JP2021137955A - Surface coated cutting tool - Google Patents

Abstract

To provide a surface coated cutting tool which exhibits excellent deposition resistance, plastic deformation resistance, and abnormal damage resistance.SOLUTION: This cutting tool has, on a tool substrate surface, 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), and a vertically longer crystal structure, and a hard coating layer in which there is maximum peak of an inclination angle section formed by normal line of a {112} plane in inclination angle sections of which an inclination angle with respect to a normal line of the tool substrate surface falls within a range of 0 to 10 degrees. In the composite carbonitride layer, ZrHf content ratio and C content ratio are changed periodically, a cycle interval between a ZrHf highest content point and an adjacent ZrHf lowest content point and a cycle interval between a C highest content point and an adjacent C lowest content point is 5 to 100 nm, an average value of content ratio differences Δx and Δz is 0.02 or more, a distance between the ZrHf highest content point and a nearest C highest content point is 1/5 or less of the interval between the adjacent highest content point and lowest content point of ZrHf component, and a composition variation structure is 10% or more in area ratio.SELECTED DRAWING: Figure 2

Description

The present invention relates to a surface covering tool having excellent cutting performance over a long period of use.

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.
Conventionally, in general, in cutting of various steels, a Ti compound layer such as a carbonitride (TiCN) layer of Ti formed by chemical vapor deposition as a lower layer is provided on the surface of a cemented carbide substrate such as a tungsten carbide group. A coating tool having a hard coating layer having an aluminum oxide layer formed by chemical vapor deposition as an upper layer is used.
However, in recent years, high efficiency has been required in the intermittent cutting of various steels, and in particular, in the intermittent cutting of heat-resistant steel, high efficiency has been required. _With inserts with a film structure of 2 O ₃ / TiCN / cemented carbide, welding chipping is likely to occur, and even if welding chipping does not occur and normal wear occurs, normal wear progresses quickly, so there is a need for it. Is becoming more difficult to deal with.

Therefore, for example, in Patent Document 1, in a coating cutting tool having a TiZr carbide film on the substrate surface, 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. However, a coated cutting tool has been proposed in which the film hardness is increased and the abrasion resistance is excellent when cutting a machine structural steel or the like due to the tensile residual stress, and the cutting durability property is excellent.
Further, in Patent Document 2, in a coated cutting tool having a TiZr carbide film, the grain boundary strength is further increased by orienting the crystal orientation of the film toward the (422) plane or the (311) plane. As a coating layer for a base material made of cemented carbide or cermet, the film hardness at high temperature is high, and the width of crystal grains near the film surface does not become coarse even as the film thickness increases, resulting in good wear resistance. Coated cutting tools that have properties and toughness and exhibit excellent cutting durability characteristics have been proposed.

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

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, heat-resistant steel (JIS- as an example). In the intermittent cutting process of SCH13), it is required to exhibit excellent welding resistance, plastic deformation resistance and abnormal damage resistance.
However, when a coating tool composed of a coating layer having a TiZr carbonitride film, which is proposed in Patent Document 1 and Patent Document 2, is used for intermittent cutting of heat-resistant steel, the former has abrasion resistance. Although the improvement effect is recognized, there is a problem that minute chipping of the film is likely to occur, welding chipping occurs frequently due to insufficient welding resistance, and the latter is not practical. Although minute chipping of the film is suppressed to some extent, there is a problem that the grain boundary strength is insufficient and the welding resistance is insufficient, so that welding chipping is likely to occur and it is not suitable for practical use. ..

Therefore, from the above-mentioned 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. As a result of diligent research on covering tools that have abnormal damage and improve the tool life, the following findings were obtained.
That is, the present inventors increase 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. As a result, the welding resistance can be improved and the problem of welding chipping, which has been a problem, can be improved. Further, in the TiZr composite carbonitride layer or the TiZrHf composite carbonitride layer, the total amount of Zr and Hf is Ti. The content ratio of Zr and Hf in the total amount (hereinafter, may be referred to as "ZrHf content ratio"), and the content ratio of C amount in the total amount of N and C (hereinafter, "C content ratio"). However, it has a composition-variable structure that changes periodically, and the composition-variable structure corresponds to this, and the content ratio of the Ti amount to the total amount of Ti, Zr, and Hf (hereinafter, "" The Ti content ratio) and the content ratio of the N amount to the total amount of N and C (hereinafter, also referred to as the “N content ratio”) change cyclically. It is a structure, and 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 point indicating the maximum content ratio for the C content ratio. By containing high-hardness crystal grains in which the period and position of the C minimum content point indicating the content ratio are synchronized, plastic deformation resistance can be exhibited and the problem of abnormal damage can be solved, and excellent in abnormal damage resistance. It was found that a hard coating layer can be obtained.
Further, by forming the composite carbonitride layer into 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, the dropping of particles from the coating layer is suppressed. Further, it was found that it exhibits abrasion resistance and abnormal damage resistance, and further, in the composite carbonitride layer, a field emitting scanning electron microscope and an electron beam backscattering diffractometer were used, and the measurement range of the cross-sectional polished surface thereof. The individual crystal grains having the rock salt type cubic crystal lattice existing inside are irradiated with an electron beam, and the normal line of the surface of the tool substrate is the normal line of the {112} plane which is the crystal plane of the crystal grain. The tilt angle is measured within the range of 0 to 45 degrees, the measured tilt angle is divided into pitches of 0.25 degrees, and the tilt angle distribution graph is obtained by totaling the degrees existing in each division. When created, 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 line is in the range of 0 to 10 degrees, and exists in the inclination angle division in the range of 0 to 10 degrees. Since the total number of degrees to be applied accounts for 35% or more of the total number of degrees in the tilt angle distribution graph, it has excellent welding resistance, plastic deformation resistance and abnormal damage resistance, and can be used for intermittent cutting of heat-resistant steel. , Found that it will improve the tool life over a long period of use.
Since the TiZr composite carbonitride and the TiZrHf composite carbonitride according to the present invention have a higher ratio of N content to C content than conventional ones, they are referred to as TiZrNC and TiZrHfNC, respectively, in the present specification. In some cases.

The present invention has been made based on the above findings.
"(1) A surface-coated cutting tool having a hard coating layer on the surface of a 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 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 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.} 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 electroemission 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 the range of 0 to 10 degrees of the inclination angle with respect to the normal of the surface of the tool substrate, 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 tilt angle distribution graph.
(2) The surface coating cutting tool according to claim 1, 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 the present invention has a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer in a hard coating layer formed on the surface of a tool substrate, and thus has a hardness due to containing C. The problem of welding chipping, which has been a problem in the intermittent cutting of heat-resistant steel, has been solved by achieving both the improvement of the welding resistance and the improvement of the welding resistance by increasing the ratio of the N content to the C content.
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, and in particular, the ZrHf maximum content point and the ZrHf minimum content point. Synchronize the period and position of the content points with the period and position of the C maximum content point and C minimum content point, respectively, to reduce the production of ZrN and HfN, which have lower hardness than ZrC, HfC, TiC, and TiN, respectively. As a result, crystal grains with higher hardness are generated as compared with the uniform TiZrHfNC layer, 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, the film particles are hard to fall off, and the {112} plane has a high corresponding grain boundary ratio, and the grain boundaries are high. Since the strength is high and plastic deformation is unlikely to occur, a coated cutting tool having such a composite carbide nitride layer as a hard coating layer has excellent welding resistance, plastic deformation resistance, and abnormal damage resistance in intermittent cutting of heat-resistant steel. It also has the property of improving the tool life over a long period of 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 the present invention 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 invention.
For example, cemented carbide (WC-based cemented carbide, WC, as well as those containing Co or added with carbonitrides such as Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.) It is preferably either a main component) or ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.).

Hard coating layer;
The hard coating layer according to the present invention has at least a lower layer and a composite carbonitride layer from the surface side of the tool substrate, and the lower layer is a compound layer containing Ti or Zr and containing carbon and nitrogen. At least one layer is included.
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 a TiZr composite carbonitride layer or a TiZrHf composite carbonitride layer.
Also, if necessary, as other layers, an intermediate layer between the tool substrate and the lower layer and / or between the lower layer and the composite carbonitride layer, and on the composite carbonitride layer. An upper layer can be provided.
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 thickness of the hard coating layer can be measured using, for example, an SEM (scanning electron microscope) or a TEM (transmission electron microscope) in a cross section perpendicular to the tool substrate.

Lower layer;
The lower layer formed on the tool substrate is a compound layer containing Ti or Zr and containing carbon and nitrogen, for example, a carbonitride layer of Ti, a carbonitride oxide layer, a carbonitride boride layer, or Zr. A tool substrate by having at least one layer composed of a carbonitride layer, a carbonitride oxide, a carbonitride boride layer, or a Ti and Zr carbonitride layer, a carbonitride oxide layer, a carbonitride boride layer, and the like. Since the adhesion to the composite carbonitride layer of Ti and Zr or the composite carbonitride layer having the composite carbonitride layer of Ti, Zr and Hf can be improved, abnormal damage such as chipping and peeling can occur. It 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 the {112} surface on the outermost surface of the lower layer is used by using the film forming method described later. The orientation can be passed on to the composite carbonitride layer via the intermediate layer.
If 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 toward the {112} plane. It is difficult to make it. On the other hand, if it 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 invention is arranged on the lower layer, and has at least an average layer thickness of 0.5 μm or more and 20.0 μm or less. Specifically, the TiZr composite nitride or the TiZrHf composite carbonitride which comprises the nitride layer and constitutes the composite carbonitride layer has a composition formula (Ti _(1-x) Zr _xy. When _{expressed in terms of Hf x (1-y)} ) (N _(1-z) C _z ), 0.10 ≦ x ≦ 0.90, 0 <y ≦ 1.0, and 0.05 <z < Each of 0.75 is satisfied.
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 is the average of the total amount of Zr to the total amount of Zr and Hf. Represents the 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 invention, the average content ratio z of C is 0.05 with respect to N, which is an element for improving welding resistance, and C, which is an element for improving hardness. By containing <z <0.75, a hard coating layer having both high welding resistance and high hardness could 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 it exceeds 20.0 μm, chipping and chipping are likely to occur. Therefore, the thickness is set to 0.5 to 20.0 μm, which exerts an excellent effect from the viewpoint of hardness and wear resistance.
For the average layer thickness of the composite carbonitride layer, a scanning electron microscope (magnification of 5000 times) was used to measure the layer thicknesses of five points in the observation field of view in the direction perpendicular to the tool substrate, and these were measured. The average layer thickness can be obtained on average.

(2) Crystal grains having a composition variation structure In the composite carbonitride (TiZrNC or TiZrHfNC) layer according to the present invention, the composition variation in which the ZrHf content ratio, Ti content ratio, C content ratio and N content ratio change periodically. Contains crystal grains with a 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 ) 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 the 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. along the direction in which, in the ZrHf maximum content point, Ti lowest proportion _{α min (= 1-x max} ) indicates, in ZrHf minimum content point, indicating a Ti highest proportion _{α max (= 1-x min} ). In addition, α is an atomic ratio.
That is, the Ti content 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 Ti and ZrHf 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) -ZrHf mean proportion (z _av) -C highest content 2 ( z _max2 ) -C average content ratio ( _zav ) -C minimum content ratio 2 (z _min2 ).
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.
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 (x max} −x _min ) between ZrHf maximum content point and ZrHf minimum content _{point and C content ratio difference (z max} −z _min ) between C maximum content point and C minimum content point;
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) Spacing (average value) between adjacent ZrHf maximum content points and ZrHf minimum content points;
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).

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 (effect of (2) in paragraph 0021), "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.

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.

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 invention has a vertically long crystal structure, so that particles are suppressed from falling off from the coating layer, and exhibit excellent wear resistance and abnormal damage resistance. do.
The vertically long crystal structure referred to here is the largest in the height (long side) of the crystal grains in the layer thickness direction for each crystal grain when observing the vertical cross section of the composite carbonitride layer. When the value is the maximum grain length (L), the width (short side) of the crystal grains in the direction perpendicular to the layer thickness direction, and the largest value is the maximum grain width (W), it is defined by L / W. It refers to a structure in which the area ratio of crystal grains having an aspect ratio of 2.0 or more in the vertical cross section of the composite carbonic nitride layer is 50% or more.
The aspect ratio and the area ratio of the vertically elongated crystal grains are measured by, for example, electron backscatter diffraction (EBSD) on a longitudinal cross-sectional image obtained by cross-sectional observation at a magnification of 5000 using a scanning electron microscope (SEM). For each crystal grain, measure the maximum particle length, maximum particle width, and longitudinal cross-sectional area, determine the aspect ratio from the maximum particle length and maximum particle width, and then at an aspect ratio of 2.0 or greater. The ratio of the area of the vertical cross section to be measured to the total area of the vertical cross section of a certain crystal grain was calculated as the area ratio.
That is, by defining that the area ratio of those having an aspect ratio of 2.0 or more is 50% or more, the effect of improving toughness and wear resistance can be exhibited.

11) Inclined angle number distribution In the present invention, the inclined angle number distribution in the composite carbonitoxide crystal grains of the composite carbonic nitride layer is obtained by using a field emission scanning electron microscope and an electron backscatter diffraction device on the cross-sectional polished surface. It can be measured by irradiating individual crystal grains having a rock salt type cubic crystal lattice existing in the measurement range 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 carbonitoxide crystal grains in the composite carbonitride layer, is set to 0 with respect to the normal of the surface of the tool substrate. When measuring within the range of ~ 45 degrees, dividing the measurement inclination angle into pitches of 0.25 degrees, and creating an inclination angle number distribution graph obtained by totaling the degrees existing in each division, the above-mentioned 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 the total number of degrees existing in the inclination angle division in the range of 0 to 10 degrees is calculated. It occupies 35% or more of the total frequency in the inclination angle number distribution graph, has a high orientation tendency of the crystal grains of the carbonitride layer with respect to the {112} plane, and has a structure in which plastic deformation is unlikely to occur. ..
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 invention, 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. Can be done.
Further, in the present invention, for example, a TiN layer, a TiC layer and the like can be provided as an intermediate layer between the lower layer and the composite carbonitride layer, and in particular, the TiN layer is a lower layer. Since the orientation of the {112} surface on the outermost surface can be inherited, it has excellent peel resistance.
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 the same when the TiN layer is provided between the tool substrate and the lower layer and when the TiN layer is provided between the lower layer and the composite carbonitride layer. Since the basic component diffuses, it becomes a fine granular structure, while in the latter, the diffusion as in the former does not occur, so it is considered that a highly oriented structure inheriting the structure of the lower layer was obtained.
(2) Upper layer In the present invention, 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.

Method of forming a hard coating layer;
The hard coating layer according to the present invention 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) Film formation method of 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 also containing carbon and nitrogen, and a usual chemical vapor deposition method is used. The film can be formed by adjusting the reaction gas composition and the reaction atmosphere such as pressure and temperature within an appropriate range for each compound layer to be formed. (See Table 3 etc. described later.)
The Ti-containing compound layer includes a Ti carbonitride layer, a carbonitride oxide layer, a carbonitride boride layer, and the like, and the Zr-containing compound layer includes a ZrCN layer, a ZrCNO layer, a ZrCNB layer, and the like. Can be selected.
Further, as a layer containing both Ti and Zr, a TiZrCN layer, a TiZrCNO layer, a TiZrCBN layer and the like can be selected.

(2) Film formation method of composite carbonitride layer (TiZrNC layer or TiZrHfNC layer) In the present invention, the composite carbonitride layer (TiZrNC layer or TiZrHfNC layer) has a specific component composition, a specific composition variation structure, a specific vertically elongated crystal structure, and The TiZrNC layer or the TiZrHfNC layer in which the crystal grains are oriented on the {112} plane forms at least the lower layer on the tool substrate, and then is formed under the following conditions, for example, by using a chemical vapor deposition method. Can be formed by performing.
That is, as the film forming conditions of the TiZrNC layer or the TiZrHfNC layer, TiCl ₄ gas, ZrCl ₄ gas or a mixed gas of _{ZrCl 4} gas and HfCl _{4 gas, CH 4} gas, N ₂ gas, and H ₂ gas are used as raw materials. The film formation temperature is 980 ° C. or higher and lower than 1080 ° C., and the pressure condition is 16 kPa or higher and lower than 40 kPa, which can be carried out by 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 above are interspersed and formed, and then, 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. By crystal growing the initial nuclei to form a vertically elongated crystal structure having the composition-variable structure and forming a TiZrNC layer or a TiZrHfNC layer oriented on the {112} plane, the grain boundary strength is high and plastic deformation is unlikely to occur. You can get the tissue.

[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 : Remaining,
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 : 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 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 If it is less than 16 kPa, a sufficient film forming 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 : 0.4-0.7%,
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 C,}
ZrCl ₄ : 0.1 to 2.2%, HfCl ₄ : 0.0 to 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%, but _{exceeds 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 : 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 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 a 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, and as a result, the above-mentioned "Zr, Hf and C enriched regions and Zr and Hf" Since the "effect of hindering the movement of dislocations and improving the hardness" between the regions where C is poor is reduced, the hardness is reduced. 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 If it is less than 16 kPa, a sufficient film forming 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 for forming an intermediate layer and an upper layer As described above, in the present invention, 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 the layers, and 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 formed and the conditions for forming the film.

Next, the covering tool of the present invention will be described by way of examples.
Here, as a specific example of the coated tool of the present invention, a tool base applied to a WC-based cemented carbide or an insert cutting tool using a cermet 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 invention. For example, cemented carbide (including WC-based cemented carbide, WC, and those containing Co or further added with carbonitrides such as Ti, Ta, Nb), 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, etc. Can be mentioned.

As raw material powders, both WC powder having an average particle size of 1 to 3 [mu] m, TiC powder, ZrC powder, TaC powder, NbC powder, _Cr 3 _{C 2} powder, TiN powder, and Co powder was prepared, these raw powders , Add wax to the compounding composition shown in Table 1, ball-mill mix in acetone for 24 hours, dry under reduced pressure, press-mold into a green compact of a predetermined shape at a pressure of 98 MPa, and press-mold this green compact. Is vacuum sintered in a vacuum of 5 Pa at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour, and after sintering, a tool made of WC-based superhard alloy having an insert shape of ISO standard CNMG120408. The substrates A to C were produced, respectively. (See Table 1)

Further, as the raw material powder, both the average (TiC / TiN = 50/50 in mass ratio) TiCN having a particle size of 0.5~2μm powder, ZrC powder, TaC powder, NbC powder, Mo ₂ C powder, WC powder , Co powder and Ni powder are prepared, these raw material powders are blended into the compounding composition shown in Table 2, wet-mixed with a ball mill for 24 hours, dried, and then 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 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 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)
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 formed by thin film deposition at the target layer thickness shown in Table 6 and under the forming conditions shown in Table 3.
(B) The hard coating layer is formed with the formation symbols of the TiZrNC layer and the TiZrHfNC layer in the film forming process of the present invention with respect to the tool substrate of Table 1 or Table 2 shown in the tool substrate symbols based on Tables 4 and 5. A film was formed according to the film conditions. 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 ZrHf maximum content ratio (average value), and the ZrHf minimum content ratio ( 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) Table 7 shows 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. That is,
(A) A lower layer having a target layer thickness shown in Table 8 was deposited and formed on the tool substrate under the formation conditions shown in Table 3.
(B) Next, based on Tables 4 and 5, the film forming conditions of the TiZrNC layer / TiZrHfNC layer forming symbols in the comparative example film forming step were formed on the tool substrates of Table 1 or Table 2 shown in the tool substrate symbols. The average composition of the TiZrNC layer and the TiZrHfNC layer of Comparative Examples Coating Tools 1 to 9, the area ratio of the composition-variable structure to the structure of the composite carbonic nitride layer, and the maximum content ratio of ZrHf (average value). ), ZrHf minimum content ratio (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), C maximum content point Table 9 shows the interval (average value) of the C minimum content points, 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 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 is cut out using a focused ion beam (FIB), and the composition of the TiZrNC layer or the TiZrHfNC layer is determined by the width in the direction parallel to the surface of the tool substrate along the layer thickness direction. Using high-angle scattering annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray analysis (EDS) for a field of view that is 10 μm and is set to include the entire thickness region of the hard coating layer. Composition at 5 different locations in a 1.0 μm × 1.0 μm field of view (when the thickness of the TiZrNC layer or TiZrHfNC layer is 1.0 μm or less, the thickness of the TiZrNC layer or TiZrHfNC layer × 1.0 μm field of view) The analysis was performed, and the average composition of the entire TiZrNC layer or the 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 EDS line analysis can be performed on the composition-variable structure of the laminated structure.
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 boundary 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, the crystal orientation relationship between each measurement point is analyzed, and adjacent measurement points are analyzed. The azimuth difference between (hereinafter, also referred to as "pixel") is measured, and if there is an azimuth 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, 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 2 pixels or more 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 obtained as the average value of the measured values (10 points for each laminated structure) in the composition-variable structure of each laminated structure by performing EDS line analysis on the composition-variable structure of five laminated structures. Is.
Tables 7 and 9 show the measured and calculated values.

Next, the tilt angle number distribution of the crystal grains constituting the composite carbonic nitride 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) is set in the lens barrel of an electric field emission type scanning electron microscope, and an electron beam having an acceleration voltage of 15 kV at an incident angle of 70 degrees is applied to the polished surface at an irradiation current of 1 nA. The measurement area of 0.3 μm × 50 μm is set to 0 by irradiating each crystal grain having a rock salt type cubic crystal lattice existing in the measurement range of. At intervals of 1 μm / step, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grains, with respect to the normal of the surface-polished surface is 0. The measurement is performed separately for each pitch of 25 degrees, and the degrees existing in each section are aggregated and represented by a tilt angle number distribution graph. Based on this measurement result, the tilt angle section is in the range of 0 to 10 degrees. The total frequency of the crystal grains inside is calculated, and the ratio of the frequency to the entire tilt angle distribution graph is calculated and shown in Tables 7 and 9.
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 layer 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 was 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. show.

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 tools 1 to 9 of Comparative Example are shown below for intermittent heat-resistant steel. A cutting test 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 10.

≪Cutting condition A≫
Cutting test: Heat-resistant steel 1 slit material Wet high-feed intermittent cutting 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 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 10, in Table 5, each component element satisfies the desired average composition, and the ZrHf content ratio and the C content ratio change periodically in Table 5. By having 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 are synchronized, for example, intermittent heat-resistant steel is provided. In cutting, the maximum wear width of the flank is small without peeling and chipping, and excellent welding resistance, plastic deformation resistance and abnormal damage resistance are 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. Since it does not have a composition-variable structure in which the ratio and the C content ratio change periodically, the desired characteristics cannot be exhibited, and due to the progress of wear, the occurrence of welding, the occurrence of chipping, etc., in a short time. It reached the end of its life.

As described above, the coating tool of the present invention has, for example, a heat-resistant steel by having a desired composition-variable structure in which the content ratio of each component changes periodically in the composite carbonitride layer included as a hard coating layer. Since it exhibits excellent welding resistance, chipping resistance, and abrasion resistance in intermittent cutting, it is sufficient for improving the performance of cutting equipment, labor saving and energy saving in cutting, and cost reduction. I am satisfied.

Claims (2)

A surface-coated cutting tool having a hard coating layer 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 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 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.} 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 electroemission 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 the range of 0 to 10 degrees of the inclination angle with respect to the normal of the surface of the tool substrate, 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 tilt angle distribution graph. The surface coating cutting tool according to claim 1, wherein the composition-variable structure is a laminated structure.

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