JP4747385B2 - Surface-coated cermet cutting tool with excellent chipping resistance thanks to thick α-type aluminum oxide layer - Google Patents

Description

In the present invention, an upper layer of a hard coating layer, that is, 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 where chemical vapor deposition is formed is particularly thick. The present invention relates to a surface-coated cermet cutting tool (hereinafter referred to as a coated cermet tool) that exhibits excellent chipping resistance even when used for cutting various steels 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, Ti composed of one or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer and having an overall average layer thickness of 0.5 to 10 μm Compound layer,
(B) an α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm as an upper layer;
There is known a coated cermet tool formed by vapor-depositing a hard coating layer composed of the above (a) and (b). It is well known to be used.

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 use of FA for cutting devices has been remarkable. On the other hand, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting work, and with this purpose, especially for the purpose of further extending the service life of cutting tools. upper layer constituting the hard coating layer, i.e. excellent but the hot hardness and thickening of one step in the α-type the Al ₂ O ₃ layer having heat resistance is strongly demanded, of the α-type the Al ₂ O ₃ layer When the layer thickness exceeds 15 μm, which is the maximum average layer thickness that has been practically used in the past, the Al ₂ O ₃ crystal grains become coarser and the denseness of the layer itself is significantly reduced. since the decrease in the high-temperature strength can not be avoided, the coated cermet tool formed by depositing formed as an upper layer of such thickening α type the Al ₂ O ₃ layer a hard coating layer, the thickening α-type Al ₂ O ₃ layer due to chipping to the cutting edge (fine Chipping) is likely to occur, since it becomes very short for this result useful life, it can not be put to practical use at present.

Therefore, the present inventors focused on the α-type Al ₂ O ₃ layer having an average layer thickness of 1 to 15 μm constituting the hard coating layer of the above-described conventional coated cermet tool from the above viewpoint, Research was conducted to develop a coated cermet tool in which chipping caused by the thickened α-type Al ₂ O ₃ layer does not occur at the cutting edge even if the layer thickness is increased to an average layer thickness exceeding 15 μm. result,
(A) When forming an α-type Al ₂ O ₃ layer as an upper layer on the surface of a tool base after forming a Ti compound layer as a lower layer, prior to the vapor deposition, for example, an ordinary chemical vapor deposition In the device
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 the low temperature condition, the Al ₂ O ₃ nuclei are formed in a state of being distributed and distributed on the surface. In this case, using a scanning electron microscope, the Al ₂ O ₃ nuclei are observed at an average value of 10,000 times. It is desirable to disperse and distribute at a rate of 5 to 200 / μm ² , and then change the atmosphere in the apparatus to an Ar atmosphere at a pressure of 3 to 13 kPa, and increase the temperature in the apparatus to 930 to 1050 ° C. _{With the} heat treatment applied to the ₂ O ₃ core, an α-type Al ₂ O ₃ layer as an upper layer of the hard coating layer is formed under a normal condition to a layer thickness of 16 to 30 μm exceeding an average layer thickness of 15 μm. Then, in the resulting thickened α-type Al ₂ O ₃ layer (hereinafter referred to as a thickened modified α-type Al ₂ O ₃ layer) deposited after the heat-treated Al ₂ O ₃ nucleation, the average Despite increasing the thickness to 16-30 μm, Al ₂ O ₃ crystal grains The coarsening is remarkably suppressed and the denseness of the layer itself is maintained, so that a decrease in high-temperature strength is prevented.

(B) Without forming the above thickened modified α-type Al ₂ O ₃ layer and the above heat-treated Al ₂ O ₃ nucleus, on the surface of the Ti compound layer, which is the lower layer, under normal conditions For a thickened α-type Al ₂ O ₃ layer (hereinafter referred to as a thickened normal α-type Al ₂ O ₃ layer) deposited with an average layer thickness of 16 to 30 μm, a field emission scanning electron microscope is used. 1 (a) and 1 (b), as schematically illustrated, the α-type Al ₂ O ₃ crystal grains having a hexagonal crystal lattice existing within the measurement range of the surface polished surface are irradiated with an electron beam, An inclination angle formed by a normal line of the (0001) plane, which is a crystal plane of the crystal grain, with respect to a normal line of the surface-polished surface with respect to the normal line of the surface-polished surface at a spacing of 0.1 μm / step using a backscatter diffraction image apparatus. Of the measured tilt angles, the measured tilt angles within a range of 0 to 45 degrees are divided for each pitch of 0.25 degrees. As with, if you create a tilt angle frequency distribution graph obtained by aggregating the frequencies present in each segment, the thickened normal α-type Al ₂ O ₃ layer is illustrated in FIG. 3, (0001) Whereas the distribution of the measured inclination angle of the surface shows an unbiased inclination angle number distribution graph within the range of 0 to 45 degrees, the film thickness reforming formed by vapor deposition on the heat-treated Al ₂ O ₃ nucleus In the α-type Al ₂ O ₃ layer, as illustrated in FIG. 2, a sharp maximum peak appears at a specific position in the tilt angle section, and this sharp maximum peak changes the distribution ratio of the Al ₂ O ₃ nuclei. As a result, the position that appears in the tilt angle section of the horizontal axis of the graph changes.

(C) According to the test results, in the above-mentioned thickening-modified α-type Al ₂ O ₃ layer, when the distribution ratio of the Al ₂ O ₃ nuclei is 5 to 200 / μm ² on average, The sharpest peak appears in the range of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees of the tilt angle section, and the sum of the frequencies existing in the range of 33 to 43 degrees is the tilt angle. An inclination angle frequency distribution graph occupying a ratio of 45 to 73% of the entire frequency in the number distribution graph is displayed, and accordingly, the inclination angle frequency distribution graph is 33.00 to 36.50 degrees or 39.00 to 43.00. The thickened reformed α-type Al ₂ O ₃ layer is hard, in which the highest peak of the inclination angle section appears in the range of degrees and the frequency ratio existing in the range of 33 to 43 degrees accounts for 45 to 73% Ti compound layer as the lower layer as the upper layer of the coating layer Coated cermet tool formed by depositing formed in the coexistence state is different from the coated cermet tool formed by depositing form thicker normal α type the Al ₂ O ₃ layer of the as the upper layer of the hard coating layer, particularly the cutting edge In addition, there is no need for chipping and the wear resistance is improved over a long period of time.
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) The lower layer is composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer, all of which are formed by chemical vapor deposition, and a whole of 0.5 to 10 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 An electron backscattered diffraction image apparatus is used to irradiate the substrate with a predetermined region of the crystal grain with respect to the normal of the surface polished surface at an interval of 0.1 μm / step (0001). The tilt angle formed by the normal of the surface is measured, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are divided for each pitch of 0.25 degrees and exist in each section. In the inclination angle number distribution graph obtained by collecting the frequencies, the highest peak exists in the inclination angle section in the range of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees , and 33 to 43 degrees. The total frequency within the range is the number of tilt angles. It shows an inclination angle frequency distribution graph in a proportion of 45-73% of the total power in the graph, and thickening modified α type with an average layer thickness of 16~30μm Al ₂ O ₃ layer,
The hard coating layer formed by vapor deposition of the hard coating layer composed of (a) and (b) above 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 thickening-modified α-type Al ₂ O ₃ layer, and the high temperature strength of the hard coating layer is improved by its excellent high temperature strength. In addition to the tool substrate and the thickened modified α-type Al ₂ O ₃ layer, and thus has an effect of improving the adhesion of the hard coating layer to the tool substrate. If the thickness is less than 0.5 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the average layer thickness exceeds 10 μm, the amount of thermoplastic deformation caused by heat generated during cutting increases beyond the allowable range. As a result, cracks are likely to occur in the thickened reformed α-type Al ₂ O ₃ layer, which is the upper layer, so the average layer thickness was determined to be 0.5 to 10 μm.

(B) Thickened modified α-type Al ₂ O ₃ layer As described above, the thickened modified α-type Al ₂ O ₃ layer formed on the heat-treated Al ₂ O ₃ nucleus is formed of Al ₂ O ₃ itself. The high temperature hardness and heat resistance of the hard coating layer improves the wear resistance of the hard coating layer, and it has a high temperature strength compared to the normal α-type Al ₂ O ₃ layer. However, the occurrence of chipping is remarkably suppressed, and it has the characteristic that the life of the product can be further extended. However, if the average layer thickness is less than 16 μm, it cannot sufficiently satisfy the demand for thick film, If the average layer thickness exceeds 30 μm and becomes too thick, chipping is likely to occur. Therefore, the average layer thickness was determined to be 16 to 30 μm.

(C) Heat-treated Al ₂ O ₃ nucleus Regarding the thickened modified α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool of the present invention, as described above, the highest peak is shown in the inclination angle number distribution graph. There is a close relationship between the inclination angle section shown and the distribution ratio of the heat-treated Al ₂ O ₃ nuclei. In this case, according to the test results, the distribution ratio of the heat-treated Al ₂ O ₃ nuclei is 5 on average. When changed within the range of ~ 200 / μm ² , the highest peak appears in the inclination angle section in the range of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees , and 33 to 43 degrees. An inclination angle frequency distribution graph in which the sum of the frequencies existing in the range occupies a ratio of 45 to 73% of the entire frequency in the inclination angle frequency distribution graph is shown. Therefore, the heat-treated Al ₂ O ₃ distribution ratio of the nucleus is less than 5 / μm ² It is in the range of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees inclination angle frequency distribution graph of the thickening modified α type the Al ₂ O ₃ layer is deposited formed on this peak height appearing insufficient, i.e. total proportion of the frequencies present in the range of the 33-43 °, if less than 45% of the total power at the inclination angle frequency distribution graph is generated, as in this case above, the high temperature strength of the thick film reforming α type the Al ₂ O ₃ layer, the conventional coated cermet tool hard layer α type the Al ₂ O ₃ layer constituting the upper layer of the above, i.e. the average layer thickness of 1~15μm The high temperature strength equivalent to the high temperature strength of the α-type Al ₂ O ₃ layer having the above cannot be maintained, and as a result, the chipping resistance is lowered, while the distribution ratio is 200 / μm ^2. by weight, inclination angle segment of appearance of the highest peak 33 00 to 36.50 degrees or addition become disengaged from 39.00 to 43.00 degrees in the range, the height of the highest peaks occur if lowered, again the thickened reforming α-type Al _{Since the} desired high-temperature strength cannot be ensured in the ₂ O ₃ layer, the distribution ratio of the heat-treated Al ₂ O ₃ nuclei formed on the Ti compound layer constituting the hard coating layer is 5 to ₂₀₀ on average. Pieces / μm ² .

  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. .

In the coated cermet tool of the present invention, the thickened modified α-type Al ₂ O ₃ layer constituting the hard coating layer thereof is 33.00 to 36.50 degrees or 39.000 as illustrated in FIG. An inclination angle number distribution graph in which the highest peak appears in the inclination angle section within the range of 43.00 degrees shows excellent chipping resistance even when the average layer thickness is increased to a layer thickness of 16 to 30 μm. For this reason, excellent wear resistance is exhibited over a long period of time by cutting various steels and cast irons, and the service life can be further extended.

  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 0.5 to 3 μm as raw material powder These raw material powders are blended into the blending composition shown in Table 1, further added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and then formed into a compact with a predetermined shape at a pressure of 98 MPa. The green compact was press-molded and vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470 ° C. for 1 hour. After sintering, the cutting edge portion had R: 0.05 mm. The tool bases A to F made of a WC-base cemented carbide having a throwaway tip shape specified in ISO · CNMG12041 were manufactured by performing the honing process.

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 d and f made of TiCN base cermet having a standard / CNMG12041 chip shape were formed.

Next, each of the tool bases A to F and the tool bases a to d and f together with a test piece for Al ₂ O ₃ nucleus distribution ratio measurement was charged into a normal chemical vapor deposition apparatus. 1-TiCN in No. 3 indicates the conditions for forming a TiCN layer having a vertically grown crystal structure described in JP-A-6-8010, and the other conditions indicate the conditions for forming a normal granular crystal structure. Under the normal conditions shown in Table 4), a Ti compound layer having a target layer thickness shown in Table 4 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,
After forming Al ₂ O ₃ nuclei under low temperature conditions, the atmosphere inside the apparatus was changed to an Ar atmosphere at a pressure of 8 kPa and the temperature inside the apparatus was raised to 1000 ° C., and the Al ₂ O ₃ nuclei were subjected to heat treatment. To heat-treat Al ₂ O ₃ nuclei,
At this time, the test piece is taken out from the apparatus, and subsequently, the thickened modified α-type Al ₂ O ₃ layer having the target layer thickness shown in Table 4 is hard-coated under the normal conditions also shown in Table 3. The coated cermet tools 1 to 12 of the present invention were produced by vapor deposition as the upper layer of each layer.
The distribution ratio of the heat-treated Al ₂ O ₃ nuclei in the Al ₂ O ₃ nucleus distribution ratio measurement test piece was observed at a magnification of 10,000 using a scanning electron microscope, and the range was 3 μm × 3 μm. The number of Al ₂ O ₃ nuclei present inside was measured at five arbitrary locations, and the measurement results are shown in Table 4 as an average value per unit area (μm ² ).

For comparison purposes, as shown in Table 5, without forming the above Al ₂ O ₃ nuclei and heating them, the film thickness is increased directly on the Ti compound layer, which is the lower layer of the hard coating layer. Comparative coated cermet tools 1 to 12 were produced under the same conditions except that the α-type Al ₂ O ₃ layer was usually formed as the upper layer.

Further, the thickened modified α-type Al ₂ O ₃ layer and the thickened normal α-type Al ₂ O ₃ constituting the hard coating layers of the above-described coated cermet tools 1 to 12 of the present invention and the comparative coated cermet tools 1 to 12 About the layer, the inclination angle number distribution graph was each created using the field emission scanning electron microscope.
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 each of the various thickened α-type Al ₂ O ₃ layers is a polished surface. An electron backscattered diffraction image is obtained by irradiating an electron beam with an acceleration voltage of 15 kV at an incident angle of 70 ° to an individual crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface with an irradiation current of 1 nA. Using an apparatus, an inclination angle formed by a normal line of the (0001) plane that is a crystal plane of the crystal grain with respect to a normal line of the surface-polished surface in a 30 × 50 μm region at an interval of 0.1 μm / step Based on the measurement result, the measurement inclination angle within the range of 0 to 45 degrees is divided into 0.25 degree pitches among the measurement inclination angles, and the frequency existing in each division is measured. Created by counting.

In the gradient angle distribution graphs of the various thickened α-type Al ₂ O ₃ layers obtained as a result, the tilt angle segment in which the (0001) plane shows the highest peak, and the tilt angle segment in the range of 33 to 43 degrees. Tables 4 and 5 show the ratio of the number of tilt angles existing in the tilt angle number distribution graph to the entire tilt angle number distribution graph.

In the inclination angle number distribution graphs of the various thickened α-type Al ₂ O ₃ layers described above, as shown in Tables 4 and 5, the heat-treated Al ₂ O ₃ nuclei of the coated cermet tool of the present invention were formed. Any of the thickening- modified α-type Al ₂ O ₃ layers has an inclination angle within the range of a measured inclination angle of (0001) plane of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees. While the highest peak appears in the section and the ratio of the tilt angle number existing in the tilt angle section within the range of 33 to 43 degrees is 45 to 73% , the comparative coated cermet Thickening of tool normal α-type Al ₂ O ₃ layers are all unbiased in the distribution of measured inclination angle of (0001) plane within the range of 0 to 45 degrees, and the highest peak does not exist. The ratio of the number of tilt angles existing in the tilt angle section within the range of degrees is also 30% or less It was indicative of the inclination angle frequency distribution graph.
Incidentally, FIG. 2, the inclination angle frequency distribution graph of the present invention thickened modified α type the Al ₂ O ₃ layer of coated cermet tool 4, Fig. 3, compare coated cermet tool 4 thickening normal α-type Al ₂ The graph of the distribution of the number of inclination angles of the O ₃ layer is shown respectively.

Further, when the thickness of the resulting present invention coated cermet tools 1 to 12 and Comparative coated cermet tool 1-12 layers constituting the hard layer of the, was measured using a scanning electron microscope (longitudinal sectional measurement) , Each showed an average layer thickness (average value of 5-point measurement) substantially the same as the target layer thickness.

Next, in the state where each of the above various coated cermet tools is screwed to the tip of the tool steel tool with a fixing jig, the present coated cermet tools 1 to 12 and the comparative coated cermet tools 1 to 12 ,
Work material: JIS / SCM415 lengthwise equidistant 4 round grooved round bars,
Cutting speed: 220 m / min,
Incision: 1.5mm,
Feed: 0.25mm / rev,
Cutting time: 30 minutes,
Dry interrupted cutting test of alloy steel under the following conditions (referred to as cutting condition A),
Work material: JIS / S35C round bar,
Cutting speed: 200 m / min,
Incision: 1.5mm,
Feed: 0.30mm / rev,
Cutting time: 30 minutes,
Dry continuous cutting test of carbon steel under the conditions (referred to as cutting condition B),
Work material: JIS / FC250 round bar,
Cutting speed: 300 m / min,
Cutting depth: 2.0 mm
Feed: 0.28mm / rev,
Cutting time: 30 minutes,
The dry continuous cutting test of cast iron was performed under the above conditions (referred to as cutting condition C), and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 6.

From the results shown in Tables 4 to 6, in the coated cermet tools 1 to 12 of the present invention, the upper layer of the hard coating layer has a (0001) plane inclination angle of 33.00 to 36.50 degrees or 39.00. A thickening modification showing an inclination angle distribution graph showing the highest peak in the inclination angle section within the range of ˜43.00 degrees and the total frequency ratio existing in the range of 33 to 43 degrees occupying 45 to 73%. consists of quality α type the Al ₂ O ₃ layer, in spite of 16~30μm and thicker in average thickness, by cutting the steel or cast iron, the thicker reforming α type the Al ₂ O ₃ layer It exhibits excellent chipping resistance, the chipping of the cutting edge is remarkably suppressed, and it exhibits excellent wear resistance over a long period of time. The upper layer of the (0001) plane has a measured inclination angle distribution in the range of 0 to 45 degrees. A unbiased manner in囲内, as seen in the comparer coated cermet tools 1 to 12 composed of a thickened normal α type the Al ₂ O ₃ layer showing the inclination angle frequency distribution graph the highest peak does not exist, either α-type Al _{When the} average thickness of the ₂ O ₃ layer exceeds 15 μm and is increased to 16 to 30 μm, the high-temperature strength is significantly reduced. As a result, chipping tends to occur at the cutting edge, and the service life is reached in a short time. It is clear.

As described above, the coated cermet tool according to the present invention can be used for various steels even when the α-type Al ₂ O ₃ layer, which is the upper layer of the hard coating layer, has an average layer thickness of 16 to 30 μm. It shows excellent chipping resistance in cutting work such as cast iron and cast iron, exhibits excellent wear resistance over a long period of time, and can extend the service life. It can cope with labor saving, energy saving and cost reduction of processing sufficiently satisfactorily.

It is a schematic diagram illustrating a measurement range of the inclination angle of the crystal grains (0001) plane in various thickened 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 thickening modified α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool 4 of the present invention. 6 is a graph showing the distribution of the number of inclination angles of the (0001) plane of the thickened normal α-type Al ₂ O ₃ layer constituting the hard coating layer of the comparative coated cermet tool 4.

Claims (1)

On the surface of the tool base composed of tungsten carbide based cemented carbide or titanium carbonitride based cermet,
(A) As a lower layer, each consists of one or two or more of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, and carbonitride oxide layer formed by chemical vapor deposition, And a Ti compound layer having an overall average layer thickness of 0.5 to 10 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 irradiated with an electron beam, and using an electron backscatter diffraction image apparatus, a predetermined region is a crystal plane of the crystal grain with respect to the normal of the surface polished surface at an interval of 0.1 μm / step (0001 ) Measure the tilt angle formed by the normal of the surface, and among the measured tilt angles, the measured tilt angles within the range of 0 to 45 degrees are divided for each pitch of 0.25 degrees and exist in each section In the inclination angle distribution graph obtained by summing up the frequencies to be detected , the highest peak exists in the inclination angle section within the range of 33.00 to 36.50 degrees or 39.00 to 43.00 degrees, and 12 to 22 degrees. The total number of frequencies within the range of Shows an inclination angle frequency distribution graph in a proportion of 45-73% of the total power at the fabric graph, and thickening modified α-type aluminum oxide layer having an average layer thickness of 16～30Myuemu,
A surface-coated cermet cutting tool that exhibits excellent chipping resistance with a thickened α-type aluminum oxide layer formed by vapor-depositing the hard coating layer composed of (a) and (b) above.

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