JP2013116549A - Surface coated cutting tool with hard coating layer exhibiting superior chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated cutting tool with a hard coating layer exhibiting superior chipping resistance and defect resistance in high speed intermittent cutting.SOLUTION: A hard coating layer comprises a chemical vapor deposited lower layer and an upper layer, wherein (a) the lower layer is a Ti compound layer comprising one or two or more layers out of a carbide layer, a nitride layer, a carbonitride layer, a carbooxide layer, and a carbonitroxide layer of Ti and having a total average layer thickness of 3-20 μm, and (b) the upper layer is an aluminum oxide layer having an average layer thickness of 2-25 μm, and wherein the aluminum oxide layer constituting the upper layer has a columnar longitudinal growth oxidized aluminum crystal structure and particulate aluminum oxide is dispersed and distributed in the structure.

Description

  In the present invention, high-speed intermittent cutting of various steels and cast irons with high heat generation and intermittent / impact loads acting on the cutting edge, the hard coating layer has excellent chipping resistance, which makes it possible to The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over use.

Conventionally, the surface of a tool substrate (hereinafter collectively referred to as a tool substrate) generally composed of tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. In addition,
(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 of the lower layers. A Ti compound layer consisting of one or more of a carbon oxide (hereinafter referred to as TiCO) layer and a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) the upper layer is an aluminum oxide layer formed by chemical vapor deposition;
A coated tool formed by forming a hard coating layer composed of (a) and (b) above is known, and this coated tool is known to be used for cutting various steels and cast irons. It has been.
However, the above-described coated tool has a problem that chipping loss or the like is likely to occur under a cutting condition in which a heavy load is applied to the cutting edge, and the tool life is short-lived. Proposals have been made.

For example, Patent Document 1 discloses that a hard coating layer includes an inner layer composed of one or more of carbides such as Ti, nitrides, carbonitrides, borides, and boronitrides, and amorphous particles having a particle size of 0.01 to 0.5 μm. It is disclosed that by having a coating layer composed of an outer layer composed of alumina and crystallized alumina, this coating layer is fine and dense, and has a high productivity.
Patent Document 2 discloses a hard coating layer containing an Al ₂ O ₃ layer on the surface of a WC-based cemented carbide substrate, for example, a TiC layer, a TiN layer, a TiCN layer, a TiO ₂ layer, a TiCO layer, a TiNO layer, and Surface coating formed by chemical vapor deposition and / or physical vapor deposition of an average layer thickness of 2 to 20 μm with one or more of Ti compound layers composed of TiCNO layers and an Al ₂ O ₃ hard coating layer in cemented carbide cutting tools, the the Al ₂ O ₃ layer constituting the hard coating layer, mainly composed of Al ₂ O ₃ is has a α-type crystal structure, and differs in the upper portion and the lower side (substrate side) crystal have a tissue, columnar the Al ₂ O ₃ layer upper portion, i.e. the crystal structure columnar crystal grains are arranged in parallel in the vertical direction, Al ₂ O where the underside particulate the Al ₂ O ₃ layer, i.e. a granular crystal structure by constructing a _three-layer,耐Chi It is disclosed to provide a coated tool having excellent ping properties.
Furthermore, in Patent Document 3, in a hard film covering member in which a hard film is coated on the surface of a base material, the hard film is made of Al oxide or oxynitride having a non-columnar crystal structure, and the thickness of the hard film is 4 to 4. It is disclosed that a long-life coated tool having excellent wear resistance and fracture resistance is provided by being 15 μm.

JP 59-28565 A JP-A-10-76406 JP-A-1-83667

  In recent years, there is a strong demand for energy saving and energy saving in cutting, and along with this, coated tools have come to be used under severer conditions. For example, Patent Documents 1 to 3 show the above. Even when a coated tool is used for high-speed intermittent cutting with high heat generation and more intermittent and impact loads on the cutting edge, the toughness of the upper layer is not sufficient. The current situation is that chipping and chipping are likely to occur on the cutting edge due to the high load of time, and as a result, the service life is reached in a relatively short time.

  In view of the above, the inventors of the present invention have an excellent hard coating layer even when used in high-speed intermittent cutting with high heat generation and intermittent and impact loads acting on the cutting edge. As a result of earnest research on coated tools that have excellent shock absorption and, as a result, excellent chipping resistance and fracture resistance over long-term use, the following findings were obtained.

That is, in the case where the conventional upper layer made of aluminum oxide is formed as the hard coating layer, the aluminum oxide is formed in a columnar shape in the direction perpendicular to the substrate. Therefore, high temperature hardness and wear resistance are improved, but on the other hand, as the anisotropy of aluminum oxide increases, the toughness of the aluminum oxide layer decreases, and as a result, sufficient chipping resistance and fracture resistance can be exhibited. In addition, the tool life was not satisfactory.
Therefore, the present inventors conducted extensive research on the aluminum oxide layer that constitutes the upper layer of the hard coating layer, and as a result, the anisotropy was reduced and the toughness was reduced without impairing the high temperature hardness and wear resistance of the aluminum oxide layer. The inventors discovered a novel finding that the chipping resistance and fracture resistance of the hard coating layer can be improved by increasing the resistance.

  Specifically, the aluminum oxide layer constituting the upper layer has a columnar vertically grown aluminum oxide crystal structure, and fine aluminum oxide is dispersed and distributed in the structure. Property is relaxed and toughness is increased.

The aluminum oxide layer having the above-described configuration can be formed by, for example, the following chemical vapor deposition method.
On the surface of the tool base, the reaction gas composition (volume%) is AlCl ₃ : 2-3%, trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as TMA): 0.75 to 1.45%, CO ₂ : 4 to 6%, HCl: 1 to 3%, H ₂ S: 0.1 to 0.5%, H ₂ : remaining, the reaction atmosphere pressure was 6 to 10 kPa, and the reaction atmosphere temperature was 870. By performing chemical vapor deposition at a temperature of -1040 ° C., a columnar vertically grown aluminum oxide crystal structure in which fine aluminum oxide is dispersed in the film can be obtained.

  In particular, when the surface density of the cross section of the fine aluminum oxide layer in the aluminum oxide layer has a surface density distribution form that periodically changes along the layer thickness direction with a period of 0.5 μm to 5 μm along the layer direction. In addition, the presence of a low area density area of fine aluminum oxide provides excellent high temperature hardness and wear resistance characteristics of columnar vertically grown aluminum oxide, and there is an area where the surface area density of fine aluminum oxide is high. By doing so, the characteristics such as excellent toughness and shock absorption by the fine aluminum oxide can be exerted at a high level, and these characteristics can be combined at a high level. Therefore, the hard coating layer has excellent chipping resistance and fracture resistance, especially when it is used for high-speed intermittent cutting of steel or cast iron that generates high heat and has intermittent and impact loads on the cutting edge. It has been found that excellent cutting performance can be exhibited over a long period of use.

The present invention has been made based on the above findings,
“(1) In a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
The hard coating layer is composed of a lower layer and an upper layer chemically vapor-deposited,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total of 3 to 20 μm. A Ti compound layer having an average layer thickness;
(B) the upper layer is an aluminum oxide layer having an average layer thickness of 2 to 25 μm;
Consists of
The aluminum oxide layer constituting the upper layer of (b) has a columnar vertically grown aluminum oxide crystal structure in which fine aluminum oxide is dispersed and distributed, and the fine aluminum oxide is granular aluminum oxide. It is a mixed phase of a crystalline phase or an amorphous aluminum oxide phase or a granular aluminum oxide crystal phase and an amorphous aluminum oxide phase. The average particle width W of columnar vertically grown aluminum oxide crystals is 50 to 2000 nm or less, and the average aspect ratio A is 5 to 50 The average particle diameter R of the fine aluminum oxide is more than 50 nm and 300 nm or less, and the surface density of the cross section of the fine aluminum oxide present in the aluminum oxide layer constituting the upper layer is 5 to 30%. A surface-coated cutting tool.
(2) The surface density distribution form in which the surface density of the cross section of the particulate aluminum oxide periodically changes along the layer thickness direction at a cycle of 0.5 μm to 5 μm is described in (1) Surface coated cutting tool. "
It has the characteristics.

  The present invention will be described in detail below.

Lower Ti compound layer:
The lower layer composed of one or two or more Ti compound layers of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer is formed under normal chemical vapor deposition conditions. In addition to having high-temperature strength, the hard coating layer has high-temperature strength by itself, and also firmly adheres to both the tool base and the upper layer made of aluminum oxide, and thus hard. Although it has the effect of contributing to the adhesion of the coating layer to the tool substrate, if the total average layer thickness is less than 3 μm, the layer thickness is so thin that the above-mentioned effect cannot be fully exhibited. When the thickness exceeds 20 μm, the crystal grains are likely to be coarsened and chipping is likely to occur. Therefore, the total average layer thickness is determined to be 3 to 20 μm.

Upper aluminum oxide layer:
It is well known that the aluminum oxide layer constituting the upper layer has high-temperature hardness and heat resistance. However, if the average layer thickness is less than 2 μm, it should ensure wear resistance over a long period of use. On the other hand, when the average layer thickness exceeds 25 μm, the aluminum oxide crystal grains are likely to be coarsened. As a result, in addition to the decrease in high-temperature hardness and high-temperature strength, the chipping resistance, Since the deficiency is lowered, the average layer thickness is set to 2 to 25 μm.

Furthermore, in addition to the above-described configuration, the present invention exhibits a further excellent effect when it has the following conditions.
The upper aluminum oxide layer has a columnar vertically grown aluminum oxide crystal structure, and fine aluminum oxide is dispersed and distributed in the structure. By adopting such a configuration, impact resistance is improved, and excellent chipping resistance is exhibited. However, for each crystal grain of the columnar vertically grown aluminum oxide crystal, when the particle width in the direction parallel to the substrate surface is w and the average value is the average particle width W, the average particle width W is smaller than 50 nm, Wear resistance over a long period of use cannot be ensured. On the other hand, if it exceeds 2000 nm, chipping resistance and chipping resistance deteriorate due to coarsening of the particles. Accordingly, the average particle width W of the columnar vertically grown aluminum oxide crystal is preferably 50 to 2000 nm. Further, for each crystal grain of columnar vertically grown aluminum oxide, the grain length in the direction perpendicular to the substrate surface is l, the ratio between the grain width w and l is the aspect ratio a of each crystal grain, When the average aspect ratio A determined for the crystal grains is the average aspect ratio A, if the average aspect ratio A is less than 5, the high wear resistance characteristic of the columnar vertically grown aluminum oxide cannot be secured, On the other hand, when it exceeds 50, toughness is lowered, and chipping resistance and chipping resistance are lowered. Therefore, it is desirable that the average aspect ratio A of the columnar vertically grown aluminum oxide crystal is 5-50. Here, in the present invention, when one particle of columnar vertically grown aluminum oxide is measured, the constant direction maximum diameter in the direction parallel to the substrate surface is called the particle width w, while the constant direction tangent in the direction perpendicular to the substrate surface. The diameter is called the particle length l.
Furthermore, regarding the fine aluminum oxide, when the particle diameter of each fine aluminum oxide is r and the average value is the average particle diameter R, the fine aluminum oxide is dispersed and distributed when the average particle diameter R is 50 nm or less. The effect of improving toughness is not exhibited. On the other hand, if it exceeds 300 nm, the toughness is reduced. Therefore, the average particle diameter R of the fine aluminum oxide is preferably more than 50 nm and 300 nm or less. Here, in the present invention, the long axis diameter which is the longest diameter of the precipitated phase of each fine aluminum oxide is referred to as the particle diameter r of the fine aluminum oxide. The fine aluminum oxide in the present invention means a granular aluminum oxide crystal phase, an amorphous aluminum oxide phase, or a mixed phase of a granular aluminum oxide crystal phase and an amorphous aluminum oxide phase. Call it.
Further, if the surface density of the fine aluminum oxide is less than 5%, the effect of dispersing and distributing the fine aluminum oxide is not exhibited. On the other hand, if it exceeds 30%, the columnar vertically grown aluminum oxide crystal is not grown. This hinders the wear resistance. Therefore, the surface density of the cross section of the fine aluminum oxide is preferably 5 to 30%. Further, as described above, the fine aluminum oxide is not uniformly distributed, but is formed by a surface density distribution form in which the surface density periodically changes along the layer thickness direction with a period of 0.5 to 5 μm. The toughness is further improved. The reason for this is that fine aluminum oxide contributes to high-temperature hardness, toughness, etc. in areas where chipping resistance is high in areas where surface density is low, and by changing this surface density, it has the excellent effect of combining these properties. However, if the surface density is less than 0.5 μm, the low and high surface density regions due to periodic changes cannot fully exhibit their respective effects. On the other hand, if the surface density exceeds 5 μm, the periodicity The synergistic effect of having excellent high-temperature hardness, wear resistance, toughness, and shock absorption due to the presence of a low area density area and a high area area due to change is not sufficiently exhibited. Therefore, it was determined that the surface density of the cross section of the fine aluminum oxide has a surface density distribution form that periodically changes along the layer thickness direction with a period of 0.5 μm to 5 μm.

Formation of dispersed aluminum oxide particles:
The fine aluminum oxide of the present invention can be formed by performing chemical vapor deposition under the following conditions during the formation process of the upper layer formed under normal chemical vapor deposition conditions.
By adding TMA as a nucleus of fine aluminum oxide into the reaction gas, finely divided aluminum oxide having a distributed distribution is formed.
Reaction gas composition (volume%):
AlCl ₃ : 2-3%,
TMA: 0.75 to 1.45%,
CO _2: 4~6%,
HCl: 1-3%
H ₂ S: 0.1~0.5%,
H ₂ : remaining,
Reaction atmosphere temperature: 870-1040 ° C.
Reaction atmosphere pressure: 6 to 10 kPa,
FIG. 1 shows a schematic diagram of a distribution form of fine aluminum oxide existing in an aluminum oxide layer constituting the upper layer of the present invention formed under the chemical vapor deposition conditions.
Also, the fine aluminum oxide is formed to have a surface density distribution form in which the surface density periodically changes along the layer thickness direction at a cycle of 0.5 to 5 μm by periodically changing the amount of TMA added. Is done. FIG. 2 shows a schematic diagram thereof.
This will be described in more detail with reference to FIG.
FIG. 3 is a surface density distribution form representing an example of a layer thickness direction position-surface density correlation in an upper layer having a surface density distribution in which the finely divided aluminum oxide of the present invention formed under the chemical vapor deposition conditions changes periodically. The figure is shown.
This surface density distribution pattern can be obtained by the following method.
First, the upper layer is divided into 0.1 μm thickness width regions in parallel with the tool base surface (in FIG. 4, the sections partitioned by a plurality of parallel lines drawn in parallel to the tool base surface are 0.00. This corresponds to a thickness width region of 1 μm.), And the area occupied by fine aluminum oxide having a maximum particle size of more than 50 nm and not more than 300 nm existing in each divided thickness width region covers a total of 10 μm in length by a scanning electron microscope (magnification 50,000 times), the surface density (%) of the thickness region of 0.1 μm is obtained, and the surface density obtained in each thickness region is graphed along the layer thickness direction. A surface density distribution pattern in the layer thickness direction as shown as 3 is created.
FIG. 5 is a diagram schematically showing the growth state of columnar vertically grown aluminum oxide crystal grains in the columnar vertically grown aluminum oxide crystal structure layer.

  In the present invention, the structure in which finely divided aluminum oxide is dispersed and distributed in the columnar vertically grown aluminum oxide crystal structure is one by one when force is applied to the columnar vertically grown aluminum oxide crystal structure due to the presence of finely divided aluminum oxide. Since a shift occurs in two columnar vertically grown aluminum oxide crystals, large toughness is generated. As a result, the effect of improving chipping resistance and chipping resistance is exhibited.

  The coated tool of the present invention comprises a lower layer and an upper layer which are chemically vapor-deposited as a hard coating layer, and (a) the lower layer is a Ti carbide layer, nitride layer, carbonitride layer, carbonate layer. And a Ti compound layer having a total average layer thickness of 3 to 20 μm, and (b) the upper layer has an average layer thickness of 2 to 25 μm. The aluminum oxide layer constituting the upper layer has a columnar vertically grown aluminum oxide crystal structure, and the fine aluminum oxide is dispersed and distributed in the structure, whereby a hard coating layer is formed. This improves the toughness of steel, cast iron and other high heat generation, and even when used for high-speed intermittent cutting where intermittent and impactful high loads are applied to the cutting edge, chipping resistance and fracture resistance As a result, It exhibits excellent cutting performance over a long period of use, and a long life of the coated tool is achieved.

The schematic diagram of the distribution form of the particulate aluminum oxide which exists in the aluminum oxide layer which comprises the upper layer of this invention is shown. The schematic diagram of the fine-grain aluminum oxide in the upper layer which takes the form of surface density distribution which changes periodically is shown. The surface density distribution form figure showing an example of the correlation of the layer thickness direction position-surface density in an upper layer is shown. The schematic model for demonstrating the method of calculating | requiring the surface density distribution form figure of FIG. 3 is shown. The figure which represented typically the growth state of the columnar vertically grown aluminum oxide crystal grain in the columnar vertically grown aluminum oxide crystal structure layer is shown.

  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 1 to 3 μm are prepared. The raw material powder is blended in the blending composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. The green compact is 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 is subjected to a honing process of R: 0.07 mm. Thus, tool bases A to E made of a WC-base cemented carbide having an insert shape specified in ISO · CNMG120212 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. After sintering, the cutting edge portion was subjected to a honing process of R: 0.09 mm. Tool bases a to e made of TiCN-based cermet having an insert shape of standard / CNMG12041 were formed.

Next, a normal chemical vapor deposition apparatus is used on the surfaces of these tool bases A to E and tool bases a to e,
(A) As a lower layer of the hard coating layer, a Ti compound layer is formed by vapor deposition under the conditions shown in Table 3 and the target layer thickness shown in Table 6.
(B) Next, a hard coating layer composed of an upper layer (aluminum oxide layer) having the conditions a to j shown in Table 4 and the target layer thickness shown in Table 6 is formed by vapor deposition. Manufactured.
(C) Further, following (a), when an upper layer (aluminum oxide layer) having the target layer thickness shown in Table 6 under the conditions of k to o shown in Table 4 is formed, it is shown in Table 4. The coated tools 11 to 15 of the present invention were manufactured by vapor-depositing an aluminum oxide layer while periodically changing the addition amount between the maximum value and the minimum value of TMA volume%.

When the aluminum oxide layer constituting the upper layer of the coated tools 1 to 10 of the present invention was observed over a plurality of fields using a scanning electron microscope (magnification 50000 times), the schematic diagram of the film configuration shown in FIG. The film structure in which fine grain aluminum oxide exists in the grain boundaries and grains of the columnar crystals shown was confirmed.
Moreover, when the aluminum oxide layer which comprises the upper layer of the said coated tool 11-15 of this invention was observed over multiple visual fields using the scanning electron microscope (50000 times magnification), the film | membrane structure model shown in FIG. The film structure in which the fine grain dispersed phase exists in the grain boundaries and grains of the columnar crystals shown in the figure was confirmed.
Furthermore, about the aluminum oxide layer which comprises the upper layer of the said coating tool 1-15 of this invention, it observes over a several visual field using a transmission electron microscope (magnification 200000 times), and electron-beam diffraction is performed about fine particle aluminum oxide. As a result, it was confirmed that the fine aluminum oxide was a granular aluminum oxide crystal phase or an amorphous aluminum oxide phase or a mixed phase of a granular aluminum oxide crystal phase and an amorphous aluminum oxide phase.

  For comparison purposes, the surfaces of the tool bases A to E and the tool bases a to e are hard as in the present invention coated tools 1 to 15 under the conditions shown in Table 3 and the target layer thicknesses shown in Table 7. A Ti compound layer as a lower layer of the coating layer was formed by vapor deposition. Next, an upper layer made of an aluminum oxide layer was formed by vapor deposition as the upper layer of the hard coating layer under the conditions shown in Tables 3 and 5 and the target layer thicknesses shown in Table 7. At this time, comparative coated tools 1 to 15 shown in Table 7 were produced by forming columnar vertically grown aluminum oxide crystal structures without adding TMA.

Moreover, the layer thickness of each component layer of this invention coated tool 1-15 and comparative coated tool 1-15 is measured using a scanning electron microscope (5000 times magnification), and the layer thickness of five points in an observation visual field is obtained. When the average layer thickness was determined by measurement and averaged, the average layer thickness was substantially the same as the target layer thickness shown in Tables 6 and 7.
Moreover, about this invention coated tool 1-15 and comparative coated tool 1-15, the particle | grains of the columnar vertically grown aluminum oxide crystal which comprises the aluminum oxide layer of an upper layer using the scanning electron microscope (5000-times multiplication factor) similarly. The width w and the grain length l are measured for columnar vertically grown aluminum oxide crystals existing in the range of a total length of 10 μm in the horizontal direction with respect to the tool base, and the average is the average value of the grain widths w obtained for each crystal grain. The average aspect ratio A, which is the average value of the aspect ratio a defined as the ratio of the particle width W and the particle width w and the particle length 1 determined for each crystal grain, was determined.
For the coated tools 1 to 10 of the present invention, the area occupied by the fine aluminum oxide existing in the aluminum oxide layer of the upper layer is the aluminum oxide in the direction perpendicular to the tool base using the same scanning electron microscope (50000 times magnification). The tool base and the horizontal direction were measured over a total length of 10 μm over the thickness corresponding to the film thickness, and the surface density (%) of the cross section was obtained.
Moreover, about this invention coated tools 11-15, the scanning oxide microscope (50000 times magnification) is used, and the aluminum oxide layer which comprises an upper layer is made into a 0.1 micrometer thickness width area | region in parallel with the tool base | substrate surface. The area of fine aluminum oxide existing in each divided thickness width region was measured over a total length of 10 μm, and the surface density of the cross section of the fine aluminum oxide existing in the thickness width region of 0.1 μm ( %). Since the surface density of the cross-section of fine aluminum oxide changes periodically while taking the maximum value and the minimum value alternately in the layer thickness direction, the maximum value and the minimum value in the layer thickness direction are obtained respectively, and the maximum value in the layer thickness direction is obtained. And the average value of the maximum value and the minimum value was obtained by averaging the minimum values.
Further, for the inventive coated tools 1 to 15, similarly, using a scanning electron microscope (magnification 50000 times), the particle size r of the fine aluminum oxide present in the aluminum oxide layer of the upper layer is set in the horizontal direction with respect to the tool base. Measurement was made over a total length of 10 μm, and the average particle size R, which is the average value of the particle size r determined for each fine aluminum oxide particle, was determined.

Next, with respect to the inventive coated tools 1-15 and comparative coated tools 1-15, a cutting test was performed under the conditions shown in Table 8, and the flank wear width of the cutting edge was measured in any cutting test.
Table 9 shows the measurement results.

  From the results shown in Table 6 and Table 9, in the coated tool of the present invention, the aluminum oxide layer constituting the upper layer of the hard coating layer has a columnar vertically grown aluminum oxide crystal structure, and fine particles are included in the structure. Dispersion and distribution of aluminum oxide improves the toughness of the hard coating layer, resulting in high heat generation of steel, cast iron, etc., and high-speed intermittent cutting with intermittent and high impact loads on the cutting edge Even when it is used, it is clear that it has excellent chipping resistance and chipping resistance, and as a result, exhibits excellent cutting performance over a long period of use.

  On the other hand, the comparative coated tools 1 to 15 in which fine aluminum oxide is not distributed and distributed in the aluminum oxide layer constituting the upper layer of the hard coating layer are accompanied by high heat generation, and the cutting edge is intermittently impacted. When it is used for high-speed intermittent cutting in which a high load is applied, it is clear that the lifetime is reached in a short time due to the occurrence of chipping, chipping and the like.

  As described above, the coated tool of the present invention has excellent chipping resistance in high-speed intermittent cutting with high heat generation such as steel and cast iron and intermittent and impact high load acting on the cutting edge. Demonstrate chipping resistance and extend the service life.

Claims (2)

In a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool base composed of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
The hard coating layer is composed of a lower layer and an upper layer chemically vapor-deposited,
(A) The lower layer is composed of one or more of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer, and a total of 3 to 20 μm. A Ti compound layer having an average layer thickness;
(B) the upper layer is an aluminum oxide layer having an average layer thickness of 2 to 25 μm;
Consists of
The aluminum oxide layer constituting the upper layer of (b) has a columnar vertically grown aluminum oxide crystal structure in which fine aluminum oxide is dispersed and distributed, and the fine aluminum oxide is granular aluminum oxide. It is a mixed phase of a crystalline phase or an amorphous aluminum oxide phase or a granular aluminum oxide crystal phase and an amorphous aluminum oxide phase. The columnar vertically grown aluminum oxide crystal has an average particle width W of 50 to 2000 nm and an average aspect ratio A of 5 to 50. The average particle diameter R of the fine aluminum oxide is more than 50 nm and 300 nm or less, and the surface density of the cross section of the fine aluminum oxide present in the aluminum oxide layer constituting the upper layer is 5 to 30%. A surface-coated cutting tool.   2. The surface coating according to claim 1, wherein the surface density of the fine aluminum oxide has a surface density distribution form in which the surface density of the cross section of the fine aluminum oxide periodically changes along the layer thickness direction at a cycle of 0.5 μm to 5 μm. Cutting tools.