JPH03146663A - Production of diamond-coated sintered hard alloy member - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of a coating layer by providing ruggedness to the surface of a base material composed of WC-base sintered hard alloy by means of electrolytic etching and then coating the above surface with diamond by a vapor phase synthetic method. CONSTITUTION:A base material composed of WC-base sintered hard alloy is used as an anode and electrolytic etching is performed by a wet process, by which ruggedness is formed on the surface of the WC layer of the base material. Subsequently, the above surface is coated with diamond by a vapor phase synthesis method. By this method, a diamond-coated sintered bard alloy member in which diamond nucleation density is increased and adhesion area is enlarged and, further, superior adhesive strength is provided owing to anchor effect can be obtained. This member is useful for tools, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a diamond-coated tungsten carbide-based cemented carbide member having excellent adhesion between a tungsten carbide-based cemented carbide substrate and a diamond coating layer.

[Prior Art] Since the development of a diamond synthesis method by vapor phase synthesis in recent years, the development of diamond-coated cemented carbide tools, etc., in which the surface of a cemented carbide base is coated with diamond, has been actively pursued. However, in this case, an important issue is to improve the adhesion between the cemented carbide substrate and the diamond coating layer, but the current situation is that a sufficiently satisfactory adhesion has not yet been achieved. As a method for improving the adhesion to the substrate, methods such as those disclosed in Japanese Patent Application Laid-Open No. 63-14869 and Japanese Patent Application Laid-Open No. 1-201475 have been proposed. The method described in JP-A-63-14869 is a method in which the surface of a cemented carbide substrate is ground with a diamond grindstone to preferentially grind the cobalt phase on the surface of the cemented carbide to make it more concave than the tungsten carbide phase. be. This method can promote diamond nucleation and improve adhesion. However, grinding with a diamond grindstone requires time and effort because cemented carbide has extremely poor grindability.

In particular, it is extremely difficult to grind cemented carbide substrates such as cutting tools that have a three-dimensionally complex shape, and it is extremely difficult to create uniform fine scratches on the surface of the cemented carbide substrate. . Furthermore, the method described in JP-A-1-201475 selectively etches and removes the cobalt phase on the surface of the cemented carbide substrate using acid, thereby selectively removing the cobalt phase in which diamond crystal nuclei are difficult to form. This is a method of creating irregularities on the surface of a hard metal substrate. This method increases the diamond nucleation density and adhesion surface area, making it possible to improve adhesion. However, with the acid treatment method, although the cobalt phase can be etched away, it is difficult to etch the surface of the tungsten carbide phase to form fine irregularities, and strong adhesion cannot be obtained. In addition, if you try to scratch the surface of the tungsten carbide phase by etching for a long time, the cobalt phase will be removed by etching more than necessary, resulting in a lack of binder phase near the surface of the cemented carbide base, which will reduce the bonding strength of the tungsten carbide phase and cause it to become carbonized. The falling acid from the tungsten particles poses problems such as a decrease in the strength of the cemented carbide base itself.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to economically produce a diamond-coated tungsten carbide-based cemented carbide member having practical adhesive strength. The purpose is to provide a method.

[Means for solving the problem] Generally, on the surface of a tungsten carbide-based cemented carbide substrate, the area occupation rate of the tungsten carbide phase is higher than that of the binder phase.
Therefore, we obtained the knowledge that improving the adhesion force on the surface of the tungsten carbide phase greatly contributes to improving the adhesion force between the diamond coating layer and the cemented carbide substrate, and we are conducting further research to achieve the above objective. However, when wet electrolytic etching is performed using a tungsten carbide-based cemented carbide substrate as an anode, the surface of the tungsten carbide phase is etched, forming fine irregularities, promoting diamond nucleation, increasing the bonding area, and forming an anchor. The present invention was made based on the knowledge that the adhesion force can be greatly improved by this effect.

At this time, cobalt, nickel, etc., which are the binder phases, are not etched (therefore, the tungsten carbide phase does not fall off and the strength of the cemented carbide itself does not decrease).

Examples of solutions used in electrolytic etching include sodium hydroxide, sodium hydroxide, and sodium chloride.
A method of electrolytic etching in an aqueous solution of sodium hydroxide and sodium phosphate, potassium hydroxide and potassium ferricyanide, etc. using a cemented carbide substrate as an anode and stainless steel or graphite as a cathode at a current density of Q, 1 to 10 A/dm2, etc. can be mentioned.

Prior to this electrolytic etching treatment, the surface of the cemented carbide substrate may be degreased with an organic solvent such as acetone or trichlene, or cathodic degreasing may be performed in an aqueous alkali or acid solution using the cemented carbide substrate as a cathode.

In the present invention, any known method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD) can be applied as a diamond vapor phase synthesis method.

[Operation] When wet electrolytic etching is performed using a tungsten carbide-based cemented carbide substrate as an anode, it is possible to form irregularities on the surface of the tungsten carbide phase that occupies most of the surface of the cemented carbide substrate, thereby reducing the diamond nucleation density. It is possible to obtain a diamond-coated tungsten carbide-based cemented carbide which has an increased adhesion area and excellent adhesion due to the anchor effect. Moreover, since the binder phase is not etched at this time, the tungsten carbide phase does not fall off and the strength of the cemented carbide itself does not decrease. Furthermore, since the irregularities are formed by wet electrolytic etching using the substrate as an anode, a large amount of cemented carbide substrates can be processed economically.

[Example] The present invention will be explained below using examples.

Example 1 First, cobalt or nickel powder was blended with tungsten carbide particles having a particle size of 1 to 2 μm and an average particle size of 1.5 μm so that the cobalt content was 4 and 7% by weight and the nickel content was 7% by weight. After that, it is sintered to a shape of 25mm
Three types of tungsten carbide-based cemented carbide substrates measuring 8 mm x 4 mm were prepared.

After polishing the surface of 25 mm x 8 mm, lapping was performed using diamond paste with a particle size of 1 μm.

Subsequently, the surface of the cemented carbide substrate was treated according to the following procedure.

(1) Wash in acetone.

(2) In an aqueous solution consisting of 2% by weight of sodium hydroxide and 2% by weight of sodium phosphate, the cemented carbide substrate was used as a cathode and a 5US304 plate was used as an anode, at 70°C for 10 seconds at a current density of 3 A'/dm2. Cathode degreasing.

(3) In an aqueous solution consisting of 2% by weight of sodium hydroxide and 2% by weight of sodium phosphate, the cemented carbide substrate was used as an anode and a SUS 304 plate was used as a cathode at 70°C for 10 seconds at a current density of 3A/d m2. Electrolytic etching.

(4) Washing with water.

When the cemented carbide substrate treated as described above was observed using a scanning electron microscope (JSM-840A manufactured by JEOL Ltd.), the cobalt phase was more concave than the tungsten carbide phase, and the tungsten carbide phase was not easily etched on the surface due to chemical etching. Fine irregularities were formed on the surface. Thereafter, a diamond coating layer was formed on the surface of these cemented carbide substrates by microwave plasma CVD.

Microwave plasma CVD conditions include microwave (2.45 GHz) power of 900 W, hydrogen gas supply amount of 99.
0SCCM, methane gas supply amount 53CCM.

After CVD treatment was performed for 2 hours at a reaction pressure of 40 TORR and a substrate temperature of 750° C., the methane gas supply amount was changed to 1103 CC and CVD treatment was performed for an additional 4 hours.

As a result, a diamond coating layer with a thickness of 4 μm consisting of cubic diamond with a clear crystal shape was formed on the surface of all the cemented carbide substrates.

The adhesion strength between the cemented carbide base and the diamond coating layer of the diamond-coated cemented carbide member thus obtained is as follows:
Evaluation was performed using a scratch test method and a tape peel test method. In the scratch test method, a load is applied to an indenter made of diamond with a radius of 0.2 mm at the tip, and the surface of the diamond-coated cemented carbide member is scratched.The adhesion force is evaluated using the load at which the diamond coating layer peels off as the critical strength. The tape peeling test method uses cellophane tape (manufactured by Chiban ■) to attach the tape to the surface of the diamond-coated cemented carbide member, and when the tape is peeled off, the adhesion strength is measured as the percentage of the area of the diamond coating layer that is peeled off. We conducted an evaluation.

As a result, in the scratch test, a coated member with diamond coating on the surface of a cemented carbide base with a cobalt content of 4% by weight weighed 3.0 kg, a coated member with a cobalt content of 7% by weight weighed 3.5 kg, and a coated member with a nickel content of 7% by weight. The 7% by weight coated member had a strength of 3.0 kg. In the tape peeling test, all the cemented carbide members were 0%, with no peeling at all, and extremely high adhesion was obtained.

Comparative Example 1 A tungsten carbide-based cemented carbide substrate sintered in the same manner as the tungsten carbide-based cemented carbide substrate used in Example 1 was prepared and lapped using a diamond paste with a particle size of 1 μm. After cleaning these cemented carbide substrates in acetone, a diamond coating layer having a thickness of 4 μm was formed on the surface by the microwave plasma CVD method in the same manner as in Example 1.

As a result of evaluating the adhesion between the cemented carbide substrate and the diamond coating layer, it was found that in the coated member with a cobalt content of 4% by weight, the diamond coating layer was peeled off when taken out from the chamber. A coated member with a cobalt content of 7% by weight weighed 0.1 kg in the scratch test and 1 kg in the tape peel test.
00% peeled off.

A coated member with a nickel content of 7% by weight was peeled off by 0.1 kg in the scratch test and 100% in the tape peel test.

Comparative Example 2 A tungsten carbide-based cemented carbide substrate sintered in the same manner as the tungsten carbide-based cemented carbide substrate used in Example 1 was prepared, and lapped with diamond paste having a particle size of 1 μm. The surfaces of these cemented carbide substrates were etched by immersing them in aqua regia for 30 minutes, washed with water, and then dried.

When the surface and cross-section of these cemented carbide substrates were observed using a scanning electron microscope, the surface of the hard dispersed tungsten carbide phase was found to have slight scratches, but the cobalt or nickel bonding phase was found to be slightly uneven. The phase was etched to a depth of 30 to 40 μm from the surface of the cemented carbide substrate, and the tungsten carbide phase had fallen off at the corners of the substrate.

A diamond coating layer having a thickness of 4 μm was formed on the surface of these cemented carbide substrates by the microwave plasma CVD method in the same manner as in Example 1.

As a result of evaluating the adhesion between the cemented carbide substrate and the diamond coating layer, the coated member with a cobalt content of 4% by weight showed 1.0 kg in the scratch test and 80% peeling in the tape peeling test.

A coated member with a cobalt content of 7% by weight was peeled off by 0.5 kg in a scratch test and by 90% in a tape peel test. A coated member with a nickel content of 7% by weight was peeled off by 0.5 kg in a scratch test and 100% in a tape peel test.

Comparative Example 3 A tungsten carbide-based cemented carbide substrate sintered in the same manner as the tungsten carbide-based cemented carbide substrate used in Example 1 was prepared and lapped using a diamond paste with a particle size of 1 μm. After grinding these cemented carbide substrates using a diamond grindstone with a grain size of 200 mesh, Example 1
A diamond coating layer having a thickness of 4 μm was formed by the microwave plasma CVD method in the same manner as above.

As a result of evaluating the adhesion between the cemented carbide substrate and the diamond coating layer, the coated member with a cobalt content of 4% by weight showed 0.5 kg in the scratch test and 100% peeling in the tape peel test. In a scratch test, a coated member with a cobalt content of 7% by weight was 1. Okg
In the tape peel test, 90% peeling was achieved. Further, in the case of a coated member having a nickel content of 7% by weight, the scratch test showed 1.0 kg, and the tape peeling test showed 80% peeling.

From the above examples and comparative examples, it is possible to improve the adhesion between the cemented carbide substrate and the diamond coating layer by removing the cobalt phase or nickel phase, which is the binder phase on the surface of the tungsten carbide-based cemented carbide substrate. However, it is clear that further improvements can be made by etching the tungsten carbide phase, which is a hard dispersed phase, and making the surface rough.

[Effects of the Invention] As explained above, according to the present invention, it is possible to form a diamond coating layer that is uniform and has excellent adhesion even on the surface of a tungsten carbide-based cemented carbide substrate having a complicated shape. Diamond-coated cemented carbide members useful as diamond-coated cemented carbide members can be mass-produced at low cost and easily. That is, the method of the present invention is an industrially useful manufacturing method suitable for manufacturing diamond-coated cemented carbide members.

Claims (1)

[Claims] When coating the surface of a tungsten carbide-based cemented carbide substrate with diamond by vapor phase synthesis, wet electrolytic etching is performed in advance using the cemented carbide substrate as an anode to create irregularities on the surface of the tungsten carbide phase, which is a hard dispersed phase. , a method for manufacturing a diamond-coated cemented carbide member, characterized in that diamond is coated by a vapor phase synthesis method.