JP3462859B2 - Coated cutting tool - Google Patents

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 having a hard coating on the surface of a base material and a method for manufacturing the same. In particular, a coating with improved peel resistance while maintaining excellent wear resistance by increasing the grain boundary strength of the columnar crystal structure of the hard coating and suppressing the development of cracks under severe cutting conditions. It relates to cutting tools.

[0002]

[Prior Art] In recent years, coated carbide tools have become more and more severe in terms of cutting speed due to energy saving, labor saving, etc., and the environment in which they are used is becoming more and more severe, and it is necessary to have even greater wear resistance. . Therefore, a vertically grown crystal structure that is effective in improving wear resistance (hereinafter, the vertically grown crystal is referred to as a columnar crystal)
In order to increase the hardness and wear resistance of titanium carbonitride having, there is a tendency to form fine columnar crystals.

In order to manufacture titanium carbonitride having fine columnar crystals, a lower layer of titanium carbonitride layer having a columnar crystal structure using an organic CN such as acetonitrile as disclosed in JP-A-11-172464. It has been proposed to interpose a titanium oxycarbonitride layer having the same columnar crystal structure.
According to this publication, titanium carbonitride is nucleated following the fine structure of titanium carbonitride oxide, so that titanium carbonitride becomes a relatively fine columnar crystal and contributes to improvement of wear resistance.

[0004]

However, this titanium carbonitride having a fine columnar crystal structure has a drawback that cracks are likely to develop at the columnar grain boundaries, resulting in peeling of the coating film. Titanium nitride, titanium oxynitride with a granular crystal structure on a hard alloy substrate,
At least titanium carbide, titanium carbonate, and titanium carbonitride
When one or more layers are coated, the coated surface becomes a cylindrical dome shape. Due to this dome-shaped effect, columnar titanium oxycarbonitride produced by the chemical vapor deposition method using an organic CN such as acetonitrile is likely to have a tapered columnar structure with a structure that widens toward the upper part in the growth direction. Therefore, as the film formation progresses, fine voids are generated between the columnar crystals. These voids weaken the bonding force between crystals and promote the development of cracks that occur in the film during cutting, which is a factor that reduces peeling resistance.

When titanium oxycarbonitride having a columnar crystal structure has a tapered shape, the outermost surface thereof has an uneven shape, and titanium carbonitride also having a columnar crystal structure, which is nucleated and film-formed above, also has a tapered shape. Become. As a result, titanium carbonitride also produces fine voids in the columnar grain boundaries, weakening the bond strength of the grain boundaries and reducing the peeling resistance, like titanium oxycarbonitride.

On the other hand, JP-A-2-31202 (Patent No. 28761)
No. 30) and the like, it has been proposed to improve the peeling resistance while maintaining wear resistance by making a mixed crystal structure of granular crystals and columnar crystals for the purpose of preventing crack propagation of the columnar crystal structure. In this technique, after the columnar crystals are generated, the pressure in the furnace is increased to a supersaturated state, and the granular crystals are precipitated at the columnar grain boundaries, whereby titanium oxycarbonitride has a mixed crystal structure of the columnar crystals and the granular crystals.

However, since the columnar crystal structure is deposited first, the titanium oxycarbonitride crystals are tapered, and due to this, the titanium carbonitride in the upper part is also tapered, which may result in excellent wear resistance. It cannot reach the improvement of the peeling resistance of titanium carbonitride having a fine columnar crystal structure.

In addition, even if a titanium carbonitride layer having a mixed structure of granular crystals and columnar crystals is used because it has both wear resistance and peeling resistance, it does not show wear resistance under recent high-speed cutting conditions. Obviously, it is far behind titanium carbonitride, which has a fine columnar crystal structure.

Further, if the dome effect of the granular crystals in the lower layer of titanium carbonitride causes the columnar crystals of titanium carbonitride to taper, there is also a method in which the hard alloy base material is smoothed and titanium carbonitride is directly formed. is there. However, the adhesion between the hard alloy base material and the titanium carbonitride film is weak, and it cannot be an excellent cutting tool.

Therefore, the main object of the present invention is to provide a coated cutting tool having excellent peeling resistance, which suppresses peeling of titanium carbonitride due to cracks between tapered columnar crystal grains, and a manufacturing method thereof. Especially.

[0011]

The inventor of the present invention has made extensive studies on the above-mentioned problems, and has obtained the following knowledge, and thus has completed the present invention.

A: To cause a reaction in which titanium oxycarbonitride granular crystals and columnar crystals are simultaneously deposited on the upper layer of the titanium oxynitride granular particles, so that the oxygen concentration and film thickness of the titanium oxycarbonitride are within the specified ranges. A film is formed. As a result, it is possible to form a film so that the granular crystals are preferentially filled in the recesses generated in each process of the film formation reaction of titanium oxycarbonitride to increase the flatness.

B: When the flatness of the surface of titanium oxycarbonitride is increased, the columnar crystals having a high film formation rate are preferentially generated, and the crystals of the grain structure which precipitate at the same time have a dome-shaped surface. It becomes so fine that it does not show.

C: Titanium carbonitride formed by nucleating and forming a film on the smoothed titanium oxycarbonitride has dense columnar crystal grain boundaries growing directly on the titanium oxycarbonitride and a strong grain boundary bonding force. Can be an organization that is hard to develop.

D: The columnar crystals of titanium oxycarbonitride become fine, and the mixed granular crystals become very fine, so that the titanium carbonitride in the upper layer becomes relatively fine, and excellent wear resistance is maintained. It becomes possible to do.

That is, the present invention provides a coated cutting tool comprising a hard alloy substrate and a hard coating formed on the surface thereof, wherein the hard coating has the following constitution. Formed on the surface of the base material, titanium nitride, titanium carbide,
A first layer consisting of a single layer or multiple layers of titanium carbonate, titanium oxynitride, titanium carbonitride, and titanium boronitride. The titanium oxycarbonitride formed directly on the first layer and having a mixed crystal structure of granular crystals and columnar crystals, the oxygen content concentration in the film satisfies 0.1% to 15% at the maximum atomic%, and the average film A second layer having a thickness of 0.2 or more and 2.0 μm or less. The third layer, which is titanium carbonitride having a columnar crystal structure formed directly on the second layer.

Here, it is preferable to further include at least one of the following configurations.

(A) The film crystal structure of the first layer has a granular structure.

(B) The average film thickness of the second layer is 0.3 μm to 1.5 μm.
At m, its oxygen content concentration is 1% to 6% at the maximum of atomic%.

(C) The crystal grain of the third layer near the edge of the cutting edge of the base material has an aspect ratio of 6 or more.

(D) The average film thickness of the third layer satisfies 2 to 20 μm.

(E) The hard coating film includes a fourth layer composed of one or more layers formed above the third layer. This fourth layer is a titanium compound and has the chemical formula Ti (Cw'Nx'Oy'Bz ') {w' +
x ′ + y ′ + z ′ = 1,0 ≦ w ′, x ′, y ′, z ′ ≦ 1}, one or more selected from aluminum oxide, zirconium oxide and hafnium oxide. The average film thickness of the entire hard coating is 2.5 to 30 μm.

(F) The base material is cemented carbide or cermet.

(G) The surface roughness in the vicinity of the edge of the cutting edge of the base material is 0.2 to 1.3 μm in Rmax with respect to the reference length of 5 μm measured by the method of observing from the cross section of the base material.

(H) The vicinity of the cutting edge ridge of the hard coating film is substantially constituted by a smooth surface having a surface roughness Rmax of 0.2 μm or less with respect to a reference length of 5 μm.

Each of the above constituent elements will be described in detail.

<Simultaneous Generation of Columnar Crystals and Granular Crystals in Titanium Carbonitride Oxide (Second Layer)> In order to simultaneously generate columnar crystals and granular crystals of titanium oxycarbonitride as the second layer, first,
A TiCN reaction using an organic CN-based gas having a columnar crystal structure and a TiCO reaction having a granular crystal structure are simultaneously advanced. And
By performing solid solution reaction of active O and N atoms generated in the reaction process, columnar crystal TiCNO and granular crystal TiCNO
Are generated simultaneously.

The reason why the granular crystals are deposited in the recesses on the film surface during the TiCNO film formation process is that the reaction gas moves on the film surface during the film formation process, and when the reaction gas moves on the film surface, the convex portion of the organic CN reacts relatively quickly.
This is because the columnar crystals using a system gas are deposited, and when the reaction gas reaches the recesses, the amount of the organic CN system gas decreases and the generation of granular crystals becomes dominant.

As a result, the granular crystals fill the recesses and the film surface becomes flat. The columnar crystals using the organic CN gas, which has a relatively fast reaction as the surface becomes flatter, are not affected by the surface shape effect and preferentially forms. At the same time, the generation of granular crystals is reduced, the granular structure is becoming finer, and the tapered growth of columnar crystals in the second layer due to the dome shape of the first layer is suppressed.

<Defining Oxygen Concentration of Titanium Carbonitride Oxide (Second Layer)> The reason for defining the oxygen concentration of titanium oxycarbonitride film is that when the maximum oxygen atom% is less than 0.1 atm%, the columnar crystal effect occurs. It appears strongly and columnar crystals do not fully precipitate in the recesses.
This is because if it exceeds 15 atm%, the precipitation of granular crystals increases, and the TiCN (third layer) of the pillar-shaped crystal structure formed on top grows in a taper shape. A more preferable range is 1 to 6 atm%.

<Definition of film thickness of titanium oxycarbonitride (second layer)>
The reason for defining the film thickness of titanium oxycarbonitride is that the thickness is 0.
If it is less than 2 μm, the titanium oxycarbonitride will not be sufficiently flattened because it will be affected by the granular crystals in the lower layer, and if it exceeds 2.0 μm, the flattening of the titanium oxycarbonitride will be saturated and there is no point in further stacking. is there. A more preferable range is 0.3 to 1.5 μm.

<Arrangement of First Layer and Second Layer> If the titanium oxycarbonitride layer (second layer) of mixed crystals of columnar crystals and granular crystals is coated directly on the granular crystal layer (first layer). Further, it is possible to further improve the adhesion of the hard coating to the base material and improve the peeling resistance as a cutting tool.

<Definition of Aspect Ratio of Titanium Carbonitride (Third Layer)> First, the aspect ratio will be described. As shown in Fig. 1, in the fracture surface of the tool, the upper end position and the lower end position corresponding to the thickness D of 70% of the film thickness A with reference to the center line of the film thickness A of the columnar crystal TiCN are obtained, and the horizontal direction at each position is calculated. The particle size B at the upper end and the particle size C at the lower end of And D / {(B + C) / 2}
Is the aspect ratio. The reason for defining the aspect ratio is that if the crystal grains of titanium carbonitride having a columnar crystal structure have an aspect ratio of 6 or more near the cutting edge ridge of the hard alloy base material, the cutting performance is desired to be increased.

<Average Thickness of Titanium Carbonitride (Third Layer)> When the average thickness of titanium carbonitride is 2.0 μm or less, excellent wear resistance cannot be exhibited, and conversely, when it exceeds 20 μm, peeling resistance is increased. The average film thickness of the third layer was set to 2.0 to 20 μm because of poor performance.

<Formation of Fourth Layer> The chemical formula Ti (Cw'Nx'Oy'Bz ') {w' + x '+ y' + z'≤1,0 is used for the outer layer of the third layer and is a titanium compound.
≦ w ', x', y ', z' ≦ 1}, aluminum oxide, zirconium oxide, hafnium oxide by coating one or more single-layer or multi-layer coating, wear resistance is further improved and cutting tools Is preferred as If the average film thickness of the entire hard coating at that time is 2.0 to 30 μm, the wear resistance and crater resistance are well balanced, and excellent performance can be exhibited for a long period of time.

<Base Material> If the base material is cemented carbide or cermet, excellent performance can be exhibited. A cemented carbide is generally used that is composed of a hard phase mainly composed of WC and a binder phase mainly composed of Co. Cermets include TiC-based, Cr ₃ C ₂ -based, Al ₂ O ₃ -based cermets.

<Substrate surface roughness> The surface roughness in the vicinity of the cutting edge ridge of the substrate in the coated cutting tool is 0.2 to 1.3 μm in Rmax with respect to the reference length of 5 μm observed from the cross section of the substrate.
If so, the cutting performance is further increased, which is desirable.

<Surface Roughness of Hard Coating> The surface roughness in the vicinity of the cutting edge ridge of the hard coating in the coated cutting tool is substantially a smooth surface having Rmax of 0.2 μm or less from the cross section of the substrate. This is because the cutting performance is further improved and is desirable.

<Manufacturing Method> The hard alloy base material in the cutting tool of the present invention can be manufactured by a known sintering method. The hard coating can be formed by a chemical vapor deposition method (CVD method). The CVD method includes a thermal CVD method, a plasma CVD method,
An optical CVD method and the like can be mentioned. The first layer, the third layer, and the fourth layer may be formed by these CVD methods under known conditions. The film thickness is controlled by adjusting the film forming time. The titanium oxycarbonitride (second layer) having a flat upper portion and a mixed crystal structure of columnar crystals and granular crystals is preferably formed by the thermal CVD method under the following conditions.

The reaction gas composition _{(volume%) TiCl 4: 0.4~4.0% CH} 3 CN: 0.1~2.0% CO: 1.0~3.0% N 2: 3.0~35% CH 4: 0.1~0.5% HCl: 0.1~0.5 % Ar: 0.5~10% H _2: remainder atmosphere temperature: eight hundred and twenty to eight hundred eighty ° C. ambient pressure: 53~267hPa (40~200torr)

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (Test Example 1) The raw material powders shown in Table 1 were used as the hard alloy base material and blended with the blending composition shown in Table 1 to prepare a ball mill.
After wet-mixing for 2 hours and drying, a green compact having a breaker shape according to ISO / CNMG120408 was press-molded and sintered in a vacuum atmosphere under the conditions shown in Table 1 to prepare a base material. After that, the surface of the base material was subjected to flat surface polishing and honing of the cutting edge, and after adjusting the surface roughness of the base material by brush polishing to the values shown in Tables 4 and 5, Table 2 using a chemical vapor deposition device (thermal CVD), 3
Hard coatings were formed under the conditions shown in Table 1 to obtain coated cutting tools shown in Tables 4, 5, and 6. The hard coatings in Table 4 have a three-layer structure from the first layer to the third layer, and the hard coatings in Tables 5 and 6 have a laminated structure from the first layer to the fourth layer, and the fourth layer is a single layer or It has multiple layers. The “total average film thickness” in Tables 4 and 6 is the total thickness of the hard coating.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

[Table 6]

Next, the titanium carbonitride layer in the obtained coated cutting tool was subjected to SIMS (Secondary Ion Mass Spectroscopy).
line) was used to calculate the maximum atm% of oxygen content. As for the structure of the titanium oxycarbonitride, a mixed crystal structure of granular crystals and columnar crystals was confirmed by using a transmission electron microscope on the film fracture surface of the coated cutting tool. The aspect ratio is
As shown in FIG. 1, it was determined by D / {(B + C) / 2}. The surface roughness of the base material was determined by Rmax for a reference length of 5 μm in the cross section near the edge of the cutting edge.

For various coated cutting tools obtained from these results, a wear test was conducted under the following condition 1 to obtain flank wear amount, and a peel resistance test was conducted under the following condition 2.
The cutting test was carried out to determine the time to failure. The results are shown in Tables 4 and 6.

(Condition 1) Work Material: SCM435 Round Bar Cutting speed: 150m / min Feed: 0.3mm / rev Notch: 1.8 mm Cutting time: 40min Cutting oil: Not used

(Condition 2) Work Material: SCM415 Grooved Round Bar Cutting speed: 400m / min Feed: 0.3mm / rev Notch: 1.5 mm Cutting oil: Not used

As is clear from Tables 4 and 6, when the coated cutting tool of the present invention was used for processing, it was revealed that it had excellent wear resistance and excellent peeling resistance. It was

(Test Example 2) Among the coated cutting tools with chip breakers obtained in Test Example 1 above, Invention Products 1 to 21 were prepared by lapping the hard coating near the edge of the cutting edge with diamond powder having an average particle diameter of 4 μm. The surface roughness of the hard coating was adjusted. The surface roughness was obtained by observing the cross section of the hard coating and measuring the surface roughness Rmax for a reference length of 5 μm. Then, a hard coating having a surface roughness of 0.2 μm or less and a hard coating having a surface roughness of more than 0.2 μm were prepared, and a cutting test was conducted under the above two cutting conditions.

As a result, it was confirmed that the wear width of the flank was reduced by about 20% under the cutting condition 1 and the life was extended by 20-40% under the cutting condition 2, and the performance was improved.

[0055]

As described above in detail, according to the method for manufacturing a coated cutting tool of the present invention, the titanium oxycarbonitride layer has a mixed crystal structure of granular crystals and columnar crystals, and the oxygen concentration thereof is set within a specific range. As a result, titanium oxycarbonitride having a smooth surface can be produced. As a result, the coated cutting tool of the present invention, the columnar crystals of the titanium carbonitride layer grow directly above rather than in a tapered shape, and its grain boundary strength increases, making it difficult to crack.
Excellent peel resistance can be provided without impairing wear resistance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of calculating an aspect ratio.

[Explanation of symbols]

1 crystal grain

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Watanabe 776 Naie, Naie-cho, Sorachi-gun, Hokkaido Inside Hokkaido Sumiden Precision Co., Ltd. (56) References JP 200-1198550 (JP, A) JP HEI 3- 26404 (JP, A) Patent 3282592 (JP, B2) Patent 2876130 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23B 27/14 C23C 16/30 C23C 16/40

Claims (10)

(57) [Claims] 1. A coated cutting tool comprising a hard alloy substrate and a hard coating formed on the surface thereof, wherein the hard coating has the following constitution. Formed on the surface of the base material, titanium nitride, titanium carbide,
A first layer consisting of a single layer or multiple layers of titanium carbonate, titanium oxynitride, titanium carbonitride, and titanium boronitride. The titanium oxycarbonitride formed directly on the first layer and having a mixed crystal structure of granular crystals and columnar crystals, the oxygen content concentration in the film satisfies 0.1% to 15% at the maximum atomic%, and the average film A second layer having a thickness of 0.2 or more and 2.0 μm or less. The third layer, which is titanium carbonitride having a columnar crystal structure formed directly on the second layer. 2. The coated cutting tool according to claim 1, wherein the film crystal structure of the first layer has a granular crystal structure. 3. The average film thickness of the second layer is 0.3 μm to 1.5 μm.
3. The coated cutting tool according to claim 1, wherein the oxygen content concentration satisfies 1% to 6% at the maximum value of atomic%. 4. The coated cutting tool according to claim 1, wherein the crystal grains of the third layer in the vicinity of the cutting edge ridge portion of the base material have an aspect ratio of 6 or more. 5. The coated cutting tool according to claim 1, wherein the average film thickness of the third layer satisfies 2 to 20 μm. 6. The hard coating comprises a fourth layer composed of a single layer or a plurality of layers formed on the third layer, the fourth layer being a titanium compound and having a chemical formula of Ti (Cw'Nx'Oy). 'B
z ') {w' + x '+ y' + z '= 1,0≤w', x ', y', z'≤1}, made of at least one selected from aluminum oxide, zirconium oxide and hafnium oxide, and hard The coated cutting tool according to any one of claims 1 to 5, wherein the coating has an average thickness of 2.5 to 30 µm. 7. The coated cutting tool according to claim 1, wherein the base material is cemented carbide or cermet. 8. The surface roughness in the vicinity of the cutting edge ridge of the base material is 0.2 to 1.3 μm in Rmax with respect to a reference length of 5 μm measured by a method of observing from the cross section of the base material. The coated cutting tool according to any one of claims 1 to 7. 9. The surface of the hard coating film near the edge of the cutting edge is substantially constituted by a smooth surface having a surface roughness Rmax of 0.2 μm or less with respect to a reference length of 5 μm. 1 ~ 8
The coated cutting tool according to any one of 1. 10. A film comprising one or more layers of titanium nitride, titanium carbide, titanium carbonate, titanium oxynitride, titanium carbonitride, and titanium boronitride having a granular crystal structure on the surface of a hard alloy substrate by a chemical vapor deposition method. And a step of forming a titanium oxycarbonitride layer having a mixed crystal structure of granular crystals and columnar crystals by causing a reaction in which granular crystals of titanium oxycarbonitride and columnar crystals are simultaneously precipitated by a chemical vapor deposition method, And a step of forming a titanium carbonitride layer having a columnar crystal structure by a chemical vapor deposition method.