JP2005205586A - Surface-coated cermet cutting tool exhibiting excellent chipping resistance in hard coated layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cermet cutting tool exhibiting excellent chipping resistance in a hard coated layer. <P>SOLUTION: A Ti compound layer consisting of one or two or more layers of chemical vapor-deposited TiC layer, TiN layer, TiCN layer, TiCO layer and TiCNO layer and having the total average layer thickness of 3-20 μm as a lower layer, and an Al<SB>2</SB>O<SB>3</SB>layer having α-type crystalline structure in a chemical vapor-deposited state, exhibiting a distribution graph of the frequency of the angle of inclination for totaling the frequency present in each section in which the maximum peak is present in the section of the angle of inclination in a range of 0-10°, and the total frequency present in the range of 0-10° occupies the ratio of ≥ 45% of the entire frequency in the distribution graph of the angle of inclination, and having the average layer thickness of 1-30 μm as an upper layer are deposited on a surface of a tool base body formed of WC-based cemented carbide or TiCN-based cermet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance with a hard coating layer, particularly in high-speed intermittent cutting of various types of steel and cast iron.

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) As a lower layer, a Ti carbide (hereinafter referred to as TiC) layer, nitride (hereinafter also referred to as TiN) layer, carbonitride (hereinafter referred to as TiCN) layer formed by chemical vapor deposition, It is composed of one or more of an oxide (hereinafter referred to as TiO) layer, a carbon oxide (hereinafter referred to as TiCO) layer, and a carbonitride oxide (hereinafter referred to as TiCNO) layer, and 3 to 3 A Ti compound layer having an overall average layer thickness of 20 μm,
(B) As an upper layer, an aluminum oxide layer (hereinafter, referred to as an α-type Al ₂ O ₃ layer) having an α-type crystal structure in a state of chemical vapor deposition and having an average layer thickness of 1 to 30 μm,
There is known a coated cermet tool formed by chemical vapor deposition (hereinafter simply referred to as vapor deposition) of the hard coating layer composed of (a) and (b) above. It is well known that it is used for continuous cutting and intermittent cutting of cast iron and the like.

In general, the Ti compound layer and the α-type Al ₂ O ₃ layer constituting the hard coating layer of the above-mentioned coated cermet tool have a granular crystal structure, and further, the TiCN layer constituting the Ti compound layer is the layer itself. For the purpose of improving the strength of the crystal, a vertically grown crystal formed by chemical vapor deposition at a medium temperature range of 700 to 950 ° C. using a mixed gas containing an organic carbonitride as a reaction gas in a normal chemical vapor deposition apparatus. It is also known to have an organization.
Japanese Unexamined Patent Publication No. 6-31503 Japanese Patent Laid-Open No. 6-8010

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 work. When cutting with heavy cutting conditions such as high feed is inevitable, the above-mentioned conventional coated cermet tools are used for continuous cutting and interrupted cutting under normal conditions such as steel and cast iron. Although there is no problem with this, especially when this is used for high-speed intermittent cutting with the severest cutting conditions, that is, high-speed intermittent cutting in which repeated thermal shock is applied to the cutting edge portion at a very short pitch, α constituting the hard coating layer Although the type Al ₂ O ₃ layer is hard and has excellent heat resistance, it does not have sufficient strength, so that the hard coating layer is likely to cause chipping (micro chipping) due to this, As a result, the service life is reached in a relatively short time.

In view of the above, the present inventors focused on the coated cermet tool in which the α-type Al ₂ O ₃ layer constitutes a hard coating layer, and conducted research to improve the chipping resistance. As a result,
(A) When the α-type Al ₂ O ₃ layer as the hard coating layer is vapor-deposited on the surface of the tool base, for example, prior to the vapor-deposition formation,
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. Subsequently, the reaction atmosphere is changed to a hydrogen atmosphere at a pressure of 3 to 13 kPa, and the reaction atmosphere temperature is raised to 1100 to 1200 ° C., and the Al ₂ O ₃ core thin film is heated. When the α-type Al ₂ O ₃ layer as a hard coating layer is formed under normal conditions, the α-type Al ₂ O ₃ layer deposited on the heat-treated Al ₂ O ₃ core thin film as a result is subjected to field emission. Using a scanning electron microscope, each α-type Al ₂ O ₃ crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface as shown in the schematic explanatory diagrams of FIGS. 1 (a) and 1 (b) An electron beam is irradiated onto the surface polished surface normal to the surface polished surface. The inclination angle formed by the normal line of the (0001) plane, which is the crystal plane of the crystal grain, is measured, and the measurement inclination angle within the range of 0 to 45 degrees out of the measurement inclination angles is set for every 0.25 degree pitch. When the slope angle number distribution graph is created by dividing and counting the frequencies existing in each section, the conventional α-Al ₂ O ₃ layer has a (0001) plane as illustrated in FIG. In contrast, the measured inclination angle distribution shows an unbiased inclination angle number distribution graph in the range of 0 to 45 degrees, whereas the α-type Al ₂ O deposited on the heat-treated Al ₂ O ₃ nuclear thin film is deposited. _As shown in FIG. 2, the _three layers have a sharp maximum peak at a specific position in the tilt angle section, and this sharp maximum peak is obtained by changing the average layer thickness of the Al ₂ O ₃ nuclear thin film. The position that appears in the tilt angle section of the horizontal axis changes.

(B) The α-type Al ₂ O ₃ layer deposited on the heat-treated Al ₂ O ₃ core thin film has a significantly improved high-temperature strength as compared with the conventional α-type Al ₂ O ₃ layer. The coated cermet tool formed by vapor deposition using the same as the upper layer of the hard coating layer exhibits excellent chipping resistance as compared with the conventional coated cermet tool formed by vapor deposition of the conventional α-type Al ₂ O ₃ layer. To be like that.

(C) According to the test results, when the average layer thickness of the Al ₂ O ₃ nuclear thin film is 20 to 200 nm, the sharp maximum peak appears in the range of 0 to 10 degrees of the inclination angle section, and the 0 An inclination angle number distribution graph in which the sum of the frequencies existing in the range of -10 degrees occupies a ratio of 45% or more of the entire frequency in the inclination angle number distribution graph is shown. The α-Al ₂ O ₃ layer in which the highest peak of the tilt angle section appears in the range of 0 to 10 degrees and the frequency ratio existing in the range of 0 to 10 degrees occupies a ratio of 45% or more is a hard coating layer The coated cermet tool formed by vapor deposition in the state of coexisting with the lower Ti compound layer as the upper layer of the above-described conventional coated cermet tool has no chipping at the cutting edge portion particularly at high-speed intermittent cutting. , Much better It is like to exhibit wear resistance.
The research results shown in (a) to (c) above were obtained.

The present invention has been made based on the above research results, and on the surface of a tool base composed of a WC-based cemented carbide or TiCN-based cermet,
(A) As a lower layer, each consists of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiO layer, a TiCO layer, and a TiCNO layer formed by chemical vapor deposition, and a total of 3 to 20 μm A Ti compound layer having an average layer thickness;
(B) As an upper layer, each crystal grain having a hexagonal crystal lattice which has an α-type crystal structure in a state where chemical vapor deposition is formed, and which exists within the measurement range of the surface polished surface using a field emission scanning electron microscope Is irradiated with an electron beam to measure the inclination angle formed by the normal line of the (0001) plane, which is the crystal plane of the crystal grain, with respect to the normal line of the surface polished surface. In the inclination angle distribution graph formed by dividing the measured inclination angles within the range of ˜45 degrees into the pitches of 0.25 degrees and totaling the frequencies existing in the respective sections, within the range of 0 to 10 degrees. An inclination angle number distribution graph in which the highest peak exists in the inclination angle section and the sum of the frequencies existing in the range of 0 to 10 degrees occupies a ratio of 45% or more of the entire frequency in the inclination angle distribution graph. And having an average layer thickness of 1 to 30 μm Al ₂ O ₃ layer,
The hard coating layer formed by vapor deposition of the hard coating layer composed of the above (a) and (b) is characterized by a coated cermet tool that exhibits excellent chipping resistance.

In addition, the reason why the numerical values of the constituent layers of the hard coating layer of the coated cermet tool of the present invention are limited as described above will be described below.
(A) Ti compound layer The Ti compound layer basically 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 tool base 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 base. However, if the average layer thickness is less than 3 μm, the above action is sufficient. On the other hand, if the average layer thickness exceeds 20 μm, it becomes easy to cause thermoplastic deformation especially at high-speed intermittent cutting with high heat generation, and this causes uneven wear. The layer thickness was determined to be 3-20 μm.

(B) The α-type the Al ₂ O ₃ layer above α-type Al ₂ O ₃ layer formed as heat treatment Al ₂ O ₃ on the nuclear membrane of the high-temperature hardness and heat resistance superior with the Al ₂ O ₃ itself In addition to improving the wear resistance of the hard coating layer, it has a higher high-temperature strength than the conventional α-type Al ₂ O ₃ layer, so it has the effect of further improving the chipping resistance of the hard coating layer. When the average layer thickness is less than 1 μm, the above-mentioned effect cannot be sufficiently exhibited. On the other hand, when the average layer thickness exceeds 30 μm, the chipping tends to occur. It was defined as 1 to 30 μm.

(C) Heat-treated Al ₂ O ₃ core thin film Regarding the α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool of the present invention, the tilt angle segment showing the highest peak in the tilt angle number distribution graph and the heat-treated Al There is a close relationship between the average layer thickness of the ₂ O ₃ core thin film. In this case, according to the test results, the average layer thickness of the heat-treated Al ₂ O ₃ core thin film is changed in the range of 20 to 200 nm. And the highest peak appears in the inclination angle section within the range of 0 to 10 degrees, and the total of the frequencies existing within the range of 0 to 10 degrees is a ratio of 45% or more of the entire degrees in the inclination angle frequency distribution graph. Therefore, if the average layer thickness of the heat-treated Al ₂ O ₃ core thin film is less than 20 nm, the α-type Al ₂ O formed on the thin film is deposited. _3-layer inclination angle frequency distribution graph of The peak height appearing in the range of 0 to 10 degrees is insufficient, that is, the total ratio of the frequencies existing in the range of 0 to 10 degrees is less than 45% of the entire frequencies in the inclination angle frequency distribution graph. In this case, as described above, the α-type Al ₂ O ₃ layer cannot secure a desired excellent high-temperature strength, and as a result, a desired improvement effect in chipping resistance cannot be obtained, while the average layer When the thickness exceeds 200 nm, the tilt angle section where the highest peak appears is out of the range of 0 to 10 degrees, and in this case as well, the desired excellent high-temperature strength cannot be secured in the α-type Al ₂ O ₃ layer. Therefore, the average layer thickness of the Al ₂ O ₃ core thin film formed on the Ti compound layer constituting the hard coating layer is 20 to 200 nm, preferably 30 to 150 nm.

  For the purpose of identification before and after the use of the coated cermet tool, a TiN layer having a golden color tone may be vapor-deposited as the outermost surface layer of the hard coating layer, but the average layer thickness in this case 0.1-1 μm may be sufficient, because 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 with an average layer thickness of up to 1 μm. .

The coated cermet tool of the present invention has an α-type Al ₂ O ₃ layer that constitutes a hard coating layer even in high-speed intermittent cutting of various steels and cast irons with extremely high mechanical and thermal shock and high heat generation. As shown in FIG. 2, the inclination angle number distribution graph in which the highest peak appears in the inclination angle section within the range of 0 to 10 degrees is shown, and since excellent chipping resistance is exhibited, excellent wear resistance is extended over a long period of time. It shows excellent cutting performance.

  Next, the coated cermet 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 performing the processing, tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape specified in ISO · CNMG120408 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 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 a standard / CNMG12041 chip shape were formed.

Subsequently, a normal chemical vapor deposition apparatus was used on the surfaces of the tool bases A to F and the tool bases a to f. First, Table 3 (l-TiCN in Table 3 is described in JP-A-6-8010). The target layer thickness shown in Table 4 under the conditions shown in Table 4 is a condition for forming a TiCN layer having a vertically grown crystal structure. The Ti compound layer is deposited as a lower layer of the hard coating layer, and then,
Reaction gas composition: volume%, AlCl ₃ : 6.5%, CO ₂ : 1.6%, C ₂ H ₄ : 0.13%, H ₂ : remaining,
Reaction atmosphere temperature: 820 ° C.
Reaction atmosphere pressure: 8 kPa,
Time: 5-80 minutes
After forming the Al ₂ O ₃ nucleus thin film having the target layer thickness shown in Table 4 under the low temperature condition (the relation between the layer thickness of the Al ₂ O ₃ nucleus thin film and the processing time is the same as in the case of the Ti compound layer) The reaction atmosphere was changed to a hydrogen atmosphere with a pressure of 8 kPa and the reaction atmosphere temperature was raised to 1135 ° C., and the Al ₂ O ₃ core thin film was subjected to heat treatment. under the conditions shown in Table 3, like-α type the Al ₂ O ₃ layer of the target layer thicknesses shown in Table 4 was vapor deposited as an upper layer of the hard coating layer, wherein the α-type the Al ₂ O ₃ layer if necessary The coated cermet tools 1 to 13 of the present invention were manufactured by vapor-depositing a TiN layer having a target layer thickness shown in Table 4 as the outermost surface layer of the hard coating layer under the same conditions as shown in Table 3 above. .

For the purpose of comparison, as shown in Table 5, prior to the formation of the α-type Al ₂ O ₃ layer of the hard coating layer, the formation of the Al ₂ O ₃ core thin film and the heat treatment thereof are not performed. Produced the conventional coated cermet tools 1 to 13 under the same conditions.

Furthermore, with respect to the α-type Al ₂ O ₃ layer constituting the hard coating layers of the above-described coated cermet tools 1 to 13 of the present invention and the conventional coated cermet tools 1 to 13, the inclination angle number distribution is obtained using a field emission scanning electron microscope. Each graph was created.
That is, the inclination angle number distribution graph is set in a lens barrel of a field emission scanning electron microscope in a state where the surface of the α-type Al ₂ O ₃ layer is a polished surface, and 70 ° on the polished surface. An electron beam having an acceleration voltage of 15 kV at an incident angle is irradiated with an irradiation current of 1 nA on each crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface, and an electron backscatter diffraction image apparatus is used. , And measuring the inclination angle formed by the normal of the (0001) plane, which is the crystal plane of the crystal grain, with respect to the normal of the polished surface at an interval of 0.1 μm / step in a 30 × 50 μm region, Based on the measurement results, the measurement inclination angles within the range of 0 to 45 degrees out of the measurement inclination angles are divided for each pitch of 0.25 degrees, and the frequencies existing in each division are tabulated. Created by.

In the slope angle distribution graphs of the various α-type Al ₂ O ₃ layers obtained as a result, the (0001) plane is present in the slope section where the highest peak is present, and the slope section within the range of 0 to 10 degrees. Tables 4 and 5 show the ratios of the tilt angle numbers to the tilt angle number distribution graph as a whole.

In the inclination angle number distribution graphs of the various α-type Al ₂ O ₃ layers described above, as shown in Tables 4 and 5, α-type formed on the heat-treated Al ₂ O ₃ core thin film of the coated cermet tool of the present invention. In the Al ₂ O ₃ layer, the highest peak appears in the tilt angle section where the distribution of the measured tilt angle on the (0001) plane is in the range of 0 to 10 degrees, and the tilt angle section is in the range of 0 to 10 degrees. 2 shows an inclination angle number distribution graph in which the ratio of the inclination angle number existing in the graph is 45% or more, whereas the α-type Al ₂ O ₃ layer of the conventional coated cermet tool has a measured inclination angle of the (0001) plane. An inclination angle in which the distribution of the angle is unbiased in the range of 0 to 45 degrees, the highest peak does not exist, and the ratio of the number of inclination angles existing in the inclination angle section in the range of 0 to 10 degrees is 30% or less. A number distribution graph was shown.
2 is an inclination angle number distribution graph of the α-type Al ₂ O ₃ layer of the coated cermet tool 10 of the present invention, and FIG. 3 is an inclination angle number distribution graph of the α-type Al ₂ O ₃ layer of the conventional coated cermet tool 10. Respectively.

Moreover, when the thickness of the constituent layer of the hard coating layer of the present coated cermet tools 1 to 13 and the conventional coated cermet tools 1 to 13 obtained as a result was measured using a scanning electron microscope (longitudinal section measurement). , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.
Note that it was extremely difficult to measure the thickness of the heat-treated Al ₂ O ₃ core thin film in the hard coating layers of the above-described coated cermet tools 1 to 13 of the present invention.

Next, with respect to the present invention coated cermet tools 1 to 7 and the conventional coated cermet tools 1 to 7 in a state where any of the above various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig. ,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 350 m / min,
Cutting depth: 1mm,
Feed: 0.25mm / rev,
Cutting time: 5 minutes
Dry high-speed intermittent cutting test of alloy steel under the conditions (normal cutting speed is 250 m / min),
Work material: JIS · S45C lengthwise equal 4 round grooved round bars,
Cutting speed: 400 m / min,
Cutting depth: 1mm,
Feed: 0.25mm / rev,
Cutting time: 5 minutes
Dry high-speed intermittent cutting test of carbon steel under the conditions (normal cutting speed is 300 m / min),
Work material: JIS / FC300 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 450 m / min,
Incision: 1.5mm,
Feed: 0.25mm / rev,
Cutting time: 5 minutes
The dry high-speed intermittent cutting test (normal cutting speed is 300 m / min) of cast iron under the conditions of

Furthermore, about this invention coated cermet tool 8-13 and conventional coated cermet tool 8-13,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 400 m / min,
Cutting depth: 0.7mm,
Feed: 0.15mm / rev,
Cutting time: 5 minutes
Dry high-speed intermittent cutting test of alloy steel under the conditions (normal cutting speed is 250 m / min),
Work material: JIS · S45C lengthwise equal 4 round grooved round bars,
Cutting speed: 400 m / min,
Cutting depth: 0.7mm,
Feed: 0.15mm / rev,
Cutting time: 5 minutes
Dry high-speed intermittent cutting test of carbon steel under the conditions (normal cutting speed is 300 m / min),
Work material: JIS / FC300 lengthwise equidistant 4 bars with vertical grooves,
Cutting speed: 450 m / min,
Cutting depth: 0.7mm,
Feed: 0.15mm / rev,
Cutting time: 5 minutes
A dry high-speed intermittent cutting test of cast iron under the conditions (normal cutting speed is 300 m / min),
In each 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, in the coated cermet tools 1 to 13 of the present invention, the upper layer of the hard coating layer is an inclination angle section within the range where the inclination angle of the (0001) plane is 0 to 10 degrees. It is composed of an α-type Al ₂ O ₃ layer showing an inclination angle number distribution graph showing a maximum peak and a total frequency ratio existing in the range of 0 to 10 degrees occupying 45% or more, and mechanical thermal shock is Even in high-speed intermittent cutting of steel and cast iron with extremely high heat generation, the α-type Al ₂ O ₃ layer exhibits excellent chipping resistance, so the occurrence of chipping at the cutting edge is remarkably suppressed, In contrast to the excellent wear resistance, the upper layer of the hard coating layer has an inclination angle in which the distribution of the measured inclination angle of the (0001) plane is unbiased within the range of 0 to 45 degrees and there is no maximum peak. composed of α-type the Al ₂ O ₃ layer indicating the number distribution graph In came coated cermet tools 1 to 13, neither withstand the mechanical and thermal shock the α type the Al ₂ O ₃ layer is severe in high speed interrupted cutting, chipping occurs in the cutting edge, a relatively short time It is clear that the service life is reached.

  As described above, the coated cermet tool of the present invention has extremely high mechanical thermal shock and high heat generation as well as continuous cutting and interrupted cutting under normal conditions such as various steels and cast iron. Because it exhibits excellent chipping resistance even in high-speed intermittent cutting with the most severe cutting conditions, and exhibits excellent cutting performance over a long period of time, it is possible to improve the performance of the cutting equipment and save labor and energy in cutting. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

Is a schematic diagram illustrating a measurement range of the inclination angle of the crystal grains (0001) plane in various 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 α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 10 of the present invention. 4 is an inclination angle number distribution graph of the (0001) plane of the α-type Al ₂ O ₃ layer constituting the hard coating layer of the conventional coated cermet tool 10.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As the lower layer, one or more of Ti carbide layer, nitride layer, carbonitride layer, oxide, carbonate layer, and carbonitride layer formed by chemical vapor deposition And a Ti compound layer having an overall average layer thickness of 3 to 20 μm,
(B) Crystal grains having an α-type crystal structure in the state of chemical vapor deposition as an upper layer and having a hexagonal crystal lattice existing within the measurement range of the surface polished surface using a field emission scanning electron microscope Individually irradiate an electron beam, measure the tilt angle formed by the normal of the (0001) plane that is the crystal plane of the crystal grain with respect to the normal of the polished surface, and among the measured tilt angles, In the inclination angle number distribution graph formed by dividing the measured inclination angles within the range of 0 to 45 degrees for each pitch of 0.25 degrees and counting the frequencies existing in each section, the range of 0 to 10 degrees Inclination angle distribution graph in which the highest peak exists in the inclination angle section and the total of the frequencies existing in the range of 0 to 10 degrees occupies 45% or more of the entire frequency in the inclination angle distribution graph And has an average layer thickness of 1 to 30 μm An aluminum oxide layer,
A surface-coated cermet cutting tool that exhibits the excellent chipping resistance of the hard coating layer formed by forming the hard coating layer constituted by (a) and (b) above.

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