JPH0478584B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a high-hardness sintered material that does not contain a binder phase that is substantially made of a metal phase and is made of a hard phase that has excellent heat resistance, oxidation resistance, abrasion resistance, corrosion resistance, thermal conductivity, and electrical conductivity. Regarding the body. Conventionally, interstitial compounds in which nonmetallic elements such as C, N, and O are dissolved in transition metals of groups 4a, 5a, and 6a of the periodic table are difficult-to-sinter materials, and as they are, they cannot be sintered at temperatures below 1600℃. Because 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 performed through eutectic reaction to promote densification and improve strength at the same time. Composite alloys such as cemented carbide and cermets 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 softening of the binder phase, resulting in poor wear resistance. The thermal expansion coefficient of the binder phase made of iron group metal and 4a,
Thermal cracks may occur, which is thought to be due to the difference in thermal expansion coefficient of the hard phase consisting of compounds of group 5a and 6a metals.Furthermore, if used in a chemical or corrosive gas atmosphere, the iron group metal, which is the binder phase, may corrode. The problem is that it becomes unusable. The high-hardness sintered body of the present invention solves the above-mentioned problems, and does not contain a binder phase substantially made of metal, has high hardness, low specific gravity, and has good thermal conductivity, electrical conductivity, and corrosion resistance. and a sintered body with excellent oxidation resistance. That is, the high hardness sintered body of the present invention contains carbides of Ti, Zr, Hf, V, Nb, Ta, and Th,
It is a sintered body made of a solid solution compound that is a combination of two or more selected from nitrides and oxides, and the solid solution compound has a modulated structure structure due to spinodal decomposition or binodal decomposition. The high hardness sintered body of the present invention includes Ti, Zr, Hf, V,
Among carbides, nitrides, and oxides of Nb, Ta, and Th,
Spinodal decomposition or binodal decomposition or It generates binodal decomposition and can be made into a compact sintered body at a low temperature of 1600℃ or less even without containing a binder phase consisting essentially of metal.It has toughness, high hardness, low specific gravity, and thermal conductivity. , which has excellent electrical conductivity, corrosion resistance, and oxidation resistance.
If two or more of the carbides, nitrides, and oxides of Ti, Zr, Hf, V, Nb, Ta, and Th are combined at a composition ratio that does not cause spinodal decomposition or binodal decomposition, high-temperature sintering at approximately 2000°C or higher Since it becomes necessary to sinter, the crystal grains of the resulting sintered body become coarse and the various properties of the sintered body deteriorate, one of the two types of compounds that are completely dissolved in metallurgy is added at 5 mol %. It is desirable to cause spinodal decomposition or binodal decomposition to occur at a composition ratio greater than or equal to the above. When the composition ratio is set to cause spinodal decomposition or binodal 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 modulated structure resulting from spinodal decomposition or binodal decomposition consists of a structure in which solid solution compounds of two or more phases with different metal and/or nonmetal contents are arranged in a periodic manner. Specifically, for example, in the case of a TiC-TiN-VC solid solution compound, a solid solution compound with a high content of Ti and/or V and a solid solution compound with a low content, or a solid solution compound with a high content of C and/or N and a solid solution compound with a low content. , or there are two or more solid solution compounds in the solid solution compound in which both of these are combined,
It is a structure in which phases of two or more solid solution compounds are arranged in a periodic manner. The high-hardness sintered body of the present invention has extremely excellent corrosion resistance because it does not contain a metal binder phase, and it is possible to make the sintered body mainly composed of group 4a metal compounds and with a high nitrogen content. As a result, it has a beautiful golden color, has high hardness and excellent scratch resistance, and has a low density, so it can be used for decorative parts such as watch exterior parts and fishing gear 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 seals, support holding jigs, guides for printing pins, sliding parts, etc., as well as sintered bodies with high nitrogen content, are used as wear-resistant materials for glass melting molds, heat-resistant molds for lens molding, porcelain head bases, tape cutters, etc. It can be used as Furthermore, the high-hardness sintered body of the present invention has excellent thermal conductivity, and since it does not contain a metal binder phase, it has good reaction resistance with work materials, so it can be used with non-ferrous metals such as hard graphite and resin. It can also be used for cutting tools. 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 interdiffuse during the sintering process, resulting in spinodal decomposition or binodal decomposition. This makes it easier for phase separation to occur, making it possible to sinter at even lower temperatures to promote sintering, which results in finer crystal grains in the sintered body, resulting in higher hardness and higher hardness.
The tendency towards higher toughness increases. For this reason, it is desirable that the starting material has a diameter of 10 μm or less, especially 0.1 μm or less, but it is preferably 2 μm or less from the viewpoint of handling since oxidation may occur. 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 them appropriately depending on the purpose. The composition of the starting materials is (a) Ti,
2 in metal powders of Zr, Hf, V, Nb, Ta, Th
A method of reaction sintering by adjusting the atmosphere using a mixed powder consisting of more than 1 species, (b) Ti, Zr, Hf, V, Nb,
One or more types of Ta, Th metal powder and Ti, Zr, Hf,
V, Nb, Ta, Th carbide powder, nitride powder,
A method of reaction sintering by adjusting the atmosphere using a mixed powder consisting of an oxide powder and one or more of these mutual solid solution compound powders, (c) Ti, Zr, Hf, V,
A possible method is to sinter in a non-oxidizing atmosphere using a powder mixture of single compound powders of carbides, nitrides, and oxides of Nb, Ta, and Th, and powders of mutual solid solution compounds thereof. Among these, using materials mixed with metal powder (a) and (b) as starting materials may result in a longer reaction sintering time, or may cause metals to remain in the sintered body, reducing corrosion resistance and hardness. In order to achieve this, it is desirable to use the composition (c) as a starting material. Among configurations (c), a combination of a composite compound powder and a single compound powder, or a combination of a single compound powder and a single compound powder as a starting material is better than using only a composite compound powder as a starting material, especially during the sintering process. In order to produce a sintered body with a modulated structure of fine particles by sintering at a low temperature by causing a phase separation phenomenon by spinodal decomposition or binodal decomposition at the same time as densification by solid phase diffusion, two or more types of A single compound powder is used as starting material. Furthermore, for example, using this starting material, controlling the sintering conditions, specifically holding it at the sintering temperature, increasing the cooling rate from the sintering temperature to about 800 °C, and then increasing the cooling rate from about 800 °C to 1200 to 1450 °C again. When the temperature is raised to .degree. C., a sintered body having a modulated structure can be formed more quickly. Even if the single compound powder or composite compound powder used as the starting material has a stoichiometric composition in which the molar ratio of metallic elements and nonmetallic elements is the same, the nonmetallic powder of carbon, nitrogen, and oxygen, which are erosive elements, The high hardness sintered body of the present invention can be obtained even if it has a non-stoichiometric structure 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. Mix and grind together with manufactured 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 alcohol and perform wet mixing and pulverization. When it is necessary to consider impurities mainly made of metal, such as for applications that utilize corrosion resistance and high-temperature abrasion resistance, it is best to use a container lined with urethane rubber and mix with surface-coated balls. A high proportion of impurities are mixed in during the mixing and grinding process, and among the cemented carbide used in the mixing and grinding process, 4a, 5a, which is the main component of cemented carbide,
While there is no problem with the ratio of group 6a metal compounds mixed as impurities, the mixing of iron group metals, which are the binder phase of cemented carbide, should be 2% by volume or less, preferably 1% by volume.
It is desirable to do the following. In the manufacturing process of the high-hardness sintered body of the present invention, the mixed powder can be formed by filling the mixed and pulverized powder into a graphite mold and hot pressing it in a non-oxidizing atmosphere, or by adding paraffin or camphor to the mixed and pulverized powder. If necessary, it is made into granules by adding a molding aid such as, for example, granules, and then filled into a metal mold and molded under pressure, or molded by isostatic 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 N ₂ gas to prevent denitrification. Furthermore, a sintered body sintered under the above conditions can be reprocessed by hot isostatic pressing (HIP) to produce a sintered body that is even denser and has higher toughness. EXAMPLES The high-hardness sintered body of the present invention will be specifically described below with reference 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 molding aid to the blended powder, a WC-based cemented carbide ball was formed in an acetone solvent. The mixture was mixed and ground in a stainless steel container. After the solvent is evaporated and dried from the obtained mixed powder, this mixed powder is 1 t/cm ² to 5 t/cm ²
Molding at a pressure of 10 ^-3 to 10 ^-2 mmHg or a non-oxidizing gas atmosphere at a temperature of 1300℃ to 1600℃ for 30 minutes.
After holding for ~90 min, this respective sintering temperature is
The cooling rate to cool down to ℃ is approximately 300℃/min,
From 800℃ again to 1300~1450℃ (100~100℃ higher than sintering temperature)
The temperature was raised to 150° C.) and maintained for 10 to 15 hours to obtain a product of the present invention. Table 1 shows the composition and sintering conditions of each sample, and Table 2 shows the properties of the sintered body of each sample. For comparison, furnace cooling (approximately 50℃/min) from sintering temperature
Comparative products 1 and 2 were obtained. These comparative products 1 and 2
The compounding composition and sintering conditions are listed in Table 1, and the properties of the sintered body are listed in Table 2.

【table】

[Table] Among the various properties shown in Table 2, 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 a pH of 3.9 to 5.0. The corrosion state of the mirror-polished surface was observed. In addition, the present invention products 1 to 9 and comparative products 1 to 2 in Table 2
When the organizational structure of the was investigated by EPMA analysis, it was found that
Inventive products 1 to 9 have solid solution compounds of two or more phases arranged regularly, whereas comparative products 1 and 2
The whole consisted of one uniform phase. Example 2 Various single compound powders and composite compound powders with an average particle size of 0.2 to 3 μm were blended at a predetermined ratio, and Example 1
A sintered body was obtained in the same manner as above. 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. When investigated by EPMA analysis, it was found that inventive products 10 to 14 in Table 4 had two or more phases of solid solution compounds arranged regularly, whereas comparative product 3 consisted of one homogeneous phase as a whole. .

【table】

[Table] Example 3 A sintered body was obtained in the same manner as in Example 1 by blending a single compound powder and a composite compound powder made of non-stoichiometric compounds 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 1, and the results are shown in Table 6. According to EPMA analysis, inventive products 15 to 21 in Table 6 have solid solution compounds of two or more phases arranged regularly, whereas comparative products 4 and 5 consist of a uniform single phase throughout. was.

【table】

[Table] In comparison with Examples 1, 2, and 3, commercially available cemented carbide and cermet were subjected to a corrosion resistance test using artificial sweat. As a result, the commercially available cemented carbide and cermet were cloudy due to corrosion of the metal bonding phase. . The mirror surfaces of the sintered bodies of sample numbers 8 and 9 of Example 1, sample number 14 of Example 2, and sample number 21 of Example 3 had a beautiful golden yellow tone. The sintered body of the present invention having a modulated structure consisting of two or more phases had significantly higher hardness, resistance, fracture toughness, and Young's modulus than the conventional sintered body of a single-phase solid solution compound. Due to these characteristics, the high hardness sintered body of the present invention can be used as a material for decorative items,
It is a material with a wide range of industrial applications, including parts for cutting tools and various wear-resistant parts.

Claims (1)

[Claims] 1 Carbide of Ti, Zr, Hf, V, Nb, Ta, Th,
A high-hardness sintered body comprising a solid solution compound composed of two or more selected from nitrides and oxides, the solid solution compound having a modulated structure structure due to spinodal decomposition or binodal decomposition. 2. The high-hardness sintered body according to claim 1, wherein the solid solution compound has a non-stoichiometric composition in which nonmetallic elements are deficient or in excess of metallic elements.