JP2021030356A - Surface-coated cutting tool - Google Patents

Abstract

To provide a surface-coated cutting tool which is excellent in chipping resistance.SOLUTION: A surface-coated cutting tool includes a base material, and a coating layer arranged on the base material. The coating layer includes a first unit layer and a second unit layer. An outermost layer of the coating layer is the first unit layer. The first unit layer contains crystal grains of Ala(TiαCr1-α)bX1-a-bN of a cubic crystal type and Ala(TiαCr1-α)bX1-a-bN of a hexagonal crystal type. The second unit layer contains crystal grains of Alc(TiβCr1-β)dZ1-c-dN of the cubic crystal type, and does not contain crystal grains of Alc(TiβCr1-β)dZ1-c-dN of the hexagonal crystal type.SELECTED DRAWING: None

Description

The present disclosure relates to surface coated cutting tools.

Conventionally, cutting of steel, castings, etc. has been performed using a cutting tool made of cemented carbide or the like. Since the cutting edge of such a cutting tool is exposed to a harsh environment such as high temperature and high stress during cutting, wear and chipping of the cutting edge are caused.
Therefore, it is important to suppress wear and chipping of the cutting edge in order to improve the life of the cutting tool.

For the purpose of improving the cutting performance of cutting tools, the development of a coating film that covers the surface of a base material such as cemented carbide is underway. For example, Japanese Patent Application Laid-Open No. 2018-161691 (Patent Document 1) describes Al as a hard film having an average layer thickness of 0.5 to 5.0 μm on the surface of a tool substrate made of WC-based cemented carbide or TiCN-based cermet. In a surface-coated cutting tool coated with a composite nitride of Ti and Ti ((Al _X Ti _1-X ) N, where 0.6 ≦ X ≦ 0.8), (a) the hard film has a crystal structure ratio. Monotonically increases from a cubic structure to a hexagonal structure as the film film thickness direction toward the surface. (B) Five visual fields of the same area are taken at equal intervals in the film thickness direction of the hard film and occupy each visual field. When the areas of the cubic phase and the hexagonal phase were measured by EBSD to obtain the area ratio of the hexagonal phase, the difference in the area ratio of the hexagonal phases in the adjacent visual fields was 5 to 20% (c). ) A surface coating cutting tool characterized in that the difference between the maximum Al concentration and the minimum Al concentration is 2.0 atomic% or less when the Al concentration of the hard film is continuously determined in the film thickness direction is disclosed. Has been done.

Further, Japanese Patent 2018-059146 (Patent Document 2), Al, a hard film containing Cr and _{N, Al m Cr 1-m} N 1-x-y-z C x B y O _In the composition formula, m is the atomic ratio of Al to the total of Al and Cr, 1-m is the atomic ratio of Cr to the total of Al and Cr, and 1-xyz is N. Atomic ratio of N to the sum of C, B, O, x is the atomic ratio of C to the sum of N, C, B, O, y is the atomic ratio of B to the sum of N, C, B, O, z is N , C, B, and O are shown, respectively, and the relational expression of 0.70 <m ≦ 0.85 is satisfied, the hardness of the hard film is H (GPa), and the hard film is H (GPa). When the Young's modulus of is E (GPa), H / E, which is the ratio of hardness to Young's modulus, is 0.050 or more and less than 0.058, and H is 20 GPa or more. The coating is disclosed.

Japanese Unexamined Patent Publication No. 2018-161691 Japanese Unexamined Patent Publication No. 2018-059146

However, since the hard film in the surface-coated cutting tool described in Patent Document 1 and the hard film described in Patent Document 2 have a coarse-grained structure, highly efficient cutting (cutting with a high feed rate, etc.) When applied to, further improvement in performance (for example, fracture resistance, chipping resistance, etc.) is required.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a surface-coated cutting tool having excellent chipping resistance.

The surface coating cutting tool according to the present disclosure is
A surface coating cutting tool including a base material and a coating layer provided on the base material.
The coating layer includes a first unit layer and a second unit layer.
In the coating layer, the outermost layer is the first unit layer.
The first unit layer consists of cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 Containing -ab} N crystal grains,
The second unit layer contains cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
The second unit layer _{does not contain hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, X represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and a is More than 0.5 and less than 0.8, b is greater than or equal to 0.2 and less than 0.5, 1-ab is greater than 0 and less than 0.1, and α is greater than or equal to 0 and less than 1. Yes,
In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, Z represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and c is More than 0.5 and less than 0.8, d is more than 0.2 and less than 0.5, 1-cd is more than 0 and less than 0.1, β is greater than or equal to 0 and 1 It is as follows.

According to the above, it becomes possible to provide a surface coating cutting tool having excellent chipping resistance.

FIG. 1 is a perspective view illustrating one aspect of a surface coating cutting tool. FIG. 2 is a schematic cross-sectional view of the surface coating cutting tool according to one aspect of the present embodiment. FIG. 3 is a schematic cross-sectional view of a surface-coated cutting tool according to another aspect of the present embodiment. FIG. 4 is a schematic cross-sectional view of a surface-coated cutting tool according to another aspect of the present embodiment. FIG. 5A is an example of an image showing an electron diffraction pattern in the second unit layer of the present embodiment. FIG. 5B is an example of an image showing an electron diffraction pattern in the first unit layer of the present embodiment.

[Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
[1] The surface coating cutting tool according to the present disclosure is
A surface coating cutting tool including a base material and a coating layer provided on the base material.
The coating layer includes a first unit layer and a second unit layer.
In the coating layer, the outermost layer is the first unit layer.
The first unit layer consists of cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 Containing -ab} N crystal grains,
The second unit layer contains cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
The second unit layer _{does not contain hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, X represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and a is More than 0.5 and less than 0.8, b is greater than or equal to 0.2 and less than 0.5, 1-ab is greater than 0 and less than 0.1, and α is greater than or equal to 0 and less than 1. Yes,
In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, Z represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and c is More than 0.5 and less than 0.8, d is more than 0.2 and less than 0.5, 1-cd is more than 0 and less than 0.1, β is greater than or equal to 0 and 1 It is as follows.

The outermost layer of the coating layer in the surface coating cutting tool is the first unit layer. Here, the "outermost layer" means the layer farthest from the base material among the layers constituting the coating layer. The first unit layer contains hexagonal crystal grains having excellent toughness in addition to cubic crystal grains having excellent hardness. Therefore, the coating layer has excellent toughness. That is, the surface-coated cutting tool can have excellent chipping resistance by having the above-mentioned configuration. "Chipping resistance" means resistance to initial chipping.

[2] The hardness H of the first unit layer is 28 GPa or more and 60 GPa or less, the Young's modulus E of the first unit layer is 280 GPa or more and 860 GPa or less, and the hardness H with respect to the Young's modulus E of the first unit layer. The ratio H / E of is 0.07 or more and 0.1 or less. By defining in this way, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance.

[3] Cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) in the first unit layer. _{The average particle size of the crystal grains of b} X _1-ab N is 2 nm or more and 20 nm or less. By defining in this way, the surface-coated cutting tool can have further excellent chipping resistance.

_{[4] The average particle size of the cubic Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains in the second unit layer is 2 nm or more and 20 nm or less. By defining in this way, the surface-coated cutting tool can have further excellent chipping resistance.

[5] The first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately laminated. In the multilayer structure, the first unit layer and the second unit layer are formed. Is included in 1 layer or more and 10 layers or less, respectively. By defining in this way, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance.

[6] The first unit layer has a thickness of 100 nm or more and 3 μm or less per layer. By defining in this way, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance.

[7] The thickness of each second unit layer is 100 nm or more and 3 μm or less. By defining in this way, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance.

[Details of Embodiments of the present disclosure]
Hereinafter, one embodiment of the present disclosure (hereinafter referred to as “the present embodiment”) will be described. However, this embodiment is not limited to this. In the present specification, the notation in the form of "A to B" means the upper and lower limits of the range (that is, A or more and B or less), and when the unit is not described in A and the unit is described only in B, A The unit of and the unit of B are the same. Further, in the present specification, when the compound is represented by a chemical formula such as "TiC" in which the composition ratio of the constituent elements is not limited, the chemical formula is any conventionally known composition ratio (element ratio). Shall include. At this time, the above chemical formula shall include not only the stoichiometric composition but also the non-stoichiometric composition. For example, the chemical formula of "TiC" includes not only the _{stoichiometric composition "Ti 1} C ₁ " but also a non-stoichiometric composition such as _{"Ti 1} C _0.8". This also applies to the description of compounds other than "TiC".

≪Surface coating cutting tool≫
The surface coating cutting tool according to the present disclosure is
A surface coating cutting tool including a base material and a coating layer provided on the base material.
The coating layer includes a first unit layer and a second unit layer.
In the coating layer, the outermost layer is the first unit layer.
The first unit layer consists of cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 Containing -ab} N crystal grains,
The second unit layer contains cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
The second unit layer _{does not contain hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, X represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and a is More than 0.5 and less than 0.8, b is greater than or equal to 0.2 and less than 0.5, 1-ab is greater than 0 and less than 0.1, and α is greater than or equal to 0 and less than 1. Yes,
In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, Z represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and c is More than 0.5 and less than 0.8, d is more than 0.2 and less than 0.5, 1-cd is more than 0 and less than 0.1, β is greater than or equal to 0 and 1 It is as follows.

The surface-coated cutting tool according to the present embodiment (hereinafter, may be simply referred to as “cutting tool”) includes, for example, a drill, an end mill, a cutting edge exchangeable cutting tip for a drill, a cutting edge exchangeable cutting tip for an end mill, and a milling tool. It may be a cutting tip with a replaceable cutting edge, a cutting tip with a replaceable cutting edge for turning, a metal saw, a gear cutting tool, a reamer, a tap, or the like.

FIG. 1 is a perspective view illustrating one aspect of a surface coating cutting tool. The cutting tool 10 having such a shape is used as a cutting tip with a replaceable cutting edge for turning.

The cutting tool 10 shown in FIG. 1 has a surface including an upper surface, a lower surface, and four side surfaces, and has a quadrangular prism shape that is slightly thin in the vertical direction as a whole. Further, the cutting tool 10 is formed with through holes penetrating the upper and lower surfaces, and at the boundary portions of the four side surfaces, the adjacent side surfaces are connected by an arc surface.

In the cutting tool 10, the upper surface and the lower surface usually form a rake face 1a, and four side surfaces (and an arc surface connecting them to each other) form a flank surface 1b, and connect the rake face 1a and the flank surface 1b. The arc surface forms the cutting edge portion 1c. "Scooping surface" means a surface for scooping out chips scraped from a work material. "Fleeing surface" means a surface whose part is in contact with the work material. The cutting edge portion is included in the portion constituting the cutting edge of the cutting tool.

When the surface-coated cutting tool is a cutting tool with a replaceable cutting edge, the cutting tool 10 includes a shape having a tip breaker and a shape not having a tip breaker. In FIG. 1, the cutting edge portion 1c is represented by an arc surface, but the shape of the cutting edge portion 1c is not limited to this. That is, the shape of the cutting edge portion 1c includes sharp edge (ridge where the rake face and flank surface intersect), honing (shape in which the sharp edge is rounded), negative land (shape with chamfered surface), honing and negative land. Among the combined shapes, any shape is included.

The shape of the cutting tool 10 and the names of the parts have been described above with reference to FIG. 1. However, in the base material of the surface-coated cutting tool according to the present embodiment, the shape corresponding to the cutting tool 10 and the names of the parts have been described. , The same terms as above will be used. That is, the base material of the surface-coated cutting tool has a rake face, a flank surface, and a cutting edge portion connecting the rake face and the flank surface.

The cutting tool 10 includes a base material 11 and a coating layer 12 provided on the base material 11 (FIG. 2). In addition to the coating layer 12, the cutting tool 10 may further include a base layer 13 provided between the base material 11 and the coating layer 12 (FIG. 4). The cutting tool 10 may further include a surface layer 14 provided on the coating layer 12 (FIG. 4). Other layers such as the base layer 13 and the surface layer 14 will be described later.
In addition, each of the above-mentioned layers provided on the above-mentioned base material may be collectively referred to as a "coating". That is, the cutting tool 10 includes a coating film 20 that covers the base material 11, and the coating film 20 includes the coating layer 12 (FIG. 2). Further, the coating film 20 may further include the base layer 13 or the surface layer 14 (FIG. 4).

<Base material>
As the base material of the present embodiment, any conventionally known base material of this type can be used. For example, the base material is a cemented carbide (for example, a cemented carbide (WC) -based cemented carbide, a cemented carbide containing Co in addition to WC, and 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 (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic crystal It is preferable to include one selected from the group consisting of a cemented carbide sintered body (cBN sintered body) and a diamond sintered body.

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

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

<Coating>
The coating film according to this embodiment includes a coating layer. The "coating" has an action of covering at least a part of the base material (for example, a part of a rake face) to improve various properties such as chipping resistance, chipping resistance, and crater wear resistance in a cutting tool. It has. The coating preferably covers the entire surface of the base material. However, even if a part of the base material is not coated with the coating film or the composition of the coating film is partially different, it does not deviate from the scope of the present embodiment.

The thickness of the coating film is preferably 0.2 μm or more and 20 μm or less, and more preferably 1 μm or more and 12 μm or less. Here, the thickness of the coating means the total thickness of each of the layers constituting the coating. Examples of the "layer constituting the coating film" include other layers such as the above-mentioned coating layer, the above-mentioned base layer and the above-mentioned surface layer. The thickness of the coating film is, for example, measured at any 10 points in a cross-sectional sample parallel to the normal direction of the surface of the base material using a transmission electron microscope (TEM), and the average of the measured thicknesses of the 10 points. It can be obtained by taking a value. The measurement magnification at this time is, for example, 10000 times. Examples of the cross-section sample include a sample obtained by thinning the cross-section of the cutting tool with an ion slicer device. The same applies to the case of measuring the thickness of each of the above-mentioned coating layer, the above-mentioned base layer, the surface layer and the like. Examples of the transmission electron microscope include JEM-2100F (trade name) manufactured by JEOL Ltd.

(Coating layer)
The coating layer 12 according to the present embodiment includes a first unit layer 121 and a second unit layer 122 (FIG. 2). The outermost layer of the coating layer 12 is the first unit layer 121. The coating layer 12 further includes an intermediate layer 123 provided between the first unit layer 121 and the second unit layer 122 as long as the effect of the surface coating cutting tool according to the present embodiment is maintained. It may be good (Fig. 4). The coating layer may be provided directly above the base material as long as the effect of the surface coating cutting tool according to the present embodiment is maintained, or the coating layer of the base material may be provided via another layer such as a base layer. It may be provided on the top (Fig. 4). The coating layer may be provided with another layer such as a surface layer on the coating layer as long as the effect of the surface coating cutting tool is maintained (FIG. 4). Further, the coating layer may be provided on the surface of the coating.

The coating layer preferably covers the rake face of the base material. The coating layer may cover the flank of the base material. It is more preferable that the coating layer covers the entire surface of the base material. However, even if a part of the base material is not coated with the coating layer, it does not deviate from the scope of the present embodiment.

The thickness of the coating layer is preferably 0.2 μm or more and 20 μm or less, more preferably 1 μm or more and 12 μm or less, and further preferably 3 μm or more and 8 μm or less. By doing so, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance. The thickness can be measured, for example, by observing the cross section of the surface-coated cutting tool as described above using a transmission electron microscope at a magnification of 10000 times.

(First unit layer)
In the present embodiment, the first unit layer is a cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and a hexagonal Al _a (Ti _α Cr _1-α). ) Includes crystal grains of _b X _{1-ab N.} That is, the first unit layer is a layer containing _{polycrystalline Al a} (Ti _α Cr _1-α ) _b X _{1-ab N.}

Cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystals Grains are identified by, for example, a diffraction pattern obtained by electron diffraction (see, for example, FIG. 5B). The detailed procedure is as follows. First, the electron diffraction measurement of the first unit layer is performed on the above-mentioned cross-sectional sample. Next, in the electron beam diffraction image obtained by the measurement, the crystal structure is identified by the diffraction pattern peculiar to each crystal structure. At this time, the electron diffraction image is indexed using the interplanar spacing in each crystal structure measured in advance by the X-ray diffraction method to identify the crystal structure.

In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, X is Si (silicon), Nb (niobium), Mo (molybdenum), Ta (tantalum), W (tungsten) and B ( Indicates at least one element selected from the group consisting of (boron).
Boron is usually regarded as a metalloid exhibiting properties intermediate between metal elements and non-metal elements. However, in the present embodiment, the element having free electrons is regarded as a metal, and boron is included in the range of the metal element.

For X, it is preferable to select an element having a large difference in atomic radius with respect to Al, Ti and Cr. By doing so, _{the crystal grains of Al a} (Ti _α Cr _1-α ) _b X _1-ab N tend to be easily distorted, and thus the toughness tends to be improved. In one aspect of this embodiment, the X preferably contains Si or Nb.

In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, a is more than 0.5 and less than 0.8, and preferably 0.65 or more and 0.75 or less. The above-mentioned a can be obtained by elemental analysis of the entire first unit layer by the energy dispersive X-ray spectroscopy (TEM-EDX) incidental to the TEM for the above-mentioned cross-sectional sample. The observation magnification at this time is, for example, 20000 times. Specifically, each of 10 arbitrary points in the first unit layer of the cross-sectional sample is measured to obtain the value of a, and the average value of the obtained 10 points is defined as a in the first unit layer. .. Here, the "arbitrary 10 points" are selected from crystal grains different from each other in the first unit layer. The same applies to the identification of b and α described later and c, d and β in the second unit layer described later. Examples of the EDX device include JED-2300 (trade name) manufactured by JEOL Ltd.

In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, b is 0.2 or more and less than 0.5, and preferably 0.25 or more and 0.35 or less. The above b can be obtained by elemental analysis of the entire first unit layer with the above-mentioned cross-section sample by TEM-EDX.

In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, 1-ab is more than 0 and less than 0.1, and is 0.01 or more and 0.05 or less. preferable. When X contains two or more kinds of elements, the above-mentioned values 1-ab mean the total value of the above two or more kinds of elements. The values of 1-ab are obtained by subtracting the values of a and b from 1.

In the above Al _a (Ti _α Cr _1-α ) _b X _1-ab N, α is 0 or more and 1 or less, and preferably 0.3 or more and 0.7 or less. When the value of α is small, the heat resistance of the first unit layer tends to improve. When the value of α is large, the hardness of the first unit layer tends to improve. The α can be obtained by elemental analysis of the entire first unit layer using TEM-EDX for the cross-sectional sample.

Examples of the compound represented by Al _a (Ti _α Cr _1-α ) _b X _1-ab N include AlTiSiN, AlCrSiN, Al (TiCr) SiN, AlTiNbN, AlCrNbN, Al (TiCr) NbN, and Al. (TiCr) BN and the like can be mentioned (however, the subscripts indicated by a, b and α in the specific compound are omitted).

The hardness H of the first unit layer is preferably 28 GPa or more and 60 GPa or less, and more preferably 32 GPa or more and 40 GPa or less. The hardness H and Young's modulus E described later can be determined by the nanoindentation method according to the standard procedure defined in "ISO 14577-1: 2015 Metallic materials-Instrumented indentation test for hardness and materials parameters-". is there. At this time, from the viewpoint of accurately obtaining the hardness H and Young's modulus E described later, the indenter's indentation depth should not exceed 1/10 of the thickness of the first unit layer in the indenter's indentation direction. As the sample, the above-mentioned cross-sectional sample may be used as long as the cross-sectional area of the first unit layer can secure a sufficient width with respect to the above-mentioned indenter. Further, a sample having a cross section inclined with respect to the normal direction of the surface of the base material may be used so that the cross-sectional area of the first unit layer can be sufficiently wide with respect to the indenter.

The Young's modulus E of the first unit layer is preferably 280 GPa or more and 860 GPa or less, and more preferably 320 GPa or more and 570 GPa or less.

The ratio H / E of the hardness H to the Young's modulus E in the first unit layer is preferably 0.07 or more and 0.1 or less, and preferably 0.085 or more and 0.095 or less.

In one aspect of the present embodiment, the hardness H of the first unit layer is 28 GPa or more and 60 GPa or less, the Young's modulus E of the first unit layer is 280 GPa or more and 860 GPa or less, and the Young's modulus of the first unit layer is 28 GPa or more. The ratio H / E of the hardness H to E is preferably 0.07 or more and 0.1 or less. By doing so, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance.

_{Cubic Al a} (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 in} the first unit layer. _{The average particle size of the crystal grains of −ab} N is preferably 2 nm or more and 20 nm or less, and more preferably 5 nm or more and 10 nm or less. By doing so, the surface-coated cutting tool can have further excellent chipping resistance. The average particle size can be measured, for example, by observing the cross section of the surface-coated cutting tool as described above using a transmission electron microscope at a magnification of 2 million times.

Specifically, the particle size (Heywood diameter: equivalent area circle diameter) of each crystal grain is calculated from the photographed image of the cross section, and the average value thereof is Al _a (Ti _α Cr _1-α ) _b X ₁ Let it be the average particle size of the crystal grains of _{−ab N.} The number of crystal grains to be measured is preferably at least 10 or more, and more preferably 20 or more. When a plurality of first unit layers are contained in the coating layer, it is preferable to obtain the average particle size of the crystal grains as follows. First, the above image analysis is performed on each first unit layer to obtain the average particle size of the crystal grains in each first unit layer. Next, the average value of the average grain size of the crystal grains obtained in each first unit layer is obtained. The obtained average value is taken as the average particle size of the crystal grains of _{Al a} (Ti _α Cr _1-α ) _b X _{1-ab N.} The number of visual fields for image analysis is preferably 2 or more, more preferably 4 or more, and even more preferably 10 or more. A series of operations for calculating the average particle size of the crystal grains as described above may be performed using image analysis software. As the image analysis software, image analysis type particle size distribution software (“Mac-View” manufactured by Mountech Co., Ltd.) can be preferably used.

The thickness of the first unit layer is preferably 100 nm or more and 3 μm or less, and more preferably 200 nm or more and 1 μm or less. By doing so, the surface-coated cutting tool can have excellent wear resistance in addition to having excellent chipping resistance. The thickness can be measured, for example, by observing the cross section of the surface-coated cutting tool as described above using a transmission electron microscope at a magnification of 10000 times.

(Second unit layer)
In this embodiment, the second unit layer contains cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains. That is, the second unit layer is a layer containing _{polycrystalline Al c} (Ti _β Cr _1-β ) _d Z _{1-c−d N.} In addition, the second unit layer _{does not contain hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains. In one aspect of the present embodiment, the second unit layer may consist only of cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
In the present embodiment, _{the composition of Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N is the composition of Al _a (Ti _α Cr _1-α ) _b X _{1-ab in the first unit layer.} It may be the same as or different from the composition of N.

Cubic crystal grains of Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N are identified by, for example, the diffraction pattern obtained by the above-mentioned electron diffraction (see, for example, FIG. 5A). .. Even if the second unit layer _{contains a very small amount of hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains, in the above diffraction pattern, the above If the pattern corresponding to the hexagonal type (the pattern indicated by the arrow in FIG. 5B) is not observed, "the second unit layer is a hexagonal Al _c (Ti _β Cr _1-β ) _d Z _{1-. It} does not contain crystal grains of cd N. "

In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, Z represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B. The Z may be the same element as the X, or may be a different element.

For Z, it is preferable to select an element having a large difference in atomic radius with respect to Al, Ti and Cr. By doing so, _{the crystal grains of Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N are likely to be distorted, and thus the toughness tends to be improved. In one aspect of this embodiment, Z preferably contains Si or Nb.

In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, c is more than 0.5 and less than 0.8, and preferably 0.55 or more and 0.65 or less. The above c can be obtained by elemental analysis of the entire second unit layer with the above-mentioned cross-section sample by TEM-EDX.

In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, d is more than 0.2 and less than 0.5, preferably 0.35 or more and 0.45 or less. The above d can be obtained by elemental analysis of the entire second unit layer using TEM-EDX for the above cross-sectional sample.

In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, 1-cd is more than 0 and less than 0.1, and is 0.01 or more and 0.05 or less. preferable. When Z contains two or more kinds of elements, the above-mentioned 1-cd value means the total value of the above two or more kinds of elements. The value of 1-c-d is obtained by subtracting the values of c and d from 1.

In the above Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, β is 0 or more and 1 or less, and preferably 0.3 or more and 0.7 or less. When the value of β is small, the heat resistance of the second unit layer tends to be improved. When the value of β is large, the hardness of the second unit layer tends to improve. The β can be obtained by elemental analysis of the entire second unit layer using TEM-EDX for the cross-sectional sample.

Examples of the compound represented by Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N include AlTiSiN, AlCrSiN, Al (TiCr) SiN, AlTiNbN, AlCrNbN, Al (TiCr) NbN, and Al. (TiCr) BN and the like can be mentioned (however, the subscripts indicated by c, d and β in the specific compound are omitted).

_{The average particle size of the cubic Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains in the second unit layer is preferably 2 nm or more and 20 nm or less, preferably 5 nm or more. It is more preferably 14 nm or less. By defining in this way, the surface-coated cutting tool can have further excellent chipping resistance. The average particle size can be measured, for example, by observing the cross section of the surface-coated cutting tool as described above using a transmission electron microscope at a magnification of 2 million times. Specifically, as in the case of obtaining the average particle size of the crystal grains of _{Al a} (Ti _α Cr _1-α ) _b X _{1-ab N, the photographed image of the cross section shows the individual crystal grains.} The particle size (Heywood diameter: equivalent area circle diameter) is calculated, and the average value thereof is taken as the average particle size of the crystal grains of _{Al c} (Ti _β Cr _1-β ) _d Z _{1-c-d N.}

The thickness of the second unit layer is preferably 100 nm or more and 3 μm or less, and more preferably 200 nm or more and 1 μm or less. By doing so, the surface-coated cutting tool can have further excellent chipping resistance. The thickness can be measured, for example, by observing the cross section of the surface-coated cutting tool as described above using a transmission electron microscope at a magnification of 10000 times.

(Multi-layer structure)
The first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately laminated (for example, FIG. 3). In the multilayer structure, the first unit layer and the first unit layer are formed. It is preferable that each of the two unit layers contains 1 layer or more and 10 layers or less. By doing so, the surface-coated cutting tool can have excellent wear resistance in addition to having further excellent chipping resistance. Here, the multilayer structure may be started from either the first unit layer or the second unit layer. That is, the lowest layer in the multilayer structure may be either the first unit layer or the second unit layer. On the other hand, the outermost layer in the multilayer structure is the first unit layer. Here, the "bottom layer" means the layer closest to the base material among the layers constituting the coating layer.

(Middle layer)
An intermediate layer 123 may be provided between the first unit layer 121 and the second unit layer 122 as long as the effect of the surface coating cutting tool according to the present embodiment is maintained (FIG. 4). When two or more layers of the first unit layer and the second unit layer are included in the multilayer structure, the intermediate layer is one of a plurality of interfaces between the first unit layer and the second unit layer. It may be provided at only one interface, or may be provided at a plurality of interfaces. The intermediate layer may be, for example, a layer made of a compound represented by AlCrN. The thickness of the intermediate layer may be, for example, 0.1 μm or more and 1 μm or less.

(Other layers)
The coating may further contain other layers as long as the effects of the present embodiment are not impaired. Examples of the other layer include a base layer provided between the base material and the coating layer, a surface layer provided on the coating layer, and the like. The underlayer may be, for example, a layer made of a compound represented by TiWN. The surface layer may be, for example, a layer made of a compound represented by TiCN. The thickness of the other layers is not particularly limited as long as the effects of the present embodiment are not impaired, and examples thereof include 0.1 μm and more and 2 μm or less.

≪Manufacturing method of surface coating cutting tool≫
The method for manufacturing the surface-coated cutting tool according to the present embodiment is as follows.
The step of preparing the base material (hereinafter, may be referred to as "first step") and
It includes a step of forming the coating layer on the base material by using a physical vapor deposition method (hereinafter, may be referred to as a “second step”).
The coating layer includes the first unit layer and the second unit layer.
The outermost layer of the coating layer is the first unit layer.

The physical vapor deposition method is a vapor deposition method in which a raw material (also referred to as an "evaporation source" or a "target") is vaporized by utilizing a physical action, and the vaporized raw material is adhered onto a base material or the like. In particular, the cathode arc ion plating method is used as the physical vapor deposition method used in this embodiment.

In the cathode arc ion plating method, a base material is placed in the apparatus and a target is placed as a cathode, and then a high current is applied to the target to generate an arc discharge. As a result, the atoms constituting the target are evaporated and ionized, and a negative bias voltage is deposited on the base material to form a film.

<First step: Step to prepare the base material>
In the first step, the base material is prepared. For example, a cemented carbide base material is prepared as a base material. As the cemented carbide base material, a commercially available base material may be used, or may be produced by a general powder metallurgy method. In the case of manufacturing by a general powder metallurgy method, for example, WC powder and Co powder or the like are mixed by a ball mill or the like to obtain a mixed powder. After the mixed powder is dried, it is molded into a predetermined shape to obtain a molded product. Further, by sintering the molded product, a WC-Co-based cemented carbide (sintered product) is obtained. Next, a base material made of a WC-Co-based cemented carbide can be produced by subjecting the sintered body to a predetermined cutting edge processing such as honing treatment. In the first step, any substrate other than the above can be prepared as long as it is conventionally known as a substrate of this type.

<Second step: Step of forming a coating layer>
In the second step, the coating layer is formed on the base material by using a physical vapor deposition method. As the method, various methods are used depending on the composition of the coating layer to be formed. For example, a method of using alloy targets having different particle sizes such as Ti, Cr, and Al, a method of using a plurality of targets having different compositions, and a method of using a bias voltage applied at the time of film formation as a pulse voltage. Examples thereof include a method of changing the gas flow rate during film formation, a method of adjusting the rotation speed of the base material holder holding the base material in the film forming apparatus, and the like.

For example, the second step can be performed as follows. First, a chip having an arbitrary shape is mounted as a base material in the chamber of the film forming apparatus. For example, the substrate is attached to the outer surface of a substrate holder on a rotary table rotatably mounted in the center of the chamber of the film forming apparatus. A bias power supply is attached to the base material holder. Nitrogen gas or the like is introduced as a reaction gas in a state where the base material is rotated in the center of the chamber. Further, the temperature of the base material is 300 to 400 ° C. (in the case of the first unit layer) or 550 to 650 ° C. (in the case of the second unit layer), the reaction gas pressure is 3 to 6 Pa, and the voltage of the bias power supply is -50 to -50. An arc current of 100 to 200 A is supplied to the evaporation source for forming the first unit layer or the evaporation source for forming the second unit layer while maintaining the range of -30V (DC power supply), respectively. As a result, metal ions are generated from the evaporation source for forming the first unit layer or the evaporation source for forming the second unit layer, and when a predetermined time elapses, the supply of the arc current is stopped and the arc current is stopped on the surface of the base material. A coating layer (first unit layer and second unit layer) is formed. At this time, the thickness of the coating layer is adjusted to be within a predetermined range by adjusting the film formation time. In the second step, in addition to the portion involved in the cutting process (for example, the rake face near the cutting edge), a coating layer may be formed on the surface of the base material other than the portion involved in the cutting process. ..

In this embodiment, the first unit layer is formed at a temperature of 300 to 400 ° C. Therefore, the first unit layer has a structure including cubic crystals and hexagonal crystals. Further, a second unit layer is formed at a temperature of 550 to 650 ° C. Therefore, the second unit layer has a structure containing cubic crystals. In the present embodiment, the first unit layer may be formed first, or the second unit layer may be formed first. However, the formation of the coating layer is completed by finally forming the first unit layer. By doing so, the outermost layer in the coating layer becomes the first unit layer.

(Raw material for the first unit layer)
In the second step, the raw material of the first unit layer contains any one or both of Ti and Cr, and Al. The raw material of the first unit layer further contains at least one selected from the group consisting of Si, Nb, Mo, Ta, W and B (the element represented by X described above). The raw material of the first unit layer may be in the form of powder or in the form of a flat plate.

The Al content ratio (atomic number ratio) is preferably more than 0.5 and 0.8 or less, preferably 0.65 or more and 0.75 or less, assuming that the entire raw material of the first unit layer is 1. More preferably. Here, the content ratio of Al with respect to the entire raw material usually corresponds to the composition ratio of Al in the first unit layer. The same applies to other elements such as Ti and Cr described later and the element represented by Z described above.

The total content ratio (atomic number ratio) of the Ti and the Cr is preferably 0.17 or more and less than 0.5, and 0.25 or more and 0, when the whole raw material of the first unit layer is 1. It is more preferably .35 or less.

Here, the content ratio (atomic number ratio) of the Ti to the total of the Ti and the Cr is preferably 0 or more and 1 or less when the total of the Ti and the Cr is 1. It is more preferably 3 or more and 0.7 or less.

The content ratio (atomic number ratio) of the element represented by X is preferably more than 0 and less than 0.1, assuming that the entire raw material of the first unit layer is 1, 0.01 or more and 0. It is more preferably 05 or less.

(Raw material for the second unit layer)
In the second step, the raw material of the second unit layer contains any one or both of Ti and Cr, and Al. The raw material of the second unit layer further contains at least one selected from the group consisting of Si, Nb, Mo, Ta, W and B (the element represented by Z described above). The composition of the raw material of the second unit layer may be the same as or different from the composition of the raw material of the first unit layer. The raw material of the second unit layer may be in the form of powder or in the form of a flat plate.

The Al content ratio (atomic number ratio) is preferably more than 0.5 and less than 0.8, preferably 0.55 or more and 0.65 or less, assuming that the entire raw material of the second unit layer is 1. More preferably. Here, the content ratio of the Al with respect to the entire raw material usually corresponds to the composition ratio of the Al in the second unit layer. The same applies to other elements such as Ti and Cr described later and the element represented by Z described above.

The total content ratio (atomic number ratio) of the Ti and the Cr is preferably more than 0.2 and less than 0.5, assuming that the entire raw material of the second unit layer is 1, 0.35. It is more preferably 0.45 or less.

Here, the content ratio (atomic number ratio) of the Ti to the total of the Ti and the Cr is preferably 0 or more and 1 or less when the total of the Ti and the Cr is 1. It is more preferably 3 or more and 0.7 or less.

The content ratio (atomic number ratio) of the element represented by Z is preferably more than 0 and less than 0.1 when the whole raw material of the second unit layer is 1, preferably 0.01 or more and 0. It is more preferably 1 or less.

In one aspect of the present embodiment, an intermediate layer may be formed between the first unit layer and the second unit layer. Examples of the raw material for the intermediate layer include AlCrN.

In the present embodiment, the above-mentioned reaction gas is appropriately set according to the composition of the above-mentioned coating layer. Examples of the reaction gas include nitrogen gas and the like.

After forming the coating layer, compressive residual stress may be applied to the coating layer. This is because the toughness is improved. The compressive residual stress can be applied by, for example, a blast method, a brush method, a barrel method, an ion implantation method, or the like.

<Other processes>
In the manufacturing method according to the present embodiment, in addition to the above-mentioned steps, an ion bombardment treatment step of performing an ion bombardment treatment on the surface of the base material between the first step and the second step, the base material and the above-mentioned An underlayer coating step of forming an underlayer between the coating layer, a surface layer coating step of forming a surface layer on the coating layer, a surface treatment step, and the like may be appropriately performed. When forming other layers such as the above-mentioned base layer and surface layer, the other layer may be formed by a conventional method. Specifically, for example, the above-mentioned other layer may be formed by the above-mentioned PVD method. Examples of the surface treatment step include surface treatment using a medium in which diamond powder is supported on an elastic material. Examples of the device for performing the surface treatment include Sirius Z manufactured by Fuji Seisakusho Co., Ltd.

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

≪Manufacturing of cutting tools≫
<Preparation of base material>
First, a cemented carbide tip for surface coating milling (JIS standard, P30 equivalent cemented carbide, SEMT13T3AGSN-G) was prepared as a base material to be formed with a film (first step: step of preparing the base material). ..

<Ion bombardment treatment>
Prior to the preparation of the coating film described later, the surface of the base material was subjected to an ion bombardment treatment according to the following procedure. First, the base material was set in an arc ion plating apparatus. Next, ion bombardment treatment was performed under the following conditions.
Gas composition: Ar (100%)
Gas pressure: 0.5 Pa
Bias voltage: -600V (DC power supply)
Processing time: 60 minutes

<Preparation of coating>
A coating was prepared by forming a coating layer and, if necessary, a base layer, an intermediate layer and a surface layer on the surface of the base material subjected to the ion bombardment treatment. Hereinafter, a method for producing the coating layer, the base layer, the intermediate layer and the surface layer will be described.

(Preparation of coating layer)
Sample No. In 1-42, nitrogen gas was introduced as a reaction gas with the base material rotated in the center of the chamber. Further, the temperature of the base material is 400 ° C. (in the case of the first unit layer) or 550 ° C. (in the case of the second unit layer), the reaction gas pressure is 6.0 Pa, and the voltage of the bias power supply is -50 V (DC power supply). Each of them was maintained to supply an arc current of 150 A to the evaporation source for forming the first unit layer or the evaporation source for the second unit layer. As a result, metal ions were generated from the evaporation source for forming the first unit layer or the evaporation source for forming the second unit layer, and the coating layers having the compositions shown in Tables 3 and 4 were formed on the surface of the base material (). Second step: a step of forming a coating layer). Here, as the evaporation source for forming the first unit layer or the evaporation source for forming the second unit layer, those having the raw material compositions shown in Tables 1 and 2 were used.

(Preparation of base layer, intermediate layer or surface layer)
Sample No. For 37, a base layer made of a compound represented by TiWN was formed between the base material and the coating layer by using a normal PVD method. Sample No. For 38, one intermediate layer composed of the compound represented by AlCrN was formed between the first unit layer and the second unit layer by using a normal PVD method. In other words, sample No. The coating film in 38 was configured to include one intermediate layer. Sample No. For 39, a surface layer composed of the compound represented by TiCN was formed on the surface of the coating layer by using a conventional PVD method.
By the above steps, the sample No. Surface coating cutting tools 1-42 were produced.

≪Characteristic evaluation of cutting tools≫
Sample No. prepared as described above. Using the cutting tools 1-42, each characteristic of the cutting tool was evaluated as follows. In addition, sample No. The cutting tools 1 to 39 correspond to the examples, and the sample No. The cutting tools 40 to 42 correspond to the comparative examples.

<Measurement of the thickness of each layer constituting the coating>
The thickness of each layer constituting the coating (that is, the thickness of each of the coating layer (first unit layer, second unit layer), base layer, intermediate layer and surface layer) is determined by transmission electron microscope (TEM) (JEOL Ltd.). Manufactured by, trade name: JEM-2100F), it is obtained by measuring any 10 points in a cross-sectional sample parallel to the normal direction of the surface of the base material and taking the average value of the thicknesses of the measured 10 points. It was. The observation magnification at this time was 10,000 times. The results are shown in Tables 3 and 4. Regarding the "total thickness" of the coating layer in Tables 3 and 4, for example, Sample No. The notation of "6 μm × 3" in 18 means that the layer structure (total 6 μm) consisting of one first unit layer (3 μm) and one second unit layer (3 μm) is repeated three times. Means. That is, the first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately laminated. In the multilayer structure, the first unit layer and the second unit layer are Each contains 3 layers. Although not shown in Table 4, the sample No. Thickness of the base layer in No. 37, sample No. Thickness of intermediate layer in No. 38 and sample No. The thickness of the surface layer in 39 was 500 nm, respectively.

<Composition analysis of each layer constituting the film>
The composition of each layer constituting the film was determined by analyzing the entire layer by energy dispersive X-ray spectroscopy (TEM-EDX) incidental to TEM. Specifically, using the above cross-sectional sample, each of 10 arbitrary points in the layer to be analyzed for composition was measured by TEM-EDX, and the composition ratio of each constituent element was calculated. The observation magnification at this time was 20000 times. For each constituent element, the average value of the obtained composition ratios of 10 points was used as the composition ratio of the constituent elements in the layer to be analyzed for the composition. Here, the "arbitrary 10 points" were selected from different crystal grains in the layer to be analyzed for the composition. As the EDX device, JED-2300 (trade name) manufactured by JEOL Ltd. was used. The obtained composition of each layer is shown in Tables 3 and 4.
In addition, by analyzing the coating layer with TEM-EDX, it was identified whether the outermost layer in the coating layer was the first unit layer or the second unit layer (Tables 3 and 4).

<Electron diffraction analysis of the first unit layer and the second unit layer>
The first unit layer and the second unit layer were analyzed by electron diffraction, and the crystal type contained in each layer was analyzed. Identification was performed by a diffraction pattern containing only cubic crystals (for example, FIG. 5A) and a diffraction pattern containing cubic crystals and hexagonal crystals (for example, FIG. 5B). The results are shown in Tables 5 and 6.

<Average particle size of crystal grains in each of the first unit layer and the second unit layer>
The average particle size of the crystal grains in each of the first unit layer and the second unit layer was measured by observing the cross-sectional sample using a TEM at a magnification of 2 million times. Specifically, the particle size (Heywood diameter: diameter equivalent to an equal area circle) of each crystal grain was calculated from the photographed image of the cross section, and the average value was taken as the average particle size of the crystal grain. The number of crystal grains to be measured was 10. Further, since the coating layer contains a plurality of first unit layers and second unit layers, the average particle size of the crystal grains was determined as follows. First, the above image analysis was performed on each first unit layer (or each second unit layer) to determine the average particle size of the crystal grains in each first unit layer (or second unit layer). Next, the average value of the average particle diameters of the crystal grains obtained in each first unit layer (or each second unit layer) was determined. The obtained average value was used as the average particle size of the crystal grains in the layer to be measured. The number of fields of view for image analysis was set to 4. A series of operations for calculating the average particle size of the crystal grains described above was performed using image analysis software (“Mac-View” manufactured by Mountech Co., Ltd.). The results are shown in Tables 5 and 6.

<Hardness and Young's modulus of the first unit layer>
Measure the hardness and Young's modulus of the first unit layer in each cutting tool by the nanoindentation method according to the standard procedure defined in "ISO 14577-1: 2015 Metallic materials-Instrumented indication test for hardness and materials parameters-". did. Here, the pushing depth was set to 100 nm. When another layer was formed on the first unit layer, the measurement was performed after exposing the first unit layer by polishing. As the measuring device, ENT-1100 (trade name) manufactured by Elionix Inc. was used. The results are shown in Tables 5 and 6.

≪Cutting test≫
<Milling test>
Sample No. prepared as described above. Using the cutting tools 1-42, the cutting distance until the cutting tool was chipped was measured under the following cutting conditions. The results are shown in Tables 5 and 6. The longer the cutting distance, the more excellent the chipping resistance can be evaluated as a cutting tool.
Cutting conditions Work material: FCD700
Cutting speed: 200 m / min
Feed amount: 0.2 mm / t
Cut amount (ap): 2 mm, dry

Regarding the cutting test, from the results in Tables 5 and 6, the sample No. Good results were obtained for the cutting tools 1 to 39 with a cutting distance of 3.3 m or more. On the other hand, sample No. The cutting tools of 40 to 42 had a cutting distance of less than 2 m. From the above results, the sample No. It was found that the cutting tools 1 to 39 have excellent chipping resistance.

Although the embodiments and examples of the present invention have been described above, it is planned from the beginning that the configurations of the above-described embodiments and the embodiments are appropriately combined.

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

1a rake surface 1b flank surface 1c cutting edge 10 surface coating cutting tool 11 base material 12 coating layer 13 base layer 14 surface layer 20 coating 121 1st unit layer 122 2nd unit layer 123 Intermediate layer.

Claims (7)

A surface coating cutting tool including a base material and a coating layer provided on the base material.
The coating layer includes a first unit layer and a second unit layer.
The outermost layer of the coating layer is the first unit layer, and the outermost layer is the first unit layer.
The first unit layer consists of cubic Al _a (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 Containing -ab} N crystal grains,
The second unit layer contains cubic Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
The second unit layer _{does not contain hexagonal Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains.
In the Al _a (Ti _α Cr _1-α ) _b X _1-ab N, X represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, where a is More than 0.5 and less than 0.8, b is greater than or equal to 0.2 and less than 0.5, 1-ab is greater than 0 and less than 0.1, and α is greater than or equal to 0 and less than 1. Yes,
In the Al _c (Ti _β Cr _1-β ) _d Z _1-c-d N, Z represents at least one element selected from the group consisting of Si, Nb, Mo, Ta, W and B, and c is More than 0.5 and less than 0.8, d is more than 0.2 and less than 0.5, 1-cd is more than 0 and less than 0.1, β is greater than or equal to 0 and less than 1. The following surface coating cutting tools. The hardness H of the first unit layer is 28 GPa or more and 60 GPa or less, the Young's modulus E of the first unit layer is 280 GPa or more and 860 GPa or less, and the ratio H of the hardness H to the Young's modulus E in the first unit layer is H. The surface coating cutting tool according to claim 1, wherein / E is 0.07 or more and 0.1 or less. _{Cubic Al a} (Ti _α Cr _1-α ) _b X _1-ab N crystal grains and hexagonal Al _a (Ti _α Cr _1-α ) _b X _{1 in} the first unit layer. The surface-coated cutting tool according to claim 1 or 2, wherein the average particle size of the crystal grains of _{−ab N is 2 nm or more and 20 nm or less. According to claim 1, the average particle size of cubic Al c} (Ti _β Cr _1-β ) _d Z _1-c-d N crystal grains in the second unit layer is 2 nm or more and 20 nm or less. Item 2. The surface coating cutting tool according to any one of Item 3. The first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately laminated. In the multilayer structure, the first unit layer and the second unit layer are each 1 The surface coating cutting tool according to any one of claims 1 to 4, which includes 10 or more layers. The surface-coated cutting tool according to any one of claims 1 to 5, wherein the first unit layer has a thickness of 100 nm or more and 3 μm or less per layer. The surface-coated cutting tool according to any one of claims 1 to 6, wherein the second unit layer has a thickness of 100 nm or more and 3 μm or less per layer.