JP2779531B2 - Diamond coated tungsten carbide based sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method for forming a diamond and / or diamond-like carbon on the surface of a base material of a ceramic sintered body containing tungsten carbide mixed with W ₂ C and WC as a main component. A diamond-coated sintered body having excellent adhesion by forming a film, specifically, for example, a cutting tool material, a wear-resistant tool material, a decoration material, etc., mainly in the electric industry, the electronics industry, and the precision equipment industry. The present invention relates to a diamond-coated tungsten carbide-based sintered body having excellent adhesion suitable as a material for parts used in the office equipment industry and the like.

(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, cutting 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.

Many diamond-coated sintered bodies that can be used as a cutting tool material by increasing the adhesion between the diamond coating and the substrate have been proposed, and as typical examples thereof,
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. 62-57802 discloses a hard carbon-coated part in which a hard carbon thin film is deposited on the surface of a base material by a gas phase and coated. A hard carbon-coated component is disclosed in which an intermediate layer of a compound thin film of W and C containing W ₂ C as a main component is present at 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 diamond-coated tungsten carbide-based sintered body.

(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 cermet base material, graphite precipitation is suppressed in the early stage of diamond gas phase synthesis, especially base material sintering consisting of hard phase of tungsten carbide mixed with W ₂ C and WC and unavoidable impurities In the case of a body, the effect of suppressing the precipitation of graphite is also increased, the nucleation density of diamond is promoted,
It has been found that the adhesion between the substrate and the diamond coating is further enhanced, and that the substrate itself has strength enough to withstand the severe conditions as a cutting tool. Based on this finding, the present invention has been completed.

That is, the diamond-coated tungsten carbide-based sintered body of the present invention has a diamond-coated tungsten carbide-based sintered body composed of a mixture of W ₂ C and WC. And / or a diamond-like carbon film is formed.

The hard phase in the diamond-coated tungsten carbide-based sintered body of the present invention is composed of only tungsten carbide in which W ₂ C and WC are mixed, or at least 50 vol% of tungsten carbide is contained in the hard phase. Periodic table 4a,
This is a case in which at least one of carbides, carbonitrides, carbonates, and nitrides of a Group 5a or 6a metal and their mutual solid solution is contained. For example, specifically, when the hard phase is WC-W ₂
C- (W, Ti) C, WC-W 2 C- (W, Ta) C, WC-W 2 C- (W, Mo)
C, WC-W ₂ C-TaC and the like can be cited.
Of these, the case where the hard phase is made of tungsten carbide of 90 vol% or more is preferable.
When wt% of W ₂ C and the remaining WC are used, the effect of suppressing the precipitation of graphite in the initial stage of the vapor phase synthesis of diamond is increased, the nucleation density of diamond is promoted, and the base material is increased. This is particularly preferable because the adhesion between the diamond coating and the diamond coating is further enhanced.

The base material in the diamond-coated tungsten carbide-based 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 starting materials. There is an impurity that is mixed during the mixing and crushing process, and the latter inevitable impurity is mixed from a mixing container or a ball,
For example, there are Co, Ni, Fe, W, Cr, Mo, etc., and even when these unavoidable impurities are contained in the base material at 0.5 vol% or less, the decrease in adhesion between the base material and the coating is small, and on the contrary, It is practical because it has the effect of supplementing the strength of the substrate. These substrates absorb graphite in the surface layer of the substrate in the initial stage of the diamond vapor phase synthesis, and as a result, the tungsten carbide present in the surface layer of the substrate may be WC. When the tungsten carbide present in the surface layer of the base material is WC, the depth of the base material surface layer mainly fluctuates depending on the conditions of the vapor phase synthesis of diamond, and the depth from the surface of the base material to at most 20 μm inward. It is particularly preferable that the tungsten carbide in the surface layer is made of WC.

The film of the diamond-coated tungsten carbide-based sintered body of the present invention exhibits properties such as electrical resistance, light transmittance, hardness and the like of diamond or properties close to that of diamond. It shows a peak at 1333 cm ^-1 which is said to be a Raman line of the. 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-mentioned surface layer, a film having excellent film quality clearly showing a peak at 1333 cm ^-1 which is said to be a Raman line of diamond in Raman spectroscopic analysis become. 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, for example, 3 to 10 μm
m thickness is preferred, and for applications as cutting tool material, 0.
A thickness of 5 to 7 μm is preferred. Among cutting tool materials, applications such as cutting tools for milling, in which impact resistance is important, and drills and end mills, or slitters, cutting blades, cutting blades, etc. in wear-resistant tool materials For applications having such a sharp cutting edge, for example, it is preferable that the thickness be 0.5 to 3 μm and the coating be thin.

In order to produce the diamond-coated tungsten carbide-based sintered body of the present invention, first, the starting material for producing the base material may be a sintered body by a conventional powder metallurgy method, specifically, For example, when the hard phase consists only of tungsten carbide, firstly, when using tungsten and carbon, secondly, when using WC and W ₂ C, or thirdly, when using WC and W Among them, when the reaction sintering is performed using the starting material of the third combination, a dense sintered body is easily obtained, which is particularly preferable. A dense sintered body can be obtained by subjecting these starting materials to mixing and pulverization, hot press sintering, or ordinary sintering followed by hot isostatic pressure treatment (HIP treatment).
The diamond coating of the present invention is formed by forming a diamond film on the surface of the base material of the sintered body thus obtained in a conventional microwave plasma, high-frequency plasma or plasma using a hot filament or the like. A tungsten carbide-based sintered body can be obtained.

(Action) The diamond-coated tungsten carbide-based sintered body of the present invention has a structure in which the hard phase constituting the base material, particularly W ₂ C in the hard phase on the surface of the base material, Absorbs graphite, and as a result acts to suppress the deposition of graphite at the interface between the coating and the substrate,
WC and W ₂ C existing on the surface of the base material or the surface layer of the base material formed by converting W ₂ C to WC promotes the nucleation density of diamond, and the adhesion between the base material and the coating It acts to enhance

Example A WC powder having an average particle diameter of 4.0 μm and a W powder having an average particle diameter of 0.5 μm were blended in a predetermined amount, and the blended powder, a cemented carbide ball and acetone were placed in a mixing vessel and wet-mixed for 30 hours. Thereafter, the mixture was dried, and the obtained mixed powder was vacuum-sintered by hot pressing to obtain a sintered body for use in the present invention products 1 to 5 shown in Table 1. Also, a predetermined amount was blended using WC powder having an average particle size of 4.0 μm and W ₂ C powder having an average particle size of 1.5 μm, and used in the same manner as described above for the present invention products 6 and 7 shown in Table 1. A sintered body was obtained. These sintered bodies were placed in a reaction vessel for diamond vapor phase synthesis, and subjected to a diamond coating treatment under the following condition (A) to obtain products 1 to 7 of the present invention.

(A) Diamond coating treatment conditions Gas composition 97 vol% H ₂ -3 vol% CH ₄ gas pressure 50 Torr Gas flow rate 200 ml / min Substrate temperature 960 ° C Processing time 7 hours Next, as a comparison, a commercially available silicon nitride ceramic sintered body And a commercially available W plate, and treated under the above-mentioned condition (A) in the same manner as the products 1 to 7 of the present invention to obtain diamond-coated sintered bodies of comparative products 1 and 2 shown in Table 1. In addition, a base material of a commercially available cemented carbide (WC-4wt% Co composition) is placed in another reaction vessel, and treated by a chemical vapor deposition method in a WF ₆ -CH ₄ -H ₂ mixed atmosphere. After coating the surface of W ₂ C with about 1.5 μm,
By processing under the above condition (A), a comparative product 3 shown in Table 1 was obtained.

The products 1 to 7 of the present invention and the comparative products 1 to 3 thus obtained were examined by X-ray diffraction, a metallographic microscope and a scanning electron microscope, and the results are shown in Table 1.

Next, using the products 1 to 7 of the present invention and the comparative products 1 to 3,
A cutting test was performed under the following conditions (B), and the average flank wear (V _B ) and damage at that time were observed. The results are also shown in Table 1.

(However, the comparative product 2 was subjected to a cutting test by brazing to a cemented carbide.) (B) Cutting test conditions Work material Al-20% Si alloy Tip shape SPGN 120308 Cutting speed 200m / min Feed 0.1mm / rev Cutting depth 0.5mm Cutting time 20min (Effects of the Invention) From the above results, the diamond-coated tungsten carbide-based sintered body of the present invention is a superhard material having a silicon nitride-based ceramic sintered body base, a W plate base, or a W ₂ C coating layer. Compared to conventional diamond-coated sintered bodies, in which a diamond coating is formed on each surface of the alloy base material, the adhesion between the coating and the base material is better, and when used as a cutting tool material, Tends to have significantly better peel resistance,
As a result, there is an effect that the wear resistance and the fracture resistance are excellent, and there is a remarkable effect that the life is improved by about 2 to 6 times.

────────────────────────────────────────────────── ─── Continued on the front page Examiner Koji Amamiya (56) References JP-A-63-100182 (JP, A) JP-A-63-53269 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) C04B 41/80-41/91

Claims (3)

(57) [Claims] A diamond and / or diamond-like carbon film is coated on the surface of a base material of a sintered body comprising a hard phase mainly composed of tungsten carbide in which W ₂ C and WC are mixed and an unavoidable impurity. A diamond-coated tungsten carbide-based sintered body characterized by being formed. 2. The method according to claim 1, wherein said tungsten carbide is 3 to 75 wt% W _2.
2. The diamond-coated tungsten carbide-based sintered body according to claim 1, comprising C and the remaining WC. 3. The substrate according to claim 1, wherein the tungsten carbide in the surface layer of up to at most 20 μm from the surface of the substrate to the inside is WC. The diamond-coated tungsten carbide-based sintered body according to the above.