JP2006305639A - CUTTING TOOL MADE OF SURFACE-COATED CERMET, WITH THICK alpha-TYPE ALUMINUM OXIDE LAYER ACHIEVING EXCELLENT ANTI-CHIPPING PERFORMANCE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool made of surface-coated cermet, with a thick α-type Al<SB>2</SB>O<SB>3</SB>layer achieving anti-chipping performance. <P>SOLUTION: This cutting tool made of surface-coated cermet comprises a tool base body composed of WC-based cemented carbide or TiCN-based cermet, coated with a hard coating layer composed of (a) a lower layer of a Ti compound layer comprising one layer or more than two layers of TiC layer, TiN layer, TiCN layer, TiCO layer, and TiCNO layer, formed by chemical vapor deposition, and having total average layer thickness of 0.5-10μm, and (b) an upper layer of a thick reformed α-type Al<SB>2</SB>O<SB>3</SB>layer having α-type crystal structure in a chemically vapor-deposited state, showing a specific inclined angle numerical distribution graph, and having an average layer thickness of 16-30μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 (a) and (b) above, and this coated cermet tool can be used for continuous cutting and intermittent cutting of various steels and cast irons, for example. 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 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,
After forming a core Al ₂ O ₃ thin film having an average layer thickness of 0.02 to 0.2 μm (20 to 200 nm) on the surface of the Ti compound layer as the lower layer under the low temperature condition of The α-type Al ₂ O ₃ layer as the hard coating layer was changed in a state where the core Al ₂ O ₃ thin film was heated under the condition that the reaction atmosphere temperature was raised to 930 to 1050 ° C. by changing to Ar of 13 kPa. Under normal conditions, when an average layer thickness of 16 to 30 μm, which exceeds 15 μm, is formed, the resulting thickened α-type Al ₂ O ₃ deposited on the heat-treated core Al ₂ O ₃ thin film is deposited. In the layer (hereinafter referred to as “thickened modified α-type Al ₂ O ₃ layer”), the Al ₂ O ₃ crystal grains are coarsened even though the average layer thickness is increased to 16 to 30 μm. Is significantly suppressed and the denseness of the layer itself is maintained, preventing a decrease in high-temperature strength. To be done.

(B) Without forming the above-described thickening-modified α-type Al ₂ O ₃ layer and the above-described heat-treated nucleus Al ₂ O ₃ thin film, normal conditions are applied to the surface of the Ti compound layer as the lower layer. 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 using a field emission scanning electron microscope, As schematically shown in FIGS. 1A and 1B, each α-type Al ₂ O ₃ crystal grain having a hexagonal crystal lattice existing within the measurement range of the surface polished surface is irradiated with an electron beam. 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 the measured inclination angle is within a range of 0 to 45 degrees. Inclination angle distribution that divides a certain measured inclination angle into pitches of 0.25 degrees and totals the frequencies existing in each section When you create a rough, the thickness is the film-forming typically α type the Al ₂ O ₃ layer, as illustrated in FIG. 3, (0001) Measurement inclination angle of the surface distribution is unbiased specific within the 0-45 degree In contrast to the tilt angle number distribution graph, the thickened modified α-type Al ₂ O ₃ layer deposited on the heat-treated nucleus Al ₂ O ₃ thin film is tilted as shown in FIG. A sharp maximum peak appears at a specific position in the angular section, and this sharp maximum peak changes in the position appearing in the tilt angle section on the horizontal axis of the graph by changing the average layer thickness of the core Al ₂ O ₃ thin film.

(C) According to the test results, in the above-described thickened modified α-type Al ₂ O ₃ layer, the sharpness is increased when the average layer thickness of the core Al ₂ O ₃ thin film is 0.02 to 0.2 μm. The highest peak appears in the range of 12 to 22 degrees of the inclination angle section, and the total of the frequencies existing in the range of 12 to 22 degrees represents a ratio of 45% or more of the total degrees in the inclination angle frequency distribution graph. An inclination angle number distribution graph to be occupied is shown, and therefore, the highest peak of the inclination angle section appears in the range of 12 to 22 degrees in the inclination angle number distribution graph, and the frequency exists in the range of 12 to 22 degrees. A coated cermet tool formed by vapor deposition in the state of coexisting with the lower Ti compound layer, with the thickened modified α-type Al ₂ O ₃ layer occupying a ratio of 45% or more as the upper layer of the hard coating layer, The above-mentioned thickened normal α-type Al ₂ O ₃ layer Compared to a coated cermet tool deposited as an upper layer of a hard coating layer, it should exhibit superior wear resistance over a long period of time without chipping particularly at the cutting edge.
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 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 number distribution graph obtained by dividing the measured inclination angles in the range of ˜45 degrees into the pitches of 0.25 degrees and totaling the frequencies existing in the respective sections, in the range of 12 to 22 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 2 to 22 degrees occupies 45% or more of the entire frequency in the inclination angle distribution graph. With an average layer thickness of 16-30 μm A thickening modified α-type 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) Thickening-modified α-type Al ₂ O ₃ layer As described above, the thickening-modified α-type Al ₂ O ₃ layer formed on the heat-treated nucleus Al ₂ O ₃ thin film includes Al ₂ O ₃ The high temperature hardness and heat resistance of its own improve the wear resistance of the hard coating layer, and it has a higher temperature strength than that of the normal α-type Al ₂ O ₃ layer. It has the effect of suppressing the occurrence of chipping in the hard coating layer, but if its average layer thickness is less than 16 μm, it cannot sufficiently satisfy the demand for thickening, while its average layer thickness is 30 μm. If the thickness is too large, the chipping tends to occur. Therefore, the average layer thickness is determined to be 16 to 30 μm.

(C) Heat-treated nucleus Al ₂ O ₃ thin film The inclination angle showing the highest peak in the inclination angle number distribution graph for the thickened modified α-type Al ₂ O ₃ layer constituting the hard coating layer of the coated cermet tool of the present invention between sections and heating core Al ₂ O ₃ average layer thickness Metropolitan of the thin film is closely related, according to this case the test results, the average layer thickness of the heat treatment core Al ₂ O ₃ thin film 0.02 When it is changed in the range of .about.0.2 .mu.m, the highest peak appears in the inclination angle section in the range of 12 to 22 degrees, and the total of the frequencies existing in the range of 12 to 22 degrees is the inclination angle number distribution graph. An inclination angle frequency distribution graph occupying a ratio of 45% or more of the entire frequency in the above is shown. Therefore, when the average layer thickness of the heat-treated nucleus Al ₂ O ₃ thin film is less than 0.02 μm, thickening modified α type is vapor deposited on Al ₂ Inclination angle frequency distribution peak height appearing in the range of 12 to 22 degrees in the graph of _three layers is unsatisfactory, i.e., the total ratio of the frequencies present in the range of the 12 to 22 degrees, the inclination angle frequency distribution graph In this case, as described above, the high-temperature strength of the thickening-modified α-type Al ₂ O ₃ layer constitutes the upper layer of the hard coating layer of the conventional coated cermet tool. α-type the Al ₂ O ₃ layer which, i.e. can not be maintained the same high-temperature strength and high temperature strength which includes an average layer thickness α type the Al ₂ O ₃ layer having a 1 to 15 m, this results chipping resistance On the other hand, when the average layer thickness exceeds 0.2 μm, the slope angle section where the highest peak appears is out of the range of 12 to 22 degrees, and in this case also the thickening modified α-type Al inevitable reduction in high-temperature strength ₂ O ₃ layer is From Rukoto is the average layer thickness of the core Al ₂ O ₃ thin film formed on the Ti compound layer as the lower layer of the hard coating layer was 0.02～0.2Myuemu.

  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 has the highest inclination angle in the range of 12 to 22 degrees as illustrated in FIG. An inclination angle number distribution graph in which a peak appears is shown, and even when it is thickened to an average layer thickness of 16 to 30 μm, it exhibits excellent chipping resistance. Therefore, in various steel and cast iron cutting processes, It exhibits excellent wear resistance over a long period of time, enabling a further increase in service life.

  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: 0.07 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 f made of TiCN-based cermet having a standard / CNMG12041 chip shape were formed.

Next, each of the tool bases A to F and the tool bases a to f together with a test piece for measuring the thickness of the core Al ₂ O ₃ thin film layer was loaded into a normal chemical vapor deposition apparatus. Among them, l-TiCN 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. The Ti compound layer having the target layer thickness shown in Table 4 is vapor-deposited as the lower layer of the hard coating layer under the normal conditions shown in FIG.
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: Time corresponding to the layer thickness of the core Al ₂ O ₃ thin film in the range of 5 to 80 minutes,
After forming the core Al ₂ O ₃ thin film having the target layer thickness shown in Table 4 under the low temperature condition (the relation between the layer thickness of the core Al ₂ O ₃ thin film and the processing time is the same as in the case of the Ti compound layer) The reaction atmosphere is changed to an Ar atmosphere having a pressure of 8 kPa and the reaction atmosphere temperature is raised to 1000 ° C., and the core Al ₂ O ₃ thin film is subjected to heat treatment to heat-treat nucleus Al _2. O ₃ thin film
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 13 of the present invention were produced by vapor deposition as the upper layer of each layer.

For comparison purposes, as shown in Table 5, the formation of the above-mentioned core Al ₂ O ₃ thin film and the heat treatment thereof are not performed, and the thickened normal α-type Al ₂ O _{3 is used} as the upper layer of the hard coating layer. Comparative coated cermet tools 1 to 13 were produced under the same conditions except that the layers were formed.

Furthermore, 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 13 of the present invention and the comparative coated cermet tools 1 to 13 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 inclination angle section in which the (0001) plane shows the highest peak, and the inclination angle section within the range of 12 to 22 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 gradient angle number distribution graphs of the various thickened α-type Al ₂ O ₃ layers described above, as shown in Tables 4 and 5, each is formed on the heat-treated core Al ₂ O ₃ thin film of the coated cermet tool of the present invention. In each of the thickening-modified α-type Al ₂ O ₃ layers, the highest peak appears in the inclination angle section within the range of 12 to 22 degrees of the measured inclination angle of the (0001) plane, and 12 to 22 degrees. In contrast, an inclination angle number distribution graph in which the ratio of the inclination angle number existing in the inclination angle section within the range of 45% is 45% or more is shown, whereas the thickened normal α-type Al ₂ O ₃ layer of the comparative coated cermet tool In any case, the measured inclination angle distribution of the (0001) plane is unbiased in the range of 0 to 45 degrees, the highest peak does not exist, and the inclination exists in the inclination angle section in the range of 12 to 22 degrees. An inclination angle number distribution graph in which the ratio of the angle number is 30% or less was also shown.
Incidentally, FIG. 2, the inclination angle frequency distribution graph of the present invention thickened modified α type the Al ₂ O ₃ layer of the coated cermet tool 5, FIG. 3 is thickened usually α-type Al ₂ comparative coated cermet tool 5 The graph of the distribution of the number of inclination angles of the O ₃ layer is shown respectively.

Moreover, the thickness of the constituent layer of the hard coating layer of the present invention coated cermet tools 1 to 13 and the comparative coated cermet tools 1 to 13 obtained as a result, and the thickness of the heat-treated core Al ₂ O ₃ thin film of the above test piece When measured using a scanning electron microscope (longitudinal section measurement), all showed an average layer thickness (average value of five-point measurement) substantially the same as the target layer thickness.

Next, with the various coated cermet tools described above, the present coated cermet tools 1 to 13 and comparative coated cermet tools 1 to 13 in a state where all the above-mentioned various coated cermet tools are screwed to the tip of the tool steel tool with a fixing jig.
Work material: JIS / S40C lengthwise equal length 4 fluted round bars,
Cutting speed: 250 m / min,
Cutting depth: 1.4mm,
Feed: 0.1 mm / rev,
Cutting time: 20 minutes,
A dry intermittent cutting test of carbon steel under the conditions (referred to as cutting condition A),
Work material: JIS / SCr420H round bar,
Cutting speed: 250 m / min,
Incision: 1.5mm,
Feed: 0.28mm / rev,
Cutting time: 20 minutes,
Dry continuous cutting test of alloy steel under the following conditions (referred to as cutting condition B),
Work material: JIS / FCD450 round bar,
Cutting speed: 250 m / min,
Cutting depth: 1.8mm,
Feed: 0.32mm / rev,
Cutting time: 20 minutes,
The dry continuous cutting test of ductile cast iron under the above conditions (referred to as cutting condition C) was performed, 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 13 of the present invention, the upper layer of the hard coating layer is an inclination angle section in which the inclination angle of the (0001) plane is in the range of 12 to 22 degrees. It is composed of a thickening-modified 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 12 to 22 degrees occupying 45% or more. Despite the film thickness of 16-30 μm, the thickened modified α-type Al ₂ O ₃ layer exhibits excellent chipping resistance when cutting steel and cast iron, and the cutting edge portion The occurrence of chipping is significantly suppressed, and the wear resistance is improved over a long period of time, and the service life can be extended. On the other hand, the upper layer of the hard coating layer has a measured inclination angle of the (0001) plane. In the range of 0 to 45 degrees, and the highest peak does not exist In comparison coated cermet tools 1 to 13 thicker typically showing the angular frequency distribution graph being composed of α-type the Al ₂ O ₃ layer, both at the thickened usually α type the Al ₂ O ₃ layer is the average layer thickness When the film thickness is increased to 16 to 30 μm, the high temperature strength is remarkably lowered, and as a result, chipping occurs at the cutting edge portion, and it is clear that the service life is reached in a short time.

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 5 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 5.

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 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 in the range of 0 to 45 degrees for each pitch of 0.25 degrees and totaling the frequencies existing in each section, the range of 12 to 22 degrees An inclination angle distribution graph in which the highest peak is present in the inclination angle section and the sum of the frequencies existing in the range of 12 to 22 degrees occupies a ratio of 45% or more of the entire frequency in the inclination angle distribution graph. And an average layer thickness of 16 to 30 μm A thickened modified α-type aluminum oxide layer,
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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