JP2554941B2 - Method for producing diamond-coated cemented carbide member - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing 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] In recent years, since a method for synthesizing diamond by vapor phase synthesis has been developed, development of a diamond-coated cemented carbide tool in which the surface of a cemented carbide substrate is coated with diamond has been vigorously pursued. However, in this case, improving the adhesion between the cemented carbide substrate surface and the diamond coating layer is an important issue,
The current situation is that we have not yet obtained satisfactory adhesion. As a method for improving the adhesion to the substrate, for example, the methods disclosed in JP-A-63-14869 or JP-A-1-201475 have been proposed. The method described in JP-A-63-14869 is a method in which the cobalt phase on the cemented carbide surface is preferentially ground by grinding the cemented carbide substrate surface with a diamond grindstone to make it concave than the tungsten carbide phase. is there. By this method, the nucleation of diamond can be promoted and the adhesion can be improved. However, the method of grinding with a diamond grindstone requires time and labor because cemented carbide has extremely poor grindability. In particular, it is very difficult to grind a cemented carbide substrate such as a cutting tool having a three-dimensionally complicated shape, and it is extremely difficult to make uniform fine scratches on the surface of the cemented carbide substrate. . In addition, JP-A 1-20
The method described in the 1475 publication selectively removes the cobalt phase on the surface of the cemented carbide substrate by etching with an acid to selectively remove the cobalt phase on which the diamond crystal nuclei are less likely to occur to form a cemented carbide substrate surface. It is a method of making unevenness.
By this method, the nucleation density of diamond and the adhesion surface area are increased, and the adhesion can be improved. However, with the method using acid treatment, although the cobalt phase can be removed by etching, it is difficult to etch the surface of the tungsten carbide phase to form fine irregularities, and a strong adhesion cannot be obtained. Also, if the surface of the tungsten carbide phase is damaged by etching for a long time, the cobalt phase is etched and removed more than necessary, the binder phase near the surface of the cemented carbide substrate becomes insufficient, and the bonding strength of the tungsten carbide phase decreases and There is a problem in that the tungsten particles fall off or the strength of the cemented carbide substrate itself decreases.

[Problems to be Solved by the Invention] The present invention has been made to solve the above problems, and an object thereof is to economically produce a diamond-coated tungsten carbide-based cemented carbide member having practical adhesion. To provide a method.

[Means for Solving the Problems] Generally, the area occupancy of the tungsten carbide phase is higher than that of the binder phase on the surface of the tungsten carbide based cemented carbide substrate. We obtained the knowledge that it greatly contributes to the improvement of the adhesion between the coating layer and the cemented carbide substrate, and conducted further diligent research to achieve the above-mentioned object. When the etching is performed, the tungsten carbide phase surface is etched to form fine irregularities, the nucleation of diamond is promoted, the adhesion area is increased, and the finding that the adhesion can be greatly improved by the anchor effect is obtained. The present invention has been completed. At this time, since the binding phase, such as cobalt and nickel, is hard to be etched, the tungsten carbide phase does not drop out and the strength of the cemented carbide itself does not decrease.

The solution used for electrolytic etching treatment is, for example, an aqueous solution of sodium hydroxide, sodium hydroxide and sodium chloride, sodium hydroxide and sodium phosphate, or potassium hydroxide and potassium ferricyanide. Examples include a method in which graphite is used as a cathode and electrolytic etching is performed at a current density of 0.1 to 10 A / dm ² .

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

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

[Function] When the tungsten carbide-based cemented carbide substrate is used as an anode and subjected to wet electrolytic etching, irregularities can be formed on the surface of the tungsten carbide phase that occupies most of the surface of the cemented carbide substrate. It is possible to obtain a diamond-coated tungsten carbide-based cemented carbide having an increased adhesiveness and an increased adhesion area and an excellent adhesion due to the anchor effect. Moreover, at this time, since the binder phase is not etched, the tungsten carbide phase does not drop out and the strength of the cemented carbide itself does not decrease. Moreover, since unevenness is formed by wet electrolytic etching using the substrate as an anode, a large amount of cemented carbide substrate can be economically processed.

[Examples] Hereinafter, the present invention will be described with reference to Examples.

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

And after polishing the surface consisting of 25mm x 8mm, the grain size is 1μ
Lapping was performed using m diamond paste.

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

(1) Wash in acetone.

(2) Cemented carbide substrate as cathode, SUS304 plate as anode in aqueous solution consisting of 2 wt% sodium hydroxide and 2 wt% sodium phosphate, current density 3A at 70 ℃
Cathode degreasing with / dm ² for 10 seconds.

(3) Current density 3A at 70 ° C at 70 ° C with a cemented carbide substrate as the cathode and a SUS304 plate as the cathode in an aqueous solution consisting of 2% by weight sodium hydroxide and 2% by weight sodium phosphate.
Electrolytic etching with / dm ² for 10 seconds.

(4) Washing with water.

When the cemented carbide substrate treated as described above was observed with a scanning electron microscope (JSM-840A manufactured by JEOL Ltd.), the cobalt phase became concave than the tungsten carbide phase, and the tungsten carbide phase was chemically etched. Fine irregularities were formed on the surface. Then, a diamond coating layer was formed on the surface of these cemented carbide substrates by the microwave plasma CVD method.

As microwave plasma CVD conditions, microwave (2.45 GHz) power 900 W, hydrogen gas supply amount 990 SCCM, methane gas supply amount 5 SCCM, reaction pressure 40 TORR and substrate temperature 750 ° C.
After the CVD treatment for 2 hours, the supply amount of methane gas was changed to 10 SCCM and the CVD treatment was further performed for 4 hours.

As a result, a diamond coating layer having a film thickness of 4 μm and formed of cubic crystal diamond having a clear crystal shape was formed on the surfaces of all the cemented carbide substrates.

The adhesion strength between the cemented carbide substrate and the diamond coating layer of the diamond-coated cemented carbide member thus obtained was evaluated by the scratch test method and the tape peeling test method. The scratch test method applies a load to an indenter made of diamond with a radius of 0.2 mm to scratch the surface of the diamond-coated cemented carbide member, and evaluates the adhesion force with the load when the diamond coating layer peels off as the critical strength, and Tape peeling test method is cellophane tape (Nichiban Co., Ltd.)
Tape) was attached to the surface of the diamond-coated cemented carbide member by using a tape, and the tape was peeled off to evaluate the adhesive strength by the ratio of the area of the diamond-coated layer peeled off.

As a result, in the scratch test, 3.0 kg was obtained for the coated member in which the surface of the cemented carbide substrate having a cobalt content of 4 wt% was coated with diamond, 3.5 kg for the coated member having a cobalt content of 7 wt%, and 7 wt% for the nickel content. The covering material is 3.0
The strength was kg. In the tape peeling test, all the cemented carbide members were 0% and did not peel at all, and extremely high adhesion was obtained.

Comparative Example 1 A tungsten carbide based cemented carbide substrate that was sintered in the same manner as the tungsten carbide based cemented carbide substrate used in Example 1 was prepared and lapped with a diamond paste having a particle size of 1 μm. After washing 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, in the coating member having a cobalt content of 4% by weight, the diamond coating layer was peeled off when taken out from the chamber. Coated material with a cobalt content of 7% by weight is 0.1 kg in the scratch test and 100% in the tape peeling test.
Peeled off. The coated member having a nickel content of 7% by weight was 0.1 kg in the scratch test and 100% in the tape peeling test.

Comparative Example 2 A tungsten carbide-based cemented carbide substrate that was sintered in the same manner as the tungsten carbide-based cemented carbide substrate used in Example 1 was prepared and lapped with a diamond paste having a particle size of 1 μm. These cemented carbide substrates were immersed for 30 minutes to etch the surface, washed with water and dried. When the surface and cross section of these cemented carbide substrates were observed with a scanning electron microscope, the surface of the tungsten carbide phase of the hard dispersed phase was slightly uneven, but the surface of the cemented carbide substrate had a slight unevenness. Phase is 30 ~ from cemented carbide substrate surface
It was etched to 40 μm, 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 coating member having a cobalt content of 4% by weight showed 0.1 kg in the scratch test and 80% in the tape peeling test. The coated member having a cobalt content of 7% by weight peeled 0.5 kg in the scratch test and 90% peeled in the tape peeling test. The coated member having a nickel content of 7% by weight was 0.5 kg in the scratch test and 100% in the tape peel test.

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

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

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 the nickel phase which is the binding phase on the surface of the tungsten carbide based cemented carbide substrate. However, it can be seen that it can be further improved by etching the tungsten carbide phase which is a hard dispersed phase to make the surface uneven.

[Effects of the Invention] As described above, according to the present invention, it is possible to form a diamond coating layer having uniform and excellent adhesion even on a surface of a tungsten carbide based cemented carbide substrate having a complicated shape,
A diamond-coated cemented carbide member useful as a tool or the like can be mass-produced inexpensively and easily. That is, the method of the present invention is an industrially useful manufacturing method suitable for manufacturing a diamond-coated cemented carbide member.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C30B 29/04 7202-4G C30B 29/04 Q

Claims (1)

(57) [Claims] 1. When coating the surface of a tungsten carbide based cemented carbide substrate with diamond by a vapor phase synthesis method, wet etching is carried out in advance using the cemented carbide substrate as an anode.
A method for producing a diamond-coated cemented carbide member, characterized in that a surface of a tungsten carbide phase, which is a hard dispersed phase, is made uneven, and then diamond is coated by a vapor phase synthesis method.