JP7190111B2 - surface coated cutting tools - Google Patents

Description

The present invention provides a hard coating layer with excellent chipping resistance and wear resistance in high-speed, high-feed, interrupted cutting, which is accompanied by high heat generation and a strong impact load acts on the cutting edge. It relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool) that exhibits excellent cutting performance over the use of.

Conventionally, on the surface of a tool substrate (hereinafter collectively referred to as a tool substrate) made of a tungsten carbide (hereinafter referred to as WC)-based cemented carbide, a Ti—Al-based composite nitriding layer is applied as a hard coating layer. There are coated tools coated with a material layer by a vapor deposition method, and these are known to exhibit excellent wear resistance.
However, although the conventional coated tool coated with the Ti—Al-based composite nitride layer has relatively excellent wear resistance, it is prone to abnormal wear when used under high-speed, high-feed, intermittent cutting conditions. , various proposals have been made for improving the hard coating layer.

For example, in Patent Document 1, a (Ti _1-x Al _x ) (C _y N _1-y ) layer (wherein the average Al content x _avg and the average C content y _avg are , 0.60≦x _avg ≦0.95 and 0≦y _avg ≦0.005), wherein the crystal grains having a NaCl-type face-centered cubic structure in the layer are {111 } orientation, the individual crystal grains having the NaCl-type face-centered cubic structure have an average grain width W of 0.1 to 2.0 μm and an average aspect ratio A of 2 to 10. In addition, in each crystal grain having the NaCl-type face-centered cubic structure, there is a periodic composition change of Ti and Al in the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ). However, a coated tool is described in which the difference Δx between the mean of the maxima and the mean of the minima of the periodically varying x is between 0.03 and 0.25.

Also, for example, US Pat.
The wear protection coating comprises at least one Ti _1-x Al _x C _y N _z (0.70≦x<1, 0≦y<0.25, 0.75≦z< 1.15) layer, wherein the Ti _1-x Al _x C _y N _z layer is a layered structure comprising a plurality of layers of 150 nm or less, having the same crystal structure (crystal phase), and containing Ti and Al A coated tool is described which is characterized by being formed of periodically alternating regions of alternating stoichiometric proportions and having a face-centered cubic crystal structure of at least 90 vol %.

JP 2016-64485 A Japanese Patent Publication No. 2017-508632

In recent years, there is a strong demand for labor saving and energy saving in cutting. Abnormal damage resistance such as peeling resistance is required, and excellent wear resistance over long-term use is also required.

Therefore, the present invention has been made in view of this situation, and even when used for high-speed, high-feed cutting of ductile cast iron, etc., it has excellent chipping resistance and wear resistance over long-term use. It is an object of the present invention to provide a coated tool that exhibits excellent performance.

The present inventor has investigated the chipping resistance and wear resistance of a coated tool containing a composite nitride layer or composite carbonitride layer of Ti and Al (hereinafter collectively referred to as "TiAlCN layer"). In order to improve it, we have made a lot of efforts.

As a result, when two groups of crystal grains having a NaCl-type face-centered cubic structure with a predetermined difference in Al content are present in a specific proportion in a cut plane of the TiAlCN layer parallel to the tool substrate, A new knowledge was obtained that the difference in thermal expansion coefficient due to the difference in the content ratio causes local strain in the TiAlCN layer and improves the chipping resistance.

The present invention is based on this finding and is as follows.
"(1) A surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool substrate,
(a) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al with an average layer thickness of 1.0 to 20.0 μm,
(b) the composite nitride layer or composite carbonitride layer of Ti and Al includes at least NaCl-type face-centered cubic crystal grains,
(c) When a cut plane parallel to the tool substrate is analyzed from a direction perpendicular to the surface of the tool substrate, a plurality of crystal grains of the NaCl type face-centered cubic structure with different Ti and Al compositions are present. , when each is divided into the crystal grain A group and the crystal grain B group,
When the crystal grain group A is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), the average X _Aavg of the content ratio X _A of Al to the total amount of Ti and Al, and The average Y _Aavg of C in the total amount of C and N (where X _Aavg and Y _Aavg are both atomic ratios) is 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively satisfying ≦Y _Aavg ≦0.0150,
When the crystal grain B group is represented by the composition formula: (Ti _1-XB Al _XB ) (C _YB N _1-YB ), the average X _Bavg of the content ratio X _B of Al in the total amount of Ti and Al, and The content ratio Y of C in the total amount of C and N The average Y _Bavg of _B (where X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X _{satisfying Aavg} −X _Bavg ≦0.25, 0.0000≦Y _Bavg ≦0.0150,
(d) in the cut surface, the area ratio occupied by the crystal grain A group is 20 to 80%;
A surface-coated cutting tool characterized by:
(2) In the crystal grains of the crystal grain group A, periodic composition changes of Ti and Al exist along one of the equivalent crystal orientations represented by <001> of the crystal grains. , the difference ΔX _A between the average value of the maximum value and the average value of the minimum value of X _A that changes periodically is 0.03 to 0.25. tool.
(3) In the crystal grains of the crystal grain group B, periodic composition changes of Ti and Al exist along one of the equivalent crystal orientations represented by <001> of the crystal grains. , wherein the difference ΔX _B between the average value of the maximum value and the average value of the minimum value of X _B that changes periodically is 0.03 to 0.25. coated cutting tools.
(4) Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer between the tool substrate and the composite nitride layer or composite carbonitride layer of Ti and Al The surface coated cutting according to any one of (1) to (3), characterized in that there is a lower layer consisting of one or more layers and having a total average layer thickness of 0.1 to 20 μm. tool.
(5) Above the composite nitride layer or the composite carbonitride layer, the upper layer containing at least an aluminum oxide layer is present with a total average layer thickness of 1 to 25 μm (1) to (4) ) The surface-coated cutting tool according to any one of ). ”

The cutting tool of the present invention exhibits excellent chipping resistance and wear resistance over a long period of use even when subjected to high-speed, high-feed cutting of ductile cast iron or the like.

It is a schematic diagram showing the structure of the TiAlCN layer of the present invention in a cut plane parallel to the tool base, and the shape and dimensions of each structure do not represent the actual sintered structure. FIG. 3 is a schematic diagram showing the period, maximum value, and minimum value of periodic composition change of Ti and Al. FIG. 2 is a schematic diagram showing composition changes in crystal grains having a NaCl-type face-centered cubic structure in which periodic composition changes of Ti and Al are present.

The coated tool of the present invention will be described in more detail below. In addition, in the present specification and claims, when a numerical range is expressed using "-", the range includes upper and lower numerical values.

1. Average layer thickness of hard coating layer:
The hard coating layer includes at least a TiAlCN layer. The hard coating layer including this TiAlCN layer has high hardness and excellent wear resistance, and the effect is conspicuous especially when the average layer thickness is 1.0 to 20.0 μm. The reason for this is that if the average layer thickness is less than 1.0 μm, the average layer thickness is too thin to ensure sufficient wear resistance over long-term use, while if the average layer thickness exceeds 20.0 μm, This is because the crystal grains of the TiAlCN layer tend to coarsen and chipping tends to occur.

2. Crystal Grains of NaCl-Type Face-Centered Cubic Structure in TiAlCN Layer It is difficult to achieve the object of the present invention unless NaCl-type crystal grains of face-centered cubic structure are included in the TiAlCN layer. In order to achieve this object, in a cross section parallel to the surface of the tool substrate, the area ratio of NaCl-type crystal grains having a face-centered cubic structure is 60% or more, preferably 80% or more, more preferably 100% ( All the crystal grains are preferably NaCl-type face-centered cubic structures).

3. Composition of the TiAlCN layer constituting the hard coating layer:
The TiAlCN layer constituting the hard coating layer includes crystal grains A group and crystal grains B group having different Al contents.
The composition of the crystal grain group A is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), the content ratio X _A of Al to the total amount of Ti and Al, the average X A _avg and The average Y _Aavg of C in the total amount of C and N (where X _Aavg and Y _Aavg are both atomic ratios) is 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively satisfying ≦Y _Aavg ≦0.0150,
The composition of the crystal grain B group is represented by the composition formula: (Ti _1-XB Al _XB ) (C _YB N _1-YB ), the content ratio X of Al in the total amount of Ti and Al, the average X _Bavg of _B , and The content ratio Y of C in the total amount of C and N The average Y _Bavg of _B (where X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X _Aavg −X _Bavg ≦0.25 and 0.0000≦Y _Bavg ≦0.0150 are preferably satisfied.

Next, the reason why the composition of the crystal grain group A and the crystal grain group B is preferably in the above range will be explained.
(1) Average content ratio of Al The average content ratio of Al satisfies 0.75 ≤ X _Aavg ≤ 0.95 in the crystal grain A group, and 0.70 ≤ X _Bavg ≤ 0.90 in the crystal grain B group. By doing so, the TiAlCN layer secures hardness and has sufficient wear resistance when subjected to high-speed, high-feed cutting of ductile cast iron and the like, and the content of Ti does not relatively decrease. This is because the chipping resistance can be ensured without causing embrittlement.
Then, when the Al content ratio of the crystal grain A group and the crystal grain B group satisfies 0.05≦X _Aavg −X _Bavg ≦0.25, the thermal expansion between the crystal grain A group and the crystal grain B group The modulus difference becomes appropriate, moderate local strain is introduced, and chipping resistance is improved.

(2) Average content ratio of C When both the average content ratios Y _Aavg and Y _Bavg of C in the crystal grain group A and the crystal grain B group are trace amounts in the range of 0.0000 or more and 0.0150 or less, the TiAlCN layer The adhesion between the TiAlCN layer and the tool substrate or the lower layer to be described later is improved, and the impact during cutting is reduced by improving the lubricity. As a result, the chipping resistance and chipping resistance of the TiAlCN layer are improved. On the other hand, if the average content of C deviates from this range, the toughness of the TiAlCN layer is lowered, which adversely impairs fracture resistance and chipping resistance, which is not preferable.

Here, the average Al content rates X _Aavg and X _Bavg and the average C content rates Y _Aavg and Y _Bavg of the TiAlCN layer were determined as follows. Using an electron beam microanalyzer (EPMA, Electron-Probe-Micro-Analyser), an electron beam is irradiated from the sample surface side to the polished surface parallel to the tool substrate from a direction perpendicular to the surface of the tool substrate, Conduct a mapping analysis. From the mapping analysis results, the average composition is obtained for each crystal grain, and the crystal grain group is divided into a crystal grain group with a relatively high Al content and a crystal grain group with a relatively low Al content, and a crystal grain group with a relatively high Al content. Average Al content X _Aavg of (crystal grain A group), average C content Y _Aavg , average Al content X _Bavg of relatively low Al content crystal grain group (crystal grain B group), C The average content ratio Y _Bavg of was determined.

4. Discrimination Between Crystal Grain Group A and Crystal Grain Group B As described above, discrimination between the crystal grain group A and the crystal grain B group is performed. If it is difficult to discriminate a sample in which Ti and Al have periodic composition changes in crystal grains by the above method, the following method is additionally used for discrimination. Mapping analysis by energy dispersive X-ray spectrometry (EDS) using a transmission electron microscope from the direction perpendicular to the surface of the tool substrate to the polished surface parallel to the tool substrate. I do. When the average composition is obtained for each crystal grain from the mapping analysis results, it is divided into a crystal grain group with a relatively high Al content and a crystal grain group with a relatively low Al content, and a crystal grain with a relatively high Al content. A group of crystal grains is referred to as a group A of crystal grains, and a group of crystal grains having a relatively low Al content is referred to as a group B of crystal grains.

5. Area Ratio Occupied by Crystal Grains A Group The area ratio occupied by the crystal grains A group in a cross section parallel to the tool base is preferably 20 to 80 area %. The reason for setting this range is that if the area is less than 20 area%, the area ratio of the crystal grain B group relatively increases, and local strain occurs due to the difference in thermal expansion coefficient from the crystal grain A group. On the other hand, when it exceeds 80 area %, the area ratio of the crystal grain group A becomes relatively dominant, and the occurrence of local strain caused by the difference in thermal expansion coefficient from the crystal grain group B is small. It is for the sake of becoming. A more preferable area ratio is 40 to 60 area %.

6. Composition change in crystal grain A group and crystal grain B group (1) crystal grain A group In the crystal grain of crystal grain A group, periodic composition change of Ti and Al occurs at <001> of the crystal grain It is preferably along one of the equivalent crystallographic orientations represented.
Here, the periodic composition change means that line analysis is performed along one of the equivalent crystal orientations represented by <001> of the crystal grains, and changes in the Al content ratio _XA are graphed. It means that the value of _XA is repeated at some interval when transformed. _As shown in FIG. 2, the change in XA is approximated by a straight line (Xm). This straight line is drawn so that the areas surrounded by the straight line and the curve showing repeated changes are equal above and below the straight line. A maximum value (P _max ) and a minimum value (P _min ) are obtained for each region where this straight line crosses this repeated change, and the difference ΔX _A between the average value of the maximum values and the average value of the minimum values is 0.03 to 0.03. 0.25 is preferred. When ΔX _A is within this range, sufficient hardness and chipping resistance are further improved.
It goes without saying that a well-known measurement noise removal method (for example, a moving average method) is performed in graphing.

(2) Crystal grain B group In the crystal grains of the crystal grain B group, periodic composition changes of Ti and Al occur in one of the equivalent crystal orientations represented by <001> of the crystal grains. preferably along.
Here, the periodic composition change is obtained in the same manner as in the crystal grain A group, and the difference ΔX _B between the average value of the maximum values and the average value of the minimum values is 0.03 to 0.25. is preferably When ΔX _B is within this range, sufficient hardness and chipping resistance are further improved.

(3) Measurement of periodic composition change of Ti and Al The periodic composition change of Ti and Al can be detected by observing the TiAlCN layer using a transmission electron microscope (TEM: for example, magnification of 200,000 times). Confirm. After that, for example, using EDS, a surface analysis is performed on a 400 nm × 400 nm region in a cross section parallel to the surface of the tool substrate, and the cubic crystal grains of the NaCl type face-centered cubic structure change in color density in stripes. is observed (see FIG. 3), it is determined that there is a periodic composition change of Ti and Al in TiAlCN within the cubic crystal grains. Then, by performing electron beam analysis on the crystal grains, a periodic composition change is observed in one of the equivalent crystal orientations represented by <001> of the crystal grains having a NaCl-type face-centered cubic structure. Based on the results of the surface analysis along the direction, set the magnification so that the composition change of about 10 cycles from the density is within the measurement range. A line analysis by EDS is performed in the range of 5 cycles along the normal direction, the change is plotted on a graph, and the Al content ratio is determined for each region defined by the straight line approximating the change in the Al content ratio. Find the maximum value and minimum value of the change of , and calculate the difference of the average value of the difference.

7. The hard coating layer including the lower layer TiAlCN layer exhibits sufficient chipping resistance and wear resistance by itself. When a lower layer composed of two or more Ti compound layers and having a total average layer thickness of 0.1 to 20.0 μm is provided, the effect of this layer combined with the effect of this layer further improves the chipping resistance. performance and wear resistance. However, when providing a lower layer composed of one or more Ti compound layers selected from Ti carbide layer, nitride layer, carbonate layer and carbonitride layer, the total average layer thickness of the lower layer is 0. If it is less than 0.1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20.0 μm, the crystal grains tend to coarsen and chipping tends to occur.

8. Upper Layer It is preferable to form a layer containing aluminum oxide on the upper portion of the TiAlCN layer so as to have a total average layer thickness of 1.0 to 25.0 μm, as it exhibits even better chipping resistance and wear resistance. Here, when the total average layer thickness is less than 1.0 μm, the effect of providing the upper layer is not sufficiently exhibited, while when it exceeds 25 μm, chipping tends to occur.

9. Tool Substrate As the tool substrate, any conventionally known substrate for this type of tool substrate can be used as long as it does not interfere with the achievement of the object of the present invention. For example, cemented carbide (WC-based cemented carbide, WC, containing Co, or containing carbonitrides such as Ti, Ta, Nb, etc.), cermets (TiC, TiN , TiCN as a main component, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body.

10. Manufacturing method The TiAlCN layer is for example deposited on the tool substrate or on the lower layer on the tool substrate by:
It can be obtained by supplying a reaction gas of a specific composition to a CVD apparatus under predetermined conditions.
That is, as reaction gases, a gas group A consisting of NH ₃ , N ₂ and H ₂ and a gas group B consisting of AlCl ₃ , Al(CH ₃ ) ₃ , TiCl ₄ , N ₂ and H ₂ are separately used in the CVD apparatus. and mixed just before the object to be deposited.

The composition of the reaction gas is, for example,
Gas group A: NH ₃ : 0.8 to 1.6%, N ₂ : 0.0 to 2.0%, H ₂ : 30.0 to 35.0%
Gas group B: AlCl ₃ : 0.5 to 0.7%, Al(CH ₃ ) ₃ : 0.00 to 0.08%,
TiCl ₄ : 0.1 to 0.3%, N ₂ : 0.0 to 6.0%, H ₂ : remainder (% of gas group A and gas group B is the total of gas group A and gas group B) is the volume % for
and
Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 750-800°C
is.

Specifically, gas group A and gas group B are supplied according to the descriptions in Japanese Patent Application Laid-Open No. 2016-117934 or Japanese Patent Application Laid-Open No. 2017-20111. is a predetermined value.

Next, examples will be described.
Here, as an example of the coated tool of the present invention, an insert cutting tool using a WC-based ultrahigh-pressure sintered body as a tool substrate will be described. The same applies to drills and end mills.

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder, all having an average particle size of 1 to 3 μm, were prepared. After blending with the composition, wax is further added and mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then pressed into a green compact of a predetermined shape at a pressure of 98 MPa. Vacuum sintered under the condition of holding for 1 hour at a predetermined temperature within the range of ~ 1470 ° C. After sintering, tool base A made of WC-based cemented carbide with insert shape of JOMU140715ZZER-M manufactured by Mitsubishi Materials Corporation ~ C were produced respectively.

Next, on the surfaces of these tool substrates A to C, a TiAlCN layer is formed by CVD under the conditions shown in Table 2 using the CVD apparatus described in JP-A-2016-117934. The coated tools 1 to 10 of the present invention were obtained.

The gas composition and the like for forming the TiAlCN layer are roughly as follows.
Gas group A: NH ₃ : 0.8 to 1.6%, N ₂ : 0.0 to 2.0%, H ₂ : 30.0 to 35.0%
Gas group B: AlCl ₃ : 0.5 to 0.7%, Al(CH ₃ ) ₃ : 0.00 to 0.08%,
TiCl ₄ : 0.1 to 0.3%, N ₂ : 0.0 to 6.0%, H ₂ : remainder (% of gas group A and gas group B is the total of gas group A and gas group B) is the volume % for
Reaction atmosphere pressure: 4.5 to 5.0 kPa
Reaction atmosphere temperature: 750-800°C

Here, gas group A and gas group B are respectively supplied as source gas A and source gas B of the CVD apparatus described in JP-A-2016-117934. The orifice angles of the tubes are as follows.
Rotation speed of gas supply pipe: 10 to 30 rpm
Jet hole angle of gas supply pipe:
α: 60-90°
β1 and β2: 90-120°
γ1 and γ2: 180°

For coated tools 4 to 10 of the present invention, the lower layer and/or upper layer shown in Table 4 was formed under the film forming conditions shown in Table 3.

For the purpose of comparison, a hard coating layer containing a TiAlCN layer shown in Table 5 was vapor-deposited on the surfaces of the tool substrates A to C under the conditions shown in Table 2 to form a comparative coated tool 1. ~10 were produced.
For the comparative coated tools 4 to 10, the lower layer and/or the upper layer shown in Table 4 were formed under the forming conditions shown in Table 3.

In addition, the cross section of the hard coating layer of the coated tools 1 to 10 of the present invention and the coated tools 1 to 10 of the comparison perpendicular to the tool substrate was measured using a scanning electron microscope (magnification: 5000 times). When the layer thickness was measured at five points and averaged to find the average layer thickness, the average layer thicknesses shown in Tables 4 and 5 were obtained.
For the hard coating layers of the present invention coated tools 1 to 10 and comparative coated tools 1 to 10, the average Al content X _Aavg and X _Bavg and the average C content Y _Aavg and Y _Bavg were calculated using the method described above. . In addition, the presence or absence of a period along the equivalent orientation represented by <001> of the composition change of Ti and Al, and the differences ΔX _A and ΔX _B between the average maximum value and the average minimum value of the Al content ratio are obtained. rice field.
These results are summarized in Table 5. Although not shown in Table 5, it has been confirmed that the area ratio of the NaCl-type face-centered cubic structure is 60% or more for all of the invention coated tools 1 to 10 and the comparative coated tools 1 to 10. .

Subsequently, each of the coated tools 1 to 10 of the present invention and the comparative coated tools 1 to 10 was clamped to the tip of a tool steel cutter having a cutter diameter of 63 mm with a fixing jig, and wet face milling of ductile cast iron was performed. A machining test was performed to measure the flank wear width of the cutting edge.

The cutting test is as follows.
Cutting test: wet face milling Work material: ductile cast iron FCD450: width 45 mm
Cutting speed: 200m/min
Notch: 1.0mm
Single blade feed amount: 1.0 mm/blade cutting time: 7 minutes (normal cutting speed: 150 m/min)
Table 6 shows the results of the cutting test. The comparison coated tools 1 to 10 reached the end of their lives due to the occurrence of chipping, so the time until the end of their lives is shown.

From the results shown in Table 6, the coated tools 1 to 10 of the present invention all have excellent chipping resistance and peeling resistance in the hard coating layer, so they are suitable for high-speed, high-feed cutting of ductile cast iron and the like. It exhibits excellent wear resistance over a long period of time without chipping even when worn. On the other hand, the comparative coated tools 1 to 10, which do not satisfy the items specified for the coated tool of the present invention, cause chipping when used for high-speed, high-feed cutting of ductile cast iron, etc., and can be used in a short time. has reached the end of its life.

As described above, the coated tool of the present invention can be used as a coated tool for high-speed, high-feed cutting of ductile cast iron, and exhibits excellent chipping resistance and peeling resistance over a long period of time. It is possible to fully satisfy the improvement of the performance of the cutting device, the saving of labor and energy in the cutting process, and the reduction of the cost.

Claims (5)

A surface-coated cutting tool having a hard coating layer on the surface of the tool substrate,
(a) the hard coating layer includes at least a composite nitride layer or composite carbonitride layer of Ti and Al with an average layer thickness of 1.0 to 20.0 μm,
(b) the composite nitride layer or composite carbonitride layer of Ti and Al includes at least NaCl-type face-centered cubic crystal grains,
(c) When a cut plane parallel to the tool substrate is analyzed from a direction perpendicular to the surface of the tool substrate, a plurality of crystal grains of the NaCl type face-centered cubic structure with different Ti and Al compositions are present. , when each is divided into the crystal grain A group and the crystal grain B group,
When the crystal grain group A is represented by the composition formula: (Ti _1-XA Al _XA ) (C _YA N _1-YA ), the average X _Aavg of the content ratio X _A of Al to the total amount of Ti and Al, and The average Y _Aavg of C in the total amount of C and N (where X _Aavg and Y _Aavg are both atomic ratios) is 0.75 ≤ X _Aavg ≤ 0.95 and _0.0000 , respectively satisfying ≦Y _Aavg ≦0.0150,
When the crystal grain B group is represented by the composition formula: (Ti _1-XB Al _XB ) (C _YB N _1-YB ), the average X _Bavg of the content ratio X _B of Al in the total amount of Ti and Al, and The content ratio Y of C in the total amount of C and N The average Y _Bavg of _B (where X _Bavg and Y _Bavg are both atomic ratios) is 0.70 ≤ X _Bavg ≤ 0.90, 0.05 ≤ X _{satisfying Aavg} −X _Bavg ≦0.25, 0.0000≦Y _Bavg ≦0.0150,
(d) in the cut surface, the area ratio occupied by the crystal grain A group is 20 to 80%;
A surface-coated cutting tool characterized by: In the crystal grains of the crystal grain group A, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains, and the periodic 2. The surface-coated cutting tool according to claim 1, wherein the difference ΔX _A between the average value of the maximum values and the average value of the minimum values of X _A changing to 0.03 to 0.25. In the crystal grains of the crystal grain B group, a periodic composition change of Ti and Al exists along one of the equivalent crystal orientations represented by <001> of the crystal grains, and the periodic 3. The surface-coated cutting tool according to claim 1 or 2, wherein the difference ΔX _B between the average value of the maximum values and the average value of the minimum values of X _B that change from 0.03 to 0.25. one of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer between the tool substrate and the composite nitride layer or composite carbonitride layer of Ti and Al A surface-coated cutting tool according to any one of claims 1 to 3, characterized in that there is a lower layer consisting of a layer or two or more layers and having a total average layer thickness of 0.1 to 20 µm. 5. The method according to any one of claims 1 to 4, wherein an upper layer containing at least an aluminum oxide layer is present on the composite nitride layer or the composite carbonitride layer with a total average layer thickness of 1 to 25 μm. coated cutting tools.

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