JP2022139720A - Surface coated cutting tool - Google Patents

Abstract

To provide a coated tool which can exhibit cutting performance such as wear resistance and so on even when used for cutting Ni-based heat-resistant alloy and the like.SOLUTION: In a surface coated cutting tool, (a) a coating layer contains a composite carbonitride layer of Ti and Al, (b) the composite carbonitride layer contains crystal grains of NaCl type face-centered cubic structure of 80 to 100% by area, (c) when a composition of TiAlCN layer is represented by the composition formula: (Ti1-xAlx)(CyN1-y), xavg, that is an average composition thereof, is 0.75 to 0.95 and yavg is 0.000 to 0.010, (d) in all crystal grains having the NaCl type face-centered cubic structure, an area α2 of 10 to 30% by area, in which x is 0.00 to 0.30, exists, (e) in the crystal grain having the NaCl type face-centered cubic structure, when a range, that is surrounded by a curve separated from a crystal grain boundary thereof into the crystal grain by 10nm and the crystal grain boundary, is represented by γ3, 60 to 100% by area of the whole of the area α2 exist in the area γ3.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

In recent years, the performance of cutting equipment has improved remarkably. Conditions are getting tougher.

As a coated tool, a coating layer containing a compound nitride (hereinafter sometimes referred to as TiAlN) layer of Al and Ti is deposited on the surface of a tool substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide by a vapor deposition method. coated coated tools are known.
Many proposals have been made to improve the cutting performance of these coated tools.

For example, US Pat. A tool is described and the coated tool is said to be highly wear resistant.

Further, for example, in Patent Document 2, a coating layer contains cubic TiAlCN and hexagonal AlN, and the cubic TiAlCN has a crystallite size of 0.1 μm or more fcc-Ti _1-x Al _x C _y N _z (where x>0.75, y=0 to 0.25, z=0.75 to 1) and contains 0.01 to 20% by mass of amorphous carbon in the grain boundary region A coated tool is described which is said to have excellent oxidation resistance.

Japanese Patent Publication No. 2011-500964 Japanese Patent Publication No. 2013-510946

The present invention has been made in view of the above circumstances and proposals, and provides a coated tool that exhibits satisfactory cutting performance such as wear resistance even when used for cutting difficult-to-cut materials such as Ni-based heat-resistant alloys. with the aim of obtaining

A surface-coated cutting tool according to an embodiment of the present invention is
Having a tool substrate and a coating layer on the surface of the tool substrate,
(a) the coating layer includes a composite carbonitride layer of Ti and Al;
(b) the composite carbonitride layer contains 80 to 100 area % of NaCl-type face-centered cubic crystal grains,
(c) When the composition of the TiAlCN layer is represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ), the average composition x _avg is 0.75 to 0.95, y _avg is between 0.000 and 0.010;
(d) in all the crystal grains having the NaCl-type face-centered cubic structure, 10 to 30 area % of the region α where x is 0.00 to 0.30 is present;
(e) In each of the crystal grains having the NaCl-type face-centered cubic structure, when the range surrounded by the curve spaced 10 nm from the crystal grain boundary into the crystal grain and the crystal grain boundary is defined as the region γ, 60 to 100 area % of the entire region α is present within the region γ.

Furthermore, the surface-coated cutting tool according to the embodiment may satisfy either or both of the following (1) and (2).

(1) With respect to the region α, the area of each region is 100 to 50000 ^nm2 ,
When a quadrangular region having a length of 20 μm in the direction parallel to the surface of the tool substrate and a length of the average layer thickness in the direction perpendicular to the surface of the tool substrate is divided into squares with a side of 1 μm, the segment where the region α exists shall account for 15 to 100 percent by number of all categories.

(2) The NaCl-type crystal grains having a face-centered cubic structure have an average grain width W of 0.10 to 2.00 μm and an average aspect ratio A of 2.0 to 5.0.

According to the above, even if it is used for cutting difficult-to-cut materials such as Ni-based heat-resistant alloys, satisfactory cutting performance such as wear resistance is exhibited.

FIG. 3 is a schematic diagram showing a region α and a region γ in the vicinity of grain boundaries;

The inventor of the present invention has made intensive studies to obtain a coated tool that achieves the above objects. As a result, it was found that when a region with a low Al content ratio exists at a predetermined ratio in the vicinity of the grain boundaries of the crystal grains of the NaCl type face-centered cubic structure that constitutes the TiAlCN layer, the wear resistance of the layer is improved. rice field.

Below, the surface coated cutting tool which concerns on embodiment of this invention is demonstrated.
In the present 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 the lower limit (A). , and the units of the upper limit (B) and the lower limit (A) are the same.

1. Coating Layer The surface-coated cutting tool according to the present embodiment has a TiAlCN layer as a coating layer.

(1) Average Layer Thickness The average layer thickness of the TiAlCN layer is preferably 1.0 to 23.0 μm. The reason for this is that if the average layer thickness is less than 1.0 μm, it may not be possible to ensure sufficient wear resistance over long-term use because the average layer thickness is thin, while the average layer thickness exceeds 23.0 μm. This is because the crystal grains of the TiAlCN layer tend to coarsen and chipping tends to occur. More preferably, the average layer thickness is 5.0 to 15.0 μm.

Here, the average layer thickness of the TiAlCN layer can be obtained by, for example, using a focused ion beam system (FIB), a cross section polisher (CP), or the like, the TiAlCN layer at any position. Surface (In the case of an insert, when the surface of the tool base is treated as a flat surface ignoring minute irregularities, the surface is perpendicular to this surface. In the case of a shaft tool such as a drill, the cross section is perpendicular to the axis.) A sample for observation is prepared by cutting with, and the longitudinal section is observed at multiple locations (e.g., 5 locations) using a scanning electron microscope (SEM) and averaged. can.

(2) Crystal grains having NaCl-type face-centered cubic structure In the TiAlCN layer, the area ratio of crystal grains having a NaCl-type face-centered cubic structure is preferably 80 area% or more in the longitudinal section. The reason for this is that the aforementioned object can be achieved when the area is 80 area % or more. This area ratio is more preferably 90 area % or more. Moreover, the upper limit may be 100 area % (all crystal grains have a NaCl-type face-centered cubic structure).
The area ratio of crystal grains having a NaCl-type face-centered cubic structure utilizes the results of determination of grain boundaries, which will be described later.

(3) Average composition of TiAlCN layer The TiAlCN layer is represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ),
The content ratio of Al in the total amount of Ti and Al (hereinafter referred to as “Al content ratio”) x average x _avg is the content ratio of C in the total amount of C and N (hereinafter referred to as “C content ratio” The average y _avg of y is 0.75 ≤ x _avg ≤ 0.95, 0.000 ≤ y _avg ≤ 0.010 (where x, y, x _avg , and y _avg are all atomic ratios) is preferably satisfied.

The ratio of (Ti _1-x Al _x ) and (C _y N _1-y ) is not particularly limited, but when (Ti _1-x Al _x ) is 1, (C _y N _1-y ) is preferably 0.8 to 1.2. The reason for this is that if the ratio of (C _y N _1-y ) to (Ti _1-x Al _x ) is within the above range, the object of the present invention can be reliably achieved.
Further, even if the TiAlCN layer contains a small amount of unavoidable impurities (impurities included unintentionally) such as O and Cl, the achievement of the above object is not impaired.

The reason why the ranges of x _avg and y _avg are preferable is as follows.
When the average x _avg of the Al content is less than 0.75, the TiAlCN layer is inferior in hardness,
This is because wear resistance is not sufficient when used for cutting difficult-to-cut materials such as Ni-based heat-resistant alloys. . x _avg is more preferably 0.80≦x _avg ≦0.90.

This is because if the content of C is within the above range, the hardness can be improved while maintaining the chipping resistance. y _avg is more preferably 0.006≦y _avg ≦0.010.

The average x _avg of the Al content ratio of the TiAlCN layer is obtained by using Auger electron spectroscopy (AES), irradiating an electron beam from the longitudinal section side of a sample (coated tool) whose longitudinal section is polished, and measuring the film thickness It is the average of the analysis results of Auger electrons obtained by performing at least five line analyzes over the entire length of the direction (perpendicular to the surface of the tool substrate).

Also, the average _yavg of the C content ratio is determined by secondary ion mass spectrometry (SIMS). That is, in a sample (coated tool) whose surface is polished, an ion beam is irradiated from the surface side of the TiAlCN layer in a range of 70 μm × 70 μm, and surface analysis by the ion beam and etching by the sputter ion beam are alternately repeated. A composition measurement in the depth direction is performed. First, the average of the data obtained by measuring a depth of at least 0.5 μm at a pitch of 0.1 μm or less from a portion of the TiAlCN layer intruded by 0.5 μm or more in the depth direction of the layer is obtained. Furthermore, the average y _avg of the C content ratio is obtained by averaging the results obtained by repeating this calculation at least at five locations on the sample surface.

(4) Region α
Crystal grains having a NaCl-type face-centered cubic structure have a region α, which is a region with a low Al content x of 0.00 to 0.30 (Ti-enriched region). The abundance ratio is preferably 10 to 30 area % with respect to the entire area of the crystal grains having the NaCl-type face-centered cubic structure.

The reason why this area ratio is preferable is that if the area ratio is less than 10 area%, the application of compressive stress to the TiAlCN layer is small, and improvement in hardness cannot be expected. This is because too much lattice defects may occur and the hardness may decrease.

The area of each region α is more preferably 100 to 50000 nm ² . The reason for this is that if the thickness is less ^than 100 nm ² , the diffusion of oxygen into the TiAlCN layer through grain boundaries during cutting cannot be suppressed, and the oxidation resistance may decrease. This is because the distortion of crystal grains becomes too large, lattice defects increase, and the hardness decreases.

Further, when a square area having a length of 20 μm in the direction parallel to the surface of the tool base and a length of the average layer thickness in the direction perpendicular to the surface of the tool base is divided into squares each having a side of 1 μm, the area It is more preferable that the sections in which α is present (excluding sections on the surface where no AlTiCN layer is present in the entire section) occupy 15 to 100% by number of all sections.

The reason for this is that if the content is less than 15% by mass, the TiAlCN layer is provided with a small compressive stress, the effect of improving the hardness cannot be expected, and the diffusion of oxygen into the TiAlCN layer through grain boundaries during cutting cannot be suppressed. This is because the oxidation resistance of the same layer may be lowered.

Here, the surface of the tool substrate is defined as the reference line of the roughness of the interface between the tool substrate and the coating layer (if there is a lower layer described later, the same shall apply hereinafter) in the observed image of the longitudinal section. That is, when the tool substrate has a flat surface like an insert, elemental mapping using EDS is performed on the longitudinal section, and the obtained elemental map is subjected to known image processing to form a coating layer. The interface of the tool substrate is determined, and the mean line is arithmetically determined for the roughness curve of the interface between the coating layer and the tool substrate thus obtained, and this is used as the surface of the tool substrate. The direction perpendicular to the average line is defined as the direction perpendicular to the tool substrate (layer thickness direction).

Also, even if the tool base has a curved surface like a drill, if the diameter of the tool is sufficiently large relative to the thickness of the coating layer, the interface between the coating layer and the tool base in the measurement area is Since it is substantially flat, the surface of the tool base can be determined by a similar method. That is, for example, in the case of a drill, elemental mapping using EDS is performed on a vertical cross section of the coating layer perpendicular to the axial direction, and the obtained elemental map is subjected to known image processing. The interface of the tool substrate is determined, and the mean line is arithmetically determined for the roughness curve of the interface between the coating layer and the tool substrate thus obtained, and this is used as the surface of the tool substrate. The direction perpendicular to the average line is defined as the direction perpendicular to the tool substrate (layer thickness direction).

(5) Ratio of the α region in the region near the grain boundary in the crystal grains having the NaCl-type face-centered cubic structure of the TiAlCN layer As shown in FIG. When the range surrounded by the curve spaced 10 nm from the grain boundary (1) in the grain and the grain boundary is defined as the region γ (3), the region α (2) is 60 to 100 area% of the whole is present in this region γ(3).

The reason for this is that if it is less than 60 area %, the diffusion of oxygen into the TiAlCN layer through grain boundaries during cutting cannot be suppressed, and the oxidation resistance is lowered.

(6) Average particle width W and average aspect ratio A
The average grain width W and the average aspect ratio A of the crystal grains having the NaCl-type face-centered cubic structure of the TiAlCN layer are 0.10 to 2.00 μm and 2.0 to 5.0, respectively. more preferred.

The reason is as follows.
If the average grain width W is smaller than 0.10 μm, the number of starting points for chipping increases due to an increase in grain boundaries, and the chipping resistance of the TiAlCN layer may decrease. This is because when the size increases, the toughness may decrease due to the presence of coarsely grown particles.

In addition, if the average aspect ratio A is less than 2.0, the interface between the granular crystals becomes likely to become a fracture starting point against the shear stress generated on the surface of the coating layer during cutting, which may cause chipping. On the other hand, if it exceeds 5.0, fine chipping occurs on the cutting edge during cutting, and when adjacent columnar crystal structures are chipped, the resistance to the shear stress generated on the surface of the coating layer tends to decrease, resulting in a columnar crystal structure. This is because when the crystal structure breaks, the damage progresses at once, and large chipping may occur.

(7) Other layers As a coating layer, the coating layer containing the TiAlCN layer has sufficient chipping resistance and wear resistance in cutting difficult-to-cut materials such as Ni-based heat-resistant alloys. Separately, it consists of one or more layers of Ti carbide layer, nitride layer, carbonitride layer, carbonate layer and carbonitride layer, and has a total average layer thickness of 0.1 to 20.0 μm. and/or at least a layer of aluminum oxide (not limited to stoichiometric compounds) provided adjacent to the tool substrate, including a layer of Ti compounds (not limited to stoichiometric compounds) having In the case where the containing layer is provided on the TiAlCN layer as an upper layer with a total average layer thickness of 1.0 to 25.0 μm, together with the effects of these layers, even more excellent chipping resistance , can exhibit wear resistance.

Here, if the total average layer thickness of the lower layer is less than 0.1 μm, the lower layer does not work sufficiently. easier. When the total average layer thickness of the upper layer including the aluminum oxide layer is less than 1.0 μm, the upper layer does not function sufficiently. Chipping is more likely to occur.

2. Tool Substrate (1) Material Any of the conventionally known substrates for this type of tool substrate can be used as long as it does not interfere with the achievement of the above-mentioned object. For example, cemented carbide (WC-based cemented carbide, containing Co in addition to WC, and further containing carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc. as a main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), or cBN sintered body.

(2) Shape The shape of the tool base is not particularly limited as long as it is a shape used as a cutting tool, examples of which include the shape of an insert and the shape of a drill.

3. Method of Identifying Grain Boundaries The grain boundaries of the crystal grains forming the TiAlCN layer are obtained and the crystal grains are identified in the following manner. That is, using a crystal orientation analyzer attached to a transmission electron microscope (TEM), a surface-polished surface (longitudinal section) perpendicular to the surface of the tool substrate is measured in the normal direction of the surface-polished surface. While irradiating an electron beam inclined at 0.5 to 1.0 degrees with respect to precession, the electron beam is scanned at an arbitrary beam diameter and interval, and the electron diffraction pattern is continuously captured, and each individual Analyze the crystal orientation of the measurement point. The crystal grain boundaries are determined with respect to an observation field of view of 50 μm in width in the direction parallel to the surface of the tool base and the thickness of the layer (average layer thickness) in the vertical direction.

The electron diffraction pattern acquisition conditions used in this measurement are an acceleration voltage of 200 kV, a camera length of 20 cm, a beam size of 2.4 nm, and a measurement step of 5.0 nm. At this time, the measured crystal orientations were obtained by discretely examining the surface to be measured, and by representing the measurement results for the area between adjacent measurement points to the middle, the orientation distribution of the entire measurement surface can be obtained. be. A square-shaped area can be exemplified as an area (hereinafter sometimes referred to as a pixel) represented by these measurement points.

If there is an angular difference in crystal orientation of 5 degrees or more between adjacent pixels, or if only one of the adjacent pixels exhibits a NaCl-type face-centered cubic structure, the region where these pixels are in contact is the grain boundary. Then, the portion surrounded by the sides that are regarded as grain boundaries is defined as one crystal grain. However, a single pixel that has an orientation difference of 5 degrees or more from all adjacent pixels, or that has no measurement point with an adjacent NaCl-type face-centered cubic structure, is not regarded as a crystal grain, and is two pixels or more. are connected as crystal grains. In this manner, grain boundary determination is performed to specify crystal grains.

(1) Area ratio of crystal grains having a NaCl-type face-centered cubic structure The area ratio of the crystal grains having the NaCl-type face-centered cubic structure thus specified in the observation field is obtained, and the crystal having the NaCl-type face-centered cubic structure is obtained. It is assumed to be the area ratio of grains.

(2) How to find the area ratio occupied by region α with respect to all crystal grains of NaCl-type face-centered cubic structure Observation including at least 10 crystal grains having NaCl-type face-centered cubic structure specified by the above procedure A field of view is defined, and area analysis is performed using Energy Dispersive X-ray Spectrometry (EDS) using a TEM (beam diameter 1 nm). Then, the five fields of view of the observation field are classified into two types of colors, the region (region α) where x is 0.30 or less and the region where x exceeds 0.30. Next, image processing is performed to determine the area ratio of the region α to all crystal grains of the NaCl-type face-centered cubic structure.

(3) Method of determining the area ratio of the region α existing in the region γ A region surrounded by grain boundaries is defined as a region γ. An observation field containing at least 10 NaCl-type crystal grains having a face-centered cubic structure is defined, and as described above for the 5 fields of this observation field of view, the area α color-coded by EDS mapping is subjected to image processing in the observation field of view. Find area. Next, the area of the region α within the region γ is determined by image processing, and the area ratio of the region α existing within the region γ to the entire region α is determined.

(4) How to find the area of each region α An observation field containing at least 10 crystal grains having a NaCl-type face-centered cubic structure is defined, and the five fields are color-coded by EDS mapping as described above. Regarding α, each individual area is obtained by image processing.

(5) How to determine the section where the region α exists With respect to the longitudinal section of the tool substrate surface of the TiAlCN layer, the measurement range is set to 10 μm in the direction parallel to the surface of the tool substrate and in the direction perpendicular to the surface of the tool substrate ( A square with a length equal to the average layer thickness in the layer thickness direction) is defined as the observation field of view, and the measurement field of view is divided into 1 μm square sections (in the surface section, the AlTiCN layer does not exist in the entire section excluding things). As described above, two types of color coding are performed by mapping, the region (region α) where x is 0.30 or less and the region where x exceeds 0.30. Among the 1 μm square sections, the sections in which the area α exists are identified by image processing, and the number ratio of the sections in which the area α exists is obtained. This calculation of the number ratio is performed for five fields of view.

(6) How to Determine Average Grain Width W and Average Aspect Ratio A of Crystal Grains A method of calculating the average grain width W and average aspect ratio A of crystal grains will be described. First, as described above, grain boundaries are determined to identify crystal grains. Next, image processing is performed, and for a certain crystal grain i, the maximum length H _i in the direction perpendicular to the surface of the tool base (layer thickness direction), the grain width W which is the maximum length in the direction horizontal to the surface of the tool base _{Find i} , and area S _i . The aspect ratio A _i of the crystal grain i is calculated as A _i =H _i /W _i . In this way, based on the grain widths W ₁ to W _n (n ≥ 20) of at least 20 or more (i = 1 to 20 or more) crystal grains in the observation field, the area-weighted average is calculated by [Equation 1]. The average grain width W of the crystal grains. Similarly, the aspect ratios A ₁ to A _n (n≧20) of the crystal grains are obtained, and the average aspect ratio A of the crystal grains is obtained by taking an area-weighted average according to [Equation 2].

4. Manufacturing Method A method for forming the TiAlCN layer of the present invention is, for example, as follows. First to n-th film formation is performed using gas group A and gas group B, which will be described later. The target thickness of the TiAlCN layer is obtained in the n-th film formation. Each film formation consists of a process 1 for increasing the layer thickness by depositing a new film on the surface and a process 2 for increasing the Ti concentration in the vicinity of the grain boundary. In each film formation, process 1 is performed for a certain period of time, and then process 2 is performed for half the time. In process 2, almost no new layer is deposited on the surface of the layer deposited in process 1, and the change in layer thickness can be practically ignored.

Examples of the two kinds of reaction gas compositions are as follows. The gas composition is defined as the composition sum of gas group A and gas group B being 100% by volume, and hereinafter abbreviated as %. A gas composition without description of the process is a composition range common to process 1 and process 2.

Reaction gas composition (% by volume):
Gas group A: NH ₃ : 2.0 to 5.0% (process 1), 0.1 to 0.3% (process 2),
H2: _65-75 %
Gas group B: AlCl ₃ : 0.64-1.12% (process 1),
0.01 to 0.04% (process 2),
_TiCl4 : 0.05-0.32%,
_N2 : 0.0 to 10.0%,
_C2H4 : _0.0-0.5 %,
H ₂ : Residual reaction atmosphere pressure: 4.0 to 5.0 kPa
Reaction atmosphere temperature: 700-850°C
Gas supply cycle: 2.00 to 15.00 seconds Gas supply time per cycle: 0.15 to 0.25 seconds Supply phase difference between gas group A and gas group B: 0.10 to 0.20 seconds

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

As raw material powders, WC 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. Then, wax is added and 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. After sintering, tool substrates A to C made of WC-based cemented carbide and having an insert shape according to ISO standard CNMG120412 were produced.

Next, on the surfaces of these tool substrates A to C, a TiAlCN layer was formed by CVD under the film forming conditions shown in Tables 2 and 4 using a CVD apparatus to obtain Examples 1 to 16 shown in Table 7. rice field.
A1 to H1 and A2 to H2 correspond to steps 1 and 2 described above, respectively.

In the process 1, formation symbols A to H and A1 to H1 indicating the formation conditions shown in Tables 2 and 4, that is, NH ₃ : 2.0 to 5.0% and H ₂ : 65 as the gas group A ~75%, gas group B: AlCl ₃ : 0.64 to 1.12%, TiCl ₄ : 0.05 to 0.32%, N ₂ : 0.0 to 10.0%, C ₂ H ₄ : 0 0-0.5%, H ₂ : balance (% is % by volume of the total gas group A and gas group B combined), reaction atmosphere pressure: 4.0-5.0 kPa, reaction atmosphere temperature: 700- 850° C., gas supply cycle: 2.00 to 15.00 seconds, gas supply time per cycle: 0.15 to 0.25 seconds, supply phase difference between gas group A and gas group B: 0.10 to A film was formed by the CVD method for a predetermined time at 0.20 seconds.

In the process 2, formation symbols A to H and A2 to H2 indicating the formation conditions shown in Tables 2 and 4, that is, NH ₃ : 0.1 to 0.3% and H ₂ : 65 as the gas group A ~75%, gas group B: AlCl ₃ : 0.01 to 0.04%, TiCl ₄ : 0.05 to 0.32%, N ₂ : 0.0 to 10.0%, C ₂ H ₄ : 0 0-0.5%, H ₂ : balance (% is % by volume of the total gas group A and gas group B combined), reaction atmosphere pressure: 4.0-5.0 kPa, reaction atmosphere temperature: 700- 850° C., gas supply cycle: 2.00 to 15.00 seconds, gas supply time per cycle: 0.15 to 0.25 seconds, supply phase difference between gas group A and gas group B: 0.10 to The Ti concentration in the vicinity of the grain boundary was increased by the CVD method for a predetermined time at 0.20 seconds.

Examples 1 to 16 shown in Table 7 were manufactured by forming the TiAlCN layer under the above conditions. Here, in Examples 2, 5, 7, 8, 12, 14 to 16, the lower layer and/or the upper layer as shown in Table 6 were formed under the film formation conditions shown in Table 5.

For comparison, TiAlCN layers were formed on the surfaces of these tool substrates A to C by CVD using a CVD apparatus with the formation symbols a to h indicating the film formation conditions shown in Tables 3 and 4. Comparative Examples 1-16 shown in 7 were obtained. Note that b1 to h1 and b2 to h2 correspond to the above-described process 1 and process 2, respectively.
Here, in Comparative Examples 2, 5, 7, 8, 12, 14 to 16, the lower layer and/or the upper layer as shown in Table 6 were formed under the film formation conditions shown in Table 5.

In Table 7,
(1) In the column "Is the individual region α between 100 and 50,000 ^nm2 ?", "○" indicates that the individual region α satisfies 100 to 50,000 ^nm2 , and "×" indicates that the individual region α is between 100 and 50,000 nm2. is not satisfied, and "-" indicates that there is no region α in the crystal grains having the NaCl-type face-centered cubic structure.
(2) ☆The ratio of the number of segments in which the region α exists is a square region with a length of 20 μm in the direction parallel to the surface of the tool base and a length of the average layer thickness in the direction perpendicular to the surface of the tool base, with one side of 1 μm. When divided into squares, the ratio of the divisions in which the area α exists.

Subsequently, for Examples 1 to 16 and Comparative Examples 1 to 16, each of the various tool substrates A to C (ISO standard CNMG120412 shape) was clamped to the tip of the tool steel cutting tool with a fixture. Cutting tests 1 and 2 shown below were performed to measure the flank wear width of the cutting edge. Tables 8 and 9 show the results of cutting test 1 and cutting test 2, respectively. As for the comparative example, the life was reached before the end of the cutting time due to the occurrence of chipping, so the time until the life is reached is shown.

Cutting test 1 (wet high-speed continuous cutting test)
Work material: Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1 (Nb+Ta) alloy (numbers indicate mass%)
Cutting speed: 150m/min
Notch: 0.75mm
Feed per blade: 0.30 mm/rev
Cutting time: 4 minutes

Cutting test 2 (wet interrupted cutting test)
Work material: Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1 (Nb+Ta) alloy (numbers indicate mass %) round bar with 8 flutes equally spaced in the length direction Cutting speed : 40m/min
Notch: 0.25mm
Feed per blade: 0.10 mm/rev
Cutting time: 5 minutes

As is clear from the results shown in Tables 8 and 9, all of the examples exhibit excellent durability without chipping of the coating layer even when subjected to cutting of difficult-to-cut materials.
On the other hand, in the comparative examples, chipping occurred due to the load during high-speed cutting, and the tool life was short.

1 grain boundary 2 region α
3 region γ

Claims (3)

A surface-coated cutting tool having a tool substrate and a coating layer on the surface of the tool substrate,
(a) the coating layer includes a composite carbonitride layer of Ti and Al;
(b) the composite carbonitride layer contains 80 to 100 area % of NaCl-type face-centered cubic crystal grains,
(c) When the composition of the TiAlCN layer is represented by the composition formula: (Ti _1-x Al _x ) (C _y N _1-y ), the average composition x _avg is 0.75 to 0.95, y _avg is between 0.000 and 0.010;
(d) in all the crystal grains having the NaCl-type face-centered cubic structure, 10 to 30 area % of the region α where x is 0.00 to 0.30 is present;
(e) In each of the crystal grains having the NaCl-type face-centered cubic structure, when the range surrounded by the curve spaced 10 nm from the crystal grain boundary into the crystal grain and the crystal grain boundary is defined as the region γ, 60 to 100 area% of the entire region α is present in the region γ,
A surface-coated cutting tool characterized by: With respect to the region α, the area of each region is 100 to 50000 nm ² ,
When a quadrangular region having a length of 20 μm in the direction parallel to the surface of the tool substrate and a length of the average layer thickness in the direction perpendicular to the surface of the tool substrate is divided into squares with a side of 1 μm, the segment where the region α exists The surface-coated cutting tool according to claim 1, wherein occupies 15 to 100% by number of all divisions. 1 or 2, wherein the NaCl-type crystal grains having a face-centered cubic structure have an average grain width W of 0.10 to 2.00 μm and an average aspect ratio A of 2.0 to 5.0 3. The surface-coated cutting tool according to 2.

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