JP2001277006A - Covered cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covered cutting tool compatible with abrasion resistance and defective resistance. SOLUTION: This tool has a hard coat 2 on a base material 1. It has a region α1 within 0.2 mm in the flank direction from a knife edge ridge line 5, a region α2 having a range of more than 0.5 times of the region α1 in the flank direction adjacent to the region α1 out of a range materially concerning cutting, a region β1 within 0.50 mm in the rake face direction from the knife edge ridge line and a region β2 having a range of more than 0.5 times of the region β1 in the rake face direction adjacent to the region β1 out of the range materially concerning cutting. In the range of the regions α1 and β1, the growing direction of crystal grains is materially in the vertical direction against the base material 1 and at an angle within ±2 deg. against a bisector of a rain boundary of the crystal grains on the hard coat. Additionally, the growing direction of the crystal grains is materially in the vertical direction against the base material and at an angle within more than ±2 deg.-±40 deg. against the bisector in the growing direction of the crystal grains on the hard coat in the range of the regions α2 and β2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated cutting tool excellent in wear resistance and fracture resistance. In particular, the present invention relates to a coated cutting tool in which the film structure of the hard coating is changed for each part of the cutting tool.

[0002]

2. Description of the Related Art As the environment in which cutting tools are used becomes more and more severe, various types of methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) are applied to the surface of cemented carbide and cermet. Coated cutting tools having a hard coating of ceramics have been put to practical use. Examples of such hard coatings include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), monolayer or multilayer, such as a titanium oxycarbonitride (TiCNO) and alumina (Al ₂ 0 ₃₎ There is a coating. These coatings not only improve the wear resistance of the cutting tool, but also prevent the reaction between the work material and the cutting tool during cutting, and as a result, improve the life of the tool. In addition, the structure of such a coating has a structure such as a granular shape, a columnar shape, and a vertically elongated growth, and it is said that characteristics utilizing various structure structures can be exhibited.

For example, in Japanese Patent Application Laid-Open No. 2-311202, the crystal form in one layer of the hard coating has a structure in which columnar crystals and granular crystals are mixed, and the hardening resistance is improved without deteriorating wear resistance. We propose excellent coated tools.

Japanese Patent Application Laid-Open No. 6-8008 proposes a coated tool excellent in chipping resistance, in which the lower layer of the titanium carbonitride layer in the hard coating has a granular crystal structure and the upper layer has a vertically long crystal structure.

[0005]

However, the coated cutting tools described in the above publications can improve the chipping resistance and chipping resistance, but cannot prevent or improve the wear resistance. .

On the other hand, as another prior art, a titanium carbonitride (TiCN) film formed by a thermal CVD method using an organic CN compound such as acetonitrile (CH ₃ CN) has a short life due to sudden defects or chipping. There was a tendency to be stable.

In order to solve this problem, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Publication No. 285001 and Japanese Patent Application Laid-Open No. 8-71814 propose a technique in which the microscopic structure of the TiCN layer is improved. However, these are limited only to the film thickness and the grain size and hardness of the crystal structure, and do not specify an appropriate structure shape.

Further, Japanese Patent Application Laid-Open No. 10-109206 discloses that the structure is controlled by defining the crystal structure, and the fine columnar structure can achieve both wear resistance and chipping resistance. However, it has not been possible to achieve various characteristics depending on the position of the cutting tool.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a coated cutting tool which can further improve wear resistance, in particular, crater wear resistance and fracture resistance, and achieve both.

[0010]

The present invention achieves the above object by providing a hard coating having a film structure corresponding to the function of each part in a cutting tool.

That is, the coated cutting tool of the present invention comprises a base material and a hard coating formed on the surface thereof, and has a flank and a rake face. This tool has the following areas α1, α2, β1 and β2. α1: Area within 0.20 mm from the ridgeline of the cutting edge in the flank direction α2: Area that is substantially adjacent to the area α1 and that has a range of 0.5 times or more the area α1 in the flank direction in the flank direction substantially related to cutting β1: Area within 0.50 mm in the rake face direction from the ridgeline β2: Area that is adjacent to area β1 and has a range of 0.5 times or more of area β1 in the rake face direction, which is substantially related to cutting.

In the range of the regions α1 and β1, the hard coating includes a layer having the following structure. The growth direction of the crystal grains is substantially perpendicular to the substrate and has an angle within ± 2 ° with respect to a bisector of a grain boundary of the crystal grains. The aspect ratio of the crystal grains is 5 or more.

Further, in the range of the regions α2 and β2, the hard coating is characterized by including a layer having the following structure. The crystal grain growth direction has an angle of more than ± 2 ° to ± 40 ° with respect to the bisector of the grain boundary of the crystal grain. The aspect ratio of the crystal grains is 5 or more.

As described above, in the cutting tool of the present invention, a hard coating having a different structure is formed depending on the position of the cutting tool, thereby achieving both wear resistance and chipping resistance.

At the parts where the cutting resistance is the largest and the load is applied to the tool, that is, the areas α1 and β1, a hard coating is formed in which crystal grains have a structure substantially perpendicular to the base material with emphasis on chipping resistance. I have. As a result, stress during cutting is applied perpendicular to the base material, cracks are introduced perpendicularly to the base material, and the crack
The chipping resistance can be improved.

On the other hand, a portion which comes off the regions α1 and β1 but comes into contact with the chip or the work material, or near the contact portion and substantially involved in cutting, that is, the regions α2 and β2 has wear resistance. The hard coating having a texture structure in which the crystal grains are inclined with respect to the base material is formed with emphasis on. This allows
Each crystal grain has anisotropy to suppress the progress of abrasion and substantially improve abrasion resistance or crater resistance.

Here, the hard coating is desirably made of a ceramic material having excellent wear resistance. For example, carbides, nitrides, carbonitrides, borides, boronitrides, borocarbonitrides, oxides, carbonates, oxynitrides, carbonitrides and aluminum oxides of the Periodic Tables IVa, Va, VIa group No. In particular, the formula _{Ti (C w N x O y} B z) (w + x +
y + z = 1, 0 ≦ w, x, y, z ≦ 1) may include a layer composed of at least one selected from the group consisting of a titanium compound, aluminum oxide, zirconium oxide and hafnium oxide. preferable. In this case, the total average film thickness is preferably from 1.0 to 30.0 μm. With this configuration, the balance between wear resistance and fracture resistance is improved, and excellent performance can be exhibited over a long period of time.

It is also desirable that the hard coating contains TiCN. In this case, the layer having an aspect ratio of crystal grains of 5 or more is
It is preferable that

Further, the film structure of the hard coating may be a single layer or a multilayer. It is desirable that the first layer formed on the substrate be TiN. When the first layer is made of TiN, the adhesion of the hard coating to the base material can be improved by suppressing the volatilization of Co on the base material surface and reducing the amount of chlorine in the film. In the case of a multilayer structure, the second layer formed on the first
It is preferable to use CN, and to make the second layer a layer having the conditions of the regions α1, α2, β1, and β2.

It is to be noted that at least one of the outermost layer and the innermost layer is provided with carbides, nitrides, carbonitrides, borides, boronitrides, borocarbonitrides, oxides, carbonates of the groups IVa, Va and VIa of the periodic table. , An oxynitride, a carbonitride, and an aluminum oxide layer may be formed. In particular, the chemical formula Ti (C _w N _x O _y B
_z ) a layer composed of at least one selected from the group consisting of a titanium compound represented by (w + x + y + z = 1, 0 ≦ w, x, y, z ≦ 1), aluminum oxide, zirconium oxide, and hafnium oxide preferable. In that case, the total average film thickness is preferably 2.0 to 31.0 μm. With this configuration, wear resistance and fracture resistance can be improved.

In addition, the periodic table IVa, Va, VI
A, IVb, Vb, and VIb group atoms may be added alone.
As a result, the strain of the crystal grains is solid-solution strengthened, and the wear resistance and fracture resistance can be further improved.

The hard coating can be formed by a known PVD method or CVD method. The layer having crystal grains substantially perpendicular to the substrate formed in the regions α1 and β1 can be realized by smoothing the surface of the region α1 or β1 in the substrate surface or the underlayer by polishing or the like. . The preferred surface roughness of the substrate surface or underlayer is 0.4 μm or less. The layer having crystal grains substantially perpendicular to the substrate is preferably formed at a high growth rate. The preferred growth rate is 0.
It is about 01 to 0.05 (μm / min).

The layer formed in the regions α2 and β2 and having the crystal grains inclined with respect to the base material is formed by roughening the surface of the base material or the surface of the base material in the regions α2 and β2 by blasting or the like. It can be realized by putting.

Further, in any of the regions α1, β1, α2, and β2, Ti formed by using an organic CN gas as a source gas is used.
A structure having an aspect ratio of 5 or more is easily obtained in the CN layer.

On the other hand, as the material of the base material, a cemented carbide or cermet is optimal. When a cemented carbide is used for the base material,
The substrate has a β-removed layer on its surface, and the average thickness of the β-removed layer is
It is preferable that the thickness be not more than μm. Even with this configuration, the wear resistance and fracture resistance can be improved, and the life of the tool can be extended.

[0026]

Embodiments of the present invention will be described below. As a base material, the raw material powders shown in Table 1 were blended into the composition shown in Table 1, wet-mixed in a ball mill for 72 hours, dried, and then press-molded into a green compact in the form of ISO / CNMG120408. In a vacuum atmosphere, sintering was performed under the conditions shown in Table 1 to produce a substrate. After that, the base material surface is polished flat and the cutting edge is honed, and the chemical vapor deposition device (thermal CV
Using D), a hard coating having the composition and crystal structure described in Tables 3 to 7 was formed under the conditions shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

[Table 7]

Here, each region of the cutting tool subjected to the test will be described with reference to FIG. A hard coating 2 is formed on the surface of the substrate 1, and the horizontal plane in the figure is the rake face 3 and the vertical plane is the flank 4. Here, 0.20 mm in the flank direction from the edge line 5
A region within the range α1 is defined as α1, and a region which is adjacent to the region α1 and has a range of 0.5 or more times the region α1 in the flank surface direction is defined as α2. In addition, the area within 0.50 mm in the rake face direction from the cutting edge ridge line 5 is β1, and an area having a range of 0.5 times or more of the area β1 in the rake face direction adjacent to the area β1 in a range substantially related to cutting. β2.

In the present embodiment, the widths of the regions α1, α2, β1, and β2 are shown in Tables 3 to 7 as "part widths". The table also shows the aspect ratio and the growth angle.

Next, a specific method of forming the hard coating will be described. The layer having crystal grains substantially perpendicular to the substrate was formed by smoothing the surface of the substrate or the surface of the region α1, β1 in the underlayer by polishing. Area α1, β1
The surface roughness of the substrate surface or the underlayer in the above is 0.4 μm or less. Further, the layer having crystal grains inclined with respect to the base material was formed by roughening the surface of the base material or the surface of the regions α2 and β2 in the base layer by blasting.
The surface roughness of the substrate surface or the underlayer in the regions α2 and β2 is 0.5 μm or more.

The characteristics of the hard coating of each cutting tool are summarized below. Inventive product 1: a single-layer hard coating, which has a structure substantially perpendicular to the substrate. Invention product 2: a two-layer hard coating in which the second layers in regions α1 and β1 have a structure substantially perpendicular to the substrate. Inventive product 3: a five-layer hard coating in which the second layers in regions α1 and β1 have a structure substantially perpendicular to the substrate. Invention product 4: a hard coating of five layers, wherein the first and second layers in the regions α1, β1 have a structure substantially perpendicular to the substrate. Inventive product 5: Four hard coatings, wherein the first layers in the regions α1 and β1 have a structure substantially perpendicular to the substrate. Invention product 6: a five-layer hard coating in which the second layers in the regions α1 and β1 have a structure substantially perpendicular to the substrate. Invention product 7: Five hard coatings, wherein the second layers in the regions α1 and β1 have a structure substantially perpendicular to the substrate.

Comparative product 8: A single-layer hard film, in which the film structure of each part was not controlled. Comparative product 9: a two-layer hard coating having a structure substantially perpendicular to the substrate at all positions. Comparative product 10: a single-layer hard film having a structure inclined at all positions with respect to the base material. Comparative product 11: a two-layer hard film having a structure substantially perpendicular to the substrate at all portions. Comparative product 12: a five-layer hard coating in which the second layers in the regions α1 and β1 have a structure substantially perpendicular to the substrate. However,
The total film thickness is as thick as 35 μm.

The method of measuring the growth direction of the structure and the aspect ratio is as follows. Polish with the cutting tool parallel or at an appropriate angle (preferably 10 ° or less) with respect to the longitudinal section, and use an appropriate corrosive liquid (such as a mixed solution of hydrofluoric acid, nitric acid, and distilled water) to form grain boundaries. After being raised, it is observed with a scanning electron microscope, and the growth direction and aspect ratio of the crystal grain size are calculated from a photograph taken at an appropriate magnification.

As shown in FIG. 2, the angle of the growth direction is, as shown in FIG.
Intersecting points 11 to 14 between the positions of / 5 and 4/5 and the grain boundaries are obtained,
The angle between the straight line formed by the intersections 11 and 13 and the straight line formed by the intersections 12 and 14 with respect to the center line 15 is calculated and obtained.

The aspect ratio is determined by calculating the ratio of the crystal grain size in the horizontal direction of the hard film ((upper grain size + lower grain size) / 2) to the film thickness 23. In FIG. 2, the crystal grain 20 has a particle diameter at the upper end 21 and a particle diameter at the lower end 22.

Then, the products 1 to 7 of the present invention and the comparison products 8 to
A continuous cutting test was performed on `` cutting conditions 1 '' for 12 to measure the flank wear and the rake crater wear,
Intermittent cutting was performed under "cutting condition 2", and the time until a defect was measured. Table 8 shows the results.

(Cutting condition 1) Work material: SCM435 round bar Cutting speed: 150m / min Feed: 0.30mm / rev Depth of cut: 1.8mm Cutting time: 40min Cutting oil: not used

(Cutting condition 2) Work material: SCM415 Grooved round bar Cutting speed: 400m / min Feed: 0.30mm / rev Depth of cut: 1.5mm Cutting oil: not used

[0045]

[Table 8]

As is clear from Table 8, when machining was performed using the coated cutting tool of the present invention, excellent wear resistance was obtained.
Crater wear resistance, chipping resistance and chipping resistance can both be achieved, and the life of the cutting tool can be stably and dramatically improved.

It should be noted that the coated cutting tool of the present invention is not limited to the above-described specific example, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0048]

As described above, according to the present invention,
By forming a hard coating having a different structure for each part of the cutting tool, a long-life cutting tool having both wear resistance and fracture resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of each area in a tool of the present invention.

FIG. 2 is an explanatory diagram of a growth angle and an aspect ratio of a crystal grain.

[Explanation of symbols]

 1 Base material 2 Hard coating 3 Rake face 4 Flank 5 Cutting edge ridgeline 10 Grain 11-14 Intersection 15 Bisection line 20 Grain 21 Upper grain size 22 Lower grain size 23 Grain thickness

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C046 FF03 FF05 FF07 FF10 FF11 FF13 FF16 FF23 FF25 4K044 AA09 AB05 BA12 BA13 BA18 BB01 BB02 BB03 BB10 BC06 CA14

Claims (9)

[Claims] 1. A coated cutting tool comprising a base material and a hard coating formed on the surface thereof, having a flank and a rake face, wherein the area α1 is within 0.20 mm in the flank direction from the edge of the cutting edge. Area α having a range of 0.5 times or more the area α1 in the flank direction adjacent to the area α1 in the area related to the cutting
2, a region β1 within 0.50 mm in the rake face direction from the cutting edge ridge line, and a region β2 having a range of 0.5 times or more of the region β1 in the rake face direction adjacent to the region β1 in a range substantially related to cutting. The hard coating in the range of the regions α1 and β1 includes a layer having the following structure, wherein the crystal grains grow in a direction substantially perpendicular to the substrate, and The hard coating has an angle within ± 2 ° with respect to the bisector of the grain boundary The aspect ratio of the crystal grain is 5 or more The hard coating includes a layer having the following structure in the range of the regions α2 and β2. A coated cutting tool, characterized in that: The growth direction of the crystal grain has an angle of more than ± 2 ° to ± 40 ° with respect to the bisector of the grain boundary of the crystal grain. The aspect ratio of the crystal grain is 5 or more. 2. The hard coating is made of a carbide, nitride, carbonitride, boride, boronitride, borocarbonitride, oxide, carbonate, oxynitride of a group IVa, Va, VIa of the periodic table. The coated cutting tool according to claim 1, comprising a layer composed of one or more selected from the group consisting of carbonitride and aluminum oxide, and having a total average thickness of 1.0 to 30.0 µm. 3. The coated cutting tool according to claim 1, wherein the hard coating contains TiCN. 4. A layer having a crystal grain aspect ratio of 5 or more is made of TiCN.
The coated cutting tool according to claim 1, wherein: 5. The coated cutting tool according to claim 1, wherein the first layer formed on the substrate is TiN. 6. The method according to claim 5, wherein the second layer formed on the first layer is TiCN, and the second layer is a layer having the conditions of the regions α1, α2, β1, and β2. A coated cutting tool according to claim 1. 7. At least one of the outermost layer and the innermost layer includes a carbide, nitride, carbonitride of a group IVa, Va, or VIa of the periodic table,
A layer composed of at least one selected from the group consisting of boride, boron nitride, borocarbonitride, oxide, carbonate, oxynitride, carbonitride, and aluminum oxide; a total average film The coated cutting tool according to claim 1, wherein the thickness is 2.0 to 31.0 μm. 8. The coated cutting tool according to claim 1, wherein the substrate is a cemented carbide or a cermet. 9. The coated cutting according to claim 1, wherein the substrate is a cemented carbide, and has a β-removed layer on the surface of the substrate, and the average thickness of the β-removed layer is 50 μm or less. tool.