JP3123117B2 - Diamond film formation 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 method for easily forming a diamond film having a strong adhesion and an excellent surface roughness on the surface of a low-friction and wear-resistant sliding part or a cutting tool by a gas phase method. It is about.

[0002]

2. Description of the Related Art Since diamond is extremely hard and has excellent wear resistance and excellent properties such as a low coefficient of friction, attempts have been made to apply it to sliding parts and cutting tools.

[0003] When a diamond film is used for a sliding part or the like, a problem is that the film may peel off during use if the film has low adhesion to a substrate and is used under severe conditions. Diamond films formed by the vapor phase method, which is a typical diamond film forming method, have poor surface roughness, and conversely, the mating material is often damaged or ground due to irregularities on the film surface.

As an attempt to enhance the adhesion to the substrate, a diamond film is deposited and formed on a substrate such as silicon, on which diamond is relatively easily deposited, by a vapor phase method, and the surface side of the diamond film is brazed to the surface of the substrate. Thereafter, a method (hereinafter referred to as a brazing method) of scraping the substrate has been proposed. (JP-A-1-15328). This method is effective when a diamond film is to be formed on the surface of a component containing Fe, Co, and Ni in which diamond is not easily deposited. However, a method such as brazing a diamond film once formed on the surface of a substrate such as silicon and then shaving off the substrate requires a thickness of the diamond film of 10 μm or more due to grinding accuracy, film strength, and the like. There was a problem that grinding itself was troublesome and required a great deal of labor and time.

[0005] On the other hand, in order to increase the surface roughness of the diamond film surface, polishing or the like has hitherto been performed. The higher the film formation rate and the higher the quality of the film with good crystallinity, the more the diamond film becomes a film with a well-developed self-shaped surface (habit habit), and the surface roughness becomes rough.

For this reason, in order to smooth the surface, a considerable thickness must be removed by polishing, laser or the like.

However, diamond is extremely hard,
A great deal of time and effort was required for such polishing. In particular,
When mass-producing a low-cost component in which a diamond film is formed on the surface of a cam or other shaped object formed of a series of complicated curved surfaces, it is necessary to minimize the portion to be removed by polishing or the like.

Further, when a target wear-resistant diamond coating layer is applied to the inner tip of a thin tubular shape such as an electric fuel injection nozzle, there is no film forming means or polishing means. Is the current situation.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and has a strong adhesion to a substrate.
It is an object of the present invention to provide a method for easily forming a diamond film having excellent surface roughness.

[0010]

Means for Solving the Problems The present inventors have paid attention to the following with respect to the above-mentioned problems of the prior art.

(1) When diamond is deposited on a substrate, a large number of nuclei are generated on the substrate, and the diamond grows in the horizontal and vertical directions around the nuclei. Paying attention to the point that it becomes a replica of the shape itself, if a complex shape is given to the substrate, it will have the same shape, and if the surface of the substrate is smooth, the surface of the diamond film formed in contact with this surface Also, a smooth surface similar to the substrate surface can be obtained, and if this smooth diamond film surface is used as the surface of an actual sliding component, the portion of the film surface to be polished can be significantly reduced. I thought.

(2) Also, paying attention to the fact that diamond can also precipitate on ceramic powders such as boron nitride, silicon nitride, silicon carbide, etc., a fine powder layer of the above ceramics is formed on the surface of the substrate. The diamond film can be easily separated from the portion of the ceramic powder by interposing and depositing diamond thereon, and this method solves the troublesome problem of shaving off the substrate in the brazing method. I thought I could.

In order to improve the brazing method, which has been conventionally performed to improve the adhesion between a diamond film and a substrate, the inventors have conducted research based on the above viewpoints, and have reached the present invention. It is a thing.

According to the method for forming a diamond film of the present invention, there is provided a step of forming a reverse mold having a smooth surface having a shape opposite to the shape of the surface of the substrate on which the diamond film is to be formed, and reacting carbon with the reverse shape. A step of forming a fine hard powder layer made of a compound that is difficult to perform, a step of forming a diamond film on the surface of the hard powder layer by a gas phase method, and a step of forming the diamond film as a substrate diamond film And a step of separating the base and the reverse mold from the hard powder layer.

[0015]

According to the method for forming a diamond film of the present invention, since the diamond film is firmly joined to the substrate by brazing or bonding with a synthetic resin, there is no problem such as separation of the diamond film.

Further, the surface of the diamond film formed by the present method is extremely smooth, and operations such as surface polishing can be remarkably reduced as compared with the conventional method. The reason is as follows. The method uses an inverse mold having an inverse shape to the surface of the substrate, forms a layer of fine hard powder on the surface of the inverse mold, and forms a diamond film on the powder layer having the smooth surface. I do. Thereafter, the inverse mold is removed from the hard powder layer portion, and the diamond film surface that has been in contact with the smooth surface of the hard powder layer can be used as the surface of the substrate.

Further, the substrate can be easily separated from the inverted mold mechanically from the portion of the hard powder layer and does not require the polishing of the inverted mold as in the prior art. Available,
In particular, in the case of a complicated shape, it is possible to implement at low cost in addition to the effect of reducing the surface polishing described above.

Moreover, this method can form a diamond film on the surface of an iron-based component, which has been impossible in the past, and on a deep portion where a conventional diamond film could not be formed. It is.

[0019]

【Example】

(Specific Example of the Present Invention) A method for forming a diamond film according to this specific example will be described in accordance with the steps.

(1) Step of Forming the Inverted Mold The shape and dimensions of the inverted mold are almost equal to the shape of the substrate, or have a size with a margin for finish polishing. That is, when the portion of the substrate on which the diamond film is to be formed is convex, the concave portion of the reverse type is made slightly larger in consideration of the thickness of the hard powder layer and the margin for finishing (FIG. 1). Conversely, if the portion of the substrate on which the film is to be formed is concave, the inverse convex is slightly smaller for the same reason.

The inverted material depends on the shape of the target substrate, but in any case, has a large thermal conductivity so that the substrate temperature required for depositing a diamond film on the surface can be controlled. Materials are preferred, and copper, tungsten and molybdenum are preferred for metals, and sintered bodies such as silicon carbide, aluminum nitride and boron carbide are preferred for ceramics. In these reverse molds, it is necessary to make the wall thickness of the surface on which diamond is deposited as uniform as possible, and to flow cooling water on the back side to control the temperature of the deposition surface uniformly and at a certain temperature.

However, in the case of using a method such as a microwave plasma method or a hot filament method, the temperature rise of the substrate is not so much a problem. Absent.

The molding and processing of the reverse mold may be performed by a general method. For an electrically conductive material, electric discharge machining, electrolytic polishing, or the like can be used for final finishing. The reverse mold may be formed into a near net shape by sintering the powder, sintering, processing and finishing by a method such as grinding.

The dimensional accuracy of the inverted surface must be as high as possible. This is necessary in order to reduce the margin at the time of processing and finishing after the diamond film is finally formed on the target shape by brazing.

On the other hand, the surface roughness does not require so high smoothness. This may have a certain degree of roughness in order to hold the hard powder layer formed on the surface of the inverse mold.

(2) Step of Forming Hard Powder Layer (FIG. 1) In order to deposit diamond on the surface of the hard powder layer,
The surface roughness of the diamond film in contact with the deposited hard powder layer is determined by the surface roughness of the surface of the hard powder layer.
For this reason, the finer the particle size of the powder constituting the hard powder layer, the more a diamond contact surface with a high surface roughness can be obtained. Therefore, the particle size must be at least 1 μm or less, and preferably 0.1 μm or less.

There is basically no problem with the powder material constituting the hard powder layer as long as it is used as a substrate material of a conventionally known vapor phase diamond film. Metals such as silicon, tungsten, molybdenum and niobium, carbides such as silicon carbide and tungsten carbide,
Borides such as aluminum nitride, silicon nitride, titanium nitride, and boron nitride, oxides such as aluminum oxide and silicon oxide, and so-called ceramics such as carbon boride can be used. The average particle size synthesized by the impact method is 5n.
m powder (trade name: cluster diamond) can also be used. However, when forming the diamond film, the temperature of the reverse mold serving as the substrate increases,
In addition, a substance that undergoes a chemical reaction with a material of thermal decomposition, melting, sintering, or the reverse type under the atmosphere is not preferable.

As described above, the powder used for the hard powder layer is very fine in sub-micron, and therefore has very good cohesiveness, and does not require a binder or the like except for special cases. A powder layer can be formed.

Usually, the hard powder layer is formed by dispersing the powder in a volatile solvent such as alcohol to form a slurry, coating the powder by a method such as spraying or coating, and drying. It forms by doing.

In order to prevent cracks after drying and to improve wettability with the reverse mold, a surfactant or a very small amount of an organic binder such as polyvinyl alcohol (PVA) may be added. .

In the case of using a coating method or the like, if the surface accuracy of the surface of the powder layer cannot be sufficiently obtained, the reverse type (the surface shape of the substrate on which the diamond film is formed, It is preferable to increase the precision of the surface by pressing lightly (with dimensions) and transferring the structure of the mirror surface.

In this case, the material of the reverse type used in the reverse type does not need to be particularly specified. If the material has abrasion resistance, it can be easily smoothed by machining, electric discharge machining, electrolytic polishing, etc., and has good dimensional accuracy. What is necessary is just to select from the viewpoint of the material from which a surface is obtained.

In addition, depending on the three-dimensional shape of the inverted mold, the powder is directly placed on the surface of the inverted mold, and the surface of the inverted mold having a mirror-polished inverted shape is press-formed with a punch. To form a powder layer.

When it is necessary to increase the mechanical strength of the hard powder layer, the hard powder layer is impregnated with a solution of an alkoxide such as silicon or aluminum in a solvent such as an alcohol by spraying or the like, and is subjected to hydrolysis. It is also effective to strengthen the product by the product.

However, various organic materials used for forming a hard powder layer having a smooth surface shape by the above treatment may become harmful when forming a diamond film. It is desirable to heat at a temperature of about 500 ° C. and to decompose and remove.

The thickness of the hard powder layer is 1 mm in dimensional accuracy.
The following is desirable. On the other hand, from the necessity of cooling during the formation of the diamond film, it is better to make the thickness as thin as possible. Therefore, the thickness of the powder layer depends on the particle size and heat conduction of the fine powder used, but is preferably 100 μm or less.
The lower limit cannot be specified unconditionally because the mechanical strength of the layer changes depending on the particle size of the fine powder and the chemical composition constituting the particles, but a thickness of about 5 times or more the average particle diameter of the powder is required,
Below this, a good powder layer cannot be obtained.

(3) Step of Forming Diamond Film (FIG. 2) A method of forming a diamond film on the surface of a hard powder layer formed on the surface of an inverse mold by a vapor phase method is any method conventionally proposed. There is basically no problem.

If a problem arises, a DC plasma jet method, a combustion method, etc., in which the hard powder layer or the fine diamond powder serving as a nucleus, which will be described in detail later, may be blown off by a fast gas flow, are not preferred. This is not the case if the method of forming the body layer or the treatment of the attachment of the fine diamond powder is performed properly.

As described above, it is known that the formation of a diamond film by a vapor phase method involves epitaxial growth on a very small portion of a substrate such as a diamond single crystal or c-BN. Generally, they are deposited and grown as a polycrystalline film by the mechanism of nucleation and grain growth. Therefore, in order to smooth the contact surface with the substrate, it is desirable to generate a large number of nuclei on a smooth substrate surface, and various means have been proposed to increase the number of generated nuclei. Here, in order to form nuclei at a high density on a layer formed by solidifying the powder, a method of forming a diamond layer of ultrafine powder thinly and uniformly is preferable. More specifically, a slurry obtained by dispersing cluster diamond in alcohol or the like is sprayed to form a diamond layer such that at least one diamond particle covers the surface of the hard powder layer.

The ultra-fine diamond used for this purpose is not limited to the above-mentioned cluster diamond. If fine diamonds can be obtained, even those obtained by pulverizing natural products or artificially synthesized ones have no effect. The diamond used in this case is separated by a water sieve or the like after pulverization, and its particle size is preferably at least smaller than the particle size of the powder used for the hard powder layer.

Further, in order to make the interface between the diamond layer serving as the core and the hard powder layer conform to the surface structure of the hard powder layer, smoothness is increased by a method such as lightly pressing again with an inverted mold. Taking measures is also effective.

The thickness of the diamond film deposited on the surface of the inverse mold having the hard powder layer and the diamond ultrafine powder layer serving as a nucleus depends on the use of the final product, and is not particularly limited. In the method of the present invention, there is no problem if the thickness is several μm or more. Even if the thicker layer has a thickness of several hundred μm or more, separation during film formation can be prevented by selecting the material and particle size of the powder constituting the hard powder layer, and there is no particular problem.
In this case, for example, silicon nitride or the like having a value as close as possible to the coefficient of thermal expansion of diamond may be used, and one of the features is that a thick film can be formed relatively easily because the powder layer relieves stress. is there.

(4) Brazing Step (FIG. 3) A reverse mold having a diamond film formed on the surface is brazed to the surface of the substrate on the surface side of the diamond. There is no particular problem with the brazing material used here as long as it is a brazing material that has been conventionally used for joining to a diamond tool or the like.

For example, there is no problem with a brazing material such as a Ti-Cu-Ag-based material. In some cases, a low-temperature solder or an epoxy-based synthetic resin can be used in a portion where no temperature or stress acts depending on the application. is there.

As the form of the brazing material, any of a foil and a powder can be used according to the shape of the component on which the diamond film is finally formed. In particular, when brazing to a surface having a complicated shape, it is easy to handle if the foil is formed into the shape in advance.

In order to improve the accuracy of the surface when brazing or the like is performed on the base, a part for positioning is provided on the base and the reverse mold, or a jig for positioning is separately formed, and the brazing material is formed. It is important to braze in place by pressing while melting. Positioning at the time of this brazing is very important, and the accuracy in this process greatly affects the clearance at the time of processing the final diamond surface, and in some cases, the film thickness when depositing the diamond film There are problems such as the need to increase the thickness.

(5) Separation Step (FIG. 4) After brazing, the substrate and the reverse mold are separated from the hard powder layer, the powder remaining on the diamond surface is mechanically removed, and the diamond surface is finished. By performing the processing, a diamond film can be formed on a target substrate.

Since the hard powder layer is easily broken by applying a tensile stress, no special device is required for separating the base and the reverse mold.

The surface of the brazed diamond has a very smooth surface, which is different from the surface of the hard powder layer having the shape of the growing surface, which is different from the surface having the self-shape on the growing side. Very easy to finish. Any of mechanical grinding, polishing, a thermochemical method, or a method combining laser and the like may be used.

(Example 1) Assuming a part in which a diamond film is firmly formed on the sliding surface of a cam-shaped part, a steel φ
An attempt was made to form a diamond film on a part of a 20-mm-thick, 10-mm-thick disk-shaped outer curved surface (FIG. 5).

A 10 mm thick inverted mold having a concave curved surface with a radius 150 μm larger than the final shape was made of stainless steel (SU).
S304). The surface roughness of the inverted concave surface is
It was 0.3 μm Rz.

A commercially available spray-like boron nitride (trade name: boron spray) was sprayed on the concave surface as a release agent to form a hard powder layer having a thickness of about 20 μm.

The inverted mold was placed in a chamber of a hot filament method CVD apparatus, and was set such that a molybdenum filament was positioned near the center of a semicircular concave part of φ20 mm attached to the inverted mold.

The diamond film formation was performed under the following conditions.

CH ₄ / H ₂ ratio: 0.5, total flow rate: 2
00 sccm, filament temperature: 2100 ° C., reverse surface temperature: 750 to 800 ° C., pressure: 50 Torr. , Film formation time: 90 hours

The film thickness of the polycrystalline diamond film formed under these conditions was about 100 μm, and the surface of the diamond polycrystalline film was (11).
1) The surface was well developed.

The brazing is performed according to JIS standard BAG-8 Cu-
Ti is applied on one side of an Ag-based 50 μm thick foil brazing material.
%, And the surface was set so as to contact the diamond film.

The inverted mold was set in the vacuum furnace so that the steel disk was on the upper side with the brazing material interposed therebetween, and 10 ^-5 Torr. , And then heated to 950 ° C. to perform brazing.

After cooling, the reverse mold and the diamond film were separated by a layer of boron nitride and polished with emery paper. As a result, a very smooth diamond surface appeared.

In the case of this embodiment, a film can be formed all around at once by using a plurality of inverted molds divided by appropriate parting lines and performing brazing at the same time. (Example 2)

Assuming that a diamond film is formed on the inner surface of the nozzle of the fuel injector for the EFI engine,
An attempt was made to form a diamond film having a high surface roughness at a portion where the inside tip of a cylindrical shape having an inner diameter of φ5 mm and a length of 100 mm was sharpened in a cone shape (FIGS. 6 and 7).

In this case, the reverse type is φ4.5 mm and the length is 150
A silicon carbide sintered body having a tip of mm was used. The surface roughness of the cone-shaped tip at the tip was finished to 1.0 μmRz.

Separately, a very small amount of PVA was added to ethyl alcohol, and a slurry in which silicon nitride having a roughness of 0.3 μm was dispersed was prepared.

The inverted tip was dipped in the slurry, pulled up and dried. Next, stainless steel (SU
S304), which has a shape corresponding to the cone-shaped point of the inside tip of the cylindrical body as the substrate, and is formed by electrolysis of an inverse mold of a diamond film and an inverse dimension of a brazing thickness. Manufactured by polishing. When the slurry applied to the reverse mold is almost completely dried, the surface is inserted into a reverse stainless steel (SUS304) reverse mold having a mirror-finished surface, and the dried slurry portion is pressed against the silicon nitride powder. At the same time as the body layer was compressed, the reverse smooth surface shape was transferred to the surface of the body layer to form a hard powder layer.

On the other hand, a suspension prepared by dispersing cluster diamonds synthesized by the impact method in cyclohexane is prepared, sprayed on the surface of the silicon nitride powder layer, and then dried three times. The entire surface was covered with ultrafine diamond particles.

A film was formed on the cone-shaped portion at the tip of the inverted mold subjected to the above treatment by the hot filament method under the same conditions as in Example 1 while rotating at a speed of 10 rpm for 90 hours. Incidentally, the thickness of the diamond film measured on another sample formed under the same conditions was about 120 μm. (FIG. 6)

The diamond film deposited on an extra portion was mechanically removed to complete a reverse mold having the diamond film formed thereon.

On the other hand, the base material made of stainless steel (SUS30
Inner diameter φ5m with a cone-shaped tip made in 4)
m, a silver brazing powder containing 1% of titanium is placed at the tip of a pipe-shaped object having a length of 100 mm, and a bar-shaped inverted mold on which a diamond film is formed is further inserted. About 200 g of a steel weight was placed on the mold.

The whole was placed in a vacuum furnace and heated to 950 ° C., and the silver solder was completely melted and cooled.

After cooling, the inverted mold was peeled off from the silicon nitride powder layer and pulled out. (FIG. 7)

The diamond film was brazed to the desired position. After that, it was polished and finished using a diamond whetstone specially made for this purpose.

In this embodiment, a tapered cone type is used. However, the effect of this embodiment is that a diamond film can be formed in a deep portion basically even in a bosh-shaped form. There is.

Example 3 An attempt was made to form a diamond film on the same shape as in Example 2.

In this case, the cone portion at the tip of the silicon carbide inverted mold was mirror-finished with diamond abrasive grains. Instead of the hard powder layer made of silicon nitride formed on the surface of the inverse mold, dip the site where the diamond film at the tip of the inverse mold is to be formed in a slurry in which cluster diamond is densely dispersed in cyclohexane, A layer of diamond ultrafine powder was made. In this case, the thickness of the layer of the ultrafine diamond powder was set to such a thickness that the reverse mold as the substrate was not exposed.

After sufficiently drying to remove cyclohexane,
In the same manner as in Example 2, a diamond film was formed by a hot filament method for 90 hours.

In the subsequent operation, a stainless steel (SUS304) pipe was brazed as in Example 2, and the inverted mold was pulled out. In this case as well, separation was easily made between the layers of the cluster diamond layer or the inverted surface, and the portion where the film was formed was cut out and examined.The purpose was to obtain a diamond film that could easily become a smooth surface by simple surface polishing. It has been found that it can be formed on a shaped object.

As described above, fine diamond powder can be used as the material of the hard powder layer. In this case, the diamond powder plays a role as the hard powder layer and the diamond nucleation layer.

The reverse type of the silicon carbide used here did not change at all, and there was no problem in using the silicon carbide again and again.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an inverted mold having a base and a hard powder layer formed thereon.

FIG. 2 is a schematic diagram showing an inverted mold having a substrate and a diamond film formed thereon.

FIG. 3 is a schematic diagram showing a base and an inverse mold joined by brazing;

FIG. 4 is a schematic diagram showing a state in which the reverse mold is separated from the base.

FIG. 5 is a schematic view showing a method of forming a diamond film on a substrate assuming a cam.

FIG. 6 is a schematic view showing a method of forming a diamond film on the tip of a pipe-shaped substrate.

FIG. 7 is a schematic view showing a method of forming a diamond film on the tip of a pipe-shaped substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Reverse type 3 Hard powder layer 4 Diamond film 5 Brazing part 6 Ultrafine diamond layer

Continuation of front page (56) References JP-A-4-132688 (JP, A) JP-A-3-126697 (JP, A) JP-A-3-141193 (JP, A) JP-A-64-16328 (JP) JP-A-4-119995 (JP, A) JP-A-1-153228 (JP, A) JP-A-4-321595 (JP, A) JP-A-4-228497 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 C23C 16/26 CA (STN)

Claims (1)

(57) [Claims] 1. A step of forming a reverse mold having a smooth surface opposite to the shape of a surface of a substrate on which a diamond film is to be formed, and a smooth surface made of a compound which is unlikely to react with carbon on the reverse shape surface. A step of forming a hard powder layer, a step of forming a diamond film on the surface of the hard powder layer by a vapor phase method, and brazing the diamond film to a surface of the substrate on which the diamond film is to be formed or by using a synthetic resin. A method of forming a diamond film, comprising: a step of bonding by adhesion; and a step of separating a substrate and a reverse mold from a hard powder layer.