JPS6016867A - High hardness sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a hard material that does not contain a binder phase substantially consisting of a metal phase and has excellent heat resistance, oxidation resistance, abrasion resistance, corrosion resistance, thermal conductivity, and electrical conductivity. The present invention relates to a high-hardness sintered body consisting of phases.

Conventionally, interstitial compounds in which nonmetallic elements such as C, N, and 0 are dissolved in transition metals of Groups 4a, 5a, and 6a of the periodic table are sinterable materials, and as they are, they can be used at temperatures below 1600°C. Since it cannot be sintered densely, cemented carbide alloys have been put into practical use in which iron group metals are added and liquid-phase sintering is carried out through a eutectic reaction to promote densification and improve strength at the same time. This cemented carbide and the composite alloy of Zamezto Kasa have a binder phase made of iron group metals, so when used under high temperature and high stress conditions, plastic deformation progresses due to the binder phase becoming glutinous, and wear resistance increases. The thermal expansion coefficient of the binder phase made of iron group metal and 4
Thermal cracks may occur due to the difference in thermal expansion coefficient of the hard phase consisting of compounds of Group A, 5A, and 6A metals, and furthermore, when used in a chemical or corrosive gas atmosphere, iron group metals as a binder phase may occur. There is a problem that the metal corrodes and becomes unusable.

The high-hardness sintered body of the present invention solves the problems listed in (-), and has high hardness, low specific gravity, thermal conductivity, and electrical conductivity without substantially containing a binder phase made of metal. The present invention provides a sintered body with excellent corrosion resistance and oxidation resistance. That is, the high hardness sintered body of the present invention contains Ti, Zr, Hf, V, Nb,
This is a sintered body made of a solid solution compound that is a combination of two or more selected from carbides, nitrides, and oxides of Ta and Tb, and inevitable impurities.

The high hardness sintered body of the present invention includes Ti, Zr, Hf, and V.

By combining two or more of carbides, nitrides, and oxides of Nb, Ta, and Th that have a complete solid solution or a solubility gap metallographically, spinodal decomposition or pinodal decomposition occurs, and substantially metal It has toughness, high hardness, low specific gravity, and has thermal conductivity, electrical conductivity, corrosion resistance, and oxidation resistance that can be made into a compact sintered body at a low temperature of 1600°C or less even without containing a binder phase. It is designed to be excellent in Ti, Zr, Hf, V, Nb,
If two or more of carbides, nitrides, and oxides of Ta and Th are combined at a composition ratio that does not cause spinodal decomposition or pinodal decomposition, it is necessary to sinter at a high temperature of about 2000 °C or higher [the resulting sintered material]. Of the two types of compounds that have a complete solid solution or a solubility gap metallographically, the crystal grains of the compact become coarse and the various properties of the sintered compact deteriorate.
It is desirable that spinodal decomposition or pi/tal decomposition occur by setting the composition ratio such that one kind is present in an amount of 5 mol % or more. When the composition ratio is set to cause spinodal decomposition or pinodal decomposition, a dense sintered body is formed at a low temperature, so that the crystal grains of the sintered body become finer and tend to have higher hardness, higher toughness, and higher heat resistance.

The high-hardness sintered body of the present invention has extremely excellent corrosion resistance because it does not contain a metal binder phase, and by making the sintered body mainly composed of group 4a metal compounds and having a high nitrogen content, It has a beautiful golden color, has high hardness, excellent scratch resistance, and has low potash and density, so it can be used for decorative parts such as watch exterior parts and fishing A parts.

In addition, the high hardness sintered body of the present invention has excellent electrical conductivity and is easy to perform electric discharge machining, so it is possible to process complicated shapes. Mechanical seat tv, support hold jig,
Guides for printing bottles, sliding members, etc., and sintered bodies with a high nitrogen content can be used as wear-resistant materials for glass melting molds, heat-resistant molds for lens molding, magnetic head bases, tape cutters, etc. Furthermore, the high hardness sintered body of the present invention is
It has excellent thermal conductivity, and since it does not contain a metal binder phase, it has good reaction resistance with rigid materials, so it can also be used as a cutting tool for non-ferrous metals such as hard graphite and resin. .

The starting material for producing the high-hardness sintered body of the present invention is such that the finer particles are used, the more metal atoms and interstitial nonmetal atoms in the compound expand mutually during the sintering process, resulting in spinodal decomposition or pinodal decomposition. This makes it easier for the phase splitting phenomenon to occur, making it possible to sinter at even lower temperatures to promote sintering, and for this reason, the crystal grains of the sintered body become microscopic, resulting in high hardness and high toughness. The tendency of For this reason, it is preferable that the starting material be 108 m or less, especially 0.1 μm or less, but 2 μm or less for handling reasons due to oxidation, etc.
The following are desirable. When the starting material is coarse particles, the mixing and pulverization may be strengthened, but since this tends to increase the amount of impurities mixed in, it is necessary to use it properly depending on the purpose. The composition of the starting raw material is (a) Ti.

2 of metal powders of Zr, Hf, V, Nb, Ta, and Th
A method of reaction sintering by adjusting the atmosphere using a mixed powder consisting of two species, (b) Ti, Zr, Hf, V, Nb,
Ta.

One or more metal powders of Th and T i, Z r + Hf
, V + Nb, Ta, Th carbide powder, nitride powder, oxide powder, and a method of reaction sintering by adjusting the atmosphere using a mixed powder consisting of one or more of these mutual solid solution compound powders, (c) T i+ Z r , Hf +
V + N b , T a .

A possible method is to sinter in a non-oxidizing atmosphere using a mixed powder consisting of a mono-compound powder of a carbonized portion of Th, a nitride, an oxide, and a powder of a 171 mutual solid solution compound of these. Among these, using (a)ω) mixed metal powder as the starting material is because the reaction sintering time becomes longer and the metal remains in the sintered body, reducing corrosion resistance and hardness. To (c
) is preferably used as a starting material. Among the configurations (c), it is better to use a combination of a composite compound powder and a single compound powder or a single compound powder and a single compound powder as starting materials rather than using only a composite compound powder as a starting material, especially during the sintering process. At the same time as densification by in-phase diffusion, phase separation phenomenon by spinodal decomposition or pinodal decomposition is caused and sintered at low temperature to produce a sintered body with a modulated structure of fine particles. It is desirable to use a single compound powder as starting material. Even if the single compound powder or composite compound powder used as the starting material is a heavy ratio compound in which the molar ratio of metallic elements and nonmetallic elements is the same, it may contain nonmetallic interstitial elements such as carbon, nitrogen, and oxygen. The high hardness sintered body of the present invention can be obtained even if it has a substoichiometric composition, which is a non-stoichiometric compound in which the solid solution is deficient or excessive.

In the manufacturing process of the high-hardness sintered body of the present invention, the starting materials are mixed and pulverized using a stainless steel container, a container lined with cemented carbide, or a container lined with urethane rubber. , mixed and ground with cemented carbide balls or surface-coated balls.

In order to improve the grinding effect and make the starting materials finer, it is best to use a stainless steel container or a container lined with cemented carbide to mix and grind together with cemented carbide balls. It is preferable to add an organic solvent such as benzene or alcohol and perform wet mixing and pulverization. For applications that utilize corrosion resistance and abrasion resistance at high temperatures, etc., and when it is necessary to take into account impurities mainly made of metal, it is recommended to use a container lined with urethane rubber and mix with balls whose surface is coated. good. A high proportion of impurities are mixed in during the mixing and pulverizing process, and only a small percentage of the cemented carbide used in the mixing and pulverizing process contains all group 4a, 5a, and 6a group metallizations, which are the main components of the cemented carbide. While there is no problem, it is desirable that the amount of iron group metals that are the binder phase of cemented carbide is kept at 2% by volume or less, preferably 1% by volume or less.

In the manufacturing process of the high-hardness sintered body of the present invention, the mixed powder is molded by filling the mixed and pulverized powder into a graphite mold and hot pressing it in a non-oxidizing atmosphere, or by adding paraffin to the mixed and pulverized powder. If necessary, it is made into granules by adding a molding aid such as camphor, and then filled into a metal mold and molded under pressure, or is molded by hydrostatic pressure using a rubber press or the like. The powder compact formed in this way can be directly sintered, or the powder compact can be pre-sintered at a temperature lower than the sintering temperature and then subjected to mechanical processing such as cutting, grinding, cutting, etc., and then sintered. It can also be tied.

In the manufacturing process of the high-hardness sintered body of the present invention, sintering can be performed by pressureless sintering or pressure sintering in a non-oxidizing atmosphere, or by sintering under reduced pressure or in a vacuum. Particularly when obtaining a sintered body containing nitrogen element, it is desirable to sinter in a non-oxidizing atmosphere containing N2 gas to prevent denitrification. Furthermore, the material sintered using the above method was subjected to hot isostatic pressing (
It is also possible to obtain a sintered body that is denser and has higher toughness by reprocessing it by HIP).

EXAMPLES The high hardness sintered body of the present invention will be specifically explained below according to Examples.

Example 1 Various single compound powders with an average particle size of 0.2 to 3 μm were blended in a predetermined ratio, and after adding 3 to 5% paraffin as a forming aid to this blended powder, WCC cemented carbide was prepared in an acetone solvent. The mixture was mixed and pulverized in a stainless steel container using a manufactured ball.

After the solvent was evaporated and dried from the obtained mixed powder, the mixed powder was molded with a pressure of 1 t/h~5 t/ca, and 10-3
~I O" rr! I; + Hfl (7) X 1300'l in empty or non-oxidizing gas atmosphere: ~1600"C
Bake 1fi L at a temperature of 30 to 90 minutes. Table 1 shows the compounding composition and sintering conditions of each sample, and Table 2 shows the properties of the sintered body of each sample.

Among the various properties shown in Table 2 below, the corrosion resistance test was performed by immersing each sample in artificial sweat containing sodium chloride, sodium sulfide, urea, sucrose, aqueous ammonia, and lactic acid, adjusted to pH 3.9 to 5.0. This is an observation of the state of corrosion on the polished surface.

Example 2 Various single compound powders and composite compound powders having an average particle size of 0.2 to 3 μm were blended at predetermined ratios 1-1 to obtain a sintered body in the same manner as in Example 1. The composition and sintering conditions of each sample are shown in Table 3, and the various properties of the sintered body of each sample obtained were determined in the same manner as in Example 1, and the results are shown in Table 4.

Example 3 A sintered body was obtained in the same manner as in Example 1 by blending a mono-compound powder and a composite compound powder consisting of a non-stoichiometric compound with an average particle size of 0.5 to 5 μm in a predetermined ratio. The composition and sintering conditions of each sample are shown in Table 5, and the various properties of the sintered body of each sample obtained were determined in the same manner as in Example I, and the results are shown in Table 6.

Below are 19 pages of blank space. In comparison with Examples 1 and 2.3, commercially available cemented carbides and cermets were subjected to corrosion resistance tests using artificial sweat. occurred. Moreover, sample numbers 8 and 9 of Example 1. The mirror surface state of the sintered bodies of Sample No. 14 of Example 2 and Sample No. 21 of Example 3 had a beautiful golden yellow tone. Due to these characteristics, the high-hardness sintered body of the present invention is a material with a wide range of industrial applications, including materials for decorative items, parts for cutting tools, and various wear-resistant parts.

Patent applicant: Toshiba Tungaloy Corporation Special opening aGO-16867 (7)

Claims (1)

[Claims] (t) Consists of two or more solid solution compounds selected from carbides, nitrides, and oxides of Ti, Zr, Hf', V, Nb, Ta, and Th, and inevitable impurities. A high hardness sintered body characterized by: (2) The high-hardness sintered body according to claim 1, wherein the solid solution compound has a modulated structure due to spinodal components or pinodal decomposition. (3) High hardness according to paragraphs 1 and 2 of the scope of the patent application, characterized in that the solid solution compound has a substoichiometric composition in which nonmetallic elements are deficient or in excess with respect to metallic elements. Sintered body.