JP2020006487A - Surface cutting tool of which hard coating layer exhibits excellent chipping resistance - Google Patents

Abstract

To provide a coated tool which exhibits excellent chipping resistance over a long-term use even when it is used for high speed intermittent cutting of cast iron.SOLUTION: A surface coated cutting tool has a coating layer, which includes a hard coating layer of which an average layer thickness is 1.0-20.0 μm and a metal oxide layer of which an average layer thickness is 0.1-5.0 μm right above the hard coating layer, on a surface of a tool base body. The hard coating layer is a composite nitride layer of Ti and Al or a composite carbonitride layer, and includes 70 area% or more of crystal grains having a face-centered cubic structure of an NaCl type. An average content ratio xof Al to a total content of Ti and Al, and an average content ratio yof C to a total content of C and N are 0.60≤x≤0.95, 0.0000≤y≤0.0050. The metal oxide layer contains 5.0 atom% or more of Al and 30.0 atom% or more of O atoms, and a ratio of an amorphous phase is 50-100 area%.SELECTED DRAWING: Figure 1

Description

  The present invention provides a hard coating layer having excellent chipping resistance in cutting of a work material requiring toughness such as cast iron, particularly during high-speed interrupted cutting in which an impact load acts on a cutting edge. Accordingly, the present invention relates to a surface-coated cutting tool (hereinafter, sometimes referred to as “coated tool”) that exhibits excellent cutting performance over a long period of use.

Conventionally, in general, tungsten carbide (hereinafter, referred to as “WC”) based cemented carbide, titanium carbonitride (hereinafter, referred to as “TiCN”) based cermet or cubic boron nitride (hereinafter, referred to as “cBN”) based A Ti-Al-based composite nitride layer is coated as a hard coating layer on the surface of a tool base made of a high-pressure sintered body (hereinafter collectively referred to as "tool base") by a PVD method or a CVD method. There are coated tools formed which are known to exhibit excellent wear resistance.
However, although the coated tool formed by coating the conventional Ti-Al-based composite nitride layer or composite carbonitride layer is relatively excellent in wear resistance, when used under high-speed interrupted cutting conditions, abnormalities such as chipping occur. Various proposals have been made on the improvement of the hard coating layer because it is likely to cause wear.

For example, Patent Document 1, as a hard coating _{layer, Ti 1-x} Al x N layer and / or a _{Ti 1-x} Al x C layer and / or a _Ti 1-x _Al x CN layer (wherein, x is 0 .65 to 0.95) on which an Al ₂ O ₃ layer is arranged as an outer layer.

In addition, for example, in Patent Document 2, as a hard coating layer, the outer layer is formed of Ti _1-x Al _x N, Ti _1-x Al _x C, and / or Ti _1-x Al _x CN (where 65 ≦ x ≦ 0.9, preferably 0.7 ≦ x ≦ 0.9), the outer layer having a compressive stress in the range of 100 to 1100 MPa, preferably in the range of 400 to 800 MPa; Or a coated tool is described in which an Al ₂ O ₃ layer is arranged below this outer layer.

  Further, for example, Patent Document 3 discloses a surface-coated cutting tool including a tool base and a hard coating formed on a surface thereof, wherein the hard coating includes one or more layers. At least one of the layers is formed by a CVD method and includes a multilayer structure in which first unit layers and second unit layers are alternately stacked, and the first unit layer includes Ti, B, C, N, and A first compound containing at least one element selected from the group consisting of O; and the second unit layer includes Al, one or more elements selected from the group consisting of B, C, N, and O; A coated tool comprising a second compound comprising:

  In addition, for example, Patent Document 4 discloses a surface-coated cutting tool including a tool base and a hard coating formed on the surface thereof, wherein the hard coating includes one or more layers. At least one layer is a layer containing hard particles, wherein the hard particles have a multilayer structure in which first unit layers and second unit layers are alternately laminated, and the first unit layer is a periodic table. A first element consisting of one or more elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements and Al, and one or more elements selected from the group consisting of B, C, N and O; A second unit layer containing at least one element selected from the group consisting of a group 4 element, a group 5 element, a group 6 element and Al in the periodic table, and a group consisting of B, C, N and O; A coated tool comprising a second compound comprising at least one element selected from the group consisting of: It is.

JP 2011-516722 A JP 2011-513594 A JP 2014-128848 A JP 2014-129562 A

In recent years, there has been a strong demand for labor saving and energy saving in cutting work, and with this, cutting work has tended to be even faster and more efficient, and coated tools have more chipping resistance, chipping resistance, In addition to being required to have abnormal damage resistance such as peel resistance, excellent wear resistance is required over a long period of use.
However, the coated tools described in Patent Literatures 1 to 4 have a predetermined hardness and excellent wear resistance, but are inferior in toughness. In addition, abnormal wear such as chipping easily occurs, and it cannot be said that it has satisfactory cutting performance.

  Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a coated tool that exhibits excellent chipping resistance over a long period of use even when subjected to high-speed interrupted cutting of cast iron.

  The present inventor has proposed a chipping resistance of a coated tool in which a hard coating layer including at least a composite nitride or composite carbonitride of Ti and Al (hereinafter sometimes referred to as “TiAlCN”) is provided on a tool base. The following findings were obtained as a result of intensive studies for improvement.

  In other words, the metal oxide layer mainly composed of an amorphous phase is present immediately above the TiAlCN layer, so that the oxidation resistance is excellent, and further, the frictional resistance is reduced and the cutting heat generated at the cutting edge is reduced, thereby lowering the cutting edge temperature. As a result, a surprising finding that the generation and propagation of thermal cracks was suppressed was obtained.

The present invention has been made based on the above findings,
"(1) A hard coating layer and a metal oxide immediately above it are formed on the surface of a tool substrate made of a tungsten carbide-based cemented carbide, a titanium carbonitride-based cermet, or a cubic boron nitride-based ultrahigh-pressure sintered body. In a surface-coated cutting tool provided with a coating layer including a layer,
(A) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm;
(B) When analyzed from a vertical section perpendicular to the surface of the tool substrate, the composite nitride layer or composite carbonitride layer of Ti and Al contains 70 area% of crystal grains having a NaCl-type face-centered cubic structure. Including
(C) the Ti and Al composite nitride layer or composition of the composition of the composite carbonitride layer _{formula: (Ti 1-x Al x} ) if (C _{y N 1-y)} expressed in, Al Ti and Al The average content ratio x _avg in the total amount of C and the average content ratio y _avg in the total amount of C and N in C (where x _avg and y _avg are both atomic ratios) are 0.60 ≦ x _avg , respectively. satisfy the ≦ 0.95,0.0000 ≦ _{y avg} ≦ 0.0050,
(D) the metal oxide layer has an average layer thickness of 0.1 to 5.0 μm;
(E) the metal oxide layer contains at least 5.0 atomic% of Al and at least 30.0 atomic% of O atoms,
(F) The surface-coated cutting tool, wherein the metal oxide layer satisfies a ratio of 50% to 100% by area of an amorphous phase.
(2) The surface-coated cutting tool according to (1), wherein the metal oxide layer contains C atoms in an amount of 0.5 to 10.0 atomic%.
(3) The surface-coated cutting tool according to (1) or (2), wherein the metal oxide layer contains 0.5 to 20.0 atomic% of Mn atoms.
(4) The surface-coated cutting tool according to any one of (1) to (3), wherein the metal oxide layer contains 0.5 to 20.0 atomic% of Si atoms. "
It is.

  The coated tool according to the present invention has excellent oxidation resistance due to the presence of the metal oxide layer mainly composed of the amorphous phase immediately above the TiAlCN layer, and particularly in the rake face, the metal oxide layer is soft. Therefore, it is possible to easily discharge the chips, reduce the wear, reduce the temperature of the cutting edge, and exhibit an excellent effect of suppressing the generation and propagation of thermal cracks.

It is a cross section showing an embodiment of a covering tool concerning the present invention.

Next, the hard coating layer of the coated tool of the present invention will be described more specifically.
In the present specification and claims, when a numerical range is expressed by "-", the range includes upper and lower numerical values.

1. Average layer thickness of TiAlCN layer The average layer thickness of the TiAlCN layer is 1.0 to 20.0 µm. The reason is that if the average layer thickness is less than 1.0 μm, the layer thickness is too thin to exhibit sufficient wear resistance over a long period of use, while if the average layer thickness exceeds 20.0 μm. This is because the crystal grains of the TiAlCN layer are likely to be coarse and chipping is likely to occur. In addition, a more preferable average layer thickness is 3.0 to 15.0 μm.

  Here, the average layer thickness of the TiAlCN layer is measured by polishing a cross section (longitudinal cross section) in a direction perpendicular to the tool base and using a scanning electron microscope at an appropriate magnification (for example, 5000 times). Then, the thickness can be obtained by measuring and averaging the layer thicknesses at five points in the observation visual field.

2. Area ratio of crystal grains having NaCl-type face-centered cubic structure in TiAlCN layer It is necessary that 70% by area or more of crystal grains having a NaCl-type face-centered cubic structure in the TiAlCN layer exist. The reason is that since the face-centered cubic structure of the NaCl type has a high hardness, the hardness of the TiAlCN layer can be ensured even when the crystal grains of the hexagonal structure are present. And insufficient damage such as chipping is likely to occur. On the other hand, the higher the area ratio is, the more preferable it is. The area ratio is more preferably 95% or more, and the upper limit is 100% by area.

  Here, the area ratio of the NaCl-type face-centered cubic structure can be calculated by the following procedure. The area ratio of the crystal grains having the NaCl-type face-centered cubic structure was analyzed at intervals of 0.1 μm in the film thickness direction in the longitudinal section using an electron beam backscattering diffractometer. Is measured in five visual fields, the number of pixels belonging to the crystal grains having a cubic structure constituting the composite nitride or composite carbonitride layer is determined, and the ratio to the total number of measured pixels in the measurement in the five visual fields is determined. The area ratio (area%) occupied by the crystal grains having the NaCl-type face-centered cubic structure of the TiAlCN layer is calculated (the size of one pixel is based on the size of the crystal grains having the NaCl-type face-centered cubic structure). Can be arbitrarily determined, for example, a size of 0.1 μm × 0.1 μm or less can be exemplified).

3. Composition of TiAlCN Layer The composition of the TiAlCN layer of the present invention, when represented by the above composition formula: (Ti _1-x Al _x ) ( _{CyN 1-y} ), average content of Al in the total amount of Ti and Al The ratio x _avg and the average content ratio y _{avg of the} total amount of C and N in C (where x _avg and y _avg are both atomic ratios) are 0.60 ≦ x _avg ≦ 0.95 and 0.50, respectively. Control is performed so as to satisfy 0000 ≦ y _avg ≦ 0.0050.
The reason is that, when the average content ratio _{xavg of} Al is less than 0.60, the TiAlCN layer is inferior in oxidation resistance, so when subjected to interrupted cutting of cast iron or high-speed interrupted cutting of alloy steel, etc., Insufficient wear resistance. On the other hand, when the average content ratio _{xavg of} Al is more than 0.95, the amount of hexagonal crystals inferior in hardness increases and the hardness decreases, so that the wear resistance decreases.

Further, when the average content ratio y _avg of the C component contained in the TiAlCN layer is a trace amount in the range of 0.0000 ≦ y _avg ≦ 0.0050, the adhesion between the TiAlCN layer and the tool base or the lower layer is improved. In addition, the improved lubricity reduces the impact during cutting, and as a result, improves the chipping resistance and chipping resistance of the TiAlCN layer. On the other hand, when the average content ratio y of the C component is out of the range of 0.0000 ≦ y _avg ≦ 0.0050, the toughness of the TiAlCN layer is reduced, and thus the chipping resistance and chipping resistance are undesirably reduced.

Here, the average Al content x x _avg of the TiAlCN layer is determined by irradiating an electron beam from the longitudinal section side of a sample whose sample section has been polished using Auger Electron Spectroscopy (AES). The average of the analysis results of Auger electrons obtained by performing line analysis of five lines. Further, the average content ratio _yavg of C can be determined by secondary ion mass spectrometry (SIMS). That is, in a sample whose surface is polished, an ion beam is irradiated to a range of 70 μm × 70 μm from the surface side of the TiAlCN layer, and the surface analysis by the ion beam and the etching by the sputter ion beam are alternately repeated so that the depth direction is increased. Perform a concentration measurement. First, an average of data obtained by measuring a length of at least 0.5 μm at a pitch of 0.1 μm or less from a portion where the TiAlCN layer has penetrated 0.5 μm or more in the depth direction of the layer is obtained. Further, the results obtained by repeatedly calculating the values at least at five points on the sample surface can be averaged to obtain the average C content _yavg .

4. Average layer thickness of metal oxide layer The average layer thickness of the metal oxide layer is 0.1 to 5.0 µm. The reason is that if the average layer thickness is less than 0.1 μm, the layer thickness is too small to exhibit sufficient wear resistance over a long period of use, while if the average layer thickness exceeds 5.0 μm. This is because separation easily occurs at the interface between the metal oxide layer and the TiAlCN layer.

  Here, the average layer thickness of the metal oxide layer is determined by polishing a cross section (longitudinal cross section) in a direction perpendicular to the tool base, and applying a suitable magnification (for example, by using a transmission electron microscope or a scanning electron microscope) to the polished cross section. , And magnification of 10,000 to 40,000), and the layer thickness at five points in the observation visual field is measured and averaged.

5. Composition of Metal Oxide Layer (General)
The metal oxide layer contains at least 5.0 atomic% of Al atoms and at least 30.0 atomic% of O atoms. The reason for this definition is that if the Al atom content is less than 5.0 atomic%, the heat resistance is reduced, the oxide layer is quickly worn, heat cracks are easily generated, and the O atom content is 30.0%. If the content is less than atomic%, the oxidation resistance is not sufficient, and the progress of wear and chipping tend to occur.
And even if this metal oxide layer contains a very small amount of Ti, Zr, B, Cr, S, Cl, etc. in addition to C, Si, and Mn atoms, the performance improving effect is not impaired.

6. Composition of metal oxide layer (details)
(1) C atom It is preferable that the metal oxide layer contains C atom in an amount of 0.5 to 10.0 atomic%. By including C atoms in a predetermined range, the lubricating property of the metal oxide layer is enhanced, and the chip discharging property is improved, so that the cutting edge temperature can be reduced. When the amount of C atoms is less than 0.5 atomic%, the above effect is reduced. When the amount of C atoms exceeds 10.0 atomic%, the metal oxide layer cannot be maintained at the time of cutting and abrasion proceeds, so that C atoms are present in the metal oxide layer. The effect cannot be obtained.

(2) Mn atom The composition of the metal oxide layer preferably contains Mn atoms in a range of 0.5 to 20.0 atomic%. By including Mn atoms in a predetermined range, the high-temperature stability of the metal oxide layer is enhanced, and the metal oxide layer can be maintained for a long time during cutting. When the Mn atom is less than 0.5 at%, the above effect is reduced, and when it exceeds 20.0 at%, Mn becomes excessive, and the high-temperature hardness of the metal oxide layer is reduced, whereby the wear resistance is reduced. The effect of the presence of Mn atoms in the metal oxide layer cannot be obtained.

(3) Si atom The metal oxide layer preferably contains 0.5 to 20.0 atomic% of Si atoms. By including Si atoms in a predetermined range, the lubricating property of the metal oxide layer is enhanced, and the chip discharging property is improved, so that the cutting edge temperature can be reduced. If the Si atom content is less than 0.5 atomic%, the above effect is reduced. If the Si atom content is more than 20.0 atomic%, the metal oxide layer cannot be maintained at the time of cutting and abrasion proceeds. Can not be obtained.

  The average content ratio of each element can be determined by Secondary-Ion-Mass-Spectrometry (SIMS). The ion beam was irradiated to a range of 70 μm × 70 μm from the surface side, and the surface analysis with the ion beam and the etching with the sputter ion beam were alternately repeated to measure the concentration in the depth direction.

7. Area Ratio of Amorphous Oxide Phase The area ratio of the area of the amorphous oxide phase to the metal oxide layer is 50 to 100% by area. The reason for this area ratio is that if it is less than 50 area%, the effect of reducing wear during cutting and lowering the cutting edge temperature cannot be obtained. Here, amorphous means that it can be regarded as substantially amorphous.
The area ratio of the amorphous oxide phase occupied in the metal oxide layer can be determined by identifying the crystallinity using a nanobeam electron diffraction from a longitudinal section or by mapping the transmission electron backscattered diffraction pattern from the vertical section. Is calculated, and the ratio of the metal oxide layer to the section in the thickness direction is measured. The area ratio is calculated by calculating at least five area ratios of different regions having a width of 500 nm and averaging them. Here, the area ratio of the amorphous oxide phase means a portion of the metal oxide layer that is not measured as a pore or a crystalline portion, and an element determined by a wavelength dispersive X-ray spectrometer (Wavelength Dispersive X-ray Spectrometer) or the like. The analysis shows the area ratio of the region confirmed to be the metal oxide phase.

8. Other Layers The hard coating layer (TiAlCN layer) included in the surface-coated cutting tool of the present invention can sufficiently exhibit the above-described effects by itself, but includes a carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbon layer of Ti. When a lower layer composed of one or two or more Ti compound layers of the nitrided oxide layers and having a total average thickness of 0.1 to 20.0 μm is provided, the effects of these layers are exhibited. In combination with this, more excellent characteristics can be created. When a lower layer composed of one or more Ti compound layers of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride layer is provided, a total average layer of the lower layers When the thickness is less than 0.1 μm, the effect of the lower layer is not sufficiently exerted. On the other hand, when the thickness is more than 20.0 μm, the crystal grains tend to be coarse and chipping is likely to occur.

9. Manufacturing Method The hard coating layer defined in the present invention can be formed on a tool substrate by, for example, a manufacturing method (manufacturing conditions) by a chemical vapor deposition method described below.
(1) Composition of reactive gas for forming TiAlCN layer (% represents volume%, and the sum of gas group A and gas group B is 100 volume%)
Gas Group _{A: NH 3: 2.0~3.0%,} H 2: 60~75%
Gas group B: AlCl ₃ : 0.60 to 1.00%, TiCl ₄ : 0.07 to 0.40%,
_{C 2 H 4: 0.00~0.50%,} N 2: 0.0~12.0%, H 2: residual reaction atmosphere pressure: 4.0～5.0KPa
Reaction atmosphere temperature: 700 to 850 ° C
Supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Phase difference of supply between gas group A and gas group B: 0.10 to 0.20 second ( 2) Metal oxide layer forming reaction gas composition (% represents volume%, and the sum of gas group A and gas group B is 100 volume%)
Gas Group _A: H 2: _30~45%
Gas group B: AlCl ₃ : 1.00 to 3.00%,
_{SiCl 4: 0.00~2.00%, Mn (} C 5 H 5) 2: 0.00~2.00%,
_{C 2 H 4: 0.00~0.50%,} CH 3 CN: 0.00~5.00%,
_{H 2 S: 0.00~0.30%, HCl} : 1.00~3.00%,
CO ₂ : 5.0 to 15.0%, H ₂ : residual reaction atmosphere pressure: 4.0 to 5.0 kPa
Reaction atmosphere temperature: 700 to 850 ° C
Supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Phase difference of supply between gas group A and gas group B: 0.10 to 0.20 second

Next, examples will be described.
Here, as a specific example of the coated tool of the present invention, a tool applied to an insert cutting tool using a WC-based ultra-high pressure sintered body as a tool base will be described. As the tool base, a TiCN-based cermet and a cBN-based ultra-high pressure sintered The same applies to the case where a body is used, and the same applies to the case of applying to a drill or an end mill.

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, ZrC powder, TiN powder and Co powder each having an average particle size of 1 to 3 μm are prepared, and these raw material powders are prepared. Compounded in the composition shown in Table 1, further added wax, mixed in a ball mill in acetone for 24 hours, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 98 MPa. Vacuum sintering at a predetermined temperature in the range of 1370 to 1470 ° C. in a vacuum of 5 Pa for 1 hour, and after sintering, a WC-based cemented carbide tool base having an insert shape of ISO standard SEEN1203AFSN Tool bases D to F made of WC-based cemented carbide having insert shapes of A to C and ISO standard CNMG120412 were manufactured, respectively.

Next, a TiAlCN layer and a metal oxide layer were formed on the surfaces of the tool bases A to F using a CVD apparatus under the film forming conditions shown in Tables 2 and 3, and shown in Table 5 under the conditions shown in Table 4. A lower layer was formed.
The film forming conditions of the TiAlCN layer are as described in Tables 2 and 3, and are generally as follows.
(1) Composition of reactive gas for forming TiAlCN layer (% represents volume%, and the sum of gas group A and gas group B is 100 volume%)
Gas Group _{A: NH 3: 2.0~3.0%,} H 2: 60~75%
Gas group B: AlCl ₃ : 0.60 to 1.00%, TiCl ₄ : 0.07 to 0.40%,
_{C 2 H 4: 0.00~0.50%,} N 2: 0.0~12.0%, H 2: residual reaction atmosphere pressure: 4.0～5.0KPa
Reaction atmosphere temperature: 700 to 850 ° C
Supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Phase difference of supply between gas group A and gas group B: 0.10 to 0.20 second ( 2) Metal oxide layer forming reaction gas composition (% represents volume%, and the sum of gas group A and gas group B is 100 volume%)
Gas Group _A: H 2: _30~45%
Gas group B: AlCl ₃ : 1.00 to 3.00%,
_{SiCl 4: 0.00~2.00%, Mn (} C 5 H 5) 2: 0.00~2.00%,
_{C 2 H 4: 0.00~0.50%,} CH 3 CN: 0.00~5.00%,
_{H 2 S: 0.00~0.30%, HCl} : 1.00~3.00%,
CO ₂ : 5.0 to 15.0%, H ₂ : residual reaction atmosphere pressure: 4.0 to 5.0 kPa
Reaction atmosphere temperature: 700 to 850 ° C
Supply cycle: 1.00 to 5.00 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Phase difference of supply between gas group A and gas group B: 0.10 to 0.20 second

  For the purpose of comparison, a TiAlCN layer was formed on the surfaces of the tool bases A to F using a CVD apparatus under the film forming conditions shown in Tables 2 and 3, and the lower layer shown in Table 5 was formed under the conditions shown in Table 4. A film was formed.

For the hard coating layers of the coated tools 1 to 16 of the present invention and the comparative coated tools 1 to 16, the average Al content ratio x _avg , the average C content ratio y _avg , The average content ratio of Al, O, C, Si, and Mn atoms in the material layer was determined, and the results are summarized in Table 6. It is assumed that C, Si, and Mn do not exist at less than 0.1 atomic%.

  Subsequently, for the coated tool of the present invention and the comparative coated tool, a wet high-speed interrupted cutting test (cutting condition 1) and a dry high-speed interrupted cut test (cutting condition 2) of cast iron shown below were performed. The wear width of the flank of the cutting edge was measured. The results are shown in Tables 7 and 8. In addition, since the life of the comparative coated tool has been reached due to chipping, the time until the life is reached is shown.

Cutting conditions 1: Wet high-speed face milling, center-cut cutting Cutter diameter: 125 mm
Work material: JIS FCD700 Block material, width 100 mm, length 400 mm Rotation speed: 891 / min
Cutting speed: 350m / min
Cut: 2.0mm
Feed amount per blade: 0.3mm / tooth Cutting time: 5 minutes (normal cutting speed is 150 to 250m / min)
Cutting condition 2: Dry high-speed intermittent cutting Work material: JIS FCD700 Round bar with vertical grooves at 8 equally spaced lengths Cutting speed: 300 m / min
Cut: 1.5mm
Feed: 0.3mm / rev
Cutting time: 5 minutes (normal cutting speed is 150 to 200 m / min)

  From the results shown in Tables 7 and 8, all of the coated tools 1 to 16 of the present invention include a hard coating layer and a coating layer including a metal oxide layer immediately above the coating tool. No chipping and excellent cutting performance over a long period. On the other hand, the comparative coated tools 1 to 16, which do not satisfy at least one of the items specified in the coated tool of the present invention, cause chipping in high-speed interrupted cutting of cast iron, and reach a service life in a short time. I have.

  As described above, the coated tool of the present invention can be used not only for high-speed interrupted cutting of work materials requiring toughness such as high-speed interrupted cutting of cast iron, but also as a coated tool for various work materials. It is capable of achieving excellent cutting performance over a long period of use, and is capable of satisfying the needs of high-performance cutting equipment, labor-saving and energy-saving cutting, and low cost. It is.

Claims (4)

Coating that includes a hard coating layer and a metal oxide layer immediately above it on the surface of a tool substrate composed of either tungsten carbide-based cemented carbide, titanium carbonitride-based cermet, or cubic boron nitride-based ultrahigh-pressure sintered compact In a surface-coated cutting tool provided with a layer,
(A) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al having an average layer thickness of 1.0 to 20.0 μm;
(B) When analyzed from a vertical section perpendicular to the surface of the tool substrate, the composite nitride layer or composite carbonitride layer of Ti and Al contains 70 area% of crystal grains having a NaCl-type face-centered cubic structure. Including
(C) the Ti and Al composite nitride layer or composition of the composition of the composite carbonitride layer _{formula: (Ti 1-x Al x} ) if (C _{y N 1-y)} expressed in, Al Ti and Al The average content ratio x _avg in the total amount of C and the average content ratio y _avg in the total amount of C and N in C (where x _avg and y _avg are both atomic ratios) are 0.60 ≦ x _avg , respectively. satisfy the ≦ 0.95,0.0000 ≦ _{y avg} ≦ 0.0050,
(D) the metal oxide layer has an average layer thickness of 0.1 to 5.0 μm;
(E) the metal oxide layer contains at least 5.0 atomic% of Al and at least 30.0 atomic% of O atoms,
(F) The surface-coated cutting tool, wherein the metal oxide layer satisfies a ratio of 50% to 100% by area of an amorphous phase.   2. The surface-coated cutting tool according to claim 1, wherein the metal oxide layer contains C atoms in an amount of 0.5 to 10.0 atomic%. 3.   3. The surface-coated cutting tool according to claim 1, wherein the metal oxide layer contains Mn atoms in a range of 0.5 to 20.0 atomic%. 4.   The surface-coated cutting tool according to any one of claims 1 to 3, wherein the metal oxide layer contains 0.5 to 20.0 atomic% of Si atoms.

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