JP6928220B2 - 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 exhibits excellent chipping resistance even when cutting steel, stainless steel, etc. is performed under high-speed intermittent high cutting conditions and high-speed intermittent high feed conditions in which a high load acts on the cutting edge. However, 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 time.

Conventionally, generally, on the surface of a substrate (hereinafter, collectively referred to as a tool substrate) composed of a tungsten carbide (hereinafter, WC) -based cemented carbide or a titanium nitride (hereinafter, TiCN) -based cermet. ,
(A) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter, also indicated by TiN) layer, a carbonitride (hereinafter, indicated by TiCN) layer, and a carbon oxide (hereinafter, TiCO). A Ti compound layer consisting of one layer or two or more of the (shown) layer and the carbonitride oxide (hereinafter referred to as TiCNO) layer.
(B) An aluminum oxide layer having an α-type crystal structure in a chemically vapor-deposited state (hereinafter referred to as an Al ₂ O ₃ layer),
As described above, a coating tool in which a hard coating layer composed of (a) and (b) is vapor-deposited is known.

However, the conventional covering tool as described above exhibits excellent cutting performance in continuous cutting of various types of steel and cast iron, for example, but when this is used for intermittent cutting, chipping of the coating layer is performed. There is a problem that the tool life is shortened.
Therefore, in order to improve the chipping resistance of the coating layer, a coating tool in which various improvements are made to the hard coating layer has been proposed.

For example, in Patent Document 1,
On the surface of the tool substrate,
(A) The lower layer is composed of two or more layers of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonic acid oxide layer, and a carbonic acid nitrogen oxide layer, all of which are chemically vapor-deposited, and 3 Ti compound layer with a total average layer thickness of ~ 20 μm,
(B) An aluminum oxide layer having an average layer thickness of 1 to 15 μm, in which the upper layer is chemically vapor-deposited.
In the coating tool formed of the hard coating layer composed of the above (a) and (b),
One layer of the Ti compound layer of (a) above is
Reaction gas composition: By volume%, TiCl ₄ : 0.1 to 0.8%, CH ₃ CN: 0.05 to 0.3%, Ar: 10 to 30%, H ₂ : Remaining,
Reaction atmosphere temperature: 930 to 1000 ° C,
Reaction atmospheric pressure: 6-20 kPa,
Under the conditions of, chemical vapor deposition is formed to an average layer thickness of 2.5 to 15 μm, and
Using a field emission scanning electron microscope, each crystal grain existing within the measurement range of the surface polishing surface is irradiated with an electron beam, and an electron backscatter diffraction imager is used to set a predetermined region at intervals of 0.1 μm / step. , The (001) plane and (001) which are the crystal planes of the crystal grains with respect to the normal line of the surface polishing plane.
011) Measure the inclination angle formed by the normal of the plane, in which case the crystal grains are Ti, carbon, at the lattice points.
Each of the constituent atoms has a NaCl-type cubic crystal structure in which constituent atoms consisting of and nitrogen are present, and each of the constituent atoms is said to be at the interface of crystal grains adjacent to each other based on the measurement inclination angle obtained as a result. Lattice points that share one constituent atom between crystal grains (constituting atom shared lattice points)
The number of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points: N (in this case, N is an even number of 2 or more due to the crystal structure of the NaCl type cubic crystal). Calculate the distribution ratio of each constituent atom shared lattice point form (unit form) represented by ΣN + 1 determined for each (up to N: 28 from the point of distribution frequency), and share each constituent atom of Σ3 to Σ29. Lattice point form (unit form)
In the constituent atom shared lattice point distribution graph showing the distribution ratio of Σ3 to Σ29 as a percentage of the total distribution ratio of the constituent atom shared lattice point forms (unit forms) of the above Σ3 to Σ29, the highest peak exists in Σ3 and the above Σ3 Titanium carbon nitride layer showing a constituent atom shared lattice point distribution graph in which the distribution ratio of is occupied 65 to 80% of the total distribution ratio of the entire constituent atom shared lattice point form (unit form).
A covering tool made of the above has been proposed, and according to this covering tool, it is said that the hard coating layer exhibits excellent chipping resistance in high-speed intermittent cutting of steel, cast iron, and the like.

Further, in Patent Document 2,
On the surface of the tool substrate,
(A) The lower layer is composed of two or more layers of a titanium carbide layer, a nitride layer, a carbonitride layer, a coal oxide layer, and a carbonitride oxide layer, all of which are chemically vapor-deposited. One of them is a titanium compound layer composed of a titanium carbide layer and having a total average layer thickness of 3 to 20 μm.
(B) An aluminum oxide layer having an average layer thickness of 1 to 15 μm, in which the upper layer is chemically vapor-deposited.
In the coating tool formed of the hard coating layer composed of the above (a) and (b),
The carbonitride layer of titanium in the titanium compound layer of (a) above is irradiated with an electron beam for each crystal grain existing in the measurement range of the vertical cross section using an electro-emission scanning electron microscope, and electron backscattering is performed. Using a diffraction image device, the inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the substrate surface at intervals of 0.1 μm / step in a predetermined region. In this case, the crystal grains have a NaCl-type surface-centered cubic crystal structure in which constituent atoms composed of Ti, carbon, and nitrogen are present at the lattice points, respectively, and the measurement inclination angle obtained as a result is obtained. Based on, at the interface of the crystal grains adjacent to each other, the distribution of lattice points (constituting atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated, and the above-mentioned The number of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points N (In this case, N is an even number of 2 or more due to the crystal structure of the NaCl type cubic crystal, but N = 28 from the point of distribution frequency. The distribution ratio of each constituent atom shared lattice point form (unit form) represented by ΣN + 1 determined for each (upper limit) is calculated, and the distribution of each constituent atom shared lattice point form (unit form) of Σ3 to Σ29 is calculated. In the constituent atom shared lattice point distribution graph showing the ratio as a ratio to the total distribution ratio of the constituent atom shared lattice point forms (unit forms) of the constituent atoms of Σ3 to Σ29, the distribution ratio of the Σ3 is the configuration in the cutting edge ridge portion. It shows 5 to 13% of the total distribution ratio of the entire atomic shared lattice point morphology (unit form), and the distribution ratio of Σ3 is the total of the entire constituent atomic shared lattice point morphology (unit form) in the region other than the cutting edge ridge. A carbon nitride layer of titanium showing a composition atom shared lattice point distribution graph occupying 50% or more of the distribution ratio,
A coating tool that exhibits excellent chipping resistance by strong intermittent machining has been proposed. According to this coating tool, the distribution ratio of Σ3 in the lower layer of the hard coating layer at the cutting edge ridge and the cutting edge ridge. By setting the distribution ratio of Σ3 in the lower layer of the hard coating layer in the region other than the part to a specific range, the abrasion resistance in strong intermittent machining where the interval between interruptions is long and a strong impact is applied to the tip of the cutting edge. It is said that excellent chipping resistance is exhibited without causing deterioration of the blade.

Japanese Patent No. 4518258 Japanese Unexamined Patent Publication No. 2015-182154

In recent years, the performance of cutting equipment has been remarkably improved, while there is a strong demand for labor saving, energy saving, and cost reduction for cutting. Along with this, the cutting speed is further increased, and a high load tends to act on the cutting edge due to heavy cutting such as high cutting and high feed, intermittent cutting and the like.
There is no particular problem when the above-mentioned conventional covering tool is used for continuous cutting and intermittent cutting under normal conditions such as steel and cast iron, but steel and stainless steel under high-speed intermittent heavy cutting conditions, which are more severe cutting conditions. When steel is processed, the plastic deformability of the hard coating layer is not sufficient, and a high load acts on the hard coating layer, so that the particles constituting the hard coating layer fall off, peel off, or chip. The tool life is reached in a relatively short time due to the occurrence of.

Therefore, from the above-mentioned viewpoints, the present inventors have high-speed intermittent heavy cutting conditions (for example,) in which an intermittent and shocking high load acts on the cutting edge and plastic deformation of the hard coating layer is likely to occur. After diligent research on the structure of the hard coating layer so that peeling and chipping of the hard coating layer do not occur even when used under high-speed high-cut intermittent cutting conditions and high-speed high-feed intermittent cutting conditions), the lower part of the hard coating layer In at least one TiCN layer constituting the layer, the TiCN constituting the lower layer is formed by setting the length ratio of the corresponding grain boundary length of Σ31 or more to 80% or more with respect to the total corresponding grain boundary length of the TiCN layer. Many grain boundaries with high toughness can be distributed in the layer, which makes it possible to distribute steel, stainless steel, etc. under high-speed high-cutting intermittent conditions or high-speed high-feed intermittent conditions in which a high load intermittently or impactfully acts on the cutting edge. It was found that the peeling of the hard coating layer and the occurrence of chipping are suppressed even when the hard coating layer is cut.

The present invention has been made based on the above findings.
"(1) In a surface-coated cutting tool in which a hard coating layer composed of a lower layer and an upper layer is provided on the surface of a tool substrate made of a tungsten carbide-based cemented carbide or a titanium nitride-based cermet.
(A) The lower layer is a Ti compound layer having a total average layer thickness of 3 to 20 μm and composed of one layer or two or more layers of TiC, TiN, TiCN, TiCO, and TiCNO. At least one layer is composed of TiCN layer,
_{(B) The upper layer is composed of an Al 2} O ₃ layer having an average layer thickness of 1 to 15 μm and an α-type crystal structure.
(C) At least one TiCN layer of the lower layer is irradiated with an electron beam for each crystal grain existing within the measurement range of the vertical cross section of the at least one TiCN layer using an electric field emission scanning electron microscope. , Using an electron rear scattering diffraction image device, the normals of the (001) and (011) planes, which are the crystal planes of the crystal grains, with respect to the normals of the surface of the substrate in a predetermined region at intervals of 0.1 μm / step. The inclination angle formed by the grains was measured, and in this case, the crystal grains had a NaCl-type surface-centered cubic crystal structure in which constituent atoms composed of Ti, carbon, and nitrogen were present at the lattice points, respectively, and the result was obtained. Based on the measurement inclination angle, the distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated at the interface of the crystal grains adjacent to each other. At the same time, when the distribution ratio of each of the constituent atom shared lattice point forms (unit forms) represented by ΣN + 1 defined for each number N of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points is calculated. In the corresponding grain boundary distribution graph showing the ratio of the corresponding grain boundary length consisting of each constituent atom shared lattice point to the total corresponding grain boundary length, the grains in the constituent atom shared lattice point form (unit form) having Σ31 or more. The boundary length occupies 80% of the grain boundary length of the constituent atomic shared lattice point form (unit form) having Σ3 or more.
(D) A surface-coated cutting tool characterized in that TiCN crystal grains having an aspect ratio of 3 or more occupy an area ratio of 80% or more in the vertical cross section of at least one TiCN layer.
(2) With respect to at least one TiCN layer of the lower layer, an electro-emission type scanning electron microscope is used to irradiate each crystal grain existing within the measurement range of the vertical cross section of the at least one TiCN layer with an electron beam. , Using an electron rear scattering diffraction image device, the normals of the (001) and (011) planes, which are the crystal planes of the crystal grains, with respect to the normals of the surface of the substrate in a predetermined region at intervals of 0.1 μm / step. The inclination angle formed by the grains was measured, and in this case, the crystal grains had a NaCl-type surface-centered cubic crystal structure in which constituent atoms consisting of Ti, carbon, and nitrogen were present at the lattice points, respectively, and the result was obtained. Based on the measurement inclination angle, the distribution of lattice points (constituting atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated at the interface of the crystal grains adjacent to each other. At the same time, when the distribution ratio of each of the constituent atom shared lattice point forms (unit forms) represented by ΣN + 1 defined for each number N of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points is calculated. In addition, the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ3 is 20% or less of the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ3 to Σ29, and the configuration of Σ5. The above (1), wherein the grain boundary length of the atomic shared lattice point form (unit form) is 30% or less of the grain boundary length of the constituent atomic shared lattice point forms (unit form) of Σ3 to Σ29. Surface coating cutting tool. "

Next, the covering tool of the present invention will be described in detail.
Lower layer:
The Ti compound layer constituting the lower layer is composed of one or more layers of the TiC layer, the TiN layer, the TiCN layer, the TiCO layer and the TiCNO layer (however, at least one of them is the TiCN layer), and is basically _{It exists as a lower layer of an Al 2} O ₃ layer (hereinafter referred to as “α-Al ₂ O ₃ layer”) having an α-type crystal structure, and is a hard coating layer due to its excellent high-temperature strength. Gives high temperature strength to. Further, the Ti compound layer adheres to both the surface of the tool substrate and the _{upper layer composed of the α-Al 2} O ₃ layer, and has an effect of maintaining the adhesion of the hard coating layer to the tool substrate.
However, when the total average layer thickness of the Ti compound layer is less than 3 μm, the above-mentioned action cannot be sufficiently exerted. On the other hand, when the total average layer thickness of the Ti compound layer exceeds 20 μm, thermoplastic deformation is likely to occur in high-speed intermittent heavy cutting, which causes uneven wear.
Therefore, the total average layer thickness of the Ti compound layer was set to 3 to 20 μm.

At least one TiCN layer of the lower layer:
The lower layer in the present invention includes at least one TiCN layer.
Then, when the constituent atom shared lattice point distribution graph is obtained for the at least one TiCN layer, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more is Σ3 or more. It is important to occupy 80% or more of the grain boundary length of the lattice point form (unit form).
When the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 or more, in the TiCN layer. By distributing a large number of grain boundaries with excellent toughness, the impact mitigation of the TiCN layer is improved, and the hard coating layer can be deformed following the deformation of the tool substrate. Therefore, steel and stainless steel. The occurrence of chipping is suppressed in high-speed intermittent heavy cutting of steel and the like.
In FIG. 1, the TiCN layer in which the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. An example of the atomic shared lattice point distribution graph of is shown.

Further, in the TiCN layer in which the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. , The grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and the constituent atoms of Σ5 When the grain boundary length of the shared lattice point form (unit form) is 30% or less of the grain boundary length of the constituent atomic shared lattice point forms (unit form) of Σ3 to Σ29, the toughness of the TiCN layer is further improved. Therefore, excellent chipping resistance is exhibited.
In FIG. 2, the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more, and further. , The grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and the constituent atoms of Σ5. Example of constituent atom shared lattice point distribution graph of TiCN layer in which the grain boundary length of the shared lattice point form (unit form) is 30% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29. Is shown.

Here, the constituent atom shared lattice point distribution graph uses an electric field emission type scanning electron microscope, as is already well known before this application, for example, a longitudinal section parallel to the layer thickness direction of the lower layer of the hard coating layer. The above-mentioned The inclination angle formed by the normals of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, is measured (in this case, the crystal grains have constituent atoms consisting of Ti, carbon, and nitrogen at the lattice points, respectively. (It is a titanium carbonitide crystal grain having a NaCl-type surface-centered cubic crystal structure), and based on the measurement inclination angle obtained as a result, at the interface of the crystal grains adjacent to each other, each of the constituent atoms is The distribution of lattice points (constituting atom shared lattice points) that share one constituent atom between the crystal grains is calculated, and the number of lattice points N (the number of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points) In this case, N is an even number of 2 or more due to the crystal structure of the NaCl-type surface-centered cubic crystal.) Calculate the grain boundary length of each constituent atom shared lattice point form (unit form) represented by ΣN + 1 determined for each. Then, the grain boundary length of each constituent atom shared lattice point form (unit form) of Σ3 or more is shown as a ratio to the total grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 or more. Create a point distribution graph.
The total grain boundary lengths of Σ31 or more are grouped together as Σ31 or more, instead of calculating the grain boundary lengths of individual Ns of Σ31 or more. That is, the grain boundary lengths of Σ3, Σ5, Σ7, Σ9, Σ11, Σ13, Σ15, Σ17, Σ19, Σ21, Σ23, Σ25, Σ27, and Σ29 are calculated, and the total grain boundaries of Σ3 or more obtained by the measurement are calculated. The value obtained by subtracting the total of the grain boundary lengths from Σ3 to Σ29 from the length was obtained as the total of the grain boundary lengths of Σ31 or more.

It has a TiCN layer in which the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. The lower layer can be formed, for example, as follows.
That is, first, the surface of the tool substrate is hard-coated with a Ti compound layer composed of one or more of the TiC layer, the TiN layer, the TiCN layer, the TiCO layer and the TiCNO layer by using a normal chemical vapor deposition apparatus. It is vapor-deposited as a lower layer of the layer (it is also possible to vapor-deposit only the TiCN layer).
Then, for at least one TiCN layer among the lower layers,
Reaction gas composition _{(volume%): TiCl 4 1~3%,} CH 3 CN 0.3~1.0%, N 2 25~60%, HCl 0.05% ~0.2%, Ar 3~15% , Remaining H ₂ ,
Reaction atmosphere temperature: 750-900 ° C,
Reaction atmospheric pressure: 5-10 kPa,
By chemical vapor deposition under the above conditions, a TiCN layer having the predetermined constituent atom shared lattice point morphology (unit morphology) can be formed.

Further, the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more formed by vapor deposition in the above is 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. In the TiCN layer that occupies, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and further. The TiCN layer in which the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ5 is 30% or less of the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ3 to Σ29 is subjected to chemical vapor deposition. It can be formed by performing under limited conditions.
For example, the conditions are as follows.
Reaction gas composition _{(volume%): TiCl 4 2~3%,} CH 3 CN 0.5~0.8%, N 2 25~45%, HCl 0.08% ~0.15%, Ar 5~10% , Remaining H ₂ ,
Reaction atmosphere temperature: 820-900 ° C,
Reaction atmospheric pressure: 5-7 kPa,
By chemical vapor deposition under the above conditions, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more is 80, which is the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 or more. The grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29. Further, the TiCN layer in which the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ5 is 30% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29 is formed. Can be done.

Aspect ratio of crystal grains of at least one TiCN layer in the lower layer:
The lower TiCN layer having a specific constituent atom shared lattice point morphology (unit morphology) formed by the chemical vapor deposition method has a columnar vertically long structure.
For example, the area ratio occupied by the columnar vertically elongated TiCN crystal grains having an aspect ratio of 3 or more obtained from the maximum particle width W of the TiCN crystal grains of the TiCN layer and the maximum particle length L in the layer thickness direction is the longitudinal section of the TiCN layer. It is 80 area% or more of the surface area, and an excellent effect of improving wear resistance, which is a characteristic of columnar vertically long structures, can be expected.
The maximum particle width W and the maximum particle length L are the crystals in the direction perpendicular to the layer thickness direction when one crystal grain in the vertical cross section of the TiCN layer is measured for the columnar vertically elongated TiCN crystal grains. The largest value in the grain width (short side) is called the maximum particle width W, while the largest value in the height (long side) of the crystal grains in the layer thickness direction is called the maximum particle length L.
The distribution of the maximum grain width W is calculated in the vertical cross section of the TiCN layer, and the value showing the maximum peak in the distribution is preferably 0.3 to 1.0 μm, and the maximum peak value of the W distribution is 0.3. TiCN crystal grains of less than less than can not be expected to have an excellent effect of improving wear resistance, which is a characteristic of columnar longitudinal structures, and when the maximum peak value of W distribution is greater than 1.0, TiCN crystal grains become coarse grains and are hard. It is easy to cause chipping of the coating layer.

Upper layer:
_{An α-Al 2} O ₃ layer of the upper layer is formed on the surface of the lower layer formed above by a conventionally known chemical vapor deposition method, but if the average layer thickness of the upper layer is less than 1 μm, it is long-term. It is not possible to exhibit excellent wear resistance over use, and on the other hand, if it exceeds 15 μm, chipping is likely to occur. Therefore, the layer thickness of the upper layer is set to 1 to 15 μm.

According to the present invention, the hard coating layer has a lower layer formed on the surface of the tool substrate and an upper layer formed on the lower layer, and the lower layer is TiC, TiN, TiCN, TiCO, TiCNO. Of these, two or more Ti compound layers are formed, and at least one of them is a TiCN layer, and the TiCN layer is a corresponding grain composed of each constituent atomic shared lattice point occupying the total corresponding grain boundary length. In the corresponding grain boundary distribution graph showing the ratio of boundary lengths, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more is of the constituent atom shared lattice point form (unit form) of Σ3 or more. It occupies 80% of the grain boundary length, or further, the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ3 is the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29. It is 20% or less, and the grain boundary length of the constituent atomic shared lattice point form (unit form) of Σ5 is 30% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29. As a result, many grain boundaries with high toughness are distributed in the TiCN layer.
Therefore, in the covering tool of the present invention, even when cutting of steel, stainless steel, etc. is performed under high-speed high-cutting intermittent conditions or high-speed high-feed intermittent conditions in which a high load intermittently or impactfully acts on the cutting edge. The occurrence of chipping and peeling of the hard coating layer is suppressed, and excellent cutting performance is exhibited over a long period of use.

One example of a constituent atom shared lattice point distribution graph showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the total corresponding grain boundary length of the TiCN layer of the lower layer of the coating tool of the present invention. Is shown. Constituent atom shared lattice showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the corresponding grain boundary lengths of Σ3 to Σ29 of the TiCN layer of the lower layer of the coating tool of the present invention shown in FIG. A point distribution graph is shown. Another example of the constituent atom shared lattice point distribution graph showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the total corresponding grain boundary length of the TiCN layer of the lower layer of the coating tool of the present invention. Is shown. Constituent atomic shared lattice points showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the corresponding grain boundary lengths of Σ3 to Σ29 of the TiCN layer of the lower layer of the coating tool of the present invention shown in FIG. The distribution graph is shown. One example of a constituent atom shared lattice point distribution graph showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the total corresponding grain boundary length of the TiCN layer in the lower layer of the comparative coating tool. show.

The covering tool of the present invention will be specifically described with reference to Examples.

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 D were produced, respectively.

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, ZrC powder, TaC 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. 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 E made of TiCN-based cermet having an insert shape of ISO standard CNMG120412 was prepared.

Then, each of these tool bases A to D and tool base E was charged into a normal chemical vapor deposition apparatus, and a hard coating layer was formed by the following steps.
(A) First, a Ti compound layer as a lower layer of the target layer thickness shown in Table 6 was deposited and formed under the conditions shown in Table 3.
(B) However, when forming at least one TiCN layer among the lower layers, the TiCN layer was vapor-deposited under the conditions A to D shown in Table 4.
(C) Next, under the conditions shown in Table 3, an α-Al ₂ O ₃ layer as an upper layer of the target layer thickness shown in Table 8 was deposited and formed.
In the steps (a) to (c) above, the coating tools 1 to 13 of the present invention having the hard coating layers shown in Tables 6 and 8, respectively, were manufactured.

Further, for the purpose of comparison, Comparative Example Coating Tools 1 to 13 having the Hard Coating Layers shown in Tables 7 and 9 are deposited by depositing a hard coating layer under conditions other than the manufacturing conditions of the coating tools 1 to 13 of the present invention. Was manufactured respectively.
Specifically, in forming the lower layer in the manufacturing steps (a) and (b) of the covering tools 1 to 13 of the present invention, the conditions a to d shown in Table 5 are formed when forming the TiCN layer among the lower layers. The TiCN layer shown in Table 7 was vapor-deposited.

Next, for the covering tools 1 to 13 of the present invention and the covering tools 1 to 13, at least one TiCN layer among the lower layers is a constituent atom shared lattice point distribution graph using a field emission scanning electron microscope. Was created respectively.
That is, the constituent atom shared lattice point distribution graph is set in the lens barrel of the electric field emission type scanning electron microscope with the vertical cross section of the lower TiCN layer as the polished surface, and is incident on the polished surface at 70 degrees. An electron beam with an acceleration voltage of 15 kV at an angle is irradiated with an irradiation current of 1 nA for each crystal grain existing within the measurement range of the vertical cross-section polished surface, and an electron rear scattering diffraction image device is used to irradiate a region of 30 × 50 μm. The inclination angle formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, was measured with respect to the normal line of the surface of the tool substrate at an interval of 0.1 μm / step. Distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains at the interface of the crystal grains adjacent to each other based on the obtained measurement inclination angle. Is calculated, and there are N lattice points that do not share a constituent atom between the constituent atom shared lattice points (N is an even number of 2 or more on the crystal structure of the NaCl-type surface-centered cubic crystal). When (unit form) is expressed as ΣN + 1, it was created by finding the ratio of the grain boundary length to the entire ΣN + 1 (however, the upper limit is set to N = 28 due to the frequency).
For the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more, the value obtained by subtracting the total of the grain boundary lengths of Σ3 to Σ29 from the total grain boundary length of Σ3 or more obtained by the measurement is subtracted. , Σ31 or more was calculated as the total grain boundary length.

In the TiCN layer of the lower layer obtained as a result, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more becomes the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 or more. The ratio of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and the configuration of Σ5. Tables 8 and 9 show the ratio of the grain boundary length of the atomic shared lattice point form (unit form) to the grain boundary length of the constituent atomic shared lattice point forms (unit form) of Σ3 to Σ29.

In FIG. 1, the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. An example of the constituent atom shared lattice point distribution graph of the TiCN layer of the invention covering tool 1 is shown.
FIG. 2 shows the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the corresponding grain boundary lengths of Σ3 to Σ29 of the TiCN layer of the coating tool 1 of the present invention. A point distribution graph is shown. In FIG. 2, it can be seen that the ratio of Σ3 to the corresponding grain boundary lengths of Σ3 to Σ29 is 26% and the ratio of Σ5 is 18%.
In FIG. 3, the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ31 or more occupies 80% or more of the grain boundary length of the constituent atom shared lattice point form (unit form) having Σ3 or more. An example of the constituent atom shared lattice point distribution graph of the TiCN layer of the coating tool 2 of the present invention is shown. As shown in FIG. 4, the grain boundary of the constituent atom shared lattice point form (unit form) of Σ3 of the covering tool 2 of the present invention The length is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ5 is Σ3 to Σ3 to Σ5. It can be seen that it is 30% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ29.

As shown in Table 8, the TiCN layer of the lower layer of the covering tool of the present invention has a constituent atom shared lattice point form (unit form) having a grain boundary length of Σ31 or more and a constituent atom shared lattice point form (unit form) of Σ3 or more. It is 80% or more of the grain boundary length of the unit form), and in some cases, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 is the constituent atom shared lattice point form of Σ3 to Σ29 (unit form). The grain boundary length of the constituent atom shared lattice point form (unit form) of Σ5 is 20% or less of the grain boundary length of the unit form), and the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29 is It was less than 30% of the world leader.
On the other hand, as shown in Table 9, for the TiCN layer of the comparative example covering tool, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more is shared by the constituent atoms of Σ3 or more. It was less than 80% of the grain boundary length of the lattice point form (unit form).
Note that FIG. 5 is a composition atom shared lattice point distribution graph showing the ratio of the grain boundary length of each constituent atom shared lattice point form (unit form) to the total corresponding grain boundary length of the TiCN layer of the comparative example covering tool 1. Although one example is shown, the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ31 or more was 60% of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 or more. ..

Further, when the thickness of each constituent layer of the hard coating layer of the coating tools 1 to 13 of the present invention and the coating tools 1 to 13 of the comparative example was measured in a vertical cross section using a scanning electron microscope, the target layer thickness and the substance were all measured. The same average layer thickness (average value of 5-point measurement) was shown.
The results are shown in Tables 6 to 9.

Further, regarding the vertical cross section of the TiCN layer of the lower layer of the covering tools 1 to 13 of the present invention and the comparative covering tools 1 to 13, using a scanning electron microscope (magnification 5000 times), 10 μm in the direction parallel to the surface of the tool substrate. The maximum particle width W and the maximum particle length L are measured for each of the TiCN crystal grains existing in the region at the height of the layer thickness of the TiCN layer in the direction perpendicular to the tool substrate, the distribution is calculated, and the maximum particle width is calculated. A value indicating the maximum peak of the distribution of W was calculated. The value of the aspect ratio L / W was determined for each of the TiCN crystal grains, and the area ratio of the crystal grains having the aspect ratio L / W of 3 or more to the vertical cross section of the TiCN layer was determined.
The results are shown in Tables 8 and 9.

Next, with respect to the various covering tools of the covering tools 1 to 13 of the present invention and the covering tools 1 to 13 of the comparative example, all of them are screwed to the tip of the tool steel cutting tool with a fixing jig.
Work material: JIS / SUS630 with 4 vertical grooves at equal intervals in the length direction,
Cutting speed: 300m / min,
Notch: 3.0 mm,
Feed: 0.3mm / rev,
Cutting time: 5 minutes,
Under the conditions (referred to as cutting condition A), a wet high-speed intermittent high-cutting cutting test for stainless steel (normal cutting speed and cutting are 70 m / min and 2.0 mm, respectively).
Work material: JIS / S60C with 4 vertical grooves at equal intervals in the length direction,
Cutting speed: 300m / min,
Notch: 1.5 mm,
Feed: 1.0 mm / rev,
Cutting time: 5 minutes,
Under the conditions (referred to as cutting condition B), wet high-speed intermittent high-feed cutting test of high carbon steel (normal cutting speed and feed amount are 100 m / min and 0.3 mm / rev, respectively).
In each cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 10.

From the results shown in Table 10, the coating tools 1 to 13 of the present invention have excellent chipping resistance because the TiCN layer of the lower layer thereof has excellent toughness, and show excellent cutting performance over a long period of use. rice field.
On the other hand, it is clear that the coating tools 1 to 13 of Comparative Examples reach their service life in a relatively short time due to chipping and peeling of the hard coating layer in high-speed intermittent heavy cutting.

As described above, the coating tool of the present invention chips and peels the hard coating layer even under severe cutting conditions such as high-speed high-cutting and high-feed heavy cutting such as carbon steel and stainless steel in which a high load acts on the cutting edge. Since it exhibits excellent cutting performance over a long period of use, it is fully satisfactory for improving the performance of cutting equipment, labor saving and energy saving of cutting processing, and cost reduction. It can be done.

Claims (2)

In a surface-coated cutting tool in which a hard coating layer consisting of a lower layer and an upper layer is provided on the surface of a tool substrate made of a tungsten carbide-based cemented carbide or a titanium nitride-based cermet.
(A) The lower layer is a Ti compound layer having a total average layer thickness of 3 to 20 μm and composed of one layer or two or more layers of TiC, TiN, TiCN, TiCO, and TiCNO. At least one layer is composed of TiCN layer,
_{(B) The upper layer is composed of an Al 2} O ₃ layer having an average layer thickness of 1 to 15 μm and an α-type crystal structure.
(C) At least one TiCN layer of the lower layer is irradiated with an electron beam for each crystal grain existing within the measurement range of the vertical cross section of the at least one TiCN layer using an electric field emission scanning electron microscope. Using an electron rear scattering diffraction image device, the normals of the (001) and (011) planes, which are the crystal planes of the crystal grains, with respect to the normals of the surface of the substrate in a predetermined region at intervals of 0.1 μm / step. The inclination angle formed by the grains was measured, and in this case, the crystal grains had a NaCl-type surface-centered cubic crystal structure in which constituent atoms composed of Ti, carbon, and nitrogen were present at the lattice points, respectively, and the result was obtained. Based on the measurement inclination angle, the distribution of lattice points (constituent atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated at the interface of the crystal grains adjacent to each other. At the same time, when the distribution ratio of each of the constituent atom shared lattice point forms (unit forms) represented by ΣN + 1 defined for each number N of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points is calculated. In the corresponding grain boundary distribution graph showing the ratio of the corresponding grain boundary length consisting of each constituent atom shared lattice point to the total corresponding grain boundary length, the grains in the constituent atom shared lattice point form (unit form) having Σ31 or more. The boundary length occupies 80% or more of the grain boundary length of the constituent atomic shared lattice point form (unit form) having Σ3 or more.
(D) A surface-coated cutting tool characterized in that TiCN crystal grains having an aspect ratio of 3 or more occupy an area ratio of 80% or more in the vertical cross section of at least one TiCN layer. With respect to at least one TiCN layer of the lower layer, an electric field emitting scanning electron microscope is used to irradiate each crystal grain existing within the measurement range of the longitudinal cross section of the at least one TiCN layer with an electron beam, and electron rearward. Using a scattering diffraction imager, the inclination formed by the normal lines of the (001) plane and the (011) plane, which are the crystal planes of the crystal grains, with respect to the normal line of the substrate surface at intervals of 0.1 μm / step in a predetermined region. The angle is measured, and in this case, the crystal grain has a NaCl-type surface-centered cubic crystal structure in which constituent atoms consisting of Ti, carbon, and nitrogen are present at the lattice points, respectively, and the measurement inclination angle obtained as a result is obtained. Based on, at the interface of crystal grains adjacent to each other, the distribution of lattice points (constituting atom shared lattice points) in which each of the constituent atoms shares one constituent atom between the crystal grains is calculated, and the above Σ3 when calculating the distribution ratio of each of the constituent atom shared lattice point forms (unit forms) represented by ΣN + 1 defined for each number N of lattice points that do not share the constituent atoms existing between the constituent atom shared lattice points. The grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29 is 20% or less of the grain boundary length of the constituent atom shared lattice point form (unit form) of Σ3 to Σ29, and the constituent atom shared lattice of Σ5. The surface coating cutting according to claim 1, wherein the grain boundary length of the point form (unit form) is 30% or less of the grain boundary length of the constituent atomic shared lattice point forms (unit form) of Σ3 to Σ29. tool.

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