JP7132548B2 - surface coated cutting tools - Google Patents

Description

The present invention is a surface-coated cutting tool (hereinafter referred to as a coated tool) in which the hard coating layer exhibits excellent chipping resistance and wear resistance in materials with high adhesion properties, and exhibits excellent cutting performance over a long period of use. there is).

Conventionally, a Ti—Al-based composite carbonitride layer is vapor-deposited as a hard coating layer on the surface of a tool substrate (hereinafter referred to as a tool substrate) such as a tungsten carbide (hereinafter sometimes referred to as WC)-based cemented carbide. There are coated tools which are coated by a method, and these are known to exhibit excellent wear resistance.
However, although the conventional coated tool coated with the Ti—Al-based composite carbonitride layer has relatively excellent wear resistance, it may cause abnormal wear such as chipping when used for cutting materials with high adhesion. Since this tends to occur, various proposals have been made to improve the hard coating layer.

For example, in Patent Document 1, a surface-coated cutting tool provided with a hard coating layer containing at least a composite nitride layer of Ti and Al having an average layer thickness of 0.5 to 10.0 μm on the surface of the tool substrate, The composite nitride layer of Ti and Al has an average composition satisfying (Ti _x Al _1-x )N, 0.10≦x≦0.35 (where x is an atomic ratio), and In the Al composite nitride layer, a belt-like region having a relatively high Ti component composition relative to the average composition x of the Ti component forms an angle of at least 30 degrees with the normal line of the tool substrate surface. A surface-coated cutting tool is described which is characterized in that it lies in the following directions:

Further, for example, Patent Document 2 describes a surface-coated cutting tool provided with a hard coating layer containing at least a composite nitride layer of Ti and Al having an average layer thickness of 0.5 to 8.0 μm on the surface of the tool substrate. wherein the composite nitride layer of Ti and Al has an average composition satisfying (Ti _x Al _1-x )N, 0.10≦x≦0.35 (where x is an atomic ratio); In the composite nitride layer of Ti and Al, a belt-like region having a relatively high Ti component composition compared to the average composition of the Ti component forms an angle of at least 35 degrees with the normal line of the tool substrate surface. A surface coated cutting tool is described which is characterized in that it lies in an orientation of greater than or equal to 70 degrees or less.

Furthermore, for example, Patent Document 3 describes a surface-coated cutting tool in which a droplet-free hard coating is produced on the surface of a tool substrate by high power pulse sputtering (HiPIMS).

JP 2018-43326 A JP 2018-144224 A Japanese Patent Publication No. 2015-501371

In the surface-coated cutting tools described in Patent Documents 1 and 2, the hard coating layer exhibits excellent chipping resistance and wear resistance in materials with high adhesion, and exhibits excellent cutting performance over long-term use. . Further, the surface-coated tool described in Patent Document 3 has a coating with high hardness and low residual stress. However, the hard coating layer is required to have further adhesion resistance in cutting at higher speeds. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a coated tool having excellent adhesion resistance.

Since the hard coating layers of the coated tools described in Patent Documents 1 and 2 are manufactured by the Arc Ion Plating (AIP) method, the hard coating layers contain mixed droplets (droplets). Surface modification mainly removes droplets present on the surface, reducing surface roughness and increasing tool life. However, when examined based on the principle of arc ion plating, the presence of droplets inside the hard coating layer, though less frequent than the droplets existing on the surface, causes wear on the surface of the hard coating layer. The period from when the droplets inside the hard coating layer are exposed to the end of the tool life is the same as when the surface is not modified. Therefore, the effect of improving the tool life by surface modification is limited only to the vicinity of the surface.

On the other hand, Patent Document 3 only states that there is no mixed droplet, and does not specifically mention the size and amount of mixed droplets that affect the tool life.

The present inventors have found that the size of mixed droplets when a region with a relatively high composition of Ti components in a composite nitride layer of Ti and Al exists at a predetermined angle with respect to the normal to the surface of the tool substrate. and tool life. As a result, the surprising finding was obtained that the tool life is improved not simply by reducing the number of mixed droplets, but by the presence of a predetermined amount of mixed droplets of a predetermined size.

The present invention is based on the above findings, and is as follows.
"(1) A surface-coated cutting tool in which a hard coating layer containing at least a composite nitride layer of Ti and Al having an average thickness of 0.5 to 8.0 μm is provided on the surface of the tool substrate, wherein the Ti and Al The composite nitride layer of
Composition formula: (Ti _x Al _1-x )N
has an average composition that satisfies 0.10 ≤ x ≤ 0.35 (where x is the atomic ratio), and the composite nitride layer of Ti and Al contains the average composition of the Ti component With respect to x, the band-shaped region with a relatively high Ti component composition exists at least in the direction toward the cutting edge ridge portion at an angle of 70 degrees or less with the normal line of the tool base surface,
The ratio of the sum of areas (Sdp) of mixed droplets having a maximum length of 50 nm or more to the area (Sc) of the hard coating layer, Sdp/Sc, is 0.100% or less, and the maximum length is Ssdp/Sc, the ratio of the sum of the areas of mixed droplets having a size of 10 nm or more and less than 50 nm (Ssdp) to the area of the hard coating layer (Sc), is 0.001% or more and 0.100% or less.
A surface-coated cutting tool characterized by:
(2) In the cutting edge ridge, when the angle formed by the extension lines of the tool surfaces is 2θ, the angle formed with the bisector of the angle is 0.70 × θ degrees or less, and the Ti component The surface-coated cutting tool according to (1) above, characterized in that band-like regions having a relatively high composition of are present on the rake face side and the flank face side, respectively.
(3) Except for the cutting edge ridge line, the belt-like region having a relatively high Ti composition forms an angle of 35 degrees or more and 70 degrees or less or 30 degrees or less with the normal line of the tool substrate surface. The surface-coated cutting tool according to (1) or (2) above.
(4) When the average composition of the Ti component in the strip-shaped region in which the Ti component is relatively high compared to the average composition of the Ti component is Y, the average of the Ti component in the composite nitride layer of Ti and Al The surface-coated cutting tool according to any one of (1) to (3), wherein the composition x and the Y satisfy the relationship of (x+0.01)≤Y≤(x+0.05).
(5) The average width W of the band-shaped region having a relatively higher Ti component composition than the average Ti component composition other than the cutting edge ridge is 30 to 500 nm. ), the surface-coated cutting tool described in .
(6) In the longitudinal section of the composite nitride layer of Ti and Al, the average area ratio of the band-shaped region having a relatively higher Ti composition than the average composition of the Ti component other than the ridge line of the cutting edge. The surface-coated cutting tool according to any one of (1) to (5), wherein St is 3 to 50 area %.
(7) Except for the cutting edge ridge, the Ti and Al composite nitride layer is composed of a mixed structure of cubic crystal grains and hexagonal crystal grains, and the Ti and Al composite nitride layer The surface-coated cutting tool according to any one of the above (1) to (6), wherein the average area ratio S of crystal grains having a cubic crystal structure in the longitudinal section is 30 area % or more. ”

In the surface-coated cutting tool of the present invention, the hard coating layer exhibits excellent chipping resistance and wear resistance in a highly adhesive material, and exhibits excellent cutting performance over long-term use even when subjected to high-speed interrupted cutting. can demonstrate.

FIG. 2 shows a schematic vertical cross-sectional view of a composite nitride layer (TiAlN layer) of Ti and Al on the flank/rake face (other than the cutting edge ridge) of the coated tool of the present invention. FIG. 2 shows a schematic vertical cross-sectional view of the TiAlN layer in the ridgeline portion of the cutting edge of the coated tool of the present invention (display of the high-Ti region is omitted). FIG. 3 shows an enlarged view of the cutting edge portion of FIG. 2 (only the ridge line of the cutting edge shows a high Ti region). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a high power pulse sputtering apparatus used for forming a TiAlN layer of a coated tool of the present invention, (a) being a schematic plan view and (b) being a schematic front view.

Next, the surface-coated cutting tool of the present invention will be described in detail.

Average layer thickness of TiAlN layer:
The hard coating layer includes at least a TiAlN layer. If the average layer thickness of the TiAlN layer is less than 0.5 μm, the long-term wear resistance improvement effect imparted by the TiAlN layer cannot be sufficiently obtained. If the thickness exceeds 8.0 μm, defects and chipping may easily occur, so the average layer thickness of the TiAlN layer is preferably 0.5 to 8.0 μm.

Average composition of TiAlN layer:
When the TiAlN layer is represented by the composition formula: (Ti _x Al _1-x )N, it preferably has an average composition that satisfies 0.10≦x≦0.35 (where x is the atomic ratio). The reason for this is that when x, which represents the average composition of the Ti component, is less than 0.10, TiAlN crystal grains with a hexagonal crystal structure are likely to be formed, and the hardness of the TiAlN layer is lowered to provide sufficient wear resistance. On the other hand, if x, which represents the average composition of the Ti component, exceeds 0.35, the composition ratio of the Al component decreases, so the high-temperature hardness and high-temperature oxidation resistance of the TiAlN layer decrease. It's for.
In addition, the atomic ratio of the content ratio of Ti, Al, and N is quantified, excluding elements such as carbon and oxygen that are unavoidably detected due to the influence of contamination of the tool substrate surface, etc., and the content ratio of Ti, Al, and N is determined. If the content of N with respect to the total atomic ratio is in the range of 0.45 or more and 0.65 or less, as long as the range of x is satisfied, the problem to be solved by the invention is solved.

Average area ratio S of crystal grains with a cubic structure in the TiAlN layer other than the cutting edge ridge:
In the TiAlN layer of the present invention, the average composition ratio 1-x (where 1-x is the atomic ratio) of the Al component is as high as 0.65 to 0.90 except for the ridgeline portion of the cutting edge, which will be described later. The layer consists of a mixed structure of crystal grains of cubic structure and crystal grains of hexagonal structure, and the average area ratio S (area %) of crystal grains of cubic structure in the longitudinal section of the TiAlN layer is 30 area% or more. It is preferable to
This is because when the average area ratio S of crystal grains having a cubic crystal structure is less than 30% by area, the area ratio of crystal grains having a hexagonal crystal structure relatively increases, so that the hardness of the TiAlN layer decreases, and as a result, This is because wear resistance may decrease.
The average area ratio S of crystal grains having a cubic crystal structure can be determined, for example, by using a field emission scanning electron microscope and an electron beam backscattering diffraction device, as described later, in the direction perpendicular to the surface of the tool substrate of the TiAlN layer. It can be determined by measuring the cross section.

High Ti band area:
In the TiAlN layer, the high-Ti belt-like region in which the composition x of the Ti component is relatively high compared to the average composition x of the Ti component preferably satisfies the following (1) to (6).

(1) Angle formed with the normal to the tool base surface (flank and rake faces other than the ridgeline of the cutting edge) The angle formed with the normal to the surface of the tool base (flank and rake face other than the ridgeline of the cutting edge) is 70 degrees. It is preferable to form so as to have the following directions (see FIG. 1).
The reason for setting this angle range is that if the angle exceeds 70 degrees, peeling in the layer thickness direction is likely to occur as in the case where the hard coating layer is a laminated film.
This angle is preferably 70 degrees or less and 35 degrees or more, or 30 degrees or less (including 0 degrees). That is, in the range of inclination from less than 35 degrees to more than 30 degrees, there is a possibility that cracks will occur and develop on the surface of the hard coating layer in cutting such as high cutting depth where a high load is applied to the cutting edge.
Since the measurement of this angle is performed after the high-Ti band-like region is specified, it will be described later in the section on specifying the high-Ti band-like region.

(2) At the cutting edge ridge, when the angle formed by the extended lines of the tool surfaces is 2θ, the angle formed with the bisector of the angle is 0.70 × θ degrees or less. It is more preferable to exist on each surface side. Here, "existing on each of the rake face side and the flank face side" means that one or more of each exists on the rake face side and the flank face side.
The presence of the high-Ti band-like region on the ridgeline of the cutting edge makes it possible to prevent the peeling of the hard coating layer more reliably than when it does not exist.
The angle formed by the bisector of this angle (13: see FIGS. 2 and 3) is measured after the high-Ti band-like region is specified. This will be explained where specificity is explained.

Here, the cutting edge ridgeline portion as used in the present invention is defined below. That is, as shown in FIGS. 2 and 3 (aspect ratios of FIGS. 2 and 3, not to scale):
In a cross section (longitudinal cross section) including the hard coating (2) perpendicular to the thickness direction of the coated tool of the present invention, straight lines that respectively approximate the rake face (3) and the flank face (4) (hereinafter, each is referred to as "rake The approximation straight line of the surface (5)" and the approximation straight line of the flank (6)", collectively referred to as the "extension line between the tool surfaces"), the intersection point (7) and this intersection point ( A straight line passing through the point (M) on the hard coating of the cross section closest to 7) is called the "normal line (8) of the cutting edge",
The point where the approximation curve (5) of the rake face loses contact with the rake face (3) is called the "rake face inflection point (9)",
When the flank surface approximation curve (6) is no longer in contact with the flank surface (4) and is called the "flank inflection point (10)",
The distance between the cutting edge normal (8) and the bending point (9) of the rake face is r1,
The distance between the cutting edge normal (8) and the bending point (10) of the flank face is r2,
Assuming R=(r1+r2)/2,
A point (11) on the rake face where the distance between the normal to the cutting edge (8) and the rake face (3) is 3R, and the distance between the normal to the cutting edge (8) and the flank (4) is It refers to the area on the hard coating (2) connecting the point (12) on the flank face that becomes 3R.

(3) Average composition of Ti component When the average composition of Ti component in the high-Ti belt-like region is Y, the average composition x and Y of Ti component in the composite nitride layer of Ti and Al is (x + 0.01) ≤ Y It is preferable to satisfy the relationship ≦(x+0.05).
This is because when Y is less than (x + 0.01), the toughness of the high Ti band-like region is not sufficient for the entire TiAlN layer, so that the impact absorption and mitigation may be insufficient, and (x + 0.05) , the high Ti band-like region cannot obtain the required hardness, and the wear resistance of the TiAlN layer as a whole may decrease.

(4) Average width W
As shown in FIG. 1, the width of the high-Ti band-like region refers to the width in the direction perpendicular to the angle at which the high-Ti band-like region is inclined. Desirably, W is 30 to 500 nm.
This is because when the W is less than 30 nm, the TiAlN layer has a substantially homogeneous composition as a whole, so that it may not be possible to expect the effect of improving toughness and the effect of absorbing and mitigating impact. This is because if it exceeds, a partial low-hardness region is formed in the TiAlN layer, and the wear resistance may be lowered due to uneven wear or the like.
Incidentally, the average width of the high-Ti band-like region is determined by, for example, an energy dispersive X-ray spectroscopy (EDS) using a transmission electron microscope (TEM) (hereinafter referred to as "TEM-EDS"), as described later. When the composition of the Ti component in the longitudinal section of the TiAlN layer is measured, the average composition Y of the Ti component is, for example, the average of the Ti band-like regions that satisfy the relationship of (x + 0.01) ≤ Y ≤ (x + 0.05) width.

(5) Average area ratio St other than the cutting edge ridge line
It is desirable that the average area ratio St of the TiAlN layer occupied by the high-Ti belt-like region other than the cutting edge ridge is 3 to 50 area %.
This is because when the St content is less than 3 area %, the effect of improving toughness and the effect of absorbing and mitigating impact due to the formation of the high-Ti band-like region are small, so the degree of improvement in chipping resistance may be low. This is because when the St content exceeds 50 area %, the Ti-rich belt-like region is formed as a low-hardness region, and as a result, the wear resistance may decrease due to uneven wear and the like.

(6) Identification of high-Ti band-shaped region In a measurement image by TEM-EDS measured in a field of view containing a band-shaped width of at least 500 nm,
The composition Y of the Ti component at a plurality of measurement points on a straight line with an angle of 70 degrees or less with respect to the normal to the surface of the substrate, other than the ridge line of the cutting edge, is
At the cutting edge ridge (both on the rake face side and the flank face side), if the angle formed by the extended lines of the tool surfaces is 2θ, the angle formed with the bisector of the angle should be 0.70×θ degrees or less. The composition Y of the Ti component at a plurality of measurement points on a straight line is
Is it in a predetermined high Ti concentration region, for example, within a range of (x + 0.01) to (x + 0.05) (where x is the average composition of the Ti component in the entire TiAlN layer described above)? It is determined whether the straight line belongs to the high-Ti belt-like region or is a straight line.
Next, when the straight line belongs to the high Ti band-like region, the composition of the Ti component is measured in the direction perpendicular to the straight line, and the measured Ti component composition is in the predetermined high Ti concentration region, for example, A position outside the relationship of (x+0.01)≦Y≦(x+0.05) is identified as the boundary of the high-Ti strip region.
Then, by measuring the composition of the Ti component at a plurality of positions in the high Ti band-like region specified above and averaging these, the average composition Y of the Ti component in the high Ti band-like region can be obtained.

Further, the average width W of the high-Ti band-like region can be determined by determining the outline of the high-Ti band-like region specified above, measuring the widths at a plurality of positions, and averaging these values.
Then, the outline of the high-Ti band-like region thus defined is used as the boundary line of the high-Ti band-like region. In areas other than the cutting edge ridge line, the angle formed with the normal to the surface of the tool substrate is measured, and the average of the measured angles for each high-Ti belt-like region is taken as the angle formed with the normal to the tool substrate. In addition, in the cutting edge ridge line, the angle formed by the bisector (13) of the angle formed by this boundary line and the extension line of the tool surface was measured, and the average for each high Ti band-like region was the bisector of the angle. The angle formed with the segment line.

Crystal structure and area fraction measurements:
The TiAlN layer of the present invention consists of a mixed structure of crystal grains of cubic crystal structure and crystal grains of hexagonal crystal structure. can be obtained by measuring the cross section of the TiAlN layer in the direction perpendicular to the surface of the tool base.

More specifically, the cross section of the TiAlN layer in the direction perpendicular to the surface of the tool substrate is set as a polished surface, and set in the lens barrel of a field emission scanning electron microscope, and the polished surface is irradiated with an incident angle of 70 degrees. An electron beam with an acceleration voltage of 15 kV is irradiated with an irradiation current of 1 nA to each crystal grain existing within the measurement range of the cross-sectional polished surface, and the length is 100 μm in the horizontal direction to the tool substrate and the direction perpendicular to the tool substrate surface. By measuring the electron beam backscatter diffraction image at intervals of 0.01 μm / step within the measurement range of the distance equal to or less than the layer thickness along the cross section, and analyzing the crystal structure of individual crystal grains, the cubic crystal structure It is possible to measure the area ratio of the crystal grains.

The measurement is performed in five measurement ranges, and the average area ratio S of crystal grains having a cubic crystal structure is calculated as the average value of these measurements. More specifically, the measurement points with an interval of 0.01 μm/step are obtained by arranging an equilateral triangle with a side of 0.01 μm so as to fill the measurement range, and measuring the vertex of each equilateral triangle. The measurement result at one measurement point is the measurement result representing the measurement result of one area of this equilateral triangle. Therefore, as described above, the area ratio can be obtained from the ratio of the number of measurement points.

Mixed droplets:
Mixed droplets are, for example, droplets that generally exist in a hard coating formed by an AIP device. It is about the grains that have been soaked. In the present invention, an entrained droplet is defined below. That is, when the composition of Al, Ti, and N components in the longitudinal section of the TiAlN layer is measured by SEM-EDS and TEM-EDS mapping analysis, Al and/or Ti are detected, and the region where the N component is not detected. do.

Area ratio of mixed droplets:
Regarding the mixed droplets, the longitudinal section of the TiAlN layer in the coating including the cutting edge ridge (both on the rake face side and the flank face side) was observed by SEM-EDS mapping analysis at a magnification of 50000 times, and the maximum length of the mixed droplets Sdp is the sum of the areas of grains having a thickness of 50 nm or more, and Sc is the area of the vertical cross section of the TiAlN layer at the ridge of the cutting edge. And, observed at a magnification of 100000 times by TEM-EDS mapping analysis, the ratio of the sum of the areas of mixed droplets (Ssdp) having a maximum length of 10 nm or more and less than 50 nm to the area of the hard coating layer (Sc), Ssdp /Sc is preferably 0.001% or more and less than 0.100%.
The reason for this is that the Sdp/Sc is in the above range, so that defects of the hard coating layer caused by coarse mixed droplets of 50 nm or more and sudden peeling and damage caused by abnormal growth can be suppressed. Furthermore, when Ssdp/Sc is within the above range, fine mixed droplets diffuse into the hard coating layer, and the mixed droplets become aluminum oxide (AlO _x ) due to the cutting atmosphere. , the effect of improving heat resistance and oxidation resistance works predominantly, improving cutting performance. In other words, unless there is a certain amount of mixed droplets having a maximum length of 10 nm or more and 50 nm or less, the coating effect due to the change to aluminum oxide does not occur.
The area Sc of the cross-sectional area referred to here requires a field of view of at least 1 μm×1 μm or more when observed at a magnification of 50,000 times by SEM-EDS mapping analysis, and the entire hard coating layer may be observed. Observe 10 fields each on the face and rake face.
Note that the maximum length refers to the maximum value between any two points on the contour line of the mixed droplet.

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.

Method for depositing TiAlN layer:
The TiAlN layer of the present invention can be formed, for example, by the following method.

Using a high-output pulse sputtering apparatus in which one of the arc power sources shown in FIG. A Ti—Al alloy target (cathode electrode) having a predetermined composition is placed in the device, the surface of the tool substrate is bombarded and cleaned, and then nitrogen gas is introduced into the device as a reaction gas and used as a sputtering gas. When argon gas is introduced and the temperature of the tool substrate is plotted from the low-temperature treatment temperature on a graph with time on the horizontal axis and treatment temperature (set temperature) on the vertical axis, the temperature change is linear or stepwise. The temperature is raised to a high-temperature treatment temperature and maintained at this temperature, a predetermined sputtering condition is applied to the Ti—Al alloy target (cathode electrode) to generate plasma discharge, and a DC low bias voltage is applied to the tool substrate. is applied for a predetermined time, the bias voltage is sequentially increased linearly or stepwise, and a high DC bias voltage is applied, and the area ratio of the mixed droplets on the edge of the cutting edge of the present invention is a predetermined value or less. of TiAlN layer can be deposited.

In the present invention, an intervening layer such as TiN may be further provided between the hard coating layer containing TiAlN and the tool substrate, and a coating layer such as Al ₂ O ₃ may be provided on the surface of the hard coating layer.

Next, the coated tool of the present invention will be specifically described with reference to examples.
As a concrete explanation, a coated tool having a tool substrate made of a WC-based cemented carbide will be described, but the same applies to a coated tool having a tool substrate such as a TiCN-based cermet or cBN sintered body.

Preparation of tool substrate:
As raw material powders, Co powder, TaC powder, NbC powder, VC powder, Cr ₃ C ₂ powder, and WC powder, each having an average particle size of 0.5 to 5 μm, were prepared. After blending with the formulation shown, wax is further added and wet-mixed in a ball mill for 72 hours, dried under reduced pressure, press-molded at a pressure of 100 MPa, and these green compacts are sintered to obtain a predetermined size. to produce WC-based cemented carbide tool substrates 1 and 2 having an insert shape of ISO standard SEEN1203AFEN.

Each of the tool substrates 1 and 2 is ultrasonically cleaned in acetone and dried, using a high-output pulse sputtering apparatus in which one of the anode power sources shown in FIG. After washing under the bombardment conditions shown in Table 2, a TiAlN layer was formed under the TiAlN layer forming conditions.
That is, first, while the inside of the apparatus is evacuated and maintained in a vacuum, the tool substrate is heated with a heater to the tool substrate temperature under the bombardment conditions shown in Table 2, and then the tool substrate is exposed to the tool substrate rotating while rotating on the rotary table. 2 is applied, and the arc current shown in Table 2 is passed through the Ti—Al alloy target (cathode electrode) to generate arc discharge, thereby bombarding the surface of the tool substrate,
Next, nitrogen gas was introduced into the apparatus as a reaction gas to set the _N2 gas pressure shown in Table 2, and argon gas was introduced as a sputtering gas to set the Ar gas pressure shown in Table 2. When the temperature of the tool base rotating while rotating is represented in a graph from the low temperature treatment temperature shown in Table 2 with time on the horizontal axis and treatment temperature (set temperature) on the vertical axis, the temperature change is linear or stepwise. The temperature was raised to the high-temperature treatment temperature and held at this temperature, and the sputtering conditions having the sputtering input power, peak current, pulse frequency, and pulse application time shown in Table 2 were applied to the Ti—Al alloy target (cathode electrode). A low DC bias voltage shown in Table 2 is applied to the tool substrate for a predetermined time shown in Table 2, and then the horizontal axis is time along the rising speed shown in Table 2. , the vertical axis is the bias voltage (−V), the bias voltage is increased linearly or stepwise in sequence, and then the high DC bias voltage shown in Table 2 is applied to form the TiAlN layer. By forming the film, the average layer thickness shown in Table 4, the average composition x of the Ti component, the average area ratio S of the crystal grains with a cubic crystal structure, and the predetermined high Ti band-like region (average composition Y of the Ti component, average width W , the coated tools 1 to 14 of the present invention having average area ratios St) were produced, respectively.

On the other hand, for comparison, the tool substrates 1 and 2 were ultrasonically cleaned in acetone, and an AIP apparatus (a high-output pulse sputtering power supply of the high-output pulse sputtering apparatus shown in FIG. 4 was used as an anode power supply) was operated. Nitrogen gas was introduced into the apparatus as a reaction gas to obtain the _N2 gas pressure shown in Table 3, and the temperature of the tool substrate rotating while rotating on the rotary table was set to the low temperature treatment temperature shown in Table 3. Then, when represented on a graph with time on the horizontal axis and processing temperature (set temperature) on the vertical axis, the temperature is raised to the high-temperature treatment temperature so that the temperature changes linearly or stepwise, and held at this temperature. Then, an arc current shown in Table 3 was caused to flow through the Ti—Al alloy target (cathode electrode) to generate an arc discharge, and a low DC bias voltage shown in Table 3 was applied to the tool substrate for a predetermined time shown in Table 3. Then, the bias voltage was sequentially increased linearly or stepwise in a graph with time on the horizontal axis and bias voltage (-V) on the vertical axis along the rate of increase shown in Table 3. , by applying a DC high bias voltage shown in Table 3 to form a TiAlN layer, the average layer thickness shown in Table 5, the average composition x of the Ti component, and the average area ratio S of crystal grains with a cubic structure , Comparative coated tools 1 to 10 each having a predetermined high Ti strip region (average composition Y of Ti component, average width W, average area ratio St) were manufactured.

Regarding the TiAlN layers of the coated tools 1 to 14 of the present invention and the coated tools 1 to 10 of the comparative examples manufactured above, the average layer thickness, the average composition x of the Ti components, the presence or absence of a high-Ti belt-like region, and the presence or absence of Ti in the region Average composition Y of components, average width w, average area ratio St, average value of the angle between the boundary line of the region and the normal to the surface of the tool base except for the ridge line of the cutting edge, and the boundary line and the tool surface between the ridge line of the cutting edge The average value of the angle formed with the bisector of the angle formed by the extension line of is obtained. The results are shown in Table 4 (invention tool) and Table 5 (comparative coated tool).

Furthermore, for the coated tools 1 to 14 of the present invention and the comparative coated tools 1 to 10, the area ratio of mixed droplets in the region including the cutting edge ridge of the TiAlN layer was determined. That is, the entire region of the TiAlN layer including the ridgeline of the cutting edge is observed by TEM-EDS at a magnification of 100,000 times, and the total area (Sdp) of mixed droplets having a maximum length of 50 nm or more is obtained. The ratio Sdp/Sc to the area of the layer (Sc), and the ratio of the sum of the areas (Ssdp) of the mixed droplets having a maximum length of 10 nm or more and less than 50 nm to the area (Sc) of the hard coating layer, Ssdp /Sc was calculated. The results are shown in Tables 4 and 5, respectively.

Next, for the coated tools 1 to 14 of the present invention and the coated tools 1 to 10 of the comparative examples, a dry high-speed face milling test, which is a type of high-speed interrupted cutting, and a center cut cutting test were performed under the following conditions. The wear width was measured.
Cutting test: dry high-speed face milling, center cut cutting Cutter diameter: 125 mm
Work material: JIS/SUS440A block material with a width of 100 mm and a length of 365 mm Cutting speed: 210 m/min
Notch: 2.5mm
Feed per blade: 0.2 mm/tooth Cutting time: 14 minutes Table 6 shows the test results.

As is clear from the cutting test results shown in Table 6, in the coated tool of the present invention, a region having a relatively high Ti content in the TiAlN layer exists at a predetermined angle with respect to the normal to the surface of the tool substrate. In addition, since there is a predetermined amount of mixed droplets of a predetermined size, high-speed intermittence of a material with high weldability is possible compared to the coated tool of the comparative example, which does not satisfy the provisions of the present invention with respect to the mixed droplets. In cutting, the hard coating layer exhibits excellent chipping resistance and wear resistance, and exhibits excellent cutting performance over long-term use.

The coated tool of the present invention exhibits excellent chipping resistance and excellent wear resistance over long-term use even when subjected to high-speed intermittent cutting of materials with high adhesion properties. It can fully satisfactorily cope with factory automation of cutting equipment, labor saving and energy saving in cutting, and further cost reduction.

1: Tool substrate 2: Hard coating 3: Rake face 4: Flank face 5: Approximate straight line of rake face 6: Approximate straight line of flank face 7: Intersection 8: Cutting edge normal 9: Inflection point of rake face 10: Rake face Inflection point 11: Point on the rake face where the distance between the normal to the cutting edge and the rake face is 3R 12: Point on the flank where the distance between the normal to the cutting edge and the flank is 3R 13: Angle bisector 14: Straight line parallel to angle bisector M: Point on hard coating closest to intersection

Claims (7)

A surface-coated cutting tool provided with a hard coating layer containing at least a composite nitride layer of Ti and Al having an average thickness of 0.5 to 8.0 μm on the surface of the tool substrate, wherein the composite nitride of Ti and Al A layer defines its composition as
Composition formula: (Ti _x Al _1-x )N
has an average composition that satisfies 0.10 ≤ x ≤ 0.35 (where x is the atomic ratio), and the composite nitride layer of Ti and Al contains the average composition of the Ti component With respect to x, the band-shaped region with a relatively high Ti component composition exists at least in the direction toward the cutting edge ridge portion at an angle of 70 degrees or less with the normal line of the tool base surface,
The ratio of the sum of areas (Sdp) of mixed droplets having a maximum length of 50 nm or more to the area (Sc) of the hard coating layer, Sdp/Sc, is 0.100% or less, and the maximum length is Ssdp/Sc, the ratio of the sum of the areas of mixed droplets having a size of 10 nm or more and less than 50 nm (Ssdp) to the area of the hard coating layer (Sc), is 0.001% or more and 0.100% or less.
A surface-coated cutting tool characterized by: In the ridgeline portion of the cutting edge, when the angle formed by the extended lines of the tool surfaces is 2θ, the angle formed with the bisector of the angle is 0.70 × θ degrees or less, and the composition of the Ti component is 2. A surface coated cutting tool according to claim 1, wherein the relatively high band-shaped areas are present on the rake face side and the flank face side respectively. The belt-like region having a relatively high Ti composition, other than the cutting edge ridge line, forms an angle of 35 degrees or more and 70 degrees or less or 30 degrees or less with the normal line of the tool base surface. Item 3. The surface-coated cutting tool according to Item 1 or 2. When the average composition of the Ti component in the strip-shaped region in which the composition of the Ti component is relatively high compared to the average composition of the Ti component is Y, the average composition of the Ti component in the composite nitride layer of Ti and Al is x and The surface-coated cutting tool according to any one of claims 1 to 3, wherein said Y satisfies the relationship of (x + 0.01) ≤ Y ≤ (x + 0.05). 5. The method according to claim 4, wherein the average width W of the belt-like region having a relatively high Ti component composition compared to the average Ti component composition is 30 to 500 nm, except for the cutting edge ridge line portion. Surface coated cutting tools. Except for the ridgeline portion of the cutting edge, the belt-like region having a Ti component relatively higher than the average composition of the Ti component occupies the longitudinal section of the composite nitride layer of Ti and Al, and the average area ratio St is 3. 6. The surface-coated cutting tool according to any one of claims 1 to 5, wherein the surface-coated cutting tool is ∼50% by area. Except for the ridgeline portion of the cutting edge, the composite nitride layer of Ti and Al is composed of a mixed structure of crystal grains with a cubic structure and crystal grains with a hexagonal structure. The surface-coated cutting tool according to any one of claims 1 to 6, wherein the average area ratio S of crystal grains having a cubic crystal structure is 30 area% or more.

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