JP2675218B2 - Polycrystalline diamond tool and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystalline diamond tool having good strength, welding resistance and heat resistance and suitable as a cutting tool or a wear resistant tool, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Diamond for tools has conventionally been made by sintering. The diamond fine powder is put into a mold and sintered under high temperature and high pressure. Tools using sintered diamond are used for cutting tools, drill bits, drawing dies and the like of non-ferrous metals. For example, Japanese Patent Publication No. 52-12126 discloses a method in which diamond powder is sintered in a state of being in contact with a powder compact of a WC-Co cemented carbide, and a part of Co is caused to enter the diamond powder as a bonding metal. Accordingly, a diamond sintered body having about 10 to 15% by volume of Co is disclosed. This diamond sintered body,
It has practical performance as a cutting tool for non-ferrous metals. However, this had a problem in heat resistance. For example, if it is heated to 700 ° C. or higher, the wear resistance and the strength are lowered. Further, at a temperature of 900 ° C. or more, the sintered body is broken.

The cause of such decrease in heat resistance is considered as follows. One is that the diamond is graphitized at the interface between the binding material Co and the diamond particles. The other is that, because the thermal expansion coefficients of Co and diamond are different, a high temperature causes a strong thermal stress at the interface between the two. In order to improve the heat resistance of such a diamond sintered body, Japanese Patent Laid-Open No. 53-114589 proposes acid treatment of the sintered body to remove Co as a binding metal. In this case, since there is no interface between Co and diamond, the problems of graphitization and thermal stress should be eliminated. However, in this method, holes are formed after Co is removed. The heat resistance is improved, but the mechanical strength is reduced. The sintering method has such difficulties, and it is difficult to produce a material having excellent strength and heat resistance. Recently, it has become possible to chemically synthesize diamond from the vapor phase. Chemical vapor deposition (C
VD method) or simply a gas phase synthesis method. Hydrocarbon gas of less than about 5% by volume is diluted with hydrogen gas to several tens of Tor
Diamond is deposited on the substrate under a reduced pressure of r. Various methods have been proposed as to how to decompose and excite the raw material gas.
There is a law. It is heated and excited by electrons and plasma.

In Japanese Patent Laid-Open No. 58-91100, a raw material gas is preheated by a thermoelectron emitting material heated to 1000 ° C. or higher, and the raw material gas is introduced to the surface of the heated base material to thermally decompose the hydrocarbon. A method of depositing diamond on a material has been proposed. JP-A-58-11049 proposes a method in which a hydrogen gas is passed through an electrodeless discharge by a microwave plasma CVD method, and then mixed with a hydrocarbon gas to precipitate diamond on a substrate. CV like this
There are many methods of synthesizing a diamond film by the D method. There are two ways to use the synthesized diamond film. One is to separate the diamond from the base material to form a simple substance of diamond. It is again mounted on a suitable tool. The other is to coat diamond with the cutting edge of a tool as a base material. In JP-A-1-153228 and JP-A-1-210201, diamond is deposited by a vapor phase synthesis method, and then the base material is removed by etching to obtain a single diamond. This is set as a tool by installing and fixing it at the tip of a separate tool main body. However, this also has insufficient fracture resistance and abrasion resistance and cannot exhibit the original performance of diamond. There is also provided a tool in which the tip of the tool is coated with polycrystalline diamond by a CVD method. The diamond is grown by the CVD method using the tool or a part of the tool as a base material. Since the cutting edge is diamond, it should have sufficient strength. However, the diamond film is thin and the adhesion strength between the diamond and the substrate is insufficient, so that sufficient performance as a tool has not been obtained. Since the base material and diamond are different, it is difficult to increase the adhesion strength. Japanese Unexamined Patent Publication (Kokai) No. 2-22471 attempts to enhance the adhesion strength by coating a diamond film with a devised composition on a cemented carbide. However, due to this, the machinability is poor and the adhesion strength is insufficient depending on the surface roughness of the material to be cut. Further difficult-to-cut materials (for example, 17% Al-S
The cutting characteristics when using an i alloy, a 25% Al-Si alloy) as the material to be cut are insufficient.

[0005]

PROBLEM TO BE SOLVED BY THE INVENTION Provided are a polycrystalline diamond tool excellent in strength, welding resistance, heat resistance and wear resistance, and particularly excellent in fracture resistance and wear resistance for difficult-to-cut materials, and a method for producing the same. It is an object of the present invention.

[0006]

A polycrystalline diamond tool of the present invention comprises a tool base material and polycrystalline diamond, and one surface of the polycrystalline diamond is brought into contact with and fixed to the base material surface of the tool cutting edge to fix the diamond. A tool having a structure of a cutting edge, wherein the diamond has a thickness of 40 μm or more, and the impurity content changes in the thickness direction of the diamond.
Impurity content X ₀ (%) on the rake face side of diamond
Is the content Y of impurities on the fixed surface of the diamond base material.
_It is characterized by being smaller than ₀ (%) (X ₀ <Y ₀ ).
Even if a conventional diamond film was vapor-phase synthesized, its composition was uniform in the thickness direction. The present invention instead varies the impurity content in the thickness direction. The surface of the diamond to be installed on the tool base material has a high content of impurities, and the rake surface on the opposite side has a low content of impurities. The easiest way to form a diamond film having different impurity contents in the thickness direction is to change the composition of the raw material gas during vapor phase synthesis.

The above-mentioned conditions define the present invention by the content of impurities only on both sides of the diamond, but can also be defined by the size of the content of impurities in a partial region having a certain depth from the surface with a larger thickness. X ₁ is the impurity content of the partial region having a thickness of 30% from the rake face side,
It is possible to define X ₁ <Y ₁ where Y ₁ is the impurity content of the partial region having a thickness of 30% from the base material fixed surface.
If the impurity content changes monotonically in the thickness direction, the definitions of both are equivalent. In actual vapor phase synthesis, the impurity content changes continuously or stepwise, but it increases monotonously and does not repeat increasing and decreasing. However, since the impurity content of an actually manufactured product has fluctuation, the first definition (X ₀ <Y ₀ ) is not sufficient. Since the second definition (X ₁ <Y ₁ ) defines the impurity content in the thick partial region, the present invention can be well defined even if there is fluctuation in the impurity content. For the actual measurement of the impurity content, the first definition is more convenient.

[0008]

FIG. 1 is a schematic view of a polycrystalline diamond tool. A polycrystalline diamond film 2 is fixedly installed at one corner of a base material 1 made of cemented carbide by a brazing layer 3. The surface that appears outside the polycrystalline diamond film 2 is the rake surface 4,
The one fixed to the base material is the base material fixed installation surface 5. In the present invention, the content of impurities differs in the thickness direction.
The base material fixed installation surface 5 has a larger impurity content, and the rake surface 4 has a smaller impurity content. The rake face side of diamond suppresses impurities other than carbon components as much as possible, and the base material fixed installation face side positively introduces an impurity element to increase the impurity content. The rake face 4 side has a low defect and high quality film, and the base material fixed installation face 5 side has a higher defect density than that. This makes it possible to reduce the stress applied to the rake face 4 side. That is, the base material fixed installation surface side functions as a stress relaxation layer. Therefore, the fracture resistance can be improved without impairing the wear resistance of the diamond film. In order to specify it more strictly, the rake face 4 is set to d = 0, and the z axis is taken in the direction perpendicular to the face. The x and y axes are taken in directions parallel to the plane. The impurity content can be expressed by W (x, y, z). When the film thickness of diamond is T, d = T corresponds to the base material fixed installation surface.

The first definition is: X ₀ = ∫W (x, y, 0) dxdy / S (1) Y ₀ = ∫W (x, y, T) dxdy / S (2) S = ∫dxdy ( 3) can be expressed as T> 40 μm (4) X ₀ <Y ₀ (5). Diamond film thickness T is 40
The reason why the thickness is more than μm is that if the thickness is less than that, the strength is lowered and it is easily damaged. Another reason is that the flank wear width at the end of its life when used as a cutting tool is 40
This is because in many cases it is more than μm. When a higher degree of wear resistance is required, the film thickness T should be 0.07 to 3.0.
It is desirable to set to mm. This is because if the thickness is 3 mm or more, the cost is high. If the film can be formed at low cost, the thickness may be 3 mm or more. Diamond has a high thermal conductivity, and the larger the film thickness, the better the heat dissipation characteristics. Then, the rise in the temperature of the cutting edge is suppressed, so that the blade is less likely to be worn.

The most characteristic feature of the present invention is the relationship X ₀ <Y ₀ . If X ₀ ≧ Y ₀ , the base material fixed installation surface side does not serve as a stress relaxation layer, the toughness is poor, the diamond film is likely to be cracked, the diamond film may be detached, and the wear resistance is poor. Both the base material fixed installation surface 5 and the rake surface 4 are surfaces exposed to the outside, and it is easy to measure the impurity content. The state and content of impurities in the diamond film are TEM (Transmission Electron Microscopy) TED (Transmission Electron Diffraction) SIMS (Secondary Ion Mass Spectroscopy) XPS (X-ray Photoelectron Spectrometry) IMA (Ion Microanalyzer) EDX (Energy Dispersive X-ray). Spectrometry) WDX (Wave Dispersive X-ray Spectrometry) EPMA (Electron Probe X-ray Microanalyzer) Density measurement or the like. , Can observe the fine structure. Information is obtained about the structure of the impurity element in diamond. Can quantitatively measure the content of impurities. As they are, only surface values can be measured. However, information on the depth direction can also be obtained by using sputtering and film cross-sectional observation together.

The invention can therefore also be defined by the impurity content in the subregions having a finite thickness in the depth direction.

[0012]

(Equation 6)

U = 0.3 TS (7) That is, X ₁ is the average value of the impurity content in the partial region of 30% of the thickness T from the rake face 4.

[0014]

(Equation 8)

Y ₁ is 30 with a thickness T from the base material fixed installation surface 5.
% Is the average value of the impurity content in the partial region. The present invention can also be defined by X ₁ <Y ₁ , T> 40 μm. Furthermore, the impurity content must not be too high. If the content of impurities is large, the hardness of the diamond cutting edge will be insufficient and the wear resistance will decrease. Therefore, the impurity content X ₁ in the partial region of 30% of the film thickness from the rake face
Is preferably 5% or less. X ₁ ≦ 5% (atomic%) (9) Here, the amount of impurities in X ₁ is preferably as small as possible from the viewpoint of wear resistance and the like, preferably 1% or less, more preferably 1000 ppm or less.

Next, the diamond manufacturing method of the present invention will be described with reference to FIG. Since the diamond film is deposited on the substrate by the vapor phase synthesis method, in order to bring about the above-mentioned change in the impurity content in the thickness direction, the impurity concentration in the source gas is changed continuously or stepwise (monotonically). Decrease or monotonically increase). The base material 6 is heated in a CVD apparatus (which will be described later), and a raw material gas is flowed to excite and decompose the base material gas to grow diamond on the base material (FIG. 2B). The impurity concentration in the source gas changes continuously or stepwise and monotonically. After the diamond film 7 is grown by such a CVD method, the base material is removed by etching with hydrofluoric nitric acid or the like (FIG. 2C). Next, one surface of the diamond film is metallized (FIG. 2 (d)). It has a flat plate structure of the diamond layer and the metallized layer 8. After that, it is cut into a predetermined size by a YAG laser or the like (FIG. 2 (e)). Then, the surface of the metallized layer is fixedly installed on the base material surface of the tool (FIG. 2f (f)).

FIG. 3 shows a cross-sectional view of a tool fitted with a diamond film. A base material of cemented carbide has a diamond film mounting seat, and the diamond layer is adhered thereto through a metallized layer. Brazing is preferred as the bonding method.
FIG. 4 shows a geometrical relationship for defining the present invention. The side farther from the base metal is the rake face. The z-axis is set in the thickness direction with a line included in the rake face as a reference line.
The rake face can be indicated by z = 0. The surface on which the base material is fixedly installed can be represented by z = T on the opposite surface. The broken lines indicate z = 0.3T and 0.7T. The average impurity contents X ₁ and Y ₁ in this partial region are a problem.
The impurity content is changed when the diamond is grown by the CVD method, but it is better to increase the impurity content monotonously. The reason is as follows. The surface that was in contact with the diamond coating substrate was flat,
The surface formed at the end of growth has large irregularities as it is. If this becomes a rake surface, irregularities will be formed on the surface of the cutting surface of the material to be cut. In order to avoid this, the surface formed at the end of growth (the surface far from the base material) should be metalized and fixed to the base material. In the present invention, the content of impurities is set to be higher on the surface on which the base material is fixedly mounted. Therefore, when growing diamond by the CVD method, it is better to lower the impurity concentration at the beginning and raise the impurity concentration at the end. Impurities are mixed into the diamond on the base metal surface side because the thermal conductivity of the diamond on the base metal surface side is lowered, and the heat of the cutting edge that has become hot during cutting is transferred to the adhesive layer with the base metal. It is also important in the sense that it lowers the cutting edge and prevents the cutting edge from falling off.

Of course, this is not an essential condition. After the diamond film is grown by the CVD method, the surface formed at the end of the growth can be polished and made flat so that it can be used as a rake surface. In this case, therefore, when the diamond is grown by the CVD method, the impurity concentration is increased. May be made large at first and then made small. Further, even if there is a slight change in concentration during growth, if the rake face side and the base material face side are tools, the above relationship is sufficient. The raw material gas for the vapor phase synthesis of diamond by the CVD method is usually hydrogen gas, carbon atom-containing gas ... Methane, ethane, acetylene,
Ethyl alcohol and acetone are common. Is any substance that contains carbon and becomes gaseous. Even liquid substances such as alcohol and acetone at room temperature become gas when heated. If the liquid is bubbled with hydrogen gas, it can be made into gas. However, hydrogen gas is not essential. For example, instead of hydrogen gas, water, hydrogen peroxide solution, CF ₄ , C ₂ F ₆ , C _{3
F 8, C-C 4 F} 8, C 5 F 12, CHF 3, CBrF
₃ , CCl ₄ , CCl ₃ F, CCl ₂ F ₂ , CClF
₃ , SF ₆ , NF ₃ , BCl ₃ , F ₂ , Cl ₂ , Br ₂
Gas such as can also be used. This may be one kind or a mixed gas of two or more kinds. In addition, an inert gas (helium,
Neon, argon, krypton, xenon, and radon) have the effect of prolonging the life of active species during diamond synthesis and synthesizing uniform diamond, and therefore may be mixed in the above gas. The following materials can be used as a substrate for CVD growth. W, Mo, Ta, Nb, Si, SiC, WC, Mo ₂
C, TaC, Si ₃ N ₄ , AlN, diamond, Al
₂ O ₃ , SiO ₂ , B, BN, TiC, TiN, Ti Further, by selecting the conditions, Cu, Al, etc. can be used as the base material.

The substrate is not always flat. If the base material has an appropriate curvature, it can be applied to a tool having a blade surface with a curvature. For example, a twisting blade,
It can be applied to tools such as end mills. In principle, impurities refer to components other than crystalline diamond,
There are two types. The first is a carbon component other than crystalline diamond, such as crystalline graphite or amorphous carbon. The second is a metal other than carbon, a nonmetal, a compound thereof, and the like. For example, Si, B, Al,
W, Mo, Co, Fe, Nb, Ta, and their carbides, oxides, and nitrides, which are finely dispersed in crystalline diamond or in the form of powder of about 0.5 to 2 μm. There are also things to go. The former can be prepared without intentionally adding impurities, but can also be prepared by intentionally mixing graphite powder or the like. The latter intentionally adds impurities, and is generally introduced in the form of a halide of the impurities to be added. For example, H
₂ gas, CH ₄ gas and WF ₆ , WCl ₆ , MoF
₆ , MoCl ₆ , SiF ₄ , Si ₂ F ₆ , BCl ₃ , R
Examples include eF ₄ , AlF ₃ , FeCl ₃ , and SiCl ₄ .
However, as an exception, SiH ₄ , B ₂ H _{6 and the} like can be applied.
Further, it can be introduced as a hydroxide. When these halides are introduced into diamond, they exist in three forms. One is dispersed and present as metal polycrystal grains such as W, Mo and Si, and the other is present as a compound with carbon such as carbides such as WC, MoC and SiC. When the reaction is insufficient, it exists as the original halide. As another method of intentionally introducing impurities, there is a method of adding powdery ceramics or the like while intermittently dropping them on a base material on which diamond is deposited, or a method of wiping it on a gas flow. . In the case of the vapor phase synthesis method, it is most desirable to continuously increase the impurity concentration, but it is difficult. Therefore, the impurity concentration in the raw material gas is changed in three or two steps. The simplest is the CVD growth in two steps, that is, the step of adding no impurities at all and the step of adding a certain amount of impurities. For example, in the first half of diamond synthesis, hydrogen-methane (methane / hydrogen = about 1%) system was synthesized, and in the latter half,
A small amount of halogenated gas such as WF ₆ and BCl ₃ is added. It is more preferable to increase the methane / hydrogen concentration in the latter half of the period as compared with the first half. The optimum concentration of impurity gas is somewhat affected by other conditions. When the oxygen atom-containing gas is added, the carbon concentration and the impurity concentration can be made higher than those when not added. As for the CVD method, the present invention can be carried out in any method capable of synthesizing diamond.

[0020]

EXAMPLES The present invention was carried out by a filament CVD method (FIG. 5), a microwave plasma CVD method (FIG. 6), a thermal CVD method (FIG. 7) and a thermal plasma CVD method (FIG. 8). The base material is common to all methods, and one side of 14 mm x 14 mm x 2.5 mm polycrystalline Si is used.
A polishing material containing abrasive grains having a particle diameter of 0.5 to 5 μm was used for lapping to obtain R _MAX <0.8 μm and flatness <1 μm. The apparatus used for each method will be described below, and the results of applying the present invention to each method will be described.

[Example] Filament CVD method FIG. 5 shows a filament CVD apparatus. Vacuum chamber 1
A base material support base 12 is provided in the unit 1. Substrate 1 on this
3 is placed. The vacuum chamber 11 has a vacuum exhaust port 14
And is connected to an evacuation device (not shown). Two electrodes 15 are provided in the vacuum chamber 11. It is connected to the filament power supply 21 through the insulator 16. A filament 17 is stretched between the two electrodes 15. A source gas is introduced into the vacuum chamber 11 from a source gas inlet 18. The pressure gauge 19 measures the degree of vacuum in the vacuum chamber. The cooling water 20 is the base material support 12
It is introduced inside and is cooling it. The filament is φ0.2 mm 4N (purity 99.99%)-W, 4N-T
a, 4N-Re was used. The filaments were stretched in parallel at intervals of 4 mm and used. The filament temperature was measured with an optical pyrometer. The distance between the filament and the substrate was 5 mm. The surface temperature of the base material was monitored by placing a chromel-alumel thermocouple spot-welded on the surface of a Mo plate having the same shape as the base material in the vicinity of the base material.

Table 1 shows the conditions for diamond synthesis by the filament CVD method. The filament temperature is 1500-
The temperature of the substrate is 2400 ° C and the temperature of the substrate is 80 to 950 ° C. A ~
H is a symbol attached to the sample. The present invention is characterized in that the impurity content of diamond is changed in the film thickness direction, but in the embodiment shown here, the impurity concentration in the source gas is changed in two or four steps (A to A). D). For comparison, Comparative Examples (E to G) grown without changing the impurity content and Comparative Example H in which the change in the impurity content is reversed are shown. The material gas that is liquid at room temperature is introduced by bubbling a part of hydrogen gas through a bubbler containing the liquid. The flow rate is controlled by controlling the vapor pressure by controlling the temperature of the constant temperature bath.

[0023]

[Table 1]

In Examples A to D and Comparative Example H of the present invention, the source gas composition and the composition ratio are changed with time. For example, Example A shows that during the first 50 hours, H ₂ 600 of Phase 1 was used.
Coating the base material with SCCM, CH ₄ 5 SCCM source gas
T2 and then step 2 H ₂ 600 SCC for the next 20 hours
That is, the coating is performed with the raw material gas of M, CH ₄ 12SCCM and WF ₆ 2.0SCCM.
B and D are changed in 2 steps, and C is changed in 4 steps. The diamond samples A to H thus manufactured were set and fixed on a base metal of cemented carbide by the process of FIG. 2 to manufacture cutting chips. However, the surface that was in contact with the base material during growth was used as the rake surface of the cutting tip, and the surface that was formed at the end of growth was set and fixed on the base material surface of the cutting tip.

A natural type IIa diamond single crystal was similarly set and fixed on a base metal as a comparative material for impurity analysis and measurement to prepare a cutting tip (referred to as sample I). The content of impurities in the thickness direction of the cutting tip diamond thus produced was measured and is shown in Table 2. SI measures impurity content
MS (Secondary Ion Mass Spectroscopy) or I
It was performed by MA (Ion Microanalyzer). In addition, “undetectable” in Table 2 means that the carbon component is analyzed as a matrix and the impurity concentration is 3 ppm or less, so that it cannot be detected.

[0026]

[Table 2]

Here, the measuring point of the impurity content is shown by a distance z (unit: micron) toward the inside in the thickness direction with reference to the rake face as shown in FIG. The first layer and the second layer are partial layers of diamond produced by switching the components of the raw material gas shown in Table 1. Since the surface formed at the beginning of growth is the rake surface, it corresponds to the first layer and the second layer in Table 2 in order from the top in Table 1. Sample J is a comparative example other than these. This is a cutting tip in which a sintered diamond made by high-pressure sintering of a diamond material having an average particle size of 10 μm containing 10% by volume of Co as a binder is attached to a tool. It is not CVD growth. In Comparative Example H, the impurity concentration in the raw material gas is opposite to that of the present invention, but the impurity content of the actually produced product is also opposite to that of the present invention. In other comparative examples, impurities are not positively added, but impurities cannot be detected even in the actually grown ones. It can be seen that the impurity content is controlled by the source gas. In all of the examples of the present invention, the impurity concentration in the raw material gas is increased along with the growth, but in the actually grown diamond, the impurity content increases toward the inner side (growth direction) almost in proportion to the raw material gas. I know that

The performance of the diamond cutting tool thus produced was evaluated under the following conditions. A390 alloy (A with four grooves extending in the axial direction formed on the outer peripheral surface as the work material)
1-17% Si) Round bar was selected. By using the cutting tool produced by the above method, the cutting speed was 800 m / min, the incision was 0.2 mm, the feed was 0.1 mm / rev. The tool performance was evaluated by dry cutting under the conditions. Since the amount of wear is an important evaluation parameter, the average wear width after cutting for 90 minutes or 30 minutes is measured. Table 3 shows the results.

[0029]

[Table 3]

As the comparative examples, those which are vapor-phase synthesized but have a small impurity content are deficient in a short time (Comparative examples F and G). Or it will wear out in a short time and become useless (E). Even if impurities are intentionally included, the impurities do not enter, or even if they enter, H where X ₁ > Y ₁ wears in a short time.
Chips of natural type IIa single crystal diamond were also chipped and chipped (I). None of these are useful. Even with J, which uses ultra-high pressure sintered diamond, wear cannot be ignored. The average wear width at 90 minutes cutting was 95 μm.
Since it is formed by sintering, it contains a binder, which probably reduces wear resistance. The cutting tools A to D according to the examples of the present invention are less worn by cutting for 90 minutes and do not cause chipping defects. This changes the impurity content in the thickness direction by the vapor phase synthesis method, and X ₁ <Y ₁ or X ₀ <
Y ₀ . Here, X ₀ is the impurity content on the rake face side of the diamond, and Y ₀ is the impurity content on the base material installation face side. X ₁ is the average impurity content of the partial region within 30% of the thickness from the rake face, and Y ₁ is the impurity content of the partial region within 30% of the thickness from the base material installation surface. Of course, these can be defined as 20% and 40%. As the impurity, a halogen element or a halide may be easily introduced. The content should not be too large. It is required to be 5% or less on the rake face side. This is because if it is 5% or more, the wear resistance is extremely deteriorated. Impurities on the rake face side are preferably 1000 ppm or less. The smaller the amount of impurities, the higher the wear resistance of diamond and the better. The thickness of diamond is 40 μm or more. The reason for this is that if the thickness is less than 40 μm, the strength is reduced and damage is likely to occur. Further, the wear width of the flank during the life of the cutting tool is often 40 μm or more. Further, when abrasion resistance is required, it is desirable to set the diamond thickness to 0.07 to 3.0 mm. By making the blade thicker, the heat dissipation characteristics become better, and the rise in the temperature of the cutting edge during use of the tool is suppressed, so wear resistance increases.

[Example] Microwave plasma CVD
Method Next, the present invention was implemented by a microwave (plasma) CVD method. FIG. 6 shows an outline of the microwave CVD apparatus.
A substrate 24 is supported by a quartz rod 23 in the quartz tube 22. A source gas 26 is introduced into the quartz tube 22 from an upper gas inlet 25. This is discharged from the vacuum exhaust port 27 below the quartz tube 22. A water cooling jacket 28 is provided on the outer periphery in the vicinity of the portion of the quartz tube where the reaction takes place. The microwave is oscillated by the magnetron 29 and is guided to the vicinity of the base material 24 through the waveguide 30. The waveguide 30 is the quartz tube 2.
Plasma is allowed to proceed perpendicularly to 2 and at right angles to the axial direction of the quartz tube 22. The source gas is excited by microwaves, and high-density plasma 31 is generated in the vicinity of the base material. The shape and size of the waveguide 30 determine the microwave mode, and the standing wave mode of the microwave can be defined by the plunger 32 moving in the waveguide 30. Such microwave plasma CVD is known. Further, the traveling direction of the microwave may be perpendicular to the substrate surface. The source gas is composed of gas containing carbon, hydrogen gas, impurity gas, etc., as in the above example. A magnet may be placed around the quartz tube to confine the plasma to form a cusp magnetic field or an axial magnetic field. This is also well known. Table 4 shows the synthesis conditions by microwave CVD.

[0032]

[Table 4]

The base material is 14 mm × 14 m as in Example I.
mx 2.5 mm polycrystalline Si was lapped with abrasive grains having a grain size of 0.5 to 5 μm, and R _MAX <0.8 μm, flatness <
It was processed to have a thickness of 1 μm. The substrate temperature was monitored with an optical pyrometer during coating. Then, it is calibrated with the data previously measured by the thermo-crayon. Various values are selected for the substrate temperature between 400 and 950. K to N are examples of the present invention. This is 2
The source gas is switched to stage 4 and stage 4, and the impurity concentration is increased in the latter stage of growth. As the impurities, WF ₆ , BCl ₃ , F ₂ , FeCl ₃ or the like is used as in the previous example. An inert gas such as Ar is included to facilitate stable excitation of microwave plasma and to increase the concentration of active species such as Hα and C ₂ . O to Q are comparative examples. O and P do not add impurities to the raw material gas. Q contains impurities, but the order is reversed and the first layer (rake face side) contains impurities. The impurity content of each layer of the diamond sample thus prepared was measured, and the results are shown in Table 5.

[0034]

[Table 5]

Here, the measuring point of the impurity content is the depth z from here (μ in the same manner as in the previous example, based on the rake face).
m) Shown. The one formed at the beginning of the growth is set as the base metal, and the one formed at the end of the growth is set as the rake face on the cemented carbide. Therefore, the raw material gas in Table 4 was changed to form the film. The second stage corresponds to the first and second layers in Table 5. This is the content of impurities in the diamond used as a tool, but the content of diamond before being made into a tool is also the same. Next, in order to evaluate the tool performance, polycrystalline diamond was brazed to a base metal of cemented carbide to produce a cutting tip. The cutting test was done by this. As the work material, an A390 alloy (Al-17% Si) round bar having four grooves extending in the axial direction on the outer peripheral surface was used. The cutting conditions are: cutting speed 800 m / min depth of cut 0.2 mm feed 0.1 mm / rev. As a dry cutting. Table 6 shows the results.

[0036]

[Table 6]

It can be seen that the diamond of the present invention formed by microwave plasma CVD has excellent wear resistance. The diamond of the present invention is the filament C of the preceding example.
Like the diamond of the present invention grown by VD, the content of impurities differs in the thickness direction. In the diamond of the present invention, the impurity content X ₀ on the rake face side is smaller than the impurity content Y ₀ on the base material installation face side (X ₀ <Y ₀ ). Alternatively, the impurity content X ₁ of the partial region of 30% of the thickness on the rake face side is smaller than the impurity content Y ₁ of the partial region of 30% of the thickness on the base material installation face side (X ₁ <Y ₁ ). Impurities other than carbon could not be detected because O and P shown as conventional examples did not intentionally introduce impurities. Therefore, they lack chipping resistance and abrasion resistance. However, the density of the P sample is 2.7 g / from the rake face to 10 μm.
cm ³ and 2.7 g / cm ³ from 90 μm to 100 μm from the rake face, which is lower than the density of crystalline diamond, so it is considered that carbon components other than crystalline diamond are uniformly mixed. To be That is, it is considered that the same amount of impurities is mixed in both the rake face side and the base metal face side, and the wear resistance is completely insufficient.
Estimated by wt%, the content of impurities other than diamond is about 36%. Regarding Q, the distribution of the impurity content is opposite to that of the present invention, but this also has insufficient strength. The average wear width of the diamond of the present invention when cut for 90 minutes is 10 to 20 μ.
Since it is extremely small in m, it is practically usable.

[Example] Thermal CVD method A polycrystalline diamond film of the present invention was produced by a thermal CVD method. FIG. 7 shows an outline of the thermal CVD apparatus. A support 36 is provided in a quartz tube 35 that can be evacuated, and a substrate 37 is supported there. A heater 38 is provided around the quartz tube 35. The raw material gas inlet 3 is provided in the quartz tube 35.
Raw material gas is introduced from 9. Waste gas is vacuum exhaust port 40
Emitted from. The raw material gas is excited by being heated by the heater, and polycrystalline diamond grows on the substrate by a gas phase reaction. To apply the present invention, the impurity content must be changed in at least two stages. Here, an example in which a diamond film is formed in two stages will be described. The base material is 14 mm × 14 mm × 2.5 mm polycrystalline Si.

(1 step) Synthesis conditions Source gas H ₂ 1000 SCCM CH ₄ 20 SCCM F ₂ 2 SCCM He 50 SCCM Pressure 100 Torr Substrate temperature 100 ° C. Growth film thickness 80 μm (2 steps) Synthesis conditions (1 step continued) Source gas H ₂ 1000 SCCM CH ₃ Br 18 SCCM F ₂ 18 SCCM He 150 SCCM WF ₆ 2.5 SCCM Pressure 100 Torr Substrate temperature 100 ° C. Growth film thickness 100 μm These were continuously grown. The total film thickness is 180 μm. This was brazed to a cemented carbide base metal by the process shown in FIG. Impurity content is as follows: First layer ··· (at a depth of 10 μm from the rake face) F 0.02% Second layer ··· (at a depth of 165 μm from the rake face) W 1.6% Br 0.1% F 0 It was .12%. The content of impurities is still high in the two layers in which the source gas has a high impurity concentration. In order to evaluate the tool characteristics, a round bar of A390 alloy (Al-17% Si) having four grooves extending in the axial direction on the outer peripheral surface was cut as a work material. The cutting conditions are the same as in the previous example. Cutting speed 800 m / min Cutting depth 0.2 mm Feed 0.1 mm / rev. Dry cutting. The Vb wear amount after 120 minutes was 15 μm. This is a very small value. Since the first layer is a high-purity diamond, it has excellent hardness and thus high wear resistance. That is, it is effective to apply the present invention to thermal CVD. It is also shown that the impurities for increasing the toughness (elasticity) of the second layer are also effective with halogens such as W, Br and F.

[Example] Thermal Plasma CVD Method FIG. 8 shows a thermal plasma CVD apparatus. Vacuum chamber 42
A concentric electrode 43 is provided above. A cooling support 44 is provided below, and a substrate 45 is placed thereon. A heater (not shown) for heating the substrate is provided outside the vacuum chamber 42. A voltage is applied between the positive and negative electrodes by the DC power supply 46. The center is the cathode and the periphery is the anode. The raw material gas 47 flows from the gap between the electrodes to the nozzle 51.
Through and into the vacuum chamber 42. Here, the source gas is ionized and becomes a plasma gas flow 52, which flows toward the substrate 45. The waste gas is exhausted from the vacuum exhaust port 49. Cooling water 50 is caused to flow inside the cooling support table 42. The raw material gas turned into plasma undergoes a gas phase reaction in the vicinity of the base material and is deposited as diamond on the base material. The base material is polycrystalline Si of 14 mm × 14 mm × 2.5 mm as in the previous example. 2 to change the content of impurities in diamond
The step growth process was continued.

(First Step) Synthesis Conditions Source Gas H ₂ 10 SLM CH ₄ 1.5 SLM F ₂ 0.05 SLM Ar 30 SLM Pressure 200 Torr Base Material Temperature 500 ° C. Growth Film Thickness 200 μm (Second Step) Synthesis Conditions Source gas H ₂ 10 SLM CH ₄ 2.8 SLM F ₂ 0.1 SLM He 20 SLM WF ₆ 0.2 SLM pressure 200 Torr substrate temperature 500 ° C. growth film thickness 300 μm (SLM) : Standard litter per minute). These growths continued. Total film thickness is 50
0 μm. According to the process of FIG. 2, polycrystalline diamond was brazed on a cemented carbide base metal to prepare a tool. The impurity content of the first layer and the second layer is 40 μm F 0.12% from the rake face (first layer) 455 μm W 3.8% Br 1.2% F 0.22 from the rake face (second layer) % Met. In order to evaluate the performance of this tool, an A390 alloy (Al
-17% Si) Using a round bar as a work material, cutting speed 800 m / min depth of cut 0.2 mm feed 0.1 mm / rev. Dry cutting was performed under the following cutting conditions. The Vb wear amount after 120 minutes was 30 μm, which was sufficiently small. This means that the present invention can be effectively applied to the growth of diamond by the thermal CVD method. Further, the impurity for imparting toughness to the second layer is W
It means that halogens such as Br and F are also effective. In the case of this method, SiC, Si ₃ N ₄ , B
Impurities can be mixed with ceramic powder such as N.

[Example] Thermal plasma CVD
Method A substrate was placed in the same manner as in Example, and a two-step growth process was performed in order to change the content of impurities in diamond. This time, as the second stage impurities, the average particle size is 2 to 5
A SiC powder of μm was added and introduced at the same time as hydrogen gas and ethylene gas. (First stage) Synthesis conditions Source gas H ₂ 10 SLM C ₂ H ₂ 0.5 SLM Pressure 50 Torr Substrate temperature 850 ° C. Growth film thickness 300 μm (Second stage) Synthesis conditions Source gas H ₂ 10 SLM C ₂ H ₂ 5 SLM Impurity SiC powder 0.2 gram / min Pressure 400 Torr Substrate temperature 980 ° C. Growth film thickness 1000 μm. According to the process of FIG. 2, polycrystalline diamond was brazed onto a cemented carbide base metal to prepare a tool. The first layer,
The impurity content of the second layer is not detected at (60 ppm) from the rake face (first layer) ... (3 ppm or less) 900 μm from the rake face of the second layer (100 from the fixed face)
.mu.m) ... Si 9%. When the same cutting test as in the example was conducted, the Vb wear amount after 90 minutes was 16 μm.
And was very small.

[Example] Filament CVD method A substrate was placed in the same manner as in the example, and an experiment was conducted by the filament CVD method. A two-step growth process was performed in order to change the content of impurities in diamond. This time second
The film was formed so that a large amount of carbon components other than crystalline diamond were included as impurities in the stage. In this example, impurities other than carbon are not added. (First stage) Synthesis condition Source gas H ₂ 1000 SCCM CH ₄ 8 SCCM Pressure 120 Torr W Filament temperature 2150 ° C. Base material temperature 800 ° C. Growth film thickness 150 μm (Second stage) Synthesis condition Source gas H ₂ 1000 SCCM C ₂ H ₂ 50 SLM pressure 80 Torr W filament temperature 2450 ° C. substrate temperature 980 ° C. growth film thickness 800 μm. According to the process of FIG. 2, polycrystalline diamond was brazed on a cemented carbide base metal to prepare a tool. The density of crystalline diamond was set to 3.52 g / cm ³ , and the impurity concentrations of the first layer and the second layer were calculated from the density. [First layer] 30 μm from rake face ... Non-diamond component is 0.05% or less [Second layer] 750 μm from rake face (50 μm from fixed face)
m) ... non-diamond component (low density carbon component)
Was about 2 to 6%. As metal impurities other than carbon components, W was detected at 0.1%. When the same cutting test as in the example was conducted, the Vb wear amount after 80 minutes was 18 μm.
Met. It is a very small value. The surface of the diamond is high in hardness with few impurities, and therefore wear is small. Further, chipping does not occur because the non-diamond component is large near the fixing surface and the toughness is high.

[Example] Impurity concentration on rake face In order to investigate the optimum value of the impurity concentration on the rake face, samples having rake faces with different impurity concentrations were measured by filament CVD method or microwave plasma CVD method. Made by. The amount of impurity concentration was divided into four as shown in Table 7. In order to evaluate these tool characteristics, four grooves extending in the axial direction were formed on the outer peripheral surface (Al-4%
Si) round bar and (Al-25% Si: difficult-to-cut material) round bar,
It was cut as a work material. Table 7 shows the results.

[0045]

[Table 7]

From these results, the impurity concentration on the rake face was 5
It can be seen that it is desirable that the content is atomic% or less. That is, a diamond tool having an impurity concentration of 5% or less on the rake face (25% Si-Al difficult-to-cut material) can cut a round bar. More preferably, the impurity concentration on the rake face should be 1% or less. The impurity concentration on the rake face is 1
It can be seen that even better results can be obtained at 000 ppm or less.

[0047]

According to the present invention, the diamond film is formed by the CVD method in which the impurity content is changed in the thickness direction.
This makes it possible to obtain a diamond film having excellent strength, abrasion resistance, welding resistance and heat resistance. Now, the reason why the present invention can form such a diamond film will be described. Conventionally, a diamond film containing few impurities was formed by the CVD method. High-purity diamond has high rigidity and is easily broken by impact. In other words, a completely crystalline diamond lacks fracture resistance. Any of the conventional examples is missing in a short period of time, but it is considered to be caused by too high rigidity because it is a perfect crystal. If so, the higher the impurity concentration, the better. If the amount of impurities is large, the rigidity is lowered and it is easily worn. Both fracture resistance and wear resistance are required for the tool. Optimum characteristics cannot be obtained by limiting the impurity content to an appropriate range. Wear resistance is essential on the surface that comes into contact with the workpiece. Also, the overall toughness must be increased.

Therefore, in the present invention, the rake face in contact with the work is made to have a high impurity content by reducing the content of impurities, and the base material surface side is increased in the content of impurities to increase the crystal defects and reduce the rigidity. Is increasing. Since the toughness of the inside (base material surface side) is higher, the diamond will not be damaged by the internal buffering action even when shocked. This gives the diamond of the present invention high performance. Abrasion resistance depends on the nature of the rake face, but since this has a low content of impurities and high rigidity, sufficient abrasion resistance can be obtained. Since the sintered diamond has a binder, wear resistance and heat resistance are inevitably lowered, but the present invention does not have such a case. The impurity element to be added to diamond in the vicinity of the fixed surface may be a metal element, ceramic or the like in addition to halogen. That is, the impurity element means something other than the carbon component. The addition of halogen may allow diamond to be synthesized at a relatively low temperature, resulting in a dense film composition. Further, since a halogen compound gas is easily obtained, it is optimal as an added impurity. It is useful for fields in which properties such as wear resistance, fracture resistance and strength are strongly required, especially for tools such as cutting tools, turning tools, excavating tools and dressers.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an example of a polycrystalline diamond tool.

FIG. 2 is a schematic perspective view showing a manufacturing process of a polycrystalline diamond tool.

FIG. 3 is a sectional view of a cutting edge portion of a polycrystalline diamond tool.

FIG. 4 is a cross-sectional view for explaining measurement points of impurity content on the cutting edge of a polycrystalline diamond tool.

FIG. 5 is a schematic sectional view of a filament CVD apparatus.

FIG. 6 is a schematic cross-sectional view of a microwave plasma CVD device.

FIG. 7 is a schematic sectional view of a thermal CVD apparatus.

FIG. 8 is a schematic sectional view of a thermal plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tool base material 2 Diamond film 3 Installation fixed layer 4 Rake surface 5 Base material installation fixed surface 6 Base material 7 Diamond film 8 Metallized layer 11 Vacuum chamber 12 Base material support 13 Base material 14 Vacuum exhaust port 15 Electrode 16 Guy 17 Filament 18 Source Gas Inlet 19 Pressure Gauge 20 Cooling Water 22 Quartz Tube 23 Quartz Rod 24 Base Material 25 Gas Inlet 26 Source Gas 27 Vacuum Exhaust Port 28 Water Cooling Jacket 29 Magnetron 30 Waveguide 31 Plasma 32 Plunger 35 Quartz Tube 36 Support 37 Base material 38 Heater 39 Raw material gas inlet 40 Vacuum exhaust port 42 Vacuum chamber 43 Electrode 44 Cooling support 45 Base material 46 DC power source 47 Raw material gas 48 Electrode gap 49 Vacuum exhaust port 50 Cooling water

Claims (12)

(57) [Claims] 1. A tool having a structure comprising a tool base material and polycrystalline diamond, wherein one surface of the polycrystalline diamond is brought into contact with and fixed to the base material surface of the tool cutting edge, and the diamond is used as the cutting edge. Is 40 μm or more, the impurity content changes in the thickness direction of the diamond,
Impurity content X ₀ (%) on the rake face side of diamond
Is the content Y of impurities on the fixed surface of the diamond base material.
A polycrystalline diamond tool characterized by being smaller than ₀ (%) (X ₀ <Y ₀ ). 2. A tool comprising a tool base material and polycrystalline diamond, wherein one surface of the polycrystalline diamond is brought into contact with and fixed to the base material surface of the tool cutting edge, and the diamond is used as the cutting edge. Is 40 μm or more, the impurity content changes in the thickness direction of the diamond,
The average impurity content X ₁ (%) of the region from the rake face side of the diamond to the thickness of 30% of the average film thickness is Less than average impurity content Y ₁ (%) (X ₁
<Y ₁ ) A polycrystalline diamond tool characterized by the following. 3. The polycrystalline diamond according to claim _{1, wherein} the impurity content X _{1 in} the region from the rake face side of the diamond to the thickness of 30% of the average film thickness is 5% or less. tool. 4. The impurity content X _{1 in} the region from the rake face side of the diamond to the thickness of 30% of the average film thickness is 1% or less, and the multi-claim according to claim 1, 2 or 3. Crystal diamond tool. 5. The impurity element contains at least a carbon component other than crystalline diamond (crystalline graphite, amorphous carbon, etc.), according to claim 1. Polycrystalline diamond tool. 6. The impurity element includes Si, B, Al,
W, Mo, Co, Fe, Nb, Ta, and their carbides, oxides, and nitrides are included.
The polycrystalline diamond tool according to any one of 2, 3, 4 and 5. 7. The method according to claim 1, wherein the impurity element contains halogen or halide.
Or the polycrystalline diamond tool according to any one of 6 above. 8. A metal of the periodic table as an impurity element,
7. A powder of one or more of any one of a semimetal, a nonmetal, and a carbide, a nitride, and an oxide thereof is contained, 7. The polycrystalline diamond tool according to any one of 7. 9. A gas containing at least carbon is used as a source gas, and halogen or a halide or SiH is used as an impurity.
₄ , Si ₂ H ₆ , PH ₃ , B ₂ H ₆ , and N ₂ are added, and a diamond film is formed on the substrate by a chemical vapor deposition method while changing the impurity addition amount. After removing the material, a method for producing a polycrystalline diamond tool, characterized in that the one having a high impurity content of the diamond film is set and fixed on the tool base material surface, and the one having a low impurity content is used as a rake surface. 10. A gas containing at least carbon is used as a raw material gas, and as impurities, powders of one or more of metals, semimetals, and their carbides, nitrides, and oxides of the periodic table are used. While changing the added amount, a diamond film is formed on the base material by the chemical vapor deposition method, and after removing the base material, the one with a high impurity content of this diamond film is set and fixed on the tool base material surface. The method for producing a polycrystalline diamond tool is characterized in that the rake face has a smaller impurity content. 11. A base material on which a diamond film is to be grown is W, Mo, Ta, Nb, Si, SiC, WC, W _2.
C, Mo ₂ C, TaC, Si ₃ N ₄ , AlN, Ti, T
iC, TiN, B, BN, B ₄ C, diamond, Al
_The method for producing a polycrystalline diamond tool according to claim 8 or 9, wherein the method is either ₂ O ₃ or SiO ₂ . 12. The method for manufacturing a polycrystalline diamond tool according to claim 8, wherein the raw material gas contains a rare gas.