JP2008178943A - Surface covered cutting tool with hard covered layer displaying excellent abrasion resistance in intermittent high feeding cutting work - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface covered cutting tool with a hard covered layer displaying excellent abrasion resistance in intermittent high feeding cutting work. <P>SOLUTION: This surface covered cutting tool is constituted by evaporating and forming a lower part layer made of a Ti compound layer having total average layer thickness of 3 to 20 μm and an upper part layer made of an Al<SB>2</SB>O<SB>3</SB>layer having average layer thickness of 2 to 15 μm and having an α type crystal structure in a chemically evaporated state on a surface of a tool base body constituted of WC group cemented carbide or a TiCN group cermet. The Al<SB>2</SB>O<SB>3</SB>layer existing on the lower part layer side and existing in a 30 to 50% layer thickness region of the upper part layer is constituted of an Al<SB>2</SB>O<SB>3</SB>layer showing a constitutional atomic covalent lattice point distribution graph a distribution ratio occupying in the whole of ΣN+1 of Σ3 of which is 60 to 80%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a surface-coated cutting tool that exhibits excellent wear resistance with a hard coating layer, especially when cutting various materials such as steel and cast iron under intermittent and high feed cutting conditions. (Hereinafter referred to as a coated tool).

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. ,
(A) Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer, carbonate (hereinafter referred to as TiCO) layer, And a lower layer made of a Ti compound layer having one or more of carbonitride oxide (hereinafter referred to as TiCNO) layers and an overall average layer thickness of 3 to 20 μm,
(B) an upper layer made of an aluminum oxide layer (hereinafter referred to as an α-type Al ₂ O ₃ layer) having an average layer thickness of 2 to 15 μm and having an α-type crystal structure in a chemical vapor deposited state;
A coated tool formed by vapor-depositing the hard coating layer constituted by (a) and (b) above is known, and this coated tool is used for continuous cutting and intermittent cutting of various steels and cast irons, for example. That is well known.

  Further, in the above-mentioned coated tool, the constituent layer of the hard coating layer generally has a granular crystal structure, and the TiCN layer constituting the Ti compound layer as the lower layer is used for the purpose of improving the strength of the layer itself. In a normal chemical vapor deposition apparatus, a gas mixture containing organic carbonitride is used as a reaction gas, and it is formed by chemical vapor deposition at an intermediate temperature range of 700 to 950 ° C. so as to have a vertically grown crystal structure. It is also known.

Further, the α-type Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated tool has a crystal structure of a corundum type hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points, that is, FIG. The atomic arrangement of the unit cell of α-type Al ₂ O ₃ is composed of crystal grains having a crystal structure represented by a schematic diagram [(a) is a perspective view, (b) is a plan view of cross sections 1 to 9]. Is also known.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

In recent years, the performance of cutting machines has been remarkable. On the other hand, there are strong demands for labor-saving and energy-saving in cutting work, as well as lower costs and higher efficiency. There is no problem when it is used for continuous cutting and interrupted cutting under normal conditions, but especially when it is used for intermittent and high-feed cutting conditions, α-type Al constituting the hard coating layer _{Since the 2} O ₃ layer does not have sufficient impact resistance, chipping (slight chipping) is likely to occur in the hard coating layer, and as a result, the service life is reached in a relatively short time. .

The present inventors have, from the viewpoint as described above, focuses on coated tool α type the Al ₂ O ₃ layer described above constituting the upper layer of the hard coating layer, in particular of the α-type the Al ₂ O ₃ layer As a result of conducting research to improve impact resistance,
(A) The α-type Al ₂ O ₃ layer as the upper layer constituting the hard coating layer of the conventional coated tool is, for example, a normal chemical vapor deposition apparatus.
Reaction gas composition: volume%, AlCl ₃ : 2 to 4%, CO ₂ : 6 to 8%, HCl: 1.5 to 3%, H ₂ S: 0.05 to 0.2%, H ₂ : remaining ,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
It is formed by vapor deposition under the conditions (called normal conditions).
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 other words, in the reaction gas composition, the content ratio of AlCl ₃ , CO ₂ , and HCl is relatively high and the atmospheric pressure is relatively low (“reaction gas component”). The α-type Al ₂ O ₃ layer is formed by vapor deposition until a predetermined layer thickness (layer thickness of 30 to 50% of the upper layer thickness) is obtained under the “high content adjustment low pressure condition”, and then the final target When an α-type Al ₂ O ₃ layer (hereinafter referred to as “conventional α-type Al ₂ O ₃ layer”) is formed by vapor deposition under the above-mentioned normal conditions so as to obtain a layer thickness, an upper layer formed under a controlled low-pressure condition containing a high content of reactive gas The α-type Al ₂ O ₃ layer (hereinafter referred to as “modified α-type Al ₂ O ₃ layer”) having a layer thickness of 30 to 50% of the thickness of the film has improved high-temperature strength and excellent mechanical shock resistance. from becoming so equipped sex, the upper layer of the hard coating layer reforming α type the Al ₂ O ₃ layer and conventional α Coated tool, which is composed of a Al ₂ O ₃ layer is especially also intermittent high feed cutting accompanying severe mechanical impact, said that the hard layer is generated chipping without, wear resistance superior over a long period To come to show.

(B) About the conventional α-type Al ₂ O ₃ layer and 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. 2A and 2B, each crystal grain existing within the measurement range of the surface polished surface is irradiated with an electron beam, The tilt angle formed by the normal lines of the (0001) plane and the (10-10) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the polished surface [FIG. 2 (a) shows the tilt angle of the crystal plane. (B) shows the case where the inclination angle is 45 degrees, all the inclination angles of the individual crystal grains including these angles are measured. In this case, the crystal grains Has a crystal structure of a corundum type hexagonal close-packed crystal in which constituent atoms composed of Al and oxygen are present at lattice points as described above, and based on the measured tilt angle, crystal grains adjacent to each other are obtained. Each of the constituent atoms shares one constituent atom between the crystal grains at the interface The distribution of child points (constituent atom shared lattice points) is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points (where N is two or more 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), and the existing constituent atomic shared lattice point form is expressed as ΣN + 1, When a constituent atom shared lattice point distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1 is created (in this case, there are constituent atomic shared lattice point forms of Σ5, Σ9, Σ15, Σ25, and Σ27) In contrast to the conventional α-type Al ₂ O ₃ layer, as shown in FIG. 5, the distribution ratio of Σ3 shows a relatively low constituent atom shared lattice point distribution graph of 30% or less. The modified α-type Al ₂ O ₃ As shown in FIG. 4, the layer shows a very high constituent atom shared lattice point distribution graph in which the distribution ratio of Σ3 is 60 to 80%, and this high distribution ratio of Σ3 indicates AlCl ₃ , CO constituting the reaction gas. ₂ , and the content ratio of HCl and further change depending on the atmospheric reaction pressure.
In the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer, units of Σ3, Σ7, and Σ11 among constituent atomic shared lattice point forms at the interface between crystal grains adjacent to each other When the form is illustrated by a schematic diagram, it is as shown in FIGS.

(C) The above-mentioned modified α-type Al ₂ O ₃ layer is superior to the conventional α-type Al ₂ O ₃ layer in addition to the excellent high-temperature hardness and heat resistance of the α-type Al ₂ O ₃ layer itself. The coated tool formed by vapor deposition of the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer as the upper layer of the hard coating layer Combined with the excellent high-temperature strength provided by the TiCN layer, which is a layer, even when used for intermittent high-feed cutting where particularly large mechanical shock is applied, the upper layer is conventionally only an α-type Al ₂ O ₃ layer. Compared to the conventional coated tool constructed, the hard coating layer exhibits even better chipping resistance, and as a result exhibits excellent wear resistance over a long period of time.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
“On the surface of the tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) It consists of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, and has an overall average layer thickness of 3 to 20 μm. A lower layer composed of a Ti compound layer,
(B) an upper layer comprising an aluminum oxide layer having an average layer thickness of 2 to 15 μm and having an α-type crystal structure in a chemical vapor deposited state;
In the surface-coated cutting tool formed by vapor-depositing the hard coating layer composed of (a) and (b) above,
(C) Surface-polishing an aluminum oxide layer located on the lower layer side and present in a layer thickness region of 30 to 50% of the average layer thickness of the upper layer (b) using a field emission scanning electron microscope Each crystal grain having a hexagonal crystal lattice existing within the measurement range of the plane is irradiated with an electron beam, and the (0001) plane that is the crystal plane of the crystal grain with respect to the normal line of the polished surface and ( 10-10) The inclination angle formed by the normal of the plane is measured. In this case, the crystal grains have a corundum hexagonal close-packed crystal structure in which constituent atoms composed of Al and oxygen are present at lattice points, Based on the measurement tilt angle obtained as a result, lattice points where each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains (constituent atom shared lattice point). And calculate the distribution between the constituent atomic shared lattice points There are N lattice points that do not share constituent atoms (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) In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1 when the existing constituent atomic shared lattice point form is expressed by ΣN + 1, The highest peak is present in Σ3, and the distribution ratio of the Σ3 in the entire ΣN + 1 is 60 to 80%.
A surface-coated cutting tool (coated tool) whose hard coating layer exhibits excellent wear resistance in intermittent high-feed cutting. "
It has the characteristics.

  Hereinafter, the reason why the numerical values of the constituent layers of the hard coating layer of the coated tool of the present invention are limited as described above will be described.

(A) Ti compound layer of the lower layer The Ti compound layer exists as a lower layer of the α-type Al ₂ O ₃ layer, and contributes to improving the high temperature strength of the hard coating layer by its excellent high temperature strength. The substrate and the α-type Al ₂ O ₃ layer are firmly adhered to each other, thereby improving the adhesion of the hard coating layer to the tool substrate. However, when the average layer thickness is less than 3 μm, the above-described operation is sufficiently achieved. On the other hand, if the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation especially in high-speed cutting with high heat generation, which causes uneven wear. Was determined to be 3 to 20 μm.

(B) the conventional α type the Al ₂ O ₃ layer prior α type the Al ₂ O ₃ layer upper layer of the upper layer, as described above, relatively low atom sharing lattice point distribution distribution ratio of 30% or less of Σ3 The graph shows excellent high-temperature hardness and heat resistance, and gives excellent wear resistance to the upper layer of the hard coating layer, but a large mechanical impact is applied to the cutting edge part called intermittent high feed cutting Under cutting conditions, chipping is likely to occur due to impact load, so a part of the conventional α-type Al ₂ O ₃ layer of the upper layer is modified to show excellent chipping resistance against impact load. By replacing with the α-type Al ₂ O ₃ layer, a hard coating layer having excellent high-temperature hardness, heat resistance and excellent impact resistance is formed as the entire upper layer.

(C) Modified α-type Al ₂ O ₃ layer of the upper layer The distribution ratio of Σ3 in the constituent atomic shared lattice distribution graph of the modified α-type Al ₂ O ₃ layer is the AlCl constituting the reaction gas as described above. ₃ , by adjusting the content ratio of CO ₂ and HCl, and further the atmospheric reaction pressure, it can be set to 60 to 80%. In this case, when the distribution ratio of Σ3 is less than 60%, in intermittent high feed cutting, Chipping does not occur in the hard coating layer, and it is not possible to ensure an excellent effect of improving high-temperature strength. Therefore, the higher the distribution ratio of Σ3, the better, but it is desirable to increase the distribution ratio of Σ3 beyond 80%. Since the layer formation is difficult, the distribution ratio of Σ3 is set to 60 to 80%. As described above, the modified α-type Al ₂ O ₃ layer has excellent high-temperature strength. However, when the layer thickness is less than 30% of the average layer thickness (2 to 15 μm) of the entire upper layer, impact resistance is improved. On the other hand, if the layer thickness exceeds 50% of the average layer thickness (2 to 15 μm) of the entire upper layer, the mechanical impact on the cutting edge is extremely high. Since chipping easily occurs, the layer thickness of the modified α-type Al ₂ O ₃ layer is determined to be 30 to 50% of the average layer thickness of the entire upper layer.

(D) Average layer thickness of the upper layer Average layer thickness of the upper layer, which is the total layer thickness of the modified α-type Al ₂ O ₃ layer constituting the upper layer and the layer thickness of the conventional α-type Al ₂ O ₃ layer Is less than 2 μm, the above-mentioned properties of the upper layer composed of the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer cannot be sufficiently provided in the hard coating layer, while the average layer thereof When the thickness exceeds 15 μm, thermoplastic deformation that causes uneven wear tends to occur, and wear accelerates. Therefore, the average layer thickness is set to 2 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 the outermost surface layer of the hard coating layer as necessary, 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 the present invention is a modified α-type Al ₂ O that constitutes the upper layer, particularly when various steels and cast irons are cut under intermittent high-feed cutting conditions with a very large mechanical impact. _The hard coating layer consisting of _three layers and the conventional α-type Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, as well as superior high-temperature strength. It exhibits excellent wear resistance and can further extend the service life.

  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 were blended into the composition shown in Table 1, added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and pressed into a green compact with a predetermined shape at a pressure of 98 MPa. The green compact was 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 portion was R: 0.07 mm honing By processing, tool bases A to F made of a WC-based cemented carbide having a throwaway tip shape defined in ISO · CNMG 160412 were produced.

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 24 hours, dried, and 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, and after the sintering, the cutting edge portion was subjected to a honing process of R: 0.07 mm. Tool bases a to f made of TiCN-based cermet having standard / CNMG 160412 chip shapes were formed.

Next, each of the tool bases A to F and the tool bases a to f was charged into a normal chemical vapor deposition apparatus. First, Table 3 (l-TiCN in Table 3 is disclosed in JP-A-6-8010). The combinations shown in Table 4 under the conditions shown in Table 4 below are the conditions for forming the TiCN layer having the vertically elongated crystal structure described, and other conditions for forming the normal granular crystal structure. Then, a Ti compound layer is deposited as a lower layer of the hard coating layer with a target layer thickness, and then any one of the modified α-type Al ₂ O ₃ layers (a) to (f) under the conditions shown in Table 3 Conventionally, any one of α-type Al ₂ O ₃ layers (a) to (f) is deposited as an upper layer of the hard coating layer with the combinations and target layer thicknesses shown in Table 4 and coated according to the present invention. Tools 1-12 were produced respectively.

For comparison purposes, as shown in Table 5, as the upper layer of the hard coating layer, any one of the conventional α-type Al ₂ O ₃ layers (a) to (f) under the conditions shown in Table 3 is used. Similarly, the conventional coated tools 1 to 12 were manufactured under the same conditions except that they were formed by vapor deposition as the upper layer of the hard coating layer with the combinations and target layer thicknesses shown in Table 5.

Then, for each of the above-mentioned present invention coated tools 1-12, the modified α-type Al ₂ O ₃ layer constituting the upper layer of the hard coating layer of the conventional coated tools 1-12, and the conventional α-type Al ₂ O ₃ layer, Using a field emission scanning electron microscope, constituent atomic shared lattice point distribution graphs were prepared.
That is, the constituent atomic shared lattice point distribution graph shows a mirror of a field emission scanning electron microscope in a state where the surfaces of the modified α-type Al ₂ O ₃ layer and the conventional α-type Al ₂ O ₃ layer are polished surfaces. 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 to each crystal grain existing within the measurement range of the surface polished surface. Using a backscatter diffraction image apparatus, a region of 30 × 50 μm is spaced at a spacing of 0.1 μm / step with respect to the normal line of the surface polished surface (0001) plane and (10 − 10) Measure the tilt angle formed by the normals of the surface, and based on the measured tilt angle obtained as a result, at the interface between adjacent crystal grains, each of the constituent atoms is one between the crystal grains. The number of lattice points that share constituent atoms (constituent atom shared lattice points) N is the number of 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 in terms of distribution frequency) When the upper limit of N is 28, the even number of 4, 8, 14, 24, and 26 does not exist.) When the existing constituent atomic shared lattice point form is expressed as ΣN + 1, each ΣN + 1 occupies the entire ΣN + 1 Created by determining the percentage.

As a result, in the constituent atomic share lattice point distribution graphs of various modified α-type Al ₂ O ₃ layers and conventional α-type Al ₂ O ₃ layers obtained as a result, the entire ΣN + 1 (from the above results, Σ3, Σ7, Σ11, Σ13, The distribution ratios of Σ3 in the total distribution ratios of Σ17, Σ19, Σ21, Σ23, and Σ29) are shown in Tables 4 and 5, respectively.

In each of the above-described various constituent atom sharing lattice point distribution graphs, as shown in Tables 4 and 5, each of the modified α-type Al ₂ O ₃ layers is a constituent atom in which the distribution ratio of Σ3 is 60 to 80%. The shared lattice point distribution graph is shown. On the other hand, the conventional α-type Al ₂ O ₃ layer shows a constituent atomic shared lattice point distribution graph in which the distribution ratio of Σ3 is 30% or less.
4 is a graph showing the distribution of constituent atomic shared lattice points of the modified α-type Al ₂ O ₃ layer of the coated tool 2 of the present invention, and FIG. 5 is a diagram showing constituent atoms of the conventional α-type Al ₂ O ₃ layer of the conventional coated tool 12. Each of the shared grid point distribution graphs is shown.

  Moreover, when the thickness of the constituent layer of the hard coating layer of the present invention coated tools 1 to 12 and the conventional coated tools 1 to 12 obtained as a result was measured using a scanning electron microscope (longitudinal section measurement), Also showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, for the various coated tools of the present invention coated tools 1 to 12 and conventional coated tools 1 to 12, all of them are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS-S53C lengthwise equal length 4 round grooved round bar,
Cutting speed: 200 m / min,
Cutting depth: 3.0 mm,
Feed: 0.4 mm / rev,
Cutting time: 8 minutes,
Dry intermittent high feed cutting test of carbon steel under the conditions (referred to as cutting condition A) (normal feed is 0.2 mm / rev),
Work material: JIS / SNCM439 round direction bar with 4 equal intervals in the length direction,
Cutting speed: 220 m / min,
Cutting depth: 3.5 mm,
Feed: 0.45 mm / rev,
Cutting time: 7 minutes,
Dry interrupted high feed cutting test of alloy steel under the conditions (cutting condition B) (normal feed is 0.15 mm / rev),
Work material: JIS / FCD700 lengthwise equal length 4 round bar with round groove,
Cutting speed: 250 m / min,
Cutting depth: 3.0 mm,
Feed: 0.4 mm / rev,
Cutting time: 8 minutes,
A dry intermittent high feed cutting test (normal feed is 0.2 mm / rev) of ductile cast iron under the conditions (cutting condition C)
In any cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, the present invention coated tools 1 to 12 are constituent atomic shared lattice points in which the upper layer of the hard coating layer is located on the lower layer side and the distribution ratio of Σ3 is 60 to 80%. It is composed of a modified α-type Al ₂ O ₃ layer showing a distribution graph and a conventional α-type Al ₂ O ₃ layer located on the upper layer, and the modified α-type Al ₂ O ₃ layer is also used for intermittent high-feed cutting of steel and cast iron with extremely high mechanical impact. The α-type Al ₂ O ₃ layer has excellent high-temperature strength, and the conventional α-type Al ₂ O ₃ layer has excellent high-temperature hardness and heat resistance, and exhibits excellent chipping resistance and wear resistance. Therefore, the occurrence of chipping in the hard coating layer is remarkably suppressed and excellent wear resistance is exhibited. On the other hand, the upper layer of the hard coating layer has a constituent atom shared lattice point with a Σ3 distribution ratio of 30% or less. conventional coating Engineering consisting only of conventional α form the Al ₂ O ₃ layer showing the distribution graph In 1 to 12, it is clear that intermittent high feed cutting has insufficient mechanical impact resistance of the hard coating layer, so that chipping occurs in the hard coating layer and the service life is reached in a relatively short time. is there.

  As described above, the coated tool of the present invention can be used not only for continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron, but also for intermittent high-feed cutting that requires particularly high mechanical shock resistance. The hard coating layer exhibits excellent chipping resistance and wear resistance, and exhibits excellent cutting performance over a long period of time. It can cope with cost reduction sufficiently.

FIG. 4 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, where (a) is a perspective view and (b) is a plan view of cross sections 1 to 9. . 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. FIG. 4 is a schematic diagram showing unit forms of constituent atomic shared lattice points at the interface between adjacent crystal grains, where (a) shows Σ3, (b) shows Σ7 (c) and Σ11 unit forms. . It is a constituent atom shared lattice point distribution graph of the modified α-type Al ₂ O ₃ layer of the coated tool 2 of the present invention. 4 is a constituent atomic shared lattice point distribution graph of a conventional α-type Al ₂ O ₃ layer of a conventional coated tool 12.

Claims (1)

On the surface of the tool base composed of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
(A) It consists of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride layer, and has an overall average layer thickness of 3 to 20 μm. A lower layer composed of a Ti compound layer,
(B) an upper layer comprising an aluminum oxide layer having an average layer thickness of 2 to 15 μm and having an α-type crystal structure in a chemical vapor deposited state;
In the surface-coated cutting tool formed by vapor-depositing the hard coating layer composed of (a) and (b) above,
(C) Surface-polishing an aluminum oxide layer located on the lower layer side and present in a layer thickness region of 30 to 50% of the average layer thickness of the upper layer (b) using a field emission scanning electron microscope Each crystal grain having a hexagonal crystal lattice existing within the measurement range of the plane is irradiated with an electron beam, and the (0001) plane that is the crystal plane of the crystal grain with respect to the normal line of the polished surface and ( 10-10) The inclination angle formed by the normal of the plane is measured. In this case, the crystal grains have a corundum hexagonal close-packed crystal structure in which constituent atoms composed of Al and oxygen are present at lattice points, Based on the measurement tilt angle obtained as a result, lattice points where each of the constituent atoms shares one constituent atom between the crystal grains at the interface between adjacent crystal grains (constituent atom shared lattice point). And calculate the distribution between the constituent atomic shared lattice points There are N lattice points that do not share constituent atoms (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) In the constituent atomic shared lattice distribution graph showing the distribution ratio of each ΣN + 1 to the entire ΣN + 1 when the existing constituent atomic shared lattice point form is expressed by ΣN + 1, The highest peak is present in Σ3, and the distribution ratio of the Σ3 in the entire ΣN + 1 is 60 to 80%.
A surface-coated cutting tool with a hard coating layer that exhibits excellent wear resistance in intermittent high-feed cutting.

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