WO2022264196A1

WO2022264196A1 - Cutting tool

Info

Publication number: WO2022264196A1
Application number: PCT/JP2021/022457
Authority: WO
Inventors: 史佳小林; アノンサックパサート; 保樹城戸; 皓祐冨永
Original assignee: 住友電工ハードメタル株式会社; 住友電気工業株式会社
Priority date: 2021-06-14
Filing date: 2021-06-14
Publication date: 2022-12-22

Abstract

A cutting tool provided with a substrate and a coating provided on the substrate, wherein: the coating includes a first layer; the first layer contains multiple crystal grains; the crystal grains comprise Al_xTi_1-xC_yN_1-y, where x is greater than 0.65 and less than 0.95, y is 0 or more and less than 0.1; the average aspect ratio of the crystal grains is 3.0 or less; the crystal grains include crystal grains having a cubic crystal structure; in the first layer, the surface area ratio of the crystal grains having a cubic crystal structure is 90% or higher; the average aspect ratio and the surface area ratio are measured at a cross section along the normal line from the interface between the substrate and the coating; and the thickness of the first layer is 2-20 μm.

Description

Cutting tools

The present disclosure relates to cutting tools.

Conventionally, cutting tools in which a film is formed on a base material have been used for cutting steel, castings, and the like (Japanese Patent Application Laid-Open No. 2016-30319 (Patent Document 1)).

JP 2016-30319 A

A cutting tool of the present disclosure comprises a substrate and a coating disposed on the substrate,
The coating comprises a first layer,
the first layer includes a plurality of grains;
The grains consist of Al _x Ti _1-x C _y N _1-y ,
The x is greater than 0.65 and less than 0.95,
The y is 0 or more and less than 0.1,
The average aspect ratio of the crystal grains is 3.0 or less,
The grains comprise grains having a cubic structure,
In the first layer, the area ratio occupied by the crystal grains having the cubic system structure is 90% or more,
The average aspect ratio and the area ratio are measured in a cross section along the normal of the interface between the substrate and the coating,
The thickness of the first layer is 2 μm or more and 20 μm or less.

1 is a perspective view illustrating one aspect of the cutting tool of the present disclosure; FIG. FIG. 2 is a sectional view taken along line II-II of FIG. FIG. 3 is a schematic cross-sectional view illustrating one aspect of the cutting tool of the present disclosure. FIG. 4 is a schematic cross-sectional view illustrating another aspect of the cutting tool of the present disclosure. FIG. 5 is a schematic cross-sectional view further illustrating another aspect of the cutting tool of the present disclosure. FIG. 6 is an example of an IPF map created in one aspect of the cutting tool of the present disclosure; FIG. 7 is an example of a crystal phase map created in one aspect of the cutting tool of the present disclosure. FIG. 8 is an example of a schematic cross-sectional view of a cutting tool of the present disclosure. FIG. 9 is a schematic cross-sectional view of a CVD apparatus used to manufacture cutting tools of the present disclosure.

[Problems to be Solved by the Present Disclosure]
Conventionally, cutting is performed under wet conditions using cutting oil for the purpose of preventing plastic deformation of a work material due to processing heat. Also, in recent years, there has been a demand for a higher cutting speed for the purpose of shortening the machining time. When cutting is performed at high speed under wet conditions, cracks (thermal cracks) tend to occur in the coating of the cutting tool due to the processing heat generated by the cutting process, so the tool life of the cutting tool is shortened. may become. For example, when cutting an alloy steel work material at high speed under wet conditions, the rake face of the cutting tool experiences a combination of thermal cracking and abrasion caused by chip abrasion. This tends to shorten the tool life of cutting tools.

Patent Document 1 discloses a cutting tool in which a coating layer having a predetermined layer thickness includes an AlTiCN layer, and the AlTiCN layer is formed to have a columnar structure in the thickness direction. By having such a configuration, it is expected that the wear resistance of the cutting tool is improved. However, with the recent increase in cutting speed, it is required to further extend the tool life of cutting tools even in high-speed cutting under wet conditions.

[Effect of the present disclosure]
According to the present disclosure, it is possible to provide cutting tools with long tool life, especially in high speed cutting under wet conditions of alloy steels.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described.
(1) A cutting tool of the present disclosure comprises a substrate and a coating disposed on the substrate,
The coating comprises a first layer,
the first layer includes a plurality of grains;
The grains consist of Al _x Ti _1-x C _y N _1-y ,
The x is greater than 0.65 and less than 0.95,
The y is 0 or more and less than 0.1,
The average aspect ratio of the crystal grains is 3.0 or less,
The grains comprise grains having a cubic structure,
In the first layer, the area ratio occupied by crystal grains having a cubic system structure is 90% or more,
The average aspect ratio and the area ratio are measured in a cross section along the normal of the interface between the substrate and the coating,
The thickness of the first layer is 2 μm or more and 20 μm or less.

The cutting tool of the present disclosure can have a long tool life, especially in high-speed cutting under wet conditions of alloy steel.

(2) the crystal grains include first crystal grains,
The inclination angle of the <111> direction of the first crystal grains with respect to the normal direction of the surface of the coating is 0° or more and 10° or less, and the first number ratio of the first crystal grains to the crystal grains is 15% or more, and the first number ratio is preferably measured in a cross section along the normal line of the interface between the substrate and the coating. This further improves the wear resistance of the cutting tool.

(3) The compressive residual stress of the first layer is preferably 1.0 GPa or more and less than 4.5 GPa. This further improves the thermal crack resistance of the cutting tool.

(4) The hardness of the first layer is preferably 30 GPa or more and 40 GPa or less. This further improves the wear resistance of the cutting tool.

[Details of the embodiment of the present disclosure]
A specific example of a cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") will be described below with reference to the drawings. In the drawings of this disclosure, the same reference numerals represent the same or equivalent parts. Also, dimensional relationships such as length, width, thickness, and depth are appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

In this specification, the notation of the form "A to B" means the upper and lower limits of the range (that is, from A to B). and the unit of B are the same.

In the present specification, when a compound or the like is represented by a chemical formula, it shall include any conventionally known atomic ratio unless the atomic ratio is particularly limited, and should not necessarily be limited only to those within the stoichiometric range. For example, when "AlTiCN" is described, the ratio of the number of atoms constituting AlTiCN includes all conventionally known atomic ratios.

In the crystallographic descriptions in this specification, individual planes are indicated by (), and aggregate orientations are indicated by <>.

[Embodiment 1: Cutting tool]
As shown in FIG. 3, the cutting tool 1 according to this embodiment is
A cutting tool 1 comprising a substrate 10 and a coating 14 disposed on the substrate 10,
The coating 14 comprises a first layer 11,
The first layer 11 includes a plurality of crystal grains,
The grains consist of Al _x Ti _1-x C _y N _1-y ,
The x is greater than 0.65 and less than 0.95,
The y is 0 or more and less than 0.1,
The average aspect ratio of the crystal grains is 3.0 or less,
The grains comprise grains having a cubic structure,
In the first layer 11, the area ratio occupied by the crystal grains having the cubic system structure is 90% or more,
The average aspect ratio and the area ratio are measured in a cross section along the normal of the interface between the substrate 10 and the coating 14,
The thickness of the first layer 11 is 2 μm or more and 20 μm or less.

The cutting tool of the present disclosure can provide a cutting tool with a long tool life, especially in high-speed cutting of alloy steel under wet conditions. The reason is presumed as follows.

(a) In the first layer, the area ratio of crystal grains having a cubic crystal structure is 90% or more, so the first layer has high hardness and the cutting tool has excellent wear resistance. can have Here, "wear resistance" means resistance to abrasion of the coating when used for cutting.

(b) As in (a) above, when the proportion of crystal grains having a cubic system structure among the crystal grains made of Al _x Ti _1-x C _y N _1-y is 90% or more, such Cutting tools have excellent wear resistance. However, in such a case, crystal grains are likely to form a columnar structure in the film thickness direction. Therefore, in such a cutting tool, the grain boundaries of the crystal grains extend in the film thickness direction. It is weak and prone to thermal cracking on the rake face. Therefore, thermal cracking of the coating of the cutting tool is likely to occur due to processing heat generated by cutting, and therefore, the cutting tool containing such crystal grains in the coating may be inferior in thermal crack resistance.

However, in the cutting tool of the present embodiment, the average aspect ratio of the crystal grains is 3.0 or less, so that the grain boundaries of the crystal grains in the first layer are prevented from extending in the film thickness direction. can. Therefore, in the first layer, cracks in the film thickness direction can be suppressed from growing linearly, so the cutting tool of the present embodiment can be used for high-speed cutting of alloy steel under wet conditions can also have excellent thermal crack resistance at the rake face. Here, the term "thermal crack resistance" means resistance to cracking of the cutting edge during cutting in which the cutting edge becomes hot.

That is, the cutting tool according to the present embodiment can have a long tool life by improving wear resistance and thermal crack resistance.

Examples of cutting tools according to the present embodiment include drills, end mills, indexable cutting inserts for drills, indexable cutting inserts for end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, and metal saws. , gear cutting tools, reamers, taps, and the like.

FIG. 1 is a perspective view illustrating one aspect of the cutting tool 1 of the present disclosure. FIG. 2 is a cross-sectional view taken along line II--II of FIG. The cutting tool 1 having such a shape is used as an indexable cutting tip such as an indexable cutting tip for turning. The cutting tool 1 includes a rake face 1a, a flank face 1b, and a cutting edge portion 1c connecting the rake face 1a and the flank face 1b.

<Base material>
Any conventionally known base material of this type can be used as the base material of the present embodiment. For example, the base material is a cemented carbide (for example, a tungsten carbide (WC)-based cemented carbide, a cemented carbide containing Co in addition to WC, a carbonitride such as Cr, Ti, Ta, Nb in addition to WC). Cemented carbide etc.), cermet (mainly composed of TiC, TiN, TiCN etc.), high speed steel, ceramics (TiC, SiC, SiN, AlN, Al ₂ O ₃ etc.), cubic type nitriding It preferably contains one selected from the group consisting of a boron sintered body (cBN sintered body) and a diamond sintered body.

Among these various base materials, it is particularly preferable to select cemented carbide (especially WC-based cemented carbide) and cermet (especially TiCN-based cermet). The reason for this is that these base materials have an excellent balance of hardness and strength, particularly at high temperatures, and have excellent properties as base materials for cutting tools for the above applications.

When a cemented carbide is used as the base material, the effect of the present embodiment is exhibited even if such a cemented carbide contains free carbon or an abnormal phase called η phase in the structure. In addition, the base material used in this embodiment may have a modified surface. For example, in the case of cemented carbide, a β-free layer may be formed on the surface, or in the case of a cBN sintered body, a surface-hardened layer may be formed. Even if the surface is modified in this way, The effect of this embodiment is shown.

When the cutting tool is an indexable cutting insert (an indexable cutting insert for turning, an indexable cutting insert for milling, etc.), the substrate may or may not have a chip breaker. included. The shape of the cutting edge is sharp edge (the ridge where the rake face and flank face intersect), honing (sharp edge rounded), negative land (chamfered shape), and a combination of honing and negative land. includes any shape.

<Coating>
FIG. 3 is a schematic cross-sectional view illustrating one aspect of the cutting tool of the present disclosure. FIG. 4 is a schematic cross-sectional view illustrating another aspect of the cutting tool of the present disclosure. FIG. 5 is a schematic cross-sectional view further illustrating another aspect of the cutting tool of the present disclosure. The coating 14 according to this embodiment includes a first layer 11 (FIGS. 3-5). The “coating” has the effect of improving various properties such as peeling resistance, chipping resistance, and wear resistance of cutting tools by covering at least a portion of the base material (for example, a portion of the rake face). have. The coating 14 preferably covers the entire surface of the substrate 10 . However, it would not be outside the scope of the present embodiment if a portion of the base material 10 were not covered with the coating 14 or the composition of the coating 14 was partially different.

The thickness of the coating is preferably 2 µm or more and 25 µm or less, more preferably 2 µm or more and 15 µm or less, and even more preferably 3 µm or more and 12 µm or less. Here, the thickness of the coating means the sum of the thicknesses of the layers constituting the coating. Examples of the "layer constituting the coating" include the first layer and other layers described later as layers other than the first layer. The thickness of the coating is, for example, using a transmission electron microscope (TEM), measuring any 10 points in a cross-sectional sample parallel to the normal direction of the surface of the substrate, and the average of the thickness of the measured 10 points It can be obtained by taking the value. Examples of the cross-sectional sample include a sample obtained by slicing the cross-section of the cutting tool with an ion slicer. The same is true when measuring the thickness of each of the first layer and the other layer. Examples of transmission electron microscopes include JEM-2100F (trade name) manufactured by JEOL Ltd.

The coating includes a first layer. Moreover, in one aspect of the present embodiment, a plurality of the first layers may be provided as long as the effects of the cutting tool are maintained. For example, when the coating includes two first layers, the coating may further include an intermediate layer (another layer) provided between the two first layers.

(first layer)
The first layer according to this embodiment includes a plurality of crystal grains. The first layer may be composed only of the crystal grains, or may contain other components. Other components include TiN, TiC, Al ₂ O ₃ , TiCN, TiCNO, TiBN, and the like. Moreover, it is more preferable that the first layer covers the entire surface of the substrate. However, it would not depart from the scope of this embodiment if a portion of the first layer were not covered by the first layer.

(crystal grain)
The crystal grains according to this embodiment consist of Al _x Ti _1-x C _y N _1-y . Here, "the crystal grains are composed of Al _x Ti _1-x CyN _1-y _" is not limited to the mode composed only of Al _x Ti _1-x CyN _1-y _, and the effects of the present disclosure As long as the above is achieved, it is a concept that includes an aspect including components other than Al _x Ti 1 _- x CyN _1-y _together with Al _x Ti _1-x CyN _1-y _.

The above x is more than 0.65 and less than 0.95. This allows the cutting tool to have excellent heat resistance. Moreover, the above x is preferably more than 0.7 and less than 0.95, more preferably more than 0.75 and less than 0.95, and even more preferably more than 0.80 and less than 0.90.

The above y is 0 or more and less than 0.1. When the content of carbon in the crystal grains is very small in the range of 0≦y<0.1, lubricity is improved, thereby improving wear resistance. On the other hand, if y deviates from the above range, the chipping resistance and chipping resistance are lowered, which is not preferable. In addition, y is preferably 0 or more and less than 0.08, more preferably 0 or more and less than 0.06, and still more preferably 0 or more and less than 0.05. Also, from the manufacturing point of view, the lower limit of y can be 0.01 or more and 0.02 or more.

The crystal grains are made of Al _x Ti _1-x C _y N _1-y , the x is more than 0.65 and less than 0.95, and the y is 0 or more and less than 0.1, It can be confirmed by using an EDX (Energy Dispersive X-ray spectroscopy) device attached to SEM or TEM. Specifically, first, a cutting tool is cut at an arbitrary position in the film thickness direction to prepare a sample including a cross section of the film. Next, for the first layer in the coating, 5 2 μm×2 μm rectangular measurement fields are arbitrarily selected and analyzed. Here, the midpoint of the diagonal line of the rectangle passes through the midpoint in the thickness direction of the first layer (the midpoint in the thickness direction between S1 or S2, which will be described later, and S3, which will be described later), and A pair of two opposite sides of the rectangle are parallel to S3, which will be described later. Thereby, the composition of the crystal grains can be determined by specifying x and y indicating the atomic ratio of each element contained in an arbitrary measurement region and obtaining the average value of each of x and y. .

(Average aspect ratio of crystal grains)
The average aspect ratio of the crystal grains is 3.0 or less. As a result, it is possible to suppress the grain boundaries of the crystal grains from extending in the film thickness direction in the first layer. Therefore, in the first layer, cracks in the film thickness direction can be prevented from linearly propagating, so that the cutting tool can have excellent thermal crack resistance. The lower limit of the average aspect ratio is preferably 1.0 or more. In terms of manufacturing, the lower limit of the average aspect ratio can be 1.2 or more and 1.4 or more. The upper limit of the average aspect ratio is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. In addition, the average aspect ratio is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.5 or less, and further preferably 1.0 or more and 2.0 or less. preferable.

<Method for measuring the average aspect ratio of crystal grains>
The average aspect ratio of the grains is measured in a cross section along the normal to the interface between the substrate and the coating. Specific measurement methods are as follows (A1) to (A5).

(A1) The cutting tool sample is embedded in epoxy resin and then polished. Using a cross-section polisher (manufactured by JEOL), the polished cutting tool is cut under conditions of 6 kV and 6 hours, and then finished under conditions of 1.5 kV and 1 hour. The cut is made in a direction along the normal to the surface of the cutting tool. The normal to the surface of the cutting tool and the normal to the interface between the substrate and the coating are substantially parallel. Thus, the cutting provides a cross section along the normal to the interface between the substrate and the coating of the first layer.

The cutting described above can be performed at any part of the cutting tool, regardless of whether it is the rake face or the flank, as long as it is performed at a position 0.1 mm or more away from the cutting edge in a direction parallel to the cutting tool surface.

(A2) Using a field emission scanning electron microscope (FE-SEM) (product name: "SUPRA35VP", manufactured by Carl Zeiss) equipped with an electron beam backscatter diffraction device (EBSD device) for the above cross section , EBSD analysis is performed under the following measurement conditions.
(Measurement condition)
Accelerating voltage: 15 kV
Irradiation current: 60 μm (with HC)
Exp: Long 0.03s
Binning: 8x8
WD: 15mm
Tilt: 70°
BKD: Background Subtraction;
dynamic background,
Normalize Intensity
Magnification: 20000 times Grain boundary definition: 15° or more

Regarding EBSD analysis, data collection is performed on the above cross section, at least from the surface S1 of the first layer or the interface S2 on the surface side of the first layer to the interface S3 on the substrate side. (the length including the entire thickness of the first layer)×10 μm (the length in the direction parallel to the interface S3 of the substrate side of the first layer) (observation area).

For the data collected by EBSD analysis, cleanup processing is performed by recognizing only data that satisfies CI > 0.1 by the CI Dilation method (single interpolation) and Grain CI Standardization. The CI value is calculated by the Voting method. Specifically, CI=(V1−V2)/Video (V1, 2:1, second solution, Video: ideal solution).

(A3) The above EBSD analysis results are analyzed using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.) to create an IPF map (Inverse Pole Tigre map). do. In creating the IPF map, a crystal grain boundary is defined as a case where the misorientation angle between adjacent measurement points is 15° or more. The IPF map shows the shape of each grain and the orientation of each grain by color coding. An example of the IPF map created for the cutting tool of this embodiment is shown in FIG. In addition, the area shown in black in FIG. 6 indicates that CI≦0.1. In other words, the areas shown in black in FIG. 6 mean areas where the shape of each crystal grain is not recognized by executing the cleanup process. In FIG. 6, the left side of the paper is the surface side of the cutting tool, and the right side of the paper is the substrate side of the cutting tool.

(A4) As shown in the schematic cross-sectional view of FIG. 8, on the IPF map, first, the surface S1 of the first layer 11 or the interface S2 on the surface side of the first layer 11 and the substrate side and the interface S3 are set by a setting method to be described later. Next, a first imaginary line L1 passing through a point 0.3 μm away from S3 toward S1 or S2 and parallel to S3 is set. Next, the length including all from S1 or S2 to L1 (the length in the film thickness direction of the first layer 11) × 10 µm (the direction parallel to the interface S3 on the substrate 10 side of the first layer 11 length) measurement area. In addition, in the IPF map, the setting method of S1, S2, and S3 is as follows.
(How to set S1, S2, and S3)
S1: When the surface of the first layer is a smooth surface, the smooth surface is set as S1. Further, when the surface of the first layer has an uneven shape, first, on the IPF map, it passes through at least one point on the surface of the first layer and is parallel to the interface between the coating and the substrate. and a virtual line VL1 (not shown) having the longest distance from the interface between the coating and the substrate, passing through at least one point on the surface of the first layer, and parallel to the interface between the coating and the substrate and a virtual line VL2 (not shown) having the shortest distance from the interface between the film and the base material. Next, a straight line whose distance from VL1 is equal to the distance from VL2 and which is parallel to the interface between the film and the substrate is set as the position of S1. In the IPF map, the smooth surface and the uneven shape are obtained by recognizing the smooth surface or the uneven shape on the SEM image of the same field of view as the IPF map, and then recognizing the smooth surface or the uneven shape. It can be recognized by superimposing the SEM image and the IPF map. The SEM image is obtained by using the FE-SEM.
S2: A line analysis is performed in the thickness direction of the film with an arbitrary point on the surface of the film as a base point. The line analysis is performed by EDX (Energy Dispersive X-ray Spectroscopy) with SEM. In the above line analysis, the beam diameter is 0.9 nm, the scanning interval is 0.1 μm, and the acceleration voltage is 15 kV. As a result, the ratio of the number of atoms of the metal element specific to the first layer (for example, Ti element when the upper layer in contact with the first layer is Al ₂ O ₃ ) in the first layer shows the maximum value. Identify points. Next, of the points indicating the half value of the maximum value, a point P1 (not shown) located on the surface side with the point indicating the maximum value as a base point and closest to the point indicating the maximum value is specified. Next, any other point on the surface of the coating is selected, and in the same way, the metal element peculiar to the first layer in the first layer (for example, the upper layer in contact with the first layer is an Al ₂ O ₃ layer In the case of Ti element), among the points that indicate the half value of the maximum value of the ratio of the number of atoms of Ti element), the point that is located on the surface side with the point that indicates the maximum value as the base point and is the closest point to the point that indicates the maximum value Identify P2 (not shown). Next, a straight line connecting P1 and P2 is set as the position of S2 on the IPF map.
S3: A line analysis is performed in the thickness direction of the coating with an arbitrary point on the coating surface as a base point. The line analysis is performed by EDX (Energy Dispersive X-ray Spectroscopy) with SEM. In the above line analysis, the beam diameter is 0.9 nm, the scanning interval is 0.1 μm, and the acceleration voltage is 15 kV. As a result, the point indicating the maximum value of the ratio of the number of atoms of the metal element peculiar to the first layer in the first layer (for example, Al element when the lower layer in contact with the first layer is a TiN layer) identify. Next, among the points indicating the half value of the maximum value, a point P3 (not shown) located on the substrate side with the point indicating the maximum value as a base point and closest to the point indicating the maximum value is specified. . Next, any other point on the surface of the coating is selected, and in the same way, the metal element peculiar to the first layer in the first layer (for example, the lower layer in contact with the first layer is a TiN layer of the points showing the half-maximum value of the ratio of the number of atoms of Al element), the point P4 is located on the substrate side with the point showing the maximum value as a base point, and is closest to the point showing the maximum value. (not shown). Next, a straight line connecting P3 and P4 is set as the position of S3 on the IPF map.

(A5) The aspect ratio is measured for each of all the crystal grains contained in the above measurement area, and the average value thereof is calculated. Here, among the crystal grains, crystal grains straddling any one of S1, S2 and L1 are excluded from the measurement. In this specification, the aspect ratio is defined as a value obtained by dividing the maximum diameter a of a crystal grain by the minor diameter b of a crystal grain. The maximum diameter a of the crystal grain is calculated by the formula “d ² = (x _i −x _j ) ² where the coordinate positions of the pixels on the outermost periphery of the crystal grain are (x _i , y _i ) and (x _j , y _j ). +(y _i −y _j ) ² ”, the maximum value of d obtained from all combinations of (x _i , y _i ) and (x _j , y _j ) in one crystal grain defined as a value. The short diameter b of the crystal grain is a numerical value calculated by the formula “b=A (particle area of the crystal grain)/πa”. The average value of the aspect ratios corresponds to the "average aspect ratio of crystal grains".

It has been confirmed that the same results can be obtained by arbitrarily selecting a different measurement range for the same cutting tool and performing the above measurements in that measurement range.

(Area ratio occupied by crystal grains having a cubic system structure)
The crystal grains include crystal grains having a cubic system structure. Further, in the first layer, the area ratio of crystal grains having a cubic system structure is 90% or more. This allows the first layer to have high hardness and the cutting tool to have excellent wear resistance. The lower limit of the area ratio is preferably 92% or more, more preferably 95% or more, and even more preferably 98% or more. Moreover, the upper limit of the area ratio is preferably 100% or less. Moreover, from the viewpoint of manufacturing, the upper limit of the area ratio can be 99.5% or less and 99% or less. The area ratio is preferably 90% or more and 100% or less, more preferably 95% or more and 100% or less, and even more preferably 98% or more and 100% or less.

<Method for measuring area ratio occupied by crystal grains having a cubic structure>
In the first layer, the area ratio occupied by grains having a cubic structure is measured in a cross section along the normal to the interface between the substrate and the coating. Specific measurement methods are as follows (B1) to (B4).

(B1) Perform EBSD analysis on the cross section of the cutting tool in the same procedure as (A1) and (A2) described in the above "Method for measuring the average aspect ratio of crystal grains".

(B2) The above EBSD analysis results are analyzed using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.) to create a crystalline phase map. In the crystal phase map, as shown in FIG. 7, the crystal system of each crystal grain is indicated by different colors. In this embodiment, mainly cubic and hexagonal systems are shown. In addition, the area shown in black in FIG. 7 indicates that CI≦0.1. In other words, the areas shown in black in FIG. 7 mean areas where the crystal system of each crystal grain is not recognized by executing the cleanup process. In FIG. 7, the left side of the paper is the surface side of the cutting tool, and the right side of the paper is the substrate side of the cutting tool.

(B3) Set the same measurement region as in (A4) above on the crystal phase map.

(B4) Calculate the percentage of the area of the cubic crystal grains to the area of the entire crystal system shown in the above measurement area. This percentage corresponds to "the area ratio occupied by crystal grains having a cubic system structure in the first layer". Here, "the entire region where the crystal system is shown" means "the region where the crystal system cannot be determined from the measurement region".

(First number ratio)
The crystal grains include first crystal grains, the inclination angle of the <111> direction of the first crystal grains with respect to the normal direction of the surface of the coating is 0° or more and 10° or less, and the crystal grains are , The first number ratio of the first crystal grains is preferably 15% or more. As a result, since the growth direction of the first crystal grains tends to be oriented in the <111> direction of the first crystal grains, the hardness of the first layer increases, so the wear resistance of the cutting tool can be further improved. The lower limit of the first number ratio is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. Also, the upper limit of the first number ratio is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. Further, the first number ratio is more preferably 15% or more and 70% or less, and even more preferably 20% or more and 50% or less.

<Method for measuring the first number ratio>
The first number ratio is measured in a cross section along the normal line of the interface between the substrate and the coating. Specific measurement methods are as follows (C1) to (C2).

(C1) Perform EBSD analysis on the cross section of the cutting tool in the same procedure as (A1) and (A2) described in the above "Method for measuring the average aspect ratio of crystal grains".

(C2) The above EBSD analysis results are analyzed using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.), and the tilt angle in the <111> direction for each pixel on the software The first number ratio is obtained by outputting a histogram of Crystal Direction and reading the cumulative ratio.

(Compressive residual stress of the first layer)
The compressive residual stress of the first layer is preferably 1.0 GPa or more and less than 4.5 GPa. As a result, the propagation of cracks generated during cutting can be suppressed, so that the thermal crack resistance of the cutting tool can be further improved. The lower limit of the compressive residual stress is preferably 1.0 GPa or more, more preferably 2.0 GPa or more, and even more preferably 2.5 GPa or more. Moreover, the upper limit of the compressive residual stress is preferably less than 4.5 GPa. Moreover, from the viewpoint of manufacturing, the upper limit of the compressive residual stress can be less than 4.0 GPa and less than 3.5 GPa. Further, the compressive residual stress is more preferably 2.0 GPa or more and less than 4.5 GPa, and even more preferably 2.5 GPa or more and less than 4.5 GPa.

<Method for Measuring Compressive Residual Stress of First Layer>
The compressive residual stress can be obtained by, for example, the 2θ-sin2 ψ method (lateral tilt method) using X-rays. Measurement conditions are as follows. For example, an average value of compressive residual stresses at arbitrary three or more points within 5 mm from the honing position of the rake face of the cutting tool toward the center position of the tool is obtained.
(Measurement condition)
X-ray output: 8.04keV
X-ray source: Radiation measurement plane: (200) plane Detector: Flat panel Condensing size: 1.5 mm × 0.5 mm
Scan axis: 2θ/θ
Scan mode: CONTINUOUS

(Hardness of first layer)
The hardness of the first layer is preferably 30 GPa or more and 40 GPa or less. This can further improve the wear resistance of the cutting tool. The lower limit of the hardness is preferably 30 GPa or more, more preferably 31 GPa or more, and even more preferably 32 GPa or more. The upper limit of the hardness is preferably 40 GPa or less, more preferably 39 GPa or less, and even more preferably 38 GPa or less. Further, the hardness is more preferably 31 GPa or more and 40 GPa or less, and even more preferably 32 GPa or more and 39 GPa or less.

<Method for Measuring Hardness of First Layer>
The hardness is measured by a method conforming to ISO14577, and the measurement load is 10 mN (1 g).

(Thickness of first layer)
The thickness of the first layer according to this embodiment is 2 μm or more and 20 μm or less. This can improve the wear resistance of the cutting tool. Also, the lower limit of the thickness of the first layer is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness of the first layer is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The thickness of the first layer is preferably 2 μm or more and 12 μm or less, more preferably 2 μm or more and 10 μm or less, and even more preferably 3 μm or more and 10 μm or less.

(other layers)
The coating may further include the other layers as long as the effects of the present embodiment are not impaired. As shown in FIGS. 4 and 5, examples of the other layers include an underlying layer 12, a surface layer 13, and the like.

(Underlayer)
The underlayer 12 is arranged between the substrate 10 and the first layer 11 . For example, a TiN layer can be used as the underlying layer. The average thickness of the underlayer is preferably 0.1 μm or more and 20 μm or less. According to this, the coating can have excellent wear resistance and chipping resistance. Further, the average thickness of the underlayer is more preferably 0.3 μm or more and 8 μm or less, and further preferably 0.5 μm or more and 5 μm or less.

(Surface layer)
The surface layer 13 preferably contains, for example, Ti (titanium) carbide, nitride, or boride as a main component. The surface layer 13 is the layer located closest to the surface of the coating 14 . However, it may not be formed at the cutting edge. The surface layer is arranged, for example, directly above the first layer.

"Consists mainly of Ti carbide, nitride, or boride" means containing 90% by mass or more of Ti carbide, nitride, or boride. Moreover, it means that it preferably consists of any one of carbide, nitride and boride of Ti except for inevitable impurities.

Among Ti carbides, nitrides, and carbonitrides, it is particularly preferable to form the surface layer mainly from Ti nitrides (that is, compounds represented by TiN). Among these compounds, TiN has the clearest color (exhibits a gold color), so it has the advantage of facilitating identification of the corners of the cutting tip after use for cutting (identification of used portions). The surface layer preferably consists of a TiN layer.

The surface layer preferably has an average thickness of 0.05 µm or more and 1 µm or less. According to this, the adhesion between the surface layer and the adjacent layer is improved. The average thickness of the surface layer is more preferably 0.1 μm or more and 0.8 μm or less, and even more preferably 0.2 μm or more and 0.6 μm or less.

[Embodiment 2: Manufacturing method of cutting tool]
The method for manufacturing a cutting tool according to this embodiment includes:
A first step of preparing the base material (hereinafter sometimes simply referred to as "first step");
and a second step of forming the coating on the substrate using a chemical vapor deposition (CVD) method (hereinafter, sometimes simply referred to as the “second step”).
In the second step, an aluminum halide gas, a titanium halide gas, an ammonia gas, and a hydrogen gas are jetted onto the substrate in an atmosphere of 650° C. or more and 900° C. or less and 0.1 kPa or more and 30 kPa or less. including doing The manufacturing method can further include a third step (hereinafter sometimes simply referred to as "third step") of subjecting the film obtained in the second step to a blasting treatment.

<First Step: Step of Preparing Base Material>
A substrate is prepared in the first step. For example, a cemented carbide substrate is prepared as the substrate. The cemented carbide substrate may be a commercially available product or may be produced by a general powder metallurgy method. When manufacturing by a general powder metallurgy method, for example, a mixed powder is obtained by mixing WC powder and Co powder with a ball mill or the like. After drying the mixed powder, it is molded into a predetermined shape (eg, SEET13T3AGSN-G, etc.) to obtain a molded body. Further, by sintering the molded body, a WC—Co-based cemented carbide (sintered body) is obtained. Then, the sintered body is subjected to a predetermined cutting edge processing such as honing treatment to produce a base material made of a WC—Co based cemented carbide. In the first step, any substrate other than those described above can be prepared as long as it is a conventionally known substrate of this type.

<Second step: step of forming a coating on the substrate>
In the second step, a CVD method is used to form a coating including the first layer on the substrate. Specifically, an aluminum halide gas, a titanium halide gas, an ammonia gas (hereinafter these gases are collectively referred to as "raw material gases"), and a carrier gas are heated at 650° C. to 900° C. A coating including the first layer is formed by jetting onto the substrate in an atmosphere of 1 kPa or more and 30 kPa or less. Thereby, the cutting tool of this embodiment is obtained. This step can be performed using, for example, a CVD apparatus described below.

(CVD equipment)
FIG. 9 shows a schematic cross-sectional view of an example of a CVD apparatus 50 used for manufacturing the cutting tool of this embodiment. As shown in FIG. 9, the CVD apparatus 50 includes a substrate setting jig 52 for setting the substrate 10, and a reaction vessel 53 made of heat-resistant alloy steel and containing the substrate setting jig 52. . A temperature controller 54 for controlling the temperature inside the reaction vessel 53 is provided around the reaction vessel 53 . In this embodiment, the substrate 10 is preferably placed on projections provided on the substrate setting jig 52 . By installing in this way, it is possible to form a uniform film on each of the rake face, the flank face, and the cutting edge.

In the reaction container 53, a gas introduction pipe 55 extends vertically in the space inside the reaction container 53, and is provided rotatably about the vertical direction. The gas introduction pipe 55 is provided with a plurality of through holes for ejecting gas to the tool substrate. In the present embodiment, it is preferable to keep a sufficient distance between the through-hole for ejecting the gas and the substrate 10 . By doing so, it is possible to prevent turbulence from occurring.

Furthermore, the reaction container 53 is provided with a gas exhaust pipe 56 for discharging the internal gas to the outside. It is discharged outside the reaction container 53 .

The inside of the reaction vessel 53 has an atmosphere of 650° C. to 900° C. (preferably 700° C. to 770° C.) and 0.1 kPa to 30 kPa (preferably 0.2 kPa to 5.0 kPa). Since the gas introduction pipe 55 has a plurality of through-holes, the introduced gas is jetted into the reaction vessel 53 from different through-holes. At this time, the gas introduction pipe 55 is rotating at a rotational speed of 2 to 4 rpm, for example, about the above-mentioned axis as indicated by the rotation arrow inside. This makes it possible to jet evenly onto the substrate.

Halide gases of aluminum include, for example, aluminum chloride gas (AlCl ₃ gas, Al ₂ Cl ₆ gas). Preferably AlCl ₃ gas is used. The concentration (% by volume) of the halide gas of aluminum is 0.1% by volume or more based on the total volume of all gases introduced into the reaction vessel (hereinafter also referred to as "total volume of introduced gas")1 It is preferably 0.0% by volume or less, more preferably 0.2% by volume or more and 0.8% by volume or less.

Titanium halide gases include, for example, titanium (IV) chloride gas ( _TiCl4 gas), titanium chloride ( _III ) gas (TiCl3 gas), and the like. Titanium (IV) chloride gas is preferably used. The concentration (% by volume) of the titanium halide gas is preferably 0.05% by volume or more and 0.3% by volume or less, based on the total volume of the introduced gas, and 0.1% by volume or more and 0.2% by volume. % or less.

The concentration (% by volume) of ammonia gas is preferably 0.2% by volume or more and 3.0% by volume or less, and 0.5% by volume or more and 2.0% by volume or less, based on the total volume of the introduced gas. It is more preferable to have

Ethylene gas (C ₂ H ₄ ) can be used in addition to the raw material gas. The concentration (% by volume) of ethylene gas is preferably 0% by volume or more and 0.3% by volume or less based on the total volume of the introduced gas.

Examples of carrier gases include argon gas and hydrogen gas. Hydrogen gas is preferably used. The gas concentration (% by volume) of the carrier gas is preferably 90% by volume or more and 99% by volume or less, more preferably 95% or more and 99% or less, based on the total volume of the introduced gas.

In the second step, the total flow rate of the introduced gas is changed by changing the flow rate of the carrier gas under the following conditions. According to this, the average aspect ratio of the crystal grains can be made 3.0 or less. The reason for this is presumed to be as follows.

In the deposition of the AlTiCN film by the CVD method, if the gas flow rate is constant, the probability of adsorption to a specific crystal plane is high, so it tends to grow in a columnar shape. On the other hand, in the present embodiment, the flow rate of the entire introduced gas is changed by changing the flow rate of the carrier gas during film formation. As a result, the raw material gas is less likely to be adsorbed on specific crystal planes, making it difficult for crystal grains to grow in a columnar shape, presumably reducing the aspect ratio of crystal grains. The present inventors have newly discovered that the average aspect ratio of crystal grains can be made 3.0 or less by changing the total gas flow rate of the introduced gas.

Conventionally, since the AlTiCN film is formed under high vacuum, it was difficult to control the pressure. Therefore, it was common to keep the gas flow velocity constant. If the gas flow velocity is changed during the formation of the AlTiCN film and the pressure fluctuation is large, it has been thought that defects such as defects tend to occur in the AlTiCN film. Therefore, the method of changing the gas flow rate during the deposition of the AlTiCN film, which is unique to this embodiment, was not adopted by those skilled in the art.

In the second step, the total gas flow rate introduced into the reaction vessel can be, for example, as follows. Here, the term "total gas flow rate" refers to the total volumetric flow rate of the gas introduced into the CVD furnace per unit time, assuming that the gas under standard conditions (0° C., 1 atm) is an ideal gas.
Flow rate (average): 100 L/min Flow rate (range of change): 80 to 120 L/min Period: 5 to 15 minutes (Over 15 minutes, the aspect ratio tends to increase.)
When the total gas flow rate is within the above range, the flow rate of the carrier gas in the introduced gas can be, for example, as follows.
Flow rate (average): 98% by volume
Flow rate (range of change): 97 to 99% by volume
Cycle: 5-15 minutes

The second step can include a step of forming other layers such as a base layer and a surface layer in addition to the step of forming the first layer. Other layers can be formed by conventional methods.

<Third step: step of blasting>
In this step, the coating is subjected to blasting. Examples of the blasting conditions include the following conditions. A desired compressive residual stress can be imparted to the coating by performing blasting.
(Conditions for blasting)
Media: Alumina particles, 500g
Projection angle: 45°
Projection distance: 30-100mm
Projection time: 2 to 8 seconds Projection pressure: 0.1 to 0.3 MPa
Rotation speed: 60rpm

<Other processes>
In the manufacturing method according to the present embodiment, in addition to the steps described above, a surface treatment step and the like may be performed as appropriate.

The present embodiment will be described more specifically with examples. However, this embodiment is not limited by these examples.

≪Manufacturing cutting tools≫
Sample no. 1 to 18, the composition consists of 2.0 wt% TaC, 1.0 wt% NbC, 10.0 wt% Co and the balance WC (including inevitable impurities), and , a cemented carbide cutting tip (manufactured by Sumitomo Electric Hardmetal Co., Ltd.) having a shape of SEET13T3AGSN-G was prepared as a base material (first step).

Next, a film was formed on the surface of the base material (second step). Specifically, using the CVD method, the conditions for forming the underlayer described in Table 1, the conditions for forming the first layer described in Table 2, and the surface described in Table 3 were applied to the entire surface of the base material. The second step was performed according to the layer formation conditions.

Furthermore, sample No. In order to produce cutting tools Nos. 1 to 16 and 18, the third step was performed under the blasting conditions described in Table 4 after the coating was formed as described above.

By executing the above steps, sample No. 1 having the configuration shown in Tables 5 and 6 was obtained. 1-18 cutting tools were made.

≪Characteristic evaluation of cutting tools≫
Sample No. prepared as described above. Using cutting tools Nos. 1 to 18, each characteristic of the cutting tools was evaluated as follows. In addition, sample no. Cutting tools 1 to 8, 11 to 13, 17 and 18 correspond to the examples, and sample No. Cutting tools 9, 10, 14-16 correspond to comparative examples.

<Measurement of thickness of coating>
Sample no. 1 to sample No. For 18 cutting tools, the thickness of each of the coating, the first layer that constitutes the coating, the base layer, and the surface layer was obtained by the method described in the first embodiment. The obtained results are shown in Tables 5 and 6 for "thickness of first layer (μm)", in Table 5 for "thickness of base layer (μm)", and in Table 5 for "thickness of surface layer (μm)". μm)”.

<Measurement of x (average value) and y (average value)>
Sample no. 1 to sample No. For 18 cutting tools, x (average value) and y (average value) were obtained by the method described in the first embodiment. The obtained results are shown in the “x (average value)” and “y (average value)” sections of “Al _x Ti _1-x C _y N _1-y ” in Tables 5 and 6, respectively.

<Measurement of average aspect ratio of crystal grains>
Sample no. 1 to sample No. For 18 cutting tools, the average aspect ratio of grains was obtained by the method described in the first embodiment. The obtained results are shown in Table 6, "Average Aspect Ratio of Crystal Grains".

<Measurement of area ratio>
Sample no. 1 to sample No. For 18 cutting tools, the area ratio occupied by crystal grains having a cubic crystal structure in the first layer was obtained by the method described in the first embodiment. The obtained results are shown in Table 6, "Area ratio (%)".

<Measurement of the first number ratio>
Sample no. 1 to sample No. For 18 cutting tools, the first number ratio was obtained by the method described in the first embodiment. The obtained results are shown in Table 6, "first number ratio (%)".

<Measurement of residual stress>
Sample no. 1 to sample No. For 18 cutting tools, the residual stress of the first layer was determined by the method described in the first embodiment. The obtained results are shown in Table 6, "Residual stress (GPa)". The description of "compression" in the "residual stress (GPa)" section of Table 6 means that the residual stress is "compressive residual stress". In addition, the description of "tensile" in the section of "residual stress (GPa)" in Table 6 means that the residual stress is "tensile residual stress".

<Measurement of hardness>
Sample no. 1 to sample No. The hardness of the first layer was determined by the method described in Embodiment 1 for 18 cutting tools. The obtained results are shown in Table 6, "Hardness (GPa)".

≪Cutting test≫
Using the obtained cutting tool, cutting was performed under the following cutting conditions. A cutting distance of 300 mm was set as one pass, and damage was confirmed for each pass, and the number of passes until the tool reached chipping due to thermal cracks and rake face wear was evaluated. The results are shown in Table 6, "Cutting Test (Pass)". Here, the term "loss" means that the maximum flank wear amount is 0.4 mm or more. Moreover, the fact that the number of passes until the tool reaches chipping is 20 or more means that the thermal crack resistance and wear resistance are good. That is, 20 passes or more means that the tool has a long tool life.
(Cutting conditions)
Work material: SCM435 block material (300mm x 80mm)
Cutting speed: 300m/min
Feed rate: 0.2mm/t
Depth of cut: 2.0 mm
Wet/Dry: Wet The cutting conditions correspond to high speed cutting of alloy steel under wet conditions.

<Results>
From the results of Table 6, sample No. according to the example. Cutting tools 1 to 8, 11 to 13, 17, and 18 were superior to sample No. 1 according to the comparative example in high-speed cutting under wet conditions. It was found to have superior thermal crack resistance and superior wear resistance compared to 9, 10, 14-16 cutting tools. Therefore, sample no. Cutting tools of 1-8, 11-13, 17, 18 were found to have long tool life, especially in high speed cutting under wet conditions of alloy steels.

Although the embodiments and examples of the present disclosure have been described as above, it is planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples and to modify them in various ways.

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

1 cutting tool, 1a rake face, 1b flank face, 1c cutting edge portion, 10 base material, 11 first layer, 12 base layer, 13 surface layer, 14 coating, 50 CVD device, 52 base material setting jig, 53 reaction Container, 54 temperature control device, 55 gas introduction pipe, 56 gas exhaust pipe, 57 gas exhaust port, S1 first layer surface, S2 first layer surface side interface, S3 substrate side interface, L1 second 1 virtual line

Claims

A cutting tool comprising a substrate and a coating disposed on the substrate,
The coating comprises a first layer,
The first layer includes a plurality of crystal grains,
The crystal grains are made of Al x Ti 1-x C y N 1-y ,
The x is more than 0.65 and less than 0.95,
The y is 0 or more and less than 0.1,
The average aspect ratio of the crystal grains is 3.0 or less,
The crystal grains include crystal grains having a cubic structure,
In the first layer, the area ratio occupied by the crystal grains having the cubic system structure is 90% or more,
The average aspect ratio and the area ratio are measured in a cross section along the normal of the interface between the substrate and the coating,
The cutting tool, wherein the first layer has a thickness of 2 μm or more and 20 μm or less.
The crystal grains include first crystal grains,
The inclination angle of the <111> direction of the first crystal grains with respect to the normal direction of the surface of the coating is 0° or more and 10° or less,
A first number ratio of the first crystal grains to the crystal grains is 15% or more,
2. The cutting tool according to claim 1, wherein said first number ratio is measured in a cross section along a normal line of an interface between said substrate and said coating.
The cutting tool according to claim 1 or 2, wherein the compressive residual stress of the first layer is 1.0 GPa or more and less than 4.5 GPa.
The cutting tool according to any one of claims 1 to 3, wherein the hardness of the first layer is 30 GPa or more and 40 GPa or less.