JPH1158106A - Diamond-coated cutting tool and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diamond-coated cutting tool, which allows high speed cutting, has a long life and gives a precise cut surface. SOLUTION: A raw material, whose coefficient of expansion is not more than 5.0×10<-6> / deg.C and which contains at least 90 wt.% of WC as a main component, is used as cemented carbide 1. A diamond-coated layer 2 is formed in such a way that the diameter of a crystal grain of diamond is not more than 3 μm and the ratio of synthesis of diamond is not more than 0.1. The diamond- coated layer 2 can easily be formed by heat-treating cemented carbide 1 first, planting the carbide with ultrafine particulate diamond, and then applying a vapor-phase synthetic method to the carbide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool used for processing non-ferrous metal materials, electronic materials, optical parts, etc., and more particularly to a cutting tool having a thin diamond coating layer formed by a vapor phase synthesis method and a method for producing the same.

[0002]

2. Description of the Related Art As a cutting tool material used for this kind of machining, natural or synthetic single crystal or polycrystalline diamond is known to be excellent due to characteristics other than hardness and heat conductivity. As the synthetic diamond, a sintered diamond formed by an ultra-high pressure sintering method and a diamond formed by a diamond coating layer formed by a low-pressure gas phase synthesis method have been put into practical use.

[0003] Each of the above-mentioned diamonds has its own characteristics, but from the viewpoint of cost and other aspects, it is most preferable to use a diamond coating layer formed by a vapor phase synthesis method. There are still problems such as instability.

[0004]

A number of methods have been proposed for increasing the adhesion of the diamond coating layer and for improving the quality and thickness of the diamond coating layer. is there. Japanese Patent Application Laid-Open No. 7-172988 proposes that nitrogen be contained in a synthetic gas in order to obtain a diamond coating layer having a high quality and a smooth surface with a reduced thickness.

The above proposal suggests that a thin layer, that is, a fine-grained thin film diamond coating layer, has an excellent effect in air nozzles, water nozzles, and the like.
It is an excellent proposal, but it seems that it has not yet reached a practical level.

[0006] In the field of cutting, a diamond layer is coated on the surface of a cemented carbide with a thickness of 10 to 30 µm, and has been put to practical use as a cutting tool. However, a diamond coating method for a thin film has not been put to practical use. Since a severe thermal shock is applied to the cemented carbide tool during cutting, it is required that the cemented carbide base material and the coating layer are bonded very firmly. As a commonly used base material for diamond coating, a Si crystal is used, and a technique for freely controlling the film thickness from a thin film to a thick film is already known. Such diamond coating on tools used under severe environmental conditions has not yet been sufficiently studied. Particularly in the field of cutting, such a fine-grained thin film coating layer has not been put to practical use. This seems to be due to the difficulty in producing the required coating layer and insufficient research on problems such as the shape of the cutting tool suitable for the coating layer.

[0007]

The present invention has been achieved by focusing on the above-mentioned problems and conducting repeated trial production research. The features of the present invention are as follows.

As a result of repeated investigations and studies on the problem of diamond coating in cutting work, it was found that peeling of the coating layer and chipping of the edge portion became problems, and that abrasion of the diamond layer was not a particularly serious problem. That is, the problem can be solved by reducing the difference between the coefficient of thermal expansion of the cemented carbide and the coefficient of thermal expansion of diamond and reducing the compressive stress applied to the cutting edge. In particular, it is very difficult to reduce the thickness of the coating layer with a cemented carbide in reducing the stress applied to the cutting edge.
That is, on a cemented carbide, the initial diamond layer changes to carbon or amorphous diamond due to the reaction of a metal such as Co or the like, so that a complete diamond crystal is not formed on the order of several μm. This is because the crystallization shown in FIG. 6 proceeds from the amorphous layer shown in FIG. 5, and when 20 to 30 μm is stacked, a complete crystal is formed as shown in FIG. 7.

The gist of the present invention is that a thin diamond coating layer having a thickness of 3 μm or less is successfully formed on a cemented carbide. Especially throwaway tips,
It is characterized by solving the problem with cutting tools, such as drills and end mills, where considerable thermal stress is applied to the tool edge.

According to the constitution of the present invention, the cemented carbide has a coefficient of thermal expansion of not more than 5.0 × 10 ⁻⁶ / ° C.
Is that the stress at the interface between the diamond coating layer and the cemented carbide layer, which is generated at the time of cutting, is reduced by using a base material having a content of 90% by weight or more. If the coefficient of thermal expansion is not less than 5.0 × 10 ⁻⁶ / ° C., the film is immediately peeled off, which is not suitable for practical use. W as the main component
When C was 90% by weight or less, a fine particle thin film could not be coated. The crystal grain of the cemented carbide is preferably 1 μm or less.
Further, the strength of the cemented carbide is desirably 200 kg / mm ² or more. If the strength is lower than this, reliability is applied.

The next requirement of the invention is that the diamond coating layer has a crystal size of 3 μm or less, and the diamond synthesis rate (the diamond peak near 1333 cm ⁻¹ and the 1500
cm amorphous ratio of the peak of the graphite structure of ^{-1 ~1600cm -1)} it is 0.1 or less, and surface roughness of the diamond coating layer is equal to or less than Rmax3myuemu. 3 μm crystal grains of diamond coating layer
When the control is performed as follows, the diamond film strength is improved and the surface roughness of the diamond coating layer is improved, so that the coefficient of friction between the diamond coating layer and the work material is reduced. Preferably, when the crystal grain size of the diamond coating layer is 1 μm or less, the peeling resistance is further improved. Therefore, precipitation of ultrafine crystals gives better results.

In the practice of the present invention, the WC
By using a cemented carbide having a fine crystal grain size, desirably a crystal of 1 μm or less, and seeding ultrafine diamond grains at the edge of the WC crystal, it is found that fine diamond grains are precipitated. Was. In the diamond coating based on the cemented carbide, it was found that fine diamond crystals were precipitated from the edge of the WC crystal of the cemented carbide.

It has also been found that if ultrafine diamond grains are seeded in advance, perfect diamonds are synthesized from the beginning of the formation. In other words, fine and perfectly crystalline diamond from the beginning of coating (Fig. 7)
Is produced, so that a vapor-phase synthetic diamond having a thin and strong strength can be obtained.

In order to further improve the adhesive strength at the interface between the cemented carbide and diamond, heat treatment as a pretreatment for coating, that is, hydrogen, CH ₄ , CO
Good results are obtained when heating is performed in the presence of a gas such as, or a solution such as an organic substance or a solid substance that forms a reducing atmosphere.

The heat treatment has the effect of reducing the content of the binding metal, particularly Co, on the surface of the cemented carbide substrate, and it is preferable to have a carbon element in the treatment atmosphere in order to increase the effect.

As the cutting tool, a rotary cutting tool, a turning tool or a throw-away tip, in which only the blade portion of the tool is formed of a cemented carbide or the entire tool is formed of an integral cemented carbide. It is a part of it.

In the case of a throw-away (TA) chip, any shape can be used as long as a diamond coating layer having the above configuration is provided on at least the cutting edge surface of a polygonal cemented carbide thin plate having the above configuration. It is good, but if the polygonal shape is specified as follows, it can be used as a complete TA chip.

That is, a part of each side is cut out on at least two or more sides of the polygon, and the cutout edge forms a concave mold blade. If this polygon is a regular polygon such as a square or an equilateral triangle, and the notched edges are formed in symmetrical positions at symmetrical positions on each side, it can be used more effectively.

In the case of a full-type TA tip having the above-described shape, it is considered that the configuration of the cemented carbide and the diamond coating layer can be used depending on the cutting conditions, even if the above requirements are not necessarily satisfied. .

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in the following embodiments.

[0021]

【Example】

(Embodiment 1) FIGS. 1 (a) and 1 (b) are a front view and a side view of an embodiment of an end mill in which the entire tool is made of an integral cemented carbide 1. The tool length A is 45 mm, the blade diameter B is 5 mm. The blade length C of the four blades is 20 mm. The material of the cemented carbide 1 is JISK10 (WC-6% Co), and the portion of the blade length C (cutting edge component) is covered with a thin film of the diamond coating layer 2 as shown by hatching by the following manufacturing method. Have been done. Although this thin film may be provided only on the cutting edge portion 3 (cutting edge), it is often more advantageous to provide it over the entire blade length C in terms of manufacturing and use.

The crystal grain size of the WC layer is 0.5 μm, the Co content of the bonding layer is 4% by weight, and the coefficient of thermal expansion is 4.5 × 10 ⁻⁶ /
1C was machined to produce an end mill substrate without the diamond coating layer 2 in FIG. This substrate was applied by the applicant to International Publication No. WO94 /
Heat treatment as described in JP 13852, that is, the substrate was charged into a hot filament CVD apparatus, and the substrate temperature was maintained at about 900 ° C. for about one hour or more in an atmosphere of H ₂ -1% CH ₄ .

This heat treatment facilitates the precipitation of diamond crystals on the surface of the cemented carbide and improves the adhesive strength. However, if precipitates or soot remain on the surface of the cemented carbide, It is necessary to remove the WC crystal so that the WC crystal comes out on the surface.

The above-mentioned precipitates and soot can be removed by replacing the atmosphere in the CVD apparatus with H ₂ and removing it by heating, or by taking out the apparatus and washing and etching it. In any case, the surface roughness of the removed surface is preferably set to about Rmax 1 μm or less for the seeding of the next ultrafine diamond or the generation of the diamond coating layer by the CVD apparatus. Removed.

The end mill substrate thus removed was thoroughly washed, and super abrasive grains of about 0 to 1/8 μm or less were dispersed and seeded on the cutting edge forming surface. The removed cutting edge forming surface had a small amount of bonding metal, a small interval between hard phase particles, and small cracks, which seemed to have a favorable effect on dispersion seeding by hand. According to the ultra-fine diamond colloid solution using the ultra-fine diamond with reduced impurities and increased hydrophilicity,
The ability to perform uniform dispersion seeding in water is described by Mr. Hiroshi Makita (New Diamond. Tokushima University, 1996.
Vol, 12No. 3), and it is considered that this is also possible.

The end mill base material from which the heat treatment and the products have been removed is placed on the hot filament C with the cutting edge side up.
The diamond coating layer was placed upright in the VD apparatus and a diamond coating layer was formed over the entire length of the cutting edge under the following conditions. Atmosphere H ₂ -1% CH ₄ Pressure 100 Torr Temperature Filament temperature 2180 ° C Base material temperature 850 ° C Reaction time 5 hours

By reducing the reaction time to about 1/2 or less of the conventional reaction time performed without seeding as described above, the grain growth of diamond is suppressed, and the density of the diamond is 1 μm or less and the thickness is 5 μm or less. A high quality fine diamond coating layer 2 was obtained with strong adhesion to the substrate surface.

When this diamond coating layer 2 was measured by Raman spectroscopy, as shown in FIG.
Only the diamond peak near 1333 cm ^-1 could be identified as a diamond phase. The surface roughness of the diamond coating layer 2 was Rmax 1 μm or less. The diamond synthesis rate of the diamond phase (the diamond peak near 1333 cm ⁻¹ and the
Ratio of amorphous peak of graphite structure of １1600 cm ⁻¹ )
Needs to be 0.1 or less.

As described above, according to the cutting edge constituted by the diamond coating layer formed of a dense and high-quality thin film having a strong adhesive force to the substrate surface, for example, a conventional sintered diamond cutting edge can be used to form a high Si--Al alloy. When cutting is performed, it is not possible to obtain a cut surface of Rmax 1 μm from chipping of the cutting edge.
Although it is about μm to 30 μm, it is difficult to form a sharp cutting edge configuration, and peeling due to thermal strain has occurred. However, these problems can be solved at once.

As shown in the perspective view of FIG. 2, the JIS symbol A
DC-12 Si-11wt%, Cu-2.5wt% residual A
1 was subjected to a cutting process, and a pseudo test of groove processing (amount of removal: 0.1 mm) of the spiral compressor by the same drill was performed. The arrows in the figure indicate the direction of rotation and the direction of travel of the end mill 1 '.

The conditions and results of the pseudo test are shown in FIG.
4 and FIG. 4, where Ad indicates axial depth and Rd = radial depth, black circles in the table indicate the same shape of cemented carbide end mills, and black triangles indicate the same standard conventional diamond coating (by CVD). 1 such as columnar crystals
The end mill and the black square are the same as those in the first embodiment.
Shown by end mill.

As can be understood from FIG. 3, the one according to the embodiment has a much smaller flank wear width than the conventional one with the cemented carbide cutting edge, and as can be understood from FIG. The surface roughness of the cut surface of the workpiece is better than that of a conventional cemented carbide cutting edge as well as that of a standard diamond coated end mill.

(Embodiment 2) FIGS. 8 (a) and 8 (b) are a plan view and a side view of a diamond-coated indexable insert (TA) chip, and FIG. This TA chip is a cemented carbide TA chip 5 formed as shown using a cemented carbide substrate of the same quality as in Example 1.
The lower limit line 6 for forming the diamond coating layer 2
That is, a diamond coating layer 2 similar to that of Example 1
Was formed.

The method of forming the diamond coating layer 2 and the quality, thickness and surface roughness thereof were the same as those of the first embodiment, but the portion where the diamond coating layer 2 was provided could be formed on almost the entire peripheral surface of the TA chip. Only the cutting edge 3 may be used.

The length E of one side of this embodiment is 6 mm, and the thickness D is 2.38 mm. A 0.2 mm radius is provided at a corner where the rake face of each side intersects, and a concave shaped blade 7 having a width F of 2.3 mm, a depth G of 0.5 mm and an inclination angle H of 90 ° is provided at the center of each side. Was formed. The first corner I of the concave shaped blade 7 is 16 °, the width K is 0.2 mm, and the second corner L is 16 °.

The above example TA was attached to a clamp-type cutting tool shank, and a full-form cutting test was performed. As a result, the same results as in Example 1 were obtained.

This is because the conventional end mill cutting edge made of a diamond coating layer having a thickness of about 10 μm to 30 μm containing coarse grains or columnar or diamond-like carbon makes it difficult to sharply form the entire shape. It seems that this was made possible by the sharp cutting edge of the high quality diamond coating layer of about 5 μm or less. Incidentally, an enlarged micrograph of the cutting edge portion 3 is shown in FIG. 10, and an enlarged micrograph of the flank of the same is shown in FIG.

(Embodiment 3) In this embodiment, as shown in FIG. 12, the shape of the square of Embodiment 2 is made a regular triangular TA chip shape, and the concave shaped blade 7 is not provided at the center portion but in a symmetrical position offset. This is an example in which the information is provided. The length E of one side is 16.5 mm, the thickness D is 3.18 mm, the width F of the cutting edge is 2.3 mm, the inclination angle H is 90 °, the first angle I is 11 °, and the second angle L is 20 °. is there. The results of this cutting test were also good.

By providing the TA chip with concave shaped blades on each side of the polygon, the life of the chip can be doubled by the number of blades provided, as compared with a single blade. Therefore, the quality of the cutting and the efficiency thereof can be remarkably improved. Note that, in the embodiment, a case in which a full-shaped blade is provided at the center or a symmetric position of each side of a regular polygon is shown, and this shape is most effective in production and use, but if necessary, some of the sides may be used. May be provided at two or more sides at a position other than the center or the symmetric position.

[0040]

As described above, according to the present invention, non-ferrous metal materials such as aluminum alloys, electronic materials, and optical parts can be cut with high precision and low surface roughness, and the life is long. In addition, when used as a TA chip, the entire shape can be cut very efficiently.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a front view and a side view of an end mill according to a first embodiment.

FIG. 2 is a perspective view for explaining a method of performing a pseudo test using the end mill according to the first embodiment.

FIG. 3 is a table showing conditions and results of a pseudo test.

FIG. 4 is a chart similar to FIG.

FIG. 5 is a chart showing the results of Raman spectroscopic analysis of a diamond layer, in which an amorphous layer appears.

FIG. 6 is a chart showing the results of Raman spectroscopic analysis of the diamond layer, showing that the crystallization of diamond is progressing in the amorphous layer.

FIG. 7 is a chart showing the results of Raman spectroscopic analysis of the diamond layer, which shows that the entire surface is made of only diamond crystals.

FIGS. 8A and 8B are a plan view and a side view of a TA chip according to a second embodiment.

FIG. 9 is a development view illustrating a blade edge portion according to the second embodiment.

FIG. 10 is an enlarged micrograph showing the structure of the cutting edge portion of Example 2.

FIG. 11 is an enlarged micrograph showing the structure of the flank of the cutting edge portion in FIG. 7;

FIG. 12A is a front view showing a TA chip according to a third embodiment;
(B) Front view, (c) Partial side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Integral cemented carbide 1 'Diamond coating end mill 2 Diamond coating layer 3 Cutting edge part 4 Al alloy block 5 Cemented carbide TA chip 6 Lower limit line of diamond coating layer 2 formation 7 Concave shaped blade A Tool length B Blade diameter C blade Length D Thickness of TA tip E Length of one side of TA tip R Width of blade notched from R F side of corner G Length of blade notched from side G Inclination angle of blade notched on side I I of concave shaped blade 1st corner KI width L 2nd corner of concave shaped blade Ad Axial depth Rd Radial depth

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Rihito Yoshitake 2-80 Hokita-cho, Sakai-shi, Osaka Osaka Diamond Co., Ltd.

Claims (5)

[Claims] 1. A tool in which only a part of a tool forming a blade portion is made of a cemented carbide, or a tool in which the entire tool is made of an integral cemented carbide, wherein a cutting edge is a cemented carbide base. Formed on the required surface of the material by a diamond coating layer produced by a vapor phase synthesis method, and the cemented carbide substrate and the diamond coating layer are the following A,
A diamond-coated cutting tool comprising all of B and C. A. The cemented carbide substrate has a coefficient of thermal expansion of 5.0 × 10 ⁻⁶ / ° C. or less and contains 90% by weight or more of WC as a main component. B. Diamond coating layer, the grain size of the crystals of diamond phase does not exceed 3μm or less, and the diamond synthesis rate by the results of Raman spectroscopic analysis (1333 cm ^-1 vicinity of the diamond peak and 1500cm ^-1 ~1600cm ^-1
(A ratio of the amorphous peak of the graphite structure) is 0.1 or less. C. The surface roughness of the diamond coating layer is Rma
x3 μm or less. 2. The cemented carbide material has a WC layer having a crystal grain size of 1
^2. The tool according to claim 1, wherein the transverse rupture strength is 200 kg / mm ² or more and the thickness of the diamond coating layer is 5 μm or less. 3. A tool formed entirely of a one-piece cemented carbide is an end mill or a drill, and the diamond coating layer of the end mill or the drill is formed on any of the following A or B: A tool according to claim 1 or claim 2. A. The diamond coating layer is formed only on the entire cutting edge component. B. The diamond coating layer is formed only on the cutting edge in the cutting edge component. 4. The tool according to claim 1, wherein the tool entirely formed of a one-piece cemented carbide is a throw-away tip. 5. A cemented carbide comprising a step of heat-treating a cemented carbide substrate in a reducing atmosphere such as carbon or hydrogen, and a step of seeding ultra-fine diamond in a portion of the substrate on which a diamond coating layer is to be formed. Inserting the alloy base material into a vapor phase synthesizing apparatus, and forming a diamond coating layer having a crystal grain diameter of 3 μm or less and a layer thickness of 3 μm or less on the seeding peripheral surface by diamond coating. Tool manufacturing method.