JP5257184B2 - Surface coated cutting tool - Google Patents

Description

  This invention has, for example, high temperature strength and interlayer adhesion strength with excellent hard coating layer even when cutting difficult-to-cut materials such as mild steel and stainless steel under high-speed cutting conditions with high heat generation, The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent chipping resistance, chipping resistance, and peeling resistance over a long period of use.

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 layers (hereinafter referred to as TiCNO layer) and having a total average layer thickness of 0.1 to 5 μm, and carbonitriding having an average layer thickness of 2.5 to 15 μm A lower layer composed of a titanium layer (hereinafter referred to as a modified TiCN layer),
(B) an upper layer composed of an α-type aluminum oxide layer (hereinafter referred to as a conventional Al ₂ O ₃ 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;
(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 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 occupying distribution ratio, a constituent atom shared lattice point distribution graph in which the highest peak exists in Σ3 and the ratio of the 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 equipment has been remarkable. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and as a result, cutting conditions have become increasingly severe. In the conventional coated tool, the lower layer is a modified TiCN layer having a relatively high high-temperature strength, and the upper layer is formed of an Al ₂ O ₃ layer having a high-temperature strength that is excellent in high-temperature hardness and heat resistance. However, when this is used for high-speed cutting conditions with high heat generation, especially for difficult-to-cut materials such as mild steel and stainless steel, where the welding tends to occur, the interlayer adhesion strength between the upper and lower layers is not sufficient. Therefore, delamination, chipping, etc. are likely to occur, and the service life is reached in a relatively short time.

  In view of the above, the present inventors have proposed a hard coating layer in order to improve chipping resistance, fracture resistance, and peeling resistance by improving the interlayer adhesion strength of the hard coating layer of the above-mentioned coated tool. As a result of diligent research focusing on the layer structure, the following findings were obtained.

The hard coating layer of the above conventional coated tool is, for example, in a normal chemical vapor deposition apparatus,
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 is deposited as a lower layer under the conditions of
On top of this,
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,
Conventionally, an Al ₂ O ₃ layer is deposited as an upper layer under the conditions described above.
The resulting upper layer composed of the conventional Al ₂ O ₃ layer has excellent high temperature strength and heat resistance in addition to the excellent high temperature hardness and heat resistance inherent in the Al ₂ O ₃ layer. Because of its lower layer-upper interlayer adhesion strength, it exhibited the specified chipping resistance in high-speed intermittent cutting, but in high-speed cutting of difficult-to-cut materials, the interlayer adhesion strength is not satisfactory. No chipping, chipping, delamination, etc. were observed.

Therefore, when forming the hard coating layer, the present inventors first made a Ti compound layer (at least one of a normal TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer. After the deposition of the modified TiCN layer in the coated tool as a lower layer, a modified chromium nitride layer (hereinafter referred to as a modified Cr ₂ N layer) is formed thereon as an intermediate layer. Further, an Al ₂ O ₃ layer (hereinafter referred to as a modified Al ₂ O ₃ layer) as an upper layer is vapor-deposited thereon, and a hard coating layer is formed as a Ti compound layer (modified TiCN). The adhesion strength between the lower layer and the intermediate layer is improved by forming a three-layer structure comprising a lower layer comprising a layer), an intermediate layer comprising a modified Cr ₂ N layer, and an upper layer comprising a modified Al ₂ O ₃ layer. Not only the middle layer-the top Interlayer adhesion strength between layers has been further improved. As a result, the high-temperature strength of the hard coating layer as a whole has been greatly improved, and the interlayer adhesion strength has also been improved. Even in high-speed cutting of difficult-to-cut materials, chipping properties and defects The present inventors have found that excellent cutting performance is exhibited over a long period of use without peeling or the like.

Here, the modified Cr ₂ N layer, which is an intermediate layer, is formed on a lower layer made of a Ti compound layer by a normal chemical vapor deposition apparatus.
Reaction gas composition: volume%, CrCl ₃ : 2 to 5%, N ₂ : 20 to 40%, HCl: 2 to 5%, H ₂ : remaining,
Reaction atmosphere temperature: 980-1040 ° C.
Reaction atmosphere pressure: 6-20 kPa,
The modified Cr ₂ N layer formed by vapor deposition under the following conditions has excellent interlayer adhesion strength to both the lower layer and the upper layer.

Then, for each of the modified Al ₂ O ₃ layer (upper layer) and the modified Cr ₂ N layer (intermediate layer), a hexagon existing within the measurement range of the surface polished surface using a field emission scanning electron microscope. Each crystal grain having a crystal lattice is irradiated with an electron beam, and the normal lines of the (0001) plane and the (10-10) plane are the crystal planes of the crystal grains with respect to the normal line of the polished surface. In this case, the crystal grains have a crystal structure of a corundum hexagonal close-packed crystal. Based on the measurement tilt angles obtained as a result, the crystal grains are arranged at the interface between adjacent crystal grains. The distribution of lattice points (constituent atom shared lattice points) in which each atom shares one constituent atom among the crystal grains is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points are calculated. (However, N is 2 on the crystal structure of the corundum hexagonal close-packed crystal. Even if the upper limit of N is 28 from the point of distribution frequency, the even number of 4, 8, 14, 24, and 26 does not exist). if you did this,
In each of the intermediate layer and the upper layer, in the constituent atom shared lattice distribution graph showing the distribution ratio of each ΣN + 1 in the entire ΣN + 1, the highest peak exists in Σ3 and the distribution ratio in the entire ΣN + 1 of the Σ3 Shows a constituent atom shared lattice point distribution graph of 60% or more,
Further, the number and position of the Σ3-corresponding grain boundary (hereinafter referred to as “intermediate Σ3-corresponding grain boundary”) of the intermediate layer existing at the interface with the upper layer is measured, and the intermediate layer is present at the interface with the intermediate layer. An intermediate layer existing at the interface between the upper layer and the upper layer when the number and positions of the upper layer Σ3 corresponding grain boundaries (hereinafter referred to as upper layer Σ3 corresponding grain boundaries) are measured. The upper layer Σ3 corresponding grain boundary is formed as a continuous grain boundary with respect to the intermediate layer Σ3 corresponding grain boundary of 30 to 70% of the Σ3 corresponding grain boundary, and between the intermediate layer and the upper layer It has been found that the presence of such a continuous grain boundary structure significantly improves the interlayer adhesion strength between the intermediate layer and the upper layer.

As described above, the intermediate layer and the upper layer of the hard coating layer are each composed of the modified Cr ₂ N layer and the modified Al ₂ O ₃ layer, and the interface between the intermediate layer and the upper layer is the interface with the upper layer. The coated tool is formed as a crystal grain boundary in which the upper layer Σ3 corresponding grain boundary is continuous with respect to the intermediate layer Σ3 corresponding grain boundary of 30 to 70% of the intermediate layer Σ3 corresponding grain boundary existing facing The interlaminar bond strength between the intermediate layer and the upper layer is remarkably improved, and the hard coating layer is excellent even when used for high-speed cutting with high heat generation of difficult-to-cut materials such as mild steel and stainless steel, which are likely to be welded. It has high temperature strength and interlaminar adhesion strength, and exhibits excellent chipping resistance, chipping resistance, and peeling resistance over a long period of use.

This invention has been made based on the above findings,
In a surface-coated cutting tool in which a hard coating layer composed of a lower layer, an intermediate layer, and an upper layer is vapor-deposited on the surface of a tool substrate,
(A) The lower layer is composed of at least one of a titanium carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride layer, and has a total layer thickness of 2 to 15 μm. Compound layer,
(B) the intermediate layer is a chromium nitride layer having a layer thickness of 0.5 to 3 μm;
(C) The upper layer consists of an aluminum oxide layer having a layer thickness of 1 to 15 μm,
(D) For each of the intermediate layer of (b) and the upper layer of (c), each crystal grain having a hexagonal crystal lattice existing in the measurement range of the surface polished surface using a field emission scanning electron microscope Is irradiated with an electron beam to measure an inclination angle formed by 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 surface polished surface. In this case, the crystal grains have a corundum type hexagonal close-packed crystal structure, and based on the measurement tilt angle obtained as a result, at the interface between adjacent crystal grains, each of the constituent atoms is interlinked with the crystal grains. The distribution of lattice points that share one constituent atom (constituent atom shared lattice point) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (where N is a corundum hexagon) Due to the close-packed crystal structure, it is an even number of 2 or more. (If the upper limit of N is 28 from the point of the cloth frequency, there is no even number of 4, 8, 14, 24, and 26) When the existing constituent atomic shared lattice point form is represented by ΣN + 1, the above (b) In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1, both the intermediate layer of (c) and the upper layer of (c) have the highest peak at Σ3, and the entire ΣN + 1 of the Σ3 Shows a constituent atom shared lattice point distribution graph in which the distribution ratio is 60% or more,
(E) Further, the number and positions of the Σ3-compatible grain boundaries of the intermediate layer existing at the interface with the upper layer are measured, and the Σ3-compatible grain boundaries of the upper layer existing at the interface with the intermediate layer are measured. When the number and position are measured, at the interface between the intermediate layer and the upper layer, Σ3 of the intermediate layer in a proportion of 30 to 70% of the grain boundary corresponding to Σ3 of the intermediate layer existing facing the interface with the upper layer A surface-coated cutting tool, wherein an upper layer Σ3 corresponding grain boundary is formed as a continuous grain boundary with respect to the corresponding grain boundary. "
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:
As the Ti compound layer constituting the lower layer, the well-known ordinary Ti carbide (TiC) layer, nitride (TiN) layer, carbonitride (TiCN) layer, carbonate (TiCO) layer and carbon A Ti compound layer composed of one or more of the nitrided oxide (TiCNO) layers 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 adheres firmly to both the tool base and the intermediate layer (modified Cr ₂ N layer). Thus, it contributes to improving the adhesion of the hard coating layer to the tool substrate.
If the total average layer thickness of the lower layer is less than 2 μm, the predetermined wear resistance cannot be ensured. On the other hand, if the total average layer exceeds 15 μm, the chipping resistance decreases rapidly. The total average layer thickness was determined to be 2-15 μm.

In addition, the lower layer can be composed of the modified TiCN layer of the conventional coated tool, but in this case, the high temperature strength of the lower layer is further improved and the adhesion strength to both the tool base and the intermediate layer is improved. Will further improve.
The modified TiCN 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 exhibits a high value with a Σ3 ratio of 60% or more.

The Σ3 ratio of the modified TiCN layer is, for example, a modified TiCN layer formed by vapor deposition under the above conditions as illustrated in the schematic explanatory diagrams of FIGS. 2A and 2B 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 plane (in FIG. 2a, when the tilt angle of the (001) plane of the crystal plane is 0 degree and the tilt angle of the (011) plane is 45 degrees, (001) ) The tilt angle of the plane is 45 degrees, and the tilt angle of the (011) plane is 0 degree, and all tilt angles of the crystal grains including these angles are measured. As described above, the crystal grains are N in which constituent atoms composed of Ti, carbon, and nitrogen are present at lattice points. A crystal structure of a Cl-type face-centered cubic crystal, and each of the constituent atoms forms one structure between the crystal grains at the interface between adjacent crystal grains based on the measured tilt angle obtained as a result. The distribution of lattice points that share atoms (constituent atomic shared lattice points) is calculated, and N lattice points that do not share constituent atoms between the constituent atomic shared lattice points (N is the crystal structure of the NaCl-type face-centered cubic crystal) The constituent atom shared lattice point form which is an even number of 2 or more is represented by ΣN + 1, and each ΣN + 1 represents a distribution ratio of the entire ΣN + 1 (provided that the upper limit value of N is 28 due to frequency) This can be obtained by creating a shared grid point distribution graph.
In the constituent atom sharing lattice distribution graph, the modified TiCN layer has the highest peak in Σ3, and the distribution ratio of Σ3 is an extremely high ratio of 60% or more.
The Σ3 ratio of the modified TiCN layer 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. .

Middle layer:
The modified Cr ₂ N layer of the intermediate layer is formed on the lower layer made of the Ti compound layer, for example,
With normal chemical vapor deposition equipment,
Reaction gas composition: volume%, CrCl ₃ : 2 to 5%, N ₂ : 20 to 40%, HCl: 2 to 5%, H ₂ : remaining,
Reaction atmosphere temperature: 980-1040 ° C.
Reaction atmosphere pressure: 6-20 kPa,
It is formed by vapor-depositing on condition of this.
This modified Cr ₂ N layer has the same hexagonal crystal structure as the modified Al ₂ O ₃ layer of the upper layer, has an excellent high temperature strength, and has a strong adhesion strength to the lower layer, In particular, its unique grain boundary structure provides stronger adhesion strength to the upper layer, and as a result, excellent chipping resistance in high-speed cutting of difficult-to-cut materials such as mild steel and stainless steel with high weldability. , Defect resistance, and delamination resistance.

About the modified Cr ₂ N layer, using a field emission scanning electron microscope, hexagonal crystals existing in the measurement range of the surface polished surface as illustrated in the schematic explanatory diagrams of FIGS. 1 (a) and 1 (b) Each crystal grain having a crystal lattice is irradiated with an electron beam, and the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, are formed with respect to the normal line of the surface polished surface. Tilt angles (FIG. 1a shows the case where the tilt angle of the crystal plane is 0 degree, and FIG. 1 (b) shows the case where the tilt angle is 45 degrees. In this case, the crystal grains have a crystal structure of a corundum hexagonal close-packed crystal, and based on the measured tilt angles obtained as a result, at the interface between adjacent crystal grains, Lattice points where each of the constituent atoms shares one constituent atom between the crystal grains (the constituent atom The number of lattice points that do not share constituent atoms between the constituent atomic shared lattice points is calculated (where N is an even number of 2 or more on the crystal structure of the corundum hexagonal close-packed crystal). (If the upper limit of N is 28 from the point of distribution frequency, there is no even number of 4, 8, 14, 24, and 26), the existing configuration of the shared atomic lattice point is represented by ΣN + 1, and each ΣN + 1 is represented by ΣN + 1 When a constituent atom shared lattice point distribution graph showing the distribution ratio in the whole is created, in the constituent atom shared lattice point distribution graph, the modified Cr ₂ N layer has the highest peak in Σ3, and ΣN + 1 of Σ3 The distribution ratio occupying the whole is an extremely high ratio of 60% or more, and such a modified Cr ₂ N layer exhibits excellent high-temperature strength.

Further, based on the measured inclination angle formed by the normal of the (0001) plane and the (10-10) plane, which are crystal planes of crystal grains, obtained by measurement using the field emission scanning electron microscope, (0001 ) When the angle between the normals of the planes and the normals of the (10-10) planes is 2 degrees or more, it is defined as a crystal grain boundary. The point form is Σ3 in which there are two lattice points that do not share constituent atoms between constituent atomic shared lattice points, and the crystal grain boundary that exists facing the interface with the upper layer (intermediate layer Σ3-corresponding grain boundary ) Number and position.
Then, the position of the grain boundary corresponding to the upper layer Σ3 specified for the upper layer, which will be described later, and the position of the grain boundary corresponding to the intermediate layer Σ3 obtained for the modified Cr ₂ N layer are put together, and at the interface between the intermediate layer and the upper layer. When 30 to 70% of the grain boundary corresponding to the intermediate layer Σ3 existing facing the interface with the upper layer has a grain boundary structure forming a grain boundary continuous with the grain boundary corresponding to the upper layer Σ3 In (see FIG. 6A), the interlayer adhesion strength between the intermediate layer (modified Cr ₂ N layer) and the upper layer (modified Al ₂ O ₃ layer) is remarkably improved.
However, in the case where the intermediate layer Σ3 corresponding grain boundary formed continuously with the upper layer Σ3 corresponding grain boundary is only less than 30% of the total intermediate layer Σ3 corresponding grain boundary (see FIG. 6B). ), Or in the case where it exceeds 70%, the continuity of the crystal grain boundary between the intermediate layer and the upper layer is small, so that the improvement of the interlayer adhesion strength cannot be ensured, or the intermediate layer and the upper layer Since there is too much continuity of grain boundaries in the layers, the gap between the residual stresses in each of the intermediate layer and the upper layer becomes too large, and the interlaminar adhesion strength tends to decrease. It is necessary that 30 to 70% of the grain boundaries corresponding to the intermediate layer Σ3 existing facing the interface form a crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3.

In addition, when the average layer thickness of the intermediate layer composed of the modified Cr ₂ N layer is less than 0.5 μm, it is not possible to exhibit excellent high temperature hardness, heat resistance and excellent interlayer adhesion strength. When the layer thickness exceeds 3 μm, chipping, chipping and the like are likely to occur in the cutting edge part under high-speed cutting conditions for difficult-to-cut materials. Therefore, the average layer thickness is set to 0.5 to 3 μm.

Upper layer:
The modified Al ₂ O ₃ layer of the upper layer is formed on the intermediate layer composed of the modified Cr ₂ N layer, for example,
(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,
In addition to the excellent high temperature hardness, heat resistance and excellent high temperature strength inherent to the Al ₂ O ₃ layer, this modified Al ₂ O ₃ layer can be formed by vapor deposition under the following conditions: Interlayer adhesion strength is further improved. As a result, generation of delamination between the intermediate layer and the upper layer can be prevented, and excellent chipping resistance can be achieved.
According to the investigation using the field emission scanning electron microscope, the improvement in the interlayer adhesion strength between the upper layer and the intermediate layer is shown in the upper layer (modified Al ₂ O ₃ layer) and the intermediate layer (adjacent to the upper layer). It is clear that this is caused by the continuity of the grain boundary structure of the grain boundary corresponding to Σ3 formed at the interface with the modified Cr ₂ N layer existing in the middle.

As in the case of the modified Cr ₂ N layer, the modified Al ₂ O ₃ layer is exemplified by schematic explanatory views in FIGS. 1A and 1B using a field emission scanning electron microscope. As described above, each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface is irradiated with an electron beam, and is a crystal plane of the crystal grain with respect to the normal line of the surface polished surface (0001 ) Plane and (10-10) plane normal angle is measured. In this case, the crystal grains have a crystal structure of a corundum hexagonal close-packed crystal, and based on the measured tilt angle obtained as a result. Calculating 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; N lattice points that do not share constituent atoms between points (where N is a corundum In the hexagonal close-packed crystal structure, the number is an even number of 2 or more. However, when the upper limit of N is 28 from the point of distribution frequency, the even number of 4, 8, 14, 24, and 26 does not exist) In the case where a constituent atomic shared lattice point distribution graph is created in which the atomic shared lattice point form is represented by ΣN + 1 and each ΣN + 1 indicates the distribution ratio of the entire ΣN + 1, the modified Al ₂ O _{The three} layers have the highest peak in Σ3, and the distribution ratio of Σ3 to the entire ΣN + 1 is extremely high, more than 60%. Such a modified Al ₂ O ₃ layer has excellent high-temperature strength. Indicates.

Further, based on the measured inclination angle formed by the normal of the (0001) plane and the (10-10) plane, which are crystal planes of crystal grains, obtained by measurement using the field emission scanning electron microscope, (0001 ) When the angle between the normals of the planes and the normals of the (10-10) planes is 2 degrees or more, it is defined as a crystal grain boundary. The point form is Σ3 in which there are two lattice points that do not share constituent atoms between constituent atomic shared lattice points, and the crystal grain boundary that exists facing the interface with the upper layer (intermediate layer Σ3-corresponding grain boundary ) Number and position.
Then, the position of the grain boundary corresponding to the upper layer Σ3 determined for the modified Al ₂ O ₃ layer is matched with the position of the grain boundary corresponding to the intermediate layer Σ3 determined for the modified Cr ₂ N layer. Grain boundary structure in which 30 to 70% of the grain boundary corresponding to the intermediate layer Σ3 existing at the interface with the upper layer forms a continuous grain boundary with the grain boundary corresponding to the upper layer Σ3. (See FIG. 6A), the interlayer adhesion strength between the intermediate layer (modified Cr ₂ N layer) and the upper layer (modified Al ₂ O ₃ layer) is remarkably improved.
However, as already described for the intermediate layer, the intermediate layer Σ3 corresponding grain boundary formed continuously with the upper layer Σ3 corresponding grain boundary seems to be less than 30% of the total intermediate layer Σ3 corresponding grain boundary. In such a case (see FIG. 6B), or in the case where it exceeds 70%, the continuity of the crystal grain boundary between the intermediate layer and the upper layer is small, so that it is possible to ensure the improvement of the interlayer adhesion strength. Or because the continuity of the grain boundaries in the intermediate layer and the upper layer is too large, the gap between the residual stresses in the intermediate layer and the upper layer becomes too large, and the interlayer adhesion strength tends to decrease. Therefore, 30 to 70% of the grain boundaries corresponding to the intermediate layer Σ3 existing facing the interface with the upper layer form a crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3. is necessary.

Furthermore, if the average layer thickness of the upper layer composed of the modified Al ₂ O ₃ layer is less than 1 μm, it is not possible to exhibit excellent lubricity, high temperature strength and excellent interlayer adhesion strength, while the average layer thickness is If the thickness exceeds 15 μm, chipping is likely to occur at the cutting edge portion in high-speed cutting of difficult-to-cut materials, so the average layer thickness was set to 1 to 15 μm.

  The coated tool of the present invention is particularly suitable for use in high-speed cutting of difficult-to-cut materials with high weldability such as mild steel, stainless steel and the like. Since it has strength, it exhibits excellent wear resistance over a long period of time without causing peeling, chipping or chipping in the hard coating layer.

The Al ₂ O ₃ layer, which is a schematic diagram showing the measurement mode of the inclination angle of the crystal grains (0001) plane and (10-10) plane in Cr ₂ N layer. 3 is a constituent atomic shared lattice point distribution graph of a modified Cr ₂ N layer that is an intermediate layer of a hard coating layer of the present coated tool 2. 6 is a constituent atomic shared lattice point distribution graph of a modified Al ₂ O ₃ layer that is an upper layer of a hard coating layer of the coated tool 2 of the present invention. (A) is a crystal in which the upper layer Σ3 corresponding grain boundary is continuous with the intermediate layer Σ3 corresponding grain boundary of 30 to 70% of all the intermediate layer Σ3 corresponding grain boundaries at the interface between the upper layer and the intermediate layer. Schematic diagram of the grain boundary structure of the coated tool 2 of the present invention forming a 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.

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

As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder and Co powder all having an average particle diameter of 1 to 3 μm are prepared. Then, blended into the composition shown in Table 1, added with wax, ball mill mixed in acetone for 36 hours, dried under reduced pressure, and press-molded into a compact of a predetermined shape at a pressure of 98 MPa. Is vacuum-sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge is subjected to honing of R: 0.07 mm. -WC based cemented carbide tool bases A to C each having a throwaway tip shape defined in CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, NbC powder, TaC powder, WC powder, Co powder, all having an average particle diameter of 0.5 to 2 μm. , And Ni powder, 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 powder is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, the cutting edge portion is subjected to a honing process of R: 0.07 mm to achieve ISO standard / CNMG120408. TiCN-based cermet tool bases a to c having the following chip shape were formed.

Next, on the surfaces of these tool bases A to C and tool bases a to c, a Ti compound layer (Ti) that is a lower layer of the hard coating layer is formed under the conditions shown in Table 3 using a normal chemical vapor deposition apparatus. The modified TiCN layer of the compound layer is formed by vapor deposition with the combinations and target layer thicknesses shown in Table 7 and then the modified Cr ₂ N layer of the intermediate layer. (A) to (C) are formed by vapor deposition under the conditions shown in Table 4 with the combinations and target layer thicknesses shown in Table 7, and then the upper modified Al ₂ O ₃ layers (a) to (f) Were formed by vapor deposition under the conditions shown in Table 5 and with the combinations and target layer thicknesses shown in Table 7, to thereby produce the inventive coated tools 1 to 8, respectively.

For comparison purposes, the surface of the above-mentioned tool bases A to C and tool bases a to c is the lower layer of the hard coating layer under the conditions shown in Table 3 using the same ordinary chemical vapor deposition apparatus. Ti compound layers (represented by (a) to (f) for the modified TiCN layer among the Ti compound layers) are formed by vapor deposition with the combinations and target layer thicknesses shown in Table 8, and then the conventional upper layer layer. Conventionally coated tools 1 to 8 were produced by vapor-depositing Al ₂ O ₃ layers (a) to (f) under the conditions shown in Table 6 with the combinations and target layer thicknesses shown in Table 8, respectively.

Subsequently, the modified Cr ₂ N layer constituting the intermediate layer of the hard coating layer of the above-mentioned coated tool of the present invention, and the modified Al ₂ O ₃ layer constituting the upper layer of the hard coated layer of the coated tool of the present invention and the conventional coated tool. For the conventional Al ₂ O ₃ layer, a constituent atom shared lattice point distribution graph was created using a field emission scanning electron microscope, and the distribution ratio of Σ3 in each layer was obtained.
Further, for the coated tool of the present invention, the number and position of the grain boundary corresponding to the intermediate layer Σ3 and the upper layer Σ3 are measured, and for the conventional coated tool, for reference, the grain boundary corresponding to the lower layer Σ3 and the upper boundary The number and position of grain boundaries corresponding to layer Σ3 were measured.
That is, in the case of the coated tool of the present invention, the constituent atomic shared lattice point distribution graph is a state where the surfaces of the intermediate layer (modified Cr ₂ N layer) and the upper layer (modified Al ₂ O ₃ layer) are polished surfaces. And 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 on the polished surface is present in the measurement range of the surface polished surface with an irradiation current of 1 nA. Each of the crystal grains having a hexagonal crystal lattice is irradiated, and using an electron backscatter diffraction image apparatus, a 30 × 50 μm region is spaced at a spacing of 0.1 μm / step with respect to the normal line of the surface polished surface. The tilt angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains of the modified Cr ₂ N layer and the modified Al ₂ O ₃ layer, is measured. Has a crystal structure of a corundum hexagonal close-packed crystal. Based on the tilt angle, 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 between adjacent crystal grains is calculated, There are N lattice points that do not share constituent atoms between the constituent atomic shared lattice points (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 is limited in terms of distribution frequency. In the case of 28, there is no even number of 4, 8, 14, 24, and 26). When the constituent atomic lattice point form existing is represented by ΣN + 1, the modified Cr ₂ N layer and the modified Al ₂ For both O ₃ layers, each ΣN + 1 was created by determining the distribution ratio of the entire ΣN + 1. These values are shown in Table 7.
Further, the grain boundary corresponding to the intermediate 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 intermediate layer, The ratio (number) of the grain boundary corresponding to the intermediate layer Σ3 forming the crystal grain boundary continuous with the grain boundary corresponding to the upper layer Σ3 at the interface with the intermediate layer to all the boundary layers corresponding to the intermediate layer Σ3 was determined. This value is shown in Table 7 as Σ3 corresponding grain boundary continuous ratio (%).
From Table 7, with respect to the Σ3-corresponding grain boundary of the intermediate layer at a ratio of 30 to 70% of the Σ3-corresponding grain boundary of the intermediate layer existing at the interface between the intermediate layer and the upper layer, facing the interface with the upper layer. The upper layer Σ3-compatible grain boundary is formed as a continuous crystal grain boundary.

  In addition, for reference, for the lower layer and the upper layer of the conventional coated tool, the constituent atom shared lattice point distribution graph is obtained in the same manner as described above, and further, the lower layer Σ3 existing facing the interface with the upper layer is supported. The grain boundary is made to correspond to the position of the grain boundary corresponding to the upper layer Σ3 existing at the interface with the lower layer, and a grain boundary continuous with the grain boundary corresponding to the upper layer Σ3 is formed at the interface between the upper layer and the lower layer. The ratio (number) of the grain boundaries corresponding to the lower layer Σ3 in the total grain boundaries corresponding to the lower layer Σ3 was determined. This value is shown in Table 8 as a continuous boundary ratio (%) corresponding to Σ3.

As shown in Tables 7 and 8, respectively, the distribution ratio of Σ3 of the intermediate layer of the coated tool of the present invention existing at the interface of the upper layer, and Σ3 of the lower layer of the conventional coated tool existing at the interface of the upper layer The distribution ratio of each is 60% or more.
On the other hand, as also shown in Table 7, in the coated tool of the present invention, all the intermediate layer Σ3-corresponding grain boundaries of the intermediate layer Σ3-corresponding grain boundary forming a grain boundary continuous with the upper layer Σ3-corresponding grain boundary. The Σ3-corresponding grain boundary continuous ratio, which represents the ratio in the above, is in the range of 30 to 70% in the coated tool of the present invention, and as a result, has excellent interlayer adhesion strength.
On the other hand, as shown in Table 8, in the conventional coated tool, all the lower layer Σ3 corresponding to the lower layer Σ3 corresponding grain boundary forming a grain boundary continuous with the upper layer Σ3 corresponding grain boundary is supported. The continuous ratio of grain boundaries corresponding to Σ3, which represents the ratio of the grain boundary, is less than 30% or more than 70%, so that 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). The former and the latter both have a Ti compound layer (including a modified TiCN layer), an intermediate layer (modified Cr ₂ N layer), and an upper layer (modified Al ₂ ) having substantially the same composition as the target composition. O ₃ layer) and a conventional upper layer (conventional Al ₂ O ₃ layer) were confirmed.
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 each of the above various coated tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated tools 1-8 and the conventional coated tools 1-8,
Work material: JIS / SS400 round bar,
Cutting speed: 485 m / min,
Cutting depth: 5 mm,
Feed: 0.9 mm / rev,
Cutting time: 10 minutes,
Dry high-speed continuous cutting test of mild steel under the conditions (cutting condition A) (normal cutting speed is 300 m / min),
Work material: JIS / SUS316 round bar,
Cutting speed: 330 m / min,
Cutting depth: 1.5 mm,
Feed: 0.3 mm / rev,
Cutting time: 10 minutes,
Wet high-speed continuous cutting test of stainless steel under the above conditions (cutting condition B) (normal cutting speed is 220 m / min),
Work material: JIS / SUS304 round bar,
Cutting speed: 315 m / min,
Cutting depth: 1.5 mm,
Feed: 0.3 mm / rev,
Cutting time: 10 minutes,
Wet high-speed continuous cutting test of stainless steel under the above conditions (cutting condition C) (normal cutting speed is 220 m / min),
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 9.

From the results shown in Tables 7 to 9, the coated tools 1 to 8 of the present invention are 30 to 70% intermediate of all the intermediate layer Σ3 corresponding grain boundaries at the interface between the intermediate layer and the upper layer of the hard coating layer. 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. Therefore, even in high-speed cutting of difficult-to-cut materials such as mild steel and stainless steel with high weldability and high heat generation, The interlayer adhesion strength between the intermediate layer and the upper layer is remarkably improved, so that it exhibits excellent chipping resistance without occurrence of delamination and excellent wear resistance, but hard coating In the conventional coated tools 1 to 8 in which the upper layer of the conventional layer is composed of the conventional Al ₂ O ₃ layer, the interlayer adhesion strength between the upper layer and the lower layer is insufficient, so that high-speed cutting of difficult-to-cut materials such as mild steel and stainless steel In the cutting process, peeling, chipping, etc. occurred in the hard coating layer. Time it is clear that through use life.

  As described above, the coated tool of the present invention is not only continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also mild steel, stainless steel, etc. that particularly require welding resistance and chipping resistance. It shows excellent chipping resistance even at high-speed cutting, and exhibits excellent cutting performance over a long period of time. It can respond satisfactorily.

Claims (1)

In the surface-coated cutting tool in which a hard coating layer composed of a lower layer, an intermediate layer and an upper layer is formed on the surface of the tool substrate by vapor deposition,
(A) The lower layer is composed of at least one of a titanium carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride layer, and has a total layer thickness of 2 to 15 μm. Compound layer,
(B) the intermediate layer is a chromium nitride layer having a layer thickness of 0.5 to 3 μm;
(C) The upper layer consists of an aluminum oxide layer having a layer thickness of 1 to 15 μm,
(D) For each of the intermediate layer of (b) and the upper layer of (c), each crystal grain having a hexagonal crystal lattice existing in the measurement range of the surface polished surface using a field emission scanning electron microscope Is irradiated with an electron beam to measure an inclination angle formed by 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 surface polished surface. In this case, the crystal grains have a corundum type hexagonal close-packed crystal structure, and based on the measurement tilt angle obtained as a result, at the interface between adjacent crystal grains, each of the constituent atoms is interlinked with the crystal grains. The distribution of lattice points that share one constituent atom (constituent atom shared lattice point) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (where N is a corundum hexagon) Due to the close-packed crystal structure, it is an even number of 2 or more. (If the upper limit of N is 28 from the point of the cloth frequency, there is no even number of 4, 8, 14, 24, and 26) When the existing constituent atomic shared lattice point form is represented by ΣN + 1, the above (b) In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1, both the intermediate layer of (c) and the upper layer of (c) have the highest peak at Σ3, and the entire ΣN + 1 of the Σ3 Shows a constituent atom shared lattice point distribution graph in which the distribution ratio is 60% or more,
(E) Further, the number and positions of the Σ3-compatible grain boundaries of the intermediate layer existing at the interface with the upper layer are measured, and the Σ3-compatible grain boundaries of the upper layer existing at the interface with the intermediate layer are measured. When the number and position are measured, at the interface between the intermediate layer and the upper layer, Σ3 of the intermediate layer in a proportion of 30 to 70% of the grain boundary corresponding to Σ3 of the intermediate layer existing facing the interface with the upper layer A surface-coated cutting tool, wherein an upper layer Σ3 corresponding grain boundary is formed as a continuous grain boundary with respect to the corresponding grain boundary.

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