JP2010214557A - Surface coated cutting tool with hard coating layer exerting excellent chipping resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface coated cutting tool with a hard coating layer exerting excellent chipping resistance in high speed heavy cutting of a difficult-to-cut material such as stainless steel and tag tile cast iron. <P>SOLUTION: In this surface coated cutting tool, (a) a Ti compound layer as a lower layer, (b) a α type Al<SB>2</SB>O<SB>3</SB>layer as an intermediate layer, and (c) a α type Al<SB>2</SB>O<SB>3</SB>layer containing Cr having a planar polygon-shaped and vertically long shaped crystal grain structure as an upper layer are formed by vapor deposition on a surface of a tool base body. The intermediate layer and the upper layer are composed of the α type Al<SB>2</SB>O<SB>3</SB>layer having a high (0001) plane orientation rate and the α type Al<SB>2</SB>O<SB>3</SB>layer containing Cr, respectively. The inside of the crystal grains of ≥60% in area rate, of the crystal grains of the upper layer, is divided by a crystal lattice interface made of an organized atom common lattice-point form expressed by at least one or more of Σ3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  For example, the present invention performs cutting of difficult-to-cut materials such as stainless steel and ductile cast iron under high-speed heavy cutting conditions in which high heat is generated and high load is applied to the cutting blade due to high feed and high cutting. Even in this case, the present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent wear resistance over a long period of use without causing chipping of the hard coating layer.

Conventionally, on the surface of a base composed of tungsten carbide (hereinafter referred to as WC) base cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) base cermet (hereinafter collectively referred to as a tool base),
(A) The lower layer is formed of one or more of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer, all formed by chemical vapor deposition, and an overall average layer of 3 to 20 μm A Ti compound layer having a thickness;
(B) the upper layer has an average layer thickness of 1 to 15 μm and an α-type crystal structure in the state of chemical vapor deposition;
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 angle formed by the normal line of the (0001) plane, which is the crystal plane, is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are classified for each pitch of 0.25 degrees. In addition, in the inclination angle number distribution graph obtained by summing up the frequencies existing in each section, the highest peak exists in the inclination angle section within the range of 0 to 10 degrees and also exists within the range of 0 to 10 degrees. A Cr-containing aluminum oxide layer showing an inclination angle distribution graph in which the total frequency to be occupied accounts for 45% or more of the entire frequency in the inclination angle distribution graph,
A coated tool (hereinafter referred to as a conventional coated tool) in which the hard coating layer formed by vapor deposition of the hard coating layer composed of the above (a) and (b) exhibits excellent chipping resistance in high-speed intermittent cutting processing is provided. This conventional coated tool is known to exhibit excellent chipping resistance in high-speed intermittent cutting because the Cr-containing aluminum oxide layer has excellent high-temperature strength.
JP 2006-289586 A

  In recent years, the performance of cutting machines 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 along with this, cutting tends to become even faster and more efficient. In the above-mentioned conventional coated tool, there is no particular problem when it is used for high-speed cutting and high-speed interrupted cutting of general steel such as low alloy steel and carbon steel, and further cast iron such as gray cast iron. When this is used for high-speed heavy cutting that is accompanied by high heat generation of difficult-to-cut materials such as stainless steel and ductile cast iron, and high feed and high cutting loads are applied to the cutting blade, it is hard. Since the high-temperature strength and surface properties of the coating layer are not satisfactory, chipping (slight chipping) is likely to occur at the cutting edge, and as a result, the service life is reached in a relatively short time.

  Therefore, the present inventors, from the viewpoint as described above, accompanied by high heat generation, and also when used for high-speed heavy cutting with high feed and high cutting acting on the cutting blade, As a result of diligent research to develop a coated tool that exhibits excellent chipping resistance and wear resistance over a long period of use, the following knowledge was obtained.

(A) The Cr-containing aluminum oxide layer (hereinafter referred to as the conventional Cr-containing Al ₂ O ₃ layer) in the above-described conventional coated tool is formed on the surface of the Ti compound layer as the lower layer, for example, with a normal chemical vapor deposition apparatus ,
First,
Reaction gas composition: by _{volume%, AlCl 3: 2.3~4%,} CrCl 3: 0.04~0.26%, CO 2: 6~8%, HCl: 1.5~3%, H 2 S : 0.05~0.2%, H _2: remainder,
Reaction atmosphere temperature: 750 to 900 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
In this case, Cr-containing Al ₂ O ₃ nuclei are formed, and in this case, the Cr-containing Al ₂ O ₃ nuclei are nuclear thin films having an average layer thickness of 20 to 200 nm (0.02 to 0.2 μm). In addition, the content ratio of Cr in the total amount with Al (Cr / (Al + Cr)) desirably satisfies 0.01 to 0.1 (however, the atomic ratio),
Subsequently, in a state where the Cr-containing Al ₂ O ₃ core thin film was subjected to a heat treatment in a hydrogen atmosphere of 6 to 10 kPa under a condition where the heating atmosphere temperature was raised to 1100 to 1200 ° C.,
Then
Reaction gas composition: by _{volume%, AlCl 3: 2.3~4%,} CrCl 3: 0.04~0.26%, CO 2: 6~8%, HCl: 1.5~3%, H 2 S : 0.05~0.2%, H _2: remainder,
Reaction atmosphere temperature: 1020 to 1050 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
Similarly, it is desirable that the Cr-containing Al ₂ O ₃ layer (Cr content ratio (Cr / (Al + Cr)) in the total amount with Al) satisfies the atomic ratio of 0.01 to 0.1. In the past, a Cr-containing Al ₂ O ₃ layer was formed by vapor deposition.

Then, a conventional Cr-containing the Al ₂ O ₃ layer described above,
Using a field emission scanning electron microscope, as shown in the schematic explanatory diagrams in FIGS. 1A and 1B, an electron beam is individually applied to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface. Irradiation is performed to measure the inclination angle formed by the normal line of the (0001) plane that is the crystal plane of the crystal grain with respect to the normal line of the surface-polished surface. When the measured inclination angle within the range is divided for each pitch of 0.25 degrees and the inclination angle number distribution graph obtained by summing up the frequencies existing in each division is created, the conventional Cr-containing Al ₂ O _{3 is used.} As illustrated in FIG. 2, the layer has a sharp maximum peak in the range of 0 to 10 degrees, and the total number of frequencies existing in the range of 0 to 10 degrees (the total of the frequency and the height of the maximum peak). Is proportional), but the overall frequency in the slope angle distribution graph Accounts for 5% or more will indicate the inclination angle frequency distribution graph,
The above conventional Cr-containing Al ₂ O ₃ layer has excellent high-temperature hardness, heat resistance, and high-temperature strength, and is excellent in mechanical and thermal shock resistance. In the case of vapor deposition, the chipping resistance was excellent even in high-speed intermittent cutting with mechanical thermal shock.

However, as described in the section of the problem to be solved by the invention, the conventional coated tool in which the conventional Cr-containing Al ₂ O ₃ layer is formed as an upper layer of the hard coating layer, such as stainless steel and ductile cast iron, is used. When used for high-speed heavy cutting of difficult-to-cut materials, that is, high-heat generation and high-speed heavy cutting with high feed and high cutting force applied to the cutting edge, the high temperature of the hard coating layer Since the strength and surface properties are not sufficiently satisfactory, there is a problem that chipping (small chipping) tends to occur at the cutting edge portion.

Therefore, the inventors of the present invention have a sharp maximum peak in the range of 0 to 10 degrees in the inclination angle number distribution graph on the lower layer of the conventional coated tool, and in the range of 0 to 10 degrees. An aluminum oxide layer (hereinafter referred to as modified Al ₂ O ₃ ) having an α-type crystal structure with a high (0001) plane orientation ratio, in which the total of the existing frequencies occupies a ratio of 45% or more of the entire frequencies in the inclination angle distribution graph. the) that layers were vapor deposited as an intermediate layer, on top of this modified the Al ₂ O ₃ layer, further, the Cr content the Al ₂ O ₃ layer grain boundary strength is enhanced (hereinafter, the modified Cr-containing Al ₂ O the) of _3-layer as an upper layer, the structure of the hard coating layer, the lower layer, by forming a three-layer structure of the intermediate layer and the upper layer, to form an excellent hard coating layer high-temperature strength and surface properties That, even this high temperature strength and surface Even when used for high-speed heavy cutting of difficult-to-cut materials such as stainless steel and ductile cast iron, the coated tool with a hard coating layer with excellent properties does not cause chipping (small chipping) at the cutting edge, and is long-term It has been found that it exhibits excellent tool properties over use.

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) the lower layer is formed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer, all formed by chemical vapor deposition; And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) the intermediate layer has an average layer thickness of 1 to 5 μm, and an aluminum oxide layer having an α-type crystal structure in the state of chemical vapor deposition;
(C) the upper layer has an average layer thickness of 2 to 15 μm, and a Cr-containing aluminum oxide layer having an α-type crystal structure in the state of chemical vapor deposition;
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) to (c) is formed by vapor deposition,
(D) The intermediate layer of (b) is irradiated with an electron beam on each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface of the tool base using a field emission scanning electron microscope. Then, the inclination angle formed by the normal line of the (0001) plane that is the crystal plane of the crystal grain is measured with respect to the normal line of the surface polished surface, and is within a range of 0 to 45 degrees of the measurement inclination angle. When the measured tilt angle is divided into pitches of 0.25 degrees and the frequency existing in each section is tabulated, the tilt angle is within a range of 0 to 10 degrees. A slope angle distribution graph in which the highest peak exists in the section and the total of the frequencies existing in the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire frequencies in the slope angle distribution graph,
(E) The upper layer of (c) is a flat polygonal shape in a plane perpendicular to the layer thickness direction and a layer in a plane parallel to the layer thickness direction when the structure is observed with a field emission scanning electron microscope. A Cr-containing aluminum oxide layer having a structure composed of crystal grains having a long shape in the thickness direction,
Further, with respect to the upper layer of (c), an electron beam is irradiated to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface of the tool base using a field emission scanning electron microscope. The inclination angle formed by the normal line of the (0001) plane, which is the crystal plane of the crystal grain, is measured with respect to the normal line of the surface polished surface, and is within a range of 0 to 45 degrees of the measured inclination angle. When a certain tilt angle is divided into pitches of 0.25 degrees, and the tilt angle distribution graph is formed by summing up the frequencies existing in each section, the tilt angle sections within the range of 0 to 10 degrees An inclination angle number distribution graph in which the highest peak is present and the total frequency within the range of 0 to 10 degrees occupies a ratio of 60% or more of the entire frequency in the inclination angle distribution graph,
Further, the upper layer of the above (c) is irradiated with an electron beam on each crystal grain existing within the measurement range of the surface polished surface using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, thereby obtaining a hexagonal crystal. Measures the angle at which each normal of the crystal lattice plane consisting of crystal lattices intersects the normal of the substrate surface, and calculates the crystal orientation relationship between adjacent crystal lattices from this measurement result, and configures the crystal lattice interface The distribution of lattice points (constituent atom shared lattice points) in which each atom shares one constituent atom between the crystal lattices is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points are calculated. (However, N is an even number of 2 or more due to the crystal structure of the corundum hexagonal close-packed crystal. However, when the upper limit of N is 28 from the point of distribution frequency, even numbers of 4, 8, 14, 24 and 26 exist. Without) sharing existing constituent atoms When the child dot form is represented by ΣN + 1, the crystal grains having an area ratio of 60% or more among the crystal grains constituting the upper layer of the above (c) are represented by at least one Σ3 It is a Cr-containing aluminum oxide layer divided by a crystal lattice interface composed of atomic shared lattice point form,
A surface-coated cutting tool characterized by that.
(2) When the upper layer of (c) is observed with a field emission scanning electron microscope, a flat hexagonal shape in a plane perpendicular to the layer thickness direction and a layer thickness in a plane parallel to the layer thickness direction The surface-coated cutting tool according to (1), wherein the crystal grains having a long shape in the direction occupy an area ratio of 35% or more of the whole in a plane perpendicular to the layer thickness direction.
(3) The surface-coated cutting tool according to either (1) or (2), wherein the upper layer of (c) has a surface roughness (Ra) in a range of 0.05 to 0.3 μm. "
It has the characteristics.

Below, the constituent layer of the hard coating layer of the coated tool of this invention is demonstrated in detail.
(A) Ti compound layer (lower layer)
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 carbonitriding The Ti compound layer composed of one or more of the material layers (hereinafter referred to as TiCNO) is basically present as a lower layer of the modified Al ₂ O ₃ layer as an intermediate layer. Excellent toughness and wear resistance contribute to improving the high-temperature strength of the hard coating layer, and also firmly adheres to both the tool substrate and the modified Al ₂ O ₃ layer, and thus the adhesion of the hard coating layer to the tool substrate Although it has an effect that contributes to improvement, if the total average layer thickness is less than 3 μm, the above-mentioned effect cannot be sufficiently exhibited. On the other hand, if the total average layer thickness exceeds 20 μm, high heat is generated and the cutting edge High speed heavy load In cutting conditions easily cause thermal plastic deformation, which is because the cause of the uneven wear, defining a total average layer thickness thereof and 3 to 20 [mu] m.

(B) Modified Al ₂ O ₃ layer (intermediate layer)
The modified Al ₂ O ₃ layer constituting the intermediate layer is
Using normal chemical vapor deposition equipment,
Reaction gas composition:% by volume, AlCl ₃ : 3 to 10%, CO ₂ : 0.5 to 3%, C ₂ H ₄ : 0.01 to 0.3%, H ₂ : remaining,
Reaction atmosphere temperature: 750 to 900 ° C.
Reaction atmosphere pressure: 3 to 13 kPa,
Under these low temperature conditions, Al ₂ O ₃ nuclei are formed on the surface of the lower Ti compound layer. In this case, the Al ₂ O ₃ nuclei are Al ₂ O ₃ nuclei thin films having an average layer thickness of 20 to 200 nm. desirable that, subsequently, the reaction atmosphere pressure: changed to a hydrogen atmosphere of 3～13KPa, while subjected to heat treatment to the Al ₂ O ₃ nuclei film under conditions by elevating the temperature of the reaction atmosphere temperature to 1100 to 1200 ° C. The α-type Al ₂ O ₃ layer as a hard coating layer can be formed under normal conditions, and the α-type Al ₂ O ₃ layer can be deposited on the heat-treated Al ₂ O ₃ core thin film.

Then, for the above reforming the Al ₂ O ₃ layer which is chemically deposited on the lower layer, using a field emission scanning electron microscope, FIG. 1 (a), the measurement range of the street, surface polishing surface shown in (b) The crystal grains having a hexagonal crystal lattice existing therein are irradiated with electron beams, and the normal of the (0001) plane, which is the crystal plane of the crystal grains, is inclined with respect to the normal of the surface polished surface The angle is measured, and the measured inclination angle within the range of 0 to 45 degrees is divided into 0.25 degree pitches among the measured inclination angles, and the degrees existing in the respective sections are totaled. When represented by an angle distribution graph, as illustrated in FIG. 2, a sharp maximum peak appears in the range of the tilt angle section 0 to 10 degrees, and exists in the range of the tilt angle section 0 to 10 degrees. The total frequency is 45% or more of the total frequency in the slope angle distribution graph. Shows an inclination angle frequency distribution graph occupying case, the modified Al ₂ O ₃ layer is seen that a high (0001) plane orientation ratio.
This modified Al ₂ O ₃ layer has excellent high temperature hardness and heat resistance, as well as excellent high temperature strength. However, the modified Al ₂ O ₃ layer formed as an intermediate layer has a (0001) plane orientation. By configuring as an intermediate layer having a high rate, the (0001) plane orientation rate of the modified Cr-containing Al ₂ O ₃ layer deposited on this can be increased, and as a result, the modified Cr-containing It is possible to improve the surface properties of the upper layer made of the Al ₂ O ₃ layer and improve the high temperature strength.
However, it is impossible to allowed to sufficiently equipped with the properties possessed by the modified Al ₂ O ₃ layer to the hard coating layer has an average layer thickness of the intermediate layer made of reforming the Al ₂ O ₃ layer is less than 1 [mu] m, while its If the average layer thickness exceeds 5 μm, the high heat generated during cutting and the high load acting on the cutting edge will tend to cause thermoplastic deformation that causes uneven wear, and the wear will accelerate. The layer thickness was determined to be 1 to 5 μm.

(C) Modified Cr-containing Al ₂ O ₃ layer (upper layer)
The upper layer composed of the modified Cr-containing Al ₂ O ₃ layer chemically vapor-deposited on the intermediate layer has an Al component that is a constituent component to improve the high-temperature hardness and heat resistance of the layer. Cr component containing a trace amount (Cr / (Al + Cr) in the proportion of the total amount with Al 0.01 to 0.1 (however, atomic ratio)) is a crystal of the modified Cr-containing Al ₂ O ₃ layer. Although the grain boundary strength is improved and it contributes to the improvement of the high temperature strength, when the content ratio of the Cr component is less than 0.01, the above effect cannot be expected, while the content ratio of the Cr component is 0.1. If exceeded, the grain interface strength decreases due to the precipitation of Cr oxide particles in the layer, so the content ratio of the Cr component in the total amount with the Al component (value of Cr / (Al + Cr) ratio) Is preferably 0.01 to 0.1 (however, atomic ratio).

The modified Cr-containing Al ₂ O ₃ layer can be formed by vapor deposition by adjusting the chemical vapor deposition conditions of the reaction gas composition, reaction atmosphere temperature, and reaction atmosphere pressure at the time of vapor deposition, for example.
First of all,
(B) Reaction gas composition (volume%):
AlCl ₃ : 2.3 to 4%,
CrCl ₃ : 0.04 to 0.26%,
CO ₂ : 6-8%,
HCl: 1.5-3%,
H ₂ S: 0.05~0.2%,
H ₂ : Remaining
(B) Reaction atmosphere temperature; 930-970 ° C.,
(C) Reaction atmosphere pressure; 6 to 10 kPa,
After performing deposition for about 1 hour under the above conditions (hereinafter referred to as initial conditions),
next,
(B) Reaction gas composition (volume%):
AlCl ₃ : 2.3 to 4%,
CrCl ₃ : 0.04 to 0.26%,
CO ₂ : 6-8%,
HCl: 1.5-3%,
H ₂ S: 0.05~0.2%,
H ₂ : Remaining
(B) Reaction atmosphere temperature; 1020 to 1050 ° C.,
(C) Reaction atmosphere pressure; 6 to 10 kPa,
When the vapor deposition layer having an average layer thickness of 2 to 15 μm is formed by performing vapor deposition under the following conditions (hereinafter referred to as film formation conditions), the value of the ratio of Cr / (Al + Cr) is 0.01 to 0 in atomic ratio. A modified Cr-containing Al ₂ O ₃ layer that is .1 can be formed.

When the microstructure of the modified Cr-containing Al ₂ O ₃ layer is observed with a field emission scanning electron microscope, as shown in FIG. 3A, when viewed in a plane perpendicular to the layer thickness direction, It has a flat plate polygonal shape with a large crystal grain size, and as shown in FIG. 3 (b), the layer surface is substantially flat when viewed in a plane parallel to the layer thickness direction. A texture structure composed of crystal grains having a long shape in the thickness direction (flat plate-shaped long crystal grains) is formed.

In the modified Cr-containing Al ₂ O ₃ layer, the normal line of the (0001) plane is formed with respect to the normal line of the surface polished surface, as in the case of the modified Al ₂ O ₃ layer constituting the intermediate layer. When an inclination angle number distribution graph is created by measuring the inclination angle, a peak exists in the inclination angle range of 0 to 10 degrees, and the sum of the frequencies in the range of 0 to 10 degrees is the inclination angle number distribution graph. The inclination angle distribution graph which occupies the ratio of 60% or more of the whole frequency in is shown, and it can be seen that the (0001) plane orientation rate of the modified Cr-containing Al ₂ O ₃ layer constituting the upper layer is high.
That is, the reforming Cr containing the Al ₂ O ₃ layer, since an intermediate layer of reforming the Al ₂ O ₃ layer (0001) plane orientation ratio is formed as more than 45%, modified Cr-containing Al _{The 2} O ₃ layer is also formed as a layer having a high (0001) plane orientation ratio (the (0001) plane orientation ratio is 60% or more).
When the upper layer is viewed in a plane parallel to the layer thickness direction, the layer surface is formed in a substantially flat plate shape and exhibits excellent surface properties. As a result, the conventional Cr-containing Al ₂ O ₃ layer Compared to the above, it shows excellent chipping resistance.

Further, in the vapor deposition of the modified Cr-containing Al ₂ O ₃ layer, a more limited condition (for example, (relatively) the ratio of HCl gas and H ₂ S gas is increased in the initial condition and film forming condition, Further, when the vapor deposition is performed under the condition that the reaction atmosphere pressure is lowered, as shown in FIG. 3C, when viewed in a plane perpendicular to the layer thickness direction, a flat hexagonal shape with a large particle size is obtained. When viewed in a plane parallel to the layer thickness direction, the layer surface is substantially flat, as shown in FIG. 3B, and the crystal grains having a long shape in the layer thickness direction are formed. Thus, a tissue structure occupying an area ratio of 35% or more of the whole in a plane perpendicular to the layer thickness direction is formed.

Further, with respect to the modified Cr-containing Al ₂ O ₃ layer, a field emission scanning electron microscope and an electron backscatter diffraction image apparatus were used to irradiate each crystal grain existing within the measurement range of the surface polished surface with an electron beam. Measuring the angle at which each normal of the crystal lattice plane consisting of hexagonal crystal lattice intersects the normal of the surface polished surface,
From this measurement result, the crystal orientation relationship between adjacent crystal lattices is calculated, and each of the constituent atoms constituting the crystal lattice interface shares one constituent atom between the crystal lattices (constituent atom shared lattice point). ) And 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 the distribution frequency) When the upper limit of N is 28 from this point, the even number of 4, 8, 14, 24 and 26 does not exist.)
As shown in FIG. 4, among the flat polygonal long crystal grains constituting the modified AlZrO layer observed with a field emission scanning electron microscope, the above flat plate polygons (including flat hexagons) are formed. It can be seen that among the long crystal grains, the interior of the crystal grains having an area ratio of 60% or more is divided by at least one Σ3-compatible interface.
Further, the presence of the above-described Σ3-corresponding interface in the long-sided crystal grains (including flat hexagons) of the modified Cr-containing Al ₂ O ₃ layer improves the intra-grain strength. As a result, during high-speed heavy cutting of difficult-to-cut materials with high load acting on the cutting edge under high temperature conditions, it is possible to suppress the occurrence of cracks in the modified Cr-containing Al ₂ O ₃ layer, Even if a crack occurs, the growth and propagation of the crack is hindered, and the chipping resistance, chipping resistance, and peel resistance are improved.

Therefore, the modified Cr-containing material has a high (0001) plane orientation ratio and a flat surface property, and a sigma-compatible interface exists inside a long plate crystal polygon (including a flat hexagon). The upper layer of the present invention consisting of an Al ₂ O ₃ layer is accompanied by high heat generation, high feed of difficult-to-cut materials such as stainless steel, ductile cast iron, etc., where high load acts on the cutting blade, high cutting, high speed heavy cutting Even during processing, chipping, chipping, peeling, etc. do not occur, and there is no occurrence of thermoplastic deformation, uneven wear, etc., and excellent chipping resistance and wear resistance are exhibited over a long period of time.
However, if the thickness of the upper layer composed of the modified Cr-containing Al ₂ O ₃ layer is less than 2 μm, the excellent characteristics of the upper layer cannot be fully exhibited, while the thickness of the upper layer is 15 μm. If it exceeds, thermoplastic deformation that causes uneven wear is likely to occur, and chipping is also likely to occur. Therefore, the average layer thickness of the upper layer is set to 2 to 15 μm.

For reference, with respect to a conventional Cr-containing Al ₂ O ₃ layer (described in Patent Document 1), a field emission scanning electron microscope and an electron backscatter diffraction image apparatus were used, and the crystal structure and structure of the upper layer crystal grains. As a result of investigating the atomic shared lattice point form, the structure of the crystal grain has a pyramidal asperity as shown in FIGS. 5 (a) and 5 (b). Therefore, the wear resistance was insufficient as compared with the modified Cr-containing Al ₂ O ₃ layer.
In addition, regarding the constituent atomic shared lattice point form of the crystal grain, the area ratio of the crystal grain in which the Σ3-corresponding interface exists in the concave and convex polygonal long crystal grain that conventionally constitutes the Cr-containing Al ₂ O ₃ layer is It was as low as 40% or less, and it could not be said that improvement in the strength within the crystal grains was achieved.
Therefore, the conventional coated tool in which the upper layer of the hard coating layer is composed of the conventional Cr-containing Al ₂ O ₃ layer is difficult to produce such as stainless steel or ductile cast iron that is accompanied by high heat generation and high load acting on the cutting edge. In the high-speed heavy cutting of the cutting material, generation of chipping, chipping, peeling, etc. cannot be prevented, and thermoplastic deformation, partial wear, etc. occur, and the tool performance is inferior.

Further, in the coated tool of the present invention, after forming the modified Cr-containing Al ₂ O ₃ layer of the upper layer, the surface thereof is subjected to polishing treatment with a grindstone or polishing treatment with wet blasting, etc. The surface roughness of the contained Al ₂ O ₃ layer can be further adjusted. For example, by adjusting the surface roughness of the modified Cr-containing Al ₂ O ₃ layer to Ra 0.05 to 0.3 μm, it is possible to suppress the occurrence of welding to the surface-coated tool during cutting.
In addition, surface roughness Ra as used in the field of this invention means the value of arithmetic mean roughness Ra prescribed | regulated by JISB0601 (1994), and the measuring method is not specifically limited.

As described above, the coated tool of the present invention has a high (0001) plane orientation ratio, and has a modified Al ₂ O ₃ layer having an excellent high-temperature strength in addition to excellent high-temperature hardness and heat resistance as an intermediate layer. At the same time, by increasing the (0001) plane orientation ratio of the modified Cr-containing Al ₂ O ₃ layer constituting the upper layer, a flat plate polygon (including a flat hexagon) having a long shape with surface flatness It has a structure composed of crystal grains, and further, by forming a Σ3-compatible interface inside the crystal grains and strengthening the strength within the crystal grains, Compared with the conventional Cr-containing Al ₂ O ₃ layer with few Σ3 interfaces, it has superior surface properties and high-temperature strength, resulting in high heat generation, high feed to the cutting edge, and high cutting depth Stainless steel, ductile cast iron, etc. Even in high-speed heavy cutting of difficult-to-cut materials, the hard coating layer exhibits excellent chipping resistance, chipping resistance, and peeling resistance, and excellent wear resistance, and the service life can be further extended.

  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, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder and Co powder each having an average particle diameter of 2 to 4 μm are prepared. The powder was blended into the blending composition shown in Table 1, further added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 105 MPa. The powder is 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 is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to E made of a WC-based cemented carbide having a throwaway tip shape specified in ISO / CNMG120408 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 e made of TiCN base cermet having a standard / CNMG120408 chip shape were formed.

Then, each of these tool bases A to E and tool bases a to e is charged into a normal chemical vapor deposition apparatus,
(A) First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically elongated crystal structure described in JP-A-6-8010, and the other conditions are ordinary granularity. Under the conditions shown in Table 7), the Ti compound layer having the target layer thickness shown in Table 7 is deposited as the lower layer of the hard coating layer.
(B) Next, under the conditions shown in Table 4, the modified Al ₂ O ₃ layer having the target layer thickness shown in Table 8 is vapor-deposited as an intermediate layer of the hard coating layer,
(C) Next, according to the vapor deposition conditions (initial conditions and film formation conditions) shown in Table 5, the modified Cr-containing Al ₂ O ₃ layer having the target layer thickness shown in Table 8 is used as the upper layer of the hard coating layer. The coated tools 1 to 15 of the present invention were manufactured by vapor deposition.

For comparison purposes, a Ti compound layer having a target layer thickness shown in Table 7 was deposited as a lower layer of the hard coating layer under the conditions shown in Table 3, and then the conditions shown in Table 6 (cores) Forming conditions and film forming conditions (corresponding to the deposition conditions of the conventional Cr-containing Al ₂ O ₃ layer disclosed in Patent Document 1), the conventional Cr-containing Al ₂ O ₃ layer having the target layer thickness shown in Table 9 is hard Conventionally, the conventional coated tools 1 to 15 were produced by vapor deposition as the upper layer of the coating layer.
The tool base type, the lower layer type, and the lower layer thickness of the conventional coated tools 1 to 15 are the same as those of the present coated tools 1 to 15, respectively.

Moreover, some modification Cr containing the Al ₂ O ₃ layer of the present invention coated tool, some of the surface of the conventional Cr-containing the Al ₂ O ₃ layer of the conventional coated tools, the projection pressure 0.15 MPa, A post-treatment consisting of a wet blast treatment was performed with 200 mesh Al ₂ O ₃ particles. Note that the post-processing may be a polishing process using an elastic grindstone.
Tables 8 and 9 show the modified Cr-containing Al ₂ O ₃ layer of the present invention-coated tool subjected to post-treatment (marked with * in Table 8), the conventional Cr-containing Al of the conventional coated tool. The value of the surface roughness (Ra (μm)) of the ₂ O ₃ layer (indicated by * in Table 9) is shown.
(For reference, the Ra values for the present coated tool and the conventional coated tool that have not been post-processed are also shown in Tables 8 and 9.)

Subsequently, the modified Al ₂ O ₃ layer constituting the intermediate layer of the hard coating layer of the above-described coated tools 1 to 15 of the present invention, the modified Cr-containing Al ₂ O ₃ layer constituting the upper layer, and the conventional coated tool With respect to 1 to 15 conventional Cr-containing Al ₂ O ₃ layers, inclination angle number distribution graphs were respectively created using a field emission scanning electron microscope.
In other words, the inclination angle number distribution graph is shown in the column of the field emission scanning electron microscope with the respective surfaces of the present invention coated tools 1 to 15 and the conventional coated tools 1 to 15 being polished surfaces. A crystal grain having a hexagonal crystal lattice existing in the measurement range of each surface polished surface with an electron beam with an acceleration voltage of 15 kV and an irradiation current of 1 nA at an incident angle of 70 degrees on the polished surface. Individually irradiated, using an electron backscatter diffraction image apparatus, a region of 30 × 50 μm at a spacing of 0.1 μm / step is a crystal plane of the crystal grain with respect to the normal of the polished surface (0001 ) The inclination angle formed by the normal of the surface is measured, and based on the measurement result, the measurement inclination angle within the range of 0 to 45 degrees of the measurement inclination angles is divided for each pitch of 0.25 degrees. As well as the frequencies present in each category By aggregate was prepared inclination angle frequency distribution graph.
As an example of the inclination angle number distribution graph, FIG. 2 shows an inclination angle number distribution graph of the (0001) plane prepared for the modified Al ₂ O ₃ layer constituting the intermediate layer of the hard coating layer of the present coated tool 14. .
The “surface” in the present invention includes not only a surface parallel to the substrate surface but also a surface inclined with respect to the substrate surface, for example, a cut surface of a layer.

Reforming the Al ₂ O ₃ layer of the resulting present invention coated tool, reforming Cr containing the Al ₂ O ₃ layer, and the inclination angle frequency distribution of the conventional Cr-containing the Al ₂ O ₃ layer prior coated tools 1 to 15 In the graph, as shown in Table 8 and Table 9, respectively, the modified Al ₂ O ₃ layer and the modified Cr-containing Al ₂ O ₃ layer of the coated tool of the present invention have a distribution of measured inclination angles on the (0001) plane, An inclination angle number distribution graph in which the highest peak appears in each inclination angle section within the range of 0 to 10 degrees is shown.
Similarly, the conventional Cr-containing Al ₂ O ₃ layers of the conventional coated tools 1 to 15 similarly have an inclination angle at which the highest peak appears in the inclination angle section where the distribution of measured inclination angles on the (0001) plane is in the range of 0 to 10 degrees. A number distribution graph was shown.
Tables 8 and 9 show the ratio of the frequency existing in the tilt angle section within the range of 0 to 10 degrees to the entire tilt angle number distribution graph.

Next, a conventional Cr-containing the Al ₂ O ₃ layer of reforming Cr containing the Al ₂ O ₃ layer and the conventional coated tool 15 constituting the upper layer of the present invention described above coated tools 1 to 15, the field emission scanning electron microscope Using an electron backscatter diffraction image apparatus, the grain structure and the constituent atomic shared lattice point morphology were investigated.
That is, first, a conventional Cr-containing the Al ₂ O ₃ layer of reforming Cr containing the Al ₂ O ₃ layer and the conventional coated tools 1 to 15 of the present invention described above coated tools 1 to 15, using a field emission scanning electron microscope As a result of the observation, in the coated tools 1 to 15 according to the present invention, crystals of a flat plate polygon (including a flat hexagon) and a long shape, which are representatively shown in FIGS. A grain structure was observed (note that FIG. 3 (a) is a schematic diagram of the structure of the coated tool 1 of the present invention viewed in a plane perpendicular to the layer thickness direction, and FIG. FIG. 2 is a schematic diagram of the structure of the coated tool 11 of the present invention as viewed in a plane perpendicular to the direction and composed of crystal grains having a large hexagonal shape and a long shape with a large particle size).
On the other hand, in the conventional coated tools 1 to 15, as typically shown in FIGS. 5 (a) and 5 (b), a polygonal and elongated crystal grain structure was observed. The diameter was smaller than that of the present invention, and as is clear from FIG. 5B, pyramidal irregularities were formed on the surface of the layer (note that FIGS. 5A and 5B). ) Is a schematic diagram of the structure of the conventional coated tool 1).

Next, with respect to the modified Cr-containing Al ₂ O ₃ layer of the present invention-coated tools 1 to 15 and the conventional Cr-containing Al ₂ O ₃ layer of the conventional coated tools 1 to 15, the inside of the crystal grains constituting each layer The area ratio of the crystal grains where the Σ3-corresponding interface exists was measured.
First, the modified Cr-containing Al ₂ O ₃ layers of the above-described coated tools 1 to 15 of the present invention are set in a lens barrel of a field emission scanning electron microscope in a state where the surface is a polished surface, and the surface polishing is performed. An electron beam with an acceleration voltage of 15 kV at an incident angle of 70 degrees on the surface is irradiated with an electron beam to each crystal grain having a hexagonal crystal lattice existing within the measurement range of each polished surface with an irradiation current of 1 nA. Then, using an electron backscatter diffraction image apparatus, the angle at which each normal line of each crystal lattice plane of the crystal grain intersects the normal line on the substrate surface is measured in a 30 × 50 μm region at an interval of 0.1 μm / step. From this measurement result, the crystal orientation relationship between adjacent crystal lattices is calculated, and each of the constituent atoms constituting the crystal lattice interface shares one constituent atom between the crystal lattices (constituent atom sharing). Distribution of grid points) 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, When the upper limit is 28, there is no even number of 4, 8, 14, 24, and 26) Measurement of the modified Cr-containing Al ₂ O ₃ layer in the case where the existing constituent atomic lattice point form is represented by ΣN + 1 Among all the crystal grains existing in the range, the area ratio of crystal grains in which at least one Σ3 corresponding interface is present inside the crystal grain is obtained, and the value is expressed as a Σ3 corresponding interface ratio (%). This is shown in FIG.
Next, with respect to the conventional Cr-containing Al ₂ O ₃ layers of the conventional coated tools 1 to 15, all the crystals existing within the measurement range of the conventional Cr-containing Al ₂ O ₃ layer are obtained by the same method as in the case of the coated tool of the present invention. Among the grains, the area ratio of the crystal grains in which at least one Σ3-corresponding interface exists inside the crystal grains was determined, and the value is shown in Table 9 as the Σ3-compatible interface ratio (%).

As shown in Tables 8 and 9, in the modified Cr-containing Al ₂ O ₃ layer of the coated tools 1 to 15 of the present invention, the area ratio of the crystal grains in which at least one Σ3 corresponding interface exists in the crystal grains is Whereas it is 60% or more, in the conventional Cr-containing Al ₂ O ₃ layer of the conventional coated tools 1 to 15, the area ratio of crystal grains in which at least one Σ3 corresponding interface exists inside the crystal grains is 40 It can be seen that the ratio of the interface corresponding to Σ3 in the crystal grains is very small.

Further, the conventional Cr-containing the Al ₂ O ₃ layer of reforming Cr containing the Al ₂ O ₃ layer and the conventional coated tools 1 to 15 of the present invention coated tools 11 to 15, using a field emission scanning electron microscope, the layer thickness direction The area ratio of large hexagonal crystal grains having a large particle diameter in a plane perpendicular to the surface area was determined. These values are shown in Tables 8 and 9.
In addition, the crystal grains of the “large hexagonal flat hexagonal shape” mentioned here are:
“The diameter of particles existing in a plane perpendicular to the layer thickness direction observed by a field emission scanning electron microscope is measured, the average value of 10 particles is 3 to 8 μm, and the vertex angle is 100 to 140 °. It is a polygonal shape with six apex angles. "
It is defined as

  Subsequently, the thickness of each constituent layer of the hard coating layer of the present coated tool 1-15, conventional coated tool 1-15 was measured using a scanning electron microscope (longitudinal cross section measurement), in either case, The average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness was shown.

Next, for the above-mentioned coated tools 1-15 of the present invention and the conventional coated tools 1-15, both are screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / SUS316 round bar,
Cutting speed: 240 m / min. ,
Cutting depth: 1.0 mm,
Feed: 0.45 mm / rev. ,
Cutting time: 5 minutes,
Wet high-speed high-feed cutting test of stainless steel under the following conditions (referred to as cutting condition A) (normal cutting speed and feed are 120 m / min. And 0.3 mm / rev., Respectively),
Work material: JIS / FCD700 round bar,
Cutting speed: 240 m / min. ,
Cutting depth: 1.0 mm,
Feed: 0.7 mm / rev. ,
Cutting time: 5 minutes,
Wet high-speed high-feed cutting test of normal cast iron under the following conditions (referred to as cutting condition B) (normal cutting speed and feed are 150 m / min. And 0.4 mm / rev., Respectively),
Work material: JIS / SMn438 round bar,
Cutting speed: 120 m / min. ,
Cutting depth: 5.5 mm,
Feed: 0.3 mm / rev. ,
Cutting time: 5 minutes,
Wet high-speed high-cut cutting test of high manganese steel under the following conditions (referred to as cutting condition C) (normal cutting speed and cutting are 80 m / min. And 2.5 mm, respectively),
In each cutting test, the flank wear width of the cutting edge was measured. The measurement results are shown in Table 10.

From the results shown in Tables 8 to 10, the inventive coated tools 1 to 15 show a high ratio in which the (0001) plane orientation ratio of the modified Al ₂ O ₃ layer, which is an intermediate layer of the hard coating layer, is 45% or more. In addition to having excellent high-temperature strength, the modified Cr-containing Al ₂ O ₃ layer constituting the upper layer has a structure of a flat plate polygonal (flat hexagonal) elongated crystal grain, The (0001) plane orientation ratio is a high ratio of 60% or more, and the crystal grain area ratio in which at least one Σ3-compatible interface exists in the crystal grains is as high as 60% or more, or In addition, the modified Cr-containing Al ₂ O ₃ layer is post-treated and its surface smoothness is improved, so that the modified Cr-containing Al ₂ O ₃ layer is further improved in high-temperature strength and in-grain strength. And also has excellent surface flatness High-speed heavy cutting of difficult-to-cut materials such as stainless steel, ductile cast iron, etc. with high heat generation, high feed to the cutting edge, and high load due to high depth of cut. In addition to exhibiting excellent wear resistance over a long period of use, it is possible to further extend the service life.
On the other hand, in the conventional coated tools 1 to 15 in which the hard coating layer is composed of a Ti compound layer and a conventional Cr-containing Al ₂ O ₃ layer, it is clear that the service life is reached in a relatively short time due to chipping and the like. is there.

  As described above, the coated tool of the present invention is not only for cutting under normal conditions such as various types of steel and cast iron, but also involves high heat generation, high feed to the cutting edge, and high load due to high cutting. Even in high-speed heavy cutting of difficult-to-cut materials such as stainless steel and ductile cast iron, it exhibits excellent wear resistance without occurrence of chipping and exhibits excellent cutting performance over a long period of time. It can fully satisfy the performance, labor saving and energy saving of cutting, and cost reduction.

It is a schematic diagram illustrating a measurement range of the inclination angle in the case of measuring the (0001) plane crystal grains of the α-type the Al ₂ O ₃ layer constituting the hard coating layer. It is an inclination angle number distribution graph of the (0001) plane of the modified Al ₂ O ₃ layer constituting the intermediate layer of the hard coating layer of the coated tool 6 of the present invention. (A) is a flat plate obtained by observing the upper layer of the modified Cr-containing Al ₂ O ₃ layer of the coated tool 1 of the present invention with a field emission scanning electron microscope in a plane perpendicular to the layer thickness direction. It is a schematic diagram which shows a polygonal-shaped crystal grain structure structure, (b) is a layer surface obtained by observation with a field emission scanning electron microscope in a plane parallel to the layer thickness direction. FIG. 4 is a schematic diagram showing a crystal grain structure having a long shape in the layer thickness direction, and (c) shows a layer for an upper layer made of the modified Cr-containing Al ₂ O ₃ layer of the coated tool 11 of the present invention. It is a schematic diagram showing a flat hexagonal crystal grain structure structure obtained by observation with a field emission scanning electron microscope in a plane perpendicular to the thickness direction. Grain boundaries in a plane perpendicular to the layer thickness direction of the upper layer composed of the modified Cr-containing Al ₂ O ₃ layer of the coated tool 1 of the present invention, measured using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus It is an analysis figure, a solid line shows the tabular polygonal crystal grain boundary observed with a field emission scanning electron microscope, and a broken line shows a Σ3-corresponding interface in the crystal grain measured by an electron backscatter diffraction image apparatus . (A) is a conventional coating an upper layer made of a conventional Cr-containing the Al ₂ O ₃ layer of the tool 1, obtained by observation with a field emission scanning electron microscope in a plane perpendicular to the thickness direction, of the polygonal FIG. 4B is a schematic diagram showing a crystal grain structure, and FIG. 5B shows pyramidal irregularities on the layer surface obtained by observation with a field emission scanning electron microscope in a plane parallel to the layer thickness direction. FIG. 6 is a schematic diagram showing a crystal grain structure having a long shape in the layer thickness direction.

Claims (3)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) the lower layer is formed of one or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride oxide layer, all formed by chemical vapor deposition; And a Ti compound layer having a total average layer thickness of 3 to 20 μm,
(B) the intermediate layer has an average layer thickness of 1 to 5 μm, and an aluminum oxide layer having an α-type crystal structure in the state of chemical vapor deposition;
(C) the upper layer has an average layer thickness of 2 to 15 μm, and a Cr-containing aluminum oxide layer having an α-type crystal structure in the state of chemical vapor deposition;
In the surface-coated cutting tool in which the hard coating layer composed of the above (a) to (c) is formed by vapor deposition,
(D) The intermediate layer of (b) is irradiated with an electron beam on each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface of the tool base using a field emission scanning electron microscope. Then, the inclination angle formed by the normal line of the (0001) plane that is the crystal plane of the crystal grain is measured with respect to the normal line of the surface polished surface, and is within a range of 0 to 45 degrees of the measurement inclination angle. When the measured tilt angle is divided into pitches of 0.25 degrees and the frequency existing in each section is tabulated, the tilt angle is within a range of 0 to 10 degrees. A slope angle distribution graph in which the highest peak exists in the section and the total of the frequencies existing in the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire frequencies in the slope angle distribution graph,
(E) The upper layer of (c) is a flat polygonal shape in a plane perpendicular to the layer thickness direction and a layer in a plane parallel to the layer thickness direction when the structure is observed with a field emission scanning electron microscope. A Cr-containing aluminum oxide layer having a structure composed of crystal grains having a long shape in the thickness direction,
Further, with respect to the upper layer of (c), an electron beam is irradiated to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface of the tool base using a field emission scanning electron microscope. The inclination angle formed by the normal line of the (0001) plane, which is the crystal plane of the crystal grain, is measured with respect to the normal line of the surface polished surface, and is within a range of 0 to 45 degrees of the measured inclination angle. When a certain tilt angle is divided into pitches of 0.25 degrees, and the tilt angle distribution graph is formed by summing up the frequencies existing in each section, the tilt angle sections within the range of 0 to 10 degrees An inclination angle number distribution graph in which the highest peak is present and the total frequency within the range of 0 to 10 degrees occupies a ratio of 60% or more of the entire frequency in the inclination angle distribution graph,
Further, the upper layer of the above (c) is irradiated with an electron beam on each crystal grain existing within the measurement range of the surface polished surface using a field emission scanning electron microscope and an electron backscatter diffraction image apparatus, thereby obtaining a hexagonal crystal. Measures the angle at which each normal of the crystal lattice plane consisting of crystal lattices intersects the normal of the substrate surface, and calculates the crystal orientation relationship between adjacent crystal lattices from this measurement result, and configures the crystal lattice interface The distribution of lattice points (constituent atom shared lattice points) in which each atom shares one constituent atom between the crystal lattices is calculated, and N lattice points that do not share constituent atoms between the constituent atom shared lattice points are calculated. (However, N is an even number of 2 or more due to the crystal structure of the corundum hexagonal close-packed crystal. However, when the upper limit of N is 28 from the point of distribution frequency, even numbers of 4, 8, 14, 24 and 26 exist. Without) sharing existing constituent atoms When the child dot form is represented by ΣN + 1, the crystal grains having an area ratio of 60% or more among the crystal grains constituting the upper layer of the above (c) are represented by at least one Σ3 It is a Cr-containing aluminum oxide layer divided by a crystal lattice interface composed of atomic shared lattice point form,
A surface-coated cutting tool characterized by that.   When the upper layer of (c) was observed with a field emission scanning electron microscope, it was flat hexagonal in a plane perpendicular to the layer thickness direction, and in the layer thickness direction in a plane parallel to the layer thickness direction. The surface-coated cutting tool according to claim 1, wherein the crystal grains having a long shape occupy an area ratio of 35% or more of the whole in a plane perpendicular to the layer thickness direction.   The surface-coated cutting tool according to claim 1, wherein the upper layer of (c) has a surface roughness (Ra) in a range of 0.05 to 0.3 μm.

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