JPS5857502B2 - Sintered material with toughness and wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cutting tools, bearings, and wire-drawn materials made of high-hardness steel, Ni-based or Co-based superalloy, which require high hardness, wear resistance, toughness, and corrosion resistance. The present invention relates to a dense sintered material containing cubic boron nitride, which has a hardness second only to diamond and is suitable for use as a die.

Conventionally, tungsten carbide (hereinafter referred to as WC)-based cemented carbide, which has excellent toughness, has generally been widely used for the above-mentioned applications, but in recent years, as the conditions for its use have become harsher, There is a strong desire to develop better materials.

Recently, in response to such demands, cubic boron nitride sintered materials and sintered materials containing small amounts of Al and iron group metals have been proposed and commercially available, but the former sintered materials have excellent Although it has wear resistance, it lacks toughness, and the latter sintered material deteriorates in wear resistance especially when used under conditions with high heat generation.
At present, neither material has satisfactory properties.

From the above-mentioned viewpoint, the present inventors conducted research focusing on cubic boron nitride (hereinafter referred to as BN) in order to obtain a sintered material with excellent wear resistance and toughness.
, W + Mo t Ta t T it and Nb
When one or more of these high melting point metals are included, a sintered material that has both the excellent wear resistance provided by the BN and the excellent toughness provided by the high melting point metal can be obtained. We obtained this knowledge.

Therefore, the sintered material of the present invention has been made based on the above knowledge, and includes one or more of the above BN: 40 to 97 capacity, WtMotTa, 'rit, and Nb. High melting point metal = 3 to 60 capacity φ,
It is characterized by a sintered material made of

Next, the reason why the composition range of the sintered material of the present invention is limited as described above will be explained.

(a) BN BN is synthesized under conditions of a temperature of 1200°C or higher and a pressure of 40kb or higher, preferably a temperature of 1800°C or higher and a pressure of 60kb or higher, and is the second hardest material after diamond, with a Vickers hardness of 6000 to 7000. 57/mrn2) and has properties that are more stable at high temperatures1 than diamond, as well as being less reactive to iron group metals.However, if its content is less than 40%, it will not reach the desired It is not possible to ensure wear resistance, and on the other hand, if the content exceeds 97 capacity, the sinterability becomes insufficient, the remaining bores become noticeable, and the decrease in toughness becomes significant, so the content should be reduced. It is determined that the capacity is 40 to 97.

(b) High melting point metal Refractory metals can be used at room and high temperatures, especially at about ioOo.

It has high hardness and strength at high temperatures above ℃, and
Although it has excellent toughness, if the content is less than 3 volume φ, the content of BN component will be relatively too large and the sinterability will be insufficient, resulting in the presence of bores. On the other hand, if the content exceeds 60 BN, the content of BN becomes relatively too low, making it impossible to maintain the desired high hardness, that is, excellent wear resistance. Since it disappears, its content is reduced to 3
~60 capacity is determined.

When producing the sintered material of the present invention, when an alloy powder consisting of two or more high-melting point metals is used as a raw material powder, the alloy powder is: (1) blended in a predetermined proportion, mixed, and vacuum (2) forming a molten alloy with a predetermined content ratio; then adding water to the molten metal; It is manufactured by methods such as obtaining atomized alloy powder by injecting a gas such as nitrogen or argon into a container.

Note that since the atomized alloy powder obtained by water injection has significant surface oxidation, it is desirable to perform a hydrogen reduction treatment upon use.

In particular, Ti, Ta, and Nb, which are difficult to reduce metals,
When producing an atomized alloy powder containing , it is desirable to use an inert gas or argon gas, and by using these gases, the alloy powder will have good properties.

In the past, the resulting atomized alloy powders were generally brittle and therefore relatively easy to grind in commonly used grinders such as ball mills, vibrating mills, and the like.

Furthermore, the sintered material of the present invention can be produced using a conventionally known ultra-high pressure and ultra-high temperature generator.

That is, BN powder and a single powder made of one type of high-melting point metal, or a mixed powder or alloy powder made of two or more types are mixed in a predetermined ratio and mixed for a long time in an iron ball mill to form a homogeneous powder. After forming a mixed powder, the mixed powder is sealed in a container made of steel or a high melting point metal.
It is charged into an ultra-high pressure and ultra-high temperature generator as described in Publication No. 8-14, and the pressure button and temperature are raised until the pressure reaches 40.
60 kb and a temperature of 1200 to 1800° C., holding this final pressure and temperature for 0.5 to 10 minutes, and releasing the pressure after cooling.

Next, the sintered material of the present invention will be explained using examples.

Example 1 Average particle size of 3 μm synthesized by non-catalytic method as raw material powder
BN powder = 70 volumes, W powder = 20 volumes which is a high melting point metal with the same particle size, and Ti powder = 10 volumes which is also a high melting point metal with the same particle size, and this blended powder W
Charged into a small high-speed motion mill lined with CC cemented carbide,
After wet mixing for 1 hour, the mixture was vacuum dried.

Then, in an argon atmosphere, the above mixed powder was
After sieving, each separately prepared 9.8-diameter Φ×
In a Ti cylindrical container with an inner diameter of 10 mm Φ and a height of 15 mm, which was attached as an underlay to the bottom of a WCC cemented carbide disk with a thickness of 2 mm, there were 7 samples with a thickness of 7. A WCC cemented carbide disk having a thickness of 2 mm was placed on the charged mixed powder, and the powder was removed from the argon atmosphere.

Next, the container was covered with a Ti top lid, and the top lid was pressed using a press to compress the mixed powder in the container to a thickness of 5.5 mm, and then the container was sealed with the top lid by welding.

The container containing the mixed powder sealed in this manner is charged into a known ultra-high pressure and ultra-high temperature generator, and held for 3 minutes under the conditions of a final applied pressure of 50 kb and a heating temperature of 1350°C. The sintered material of the present invention was manufactured in a state in which it was diffusion bonded to upper and lower disks made of

Next, the above-mentioned sintered material of the present invention was cut and polished into a cutting edge having a 90° angle, and the above-mentioned WCC
With the cemented carbide discs connected together, they were fixed using a separately prepared larger rectangular WCC cemented carbide chip with silver solder, and the nose radius was finished to Q, 4tnm. A cutting tool made of the invented sintered material was manufactured.

When the above-mentioned sintered material of the present invention was used for finishing cutting of an automobile axle, it exhibited a service life approximately 20 times longer than that of a conventional cermet cutting tool.

Example 2 Ta powder with an average particle size of 5 μm = 50 capacity and 0.6 μm
m of Mo powder=50 volume were wet mixed in a ball mill for 24 hours, dried in the air, and then the resulting mixed powder was mixed under a pressure of 50 KI! /i to form a green compact,
The green compact was subjected to a pressure of 10-4 mm H? Ta-Mo solid solution powder, which is a high-melting point metal, was prepared as a raw material powder by holding the temperature at 1300° C. for 1 hour in a vacuum to cause a solid solution diffusion reaction.

Next, the above T was crushed to a particle size of 100 mesh or less.
a-Mo solid solution powder = 40 volume and same 10
0 mesh or less BN powder = 60 volume ratio is blended, and this blended powder is wet mixed for 1 hour in a WCC cemented carbide high speed planetary motion mill.
d to form a cylindrical green compact with a diameter of 9.5 mm and a height of 10 mm, and this green compact was charged into a mold equipped with upper and lower punches made of graphite, and heated at a temperature of 900°C. Pressure 200 K9/i
Hot press for 5 minutes under the following conditions to achieve a density of 85%.
The pre-sintered material having the following properties was molded.

Subsequently, the pre-sintered material was charged into a stainless steel container and sealed, and then sintered by holding it for 5 minutes at a pressure of 45 kb and a temperature of 1350° C. in a known ultra-high pressure and ultra-high temperature generator. The sintered material of the present invention was produced by the following steps.

The resulting sintered material of the present invention has a dense structure without bores, and has a density of 8.1? /d, Vickers hardness 200/-) 3600/2.

Example 3 The raw material powders were mixed in appropriate proportions to have the component composition shown in Table 1, and the final pressure and temperature, which are the manufacturing conditions, were the same (except for the conditions shown in Table 1). Sintered materials 1 to 4 of the present invention and comparative sintered materials 1 and 2 having component compositions outside the range of the present invention were produced under the same conditions as in Example 1, respectively.

Next, the above-mentioned sintered materials 1 to 4 of the present invention, comparative sintered material 1,
Cutting tools were manufactured from 2 and a commercially available cubic boron nitride sintered material under the same conditions as in Example 1. Work material: JIS@SNCM-8 (HRC: 53), cutting speed: A cutting test was conducted under the following conditions: 100 m/rev, depth of cut = 0.5, feed rate = 0.1 m/rev, and the cutting time until flank wear reached 0.1 mm was measured.

The measurement results are shown in Table 2, which also shows the specific gravity and Vickers hardness of the various sintered materials.

As shown in Table 2, it is clear that the sintered material of the present invention, when used as a cutting tool, exhibits significantly superior cutting performance compared to the comparative sintered material and the commercially available sintered material.

As mentioned above, the sintered material of the present invention has excellent toughness comparable to that of WCC cemented carbide, and excellent durability due to the inclusion of cubic boron nitride, which has a hardness second only to diamond. Because of its abrasive properties, high hardness steel,
Ni group or C.

When used for cutting materials such as base super alloys, it shows excellent cutting performance in a wide range of applications from general cutting to finishing cutting.It also has excellent corrosion resistance, so it is used in the manufacture of bearings and wire drawing dies. It also exhibits excellent performance in many cases.

Claims (1)

[Claims] 1 Cubic boron nitride = 40-97 capacity coefficient, W, Mo
tTa? One stack of Tit$- and Nb, two or more high melting point metals and unavoidable impurities = 3 to 6
A sintered material having toughness and wear resistance characterized by having a capacity of 0, φ.