width of the columnar crystal grains within 20% respectively are formed on the tool base surface. Occupies an area ratio of 50% or more of the vertical cross-sectional area of the vertical B layer,
(D) When the diffraction peak intensity on the (200) plane was determined as I (200) and the diffraction peak intensity on the (111) plane was determined as I (111) by X-ray diffraction for the A layer and the entire hard coating layer, (200) / I (111) is 7-20, The surface coating cutting tool characterized by the above-mentioned.