JP5995082B2 - A surface-coated cutting tool with a hard coating layer that exhibits excellent peeling and chipping resistance in high-speed intermittent cutting. - Google Patents

Description

  This invention has excellent resistance to peeling even when various cutting processes such as steel and cast iron are performed at high speed and under intermittent cutting conditions in which intermittent and impact loads are applied to the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that exhibits chipping resistance and exhibits excellent wear resistance 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 referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet. ,
(A) The lower layer is a Ti carbide (hereinafter referred to as TiC) layer, a nitride (hereinafter also referred to as TiN) layer, a carbonitride (hereinafter referred to as TiCN) layer, a carbon oxide (hereinafter referred to as TiCO). And a Ti compound layer composed of one or more of a carbonitride oxide (hereinafter referred to as TiCNO) layer,
(B) an aluminum oxide layer (hereinafter, referred to as an Al ₂ O ₃ layer) having an α-type crystal structure in a state where the upper layer is chemically vapor-deposited;
A coated tool formed by vapor-depositing the hard coating layer constituted by (a) and (b) is known.

However, the above-mentioned conventional coated tools exhibit excellent wear resistance in continuous cutting and intermittent cutting of various steels and cast irons, for example, but when this is used for high-speed intermittent cutting, peeling and chipping are not possible. There was a problem that it was easy to occur and the tool life was shortened.
Therefore, various proposals have been made for the layer structure of the hard coating layer for the purpose of suppressing the peeling and chipping of the coating layer.

For example, as shown in Patent Document 1, at least one of a TiC layer, a TiN layer, and a TiCN layer having a flat surface property as an inner layer is formed on the surface of the tool base, and a surface property is flat as an outer layer. In a coated tool coated with a new Al ₂ O ₃ layer, by forming at least one of a TiCO layer and a TiCNO layer having a sharpened needle crystal surface as an intermediate layer between the inner layer and the outer surface, the anti-resistance It has been proposed to improve chipping.

Further, for example, as shown in Patent Document 2, in a coated tool in which a multilayer hard coating layer is formed on the surface of a tool base, an oxide layer made of Al ₂ O ₃ or the like as the hard coating layer, and the oxidation Comprising a reinforcing layer made of Ti carbide or the like provided directly under the physical layer, the unevenness difference of the interface between the oxide layer and the reinforcing layer being 0.2 μm or more, and the average interval between the convex portions being 3 μm or less. It has been proposed to prevent breakage and peeling of the hard coating layer by improving the adhesion of the layer.

  For example, as shown in Patent Document 3, a lower layer made of an adhesive Ti compound layer and a modified titanium carbonitride layer and an upper layer made of a thickened modified α-type aluminum oxide layer are formed on the surface of the tool base. In the provided coated tool, for the modified titanium carbonitride layer of the lower layer, when the inclination angle formed by the normal of the {112} plane of the crystal grain is measured and totaled with respect to the normal of the surface polished surface, 0 The highest peak exists in the tilt angle section of -10 degrees, and the frequency ratio in the tilt angle section is 45% or more of the whole, and the thickened modified α-type aluminum oxide layer has a surface polished surface. When the inclination angle formed by the (0001) normal line of the crystal grain is measured and aggregated with respect to the normal line, the highest peak exists in the inclination angle section within the range of 0 to 10 degrees, and the inclination angle Chipping resistance by making the frequency ratio in the category 45% or more of the whole It has been proposed to improve the performance.

Further, for example, as shown in Patent Document 4, on the surface of the tool base, an adhesive Ti compound layer and a lower layer composed of a modified Ti carbonitride layer having a vertically grown crystal structure, and an Al ₂ O ₃ layer In the coated tool having the upper layer formed thereon, with respect to the modified Ti-based carbonitride layer, the {112} plane, the {110} plane, and the {111} are the crystal planes of the crystal grains with respect to the normal line of the surface polished surface. } The inclination angle formed by each normal of the surface is measured, and the measured inclination angles for the {112}, {110}, and {111} planes are 0 to 10 degrees with respect to the normal of the surface polished surface. When the total area of each crystal grain within the range of the inclination angle is A, B, and C, respectively, the values of A / B and A / C are 2 to 8, respectively. By forming a modified Ti carbonitride layer, chipping resistance, abrasion resistance It has been proposed to improve the resistance.

Japanese Patent No. 3250134 Japanese Patent Laid-Open No. 11-229144 JP 2006-315154 A JP 2009-166195 A

In recent years, there has been a strong demand for labor saving and energy saving and further cost reduction for cutting work, and along with this, cutting speed has been further increased, and high load tends to act on the cutting edge in intermittent cutting etc. In the conventional coated tools shown in the above-mentioned patent documents 1 to 4, there is no problem when this is used for continuous cutting or interrupted cutting under normal conditions such as steel or cast iron. When used in the above, the adhesion strength between the Ti compound layer and the Al ₂ O ₃ layer constituting the hard coating layer becomes insufficient, and due to the occurrence of abnormal damage such as peeling and chipping between the upper layer and the lower layer, The current situation is that the service life is reached in a short time.

In view of the above, the present inventors have improved the adhesion strength of the lower layer made of the Ti compound layer and the upper layer made of the Al ₂ O ₃ layer, thereby causing abnormal damage such as peeling and chipping. As a result of earnest research to improve tool life and prevent tool life,
A lower layer made of a Ti compound layer is formed as a three-layer structure of a base Ti compound layer, an adhesive TiCN layer, and an upper TiCN layer, and the adhesive TiCN layer is configured as a layer having a wedge-shaped crystal structure. In addition, the normal of the {110} plane of the crystal grains of the layer has a specific inclination angle number distribution, and the normal of the {112} plane of the crystal grains of the layer is also applied to the upper TiCN layer. It has been found that the adhesive strength of the entire lower layer is improved by improving the adhesiveness between the adhesive TiCN layer and the upper TiCN layer in the case of taking a specific inclination angle number distribution.
Therefore, if a coated tool with such a hard coating layer is used for high-speed intermittent cutting that is accompanied by high heat generation and intermittent / impact high loads are applied to the cutting edge, peeling, chipping, etc. It has been found that the occurrence of abnormal damage can be suppressed and that excellent cutting performance is exhibited over a long period of use.

This 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 vapor-deposited on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
(A) The lower layer has a total average layer thickness of 3 to 20 μm, and has a three-layer structure of a base Ti compound layer, an adhesive TiCN layer, and an upper TiCN layer, and the upper layer has a thickness of 2 to 15 μm. And an Al ₂ O ₃ layer having an α-type crystal structure in the state of chemical vapor deposition,
(B) The underlying Ti compound layer of the lower layer is composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer, and the total average layer thickness is 0.5-2. 5 μm,
(C) The adhesive TiCN layer of the lower layer has a wedge-shaped crystal structure, the average height difference of the concave and convex portions of the wedge-shaped crystal structure is 1 to 3 μm, the average interval of the convex portions is 1 to 3 μm, With respect to the TiCN crystal grains having the wedge-shaped crystal structure, using a field emission scanning electron microscope and an electron beam backscattering diffractometer, each crystal grain having a cubic crystal lattice existing within the measurement range of the cross-sectional polished surface has electrons. The angle of inclination formed by the normal of the {110} plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface of the tool base. When the measured inclination angle within the range of degrees is divided into pitches of 0.25 degrees and the frequency existing in each division is represented by an inclination angle number distribution graph, the range of 0 to 10 degrees The highest peak exists in the tilt angle section, and The total of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees occupies a ratio of 40% or more of the entire degrees in the inclination angle frequency distribution graph,
(D) The upper TiCN layer of the lower layer is irradiated with an electron beam to each crystal grain having a cubic crystal lattice existing within the measurement range of the cross-sectional polished surface, and the normal line on the surface of the tool base is Then, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured, and the measurement inclination angle within the range of 0 to 45 degrees out of the measurement inclination angles is set to a pitch of 0.25 degrees. When it is divided into each, and is represented by an inclination angle distribution graph obtained by counting the frequencies existing in each division, the highest peak exists in the inclination angle division within the range of 0 to 10 degrees, and 0 to 10 A surface-coated cutting tool characterized in that the sum of the frequencies existing in the inclination angle division within the range of degrees occupies a ratio of 60% or more of the entire degrees in the inclination angle frequency distribution graph.
(2) The surface-coated cutting tool according to (1), wherein the wedge-shaped crystal structure of (c) is composed of an aggregate of TiCN crystal grains having an average particle diameter of 0.05 to 1 μm. . "
It has the characteristics.

Hereinafter, the constituent layers of the hard coating layer of the coated tool of the present invention will be described in detail.
Lower layer:
As shown in the schematic longitudinal sectional view of FIG. 1, the lower layer of the present invention has a total average layer thickness of 3 to 20 μm, and has a three-layer structure of a base Ti compound layer, an adhesive TiCN layer and an upper TiCN layer. Configured as
The lower layer basically exists as a lower layer of an Al ₂ O ₃ (hereinafter simply referred to as “Al ₂ O ₃ ”) layer having an α-type crystal structure, and is hard due to its excellent high-temperature strength. In addition to the high temperature strength of the coating layer, the coating layer is in close contact with both the tool substrate and the Al ₂ O ₃ layer, and has an effect of maintaining the adhesion of the hard coating layer to the tool substrate.
However, if the total average layer thickness of the lower layer is less than 3 μm, the above-mentioned effect cannot be sufficiently exerted. On the other hand, if the total average layer thickness exceeds 20 μm, the thermoplastic deformation is caused particularly in high-speed intermittent cutting with high heat generation. Since it becomes easy to occur and this causes uneven wear, the total average layer thickness of the lower layer was determined to be 3 to 20 μm.

(A) The underlying Ti compound layer of the lower layer:
An underlayer Ti compound layer is formed immediately above the surface of the tool substrate. The underlayer Ti compound layer is one or more of TiC layers, TiN layers, TiCN layers, TiCO layers, and TiCNO layers that are conventionally known. For example, it can be formed by a chemical vapor deposition method well known to those skilled in the art.
However, when the total average layer thickness of the underlying Ti compound layer is less than 0.5 μm, the level difference of the concave and convex portions of the wedge-shaped crystal structure cannot be obtained sufficiently, and the upper TiCN layer formed on this Adhesive strength cannot be obtained sufficiently. On the other hand, if the total average layer thickness exceeds 2.5 μm, the slope formed by the normal of the {110} plane that is the crystal plane of the adhesive TiCN crystal grains of the lower layer When the angle is measured, the sum of the frequencies existing in the tilt angle section within the range of 0 to 10 degrees does not exceed 40% of the total power in the tilt angle frequency distribution graph, and a desired orientation pattern cannot be obtained. Therefore, the total average layer thickness of the base Ti compound layer needs to be 0.5 to 2.5 μm.

(B) Adhesive TiCN layer of the lower layer:
An adhesive TiCN layer is formed on the above-mentioned base Ti compound layer. The adhesive TiCN layer has a unique structure called a wedge-shaped crystal structure, and {110 of crystal grains constituting the adhesive TiCN layer. } When the inclination angle formed by the normal of the surface to the normal of the surface of the tool base is measured, a specific distribution of the number of inclination angles is shown.
The wedge-shaped crystal structure will be described below. TiCN crystal grains whose inclination angle formed by the normal of the {110} plane grown on the underlying Ti compound layer of the lower layer is within the range of 0 to 10 degrees with respect to the normal of the surface of the tool base are adjacent to each other. The angle at which the normals of the {112} planes intersect at the interface between the crystal grains is obtained, and when the angle difference is in the range of less than 20 degrees, each has a wedge-shaped crystal structure, and the range of the angle difference In the case of deviating from the above, the crystal grain boundary becomes a part that separates the wedge-shaped crystal structure and the upper TiCN crystal grains described later.
In addition, as shown in the schematic longitudinal cross-sectional schematic diagram of a hard coating layer in FIG. 1, the wedge-shaped crystal structure said by this invention is formed with the aggregate | assembly of the TiCN crystal grain which has various particle sizes, The entire wedge-shaped crystal structure is defined as a structure having irregularities in the film thickness direction.
That is, the adhesive TiCN layer first has a wedge-shaped crystal structure on the surface facing the upper TiCN layer, and the average height difference of the concave and convex portions of the wedge-shaped crystal structure is 1 to 3 μm. The average interval between the convex portions is 1 to 3 μm.
The adhesive TiCN layer is provided with the wedge-shaped crystal structure as described above, thereby improving the adhesion strength with the upper TiCN layer formed thereon. As a result, the chipping resistance and resistance of the hard coating layer are improved. The peelability is improved.
However, when the average height difference of the concave and convex portions of the wedge-shaped crystal structure is less than 1 μm,
If the surface area of the contact interface between the TiCN crystal grains constituting the wedge-shaped crystal structure and the upper TiCN layer formed thereon cannot be increased, and the average height difference exceeds 3 μm, the upper portion that grows on the upper layer Since the orientation of the TiCN layer does not become a desired one, the average height difference of the concave and convex portions of the wedge-shaped crystal structure needs to be 1 to 3 μm.
In addition, when the average interval between the convex portions of the wedge-shaped crystal structure is less than 1 μm, pores are easily formed at the interface between the concave portion of the wedge-shaped crystal structure and the upper TiCN layer growing on the upper portion thereof. When the distance exceeds 3 μm, it is not possible to increase the surface area of the interface between the TiCN crystal grains of the adhesive TiCN layer constituting the wedge-shaped crystal structure and the TiCN crystal grains of the upper TiCN layer. Is required to be 1 to 3 μm.
Further, the wedge-shaped crystal structure is formed by an aggregate of TiCN crystal grains having various grain sizes. When the average grain size of individual TiCN crystal grains constituting the aggregate is less than 0.05 μm, the lower layer is formed. Adhesive strength of the surface of the underlying Ti compound layer to the surface becomes worse, so that the adhesion strength between the underlying Ti compound layer of the lower layer and the adhesive TiCN layer decreases, while the average particle diameter of the individual TiCN crystal grains constituting the aggregate When the thickness exceeds 1 μm, the grain size of the TiCN crystal grains of the upper TiCN layer formed thereon becomes large, the chipping resistance decreases, and the TiCN crystal of the adhesive TiCN layer constituting the wedge-shaped crystal structure The pores are easily formed at the interface between the grains and the TiCN crystal grains of the upper TiCN layer, so that the hardness and strength are reduced, and the adhesion strength between the adhesive TiCN layer and the upper TiCN layer is reduced. Therefore, the average grain size of the TiCN crystal grains of the adhesive TiCN layer constituting the wedge-shaped crystal structure is preferably in the range of 0.05 to 1 μm.

Next, the above-mentioned adhesive TiCN layer is present within the measurement range of the cross-sectional polished surface of the layer, using a field emission scanning electron microscope and an electron beam backscatter diffraction device, for the TiCN crystal grains constituting the layer. Each crystal grain having a cubic crystal lattice is irradiated with an electron beam, and the inclination angle formed by the normal of the {110} plane which is the crystal plane of the crystal grain is measured with respect to the normal of the surface of the tool base. In the inclination angle distribution graph, the measurement inclination angles within the range of 0 to 45 degrees among the measurement inclination angles are divided for each pitch of 0.25 degrees, and the frequencies existing in each division are totaled. When created, the highest peak is present in the inclination angle section within the range of 0 to 10 degrees, and the total of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is the entire frequency in the inclination angle distribution graph. Of inclination angle that occupies 40% or more of It is shown.
Here, in the inclination angle number distribution graph, when the highest peak does not exist in the inclination angle section within the range of 0 to 10 degrees, or the sum of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is In the case where the ratio is less than 40% of the entire frequency in the inclination angle number distribution graph, the adhesion strength with the upper TiCN layer formed on the adhesive TiCN layer is lowered, and desired peeling resistance is obtained. For the TiCN crystal grains of the adhesive TiCN layer, in the inclination angle number distribution graph, the highest peak exists in the inclination angle section in the range of 0 to 10 degrees, and the range of 0 to 10 degrees. It is necessary to show an inclination angle number distribution in which the total of the frequencies existing in the inclination angle section occupies a ratio of 40% or more of the entire degrees in the inclination angle number distribution graph.
The adhesive TiCN layer having the wedge-shaped crystal structure and having the inclination angle number distribution form can be formed by, for example, chemical vapor deposition conditions described later.
FIG. 2 shows an example of an inclination angle number distribution graph obtained by measuring the adhesive TiCN layer.

(C) Lower TiCN upper TiCN layer:
The upper TiCN layer can be formed on the adhesive TiCN layer by, for example, chemical vapor deposition conditions described later. For the upper TiCN layer, a cubic crystal lattice existing within the measurement range of the cross-sectional polished surface is formed. Each crystal grain is irradiated with an electron beam, and an inclination angle formed by a normal of a {112} plane which is a crystal plane of the crystal grain is measured with respect to a normal line of the surface of the tool base, and the measurement inclination angle When a measured inclination angle within a range of 0 to 45 degrees is divided for each pitch of 0.25 degrees, and an inclination angle number distribution graph formed by counting the frequencies existing in each section is 0 The highest peak exists in the inclination angle section within the range of -10 degrees, and the sum of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is 60% or more of the entire frequencies in the inclination angle distribution graph. Number of tilt angles that occupy a percentage Show the cloth.
Here, in the inclination angle number distribution graph, when the highest peak does not exist in the inclination angle section within the range of 0 to 10 degrees, or the sum of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is When the ratio is less than 60% of the entire frequency in the inclination angle number distribution graph, desired high-temperature hardness and heat resistance cannot be obtained.
Therefore, for the TiCN crystal grains of the upper TiCN layer, in the tilt angle number distribution graph, the highest peak exists in the tilt angle section within the range of 0 to 10 degrees, and the tilt angle section within the range of 0 to 10 degrees. It is necessary to show an inclination angle frequency distribution in which the sum of the frequencies existing in the graph occupies 60% or more of the entire frequency in the inclination angle frequency distribution graph.
FIG. 3 shows an example of an inclination angle number distribution graph obtained by measuring the upper TiCN layer.

(D) Formation of lower layer (underlying Ti compound layer, adhesive TiCN layer and upper TiCN layer) having a three-layer structure:
In the present invention, the lower layer having a three-layer structure can be formed by, for example, the following three-stage chemical vapor deposition method.
That is, as a first stage, a base Ti compound layer is formed by vapor deposition on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet, and then as a second stage, A lower layer having a three-layer structure can be formed by depositing an adhesive TiCN layer thereon and then depositing an upper TiCN layer as a third step.
More specifically, it is as follows.
≪First stage≫
Using a normal chemical vapor deposition apparatus, a TiC layer is formed on the surface of the tool base under normal conditions (for example, conditions as shown in Table 3 below) so that the total average layer thickness is 0.5 to 2.5 μm. One or more of the TiN layer, the TiCN layer, the TiCO layer, and the TiCNO layer are formed by vapor deposition.
≪Second stage≫
Then
Reaction gas composition (volume%): TiCl ₄ 3-5%, N ₂ 15-25%,
CH ₃ CN 0.2~0.5%, remainder _H 2,
Atmospheric temperature: 900-950 ° C.
Atmospheric pressure: 10-20 kPa,
Time: 5-60 min,
Vapor deposition is performed under the conditions.
The vapor deposition under the above conditions has a predetermined wedge-shaped crystal structure, and has a predetermined inclination angle number distribution form (that is, the normal of the {110} plane of the crystal grain is normal to the normal of the surface of the tool base) In the inclination angle distribution graph that measures and summarizes the inclination angle, the highest peak exists in the inclination angle section within the range of 0 to 10 degrees, and the frequency exists in the inclination angle section within the range of 0 to 10 degrees. Can occupy 40% or more of the entire frequency of the inclination angle number distribution graph).
≪Third stage≫
Then
Reaction gas composition (volume%): TiCl ₄ 3-5%, N ₂ 15-25%,
CH ₃ CN 0.6~1.0%, remainder _H 2,
Atmospheric temperature: 800-900 ° C
Atmospheric pressure: 3-10 kPa,
Time: (until the target total average layer thickness is reached)
The upper TiCN layer is deposited under the conditions.
Then, by vapor deposition under the above conditions, the inclination angle number distribution form (that is, the inclination angle obtained by measuring and counting the inclination angle formed by the normal of the {112} plane of the crystal grain with respect to the normal of the surface of the tool base) In the number distribution graph, the highest peak exists in the inclination angle section within the range of 0 to 10 degrees, and the total of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is the sum of the inclination angle number distribution graph. An upper TiCN layer having a ratio of 60% or more of the entire frequency) can be deposited.
The lower layer having the three-layer structure formed as described above has a unique structure called an adhesive TiCN layer called a wedge-shaped crystal structure, and the normal of the {110} plane of the crystal grains constituting the adhesive TiCN layer is When the inclination angle formed with respect to the normal of the surface of the substrate is measured, the ratio of the total frequency existing in the inclination angle section within the range of 0 to 10 degrees is 40% or more of the entire frequency in the inclination angle frequency distribution graph. The upper TiCN layer measures the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, and the sum of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees is the inclination angle. It has a feature that it accounts for 60% or more of the total frequency in the number distribution graph. When the values of the total ratio of the frequencies indicated by the respective layers cannot obtain these values, the bond between the adhesive TiCN layer and the upper TiCN layer becomes weak, and a desired adhesion strength cannot be obtained.

(E) Upper Al ₂ O ₃ layer:
On the lower layer formed by vapor deposition above, for example, using a normal chemical vapor deposition apparatus,
Reaction gas composition (volume%): AlCl ₃ 1-3%, CO ₂ 3-7%,
HCl 1.0-2.5%, H ₂ S 0.1-0.25%, balance H ₂ ,
Reaction atmosphere temperature: 980-1020 ° C.
Reaction atmosphere pressure: 3 to 10 kPa,
Time: (until the target upper layer thickness is reached)
By vapor deposition under the conditions, an upper layer composed of an Al ₂ O ₃ layer can be formed by vapor deposition.
Here, the upper layer includes an adhesive TiCN layer having a specific wedge-shaped crystal structure and having a specific inclination angle number distribution form, and further an upper TiCN layer having a specific inclination angle number distribution form. By forming the upper layer by vapor deposition, the adhesion strength between the adhesive TiCN layer and the upper TiCN layer is improved, so that the adhesion strength of the entire lower layer is improved. In addition, when the normal of the {112} plane of the crystal grain has a specific inclination angle number distribution on the outermost surface of the lower layer, the adhesion strength is improved by maintaining an epitaxial relationship with the upper layer grown thereon. At the same time, the strength of the coating layer itself is improved. As a result, excellent peeling resistance and chipping resistance are exhibited even in high-speed intermittent cutting with high heat generation and impact and intermittent high load acting on the cutting edge.
If the average layer thickness of the upper layer is less than 2 μm, excellent high-temperature strength and high-temperature hardness cannot be exhibited over a long period of use, whereas if it exceeds 15 μm, chipping is likely to occur. The layer thickness of the upper layer was determined to be 2 to 15 μm.

  The coated tool of the present invention is a hard coating layer composed of a lower layer and an upper layer, wherein the lower layer is formed as a three-layer structure of a base Ti compound layer, an adhesive TiCN layer and an upper TiCN layer, and the adhesive TiCN layer Has a specific wedge-shaped crystal structure and a specific inclination angle number distribution form, and since the upper TiCN layer also has a specific inclination angle number distribution form, the adhesion strength between the lower layers is increased, and the hard layer is hard. The strength of the coating layer itself is also improved. As a result, it is accompanied by high heat generation, and it can be used for a long time without peeling or chipping even in high-speed intermittent cutting conditions where impact and intermittent high loads act on the cutting edge. Exhibits excellent cutting performance.

The schematic longitudinal cross-sectional schematic diagram of the hard coating layer of this invention coated tool is shown. The inclination angle number distribution graph of the TiCN crystal grain measured about the adhesive TiCN layer of this invention coated tool 1 is shown. The inclination angle number distribution graph of the TiCN crystal grain measured about the upper TiCN layer of this invention coated tool 1 is shown.

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

As raw material powders, WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder and Co powder all having an average particle diameter of 1 to 3 μm are prepared. Then, blended into the composition shown in Table 1, added with wax, ball mill mixed in acetone for 24 hours, dried under reduced pressure, and then press-molded into a green compact of a predetermined shape at a pressure of 98 MPa. Is vacuum-sintered at a predetermined temperature in the range of 1370 to 1470 ° C. for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge is subjected to honing of R: 0.07 mm. -WC base cemented carbide tool bases A to F each having an insert shape defined in CNMG12041 were manufactured.

In addition, as raw material powders, TiCN (mass ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder, all having an average particle diameter of 0.5 to 2 μm. Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and pressed into a compact at a pressure of 98 MPa. The green compact was sintered in a nitrogen atmosphere of 1.3 kPa at a temperature of 1540 ° C. for 1 hour, and after sintering, a chamfer with a width of 0.1 mm and an angle of 20 degrees at the cutting edge portion. By performing honing, tool bases a to f made of TiCN-based cermet having an ISO standard / CNMG120212 insert shape were formed.

Then, each of these tool bases A to F and tool bases a to f is charged into a normal chemical vapor deposition apparatus,
(A) First, Table 3 (l-TiCN in Table 3 indicates the conditions for forming a TiCN layer having a vertically elongated crystal structure described in JP-A-6-8010, and the other conditions are ordinary granularity. Under the conditions shown in Table 6), the underlying Ti compound layer of the lower layer is formed by vapor deposition at the target layer thickness shown in Table 6.
(B) Next, under the conditions shown in Table 4, the lower layer adhesive TiCN layer shown in Table 7 was formed by vapor deposition at a predetermined target layer thickness. Further, under the conditions shown in Table 5, the lower layer The upper TiCN layer shown in Table 7 is also formed by vapor deposition until a predetermined target total average layer thickness of
(C) Next, on the surface of the lower layer composed of the three-layer structure of the base Ti compound layer, the adhesive TiCN layer and the upper TiCN layer formed by vapor deposition as described above, the predetermined conditions shown in Table 7 are applied under the conditions shown in Table 3. By vapor-depositing an upper layer composed of an Al ₂ O ₃ layer with a target average layer thickness,
Invention coated tools 1 to 13 shown in Table 7 (however, see Table 6 for the base Ti compound layer of the hard coating layer) were produced.

  Moreover, for the purpose of comparison, after the underlayer Ti compound layer shown in Table 6 was formed by vapor deposition under the same conditions (conditions shown in Table 3) as those of the invention-coated tools 1-13, Comparative coating tools 1 to 13 shown in Table 8 (however, by depositing the adhesive TiCN layer and the upper TiCN layer under the conditions deviating from the step (b) (Tables 4 and 5 are shown as outside the present invention, respectively) For the underlying Ti compound layer, see Table 6).

Subsequently, the inclination angle number distribution of the TiCN crystal grains of the adhesive TiCN layer of the lower layer of the hard coating layer was measured using a field emission scanning electron microscope and an electron beam backscatter diffraction apparatus.
That is, 0.3 μm in the thickness direction of the adhesive TiCN layer from the interface between the adhesive TiCN layer of the lower layer of the present invention coated tools 1 to 13 and the comparative coated tools 1 to 13 and the underlying Ti compound layer, and the tool substrate A measurement range (1 μm × 50 μm) of a 50 μm cross-section polished surface in a direction parallel to the surface is set in a lens barrel of a field emission scanning electron microscope, and an electron with an acceleration voltage of 15 kV at an incident angle of 70 degrees on the polished surface. Using a field emission scanning electron microscope and an electron beam backscatter diffraction image apparatus, the line is irradiated with individual crystal grains having a cubic crystal lattice existing within the measurement range of each polished surface with an irradiation current of 1 nA. With respect to the TiCN crystal grains, the normal region of the {110} plane, which is the crystal plane of the crystal grains, with respect to the normal line of the surface of the tool base with a measurement region of 0.3 × 50 μm at an interval of 0.1 μm / step The angle of inclination An inclination angle number distribution obtained by measuring and dividing the measurement inclination angles within the range of 0 to 45 degrees among the measurement inclination angles for each pitch of 0.25 degrees and totaling the frequencies existing in each division It represented by a graph and calculated | required by measuring the sum total of the frequency of the crystal grain whose measurement inclination | tilt angle is 0-10 degree | times.
Tables 7 and 8 show these values.
In FIG. 2, the inclination angle number distribution graph of the TiCN crystal grain of the adhesive TiCN layer measured about this invention coated tool 1 is shown.

Moreover, about the crystal grain of the upper TiCN layer of the lower layer of the hard coating layer of the present coated tools 1 to 13 and the comparative coated tools 1 to 13, from the interface between the upper TiCN layer and the upper layer to the depth direction of the upper TiCN layer. The measurement range (1 μm × 50 μm) of the cross-section polished surface of 0.3 μm and 50 μm in the direction parallel to the surface of the tool base is measured using a field emission scanning electron microscope and an electron beam backscatter diffractometer. A {112} plane which is a crystal plane of the crystal grain with respect to the normal of the surface of the tool base by irradiating an electron beam to each crystal grain having a cubic crystal lattice existing within the measurement range of the polished surface The inclination angle formed by the normal line is measured, and the measurement inclination angle within the range of 0 to 45 degrees among the measurement inclination angles is divided for each pitch of 0.25 degrees, and the frequency existing in each division is determined. Represented by a graph of the distribution of the number of tilt angles It was determined by measuring the total frequency of crystal grains having an inclination angle of 0 to 10 degrees.
Tables 7 and 8 show these values.
In FIG. 3, the inclination angle number distribution graph of the TiCN crystal grain of the upper TiCN layer measured about this invention coated tool 1 is shown.

Moreover, about the crystal grain of the adhesive TiCN layer of the lower layer of the hard coating layer of the present invention coated tools 1 to 13 and comparative coated tools 1 to 13, using a field emission scanning electron microscope and an electron beam backscatter diffraction device, Similarly, by irradiating an electron beam to each crystal grain having a hexagonal crystal lattice existing within the measurement range of the cross-sectional polished surface, the average interval between the convex portions of the wedge-shaped crystal structure, the average height difference of the concave and convex portions, The average grain size of TiCN crystal grains constituting the wedge-shaped crystal structure was calculated.
The average interval between the convex portions of the wedge-shaped crystal structure is measured by measuring the distance between adjacent convex portions of the wedge-shaped crystal structure described in the present invention as shown in part a of FIG. It was set as the average space | interval of a convex part. The average height difference between the concave and convex portions of the wedge-shaped crystal structure was measured by measuring the distance between the concave portion of the crystal group and the adjacent convex portion described in the present invention as shown in part c of FIG. The value was defined as the average height difference of the uneven portions. The average grain size of the adhesive TiCN crystal grains constituting the wedge-shaped crystal structure is determined from the average of the measured values at the ten points of the horizontal line segment measurement points in the {110} -oriented TiCN crystal grains immediately above the lower Ti compound layer. The transverse average grain size of TiCN crystal grains constituting the shape crystal structure was determined.
Tables 7 and 8 show these values.

Furthermore, the thickness of each component layer of the hard coating layer of the present invention coated tools 1 to 13 and comparative coated tools 1 to 13 was measured (longitudinal section measurement) using a scanning electron microscope.
The structure of the adhesive TiCN layer and the upper TiCN layer will be described below.
For the adhesive TiCN layer, as shown in FIG. 1, the distance b from the interface with the underlying Ti compound layer to the apex of the concave portion of the wedge-shaped crystal structure in the film thickness direction, and the average height difference of the concave and convex portions of the wedge-shaped crystal structure c was measured, and the average value of each of the five measurements was shown in Tables 7 and 8.
For the upper TiCN layer, as shown in FIG. 1, the distance d from the interface with the Al ₂ O ₃ layer to the convex vertex of the wedge-shaped crystal structure of the adhesive TiCN layer is measured in the film thickness direction. The average values of the measurements are shown in Tables 7 and 8.
The thicknesses of the constituent layers of the hard coating layers of the invention coated tools 1 to 13 and the comparative coated tools 1 to 13 all showed substantially the same average layer thickness as the target layer thickness.
Tables 6 to 8 show these values.
The total thickness of the lower layer is “underlying Ti compound layer + b + c + d” according to FIG.

Next, for the various coated tools of the present invention coated tools 1 to 13 and comparative coated tools 1 to 13, all of them are screwed with a fixing jig to the tip of the tool steel tool,
Work material: JIS / SCM440 lengthwise equal 8 round bars with vertical grooves,
Cutting speed: 380 m / min,
Incision: 1.5mm,
Feed: 0.3mm / rev,
Cutting time: 7 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 200 m / min) of alloy steel under the above conditions (referred to as cutting condition A),
Work material: JIS · 45C length direction equally spaced 8 vertical grooved round bar,
Cutting speed: 380 m / min,
Cutting depth: 1.8mm,
Feed: 0.3mm / rev,
Cutting time: 7 minutes
Wet high-speed intermittent cutting test of carbon steel under the above conditions (referred to as cutting condition B) (normal cutting speed is 200 m / min),
Work material: JIS / FCD700 lengthwise equal 8 round grooved round bars,
Cutting speed: 300 m / min,
Incision: 1.5mm,
Feed: 0.3mm / rev,
Cutting time: 7 minutes
Wet high-speed intermittent cutting test (normal cutting speed is 180 m / min) of ductile cast iron under the above conditions (referred to as cutting condition C),
In each cutting test, the flank wear width of the cutting edge was measured.
Table 9 shows the measurement results.

From the results shown in Tables 6 to 9, in the coated tools 1 to 13 of the present invention, the adhesive TiCN layer of the lower layer shows a wedge-shaped crystal structure, and the TiCN crystal grains of the layer have a specific inclination angle number distribution. In addition, since the TiCN crystal grains of the upper TiCN layer of the lower layer also show a specific inclination angle number distribution, high-temperature intermittent cutting conditions that cause high heat generation and intermittent / impact load acts on the cutting edge Even when it is used for, the peel resistance of the hard coating layer is excellent and the chipping resistance is also excellent.
On the other hand, it is apparent that the comparative coated tools 1 to 13 reach the service life in a relatively short time due to occurrence of peeling and chipping of the hard coating layer in high-speed intermittent cutting.

As described above, the coated tool of the present invention generates high heat as well as continuous cutting and intermittent cutting under normal conditions such as various steels and cast irons, and the cutting blade is subjected to intermittent and impactful high loads. Even under severe cutting conditions such as high-speed intermittent cutting that acts, the hard coating layer does not peel or chipping, and it exhibits excellent cutting performance over a long period of use. In addition, it is possible to sufficiently satisfy the labor-saving and energy-saving of the cutting process and the cost reduction.

Claims (2)

In a surface-coated cutting tool in which a hard coating layer composed of a lower layer and an upper layer is vapor-deposited on the surface of a tool base composed of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
(A) The lower layer has a total average layer thickness of 3 to 20 μm, and has a three-layer structure of a base Ti compound layer, an adhesive TiCN layer, and an upper TiCN layer, and the upper layer has a thickness of 2 to 15 μm. And an Al ₂ O ₃ layer having an α-type crystal structure in the state of chemical vapor deposition,
(B) The underlying Ti compound layer of the lower layer is composed of one or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer, and the total average layer thickness is 0.5-2. 5 μm,
(C) The adhesive TiCN layer of the lower layer has a wedge-shaped crystal structure, the average height difference of the concave and convex portions of the wedge-shaped crystal structure is 1 to 3 μm, the average interval of the convex portions is 1 to 3 μm, With respect to the TiCN crystal grains having the wedge-shaped crystal structure, using a field emission scanning electron microscope and an electron beam backscattering diffractometer, each crystal grain having a cubic crystal lattice existing within the measurement range of the cross-sectional polished surface has electrons. The angle of inclination formed by the normal of the {110} plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface of the tool base. When the measured inclination angle within the range of degrees is divided into pitches of 0.25 degrees and the frequency existing in each division is represented by an inclination angle number distribution graph, the range of 0 to 10 degrees The highest peak exists in the tilt angle section, and The total of the frequencies existing in the inclination angle section within the range of 0 to 10 degrees occupies a ratio of 40% or more of the entire degrees in the inclination angle frequency distribution graph,
(D) The upper TiCN layer of the lower layer is irradiated with an electron beam to each crystal grain having a cubic crystal lattice existing within the measurement range of the cross-sectional polished surface, and the normal line on the surface of the tool base is Then, the inclination angle formed by the normal of the {112} plane, which is the crystal plane of the crystal grain, is measured, and the measurement inclination angle within the range of 0 to 45 degrees out of the measurement inclination angles is set to a pitch of 0.25 degrees. When it is divided into each, and is represented by an inclination angle distribution graph obtained by counting the frequencies existing in each division, the highest peak exists in the inclination angle division within the range of 0 to 10 degrees, and 0 to 10 A surface-coated cutting tool characterized in that the sum of the frequencies existing in the inclination angle division within the range of degrees occupies a ratio of 60% or more of the entire degrees in the inclination angle frequency distribution graph. 2. The surface-coated cutting tool according to claim 1, wherein the wedge-shaped crystal structure of (c) is composed of an aggregate of TiCN crystal grains having an average grain size of 0.05 to 1 μm.