JP6795456B2 - Surface coating cutting tool - Google Patents

Description

The present invention relates to a surface coated cutting tool comprising a substrate and a coating formed on the substrate.

In recent years, there has been a demand for cutting tools that exhibit excellent tool life under various cutting conditions. As the required performance of the tool material, it is more important to improve the wear resistance and the fracture resistance, which are directly related to the tool life. Therefore, in order to improve these characteristics, a coating cutting tool in which two types of coatings are alternately laminated on the surface of a base material is used.

Japanese Patent Application Laid-Open No. 08-134629 (Patent Document 1) states that the surface of a composite high-hardness material for tools has a laminated structure including two or more compound layers composed of fine particles, thereby having excellent wear resistance. A composite high hardness material for tools showing the above is disclosed.

According to Japanese Patent No. 6004366 (Patent Document 2), the coating layer of a coating cutting tool has an alternating laminated structure in which two or more compound layers having different compositions are alternately laminated. A coated cutting tool with improved fracture resistance is disclosed.

Japanese Unexamined Patent Publication No. 08-134629 Japanese Patent No. 6004366

However, the composite high-hardness material for tools of Patent Document 1 has a small difference in lattice constant between each compound layer, and further improvement in fracture resistance is desired.

Further, the coated cutting tool of Patent Document 2 also has a small difference in lattice constant between each compound layer, and has insufficient fracture resistance in high-speed, high-efficiency machining with a high heat load.

Therefore, an object of the present invention is to provide a surface-coated cutting tool that exhibits excellent fracture resistance in high-speed, high-efficiency machining with a high heat load.

The surface coating cutting tool according to one aspect of the present invention is
(1) A surface-coated cutting tool including a base material and a coating film formed on the base material.
The coating comprises a laminated structure in which layers A, B and C are repeatedly laminated in this order.
Each of the A layer, the B layer and the C layer is at least two or more elements selected from the group consisting of group 4 elements, group 5 elements, group 6 elements, Al, Si, B and Y in the periodic table. It is a nitride of
Lattice constant _{L A} of the A layer, the lattice constant _{L C} of the lattice constants _{L B} and the layer C of the B layer satisfies the relation of the following formula (I) or Formula (II),
_{L A} <L B <L _C Formula (I)
_{L C} <L B <L _A formula (II)
The lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less.
Each of the A layer, the B layer, and the C layer has a cubic crystal structure.
It is a surface coating cutting tool.

According to the above aspect, it is possible to provide a surface coating cutting tool exhibiting excellent fracture resistance in high-speed, high-efficiency machining with a high heat load.

It is a figure explaining the structural example of the surface covering cutting tool which concerns on Embodiment 1 of this invention. It is another figure explaining the structural example of the surface covering cutting tool which concerns on Embodiment 1 of this invention. It is a figure explaining the structural example of the surface covering cutting tool which concerns on Embodiment 2 of this invention.

[Explanation of Embodiments of the Present Invention]
First, embodiments of the present invention will be listed and described.

The surface coating cutting tool according to one aspect of the present invention is
(1) A surface-coated cutting tool including a base material and a coating film formed on the base material.
The coating comprises a laminated structure in which layers A, B and C are repeatedly laminated in this order.
Each of the A layer, the B layer and the C layer is a group 4 element (Ti, Zr, Hf, etc.), a group 5 element (V, Nb, Ta, etc.) and a group 6 element (Cr, Mo) in the periodic table. , W, etc.), Al, Si, B, and Y are nitrides of at least two or more elements selected from the group.
Lattice constant _{L A} of the A layer, the lattice constant _{L C} of the lattice constants _{L B} and the layer C of the B layer satisfies the relation of the following formula (I) or Formula (II),
_{L A} <L B <L _C Formula (I)
_{L C} <L B <L _A formula (II)
The lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less.
Each of the A layer, the B layer, and the C layer has a cubic crystal structure.
It is a surface coating cutting tool.

The surface coating cutting tool can exhibit excellent fracture resistance in high-speed, high-efficiency machining with a high heat load because the lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less. It will be possible. The reason for this is not clear, but if the lattice constant difference between the A layer and the C layer is 0.1100 Å or more, the strain on both sides at the time of lattice matching is sufficient, so that the fracture resistance is improved and the lattice constant difference becomes large. When it is 0.1500 Å or less, it is estimated that the fracture resistance is improved because the crystallinity of the cubic crystal structure is good at the interface.

(2) The lattice constant difference between the A layer and the B layer and the lattice constant difference between the B layer and the C layer are preferably 0.0500 Å or more and 0.1000 Å or less, respectively. When the lattice constant difference between the A layer and the B layer and the B layer and the C layer is within the above range, it is possible to exhibit excellent fracture resistance in high-speed, high-efficiency machining with a high heat load.

(3) It is preferable that the A layer, the B layer and the C layer each have a layer thickness of 1 nm or more and 110 nm or less. If the layer thickness is less than 1 nm, the laminated structure is almost eliminated due to the diffusion of elements between the layers, a mixed layer is formed, and the fracture resistance may be lowered. On the other hand, if the layer thickness exceeds 110 nm, a region having a small lattice strain is formed in the laminated structure, and the fracture resistance may be lowered.

(4) The laminated structure preferably has a total thickness of 0.5 μm or more and 10.0 μm or less. If the thickness is less than 0.5 μm, the wear resistance and the fracture resistance may decrease. On the other hand, if it exceeds 10.0 μm, an abnormal defect may occur.

(5) The coating film further comprises Group 4 elements (Ti, Zr, Hf, etc.), Group 5 elements (V, Nb, Ta, etc.), Group 6 elements (Cr, Mo, W, etc.), Al, and Al. One layer containing at least one element selected from the group consisting of Si, or a compound having the at least one element and at least one element selected from the group consisting of C, N, O and B. It is preferable to provide more than one layer. When such a compound layer exists between the base material and the laminated structure, the adhesion between the base material and the coating film is improved. Further, when such a compound layer is present on the surface side of the laminated structure, the wear resistance, adhesion resistance and fracture resistance of the surface-coated cutting tool are improved.

(6) The base material preferably contains at least one selected from the group consisting of cemented carbide, cermet, cubic boron nitride sintered body, high-speed steel, ceramics and diamond sintered body. According to this, the surface coating cutting tool is extremely used as, for example, a drill, an end mill, a cutting tip with a replaceable cutting edge for milling or turning, a metal saw, a gear cutting tool, a reamer, a tap, or a tip for pin milling of a crank shaft. It can be used usefully.

[Details of Embodiments of the present invention]
A specific example of the surface-coated cutting tool according to the embodiment of the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

<Embodiment 1>
(Surface coating cutting tool)
As shown in FIGS. 1 and 2, the surface-coated cutting tools 10 and 11 include a base material 1 and a coating film 5 formed on the base material 1, and the coating film 5 includes layers A 2 and B. A laminated structure 8 in which the layers 3 and C layers 4 are repeatedly laminated in this order is included.

The surface-coated cutting tool of the present embodiment is extremely used as, for example, a drill, an end mill, a cutting tip with a replaceable cutting edge for milling or turning, a metal saw, a gear cutting tool, a reamer, a tap, or a tip for pin milling of a crank shaft. It can be used usefully.

(Base material)
As the base material 1, a conventionally known base material known as a base material for a cutting tool can be used without particular limitation. For example, cemented carbide (for example, WC-based cemented carbide, WC, as well as those containing Co or further added with carbonitrides such as Ti, Ta, Nb), cermet (TiC, TiN, TiCN, etc.), cermet, etc. (Main component), cubic boron nitride sintered body, high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof, etc.), diamond sintered body Etc. can be mentioned as an example of such a base material.

When a cemented carbide is used as a base material, the effect of the present invention is exhibited even if such a cemented carbide contains an abnormal phase called a free carbon or an η phase in the structure. The base material used in the present invention 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 cermet, a surface hardened layer may be formed, and even if the surface is modified in this way, the present invention The effect is shown.

(Coating)
The coating film 5 includes any aspect of covering the entire surface of the substrate, a mode in which a coating film is not partially formed, and a mode in which a part of the coating film is partially laminated differently.

The coating film 5 includes a laminated structure 8 in which A layer 2, B layer 3 and C layer 4 are repeatedly laminated in this order. As long as the A layer, the B layer and the C layer are repeatedly laminated in this order in the laminated structure, any of the A layer, the B layer and the C layer may be arranged on the side in contact with the base material.

For example, as shown in FIG. 1, the A layer 2 is arranged in contact with the base material 1, the B layer 3 and the C layer 4 are arranged in this order on the A layer 2, and the C layer 4 is on the C layer 4. Further, the A layer 2, the B layer 3 and the C layer 4 may be arranged in this order (form (a)). Further, as shown in FIG. 2, the C layer 4 is arranged in contact with the base material 1, the B layer 3 and the A layer 2 are arranged on the C layer 4 in this order, and the B layer 3 and the A layer 2 are arranged on the A layer 2. Further, the C layer 4, the B layer 3 and the A layer 2 may be arranged in this order (form (b)). Further, although not shown in the figure, each layer may be arranged as in the following forms (c) to (f).

Form (c): The B layer is arranged in contact with the base material, the C layer and the A layer are arranged in this order on the B layer, and the B layer, the C layer and the A layer are further arranged on the A layer. A form arranged in this order.

Form (d): The A layer is arranged in contact with the base material, the C layer and the B layer are arranged in this order on the A layer, and the A layer, the C layer and the B layer are further arranged on the B layer. A form arranged in this order.

Form (e): The C layer is arranged in contact with the base material, the A layer and the B layer are arranged in this order on the C layer, and the C layer, the A layer and the B layer are further arranged on the B layer. A form arranged in this order.

Form (f): The B layer is arranged in contact with the base material 1, the A layer and the C layer are arranged in this order on the B layer, and the B layer, the A layer and the C layer are further arranged on the C layer. Is arranged in this order.

The laminated structure may have a form including two or more unit layers including one layer each of the A layer, the B layer, and the C layer. Further, one unit layer may be combined with any one or two layers of the A layer, the B layer and the C layer.

The surface layer on the opposite side to the base material of the laminated structure may be any of the A layer, the B layer, and the C layer.
Each of layer A 2, layer B 3 and layer C 4 is at least two or more elements selected from the group consisting of group 4 elements, group 5 elements, group 6 elements, Al, Si, B and Y in the periodic table. It is a nitride of. Specifically, AlCrN, AlCrSiN, AlCrHfN, CrSiN, CrAlN, CrTiN, TiAlN, TiSiN, TiTaN, TiWN, TiNbN, TiZrN, TiBN, TimoN, TiHfN, TiAlYN, AlCrYN and the like can be used.

In the present specification, when a compound is represented by a chemical formula as described above, if the atomic ratio is not particularly limited, it shall include all conventionally known atomic ratios, and is not necessarily limited to those in the stoichiometric range. .. For example, when simply writing "AlCrN", the atomic ratio of "Al", "Cr" and "N" is not limited to 25:25:50, and when writing "CrN", "Cr" and "N" are also used. The atomic ratio of "" is not limited to the case of 50:50, and any conventionally known atomic ratio is included.

The composition of the compounds constituting each layer can be confirmed by TEM-EDX (energy dispersive X-ray spectroscopy). In TEM-EDX, for example, the following conditions can be preferably used.

<Measuring equipment>
Measuring equipment: VG, HB501
EDX: KEVEX Super8000 Quantitative Total System Energy Dispersive X-ray Analyzer (Si <Li> Semiconductor Detector, UTW Type)
EELS: VG, ELS-80 spectrometer (energy resolution: 0.56 eV)
<Measurement conditions>
Acceleration voltage: 100kV
Sample absorption current: 10 ^-9 A
Counting time: 50 to 100 seconds Analytical probe diameter: 1 nmφ

Lattice constant _{L C} of the lattice constant of the layer A _L A, B layer lattice constant _{L B} and C layers satisfies the relationship of the following formula (I) or Formula (II),
_{L A} <L B <L _C Formula (I)
_{L C} <L B <L _A formula (II)
The lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less. Here, the difference in lattice constant between the A layer and the C layer, when the respective lattice constants satisfy the relationship of formula (I), a value calculated by (L C _{-L A),} each grating If the constant satisfies the relation of the _(II), is a value calculated by _(L a -L _C). The surface coating cutting tool can exhibit excellent fracture resistance in high-speed, high-efficiency machining with a high heat load because the lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less. It will be possible. The reason for this is not clear, but if the lattice constant difference between the A layer and the C layer is 0.1100 Å or more, the strain on both sides at the time of lattice matching is sufficient, so that the fracture resistance is improved and the lattice constant difference becomes large. When it is 0.1500 Å or less, it is presumed that the defect resistance is improved because the crystallinity of the cubic crystal structure is good at the interface. The lattice constant difference between the A layer and the C layer is preferably 0.1150 Å or more and 0.1400 Å or less, and more preferably 0.1200 Å or more and 0.1350 Å or less.

Here, one of the following values is used as the "lattice constant".
(1) When the material of each layer is described on the JCPDS card (JCPDS: Joint Committee on Powerfraction Standards), the value of the lattice constant described.
(2) When the material of each layer is a composite of materials described on the JCPDS card, the lattice constant was calculated using the lattice constant described on the JCPDS card of each material and the composition ratio of the composite. value. For example, the lattice constant L _TiCrN of Ti _A Cr _1- AN (0 <A <1) is described in the JCPDS card as the lattice constant L _TiN (4.23 Å) of _TiN described in the JCPDS card. Using the lattice constant L _CrN (4.16 Å) of _CrN , it is obtained as follows.
L _TiCrN = L _TiN · A + L _CrN (1-A) = (L _TiN −L _CrN ) × A + L _CrN = (4.239-4.136) × A + 4.136 [Å]
(3) If the lattice constant cannot be calculated from (2) above, each layer is formed on a substrate (K10 cemented carbide (JIS)) under the following conditions by the arc ion plating method, and X A value obtained by calculating the lattice constant from the peak angle of the θ / 2θ method of the line analysis method (XRD). In the arc ion plating method, N ₂ gas is introduced so that the pressure in the chamber becomes 4.0 Pa, the substrate temperature is 600 ° C., the arc current is 150 A, the bias voltage is -15 V, and the film thickness is 2.0 μm. The film is formed until it becomes. After film formation, the film is heated in a high temperature XRD at 650 ° C. in vacuum until the peak position stabilizes, and then the peak angle is measured after the peak position stabilizes.

The lattice constant difference between the A layer and the B layer and the lattice constant difference between the B layer and the C layer are preferably 0.050 Å or more and 0.1000 Å or less, respectively. Here, the difference in lattice constant between the A layer and the B layer, if each of the lattice constants satisfy the relationship of formula (I), a value calculated by (L B _{-L A),} each grating If the constant satisfies the relation of the _(II), is a value calculated by _(L a -L _B). Also, the difference in lattice constant between the B layer and the C layer, when the respective lattice constants satisfy the relationship of formula (I), a value calculated by (L C _{-L B),} each grating If the constant satisfies the relation of the _(II), is a value calculated by _(L B -L _C). When the lattice constant difference between the A layer and the B layer and the B layer and the C layer is within the above range, it is possible to exhibit excellent fracture resistance in high-speed, high-efficiency machining with a high heat load. The lattice constant difference between the A layer and the B layer and the lattice constant difference between the B layer and the C layer are more preferably 0.0550 Å or more and 0.0900 Å or less, and further preferably 0.0600 Å or more and 0.0700 Å or less.

It is preferable that the A layer, the B layer and the C layer each have a layer thickness of 1 nm or more and 110 nm or less. If the layer thickness of each of the A layer, the B layer, and the C layer is less than 1 nm, the laminated structure is almost eliminated by the diffusion of each element, a mixed layer is formed, and the fracture resistance may be lowered. On the other hand, if the layer thickness exceeds 110 nm, a region having a small lattice strain is formed in the laminated structure, and the fracture resistance may be lowered. The layer thickness of each of the A layer, the B layer and the C layer is preferably 1 nm or more and 50 nm or less, more preferably 3 nm or more and 20 nm or less, and further preferably 6 nm or more and 12 nm or less.

The laminated structure preferably has a total thickness of 0.5 μm or more and 10.0 μm or less. If the total thickness of the laminated structure is less than 0.5 μm, the wear resistance and the fracture resistance may decrease. On the other hand, if it exceeds 10.0 μm, an abnormal defect may occur. The overall thickness of the laminated structure is more preferably 1.0 μm or more and 6.0 μm or less, and further preferably 1.5 μm or more and 4.0 μm or less.

Here, the "layer thickness of each layer" or the "thickness of the entire laminated structure" is obtained as follows. First, a measurement sample including a cross section parallel to the normal direction of the surface of the base material is prepared. Next, the cross section is observed with a scanning transmission electron microscope (STEM), and the magnification is adjusted so that the observed image includes the entire area in the thickness direction of the coating film. Then, the thickness is measured at 5 points or more, and the average value is taken as the thickness. In STEM, for example, the following conditions can be preferably used.

<STEM analysis conditions>
Measuring equipment: Made by Hitachi, Product name: HD-2700
Acceleration voltage: 200kV
Magnification: 200,000-8 million times

The number of layers A, B, and C in the laminated structure is naturally determined when the total thickness of the laminated structure and the thickness of each of these layers are determined, but 6 or more layers are preferable. Layers and above are more preferred.

Each of the A layer, the B layer and the C layer has a cubic crystal structure. The crystal structure can be analyzed by a TEM (transmission electron microscope) diffraction pattern. When the material of each layer has a cubic crystal structure, a surface-coated cutting tool having excellent hardness, heat resistance, oxidation resistance, and chemical stability can be obtained.

(Production method)
In order to form (deposit) the laminated structure on the surface of the substrate, it is preferable that the film forming process is capable of forming a compound having a cubic crystal structure. Specifically, it is preferable to use a physical vapor deposition method.

As the physical vapor deposition method, a sputtering method, an ion plating method and the like are known, and any of such conventionally known physical vapor deposition methods can be adopted. Above all, it is preferable to adopt the cathode arc ion plating method in which the ion ratio of the raw material element is high. By adopting the cathode arc ion plating method, it is possible to perform metal or gas ion bombardment treatment on the surface of the base material before forming the film, which dramatically improves the adhesion of the film. Can be done.

As the conditions of the cathode arc ion plating method, conventionally known conditions can be adopted without particular limitation.

<Embodiment 2>
(Surface coating cutting tool)
As shown in FIG. 3, the surface-coated cutting tool 12 may have an intermediate layer 6 between the base material 1 and the laminated structure 8. Further, as shown in FIG. 3, the surface-coated cutting tool 12 may have a surface layer 7 on the surface opposite to the substrate of the laminated structure 8. Further, although not shown in the drawing, the surface coating cutting tool may have an intermediate layer between the laminated structure and the surface layer.

The intermediate layer 6 and the surface layer 7 are composed of at least one element selected from the group consisting of group 4 elements, group 5 elements, group 6 elements, Al and Si in the periodic table, or at least one element. It preferably contains a compound having at least one element selected from the group consisting of C, N, O and B. When the intermediate layer contains the compound, the adhesion strength between the base material and the laminated structure or the laminated structure and the surface layer is improved, and peeling of both can be suppressed. When the surface layer contains the compound, the wear resistance of the surface coating cutting tool is improved.

As the compound, for example, TiWCN, TiNbN, CrWCN, TiCN, AlN, TiAlSiN, TiWCNO, TiAlBN and the like can be used.

The intermediate layer and the surface layer may be composed of a single layer, or may have a multi-layer structure in which different compounds are laminated.

The layer thickness of the intermediate layer is preferably 1 nm or more and 500 nm or less from the viewpoint of adhesion and productivity. The thickness of the surface layer is preferably 0.1 μm or more and 5 μm or less from the viewpoint of wear resistance and adhesiveness.

The present embodiment will be described in more detail with reference to Examples. However, these embodiments do not limit the present embodiment. The layer thickness of each layer or the thickness of the entire laminated structure in the examples is measured by observing the cross section of each layer or the entire laminated structure using a TEM (transmission electron microscope), and the composition of the compounds constituting each layer. Was confirmed by TEM-EDX (Energy Dispersive X-ray Spectroscopy). The crystal structure was analyzed by a TEM (transmission electron microscope) diffraction pattern and a lattice image. As described above, the lattice constant of each layer is (1) the value of the lattice constant described on the JCPDS card, (2) the value calculated from the lattice constant described on the JCPDS card, or (3) from the desired material. The layer was formed under predetermined conditions, and the lattice constant was calculated from the peak angle of the θ / 2θ method of the X-ray analysis method (XRD). For the lattice constant difference, 4 significant figures (4 digits after the decimal point) were used.

<Manufacturing of surface coating cutting tools>
In this example, a surface-coated cutting tool was prepared as follows, and a turning test and a milling test were performed to evaluate the performance.

(Samples 1-41, 46-49)
As a base material for a surface-coated cutting tool, a cutting tip with a replaceable cutting edge for turning, which is made of K20 cemented carbide (JIS) and has a shape of CNMG120408 (JIS), was prepared for the turning test. For the milling test, a milling cutting edge exchangeable cutting tip having a material of P20 cemented carbide (JIS) and a shape of SEET13T3AGSN (JIS) was prepared.

Next, a film was formed on the substrate. Specific formation conditions are shown below by taking Sample 1 shown in Table 1 as an example.

As target materials, an alloy in which Al is 80 atomic% and Cr is 20 atomic% (target for forming the A layer) and an alloy in which Ti is 45 atomic% and Al is 55 atomic% (for forming the B layer). A target) and an alloy having Ti of 95 atomic% and Si of 5 atomic% (C layer forming target) were prepared. In addition, although all target materials contain a small amount of unavoidable impurities, the notation excludes them.

The substrate was mounted on a cathode arc ion plating sputtering apparatus. The surface of the base material was cleaned for 15 minutes by introducing Ar gas into the chamber, maintaining the pressure in the chamber at 3.0 Pa, and gradually increasing the bias voltage to −1000 V. After that, Ar gas was exhausted. As a result, Ar ions cleaned the surface of the base material to remove strong stains and oxide film.

Next, layer A is formed on the base material. That is, N ₂ gas was introduced so that the pressure in the chamber was 5.0 Pa, the base material temperature was set to 500 ° C., and the base material bias voltage was set to 65 V. The A layer forming target was ionized by arc discharge and reacted with N ₂ gas to form an A layer having a layer thickness of 110 nm composed of cubic Al _0.8 Cr _0.2 N so as to be in contact with the base material. ..

Subsequently, the B layer is formed on the A layer. That is, N ₂ gas was introduced so that the pressure in the chamber was 5.0 Pa, the base material temperature was set to 500 ° C., and the base material bias voltage was set to 65 V. The target for forming the B layer was ionized by an arc discharge and reacted with N ₂ gas, whereby the B layer having a layer thickness of 80 nm composed of cubic Ti _0.45 Al _0.55 N was laminated on the A layer.

Subsequently, a C layer is formed on the B layer. That is, N ₂ gas was introduced so that the pressure in the chamber was 5.0 Pa, the base material temperature was set to 500 ° C., and the base material bias voltage was set to 65 V. By ionizing the C layer forming target by arc discharge and reacting with N ₂ gas, a C layer having a layer thickness of 100 nm composed of cubic Ti _0.95 Si _0.05 N was laminated on the B layer.

Next, the A layer, the B layer, and the C layer were repeatedly laminated on the C layer in this order in the same manner as described above. As a result, a surface-coated cutting tool in which a coating having a laminated structure having an overall layer thickness of 2.0 μm was formed on the base material was obtained.

Samples 2 to 41, 46 to 49 are the same as those of Sample 1, except that the target material and the sputtering conditions are appropriately changed so that the A layer, the B layer and the C layer have the composition and the layer thickness shown in Table 1, respectively. It was prepared by the method of. That is, the base material is mounted on a cathode arc ion plating sputtering device, N ₂ gas is introduced so that the pressure in the chamber becomes 1.6 Pa to 5.0 Pa, and the base material temperature is 430 ° C. to 620 ° C. The substrate bias voltage was set to 15V to 150V. A target having a desired composition was ionized by arc discharge and reacted with N ₂ gas to prepare A layer, B layer and C layer having desired thicknesses.

In Sample 3 and Sample 35, a B layer is formed on the base material, then a C layer and an A layer are formed on the B layer in this order, and then a B layer, a C layer, and an A layer are formed. The layers were repeatedly laminated in this order. In Sample 4 and Sample 28, a C layer is formed on the base material, then A layer and B layer are formed on the C layer in this order, and then C layer, A layer, and B layer are formed in this order. Repeatedly laminated with. In the sample 9, the C layer is formed on the base material, then the B layer and the A layer are formed on the C layer in this order, and the C layer, the B layer, and the A layer are repeatedly laminated in this order. did. In the sample 13, the A layer is formed on the base material, then the C layer and the B layer are formed on the A layer in this order, and the A layer, the C layer, and the B layer are repeatedly laminated in this order. did. In the sample 33, the B layer is formed on the base material, then the A layer and the C layer are formed on the B layer in this order, and the B layer, the A layer, and the C layer are repeatedly laminated in this order. did. Samples other than the above had the same stacking order as sample 1. The stacking order for each sample is summarized in the "Stacking order" column of Table 1.

(Samples 42 to 45)
A substrate similar to that of Sample 1 was prepared. Next, the intermediate layer, the laminated structure and the surface layer were laminated in this order on the base material to form a coating film. As for the method of forming the intermediate layer, the laminated structure and the surface layer, the target material and the sputtering conditions were appropriately changed so that the intermediate layer, the laminated structure and the surface layer had the composition and the layer thickness shown in Table 1, respectively. It was prepared in the same manner as in 1.

The surface layer of sample 45 has a super-multilayer structure, which was prepared under conventionally known conditions. That is, using a target having a target composition (composition shown in Table 1), N ₂ gas is introduced so that the pressure in the chamber becomes 2.6 Pa, the substrate temperature is 550 ° C, and the substrate bias voltage is 40 V. By repeating the operation of forming a TiAlSiN layer at 15 nm and the operation of forming a TiNbN layer at 10 nm with a substrate temperature of 550 ° C and a substrate bias voltage of 40 V, an ultra-multilayer structure having an overall thickness of 1.0 μm is formed. Was produced.

<Performance evaluation>
The fracture resistance of each of the surface-coated cutting tools of Samples 1 to 49 prepared above was evaluated by performing a turning test and a milling test under high-speed, high-efficiency machining conditions with a high heat load. The specific conditions of the turning test and the milling test are as follows.

(Turning test)
Work Material: Inconel 718 Round Bar Cutting Speed: 75m / min Cutting: 2.0mm
Feed: 0.25 mm / rev
DRY / WET: WET

The evaluation was performed by measuring the time until a defect occurs in the surface coating cutting tool as the cutting time. The results are shown in Table 2. A long cutting time indicates excellent fracture resistance.

Samples 1 to 45 had a lattice constant difference between the A layer and the C layer of 0.1100 Å or more and 0.1500 Å or less, and showed excellent fracture resistance. Sample 46 had a lattice constant difference of 0.1007 Å between the A layer and the C layer, and was inferior in fracture resistance. Samples 47 to 49 had a lattice constant difference of more than 0.1500 Å between the A layer and the C layer, and were inferior in fracture resistance.

(Milling test)
Work material: SCM435
Cutting speed: 270 m / min Cutting: 1.5 mm
Feed: 0.2mm / rev
DRY / WET: DRY

The evaluation was carried out by measuring the time until the amount of wear on the flank of the surface-coated cutting tool reaches 0.2 mm or the time until a defect occurs as the cutting time. The results are shown in Table 2. A long cutting time indicates excellent fracture resistance.

In Samples 1 to 45, the lattice constant difference between the A layer and the C layer was 0.1100 Å or more and 0.1500 Å or less, and showed excellent fracture resistance. Sample 46 had a lattice constant difference of 0.1007 Å between the A layer and the C layer, and was inferior in fracture resistance. Samples 47 to 49 had a lattice constant difference of more than 0.1500 Å between the A layer and the C layer, and were inferior in fracture resistance.

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 indicated by the scope of claims rather than the embodiments described above, and is intended to include meaning equivalent to the scope of claims and all modifications within the scope.

1 base material, 2 A layer, 3 B layer, 4 C layer, 5 coating, 6 intermediate layer, 7 surface layer, 8 laminated structure, 10, 11, 12 surface coating cutting tool

Claims (6)

A surface-coated cutting tool comprising a base material and a coating formed on the base material.
The coating comprises a laminated structure in which layers A, B and C are repeatedly laminated in this order.
Each of the A layer, the B layer, and the C layer has a different composition from each other, and is selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al, Si, B, and Y in the periodic table. It is a nitride of at least two elements.
Lattice constant _{L A} of the A layer, the lattice constant _{L C} of the lattice constants _{L B} and the layer C of the B layer satisfies the relation of the following formula (I) or Formula (II),
_{L A} <L B <L _C Formula (I)
_{L C} <L B <L _A formula (II)
The lattice constant difference between the A layer and the C layer is 0.1100 Å or more and 0.1500 Å or less.
Each of the A layer, the B layer, and the C layer has a cubic crystal structure.
Surface coating cutting tool. The surface coating cutting according to claim 1, wherein the lattice constant difference between the A layer and the B layer and the lattice constant difference between the B layer and the C layer are 0.0500 Å or more and 0.1000 Å or less, respectively. tool. The surface-coated cutting tool according to claim 1 or 2, wherein each of the A layer, the B layer, and the C layer has a layer thickness of 1 nm or more and 110 nm or less. The surface-coated cutting tool according to any one of claims 1 to 3, wherein the laminated structure has a total thickness of 0.5 μm or more and 10.0 μm or less. The film is further formed by at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al and Si in the periodic table, or at least one element and C, N, The surface coating cutting tool according to any one of claims 1 to 4, further comprising one or more layers containing a compound having at least one element selected from the group consisting of O and B. The base material comprises at least one selected from the group consisting of cemented carbide, cermet, cubic boron nitride sintered body, high-speed steel, ceramics and diamond sintered body, claims 1 to 5. The surface coating cutting tool according to any one of the above items.

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