WO2020158426A1 - Cutting tool and method for manufacturing same - Google Patents

Abstract

A cutting tool comprising a substrate and a coating film provided upon the substrate, wherein the coating film has a first layer provided on the substrate side and a second layer provided upon the first layer, the first layer consists of a nitride or carbonitride of AlxTi1-x, and the second layer consists of a composite compound including α-Al2O3 and TiSy. Therein, x satisfies the relationship 0.7≤x<1, and y satisfies the relationship 1.0≤y≤2.0.

Description

Cutting tool and manufacturing method thereof

The present disclosure relates to a cutting tool and a manufacturing method thereof. This application claims the priority right based on Japanese Patent Application No. 2019-013929 filed on January 30, 2019. All contents described in the Japanese patent application are incorporated herein by reference.

A cutting tool made of cemented carbide often has problems such as wear or chipping because the cutting edge is exposed to harsh environments such as high temperature and high load during cutting. Therefore, for the purpose of improving the cutting performance of the cutting tool, development of a coating for coating the surface of a base material such as cemented carbide has been promoted.

For example, a coating film made of a compound of titanium (Ti) and aluminum (Al) and nitrogen (N) and/or carbon (C) (hereinafter, also referred to as AlTiN, AlTiCN, etc.) has high hardness. It is known that the oxidation resistance can be improved by increasing the Al content ratio (Japanese Patent Laid-Open No. 2017-508632 (Patent Document 1)). It is expected that the performance of the cutting tool will be improved by coating the cutting tool with such a coating.

Demand for high-efficiency machining to improve productivity and reduce machining costs and dry cutting that considers the environment is increasing in recent years. In high-efficiency machining and dry cutting, the temperature of the cutting edge of the tool during machining is as high as about 1000°C. AlTiN and AlTiCN react with oxygen in the air at a high temperature of about 1000° C. or higher to decompose. Therefore, when a cutting tool having a coating made of AlTiN or AlTiCN is used for high-efficiency machining or dry cutting of steel, SUS or the like, the coating may be prematurely worn and chipped.

In order to suppress early wear and damage of the above-mentioned coating film made of AlTiN or AlTiCN, the coating film made of AlTiN or AlTiCN is coated with an Al ₂ O ₃ layer having heat insulation and excellent high temperature oxidation resistance and reaction resistance. It is possible to do it.

Special table 2017-508632

A cutting tool according to an aspect of the present disclosure is a cutting tool including a base material and a coating film provided on the base material,
The coating film has a first layer provided on the base material side and a second layer provided on the first layer,
The first layer consists of a nitride or carbonitride of Al _x Ti _1-x ,
The second layer is a cutting tool composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y .

Here, the x satisfies 0.7≦x<1, and the y satisfies 1.0≦y≦2.0.
A method of manufacturing a cutting tool according to another aspect of the present disclosure is the method of manufacturing a cutting tool described above,
A step of preparing a base material,
A step of forming a coating film on the base material by a chemical vapor deposition method,
The step of forming the coating includes the step of forming a first layer and the step of forming a second layer,
The first layer consists of a nitride or carbonitride of Al _x Ti _1-x ,
The second layer is composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y ,
The step of forming the second layer is performed at a film forming temperature of 750° C. or higher and 850° C. or lower by using a mixed gas containing TiCl ₄ gas, H ₂ S gas and Ar—H ₂ O gas. It is a manufacturing method.

Here, x satisfies 0.7≦x<1, and y satisfies 1.0≦y≦2.0.

FIG. 1 is a diagram schematically illustrating a cross section of a cutting tool according to an aspect of the present disclosure. FIG. 2 is an electron micrograph of a cross section of a coating of a cutting tool according to an aspect of the present disclosure. FIG. 3 is an electron micrograph of the second layer of the cutting tool according to one aspect of the present disclosure. FIG. 4 is a diagram showing an example of a CVD apparatus.

[Problems to be solved by the present disclosure]
Al ₂ O ₃ includes α-Al ₂ O ₃ , γ-Al ₂ O ₃ , κ-Al ₂ O _{3 and the} like depending on the crystal form. Among them, α-Al ₂ O ₃ is suitable as a material for the coating because it has excellent oxidation resistance at high temperatures.

On the other hand, usually, when α-Al ₂ O ₃ is produced by a chemical vapor deposition (CVD) method, the film forming temperature is as high as 1000° C. or higher. Therefore, when the α-Al ₂ O ₃ layer is formed on the layer made of AlTiN or AlTiCN by the CVD method, AlTiN and AlTiCN are thermally decomposed, which tends to shorten the tool life.

Therefore, an object of the present invention is to provide a layer composed only of AlTiN or AlTiCN and a layer containing α-Al ₂ O ₃ and have an excellent tool life even when used for high efficiency machining or dry machining. The purpose is to provide a cutting tool capable of performing.
[Effect of the present disclosure]
According to the above aspect, the cutting tool can have an excellent tool life even when used for high efficiency machining or dry machining.

[Description of Embodiments of the Present Disclosure]
First, embodiments of the present disclosure will be listed and described.

(1) A cutting tool according to one aspect of the present disclosure is a cutting tool including a base material and a coating film provided on the base material,
The coating film has a first layer provided on the base material side and a second layer provided on the first layer,
The first layer is composed only of a nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1),
The second layer is a cutting tool composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y (which satisfies 1.0≦y≦2.0).

According to the above aspect, the cutting tool can have an excellent tool life even when used for high efficiency machining or dry machining.

(2) The TiS _y preferably has a plate-like structure and is dispersed in the α-Al ₂ O ₃ . This improves wear resistance among the various characteristics of the cutting tool.

(3) It is preferable that the second layer has a TiS _y area ratio of 0.5% or more and 20% or less in a cross section parallel to the surface of the coating film. According to this, the wear resistance of the cutting tool is further improved.

(4) The area ratio of TiS _y is preferably 1% or more and 15% or less. According to this, the wear resistance of the cutting tool is further improved.

(5) The area ratio of TiS _y is preferably 2% or more and 10% or less. According to this, the wear resistance of the cutting tool is further improved.

(6) The second layer preferably has a thickness of 0.5 μm or more and 5 μm or less. According to this, the tool life of the cutting tool is further improved.

(7) The coating preferably has a thickness of 3 μm or more and 30 μm or less. According to this, the tool life of the cutting tool is further improved.

(8) It is preferable that the coating film has a third layer between the first layer and the second layer, and the third layer is made of only TiCN. According to this, crystal growth of the second layer can be promoted in the process of manufacturing the coating film.

(9) It is preferable that the first layer is composed only of a compound represented by Al _x Ti _1-x C _a N _b . Here, it is preferable that the x satisfies 0.7≦x<1, the a satisfies 0≦a<0.25, and the b satisfies 0.75≦b<1.5.

This improves wear resistance among the various characteristics of the cutting tool.
(10) It is preferable that x satisfies 0.75≦x<0.95. This improves wear resistance among the various characteristics of the cutting tool.

(11) It is preferable that x satisfies 0.8≦x<0.9. This improves wear resistance among the various characteristics of the cutting tool.

(12) It is preferable that the a satisfies 0≦a<0.1. This improves wear resistance among the various characteristics of the cutting tool.

(13) It is preferable that the a satisfies 0≦a<0.05. This improves wear resistance among the various characteristics of the cutting tool.

(14) It is preferable that b satisfies 0.8≦b<1.2. This improves wear resistance among the various characteristics of the cutting tool.

(15) It is preferable that b satisfies 0.9≦b<1.1. This improves wear resistance among the various characteristics of the cutting tool.

(16) It is preferable that y satisfies 1.0≦y≦2.0. This improves wear resistance among the various characteristics of the cutting tool.

(17) It is preferable that y satisfies 1.4≦y≦1.8. This improves wear resistance among the various characteristics of the cutting tool.

(18) It is preferable that the coating film includes a base layer disposed between the base material and the first layer. According to this, the adhesiveness between the base material and the coating can be enhanced.

(19) A method for manufacturing a cutting tool according to another aspect of the present disclosure is the method for manufacturing a cutting tool according to any one of (1) to (18) above,
A step of preparing a base material,
A step of forming a coating film on the base material by a chemical vapor deposition method,
The step of forming the coating includes the step of forming a first layer and the step of forming a second layer,
The first layer consists of a nitride or carbonitride of Al _x Ti _1-x ,
The second layer is composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y ,
The step of forming the second layer is performed at a film forming temperature of 750° C. or higher and 850° C. or lower by using a mixed gas containing TiCl ₄ gas, H ₂ S gas and Ar—H ₂ O gas. It is a manufacturing method.

Here, the x satisfies 0.7≦x<1, and the y satisfies 1.0≦y≦2.0.
According to the above aspect, it is possible to manufacture a cutting tool having an excellent tool life even when used for high efficiency machining or dry machining.

[Details of the embodiment of the present disclosure]
Specific examples of the cutting tool and the manufacturing method thereof according to an embodiment of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. The dimensional relationships such as length, width, thickness, and depth are appropriately changed for the sake of clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

In the present specification, the notation of the form "AB" means the upper and lower limits of the range (that is, A or more and B or less), and when A does not have a unit and B only has a unit, The unit of B and the unit of B are the same.

In the present specification, when a compound or the like is represented by a chemical formula, when the atomic ratio is not particularly limited, it includes all conventionally known atomic ratios, and is not necessarily limited to the stoichiometric range. For example, when "AlTiN" is described, the ratio of the number of atoms forming AlTiN is not limited to Al:Ti:N=0.8:0.2:1, and any conventionally known atomic ratio is included. This also applies to the description of compounds other than "AlTiN". In the present embodiment, in any compound, a metal element such as titanium (Ti), aluminum (Al), tantalum (Ta), and chromium (Cr), and nitrogen (N), oxygen (O), carbon (C), and the like. The non-metal element does not necessarily have to constitute a stoichiometric composition.

<Cutting tool>
As shown in FIGS. 1 and 2, the cutting tool 10 according to the present embodiment includes a base material 1 and a coating film 2 provided on the base material 1. The coating preferably covers the entire surface of the substrate. However, it does not depart from the scope of the present disclosure even if a part of the base material is not covered with this coating or the structure of the coating is partially different.

Cutting tools include drills, end mills, exchangeable cutting tips for drills, exchangeable cutting tips for end mills, exchangeable cutting tips for milling, exchangeable cutting tips for turning, metal saws, gear cutting tools, reamers, It can be suitably used as a cutting tool such as a tap.

<Substrate>
As the base material 1, any base material conventionally known as this type of base material can be used. For example, cemented carbide (for example, WC-based cemented carbide, WC, including Co or containing carbonitrides such as Ti, Ta, and Nb), cermet (TiC, TiN, TiCN, etc.) Main component), high speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body or diamond sintered body preferable.

Among these various base materials, it is preferable to select cemented carbide (particularly WC-based cemented carbide) or cermet (particularly TiCN-based cermet). These base materials have an excellent balance of hardness and strength at high temperatures, and have excellent properties as base materials for cutting tools for the above applications. When a WC-based cemented carbide is used as the base material, its structure may contain free carbon and an abnormal layer called η phase or ε phase.

Furthermore, the base material may have a modified surface. For example, in the case of cemented carbide, a debeta layer may be formed on the surface thereof, or in the case of cermet, a surface hardened layer may be formed. The substrate exhibits the desired effect even if its surface is modified.

When the cutting tool is a cutting edge exchange type cutting tip, etc., the base material may or may not have a chip breaker. The shape of the ridge of the cutting edge is a combination of sharp edges (ridges where the rake face and flank intersect), honing (sharp edges are given), negative land (chamfered), and honing and negative land. Among things, any thing is included.

<Coating>
The coating film 2 has a first layer 4 provided on the base material 1 side and a second layer 6 provided on the first layer 4. The coating 2 can include layers other than the first layer 4 and the second layer 6. As other layers, for example, a base layer 3 arranged between the base material 1 and the first layer 4, a third layer 5 arranged between the first layer 4 and the second layer 6, and a second layer A surface layer (not shown) disposed on the layer 6 is mentioned.

The total thickness of the coating is preferably 3 μm or more and 30 μm or less. When the thickness of the coating is within this range, the fracture resistance can be improved while maintaining the wear resistance. If the thickness of the coating film is less than 3 μm, the hardness tends to decrease, and if it exceeds 30 μm, the coating film tends to peel off from the substrate during cutting. The total thickness of the coating film is more preferably 5 μm or more and 20 μm or less, and further preferably 7 μm or more and 15 μm or less, from the viewpoint of improving the characteristics.

The thickness of the coating film is measured, for example, by obtaining a cross-section sample parallel to the normal direction of the surface of the base material and observing the sample with a scanning transmission electron microscope (STEM: Scanning Transmission Electron Microscopy). As a measuring method using such a STEM, a STEM high-angle scattering dark field method (HAADF-STEM: High-Angle Annular Dark-field Scanning Transmission Electron Microscopy) can be mentioned.

In the present specification, the term "thickness" means the average thickness. Specifically, the observation magnification of the cross-section sample is set to 5000 to 10000 times, the observation area is set to 100 to 500 μm ² , thickness widths at 10 locations in one visual field are measured, and the average value thereof is defined as “thickness”. The same applies to the thickness of each layer described below unless otherwise specified.

<First layer>
The first layer 4 is composed only of a nitride or carbonitride of Al _x Ti _1-x . Here, x satisfies 0.7≦x<1. Nitrides of Al _x Ti _{1-x is} shown as Al _{x Ti 1-x N,} carbonitrides of Al _{x Ti 1-x} is shown as _Al x _{Ti 1-x} CN. The first layer 4 is a compound represented by Al _x Ti _1-x C _a N _b (satisfying 0.7≦x<1, 0≦a<0.25, 0.75≦b<1.5). It is preferably composed of only.

In a nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1), Al is contained in an atomic ratio of 70% or more with respect to the total of Al and Ti, and carbon ( C) or carbon (C) and nitrogen (N). The first layer made of only such a compound can have high hardness and excellent wear resistance.

Regarding the composition of the compound forming the first layer, 0.75≦x<0.95 is preferable, 0.8≦x<0.9 is more preferable, 0≦a<0.1 is preferable, and 0≦a< 0.05 is more preferable, 0.8≦b<1.2 is preferable, and 0.9≦b<1.1 is more preferable.

The composition of the first layer can be confirmed by using an EDX (Energy Dispersive X-ray spectroscopy) device with SEM or TEM. Specifically, first, an arbitrary position of the cutting tool 10 is cut, and a sample including the cross section of the coating film 2 is prepared.

Next, regarding the first layer of the coating 2, five rectangular measurement fields of 10 μm×20 μm are arbitrarily selected, and this region is analyzed. Thereby, the atomic ratio of each element contained in an arbitrary measurement region can be specified, and the composition of the first layer can be determined from this atomic ratio.

In addition, as long as the measurement is carried out by the applicant, as long as the measurement is performed on the same sample, even if the measurement result of the composition of the first layer is changed a plurality of times by changing the selected position of the measurement field of view, the dispersion of the measurement result is It was confirmed that there is almost no.

The first layer is a layer (hereinafter, also referred to as a first unit layer) having a thickness of 150 nm or less, which is made of only a nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1). It is preferably a layered structure containing a plurality of layers. According to this, the first layer can have high thermal shock resistance. The number of stacked first unit layers included in the first layer is preferably 5 or more and 5000 or less, and more preferably 10 or more and 2500 or less.

The first layer is composed of the above-mentioned layered structure, and each layer constituting the layered structure has the same face-centered cubic lattice structure, and the first unit layers having different stoichiometric ratios of Ti and Al alternate. It is preferable to form regions that alternately alternate. According to this, the first unit layer can maintain a cubic crystal structure and can have higher thermal stability.

As for the first layer having a layered structure and the number of laminated first unit layers, a cross-section sample parallel to the normal direction of the surface of the substrate was obtained, and this sample was subjected to a scanning transmission electron microscope (STEM: Scanning). It is measured by observing with Transmission Electron Microscopy).

90% by volume or more of the first layer preferably has a face-centered cubic lattice structure. According to this, the decrease in hardness of the first layer can be controlled to a minimum, and the first layer can have excellent wear resistance and chipping resistance. The proportion of the face-centered cubic lattice structure in the first layer is more preferably 95% by volume or more, and most preferably 100% by volume.

The first layer has a face-centered cubic lattice structure, and the volume ratio thereof is determined by using an X-ray diffractometer, a scanning electron microscopy electron scattering back scattering (SEM-EBSD) apparatus, a TEM (Transmission Electron Microscopy) apparatus, and the like. You can check.

The first layer preferably has a total thickness of 1 μm or more and 15 μm or less. According to this, the tool life of the cutting tool is improved. If the thickness of the first layer is less than 1 μm, the effect of improving the wear resistance by the first layer tends to be reduced, and if it exceeds 15 μm, the coating film is likely to be peeled from the base material during cutting. The thickness of the first layer is more preferably 2 μm or more and 10 μm or less, still more preferably 4 μm or more and 8 μm or less.

The total thickness of the first layer can be measured by the same method as that used for measuring the thickness of the coating film.

The first layer may contain unavoidable impurities in addition to the nitride or carbonitride of Al _x Ti _1-x as long as the effect is exhibited. Examples of unavoidable impurities include oxygen, argon, hydrogen, chlorine, and sulfur.

<Second layer>
The second layer 6 is composed only of a composite compound containing α-Al ₂ O ₃ (aluminum oxide having a crystal structure of α type) and TiS _y (titanium sulfide). Here, y satisfies 1.0≦y≦2.0. Since the second layer is composed only of the composite compound containing α-Al ₂ O ₃ and TiS _y , the cutting tool according to the present embodiment is excellent even when used for high efficiency machining or dry machining. It has high temperature stability and high temperature oxidation resistance and can achieve long tool life. The reason for this is not clear, but it is presumed to be as follows (a) to (d).

(A) α-Al ₂ O ₃ has heat insulating properties, high temperature oxidation resistance, and reaction resistance. Therefore, when the second layer contains α-Al ₂ O ₃ , when the cutting tool is used, it is possible to suppress decomposition or oxidation of the first layer composed of only AlTiN or AlTiCN due to cutting heat. The wear resistance of the tool is improved.

(B) The second layer containing α-Al ₂ O ₃ and TiS _y can be formed under the temperature condition of 750 to 850° C. Therefore, the first layer made of only AlTiN or AlTiCN is not thermally decomposed during film formation, and the cutting tool can maintain excellent wear resistance.

(C) TiS _y has high temperature lubricity. Therefore, when the second layer contains TiS _y , the cutting resistance is reduced when the cutting tool is used, so that the wear of the rake face can be suppressed and the wear resistance of the cutting tool is improved.

(D) TiS _y has high temperature lubricity. Therefore, when the second layer contains TiS _y , the cutting resistance is reduced when the cutting tool is used, and the rise in the cutting edge temperature can be suppressed. This can prevent the first layer made of only AlTiN or AlTiCN from being decomposed or oxidized by cutting heat, and the wear resistance of the cutting tool is improved.

With respect to the composition of TiS _y , 1.0≦y≦2.0 is preferable, and 1.4≦y≦1.8 is more preferable. The composition of TiSy can be measured by the same method as that used for measuring the composition of the first layer.

Specifically, the fact that the second layer contains α-Al ₂ O ₃ and TiS _y can be confirmed by using an EDX (Energy Dispersive X-ray spectroscopy) device with SEM or TEM. it can. Observing any area of the surface of the second layer of the cutting tool 10 in SEM, for example, as shown in Figure 3, the _alpha-Al 2 _{O 3} region 7 consisting only _{α-Al 2 O 3, TiS} y only TiS _y region 8 consisting of By analyzing each of the α-Al ₂ O ₃ region 7 and the TiS _y region 8, the atomic ratio of each element contained in each region can be specified. From this atomic ratio, the α-Al ₂ O ₃ region and TiS _y region can be specified. The composition of the region can be determined.

If a surface layer is further present on the second layer, polish the surface layer to expose the second layer, and measure the composition on the exposed surface.

As long as the measurement is carried out by the applicant, the measurement results of the composition of the α-Al ₂ O ₃ region and the TiS _y region are calculated multiple times by changing the selected position of the measurement visual field as long as the measurement is performed on the same sample. However, it was confirmed that there was almost no variation in the measurement results.

In the second layer, TiS _y preferably has a plate-like structure and is dispersed in α-Al ₂ O ₃ . When TiS _y has a plate-like structure, the hardness of TiS _y increases. Therefore, the second layer can have high hardness.

In the second layer, TiS _y has a plate-like structure, and the axial direction of the plate-like structure is from the surface of the second layer to the interface between the second layer and the layer existing thereunder, the thickness of the second layer. It is preferable that it exists extending in the direction. When TiS _y is present in a columnar form in a matrix consisting of α-Al ₂ O ₃ only, TiS _y is exposed on the surface of the cutting tool from the beginning to the end of cutting, so the lubrication effect of TiS _y is maintained. It Therefore, the effect of improving wear resistance can be obtained from the initial stage to the final stage of cutting, and the tool life is improved.

It can be confirmed by observing the surface of the second layer with STEM that TiS _y has a plate-like structure. When a surface layer is further present on the second layer, the surface layer is polished to expose the second layer, and the exposed surface is observed by STEM. The fact that the axial direction of the plate-like structure extends in the thickness direction of the second layer means that a cross-section sample parallel to the normal direction of the surface of the base material is obtained and the cross section of this second layer is STEM. It can be confirmed by observing.

The second layer preferably has an area ratio of TiS _y of 0.5% or more and 20% or less in a cross section parallel to the surface of the coating film. According to this, the wear resistance of the cutting tool is improved. The area ratio of TiS _y is more preferably 1% or more and 15% or less, still more preferably 2% or more and 10% or less.

The area ratio of TiS _y in the second layer is calculated according to the following procedures (a) to (d).

(A) Setting of measurement field of view In the second layer of the cutting tool, the depth from the surface side of the second layer (when another layer (for example, surface layer) is provided on the surface side of the second layer, The depth from the interface between the second layer and the other layer) was 0.5 μm, and the exposed cross section was cut in a direction parallel to the surface of the film using a wire electric discharge machine, and the exposed cross section had an average particle size of It is mirror-polished using a 3 μm diamond slurry. When the surface of the coating film has irregularities, the surface is polished until it becomes a flat surface, cut in a direction parallel to the flat surface, and the exposed cross section is mirror-polished using a diamond slurry having an average particle diameter of 3 μm. When the outermost surface of the cutting tool is the second layer, the surface of the second layer is mirror-polished with diamond slurry having an average particle size of 3 μm without cutting.

In the mirror-polished cross section or surface of the second layer, five rectangular measurement fields of 10 μm×20 μm are randomly selected. In addition, as long as the measurement is performed by the applicant, as long as the measurement is performed on the same sample, even if the measurement result of the TiS _y area ratio to be described later is calculated multiple times by changing the selected portion of the measurement visual field, It was confirmed that there was almost no variation.

(B) Imaging of measurement visual field Each measurement visual field is imaged using the following equipment under the following conditions.

Optical microscope: "AXIO Vert. A1" manufactured by Carl Zeiss (product name)
Lens: "EC Epiplan 100x/0.85 HD M27" manufactured by Carl Zeiss (product name)
Imaging conditions: time: 700 ms, intensity: 80%, gamma: 0.45.

(C) Binarization process of the captured image The image captured in (b) above is binarized using the following image processing software according to the following procedure.

Image processing software: Win Roof ver. 7.4.5
Processing procedure:
1. Histogram average brightness correction (correction reference value 128)
2. Background removal (object size 30 μm)
3. Binarization with a single threshold (threshold 100)
4. Brightness inversion.

(D) Analysis of binarized image In the image obtained in (c) above, the bright field corresponds to TiS _y and the dark field corresponds to Al ₂ O ₃ . Therefore, the area ratio of TiS _y in the second layer can be obtained by calculating the area ratio of the pixels derived from the bright field (pixels derived from TiS _y ) in the total area of the measurement field of view (second layer). it can.

Note that the second layer preferably has a thickness of 0.5 μm or more and 5 μm or less. According to this, the tool life of the cutting tool is improved. If the thickness of the second layer is less than 0.5 μm, the effect of improving wear resistance by the second layer tends to decrease, and if it exceeds 5 μm, the second layer is likely to peel off during cutting. The thickness of the second layer is more preferably 1 μm or more and 4 μm or less, still more preferably 2 μm or more and 3 μm or less.

The thickness of the second layer can be measured by the same method as that used for measuring the thickness of the above coating.

The hardness of the second layer is preferably 15 GPa or more and 35 GPa or less as measured by the nanoindentation method. According to this, the wear resistance of the cutting tool is improved. If the hardness of the second layer is less than 15 GPa, the wear resistance tends to decrease, and if it exceeds 35 GPa, the fracture resistance tends to decrease. The hardness of the second layer is more preferably 20 GPa or more and 30 GPa or less, and further preferably 22 GPa or more and 28 GPa or less.

The above hardness is measured by the method according to ISO14577, and the measurement load is 10 mN. A nanoindentation hardness meter (ENT1100a; manufactured by Elionix) is used as a measuring instrument.

The second layer may contain unavoidable impurities in addition to the composite compound containing α-Al ₂ O ₃ and TiS _y , as long as the effect is exhibited. Examples of unavoidable impurities include hydrogen, chlorine, and argon.

<Other layers>
The coating 2 may include other layers in addition to the first layer 4 and the second layer 6. As other layers, for example, a base layer 3 arranged between the base material 1 and the first layer 4, a third layer 5 arranged between the first layer 4 and the second layer 6, and a second layer A surface layer (not shown) disposed on the layer 6 is mentioned.

(Underlayer)
The base layer 3 is disposed between the base material 1 and the first layer 4, whereby the adhesion of the first layer in the coating film can be increased and the adhesion between the base material and the coating film can be increased. As the underlayer, for example, a TiN layer, a TiCN layer, a TiCNO layer, a TiBN layer or the like can be used. The underlayer can be composed of one layer. It can also consist of multiple layers. The underlayer can be formed by a known method.

When the TiN layer is used as the underlayer, the average thickness is preferably 0.3 to 1 μm. With the thickness in this range, the adhesion of the first layer in the coating can be further enhanced. The TiN layer is more preferably 0.4 to 0.8 μm.

When the TiCN layer and the TiBN layer are used as the underlayer, the average thickness is preferably 2 to 20 μm. If this average thickness is less than 2 μm, abrasion may be likely to proceed. If the average thickness exceeds 20 μm, the fracture resistance may decrease.

The thickness of the underlayer can be measured by the same method as used for measuring the thickness of the above coating.

(Third layer)
By disposing the third layer 5 between the first layer 4 and the second layer 6, crystal growth of the second layer 6 can be promoted. As the third layer, for example, a TiCN layer, a TiCNO layer or the like can be used. In particular, when the TiCN layer is used as the third layer, the pretreatment step when forming the second layer containing α-Al ₂ O ₃ can be performed in a short time, and the crystal growth of the second layer is further promoted. Therefore, it is preferable. The third layer can consist of one layer. It can also consist of multiple layers.

The average thickness of the third layer 5 is preferably 0.2 to 2.0 μm, more preferably 0.5 to 1.5 μm. If the average thickness of the third layer is less than 0.2 μm, the effect of promoting crystal growth of the second layer tends to decrease. If the average thickness of the third layer exceeds 2.0 μm, the adhesion between the second layer and the layer adjacent to the third layer may be reduced.

The thickness of the third layer can be measured by the same method as that used for measuring the thickness of the above coating.

(Surface layer)
The surface layer (not shown) is a layer arranged on the surface side of the coating 2. The surface layer is arranged immediately above the second layer 6, for example. The surface layer can be made of, for example, a compound containing Ti carbide, nitride, or boride as a main component. Here, "containing any of Ti carbide, nitride or boride as a main component" means containing 90 mass% or more of Ti carbide, nitride or boride. Further, it preferably means that it is made of any one of Ti carbide, nitride and boride except for inevitable impurities. The surface layer can consist of one layer. It can also consist of multiple layers.

　When the surface layer is configured, it becomes easy to identify the corner of the cutting tip (identification of the used part) after cutting and using due to the effect of showing a clear color.

The surface layer preferably has an average thickness of 0.05 to 1 μm. The upper limit of the average thickness of the surface layer is preferably 0.8 μm, more preferably 0.6 μm. The lower limit of this average thickness is preferably 0.1 μm, more preferably 0.2 μm. If the average thickness is less than 0.05 μm, the fracture resistance may not be sufficiently obtained. If this average thickness exceeds 1 μm, the adhesion with the layer adjacent to the surface layer may be reduced. The thickness of the surface layer can be measured by the same method as that used for measuring the thickness of the coating film.

<Method of manufacturing cutting tool>
A method for manufacturing a cutting tool according to the present embodiment is a method for manufacturing a cutting tool described above, including a step of preparing a base material, and a step of forming a coating film on the base material by a chemical vapor phase synthesis method, The step of forming the coating includes a step of forming a first layer and a step of forming a second layer, the first layer consisting only of a nitride or carbonitride of Al _x Ti _1-x , and the second layer Is composed only of a complex compound containing α-Al ₂ O ₃ and TiS _y, and the step of forming the second layer is a mixed gas containing TiCl ₄ gas, H ₂ S gas and Ar—H ₂ O gas. Is used at a film forming temperature of 750° C. or higher and 850° C. or lower. Here, x satisfies 0.7≦x<1 and y satisfies 1.0≦y≦2.0. As a result, a cutting tool having the above configuration and effects can be manufactured.

First, an example of a CVD apparatus used in the method for manufacturing the cutting tool according to this embodiment will be described with reference to FIG. As shown in FIG. 4, the CVD apparatus 100 includes a plurality of base material holding jigs 21 for installing the base material 1 and a reaction container 22 made of a heat-resistant alloy steel surrounding the base material holding jigs 21. I have it. A temperature controller 23 for controlling the temperature inside the reaction container 22 is provided around the reaction container 22.

In the reaction container 22, a gas introduction pipe having a first gas introduction pipe 24 and a second gas introduction pipe 25 joined adjacent to each other extends vertically in a space inside the reaction container 22 and has an axis 26 thereof. It is provided so that it can be rotated. In the gas introduction pipe, the gas introduced into the first gas introduction pipe 24 and the gas introduced into the second gas introduction pipe 25 are not mixed inside. A part of the first gas introducing pipe 24 and the second gas introducing pipe 25 is provided with a base on which the gas flowing inside the first gas introducing pipe 24 and the second gas introducing pipe 25 is installed in the base material holding jig 21. A plurality of through holes for ejecting the material 1 are provided.

Furthermore, the reaction container 22 is provided with a gas exhaust pipe 27 for exhausting the gas inside the reaction container 22 to the outside. The gas inside the reaction container 22 passes through the gas exhaust pipe 27 and is discharged to the outside of the reaction container 22 through the gas exhaust port 28.

Next, a method of manufacturing a cutting tool using the CVD device 100 will be described. Hereinafter, for convenience of description, the first layer consisting of only a nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1) is directly formed on the substrate, and the first layer Although the case where the second layer is formed immediately above is described, the first layer may be formed after forming another layer such as an underlayer on the base material. Further, after forming the first layer, the third layer may be formed, and the second layer may be formed on the third layer. Furthermore, a surface layer can be formed on the second layer. As the method of forming the underlayer, the third layer and the surface layer, any conventionally known method can be used.

<Step of preparing a substrate>
First, the base material 1 is prepared. As the base material, a commercially available material may be used, or a general powder metallurgy method may be used. For example, when a cemented carbide base material is manufactured as a base material by a general powder metallurgy method, a mixed powder can be obtained by mixing WC powder and Co powder with a ball mill or the like. After the mixed powder is dried, it is molded into a predetermined shape to obtain a molded body. Further, by sintering the compact, a WC—Co based cemented carbide (sintered body) is obtained. Then, the sintered body is subjected to predetermined cutting edge processing such as honing treatment, whereby a base material made of a WC-Co based cemented carbide can be manufactured. As the base materials other than the above, any of the conventionally known base materials of this type can be prepared.

<Process of forming coating>
In the step of forming the coating film, the coating film is formed on the base material 1 by the CVD method using the CVD apparatus 100. The step of forming the coating includes the step of forming the first layer and the step of forming the second layer.

<Step of forming first layer>
First, a chip having an arbitrary shape as the base material 1 is mounted on the base material holding jig 21 in the reaction container 22 of the CVD apparatus 100. Then, the temperature of the base material 1 installed on the base material holding jig 21 is raised to 680 to 780° C. by using the temperature controller 23. Further, the pressure inside the reaction container 22 is set to 0.1 to 3.0 kPa.

Next, while rotating the first gas introduction pipe 24 and the second gas introduction pipe 25 around the shaft 26, a first gas group containing TiCl ₄ gas and AlCl ₃ gas is introduced into the first gas introduction pipe 24, A second gas group containing NH ₃ gas is introduced into the second gas introduction pipe 25. As a result, the first gas group and the second gas group are jetted into the reaction container 22 through the through hole of the first gas introduction pipe 24 and the through hole of the second gas introduction pipe 25, respectively.

The first gas group preferably contains H ₂ gas as a carrier gas together with TiCl ₄ gas and AlCl ₃ gas. The second gas group preferably contains H ₂ gas as well as NH ₃ gas.

The ejected first gas group and second gas group are uniformly mixed in the reaction container 22 by the rotating operation, and the mixed gas moves toward the base material 1. Then, the gas component contained in the first gas group and the gas component contained in the second gas group chemically react with each other to cause Al _x Ti _1-x (satisfying 0.7≦x<1) on the base material 1. Nuclei of crystal grains consisting only of the nitride or carbonitride are generated. Subsequently, the first gas group is ejected from the through hole of the first gas introduction pipe 24, and the second gas group is ejected from the through hole of the second gas introduction pipe 25. As a result, the nuclei of the crystal grains grow, and the first layer is formed only of the nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1).

In the step of forming the first layer, the thickness of the first layer can be adjusted by controlling the flow rates of the first gas group and the second gas group and the film formation time. The flow rate of the first gas group is preferably 20 NL/min or more and 100 NL/min or less, and more preferably 40 NL/min or more and 80 NL/min or less. The film formation time is preferably 10 minutes or more and 300 minutes or less, and more preferably 30 minutes or more and 180 minutes or less. The flow rate of the second gas group is preferably 5 NL/min or more and 50 NL/min or less, more preferably 10 NL/min or more and 25 NL/min or less. The film formation time is preferably 10 minutes or more and 300 minutes or less, and more preferably 30 minutes or more and 180 minutes or less.

In the present embodiment, when forming the first layer, it is preferable to grow the crystal grains while modulating the flow rates of both or either one of the AlCl ₃ gas and the TiCl ₄ gas. This method includes a first crystal growth method in which the proportion (volume %) of TiCl ₄ gas is modulated while maintaining the proportion (volume %) of AlCl ₃ gas in the total reaction gas constant, and the first crystal growth method There is a second crystal growth method in which the proportion (volume %) of AlCl ₃ gas is modulated while the proportion (volume %) of TiCl ₄ gas is kept constant.

In the first crystal growth method, the atomic ratio of Ti can be controlled (that is, the atomic ratio of Al can also be controlled) by adjusting the flow rate of TiCl ₄ gas. For example, while maintaining the ratio of AlCl ₃ gas constant at 0.2 to 0.3% by volume, the ratio of TiCl ₄ gas is set at 0.1 to 0.2% by volume (high flow rate: High Flow), and the ratio is 5 to 15%. The first gas group is introduced into the first gas introduction pipe 24 under the condition of being maintained for a second. Immediately thereafter, TiCl ₄ by switching the high and low flow rate of the gas TiCl ₄ the proportion of gas 0.02-0.04% by volume (low flow: Low Flow) the first gas group in conditions that maintain 45-55 seconds as the It is introduced into the 1 gas introduction pipe 24. After that, the flow rate of TiCl ₄ gas is further switched between high and low. By repeating this operation a plurality of times, it is possible to form the first layer including crystal grains having a laminated structure in which the first unit layers having different Ti atomic ratios are alternately laminated.

In the second crystal growth method, the atomic ratio of Al can be controlled (that is, the atomic ratio of Ti can also be controlled) by adjusting the flow rate of AlCl ₃ gas. Specifically, while maintaining the proportion of TiCl ₄ gas constant at 0.02 to 0.04% by volume, the proportion of AlCl ₃ gas is set to 1 to 2% by volume (high flow rate: High Flow) for 10 to 15 seconds. The first gas group is introduced into the first gas introduction pipe 24 under the condition of being maintained. Immediately thereafter, AlCl ₃ switches the level of the flow rate of the gas 0.2-0.4% by volume ratio of AlCl ₃ gas (low flow: Low Flow) the first gas group in conditions that maintain 45-50 seconds as the It is introduced into the 1 gas introduction pipe 24. After that, the flow rate of the AlCl ₃ gas is further switched between high and low. By repeating this operation a plurality of times, it is possible to form the first layer containing crystal grains having a laminated structure in which the first unit layers having different Al atomic ratios are alternately laminated.

In the first crystal growth method and the second crystal growth process, a high flow rate (High Flow) in TiCl ₄ times for jetting gas or AlCl ₃ gas, low flow (Low Flow) at the time of ejecting a TiCl ₄ gas or AlCl ₃ gas , TiCl ₄ gas or AlCl ₃ gas by adjusting the number of times of switching the flow rate from a high flow rate to a low flow rate, or from a low flow rate to a high flow rate, by adjusting the thickness of each first unit layer and the total thickness of the first layer. Each can be controlled to a desired thickness.

Further, by setting the pressure inside the reaction container 22 and the temperature of the base material 1 within the above ranges, the orientation of the crystal grains contained in the first layer can be controlled.

<Step of forming second layer>
Next, the temperature of the substrate is adjusted to 750°C or higher and 850°C or lower. This means that the temperature of the reaction atmosphere during formation of the second layer (hereinafter, also referred to as film formation temperature) is 750° C. or higher and 850° C. or lower. If the film formation temperature is lower than 750° C., a sufficient film formation rate may not be obtained. On the other hand, when the film forming temperature exceeds 850° C., AlTiN or AlTiCN forming the first layer may be thermally decomposed. The film forming temperature is preferably 770° C. or higher and 830° C. or lower, and more preferably 780° C. or higher and 820° C. or lower.

-In addition to adjusting the temperature of the base material, the pressure inside the reaction container 22 is adjusted to 5 kPa or more and 10 kPa or less.

Next, while rotating the gas first gas introduction pipe 24 and the second gas introduction pipe 25 around the shaft 26, a mixed gas containing TiCl ₄ gas, H ₂ S gas, and Ar—H ₂ O gas (hereinafter, referred to as “ Also referred to as "second layer mixed gas") is introduced into the first gas introduction pipe or the second gas introduction pipe. H ₂ S gas and Ar—H ₂ O gas are catalysts. Ar—H ₂ O gas means Ar gas containing H ₂ O at a concentration of 30 to 300 ppm. As a result, the second layer mixed gas is ejected into the reaction container from the through hole of the first gas introduction pipe 24 or the through hole of the second gas introduction pipe 25.

The ejected mixed gas for the second layer is uniformly mixed in the reaction vessel 22 by the rotating operation, and the gas components chemically react, so that nuclei of crystal grains composed of only α-Al ₂ O ₃ are formed on the first layer. , And nuclei of crystal grains consisting of TiS _y only are generated. Subsequently, the mixed gas is ejected from the through hole of the first gas introducing pipe 24 or the through hole of the second gas introducing pipe 25. As a result, the nuclei of the crystal grains grow, and the second layer including the crystal grains composed of only α-Al ₂ O ₃ and the crystal grains composed of TiS _y is formed.

In the step of forming the second layer, the thickness of the second layer can be adjusted by controlling the flow rate of the mixed gas for the second layer and the film formation time. The flow rate of the mixed gas for the second layer is preferably 20 NL/min or more and 80 NL/min or less, and more preferably 40 NL/min or more and 60 NL/min or less. The film formation time is preferably 30 minutes or more and 300 minutes or less, and more preferably 60 minutes or more and 180 minutes or less.

The film formation rate of the second layer is preferably 0.5 μm/hr or more and 2 μm/hr or less, more preferably 0.7 μm/hr or more and 1.5 μm/hr or less.

Conventionally, when forming an Al ₂ O ₃ layer by the CVD method, the reaction paths represented by the following reaction formulas (1) and (2) have been used.

H ₂ +CO ₂ →H ₂ O+CO (1)
2AlCl ₃ +3H ₂ O→Al ₂ O ₃ +6HCl (2)
In the above reaction formula (1), the formation reaction of H ₂ O as a reaction intermediate is thermodynamically calculated as ΔG=0 kJ at 800° C. Therefore, a temperature of about 1000° C. is necessary to secure a sufficient Al ₂ O ₃ generation rate.

On the other hand, a nitride or carbonitride of Al _x Ti _1-x (satisfying 0.7≦x<1) (eg, AlTiN, AlTiCN) forming the first layer is Pyrolyzes. Therefore, as a result of diligent studies of the reaction conditions under which the formation of the Al ₂ O ₃ layer can be performed at a lower temperature, the present inventors have found that the reaction pathways represented by the following reaction formulas (1′) and (2′) Was newly devised.

3TiCl ₄ +6H ₂ +5CO ₂ →Ti ₃ O ₅ +5CO+12HCl (1′)
10AlCl ₃ +3Ti ₃ O ₅ +1.5H ₂ →5Al ₂ O ₃ +9TiCl ₃ +3HCl (2′)
In the reaction paths represented by the reaction formulas (1′) and (2′), the reaction intermediate is Ti ₃ O ₅ instead of H ₂ O. The formation reaction (1′) of Ti ₃ O ₅ is thermodynamically calculated as ΔG=0 kJ) at around 50° C. Further, in the Al ₂ O ₃ formation reaction (2′), ΔG is negative at 850° C. or lower. Therefore, in the reaction route, it is possible to secure a sufficient Al ₂ O ₃ generation rate at a low temperature of 750 to 800°C. In the present embodiment, the crystal structure of Al ₂ O ₃ produced at a low temperature of 750 to 800° C. is α-Al ₂ O ₃ .

Furthermore, the inventors of the present invention have controlled the proportion of H ₂ S gas in the mixed gas so that the crystal grains made of only TiS _y having high-temperature lubricity are contained in the matrix region made of only α-Al ₂ O _3. It has been found that it is possible to precipitate. Thereby, the obtained second layer can have adiabatic property derived from α-Al ₂ O ₃ , high temperature oxidation resistance and reaction resistance as well as high temperature lubricity derived from TiS _y .

The proportion of H ₂ S gas in the mixed gas for the second layer is preferably 0.1 vol% or more and 1.0 vol% or less, more preferably 0.2 vol% or more and 0.8 vol% or less, and 0.3 More preferably, it is not less than 0.5% by volume and not more than 0.5% by volume. If the proportion of H ₂ S gas is less than 0.1% by volume, the amount of TiS _y deposited tends to be insufficient, and there is a tendency that high temperature lubricity cannot be ensured. On the other hand, when the proportion of H ₂ S gas exceeds 1.0% by volume, the hardness of the second layer tends to decrease.

The proportion of the TiCl ₄ gas in the mixed gas for the second layer is preferably 0.05 volume% or more and 0.5 volume% or less, more preferably 0.1 volume% or more and 0.4 volume% or less, and 0.2 volume% or less. % Or more and 0.3 volume% or less is more preferable. If the proportion of TiCl ₄ gas is less than 0.05% by volume, the amount of TiS _y deposited tends to be non-uniform. On the other hand, when the proportion of TiCl ₄ gas exceeds 0.5% by volume, the TiS _y structure tends to become coarse.

The proportion of the Ar—H ₂ O gas in the mixed gas for the second layer is preferably 0.01 volume% or more and 1.0 volume% or less, more preferably 0.05 volume% or more and 0.8 volume% or less, and 0 More preferably, it is 1% by volume or more and 0.5% by volume or less. If the proportion of Ar—H ₂ O gas is less than 0.01% by volume, α-Al ₂ O ₃ will tend to be non-uniformly precipitated. On the other hand, if the proportion of Ar—H ₂ O gas exceeds 1% by volume, the adhesion of α-Al ₂ O ₃ tends to be insufficient.

The second layer mixed gas may include H ₂ gas, N ₂ gas, CO ₂ gas, CO gas, HCl gas, and AlCl ₃ gas together with TiCl ₄ gas, H ₂ S gas, and Ar—H ₂ O gas. it can.

The flow rate of the mixed gas for the second layer is preferably 20 NL/min or more and 80 NL/min or less, and more preferably 40 NL/min or more and 60 NL/min or less. The film formation time is preferably 30 minutes or more and 300 minutes or less, and more preferably 60 minutes or more and 180 minutes or less.

The step of forming the second layer preferably includes a pretreatment step, a nucleation step and a nucleus growth step.

The pretreatment step is, before forming the second layer, the surface of the layer serving as the base of the second layer (when the first layer and the second layer are in contact with each other, the surface of the first layer, the first layer and the second layer). When the third layer is arranged between the two layers, it is a step of adsorbing AlCl ₃ on the surface of the third layer which is in contact with the second layer.

The pretreatment step is preferably carried out at a temperature of 750° C. or higher and 850° C. or lower and a pressure condition of 5 to 10 kPa.

In the pretreatment step, it is preferable to use a mixed gas containing AlCl ₃ gas and CO ₂ gas but not CO gas (hereinafter, also referred to as “mixed gas for pretreatment step”). This is because it facilitates the formation of α-Al ₂ O ₃ .

The proportion of CO ₂ gas in the mixed gas for the pretreatment step is preferably 0.2 vol% or more and 4.0 vol% or less, more preferably 0.4 vol% or more and 3.0 vol% or less, and 1.0 vol% or less. % To 2.0% by volume is more preferable. When the proportion of CO ₂ gas is less than 0.2% by volume, κ-Al ₂ O ₃ tends to be mixed depending on the position in the furnace. On the other hand, when the proportion of CO ₂ gas exceeds 4.0% by volume, the adhesion of α-Al ₂ O ₃ tends to be insufficient.

The mixed gas for the pretreatment step may include H ₂ gas, N ₂ gas, HCl gas, and Ar—H ₂ O gas together with AlCl ₃ gas and CO ₂ gas.

The flow rate of the mixed gas for the pretreatment step is preferably 40 NL/min or more and 100 NL/min or less, and more preferably 60 NL/min or more and 80 NL/min or less. The time of the pretreatment step is preferably 1 minute or more and 10 minutes or less, more preferably 2 minutes or more and 5 minutes or less.

A nucleation step can be performed after the pretreatment step. The nucleation step is a step of generating nuclei of crystal grains containing α-Al ₂ O ₃ from AlCl ₃ adsorbed on the surface of the layer on which the second layer is formed in the pretreatment step.

The nucleation step is preferably carried out at a temperature of 750° C. or higher and 850° C. or lower and a pressure condition of 5 kPa or higher and 10 kPa or lower.

In the nucleation step, it is preferable to use a mixed gas containing AlCl ₃ gas, TiCl ₄ gas, H ₂ gas, CO ₂ gas, CO gas and HCl gas (hereinafter, also referred to as “mixed gas for nucleation step”). .. According to this, α-Al ₂ O ₃ can be produced by the reaction paths represented by the above reaction formulas (1′) and (2′).

The proportion of AlCl ₃ gas in the mixed gas for the nucleation step is preferably 0.5 volume% or more and 5.0 volume% or less, more preferably 0.75 volume% or more and 3.0 volume% or less, and 1.0 volume% or less. % To 2.0% by volume is more preferable. If the proportion of AlCl ₃ gas is less than 0.5% by volume, the structure of α-Al ₂ O ₃ tends to be non-uniform. On the other hand, when the proportion of AlCl ₃ gas exceeds 5.0% by volume, the structure of α-Al ₂ O ₃ tends to become coarse.

The proportion of TiCl ₄ gas in the mixed gas for the nucleation step is preferably 0.01 volume% or more and 1.0 volume% or less, more preferably 0.05 volume% or more and 0.75 volume% or less, and 0.1 volume% or less. % Or more and 0.5 volume% or less is more preferable. When the proportion of TiCl ₄ gas is less than 0.01% by volume, the structure and film thickness of α-Al ₂ O ₃ tend to be non-uniform. On the other hand, when the proportion of TiCl ₄ gas exceeds 1.0% by volume, the structure of α-Al ₂ O ₃ tends to become coarse.

The proportion of H ₂ gas in the mixed gas for the nucleation step is preferably 60% by volume or more and 99% by volume or less, more preferably 70% by volume or more and 95% by volume or less, and further preferably 85% by volume or more and 95% by volume or less. If the proportion of H ₂ gas is less than 60% by volume, the structure of α-Al ₂ O ₃ tends to become coarse. On the other hand, when the proportion of H ₂ gas exceeds 99% by volume, the film thickness of α-Al ₂ O ₃ tends to be nonuniform.

The proportion of CO ₂ gas in the mixed gas for the nucleation step is preferably 0.5 volume% or more and 4.0 volume% or less, more preferably 1.0 volume% or more and 3.0 volume% or less, and 1.5 volume% or less. % To 2.5% by volume is more preferable. If the proportion of CO ₂ gas is less than 0.5% by volume, the structure of α-Al ₂ O ₃ tends to be non-uniform. On the other hand, if the proportion of CO ₂ gas exceeds 4.0% by volume, the structure of α-Al ₂ O ₃ tends to become coarse.

The proportion of CO gas in the mixed gas for the nucleation step is preferably 0.25% by volume or more and 2.5% by volume or less, more preferably 0.5% by volume or more and 2.0% by volume or less, and 0.75% by volume. It is more preferably not less than 1.5% by volume. If the proportion of CO gas is less than 0.25% by volume, the structure of α-Al ₂ O ₃ tends to become coarse. On the other hand, when the proportion of CO gas exceeds 2.5% by volume, the structure of α-Al ₂ O ₃ tends to be nonuniform.

The proportion of HCl gas in the mixed gas for the nucleation step is preferably 0.1 volume% or more and 3.0 volume% or less, more preferably 0.5 volume% or more and 2.0 volume% or less, and 0.7 volume% or less. It is more preferably not less than 1.5% by volume. If the proportion of HCl gas is less than 0.1% by volume, the structure of α-Al ₂ O ₃ tends to become coarse. On the other hand, when the proportion of HCl gas exceeds 3.0% by volume, the structure of α-Al ₂ O ₃ tends to be nonuniform.

The flow rate of the mixed gas for the nucleation step is preferably 40 NL/min or more and 80 NL/min or less, and more preferably 50 NL/min or more and 70 NL/min or less. The time of the nucleation step is preferably 1 minute or more and 30 minutes or less, more preferably 5 minutes or more and 25 minutes or less.

　Nuclear growth process can be performed after nucleation process. The nucleus growth step is a step of growing the nuclei of the crystal grains generated in the nucleation step to obtain the second layer.

The nuclear growth step is preferably performed at a temperature of 750° C. or higher and 850° C. or lower and a pressure condition of 5 kPa or higher and 20 kPa or lower.

The nuclear growth step is performed by using a mixed gas containing AlCl ₃ gas, TiCl ₄ gas, H ₂ gas, CO ₂ gas, CO gas, HCl gas, H ₂ S gas, and Ar—H ₂ O gas (hereinafter, referred to as “nuclear growth gas”). Also referred to as "process mixed gas". According to this, α-Al ₂ O ₃ nuclei grow and TiS _y nuclei grow by the reaction paths represented by the above reaction formulas (1′) and (2′).

The proportion of H ₂ S gas in the mixed gas for the nuclear growth step is preferably 0.05% by volume or more and 3.0% by volume or less, more preferably 0.1% by volume or more and 2.0% by volume or less, and 0.3 More preferably, it is not less than 1.0% by volume and not more than 1.0% by volume. When the proportion of H ₂ S gas is less than 0.05% by volume, the amount of TiS _y deposited tends to be insufficient, and high temperature lubricity may not be ensured. On the other hand, when the proportion of H ₂ S gas exceeds 3.0% by volume, the hardness of the second layer tends to decrease.

The ratio of the Ar—H ₂ O gas in the mixed gas for the nucleus growth step is preferably 0.01% by volume or more and 2.0% by volume or less, more preferably 0.1% by volume or more and 1.5% by volume or less, and 0 It is more preferably 0.2% by volume or more and 1.0% by volume or less. When the proportion of Ar—H ₂ O gas is less than 0.01% by volume, the film formation rate of the second layer tends to decrease. On the other hand, when the proportion of Ar—H ₂ O gas exceeds 2.0% by volume, the adhesion of the second layer tends to deteriorate.

The proportions of AlCl ₃ gas, TiCl ₄ gas, H ₂ gas, CO ₂ gas, CO gas, and HCl gas in the mixed gas for the nucleus growth step are the same as the proportions of the respective gases in the mixed gas for the nucleation step. Can be

The flow rate of the mixed gas for the nuclear growth step is preferably 40 NL/min or more and 100 NL/min or less, and more preferably 60 NL/min or more and 80 NL/min or less. The film formation time in the nucleus growth step is preferably 30 minutes or more and 300 minutes or less, and more preferably 60 minutes or more and 180 minutes or less.

The cutting tool according to the present embodiment can be manufactured as described above.

The present embodiment will be described more specifically by way of examples. However, the present embodiment is not limited to these examples.

[Sample 1 to Sample 14]
<Preparation of substrate>
A base material A and a base material B were prepared. Specifically, raw material powders having the blending composition (% by mass) shown in Table 1 were uniformly mixed. The term "remaining" in Table 1 means that WC occupies the rest of the blended composition (% by mass). Next, this mixed powder is pressure-molded into a predetermined shape and then sintered at 1300 to 1500° C. for 1 to 2 hours to form a base material A (shape: CNMG120408NGU) and a base material B (made of cemented carbide). Shape: ONMT05T6ANER-G) was obtained. All of these shapes are the same as the products manufactured by Sumitomo Electric Hardmetal Co., Ltd.

The base material A, CNMG120408NGU, is in the shape of a cutting edge exchange type cutting tip for turning. Seven base materials A were prepared and used for Sample 1 to Sample 7, respectively.

ONMT05T6ANER-G which is the base material B is in the shape of a cutting edge exchange type cutting tip for milling. Seven base materials B were prepared and used for Samples 8 to 14, respectively.

<Formation of coating>
The base material A or the base material B was set in a CVD apparatus, and a coating film was formed on each of the surfaces by the CVD method.

In Samples 1 to 7, the coating film was formed so as to be a TiN layer, an Al _0.8 Ti _0.2 N layer (first layer), a TiCN layer, and a second layer in this order from the base material side. In Samples 8 to 14, the coating was formed so as to be a TiN layer, an Al _0.8 Ti _0.2 N layer (first layer), and a second layer in this order from the base material side. The thickness of each layer is as shown in Table 4.

Regarding film forming conditions, Table 2 shows the film forming conditions for each layer except the second layer.

For example, in the column of "TiN layer" in Table 2, the conditions for forming the TiN layer are shown. According to Table 2, the TiN layer was prepared by placing the substrate in the reaction vessel of a known CVD apparatus as shown in FIG. 4, and adding 2.0% by volume of TiCl ₄ gas and 39.7 volume in the reaction vessel. % N ₂ gas and 58.3% by volume H ₂ gas mixed gas (first gas group) is ejected at a total gas flow rate of 44.7 NL/min in an atmosphere having a pressure of 7.0 kPa and a temperature of 900° C. Can be formed.

In the column of “Al _0.8 Ti _0.2 N layer” in Table 2, the first gas group containing H ₂ gas, TiCl ₄ gas and AlCl ₃ gas, and the first gas group containing H ₂ gas and NH ₃ gas. Two gas groups are listed. In this case, the first gas group and the second gas group are introduced into the reaction vessel from separate source gas introduction pipes of the CVD apparatus.

The thickness of each layer can be controlled by the time for which the source gas for each layer is ejected.
The film formation of the second layer was performed using a known CVD apparatus as shown in FIG. 4 under any of the film forming conditions a to e, k and l shown in Table 3. Each film forming condition includes a pretreatment process, a nucleation process and a nucleation growth process.

A specific film forming method will be described using film forming condition a. As shown in Table 3, the pretreatment process under the film forming condition a is performed using a pretreatment process mixed gas containing H ₂ gas, N ₂ gas, CO ₂ gas, HCl gas, and AlCl ₃ gas. The film forming time in the pretreatment process is 5 minutes, the temperature of the reaction atmosphere is 800° C., the pressure is 5.0 kPa, and the total gas flow rate of the mixed gas for the pretreatment process is 59.8 NL/min.

As shown in Table 3, the nucleation process under the film forming condition a uses a mixed gas for nucleation process containing H ₂ gas, CO ₂ gas, CO gas, HCl gas, AlCl ₃ gas, and TiCl ₄ gas. Done. The film formation time in the nucleation step is 10 minutes, the temperature of the reaction atmosphere is 800° C., the pressure is 5.0 kPa, and the total gas flow rate of the mixed gas for the nucleation step is 60.2 NL/min.

As shown in Table 3, the nuclei growth step under the film forming condition a is H ₂ gas, CO ₂ gas, CO gas, H ₂ S gas, HCl gas, AlCl ₃ gas, TiCl ₄ gas, Ar—H ₂ O. It is performed using a mixed gas for a nuclear growth step containing a gas (Ar gas containing 300 ppm H ₂ O). The film formation time in the nucleus growth step is 120 minutes, the temperature of the reaction atmosphere is 800° C., the pressure is 5.0 kPa, and the total gas flow rate of the mixed gas for the nucleus growth step is 61.4 NL/min.

<Characteristics of second layer>
Regarding the second layer obtained under each of the film forming conditions a to e, k, and l shown in Table 3, the composition of the second layer, the measurement of the area ratio of TiS _y , the measurement of the film hardness, and the high temperature sliding test. I went.

A test sample for investigating the characteristics of the second layer was prepared by the following procedure, in addition to Samples 1 to 14. First, a base material A was prepared, and a TiN layer (thickness 1.1 μm), an Al _0.8 Ti _0.2 N layer (thickness 6.0 μm), and a TiCN layer (thickness 3.0 μm) were formed on this in this order. A laminated product was prepared. Each test sample was prepared by forming the second layer on the TiCN layer under any of the film forming conditions a to e, k, and l.

(Composition of the second layer)
In each of the test samples obtained under the film forming conditions a to e, k and l, the composition of the second layer was analyzed by an electron beam diffraction attached to SEM or TEM and an EDX apparatus.

In the test samples under the film forming conditions a to e, it was confirmed that the second layer contained α-Al ₂ O ₃ and TiS _y . In these test samples, the value of _y in TiS _y was within the range of 1.2 or more and 2.0 or less.

It was confirmed that in the test samples under the film forming conditions k and l, the second layer contained α-Al ₂ O ₃ and did not contain TiS _y .

(Area ratio of TiS _y )
The area ratio of TiS _y in each of the test samples obtained under the film forming conditions a to e, k and l was calculated according to the following steps (a) to (d).

(A) Setting of measurement visual field The surface of the second layer obtained under each of the film forming conditions a to e, k and l is mirror-polished using a diamond slurry having an average particle size of 3 μm.

On the mirror-polished surface of the second layer, randomly select 5 measurement fields of 10 μm×20 μm rectangular.

(B) Imaging of measurement visual field Each measurement visual field is imaged using the following equipment under the following conditions.

Optical microscope: "AXIO Vert. A1" manufactured by Carl Zeiss (product name)
Lens: "EC Epiplan 100x/0.85 HD M27" manufactured by Carl Zeiss (product name)
Imaging conditions: time: 700 ms, intensity: 80%, gamma: 0.45.

(C) Binarization process of the captured image The image captured in (b) above is binarized using the following image processing software according to the following procedure.

Image processing software: Win Roof ver. 7.4.5
Processing procedure:
1. Histogram average brightness correction (correction reference value 128)
2. Background removal (object size 30 μm)
3. Binarization with a single threshold (threshold 100)
4. Brightness inversion.

Under the film forming conditions a to e, a bright field and a dark field were confirmed in the binarized image.

Under film forming conditions k and l, in the binarized image, only the dark field was confirmed, and the bright field was not confirmed.

(D) Analysis of binarized image From the image obtained in (c) above, the area of pixels (pixels derived from TiS _y ) derived from the bright field occupying the area of the measurement field (second layer). The ratio, ie the area ratio of TiS _{y in} the measurement field of view, is calculated.

Under the film forming conditions a to e, an arbitrary area of each of the bright field and the dark field in the measurement field (second layer) was analyzed by electron beam diffraction and EDX with SEM or TEM, and the bright field was only TiS _y. It was confirmed that the dark field consists of α-Al ₂ O ₃ only.

Under the film forming conditions k and l, an arbitrary region of the dark field in the measurement field (second layer) was analyzed by electron beam diffraction and EDX accompanied by SEM or TEM, and the dark field consisted of only α-Al ₂ O _3. It was confirmed.

When the surface of the second layer was observed by STEM under the film forming conditions a to e, it was confirmed that TiS _y had a plate-like structure under the film forming conditions a to e.

(Measurement of film hardness)
The film hardness of the second layer obtained under each of the film forming conditions a to e, k and l is measured by the nanoindentation method. The measurement is performed by a method according to ISO14577, and the measurement load is 10 mN. A nanoindentation hardness meter (ENT1100a; manufactured by Elionix) is used as a measuring instrument.

(High temperature sliding test)
The surface friction coefficient of the second layer obtained under each of the film forming conditions a to e, k, and 1 was measured using a high temperature tribometer having a ball-on-disk structure (manufactured by CMS Instruments, Switzerland). The ball-on-disk test was performed in an atmosphere of AISI: 316 balls (6 mmφ), sliding speed 25 cm/s, sliding radius 5 mm, load 1N, temperature 700° C., and humidity 25%. The total slip time was reduced to 1 minute in order to suppress the formation of oxidized tribofilm between the ball contact interface and the friction coating. This corresponds to a sliding distance of 15 m (about 480 laps). The surface roughness and wear trace of the coating were examined with a 3D laser microscope (VK-8710, Keyence Corporation) and an electron beam microanalyzer (EPMA), respectively.

Measurement of the value of y in the area ratio and TiS _y of TiS _y, measurement of film hardness, and Table 3 shows the results of high-temperature slide test.

<Production of cutting tool>
The base material A or the base material B was coated with the coating film formed by the method as described above, and the cutting tools of Sample 1 to Sample 14 as shown in Table 4 were produced. Samples 1 to 5 and 8 to 12 are examples, and samples 6, 7, 7, 13 and 14 are comparative examples.

For example, according to Table 4, the cutting tool of Sample 1 shows that the TiN layer having a thickness of 1.2 μm and the Al _0.8 Ti _0.2 N layer having a thickness of 5.6 μm (first Layer) A TiCN layer having a thickness of 3.2 μm and a second layer having a thickness of 2.5 μm formed under the film forming condition a are laminated in this order to form a coating film.

<Cutting test 1>
With respect to the cutting tools of Sample 1 to Sample 7, a cutting test was performed under the following cutting conditions to evaluate wear resistance. In the evaluation of wear resistance, each of the above cutting tools was set on an NC lathe, and the time from when the cutting of the work material was started to when the flank wear width Vb exceeded 0.2 mm was evaluated. It can be evaluated that the longer this time is, the more excellent the wear resistance is and the longer the tool life is. The results are shown in Table 5.

(Cutting conditions)
Work Material: FC300 (Hardness HV240)
Peripheral speed: 300m/min
Feed: 0.2 mm/rev
Notch: 1.0 mm
Cutting fluid: None Evaluation: Time until flank wear width Vb exceeds 0.2 mm.

∙ The cutting conditions correspond to high efficiency machining and dry machining.

(Evaluation)
In the cutting tools of Samples 1 to 5, the first layer consisted only of the Al _0.8 Ti _0.2 N layer, and the second layer consisted only of the composite compound containing α-Al ₂ O ₃ and TiS _y. Become. In the cutting tools of Sample 6 and Sample 7, the first layer consisted only of the Al _0.8 Ti _0.2 N layer, the second layer contained α-Al ₂ O ₃ , and did not contain TiS _y . It was confirmed that the cutting tools of Samples 1 to 5 have excellent wear resistance and a long tool life even when used for high efficiency machining and dry machining, as compared with the cutting tools of Samples 6 and 7. ..

<Cutting test 2>
The cutting edge exchange type cutting tip for milling, which consists of the cutting tools of Samples 8 to 14, was attached to a cutter (shape: "DGCM13125", manufactured by Sumitomo Electric Hardmetal Co., Ltd.), and a cutting test was performed under the following cutting conditions to withstand cutting. The wear resistance was evaluated. In the evaluation of wear resistance, the time from the start of cutting of the work material until the flank wear width Vb exceeds 0.2 mm was evaluated. It can be evaluated that the longer this time is, the more excellent the wear resistance is and the longer the tool life is. The results are shown in Table 6.

(Cutting conditions)
Work Material: FCD600 (Hardness HV280)
Peripheral speed: 300m/min
Feed per blade (fz): 0.2 mm/t
Cutting width (ae): 60 mm
Depth of cut (ap): 1.0 mm
Cutting fluid: None Evaluation: Time until flank wear width Vb exceeds 0.2 mm.

∙ The cutting conditions correspond to high efficiency machining and dry machining.

(Evaluation)
In the cutting tools of Samples 8 to 12, the first layer is composed only of the Al _0.8 Ti _0.2 N layer, and the second layer is composed of a composite compound containing α-Al ₂ O ₃ and TiS _y. .. In the cutting tools of Sample 13 and Sample 14, the first layer consisted only of the Al _0.8 Ti _0.2 N layer, the second layer contained α-Al ₂ O ₃ , and did not contain TiS _y . It was confirmed that the cutting tools of Samples 8 to 12 are superior in wear resistance and have a longer tool life than the cutting tools of Samples 13 and 14 even when used for high efficiency machining and dry machining. ..

The embodiments and examples disclosed this time are to be considered as illustrative in all points 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 meanings equivalent to the scope of claims and all modifications within the scope.

1 Base Material, 2 Coating, 3 Underlayer, 4 1st Layer, 5 3rd Layer, 6 2nd Layer, 7 α-Al ₂ O ₃ Region, 8 TiS _y Region, 10 Cutting Tool, 21 Base Material Holding Jig , 22 reaction vessel, 23 temperature control device, 24 first gas introduction pipe, 25 second gas introduction pipe, 26 shaft, 27 gas exhaust pipe, 28 gas exhaust port, 100 CVD device

Claims (19)

1. A cutting tool comprising a substrate and a coating provided on the substrate,
   The coating film has a first layer provided on the base material side and a second layer provided on the first layer,
   The first layer consists of a nitride or carbonitride of Al _x Ti _1-x ,
   The cutting tool, wherein the second layer is composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y .
   Here, the x satisfies 0.7≦x<1, and the y satisfies 1.0≦y≦2.0.
2. The cutting tool according to claim 1, wherein the TiS _y has a plate-like structure and is dispersed in the α-Al ₂ O ₃ .
3. The cutting tool according to claim 1, wherein the second layer has a TiS _y area ratio of 0.5% or more and 20% or less in a cross section parallel to the surface of the coating.
4. The cutting tool according to claim 3, wherein the area ratio of TiS _y is 1% or more and 15% or less.
5. The cutting tool according to claim 3 or 4, wherein the area ratio of TiS _y is 2% or more and 10% or less.
6. The cutting tool according to any one of claims 1 to 5, wherein the second layer has a thickness of 0.5 µm or more and 5 µm or less.
7. The cutting tool according to any one of claims 1 to 6, wherein the coating has a thickness of 3 µm or more and 30 µm or less.
8. The coating has a third layer between the first layer and the second layer,
   The cutting tool according to any one of claims 1 to 7, wherein the third layer is made of TiCN only.
9. The first layer _may consist of only the compound represented by _{Al x Ti 1-x C a} N b, the cutting tool according to any one of claims 1 to 8.
   Here, the x satisfies 0.7≦x<1, the a satisfies 0≦a<0.25, and the b satisfies 0.75≦b<1.5.
10. The cutting tool according to any one of claims 1 to 9, wherein the x satisfies 0.75 ≤ x <0.95.
11. The cutting tool according to any one of claims 1 to 10, wherein the x satisfies 0.8≦x<0.9.
12. The cutting tool according to any one of claims 9 to 11, wherein the a satisfies 0≦a<0.1.
13. The cutting tool according to any one of claims 9 to 12, wherein the a satisfies 0≦a<0.05.
14. The cutting tool according to any one of claims 9 to 13, wherein the b satisfies 0.8≦b<1.2.
15. The cutting tool according to any one of claims 9 to 14, wherein the b satisfies 0.9≦b<1.1.
16. The cutting tool according to any one of claims 1 to 15, wherein the y satisfies 1.0 ≤ y ≤ 2.0.
17. The cutting tool according to any one of claims 1 to 16, wherein the y satisfies 1.4≦y≦1.8.
18. The cutting tool according to any one of claims 1 to 17, wherein the coating includes an underlayer disposed between the base material and the first layer.
19. A method of manufacturing a cutting tool according to any one of claims 1 to 18,
    A step of preparing a base material,
    A step of forming a coating film on the base material by a chemical vapor deposition method,
    The step of forming the coating includes the step of forming a first layer and the step of forming a second layer,
    The first layer consists of a nitride or carbonitride of Al _x Ti _1-x ,
    The second layer is composed only of a composite compound containing α-Al ₂ O ₃ and TiS _y ,
    The step of forming the second layer is performed at a film forming temperature of 750° C. or higher and 850° C. or lower using a mixed gas containing TiCl ₄ gas, H ₂ S gas and Ar—H ₂ O gas. Production method.
    Here, the x satisfies 0.7≦x<1, and the y satisfies 1.0≦y≦2.0.

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