WO2021177406A1 - Surface-coated cutting tool - Google Patents

Abstract

This surface-coated cutting tool has, on a surface of a tool base, a hard coating layer comprising a composite carbonitride layer containing (Ti_(1-x)Zr_xyHf_x(1-y))(N_(1-z)C_z) (0.10 ≤ x ≤ 0.90, 0 < y ≤ 1.0, and 0.05 < z < 0.75), wherein: a ZrHf content ratio and a C content ratio vary periodically; a periodic interval between a maximum ZrHf content point and an adjacent minimum ZrHf content point, and a periodic interval between a maximum C content point and an adjacent minimum C content point are 5–100 nm; an average value of content ratio differences Δx and Δz is at least 0.02; a distance between the maximum ZrHf content point and the closest maximum C content point is no greater than 1/5 a distance between the maximum content point and the minimum content point of the ZrHf component adjacent to each other; and a composition variation structure is at least 10% in area ratio. The hard coating layer has a longitudinal crystalline structure, and a maximum peak of an inclination angle segment formed by a normal to the {112} face is present in an inclination angle segment within a range of inclination angles of 0–10 degrees with respect to a normal to the surface of the tool base.

Description

Surface coating cutting tool

The present invention relates to a surface covering tool having excellent cutting performance over a long period of use. More specifically, the present invention relates to a surface coating tool having excellent cutting performance over a long period of time because the hard coating layer has excellent welding resistance, plastic deformation resistance and abnormal damage resistance. be.
The present application claims priority based on Japanese Patent Application No. 2020-038704 filed in Japan on March 6, 2020 and Japanese Patent Application No. 2021-011702 filed in Japan on January 28, 2021. The contents are used here.

Conventionally, in the cutting of various steels, a coating tool having a cemented carbide substrate such as a tungsten carbide group and a hard coating layer formed on the surface of the cemented carbide substrate has been generally used. The hard coating layer has a Ti compound layer such as a carbonitride (TiCN) layer of Ti chemically vapor-deposited as a lower layer, and an aluminum oxide layer chemically vapor-deposited as an upper layer.
However, in recent years, there has been a demand for higher efficiency in intermittent cutting of various steels. In particular, in the intermittent cutting of heat-resistant steel, while high efficiency is required, welding chipping occurs in the _{conventional covering tool, for example, a conventional insert having a film structure of Al 2} O _{3 / TiCN / cemented carbide.} It is easy to do, welding chipping does not occur, and even when normal wear occurs, normal wear progresses quickly. For this reason, it is becoming difficult to meet the needs.

Therefore, for example, in Patent Document 1, in a coating cutting tool having a TiZr carbonitride film on the surface of a substrate, the film contains Zr in an amount of 0.3% by mass or more and 50% by mass or less and chlorine in an amount of 2% by mass or less. Coated cutting tools have been proposed. Since this coated cutting tool has tensile residual stress, it has high film hardness and excellent wear resistance when cutting machine structural steel and the like, and also has excellent cutting durability characteristics.
Further, in Patent Document 2, in a coated cutting tool having a TiZr carbonitride film, the grain boundary strength is further increased by orienting the crystal orientation of the film toward the (422) plane or the (311) plane. Coated cutting tools have been proposed. In this coating cutting tool, the film hardness at high temperature is high as a coating layer for a base material made of cemented carbide or cermet, and the width of crystal grains near the film surface becomes coarser as the film thickness increases. However, it has good wear resistance and toughness, and exhibits excellent cutting durability characteristics.

In recent years, there has been a strong demand for labor saving and energy saving in cutting, and along with this, covering tools have come to be used under more severe conditions. Therefore, for example, in the intermittent cutting of heat-resistant steel (JIS-SCH13 as an example), it is required to exhibit excellent welding resistance, plastic deformation resistance, and abnormal damage resistance.
However, when the coating tool provided with the coating layer having the TiZr carbonitride film proposed in Patent Document 1 and Patent Document 2 is used for intermittent cutting of heat-resistant steel, the following problems are raised. Was done. In the former case, although the effect of improving wear resistance is recognized, there is a problem that minute chipping of the film is likely to occur, and welding chipping occurs frequently due to insufficient welding resistance, which makes it unusable for practical use. Was there. Further, in the latter case, although minute chipping of the film is suppressed to some extent, the grain boundary strength is insufficient and the welding resistance is insufficient, so that welding chipping is likely to occur, which is not suitable for practical use. Had had.

Japanese Unexamined Patent Publication No. 2001-11632 Japanese Unexamined Patent Publication No. 2001-170804

INDUSTRIAL APPLICABILITY The present invention has excellent welding resistance, plastic deformation resistance, and abnormal damage resistance over a long period of time even when used for intermittent cutting of heat-resistant steel, and brings about an improvement in tool life. The purpose is to provide.

Therefore, from the above viewpoint, the present inventors have excellent welding resistance, plastic deformation resistance and resistance to welding even when used for intermittent cutting of heat-resistant steel in the covering tool over a long period of time. We conducted intensive research on coated tools that have abnormal damage and improve tool life. As a result, the following findings were obtained.
In a hard coating layer having a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer, the welding resistance is enhanced by increasing the ratio of the amount of N to the amount of C of the TiZr composite carbonitride or the TiZrHf composite carbonitride. , It was found that the problem of welding chipping, which was a problem, can be improved.
Further, 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 content ratio"). (Sometimes), and the content ratio of the amount of C to the total amount of N and C (hereinafter, also referred to as “C content ratio”) has a composition-variable structure that changes periodically. Correspondingly, the composition-variable structure has a content ratio in which the Ti content accounts for the total amount of Ti, Zr, and Hf (hereinafter, may be referred to as "Ti content ratio"), and an N content is N and C. A composition-variable structure in which the content ratio in the total amount (hereinafter, also referred to as “N content ratio”) changes periodically. In particular, the period and position of the ZrHf maximum content point indicating the maximum content ratio and the ZrHf minimum content point indicating the minimum content ratio for the ZrHf content ratio, and the C maximum content point and the minimum content ratio indicating the maximum content ratio for the C content ratio are shown. C Contains high-hardness crystal grains in which the period and position of the lowest content point are synchronized. As a result, it was found that a hard coating layer having excellent plastic deformation resistance, which can exhibit the problem of abnormal damage and can solve the problem of abnormal damage, can be obtained.
Further, the composite carbonitride layer has a vertically long crystal structure, that is, a structure containing 50% or more of crystals having an aspect ratio of 2.0 or more in terms of area ratio. As a result, it was found that the particles were suppressed from falling off from the coating layer, and that they exhibited wear resistance and abnormal damage resistance.
Further, in the composite carbonitride layer, an electric field emission scanning electron microscope and an electron backscatter diffraction device are used to form individual crystal grains having a rock salt-type cubic crystal lattice existing within the measurement range of the cross-section polished surface. Irradiate an electron beam. The inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured within the range of 0 to 45 degrees with respect to the normal of the surface of the tool substrate. A slope angle distribution graph is created by classifying the measurement tilt angle for each pitch of 0.25 degrees and summing up the degrees existing in each section. The tilt angle number distribution graph is a graph in which the horizontal axis is the tilt angle and the vertical axis is the frequency. In this case, the highest peak exists in the inclination angle division in which the inclination angle of the surface of the tool substrate with respect to the normal is in the range of 0 to 10 degrees, and exists in the inclination angle division in the range of 0 to 10 degrees. The total frequency accounts for 35% or more of the total frequency in the inclination angle distribution graph. As a result, it has been found that it has excellent welding resistance, plastic deformation resistance and abnormal damage resistance, and also for intermittent cutting of heat-resistant steel, it brings about an improvement in tool life over a long period of use.
Since the TiZr composite carbonitride and the TiZrHf composite carbonitride according to one aspect of the present invention have a higher ratio of N content to C content than the conventional ones, in the present specification, TiZrNC and TiZrNC, respectively, It may also be expressed as TiZrHfNC.

One aspect of the present invention has been made based on the above findings and has the following requirements.
(1) A surface-coated cutting tool having a tool substrate and a hard coating layer provided on the surface of the tool substrate.
(A) The hard coating layer has at least a lower layer and a composite carbonitride layer from the surface side of the tool substrate.
(B) The lower layer has at least one compound layer containing Ti and / or Zr and also containing carbon and nitrogen, and the total film thickness thereof is 0.8 μm or more.
(C) The composite carbonitride layer includes at least one layer 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.
(D) The composite carbonitride layer contains a TiZr composite carbonitride or a TiZrHf composite carbonitride, and the composite carbonitride has a 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 amount of C with respect to the total amount of and is 0.10 ≦ x ≦ 0.90 and 0 <y ≦ 1.0, respectively. , And have an average composition satisfying 0.05 <z <0.75.
(E) 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 are contained in at least a part of the crystal grains. It has a composition-variable structure in which the content ratio of C amount to the total amount of C changes periodically.
(E-1) In the vertical cross-sectional observation, the area ratio of the composition-variable structure to the structure of the composite carbonitride layer is 10% or more.
(E-2) Regarding the content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf in the composition-variable structure, the maximum content ratio x _max of ZrHf content point and the minimum content The ZrHf minimum content point indicating the ratio x _min is repeated, and the average interval, which is the average value of the intervals between the repeated adjacent ZrHf maximum content points and the ZrHf minimum content points, is 5 to 100 nm. The average value of the absolute value of the difference Δx between the maximum content ratio x _max and the minimum content ratio x _{min of the ZrHf minimum content point is 0.02 or more.}
(E-3) Regarding the content ratio of the C amount to the total amount of the N and C in the composition-variable structure, the C maximum content point indicating the _{maximum content ratio z max} and the C minimum content indicating the _{minimum content ratio z min.} The content points are repeated, and the average interval, which is the average value of the intervals between the repeated adjacent C maximum content points and the C minimum content points, is 5 to 100 nm, and the maximum content ratio z _max of the C maximum content points and the above The average value of the absolute values of the difference Δz from the C minimum content ratio z _{min is 0.02 or more.}
(E-4) Regarding the content ratio of the total amount of Zr and Hf to the total amount of the Ti, Zr and Hf in the composition-variable structure, the ZrHf maximum content point and the minimum content indicating the _{maximum content ratio x max.} Regarding the respective cycles and positions of the ZrHf minimum content point indicating the ratio x _min , and the content ratio of the C amount to the total amount of the N and C, the _{C maximum content point indicating the maximum content ratio z max} and the C maximum content point indicating the maximum content ratio z max. The respective cycles and positions of the C minimum content point indicating the minimum content ratio z _min are synchronized with each other, and the ZrHf maximum content point and the C maximum position closest to the ZrHf maximum content point are synchronized with each other. The average value of the interval from the content point is 1/5 or less of the average interval between the ZrHf maximum content point and the adjacent ZrHf minimum content point.
(F) The composite carbonitride layer has a vertically long crystal structure and has a vertically long crystal structure.
(G) Using an electro-emission scanning electron microscope and an electron beam backscattering diffractometer, electrons are generated in each of the crystal grains having a rock salt type cubic crystal lattice existing within the measurement range of the cross-sectional polished surface of the composite carbonitride layer. A line is irradiated, and the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured within the range of 0 to 45 degrees with respect to the normal of the surface of the tool substrate. When the number distribution graph is created, the highest peak exists in the inclination angle division in which the inclination angle with respect to the normal of the surface of the tool substrate is in the range of 0 to 10 degrees, and the inclination angle division in the range of 0 to 10 degrees is described. A surface coating cutting tool characterized in that the total number of degrees present in is at least one layer that occupies 35% or more of the total degrees in the inclination angle distribution graph.
(2) The surface coating cutting tool according to (1) above, wherein the composition-variable structure is a laminated structure.
In the description of the present specification and the claims, when the numerical range is expressed by using "-" or "-", the range includes the upper limit and the lower limit of the numerical value. means.

The surface-coated cutting tool according to one aspect of the present invention contains C by having a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer in a hard coating layer formed on the surface of a tool substrate. It solves the problem of welding chipping, which has been a problem in intermittent cutting of heat-resistant steel, by achieving both the improvement of hardness and the improvement of welding resistance by increasing the ratio of N content to C content. be.
Further, the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer has a composition-variable structure in which the ZrHf content ratio and the C content ratio change periodically. In particular, the period and position of the ZrHf maximum content point and the ZrHf minimum content point are synchronized with the period and position of the C maximum content point and the C minimum content point, respectively, and the hardness is lower than that of ZrC, HfC, TiC, and TiN. Reduce the production of ZrN and HfN. As a result, compared to the uniform TiZrHfNC layer, crystal grains having higher hardness are generated, excellent plastic deformation resistance is exhibited, and the problem of abnormal damage is solved.
In addition, since the structure is a vertically long crystal structure, there are few grain boundaries parallel to the surface of the substrate, and the film particles are unlikely to fall off. Further, since the structure has a {112} plane, the corresponding grain boundary ratio is high, the grain boundary strength is high, and plastic deformation is unlikely to occur. Therefore, a 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 in intermittent cutting of heat-resistant steel, and has a long-term effect. It improves the tool life over use.
Further, by orienting the TiZrNC film on the {112} plane, when TiCN + α-Al ₂ O ₃ is formed as an upper layer, α-Al ₂ O ₃ is oriented on the {0001} plane having excellent wear resistance. It has the characteristic of

The composition variation of the TiZrHf composite carbonitride layer of the coating tool of the present invention The ZrHf content ratio and the C content ratio in the composition variation direction of the structure will be described below with respect to the ZrHf maximum content ratio, the ZrHf minimum content ratio, and the ZrHf average content ratio. , C maximum content ratio, C minimum content ratio, and C average content ratio, and ZrHf maximum content point, ZrHf minimum content point, ZrHf average content point, C maximum content point, C minimum content corresponding to each content ratio. It is a conceptual diagram which shows the relationship with the position of a point and a C average content point. 6 is a graph of inclination angle number distribution of {112} plane in the TiZrHf carbonitride layer constituting the composite carbonitride layer of the hard coating layer of the coating tool 5 of the present invention.

Next, the covering tool of this embodiment will be described in detail.

Tool base;
As the tool substrate, any substrate conventionally known as this type of tool substrate can be used as long as it does not hinder the achievement of the object of the present embodiment.
For example, cemented carbide (WC-based cemented carbide, WC, as well as those containing Co, or those containing carbides such as Ti, Ta, Nb, etc.), cermets (TiC, TiN, TiCN, etc.), cermets, etc. Is the main component, etc.), or ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.) are preferable.

Hard coating layer;
The hard coating layer according to the present embodiment has at least a lower layer and a composite carbonitride layer from the surface side of the tool substrate, and the lower layer contains either one or both of Ti and Zr. Moreover, it contains at least one compound layer containing carbon and nitrogen.
By changing the conventional composition-variable structure made of nitride to a composition-variable structure made of carbonitride, the hardness can be further improved.
Further, the composite carbonitride layer includes at least one layer of a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer.
Further, if necessary, as another layer, an intermediate layer can be provided between the tool substrate and the lower layer and / or between the lower layer and the composite carbonitride layer, and the composite carbonitride can be provided. An upper layer can be provided on top of the layer.
Here, if the average thickness of the hard coating layer is less than 1.3 μm, long-term wear resistance cannot be exhibited, while if it exceeds 30.0 μm, the hard coating layer as a whole is chipped or chipped. It is desirable to set it to 1.3 to 30.0 μm because it is likely to occur.
The average layer thickness of the hard coating layer is measured, for example, by using an SEM (scanning electron microscope) or a TEM (transmission electron microscope) in a cross section perpendicular to the tool substrate (cross section along the thickness direction). be able to.

Lower layer;
The lower layer formed on the tool substrate is a compound layer containing either one or both of Ti and Zr and containing carbon and nitrogen, for example, a carbonitride layer of Ti, a carbon dioxide oxide layer of Ti, and Ti. Boride layer of carbon dioxide, or carbonitoxide layer of Zr, carbon dioxide oxide of Zr, boron dioxide layer of Zr, or carbonitoxide layer of Ti and Zr, carbon dioxide oxide of Ti and Zr. It has at least one layer, which is composed of a layer, a charcoal-boride layer of Ti and Zr, and the like. As a result, the adhesion between the tool substrate and the composite carbonitride layer having a Ti and Zr composite carbonitride layer or the composite carbonitride layer having a Ti and Zr and Hf composite carbonitride layer can be enhanced, so that defects, peeling, etc. can be achieved. The occurrence of abnormal damage can be suppressed.
Further, by forming a composite carbonitride layer on the lower layer by a limited method described later, the composite carbonitride layer can be oriented in the {112} plane. The reason why the composite carbonitride layer is oriented on the {112} plane is that at least the outermost surface of the lower layer is oriented on the {112} plane, and the film forming method described later (that is, the film forming proceeds by the surface reaction). It is considered that the composite carbonitride layer inherited the orientation from the outermost surface of the lower layer by forming the composite carbonitride layer by a film forming method in which the vapor phase reaction hardly contributes.
When an intermediate layer is provided between the lower layer and the composite carbonitride layer, the intermediate layer is, for example, a TiN layer, and by using the film forming method described later, the outermost surface of the lower layer is {112}. The plane orientation can be passed on to the composite carbonitride layer via the intermediate layer.
When the total average layer thickness of the lower layer is less than 0.8 μm, the film thickness is thin and the orientation planes are not aligned with the {112} plane on the outermost surface of the lower layer, so that the composite carbonitride layer is oriented to the {112} plane. It's difficult. On the other hand, when the total average layer thickness of the lower layer exceeds 20.0 μm, the crystal grains are likely to be coarsened and chipping is likely to occur. Therefore, the total average layer thickness of the lower layer is preferably 0.8 to 20.0 μm.

Composite carbonitride layer;
(1) Component Composition, Average Layer Thickness The composite carbonitride layer according to the present embodiment is arranged on the lower layer, and is a TiZr composite carbonitride layer or a TiZrHf composite having an average layer thickness of 0.5 μm or more and 20.0 μm or less. It comprises at least one layer of carbonitride layer. Specifically, the TiZr composite carbonitride or the TiZrHf composite carbonitride constituting the composite carbonitride layer has a composition formula (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) (N _{(1). -z)} when expressed in _{C z), 0.10 ≦ x ≦} 0.90,0 <y ≦ 1.0, and satisfy 0.05 <z <0.75, respectively.
Here, x represents the average content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf, and y represents the average content ratio of the total amount of Zr and Hf to the total amount of Zr and Hf. Represents the average content ratio. Further, z indicates the average content ratio of the amount of C 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 according to the present embodiment, the average content ratio of C is about N, which is an element for improving welding resistance, and C, which is an element for improving hardness. z is contained at 0.05 <z <0.75. As a result, a hard coating layer having both high welding resistance and high hardness can be obtained.
Here, when x is smaller than 0.10 or x is larger than 0.90, sufficient lattice strain is not introduced and sufficient hardness cannot be secured, so 0.10 ≦ x. It was defined as ≤0.90.
In addition to the components Ti, Zr, Hf, N, and C, the composite carbonitride layer also contains impurity elements that are inevitably contained in production, and in particular, it contains 5.0 atoms of oxygen (O). % Or less, chlorine can be contained in 0.50 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 the average layer thickness of the composite carbonitride layer exceeds 20.0 μm. , Defects and chipping are likely to occur. Therefore, in order to exert excellent effects from the viewpoint of hardness and wear resistance, the average layer thickness of the composite carbonitride layer is set to 0.5 to 20.0 μm.
The average thickness of the composite carbonitride layer is 5 within the observation field of view in the direction perpendicular to the tool substrate (cross section along the thickness direction) using a scanning electron microscope (magnification 5000 times). The layer thickness of the points can be measured and averaged to obtain the average layer thickness.

(2) Crystal grains having a composition-variable structure In the composite carbonitride (TiZrNC or TiZrHfNC) layer according to the present embodiment, the composition in which the ZrHf content ratio, Ti content ratio, C content ratio and N content ratio change periodically. Contains crystal grains with variable structure.

1) Definitions of ZrHf maximum content point, ZrHf maximum content ratio (x _max ), ZrHf minimum content point, ZrHf minimum content ratio (x _min );
In the composition-variable structure, the ZrHf content ratio is, for example, ZrHf maximum content ratio-ZrHf minimum content ratio-ZrHf maximum content ratio-along the direction in which the periodic width of the periodic composition change of the ZrHf content ratio is minimized. ZrHf minimum content ratio, etc., keeps a predetermined interval and shows a periodic change in the content ratio.
ZrHf maximum content referred to herein (x _max), will be described. ZrHf lowest proportion (x _min), ZrHf The highest proportion (x _max), ZrHf content at each measurement point, the total layer 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) The maximum value of the ZrHf content ratio in a continuous region equal to or higher than the content ratio (x _{av) value.} When there are a plurality of regions that continuously exceed the value of the ZrHf average content ratio (x _av ), 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 defined as the maximum content ratio. The position where the maximum value is taken is defined as the ZrHf maximum content point in each region. Hereinafter, the maximum content ratio of ZrHf may be described 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 of the entire layer (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) (N _{(1-). z)} The minimum value of the ZrHf content ratio in a continuous region that is equal to or less than the value of the _{average content ratio (x av} ) of the total amount of Zr and Hf with respect to the total amount of Ti, Zr, and Hf in C _z). say. When _{there are a plurality of regions that are continuously equal to or less than the value of x av} , 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 lowest ZrHf content point in each region. Hereinafter, the minimum content ratio of ZrHf may be described as _{x min.}
According to this definition, when there is a periodic change in the vicinity of the value of x, the ZrHf maximum content point and the ZrHf minimum content point appear alternately.
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 maximum content point and the ZrHf minimum content point appear alternately.
Specifically, it will be described with reference to FIG. When the left side of FIG. 1 is the stacking upper position, the ZrHf content ratio is as follows: 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 2 (Pmin2) -ZrHf average content point (P5) 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 _min 1) -ZrHf average content ratio (x _av ) -ZrHf The maximum content ratio 2 (x _max2 ) -ZrHf average content ratio (x _av ) -ZrHf minimum content ratio 2 (x _min2 ) -ZrHf average content ratio (x _av ) changes in this order.
Here, for example, between the positions of the ZrHf average content point (P2) and the ZrHf average content point (P3), the _{minimum points continuously below the average content ratio (x av} ) of ZrHf are (Pmin1) and (Pq). In that case, the position (Pmin1) showing a lower ZrHf content ratio (x _min1 ) is defined as the ZrHf minimum content point according to the above definition.
Hereinafter, with respect to the Ti component, the C component, and the N component, the position where the maximum value is taken in each region in a continuous region equal to or higher than the value of the average content ratio is referred to as the maximum content point in each region, and the content of each component is defined as the maximum content point. The position where the minimum value is taken in the continuous region below the value of the average content ratio is called the minimum content point in each region.

2) Definitions of Ti maximum content point, Ti maximum content ratio α _max , Ti minimum content point, Ti minimum content ratio α _min;
In the composition-variable structure, the content ratio of the Ti amount to the total amount of Ti, Zr, and Hf (hereinafter, also referred to as the Ti content ratio) is such that the periodic width of the periodic composition change of the ZrHf content ratio is the minimum. At the ZrHf maximum content point, the Ti minimum content ratio α _min (= 1-x _max ) is shown, and at the ZrHf minimum content point, the Ti maximum content ratio α _max (= 1-x _min ) is shown. In addition, α is an atomic ratio.
That is, the Ti content ratio is the Ti minimum content ratio-Ti maximum content ratio-Ti minimum 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 is minimized. It shows the change of the content ratio such as the maximum content ratio. The definitions of the Ti maximum content point, the Ti maximum content ratio, the Ti minimum content point, and the Ti minimum content ratio referred to here are the same definitions in which ZrHf is replaced with Ti.

3) Definitions of C maximum content point, C maximum content ratio (z _max ), C minimum content point, C minimum content ratio (z _min);
In the composition-variable structure, the C content ratio is C maximum content ratio-C minimum content ratio-C maximum content ratio-C minimum along the direction in which the periodic width of the periodic composition change of the ZrHf content ratio is minimized. A predetermined interval is maintained, such as the content ratio, and a periodic change in the content ratio is shown.
Explaining the C maximum content ratio and the C minimum content ratio here, the C maximum content ratio means that the C content ratio at each measurement point is the composition formula of the entire layer (Ti _(1-x) Zr _xy Hf _{x (1). -y)) (N (1-} z) the maximum value of C content in the contiguous area of greater than or equal to the average proportion of the amount of C is occupied (z _av) against the total amount of N and C in _{C z)} To say. When _{there are multiple regions that continuously exceed the value of (zav} ), the maximum value of the C content ratio in each region is defined as the maximum C content ratio, and the C content ratio in each region takes the maximum value. The position is defined as the highest C content point in each region. Hereinafter, the maximum C content ratio may be referred to as z _max .
Similarly, the C minimum content point means that the C content ratio at each measurement point is the composition formula of the entire layer (Ti _(1-x) Zr _xy Hf _{x (1-y)} ) (N _(1-z) C _z. ) refers to a minimum value of C content in the continuous area to be the value or less of the average proportion of the amount of C is occupied (z _av) against the total amount of N and C in. When _{there are a plurality of regions that are continuously equal to or less than the value of (zav} ), the minimum value of the C content ratio in each region is defined as the C minimum content ratio, and the C content ratio in each region takes the minimum value. The position is defined as the C minimum content point in each region. Hereinafter, the minimum C content ratio may be referred to as z _min .
According to this definition, when _{there is a periodic change near the value of the C average content ratio (zav} ), the highest content point and the lowest content point appear alternately.
The C content ratio is also specifically shown in FIG. 1 in the same manner as the ZrHf content ratio. When the left side of FIG. 1 is the upper layer position, the C content ratio is as follows: C average content point (R1) -C maximum content point 1 (Rmax1) -C average content point (R2) -C minimum content point 1 (Rmin1). ) -C average content point (R3) -C maximum content point 2 (Rmax2) -C average content point (R4) -C minimum content point 2 (Rmin2) -C average content point (R5) ratio (z _av) -C highest proportion 1 (z _max1) -C mean proportion (z _av) -C minimum content 1 (z _min1) -C mean proportion (z _av) -C highest content 2 ( z _max2 ) -C average content ratio ( _zav ) -C minimum content ratio 2 (z _min2 ) -C average content ratio ( _zav ).
Here, for example, C average content point and (R2) between the position of the C average content point (R3), the minimum point below the average content of C in succession (z _av) is the (Rmin1) (Rq) In that case, the position (R min1) showing the lower C content ratio (z _min1 ) is defined as the C minimum content point according to the above definition.

4) N maximum content point, N maximum content ratio (β _max ), N minimum content point, N minimum content ratio (β _min );
In the composition-variable structure, the content ratio of the N amount to the total amount of N and C (hereinafter, also referred to as the N content ratio) is the direction in which the periodic width of the periodic composition change of the C content ratio becomes the minimum. At the C maximum content point, the N minimum content ratio β _min (= 1-z _max ) is shown, and at the C minimum content point, the N maximum content ratio β _max (= 1-z _min ) is shown. In addition, β is an atomic ratio. The direction in which the periodic width of the periodic composition change of the C content ratio is minimized is the same as the direction in which the periodic width of the periodic composition change of the ZrHf content ratio is minimized.
That is, the N content ratio is N minimum content ratio-N maximum content ratio-N minimum content ratio-N in the same cycle along the direction in which the periodic width of the periodic composition change of the C content ratio is minimized. It shows the change of the content ratio such as the maximum content ratio. The definitions of the N maximum content point, the N maximum content ratio, the N minimum content point, and the N minimum content ratio referred to here are the same definitions in which C is replaced with N.

5) ZrHf content ratio difference between ZrHf maximum content point and ZrHf minimum content point (x _max -x _min ) and C content ratio difference between C maximum content point and C minimum content point (z _max -z _min );
The positions of the ZrHf maximum content point and the C maximum content point, and the cycles of the respective maximum content points and the minimum content points can be synchronized in the film forming method described later.
Further, the average value of the absolute values 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 is absolute.} The hardness is improved by using a composition-variable structure having an average value of 0.02 or more. The following two points can be considered as factors for improving the hardness.
(1) The movement of dislocations is hindered and the hardness is improved between the region where Zr, Hf and C are increased (enriched region) and the region where Zr, Hf and C are decreased (poor region). be able to.
(2) Since C is increased in the region where Zr and Hf are increased, the "effect of the bond between Zr and N" and the "effect of the bond between Hf and N" are smaller than those of the uniform TiZrHfNC layer. Since ZrN and HfN have lower hardness than 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. More preferably, it is 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. Although the cause of this is not clear, it is presumed that the change in the lattice constant within the composition-variable structure becomes too large and the toughness as a crystal grain decreases.

6) The interval between the adjacent ZrHf maximum content points and the ZrHf minimum content points (average value), and the interval between the adjacent C maximum content points and the C minimum content points (average value);
Regarding the interval between the highest ZrHf content point and the lowest ZrHf content point, "In the vertical cross-sectional observation of the composite carbonitride layer, the average interval measured in the direction that minimizes the period of periodic composition change is 5 to 100 nm. Is necessary for improving hardness.
In order to exert the hardness improving effect, 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 clearly distinguish each of them, so that the desired hardness cannot be obtained and the wear resistance cannot be ensured.
For example, in FIG. 1, the interval (Pmin1-Pmax1) between the ZrHf maximum content point 1 (Pmax1) and the ZrHf minimum content point 1 (Pmin1), and the ZrHf maximum content point 2 (Pmax2) and the ZrHf minimum content point 2 (Pmin2) It can be obtained as an average value with the interval (Pmin2-Pmax2).
Similarly, regarding the interval between the C maximum content point and the C minimum content point, "In the vertical cross-sectional observation of the composite carbonitride layer, the average interval measured in the direction in which the period of periodic composition change is minimized is 5 to 5 to. It is necessary to be 100 nm.
In the present specification, the vertical cross section is a cross section along the thickness direction of the coating layer.

7) The average value of the distance between the highest ZrHf content point and the highest C content point closest to the highest ZrHf content point;
In order to exert the hardness improving effect (the effect of the above-mentioned item (2)), "the average value of the intervals between the ZrHf maximum content point and the C maximum content point closest to the ZrHf maximum content point". "Is smaller, and needs to be 1/5 or less of the average interval between the adjacent ZrHf maximum content points and the ZrHf minimum content points. The lower limit of "the average value of the intervals between the ZrHf maximum content point and the C maximum content point closest to the ZrHf maximum content point" is not particularly limited and is 0 or more.

8) Area ratio of the composition-variable structure to the structure of the composite carbonitride layer;
In order to exert the hardness improving effect, it is preferable that the composition-variable structure occupies a large area ratio in the structure of the composite carbonitride layer. It is necessary that the area ratio of the nitride layer to the structure is 10% or more. The upper limit of the area ratio of the composition-variable structure to the structure of the composite carbonitride layer is not particularly limited, and is 100% or less, preferably 96% or less.

9) Laminated structure;
In order to further exert the hardness improving effect, the composition-variable structure is preferably a laminated structure. From the viewpoint of improving hardness, the stacking direction of the laminated structure (the direction in which the period of periodic composition change is minimized in the vertical cross-sectional observation of the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer) is the film thickness. 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 can be 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 is not a laminated structure, or there are cases where any of the elements Ti, Zr, Hf, C, N, O, and Cl is concentrated near the grain boundary. When the area ratio of the structure (in this case, the composition-variable 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, as described above, the composite carbonitride layer according to the present embodiment has a vertically long crystal structure, so that particles are suppressed from falling off from the coating layer, and the composite carbonitride layer has excellent wear resistance and abnormal damage resistance. Demonstrate.
The vertically elongated crystal structure referred to here is defined as follows. When observing the longitudinal cross section of the composite carbonitride layer, the maximum value of the height (long side) of the crystal grains in the layer thickness direction was defined as the maximum particle length (L) for each crystal grain. The maximum grain width (W) is the largest value in the width (short side) of the crystal grains in the direction perpendicular to the layer thickness direction. At this time, the structure in which the area ratio of the crystal grains (vertical crystal grains) having an aspect ratio of 2.0 or more defined by L / W in the vertical cross section of the composite carbonic nitride layer is 50% or more is vertically long. It is called a crystal structure.
The aspect ratio and the area ratio of the vertically elongated crystal grains are measured, for example, as follows. For vertical cross-sectional images obtained by cross-sectional observation at a magnification of 5000 using a scanning electron microscope (SEM), the maximum particle length and maximum particle width for each crystal grain by electron backscatter diffraction (EBSD). , And measure the area of the longitudinal section. Obtain the aspect ratio from the maximum particle length and maximum particle width. Next, the total area of the crystal grains having an aspect ratio of 2.0 or more in the vertical cross section is divided by the area of the vertical cross section to be measured to obtain a ratio, and this ratio is obtained as the area ratio.
That is, by defining a structure in which the area ratio of crystal grains having an aspect ratio of 2.0 or more is 50% or more as a vertically long crystal structure, the effect of improving toughness and wear resistance can be exhibited.

11) Inclined angle number distribution In the present embodiment, the inclined angle number distribution in the composite carbonic nitride crystal grains of the composite carbonic nitride layer is obtained by using a field emission scanning electron microscope and an electron backscatter diffraction device, and the cross-sectional polished surface thereof. It can be measured by irradiating individual crystal grains having a rock salt-type cubic crystal lattice existing within the measurement range (cross section along the thickness direction of the coating layer) with an electron beam.
That is, specifically, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the composite carbonitride crystal grains in the composite carbonitride layer, is 0 with respect to the normal of the surface of the tool substrate. Measure within the range of ~ 45 degrees. The measurement inclination angle is divided into pitches of 0.25 degrees, and the degrees existing in each division are totaled to create an inclination angle number distribution graph. The tilt angle number distribution graph is a graph in which the horizontal axis is the tilt angle and the vertical axis is the frequency. The frequency is the number of pixels, and the pixel is the smallest unit measured by electron backscatter diffraction (EBSD), and the unit size of the pixel is 10 nm × 10 nm. In this case, the highest peak exists in the inclination angle division in which the inclination angle of the surface of the tool substrate with respect to the normal is in the range of 0 to 10 degrees, and exists in the inclination angle division in the range of 0 to 10 degrees. The total frequency accounts for 35% or more of the total frequency in the inclination angle distribution graph. The carbonitride layer has a structure in which the crystal grains have a high orientation tendency with respect to the {112} plane and are less likely to undergo plastic deformation. The upper limit of the ratio of the total of the frequencies existing in the inclination angle division within the range of 0 to 10 degrees to the entire frequency is not particularly limited, and is 100% or less, preferably 96% or less.
In the EBSD analysis, when determining the inclination angle number distribution, in the case of ideal random orientation, the inclination angle number is constant regardless of the inclination angle formed by the normal direction of a certain crystal plane with respect to the normal direction of the tool substrate surface. It is standardized so that it becomes the value of.

Other layers;
(1) Intermediate layer In the present embodiment, a Ti compound layer such as TiN or TiC is provided as an intermediate layer between the tool substrate and the lower layer to improve the adhesion between the tool substrate and the lower layer. be able to.
Further, in the present embodiment, for example, a TiN layer, a TiC layer, or the like can be provided as an intermediate layer between the lower layer and the composite carbonitride layer. In particular, the TiN layer has excellent peel resistance because it can inherit the orientation of the {112} plane on the outermost surface of the lower layer.
It is considered that this is because the TiN layer has high adhesion strength in both the lower layer and the composite carbonitride layer and high deformation followability.
The conditions for forming the TiN layer are common when it is provided between the tool substrate and the lower layer and when it is provided between the lower layer and the composite carbonitride layer. However, in the former case, basic components such as Co and C are diffused from the substrate, resulting in a fine granular structure. On the other hand, in the latter case, since diffusion unlike the former does not occur, it is considered that a highly oriented structure that inherits the structure of the lower layer is obtained.
(2) Upper layer In the present embodiment, an upper layer such as an Al oxide or a titanium compound such as TiN or TiCN can be further provided on the composite carbonitride layer, and a peening treatment or the like is performed after the film formation. You can also do it.

Method of forming a hard coating layer;
The hard coating layer according to the present embodiment can be formed in the order of at least the lower layer and the composite carbonitride layer, for example, by using the film forming method shown below.
(1) Method for forming a film on the lower layer The lower layer of the hard coating layer has at least one layer of a compound layer containing Ti and / or Zr and containing carbon and nitrogen. The lower layer can be formed by using a normal chemical vapor deposition method and adjusting the reaction gas composition and the reaction atmosphere such as pressure and temperature for each compound layer to be formed within an appropriate range. (See Table 3 etc. described later.)
The compound layer containing Ti can be selected from a carbonitride layer of Ti, a carbonitride oxide layer, a carbonitride boride layer, and the like. Further, the compound layer containing Zr can be selected from a ZrCN layer, a ZrCNO layer, a ZrCNB layer and the like.
Further, the compound layer containing both Ti and Zr can be selected from a TiZrCN layer, a TiZrCNO layer, a TiZrCBN layer and the like.

(2) Film formation method of composite carbonitride layer (TiZrNC layer or TiZrHfNC layer) The TiZrNC layer or TiZrHfNC layer in the present embodiment has a specific component composition, a specific composition variation structure, and a specific vertically long structure. It has a crystal structure and the crystal grains are oriented in the {112} plane. The TiZrNC layer or the TiZrHfNC layer can be formed by forming at least the lower layer on the tool substrate and then forming a film under the following conditions, for example, by using a chemical vapor deposition method.
That is, the film forming conditions of the TiZrNC layer or the TiZrHfNC layer are shown below. As raw materials, 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 are used, and the film formation temperature is 980 ° C or higher and lower than 1080 ° C, pressure. The condition is that the film can be formed at 16 kPa or more and less than 40 kPa using a CVD apparatus capable of periodic supply.
Specifically, first, in the first step (initial nucleation step), the gas group A and the gas group B are periodically introduced into the furnace as many times as necessary and repeatedly reacted to cause TiNC and TiZrNC or TiZrHfNC. The initial nuclei of the are scattered and formed. Next, in the second step (crystal growth step), the gas group C and the gas group D are periodically introduced into the furnace as many times as necessary and reacted to grow the initial nuclei into crystals. As a result, by forming a TiZrNC layer or a TiZrHfNC layer having a vertically elongated crystal structure having the composition-variable structure and oriented on the {112} plane, it is possible to obtain a structure having high grain boundary strength and less likely to cause plastic deformation. can.

[Film formation conditions]
1) First step (initial nucleation step)
a) Reaction gas composition (% by volume):
Gas group A; TiCl ₄ : 0.4-0.7%,
N ₂ : 15.0 to 60.0%,
H ₂ : The rest,
Gas group B; ZrCl ₄ : 0.1 to 1.3%, HfCl ₄ : 0.0 to 1.2%,
However, ZrCl ₄ + HfCl ₄ : 0.5 to 1.3%,
CH ₃ CN: 0.2-0.6%,
N ₂ : 15.0 to 60.0%,
H ₂ : The rest,
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 group A and the gas group 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 becomes 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 initial nuclei in which TiNC and TiZrNC or TiZrHfNC are interspersed. Therefore, 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: 980 ° C. or higher and lower than 1080 ° C. Regarding the reaction atmosphere temperature, if it is lower than 980 ° C., it tends to be difficult to obtain a sufficient film formation rate. On the other hand, at 1080 ° C. or higher, elements such as C may diffuse into the film from the cemented carbide base material, and sufficient adhesion strength may not be obtained. Therefore, the reaction atmosphere temperature is preferably 980 ° C. or higher and lower than 1080 ° C.
d) Reaction atmosphere pressure: 16 kPa or more and less than 40 kPa At less than 16 kPa, a sufficient film forming rate cannot be obtained, and at 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 : 0.4-0.7%,
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 : The rest,
Gas group D; TiCl ₄ : 0.2 to 0.5%, but less than _{the TiCl 4 concentration of gas group C,}
ZrCl ₄ : 0.1-2.2%, HfCl ₄ : 0.0-2.2%,
However, ZrCl ₄ + HfCl ₄ : 0.8 to 2.2%,
_{And the concentration of ZrCl 4} + HfCl ₄ in the gas group C was exceeded,
CH ₄ : 2.0 to 8.0%, however, _{exceeding the CH 4} concentration of gas group C,
N ₂ : 15.0 to 50.0%, but less than _{the N 2 concentration of gas group C,}
H ₂ : The rest,
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 the gas group C and the 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 becomes difficult to clearly distinguish and form the composition-variable structure. On the other hand, as the gas supply time per cycle is lengthened, the composition fluctuation of the composition variation structure in the crystal grains becomes longer. As a result, the above-mentioned "effect of hindering the movement of dislocations between the region enriched with Zr, Hf and C and the region enriched with Zr, Hf and C" and improving the hardness is reduced. Hardness decreases. In order to set the period 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: 980 ° C. or higher and lower than 1080 ° C. As for the reaction atmosphere temperature, if the temperature is lower than 980 ° C., a sufficient film forming rate cannot be obtained, and the chlorine content of the TiZrNC layer or the TiZrHfNC layer tends to increase. On the other hand, at 1080 ° C. or higher, elements such as C may diffuse into the film from the cemented carbide base material, and sufficient adhesion strength may not be obtained. Therefore, the reaction atmosphere temperature is preferably 980 ° C. or higher and lower than 1080 ° C.
d) Reaction atmosphere pressure: 16 kPa or more and less than 40 kPa At less than 16 kPa, a sufficient film forming rate cannot be obtained, and at 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 for forming an intermediate layer and an upper layer As described above, in the present embodiment, between the tool substrate and the lower layer and / or between the lower layer and the composite carbonitride layer (TiZrNC layer or TiZrHfNC layer). An intermediate layer can be provided between and. Further, an upper layer can be formed on the composite carbonitride layer (TiZrNC layer or TiZrHfNC layer).
See Table 3 below for the compounds to be filmed and the filming conditions.

Next, the covering tool of this embodiment will be described by way of examples.
Here, as a specific example of the coated tool of the present invention, a tool applied to a WC-based cemented carbide or an insert cutting tool using a cermet as a tool base will be described, but the tool base may be a conventionally known base material. For example, any of them can be used as long as it does not hinder the achievement of the object of the present embodiment. For example, cemented carbide (including WC-based cemented carbide, WC, those containing Co, or those to which carbides such as Ti, Ta, Nb are added), cermet (TiC, TiN, TiCN, etc.), cermet (TiC, TiN, TiCN, etc.) (Main component), cubic boron nitride sintered body, high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and mixtures thereof, etc.), diamond sintered body And so on.

As raw material powders, both WC powder having an average particle size of 1 ~ 3 [mu] m, TiC powder, ZrC powder, were prepared TaC powder, NbC powder, _Cr 3 _{C 2} powder, TiN powder, and Co powder. These raw material powders were blended into the blending composition shown in Table 1, wax was further added, the mixture was ball mill mixed in acetone for 24 hours, and dried under reduced pressure. Then, it was press-molded into a green compact having a predetermined shape at a pressure of 98 MPa. This green compact was vacuum sintered in a vacuum of 5 Pa under the condition of holding at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour. After sintering, tool bases A to C made of WC-based cemented carbide having an insert shape of ISO standard CNMG120408 were manufactured (see Table 1).

Further, as the raw material powder, both (TiC / TiN = 50/50 in mass ratio) TiCN having an average particle diameter of 0.5 ~ 2 [mu] m powder, ZrC powder, TaC powder, NbC powder, Mo ₂ C powder, WC powder , Co powder and Ni powder were prepared. These raw material powders were blended into the blending composition shown in Table 2, wet-mixed with a ball mill for 24 hours, and dried. Then, it was press-molded into a green compact at a pressure of 98 MPa. This green compact was sintered in a nitrogen atmosphere of 1.3 kPa under the condition of holding at a temperature of 1500 ° C. for 1 hour. After sintering, tool bases D and E made of TiCN-based cermet having an insert shape of ISO standard CNMG120408 were prepared (see Table 2).

Then, each of these tool substrates A to E is charged into a chemical vapor deposition apparatus, and the lower layer and the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer are formed in this order to form a film. Invention covering tools 1 to 16 were manufactured, respectively (see Tables 4 and 5 and Tables 6 and 7).
At that time, if necessary, an intermediate layer is provided between the tool substrate and the lower layer and / or between the lower layer and the composite carbonitride layer, and the composite carbonitride layer is provided. An upper layer was provided on the upper part.
(A) The intermediate layer, the lower layer and the upper layer were vapor-deposited at the target layer thickness shown in Tables 8 and 9 and under the forming conditions shown in Table 3.
(B) The hard coating layer is the TiZrNC layer / TiZrHfNC layer of the film forming step of the present invention with respect to the tool substrate of Table 1 or Table 2 shown by the tool substrate symbol based on Tables 4 and 5 and Tables 6 and 7. Film formation was performed according to the film formation conditions of the formation symbol. The average composition of the TiZrNC layer and the TiZrHfNC layer of the obtained coating tools 1 to 16 of the present invention, the area ratio of the composition-variable structure to the structure of the composite carbonic nitride layer, the maximum content ratio (average value) of ZrHf, and the minimum content ratio of ZrHf (average value). Average value), C maximum content ratio (average value), C minimum content ratio (average value), interval between ZrHf maximum content point and ZrHf minimum content point (average value), interval between C maximum content point and C minimum content point (average value) Tables 10 to 12 show the average value), the interval (average value) between the ZrHf maximum content point and the C maximum content point closest to the ZrHf maximum content point, and the average film thickness.

Further, for the purpose of comparison, Comparative Example Covering Tools 1 to 9 were manufactured in the same procedure as the Covering Tools 1 to 16 of the present invention.
(A) A lower layer having a target layer thickness shown in Table 13 was deposited and formed on the tool substrate under the formation conditions shown in Table 3.
(B) Next, based on Tables 4 and 5 and Tables 6 and 7, the formation symbols of the TiZrNC layer and the TiZrHfNC layer in the comparative example film forming step were applied to the tool substrates of Table 1 or Table 2 shown in the tool substrate symbols. The film was formed according to the film forming conditions of. Obtained Comparative Examples The average composition of the TiZrNC layer and the TiZrHfNC layer of the covering tools 1 to 9, the area ratio of the composition-variable structure to the structure of the composite carbonic nitride layer, the maximum content ratio (average value) of ZrHf, and the minimum content ratio of ZrHf (average value). Average value), C maximum content ratio (average value), C minimum content ratio (average value), interval between ZrHf maximum content point and ZrHf minimum content point (average value), interval between C maximum content point and C minimum content point (average value) Tables 14 to 16 show the average value), the interval (average value) between the ZrHf maximum content point and the C maximum content point closest to the ZrHf maximum content point, and the average film thickness.

Here, the analysis methods of the covering tools 1 to 16 of the present invention and the covering tools 1 to 9 of the comparative example will be described.
A scanning electron microscope (magnification of 5000 times) was used to measure the film thickness. First, on the rake face near the cutting edge, polishing was performed so that the cross section in the direction perpendicular to the surface of the tool substrate was exposed at a position 100 μm away from the cutting edge. Next, the TiZrNC layer and the TiZrHfNC layer were observed with a field of view of 5000 times so as to include a position 100 μm away from the cutting edge of the rake face near the cutting edge, the layer thicknesses of 5 points in the observation field of view were measured, and the average values were averaged. The layer thickness was set.

Next, a vertical cross section perpendicular to the surface of the tool substrate was cut out using a focused ion beam (FIB), and the composition of the TiZrNC layer or the TiZrHfNC layer was measured as follows. High-angle scattering annular dark-field scanning transmission microscopy ( HAADF-STEM) and energy dispersive X-ray analysis (EDS) with a 1.0 μm × 1.0 μm field of view (TiZrNC layer or TiZrHfNC layer if the thickness of the TiZrNC layer or TiZrHfNC layer is 1.0 μm or less, the TiZrNC layer or TiZrHfNC layer Composition analysis was performed at five different locations with a film thickness (field of view of 1.0 μm), and the average composition of the entire TiZrNC layer or TiZrHfNC layer was determined from the average value.

Next, HAADF-STEM was used to determine the area ratio of the composition-variable structure to the structure of the composite carbonitride layer. Specifically, in a field of view of 1.0 μm × 1.0 μm (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 field of view), HAADF -The STEM image was observed in five different visual fields, and the composition-variable structure was determined as the average value of the area ratio of the composite carbonitride layer to the structure.
Since the contrast in the HAADF-STEM image is strong due to the difference in atomic weight of the constituent elements, the "texture with periodic light and darkness in the HAADF-STEM image" observed here is "periodic between Ti, Zr and Hf". It can be presumed that the tissue has a composition change.
Next, it was confirmed whether or not the tissue having periodic light and dark had a periodic compositional change between Ti, Zr and Hf by using a line analysis method using EDS.

According to the HAADF-STEM image, a plurality of composition-variable structures of the laminated structure can be seen in the crystal grains, and the composition-variable structure of the laminated structure can be line-analyzed by EDS.
First, from the HAADF-STEM image, "the direction in which the period of periodic composition change between Ti, Zr, and Hf is minimized (that is, the direction in which the period width of the contrast between light and dark in the HAADF-STEM image is minimized)". I asked.
As described above, in the HAADF-STEM image, the contrast due to the difference in atomic weight of the constituent elements is strong, and in the HAADF-STEM image, the brighter the portion, the more Zr is contained. If the grain boundaries cannot be clearly observed by HAADF-STEM, the crystal orientation mapping by the electron diffraction pattern is measured at 10 nm intervals at the same location, and the crystal orientation relationship between the measurement points is analyzed. The directional difference between adjacent measurement points (hereinafter, also referred to as "pixels") is measured, and if there is a directional difference of 5 degrees or more, that is defined as a grain boundary. Then, the region surrounded by the grain boundaries is defined as one crystal grain. However, pixels that exist independently with all adjacent pixels and an orientation difference of 5 degrees or more are not treated as crystal grains, and those in which two or more pixels are connected are treated as crystal grains.
Then, by performing a line analysis by EDS in the above-mentioned "direction in which the periodic width of the periodic composition change between Ti, Zr and Hf is minimized", the ZrHf maximum content ratio, the ZrHf minimum content ratio, and the C maximum content ratio, The C minimum content ratio, the interval between the ZrHf maximum content point and the ZrHf minimum content point, the interval between the C maximum content point and the C minimum content point, and the ZrHf maximum content point and the C located closest to the ZrHf maximum content point. The distance from the highest content point was measured.
All of these were line-analyzed by EDS for the composition-variable structures of five laminated structures, and obtained as the average value of the measured values (10 points for each laminated structure) in the composition-variable structure of each laminated structure. It is a thing.
Tables 10 to 12 and 14 to 16 show the measured values and the calculated values, respectively.

Next, the tilt angle number distribution of the crystal grains constituting the composite carbide layer of the hard coating layers of the coating tools 1 to 16 of the present invention and the coating tools 1 to 9 of the comparative examples was examined with a field emission scanning electron microscope and an electron beam rear. It was measured using a scattering diffractometer.
That is, the measurement range of the cross-sectional polished surface (0. 3 μm × 50 μm) was set in the lens barrel of a field emission scanning electron microscope. An electron beam with an acceleration voltage of 15 kV is irradiated to the polished surface at an incident angle of 70 degrees with an irradiation current of 1 nA, and each crystal grain having a rock salt-type cubic crystal lattice existing in the measurement range of the polished surface is individually irradiated. bottom. Using a field emission scanning electron microscope and an electron backscatter diffraction imager, a measurement region of 0.3 μm × 50 μm was measured at intervals of 0.1 μm / step with respect to the normal of the tool substrate surface on the surface polished surface. , The inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured by dividing it into pitches of 0.25 degrees over a range of 0 to 45 degrees, and the frequencies existing in each division are measured. To create a tilt angle number distribution graph. Based on this measurement result, the total frequency of the crystal grains whose inclination angle classification is in the range of 0 to 10 degrees is obtained, and further, the frequency ratio of the total frequency to the entire inclination angle frequency distribution graph is obtained. It is shown in Tables 10 to 12 and Tables 14 to 16.
In finding the distribution of the number of tilt angles, in the case of ideal random orientation, the number of tilt angles should be a constant value regardless of the tilt angle formed by the normal direction of a certain crystal plane with respect to the normal direction of the surface of the tool substrate. It is standardized to.

Further, regarding the vertical cross section of the composite carbonitride layer of the hard coating layers of the coating tools 1 to 16 of the present invention and the coating tools 1 to 9 of the comparative examples, a scanning electron microscope (SEM) was used, and the tool substrate and the tool substrate were used at a magnification of 5000. Maximum particle width W and maximum particle length L for each of the composite carbonitride crystal grains existing in the region of 10 μm in the parallel direction and the height of the layer thickness of the composite carbonitride layer in the direction perpendicular to the tool substrate. The value of the aspect ratio L / W was obtained, 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 obtained. 14 to 16 are shown.

Next, with the various covering tools clamped to the tip of the tool steel cutting tool with a fixing jig, the covering tools 1 to 16 of the present invention and the comparative example tools 1 to 9 are subjected to intermittent cutting of the heat-resistant steel shown below. The test was carried out. The wear width of the flank of the cutting edge was measured, and the presence or absence of welding was observed, and the results are shown in Table 17.

≪Cutting condition A≫
Cutting test: Heat-resistant steel 1 slit material Wet high-feed intermittent cutting processing test Work material: JIS / SCH13,
Cutting speed: 115m / min,
Notch: 1.6 mm,
Feed amount: 0.42 mm / rev,
Cutting time: 4.0 minutes,
≪Cutting condition B≫
Cutting test: Heat-resistant steel 1 slit material Wet high-feed intermittent cutting processing test Work material: JIS / SCH13,
Cutting speed: 95m / min,
Notch: 1.3 mm,
Feed amount: 0.37 mm / rev,
Cutting time: 1.0 minutes,

As is clear from the cutting test results in Table 17, in Tables 10 to 12, each component element satisfies the desired average composition, and the ZrHf content ratio and the C content ratio are periodic. It had a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer having a composition-variable structure of a laminated structure in which the periods and positions of the ZrHf maximum content point and the C maximum content point were synchronized with each other. As a result, for example, in the intermittent cutting of heat-resistant steel, peeling and chipping did not occur, the maximum wear width of the flank was small, and excellent welding resistance, plastic deformation resistance, and abnormal damage resistance were exhibited.
On the other hand, the comparative example coating tool contains ZrHf even when the composite carbonitride layer contained as the hard coating layer does not satisfy the desired average composition or satisfies the desired average composition. It did not have a composition-variable structure in which the ratio and the C content ratio changed periodically. As a result, the desired characteristics could not be exhibited, and the life was reached in a short time due to the progress of wear, the occurrence of welding, the occurrence of chipping, and the like.

As described above, the coating tool of the present embodiment has a desired composition-variable structure in which the content ratio of each component changes periodically in the composite carbonitride layer included as the hard coating layer. As a result, for example, in intermittent cutting of heat-resistant steel, excellent welding resistance, chipping resistance, and wear resistance are exhibited. Therefore, the covering tool of the present embodiment is sufficiently satisfied with high performance of the cutting device, labor saving and energy saving of the cutting process, and cost reduction.

Claims (2)

1. A surface-coated cutting tool having a tool substrate and a hard coating layer provided on the surface of the tool substrate.
   (A) The hard coating layer has at least a lower layer and a composite carbonitride layer from the surface side of the tool substrate.
   (B) The lower layer has at least one compound layer containing Ti and / or Zr and also containing carbon and nitrogen, and the total film thickness thereof is 0.8 μm or more.
   (C) The composite carbonitride layer includes at least one layer 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.
   (D) The composite carbonitride layer contains a TiZr composite carbonitride or a TiZrHf composite carbonitride, and the composite carbonitride has a 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 amount of C with respect to the total amount of and is 0.10 ≦ x ≦ 0.90 and 0 <y ≦ 1.0, respectively. , And have an average composition satisfying 0.05 <z <0.75.
   (E) 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 are contained in at least a part of the crystal grains. It has a composition-variable structure in which the content ratio of C amount to the total amount of C changes periodically.
   (E-1) In the vertical cross-sectional observation, the area ratio of the composition-variable structure to the structure of the composite carbonitride layer is 10% or more.
   (E-2) Regarding the content ratio of the total amount of Zr and Hf to the total amount of Ti, Zr and Hf in the composition-variable structure, the maximum content ratio x _max of ZrHf content point and the minimum content The ZrHf minimum content point indicating the ratio x _min is repeated, and the average interval, which is the average value of the intervals between the repeated adjacent ZrHf maximum content points and the ZrHf minimum content points, is 5 to 100 nm. The average value of the absolute value of the difference Δx between the maximum content ratio x _max and the minimum content ratio x _{min of the ZrHf minimum content point is 0.02 or more.}
   (E-3) Regarding the content ratio of the C amount to the total amount of the N and C in the composition-variable structure, the C maximum content point indicating the _{maximum content ratio z max} and the C minimum content indicating the _{minimum content ratio z min.} The content points are repeated, and the average interval, which is the average value of the intervals between the repeated adjacent C maximum content points and the C minimum content points, is 5 to 100 nm, and the maximum content ratio z _max of the C maximum content points and the above The average value of the absolute values of the difference Δz from the C minimum content ratio z _{min is 0.02 or more.}
   (E-4) Regarding the content ratio of the total amount of Zr and Hf to the total amount of the Ti, Zr and Hf in the composition-variable structure, the ZrHf maximum content point and the minimum content indicating the _{maximum content ratio x max.} Regarding the respective cycles and positions of the ZrHf minimum content point indicating the ratio x _min , and the content ratio of the C amount to the total amount of the N and C, the _{C maximum content point indicating the maximum content ratio z max} and the C maximum content point indicating the maximum content ratio z max. The respective cycles and positions of the C minimum content point indicating the minimum content ratio z _min are synchronized with each other, and the ZrHf maximum content point and the C maximum position closest to the ZrHf maximum content point are synchronized with each other. The average value of the interval from the content point is 1/5 or less of the average interval between the ZrHf maximum content point and the adjacent ZrHf minimum content point.
   (F) The composite carbonitride layer has a vertically long crystal structure and has a vertically long crystal structure.
   (G) Using an electro-emission scanning electron microscope and an electron beam backscattering diffractometer, electrons are generated in each of the crystal grains having a rock salt type cubic crystal lattice existing within the measurement range of the cross-sectional polished surface of the composite carbonitride layer. A line is irradiated, and the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured within the range of 0 to 45 degrees with respect to the normal of the surface of the tool substrate. When the number distribution graph is created, the highest peak exists in the inclination angle division in which the inclination angle with respect to the normal of the surface of the tool substrate is in the range of 0 to 10 degrees, and the inclination angle division in the range of 0 to 10 degrees is described. A surface coating cutting tool characterized in that the total number of degrees present in is at least one layer that occupies 35% or more of the total degrees in the inclination angle distribution graph.
2. The surface coating cutting tool according to claim 1, wherein the composition-variable structure is a laminated structure.

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