JPH05195223A - Coated sintered body and its production - Google Patents

Abstract

PURPOSE:To form a diamond film or a high hardness carbon film having good crystallinity with good adhesive strength by specifying the occupancy area ratio of cobalt in the surface of a sintered body. CONSTITUTION:The occupancy area ratio of cobalt in the surface of a tungsten carbide-cobalt base sintered body is specified to <=10% so as to suppress the solid solution of carbon into cobalt caused at the time of forming a film. As the method for redering the occupancy area ratio of cobalt in the surface of a sintered body to <=10%, after sintering, grinding and polishing, etc., the heat treatment is executed at 1250-1310 deg.C which is near the eutectic temp. of W-C-Co system in an inert atmosphere. The cobalt near the surface intrudes into the sintered body and almost disappear from the surface. The roughness of tungsten carbide apprears on the upper surface of the sintered body. Thereby, a diamond film or a high hardness carbon film having good crystallinity can be easily formed on the upper surface with good adhesion property.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coated sintered body used for cutting tools, wear resistant tools, dies, wear resistant parts, ornaments and the like.

[0002]

2. Description of the Related Art High-performance, highly wear-resistant tools, wear-resistant parts, etc. are mainly composed of tungsten carbide, titanium carbide, etc., so-called cemented carbide, sintered material called cermet, alumina, etc. Ceramic sintered bodies such as silicon nitride were also widely used. In recent years, chemical vapor deposition (CVD
Method) or physical vapor deposition method (PVD method), and a sintered ceramic body coated with a ceramic film such as titanium carbide, titanium nitride, or alumina, or a diamond or hard carbon film in order to further improve the performance of the above materials. Became widely used.

[0003]

In recent years, among the above-mentioned coating materials, a hard carbon film having the hardest diamond in the materials or a hardness close to that of diamond (in many cases, containing fine crystalline diamond) is used. Attention has been focused on the coated sintered body. As a method for producing this diamond or hard carbon film, hydrogen gas and a carbon-containing substance are generally used as raw materials and synthesized by a plasma CVD method using microwaves or a hot filament CVD method. When these methods are used to synthesize and form a diamond or hard carbon film on a substrate obtained by sintering tungsten carbide, which is most widely used as a material for cutting tools, etc., with cobalt as a binder, the substrate is about 800 Since the temperature was ℃, the precipitated carbon component dissolved in cobalt as a binder to form a desired diamond or hard carbon film.

As a method for solving this problem, it is conceivable to reduce the content of cobalt as a binder. However, if the content of cobalt is extremely reduced, the strength of the sintered body after sintering is extremely lowered. Not preferable. Also,
Even with a content of appropriate strength (for example, Co4 wt%), cobalt having a lower hardness than tungsten carbide causes so-called sagging and covers the outermost surface by processing such as grinding and polishing after sintering. Occupies a large area, and this method could not be a sufficient solution to this problem. Furthermore, even if it was deposited as a diamond or hard carbon film without forming a solid solution in cobalt, there was a large difference in the coefficient of thermal expansion between the substrate and the deposited film, so there was a problem that peeling would occur when the film thickness increased. ..

[0005]

In order to solve such a problem, in the present invention, a diamond or hard carbon film is provided on the tungsten carbide-cobalt sintered body which is the base body, by the above CV.
In synthesizing and forming by the D method, the ratio of the area occupied by cobalt on the surface of the sintered body, in other words, the area occupied by cobalt on the surface where the sintered body adheres to the diamond or hard carbon film is set to 10% or less. In this case, as a method for reducing the area ratio of cobalt on the surface to 10% or less, the content of cobalt as a binder is reduced as much as possible, and after sintering, processing such as grinding and polishing into a desired shape is performed. WC
1250 ° C. to 13 which is a temperature near the eutectic temperature of the Co type
Heat treatment is performed in a vacuum or argon atmosphere in the range of 10 ° C.

[0006]

[Function] When synthesizing and forming a diamond or hard carbon film on a tungsten carbide-cobalt-based sintered body,
By setting the area ratio of cobalt on the surface of the sintered body to 10% or less, it is possible to suppress the solid solution of carbon in cobalt that occurs during the formation of these films.
By the method, a diamond film or a highly hard carbon film having good crystallinity can be obtained. In addition, since the amount of cobalt on the surface is reduced, the ratio of the tungsten carbide surface close to the thermal expansion coefficient of diamond is increased due to the surface,
Peeling is less likely to occur due to the difference in coefficient of thermal expansion, and improvement in adhesion is achieved.

Further, as a method for making the ratio of cobalt on the surface of the sintered body 10% or less, after processing such as sintering, grinding and polishing, WC-Co in vacuum or an inert atmosphere such as argon. 1250 ℃, which is near the eutectic temperature in the system
By performing the heat treatment in the range of up to 1310 ° C., cobalt near the surface infiltrates into the inside of the sintered body, a part of it evaporates, and it almost disappears near the surface, especially at the surface part. At this time, since the tungsten carbide is in the form of particles, after the heat treatment, the outermost layer of the tungsten carbide particles is firmly bonded to cobalt on the inner surface of the sintered body, and the strength of the sintered body is not reduced. In addition, irregularities on the tungsten carbide surface appear on the outer surface.

Further, by the CVD method on this upper surface, there is no solid solution of carbon in cobalt, not only the difference in thermal expansion is suppressed, but also the so-called anchor effect due to the fine unevenness of the tungsten carbide surface appears, so that adhesion is improved. A diamond or highly hard carbon film having excellent properties and good crystallinity can be easily formed. Here, the heat treatment temperature is set to 125
If the temperature is lower than 0 ° C, migration of cobalt into the inside of the sintered body and evaporation from the surface will be insufficient, and the ratio of cobalt on the outermost surface of the sintered body will be high, resulting in a coated sintered body having excellent properties. On the other hand, if the temperature is higher than 1310 ° C, on the contrary, the migration of cobalt into the sintered body and the evaporation from the surface become too much, and the bond strength of the tungsten carbide particles on the outermost surface weakens, causing dropout after heat treatment. When the diamond or hard carbon film is formed, the tungsten carbide particles and the film are likely to come off or peel. Therefore, the heat treatment temperature is in the vicinity of the W—C—Co eutectic temperature, that is, in the range of 1250 ° C. to 1310 ° C., and the coated sintered body is excellent.

[0009]

EXAMPLES The present invention will be described below based on examples in which the present invention is applied to a tungsten carbide-cobalt sintered body throw-away tip which is used as a wear resistant component under the most severe conditions. A cemented carbide throw-away tip, the surface of which was made of a tungsten carbide-cobalt-based sintered body (weight ratio Co4% JIS standard K-10 equivalent product) was ground, was heat-treated at 1290 ° C. for 15 minutes using a vacuum heat-treatment furnace. .. The degree of vacuum at this time was 10 ⁻⁶ TOrr. Using the microwave CVD (2.45MHz) plasma CVD device for the carbide hard throw-away tip and the untreated article, the total gas flow rate was 300CC.
/ Min, methane flow rate ratio 0.3%, gas pressure 30 Tor
r, microwave output was 500 W, and a film containing diamond as a main component was formed.

During the diamond film synthesis, the throw-away tip, which is the base material, was heated to about 800 ° C. by microwaves. After the film synthesis and cooling, the sample was taken out from the CVD apparatus. In the entire range shown in Table 1, no defects such as film thickness peeling were observed, whereas 3 μm was obtained for the sample not subjected to the heat treatment.
Peeling occurred at a film thickness of m or more.

Next, of the representative samples listed in Table 1 which did not cause peeling, a typical sample was prepared using an NC lathe.
The Al-Si (12%) alloy was cut under the cutting conditions shown in Fig. 1 and the results of flank wear are shown in Fig. 1.
In the sample 1 which was not heat-treated, chipping and peeling occurred in all the samples at the initial stage, there was no effect of the diamond film coating, and the result was almost the same as that of the sample 2 having only the base material. In the sample 3 thus produced, phenomena such as chipping and peeling did not appear, and extremely high machinability was exhibited. For this sample with good machinability, in order to know the element distribution state of the outermost surface without forming a diamond film, surface analysis by Auger electron spectroscopy was performed, and the area ratio of cobalt was about 5%. Was becoming.

[0012]

[Table 1]

[0013]

[Table 2]

Next, in order to know the conditions and effects of heat treatment,
Table 3 shows the results of the area ratio of cobalt on the outermost surface obtained by Auger electron spectroscopy analysis and the results of adhesion and machinability when the heat treatment conditions were changed. From these results, it was confirmed that setting the area ratio of cobalt in the tungsten carbide-cobalt sintered body to 10% or less gives an excellent coated sintered body. It was found that the temperature range of the heat treatment that gives this condition is preferably 1250 ° C to 1310 ° C. The atmosphere for heat treatment is preferably vacuum or an atmosphere such as argon in order to prevent oxidation, and the heat treatment time depends on the composition of the sintered material, the size of particles (particularly tungsten carbide particles), and the shape of the processed material. A few minutes to a few tens of minutes are appropriate, and if it is too long, the surface tungsten carbide particles will fall off or the diamond film will be removed / peeled off due to residual internal stress, and if it is too short, the proportion of cobalt will be too large. I have confirmed.

[0015]

[Table 3]

Finally, the diamond film synthesis of the samples shown in Tables 1 and 3 was carried out under the above conditions.
Similar results were obtained by changing the flow rate, the pressure, the microwave output, and the gas source serving as the carbon source to another hydrocarbon gas, oxygen-containing organic matter, or carbon monoxide. The same applies to a high hardness carbon film having a diamond film, a hard film containing diamond as a main component, or a hard carbon film containing no diamond.

Further, similar results are obtained not only for the sintered body corresponding to K-10 but also for other tungsten carbide-cobalt based sintered bodies.

[0018]

As described above, according to the present invention, an excellent diamond or hard diamond is obtained for a tungsten carbide-cobalt sintered body having high versatility in tools, wear-resistant tools, dies, wear-resistant parts and ornaments. A coated sintered body on which a carbon film is formed and a method for manufacturing the same can be provided. That is, by making the area occupied by cobalt on the surface of the tungsten carbide-cobalt sintered body 10% or less, diffusion of carbon into cobalt in the substrate during formation of diamond, a diamond-containing carbon film, or a hard carbon film. It is possible to prevent the phenomenon of solid solution and to improve the characteristics of the formed film itself, and to reduce the difference in thermal expansion between the film and the base material, and also to improve the adhesion called the anchor effect. Since it occurs at the same time, it is possible to manufacture a high-performance coated sintered body, and for a wear resistant product such as a cutting tool having a shape that is difficult to form with a diamond sintered body,
Wide application is possible.

In the examples, the throw-away tip was taken up, but a processed object made of a tungsten carbide-cobalt sintered body, for example, a cutting tool such as a drill or an end mill, a wear-resistant tool such as a die, a punch, a die, Obviously, the present invention can be applied to any component. Further, in forming the diamond or hard carbon film, the microwave CVD method was used in the embodiment, but other methods such as CVD using a hot filament are used.
It is obvious that the method can be applied to the method, a method using a plasma jet, and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a cutting test result according to the present invention.

[Explanation of symbols]

 1 sample without heat treatment 2 sample with base material 3 sample with heat treatment

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenichi Ogawa 6-31-1, Kameido, Koto-ku, Tokyo Seiko Denshi Kogyo Co., Ltd.

Claims (3)

[Claims] 1. In a cemented carbide tool, wear-resistant tool, mold, wear-resistant component, decorative article, etc. sintered using tungsten carbide or cobalt as a main component of binder, cobalt on the sintered surface occupies Ratio is 10% in area ratio
A coated sintered body which is the following and has a diamond film or a hard carbon film on the surface thereof. 2. A tungsten carbide and cobalt sintered body is processed into a desired shape and then heat treated to reduce the area ratio of cobalt on the surface of the sintered body to 10% or less, and then a diamond film or a hard carbon film is formed. The method for producing a coated sintered body according to claim 1, wherein. 3. The heat treatment is performed in vacuum or in an inert atmosphere such as argon, and the heat treatment temperature is 1250 ° C. to 13 ° C.
The method for producing a coated sintered body according to claim 2, wherein the temperature is 10 ° C.