WO2020162365A1 - Surface-coated cutting tool having hard coating layer exhibiting superior deposition resistance, plastic-deformation resistance, and abnormal damage resistance - Google Patents

Abstract

Provided is a surface-coated cutting tool that has, on a tool substrate surface, a hard coating layer: that has a composite carbonitride layer containing (Ti(1-x)ZrxyHfx(1-y))(N(1-z)Cz)(0.10 ≤ x ≤ 0.90, 0 < y ≤ 1.0 and 0.05 < z <0.75); in which the ZrHf-content proportion and the C-content proportion periodically fluctuate; in which a periodic interval between a highest ZrHf-content point and an adjacent lowest ZrHf-content point and a periodic interval between a highest C-content point and an adjacent lowest C-content point are 5-100 nm; in which the content proportion difference Δx and average Δz are 0.02 or greater; in which the distance between the highest ZrHf-content point and the nearest highest C-content point is 1/5 or less of the interval between the highest content point and the lowest content point of the adjacent ZrHf component; that has a 10% or greater amount of composition fluctuating structure in terms of the area proportion; that additionally has a vertical crystal structure; and in which the highest peak of an inclination angle category for the angle formed by the normal of a plane (111) is present in an inclination angle category in which an inclination angle with respect to the normal of the tool substrate surface is in a range of 0-10º.

Description

Surface-coated cutting tool with excellent hard coating layer that exhibits excellent welding resistance, plastic deformation resistance and abnormal damage resistance

INDUSTRIAL APPLICABILITY The present invention has an impact high load acting on a cutting edge, for example, in high feed interrupted cutting of precipitation hardening stainless steel, a hard coating layer has excellent welding resistance, plastic deformation resistance and abnormal resistance. The present invention relates to a surface-coated tool which has excellent cutting performance due to its damaging property over a long-term use.
The present application claims priority based on Japanese Patent Application No. 2019-020911 filed in Japan on February 7, 2019 and Japanese Patent Application No. 2020-004689 filed in Japan on January 15, 2020, and the contents thereof Is used here.

Conventionally, generally, in the cutting of various steels, a Ti compound layer such as a Ti carbonitride (TiCN) layer formed by chemical vapor deposition is formed as a lower layer on the surface of a cemented carbide substrate such as a tungsten carbide base, Coated tools have been used which have a hard coating layer with a chemical vapor deposited aluminum oxide layer as the top layer.
However, in recent years, there has been a demand for higher efficiency in intermittent cutting of various steels, and in particular, in intermittent cutting of precipitation hardening stainless steel, while high feed is required, in the conventional coated tool, welding Since chipping is likely to occur and normal wear does not occur when welding chipping does not occur, normal wear progresses quickly, so that it is not sufficient to cope with high feed rate.

Therefore, for example, in Patent Document 1, in a coated cutting tool having a TiZr carbonitride coating on the surface of the substrate, the coating contains 0.3% by mass or more and 50% by mass or less of Zr and 2% by mass or less of chlorine. However, a coated cutting tool having a tensile residual stress has been proposed, which has high film hardness and excellent wear resistance during cutting of machine structural steel and the like, and has excellent cutting durability characteristics.
Further, in Patent Document 2, in a coated cutting tool having a TiZr carbonitride coating, by further orienting the crystal orientation of the coating to the (422) plane or the (311) plane, the grain boundary strength is increased, As a coating layer for a base material made of hard metal or cermet, the hardness of the film is high at high temperature, and even if the film thickness increases, the width of the crystal grains near the film surface does not become coarse and good wear resistance. A coated cutting tool having excellent toughness and excellent cutting durability has been proposed.

Japanese Patent Laid-Open No. 2001-11632 (A) Japanese Patent Laid-Open No. 2001-170804 (A)

In recent years, there has been a strong demand for labor saving and energy saving in cutting work, and accordingly, coated tools have come to be used under more severe conditions. In the intermittent feed cutting, it is required to exhibit excellent welding resistance, plastic deformation resistance and abnormal damage resistance.
However, in the case of using the coated tool composed of the coating layer having the TiZr carbonitride coating proposed in Patent Document 1 and Patent Document 2 described above for high feed interrupted cutting of precipitation hardening stainless steel, However, although the effect of improving wear resistance is recognized, there is a problem that fine chipping of the coating is likely to occur, and welding chipping occurs due to lack of welding resistance. Although suppressed, the grain boundary strength is still insufficient and the welding resistance is insufficient, so that welding chipping occurs, which is not suitable for practical use.

Therefore, from the above-mentioned viewpoint, the inventors of the present invention, in the above-mentioned coated tool, have excellent welding resistance and excellent resistance to welding over a long period of time even when used for high-feed interrupted cutting of precipitation hardening stainless steel. The following findings were obtained as a result of diligent research on a coated tool that has both plastic deformability and abnormal damage resistance and improves the tool life.
That is, the inventors have increased the ratio of the amount of N to the amount of C of the TiZr composite carbonitride or the TiZrHf composite carbonitride in the hard coating layer having the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer. It has been found that by doing so, the welding resistance is enhanced and, for example, the problem of welding chipping, which has been a problem in high feed interrupted cutting of precipitation hardening stainless steel, can be solved.
Furthermore, the present inventors have found that in the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer, the content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr, and Hf (hereinafter referred to as “ZrHf And a composition variation structure in which the content of C in the total amount of N and C (hereinafter also referred to as “C content”) periodically changes. In addition, the Ti content corresponds to the composition variation of the content ratio of the total content of ZrHf and the content ratio of the C content, and the content ratio of Ti content in the total content of Ti, Zr, and Hf (hereinafter, “Ti And a content ratio of N in the total amount of N and C (hereinafter, also referred to as “N content ratio”) similarly change periodically. A variable structure, in particular, the cycle and position of the ZrHf highest content point showing the highest content rate and the ZrHf lowest content point showing the lowest content rate with respect to the ZrHf content rate, and the C highest content point showing the highest content rate with respect to the C content rate. And, by synchronizing the cycle and the position of the C lowest content point showing the lowest content ratio with each other to obtain a structure containing high hardness crystal grains, plastic deformation resistance can be exhibited, and the problem of abnormal damage can be solved. It was found that a hard coating layer having excellent abnormal damage resistance can be obtained.
Further, the composite carbonitride layer is made to have a vertically long crystal structure, that is, a structure in which a crystal having an aspect ratio of 2.0 or more is contained in an area ratio of 50% or more, and the normal line of the surface of the tool base is set. On the other hand, when the inclination angle formed by the normal to the (111) plane, which is the crystal plane of the crystal grains, is measured within the range of 0 to 45 degrees, and the inclination angle number distribution graph is created, the surface of the tool base is The maximum peak exists in the tilt angle section within the range of 0 to 10 degrees and the total of the frequencies existing in the tilt angle section within the range of 0 to 10 degrees is the tilt angle number distribution graph. By having at least one layer that occupies 35% or more of the total frequency in the above, it has excellent welding resistance, plastic deformation resistance and abnormal damage resistance, and is used for high feed interrupted cutting of precipitation hardening stainless steel. However, it has been found that the tool life is improved over a long period of use.
Since the TiZr composite carbonitride and the TiZrHf composite carbonitride included in the surface-coated cutting tool of the present invention have a higher ratio of N content to C content than in the past, in the present specification, TiZrNC and TiZrNC, respectively. It may be expressed as TiZrHfNC.

The present invention has been made based on the above findings, and includes the following aspects.
(1) A surface-coated cutting tool having a hard coating layer on the surface of a tool base,
(A) The hard coating layer includes at least one of a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer having an average layer thickness of 0.5 μm or more and 20.0 μm or less,
(B) said composite carbonitride layer contains TiZr complex carbonitride or TiZrHf complex carbonitride, said composite carbonitride, the composition formula _{(Ti (1-x) Zr} xy Hf x (1-y ₎ )(N _(1-z) C _z ),
The average content ratio x of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf, the average content ratio y of the Zr amount to the total amount of Zr and Hf, and N and C. The average content ratio z (where x, y and z are all atomic ratios) of the C content with respect to the total amount thereof is 0.10≦x≦0.90 and 0<y≦1.0, respectively. , And an average composition satisfying 0.05<z<0.75,
(C) In the composite carbonitride layer, the content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf, and N and C in at least a part of the crystal grains. Has a composition-varying structure in which the content ratio of the C content relative to the total content of
(C-1) In a longitudinal cross-section observation, the area ratio of the composition varying structure to the structure of the composite carbonitride layer is 10% or more,
(C-2) Regarding the content ratio of the total amount of Zr and Hf with respect to the total amount of Ti, Zr and Hf in the composition varying structure, the maximum content point and the minimum content of ZrHf showing the maximum content ratio x _max. The ZrHf minimum content point indicating the ratio x _min is repeated, and the average interval between the repeated ZrHf highest content points and the ZrHf lowest content point is 5 to 100 nm, and the ZrHf highest content point is The average value of the absolute values of the differences Δx between the highest content rate x _max and the lowest content rate x _min of the ZrHf lowest content point is 0.02 or more,
(C-3) Regarding the content ratio of the C content with respect to the total amount of N and C in the composition varying structure, the C highest content point showing the highest content ratio z _max and the C lowest content showing the lowest content ratio z _min. The content point is repeated, and the average interval, which is the average value of the intervals between the adjacent C highest content point and C lowest content point, is 5 to 100 nm, and the highest content ratio z _max of the C highest content point and the above The average absolute value of the difference Δz from the C minimum content ratio z _min is 0.02 or more,
(C-4) Regarding the content ratio of the total amount of Zr and Hf with respect to the total amount of Ti, Zr and Hf in the composition varying structure, the maximum content point and the minimum content of ZrHf showing the maximum content ratio x _max. Each cycle and position of the ZrHf minimum content point indicating the ratio x _min , and the content ratio of the C content relative to the total amount of N and C, the C maximum content point indicating the maximum content ratio z _max , The respective cycles and positions with the C lowest content point indicating the lowest content ratio z _min are correspondingly synchronized with each other, and the highest ZrHf content point and the highest C point at the position closest to the highest ZrHf content point. The average value of the distance from the content point is 1/5 or less of the average distance between the ZrHf highest content point and its adjacent ZrHf lowest content point,
(D) The composite carbonitride layer has a vertically long crystal structure,
(E) Using a field emission scanning electron microscope and an electron beam backscattering diffractometer, an electron is applied to each crystal grain having a rock salt type cubic crystal lattice present within the measurement range of the cross-section polished surface of the composite carbonitride layer. Line, and an inclination angle formed by the normal line of the (111) plane, which is the crystal plane of the crystal grain, with respect to the normal line of the surface of the tool base is measured within a range of 0 to 45 degrees. When a number distribution graph is created, the highest peak exists in the tilt angle section within the range of 0 to 10 degrees with respect to the normal to the surface of the tool base, and the tilt angle section within the range of 0 to 10 degrees. The surface-coated cutting tool is characterized by having at least one layer in which the total of the frequencies present in 3) accounts for 35% or more of the total frequencies in the inclination angle frequency distribution graph.
(2) The surface-coated cutting tool as described in (1) above, wherein the composition varying structure is a laminated structure.
In the present specification and the description of the embodiments of the present invention, when a numerical range is indicated by "to" or "-", it means that the range includes the lower limit and the upper limit of the numerical value. ..

A surface-coated cutting tool according to an aspect of the present invention (hereinafter, referred to as “surface-coated cutting tool of the present invention”, “coated tool of the present invention” or “present invention coated tool”) is formed on the surface of a tool base. The hard coating layer has a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer, and by increasing the ratio of the N content to the C content, the welding resistance is increased and the precipitation hardening stainless steel This is a solution to the problem of welding chipping, which was a problem in high-feed intermittent cutting.
Furthermore, the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer has a composition variation structure in which the ZrHf content ratio and the C content ratio change periodically, and in particular, the ZrHf highest content point and the ZrHf lowest By containing high hardness crystal grains in which the cycles and positions of the content points and the cycles and positions of the C highest content points and the C lowest content points are synchronized, excellent plastic deformation resistance is exhibited, and abnormal damage is caused. Is a solution.
And, the coated cutting tool having such a composite carbonitride layer as a hard coating layer has excellent welding resistance, plastic deformation resistance and abnormal damage resistance, so that high feed interrupted cutting of precipitation hardening stainless steel is performed. It is intended to improve the tool life over long-term use for machining.

Regarding the ZrHf content ratio and the C content ratio in the composition fluctuation direction of the composition fluctuation structure of the TiZrHf composite carbonitride layer of the coated tool of the present invention, the ZrHf highest content ratio, the ZrHf lowest content ratio, and the ZrHf average content ratio will be described below. , C highest content rate, C lowest content rate, and C average content rate, and ZrHf highest content point, ZrHf lowest content point, ZrHf average content point, C highest content point, C lowest content corresponding to each content rate. It is a conceptual diagram which shows the relationship with a point and the position of a C average content point. It is a tilt angle number distribution graph of {111} plane in TiZrHf carbonitride which comprises the composite carbonitride layer of the hard coating layer of the coating tool 5 of this invention.

Next, an embodiment of the coated tool of the present invention will be described in detail.

Tool base;
As the tool base, any base can be used as long as it is a base conventionally known as a tool base of this type, as long as it does not impair the achievement of the object of the present invention.
For example, cemented carbide (including WC-based cemented carbide, WC, Co, or those containing carbonitrides such as Ti, Ta, and Nb), cermet (TiC, TiN, TiCN, etc.) It is preferable that it is one of the main components) or ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.).

Hard coating layer;
The hard coating layer included in the surface-coated cutting tool of the present invention has at least a composite carbonitride layer, and the composite carbonitride layer includes a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer. It consists of
In addition, as the hard coating layer, as another layer, a lower layer may be provided between the tool base and the composite carbonitride layer, or an upper layer may be provided on the composite carbonitride layer, if necessary. You can
Here, if the average layer thickness of the hard coating layer is less than 0.5 μm, long-term wear resistance cannot be exhibited, while if it exceeds 30.0 μm, the hard coating layer as a whole will suffer defects and chipping. Since it is likely to occur, it is preferable to set the thickness to 0.5 to 30.0 μm.
The average layer thickness of the hard coating layer can be measured using, for example, a SEM (scanning electron microscope) or a TEM (transmission electron microscope) in a cross section in the direction perpendicular to the tool substrate.

Composite carbonitride layer;
(1) Component composition, average layer thickness The composite carbonitride layer provided in the surface-coated cutting tool of the present invention comprises a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer, and the composite carbonitride is the same. The TiZr composite carbonitride or the TiZrHf composite carbonitride constituting the layer is represented by a composition formula (Ti _(1-x) Zr _xy Hf _{x (1-y)} )(N _(1-z) C _z ). In this case, 0.10≦x≦0.90, 0<y≦1.0, and 0.05<z<0.75 are satisfied.
Here, x represents the average content ratio of the total amount of Zr and Hf with respect to the total amount of Ti, Zr, and Hf, and y represents the average content of the Zr amount with respect to the total amount of Zr and Hf. Indicates the content rate. Further, z represents the average content ratio of the amount of C with respect to the total amount of N and C. However, x, y, and z are all atomic ratios.
In the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer provided in the surface-coated cutting tool of the present invention, the average content ratio z of C is N for the welding resistance improving element N and the hardness improving element C. Was added in an amount of 0.05<z<0.75, a hard coating layer excellent in both welding resistance and high hardness could be obtained.
Here, when x is smaller than 0.10 or larger than 0.90, sufficient lattice strain is not introduced and sufficient hardness cannot be ensured, so 0.10≦x It was defined as ≤0.90.
The composite carbonitride layer contains oxygen (O) and chlorine (Cl) as impurities in addition to the components of Ti, Zr, Hf, N, and C, and contains 3.0 atoms of oxygen (O). % Or less, and chlorine (Cl) may be contained at 0.20 atomic% or less.

Further, if the average layer thickness of the composite carbonitride layer is less than 0.5 μm, long-term wear resistance cannot be exhibited, while if it exceeds 20.0 μm, chipping or chipping tends to occur. Therefore, the thickness is 0.5 to 20.0 μm, which is excellent in terms of hardness and wear resistance.
The average layer thickness of the composite carbonitride layer was measured by using a scanning electron microscope (magnification: 5000 times) to measure the layer thickness at five points in the observation field of view of the cross section in the direction perpendicular to the tool base. The average layer thickness can be determined on average.

(2) Crystal grains having a composition varying structure In the composite carbonitride (TiZrNC or TiZrHfNC) layer included in the surface-coated cutting tool of the present invention, ZrHf content ratio, Ti content ratio, C content ratio and N content ratio are periodic. It includes crystal grains having a composition variation structure that changes to.

1) Definition of ZrHf highest content point, ZrHf highest content rate (x _max ), ZrHf lowest content point, ZrHf lowest content rate (x _min );
In the composition-varying structure, the ZrHf content ratio is determined by, for example, a ZrHf maximum content ratio-ZrHf minimum content ratio-ZrHf maximum content ratio-in the direction in which the period width of the periodic composition change of the ZrHf content ratio becomes the minimum. The ZrHf minimum content ratio is maintained at a predetermined interval such that a periodic change in the content ratio is shown.
Explaining the ZrHf maximum content ratio (x _max ) and the ZrHf minimum content ratio (x _min ) here, the ZrHf maximum content ratio (x _max ) means that the ZrHf content ratio at each measurement point is the composition formula ( ZrHf average of the total amount of Zr and Hf with respect to the total amount of Ti, Zr and Hf in Ti _(1-x) Zr _xy Hf _x(1-y) )(N _(1-z) C _z ). It means the maximum value of the ZrHf content ratio in a continuous region that is equal to or greater than the content ratio (x _av ). When there are a plurality of regions in which the ZrHf average content ratio (x _av ) is continuously equal to or higher than the value, the maximum value of the ZrHf content ratio in each region is defined as the ZrHf maximum content ratio, and the ZrHf content ratio in each region is The position where the maximum value is obtained is defined as the ZrHf highest content point in each region. Hereinafter, the maximum ZrHf content may be referred to as x _max .
Similarly, the ZrHf minimum content ratio (x _min ) means that the ZrHf content ratio at each measurement point is the composition formula (Ti _(1-x) Zr _xy Hf _x(1-y) )(N _(1- the minimum value of ZrHf content in continuous area becomes a value less than the mean content of total amount occupied of Zr and Hf _{(x av)} against the total amount of Ti and Zr and Hf in _{z) C z)} Say. When there are a plurality of regions in which the value of x _av is continuously less than or equal to, the minimum value of the ZrHf content ratio in each region is defined as the ZrHf minimum content ratio (x _min ), and the ZrHf content ratio in each region is the minimum value. Is defined as the ZrHf minimum content point in each region. Hereinafter, the minimum content ratio of ZrHf may be referred to as x _min .
According to this definition, when there is a periodic change in the vicinity of the value of the ZrHf average content ratio (x _av ), the ZrHf highest content point and the ZrHf lowest content point appear alternately.
This will be specifically described with reference to FIG. Assuming that the left side of FIG. 1 is the stack upper position, the ZrHf content ratio is as follows from the top: ZrHf average content point (P1)-ZrHf maximum content point 1 (Pmax1)-ZrHf average content point (P2)-ZrHf minimum content point 1 (Pmin1 )-ZrHf average content point (P3)-ZrHf maximum content point 2 (Pmax2)-ZrHf average content point (P4)-ZrHf minimum content point 1 (Pmin2)-ZrHf average content point (P5), ZrHf content ratio Is the ZrHf average content ratio (x _av )-ZrHf maximum content ratio 1 (x _max1 )-ZrHf average content ratio (x _av )-ZrHf minimum content ratio 1 (x _min1 )-ZrHf average content ratio (x _av )-ZrHf The highest content ratio 2 (x _max2 )-ZrHf average content ratio (x _av )-ZrHf lowest content ratio 1 (x _min2 ) changes in this order.
Here, for example, between the positions of the ZrHf average content point (P2) and the ZrHf average content point (P3), local minimum points continuously lower than the average content ratio (x _av ) of ZrHf are (Pmin1) and (Pq). , And in that case, the (Pmin1) position showing the lower ZrHf content ratio (x _min1 ) is defined as the ZrHf minimum content point according to the above definition.
Hereinafter, also for Ti component, C component, and N component, in a continuous region having a value equal to or more than the average content ratio, the position having the maximum value in each region is referred to as the highest content point in each region, The position at which the minimum value is obtained in a continuous region that is less than or equal to the average content ratio value is called the minimum content point in each region.

2) Definition of the highest Ti content point, the highest Ti content rate (α _max ), the lowest Ti content point, and the lowest Ti content rate (α _min );
In the composition varying structure, the content ratio of the Ti amount to the total amount of Ti, Zr, and Hf (hereinafter also referred to as Ti content ratio) is such that the periodic width of the periodic composition change of the ZrHf content ratio is the minimum. Along the direction, the ZrHf highest content point indicates the Ti minimum content ratio α _min (=1-x _max ) and the ZrHf lowest content point indicates the Ti maximum content ratio α _max (=1-x _min ). Note that α is an atomic ratio.
That is, the Ti content ratio is the minimum Ti content ratio-the maximum Ti content ratio-the minimum Ti content ratio-Ti in the same cycle along the direction in which the periodic width of the periodic composition change of the ZrHf content ratio becomes the minimum. The change of the content ratio of the highest content ratio is shown. Here, the definitions of the highest Ti content point, the highest Ti content rate, the lowest Ti content point, and the lowest Ti content rate are the same as those in which ZrHf is replaced with Ti.

3) Definition of C highest content point, C highest content rate (z _max ), C lowest content point, C lowest content rate (z _min );
In the composition-varying structure, the C content ratio is as follows: C highest content ratio-C lowest content ratio-C highest content ratio-C lowest along the direction in which the periodic width of the periodic composition change of Ti and ZrHf becomes the minimum. Content ratio shows a periodic change in content ratio with a predetermined interval.
The maximum C content and the minimum C content here will be described. The maximum C content means that the C content at each measurement point is the composition formula (Ti _(1-x) Zr _xy Hf _{x(1 -Y)} ) (N _(1-z) C _z ) The maximum value of the C content ratio in a continuous region that is equal to or greater than the average content ratio (z _av ) of the C content relative to the total amount of N and C Say. When there are a plurality of regions that continuously exceed the value of z _av , the maximum value of the C content ratio in each region is defined as the C maximum content ratio, and the position where the C content ratio in each region has the maximum value is defined. It is defined as the highest C content point in each region. Hereinafter, the highest C content may be referred to as z _max .
Similarly, the C minimum content point, C content at each measurement point, the overall composition formula layer _{(Ti (1-x) Zr} xy Hf x (1-y)) (N (1-z) C z ) Is the minimum value of the C content ratio in a continuous region where the amount of C occupies the total amount of N and C in () and is equal to or less than the value of the average content ratio (z _av ). When there are a plurality of regions in which the value of z _av is continuously less than or equal to, the minimum value of the C content ratio in each region is defined as the C minimum content ratio, and the position where the C content ratio in each region has the minimum value is defined. It is defined as the C lowest content point in each region. Hereinafter, the lowest C content may be referred to as z _min .
According to this definition, when there is a periodic change in the vicinity of the value of the C average content ratio (z _av ), the highest content point and the lowest content point appear alternately.
The C content ratio is also specifically shown in FIG. 1, like the ZrHf content ratio. When the left side of FIG. 1 is the upper position of the stack, the C content ratio is as follows: C average content point (R1)-C highest content point 1 (Rmax1)-C average content point (R2)-C lowest content point 1 (Rmin1 )-C average content point (R3)-C highest content point 2 (Rmax2)-C average content point (R4)-C lowest content point 1 (Rmin2)-C average content point (R5) Ratio (z _av )-C maximum content ratio 1 (z _max1 )-C average content ratio (z _av )-C minimum content ratio 1 (z _min1 )-ZrHf average content ratio (z _av )-C maximum content ratio 2 ( z _max2 )-C average content ratio (z _av )-C minimum content ratio 1 (z _min2 ).
Here, for example, between the positions of the C average content point (R2) and the C average content point (R3), local minimum points continuously lower than the average content ratio (z _av ) of C are (Rmin1) and (Rq). In this case, the position (Rmin1) showing a lower C content ratio (z _min1 ) is defined as the C minimum content point in that case.

4) N highest content point, N highest content rate (β _max ), N lowest content point, N lowest content rate (β _min );
In the composition varying structure, the content ratio of the N content relative to the total content of N and C (hereinafter also referred to as N content ratio) is such that the cycle width of the periodic composition change of the C content ratio is minimized. Along the line, the C highest content point indicates the N lowest content ratio β _min (=1-z _max ), and the C lowest content point indicates the N highest content ratio β _max (=1-z _min ). Note that β is an atomic ratio.
That is, the N content ratio is the N minimum content ratio-N highest content ratio-N lowest content ratio-N in the same cycle along the direction in which the cycle width of the periodic composition change of the C content ratio becomes the minimum. The change of the content ratio of the highest content ratio is shown. Here, the definitions of the N highest content point, the N highest content ratio, the N lowest content point, and the N lowest content ratio are the same as those in which C is replaced with N.

5) ZrHf content ratio difference (x _max -x _min ) at the ZrHf highest content point and ZrHf lowest content point, and C content ratio difference (z _max -z _min ) at the C highest content point and the C lowest content point.
The positions of the ZrHf highest content point and the C highest content point, and the cycles of the highest content point and the lowest content point can be synchronized in the film forming method described later.
Furthermore, the average absolute value of the difference Δx between the ZrHf maximum content ratio x _max and the ZrHf minimum content ratio x _min is 0.02 or more, and the absolute value of the difference Δz between the C maximum content ratio z _max and the C minimum content ratio z _min. The hardness is improved by setting the composition varying structure in which the average value of the values is 0.02 or more. The following two points are considered as factors that improve hardness.
(1) The hardness is increased by preventing dislocation movement between the region where Zr and Hf and C are increased (enriched region) and the region where Zr and Hf and C are decreased (poor region). Can be improved.
(2) Since C is increased in the region where Zr and Hf are increased, “the influence of the bond of Zr and N” and “the influence of the bond of Hf and N” are smaller than that of the uniform TiZrHfNC layer. Since ZrN and HfN are inferior in hardness to ZrC, TiC and TiN, the hardness can be improved by reducing the influence of the bond between Zr and Hf and N.
The difference between the ZrHf maximum content ratio x _max and the ZrHf minimum content ratio x _min is more preferably 0.02 or more and 0.90 or less, and the difference between the C maximum content ratio z _max and the C minimum content ratio z _min is 0. It is more preferably 0.02 or more and 0.75 or less. If these differences are too large, abnormal damage such as minute chipping is likely to occur. The cause of this is not clear, but it is presumed that the change in the lattice constant within the compositionally varying structure becomes too large, and the toughness as crystal grains deteriorates.

6) Distance between adjacent ZrHf highest content points and ZrHf lowest content points (average value);
Regarding the distance between the highest content point of ZrHf and the lowest content point of ZrHf, "When observing the longitudinal section of the composite carbonitride layer, the average distance measured in the direction in which the period of periodic composition change is the minimum is 5 to 100 nm. Is necessary for improving hardness.
In order to exert the effect of improving the hardness, it is desirable that the average interval is small, and it is necessary that the average interval is 100 nm or less. On the other hand, if the average interval is less than 5 nm, it is difficult to form the layers so that they are clearly distinguished from each other, so that desired hardness cannot be obtained and wear resistance cannot be secured.
For example, in FIG. 1, the interval (Pmin1-Pmax1) between the ZrHf highest content point 1 (Pmax1) and the ZrHf lowest content point 1 (Pmin1), and the ZrHf highest content point 2 (Pmax2) and the ZrHf lowest content point 2 (Pmin2). Can be obtained as an average value with the interval (Pmin2-Pmax2).

7) The average value of the interval between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point;
In order to exert the hardness improving effect (the effect of paragraph (0020) of paragraph 0020), "the average value of the intervals between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point. "Is preferably as small as possible and needs to be ⅕ or less of the average interval between the ZrHf highest content point and the ZrHf lowest content point which are adjacent to each other.
It should be noted that, as described above, it is considered that it is preferable that the "average value of the intervals between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point" is preferably small, but it is disclosed in the present invention. Depending on the method, the average value of the distances between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point is the average distance between the ZrHf highest content point and its adjacent ZrHf lowest content point. It has been confirmed that the effect is exhibited even at 15/100. Although not particularly limited, the lower limit value of this average interval is more than 0.
For the average value of the interval between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point, for example, in FIG. 1, the ZrHf highest content point 1 (Pmax1) and the ZrHf highest content point are shown. The interval (Rmax1-Pmax1) from the C highest content point 1 (Rmax1) closest to the point 1 (Pmax1), the ZrHf highest content point 2 (Pmax2), and the ZrHf highest content point 2 (Pmax2) It can be obtained as an average value with the interval (Rmax2-Pmax2) between the C highest content point 2 (Rmax2) at a close position.
This value is set to the interval (average value) between the adjacent ZrHf highest content point and ZrHf lowest content point, that is, the interval (Pmin1-Pmax1) between the ZrHf highest content point 1 (Pmax1) and the ZrHf lowest content point 1 (Pmin1), The presence or absence of the effect can be judged by comparing with 1/5 of the average value of the interval (Pmin2-Pmax2) between the ZrHf highest content point 2 (Pmax2) and the ZrHf lowest content point 2 (Pmin2).

8) Area ratio of the composition varying structure to the structure of the composite carbonitride layer;
In order to exert the effect of improving the hardness, it is preferable that the composition variation structure has a large area ratio in the structure of the composite carbonitride layer, and in the longitudinal cross-section observation of the composite carbonitride layer, the composition variation structure is It is necessary that the area ratio of the nitride layer to the structure is 10% or more.
As described above, it is considered that it is preferable that the “area ratio of the composition varying structure to the structure of the composite carbonitride layer” is large, but according to the method disclosed in the present invention, the composition varying structure has the composite carbonitride layer. It has been confirmed that the effect is exhibited even if the area ratio of the above structure is 15%. Although not particularly limited, the upper limit of this area ratio is less than 98.

9) Layered structure;
In order to further exert the effect of improving the hardness, the composition varying structure is preferably a laminated structure. The term “laminated structure” as used herein refers to “of the composition-varying structure, only one ZrHf maximum content point or one ZrHf minimum content point exists between adjacent ZrHf average content points, In between, it refers to a tissue in which only one C-maximum content point or one C-minimum content point exists.
From the viewpoint of improving hardness, the film thickness is in the lamination direction (direction in which the cycle of periodic composition change is the minimum in the longitudinal cross-sectional observation of the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer). It does not have to match the direction. In the case of the film forming method described later, a composite carbonitride layer containing crystal grains having a laminated structure is obtained, but the laminated direction of the laminated structure does not always coincide with the film thickness direction.
In addition, there are cases where the vicinity of the grain boundary does not have a laminated structure, or where any of the elements Ti, Zr, Hf, C, N, O, and Cl is concentrated near the grain boundary. If the area ratio of the structure (in this case, composition change structure of the laminated structure) to the structure of the composite carbonitride layer is 10% or more, the hardness improving effect is exhibited.

10) Vertical crystal structure;
Further, the composite carbonitride layer provided in the surface-coated cutting tool of the present invention, as described above, by having a vertically elongated crystal structure, the falling of particles from the coating layer is suppressed, wear resistance and abnormal damage resistance. Exhibits excellent characteristics.
The longitudinal crystal structure referred to here means the height of the crystal grain in the layer thickness direction of each crystal grain when the longitudinal cross section of the composite carbonitride layer (cross section perpendicular to the surface of the tool base) is observed. In the length (long side), the largest value is the maximum grain length (L), and in the width (short side) of the crystal grain in the direction perpendicular to the layer thickness direction, the largest value is the largest grain width (W). Is defined as a structure in which the area ratio of crystal grains having an aspect ratio defined by L/W of 2.0 or more in the vertical cross section of the composite carbonitride layer is 50% or more.
The aspect ratio and the area ratio of the elongated crystal grains are measured, for example, by using a scanning electron microscope (SEM), and a longitudinal cross-sectional image obtained by observing the cross section at a magnification of 5000 times is subjected to electron backscatter diffraction (EBSD). By measuring the maximum grain length, the maximum grain width, and the area of the vertical cross section for each crystal grain, determine the aspect ratio from the maximum grain length and the maximum grain width, and then measure the vertical cross section that was the measurement target. The ratio of the total area of the crystal grains having an aspect ratio of 2.0 or more with respect to the area in the vertical section was determined as the area ratio.
That is, by defining the area ratio of those having an aspect ratio of 2.0 or more to be 50% or more, the effect of improving toughness and wear resistance can be exhibited.

11) Inclination angle number distribution In the present invention, the inclination angle number distribution in the composite carbonitride crystal grains of the composite carbonitride layer is measured on the surface of the tool base using a field emission scanning electron microscope and an electron beam backscattering diffractometer. The measurement can be performed by irradiating each crystal grain having a rock salt type cubic crystal lattice existing within the measurement range of the polished surface of the vertical section with an electron beam.
That is, specifically, with respect to the normal line of the surface of the tool base, the inclination angle formed by the normal line of the {111} plane that is the crystal plane of the composite carbonitride crystal grains in the composite carbonitride layer is 0. In the case of measuring within a range of up to 45 degrees, dividing the measured tilt angle into pitches of 0.25 degrees, and creating a tilt angle number distribution graph that aggregates the frequencies present in each section, The highest peak exists in the tilt angle section in which the tilt angle with respect to the normal to the surface of the tool base is in the range of 0 to 10 degrees, and the total of the frequencies existing in the tilt angle section in the range of 0 to 10 degrees is The inclination angle number distribution graph occupies 35% or more of all the frequencies, and the {111} planes of the crystal grains of the carbonitride layer have a high orientation tendency and have a structure in which plastic deformation hardly occurs. ..

(3) Film-forming method of composite carbonitride layer (TiZrNC layer or TiZrHfNC layer) In the present invention, the composition of components is regulated, the composition has a specific composition variation structure, the composition has a specific longitudinal crystal structure, and The TiZrNC layer or the TiZrHfNC layer in which the crystal grains are oriented in the (111) direction is formed by, for example, forming a film on a tool base using a chemical vapor deposition method under the following conditions. can do.
That is, the film forming conditions of the TiZrNC layer or the TiZrHfNC layer are as follows: TiCl ₄ gas, ZrCl ₄ gas or a mixed gas of ZrCl ₄ gas and HfCl ₄ gas, CH ₄ gas, N ₂ gas, H ₂ gas, The film forming temperature is 1000° C. or more and less than 1080° C., and the pressure condition is 16 kPa or more and less than 40 kPa, and a CVD apparatus capable of periodic gas supply can be used.
Specifically, first, as the first step (initial nucleation step), the gas group A and the gas group B were periodically introduced into the furnace a required number of times, so that TiNC and TiZrNC were scattered. Initial nuclei are formed, and in the second step (crystal growth step), crystal growth of the initial nuclei produces a vertically elongated crystal structure, and TiZrNC is (111) oriented on the initial nuclei, so that the grain boundary strength is A structure that is high and is less likely to undergo plastic deformation is obtained.

[Film forming conditions]
1) First step (initial nucleation step)
a) Reaction gas composition (% by volume):
Gas group A; TiCl ₄ : 0.4 to 0.7%,
CH ₄ : 2.0 to 8.0%,
N ₂ : 15.0 to 60.0%,
H ₂ : Remaining
Gas group B; TiCl ₄ : 0.4 to 0.7%,
ZrCl ₄ : 0.1 to 1.8%, HfCl ₄ : 0.0 to 1.7%,
However, ZrCl ₄ +HfCl ₄ : 0.5 to 1.8%,
CH ₄ : 1.0 to 6.0%,
N ₂ : 25.0 to 60.0%,
H ₂ : Remaining
b) Supply cycle:
This is repeated with (gas group A→gas group B) as one cycle.
The supply time of each gas group is 5 seconds or more for both the gas groups A and B, and the gas supply time per cycle is 10 seconds or more. If the gas supply time per cycle is less than 10 seconds, it will be difficult to clearly distinguish and form the initial nuclei. On the other hand, if the gas supply time per cycle is too long, it is difficult to obtain the initial nuclei in which TiNC and TiZrNC are scattered, so the gas supply time per cycle is preferably 180 seconds or less.
Therefore, the gas supply time per cycle is preferably 10 seconds or more and 180 seconds or less.
c) Reaction atmosphere temperature: 1000° C. or higher and lower than 1080° C. As for the reaction atmosphere temperature lower than 1000° C., it tends to be difficult to obtain a sufficient film formation rate. On the other hand, at a temperature of 1080° C. or higher, elements such as C may diffuse from the cemented carbide base material into the coating, and sufficient adhesion strength may not be obtained. Therefore, the reaction atmosphere temperature is preferably 1000° C. or higher and lower than 1080° C.
d) Reaction atmosphere pressure: 16 kPa or more and less than 40 kPa If it is less than 16 kPa, a sufficient film formation rate cannot be obtained, and if it is 40 kPa or more, pores are likely to be contained in the film. Therefore, the reaction atmosphere pressure is preferably 16 kPa or more and less than 40 kPa.

2) Second step (crystal growth step)
a) Reaction gas composition (% by volume):
Gas group C; TiCl ₄ : 0.4 to 0.7%,
ZrCl ₄ : 0.1 to 1.8%, HfCl ₄ : 0.0 to 1.7%,
However, ZrCl ₄ +HfCl ₄ : 0.5 to 1.8%,
CH ₄ : 1.0 to 6.0%,
N ₂ : 25.0 to 60.0%,
H ₂ : Remaining
Gas group D; TiCl ₄ : 0.2 to 0.5%, but less than the TiCl ₄ concentration of gas group A ZrCl ₄ : 0.1 to 2.2%, HfCl ₄ : 0.0 to 2.2%,
However, ZrCl ₄ +HfCl ₄ :0.8 to 2.2%,
Moreover, the concentration of ZrCl ₄ +HfCl ₄ in the gas group C is exceeded,
CH ₄ : 2.0 to 8.0%, however, exceeding CH _{4 of} gas group C N ₂ : 15.0 to 50.0%, but less than N ₂ concentration of gas group C H ₂ : remaining,
b) Supply cycle:
This is repeated with (gas group C→gas group D) as one cycle.
The supply time of each gas group is 5 seconds or more for both gas group C and gas group D, and the gas supply time per cycle is 10 seconds or more. If the gas supply time per cycle is less than 10 seconds, it will be difficult to clearly distinguish and form the composition variation structure. On the other hand, as the gas supply time per cycle is lengthened, the composition fluctuation of the composition fluctuation structure in the crystal grains becomes longer, and as a result, the above-mentioned "Zr and Hf and C-rich regions and Zr and Hf Since the effect of hindering the movement of dislocations between regions where C is poor and improving the hardness is small, the hardness is lowered. In order to set the cycle of periodic composition change to 100 nm or less, the gas supply time per cycle is preferably 180 seconds or less. Therefore, the gas supply time per cycle is preferably 10 seconds or more and 180 seconds or less.
The layer thickness of the composite carbonitride layer is adjusted by increasing or decreasing the number of repetitions of the gas supply cycle (gas group C→gas group D).
c) Reaction atmosphere temperature: 1000° C. or more and less than 1080° C. Regarding the reaction atmosphere temperature, if the reaction atmosphere temperature is less than 1000° C., a sufficient film formation rate cannot be obtained and the chlorine content of the TiZrNC layer or TiZrHfNC layer tends to increase. On the other hand, at a temperature of 1080° C. or higher, elements such as C may diffuse from the cemented carbide base material into the coating, and sufficient adhesion strength may not be obtained. Therefore, the reaction atmosphere temperature is preferably 1000° C. or higher and lower than 1080° C.
d) Reaction atmosphere pressure: 16 kPa or more and less than 40 kPa If it is less than 16 kPa, a sufficient film formation rate cannot be obtained, and if it is 40 kPa or more, pores are likely to be contained in the film. Therefore, the reaction atmosphere pressure is preferably 16 kPa or more and less than 40 kPa.

(4) Method of Forming Lower Layer and Upper Layer In the present invention, a lower layer is provided between the tool substrate and the composite carbonitride layer (TiZrNC layer or TiZrHfNC layer), and a composite carbonitride layer (TiZrNC layer or TiZrHfNC layer). A top layer can be deposited over the (layer).
See Table 3 below for the compounds to be deposited and the deposition conditions.

Next, the coated tool of the present invention will be specifically described with reference to examples.

As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, and Co powder each having an average particle diameter of 1 to 3 μm are prepared, and these raw material powders are prepared. Compounded with the compounding composition shown in Table 1, wax was further added, the mixture was ball-milled in acetone for 24 hours, dried under reduced pressure, and then press-molded at a pressure of 98 MPa into a powder compact having a predetermined shape. Is vacuum-sintered in a vacuum of 5 Pa at a predetermined temperature within a range of 1370 to 1470° C. for 1 hour, and after sintering, a tool made of WC-based cemented carbide having an insert shape of ISO standard CNMG120408 Substrates A to C were manufactured respectively.

Further, as raw material powders, TiCN (TiC/TiN=50/50 by mass ratio) powders, ZrC powders, TaC powders, NbC powders, Mo ₂ C powders, and WC powders each having an average particle diameter of 0.5 to 2 μm. , Co powder and Ni powder were prepared, and these raw material powders were blended to the blending composition shown in Table 2, wet-mixed in a ball mill for 24 hours, dried, and then pressed into a green compact at a pressure of 98 MPa, This green compact is sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1500° C. for 1 hour, and after sintering, a tool base D made of TiCN-based cermet having an insert shape of ISO standard CNMG120408, E was produced.

Then, each of these tool substrates A to E is charged into a chemical vapor deposition apparatus, and a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer is formed to form the coated tools 1 to 14 of the present invention, respectively. Manufactured.
The lower layer and the upper layer were provided as needed.
Specifically, first, in Table 5, the tool substrate is selected from Table 1 or Table 2 based on the tool substrate symbol, and then based on the formation symbol, from Table 4, the TiZrNC layer of the film forming step of the present invention or The film forming conditions of the TiZrHfNC layer were selected, and the TiZrNC layer or the TiZrHfNC layer having the target average layer thickness shown in Table 5 was formed.
When the lower layer and/or the upper layer were provided, the film was formed under the formation conditions shown in Table 3 and the average target layer thickness shown in Table 5.
Then, the obtained TiZrNC layer/TiZrHfNC layer of the coated tools 1 to 14 of the present invention have an average composition, an area ratio in which the composition varying structure occupies the structure of the composite carbonitride layer, a ZrHf maximum content ratio (average value), and a ZrHf minimum value. Content ratio (average value), C highest content ratio (average value), C lowest content ratio (average value), interval between ZrHf highest content point and ZrHf lowest content point (average value), C highest content point and C lowest content point Table 5 shows the interval (average value), the interval (average value) between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point, and the average film thickness.

For the purpose of comparison, Comparative coated tools 1 to 9 were manufactured in the same procedure as the coated tools 1 to 14 of the present invention.
Specifically, in Table 6, a tool substrate is selected from Table 1 or Table 2 based on the tool substrate symbol, and then based on the formation symbol, from Table 4, the TiZrNC layer or the TiZrHfNC layer in the comparative example film forming step is selected. The film forming conditions were selected, and the TiZrNC layer or the TiZrHfNC layer having the target average layer thickness shown in Table 6 was formed.
When providing the lower layer and/or the upper layer, the film formation was performed under the formation conditions shown in Table 3 and with the average target layer thickness shown in Table 6.
Then, the average composition of the obtained TiZrNC layer and TiZrHfNC layer of the coated tools 1 to 9 of the comparative example, the area ratio of the composition varying structure in the structure of the composite carbonitride layer, the ZrHf maximum content ratio (average value), and the ZrHf minimum Content ratio (average value), C highest content ratio (average value), C lowest content ratio (average value), interval between ZrHf highest content point and ZrHf lowest content point (average value), C highest content point and C lowest content point Table 6 shows the interval (average value), the interval (average value) between the ZrHf highest content point and the C highest content point closest to the ZrHf highest content point, and the average film thickness.

Next, here, the analysis methods of the coated tools 1 to 14 of the present invention and the coated tools 1 to 9 of the comparative examples will be described.
The film thickness was measured with a scanning electron microscope (magnification: 5000 times). First, polishing was performed at a position 100 μm away from the cutting edge on the rake face near the cutting edge so that the cross section in the direction perpendicular to the tool base was exposed. Next, the TiZrN layer and the TiZrHfN layer were observed with a field of view of 5000 times so as to include a position 100 μm away from the cutting edge on the rake face in the vicinity of the cutting edge, and the layer thickness at 5 points in the observation field was measured and averaged. The value was taken as the average layer thickness.

Next, using a focused ion beam (FIB), a vertical section perpendicular to the tool substrate surface is cut out, and the composition of the TiZrNC layer or TiZrHfNC layer is measured along the layer thickness direction so that the width in the direction parallel to the tool substrate surface is High-angle scattering annular dark-field scanning transmission microscopy (HAADF-STEM) and energy dispersive X-ray analysis (EDS) were applied to the visual field of 10 μm, which was set to include the entire thickness region of the hard coating layer. Composition at 5 different points in 1.0 μm×1.0 μm field of view (when the film thickness of the TiZrNC layer or TiZrHfNC layer is 1.0 μm or less, the film thickness of the TiZrNC layer or TiZrHfNC layer×1.0 μm) Analysis was performed and the average composition of the entire TiZrNC layer or the TiZrHfNC layer was determined from the average value.

Next, the area ratio of the composition varying structure to the structure of the composite carbonitride layer was determined using HAADF-STEM. Specifically, in the field of view of 1.0 μm×1.0 μm (when the thickness of the TiZrNC layer or the TiZrHfNC layer is 1.0 μm or less, the thickness of the TiZrNC layer or the TiZrHfNC layer×the field of view of 1.0 μm), the HAADF -STEM images are observed in five different visual fields, and in each visual field, the area ratio of the composition varying structure to the composite carbonitride layer is determined, and the average value is calculated as the composition varying structure of the composite carbonitride layer structure. It was defined as the area ratio.
Since the HAADF-STEM image has a strong contrast due to the difference in atomic weight of the constituent elements, the "structure with periodic light and dark in the HAADF-STEM image" observed here is "a periodic structure of Ti, Zr and Hf. It is possible to presume that it is “a tissue having a composition change”.
Next, it was confirmed that the above-mentioned periodic bright and dark tissue has a periodic composition change of Ti with Zr and Hf by using a line analysis method by EDS.

According to the HAADF-STEM image, a plurality of composition variation structures of the laminated structure can be seen in the crystal grain, and the EDS line analysis can be performed on the composition variation structure of the laminated structure.
First, from the HAADF-STEM image, "the direction in which the period of the periodic composition change of Ti with Zr and Hf becomes the minimum (that is, the direction in which the period width of the contrast of light and dark in the HAADF-STEM image becomes the minimum)" I asked.
As described above, the HAADF-STEM image has a strong contrast due to the difference in the atomic weights of the constituent elements, and in the HAADF-STEM image, the brighter portion contains more Zr. If the grain boundaries cannot be clearly observed by HAADF-STEM, the crystal orientation mapping by electron diffraction pattern is measured at 10 nm intervals at the same location, and the crystal orientation relationship between the measurement points is analyzed to determine the adjacent measurement points. The orientation difference between (hereinafter, also referred to as “pixel”) is measured, and when there is an orientation difference of 5 degrees or more, it is defined as a grain boundary. Then, the region surrounded by the grain boundaries is defined as one crystal grain. (However, a single pixel having an orientation difference of 5 degrees or more with all the adjacent pixels is not a crystal grain, but a pixel in which two or more pixels are connected is treated as a crystal grain.)
Then, by performing a line analysis by EDS in the "direction in which the periodic width of the periodic composition change of Ti and Zr and Hf is the minimum", ZrHf maximum content ratio, ZrHf minimum content ratio, C maximum content ratio, C lowest content ratio, distance between ZrHf highest content point and ZrHf lowest content point, distance between C highest content point and C lowest content point, and C at the position closest to the ZrHf highest content point and the ZrHf highest content point The distance from the highest content point was measured.
These were all obtained by performing EDS line analysis on the composition variation structure of five laminated structures and averaging the measured values (10 points for each laminated structure) in the composition variation structure of each laminated structure. Is.
Table 5 and Table 6 show the measured and calculated values.

Next, the inclination angle number distributions of the crystal grains forming the composite carbonitride layer of the hard coating layers of the coated tools 1 to 14 of the present invention and the coated tools 1 to 9 of the comparative examples were measured by using a field emission scanning electron microscope and an electron beam backward. It was measured using a scattering diffractometer.
That is, from the interface between the lower layer and the composite carbonitride layer, 0.3 μm in the layer thickness direction of the composite carbonitride layer, and 50 μm in the direction parallel to the surface of the tool substrate, the measurement range (0. 3 μm×50 μm) is set in the lens barrel of a field emission scanning electron microscope, and an electron beam with an acceleration voltage of 15 kV is applied to the polishing surface at an incident angle of 70 degrees with an irradiation current of 1 nA to each polishing surface. Of the crystal grains having the rock salt type cubic crystal lattice existing within the measurement range of 0.1 μm×50 μm using a field emission scanning electron microscope and electron backscattering diffraction imager. At an interval of 1 μm/step, an inclination angle formed by the normal line of the {111} plane, which is the crystal plane of the crystal grain, with respect to the normal line of the surface-polished surface is 0 to 45 degrees. It is divided into 25-degree pitches and measured, and the tilt angles are distributed in a range of 0 to 10 degrees on the basis of the measurement result, which is represented by a distribution graph of the tilt angle number obtained by totaling the frequencies present in each section. The sum of the frequencies of the crystal grains inside is calculated, and the frequency ratio occupying the entire inclination angle frequency distribution graph is calculated, and shown in Tables 5 and 6. (In obtaining the tilt angle number distribution, in the case of ideal random orientation, the tilt angle number has a constant value regardless of the tilt angle formed by the normal direction of a certain crystal plane to the normal direction of the tool substrate surface. Is standardized as follows.)

Further, the longitudinal section of the composite carbonitride layer of the hard coating layers of the coated tools 1 to 14 of the present invention and the coated tools 1 to 9 of the comparative example was examined with a scanning electron microscope (SEM) at a magnification of 5000 times to give a tool substrate. The maximum particle width W and the maximum particle length for each of the composite carbonitride crystal grains existing in the region of 10 μm in the direction parallel to and the height of the thickness of the composite carbonitride layer in the direction perpendicular to the tool substrate. While measuring L, the value of the aspect ratio L/W was calculated, and the area ratio of the crystal grains having the aspect ratio L/W of 2 or more to the vertical cross section of the composite carbonitride layer was calculated. Shown in.

Next, in the state where the above-mentioned various coated tools are clamped at the tip of the tool steel bite by a fixing jig, the following precipitation-hardening stainless steels of the coated tools 1 to 14 of the present invention and the comparative tools 1 to 9 are shown below. A high-feed interrupted cutting test of steel was carried out, the flank wear width of the cutting edge was measured, and the presence or absence of welding was observed, and the results are shown in Table 7.

≪Cutting condition A≫
Cutting test: Precipitation hardening type stainless steel 1 slit material Wet high feed intermittent cutting processing work material: JIS/SUS630
Cutting speed: 110m/min,
Notch: 1.5 mm,
Feed rate: 0.42 mm/rev. ,
Cutting time: 4.0 minutes,
≪Cutting condition B≫
Cutting test: Precipitation hardening type stainless steel 4 slit material Wet intermittent high feed cutting test work material: JIS/SUS630
Cutting speed: 90m/min,
Notch: 1.2 mm,
Feed amount: 0.37 mm/rev. ,
Cutting time: 1.0 minutes,

As is clear from the cutting test results of Table 7, in the coated tool of the present invention, in Table 5, each component element satisfies the desired average composition, and the ZrHf content ratio and the C content ratio change periodically. , A TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer having a composition variation structure of a laminated structure in which the cycles and positions of the ZrHf highest content point and the C highest content point are synchronized, for example, precipitation hardening stainless steel In intermittent high-feed cutting of steel, it does not cause peeling or chipping, has a small flank maximum wear width, and exhibits excellent welding resistance, plastic deformation resistance, and abnormal damage resistance.
On the other hand, in the comparative example coated tool, even if the composite carbonitride layer included as the hard coating layer does not satisfy the desired average composition or the desired average composition is satisfied, ZrHf is contained. Since it does not have a compositionally varying structure in which the ratio and the C content change periodically or does not have the desired orientation, the desired properties cannot be exhibited, and wear progress and welding Due to the occurrence of chipping and chipping, the life was shortened.

As described above, the coated tool of the present invention, in the composite carbonitride layer included as a hard coating layer, the content ratio of each component changes periodically, by having a desired compositional variation structure, for example, precipitation hardening In intermittent high-feed cutting of type stainless steel, it exhibits excellent welding resistance, chipping resistance, and wear resistance. It is fully satisfied with the cost reduction.

Claims (2)

1. A surface-coated cutting tool having a hard coating layer on the surface of a tool base,
   (A) The hard coating layer includes at least one of a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer having an average layer thickness of 0.5 μm or more and 20.0 μm or less,
   (B) said composite carbonitride layer contains TiZr complex carbonitride or TiZrHf complex carbonitride, said composite carbonitride, the composition formula _{(Ti (1-x) Zr} xy Hf x (1-y ₎ )(N _(1-z) C _z ),
   The average content ratio x of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf, the average content ratio y of the Zr amount to the total amount of Zr and Hf, and N and C. The average content ratio z (where x, y and z are all atomic ratios) of the C content with respect to the total amount thereof is 0.10≦x≦0.90 and 0<y≦1.0, respectively. , And an average composition satisfying 0.05<z<0.75,
   (C) In the composite carbonitride layer, the content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf, and N and C in at least a part of the crystal grains. Has a composition-varying structure in which the content ratio of the C content relative to the total content of
   (C-1) In a longitudinal cross-section observation, the area ratio of the composition varying structure to the structure of the composite carbonitride layer is 10% or more,
   (C-2) Regarding the content ratio of the total amount of Zr and Hf with respect to the total amount of Ti, Zr and Hf in the composition varying structure, the maximum content point and the minimum content of ZrHf showing the maximum content ratio x _max. The ZrHf minimum content point indicating the ratio x _min is repeated, and the average interval between the repeated ZrHf highest content points and the ZrHf lowest content point is 5 to 100 nm, and the ZrHf highest content point is The average value of the absolute values of the differences Δx between the highest content rate x _max and the lowest content rate x _min of the ZrHf lowest content point is 0.02 or more,
   (C-3) Regarding the content ratio of the C content with respect to the total amount of N and C in the composition varying structure, the C highest content point showing the highest content ratio z _max and the C lowest content showing the lowest content ratio z _min. The content point is repeated, and the average interval, which is the average value of the intervals between the adjacent C highest content point and C lowest content point, is 5 to 100 nm, and the highest content ratio z _max of the C highest content point and the above The average absolute value of the difference Δz from the C minimum content ratio z _min is 0.02 or more,
   (C-4) Regarding the content ratio of the total amount of Zr and Hf with respect to the total amount of Ti, Zr and Hf in the composition varying structure, the maximum content point and the minimum content of ZrHf showing the maximum content ratio x _max. Each cycle and position of the ZrHf minimum content point indicating the ratio x _min , and the content ratio of the C content relative to the total amount of N and C, the C maximum content point indicating the maximum content ratio z _max , The respective cycles and positions with the C lowest content point indicating the lowest content ratio z _min are correspondingly synchronized with each other, and the highest ZrHf content point and the highest C point at the position closest to the highest ZrHf content point. The average value of the distance from the content point is 1/5 or less of the average distance between the ZrHf highest content point and its adjacent ZrHf lowest content point,
   (D) The composite carbonitride layer has a vertically long crystal structure,
   (E) Using a field emission scanning electron microscope and an electron beam backscattering diffractometer, an electron is applied to each crystal grain having a rock salt type cubic crystal lattice present within the measurement range of the cross-section polished surface of the composite carbonitride layer. Line, and an inclination angle formed by the normal line of the (111) plane, which is the crystal plane of the crystal grain, with respect to the normal line of the surface of the tool base is measured within a range of 0 to 45 degrees. When a number distribution graph is created, the highest peak exists in the tilt angle section within the range of 0 to 10 degrees with respect to the normal to the surface of the tool base, and the tilt angle section within the range of 0 to 10 degrees. The surface-coated cutting tool is characterized in that the surface-coated cutting tool has at least one layer in which the total of the frequencies present in 3) accounts for 35% or more of the total frequencies in the inclination angle frequency distribution graph.
2. The surface-coated cutting tool according to claim 1, wherein the composition-varying structure is a laminated structure.

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