JP5286930B2 - Surface-coated cutting tool that exhibits excellent chipping resistance with a hard coating layer in high-speed heavy cutting - Google Patents

Description

  This invention has a hard coating layer with high temperature strength and interlaminar adhesion strength, accompanied by high heat generation, and high-speed heavy cutting such as various steels and cast irons that are subject to high loads on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent chipping resistance.

Conventionally, generally on the surface of a substrate (hereinafter collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. The hard coating layer formed by vapor deposition
(A) Ti carbide layer (hereinafter referred to as TiC layer), nitride layer (hereinafter referred to as TiN layer), carbonate layer (hereinafter referred to as TiCO layer), and carbonitride oxide, all formed by chemical vapor deposition Adhesive Ti compound layer comprising one or more of the layers (hereinafter referred to as TiCNO layer) and having a total average layer thickness of 0.1 to 5 μm, and a modification having an average layer thickness of 2.5 to 15 μm A lower layer composed of a titanium carbonitride layer (hereinafter referred to as a modified TiCN layer),
(B) An upper portion made of an α-type aluminum oxide layer (hereinafter referred to as an α-type Al ₂ O ₃ layer hereinafter) having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition. layer,
(A) and (b), and
The modified TiCN layer in the lower layer of (a) is
Using a field emission scanning electron microscope, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, and the crystal plane of the crystal grain is normal to the surface polished surface ( The inclination angle formed by the normal lines of the (001) plane and the (011) plane is measured. In this case, the crystal grains are NaCl-type face-centered cubic crystals each having a constituent atom composed of Ti, carbon, and nitrogen at lattice points. A lattice point having a crystal structure, and each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains based on the measured tilt angle obtained as a result ( The distribution of the constituent atomic shared lattice points) is calculated, and N lattice points that do not share the constituent atoms between the constituent atomic shared lattice points (N is an even number of 2 or more on the crystal structure of the NaCl type face centered cubic crystal) Existing constituent atomic shared lattice point form is ΣN + 1 In the constituent atom sharing lattice distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1 (where the upper limit value of N is 28 due to the frequency), the highest peak exists in Σ3, and A constituent atom shared lattice point distribution graph in which the ratio of Σ3 to the entire ΣN + 1 is 60% or more,
The conventional α-type Al ₂ O ₃ layer of (b) above is
Using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polishing surface is irradiated with an electron beam, and the crystal grain is compared with the normal line of the surface polishing surface. The tilt angles formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the above, are measured. In this case, the crystal grains are corundum type in which constituent atoms composed of Al and oxygen are present at lattice points. Based on the measured tilt angle obtained as a result of the hexagonal close-packed crystal structure, each of the constituent atoms forms one constituent atom between the crystal grains at the interface between adjacent crystal grains. The distribution of shared lattice points (constituent atom shared lattice points) is calculated, and there are N lattice points that do not share constituent atoms between the constituent atom shared lattice points (where N is the crystal structure of the corundum hexagonal close-packed crystal) Even number of 2 or more, but distribution frequency When the upper limit of N from the point is 28, the even number of 4, 8, 14, 24, and 26 does not exist.) When the existing constituent atom shared lattice point form is expressed as ΣN + 1, each ΣN + 1 is included in the entire ΣN + 1 In the constituent atom shared lattice point distribution graph showing the proportion of distribution, the constituent atom shared lattice point distribution graph in which the highest peak exists in Σ3 and the ratio of Σ3 to the entire ΣN + 1 is 60% or more,
It is known that when this coated tool is used for high-speed intermittent cutting of high-hardness steel, the hard coating layer exhibits excellent chipping resistance.
JP 2006-297579 A

In recent years, the performance of cutting machines has been remarkable. On the other hand, there is a strong demand for labor saving, energy saving, and cost reduction for cutting work, and along with this, cutting work tends to be further accelerated. In the coated tool, the lower layer is a modified TiCN layer having a relatively high high-temperature strength, and the upper layer is a conventional α-type Al ₂ O ₃ layer having a high-temperature strength that is excellent in high-temperature hardness and heat resistance. However, especially when this is used for high-speed heavy cutting such as various steels and cast iron that generate high heat and a high load acts on the cutting edge, the interlayer adhesion strength between the upper and lower layers is sufficient. Therefore, delamination and chipping are likely to occur, and the service life is reached in a relatively short time.

In view of the above, the inventors of the present invention, in order to improve the chipping resistance by improving the interlaminar adhesion strength of the hard coating layer of the above-mentioned coated tool, in particular, the conventional α-type Al which is the upper layer thereof. ₂ O ₃ layer, that is, the atomic arrangement of the unit cell of α-type Al ₂ O ₃ in FIG. 3 is schematically shown (perspective view and plan view of cross sections 1 to 9). Focusing on the grain boundary structure of the α-type Al ₂ O ₃ layer having a corundum type hexagonal close-packed crystal structure in which each of the constituent atoms is present, as a result of earnest research, the following knowledge was obtained. .

The conventional α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the conventional coating tool is, for example, applied to a normal chemical vapor deposition apparatus on the modified titanium carbonitride layer (modified TiCN layer). And
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
Vapor deposition is performed under the conditions (referred to as conventional conditions)
For example, the modified TiCN layer is a lower layer, and on this,
Reaction gas composition: by _{volume%, AlCl 3: 0.5~2%,} CO 2: 0.1~2%, HCl: 0.1~1%, H 2 S: 0.15~0.4%, H ₂ : Remaining
Reaction atmosphere temperature: 930-980 ° C.,
Reaction atmosphere pressure: 3 to 5 kPa,
In the reaction gas composition, the content ratio of AlCl ₃ , CO ₂ and HCl is relatively low, the content ratio of H ₂ S is relatively high, and the ambient temperature The film is formed by vapor deposition for 10 to 60 minutes under the condition of relatively low (hereinafter referred to as initial formation conditions)
Then
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
When the upper layer is formed by vapor deposition under the same conditions as the above-described conventional conditions, the upper layer is formed from the resulting α-type Al ₂ O ₃ layer (hereinafter referred to as “modified α-type Al ₂ O ₃ layer”). In addition to the excellent high-temperature hardness and heat resistance inherent to the α-type Al ₂ O ₃ layer, it has excellent high-temperature strength, and the interlayer adhesion strength with the lower layer is further improved, Generation of delamination between the lower layers can be prevented, and as a result, excellent chipping resistance can be provided.

The modified TiCN layer is
Reaction gas composition: by _{volume%, TiCl 4: 0.1~0.8%,} CH 3 CN: 0.05~0.3%, Ar: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 930 to 1000 ° C.
Reaction atmosphere pressure: 6-20 kPa,
The modified TiCN layer can be formed under the following conditions using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams of FIGS. 2 (a) and 2 (b). Each crystal grain having a face-centered cubic lattice existing within the measurement range is irradiated with an electron beam, and the (001) plane and (011) which are crystal planes of the crystal grain with respect to the normal line of the cross-section polished surface ) Plane normal angle (FIG. 2 (a) shows the case where the (001) plane tilt angle is 0 degree and the (011) plane tilt angle is 45 degrees out of the crystal plane (b) Shows the case where the tilt angle of the (001) plane is 45 degrees and the tilt angle of the (011) plane is 0 degrees. All tilt angles of the crystal grains including these angles are measured. In this case, as shown in FIGS. 1A and 1B, the crystal grains are composed of Ti, carbon, and nitrogen at lattice points. Each of the constituent atoms has the crystal structure at the interface between crystal grains adjacent to each other based on the measurement tilt angle obtained as a result. The distribution of lattice points (constituent atom shared lattice points) that share one constituent atom between grains is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is a NaCl-type surface) The constituent atomic shared lattice point form that exists is an even number of 2 or more on the crystal structure of the center cubic crystal is represented by ΣN + 1, and each ΣN + 1 is an entire ΣN + 1 (however, the upper limit value of N is 28 due to frequency) When a constituent atom shared lattice point distribution graph showing the distribution ratio occupied is created, the distribution ratio (ratio) of Σ3 should be an extremely high constituent atom shared lattice point distribution graph of 60% or more.

In addition, when the upper layer composed of the modified α-type Al ₂ O ₃ layer is directly deposited on, for example, the modified TiCN layer, the (001) plane and (011) measured for the modified TiCN layer. In the case where the angle between the normal lines of the (001) plane and the normal lines of the (011) plane intersects each other between two adjacent crystal grains based on the measured inclination angle of the plane normal line It is defined as a boundary, and is formed between lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at an interface between adjacent crystal grains. A crystal grain boundary having a configuration of shared atomic lattice points in which two lattice points that do not share atoms exist, and a lower grain boundary (hereinafter referred to as a lower layer Σ3) that faces the interface with the upper layer The number and position of the corresponding grain boundaries)
Further, for the upper layer composed of the modified α-type Al ₂ O ₃ layer, similarly to the above, using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. 4 (a) and 4 (b), An electron beam is irradiated to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the film cross-section polished surface, and is a crystal plane of the crystal grain with respect to the normal of the cross-section polished surface (0001) The tilt angle formed by the normal of the plane and the (10-10) plane (FIG. 4A shows the case where the tilt angle of the crystal plane is 0 degree, and FIG. 4B shows the case where the tilt angle is 45 degrees. However, in this case, the crystal grains are corundum type hexagonal close-packed in which constituent atoms composed of Al and oxygen are present at lattice points, respectively. Based on the measured tilt angle obtained as a result. A case where the angle between the normal lines of the (0001) planes and the normal lines of the (10-10) planes intersects each other is defined as a crystal grain boundary, and is adjacent to each other. Constituent atoms in which there are two lattice points that do not share constituent atoms between lattice points where each of the constituent atoms shares one constituent atom between the crystal grains (constituent atomic shared lattice points) at the crystal grain interface When the number and position of crystal grain boundaries having a shared lattice point form and existing at the interface with the lower layer (hereinafter referred to as upper layer Σ3 grain boundaries) are measured,
At the interface between the lower layer and the upper layer, 30% to 70% of the grain boundary corresponding to the lower layer Σ3 existing at the interface with the upper layer corresponds to the upper layer Σ3. It has a grain boundary structure in which the grain boundaries are formed as continuous grain boundaries (see FIG. 5A), and the interlayer adhesion strength between the upper layer and the lower layer is remarkably improved.

Further, the upper layer composed of the modified α-type Al ₂ O ₃ layer is not directly deposited on the modified TiCN layer, but a Ti carbonitride layer (TiCN layer) on the modified TiCN layer. A thin layer (preferably, a total layer thickness of 0.05 to 0.3 μm) of a Ti compound layer composed of at least one of a carbon oxide layer (TiCO layer) and a carbonitride oxide layer (TiCNO layer) is usually used. Even when an upper layer composed of a modified α-type Al ₂ O ₃ layer is further formed on the thin layer via vapor deposition under the following vapor deposition conditions, it is formed on the modified TiCN layer. All of the thin layers of the Ti compound layer composed of the TiCN layer, the TiCO layer, and the TiCNO layer are so-called epitaxially grown and take over the grain boundary structure of the modified TiCN layer, and the TiCN layer, the TiCO layer, and the TiCNO layer have the above-mentioned Of modified TiCN layer A similar grain boundary structure is formed.
Therefore, instead of directly depositing the upper layer on the modified TiCN layer, a thin Ti compound layer composed of one or more of the TiCN layer, TiCO layer, and TiCNO layer is deposited on the surface of the modified TiCN layer. Even when the upper layer is formed by vapor deposition through this thin layer, the grain boundary of the lower layer Σ3 corresponding to the interface between the lower layer and the upper layer and facing the interface with the upper layer When the upper layer Σ3 corresponding grain boundary is formed as a continuous grain boundary with respect to the lower layer Σ3 corresponding grain boundary of 30 to 70%, the interlayer adhesion strength between the lower layer and the upper layer is improved. Generation of delamination between the lower layer and the upper layer can be prevented, and as a result, excellent chipping resistance can be exhibited.

  In addition, for each lower layer extending from the interface between the lower layer and the upper layer to a depth region of at least 1 μm on the substrate surface side, each ΣN + 1 (however, the upper limit value of N is set to 28 due to the frequency) is the entire ΣN + 1 When the constituent atomic shared lattice point distribution graph showing the distribution ratio in the region is created, when the ratio of Σ3 in the above region to the entire ΣN + 1 is 60% or more (corresponding to claim 2), the Σ3 ratio in the lower layer As a result, the absolute number of grain boundaries corresponding to the lower layer Σ3, which is continuous with the upper layer Σ3 corresponding grain boundary, increases, thereby improving the high temperature strength of the lower layer itself and further improving the interlayer adhesion strength. In addition, the chipping resistance is even better.

  Furthermore, with respect to the upper layer made of the modified α-type aluminum oxide layer, each ΣN + 1 (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but the upper limit of N in terms of distribution frequency) Is 28, the even number of 4, 8, 14, 24 and 26 does not exist), and when the constituent atomic shared lattice point distribution graph showing the distribution ratio of the entire ΣN + 1 is created, the entire ΣN + 1 of Σ3 in the upper layer When the ratio of the upper layer and the lower layer is 60% or more (corresponding to claim 3), in addition to improving the adhesion strength between the upper layer and the lower layer, the high temperature strength of the upper layer itself is improved. It will show the chipping resistance.

As described above, the hard coating layer, the lower layer comprising a Ti compound layer containing at least reformed TiCN layer is composed of an upper layer made of modified α type the Al ₂ O ₃ layer, reforming α type the Al ₂ O ₃ layer The grain boundaries corresponding to the lower layer Σ3 corresponding to the lower layer Σ3 corresponding to the lower layer Σ3 corresponding to the lower layer Σ3 existing at the interface with the upper layer are continuous grain boundaries. The coated tool is designed to improve the interlaminar adhesion strength and has excellent high-temperature strength. Therefore, high-speed heavy loads such as various steels and cast iron, which have a particularly large mechanical load on the cutting edge at high temperatures. Even in cutting, the hard coating layer exhibits excellent chipping resistance without causing delamination, and exhibits excellent wear resistance over a long period of time.

This invention has been made based on the above findings,
“(1) On the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) a lower layer composed of a chemical vapor deposited Ti compound layer comprising a modified titanium carbonitride layer having an average layer thickness of at least 2 to 15 μm;
(B) an upper layer composed of a modified α-type aluminum oxide layer having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition;
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is formed,
For the lower layer of (a) above, the cross-sectional polishing is performed by irradiating an electron beam to each crystal grain having a face-centered cubic lattice existing within the measurement range of the coated cross-sectional polished surface using a field emission scanning electron microscope. The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, is measured with respect to the plane normal line. In this case, the crystal grains are NaCl type face centered cubic crystals. Based on the measured tilt angle obtained as a result of the crystal structure, the angles at which the (001) plane normal lines and the (011) plane normal lines cross each other at the interface between adjacent crystal grains are obtained. When the angle between the normal lines of the (001) planes and the normal lines of the (011) planes is 2 degrees or more, the crystal grain boundary is used, and at the interface between the crystal grains adjacent to each other, Each atom is one constituent element between the grains. The distribution of lattice points (constituent atomic shared lattice points) that share the same is calculated, and the constituent atomic shared lattice point form in which there are two lattice points that do not share constituent atoms between the constituent atomic shared lattice points is represented by Σ3. Measure the number and position of grain boundaries corresponding to the lower layer Σ3 existing at the interface with the layer,
Further, with respect to the upper layer of the above (b), by using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the coated cross-section polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (0001) plane and (10-10) plane, which are the crystal planes of the crystal grains, is measured with respect to the normal line of the polished surface. And a corundum-type hexagonal close-packed crystal structure in which constituent atoms composed of oxygen and oxygen exist, respectively, and based on the measured tilt angle obtained as a result of this, the (0001) plane at the interface between adjacent crystal grains The angle at which the normal lines intersect with each other and the (10-10) plane normal lines intersect, and the angle between the (0001) plane normal lines and the (10-10) plane normal lines intersect is 2 degrees or more. Be a grain boundary, and A distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at an interface between adjacent crystal grains; When constitutive atomic shared lattice point form with two lattice points that do not share constituent atoms in between is represented by Σ3, and the number and position of the upper layer Σ3-corresponding grain boundaries existing facing the interface with the lower layer are measured In addition,
At the interface between the lower layer and the upper layer, 30% to 70% of the grain boundary corresponding to the lower layer Σ3 existing at the interface with the upper layer corresponds to the upper layer Σ3. A surface-coated cutting tool, wherein the grain boundaries are formed as continuous crystal grain boundaries.
(2) A surface existing within the measurement range of the coated cross-section polished surface, using a field emission scanning electron microscope, for the lower layer extending from the interface between the lower layer and the upper layer to a depth region of at least 1 μm on the substrate surface side Each crystal grain having a centered cubic lattice is irradiated with an electron beam, and the normal lines of the (001) plane and the (011) plane, which are crystal planes of the crystal grains, form the normal line of the cross-section polished surface. The tilt angle is measured. In this case, the crystal grains have a crystal structure of NaCl-type face-centered cubic crystal, and based on the measured tilt angle obtained as a result, (001) at the interface between adjacent crystal grains. ) Surface normals and (011) surface normals intersect each other, and the (001) surface normals and (011) surface normals intersect each other at an angle of 2 degrees or more. Are grain boundaries and are adjacent to each other The distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface of the crystal grains is calculated, and the constituent atoms between the constituent atom shared lattice points are calculated. When the number of lattice points that do not share N (provided that the upper limit of N is 28 from the point of frequency) is represented by ΣN + 1, and the ratio of each ΣN + 1 to the entire ΣN + 1 is obtained, The surface-coated cutting tool according to (1), wherein the ratio of Σ3 to the entire ΣN + 1 in the region is 60% or more.
(3) For the upper layer, use a field emission scanning electron microscope to irradiate each crystal grain having a hexagonal crystal lattice existing within the measurement range of the film cross-section polished surface with The inclination angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, is measured with respect to the lines. In this case, the crystal grains are composed of Al and oxygen at lattice points. Corundum type hexagonal close-packed crystal structure in which each constituent atom exists, and based on the measured tilt angle obtained as a result, the normals of (0001) planes at the interfaces between adjacent crystal grains and The angle at which the normals of the (10-10) plane intersect is determined, and the angle at which the normals of the (0001) plane and the (10-10) plane intersect each other is 2 degrees or more at the grain boundary. And then adjacent to each other The distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface of the crystal grains is calculated, and the constituent atoms between the constituent atom shared lattice points are calculated. There are N lattice points that do not share (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but when the upper limit of N is 28 in terms of distribution frequency, 4, 8, 14 , 24 and 26 are not present.) When the existing configuration of the shared atomic lattice point is represented by ΣN + 1 and the ratio of each ΣN + 1 to the entire ΣN + 1 is determined, the ratio of Σ3 in the upper layer to the entire ΣN + 1 is 60. The surface-coated cutting tool according to (1) or (2), which is at least%. "
It has the characteristics.

  Next, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail below.

<Lower layer>
The modified TiCN layer is essential as the Ti compound layer constituting the lower layer, but other Ti compound layers include Ti carbide (TiC) layers, nitride (TiN) layers, carbon A Ti compound layer composed of one or more of a nitride (TiCN) layer, a carbon oxide (TiCO) layer, and a carbonitride oxide (TiCNO) layer can be formed by vapor deposition. The Ti compound layer composed of one or more of the TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer is not only a modified TiCN layer but also a tool substrate, an upper layer (modified α-type Al ₂ O ₃ layers) has a function of contributing to improvement in adhesion of the hard coating layer to the tool substrate.

The modified TiCN layer, which is an indispensable layer constituting the lower layer, is a normal chemical vapor deposition apparatus, for example,
Reaction gas composition: by _{volume%, TiCl 4: 0.1~0.8%,} CH 3 CN: 0.05~0.3%, Ar: 10~30%, H 2: remainder,
Reaction atmosphere temperature: 930 to 1000 ° C.
Reaction atmosphere pressure: 6-20 kPa,
The modified TiCN layer formed under these conditions is formed with a high ratio of Σ3 indicating a specific constituent atom shared lattice point form.

Regarding the ratio of Σ3 in the lower layer, for example, a modified TiCN layer formed by vapor deposition under the above-mentioned conditions as illustrated in FIGS. 2 (a) and 2 (b) using a field emission scanning electron microscope. The crystal grains existing within the measurement range of the cross-section polished surface of the film are irradiated with an electron beam, and the (001) plane and (011) which are crystal planes of the crystal grains with respect to the normal line of the cross-sectional polished plane The tilt angle formed by the normal of the surface (FIG. 2 (a) shows that the (001) plane tilt angle is 0 degree and the (011) plane tilt angle is 45 degrees among the crystal planes shown in FIG. Shows the case where the inclination angle of the (001) plane is 45 degrees and the inclination angle of the (011) plane is 0 degree, and all inclination angles of the individual crystal grains including these angles are measured, In this case, the crystal grains each have a constituent atom composed of Ti, carbon, and nitrogen at the lattice points as described above. Based on the measured tilt angle obtained as a result of this, the structure of each of the constituent atoms is 1 between the crystal grains at the interface between adjacent crystal grains. The distribution of lattice points that share two constituent atoms (constituent atom shared lattice points) is calculated, and there are N lattice points that do not share constituent atoms between the constituent atom shared lattice points (N is a NaCl-type face-centered cubic crystal) An existing constituent atom shared lattice point form is represented by ΣN + 1, and the distribution ratio of each ΣN + 1 to the whole ΣN + 1 (however, the upper limit value of N is 28 in terms of frequency) is shown. It can be obtained by creating a constituent atom shared lattice point distribution graph. In this constituent atom shared lattice point distribution graph, in the modified TiCN layer, the highest peak exists in Σ3, and the distribution ratio of Σ3 is 6 It is a very high ratio of 0% or more.
The ratio of Σ3 can be set to 60% or more by adjusting the TiCl ₄ , CH ₃ CN, Ar content in the reaction gas during chemical vapor deposition, and the atmospheric reaction temperature as described above. In order to impart excellent high temperature strength to the lower layer itself by high speed heavy cutting such as cast iron, the ratio of Σ3 is desirably 60% or more.

Further, when the modified TiCN layer exists facing the interface with the modified α-type Al ₂ O ₃ layer of the upper layer, the grain boundary corresponding to the lower layer Σ3 existing facing the interface with the upper layer is A modified TiCN layer extending over a depth region of up to 1 μm from the interface between the lower layer and the upper layer to at least the substrate surface side from the interface between the lower layer and the upper layer is used as the film cross-section polished surface, and the crystal grains existing in that region By individually irradiating an electron beam and determining the configuration of the constituent atomic shared lattice points, the number and positions of grain boundaries corresponding to the lower layer Σ3 existing at the interface with the upper layer can be measured. The grain boundary corresponding to the upper layer Σ3 is formed as a continuous grain boundary with respect to the grain boundary corresponding to the lower layer Σ3 of the proportion corresponding to the lower layer Σ3 existing at the interface of the lower layer Σ3. In some cases, good interlayer adhesion strength between upper and lower layers Is obtained.

  Further, a TiCN layer as a Ti compound layer having a thin layer thickness (preferably, a total layer thickness of 0.05 to 0.3 μm) is formed on the modified TiCN layer having a ratio of Σ3 corresponding grain boundaries of 60% or more, Even in the lower layer structure in which at least one of the TiCO layer and the TiCNO layer is formed by vapor deposition under normal conditions and any one of the TiCN layer, the TiCO layer, and the TiCNO layer exists adjacent to the upper layer, the TiCN layer, the TiCO layer, Since the layer and the TiCNO layer inherit the Σ3-compatible grain boundary structure of the modified TiCN layer, the ratio of the Σ3-compatible grain boundary of the TiCN layer, TiCO layer, and TiCNO layer is 60% or more, and Grain boundaries corresponding to the lower layer Σ3 corresponding to the lower layer Σ3 corresponding to the lower layer Σ3 of the TiCN layer, TiCO layer, and TiCNO layer existing facing the interface are connected to the upper layer Σ3 corresponding grain boundary. When forming the grain boundaries, an inter-layer adhesion strength was excellent in the lower layer and the upper layers is ensured.

The modified TiCN layer has an even higher temperature strength in addition to the high temperature hardness and high temperature strength of the conventional TiCN layer. However, if the average layer thickness is less than 2 μm, a Σ3-compatible grain boundary cannot be sufficiently formed. Therefore, it is not possible to expect the desired excellent high-temperature strength improvement effect. On the other hand, when the average layer thickness exceeds 15 μm, thermoplastic deformation that causes uneven wear tends to occur, and wear is accelerated. Therefore, the average layer thickness was set to 2 to 15 μm.
Further, the total average layer thickness of the lower layer composed of the modified TiCN layer and the other Ti compound layer is not able to ensure the predetermined wear resistance when the layer thickness is less than 3 μm, while the total average When the layer exceeds 20 μm, the chipping resistance suddenly deteriorates. Therefore, the total average layer thickness of the lower layer is preferably 3 μm or more and 20 μm or less.

《Upper layer》
The modified α-type Al ₂ O ₃ layer of the upper layer is formed on the lower layer composed of a Ti compound layer including at least the modified TiCN layer.
(A) First,
Reaction gas composition: by _{volume%, AlCl 3: 0.5~2%,} CO 2: 0.1~2%, HCl: 0.1~1%, H 2 S: 0.15~0.4%, H ₂ : Remaining
Reaction atmosphere temperature: 930-980 ° C.,
Reaction atmosphere pressure: 3 to 5 kPa,
In other words, the reaction gas composition has a relatively low content of AlCl ₃ , CO ₂ , and HCl, a relatively high content of H ₂ S, and an ambient temperature of Vapor deposition for 10-60 minutes under relatively low conditions (initial formation conditions)
(B) Then
Reaction gas composition: by _{volume%, AlCl 3: 6~10%,} CO 2: 10~15%, HCl: 3~5%, H 2 S: 0.05~0.2%, H 2: remainder,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 3 to 5 kPa,
The modified α-type Al ₂ O ₃ layer is excellent in addition to the excellent high-temperature hardness and heat resistance inherent in the α-type Al ₂ O ₃ layer. It has high-temperature strength and further improved interlayer adhesion strength. As a result, it has excellent chipping resistance.
According to the measurement using a field emission scanning electron microscope, the improvement in the interlayer adhesion strength between the upper layer and the lower layer was observed at the interface between the upper layer (modified α-type Al ₂ O ₃ layer) and the lower layer. It is brought about by the continuity of the grain boundary structure of the formed Σ3 corresponding grain boundary, and the upper layer Σ3 corresponding grain boundary is 30 to 70 of the lower layer Σ3 corresponding grain boundary existing facing the interface with the upper layer. %, If the grain boundary continuous with the lower layer Σ3 corresponding grain boundary is not formed, the improvement of the interlaminar adhesion strength cannot be ensured (if less than 30%), or the lower layer The residual stress gap in each of the upper layers becomes too large, and the interlayer adhesion strength tends to decrease (when it exceeds 70%).

For example, as described above, the field emission scanning electron microscope for the lower layer (modified TiCN layer, other Ti compound layer) existing adjacent to the modified α-type Al ₂ O ₃ layer (upper layer). The number and positions of the grain boundaries corresponding to the lower layer Σ3 existing at the interface with the upper layer are specified by measurement using.
Next, with respect to the modified α-type Al ₂ O ₃ layer, using a field emission scanning electron microscope, as illustrated in the schematic explanatory diagrams in FIGS. Inclination made by irradiating an electron beam to each of the crystal grains present in the surface and normal lines of the (0001) plane and (10-10) plane, which are crystal planes of the crystal grains, with respect to the normal line of the cross-section polished surface FIG. 4 (a) shows the case where the tilt angle of the crystal plane is 0 degree, and FIG. 4 (b) shows the case where the tilt angle is 45 degree. In this case, the crystal grains have a crystal structure of a corundum hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points as described above. Based on the measured tilt angles, the normals of the (0001) planes and the normal of the (10-10) planes A case where the angle at which the crossing angle is 2 degrees or more is defined as a crystal grain boundary, and at each crystal grain boundary adjacent to each other, each of the constituent atoms shares one constituent atom between the crystal grains ( The distribution of constituent atomic shared lattice points) is obtained, and when the constituent atomic shared lattice point form in which there are two lattice points that do not share constituent atoms between constituent atomic shared lattice points is represented by Σ3, the modified α-type Al ₂ O The number of crystal grain boundaries (grain boundaries corresponding to the upper layer Σ3) existing in the boundary with the lower layer, which are crystal grain boundaries having a Σ3 constituting atomic shared lattice point form formed in _three layers; Find the position.
Then, the position of the grain boundary corresponding to the lower layer Σ3 specified for the lower layer and the position of the grain boundary corresponding to the upper layer Σ3 obtained for the modified α-type Al ₂ O ₃ layer are put together, and the upper layer and the lower layer The grain boundary structure in which 30 to 70% of the grain boundaries corresponding to the lower layer Σ3 existing at the interface with the upper layer form a grain boundary continuous with the grain boundary corresponding to the upper layer Σ3. (See FIG. 5 (a)), the upper layer has not only excellent high-temperature hardness and heat resistance, but also the interlayer adhesion strength between the upper layer (modified α-type Al ₂ O ₃ layer) and the lower layer. Is significantly improved.
However, when the grain boundary corresponding to the lower layer Σ3 formed continuously with the grain boundary corresponding to the upper layer Σ3 is only less than 30% of the grain boundaries corresponding to the lower layer Σ3 (see FIG. 5B). ), Or in the case where it exceeds 70%, the continuity of the crystal grain boundary between the lower layer and the upper layer is small, so that the improvement of the interlayer adhesion strength cannot be ensured, or the lower layer and the upper layer Since there is too much continuity of grain boundaries in the layers, the gap between the residual stresses in the lower layer and the upper layer becomes too large, and the interlayer adhesion strength tends to decrease. It is necessary that 30 to 70% of the grain boundaries corresponding to the lower layer Σ3 existing facing the interface of the upper layer Σ3 form a crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3.

Further, in order to further improve the chipping resistance of the modified α-type Al ₂ O ₃ layer (the ratio of Σ3 to total .SIGMA.N + 1) ratio of Σ3 of the modified α type the Al ₂ O ₃ layer a 60% It is more desirable to improve the high temperature strength of the modified α-type Al ₂ O ₃ layer itself.

Furthermore, when the average layer thickness of the upper layer composed of the modified α-type Al ₂ O ₃ layer is less than 1 μm, it cannot exhibit excellent high-temperature hardness, heat resistance and excellent interlayer adhesion strength, When the average layer thickness exceeds 15 μm, chipping tends to occur at the cutting edge portion under severe cutting conditions such as high-speed heavy cutting. Therefore, the average layer thickness is set to 1 to 15 μm.

  In addition, for the purpose of identification before and after the use of the cutting tool, a TiN layer having a golden color tone may be vapor-deposited as necessary as the outermost surface layer of the hard coating layer, but the average layer thickness in this case is It may be 0.1 to 1 μm, and if the thickness is less than 0.1 μm, a sufficient discrimination effect cannot be obtained, while the discrimination effect by the TiN layer is sufficient for an average layer thickness of up to 1 μm.

  The coated tool of this invention is accompanied by high heat generation, and even in high-speed heavy cutting processes such as various steels and cast irons in which a high load is applied to the cutting edge, the lower layer and the upper layer of the hard coating layer are more excellent in high-temperature strength, Since it has an interlaminar adhesion strength, it exhibits excellent wear resistance over a long period of time without causing peeling or chipping to the hard coating layer.

  Next, the coated tool of the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders are blended into the blending composition shown in Table 1, added with wax, ball milled in acetone for 36 hours, dried under reduced pressure, and pressed into a compact of a predetermined shape at a pressure of 98 MPa. Then, this green compact was vacuum sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour, and after sintering, the cutting edge portion was R: 0.08 mm honing By performing the processing, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape defined in ISO · CNMG12041 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 36 hours, dried, and then pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour. After sintering, the cutting edge portion was subjected to a honing process of R: 0.08 mm. Tool bases a to f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

Next, the lower layers (a) to (f) of the hard coating layer are formed on the surfaces of the tool bases A to F and the tool bases a to f using normal chemical vapor deposition equipment under the conditions shown in Table 3. Are formed by vapor deposition with the combinations and target layer thicknesses shown in Table 6, and then the modified α-type Al ₂ O ₃ layers (a) to (f) of the upper layer are formed under the conditions shown in Table 4. The coated tools 1 to 13 of the present invention were manufactured by vapor deposition with the combinations shown in FIG.

For the purpose of comparison, the lower layer of the hard coating layer (a) is used on the surfaces of the tool bases A to F and the tool bases a to f using the same ordinary chemical vapor deposition apparatus under the conditions shown in Table 3. ) To (f) are formed by vapor deposition at the combinations and target layer thicknesses shown in Table 7, and then the conventional α-type Al ₂ O ₃ layers (a) to (f) as upper layers are subjected to the conditions shown in Table 5. Thus, the conventional coated tools 1 to 13 were manufactured by vapor deposition with the combinations and target layer thicknesses shown in Table 7, respectively.

Next, with respect to the hard coating layer of the above-described coated tool of the present invention and the conventional coated tool, a modified TiCN layer existing adjacent to the upper layer, a lower layer composed of other Ti compound layers, and a modified α constituting the upper layer For the Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer, using a field emission scanning electron microscope, a constituent atom sharing lattice distribution graph is created to obtain the ratio of Σ3 in each layer, and the lower layer Σ3 The number and position of corresponding grain boundaries and upper layer Σ3 corresponding grain boundaries were measured.
That is, the above-mentioned constituent atomic shared lattice point distribution graph shows that the modified TiCN layer, the other Ti compound layer, the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer existing adjacent to the upper layer. In a state where the cross section of the electrode is a polished surface, it is set in a lens barrel of a field emission scanning electron microscope, and an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees is applied to the polished surface with an irradiation current of 1 nA. Irradiate each individual crystal grain within the measurement range of the polished surface, and use an electron backscatter diffraction image apparatus to divide the 30 × 50 μm region at a spacing of 0.1 μm / step relative to the normal of the cross-section polished surface. For the modified TiCN layer and other Ti compound layers, the (001) plane and (011) plane, which are crystal planes of crystal grains, the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer. For the layer, the (0001) plane which is the crystal plane of the crystal grain And the inclination angle formed by the normal of the (10-10) plane, respectively, and based on the measurement inclination angle obtained as a result, each of the constituent atoms is the crystal grain at the interface between adjacent crystal grains. The distribution of lattice points that share one constituent atom among them (constituent atom shared lattice points) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (in this case, the modification Regarding the TiCN layer and other Ti compound layers, N is an even number of 2 or more in the crystal structure of the NaCl type face centered cubic crystal, while the modified α type Al ₂ O ₃ layer and the conventional α type Al ₂ O ₃ layer are used. N is an even number of 2 or more due to the crystal structure of the corundum hexagonal close-packed crystal, but when the upper limit of N is 28 from the point of distribution frequency, even numbers of 4, 8, 14, 24, and 26 exist. Existing constituent atomic shared lattice points When representing the state in .SIGMA.N + 1, each .SIGMA.N + 1 is created by determining the ratio of total .SIGMA.N + 1. These values are shown in Tables 6 and 7.
Next, regarding the number and position of the grain boundaries corresponding to the lower layer Σ3 existing facing the interface with the upper layer, the normal lines of the (001) plane and the (011) plane at the interface between the adjacent crystal grains respectively. The angle at which the normals cross each other is obtained, and the case where the angle between the normals of the (001) plane and the normals of the (011) plane is 2 degrees or more is a grain boundary based on the measured inclination angle. As a result, the number and position of all grain boundaries corresponding to the lower layer Σ3 existing at the interface with the upper layer were obtained.
Further, for the number and position of the grain boundaries corresponding to the upper layer Σ3, the angles at which the normal lines of the (0001) plane and the normal lines of the (10-10) plane intersect each other at the interface between adjacent crystal grains are obtained, Based on this measured inclination angle, the interface with the lower layer is defined as a grain boundary when the angle between the normals of the (0001) planes and the normals of the (10-10) planes is 2 degrees or more. The number and position of all the upper layer Σ3-corresponding grain boundaries existing at
Then, the grain boundary corresponding to the lower layer Σ3 existing facing the interface with the upper layer determined as described above is made to correspond to the position of the grain boundary corresponding to the upper layer Σ3 existing facing the interface with the lower layer, At the interface with the lower layer, the ratio of the grain boundary corresponding to the lower layer Σ3 forming the crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3 to the total grain boundary corresponding to the lower layer Σ3 was determined. This value is shown in Tables 6 and 7 as Σ3 corresponding grain boundary continuous ratio (%).
Note that the Σ3 ratio of the lower layer is an average value of the ratio of Σ3 obtained over the depth region from the interface between the lower layer and the upper layer up to 1 μm on the substrate surface side, and the Σ3 ratio of the upper layer is the upper layer It is the average value of the ratio of Σ3 obtained throughout.

As shown in Tables 6 and 7, respectively, in both the present coated tool and the conventional coated tool, the Σ3 ratio of the lower layer is 60% or more, and the lower layer has excellent high-temperature strength.
On the other hand, as also shown in Tables 6 and 7, the ratio of the grain boundary corresponding to the lower layer Σ3 forming the crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3 to the grain boundary corresponding to all the lower layers Σ3 The Σ3-corresponding grain boundary continuity expressed represents a range of 30 to 70% in the coated tool of the present invention. As a result, the conventional coated tool has an excellent interlayer adhesion strength. Since the value is less than 30%, the interlayer adhesion strength is unsatisfactory.

  Further, regarding the above-described coated tools 1 to 13 of the present invention and the conventional coated tools 1 to 13, the hard coating layer was observed using an electron beam microanalyzer (EPMA) and an Auger spectrometer (longitudinal section of the layer). As a result, it was confirmed that both the former and the latter consisted of layers having substantially the same composition as the target composition. Moreover, when the thickness of each constituent layer of the hard coating layer of these coated tools was measured using a scanning electron microscope (similarly longitudinal section measurement), the average layer thickness substantially the same as the target layer thickness ( Average value of 5-point measurement) was shown.

Next, in the state where all of the above various coated tools are screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1 to 13 and the conventional coated tools 1 to 13,
Work material: JIS / SS400 round bar,
Cutting speed: 480 m / min,
Cutting depth: 4 mm,
Feed: 0.8 mm / rev,
Cutting time: 10 minutes,
Dry high-speed continuous high cutting / high feed cutting test under normal conditions (cutting condition A) (normal cutting speed, cutting and feed are 300 m / min, 1.5 mm, 0.3 mm / rev, respectively)
Work material: JIS / SCr420H round bar,
Cutting speed: 450 m / min,
Cutting depth: 1.5 mm,
Feed: 0.6 mm / rev,
Cutting time: 10 minutes,
Dry high-speed high-feed cutting test of alloy steel under the following conditions (cutting condition B) (normal cutting speed and feed are 280 m / min and 0.25 mm / rev, respectively)
Work material: JIS / FC250 lengthwise equidistant round bars with 4 vertical grooves,
Cutting speed: 400 m / min,
Cutting depth: 1.5 mm,
Feed: 0.6 mm / rev,
Cutting time: 10 minutes,
Wet high-speed intermittent high-feed cutting test of cast iron under the above conditions (cutting condition C) (normal cutting speed and feed are 230 m / min and 0.3 mm / rev, respectively)
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 7.

From the results shown in Tables 6 to 8, the coated tools 1 to 13 of the present invention are at the interface between the lower layer and the upper layer of the hard coating layer, and the lower part of 30 to 70% of all the lower layer Σ3 corresponding grain boundaries. The grain boundary corresponding to the layer Σ3 forms a crystal grain boundary that is continuous with the grain boundary corresponding to the upper layer Σ3, or further, a depth region from the interface between the lower layer and the upper layer to at least 1 μm on the substrate surface side The lower layer has a Σ3 ratio of 60% or more, and the lower layer has an excellent high-temperature strength and an excellent interlayer adhesion strength between the lower layer and the upper layer. %, And the upper layer has excellent high-temperature strength. Therefore, even in high-speed heavy cutting such as various steels and cast irons that cause high heat generation and a high load acts on the cutting edge portion, The high-temperature strength of the upper layer is further improved, and in addition, the interlayer between the two layers Because strength and is obtained by markedly improved, with exhibits chipping resistance was good without occurrence of delamination, indicating excellent wear resistance.
However, in the conventional coated tools 1 to 13 in which the upper layer of the hard coating layer is a conventional α-type Al ₂ O ₃ layer, the interlayer adhesion strength between the upper layer and the lower layer is insufficient, so It is apparent that due to the high load acting in the cutting process, peeling, chipping, etc. occur in the hard coating layer, and the service life is reached in a relatively short time.

  As described above, the coated tool of the present invention has a high-speed heavy load that acts on the cutting edge portion at a high temperature as well as continuous cutting and intermittent cutting under normal conditions such as various steels and cast iron. Excellent chipping resistance even in the cutting process, and excellent cutting performance over a long period of time, fully satisfying the high performance of cutting equipment, labor saving and energy saving of cutting work, and further cost reduction It can cope with.

It is a schematic diagram which shows the crystal structure of the NaCl type face centered cubic crystal which the modified TiCN layer which comprises the lower layer of a hard coating layer has. It is a schematic explanatory drawing which shows the measurement aspect of the inclination angle of the (001) plane of a crystal grain and the (011) plane in the modified TiCN layer which comprises the lower layer of a hard coating layer. It is a schematic diagram showing an atomic arrangement of a unit cell of a corundum type hexagonal close-packed crystal constituting an α-type Al ₂ O ₃ layer. It is a schematic diagram showing the measurement mode of the inclination angle of the crystal grains (0001) plane and (10-10) plane in the α-type the Al ₂ O ₃ layer. (A) is a crystal in which the upper layer Σ3 corresponding grain boundary is continuous with the lower layer Σ3 corresponding grain boundary of 30 to 70% of all the lower layer Σ3 corresponding grain boundaries at the interface between the upper layer and the lower layer. Schematic diagram of the grain boundary structure of the present coated tool 3 forming the grain boundary, (b) is the interface between the upper layer and the lower layer, less than 30% of all the grain boundaries corresponding to the lower layer Σ3 It is a schematic diagram of the crystal grain boundary structure of the conventional coated tool 3 in which the grain boundary corresponding to the upper layer Σ3 is continuous with the grain boundary corresponding to the lower layer Σ3.

Claims (3)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) a lower layer composed of a chemical vapor deposited Ti compound layer comprising a modified titanium carbonitride layer having an average layer thickness of at least 2 to 15 μm;
(B) an upper layer composed of a modified α-type aluminum oxide layer having an average layer thickness of 1 to 15 μm and having an α-type crystal structure in a state of chemical vapor deposition;
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) and (b) is formed,
For the lower layer of (a) above, the cross-sectional polishing is performed by irradiating an electron beam to each crystal grain having a face-centered cubic lattice existing within the measurement range of the coated cross-sectional polished surface using a field emission scanning electron microscope. The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, is measured with respect to the plane normal line. In this case, the crystal grains are NaCl type face centered cubic crystals. Based on the measured tilt angle obtained as a result of the crystal structure, the angles at which the (001) plane normal lines and the (011) plane normal lines cross each other at the interface between adjacent crystal grains are obtained. When the angle between the normal lines of the (001) planes and the normal lines of the (011) planes is 2 degrees or more, the crystal grain boundary is used, and at the interface between the crystal grains adjacent to each other, Each atom is one constituent element between the grains. The distribution of lattice points (constituent atomic shared lattice points) that share the same is calculated, and the constituent atomic shared lattice point form in which there are two lattice points that do not share constituent atoms between the constituent atomic shared lattice points is represented by Σ3. Measure the number and position of grain boundaries corresponding to the lower layer Σ3 existing at the interface with the layer,
Further, with respect to the upper layer of the above (b), by using a field emission scanning electron microscope, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the coated cross-section polished surface is irradiated with an electron beam, The inclination angle formed by the normal lines of the (0001) plane and (10-10) plane, which are the crystal planes of the crystal grains, is measured with respect to the normal line of the polished surface. And a corundum-type hexagonal close-packed crystal structure in which constituent atoms composed of oxygen and oxygen exist, respectively, and based on the measured tilt angle obtained as a result of this, the (0001) plane at the interface between adjacent crystal grains The angle at which the normal lines intersect with each other and the (10-10) plane normal lines intersect, and the angle between the (0001) plane normal lines and the (10-10) plane normal lines intersect is 2 degrees or more. Be a grain boundary, and A distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at an interface between adjacent crystal grains; When constitutive atomic shared lattice point form with two lattice points that do not share constituent atoms in between is represented by Σ3, and the number and position of the upper layer Σ3-corresponding grain boundaries existing facing the interface with the lower layer are measured In addition,
At the interface between the lower layer and the upper layer, 30% to 70% of the grain boundary corresponding to the lower layer Σ3 existing at the interface with the upper layer corresponds to the upper layer Σ3. A surface-coated cutting tool, wherein the grain boundaries are formed as continuous crystal grain boundaries.   Face-centered cubic crystals that exist within the measurement range of the polished surface of the film cross-section using a field emission scanning electron microscope for the lower layer extending from the interface between the lower layer and the upper layer to a depth region of at least 1 μm on the substrate surface side. Each crystal grain having a lattice is irradiated with an electron beam, and the inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the cross-section polished surface In this case, the crystal grains have a crystal structure of NaCl-type face-centered cubic crystals, and based on the measured tilt angle obtained as a result, the (001) planes at the interfaces between adjacent crystal grains are measured. The angle at which the normal lines intersect with each other and the (011) plane normal lines intersect with each other and the angle between the (001) plane normal lines and the (011) plane normal lines is 2 degrees or more. Suppose there is a crystal adjacent to each other The distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated at the interface, and the constituent atoms are shared between the constituent atom shared lattice points. In the case where the number of lattice points to be removed is N (provided that the upper limit of N is 28 from the point of frequency), the constituent atom shared lattice point form is represented by ΣN + 1, and the ratio of each ΣN + 1 to the entire ΣN + 1 is obtained as described above. The surface-coated cutting tool according to claim 1, wherein a ratio of Σ3 to ΣN + 1 is 60% or more.   For the upper layer, a field emission scanning electron microscope was used to irradiate each crystal grain having a hexagonal crystal lattice existing within the measurement range of the coated cross-section polished surface with respect to the normal of the cross-sectional polished surface. Then, the inclination angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are the crystal planes of the crystal grains, is measured. Each of the corundum-type hexagonal close-packed crystals has a crystal structure, and based on the measured tilt angle obtained as a result, the normals of the (0001) planes at the interfaces between adjacent crystal grains and (10− 10) The angle at which the normals of the planes intersect is determined, and the case where the angle between the normals of the (0001) planes and the normals of the (10-10) planes is 2 degrees or more is a grain boundary, And crystal grains adjacent to each other At the interface, the distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom among the crystal grains is calculated, and the constituent atoms are not shared between the constituent atom shared lattice points. There are N lattice points (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal, but when the upper limit of N is 28 in terms of distribution frequency, 4, 8, 14, 24 and (The even number of 26 does not exist) When the constituent atomic lattice point form existing is represented by ΣN + 1 and the ratio of each ΣN + 1 to the entire ΣN + 1 is obtained, the ratio of the Σ3 in the upper layer to the entire ΣN + 1 is 60% or more The surface-coated cutting tool according to claim 1 or 2.

Images