JP7574906B2 - Cutting Tools - Google Patents

Description

This disclosure relates to cutting tools.

Conventionally, various studies have been conducted with the aim of extending the life of cutting tools. For example, International Publication No. 2017/061328 (Patent Document 1) discloses a coated cutting tool including a substrate and a coating layer formed on a surface of the substrate, the coating layer including at least one predetermined layer, and the predetermined layer is represented by the following formula:
(Al _x Ti _y M _1-x-y )N
[In the formula, M represents at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Si, x represents the atomic ratio of Al element to the total of Al element, Ti element, and element represented by M, and y represents the atomic ratio of Ti element to the total of Al element, Ti element, and element represented by M, and satisfies 0.60≦x≦0.85, 0≦y≦0.40, and 0.60≦x+y≦1.00.]
the average thickness of the predetermined layer is 1.4 μm or more and 15 μm or less, and the predetermined layer has an upper region and a lower region which satisfy predetermined conditions (1), (2), and (3).

International Publication No. 2014/142190 (Patent Document 2) discloses a hard coating having a composition represented by (Al _x Ti _y M _z ) _a N _1-a (wherein M element is Cr and/or W, and x, y, z, and a are numbers that satisfy, in atomic ratio, 0.6≦x≦0.9, 0.05≦y≦0.4, 0≦z≦0.2, x+y+z=1, and 0.2≦a≦0.8), which is formed by an arc ion plating method, and which is characterized in that the X-ray diffraction pattern of the hard coating shows a wurtzite-type single structure, and the X-ray diffraction peak of the (002) plane of the wurtzite-type structure is the maximum peak.

International Publication No. 2017/061328 International Publication No. 2014/142190

In recent years, there has been a demand for more efficient cutting (e.g., faster feed speeds), and further improvements in performance (e.g., reducing chipping and wear of the cutting edge) are expected. There is also a demand for the development of cutting tools that are suitable for different workpiece materials.

This disclosure has been made in consideration of the above circumstances, and aims to provide a cutting tool that has excellent wear resistance, chipping resistance, and adhesion resistance.

A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating layer disposed on the substrate,
The coating layer is made of a nitride containing aluminum, titanium, and tungsten as constituent elements,
When the total amount of the aluminum, titanium, and tungsten in the coating layer is used as a reference, the atomic ratio a of the aluminum, the atomic ratio b of the titanium, and the atomic ratio c of the tungsten are expressed by the following formulas 1 to 5,
1/3<(b+2c)/a<1 Formula 1
0.05<b<0.2 Formula 2
0.1<c≦0.29 Formula 3
a + b + c = 1 Equation 4
b < c Equation 5
Fulfilling
The coating layer does not contain silicon as a constituent element.

As a result of the above, it is possible to provide a cutting tool that has excellent wear resistance, chipping resistance, and adhesion resistance.

FIG. 1 is a perspective view illustrating one embodiment of a cutting tool. FIG. 2 is a schematic cross-sectional view of a cutting tool according to one aspect of this embodiment. FIG. 3 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment. FIG. 4 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment.

[Description of the embodiments of the present disclosure]
First, the embodiments of the present disclosure will be listed and described.
[1] A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating layer disposed on the substrate,
The coating layer is made of a nitride containing aluminum, titanium, and tungsten as constituent elements,
When the total amount of the aluminum, titanium, and tungsten in the coating layer is used as a reference, the atomic ratio a of the aluminum, the atomic ratio b of the titanium, and the atomic ratio c of the tungsten are expressed by the following formulas 1 to 5,
1/3<(b+2c)/a<1 Formula 1
0.05<b<0.2 Formula 2
0.1<c≦0.29 Formula 3
a + b + c = 1 Equation 4
b < c Equation 5
Fulfilling
The coating layer does not contain silicon as a constituent element.

The cutting tool is considered to have excellent wear resistance, chipping resistance, and adhesion resistance due to the above-mentioned configuration. In particular, the cutting tool is considered to be suitable for high-efficiency machining of Ni-based alloys. Here, "wear resistance" means resistance to wear of the coating including the coating layer when used in cutting. "Crack resistance" means resistance to chipping that occurs in the coating including the coating layer when used in cutting. "Adhesion resistance" means resistance to adhesion of the coating including the coating layer to the workpiece or chips when used in cutting.

[2] When a line analysis is performed along the lamination direction of the coating layer at any cross section of the coating layer, it is preferable that the difference between the maximum value of the aluminum atomic ratio and the minimum value of the aluminum atomic ratio is 0.03 or less. This ensures that the coating layer wears evenly when used in cutting, resulting in a cutting tool with excellent stability.

[3] The atomic ratio c of tungsten is preferably greater than 0.2 and less than or equal to 0.25. This results in a cutting tool with even better wear resistance and adhesion resistance.

[4] The thickness of the coating layer is preferably 0.5 μm or more and 5 μm or less. This results in a cutting tool with even better wear resistance, chipping resistance, and adhesion resistance.

[5] The electrophotographic printing apparatus further includes at least one underlayer disposed between the substrate and the coating layer,
the underlayer includes at least a first unit layer having a composition different from that of the coating layer,
The first unit layer is preferably made of at least one metal element selected from the group consisting of Group 4, 5, and 6 elements of the periodic table, aluminum, and silicon, or a compound of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron, thereby providing a cutting tool with even more excellent wear resistance and adhesion to the substrate.

[6] The first unit layer is preferably made of at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. This results in a cutting tool with even better wear resistance.

[7] The underlayer further includes a second unit layer having a composition different from that of the coating layer and the first unit layer,
The second unit layer is preferably made of at least one metal element selected from the group consisting of Group 4, 5, and 6 elements of the periodic table, aluminum, and silicon, or a compound of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron, thereby providing a cutting tool with even more excellent wear resistance and adhesion to the substrate.

[8] The second unit layer is preferably made of at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. This results in a cutting tool with even better wear resistance.

[9] It is preferable that the first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately stacked. This results in a cutting tool with even better chipping resistance.

[10] The sum of the thickness of the first unit layer and the thickness of the second unit layer is preferably 1 nm or more and 100 nm or less. This results in a cutting tool with even better chipping resistance.

[11] Further comprising a surface layer disposed on the coating layer,
the surface layer is made of at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron;
The surface layer preferably has a composition different from that of the coating layer, which results in a cutting tool with even more excellent wear resistance and sliding properties.

[12] The surface layer is preferably made of at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. This results in a cutting tool with even better wear resistance.

[13] The substrate preferably contains at least one selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body. This results in a cutting tool with excellent hardness and strength at high temperatures.

[Details of the embodiment of the present disclosure]
Hereinafter, an embodiment of the present disclosure (hereinafter, referred to as "the present embodiment") will be described. However, the present embodiment is not limited to this. In this specification, the notation in the form of "A to Z" means the upper and lower limits of a range (i.e., A to Z). When no unit is described in A and only a unit is described in Z, the unit of A and the unit of Z are the same. Furthermore, in this specification, when a compound is represented by a chemical formula in which the ratio of the constituent elements is not limited, such as "TiN", the chemical formula includes all conventionally known composition ratios (element ratios). In this case, the chemical formula includes not only stoichiometric compositions but also non-stoichiometric compositions. For example, the chemical formula of "TiN" includes not only the stoichiometric composition "Ti ₁ N ₁ " but also non-stoichiometric compositions such as "Ti ₁ N _0.8 ". This also applies to the description of compounds other than "TiN", such as "ZrN".

<Cutting tools>
The cutting tool according to the present disclosure comprises:
A cutting tool comprising a substrate and a coating layer disposed on the substrate,
The coating layer is made of a nitride containing aluminum, titanium, and tungsten as constituent elements,
When the total amount of the aluminum, titanium, and tungsten in the coating layer is used as a reference, the atomic ratio a of the aluminum, the atomic ratio b of the titanium, and the atomic ratio c of the tungsten are expressed by the following formulas 1 to 5,
1/3<(b+2c)/a<1 Formula 1
0.05<b<0.2 Formula 2
0.1<c≦0.29 Formula 3
a + b + c = 1 Equation 4
b < c Equation 5
Fulfilling
The coating layer does not contain silicon as a constituent element.

The cutting tool 50 of this embodiment includes a substrate 10 and a coating layer 11 disposed on the substrate 10 (hereinafter, may be simply referred to as a "cutting tool") (FIG. 2). In addition to the coating layer 11, the cutting tool 50 may further include a surface layer 12 disposed on the coating layer 11 (FIG. 3). The cutting tool 50 may further include a base layer 13 disposed between the substrate 10 and the coating layer 11 (FIG. 3). The surface layer 12 and the base layer 13 will be described later.
The above-mentioned layers disposed on the substrate 10 may be collectively referred to as a "coating." That is, the cutting tool 50 includes a coating 40 disposed on the substrate 10, and the coating 40 includes the coating layer 11. The coating 40 may further include the surface layer 12. The coating 40 may further include the underlayer 13. In one aspect of the present embodiment, the coating may cover the rake face of the substrate, or may cover a portion other than the rake face (e.g., a flank face).

The cutting tool may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for milling, an indexable cutting tip for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.

<Substrate>
The substrate of this embodiment can be any substrate known in the art. For example, the substrate preferably includes at least one selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide containing carbonitrides such as Cr, Ti, Ta, Nb in addition to WC, 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 boron nitride sintered body (cBN sintered body) and diamond sintered body. It is more preferable that the substrate includes at least one selected from the group consisting of cemented carbide, cermet and cBN sintered body.

Among these various substrates, it is preferable to select WC-based cemented carbide or cBN sintered body. This is because these substrates have an excellent balance of hardness and strength, especially at high temperatures, and have excellent properties as substrates for cutting tools for the above-mentioned applications.

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

Figure 1 is a perspective view illustrating one embodiment of a substrate for a cutting tool. Substrates of this shape are used, for example, as substrates for indexable cutting inserts for turning. The substrate 10 has a rake face 1, a clearance face 2, and a cutting edge ridge 3 where the rake face 1 and clearance face 2 intersect. In other words, the rake face 1 and clearance face 2 are connected via the cutting edge ridge 3. The cutting edge ridge 3 constitutes the tip of the cutting edge of the substrate 10. The shape of the substrate 10 can also be understood as the shape of the cutting tool.

When the cutting tool is an indexable cutting tip, the substrate 10 may have a shape with or without a chip breaker. The shape of the cutting edge ridge 3 may be any of the following: sharp edge (the ridge where the rake face and flank face intersect), honing (a shape in which a radius is added to the sharp edge), negative land (a chamfered shape), and a combination of honing and negative land.

The shape of the base material 10 and the names of each part have been described above using FIG. 1, but in the cutting tool 50 according to this embodiment, the shape and the names of each part corresponding to the base material 10 will use the same terms as above. That is, the cutting tool has a rake face, a clearance face, and a cutting edge ridge portion connecting the rake face and the clearance face.

<Coating>
The coating 40 according to this embodiment includes a coating layer 11 disposed on the substrate 10 (see FIG. 2). The "coating" has the effect of improving various characteristics of the cutting tool, such as chipping resistance, wear resistance, and adhesion resistance, by covering at least a portion of the substrate (for example, the rake face that comes into contact with the workpiece during cutting). The coating is preferably used to cover the entire surface of the substrate, not just a portion of the substrate. However, even if a portion of the substrate is not covered with the coating or the coating has a partially different configuration, this does not depart from the scope of this embodiment.

The thickness of the coating is preferably 0.5 μm or more and 14 μm or less, more preferably 1.2 μm or more and 7 μm or less, and even more preferably 1.4 μm or more and 4.1 μm or less. If the thickness is less than 0.5 μm, the abrasion resistance tends to decrease. If the thickness exceeds 14 μm, the frequency of peeling or destruction of the coating tends to increase when a large stress is applied between the coating and the substrate during interrupted processing. Here, the thickness of the coating means the sum of the thicknesses of the layers constituting the coating, such as the coating layer, the underlayer, and the surface layer, which will be described later.

The thickness of the coating can be determined, for example, by using a transmission electron microscope (TEM) to measure any three points on a cross-sectional sample parallel to the normal direction of the substrate surface, and averaging the thicknesses at the three measured points. The same applies when measuring the thicknesses of the coating layer, underlayer (first unit layer, second unit layer), and surface layer. An example of a transmission electron microscope is the spherical aberration corrector JEM-2100F (product name) manufactured by JEOL Ltd.

(Covering layer)
The coating layer is made of a nitride containing aluminum, titanium, and tungsten as constituent elements. Here, "made of a nitride containing aluminum, titanium, and tungsten as constituent elements" means that the coating layer is not limited to an embodiment in which the coating layer is made of only the nitride, but also includes an embodiment in which the coating layer is made of the nitride and inevitable impurities. Examples of the nitride include a compound represented by AlTiWN. Examples of the inevitable impurities include iron (Fe) and chromium (Cr). The content ratio of the inevitable impurities is preferably 0 mass% or more and 0.2 mass% or less with respect to the total mass of the coating layer.

The coating layer is disposed on the substrate. Here, "disposed on the substrate" is not limited to the case where the coating layer is disposed directly on the substrate (see FIG. 2), but also includes the case where the coating layer is disposed on the substrate via another layer (see FIG. 3). In other words, the coating layer may be disposed directly on the substrate, or may be disposed on the substrate via another layer, such as a base layer, as described below, as long as the effects of the present disclosure are achieved. The coating layer may also be the outermost surface of the coating.

In the present embodiment, when the total amount of the aluminum, titanium, and tungsten in the coating layer is used as a reference, the atomic ratio a of the aluminum, the atomic ratio b of the titanium, and the atomic ratio c of the tungsten are expressed by the following formulas 1 to 5,
1/3<(b+2c)/a<1 Formula 1
0.05<b<0.2 Formula 2
0.1<c≦0.29 Formula 3
a + b + c = 1 Equation 4
b < c Equation 5
Meet the following.

The atomic ratio a of aluminum, the atomic ratio b of titanium, and the atomic ratio c of tungsten can be determined by obtaining a cross-sectional sample parallel to the normal direction of the surface of the substrate in the coating layer, and analyzing the crystal grains appearing in the cross-sectional sample using a scanning electron microscope (SEM) or an energy dispersive X-ray spectroscopy (EDX) device attached to a TEM. For example, when determining the atomic ratio a of aluminum, specifically, each of three arbitrary points in the coating layer of the cross-sectional sample is measured to determine the value of a, and the average value of the three values obtained is taken as the atomic ratio a of aluminum in the coating layer of the cross-sectional sample. The atomic ratio b of titanium and the atomic ratio c of tungsten, as well as the composition of the underlayer and surface layer described later, are also determined in a similar manner. Here, the "arbitrary three points" refers to three arbitrary 30 nm x 30 nm areas selected in each layer. If the thickness of the layer to be measured is less than 50 nm, the region is set to be a square with one side having a length of 60% of the thickness of the layer to be measured. An example of the EDX device is a silicon drift detector, JED-2200 (product name), manufactured by JEOL Ltd.

In the above formula 1, the value of (b+2c)/a is greater than 1/3 and less than 1, and is preferably 0.59 to 0.95, and more preferably 0.7 to 0.83. By making the value of (b+2c)/a fall within the above range, a cutting tool with excellent chipping resistance and adhesion resistance can be obtained.

In the above formula 2, the titanium atomic ratio b is greater than 0.05 and less than 0.2, preferably 0.07 or more and 0.17 or less, and more preferably 0.08 or more and 0.13 or less. By making the titanium atomic ratio b a value within the above range, a cutting tool with excellent chipping resistance and wear resistance can be obtained.

In the above formula 3, the atomic ratio c of tungsten is greater than 0.1 and less than 0.29, preferably greater than 0.15 and less than 0.27, and more preferably greater than 0.2 and less than 0.25. By making the atomic ratio c of tungsten fall within the above range, a cutting tool with excellent adhesion resistance and wear resistance can be obtained.

Conventionally, it was thought that if the atomic ratio of tungsten in AlTiWN was large, the crystal lattice of AlTiWN would collapse, causing a decrease in hardness. However, by forming a coating layer using the manufacturing method described below, the inventors have succeeded in increasing the atomic ratio of tungsten without significantly decreasing hardness, thereby creating a coating layer with excellent adhesion resistance.

In this embodiment, the sum of the atomic ratio a of aluminum, the atomic ratio b of titanium, and the atomic ratio c of tungsten is 1 (Equation 4). Furthermore, the atomic ratio c of tungsten is greater than the atomic ratio b of titanium (Equation 5).

The coating layer does not contain silicon as a constituent element. This makes it possible to produce a cutting tool with excellent adhesion resistance. The inventors believe that the absence of silicon in the coating layer suppresses the formation of minute amorphous phases, resulting in improved adhesion resistance.

When a line analysis is performed along the lamination direction of the coating layer in any cross section of the coating layer, the difference between the maximum value of the atomic ratio of aluminum and the minimum value of the atomic ratio of aluminum is preferably 0.03 or less. This results in a uniform distribution of aluminum in the coating layer. As a result, when used in cutting, the coating layer is uniformly worn, resulting in a cutting tool with excellent stability. Here, any cross section of the coating layer is a cross section parallel to the normal direction of the surface of the substrate. The line analysis can be performed using the above-mentioned EDX. At this time, the difference between the above-mentioned maximum value and the minimum value is calculated in at least three fields of view, and the average value of the calculated values is taken as the difference (Δa) between the maximum value of the atomic ratio of aluminum in the coating layer and the minimum value of the atomic ratio of aluminum. The lower limit of Δa is not particularly limited, but may be, for example, 0 or more.

The thickness of the coating layer is preferably 0.5 μm or more and 5 μm or less, more preferably 1 μm or more and 4.5 μm or less, and even more preferably 2 μm or more and 4 μm or less. By making the thickness of the coating layer within the above range, a cutting tool with excellent adhesion resistance and wear resistance can be obtained. The thickness of the coating layer can be determined by analyzing the above-mentioned cross-sectional sample with a TEM.

(Base layer)
The cutting tool preferably further comprises at least one underlayer 13 disposed between the substrate 10 and the coating layer 11 (see FIG. 3). For example, the underlayer may be one layer, two layers, or three or more layers. The underlayer preferably includes at least a first unit layer having a different composition from the coating layer, and more preferably includes a second unit layer having a different composition from the coating layer and the first unit layer. Here, "disposed between the substrate and the coating layer" means that the underlayer is disposed below the coating layer (substrate side), and the underlayer and the coating layer do not necessarily need to be in contact with each other. In other words, another layer may be disposed between the substrate and the coating layer. The underlayer is preferably disposed directly under the coating layer. In addition, the underlayer does not necessarily need to be in contact with the substrate. In other words, another layer may be disposed between the substrate and the coating layer.

(First unit layer)
The first unit layer is preferably made of at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si), or a compound consisting of at least one of the above metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen and boron. The first unit layer is more preferably made of at least one metal element selected from the group consisting of titanium (Ti), chromium (Cr), aluminum and silicon, or a compound consisting of at least one of the above metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen and boron. Examples of Group 4 elements include titanium, zirconium (Zr), hafnium (Hf), etc. Examples of Group 5 elements include vanadium (V), niobium (Nb), tantalum (Ta), etc. Examples of Group 6 elements include chromium, molybdenum (Mo), tungsten (W), etc.

Examples of compounds constituting the first unit layer include TiWN, TiN, ZrC, TiCNO, TiAlSiN, TiSiN, TiAlN, AlCrN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrSiN, TiZrN, TiAlMoN, TiAlNbN, AlCrTaN, AlTiVN, _TiB2 , TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiAlBN, TiAlCrSiBCNO, ZrN, and ZrCN.

When the underlayer consists of only the first unit layer, the thickness of the first unit layer (i.e., the underlayer) is preferably 0.002 μm or more and 10 μm or less, and more preferably 0.005 μm or more and 1.5 μm or less. The thickness of the first unit layer can be determined by analyzing the above-mentioned cross-sectional sample with a TEM.

(Second unit layer)
The second unit layer is preferably made of at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum, and silicon of the periodic table, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. The second unit layer is more preferably made of at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. The second unit layer has a different composition from the coating layer and the first unit layer.

The compound constituting the second unit layer can be the same compound as the compound constituting the first unit layer.

Furthermore, it is preferable that the first unit layer and the second unit layer each form a multilayer structure in which one or more layers are alternately stacked. That is, as shown in FIG. 4, it is preferable that the base layer 13 includes a multilayer structure consisting of a first unit layer 131 and a second unit layer 132. Here, the multilayer structure may start stacking from either the first unit layer or the second unit layer. That is, the interface on the substrate side in the multilayer structure may be composed of either the first unit layer or the second unit layer. In addition, the interface on the coating layer side in the multilayer structure may be composed of either the first unit layer or the second unit layer. By forming a multilayer structure, it is possible to suppress crack propagation.

When the underlayer includes the multilayer structure, the thickness of the underlayer is preferably 0.002 μm or more and 10 μm or less, and more preferably 0.005 μm or more and 1.5 μm or less. The thickness of the underlayer can be determined by analyzing the cross-sectional sample described above with a TEM.

When the first unit layer and the second unit layer form the multilayer structure, the sum of the thickness of the first unit layer and the thickness of the second unit layer (stacking period) is preferably 1 nm or more and 100 nm or less. Here, "the sum of the thickness of the first unit layer and the thickness of the second unit layer" means the sum of the thickness of one first unit layer and the thickness of one second unit layer. By making the stacking period a value within the above range, a cutting tool with improved crack propagation suppression effect can be obtained.

The number of layers in the multilayer structure may include a configuration in which the first unit layer and the second unit layer are laminated one by one, as long as the thickness of the entire base layer is within the above range, and the layers may be alternately laminated in two or more layers, specifically 20 to 2500 layers each.

(Surface layer)
The cutting tool preferably further includes a surface layer 12 disposed on the coating layer (see FIG. 3). The surface layer preferably has a composition different from that of the coating layer. Here, "disposed on the coating layer" means that the surface layer is disposed on the upper side of the coating layer (opposite the substrate), and the coating layer and the surface layer do not necessarily need to be in contact with each other. In other words, another layer may be disposed between the coating layer and the surface layer. The surface layer is preferably disposed directly on the coating layer. In one aspect of the present embodiment, the surface layer may have the same composition as or different from that of the first unit layer. The surface layer may have the same composition as or different from that of the second unit layer.

The surface layer is preferably made of at least one metal element selected from the group consisting of Group 4, 5, and 6 elements of the periodic table, aluminum, and silicon, or a compound consisting of at least one of the above metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron. The surface layer is more preferably made of at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound consisting of at least one of the above metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron.

The compound constituting the surface layer can be the same as the compound constituting the first unit layer.

The thickness of the surface layer is preferably 0.002 μm or more and 10 μm or less, and more preferably 0.005 μm or more and 1.5 μm or less. The thickness of the surface layer can be determined by analyzing the above-mentioned cross-sectional sample with a TEM.

<Cutting tool manufacturing method>
The method for manufacturing a cutting tool according to the present embodiment includes the steps of:
Providing a substrate;
forming a coating layer on the substrate;
The method for manufacturing a cutting tool according to the present embodiment may include other steps as long as it includes these steps. Each step will be described below.

<Step of Preparing Substrate>
In this step, the substrate is prepared. As described above, any substrate that is conventionally known as this type of substrate can be used. The substrate may be manufactured or purchased commercially. When manufacturing the substrate, it may be manufactured using a conventionally known method. For example, when the substrate is made of cemented carbide, first, raw material powders having a predetermined composition (mass%) are mixed uniformly using a commercially available attritor, and then the mixed powder is pressure-molded into a predetermined shape (for example, SEET13T3AGSN, CNMG120408, AXMT170512, etc.). The above-mentioned molded body is then sintered in a predetermined sintering furnace at 1300 to 1500 ° C. or less for 1 to 2 hours to obtain the substrate made of cemented carbide. When purchasing a commercially available product, for example, EH520 (product name) manufactured by Sumitomo Electric Hardmetal Corporation can be mentioned.

<Step of forming a coating layer on a substrate>
In this step, a coating layer is formed on the substrate.

The method for forming the coating layer is not particularly limited, but may be, for example, a physical vapor deposition (PVD) method for forming the coating layer on the substrate.

As the physical vapor deposition method, any conventionally known physical vapor deposition method can be used without any particular limitation. Examples of such physical vapor deposition methods include sputtering, ion plating, arc ion plating, and electron ion beam deposition. In particular, the use of cathodic arc ion plating or sputtering, which have a high ionization rate of the raw material elements, is preferable because it allows metal or gas ion bombardment treatment of the substrate surface before forming the coating, thereby significantly improving the adhesion between the coating and the substrate.

When forming a coating layer by the arc ion plating method, the following conditions can be mentioned. That is, first, a W target and an AlTi target are set in adjacent arc-type evaporation sources in the device, and the substrate (base material) temperature is set to 400 to 650°C and the gas pressure in the device is set to 0.5 to 5 Pa. As the gas, for example, nitrogen gas is introduced. Then, while maintaining the bias voltage on the substrate side (negative) at 20 to 100 V and pulse DC (frequency 10 to 300 kHz), a constant arc current of 80 to 150 A is supplied to the cathode electrode, and metal ions derived from the target are generated from the arc-type evaporation source, thereby forming a coating layer. The inventors believe that by making the arc current a constant current, a coating layer in which aluminum is uniformly distributed along the lamination direction can be formed. An example of an apparatus used in the arc ion plating method is AIP (product name) manufactured by Kobe Steel, Ltd.

<Other processes>
In the manufacturing method according to the present embodiment, in addition to the above-mentioned steps, a step of forming a base layer between the substrate and the coating layer, a step of forming a surface layer on the coating layer, etc. may be appropriately performed. The above-mentioned base layer and surface layer may be formed by a conventional method. Specifically, for example, the base layer and surface layer may be formed by the above-mentioned PVD method.

The present embodiment will be explained in more detail with reference to examples. However, the present embodiment is not limited to these examples.

<Manufacturing of cutting tools>
(Step of Preparing Substrate)
First, in the step of preparing the substrate, JIS K20 cemented carbide (shape: JIS AXMT170512) was prepared as the substrate. Next, each of the substrates was set at a predetermined position in an arc ion plating device (manufactured by Kobe Steel, Ltd., product name: AIP).

(Step of forming coating layer)
Next, as a step of forming a coating layer, a coating layer was formed on the substrate by the arc ion plating method. Specifically, the method was as follows. First, an AlTi target (a target whose composition is AlTi and whose atomic ratio of each metal element corresponds to the atomic ratio shown in Table 1 or Table 2) and a W target were set in the adjacent arc type evaporation source of the arc ion plating device. Next, the substrate temperature was set to 520°C and the gas pressure in the device was set to 2.6 Pa. Nitrogen gas was introduced as the gas. Then, while maintaining the bias voltage on the substrate side (negative) at 30 V and pulse DC (frequency 30 kHz), constant arc currents of 150 A and 100 A were supplied to the cathode electrode of the AlTi target and the cathode electrode of the W target, respectively. The supply of the arc current generated metal ions derived from the target from the arc type evaporation source to form a coating layer. For sample 105, AlTiSi was used as the target instead of AlTi.

(Formation of base layer)
For samples 29, 31 and 32, an underlayer was formed on the substrate before the step of forming the coating layer. For sample 32, a first underlayer was first formed on the substrate, and then a second underlayer was formed on the first underlayer. The targets used at this time were WCr (sample 29), AlTiB (sample 31), WTi (first underlayer of sample 32), AlTi and AlTiB (second underlayer of sample 32). First, the substrate temperature was set to 450°C and the gas pressure in the device was set to 1.0 Pa. As the gas, a mixed gas of _N2 and _CH4 (sample 29), _N2 gas (sample 31) or a mixed gas of _N2 and _CH4 (sample 32) was introduced. Then, an arc current of 150A was supplied to the cathode electrode while maintaining the bias voltage on the substrate side (negative) at 60V and DC. An underlayer was formed on the substrate by generating metal ions and the like derived from a target from an arc-type evaporation source by supplying an arc current.

(Formation of surface layer)
For samples 30 and 31, after the step of forming the coating layer, a surface layer was formed on the coating layer. The targets used at this time were Zr (sample 30) and Ti (sample 31), respectively. First, the substrate temperature was set to 450° C., and the gas pressure in the device was set to 1.0 Pa. As the gas, nitrogen gas (samples 30 and 31) was introduced. Then, while the bias voltage on the substrate side (negative) was maintained at 30 V (sample 30) or 50 V (sample 31) and DC, an arc current of 150 A was supplied to the cathode electrode. The supply of the arc current generated metal ions derived from the target from the arc evaporation source, forming a surface layer on the coating layer.

Using the above procedure, cutting tools were produced as samples 1 to 32 and samples 101 to 105. Here, samples 1 to 32 correspond to examples, and samples 101 to 105 correspond to comparative examples.

<Cutting tool evaluation>
(Measurement of thickness of each layer)
The thickness of each of the coating layer, underlayer, and surface layer was determined as follows. First, a transmission electron microscope (TEM) (manufactured by JEOL Ltd., product name: JEM-2100F) was used to measure three arbitrary points in each layer of a cross-sectional sample parallel to the normal direction of the surface of the substrate. Then, the thickness was determined by averaging the thicknesses measured at the three points. The results are shown in Tables 1 and 2. In the tables, the notation "-" indicates that the corresponding layer was not present in the coating. In addition, the notation "[( _{Al0.64Ti0.36N )} 7 nm/( _{Al0.56Ti0.41B0.03N )} 8 nm _] x 100 _" in Sample 32 indicates that the underlayer is formed of a multilayer structure (total thickness _1.5 μm) in which layers (first unit layers) made of _{Al0.64Ti0.36N} and layers (second unit layers) made of _{Al0.56Ti0.41B0.03N} and having a thickness of 7 nm are alternately laminated ₁₀₀ times.

(Composition of each layer)
The compositions of the coating layer, underlayer, and surface layer were measured by EDX (manufactured by JEOL Ltd., product name: JED-2200) attached to a TEM. Specifically, three arbitrary points in each layer of the cross-sectional sample were measured to determine the atomic ratio of each constituent element, and the average value of the three values was taken as the atomic ratio in each layer of the cross-sectional sample. Here, the "arbitrary three points" were selected from three arbitrary 30 nm x 30 nm areas in each layer. When the thickness of the layer to be measured was less than 50 nm, the area was set to be a square with one side having a length of 60% of the thickness of the layer to be measured. The results are shown in Tables 1 and 2.

(Distribution of aluminum in the coating layer in the lamination direction)
The distribution of aluminum in the coating layer in the lamination direction was determined using the above-mentioned EDX. Specifically, a line analysis was performed on the coating layer of the cross-sectional sample along the lamination direction of the coating layer. Next, based on the results of the line analysis, the maximum value of the atomic ratio of aluminum and the minimum value of the atomic ratio of aluminum were determined, and the difference between them was determined. This measurement was performed in at least three fields of view. The average value of the last obtained difference was taken as the difference (Δa) between the maximum value of the atomic ratio of aluminum in the coating layer and the minimum value of the atomic ratio of aluminum. The results are shown in Tables 1 and 2. From the results of Tables 1 and 2, it was found that in the cutting tools of Samples 1 to 32, the difference Δa was 0.03 or less, and aluminum was uniformly distributed in the coating layer.

<Cutting test>
A face milling test was carried out using the cutting tools of Samples 1 to 32 and Samples 101 to 105 prepared as described above. The cutting conditions for the cutting test are shown below. Here, Inconel 718 used as the work material is a Ni-based alloy known to be a difficult-to-cut material. In the above cutting test, the longer the cutting time, the more excellent the cutting tool's wear resistance, chipping resistance, and adhesion resistance can be evaluated. The results are shown in Tables 3 and 4.

(Cutting conditions for face milling test)
Work material (material): Inconel718
Speed: 30 m/min Feed: 0.03 mm/Blade depth: ap 0.8 mm, ae 30 mm
Cutting environment: Wet
Evaluation method: Cutting time until the cutting tool breaks

From Tables 3 and 4, it can be seen that the cutting tools of samples 1 to 32 had cutting times of 39 minutes or more, and thus achieved good results. On the other hand, the cutting tools of samples 101 to 105 had cutting times of 35 minutes or less. These results show that the cutting tools of samples 1 to 32 have superior chipping resistance, reactivity resistance, and wear resistance compared to the cutting tools of samples 101 to 105. It is suggested that the cutting tools of samples 1 to 32 are particularly suitable for cutting Ni-based alloys such as Inconel 718.

Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to combine the configurations of the above-mentioned embodiments and examples as appropriate.

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

REFERENCE SIGNS LIST 1 cutting face 2 flank face 3 cutting edge ridge 10 substrate 11 coating layer 12 surface layer 13 undercoat layer 40 coating 50 cutting tool 131 first unit layer 132 second unit layer

Claims (11)

A cutting tool comprising a substrate and a coating layer disposed on the substrate,
the coating layer is made of a nitride containing aluminum, titanium, and tungsten as constituent elements;
When the total amount of the aluminum, the titanium, and the tungsten in the coating layer is used as a reference, the atomic ratio a of the aluminum, the atomic ratio b of the titanium, and the atomic ratio c of the tungsten are expressed by the following formulas 1 to 5,
1/3<(b+2c)/a<1 Formula 1
0.05<b<0.2 Formula 2
0.1<c≦0.29 Formula 3
a + b + c = 1 Equation 4
b < c Equation 5
Fulfilling
The coating layer does not contain silicon as a constituent element,
a difference between a maximum value of the atomic ratio of aluminum and a minimum value of the atomic ratio of aluminum of 0.03 or less when a line analysis is performed in a lamination direction of the coating layer at any cross section of the coating layer. The cutting tool according to claim 1 , wherein the coating layer has a thickness of 0.5 μm or more and 5 μm or less. The coating layer further includes at least one undercoat layer disposed between the substrate and the coating layer.
the underlayer includes at least a first unit layer having a composition different from that of the coating layer,
3. The cutting tool according to claim 1 or 2, wherein the first unit layer comprises at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound comprising at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen , and boron. 4. The cutting tool according to claim 3, wherein the first unit layer comprises at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound comprising at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron . The underlayer further includes a second unit layer having a composition different from that of the coating layer and the first unit layer,
5. The cutting tool according to claim 3 or 4, wherein the second unit layer comprises at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound comprising at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen , and boron . 6. The cutting tool according to claim 5, wherein the second unit layer comprises at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound comprising at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron . The cutting tool according to claim 5 or 6 , wherein the first unit layers and the second unit layers are each alternately stacked in one or more layers to form a multilayer structure. The cutting tool according to claim 7 , wherein a sum of a thickness of the first unit layer and a thickness of the second unit layer is equal to or greater than 1 nm and equal to or less than 100 nm. Further comprising a surface layer disposed on the coating layer,
the surface layer is made of at least one metal element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound consisting of at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron,
The cutting tool according to claim 1 , wherein the surface layer has a different composition than the coating layer. 10. The cutting tool according to claim 9, wherein the surface layer comprises at least one metal element selected from the group consisting of titanium, chromium, aluminum, and silicon, or a compound comprising at least one of the metal elements and at least one nonmetal element selected from the group consisting of carbon, nitrogen, oxygen, and boron . The cutting tool according to any one of claims 1 to 10 , wherein the substrate comprises at least one selected from the group consisting of cemented carbide, cermet, high speed steel, ceramics, a cubic boron nitride sintered body, and a diamond sintered body.

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