JP7453613B2 - surface coated cutting tools - Google Patents

Description

In particular, in high-speed interrupted cutting of alloy steel, etc., the hard coating layer has excellent wear resistance, chipping resistance, and chipping resistance, so that excellent cutting performance can be achieved over long periods of use. The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a "coated tool") that exhibits excellent performance.

Conventionally, the surface of a tool base made of tungsten carbide (hereinafter referred to as "WC")-based cemented carbide is coated with a Ti-Al-based composite nitride layer or composite carbonitride layer as a hard coating layer by vapor deposition. There are formed coated tools which are known to exhibit excellent wear resistance.
In order to further improve the wear resistance and chipping resistance of coated tools coated with the hard coating layer, various proposals have been made for improving the hard coating layer.

For example, in Patent Document 1, in a hard coating layer containing a composite nitride layer of Ti and Al (hereinafter also referred to as a TiAlN layer), a TiAlN film with a small amount of Al is placed on the cutting edge portion where the load is large, and the film is A coated tool is described in which the hardness is deliberately reduced to ensure the toughness of the cutting edge and ensure chipping resistance.

Furthermore, for example, Patent Document 2 discloses a coated tool that exhibits extremely advantageous performance in machining cast materials by aligning the crystal growth direction and the normal direction of the {111} plane of the crystal in the hard coating layer. is listed.

Further, for example, Patent Document 3 describes a coated tool having a composite carbonitride layer of Ti and Al, and it is known that the preferential crystal growth orientation of the layer exists in relation to the crystallographic {111} plane. , is said to be particularly preferred.

JP 2017-124463 Publication Special Publication No. 2016-522323 Special table 2017-508632 publication

In recent years, there has been a strong demand for labor-saving and energy-saving in cutting processes, and as a result, there has been a trend toward faster and more efficient cutting processes. Therefore, coated tools are required to have even greater resistance to abnormal damage such as chipping resistance and chipping resistance, as well as excellent wear resistance over long-term use.
However, the coated tools proposed in Patent Documents 1 to 3 do not yet have sufficient wear resistance, chipping resistance, and chipping resistance in high-speed interrupted cutting of alloy steel, etc., and do not have satisfactory tool life. I cannot say that I am doing so. The reason is as follows.

The TiAlN layer described in Patent Document 1 has a film with low hardness on the cutting edge, which is subjected to the greatest load during cutting, so during high-speed intermittent cutting with a higher load, uneven wear of the cutting edge and the resulting wear occur. Crack propagation occurs, and it cannot be said that the desired wear resistance and chipping resistance can be exhibited.

In the coated tools described in Patent Documents 2 and 3, it has been shown that a structure with strong orientation in the normal direction of the {111} plane is more suitable for the hard coating layer. When the strength of the cutting material is high, fractures and chipping often occur due to peeling of the hard coating layer and falling off of crystal grains, and the fracture resistance and chipping resistance are insufficient.

Therefore, the present invention provides excellent wear resistance, chipping resistance, and chipping resistance in high-speed interrupted cutting of alloy steel (special steel), etc., which is accompanied by high heat generation and an impact load is applied to the cutting edge. The purpose is to provide a coated tool that exhibits excellent properties. Here, the high-speed intermittent cutting process refers to a process in which the workpiece and the cutting tool repeatedly cut and idle at a cutting speed higher than the cutting speed of 200 m/min.

The present inventor has conducted intensive studies on the wear resistance, chipping resistance, and chipping resistance of high-speed interrupted cutting when the crystal grains constituting the TiAlN hard coating layer (hard coating) on the cutting edge have an orientation distribution. went. As a result, there is a layer mainly oriented in the normal direction of the {111} plane of the crystal grains in a predetermined range of the rake face and flank face near the cutting edge ridgeline, and a layer oriented mainly in the normal direction of the {111} plane of the crystal grains, and a predetermined area far from the cutting edge edge line with respect to this layer. 100} plane, and if necessary, in addition to these layers, a layer oriented in the normal direction of the {110} plane is arranged. A novel finding has been made that it is possible to obtain a hard coating layer with excellent chipping resistance and chipping resistance while ensuring the following properties.

The present invention is a surface-coated cutting tool based on the above findings, and is as follows.
"(1) A surface-coated cutting tool having a tool base and a hard coating layer provided on the surface of the tool base,
(a) The hard coating layer includes at least a composite nitride layer of Ti and Al with an average layer thickness of 1.0 to 20.0 μm,
(b) the composite nitride layer of Ti and Al includes crystal grains having a NaCl-type face-centered cubic structure;
(c) When the composition of the composite nitride layer of Ti and Al is expressed by the composition formula: (Ti _(1-x) Al _x )N, the average content ratio of Al to the total amount of Ti and Al x (however, , x is the atomic ratio) satisfies 0.60≦x≦0.95,
(d) The composite nitride layer of Ti and Al has a face-centered surface of the NaCl type in which the angle of inclination of the normal direction of the {111} plane to the normal direction of the surface of the tool base is within 10°. An oriented layer in which crystal grains having a cubic structure account for 30% or more is arranged from the cutting edge ridge in the direction of the flank face and the rake face at a point closest to the cutting edge ridge whose distance from the cutting edge ridge does not exceed 50 μm; Continuously between the point farthest from the cutting edge ridge and having a distance of 100 to 500 μm from the cutting edge ridge,
(e) The composite nitride layer of Ti and Al has a distance of 50 in the direction away from the cutting edge ridge in the direction of the flank face and in the direction of the rake face, starting from the point farthest from the cutting edge ridge of the oriented layer. In a region having a length of 50 μm or more in the range of 500 μm or more, the inclination angle of the normal direction of the {100} plane to the normal direction of the surface of the tool base is within 10°. having an oriented layer in which 30% or more of crystal grains have a face-centered cubic structure;
A surface-coated cutting tool characterized by:
(2) The composite nitride layer of Ti and Al is formed on the tool base in a region where the distance in the direction away from the cutting edge ridgeline toward the flank face and the rake face is 50 μm or more within a range of 100 to 600 μm. has an oriented layer in which the NaCl-type crystal grains having a face-centered cubic structure account for 20% or more, and the inclination angle formed by the normal direction of the {110} plane with respect to the normal direction of the surface of is within 10 degrees. The surface-coated cutting tool according to (1) above.
(3) In the above (1) or (2), the composite nitride layer of Ti and Al has a ratio of 50% by area or more of crystal grains having a face-centered cubic structure of the NaCl type. Surface coated cutting tool as described. ”

According to the present invention, it is possible to obtain a coated tool with excellent fracture resistance and chipping resistance while ensuring wear resistance.

FIG. 2 is a schematic diagram showing an example of the distribution of layers oriented in the flank direction and the rake direction from the cutting edge ridge in the surface-coated cutting tool of the present invention.

The surface-coated cutting tool of the present invention will be explained in detail below. In this specification and claims, when a numerical range is expressed as "A to B" (A and B are both numerical values), the range includes the upper limit (B) and lower limit (A). . Moreover, the units of the upper limit (B) and the lower limit (B) are the same.

Average layer thickness of TiAlN layer:
The hard coating layer of the present invention includes at least a TiAlN layer represented by the composition formula: (Ti _1-x Al _x )N described below. This TiAlN layer has high hardness and excellent chipping resistance and abrasion resistance, and these characteristics are particularly noticeable when the average layer thickness 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 ensure sufficient wear resistance over long-term use, whereas if the average layer thickness exceeds 20.0 μm, TiAlN This is because the crystal grains of the layer tend to become coarser and chipping tends to occur. A more preferable average layer thickness is 2.0 to 10.0 μm.

Here, the average layer thickness is measured, for example, in a cross section (longitudinal cross section) in the direction perpendicular to the tool base of each constituent layer at the flank and rake surfaces in the area where the tool and the workpiece come into direct contact during cutting. can be observed using a scanning electron microscope at a magnification of 5,000 times, and can be determined by averaging five points within the observation field.

NaCl Type Face-Centered Cubic Structure The TiAlN layer of the present invention preferably contains crystal grains having a NaCl-type face-centered cubic structure. In the present invention, the existence ratio (area %) of these NaCl-type face-centered cubic crystal grains is defined as the ratio in the cross section normal to the direction of the cutting edge, and the value is preferably 50 area % or more, and is more preferably 70 area % or more. The reason for this is that the ratio of crystal grains having a face-centered cubic structure of the NaCl type, which has high hardness, is higher than that of crystal grains having a hexagonal crystal structure, and the hardness is improved. Note that the upper limit of the area ratio may be 100 area % (all have a NaCl type face-centered cubic structure).

Composition of TiAlN layer:
The composition of the TiAlN layer in the present invention is represented by the composition formula: (Ti _{1-x Al} ) x preferably satisfies 0.60≦x≦0.95 (where x is an atomic ratio).

The reason is as follows.
If the average Al content x is less than 0.60, the TiAlN layer will have poor oxidation resistance, and therefore will not have sufficient wear resistance when subjected to high-speed interrupted cutting of alloy steel, etc. When it exceeds 95, the amount of precipitated hexagonal crystals, which are inferior in hardness, increases, resulting in a decrease in hardness and a decrease in wear resistance. Therefore, 0.60≦x≦0.95 is preferable. More preferably, 0.70≦x≦0.90. Note that (Ti _(1-x) Al _x ) and N are not limited to a 1:1 combination.

TiAlN layer oriented in the normal direction of the {111} plane existing from the cutting edge ridge to the flank and rake faces:
The proportion of NaCl-type face-centered cubic structure crystal grains (frequency proportion described later) in which the inclination angle of the normal direction of the {111} plane is within 10° with respect to the normal direction of the surface of the tool base is 30 It is preferable to have an oriented TiAlN layer (sometimes referred to as a layer oriented in the normal direction of the {111} plane) that accounts for % or more. The normal orientation layer of the {111} plane is oriented in the direction from the cutting edge ridge to the flank and rake faces, from a point whose distance from the cutting edge ridge does not exceed 50 μm (the point closest to the cutting edge ridge) to the cutting edge ridge. It exists continuously between a point with a distance of 100 to 500 μm (the point farthest from the cutting edge ridge line) (Existence area in the flank direction (l) and Existence area in the rake face direction (l') shown in Fig. 1) may have different lengths).

Here, regarding the layer oriented in the normal direction of the {111} plane, the proportion (frequency proportion) of oriented crystal grains is 30% or more, and the point closest to the cutting edge ridge line and the point farthest from the edge line are continuous. The reason why it is preferable that these conditions are satisfied is that by satisfying these conditions, the properties of the layer oriented in the normal direction of the {111} plane are fully expressed, and the fracture resistance and chipping resistance are fully exhibited. It is.

A TiAlN layer oriented in the normal direction of the {100} plane, which exists in a direction away from the cutting edge ridge in the direction of the flank face and the rake face with respect to the layer oriented in the normal direction of the {111} plane:
A length of 50 μm or more in the range of 50 to 500 μm in a distance from the point farthest from the cutting edge ridge in the normal direction orientation layer of the {111} plane in the direction away from the cutting edge ridge in the direction of the flank face and the direction of the rake face. In the area of the width (the length (m) of the area in the flank direction and the length (m') of the area in the rake face direction shown in FIG. 1 may be different), the normal direction of the surface of the tool base An oriented TiAlN coating layer ( It is preferable to have a {100} plane normal orientation layer).

Here, in the {100} plane normal direction orientation layer, it is preferable that the ratio (frequency ratio) of oriented crystal grains is 30% or more, and that the crystal grains exist in the region having a length of 50 μm or more. The reason is that by satisfying these requirements, the properties of the {100} plane normal orientation layer are fully expressed, and the fracture resistance and chipping resistance are fully exhibited.

TiAlN layer oriented in the normal direction of the {110} plane:
An inclination angle formed by the normal direction of the {110} plane with respect to the normal direction of the surface of the tool base in a range of 100 to 600 μm from the cutting edge ridgeline in the direction of the flank face and the rake face direction, and in a region of at least 50 μm or more There is an oriented layer (sometimes referred to as a layer oriented in the normal direction of the {110} plane) in which the proportion (frequency proportion) of crystal grains having a NaCl-type face-centered cubic structure whose angle is within 10° is 20% or more. It is more preferable to do so.

The reason why the ratio (frequency ratio) of the crystal grains is 20% or more and the length of the {110} plane normal direction orientation layer is 50 μm or more is that when this numerical range is satisfied, the {110} This is because the characteristics of the layer oriented in the normal direction of the surface are fully expressed, and the fracture resistance and chipping resistance are further improved.

Note that the cutting edge ridgeline refers to the intersection line where the flank and rake surfaces are each approximated by a plane, and when the planes are extended, the two extended planes intersect, and the distance from the cutting edge ridgeline is defined as This refers to the distance along the flank and rake faces on each cross section from the intersection with the cutting edge ridgeline in the cross section.

Measurement of the angle between the normal to the surface of the tool base and the normal to a specific crystal plane of a crystal grain having a NaCl-type face-centered cubic structure and its ratio:
The angle between the normal to the surface of the tool base and the normal to a specific crystal plane ({111} plane, {110} plane, {100} plane) of a crystal grain having an NaCl type face-centered cubic structure in the TiAlN layer. The measurement is performed as follows. First, the TiAlN layer is set in the lens barrel of a field emission scanning electron microscope, with a cross section of the TiAlN layer normal to the direction of the cutting edge as a polishing surface. Next, a predetermined observation range (for example, a width of 10 μm in a direction parallel to the surface of the tool base, with the midpoint of this width separated by 25 μm) is set on the polished surface.

Next, with respect to the normal direction of the surface of the tool base (direction perpendicular to the surface of the tool base on the cross-sectional polished surface), the {111} plane and {110} plane of the crystal grains at each measurement point within the observation range are measured. In order to measure the inclination angle formed by the normal to the {100} plane, the angle of incidence was 70 degrees, the acceleration voltage was 10 kV, the irradiation current was 1 nA, and the angle was 0.1 μm/step with respect to the normal to the polished surface. Depending on the interval, the observation range is irradiated with an electron beam, an electron beam backscattering analysis image is obtained, and the tilt angle is measured. Then, the obtained electron beam backscattering analysis image is displayed in Pole Plots, and the frequency ratio of crystal grains whose inclination angle formed by the normal line is within 10° is determined.

The Pole Plots are, for example, as described in the document "J.A. Nucci, et al., Appl. Phys. Lett. 69 (1996) 4017." for Cu having a face-centered cubic structure. This is an index that indicates in which direction the substance to be measured is biased, compared to a state in which it has a completely random polycrystalline structure. In the above literature, frequency is expressed in units of "times random". In the processing of the measurement results of the present invention, a crystal having an inclination angle of 0° to 10° with respect to the total frequency of crystal grains for an inclination angle of up to 90°, with the normal direction of the plane orientation as a reference being 0°. The total frequency of grains (frequency ratio) is calculated in % as the ratio of grains oriented in the normal direction of the plane of interest, and this ratio is calculated as a specific value (normal to {111} and {100} 30% in the direction, 20% in the normal direction to the {110} plane) is treated as an oriented hard coating layer.

The frequency ratio of the oriented layer does not change rapidly, and by measuring using the above method, it is possible to avoid the influence of errors in measurement (mainly variations in each grain, position and angle of the measurement sample). ), and it becomes possible to determine whether the observed region is an alignment layer. In addition, the present invention provides that when adjacent observation areas are both determined to be alignment layers based on the frequency ratio of the observation areas, the area existing between these adjacent observation areas can also be said to be an alignment layer. This was confirmed during the derivation process.

Further, if the end of the alignment layer cannot be considered to be an alignment layer based on the frequency ratio of one of the adjacent observation ranges, the end portion of the alignment layer is set at the midpoint of the observation range that is determined to be an alignment layer based on the frequency ratio of the alignment layer.

In addition, the ratio of crystal grains having a NaCl-type face-centered cubic structure is calculated using the total number of measurement points in the TiAlN layer portion in the observation range as the denominator, and the ratio of crystal grains having a NaCl-type face-centered cubic structure is calculated using the total number of measurement points in the TiAlN layer portion in the observation range as the denominator. The "area %" is calculated from the ratio of the number of measurement points of the part as the numerator.

Tool base:
As the tool base, any base material conventionally known as this type of tool base can be used as long as it does not impede achieving the object of the present invention. To give an example, cemented carbide (WC-based cemented carbide, containing WC and Co, and also containing carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, (TiN, TiCN, etc. as main components), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body.

Bottom layer and top layer:
In the present invention, by providing a layer having the TiAlN layer as a hard coating layer, sufficient wear resistance, chipping resistance, and chipping resistance are obtained. When a lower layer including a Ti compound layer is formed of one or more of a compound layer and a carbonitride layer and has a total average layer thickness of 0.1 to 20.0 μm, and/or When the upper layer including at least the aluminum oxide layer is provided with a total average layer thickness of 1.0 to 25.0 μm, even more excellent properties can be exhibited in conjunction with the effects of these layers. can.

Note that the compositions of the Ti carbide layer, nitride layer, carbonitride layer, carbonate layer, carbonitride oxide, and aluminum oxide layer are not limited to stoichiometric proportions.

Ti consisting of one or more layers of a carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride layer of Ti, and having a total average layer thickness of 0.1 to 20.0 μm When providing a lower layer including a compound layer, if the total average layer thickness of the lower layer is less than 0.1 μm, the effect of the lower layer will not be sufficiently exhibited, whereas if it exceeds 20.0 μm, crystal grains tend to become coarse. , chipping is more likely to occur. In addition, if the total average layer thickness of the upper layer including the aluminum oxide layer is less than 1.0 μm, the effect of the upper layer will not be sufficiently exhibited, while if it exceeds 25.0 μm, crystal grains tend to become coarse and chipping may occur. It is more likely to occur.

Production method:
The TiAlN layer of the present invention can be produced, for example, by CVD under the following conditions.
Reaction gas composition (% represents volume %, the sum of gas group A and gas group B is 100 volume %)
Gas group A: _NH3 : 0.3 to 0.6%, Ar: 25.0 to 35.0%,
_H2 : 20.0-30.0%,
Gas group B: AlCl ₃ : 0.04-0.06%,
_TiCl4 : 0.01-0.03%,
N ₂ : 25.0-30.0%, H ₂ : Residual reaction atmosphere pressure: 4.5-5.5 kPa
Reaction atmosphere temperature: 700-850℃
Supply cycle: 8.0 to 15.0 seconds Gas supply time per cycle 0.2 to 0.6 seconds Phase difference between supply of gas group A and gas group B 0.10 to 0.15 seconds

As raw material powders, WC powder, TiC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder, all of which have an average particle size of 1 to 3 μm, were prepared. These raw material powders were blended into the composition shown in Table 1, further added with wax, mixed in a ball mill for 24 hours in acetone, dried under reduced pressure, and then press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. This green compact was vacuum sintered in a vacuum of 5 Pa under conditions of holding at a predetermined temperature within the range of 1370 to 1470° C. for 1 hour. After sintering, a tool base A made of WC-based cemented carbide and having an insert shape of ISO standard SEEN1203AFSN was produced.

Next, a TiAlN layer was formed on the surface of these tool bases A using a CVD device. The conditions for film formation by CVD are as follows.
The film forming conditions A to I shown in Tables 3 and 4 are gas group A consisting of NH ₃ , Ar, and H ₂ , gas group B consisting of AlCl ₃ , TiCl ₄ , N ₂ , and H ₂ , and each As for the gas supply method, the reaction gas composition (volume % of the total of gas group A and gas group B) is set as gas group A: NH ₃ : 0.3 to 0.6%, Ar: 25.0 to 35%. .0%, H ₂ : 20.0 to 30.0%, AlCl ₃ as gas group B: 0.04 to 0.06%, TiCl ₄ : 0.01 to 0.03%, N ₂ : 25.0 ~30.0%, H ₂ :Remaining, Reaction atmosphere pressure: 4.5~5.5kPa, Reaction atmosphere temperature: 700~850°C, Supply cycle 8.0~15.0 seconds, Gas supply time per cycle Film formation was performed for a predetermined time with a phase difference of 0.2 to 0.6 seconds and a phase difference between the supply of gas group A and gas group B of 0.10 to 0.15 seconds.

By forming a TiAlN layer under these conditions, coated tools 1 to 9 of the present invention having an average layer thickness and an average Al content x shown in Table 6 were manufactured.
For coated tools 1 to 3 and 9 of the present invention, the lower layer shown in Table 5 was formed under the forming conditions shown in Table 2.

For comparison purposes, a film was formed on the surface of tool base A by CVD under the formation conditions shown in Tables 3 and 4, and had an average layer thickness shown in Table 7, and included at least a TiAlN layer. Comparative coated tools 1 to 8 were manufactured by depositing a hard coating layer.
For comparison coated tools 1 to 3, the lower layer shown in Table 5 was formed under the formation conditions shown in Table 2.

The average layer thickness was determined by scanning a cross section (longitudinal cross section) perpendicular to the tool base of each constituent layer on the flank and rake surfaces of the coated tools 1 to 9 of the present invention and the comparative coated tools 1 to 8 using a scanning electron microscope. Observe at a magnification of 5,000 times using a microscope, draw five perpendicular lines to the substrate surface at equal intervals within the observation field, and mark the boundary line between the substrate surface or the lower layer and the TiAlN layer and the TiAlN layer on each perpendicular line. The distances between the points where the surface intersects with the perpendicular line were measured and averaged.

The average content ratio x of Al in the TiAlN layer was determined by using an electron-probe-micro-analyser (EPMA) to determine the difference between the sample surface relative to the flank face and rake face in a sample where the surface of the tool base was polished. Observation was made from the side at a magnification of 2000 times, electron beams were irradiated at 10 spots at random within the observation range, and the analysis results of characteristic X-rays obtained at each spot were averaged.
Tables 6 and 7 show the values of x determined above (x is the ratio of the number of Al atoms to the total number of Ti and Al atoms, and using the measurement results of Ti and Al, (It is calculated without using other elements such as C and O that are unavoidably included.)

The measurement and ratio of the angle between the normal to the surface of the tool base and the normal to a specific crystal plane of a crystal grain having a NaCl-type face-centered cubic structure, and the area ratio (area %) of the face-centered cubic structure are as follows: It was determined by the method described above and shown in Tables 6 and 7. In addition, in these tables, those indicated by "-" indicate that the corresponding alignment layer does not exist. Further, the numerical value described as "lower) orientation ratio" indicates the orientation ratio at the position indicated by "upper)" in that column.

Next, with each of the above-mentioned coated tools clamped to the tip of an alloy steel cutter with a cutter diameter of 125 mm using a fixing jig, the coated tools 1 to 9 of the present invention and the comparative coated tools 1 to 8 are described below. A center-cut cutting test was conducted using a dry high-speed face milling cutter, which is a type of high-speed interrupted cutting of alloy steel, and the width of flank wear of the cutting edge was measured.

Cutting test: Wet high-speed face milling, center cut cutting Workpiece material: JIS/SCM440 block material with a width of 100 mm and a length of 400 mm Rotational speed: 892 min ^-1
Cutting speed: 350 m/min
Cut depth: 2.0 mm
Single blade feed rate: 0.30 mm/blade Cutting time: 5 minutes (normal cutting speed: 200 m/min)

From the results shown in Table 8, even when the coated tool of the present invention is used for high-speed interrupted cutting of alloy steel, etc., there is no occurrence of chipping or chipping, and it exhibits excellent wear resistance over a long period of use.

On the other hand, comparative coated tools whose TiAlN layer does not satisfy at least one of the requirements stipulated by the present invention suffer from abnormal damage such as chipping or accelerated wear during high-speed interrupted cutting of alloy steel, etc. It is clear that the life span is reached in a short period of time.

As mentioned above, the coated tool of the present invention can be used not only for high-speed interrupted cutting of alloy steel, etc., but also as a coated tool for various work materials, and moreover, exhibits excellent cutting performance over long periods of use. Therefore, it is possible to satisfactorily improve the performance of the cutting device, save labor and energy in the cutting process, and further reduce the cost.

Claims (3)

A surface-coated cutting tool having a tool base and a hard coating layer provided on the surface of the tool base,
(a) The hard coating layer includes at least a composite nitride layer of Ti and Al with an average layer thickness of 1.0 to 20.0 μm,
(b) the composite nitride layer of Ti and Al includes crystal grains having a NaCl-type face-centered cubic structure;
(c) When the composition of the composite nitride layer of Ti and Al is expressed by the composition formula: (Ti _(1-x) Al _x )N, the average content ratio of Al to the total amount of Ti and Al x (however, , x is the atomic ratio) satisfies 0.60≦x≦0.95,
(d) The composite nitride layer of Ti and Al has a face-centered surface of the NaCl type in which the angle of inclination of the normal direction of the {111} plane to the normal direction of the surface of the tool base is within 10°. An oriented layer in which crystal grains having a cubic structure account for 30% or more is arranged from the cutting edge ridge in the direction of the flank face and the rake face at a point closest to the cutting edge ridge whose distance from the cutting edge ridge does not exceed 50 μm; Continuously between the point farthest from the cutting edge ridge and having a distance of 100 to 500 μm from the cutting edge ridge,
(e) The composite nitride layer of Ti and Al has a distance of 50 in the direction away from the cutting edge ridge in the direction of the flank face and in the direction of the rake face, starting from the point farthest from the cutting edge ridge of the oriented layer. In a region having a length of 50 μm or more in the range of 500 μm or more, the inclination angle of the normal direction of the {100} plane to the normal direction of the surface of the tool base is within 10°. having an oriented layer in which 30% or more of crystal grains have a face-centered cubic structure;
A surface-coated cutting tool characterized by: The composite nitride layer of Ti and Al covers the surface of the tool base in a region of 50 μm or more in the range of 100 to 600 μm in distance in a direction away from the cutting edge ridgeline toward the flank face and the rake face. Claim 1 comprising an oriented layer in which the crystal grains having a face-centered cubic structure of the NaCl type account for 20% or more, in which the inclination angle formed by the normal direction of the {110} plane with respect to the normal direction is within 10 degrees. The surface-coated cutting tool described in . The surface-coated cutting tool according to claim 1 or 2, wherein the Ti and Al composite nitride layer has a crystal grain having a face-centered cubic structure of the NaCl type that accounts for 50% by area or more. .

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