JP6761597B2 - Surface coating cutting tool with excellent chipping resistance due to the hard coating layer - Google Patents

Description

According to the present invention, the hard coating layer has excellent chipping resistance in high-speed intermittent cutting of carbon steel, alloy steel, cast iron, etc., which is accompanied by high heat generation and exerts a shocking load on the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits excellent cutting performance over a long period of use.

Conventionally, it is generally composed of tungsten carbide (hereinafter referred to as WC) -based cemented carbide, titanium carbonitride (hereinafter referred to as TiCN) -based cermet or cubic boron nitride (hereinafter referred to as cBN) -based ultrahigh-pressure sintered body. A coated tool in which a Cr-Al-based composite nitride layer is coated and formed as a hard coating layer on the surface of a tool substrate (hereinafter, collectively referred to as a tool substrate) by a physical vapor deposition method is known. These are known to exhibit excellent wear resistance.
However, although the conventional coating tool coated with the Cr-Al-based composite nitride layer has excellent high-temperature strength, it is liable to cause abnormal wear such as chipping when used under high-speed intermittent cutting conditions. Therefore, various proposals have been made for improving the hard coating layer.

Patent Document 1, a lower layer hard coating layer is made of a Ti compound layer, the coated tool made up of an upper layer of Al ₂ O ₃ layer, in the Al ₂ O ₃ layer in the upper layer, pore diameter 2 In high-speed intermittent cutting, by forming minute pores with a pore diameter distribution of ~ 50 nm and a bimodal distribution, the impact acting on the upper layer during cutting is mitigated and the heat shielding effect is exerted. It has been proposed to improve chipping resistance and fracture resistance.

For example, in Patent Document 2, in a coating tool in which the hard coating layer is composed of a lower layer, an intermediate layer, and an upper layer, (a) the lower layer is a Ti _1-X Al _X N layer and a Ti _1-X Al _X C layer. , Ti _1-X Al _X CN layer (where X indicates the content ratio of Al in the total amount of Ti and Al, and the atomic ratio is 0.65 ≦ X ≦ 0.95), or 1 layer or 2 It is composed of Ti and Al nitrides, carbides or carbon nitrides having a cubic crystal structure composed of layers or more, and (b) the intermediate layer is a Cr _1-Y Al _Y N layer or a Cr _1-Y Al _Y C layer. , Cr _1-Y Al _Y CN layer (where Y indicates the content ratio of Al in the total amount of Cr and Al, and the atomic ratio is 0.60 ≦ Y ≦ 0.90), or 1 layer or 2 It is composed of Cr and Al nitrides, carbides or carbon nitrides having a cubic crystal structure composed of layers or more, and (c) the upper layer has a pore diameter of 2 to 30 nm and a pore density of 100 to 500 cells / μm ^2. It has been proposed to improve chipping resistance and abrasion resistance when high-speed cutting of heat-resistant alloys such as precipitation-hardened stainless steel and inconel, for example, by constructing Al ₂ O ₃ having the fine pores of. ing.

Further, in Patent Document 3, in a coating tool in which the hard coating layer is composed of a lower layer, an intermediate layer and an upper layer, (a) the lower layer is a Ti _1-X Al _X N layer and a Ti _1-X Al _X C layer. , Ti _1-X Al _X CN layer (where X indicates the content ratio of Al in the total amount of Ti and Al, and the atomic ratio is 0.65 ≦ X ≦ 0.95), or 1 layer or 2 It is composed of Ti and Al nitrides, carbides or carbonitrides having a cubic crystal structure composed of layers or more, and (b) the intermediate layer is a Cr _1-Y Al _Y N layer or a Cr _1-Y Al _Y C layer. , Cr _1-Y Al _Y CN layer (where Y indicates the content ratio of Al in the total amount of Cr and Al, and the atomic ratio is 0.60 ≦ Y ≦ 0.90), or 1 layer or 2 nitride of Cr and Al having a cubic crystal structure having the above layers, composed of a carbide or carbonitride, composed of _Al 2 _{O 3} containing Zr of (c) an upper layer, _Al 2 _{O 3} or trace It has been proposed to improve the chipping resistance and abrasion resistance when a difficult-to-cut material such as stainless steel or Ti alloy is machined at high speed.

In Patent Document 4, 0.3 ≦ X ≦ 0.6 (where X indicates an atomic ratio) is expressed on the surface of the tool substrate by the composition formula: (Cr _X Al _1-X ) N. In a coating tool forming a hard coating layer composed of a satisfying composite nitride layer of Al and Cr, the {100} plane which is a crystal plane of crystal grains having a cubic crystal lattice with respect to the normal of the surface polishing surface. When the inclination angle formed by the normals of the above is measured and the inclination angle number distribution graph is obtained, the total number of degrees existing in the range of 30 to 40 degrees is 60% or more of the total degree in the inclination angle number distribution graph. Forming a tilt angle number distribution that occupies a ratio, or further, in the constituent atom shared lattice point distribution graph, the constituent atoms that have the highest peak in Σ3 and the distribution ratio of Σ3 to the entire ΣN + 1 is 50% or more. It has been proposed to improve the fracture resistance in heavy cutting of steel or cast iron, which applies a large mechanical load to the cutting edge, by forming a shared lattice point distribution graph.

Japanese Unexamined Patent Publication No. 2012-161847 Japanese Unexamined Patent Publication No. 2014-198362 Japanese Unexamined Patent Publication No. 2014-208394 JP-A-2009-56539

In the covering tool proposed in Patent Document 1, the impact during cutting is alleviated to some extent by forming micropores in the Al ₂ O ₃ layer of the upper layer, but the cutting conditions are strict. Therefore, when a higher load is applied by the cutting edge, it cannot be said that the heat impact resistance and the chipping resistance are sufficient.
Further, in the coating tools proposed in Patent Documents 2 and 3, the lower layer and the upper layer are formed by interposing Cr and Al nitrides, carbides or carbonitrides as an intermediate layer of the hard coating layer. Although the adhesion strength is improved and the chipping resistance is improved, the strength and hardness of Cr and Al nitrides, carbides or carbonitrides themselves are not sufficient, so when they are used for high-speed intermittent cutting. , Chipping resistance and abrasion resistance are not sufficient.
In the coating tool proposed in Patent Document 4, the Cr content ratio of the hard coating layer composed of (Cr _X Al _1-X ) N is adjusted, and the crystal orientation and the constitutive atom shared lattice point distribution form are adjusted. By controlling, the strength of the hard coating layer can be improved, and as a result, the chipping resistance and the fracture resistance can be improved, but the strength and hardness of the (Cr _X Al _1-X ) N layer are also improved. However, excellent chipping resistance and abrasion resistance cannot be exhibited over a long period of use, and there is a problem that the tool life is short in high-speed intermittent cutting of alloy steel.
Therefore, in high-speed intermittent cutting, which is accompanied by high heat generation of carbon steel, alloy steel, cast iron, etc. and an impact load acts on the cutting edge, the hard coating layer has excellent chipping resistance and excellent wear resistance. There is a demand for a covering tool that combines the above.

From the above viewpoint, the present inventors have formed a coating obtained by vapor deposition of a hard coating layer containing at least a composite nitride of Cr and Al or a composite carbonitride (hereinafter, may be referred to as “CrAlCN”) layer by chemical vapor deposition. As a result of intensive research to improve chipping resistance in tools,
By forming CrAlCN under limited conditions, pores can be formed in the CrAlCN layer, and further, by optimizing the average area ratio and average pore size of the pores formed in the layer, It will be possible to suppress the progress of cracks, and as a result, it will exhibit excellent chipping resistance in high-speed intermittent cutting of carbon steel, alloy steel, cast iron, etc., where a high load acts on the cutting edge. I found that.

The present invention has been made based on the above findings.
"(1) Surface coating cutting in which a hard coating layer is provided on the surface of a tool substrate composed of either a tungsten carbide-based cemented carbide, a titanium nitride-based cermet, or a cubic boron nitride-based cemented carbide. In the tool
(A) The hard coating layer contains at least a composite nitride or composite carbonitride layer of Cr and Al having an average layer thickness of 1 to 20 μm.
(B) The composite nitride or composite carbonitride layer contains at least a composite nitride or composite carbonitride phase having a NaCl-type face-centered cubic structure.
(C) The composite nitride or composite carbonitride layer is
Composition formula: (Cr _1-x Al _x ) ( _Cy N _1-y )
When represented by, the average content ratio X _avg in the total amount of Cr and Al of Al and the average content ratio Y _avg in the total amount of C and N of C (however, both X _avg and Y _avg are atomic ratios). Satisfy 0.70 ≤ X _avg ≤ 0.95 and 0 ≤ Y _avg ≤ 0.005, respectively.
(D) Pore is present in the composite nitride or composite carbonic nitride layer, and when the average layer thickness of the composite nitride or composite carbonitride layer is _Lavg (μm), the average layer thickness The range of 1 μm × 1 μm of the vertical cross section of each section obtained by dividing _Lavg (μm) by [ _Lavg / 2] + 1 in the layer thickness direction was observed with a scanning electron microscope at a magnification of 50,000 times, and each observation area of each section was observed. When the area ratio A occupied by the pores in the area and the pore diameter D in the observation area were obtained and the average area ratio A _avg and the average pore diameter D _avg of the pores in each section were calculated, 0.1 area% ≤ A _avg ≤ 10 Area%, 4 nm ≤ D _avg ≤ 50 nm ,
(E) The range of 1 μm × 1 μm of the longitudinal cross section of the composite nitride or composite carbonic nitride layer is observed with a scanning electron microscope at a magnification of 50,000 times for 5 fields or more, and the average pore number density _Navg and the standard deviation σ are obtained. A surface coating cutting tool characterized in that the coefficient of variation is 1 or less when the coefficient of variation is calculated from the standard deviation σ / average number density _Navg .
(2) The composite nitride or composite carbonitride layer is characterized by being composed of a single phase of a composite nitride or composite carbonitride of Cr and Al having a NaCl-type face-centered cubic structure (1). Described surface coating cutting tool.
(3) Between the tool substrate and the composite nitride or composite carbonitride layer, one layer of Ti carbide layer, nitride layer, carbonitride layer, coal oxide layer and carbonitride oxide layer or The surface coating cutting tool according to (1) or (2), wherein a lower layer composed of two or more Ti compound layers and having a total average layer thickness of 0.1 to 20 μm is present.
(4) The above-mentioned composite nitride or composite carbonitride layer is characterized in that an upper layer containing at least an aluminum oxide layer is present with a total average layer thickness of 1 to 25 μm (1) to (3). The surface coating cutting tool described in either. "
It has the characteristics of.

The present invention will be described in detail below.

Average thickness of CrAlCN layer:
Hard layer of the present invention, the composition _formula: comprising at least a _{(Cr 1-x Al x)} (C y N 1-y) composite nitride of Cr and Al represented by or composite carbonitride (CrAlCN) layer .. Since the Cr component in the CrAlCN layer contributes to maintaining high-temperature strength and the Al component contributes to improving high-temperature hardness and heat resistance, the CrAlCN layer has predetermined high-temperature strength, high-temperature hardness and heat resistance, but is particularly average. When the layer thickness is 1 to 20 μm, the effect is remarkably exhibited. The reason is that if the average layer thickness is less than 1 μm, sufficient wear resistance cannot be ensured over a long period of time because the layer thickness is thin, while if the average layer thickness exceeds 20 μm, the CrAlCN layer The crystal grains of the above are likely to be coarsened, and chipping is likely to occur. Therefore, the average layer thickness was set to 1 to 20 μm.

Composition of CrAlCN layer:
The CrAlCN layer of the present invention has a component composition thereof.
Composition formula: (Cr _1-x Al _x ) ( _Cy N _1-y )
When represented by, the average content ratio X _avg in the total amount of Cr and Al of Al and the average content ratio Y _avg in the total amount of C and N of C (however, both X _avg and Y _avg are atomic ratios). Are controlled so as to satisfy 0.70 ≦ X _avg ≦ 0.95 and 0 ≦ Y _avg ≦ 0.005, respectively.
The reason is that if the average Al content ratio X _avg is less than 0.70, the CrAlCN layer is inferior in oxidation resistance, so that it is resistant to high-speed intermittent cutting of carbon steel, alloy steel, cast iron, etc. Insufficient wear resistance. On the other hand, when the average content ratio X _{avg of} Al exceeds 0.95, the precipitation amount of hexagonal crystals inferior in hardness increases and the hardness decreases, so that the wear resistance decreases. Therefore, the average content ratio X _avg of Al was set to 0.70 ≦ X _avg ≦ 0.95.
Further, when the average content ratio Y _avg of the C component contained in the CrAlCN layer is a small amount in the range of 0 ≦ Y _avg ≦ 0.005, the adhesion between the CrAlCN layer and the tool substrate or the lower layer is improved, and the adhesion is improved. By improving the lubricity, the impact at the time of cutting is alleviated, and as a result, the fracture resistance and chipping resistance of the CrAlCN layer are improved. On the other hand, if the average content ratio Y _avg of the C component is out of the range of 0 ≦ Y _avg ≦ 0.005, the toughness of the CrAlCN layer is lowered and the fracture resistance and chipping resistance are lowered, which is not preferable. Therefore, the average content ratio Y _avg of C was set to 0 ≦ Y _avg ≦ 0.005. However, the content ratio of C excludes the unavoidable content ratio of C contained even if a gas containing C is not intentionally used as a gas raw material. Specifically, the content ratio (atomic ratio) of the C component contained in the CrAlCN layer when the supply amount of C ₂ H ₄ is 0 is obtained as the unavoidable C content ratio, and C ₂ H ₄ is intentionally used. the value obtained by subtracting the content of the unavoidable C from the content of the C component contained in CrAlCN layer obtained when supplied (atomic ratio) was calculated as Y _avg.

Pore present in the CrAlCN layer:
FIG. 1 shows a partially enlarged view of the CrAlCN layer of the present invention.
As shown in FIG. 1, in the CrAlCN layer of the present invention, pores having a predetermined average area ratio and a predetermined average pore diameter are formed in the layer, and cracks are generated in the layer due to a high load during cutting. Even in such a case, the presence of such pores suppresses the growth of cracks, and as a result, exhibits excellent chipping resistance even under high-speed intermittent cutting conditions such as alloy steel in which a high load acts on the cutting edge. Will be.
It is desirable that the pores are present at the grain boundaries, but even if they are present in a small amount in the crystal grains, the cutting performance is not significantly impaired.
The average pore diameter _{D avg} of the pores, crack development suppression effect is less than 4nm is insufficient, whereas, a 50nm greater than the average pore diameter _{D avg} is the hardness of CrAlCN layer is locally reduced, crack origin of The chipping resistance and fracture resistance are reduced.
Thus, the average pore diameter _{D avg} pores formed in the CrAlCN layer to 4nm or 50nm or less.
Further, when the average area ratio _{Avg of the} pores is less than 0.1%, the effect of suppressing the growth of cracks cannot be sufficiently brought out, while when the average area ratio _Avg exceeds 10% , the entire CrAlCN layer The average area ratio _Avg of the pores is 0.1 area% or more and 10 area% because the hardness decreases due to the pores, which increases the crack origin and reduces the chipping resistance and fracture resistance due to the decrease in wear resistance. It was as follows.
Further, in a film in which the pores are formed mainly in the grain boundaries instead of the grain boundaries, the strength of the crystal grains themselves is reduced, and the load acting on the cutting edge during cutting causes intragranular fracture, resulting in a decrease in chipping resistance. It causes. Therefore, the area of the pores existing in the crystal grains is preferably 10 area% or less with respect to the total area of the pores.

Here, the average area ratio A _{avg pore,} average pore size D _avg pore can be measured and calculated by the following method.
First, observing the vertical section of the hard coating layer with a scanning electron microscope (5000 magnification), measuring the average layer thickness _{L avg} of CrAlCN layer ([mu] m).
Then, the range of 1 μm × 1 μm of the vertical cross section of each section obtained by dividing the average layer thickness _Lavg (μm) into [ _Lavg / 2] + 1 in the layer thickness direction was observed with a scanning electron microscope at a magnification of 50,000 times. With respect to the obtained image, image processing software, for example, Photoshop (registered trademark) of Adobe (registered trademark) or other known ones, identifies pores and non-pore areas and colors them.
Then, by measuring the total colored area in the measured section, the area ratio A of the pores in the measured section can be obtained.
Also, by counting the circles or ellipses identified as pores and dividing the total area of the pores by the total area, the average area per pore in that section is calculated, and the diameter of the circle having that area is calculated. It can be calculated and the value can be obtained as the pore diameter D in the section.
Then, the pore area ratio A and the pore pore diameter D obtained above are obtained in each section divided by [ _Lavg / 2] + 1, and by averaging these, the average area ratio _Avg occupied by the pores in the CrAlCN layer is obtained. And the average pore diameter _Davg can be obtained.
Here, [ _Lavg / 2] is a Gaussian symbol, and [ _Lavg / 2] is a mathematical symbol representing the maximum integer that does not exceed _Lavg / 2. In other words, [ _Lavg / 2] means a numerical value n (where n is an integer) defined by _n≤Lavg / 2 <n + 1.
For example, if the average layer thickness _{L avg} of CrAlCN layer (μm) = 1.5 (μm) , _"[if L _a vg / 2] +1 resolution" [1.5 / 2] + 1 = 1 divided by There, and when the average layer thickness _{L avg (μm) = 15 (} μm), _"[L avg / 2] +1 resolution", it comes to [15/2] + 1 = 8 division.

In the present invention, the average pore diameter D _avg average area ratio A _avg and pores of pore in CrAlCN layer defined as above, locally if pores are such as unevenly distributed, high pore density points destruction Since it tends to be a starting point, it is preferable that the pores in the layer are uniformly dispersed, that is, the coefficient of variation obtained from the average number density and standard deviation of the pores is 1 or less.
The coefficient of variation can be obtained as follows.
The vertical cross section of the CrAlCN layer is observed with a scanning electron microscope in a range of 1 μm × 1 μm at a magnification of 50,000 times, the number density of pores (pieces / μm ² ) is measured, and the pores are measured in 5 or more visual fields. It is preferable that the coefficient of variation obtained from the standard deviation σ / average number density _Navg by calculating the average number density N _avg (pieces / μm ² ) and the standard deviation σ is 1 or less.

Phases constituting the CrAlCN layer:
In the CrAlCN layer of the present invention, the CrAlCN crystal grains constituting the layer are preferably composed of crystal grains having a NaCl-type face-centered cubic structure, but have a hexagonal structure in which the area ratio to the vertical cross section is 5 area% or less. The content of the fine crystal grains may be contained because it does not significantly affect the cutting performance.

Component composition defined in the present invention, the average area ratio _{A avg} pore, CrAlCN layer having an average pore diameter _{D avg} pore, furthermore, CrAlCN layer having a preferred variation coefficient of pores, for example, chemical vapor deposition conditions shown below It can be formed by the method.
Film formation conditions:
Reaction gas composition (volume%): Gas group A: NH ₃ 1.0 to 2.0%, H ₂ 65 to 75%,
Gas group B: AlCl ₃ 0.2 to 0.4%, CrCl ₃ 0.08 to 0.1%, N ₂ : 0.0 to 10.0%, C ₂ H ₄ 0.0 to 0.05% , H ₂ : Remaining,
Reaction atmosphere pressure: 4.0-5.0 kPa,
Reaction atmosphere temperature: 700-900 ° C
Supply cycle: 10 to 30 seconds,
Gas supply time per cycle: 0.5-2.0 seconds,
Phase difference between the supply of gas group A and the supply of gas group B: 0.5 to 1.5 seconds,
Under the above chemical vapor deposition conditions, the pore formation density and size in the film change depending on the supply amount and supply rate of the raw material gas. Using this, the average area ratio A _avg and an average pore diameter D _avg pore pores, by varying the proportions and the supply period of the metal source gas can be controlled.

Lower and upper layers:
The CrAlCN layer of the present invention exerts a sufficient effect by itself, but one or more Ti of the carbide layer, nitride layer, carbon nitride layer, carbon oxide layer and carbon dioxide oxide layer of Ti. When a lower layer composed of a compound layer and having a total average layer thickness of 0.1 to 20 μm is provided, and / or when an upper layer including at least an aluminum oxide layer is provided with a total average layer thickness of 1 to 25 μm. Can create even better characteristics in combination with the effects of these layers. When a lower layer composed of one or more Ti compound layers of a carbide layer, a nitride layer, a carbonitride layer, a coal oxide layer and a carbon dioxide oxide layer of Ti is provided, the total average layer of the lower layers is provided. If the thickness is less than 0.1 μm, the effect of the lower layer is not sufficiently exhibited, while if it exceeds 20 μm, the crystal grains are likely to be coarsened and chipping is likely to occur. Further, if the total average layer thickness of the upper layer including at least the aluminum oxide layer is less than 1 μm, the effect of the upper layer is not sufficiently exhibited, while if it exceeds 25 μm, the crystal grains are likely to be coarsened and chipping is likely to occur. Become.

The present invention, the surface of the tool substrate, the surface-coated cutting tool having a hard coating layer, the hard coating layer includes at least a CrAlCN layer, the CrAlCN _{formula: (Cr 1-x Al x} ) (C y When represented by N _1-y ), the average content ratio X _{avg of} Al in the total amount of Cr and Al and the average content ratio Y _avg of C in the total amount of C and N are 0.70 ≦ X, respectively. Satisfying _avg ≤ 0.95 and 0 ≤ Y _avg ≤ 0.005 (however, X _avg and Y _avg are both atomic ratios), a NaCl-type face-centered cubic structure is formed in the crystal grains constituting the CrAlCN layer. Since the CrAlCN crystal grains having CrAlCN crystals are present and the pores having a predetermined average area ratio A _avg and average pore size D _avg are present in the CrAlCN layer, the propagation and propagation of cracks in the layer are suppressed. Demonstrates excellent chipping resistance in high-speed intermittent cutting of carbon steel, alloy steel, cast iron, etc., where a high load acts on the cutting edge.

It is a schematic schematic diagram of the layer structure which schematically represented the longitudinal section of the CrAlCN layer of this invention.

Next, the covering tool of the present invention will be specifically described with reference to Examples.
In the examples, a case where a WC-based cemented carbide and a TiCN-based cermet are used as a tool substrate will be described, but the same effect can be obtained when a cubic boron nitride-based ultrahigh-pressure sintered body is used as a tool substrate. can get.

As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder and Co powder having an average particle size of 1 to 3 μm are prepared, and these raw material powders are blended as shown in Table 1. It was blended into the composition, further added with wax, mixed in a ball mill in acetone for 24 hours, dried under reduced pressure, press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, and this green compact was pressed in a vacuum of 5 Pa at 1370. Vacuum sintered at a predetermined temperature within the range of ~ 1470 ° C. under the condition of holding for 1 hour, and after sintering, manufacture tool bases A to C made of WC-based superhard alloy having an insert shape of ISO standard SEEN1203AFSN. did.

Further, as the raw material powder, both (TiC / TiN = 50/50 in mass ratio) TiCN having an average particle diameter of 0.5~2μm powder, Mo ₂ C powder, ZrC powder, NbC 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. The body 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 SEEN1203AFSN was prepared.

Next, a chemical vapor deposition apparatus was used on the surfaces of these tool bases A to D.
The formation conditions A to H shown in Table 4, that is, the gas group A consisting of NH ₃ and H ₂ , the gas group B consisting of AlCl ₃ , CrCl ₃ , N ₂ , C ₂ H ₄ , and H ₂ , and each of them. As a gas supply method, the reaction gas composition (volume% of the total of the gas group A and the gas group B) is adjusted to NH ₃ : 1.0 to 2.0% and H ₂ : 65 to 75% as the gas group A. As gas group B, AlCl ₃ 0.2 to 0.4%, CrCl ₃ 0.08 to 0.1%, N ₂ : 0.0 to 10.0%, C ₂ H ₄ 0.0 to 0.05 %, H ₂ : Residual, reaction atmosphere pressure: 4.0 to 5.0 kPa, reaction atmosphere temperature: 700 to 900 ° C., supply cycle 10 to 30 seconds, gas supply time per cycle 0.5 to 2.0 seconds The thermal CVD method was performed for a predetermined time with a phase difference of 0.5 to 1.5 seconds between the supply of the gas group A and the supply of the gas group B, and the CrAlCN layer shown in Table 6 was formed to form the coating of the present invention. Tools 1-12 were manufactured.
For the covering tools 5 to 12 of the present invention, the lower layer and the upper layer shown in Table 5 were formed under the formation conditions shown in Table 3.

Further, for the purpose of comparison, the covering tool 1 of the present invention has a target average layer thickness (μm) shown in Table 7 under the conditions of the comparative film forming process shown in Tables 3 and 4 on the surfaces of the tool substrates A to D. In the same manner as in ~ 12, a hard coating layer containing at least a CrAlCN layer was vapor-deposited to form comparative coating tools 1 to 12. At this time, comparative coating tools 5 to 12 were manufactured by forming a hard coating layer so that the reaction gas composition on the surface of the tool substrate did not change with time during the film formation step of the CrAlCN layer.
Similar to the covering tools 5 to 12 of the present invention, the comparative covering tools 10 to 12 were formed with the lower layer and the upper layer shown in Table 5 under the formation conditions shown in Table 3.

Then, the vertical cross section of each of the constituent layers of the covering tools 1 to 12 and the comparative covering tools 1 to 12 in the direction perpendicular to the surface of the tool substrate is measured using a scanning electron microscope (magnification: 5000 times), and the observation field is observed. When the average layer thickness was obtained by measuring the layer thicknesses of the five points and averaging them, all of them showed substantially the same target average layer thickness as the target layer thicknesses shown in Tables 6 and 7. The average layer thickness of CrAlCN layer are indicated by _{L avg (μm).}
The average Al content ratio X- _avg of the CrAlCN layer was obtained by irradiating the sample with an electron beam microanalyzer (EPMA, Electron-Probe-Micro-Analyzer) from the sample surface side. The average Al content ratio X _avg of Al was obtained from the 10-point average of the analysis results of the characteristic X-rays obtained.
The average C content ratio _Yavg was determined by secondary ion mass spectrometry (SIMS, Secondary-Ion-Mass-Spectroscopy). An ion beam was irradiated in a range of 70 μm × 70 μm from the sample surface side, and the concentration of the components released by the sputtering action was measured in the depth direction. Average C content _{Y avg} represents the average value of the depth direction for TiAlCN layer.
However, the content ratio of C excludes the unavoidable content ratio of C contained even if a gas containing C is not intentionally used as a gas raw material. Specifically, the content ratio (atomic ratio) of the C component contained in the CrAlCN layer when the supply amount of C ₂ H ₄ is 0 is obtained as the unavoidable C content ratio, and C ₂ H ₄ is intentionally used. the value obtained by subtracting the content of the unavoidable C from the content of the C component contained in CrAlCN layer obtained when supplied (atomic ratio) was calculated as Y _avg.
Tables 6 and 7 show the values of X _avg and Y _avg .

Then, the present invention coated tool 12, the comparative coated tool 12, respectively, the average area ratio _{A avg} and average pore size _{D avg} pore present in CrAlCN layer was determined by the following procedure.
First, a scanning electron microscope (5000 magnification) was used to observe a longitudinal section of the hard coating layer, and measuring the average layer thickness _{L avg} of CrAlCN layer ([mu] m), then, the average layer thickness _{L avg} ([mu] m) The range of 1 μm × 1 μm of the vertical cross section of each section divided into [ _Lavg / 2] + 1 in the layer thickness direction was observed with a scanning electron microscope (magnification 50,000 times), and image processing software, for example, was used for the obtained image. Identify and color pores and non-pore areas with a microscope (registered trademark) from Adobe® and other known sources.
Then, by measuring the total area colored in the measured section, the area ratio A of the pores in the measured section is obtained.
Also, by counting the number of circles or ellipses identified as pores and dividing the total area of the pores by the total area, the average area per pore in that section is calculated, and the circle having that area is calculated. The diameter is calculated, and the value is obtained as the pore diameter D in the section.
Next, the pore area ratio A and the pore diameter D obtained above were obtained in each section divided by [ _Lavg / 2] + 1, and by averaging these, the average area ratio _Avg occupied by the pores in the CrAlCN layer was obtained. And the average pore diameter _Davg .
In addition, [L _avg / 2] + 1 division means, as already described, the average layer thickness of the CrAlCN layer according to the numerical value n (where n is an integer) defined by n ≦ L _avg / 2 <n + 1. It means to divide _Lavg (μm) into n.
Further, the area ratio of the pores existing in the crystal grains of the CrAlCN layer (that is, excluding the pores existing at the grain boundaries) is the total area of the pores included in one crystal grain in each section. By dividing by, the area ratio of the pores existing in the crystal grains in the section was obtained, and then the area ratio of the pores existing in the grains in each section was averaged.
The results are shown in Tables 6 and 7.

Moreover, the dispersibility of the pores existing in the CrAlCN layer was measured by the following method.
The average layer thickness _{L avg} of CrAlCN layer foregoing method ([mu] m) on each section divided into n, a longitudinal section of CrAlCN layer, scanning the electron microscope to observe the range of 1 [mu] m × 1 [mu] m at a magnification 50,000 times the pore The number density (pieces / μm ² ) was measured. The average number density _Navg (pieces / μm ² ) and standard deviation σ of the pores were calculated by measuring in 5 or more fields, and the coefficient of variation obtained from the standard deviation σ / average number density _Navg was evaluated. When n <5, move so that the visual fields do not overlap in the direction of 90 degrees with respect to the layer thickness direction in each section so that the visual fields are 5 or more, and similarly calculate the average number density of pores and 5 visual fields. Make the above observations.
The results are shown in Tables 6 and 7.

The CrAlCN layer constituting the hard coating layer of the coating tools 1 to 12 of the present invention and the comparative coating tools 1 to 12 was observed over a plurality of fields using a transmission electron microscope, and the CrAlCN crystal grains were NaCl-type cubic crystals. It was confirmed by analyzing the electron diffraction pattern using a transmission electron microscope whether the structure consisted of a single phase or the presence of hexagonal crystal grains.
The results are shown in Tables 6 and 7.

Next, with the various covering tools of the present invention clamped to the tip of a tool steel cutter having a cutter diameter of 125 mm with a fixing jig, the covering tools 1 to 12 of the present invention and the comparative covering tools 1 to 12 are described below. The dry high-speed face milling cutter, which is a type of high-speed intermittent cutting for alloys, and the center-cut cutting process test were carried out, and the flank wear width of the cutting edge was measured in each case.

<Cutting test: Dry high-speed face milling cutter, center cut cutting process>
Tool Base: Tungsten Carbide Cemented Carbide, Titanium Nitride Cermet,
Cutting test: Dry high-speed face milling cutter, center cut cutting,
Work material: JIS / SCM440 Block material with a width of 100 mm and a length of 400 mm,
Rotation speed: 866 min ^-1 ,
Cutting speed: 340 m / min,
Notch: 2.5 mm,
Single blade feed amount: 0.3 mm / blade,
Cutting time: 8 minutes,
(Normal cutting speed is 220 m / min)
Table 8 shows the results of the cutting test.

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, prepared TiN powder and Co powder, these raw material powders, It was blended to the blending composition shown in Table 9, further added with wax, mixed in a ball mill in acetone for 24 hours, dried under reduced pressure, and then press-molded into a green compact having a predetermined shape at a pressure of 98 MPa to obtain this green compact. In a vacuum of 5 Pa, vacuum sintering is performed under the condition of holding at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour, and after sintering, the cutting edge is honed with R: 0.07 mm to ISO standard. Tool bases α to γ made of WC-based superhard alloy having an insert shape of CNMG120412 were manufactured.

Further, as raw material powders, TiCN (TiC / TiN = 50/50 by mass ratio) powder, NbC powder, WC powder, Co powder, and Ni powder, each having an average particle size of 0.5 to 2 μm, were prepared. These raw material powders were blended into the compounding composition shown in Table 10, wet-mixed with a ball mill for 24 hours, dried, and then press-molded into a green compact at a pressure of 98 MPa, and the green compact was pressed with 1.3 kPa of nitrogen. TiCN group with insert shape of ISO standard CNMG120412 by sintering in atmosphere under the condition of holding at temperature: 1500 ° C for 1 hour, and then applying honing processing of R: 0.09 mm to the cutting edge part. A tool substrate δ made of cermet was formed.

Next, on the surfaces of these tool bases α to γ and the tool base δ, a normal chemical vapor deposition apparatus was used, and the formation conditions A to H shown in Table 4, that is, the gas group A composed of NH ₃ and H ₂ were formed. , AlCl ₃ , CrCl ₃ , N ₂ , C ₂ H ₄ , H ₂ , and as a method of supplying each gas, the reaction gas composition (volume% of the total of gas group A and gas group B). ) As the gas group A: NH ₃ : 1.0 to 2.0%, H ₂ : 65 to 75%, and as the gas group B, AlCl ₃ 0.2 to 0.4%, CrCl ₃ 0.08 to 0. 1%, N ₂ : 0.0 to 10.0%, C ₂ H ₄ 0.0 to 0.05%, H ₂ : Residual, reaction atmosphere pressure: 4.0 to 5.0 kPa, reaction atmosphere temperature: 700 ~ 900 ° C., supply cycle 10 to 30 seconds, gas supply time per cycle 0.5 to 2.0 seconds, phase difference between gas group A supply and gas group B supply 0.5 to 1.5 seconds , The thermal CVD method was carried out for a predetermined time, and the CrAlCN layer shown in Table 12 was formed to form the coating tools 13 to 24 of the present invention.
For the covering tools 16 to 24 of the present invention, the lower layer and the upper layer shown in Table 11 were formed under the formation conditions shown in Table 3.

Further, for the purpose of comparison, the same chemical vapor deposition apparatus is used on the surfaces of the tool substrates α to γ and the tool substrate δ, and the conditions shown in Tables 3 and 4 and the target average layer thickness shown in Table 13 are used. Comparative coating tools 13 to 24 shown in Table 13 were manufactured by vapor-depositing a hard coating layer in the same manner as the coating tool of the present invention.
Similar to the covering tools 16 to 24 of the present invention, the comparative covering tools 16 to 24 formed the lower layer and the upper layer shown in Table 11 under the formation conditions shown in Table 3.

Next, the vertical cross section of each of the constituent layers of the covering tools 13 to 24 and the comparative covering tools 13 to 24 of the present invention in the direction perpendicular to the surface of the tool substrate is measured using a scanning electron microscope (magnification of 5000 times), and the observation field of view is measured. When the average layer thickness was obtained by measuring the layer thicknesses of the five points and averaging them, all of them showed substantially the same target average layer thickness as the target layer thicknesses shown in Tables 6 and 7. The average layer thickness of CrAlCN layer are indicated by _{L avg (μm).}
The average Al content ratio X- _avg of the CrAlCN layer was obtained by irradiating the sample with an electron beam microanalyzer (EPMA, Electron-Probe-Micro-Analyzer) from the sample surface side. The average Al content ratio X _avg of Al was obtained from the 10-point average of the analysis results of the characteristic X-rays obtained.
The average C content ratio _Yavg was determined by secondary ion mass spectrometry (SIMS, Secondary-Ion-Mass-Spectroscopy). An ion beam was irradiated in a range of 70 μm × 70 μm from the sample surface side, and the concentration of the components released by the sputtering action was measured in the depth direction. Average C content _{Y avg} represents the average value of the depth direction for TiAlCN layer.
However, the content ratio of C excludes the unavoidable content ratio of C contained even if a gas containing C is not intentionally used as a gas raw material. Specifically, the content ratio (atomic ratio) of the C component contained in the CrAlCN layer when the supply amount of C ₂ H ₄ is 0 is obtained as the unavoidable C content ratio, and C ₂ H ₄ is intentionally used. the value obtained by subtracting the content of the unavoidable C from the content of the C component contained in CrAlCN layer obtained when supplied (atomic ratio) was calculated as Y _avg.
Tables 12 and 13 show the values of X _avg and Y _avg .

Then, the present invention coated tool 13-24 and Comparative coated tool 13-24, respectively, the average area ratio _{A avg} and average pore size _{D avg} pore present in CrAlCN layer was determined by the following procedure.
First, a scanning electron microscope (5000 magnification) was used to observe a longitudinal section of the hard coating layer, and measuring the average layer thickness _{L avg} of CrAlCN layer ([mu] m), then, the average layer thickness _{L avg} ([mu] m) The range of 1 μm × 1 μm of the vertical cross section of each section divided into [ _Lavg / 2] + 1 in the layer thickness direction was observed with a scanning electron microscope (magnification 50,000 times), and image processing software, for example, was used for the obtained image. Identify and color pores and non-pore areas with a microscope (registered trademark) from Adobe® and other known sources.
Then, by measuring the total area colored in the measured section, the area ratio A of the pores in the measured section is obtained.
Also, by counting the number of circles or ellipses identified as pores and dividing the total area of the pores by the total area, the average area per pore in that section is calculated, and the circle having that area is calculated. The diameter is calculated, and the value is obtained as the pore diameter D in the section.
Next, the pore area ratio A and the pore diameter D obtained above were obtained in each section divided by [ _Lavg / 2] + 1, and by averaging these, the average area ratio _Avg occupied by the pores in the CrAlCN layer was obtained. And the average pore diameter _Davg .
In addition, [L _avg / 2] + 1 division means, as already described, the average layer thickness of the CrAlCN layer according to the numerical value n (where n is an integer) defined by n ≦ L _avg / 2 <n + 1. It means to divide _Lavg (μm) into n.
Further, the area ratio of the pores existing in the crystal grains of the CrAlCN layer (that is, excluding the pores existing at the grain boundaries) is the total area of the pores included in one crystal grain in each section. By dividing by, the area ratio of the pores existing in the crystal grains in the section was obtained, and then the area ratio of the pores existing in the grains in each section was averaged.
The results are shown in Tables 12 and 13.

The average layer thickness _{L avg} of CrAlCN layer foregoing method ([mu] m) on each section divided into n, a longitudinal section of CrAlCN layer, scanning the electron microscope to observe the range of 1 [mu] m × 1 [mu] m at a magnification 50,000 times the pore The number density (pieces / μm ² ) was measured. The average number density _Navg (pieces / μm ² ) and standard deviation σ of the pores were calculated by measuring in 5 or more fields, and the coefficient of variation obtained from the standard deviation σ / average number density _Navg was evaluated. When n <5, move so that the visual fields do not overlap in the direction of 90 degrees with respect to the layer thickness direction in each section so that the visual fields are 5 or more, and similarly calculate the average number density of pores and 5 visual fields. Make the above observations.
The results are shown in Tables 12 and 13.

The CrAlCN layer constituting the hard coating layer of the coating tools 13 to 24 of the present invention and the comparative coating tools 13 to 24 was observed over a plurality of fields using a transmission electron microscope, and the CrAlCN crystal grains were NaCl-type cubic crystals. It was confirmed by analyzing the electron diffraction pattern using a transmission electron microscope whether the structure consisted of a single phase or the presence of hexagonal crystal grains.
The results are shown in Tables 12 and 13.

Next, the covering tools 13 to 24 of the present invention and the comparative covering tools 13 to 24 are shown below in a state where all of the various covering tools are screwed to the tip of the tool steel cutting tool with a fixing jig. Wet high-speed intermittent cutting tests of carbon steel and cast iron were carried out, and the flank wear width of the cutting edge was measured in both cases.
Cutting condition 1:
Work material: JIS / S15C round bar with 4 vertical grooves at equal intervals in the length direction,
Cutting speed: 280 m / min,
Notch: 2.5 mm,
Feed: 0.32 mm / rev,
Cutting time: 5 minutes,
(Normal cutting speed is 200m / min),
Cutting condition 2:
Work material: JIS / FCD450 round bar with four vertical grooves at equal intervals in the length direction,
Cutting speed: 270 m / min,
Notch: 2.2 mm,
Feed: 0.32 mm / rev,
Cutting time: 5 minutes,
(Normal cutting speed is 200m / min),
Table 14 shows the results of the cutting test.

From the results shown in Tables 8 and 14, in the coating tool of the present invention, the presence of pores having a predetermined average area ratio and a predetermined average pore size in the CrAlCN layer suppresses the propagation and propagation of cracks in the layer. It exhibits excellent chipping resistance and wear resistance in high-speed intermittent cutting of carbon steel, alloy steel, cast iron, etc., which exerts a high load on the cutting edge.
On the other hand, in the comparative covering tool in which the CrAlCN layer does not have the pores having the average area ratio and the average pore diameter specified in the present invention, high heat is generated and the cutting edge is intermittently and impactfully loaded. It is clear that when it is used for high-speed intermittent cutting, it reaches the end of its life in a short time due to the occurrence of chipping, chipping, etc.

The coating tool of the present invention can be used not only for high-speed intermittent cutting of carbon steel, alloy steel, and cast iron, but also as a coating tool for various work materials, and has excellent chipping resistance over a long period of use. Since it exhibits abrasion resistance, it can sufficiently satisfactorily cope with high performance of cutting equipment, labor saving and energy saving of cutting processing, and cost reduction.

Claims (4)

In a surface-coated cutting tool in which a hard coating layer is provided on the surface of a tool substrate composed of either a tungsten carbide-based cemented carbide, a titanium nitride-based cermet, or a cubic boron nitride-based ultrahigh-pressure sintered body.
(A) The hard coating layer contains at least a composite nitride or composite carbonitride layer of Cr and Al having an average layer thickness of 1 to 20 μm.
(B) The composite nitride or composite carbonitride layer contains at least a composite nitride or composite carbonitride phase having a NaCl-type face-centered cubic structure.
(C) The composite nitride or composite carbonitride layer is
Composition formula: (Cr _1-x Al _x ) ( _Cy N _1-y )
When represented by, the average content ratio X _avg in the total amount of Cr and Al of Al and the average content ratio Y _avg in the total amount of C and N of C (however, both X _avg and Y _avg are atomic ratios). Satisfy 0.70 ≤ X _avg ≤ 0.95 and 0 ≤ Y _avg ≤ 0.005, respectively.
(D) Pore is present in the composite nitride or composite carbonic nitride layer, and when the average layer thickness of the composite nitride or composite carbonitride layer is _Lavg (μm), the average layer thickness The range of 1 μm × 1 μm of the vertical cross section of each section obtained by dividing _Lavg (μm) by [ _Lavg / 2] + 1 in the layer thickness direction was observed with a scanning electron microscope at a magnification of 50,000 times, and each observation area of each section was observed. When the area ratio A occupied by the pores in the area and the pore diameter D in the observation area were obtained and the average area ratio A _avg and the average pore diameter D _avg of the pores in each section were calculated, 0.1 area% ≤ A _avg ≤ 10 Area%, 4 nm ≤ D _avg ≤ 50 nm ,
(E) The range of 1 μm × 1 μm of the longitudinal cross section of the composite nitride or composite carbonic nitride layer is observed with a scanning electron microscope at a magnification of 50,000 times for 5 fields or more, and the average pore number density _Navg and the standard deviation σ are obtained. A surface coating cutting tool characterized in that the coefficient of variation is 1 or less when the coefficient of variation is calculated from the standard deviation σ / average number density _Navg . The surface according to claim 1, wherein the composite nitride or composite carbonitride layer is composed of a single phase of a Cr and Al composite nitride or composite carbonitride having a NaCl-type face-centered cubic structure. Coated cutting tool. One or more of a carbide layer, a nitride layer, a carbonitride layer, a coal oxide layer and a carbonitride oxide layer of Ti between the tool substrate and the composite nitride or composite carbonitride layer. The surface coating cutting tool according to claim 1 or 2, wherein there is a lower layer composed of the Ti compound layer of the above and having a total average layer thickness of 0.1 to 20 μm. The present invention according to any one of claims 1 to 3, wherein an upper layer including at least an aluminum oxide layer is present above the composite nitride or composite carbonitride layer with a total average layer thickness of 1 to 25 μm. The surface coating cutting tool described.