JP2019089146A - Diamond-coated cutting tool - Google Patents

Abstract

To provide a diamond-coated cutting tool that has sufficient durability for a long period in cutting of a hard-to-cut material such as a CFRP material.SOLUTION: A diamond-coated cutting tool has a WC-based carbide alloy tool base body surface coated with a diamond coating of 3-25 μm in total thickness, and is characterized in that in a lower region in a range of 1.5-2.5 μm from right above a tool base body surface of the diamond coating in its normal direction; a crystal forming the diamond coating has a grain size of 0.1-1.0 μm; a peak intensity ratio of spbonding/spbonding of the region found through Raman spectroscopic measurement in the normal direction is 1.8-5.0; a half-value value of a spbonding-derived Raman peak is 8.0-13.0 cm; and a B content is 0.05-0.50 atm%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diamond-coated cutting tool that exhibits excellent wear resistance over a long period of time in cutting difficult-to-cut materials such as CFRP materials.

  In recent years, carbon fiber reinforced plastic (CFRP) materials and CFRP / metal stack materials (hereinafter collectively referred to as CFRP materials), which are carbon fiber bundled and hardened with epoxy resin, occupy as structural materials for aircraft and automobiles. The proportion is growing. A diamond-coated cutting tool is mainly used for cutting of CFRP material, and a further improvement of the life for shortening the processing time and reducing the cost is required.

  When cutting a difficult-to-cut material such as CFRP material using a diamond-coated cutting tool, the wear of the diamond film is dominated by abrasive wear. For this reason, the long-term use increases the unevenness on the wear surface caused by the grain shedding, the occurrence of abnormal damage such as chipping starting from this, and the exposure of the substrate to cause the tool life. There is a possibility that it becomes one, or the processing surface quality of the work material is lowered. Therefore, many proposals have been made to improve the wear resistance of diamond films.

  For example, in Patent Document 1, as an object to be cut, a cast iron or carbon steel is exemplified, and the surface of a processed portion is provided with a diamond film to which 0.05 to 2 atomic% of boron (B) is added. A tool is described, and it is described that B addition forms B oxide and improves the oxidation resistance, lubricity and durability of the diamond film.

  Further, for example, Patent Document 2 describes a tool provided with a diamond film to which B is added, and it is possible to electroprocess the film by imparting conductivity by adding B, and the tool It is described as being excellent in fracture resistance and suitable as various tools for removing press such as drawing die for dry pressing, drawing die, die for punching die and punch, cutting, turning, engraving and the like.

  Furthermore, for example, in Patent Document 3, a hard film is coated with a diamond film to which B is added on the surface of a processed portion, and a surface film made of an intermetallic compound is provided on the diamond film. Since the processing tool is described and B is added to the diamond film, the adhesion strength of the surface film to the diamond film is improved, and the composite material containing an iron-based material, Ti having a high cutting point, etc. It is described that excellent durability can be obtained also in cutting of the heat-resistant alloy of the above.

JP, 2006-152422, A JP, 2009-280421, A JP, 2006-152424, A

  In the tools described in the above patent documents, the durability of the diamond film is improved by the addition of B to the diamond film as described in these documents, but the cutting object of these tools is steel, cast iron And Ti alloys, which do not have sufficient durability to difficult-to-cut materials such as CFRP materials, which are increasingly used as structural materials for aircraft and automobiles in recent years.

  Therefore, the problem to be solved by the present invention, that is, the object of the present invention is to provide a diamond-coated tool having sufficient durability over a long period to a difficult-to-cut material such as CFRP material.

The inventors of the present invention conducted intensive studies to solve the above problems, and found that adding B into the diamond film and adjusting only the amount of B in the film can not solve the problem, and thus CFRP materials etc. Phenomena leading to tool life when cutting difficult-to-cut materials, that is, as a result of detailed analysis of the progress of wear in cutting of difficult-to-cut materials such as CFRP, crystal grain diameter immediately above the substrate of diamond film, sp ³ We have obtained new findings that the tool life can be dramatically extended by controlling the ratio of bonding components, the crystallinity and the amount of B in the film to predetermined values.

That is, the present invention
“(1) A diamond-coated cutting tool having a total thickness of 3 to 25 μm coated with a diamond film on the surface of a WC-based cemented carbide tool substrate,
In the lower region in the range of 1.5 to 2.5 μm in the normal direction from directly above the tool substrate surface of the diamond film,
The crystal grain size forming a diamond film is 0.1 to 1.0 μm, and the peak intensity ratio of sp ³ bond / sp ² bond determined by Raman spectroscopy in the normal direction of the region concerned is 1.8 to And the half value width of the Raman peak derived from sp ³ bond is from 8.0 to 13.0 cm ⁻¹ , and the B content is from 0.05 to 0.50 atomic%,
Diamond coated cutting tool characterized by
(2) The diamond-coated cutting tool according to (1), wherein the total thickness of the diamond film is 5 to 15 μm.
(3) The diamond-coated cutting tool according to (1) or (2), wherein the diamond film immediately above the lower region is a single layer or two or more layers. "
It is.

The diamond-coated cutting tool according to the present invention relates to a diamond film, and the peak intensity ratio of sp ³ bond / sp ² bond in the lower region in the range of 1.5 to 2.5 μm from directly above the tool substrate surface to its normal direction Providing the appropriate stress and crystallinity indicated by the half value width of the Raman peak derived from the sp ³ bond has a remarkable effect that the tool life can be extended in cutting of difficult-to-cut materials such as CFRP materials.

It is a schematic diagram which shows the structure of the diamond film of this invention.

  Hereinafter, the present invention will be described in detail, including the description of the optimum range of matters defined in the present invention.

-Total thickness of diamond film In the present invention, the total thickness of the diamond film is the sum of the thicknesses of the lower region and the portion immediately above it (hereinafter referred to as the upper region), and is 3 to 25 μm. The lower limit (3 μm) is necessary to obtain a satisfactory life in cutting of difficult-to-cut materials such as CFRP materials, in addition to the fact that the thickness of the lower region described later needs 1.5 to 2.5 μm. It is the lower limit. On the other hand, the upper limit value (25 μm) is an upper limit for securing the sharpness of the cutting edge of the tool, obtaining processing accuracy, preventing burrs and delamination, and not lowering the processing surface quality. In order to more reliably achieve the purpose of defining the lower limit value and the upper limit value, it is desirable that the total thickness of the diamond film be 5 to 15 μm.
Here, the total thickness of the diamond film is a thickness of a cross section (longitudinal cross section) in a direction normal to the tool substrate, and for example, an observation range is set to 50 μm × 50 μm by a scanning electron microscope, Three fields of view are observed, and five observation points are optionally provided in each field of view, and the thickness at each point is obtained and the average value thereof is calculated.

2. Lower Region of Diamond Film The lower region of the diamond film is in the range of 1.5 to 2.5 μm in the normal direction from immediately above the tool substrate surface. If the thickness is less than 1.5 μm, the amount of sp ³ bonding is significantly reduced, and there is a possibility that the wear resistance and adhesion of the lower region may not be sufficiently exhibited. On the other hand, if it exceeds 2.5 μm, the crystal grains become too large, and the precipitation is dominant, so that processing accuracy can not be obtained, burrs and delamination may occur, and the processed surface quality may be degraded. .

3. Crystal grain size of lower region of diamond film The crystal grain diameter of the diamond film in the lower region is 0.1 to 1.0 μm. If the thickness is less than 0.1 μm, the amount of sp ² bonding is too large, which may reduce the wear resistance. On the other hand, if it exceeds 1.0 μm, crystal grains become too large, and chipping may easily occur from these crystal grains as a starting point.

  Here, the crystal grain size is measured as follows. That is, in the lower area of the diamond film, an area of 15 μm × 15 μm parallel to the tool substrate surface is processed by focused ion beam method, and the processed surface is observed by a transmission electron microscope, and a line of 5 μm in the direction parallel to the substrate surface. Arbitrary five lines were defined, and it was set as the average value divided by the number of crystal grains crossing each line segment.

4. Peak intensity ratio of sp ³ bond / sp ² bond determined by Raman spectroscopy in the direction normal to the tool substrate surface in the lower region of the diamond film Raman spectroscopy in the direction normal to the tool substrate surface in the lower region of the diamond film The peak intensity ratio of sp ³ binding / sp ² binding determined by measurement is 1.8 to 5.0. If the ratio is less than 1.8, the amount of sp ² bonding in the lower region is too large, which may lower the adhesion between the diamond film and the tool substrate. On the other hand, if it exceeds 5.0, the amount of sp ³ bonding component in the lower region is too large, and excessive compressive stress acts on the interface of the tool substrate, so that the diamond film is easily peeled off from the interface of the tool substrate. And the peak intensity ratio of sp ³ bond / sp ² bond is preferably in the range of 2.1 to 4.7.

Here, the peak intensity ratio of sp ³ bond / sp ² bond is determined by Raman spectroscopy. The light source used for the measurement is a laser beam with a wavelength of 532 nm. The obtained Raman spectrum is waveform separated, and the peak intensity of sp ³ bond observed near 1332 cm ⁻¹ and the peak intensity of sp ² bond observed near 1580 cm ⁻¹ after waveform separation are measured, sp ³ bond / sp Calculate the peak intensity ratio of ² bonds.

5. Half-width of Raman peak from sp ³ bond in lower region of diamond film The half-width of the Raman peak from sp ³ bond is set to 8.0 to 13.0 cm ⁻¹ . If it is less than 8.0 cm- ¹ , the crystallinity of the diamond film in the lower region is high, so excessive compressive stress acts on the diamond film, and the diamond film is easily peeled off from the interface of the tool substrate. On the other hand, when it exceeds 13.0 cm ⁻¹ , the crystallinity of the diamond film in the lower region is low, and the wear resistance of the diamond film is lowered. And as for the half value width of the Raman peak derived from sp < ³ > coupling | bond, 9.0-12.0 cm < ^-1 > is a desirable range.

6. B Content in Lower Region of Diamond Film B content in diamond film in lower region is 0.05 to 0.50 atomic%. If the content is less than 0.05 atomic%, the effect of alleviating compressive stress in the lower region diamond film is insufficient, so that the diamond film tends to be peeled off from the interface of the tool substrate. On the other hand, if it exceeds 0.50 atomic%, the crystallinity of the diamond film in the lower region is lowered, and the wear resistance of the diamond film is lowered. The B content in the diamond film in the lower region is desirably in the range of 0.10 to 0.40 atomic percent. The amount of B added to the membrane can be determined by time-of-flight secondary ion mass spectrometry or the like.

7. Diamond film directly above lower region (upper region) The upper region of the diamond film is in direct contact with a difficult-to-cut material such as CFRP material, and is not particularly limited as long as it is a known diamond film. For example, in the upper layer portion, B may be doped or not, and even if it consists only of columnar crystals (sometimes referred to as a single crystal layer or a crystal layer), crystal growth of crystal grains It may have a laminated structure of only microcrystals whose length in the direction is equal to or less than a predetermined dimension, or a laminated structure consisting of the columnar crystals and the microcrystals.
Specifically, B does not contain or B consists only of columnar crystals with a content of 1.00 atomic% or less, B is added with 1.00 atomic% or less, and the crystal grain size of the longitudinal cross section or the longitudinal cross sectional direction 2. The width of the crystal grains is 0.5 to 3.0 μm, and each layer is formed of only microcrystals having a growth direction length of 10 to 200 nm, and B is further added at 1.00 atomic% or less. What laminated | stacked the unit layer which consists of the columnar crystal which has a growth direction length of 0 micrometer or less, and the microcrystal of the growth direction length of 30-400 nm can be illustrated.

7. Method of producing a diamond film It is desirable to use a hot filament CVD method for producing a diamond film in the diamond-coated cutting tool of the present invention. However, it can also be manufactured using a synthesis method such as a high frequency plasma method or a microwave plasma method which is a generally known film forming method.

Next, an example will be described.
Here, a diamond-coated drill will be described as a specific example of the diamond-coated cutting tool according to the present invention, but the present invention is not limited to this and can be applied to diamond cutting tools such as diamond-coated end mills and diamond-coated inserts Needless to say.

(A) Tool substrate manufacturing process As a raw material powder, WC powder, Co powder, TaC powder, NbC powder, Cr ₃ C ₂ powder having a predetermined average particle diameter within the range of 0.5 to 0.9 μm are listed. The mixture was compounded in the proportion shown in 1 and further mixed with paraffin as a binder and toluene as a solvent, or toluene as a solvent, or xylene, mesitylene, tetralin or decalin, ball mill mixed in acetone for 24 hours, and dried under reduced pressure. Thereafter, they are extruded and molded into round bar compacts having a diameter of 10 mm and a length of 150 mm, and these round bar compacts are subjected to 1 to 2 at a temperature of 1380 to 1500 ° C. in a vacuum atmosphere of 1 Pa. It sintered on the sintering conditions of hold | maintaining time, and obtained the sintered compact. Thereafter, the sintered body was polished to produce a WC-based cemented carbide sintered body.
Next, the WC-based cemented carbide sintered body is ground so that the outer diameter of the groove-forming portion is 7 mm, whereby a WC cemented carbide drill tool base (hereinafter simply referred to as “drill base” or “ Substrates A to B) were prepared.

Before forming a diamond film on the drill substrate, the Co existing in the vicinity of the surface of the drill substrate is removed by chemical treatment to form fine irregularities on the surface of the substrate. The drill substrate is subjected to an ultrasonic treatment with a solution in which a diamond powder having a particle diameter of 0.5 μm or less and a surfactant are added to isopropyl alcohol, and then subjected to an ultrasonic treatment.
Subsequently, the drill substrate A and the drill substrate B were loaded into a hot filament CVD apparatus, and a B-added diamond film was formed on the lower region under the film forming conditions described in Table 2; Under the film forming conditions, a columnar crystal diamond film having B added or not added to the upper region was formed. As a raw material of B, a mixed gas containing 1000 ppm of trimethylboron: B (CH ₃ ) _{3 in} hydrogen gas was used. In addition, the following "%" is "volume%", and the following numerical ranges show the range of what was described in Table 2, 3 roughly.
(Deposition condition of lower region)
Gas composition CH ₄ : 1.0 to 2.0%, (B (CH ₃ ) ₃ + H ₂ ) mixed gas: 0.5 to 5.0% H ₂ : balance of gas flow rate CH ₄ : 20 to ₄₀ sccm, (B (CH ₃ ) ₃ + H ₂ ) mixed gas + H ₂ : 2000 sccm
Pressure 700-800Pa
Filament temperature 2270-2330 ° C
Drill base temperature 930 to 970 ° C
(Deposition condition of upper region)
Gas composition CH ₄ : 0.9%, (B (CH ₃ ) ₃ + H ₂ ) mixed gas: 0 or 6.3%, H ₂ : remaining gas flow rate CH ₄ : 18 sccm, (B (CH ₃ ) ₃ + H ₂ ) Mixed gas + H ₂ : 2000 sccm
Pressure 1000Pa
Filament temperature: 2800 to 2120 ° C
Drill base temperature 780 ~ 820 ° C
Under these conditions, the diamond film in the lower region and the crystal layer diamond film in the upper region are formed, and the total thickness of the diamond film shown in Table 5, the crystal grain size in the lower region, and the Raman spectroscopy measurement in the normal direction Invention coated tools 1 to 11 and 1 ′ to 11 ′ having the peak intensity ratio of sp ³ bond / sp ² bond, and the half width of the Raman peak derived from sp ³ bond and the B content were produced.

Further, for the purpose of comparison, a diamond film of the lower region to which B is added is formed on the above-mentioned drill substrate under the film forming conditions described in Table 4, and subsequently B is formed on the upper region under the film forming conditions described in Table 3. Were deposited to form columnar crystal diamond films with or without B added, to produce comparative coated tools 1 to 12 and 1 ′ to 12 ′ shown in Table 6. In the lower region deposition, trimethoxyboron was used instead of trimethylboron to make some comparative coated tools. Outside the reaction furnace, while bubbling hydrogen as carrier gas in liquid trimethoxyboron, the heater is heated and vaporized by a heater, and the mixed gas containing 1000 ppm of trimethoxyboron in hydrogen is controlled in the furnace while controlling the flow rate Introduced to Since an oxygen atom is present in trimethoxyboron and this removes sp ² components during film formation, a diamond film formed using trimethoxyboron (B (OCH ₃ ) ₃ ) has sp ³ bonds / The peak intensity ratio of sp ² binding is too high. As a result, excessive compressive stress acts on the tool substrate interface, and the diamond film is easily peeled off from the tool substrate interface.

Next, for the coated tools 1 to 11 and 1 ′ to 11 ′ of the present invention and the comparative coated tools 1 to 12 and 1 ′ to 12 ′, a cutting test by cutting through holes of a work material shown below is carried out. The number of cutting holes reached the end of life was measured.
<Cutting test 1>
Work material: CFRP
CFRP (20 mm in thickness)
Feeding: 0.15 mm / rev
Cutting speed: 150 m / min
<Cutting test 2>
Work material: CFRP / Al alloy stack material (upper part is CFRP, lower part is Al alloy)
CFRP (20 mm in thickness)
Feeding: 0.15 mm / rev
Cutting speed: 150 m / min
Al alloy (A 7075, thickness 10 mm)
Feeding: 0.1 mm / rev
Cutting speed: 60 m / min
Cutting speed: cutting was started at 150 m / min, and the cutting speed was decreased from 2.0 mm before penetrating the CFRP so as to be 60 m / min when cutting Al alloy.
<Cutting test 3>
Work material: CFRP / Ti alloy stack material (upper part is CFRP, lower part is Ti alloy)
CFRP (thickness: 20 mm)
Feeding: 0.15 mm / rev
Cutting speed: 150 m / min
Ti alloy (Ti-6Al-4V alloy, thickness 10 mm)
Feeding: 0.05 mm / rev
Cutting speed: 20 m / min
Cutting speed: cutting was started at 150 m / min, and the cutting speed was decreased from 2.0 mm before penetrating the CFRP so that it was 20 m / min when cutting Ti alloy.
Tables 7 to 9 show the results of cutting tests 1 to 3. The number of final service life holes is the result of observing the flanks of the drill bit after every first 10 drillings and every 10 drillings thereafter. In addition, the life was judged by the abrasion and abnormal damage by normal abrasion.

As apparent from the results shown in Tables 7 to 9, the diamond-coated cutting tool of the present invention (the coated tool of the present invention) is coated with a diamond film having a total thickness of 3 to 25 μm. In the lower region in the range of 1.5 to 2.5 μm in the normal direction, the crystal grain size for forming a diamond film is 0.1 to 1.0 μm, and Raman spectroscopy measurement of the region in the normal direction The peak intensity ratio of sp ³ bond / sp ² bond determined by the method is 1.8 to 5.0, and the half value width of the Raman peak derived from sp ³ bond is 8.0 to 13.0 cm ⁻¹ Since the B content is 0.05 to 0.50 atomic percent, sufficient durability over a long period of time can be achieved for difficult-to-cut materials such as CFRP regardless of the content of B in the upper region diamond film. Have .
On the other hand, the comparison coated tool which does not satisfy even one of the items defining the diamond coated cutting tool of the present invention is the cutting of difficult-to-cut materials such as CFRP regardless of the inclusion of B in the upper region diamond film. In the short-term to reach the end of life.

  As described above, the coated tool of the present invention can be used not only for cutting of difficult-to-cut materials such as CFRP materials, but also as coated tools for various types of work materials, and has excellent cutting performance over long-term use By doing this, it is possible to sufficiently satisfy the demand for higher performance of the cutting device, labor saving and energy saving of the cutting process, and cost reduction.

Claims (3)

A diamond-coated cutting tool having a total thickness of 3 to 25 μm coated with a diamond film on the surface of a WC-based cemented carbide tool substrate,
In the lower region in the range of 1.5 to 2.5 μm in the normal direction from directly above the tool substrate surface of the diamond film,
The crystal grain size forming a diamond film is 0.1 to 1.0 μm, and the peak intensity ratio of sp ³ bond / sp ² bond determined by Raman spectroscopy in the normal direction of the region concerned is 1.8 to And the half value width of the Raman peak derived from sp ³ bond is from 8.0 to 13.0 cm ⁻¹ , and the B content is from 0.05 to 0.50 atomic%,
Diamond coated cutting tool characterized by   The diamond-coated cutting tool according to claim 1, wherein a total thickness of the diamond film is 5 to 15 m.   The diamond-coated cutting tool according to claim 1 or 2, wherein the diamond film directly above the lower region is a single layer or two or more layers.