JP2008100301A - Diamond coated cutting insert and cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond coated cutting insert 1 which has a thin diamond coated film having excellent peeling resistance on the base material of the cutting insert, and has high durability, and further to provide a cutting tool 2 having the diamond coated cutting insert 1. <P>SOLUTION: The diamond coated cutting insert 1 has a coated film formed thereon. The coated film has a Raman spectrum having peaks at 1,140±30 cm<SP>-1</SP>, 1,330±10 cm<SP>-1</SP>, 1,480±50 cm<SP>-1</SP>, and 1,580±20 cm<SP>-1</SP>, and the intensity of the peak at 1,480±50 cm<SP>-1</SP>is larger than that of the peak at 1,580±20 cm<SP>-1</SP>in the Raman spectrum analysis. The cutting tool 2 is configured so as to comprise the diamond coated cutting insert 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a diamond-coated cutting insert and a cutting tool, and more particularly to a diamond-coated cutting insert having excellent durability and a cutting tool including the diamond-coated cutting insert.

  The cutting tool 1 is a disposable cutting edge 1 (also referred to as a throw-away tip, a cutting edge replacement tip, or the like) at the tip of a support called a holder 3 as in the outer diameter machining cutting tool 2 illustrated in FIG. There are many structures that are attached. Various materials are used for the cutting insert depending on the type of work material, the machining process, the cutting speed, and the like. For example, cemented carbides, cermets, ceramics, boron nitride, and materials in which a high hardness and wear resistant coating is coated on these surfaces are used. However, the required performance of cutting insert materials has become increasingly severe in recent years, and further higher performance and lower cost are also required. Under such circumstances, a cutting insert coated with a diamond thin film is considered to have excellent wear resistance and durability, and thus attracts attention as a material for processing an aluminum alloy.

  Diamond has higher hardness than alumina, silicon nitride, cemented carbide, etc., which have been widely used as cutting insert materials, and has high thermal conductivity, so diamond has been developed as a cutting insert material. It was. However, a diamond sintered body insert using a diamond sintered body synthesized by sintering under ultra-high pressure and high temperature is expensive, and since there is no material that is harder than diamond, cutting after sintering is performed. The shape of the insert was limited because it was difficult to process the insert. Therefore, a hard thin film mainly composed of diamond (hereinafter simply referred to as a diamond thin film) is obtained by a chemical vapor phase synthesis method (CVD method) using a carbon-containing gas excited by a microwave or a hot filament as a raw material gas. Many diamond-coated cutting inserts have been developed on the base material. According to this method, a diamond thin film can be formed easily and inexpensively even on a tool base material having a complicated shape. Therefore, research and development of diamond-coated tools are actively promoted by applying this technique. Recently, attempts have been made to improve the performance as a cutting tool material by specifying the method of forming a diamond thin film and the form of the formed diamond thin film.

As a diamond-coated tool, for example, Patent Document 1 discloses a thin film having a waveform having peaks on both sides of a peak indicating a diamond crystal in a laser Raman spectrum of a hard carbonaceous film formed on the surface of a tungsten carbide base cemented carbide substrate. A cutting tool coated with is disclosed. Further, Patent Document 2 discloses a high performance that specifies the intensity ratio between a peak indicating a diamond crystal and a peak indicating a non-diamond component in a Raman spectrum of a diamond thin film coated on the tip of the cutting tool base material. A cutting tool is disclosed. In addition, in the manufacturing method of a diamond coating industrial blade (patent document 3), a diamond-like carbon coating cemented carbide cutting tool made of a plasma CVD film (patent document 4), a Raman spectrum of a hard carbon film coated on the surface Many diamond thin film-related technologies have been developed, such as a high-performance sliding member (Patent Document 5) that specifies the intensity ratio between a peak indicating diamond crystal and another peak.
Japanese Examined Patent Publication No. 62-6747 JP-A-5-123098 JP 2004-76106 A JP-A-5-342834 JP-A-4-3544871

  As described above, a diamond-coated cutting insert in which a diamond thin film is formed on a base material is used as an excellent cutting tool having high hardness and high thermal conductivity. However, the conventional diamond-coated cutting insert has a large internal stress in the thin film and low adhesion strength with the base material, and because of its low toughness, the film peels or breaks instantly during processing such as cutting. There was a drawback that there was. Therefore, it has been demanded to further increase the bond strength of diamond particles, prevent the diamond thin film from being broken or peeled off, and further improve the wear resistance during high-speed cutting.

  An object of the present invention is to provide a diamond coated cutting insert and a cutting tool having high durability by coating a diamond thin film having excellent peeling resistance on a base material for a cutting insert.

As described above, a problem with the diamond-coated cutting insert is that the thin film is peeled off during processing such as cutting. The cause of the peeling is considered to be because the stress based on the difference in thermal expansion coefficient between the diamond thin film and the base material, particularly the compressive stress due to the thermal expansion in the diamond thin film is large. Therefore, the inventors examined a method for relaxing the compressive stress inside the diamond thin film. As a result, the diamond crystal particles in the diamond thin film are atomized to nano-size, and when there are amorphous diamond and graphite in the diamond thin film, these act as a binder for the diamond particles, It has been found that the compressive stress generated inside the diamond thin film is relaxed without impairing the wear resistance of the thin film. The diamond-coated cutting insert coated with such a diamond thin film was found to have an extremely long life. Based on the above findings, the inventors have found the following means for solving the above problems.
As means for solving the problems,
Claim 1 is a diamond-coated cutting insert in which a coating film is formed. In a Raman spectrum analysis of this coating film, 1140 ± 30 cm ⁻¹ , 1330 ± 10 cm ⁻¹ , 1480 ± 50 cm ⁻¹ and 1580 ± 20 cm ^−1. A diamond-coated cutting insert having a Raman spectrum with a peak at 1480 ± 50 cm ⁻¹ and a peak intensity at 1480 ± 50 cm ⁻¹ greater than the peak intensity at 1580 ± 20 cm ⁻¹ ,
Claim 2 is the diamond-coated cutting insert according to claim 1, wherein the coating film is formed by a vapor phase synthesis method.
Claim 3 is the diamond-coated cutting insert according to claim 1 or 2, wherein the coating film has a thickness of 3 to 30 µm.
The diamond according to any one of claims 1 to 3, wherein the base material surface covered with the coating film is a tungsten carbide cemented carbide containing a β phase mainly composed of titanium carbonitride. A coated cutting insert,
Claim 5 is a diamond-coated cutting insert according to any one of claims 1 to 4, wherein the coating film has a structure in which diamond fine particles smaller than the film thickness are stacked.
A sixth aspect of the present invention is a cutting tool including the diamond-coated cutting insert according to any one of the first to fifth aspects.

  In the diamond-coated cutting insert of the present invention, the diamond particles forming the coating film are nano-sized fine particles, and it is considered that the diamond particles are bonded to each other by amorphous diamond particles and graphite. Therefore, even if individual particles near the surface of the coating film are peeled off, cracks generated on the surface of the coating film do not reach the base material all at once, and therefore the coating film is immediately peeled off from the surface of the base material. In this way, a long-life diamond-coated cutting insert and cutting tool with high peel resistance and wear resistance can be obtained. In particular, even when cutting under high temperature conditions such as high-speed cutting, the thermal stress between the diamond particles in the coating film or between the coating film and the base material is small, and the diamond particles are excellent in resistance to peeling. The durability of the cutting insert and the cutting tool can be further improved.

The diamond-coated cutting insert of the present invention is formed by forming a coating film on the surface of a base material in the shape of a cutting insert by a gas phase synthesis method. Then, the coating film is in the Raman spectrum analysis, shows a spectrum at least ^{1140 ± 30cm -1, 1330 ± 10cm} -1, a peak at 1480 ± 50 cm ^-1 and 1580 ± 20 cm ^-1 is present. Further, this coating film shows a Raman spectrum in which the peak intensity I ₁ at 1480 ± 50 cm ⁻¹ is larger than the peak intensity I ₂ at 1580 ± 20 cm ⁻¹ . Usually, a peak appearing at 1330 ± 10 cm ⁻¹ indicates a diamond crystal. And it is shown by the peak of 1140 ± 30 cm ⁻¹ that this diamond crystal is nano-sized fine particles. In the Raman spectrum of the present invention, the peak at 1480 ± 50 cm ⁻¹ indicates the presence of amorphous diamond, and the peak appearing at 1580 ± 20 cm ⁻¹ indicates the presence of graphite.

  The thickness of the coating film in the diamond-coated cutting insert of the present invention is usually 1 to 40 μm, preferably 3 to 30 μm, and more preferably 5 to 30 μm. That is, since the diamond particles in the coating film of the diamond-coated cutting insert of the present invention are much smaller than the film thickness of the coating film, the coating film is formed as a multilayer diamond particle layer as shown in FIGS. Forming. In other words, nano-sized diamond particles having a thickness of about 1/5 to 1/1000 are stacked in a stone wall shape to form a coating film. The cutting insert coated with such a coating film, even if the individual diamond particles are peeled off during use as a cutting tool, only the individual diamond particles are peeled off one by one. Peeling is difficult to proceed to the surface of the base material. Further, since the individual diamond particles are small, the amount of deformation of the diamond particles is small even at high temperatures, and the thermal stress between the diamond particles in the coating film and the surrounding amorphous diamond and graphite is small. Here, the amorphous diamond is formed by irregularly forming the three-dimensional skeleton of carbon atoms having the isotropic property of diamond, and the dangling bonds of carbon atoms are stabilized by the bonding of hydrogen. It is a substance. On the other hand, a diamond-coated cutting insert in which a coating film having a film thickness of 3 to 30 μm is formed of diamond particles having a large particle size of micron size, as schematically shown in FIG. Since almost one layer of the coating layer is formed of diamond particles having a diameter, when one diamond particle is peeled off, the coating film in that portion is lost and the surface of the base material is exposed. Since the base material has less wear resistance than the coating film formed of diamond, the life as a cutting tool ends when the surface of the base material is exposed.

Furthermore, in the present invention, in the diamond coating, the peak intensity I ₁ at 1480 ± 50 cm ⁻¹ of the Raman spectrum is larger than the peak intensity I ₂ at 1580 ± 20 cm ⁻¹ . The diamond coating in the diamond-coated cutting insert of the present invention has two obvious peaks in the vicinity of 1500 to 1600 cm ⁻¹ , and the intensity ratio of these peaks is important. That is, the ratio of the peak intensity I ₁ at 1480 ± 50 cm ⁻¹ of the Raman spectrum to the peak intensity I ₂ at 1580 ± 20 cm ⁻¹ , I ₁ / I ₂ is 1 or more, preferably 1 to 1.4. is there. In the Raman spectrum of the present invention, the peak appearing at 1480 ± 50 cm ⁻¹ indicates amorphous diamond, and the peak appearing at 1580 ± 20 cm ⁻¹ indicates graphite. That I ₁ / I ₂ is 1 or more indicates that the graphite content in the coating film in the present invention is not more than a predetermined value with respect to the amorphous diamond content. This is presumed that the binder-like action of amorphous diamond contributes more to the diamond fine particles than the binder-like action of graphite.

  If the above explanation is explained qualitatively and schematically, as shown in FIG. 5, the coating film according to the present invention has a state in which diamond crystal particles of nano-sized fine particles are stacked. The crystal particles are bonded by graphite and amorphous diamond. The content ratio of graphite and amorphous diamond bonding diamond crystal particles can be specified by the ratio of the intensity of the peak representing each component.

  In the diamond-coated cutting insert according to the present invention, the base material of the cutting insert is not particularly limited as long as it can be used for the cutting insert. Examples of the base material include cemented carbide, alumina ceramics, CBN, silicon nitride, sialon, and the like. Among these, a cemented carbide and a tungsten carbide cemented carbide having a β phase mainly composed of titanium carbonitride on the surface are particularly preferable because the bond between the matrix and the coating film becomes strong. This β phase is a solid solution in tungsten carbide, for example, Ti, Ta, Nb, etc. are precipitated as carbonitrides, and can be expressed as Ti (C, N) in the chemical formula. For example, the β phase is cemented carbide. It is possible to modify the surface of the ceramic material by precipitating on the surface. The diamond-coated cutting insert of the present invention may have any shape as long as it can be cut, and may take the shape of various throw-away tips conventionally used. In the diamond-coated cutting insert of the present invention, the thickness of the coating film is usually several tens of microns or less as described above, and is so thin that it can be ignored compared to the size of the base material. The shape is substantially determined by the shape of the base material.

  Any kind of cutting tool having the diamond-coated cutting insert according to the present invention may be used. For example, a grooving tool, a thread cutting tool, an outer diameter machining tool, an inner diameter machining tool, a chamfering tool, an end mill, a miniature drill Etc. Usually, the above-mentioned tool is a tip exchange type tool provided with a tip called a throw-away tip. The cutting tool of this invention can remarkably improve durability compared with the cutting tool provided with the conventional diamond covering cutting insert.

  The method for forming the coating film on the surface of the base material is not particularly limited as long as it is a gas phase synthesis method. Examples of the method for forming the coating film in the present invention include various chemical vapor deposition methods such as a microwave plasma CVD method, a hot filament CVD method, and a high frequency plasma CVD method. In some cases, various physical vapor deposition methods such as an arc ion plating method and a reactive ion plating method can also be used as a method for forming a coating film. The raw material gas used for forming the coating film may be a compound gas containing carbon atoms, in addition to hydrocarbon gases such as methane, ethane, and propane, alcohol gases such as methanol and ethanol, or A carbon oxide gas such as carbon monoxide can also be used. In general, methane gas is preferably used, and a mixed gas obtained by diluting a carbon-containing gas such as methane with hydrogen is used. Furthermore, in the formation of the diamond-coated cutting insert of the present invention, it is preferable to add an inert gas such as argon gas, helium gas, or nitrogen gas to the mixed gas.

  In forming the coating film in the present invention, a hot filament method can be suitably used. FIG. 7 is an explanatory diagram of the hot filament chemical vapor deposition apparatus 19 used for forming the coating film in the present invention. Reference numeral 11 denotes a chamber of the apparatus, 12 denotes an exhaust pipe thereof, and 13 denotes a mixed gas introducing pipe such as methane and hydrogen introduced into the chamber 11. Reference numeral 14 denotes a pedestal in the chamber 11, and 15 denotes a covering base material placed on the pedestal 14. Reference numeral 16 denotes a heat filament disposed above the base material 15, and 17 denotes an electrode also serving as a support column for the heat filament 16. Reference numeral 18 denotes a power source.

  An example of a method for forming a coating film on the base material 15 by the hot filament chemical vapor deposition apparatus 19 will be described. The pressure in the chamber when forming a coating film containing diamond particles is usually 1333.22 Pa or more and 26664.4 Pa or less (10 Torr or more and 200 Torr or less). In order to form a coating film containing nano-sized diamond fine particles on the surface of the base material, it is preferable to increase the pressure in this chamber, and in a normal case, 3999.66 Pa to 15998.64 Pa (30 Torr to 120 Torr) It is. The temperature of the base material disposed in the chamber is usually 700 to 1000 ° C. In order to form a coating film containing nano-sized fine diamond particles on the surface of the base material, it is preferable to increase the temperature of the base material, and in a normal case, the temperature is 750 to 1000 ° C. The applied voltage to the hot filament 16 is 10 to 50 V, the current value is 30 to 100 A, and the hot filament power source 18 is AC or DC. The composition ratio of methane and hydrogen is 1 to 10 vol%, preferably 3 to 7 vol% of methane. Note that it is preferable to add an inert gas such as nitrogen to the carbon source gas such as methane in an amount of 1 to 20 vol%, preferably 5 to 15 vol% because a coating film containing nano-sized diamond particles can be formed. The distance between the hot filament 16 and the base material 15 is 5 to 20 mm. In this embodiment, the base material 15 was a tungsten carbide cemented carbide chip (square chip shown in FIG. 1: inscribed circle 12.7 mm, thickness 3.18 mm). And if a coating operation is continued until a 3-30 micrometers diamond thin film is formed on a chip | tip, the diamond covering cutting insert of this invention can be manufactured.

  In the Raman spectrum analysis of the coating film in the diamond-coated cutting insert of the present invention, as an oscillation source, an argon laser (oscillation lines 457.9 nm, 472.7 nm, 488.0 nm, 501.7 nm, etc.), a krypton laser (oscillation line) 476.2 nm, 520.8 nm, 568.2 nm, 676.5 nm, etc.) are preferably used.

  The above-described diamond-coated cutting insert of the present invention is excellent in hardness and wear resistance at high temperatures, and has excellent properties as a cutting edge of a cutting tool for high-speed cutting such as high-hardness steel. This diamond-coated cutting insert is useful as a throw-away tip for long-life cutting with excellent heat resistance and wear resistance. Further, this diamond-coated cutting insert is installed in a holder for a cutting tool as shown in FIG. The cutting tool of the present invention can be suitably used as an excellent cutting tool for various types of cutting, particularly high-speed cutting.

(1) Production of diamond-coated cutting inserts (Examples 1 to 5)
A diamond-coated cutting insert is manufactured by forming a coating film on the surface of a base material made of cemented carbide containing β-tungsten carbide and having a shape as shown in FIG. 1 by a hot filament method apparatus 19 shown in FIG. did.

The conditions for forming the coating film were as follows.
Chamber internal pressure: 3999.66 Pa (30 Torr),
Base material temperature: 800 ° C.
Mixed gas supply rate: 500 ml / min,
Mixed gas composition ratio (volume ratio): hydrogen / methane / nitrogen = 960/40/4,
Filament applied voltage / current: 20V / 100A,
Filament temperature: 1800 ° C
Coating film formation time: 3 to 30 hours,
Coating thickness: shown in Table 1 for each example.
An SEM photograph of the coating film formed in Example 3 is shown in FIG.

(Comparative Examples 1, 2, 5, 6)
In the conditions for forming the coating film in Examples 1 to 5, Comparative Example 1 and Comparative Example 2 formed the coating film without introducing nitrogen, and Comparative Example 5 and Comparative Example 6 were mixed gas of nitrogen. A diamond-coated cutting insert was produced by forming a coating film on the surface of the base material in the same manner as in Examples 1 to 5 except that the coating film was formed with a content of 8 vol% with respect to methane. . Moreover, the film thicknesses of Comparative Example 1 and Comparative Example 2, and Comparative Example 5 and Comparative Example 6 are different because of the difference in the time for forming the coating film. An SEM photograph of the coating film formed in Comparative Example 2 is shown in FIG.
(Comparative Examples 3 and 4)
A diamond-coated cutting insert was produced in the same manner as in Example 3 described in Japanese Patent Publication No. 62-6747.

(2) Raman spectrum of diamond-coated cutting insert and evaluation of cutting performance Table 1 shows the results of Raman spectrum analysis of the diamond-coated insert manufactured in Examples and Comparative Examples, and the results of cutting peeling test.
Raman spectrum analysis A Raman spectrum was measured using an argon laser beam (wavelength 488 nm). Strength, making linear baseline in the section 1000 cm ^-1 and 1800 cm ^-1 of the Raman spectrum were measured at a height relative to this. The Raman spectrum of the coating film formed on the base material in Example 3 is shown in FIG.
・ Cutting and peeling test Cutting is started at a constant cutting speed and incision, and the cutting feed is increased for each fixed machining length until the coating film peels. Evaluation was made by cutting feed when peeling of the coating film occurred.
Work material: Aluminum alloy (AC4A),
Tip shape: SPGN120308 Cutting edge treatment: None Cutting speed: 471 mm / min, Feed: f = 0.1 mm / rev
Cutting depth: d = 0.5mm, Cutting oil: Available

表１において、ラマンピークの欄における○はピークのあることを示し、×はピークの観測されなかったことを示す。また、表１中の「ピークが一体化」は、それぞれのラマンピーク（１４８０±５０ｃｍ^−１及び１５８０±２０ｃｍ^−１）の部分にブロードな膨らみが観測され、かつその膨らみの近傍部が重なっていたのでピークを検出できなかったことを示す。

In Table 1, ◯ in the Raman peak column indicates that there is a peak, and × indicates that no peak was observed. In Table 1, “peaks are integrated” indicates that broad bulges are observed in the respective Raman peaks (1480 ± 50 cm ⁻¹ and 1580 ± 20 cm ⁻¹ ), and the vicinity of the bulges overlaps. This indicates that no peak could be detected.

  As shown in Table 1, the cutting tools (Examples 1 to 5) provided with the diamond-coated cutting insert of the present invention are diamond coatings that do not contain nano-sized diamond particles (Comparative Examples 1 and 2), and graphite. Diamond film (Comparative Examples 3 and 4) in which the Raman spectrum peak shown by different amorphous diamonds is unclear. Even if there is a Raman spectrum peak shown by amorphous diamonds different from graphite, the relative intensity is small. It can be seen that the cutting feed is large and the durability is high as compared with a cutting tool provided with a diamond-coated cutting insert formed with a diamond coating (Comparative Examples 5 and 6) that does not fall within the range of. In addition, the cutting tool equipped with the diamond-coated cutting insert of the present invention can be used until the cutting feed becomes large when the thickness of the coating film substantially formed of nano-sized diamond particles is 3 to 30 μm. It can be seen that the durability becomes high.

  The diamond-coated cutting insert according to the present invention and the cutting tool equipped with the diamond-coated cutting insert can be used, for example, for processing an aluminum alloy, particularly for high-speed machining, as a long-life throw-away tip and a cutting tool excellent in wear resistance and peeling resistance.

FIG. 1 is a perspective view of a cutting insert. FIG. 2 is a front view of a cutting tool in which an insert is attached to an outer diameter processing holder. FIG. 3 is an electron micrograph of the diamond-coated cutting insert of the present invention. FIG. 4 is an electron micrograph of a conventional diamond-coated cutting insert. FIG. 5 is a schematic view of the diamond multilayer of the present invention. FIG. 6 is a schematic diagram of a conventional diamond multilayer. FIG. 7 is an explanatory diagram of a hot filament chemical vapor deposition apparatus. FIG. 8 is a Raman spectrum chart of the coating film formed on the base material in Example 3.

Explanation of symbols

1: Insert 2: Cutting tool 3: Holder A, B: Layer thickness of coating film 4: Coating film 5 of the present invention: Conventional coating film 6: Nano-sized diamond particles 7: Micron-sized diamond particles 8 : Graphite 9: Non-diamond component other than graphite 10: Base material 11: Chamber 12: Exhaust pipe 13: Mixed gas introduction pipe 14: Pedestal 15: Base material 16: Hot filament 17: Electrode 18 also serving as support column: Power supply 19: Hot filament chemical vapor deposition system

Claims (6)

It is a diamond-coated cutting insert with a coating film, and in the Raman spectrum analysis of this coating film, there are peaks at 1140 ± 30 cm ⁻¹ , 1330 ± 10 cm ⁻¹ , 1480 ± 50 cm ⁻¹ and 1580 ± 20 cm ^−1. A diamond-coated cutting insert having a Raman spectrum with a peak intensity at 1480 ± 50 cm ⁻¹ greater than the peak intensity at 1580 ± 20 cm ⁻¹ .   The diamond-coated cutting insert according to claim 1, wherein the coating film is formed by a gas phase synthesis method.   The diamond-coated cutting insert according to claim 1 or 2, wherein the coating film has a thickness of 3 to 30 µm.   The diamond-coated cutting insert according to any one of claims 1 to 3, wherein the surface of the base material coated with the coating film is a tungsten carbide cemented carbide containing a β phase mainly composed of titanium carbonitride.   The diamond-coated cutting insert according to any one of claims 1 to 4, wherein the coating film has a structure in which diamond fine particles smaller than the film thickness are stacked.   The cutting tool provided with the diamond covering cutting insert of any one of Claims 1-5.

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