JP2620971B2 - Diamond coated sintered body with excellent adhesion and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an adhesion obtained by forming a film of diamond and / or diamond-like carbon on a surface of a ceramic sintered body containing tungsten carbide as a main component. More specifically, the present invention relates to a diamond-coated sintered body having excellent properties and a method for producing the same. The present invention relates to a diamond-coated sintered body having excellent adhesion suitable as a material for parts used in industry and the like, and a method for producing the same.

(Prior art) Conventionally, a diamond-coated sintered body formed by forming a diamond and / or diamond-like coating on the surface of a substrate made of a sintered body such as a metal, an alloy or a ceramic has been studied for practical use. Have been done. Since the diamond-coated sintered body has poor wettability with other substances, a diamond and / or diamond-like carbon coating is applied to the surface of the base material to improve the adhesion and adhesion. The biggest problem is whether it can be coated on the surface. In particular, turning tools, milling tools,
In the case of cutting tool materials such as drills and end mills, since they are used under the most severe conditions, adhesion and adhesion between the coating film and the substrate become more important.

A number of diamond-coated sintered bodies that can be used as a cutting process material by increasing the adhesion between the diamond coating and the base material have been proposed.
There are JP-A-62-57802, JP-A-62-166904, and JP-A-63-99102.

(Problems to be Solved by the Invention) Japanese Patent Application Laid-Open No. Sho 62-57802 discloses that a hard carbon-coated component of a hard carbon-coated component coated by depositing a hard carbon thin film on the surface of a substrate by a gas phase. W containing W ₂ C as the main component
And a hard carbon-coated component comprising an intermediate layer of a compound thin film of C and C having a thickness of 0.1 μm or more. The invention according to this publication discloses a compound thin film of W and C containing W ₂ C as a main component by a CVD method (chemical vapor deposition method) or a PVD method (physical vapor deposition method) on a surface of a substrate made of a hard metal or ceramics. When the intermediate layer is coated, a diffusion intermediate layer consisting of WC is formed at the interface between the hard carbon and W ₂ C, and as a result, the adhesion strength has been improved. After the layer is formed, the process of coating the hard carbon thin film in another reaction vessel is complicated, and the adhesion of the intermediate layer and the hard carbon thin film is difficult because impurities easily adhere to the surface of the intermediate layer. Is inferior.

Japanese Patent Application Laid-Open No. Sho 62-166904 discloses that a ceramic sintered body containing silicon nitride, silicon carbide, zirconium oxide, and aluminum oxide as a main component is used as a base material, and a hard carbon thin film is formed on its surface under reduced pressure by 0.5 to 50 μm. A cutting tool coated with a hard carbon film for processing a ceramic sintered body is disclosed. Although the invention of this publication uses ceramics having a high deformation resistance as a base material and forms a hard carbon thin film on the surface thereof, it is possible to cut fine ceramics which are difficult-to-cut materials, For example, the higher the content of diamond in the thin film of hard carbon, the more the adhesion between the substrate and the thin film deteriorates, and conversely, the lower the content of diamond, the lower the wear resistance. .

Japanese Patent Application Laid-Open No. 63-99102 discloses a coated tungsten tool in which tungsten is used as a base material and the base material is coated with diamond in an amount of 1 to 100 μm. The invention of this publication discloses that while a conventional diamond-coated tool in which a diamond thin film is formed on the surface of a cemented carbide or ceramic substrate has a problem in the adhesive strength between the thin film and the substrate, tungsten is used for the substrate. This solves the problem of adhesive strength, but the tungsten itself is soft and easily deformed plastically, and has a short life even when used as a cutting tool.

The present invention has solved the above-mentioned problems, and specifically, has excellent peeling resistance between the substrate and the diamond and / or diamond-like carbon coating, and can be practically used as a cutting tool material. It is an object of the present invention to provide a simple diamond-coated sintered body and a method for producing the same.

(Means for Solving the Problems) When the present inventors coat a substrate with a diamond film formed by a vapor phase synthesis method, the present inventors consider the type of the substrate, the thickness of the film, and the film formation conditions. When the diamond coating was formed on the surface of the base material of the sintered body made of tungsten carbide, a cemented carbide containing Fe group metal or Unlike the cermet substrate, the precipitation of graphite in the early stage of the diamond vapor phase synthesis method is suppressed, and the decarburization treatment is performed before forming the diamond film in the diamond vapor phase synthesis method, and then the formation of the diamond film is performed. By doing so, it has been found that the adhesion between the tungsten carbide substrate and the coating film is further enhanced, and the tungsten carbide substrate can be practically used as a cutting tool material. Based on this finding, the present invention has been completed.

That is, the diamond-coated sintered body having excellent adhesion of the present invention comprises a hard phase of tungsten carbide or 50 vol% or more of tungsten carbide, and the balance is carbides or carbonitrides of metals of groups 4a, 5a and 6a of the periodic table. And forming a film of diamond and / or diamond-like carbon on the surface of a base material of a sintered body comprising a hard phase comprising at least one of these mutual solid solutions and 0.5 vol% or less of unavoidable impurities. It is a feature.

The hard phase in the diamond-coated sintered body of the present invention is composed of only tungsten carbide, or contains at least 50 vol% of tungsten carbide in the hard phase, and further includes a carbide of a metal of Group 4a, 5a, or 6a in the periodic table, This is the case where at least one of carbonitride and these mutual solid solutions is contained. Among them, particularly when the hard phase is made of tungsten carbide of 90 vol% or more, for example, when it is made only of tungsten carbide made of WC or WC-W ₂ C, or made of 90 vol% or more of these tungsten carbides and remaining molybdenum carbide _{WC-Mo 2 C, WC-} W 2 C-Mo 2 C or WC- (W, MC)
The case of C is preferable because the adhesion between the coating and the substrate is excellent and the strength of the substrate is also excellent. In addition, when the hard phase is a mixture of WC and W ₂ C, in other words, in the case of a sintered body base material composed of WC, W ₂ C and unavoidable impurities, the removal as described below is performed. Even without a pretreatment in a carbonaceous atmosphere, W ₂ C present on the surface of the substrate absorbs the carbon generated during diamond synthesis, resulting in improved adhesion between the coating and the substrate. This is preferred because it promotes nucleation and forms a self-defined coating.

The substrate in the diamond-coated sintered body of the present invention contains unavoidable impurities in addition to the above-described hard phase, and the unavoidable impurities are mainly impurities contained in the starting material and mixed and pulverized starting material. There is an impurity mixed in during the process, and the latter inevitable impurity is mixed from a mixing container or a ball. For example, Co, Ni, Fe,
W, Cr, Mo, etc., and these unavoidable impurities
Even if it is contained in an amount of 0.5 vol or less, it can be practically used because there is little decrease in the adhesion between the substrate and the coating, and there is also an effect of supplementing the strength of the substrate. In these substrates, the particle size of tungsten carbide present in the surface layer of at most 10 μm from the surface of the substrate toward the inside is smaller than that of the surface layer. It is particularly preferable that the composition is finer than the particle size, because the adhesion between the base material and the coating is improved and the quality of the coating is improved.

In particular, the particle size of tungsten carbide in the surface layer is 1.0 μm
Below, preferably 0.5 μm or less is preferable because the adhesion between the substrate and the coating tends to be further improved.

The film in the diamond-coated sintered body of the present invention exhibits properties such as electrical resistance, light transmittance, hardness and the like of diamond or properties similar to diamond. It shows a peak at 1333 cm ^-1 which is said to be. More specifically, this coating is made of only diamond, or contains diamond and other amorphous carbon or glassy carbon, or has been close to diamond conventionally without containing diamond. It may be made of diamond-like carbon which is said to exhibit properties. In particular, in the case of a film formed on a substrate having the above-described surface layer, it is said to be a Raman line of diamond in Raman spectroscopic analysis.
The film at 1333cm ^-1 clearly shows excellent film quality. The thickness of the coating varies depending on the application and the shape. In particular, for applications in which crevice wear resistance is more important than impact resistance, a thickness of, for example, 3 to 10 μm is preferable. It is preferable that the thickness is 0.5 to 7 μm. Among the cutting process materials, applications such as cutting tools for milling, which emphasize impact resistance, and drills and end mills,
Alternatively, for applications having sharp cutting edges such as slitters, cutting blades, cutting blades, etc. in abrasion-resistant process materials,
It is preferable that the thickness is 0.5 to 3 μm and the thickness of the coating is thin.

The diamond-coated sintered body of the present invention is characterized in that a starting material for forming a hard phase mainly composed of tungsten carbide is formed into a sintered body by a conventional powder metallurgy method, and the starting material is formed on a surface of a base material of the sintered body. Although it can be obtained by forming a diamond film by vapor phase synthesis in conventional microwave plasma, high frequency plasma or plasma by thermal filament, the adhesion between the substrate and the film is improved by the following method. This is preferable because it is excellent.

In other words, the method of the present invention for producing a diamond-coated sintered body having excellent adhesion is that the hard phase of tungsten carbide or tungsten carbide is at least 50 vol% and the balance is
a hard phase comprising at least one of carbides, carbonitrides and mutual solid solutions of a, 5a, 6a group metals and 0.5 vol%
A base material of a sintered body comprising the following unavoidable impurities is placed in a reaction vessel, and the inside of the reaction vessel is heated in a decarburizing atmosphere to decarburize the surface layer of the base material. A film of diamond and / or diamond-like carbon is formed on the surface of the surface layer of the material by a vapor phase synthesis method, and the surface layer of the base material is again made of a carbide layer containing tungsten carbide as a main component. It is a method.

In the method for producing a diamond-coated sintered body of the present invention, the base material is a starting material of tungsten carbide or 50 vol% or more of tungsten carbide, and the remainder is periodic table 4a, 5a, 6a.
After mixing and pulverizing a starting material composed of a group III metal carbide, carbonitride and at least one of these mutual solid solutions, hot press sintering or ordinary sintering, hot isostatic pressure treatment (HI
By performing the P treatment, a dense sintered body can be obtained. The substrate thus obtained is placed in a reaction vessel for the vapor phase synthesis of diamond, and the inside of the reaction vessel is heated in a decarburizing atmosphere to remove a surface layer from the surface of the substrate to at most 10 μm inside. After carbonization, a diamond coating process by a vapor phase synthesis method is performed to convert the once decarburized surface layer into a layer of recrystallized tungsten carbide or a carbide containing tungsten carbide as a main component, and on this surface layer. This is a method for forming a film of diamond and / or diamond-like carbon.

Thus, after decarburizing the surface layer of the substrate, the recrystallized tungsten carbide formed again as a carbide can have a finer particle size than the tungsten carbide inside the substrate than the surface layer.

When the inside of the reaction vessel in the method for producing a diamond-coated sintered body of the present invention is set to a decarburizing atmosphere, it can be carried out by a method using various gas atmospheres. In order to perform the mixing, it is preferable that the atmosphere be a mixed gas of hydrogen gas and oxygen gas, or a mixed gas of hydrogen gas, oxygen gas, and a gas that can be a supply source of carbon. In the case of gas, it is necessary to be careful because explosion occurs depending on the mixing ratio, and especially when the gas is a decarburizing atmosphere consisting of 0.1 to 5 vol% of oxygen gas and the remaining hydrogen gas, the stability is high. This is preferable because it is a surface layer made of fine-grained carbides and has excellent peeling resistance between the surface layer and the coating. The gas that can be a source of carbon here is, for example, methane, ethane, propane,
Organic compounds containing carbon and hydrogen or carbon, hydrogen and oxygen, such as butane, methanol, ethanol, propanol, butanol, methyl ether and ethyl ether, can be mentioned. When the temperature is raised in this decarburizing atmosphere, it is preferable to perform the plasma treatment at a substrate temperature of 500 to 1200 ° C. The plasma treatment at this time can be performed by a conventional microwave, high frequency or thermal filament method, and the diamond coating treatment by the conventional gas phase synthesis method is continuously performed in the same reaction vessel in the plasma treatment state. This is preferable because impurities hardly adhere between the surface layer and the coating.

(Function) In the diamond-coated sintered body having excellent adhesion of the present invention, tungsten carbide in the base material has an effect of increasing the adhesion with the coating film, and is particularly formed on the surface layer of the base material. The recrystallized fine tungsten carbide enhances the adhesion to the coating and improves the quality of the coating, thereby increasing the wear resistance and peeling resistance of the coating.

The method for producing a diamond-coated sintered body having excellent adhesion according to the present invention includes a carbide recrystallized in fine grains by a treatment step in a decarburizing atmosphere and an initial step in a diamond coating treatment by a gas phase synthesis method. In particular, a surface layer made of tungsten carbide is formed, and the decarburizing atmosphere during the plasma treatment and the diamond coating during the plasma treatment can be continuously performed in the same reaction vessel. Impurities are less likely to be generated at the interface between the surface layer and the coating, and furthermore, the promotion of diamond nucleation is enhanced, and the formation of a dense and fine-grain coating is facilitated.

(Example) Example 1 WC and Mo ₂ C having an average particle diameter of 3.0 μm are mixed with a ball made of cemented carbide in a wet ball mill, pulverized and dried, and then hot-pressed and sintered in a vacuum to mainly contain WC. A substrate of a sintered body was obtained. After making the surface state of this base material a burnt surface or a ground surface as shown in Table 1, it was subjected to decarburization treatment under the following decarburizing atmosphere conditions (A), and subsequently in the same reaction vessel, A diamond coating was formed on the surface of the substrate under the diamond coating treatment conditions of (B) to obtain the products 1, 2, and 4 of the present invention.
The decarburization treatment under the following condition (A) was omitted, and a diamond coating was formed on the surface of the base material under the following condition (B) to obtain a product 3 of the present invention.

(A) Decarburizing atmosphere conditions Gas composition 99vol% H ₂ -1vol% O ₂ Gas pressure 60Torr Base material temperature 630 ° C Microwave output 0.7kw Processing time 30min (B) Diamond coating processing conditions Gas composition 98vol% H ₂ -2vol % CH ₄ gas pressure 80 Torr Substrate temperature 1060 ° C. Microwave output 1.0 kw Processing time 120 min As a comparative product, the surface of a commercially available silicon nitride-based ceramic substrate was subjected to the above treatment (B) to obtain Comparative Product 1. .
In addition, a commercially available cemented carbide base material is installed in another reaction vessel,
After performing CVD treatment in a WF ₆ -CH ₄ -H ₂ mixed atmosphere to coat the surface of the base material with W ₂ C at about 1.5 μm, the treatment (B) was performed to obtain a comparative product 2. Further, a commercially available W plate was used as a base material, and the base material was subjected to the treatment of the above (B) to obtain a comparative product 3.

Table 1 shows the thicknesses of the diamond coatings of the inventive products 1, 2, 3, 4 and the comparative products 1, 2, 3 thus obtained. Also,
The surface layers of the samples of the present invention 1, 2, and 4 subjected to the treatment (A) were examined by X-ray diffraction and SEM, and the results are shown in Table 1.

Using these inventive products 1,2,3,4 and comparative products 1,2,3,
Cutting tests were performed under the following conditions (C) and (D), and the average flank wear and damage at that time were observed. The results are shown in Table 2.

(C) Turning test conditions Workpiece material Al-18% Si alloy Tip shape SPGN 120308 Cutting speed 226m / min Feeding 0.1mm / rev Depth of cut 0.5mm Cutting time 20min Evaluation Average flank wear (V _B mm) (D ) Turning test conditions Work material Hard carbon Tip shape SNCN 43ZFN Cutting speed 356m / min Feed 0.06mm / rev Cutting depth 0.5mm Cutting time 60min (Effects of the Invention) From the above results, the diamond-coated sintered body of the present invention having excellent adhesion was found to be a silicon nitride-based ceramic substrate, W ₂ C
The adhesion between the coating and the substrate is lower than that of a conventional diamond-coated sintered body in which a diamond coating is formed on each surface of a cemented carbide substrate having a coating layer or a W substrate. It is excellent and when used as a cutting tool material,
The coating has remarkably excellent peeling resistance, and as a result, has an effect of being excellent in abrasion resistance and fracture resistance, and has an effect of being about 20% to 8 times in life.

In the method for producing a diamond-coated sintered body having excellent adhesion according to the present invention, the surface of the base material can be a fine-grain surface layer containing tungsten carbide as a main component. There is an effect that the adhesion can be further improved.

 ──────────────────────────────────────────────────続 き Continued on the front page Judge Tokio Nakayama Judge Yoshiaki Moritake Judge Yoshihisa Chief Judge (56) References JP-A-63-100182 (JP, A) JP-A-63-53269 (JP, A) 62-67174 (JP, A) JP-B 55-29152 (JP, B2)

Claims (6)

(57) [Claims] 1. A hard phase of tungsten carbide or 50 vol% or more of tungsten carbide, and the balance is at least one of carbides, carbonitrides, and mutual solid solutions of metals of Group 4a, 5a, 6a of the periodic table. Excellent in adhesiveness, characterized in that a diamond and / or diamond-like carbon film is formed on the surface of a sintered body base material comprising a hard phase comprising: and a unavoidable impurity of 0.5 vol% or less. Coated sintered body. 2. The diamond-coated sintered body having excellent adhesion according to claim 1, wherein said hard phase is 90 vol% or more of tungsten carbide. 3. The substrate according to claim 1, wherein the particle size of tungsten carbide in a surface layer of at most 10 μm from the surface of the substrate toward the inside is an average particle size of tungsten carbide present inside the surface layer excluding the surface layer. The diamond-coated sintered body having excellent adhesion according to claim 1 or 2, characterized in that the sintered body is finer than that of (1). 4. A diamond-coated sintered body having excellent adhesion according to claim 1, wherein said coating has a thickness of 0.5 to 10 μm. 5. A hard phase of tungsten carbide or 50 vol% or more of tungsten carbide, the balance being at least one of carbides, carbonitrides and mutual solid solutions of metals of groups 4a, 5a and 6a of the periodic table. A base material of a sintered body comprising a hard phase consisting of and a unavoidable impurity of 0.5 vol% or less is placed in a reaction vessel, and the inside of the reaction vessel is heated in a decarburizing atmosphere to raise the surface of the base material. After decarburizing the layer, a film of diamond and / or diamond-like carbon is formed on the surface of the surface layer of the substrate by a vapor phase synthesis method, and the surface layer of the substrate is mainly made of tungsten carbide. A method for producing a diamond-coated sintered body having excellent adhesion, characterized by forming a layer. 6. The decarburizing atmosphere comprises a mixed gas of hydrogen gas and oxygen gas, or a mixed gas of hydrogen gas, oxygen gas and a gas that can be a supply source of carbon. 6. The method for producing a diamond-coated sintered body having excellent adhesion according to claim 5.