JP5158560B2 - Surface coated cutting tool with excellent chipping resistance due to hard coating layer in heavy cutting - Google Patents

Description

  The present invention provides a surface-coated cutting tool that exhibits excellent chipping resistance with a hard coating layer in heavy cutting processing such as steel and cast iron that is particularly subjected to a high thermal and mechanical load on the cutting edge portion (hereinafter referred to as “cutting blade”). (Referred to as a coated tool).

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition of the lower layers. A Ti compound layer consisting of two or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having a total average layer thickness of 3 to 20 μm,
(B) an aluminum oxide (hereinafter referred to as Al ₂ O ₃ ) layer having an average layer thickness of 1 to 15 μm, in which the upper layer is formed by chemical vapor deposition;
A coated tool formed by forming a hard coating layer composed of the above (a) and (b) is known, and this coated tool is used for continuous cutting and intermittent cutting of various steels and cast irons, for example. It is also known that

In the above-mentioned coated tool, the TiCN layer constituting the Ti compound layer which is the lower layer is mixed gas containing organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus for the purpose of improving the strength of the layer itself. It is also known that the film is formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. to have a vertically grown crystal structure.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving, energy saving, and cost reduction for cutting work, and along with this, cutting work tends to be further accelerated. For coated tools, there is no problem when this is used for continuous cutting or interrupted cutting under normal conditions such as steel or cast iron. When used for feed and high cutting heavy cutting conditions, the hard coating layer constituting this has high temperature strength by the lower Ti compound layer, high temperature hardness and heat resistance by the upper Al ₂ O ₃ layer. However, since the high temperature strength by the Ti compound layer is insufficient, the hard coating layer is likely to be chipped (small chipping), and as a result, the service life is reached in a relatively short time. .

In view of the above, the inventors of the present invention, from the above viewpoint, in order to improve the chipping resistance of the hard coating layer of the above-mentioned coated tool, the TiCN layer constituting the Ti compound layer, which is the lower layer of the hard coating layer, in particular, Ti NaCl having a relatively high high-temperature hardness and high-temperature strength among the compound layers, and having constituent atoms composed of Ti, carbon, and nitrogen at lattice points, respectively, as schematically shown in FIG. Focusing on a TiCN layer (hereinafter referred to as an l-TiCN layer) having a vertically grown crystal structure having a crystal structure of a mold face centered cubic crystal (FIG. 1 (b) shows a state cut by the (011) plane). , As a result of research,
(A) The l-TiCN layer as the lower layer constituting the hard coating layer of the conventional coated tool is, for example, a normal chemical vapor deposition apparatus.
Reaction gas composition: by _{volume%, TiCl 4: 2~10%,} CH 3 CN: 0.5~3%, N 2: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 800 to 900 ° C.
Reaction atmosphere pressure: 6-20 kPa,
Vapor deposition is performed under the conditions (normal conditions), but this vapor deposition condition is changed,
First, as the first step,
Reaction gas composition: by _{volume%, TiCl 4: 5~15%,} C 3 H 3 N: 0.7~2.5%, N 2: 7~20%, H 2: remainder,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
Under the conditions, vapor deposition is performed until the layer thickness of the vapor deposition layer is about 20% of the target layer thickness,
Then, as the second step,
Reaction gas composition: by _{volume%, TiCl 4: 3~12%,} CH 3 CN: 0.2~2%, C 3 H 3 N: 0.1~0.5%, Ar: 10~30%, H ₂ : the rest,
Reaction atmosphere temperature: 700-850 ° C.
Reaction atmosphere pressure: 6-20 kPa,
When the vapor deposition is performed until the target layer thickness is reached under the above conditions, the l-TiCN layer (hereinafter referred to as “modified TiCN layer”) sequentially formed under the conditions of the first step and the second step is cut. Since it has the action of relaxing and absorbing the stress generated in the layer from time to time and the high temperature strength is further improved, the upper layer of the hard coating layer is composed of the Al ₂ O ₃ layer, and the lower layer is a TiC layer, It is composed of two or more Ti compound layers of a TiN layer, a TiCN layer, a 1-TiCN layer, a TiCO layer, and a TiCNO layer, and at least one of the Ti compound layers is composed of the modified TiCN layer The resulting coated tool will exhibit excellent chipping resistance even during heavy cutting, especially when heavy thermal and mechanical loads are applied, and will exhibit excellent wear resistance over a long period of time. .

(B) About the 1-TiCN layer (henceforth "conventional TiCN layer") which comprises the lower layer of the hard coating layer of said conventional coated tool, and the modified TiCN layer of said (a),
Using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. 2A and 2B, each crystal grain existing within the measurement range of the vertical cross-section polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the vertical cross-section polished surface (FIG. When the tilt angle of the (001) plane is 0 degree and the tilt angle of the (011) plane is 45 degrees, the tilt angle of the (001) plane is 45 degrees and the tilt angle of the (011) plane is 0 degree. In this case, all inclination angles of the crystal grains including these angles are measured. In this case, the crystal grains are composed of Ti, carbon, and nitrogen at lattice points as described above. It has a NaCl-type face-centered cubic crystal structure in which each atom exists, and based on the measured tilt angle obtained as a result, When the angles at which the (001) plane normal lines and the (011) plane normal lines intersect each other at the interface between the adjacent crystal grains are obtained, the (001) plane normal lines, and (011) The case where the angle between the normals of the planes is 2 degrees or more is set as a grain boundary, and using the field emission electron microscope, the vertical cross-section polished surface of the modified TiCN layer is For example, the angle between the normal lines of the (001) planes and the normal lines of the (011) planes is 15 degrees or more among the portions that are measured as a height 15 μm × width 30 μm and are identified as grain boundaries. When the length of the grain boundary (μm, hereinafter referred to as GBL) is obtained, and the ratio of the thickness of the GBL to the modified TiCN layer (μm, hereinafter denoted by T) (that is, GBL / T) is determined. As shown in Table 5, the conventional TiCN layer has a small GBL / T. On the other hand, as shown in Table 4, the modified TiCN layer shows a large value of GBL / T of 295 to 520, and this high GBL / T value is a reaction gas during film formation. Change depending on the combination of composition, reaction atmosphere temperature, and reaction atmosphere pressure.

(C) Since the above-mentioned modified TiCN layer has the effect of relaxing and absorbing stress generated in the modified TiCN layer during cutting in addition to the high-temperature hardness and high-temperature strength of the TiCN itself, A coated tool having a higher high-temperature strength than the above-mentioned and formed by vapor deposition as a lower layer of the hard coating layer has excellent high-temperature hardness and an Al ₂ O ₃ layer as the upper layer. Combined with heat resistance, the conventional TiCN layer is also vapor-deposited when used in heavy cutting conditions such as high feed and high cutting, which require a large thermal and mechanical load on the cutting edge. Compared to conventional coated tools, the hard coating layer will exhibit even better chipping resistance.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
On the surface of the tool base composed of WC-based cemented carbide or TiCN-based cermet,
(A) The lower layer is composed of two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, all formed by chemical vapor deposition, and 3 A Ti compound layer having a total average layer thickness of ˜20 μm,
(B) an aluminum oxide layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
In the surface-coated cutting tool formed with the hard coating layer composed of (a) and (b) above,
At least one of the Ti compound layers of (a) has an average layer thickness of 2.5 to 15 μm, and
Using a field emission scanning electron microscope, each of the crystal grains existing within the measurement range of 30 μm in width of the vertical cross-section polished surface of the layer was irradiated with an electron beam, and the normal to the vertical cross-section polished surface was The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, is measured, and the normal line of the (001) plane at the interface between adjacent crystal grains is determined based on the measured tilt angles. And the (011) plane normals intersect with each other, and the (001) plane normals and (011) plane normals intersect with each other at an angle of 2 degrees or more. Then, using a field emission electron microscope, the normal of the (001) plane among the parts identified as grain boundaries in the measurement region on the vertical cross-section polished surface of the layer, and (011 ) The angle where the normals of the surfaces intersect is 15 degrees or more The grain boundary length (μm) is obtained, and the ratio of the grain boundary length (μm) to the measured thickness of the Ti compound layer (μm) has a vertically grown crystal structure showing 295 to 520 Titanium carbonitride layer,
A surface-coated cutting tool (coated tool) that exhibits excellent chipping resistance with a hard coating layer that is characterized by comprising
It has the characteristics.

Next, the reason why the constituent layers of the hard coating layer of the coated tool of the present invention are numerically limited as described above will be described below.
(A) Lower layer (Ti compound layer)
Ti compound layer consisting of TiC layer, TiN layer, TiCN layer (including 1-TiCN layer), TiCO layer, TiCNO layer and modified TiCN layer described later has high-temperature strength itself, and due to its presence, hard coating layer In addition to having high-temperature strength, it firmly adheres to both the tool base and the upper Al ₂ O ₃ layer, thereby contributing to improved adhesion of the hard coating layer to the tool base. When the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exhibited. On the other hand, when the total average layer thickness exceeds 20 μm, chipping is likely to occur particularly in high-speed intermittent cutting with high heat generation. Therefore, the total average layer thickness was determined to be 3 to 20 μm.

(B) Modified TiCN layer of the lower layer The crystal grains constituting the modified TiCN layer of the lower layer have a crystal structure of NaCl type face centered cubic crystal in which constituent atoms composed of Ti, carbon, and nitrogen are present at lattice points, respectively. However, for the modified TiCN layer, using a field emission scanning electron microscope, each crystal grain of the modified TiCN layer existing within the measurement range of the vertical cross-section polished surface is irradiated with an electron beam, The inclination angles formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, are measured with respect to the normal line of the longitudinal cross-section polished surface. The angles at which the (001) plane normals and the (011) plane normals intersect at the interface between adjacent crystal grains are obtained, and the (001) plane normals and the (011) plane If the angle between the two normals is 2 degrees or more After setting the combination as a grain boundary, the vertical cross-section polished surface of the modified TiCN layer was measured in a measurement region, for example, a range of 15 μm in height × 30 μm in width, using a field emission electron microscope. Among the parts identified as boundaries, the grain boundary length GBL (μm) of the grain boundaries in which the normals of the (001) planes and the normal lines of the (011) planes intersect is 15 degrees or more. When the ratio between GBL (μm) and the thickness T (μm) of the modified TiCN layer is determined, GBL / T shows a value of 295 to 520, and GBL / T is 295 to 520. The modified TiCN layer showing a large value has the action of relaxing and absorbing the stress generated at that time even if a large thermal / mechanical load is applied to the cutting edge part by heavy cutting. To have excellent high-temperature strength The risk of chipping in the hard coating layer can be greatly reduced. However, when the GBL / T value is less than 295, the stress relaxation / absorption action cannot be expected. When the / T value exceeds 520, the modified TiCN layer itself tends to become brittle, so the GBL / T value was set to 295 to 520.
In addition, since the value of GBL / T in the conventional TiCN layer is a small value of about 100 to 200 (see Table 5) and is a TiCN layer that does not have a stress relaxation / absorption function, Chipping was observed in the hard coating layer (see Table 6).
In addition to the high temperature hardness and high temperature strength of TiCN itself as described above, the modified TiCN layer has a further excellent high temperature strength. However, if the average layer thickness is less than 2.5 μm, it is desirable. Since the hard coating layer cannot be sufficiently provided with excellent stress relaxation / absorption action and high-temperature strength improvement effect, on the other hand, if its average layer thickness exceeds 15 μm, chipping tends to occur. The thickness was determined to be 2.5-15 μm.

(C) Upper layer (Al ₂ O ₃ layer)
The upper layer composed of the Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance and contributes to improving the wear resistance of the hard coating layer. However, if the average layer thickness is less than 1 μm, it is sufficient for the hard coating layer. On the other hand, since the wear resistance cannot be exhibited, and when the average layer thickness exceeds 15 μm, chipping tends to occur. Therefore, the average layer thickness is set to 1 to 15 μm.

  In addition, for the purpose of identification before and after the use of the cutting tool, a TiN layer having a golden color tone may be vapor-deposited as necessary, but the average layer thickness in this case may be 0.1 to 1 μm, This is because if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient with an average layer thickness of up to 1 μm.

  The coated tool of the present invention constitutes at least one layer of the lower layer of the hard coating layer even in heavy cutting such as steel and cast iron that is accompanied by a large heat generation and requires a large mechanical load on the cutting edge portion. The modified TiCN layer has a stress relieving / absorbing action and has a further excellent high-temperature strength. Therefore, the hard coating layer has no chipping and exhibits excellent wear resistance.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was vacuum sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge portion was R: 0.07 mm honing By performing the processing, tool bases A to F made of WC-based cemented carbide having an insert shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having an insert shape of standard / CNMG12041 were formed.

Next, a Ti compound layer excluding the modified TiCN layer is shown in Table 3 as the lower layer of the hard coating layer on the surfaces of the tool bases A to F and the tool bases a to f using a normal chemical vapor deposition apparatus. Formed under the conditions
Next, the modified TiCN layer is
First, as the first step,
By _volume%, TiCl 4:: Reaction gas composition predetermined amount in the range 5-15% _of, C ₃ H ₃ N: a predetermined amount in the range of _0.7~2.5%, N 2: 7~20% A predetermined amount within the range, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 700 to 850 ° C.,
Reaction atmosphere pressure: a predetermined pressure in the range of 6 to 20 kPa,
Under the conditions, vapor deposition is performed until the layer thickness reaches about 20% of the target layer thickness,
Then, as the second step,
Reaction gas composition:% by volume, TiCl ₄ : predetermined amount in the range of 3-12%, CH ₃ CN: predetermined amount in the range of 0.2-2%, C ₃ H ₃ N: 0.1-0 A predetermined amount within a range of 5%, Ar: a predetermined amount within a range of 10 to 30%, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature within a range of 700 to 850 ° C.,
Reaction atmosphere pressure: a predetermined pressure in the range of 6 to 20 kPa,
Under the conditions shown in Table 4 and with the target layer thickness shown in Table 4, and after that, the Al ₂ O ₃ layer as the upper layer is also shown under the conditions shown in Table 3. The coated tools 1 to 13 of the present invention were produced by vapor deposition with the combination shown in FIG.

Further, for comparison purposes, as a lower layer of the hard coating layer, a Ti compound layer excluding the conventional TiCN layer under the conditions shown in Table 3, and the conventional TiCN layer,
Reaction gas composition:% by volume, TiCl ₄ : predetermined amount in the range of 2 to 10%, CH ₃ CN: predetermined amount in the range of 0.5 to 3%, N ₂ : in the range of 10 to 30% Predetermined amount, H ₂ : remaining,
Reaction atmosphere temperature: a predetermined temperature in the range of 800 to 900 ° C,
Reaction atmosphere pressure: 6 kPa,
Under the conditions shown in Table 5 and with the target layer thickness shown in Table 5 as well, and an Al ₂ O ₃ layer as the upper layer is formed under the conditions shown in Table 3 and the target layer. Conventionally, the coated tools 1 to 13 were manufactured by vapor deposition with a thickness.

Next, with respect to the modified TiCN layer and the conventional TiCN layer constituting the hard coating layer of the present invention-coated tool and the conventional coated tool, using a field emission scanning electron microscope, the GBL (μm ) Was measured, and the ratio of GBL (μm) to the layer thickness (μm) of the modified TiCN layer was determined.
That is, the modified TiCN layer and the conventional TiCN layer are set in a lens barrel of a field emission scanning electron microscope in a state where the vertical cross section of the TiCN layer is a polished surface, and accelerated to 15 kV at an incident angle of 70 degrees on the polished surface. A voltage electron beam is irradiated at an irradiation current of 1 nA to individual crystal grains existing within the measurement range of the vertical cross-section polished surface, and a predetermined measurement region is set to 0.1 μm / step using an electron backscatter diffraction image apparatus. At an interval, the inclination angle formed by the normal lines of the (001) plane and (011) plane, which are crystal planes of the crystal grains, is measured with respect to the normal line of the vertical cross-section polished surface, and the measured inclination obtained as a result Based on the angles, the angles at which the (001) plane normal lines and the (011) plane normal lines intersect each other at the interface between adjacent crystal grains are obtained. , And (011) plane normals When the crossing angle is 2 degrees or more is set as a grain boundary, a field-emission scanning electron microscope is used to measure the longitudinally polished surface of the modified TiCN layer (a region in the range of 15 μm in height × 30 μm in width) ), And in the measurement region, among the parts identified as grain boundaries, the (001) plane normals and the (011) plane normals intersect at an angle of 15 degrees or more. The grain boundary length GBL (μm) was obtained. Then, the value of the ratio between GBL (μm) and the layer thickness T (μm) of the modified TiCN layer (corresponding to the length of the grain boundary per unit layer thickness of the modified TiCN layer) was determined.

  Tables 4 and 5 show the values of GBL, T, and GBL / T for various modified TiCN layers and conventional TiCN obtained as a result.

  As shown in Tables 4 and 5, respectively, the modified TiCN layer of the coated tool of the present invention has a GBL / T value in the range of 295 to 520, whereas the conventional TiCN of the conventional coated tool. All the layers had a GBL / T value of less than 295.

Further, regarding the above-described coated tools 1 to 13 of the present invention and the conventional coated tools 1 to 13, the hard coating layer was observed using an electron beam microanalyzer (EPMA) and an Auger spectrometer (longitudinal section of the layer). As a result, it was confirmed that both the former and the latter were composed of a Ti compound layer and an Al ₂ O ₃ layer having substantially the same composition as the target composition.
Moreover, when the thickness of the constituent layer of the hard coating layer of these coated tools was measured using a scanning electron microscope (similarly longitudinal section measurement), the average layer thickness (5 The average value of point measurement) was shown.

Next, in the state where all of the above various coated tools are screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1 to 13 and the conventional coated tools 1 to 13,
Work material: JIS-S35C lengthwise equal length 4 round fluted round bars,
Cutting speed: 400 m / min,
Cutting depth: 1.0 mm,
Feed: 0.55 mm / rev,
Cutting time: 5 minutes,
Carbon steel dry high feed intermittent cutting test under the following conditions (cutting condition A) (normal cutting speed and feed are 250 m / min and 0.25 mm / rev, respectively),
Work material: JIS / SNCM220 lengthwise equal 4 round bars with longitudinal grooves,
Cutting speed: 350 m / min,
Cutting depth: 4.0 mm,
Feed: 0.3 mm / rev,
Cutting time: 5 minutes,
Of high-cut intermittent cutting of alloy steel under the above conditions (cutting condition B) (normal cutting speed and cutting are 250 m / min and 1.5 mm, respectively),
Work material: JIS / FC300 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 450 m / min,
Cutting depth: 1.5 mm,
Feed: 0.5 mm / rev,
Cutting time: 5 minutes,
The dry high feed intermittent cutting test (normal cutting speed and feed are 250 m / min and 0.3 mm / rev, respectively) of the cast iron under the above conditions (cutting condition C). The surface wear width was measured. The measurement results are shown in Table 6.

  From the results shown in Tables 4 to 6, all of the coated tools 1 to 13 of the present invention are modified TiCN layers in which at least one of the lower layers of the hard coating layer is GBL / T = 295 to 520. Even in heavy cutting of steel and cast iron, which is constructed and has extremely high thermal and mechanical loads, the modified TiCN layer has a stress relaxation / absorption action, and has a superior high-temperature strength. Demonstrates chipping properties, the occurrence of chipping in the hard coating layer is remarkably suppressed, and exhibits excellent wear resistance, whereas the TiCN layer of the lower layer of the hard coating layer has a GBL / T value of less than 295 In the conventional coated tools 1 to 13 composed of a certain conventional TiCN layer, the hard coating layer has insufficient resistance to thermal and mechanical loads, so chipping occurs in the hard coating layer in heavy cutting. And It is clear that lead to comparatively short time service life.

  As described above, the coated tool of the present invention is required not only for continuous cutting and intermittent cutting under normal conditions such as various types of steel and cast iron, but also for higher thermal and mechanical loads, which require even higher high-temperature strength. The hard coating layer exhibits excellent chipping resistance even during heavy cutting, and exhibits excellent cutting performance over a long period of time. It can cope with cost reduction sufficiently satisfactorily.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the TiCN layer which comprises the lower layer of a hard coating layer has. It is a schematic explanatory drawing which shows the measurement aspect of the inclination angle of the (001) plane of a crystal grain and the (011) plane in the TiCN layer which comprises the lower layer of a hard coating layer.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) The lower layer is composed of two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, all formed by chemical vapor deposition, and 3 A Ti compound layer having a total average layer thickness of ˜20 μm,
(B) an aluminum oxide layer having an average layer thickness of 1 to 15 μm, wherein the upper layer is formed by chemical vapor deposition;
In the surface-coated cutting tool formed with the hard coating layer composed of (a) and (b) above,
At least one of the Ti compound layers of (a) has an average layer thickness of 2.5 to 15 μm, and
Using a field emission scanning electron microscope, each of the crystal grains existing within the measurement range of 30 μm in width of the vertical cross-section polished surface of the layer was irradiated with an electron beam, and the normal to the vertical cross-section polished surface was The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, is measured, and the normal line of the (001) plane at the interface between adjacent crystal grains is determined based on the measured tilt angles. And the (011) plane normals intersect with each other, and the (001) plane normals and (011) plane normals intersect with each other at an angle of 2 degrees or more. Then, using a field emission electron microscope, the normal of the (001) plane among the parts identified as grain boundaries in the measurement region on the vertical cross-section polished surface of the layer, and (011 ) The angle where the normals of the surfaces intersect is 15 degrees or more The grain boundary length (μm) is obtained, and the ratio of the grain boundary length (μm) to the measured thickness of the Ti compound layer (μm) has a vertically grown crystal structure showing 295 to 520 Titanium carbonitride layer,
A surface-coated cutting tool that exhibits excellent chipping resistance with a hard coating layer in heavy cutting, characterized by comprising

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