JPH0722586B2 - Dental cutting tool manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement in a method for manufacturing a dental cutting tool used for dental treatment or dental technique.

(Prior Art) A conventional dental cutting tool is made of ferrous alloy steel, cemented carbide, ultrafine grained cemented carbide or cermet, and has a cutting blade and a groove in its head A. A dental bar having the following configuration is used. Here, the human tooth, which is the object to be cut, has a Knoop hardness of around 343 in the case of enamel, which is as high as that of ordinary glass, so the durability of the cutting blade during cutting is poor, and it rapidly increases during work. However, there is a drawback in that the cutting performance is deteriorated. In addition, the head B has a cutting surface on which a diamond powder is strongly electrodeposited by nickel or chrome plating on the surface of the metal base material.
A dental diamond point with the configuration shown in the figure is also used.This is suitable for grinding objects with high hardness such as enamel, but with Knoop hardness of around 68, it is more flexible. Unlike dental bars, in grinding dentin,
Since there is no blade groove for discharging chips, there is a disadvantage that the cutting performance deteriorates due to clogging. If such a cutting tool with deteriorated cutting performance is continuously used, not only the workability is deteriorated, but also a large amount of frictional heat and slight vibration are generated, and this fever causes discomfort and pain to the patient, and Micro-vibration may induce the generation of secondary caries. Furthermore, with the recent widespread use of high-speed rotating handpieces that use air turbines and air bearings, dental cutting tools have been required to have even higher durability.

(Problems to be Solved by the Invention) The above-mentioned disadvantages and drawbacks are solved, a stable metal grinding performance is maintained from beginning to end regardless of the hardness of a work piece, and a metal dental bar as a highly durable dental cutting tool. Although it was considered to form a diamond thin film on the surface of, the formation of a diamond film on iron-based alloy steel is extremely difficult. Therefore, even if a cemented carbide, an ultrafine particle cemented carbide or a cermet is used, its adhesion to a diamond film is usually poor, so a technique has been developed to improve the adhesion through various intermediate films. For example, in JP-A-58-126972,
It is described that a diamond thin film is formed after forming a ceramic-based intermediate film. In addition, JP-A-59-159
Japanese Patent Publication No. 981 describes a tool in which a diamond thin film is formed on a metal intermediate film. However, since any of these methods consists of combining the separate and independent steps of forming the diamond film after forming the intermediate film, the adhesion between the layers is not always sufficient, and these techniques are not applicable. It is difficult to obtain a practical dental cutting tool.

The present invention is intended to provide a dental cutting tool which has stable cutting performance from the beginning to the end regardless of the hardness of the object to be cut and has excellent durability.

(Means for Solving the Problem) In order to solve such a problem, the inventors of the present invention have variously studied a method for forming a diamond thin film on the surface of a cutting blade, and as a result, a cemented carbide, an ultrafine particle cemented carbide or a cermet After coating a thin film of W on the surface of the base material, it is carburized by a microwave-excited plasma gas containing a carbon source to produce WC.
At the same time, the dental cutting tool in which the diamond-like carbon polycrystal layer is formed by adhering the intermediate film made of WC by sinter-adhering to the surface of the substrate at the same time and subsequently forming the diamond-like carbon polycrystal layer on the intermediate film has the above-mentioned problems. The present invention has been completed and the present invention has been completed. The gist is that a dental bar made of one kind of material selected from cemented carbide, ultrafine particle cemented carbide and cermet is used as a base material, and W is 0.01 on the surface of a cutting blade having a groove on its head. After vapor deposition to a thickness of ~ 1.0 μm, the deposited film is carburized in microwave-excited plasma gas using hydrogen and hydrocarbon gas as raw material to form WC. And a diamond-like carbon polycrystal film is formed on the surface of the intermediate film, and a method for manufacturing a dental cutting tool, and from among cemented carbide, ultrafine particle cemented carbide and cermet Thickness of 0.01 ~ on the surface of the cutting blade substrate made of one selected material
After coating a vapor-deposited film of W of 1.0 μm, it is carburized in a microwave-excited plasma gas using hydrogen and hydrocarbon gas as a raw material to form a WC intermediate film, and at the same time, the WC intermediate film is formed by thermal radiation of the plasma gas. 1,000 to 1,500 ℃ on the material surface
To sinter and adhere to the surface of the interlayer film and the volume ratio of hydrogen to hydrocarbon gas is 50: 1 to 200: 1.
The method for producing a dental cutting tool is characterized in that a diamond-like carbon polycrystal film is formed by a vapor deposition method using microwave-excited plasma using the mixed gas as a raw material.

Hereinafter, the present invention will be described in detail.

The dental cutting tool of the present invention is based on a dental bar made of a material selected from cemented carbide defined in JIS B 4053, ultrafine particle cemented carbide or cermet, and its alloy composition is In the case of cemented carbide, a hard body containing Co as a metal phase is a sintered body composed of WC, and in the case of ultrafine grained cemented carbide, among the metal carbides of W, Ti, Ta, V and Cr 1
A sintered body containing at least one kind of hard phase and Co as a metal phase. Cermet has a hard phase containing Ti, Ta and Nb.
Is a sintered body in which Co or Ni is used for each metal carbide and / or each nitride in the metal phase. The content of Co or Ni, which is the metal phase of the above three alloy compositions, is preferably 5 to 15% by weight.

Next, a method for manufacturing a dental cutting tool will be described. First, a metal powder, a metal carbide or a nitride powder corresponding to each of the above alloy compositions is mixed with an organic solvent, paraffin, etc. and sufficiently kneaded. A cutting blade having a is formed into a dental cutting tool having. Then pre-sinter in a hydrogen stream at 800 to 1,000 ℃, give a cutting edge and a groove by grinding, and finally 1,350 to
Main sintering is carried out at a temperature of 1,550 ° C, and finished as a dental bar base material. Then, this dental bar base material was placed in a vacuum vapor deposition device, and the W film had a thickness of 0.01 to 1.0 μm with the system pressure reduced to 2 × 10 ⁻⁵ to 1 × 10 ⁻⁷ Torr. Vapor deposition and coating. The above-described method for producing a sintered body and the vacuum vapor deposition method may be known as known methods.

The greatest feature of the present invention is that the surface of the W-coated cemented carbide, ultrafine grained cemented carbide or cermet dental bar substrate is carburized and sintered to give a WC intermediate film, and then diamond-like polycrystal. It means that carbon is adhered and long-term cutting durability is maintained without selecting the material to be cut. This carburizing and sintering treatment is performed by converting hydrocarbon gas into plasma by microwaves to create active carbon molecules, which are reacted with W vapor deposition film to form WC, and at the same time, by heating with plasma, this WC and substrate surface Is a method of sintering and integrating. In the WC phase obtained by this carburization and sintering, the Co component on the surface of the base material is WC during the reaction.
It diffuses and moves into the phase and firmly bonds to the surface of the substrate. As a raw material, a mixed gas of hydrocarbon gas such as methane, ethane and propane and hydrogen gas is used as a carbon source. The volume ratio of this mixed gas is preferably hydrogen: hydrocarbon = 50: 1 to 600: 1, and is treated using the apparatus shown in FIG. After setting a raw dental bar on the substrate support base 2 inside the quartz glass reactor 3 of this device (only the head is exposed to the microwave and the handle is shielded), 1 × 10 ^-5 to 1 × 10
^The pressure is reduced by the vacuum pump 5 so that the pressure becomes ⁻³ Torr. Then, the hydrocarbon gas and the hydrogen gas in the above-mentioned ratios are introduced into the reactor from the respective cylinders 10 and 11, and are mixed and circulated. The pressure in the reactor has a great influence on the temperature of the bar in the reactor and the degree of carburization of the W film on the surface of the bar,
In the present invention, the pressure is adjusted by the pressure adjusting valve 6 so as to be in the range of 2 to 50 Torr. The microwave of the frequency of 2.45 GHz oscillated by the magnetron oscillator 13 and propagated in the rectangular waveguide 12 for 2.45 GHz and the reflected wave of the microwave reflected by the microwave reflection plate 4 flow in the reactor. A plasma flame is generated by being absorbed by the mixed gas. This microwave reflector 4 is 2.45GH behind the reactor.
The z-shaped waveguide can be moved within a range of about 7 cm, and the position of the plasma flame generated around the bar can be adjusted.
The impedance matching stub 7 is a metal rod inserted in the 2.45 GHz rectangular waveguide for the purpose of effectively absorbing microwaves into the mixed gas. Is made variable by the automatic impedance matching device 8. Microwave high-frequency power has a bar surface temperature of 800-
The temperature is adjusted to 1,500 ° C, preferably 1,000 to 1,500 ° C. If the bar temperature is less than 800 ° C, the sintering reaction between WC carburized by plasma and the bar substrate is slow, and if it exceeds 1,500 ° C, too much Co migrates from the substrate surface and this Co is active. Since a graphite component adheres to the surface by reacting with various carbon molecules, it becomes difficult to form a diamond-like polycrystalline carbon film described later. In order to sufficiently carburize the W vapor-deposited film, it is difficult for the W vapor-deposited film to be too thick, and it is preferably less than 1.0 μm.

Subsequently, a diamond-like polycrystalline carbon film is formed on the WC intermediate film formed by the above carburization and sintering. This diamond-like carbon film may be formed by a vapor deposition method using microwave-excited plasma, which is a known method, and the film forming conditions suitable for the present invention are that the carbon source is a hydrocarbon gas such as methane, ethane or propane. And a mixed gas with hydrogen gas is used. The volume ratio of this mixed gas is preferably hydrocarbon gas: hydrogen = 1: 50 to 1: 200. If this hydrocarbon gas / hydrogen ratio is less than 1/200, the crystal grain agglomerates forming the diamond-like carbon film to be deposited become coarse, and the peel strength of the formed diamond-like carbon film decreases. , 1/50 on the contrary
If it exceeds, the mixture of the graphite component becomes conspicuous in the formed diamond film, and it becomes impossible to obtain a film hardness sufficient to improve durability during cutting. This microwave-excited plasma deposition method is carried out using the apparatus shown in FIG. 3, as in the formation of the WC intermediate film. Subsequent to the above carburizing and sintering treatment, the hydrocarbon gas and the hydrogen gas in the above-described ratios are introduced into the reactors 10 and 11 from the respective cylinders 10, and are mixed and circulated. Although the pressure in the reactor has a great influence on the temperature of the bar in the reactor and the shape and composition of the crystals forming the diamond-like carbon film formed, in the present invention,
The pressure is adjusted by the pressure adjusting valve 6 so as to be in the range of 15 to 10 Torr. The microwave high frequency power is adjusted so that the surface temperature of this bar is 800-1,100 ℃. Bar temperature is 800
Below ℃, the diamond-like carbon film formation is slow,
Since the graphite component becomes conspicuous in the formed diamond film at a temperature of 100 ° C. or higher, the temperature of the bar during the reaction is preferably in the range of 800 ° C. to 1,100 ° C. Under such reaction conditions, the hydrocarbon gas is thermally decomposed by the plasma containing hydrogen as a main component, and is formed as a uniform diamond-like polycrystalline carbon film on the WC intermediate film.

Hereinafter, the embodiments of the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

(Examples 1 to 9 and Comparative Examples 1 to 5) Using a cemented carbide containing 10% by weight of Co and 20% by weight of Ti, the other of which is WC A dental bar having a shape (Fig. 1) was prepared. Next, this bar was washed with acetone, placed in a vacuum evaporator, the pressure in the system was reduced to 3 × 10 ⁻⁶ Torr, and the bar surface was heated to 200 ° C. by an infrared lamp. Next, W was melted and evaporated by an electron beam, and W was vapor-deposited for 20 to 60 minutes so that the film thickness of the W vapor-deposited film on the bar blade surface became the predetermined film thickness shown in Table 1. Next, this bar was installed in the reactor, the pressure inside the reactor was reduced to 0.01 Torr, and a mixed gas adjusted so that the ratio of hydrogen and methane gas was 200: 1 was introduced in the system at a flow rate of 100 cc / min. The system pressure was maintained at 8 Torr while being introduced and distributed in. In this atmosphere, a microwave of frequency 2.45 GHz oscillated from a magnetron was introduced into the reactor to generate a plasma flame around the bar,
The oscillation output of the magnetron was adjusted so that the bar temperature was 1020 ° C., and carburization and sintering were performed for 3 hours. After that, while maintaining the plasma flame, the ratio of hydrogen and methane gas was adjusted to the predetermined ratio shown in Table 1, the system pressure was set to 30 Torr, and the bar temperature was 850 ° C.
The magnetron oscillation output was adjusted so that the reaction was carried out for 15 hours to form a diamond-like carbon film. Regarding the dental cutting tool obtained in this way, JI
In accordance with the side edge cutting test of ST 5201, two consecutive cutting tests were performed, and the time required for cutting and the state of the blade surface after cutting were examined and used as a durability test.

[Cutting test conditions] Material to be cut: Acrylic plate (plate thickness 1mm), Cutting speed: 2,000r
pm, side edge cutting distance: 10 mm each for the first and second cutting, cutting load: 0.5 kgf.

The composition of the WC intermediate film formed by carburizing and sintering, which was examined by X-ray diffraction by the thin film method, is also shown in Table 1 together with the results of this durability test. This composition shows that the Co component on the surface of the base material diffuses and migrates to the WC phase during the reaction in the WC phase obtained by carburization and sintering, and is firmly bonded to the surface of the base material. From this, it can be seen that the dental cutting tool according to the present invention completes cutting within 20 seconds in both cutting tests. Further, the dental cutting tool according to the present invention has more stable cutting force and durability as compared with the conventional dental cutting tools of Comparative Examples 1 and 5. Is clear.

(Effects of the Invention) According to the present invention, it is possible to operate a dental cutting tool having more stable cutting force and excellent durability as compared with the conventional one, and its utility value in dental care is high. Extremely high.

[Brief description of drawings]

FIG. 1 is a side view of a dental bar having a cutting blade and a groove, and FIG. 2 is a side view of a diamond point. FIG. 3 is a conceptual diagram of a microwave plasma vapor deposition method reactor. The main symbols are as follows. A: Dental bar head (cutting blade and groove) B ... Dental diamond point head (grinding surface) 1 ... Dental bar, 2 ... Substrate support 3 ... Reaction tube, 4 ... … Reflector 5 …… Vacuum pump, 6 …… Pressure control valve 7 …… Impedance matching stub 8 …… Automatic impedance matching device 9 …… Flow control valve 10 …… Hydrocarbon gas cylinder 11 …… Hydrogen gas cylinder 12 …… 2.45 Rectangular waveguide for GHz 13 ... Magnetron oscillator

Claims (4)

[Claims] 1. A dental bar made of one kind of material selected from cemented carbide, ultrafine particle cemented carbide and cermet as a base material, and a tungsten ( W) is vapor-deposited to a thickness of 0.01 to 1.0 μm, and the vapor-deposited film is carburized in a microwave-excited plasma gas using hydrogen and a hydrocarbon gas as raw materials to form tungsten carbide (WC). 1. A method for manufacturing a dental cutting tool, comprising: forming an intermediate film of WC by sinter-adhering to and forming a diamond-like carbon polycrystalline film on the surface of the intermediate film. 2. The WC intermediate film according to claim 1, wherein the W vapor-deposited film is carburized in a microwave-excited plasma gas in which the volume mixing ratio of hydrogen to hydrocarbon gas is 50: 1 to 600: 1. Manufacturing method of dental cutting tools. 3. The diamond-like carbon polycrystalline film according to claim 1, wherein the volume mixing ratio of hydrogen to hydrocarbon gas is 50: 1 to 20.
The method for manufacturing a dental cutting tool according to claim 1 or 2, wherein the film is formed by a vapor deposition method using microwave excited plasma of 0: 1. 4. A surface of a cutting blade substrate made of one kind of material selected from cemented carbide, ultrafine grained cemented carbide and cermet is coated with an evaporated film of W having a thickness of 0.01 to 1.0 μm. After that, the WC intermediate film is carburized in a microwave-excited plasma gas using hydrogen and a hydrocarbon gas as raw materials, and at the same time, the WC intermediate film and the substrate surface are brought to a range of 1,000 to 1,500 ° C by thermal radiation of the plasma gas. It is heated and sinter-bonded, and further, on the surface of this interlayer film, by a gas phase deposition method using microwave-excited plasma with a mixed gas having a volume mixing ratio of hydrogen to hydrocarbon gas of 50: 1 to 200: 1. A method for manufacturing a dental cutting tool, which comprises forming a diamond-like carbon polycrystalline film.