JPS5911551B2 - Manufacturing method of composite sintered body for cutting tool edge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a composite sintered body of cubic boron nitride and diamond, which is suitable for use as a cutting tool tip for high-hardness steel, Ni-based, and Co-based super super heat-resistant alloys. .

Conventionally, cubic boron nitride (hereinafter referred to as CBN) was used for cutting tool edges.
As a sintered body containing a sintered body of (abbreviated as ) and diamond, (1, I CBN, carbon and Fe + Co v
Nr y Cr r A sintered body made by processing one or more types of transition metal powder such as manganese under high temperature and high pressure, for example, C containing 30% by weight of cobalt powder.
BN/diamond/metal composite sintered body.

(Refer to Japanese Patent Publication No. 43-30409) (2) Compax body consisting of a CBN layer and a carbide layer, where the CBN layer contains 70% by volume or more of CBN, and the remainder may contain diamond particles. , a sintered body containing a metal phase containing aluminum and at least one alloying element selected from nickel, cobalt, manganese, iron, vanadine and chromium (Japanese Patent Publication No. 52-438
46) is known.

The sintered body of (1) has a structure in which the gaps between CBN particles and diamond particles are filled with metal, and has a drawback of lacking toughness.

Furthermore, the sintered body of (2) above has a drawback in that the bond between CBN and diamond particles in the CBN layer is weak.

As described above, the conventional sintered bodies did not have sufficient strength, wear resistance, etc.

The present invention improves the conventional drawbacks and provides a method for manufacturing a sintered body for cutting tool edges that has high strength, high hardness, and excellent toughness.

As a result of research to obtain a strong CBN/diamond composite sintered body, the present inventors found that 1) When using a starting material mixed with metal powder in advance, the difference between diamond particles, between CBN particles, and between CBN-diamond particles (metal gets into each of these, and only low strength can be obtained.

2) Since the bonds between CBN particles generally tend to be weak,
It is easier to obtain a high-strength sintered body by strengthening the bond between CBN and diamond particles.

3) To increase the bond between CBN-diamond particles, it is much better to use CBN and graphite as starting materials and sinter them with the conversion of graphite to diamond than to use a mixed powder of CBN and diamond. High strength can be obtained.

4) If a mixed powder of hexagonal BN and diamond is used as a raw material, a dense sintered body cannot be obtained.

5) Conversion of graphite to diamond requires approximately 50 to 80
In the kilobar pressure range, the CBN and graphite mixed powder is packed in an alloy container containing at least one of iron, nickel, and cobalt, or the mixed powder is layered on the alloy plate, and then heated at high temperature. High pressure treatment is preferred.

6) At this time, very small amounts of iron, nickel, and cobalt infiltrate into the CBN and graphite mixture as diamonds are formed, but only a small amount of them remain between the grains of the CBN/diamond composite sintered body. , is not harmful to the CBN-diamond particle bond and does not cause a decrease in the strength of the sintered body.

7) It is preferable that the graphite to be mixed into CBN be finer.

Even if the graphite grain size is several tens of micrometers, a good sintered body can be obtained as long as diamond grain growth is suppressed.

Instead of directly mixing graphite particles, 5X1 diamond
Graphitized diamond obtained by heating at 0-5 torr and 1460° C. or higher to graphitize the surface of diamond particles by about 75% by weight may be used.

In this case, even better results can be obtained.

Having discovered these things, we have completed the present invention.

That is, the present invention uses cubic boron nitride powder and an average particle size of 1
A mixture with graphite powder of ~70 μm in an alloy container selected from metal alloys, carbide alloys, nitride alloys, and boride alloys containing at least 5% by weight of one or more of iron, nickel, and cobalt. at least 1400°C below the diamond stability range of the graphite-diamond pressure-temperature phase diagram when filled with or laminated with an alloy substrate
This is a method for producing a composite for a cutting tool edge, which is characterized by heating to a temperature above and sintering.

When the CBN content of the starting material for the sintered body of the present invention is less than 40% by weight, the diamond particles converted from graphite tend to grow abnormally and become coarse, and a strong bond between the CBN particles and the diamond particles cannot be obtained. do not have.

On the other hand, if the CBN content exceeds 86% by weight, the main bonds of the sintered body will be bonds between CBN particles, resulting in a decrease in strength, making it unsuitable for use as a cutting tool edge.

The particle size of the CBN particles used is usually about 1 to 100 μm.

The strength of the CBN/diamond sintered body according to the present invention is achieved by the bonding between CBN particles and diamond particles, so sintering does not proceed unless particularly fine CBN is used, unlike in conventional methods. There isn't.

However, the finer the diamond particles are, the more
Since the bond between CBN and diamond particles increases, it is preferable that the graphite mixed in the starting material be fine particles.

The optimum particle size is about 1 to 70 μm.

When the thickness exceeds 70 μm, the strength of the sintered body decreases rapidly.

The raw material mixture described above is molded, and the molded product is made of cobalt, cobalt,
Graphite-diamond is packed in an alloy container containing at least one of iron and nickel, such as a metal alloy, carbide alloy, nitride alloy, or boride alloy, or is laminated on an alloy substrate thereof. CBN heated to a temperature of at least 1400° C. in the diamond stability region of the pressure-temperature phase diagram, e.g. at a pressure of 50 to 80 kbar.
A composite sintered body consisting of and diamond is obtained.

The composite sintered body of the present invention has high hardness, high wear resistance, and toughness, and is an industrially useful material that exhibits excellent effects as a cutting tool tip for difficult-to-cut materials such as Co-based super alloys. It is something.

EXAMPLE Sintered bodies 1 to 2 were produced using the starting materials, filling containers, temperatures, pressures, and heating times shown in Table 1.

Moreover, [phase] is a comparative example.

The obtained sintered bodies (1) to (2) were all composite sintered bodies consisting essentially of CBN and diamond.

However, very small amounts of alloying components were detected.

The sintered bodies of samples ■ and ■ were processed as tool lights, and Co
When cutting the base super alloy, the wear resistance of each tool was more than four times that of commercially available tools.

In addition, all of the sintered bodies ① to ② were dense sintered bodies, and could easily scratch the surface of the Wc-5.5% Co alloy.

However, the sintered body of the comparative example [phase] was made from CBN and diamond mixed powder as the starting material, and although cobalt slightly penetrated from the base material, it was a low-strength sintered body, and the sintered body according to the present invention Compared to that, the wear resistance during cutting of the Co-based super alloy was 1/10 or less.

Claims (1)

[Claims] 1. A mixture of cubic nitride boron powder and graphite powder with an average particle size of 1 to 70 μm, a metal alloy, a carbide alloy, containing 5% by weight or more of one or more metals of iron and Nitsukenopecobalt, Filled in an alloy container selected from nitride alloys and boride alloys or laminated with the alloy substrate, the temperature is at least 1400°C under the diamond stability range of the graphite-diamond pressure/temperature phase diagram. A method for producing a composite sintered body for a cutting tool edge, characterized by heating and sintering to a temperature above.