JPH0623432B2 - High adhesion diamond-coated sintered body and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a coating of diamond and / or diamond-like carbon on the surface of a sintered body containing tungsten carbide as a main component as represented by cemented carbide. Formed. For example, the present invention relates to a highly adherent diamond-coated sintered body suitable for a cutting tool material, a wear-resistant tool material, a decorative material, and the like, and a method for producing the same.

(Prior Art) Conventionally, studies have been conducted for practical application of a coated sintered body in which a coating film of diamond and / or diamond-like carbon is formed on the surface of a base material which is a sintered body of metal, alloy or ceramics. It is being appreciated. The biggest problem with this coated sintered body is that since diamond has poor wettability with other substances, how is the adhesion and adhesion strength between the diamond and / or diamond-like carbon coating and the substrate? There is something to raise. In particular, in the case of a diamond-coated sintered body obtained by forming a diamond and / or diamond-like carbon coating on a cemented carbide base material, it is intended for the most severe applications such as cutting tool materials and wear resistant materials. Therefore, the adhesiveness and the adhesive strength between the coating film and the base material become more important problems.

There have been many proposals regarding the adhesion and adhesion strength between the cemented carbide base material and the coating in the diamond-coated sintered body, and representative ones thereof are Japanese Patent Laid-Open Nos. 58-126972 and 62-62. -57802 and JP-A-63-53269.

(Problems to be Solved by the Invention) Japanese Patent Laid-Open No. 58-126972 discloses that an inner layer adjacent to a base material of a cemented carbide containing one or more kinds of carbides and / or nitrides has 4a, 5
Carbides, nitrides, borides, oxides of a and 6a group elements and their compounds, mixtures and Al ₂ O ₃ , AlN, B ₄ C, SiC, S
A coated cemented carbide tool made of at least one selected from i ₃ N ₄ and SiO ₂ and having an outer layer of diamond is shown.
The invention according to this Japanese Patent Laid-Open No. 58-126972 has the problem that when a cemented carbide containing Co or Ni is directly coated with a coating of dilamond, the diamond transforms and becomes graphitized between the cemented carbide and the diamond coating. Although it is an attempt to solve this problem by interposing an intermediate layer of WC, which does not include metals such as Fe, Co, and Ni, in the case of forming a diamond film by the vapor phase synthesis method, before the transformation of diamond. There is a problem in that graphite is generated, and therefore graphite is present at the boundary between the intermediate layer and the coating film, which reduces the adhesive strength between the intermediate layer and the coating film.
Further, the invention according to Japanese Patent Laid-Open No. 58-126972 is a completely different reaction container in which an intermediate layer is formed by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method), and then a diamond film is formed. It becomes complicated because it requires a process by
Impurities are likely to adhere to the boundary between the intermediate layer and the coating, which causes a problem that the adhesion strength between the intermediate layer and the coating is reduced.

JP-A-62-57802 discloses that a hard carbon thin film of a hard carbon thin film coated with a hard carbon thin film deposited on the surface of a base material by vapor deposition has W ₂ C as a main component between the hard carbon thin film and the base material. There is shown a hard carbon-coated part in which an intermediate layer of a compound thin film of W and C is present in a thickness of 0.1 μm or more. This JP 62
In the invention according to Japanese Patent No. 57802, the improvement of the adhesion strength was hardly recognized even when the intermediate layer of WC was formed on the surface of the base material made of cemented carbide or ceramics, while the CVD method or P
By the VD method, a diffusion intermediate layer made of WC is formed at the interface between hard carbon and W ₂ C, which covers the intermediate layer of the compound thin film containing W ₂ C as the main component and W and C, and as a result, adhesion Although it was possible to improve the strength, impurities are likely to adhere to the boundary between the intermediate layer and the base material because it is an intermediate layer formed by the CVD method or PVD method. Poor adhesion strength at the interface with, and also like the invention of JP-A-58-126972, impurities are likely to adhere to the boundary between the intermediate layer and the hard carbon thin film, and therefore the intermediate layer and the hard carbon thin film However, there is a problem that the adhesion strength is poor and the process becomes complicated.

Japanese Unexamined Patent Publication No. 63-53269 discloses a tungsten carbide-based cemented carbide containing 1 to 4 wt% of Co, the balance consisting of tungsten carbide and unavoidable impurities, and having a coarse grain structure with an average grain size of tungsten carbide of 2 to 10 μm. A diamond-coated cutting tool tip in which a low-pressure vapor-phase synthetic diamond coating layer is formed on the surface of a substrate via an etching layer is shown. Those invention of this Japanese 63- fifty-three thousand two hundred sixty-nine Patent Publication, having formed an intermediate layer of WC or W ₂ C from the outside as in JP 58-126972 and JP 62- 57802 JP above Unlike, the surface of the cemented carbide base material is etched by acid treatment to remove the Co existing on the base material surface, and the diamond coating layer is formed on the surface of the etching layer. When there is no problem and the adhesion strength between the etching layer and the substrate is not deteriorated, but graphite adheres to the interface between the diamond coating layer and the etching layer, and the Co portion removed by etching remains as voids. Therefore, there is a problem that the adhesion strength between the diamond coating layer and the etching layer is extremely reduced, and the diamond coating layer is apt to be missing.

The present invention has solved the above-mentioned problems, and specifically, decarburizes tungsten carbide on the surface portion of a sintered body containing tungsten carbide as a main component by vapor phase treatment to form tungsten. For example, when a binder phase of a metal such as Co is present on the surface of the sintered body, the binder layer on the surface is removed as metal carbonyl at the same time, and then diamond vapor phase synthesis treatment is performed, followed by firing at the initial stage. High-adhesion diamond-coated sintered body obtained by forming tungsten on the surface of the bonded body into a surface-refined layer made of recrystallized tungsten carbide, and then forming a diamond coating adjacent to the surface-refined layer, and manufacturing thereof It is intended to provide a method.

(Means for Solving the Problems) The present inventors, in the case of forming a diamond film by a vapor phase synthesis method on the surface of a sintered body containing tungsten carbide as a main component, for example, a cemented carbide substrate, When we examined the surface condition of the base material before forming the film, and the conditions for forming the film and the surface condition of the substrate after forming the film, firstly, etching the Co metal present on the surface part of the substrate. Even when a diamond coating is formed on the surface of the etching layer of the base material removed by the treatment by a vapor phase synthesis method, the precipitation of graphite is suppressed in the initial stage of the vapor phase synthesis method, but the base material and the coating layer We have obtained the knowledge that a trace amount of graphite is found at the interface of.

Secondly, when a small amount of oxygen gas was introduced before forming the diamond film in order to completely suppress the precipitation of graphite according to the first finding, decarburization and removal of metals such as Co occurred on the surface of the base material. Then, when a diamond film is formed, the surface of the base material becomes a surface refining layer made of recrystallized tungsten carbide, and when a diamond film is formed on the surface of this surface refining layer, adhesion control and adhesion strength are obtained. It has been found that it is excellent in sex. The present invention has been completed based on the above findings.

That is, the highly adherent diamond-coated sintered body of the present invention comprises a sintered body containing tungsten carbide as a main component as a base material, and forming a coating film of diamond and / or diamond-like carbon on the surface of the base material. In the diamond-coated sintered body, at least 0.1 μm from the surface of the base material adjacent to the coating to the inside of the base material is a surface refining layer made of recrystallized tungsten carbide. To do.

The base material in the high-adhesion diamond-coated sintered body of the present invention contains at least 50 vol% of a sintered body composed of only tungsten carbide or tungsten carbide, and the rest is, for example, a carbide of a group 4a, 5a, 6a element of the periodic table, It is composed of nitrides and mutual solid solutions thereof, or metal compounds, metals or alloys such as Fe, Co, Ni, W, Cr, V, Mn, Si and Cu. Of these, a base material composed of Co and / or Ni of 2 to 6 wt% and the remaining tungsten carbide and unavoidable impurities is preferable from the viewpoint of both the strength of the base material itself and the ease of adjusting the surface tempered layer. Is.

The surface refining layer in the highly adherent diamond-coated sintered body of the present invention has a thickness of 50 μm from the surface of the substrate toward the inside.
It is possible to adjust the thickness to about m, but it is preferable that the thickness is as thin as possible from the viewpoint of the strength of the surface-tempered layer, the adhesion between the coating and the surface-tempered layer, and the adhesion strength. Is preferred. Also, the particle size of tungsten carbide in the surface heat treatment layer is adjusted from the particle size of tungsten carbide contained in the base material to a particle size extremely finer than the particle size of tungsten carbide contained in the base material. Possible,
For example, when the entire surface-conditioned layer is a fine-grained tungsten carbide layer, or only the surface-conditioned layer adjacent to the coating is a fine-grained tungsten carbide layer, and the surface-modified layer on the inner side of the other substrate is It is also possible to employ a structure including a coarse-grained tungsten carbide layer. The surface conditioning layer preferably has a particle size of 0.3 μm.
The following fine-grain tungsten carbide layer, and more preferably a fine-grain tungsten carbide layer having a grain size of 0.1 μm or less, and the case where the coating is formed adjacent to the fine-grain tungsten carbide layer It is preferable in terms of adhesion and adhesion strength.

Further, the recrystallized tungsten carbide forming the surface-conditioned layer is a layer of WC when the whole is a WC layer, or the part adjacent to the coating is a WC layer depending on the thickness and treatment conditions of the surface-conditioned layer. In some cases, the part away from the film may be W ₂ C or a layer in which W ₂ C and WC are mixed. This recrystallized tungsten carbide is obtained by recrystallizing as tungsten carbide after the tungsten carbide contained in the sintered body itself once becomes tungsten.

The coating film of diamond and / or diamond-like carbon in the highly adherent diamond-coated sintered body of the present invention is
Electric resistance, light transmittance, hardness, etc. have properties of diamond or properties close to those of diamond. Specifically, a peak appears at 1333 cm ^-1 which is said to be the Raman line of diamond when analyzed by Raman spectroscopy. It is a thing. Furthermore, in more detail, the coating film is composed of only diamond or contains diamond and other materials such as amorphous carbon. The thickness of this coating may be conventionally proposed, for example, about 0.1 μm to 20 μm, and a thicker coating may be used for applications in which only scrape abrasion is important without impact. In addition, it is preferable to use a thin coating for applications such as a milling cutting tool to which an impact is applied and applications such as a drill and a slitter having a sharp cutting edge.

The method for producing a high-adhesion diamond-coated sintered body of the present invention is, for example, exposing the surface portion of the base material of the sintered body containing tungsten carbide as a main component to an oxidizing gas atmosphere to remove the surface portion of the base material. After decarburization, the diamond coating process is subsequently performed by the vapor phase synthesis method, or the surface of the substrate is decarburized by some method, and then exposed to an atmosphere containing carbon monoxide gas in another reaction vessel. Although it is conceivable to apply a diamond film treatment by a vapor phase synthesis method after that, the following method is used because of the simplification of the process, the difficulty of adhering impurities, and the easy control of the substrate surface heat treatment layer. It is preferable.

That is, the method for producing a high-adhesion diamond-coated sintered body according to the present invention, a base material of a sintered body containing tungsten carbide as a main component is placed in a reaction vessel, and hydrogen gas and oxygen gas are placed in the reaction vessel. Or a mixed gas of hydrogen gas, oxygen gas and a gas that can be a carbon source, is flown in, the base material is plasma-treated at a temperature of 500 to 1200 ° C., and then the gas phase synthesis method is used. A diamond coating treatment is performed to form a surface refining layer made of recrystallized tungsten carbide on the surface of the base material, and a coating film made of diamond and / or diamond-like carbon is formed adjacent to the surface refining layer. Is a method characterized by.

The mixed gas to be introduced into the reaction vessel in the method for producing a highly adherent diamond-coated sintered body of the present invention is 0.1 to 5 vol of oxygen gas in the case of mixed gas of hydrogen gas and oxygen gas.
%, The ratio of the remaining hydrogen gas is preferable, and in this case, a surface-refined layer composed of fine-grained recrystallized tungsten carbide is obtained. Further, when the mixed gas is a mixed gas of hydrogen gas, oxygen gas, and a gas that can be a supply source of carbon, the decarburization rate of the surface portion of the base material is moderated and coarse recrystallized tungsten carbide is formed. A surface refining layer is obtained. The mixed gas ratio at this time varies depending on the compositional components of the gas that can be the carbon supply source, but it is sufficient if the ratio of hydrogen and oxygen is the above mixed gas ratio of hydrogen gas and oxygen gas. Examples of the gas that can be a source include organic compounds containing carbon and hydrogen or carbon, hydrogen and oxygen, such as methane, ethane, propane, butane, methanol, ethanol, propanol, butanol, methyl ether, and ethyl ether. .

The plasma treatment in the method for producing a high-adhesion diamond-coated sintered body of the present invention can be performed by microwave, high frequency, etc. which have been conventionally performed, and the diamond coating treatment by the vapor phase synthesis method has also been conventionally performed. The method used can be applied as it is.

(Operation) In the high-adhesion diamond-coated sintered body of the present invention, Co is removed as cobalt carbonyl when a metal such as Co is present on the surface of the base material containing tungsten carbide as a main component. On the other hand, after tungsten carbide existing on the surface of the base material is decarburized into tungsten or tungsten carbonyl, it is then carburized at the initial stage of diamond film formation by vapor phase synthesis to recrystallize the surface of the base material. A surface refining layer made of tungsten carbide, which is formed by a continuous process on the surface of a surface refining layer made of tungsten carbide recrystallized from the tungsten carbide originally contained in the base material. Therefore, the surface conditioning layer has the function of enhancing the adhesiveness and adhesive strength of the coating. Further, the high-adhesion diamond-coated sintered body of the present invention, when a metal such as Co is present on the surface portion of the base material, the fine tungsten carbide of the surface refining layer is also present at the location where the metal is removed. Since it is embedded into a wedge shape, the adhesive strength at the boundary between the surface-refined layer and the inside of the substrate whose surface has not been refined is remarkably enhanced.

The method for producing a high-adhesion diamond-coated sintered body according to the present invention has an action of removing a metal such as Co existing in the surface portion of the substrate by the plasma treatment in a mixed gas containing oxygen gas, In the initial stage of the plasma treatment and the diamond coating treatment by the vapor phase synthesis method, the surface refining layer of recrystallized tungsten carbide is formed on the surface of the substrate. Furthermore, in the method for producing a highly adherent diamond-coated sintered body of the present invention, since the surface portion of the sintered body can be used as the surface-tempered layer and the film can be formed at the same time, the surface-tempered layer and the film are Impurities are unlikely to occur at the interface, and as a result, the action of promoting the nucleation of diamond is high, and it is easy to form a dense and fine film.

(Example) Example 1 After the surface of the base material of the WC-4wt% Co sintered body was polished or burnished, it was placed in a reaction vessel for performing a vapor phase synthesis treatment of diamond. Plasma treatment and diamond coating treatment (B) were performed to obtain the products 1 and 2 of the present invention.

Plasma composition of (A) Gas composition 98vol% H ₂ -2vol% O ₂ Gas pressure 92 Torr Substrate temperature 1040 ℃ Microwave power 0.8 kw Processing time 15 min Diamond coating gas composition 98vol% H ₂ − 2vol% CH ₄ gas pressure 90 Torr Base material temperature 1050 ℃ Microwave output 1.0 kw Treatment time 120 min For comparison, the same base material as above was used and after polishing the base material surface, it was applied to the base material surface by CVD method. 2μ of W ₂ C intermediate layer
m thickness comparison, then placed in a reaction vessel for performing a vapor phase synthesis treatment of diamond, and subjected to the diamond coating treatment of (B) above to form a diamond coating on the surface of the intermediate layer to obtain Comparative product 1. It was Also, among the comparative products 1, except that the WC intermediate layer was coated to a thickness of 2 μm on the substrate surface by the CVD method,
Comparative product 2 was obtained in the same manner as comparative product 1. Furthermore, the surface of the same base material was treated with an acid, and Co
After removing the above, the diamond was placed in a reaction vessel for performing a vapor phase synthesis treatment of diamond, and the diamond coating treatment of (B) was performed to obtain a comparative product 3.

The respective cross sections of the inventive products 1 and 2 and the comparative products 1, 2 and 3 thus obtained were examined by SEM, and the thicknesses of the surface conditioning layer, the intermediate layer and the coating film are shown in Table 1.

In addition to the present invention products 1 and 2 and comparative products 1, 2, and 3, a commercially available sintered body (JIS standard cemented carbide K10) is added as a comparative product 4, and the work material is hard carbon and the cutting speed is: 300m / min, feed: 0.1mm / tooth, depth of cut: 0.5mm, cutting time: 90
min, chip shape: A milling cutting test was performed under the conditions of SPP422, and the average flank wear (V _B ) amount at that time was calculated and listed in Table 1.

The products 1 and 2 of the present invention are different from the samples in Table 1 in the surface of the base material, the surface after the plasma treatment of the above (A) and the surface after the diamond coating after the diamond coating of the above (B). When examined by X-ray diffraction with a chip, the surface of the base material is the diffraction line of WC, the surface after (A) treatment is the diffraction line of W, and the surface after removing the coating after (A) and (B) treatment It was confirmed that was again the diffraction line of WC. Further, the boundary between the surface-conditioned layer of each of the products 1 and 2 of the present invention and the inside of the substrate not surface-conditioned was severely uneven, and the surface of the substrate was fine (0.1 μm) up to the point where Co escaped. It was possible to observe by SEM that the WC was closely embedded. On the other hand, in Comparative Products 1 and 2, the boundary portion between the base material and the intermediate layer was clearly distinguished linearly.

Example 2 Inventive products 1 and 2 and comparative products 1, 2, 3 obtained in Example 1
4 and a WC sintered body as a base material, and after polishing the surface of the base material, the plasma treatment of (A) in Example 1 and
The diamond coating treatment of (B) was performed to obtain the product 3 of the present invention. Further, among the products 3 of the present invention, the plasma treatment of (A) was omitted and the other processes were performed in the same manner to obtain a comparative product 5. Using these invention products 1, 2, 3 and comparative products 1, 2, 3, 4, 5, work material: Al: 30% SiC whisker alloy, cutting speed: 355 m / min, feed: 0.1 mm / rev, depth of cut: 0.5 m
m, Cutting time: 30 min Insert shape: SPGN120308 A continuous outer circumference turning test was performed, and the average flank wear (V
_The amount of _B ) was determined and is shown in Table 2.

The present invention product 3 and the comparative product 5 were also examined by X-ray diffraction and SEM in the same manner as the other samples in Example 1. As a result, the present invention product 3 was different from the WC grains inside the base material. about
It has a 0.1μm fine-grained surface refining layer, and the surface refining layer at the interface with the coating consists of a WC layer. It consisted of mixed W ₂ C layers. In Comparative Product 5, graphite was present at the boundary between the coating and the substrate.

(Effects of the Invention) The highly adherent diamond-coated sintered body of the present invention has a conventional WC intermediate layer or W ₂ C intermediate layer formed by a CVD method between a cemented carbide substrate and a diamond coating. Compared with the diamond-coated sintered body, the coating has excellent peeling resistance, and as a result, it has the effect of improving the life by 40% to 140% in the cutting test using hard carbon as the work material.
In a cutting test using l-Si alloy as a work material, approximately 25% ~
It has the effect of improving life by 130%. Further, the high-adhesion diamond-coated sintered body of the present invention is more resistant to peeling than the conventional diamond-coated sintered body formed by forming a diamond coating on the surface of a cemented carbide base material that has been etched with an acid. It has excellent properties, and as a result, in a cutting test using hard carbon or Al-Si alloy as a work material, the life is improved by about 27% to 110%.

Furthermore, the method for producing a high-adhesion diamond-coated sintered body of the present invention, the plasma treatment for superficializing the base material and the diamond coating treatment for forming a coating can be continuously performed in the same reaction vessel, Therefore, the effect of impurities is small, and it is possible to form a dense and highly adherent coating.

Claims (4)

[Claims] 1. A diamond-coated sintered body comprising, as a base material, a sintered body containing tungsten carbide as a main component, and a coating film of diamond and / or diamond-like carbon formed on the surface of the base material. A highly adherent diamond-coated sintered body, characterized in that at least 0.1 μm is a surface refining layer made of recrystallized tungsten carbide from the surface of the substrate adjacent to the inside of the substrate. 2. The above sintered body is Co and / or Ni 2-6 wt%
And the remaining tungsten carbide and unavoidable impurities, The highly adherent diamond-coated sintered body according to claim 1, characterized in that 3. The surface refining layer has a fine-grained tungsten carbide layer having a grain size of 0.3 μm or less, and the coating is formed adjacent to the fine-grained tungsten carbide layer. The highly adherent diamond-coated sintered body according to claim 1 or 2, which is characterized in that. 4. A base material of a sintered body containing tungsten carbide as a main component is placed in a reaction vessel, and a mixed gas of hydrogen gas and oxygen gas or carbon of hydrogen gas and oxygen gas is placed in the reaction vessel. After inflowing a mixed gas with a gas that can be a source of
Plasma treatment of the base material at a temperature of 500 to 1200 ° C., and then diamond coating treatment by a vapor phase synthesis method,
The surface portion of the base material is a surface refining layer made of recrystallized tungsten carbide, and diamond and / or diamond is provided adjacent to the surface refining layer.
Alternatively, a method for producing a high-adhesion diamond-coated sintered body, which comprises forming a coating film made of diamond-like carbon.