JPS6035316B2 - SiC-Si↓3N↓4-based sintered composite ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel SIC-Si3N4-based competitive composite ceramic material, and more specifically, the present invention relates to a novel SIC-Si3N4-based competitive composite ceramic material, and more specifically, a Si3 material containing dispersed fibrous SIC and having high electrical conductivity and capable of electrical discharge machining.
Regarding the N4 fastener.

Silicon nitride ceramics, whose main component is Si3N4, have excellent strength, oxidation resistance, abrasion resistance, thermal shock resistance, etc., so they are used as heat-resistant parts for gas turbines, materials for heat exchangers, etc. Because of its excellent properties, it is attracting attention as a material for various types of die-casting holes, nozzles, etc.

Generally, in order to obtain high-strength, high-density Si3N4 ceramics, it is preferable to use a hot pressing method, the so-called hot press method. However, in this method, the Si3N4 material is pressurized in a mold with a relatively simple shape, so it is difficult to mold and manufacture parts with complex shapes, such as mechanical gears and gas turbine impellers. This point is a major technical limitation of the hot press method. Therefore, in order to effectively utilize the various excellent properties of Si3N4 ceramics and widely use them as various structural materials in place of conventional metal materials, it is necessary to form them into desired shapes like metal materials. It is necessary to develop technology and/or new materials that can be processed with high precision. For example, manufacturing gas turbine impellers requires not only simple cutting but also three-dimensional processing. When manufacturing metal materials such as gas turbine impellers and molds with complex shapes, it is possible to process curved surfaces with high precision using electric discharge machining, but conventional Si3N4 ceramics with low electrical conductivity cannot be It was impossible to carry out any processing. Si3N4
Attempts have also been made to make electrical discharge machining possible by adding second component powder or particles such as highly electrically conductive silicon carbide or titanium carbide to the Si3N4 sintered material to improve the electrical conductivity of the entire Si3N4 sintered material. ing. However, in order to reduce the resistivity of the Si3N4 material to the extent that electrical discharge machining is possible, it is necessary to add and mix powder or particles of silicon carbide, titanium carbide, etc. in an amount of 30% or more of the weight of S;3N4. be. In this case, even if electric discharge machining of the Si3N4 material becomes possible, the excellent properties originally inherent in the Si-4 condensed material are often impaired, and in particular, there is a major drawback in that the high-temperature strength is significantly reduced. As a result of various researches aimed at solving or reducing the processing problems of known Si3N4-based materials, the present inventors discovered that a specific amount of fibrous SIC crystals (usually called whiskers or whiskers) were found in Si3N4. It has been found that a sintered composite material containing dispersed carbonaceous materials (containing 100% carbon dioxide) satisfies these requirements.

That is, in the present invention, 5 to 50% of the weight of Si3N4 is contained in Si3N4.
5% by weight, length 10-500m, thickness 0.5m.
Contains dispersed fibrous SIC crystals with a size of 1 to 10 degrees, and has an IQ-
The present invention relates to Si3N4-based composite ceramics characterized by having a resistivity of less than or equal to . In the present invention, fibrous SI having a length of 10 to 500 m and a thickness of 0.1 to 10 m
Requires use of C crystal. If the length is less than 10 m, the same result as when molding with granular SIC is produced, and it is difficult to obtain the high temperature characteristics inherent to Si3N4. On the other hand, if the length exceeds 500 mm, they will become entangled with each other during molding, hindering the molding operation, and making it difficult to produce a compact molded product. Furthermore, if the thickness of the fibrous SIC is less than 0.1 mm, the fibers will break during molding, resulting in the same result as when using granular SIC. Also, if the thickness exceeds 10 m, a large amount of SIC is required to provide sufficient electrical conductivity.
This creates the need to add 20% of Si3N4, changing the properties of Si3N4.
The amount of fibrous SIC crystals relative to Si3N4 is
5 to 50 parts by weight of the latter. If the amount of SIC is less than 5% of the weight of S-3N4, the electrical conductivity of the Akatsuki compact will not be sufficiently improved, while if it exceeds 50%, the electrical discharge machinability of the compact will be further improved. However, the density tends to decrease later. The amount of fibrous SIC crystal added is
More preferably, the content is 10 to 40% of the weight of 3N4.
The SIC-Si3N4-based sintered composite ceramic of the present invention is manufactured as follows.

'i' Add and mix a predetermined amount of fibrous SIC crystals to Si3N4 powder with a particle size of about 0.1 to 5〃m, and after uniformly dispersing it, add a binder of about 0.1 to 2% of the weight of the mixture. In addition, after shaping and drying, it is sintered to form the desired composite ceramic.

As the binder, preferably used is a solution of polyvinyl alcohol, acrylic resin, cellulose, sodium alginate, etc. in water, alcohol, or other organic solvent. S
A paste consisting of i3N4, SIC, and a binder is molded into a predetermined shape by injection molding, extrusion molding, etc., and the obtained molded product is pre-dried under heat or reduced pressure, and then dried at 60°C.
The binder is removed by heating to below 0.000C. Next, the dried molded body is heated for 1,600 to 185,000 with or without pressure.
Sinter at a temperature of about 'ii' or particle size 1-1
A uniform base obtained by adding fibrous SIC crystals to silicon powder of about 0 French m and adding a binding agent in the same manner as above is formed into a predetermined shape by cold pressing, etc., dried, and heated with nitrogen. It is fired in an atmosphere at a temperature of about 1,200 to 140,000 to convert silicon into silicon nitride.

In this method, silicon powder is mixed into fibrous SIC so that the ratio of Si3N4 and SIC in late consolidation is within a predetermined range.
Mix the crystals in advance. In addition, the above {i] and (ii)
} In either case, Mg○, A203 as necessary.
, Zr02 and oxides such as lanthanide coordinations such as Y203 and I203, and nitrides such as ASON and BeN2.

The SIC-Sj3N4-based composite ceramics of the present invention has high electrical conductivity, and therefore has excellent electrical discharge machinability. When SIC is used as powder or particles, each particle component is surrounded by non-conductive Si3N4 components and tends to become isolated, so a large amount must be used in order to sufficiently increase electrical conductivity. As mentioned above, the characteristics of the dawn concretion are reduced. However, in the present invention, since the fibrous SIC crystal also functions as a reinforcing material for the Si3N4 sintered body, the Si3N
, it also has the effect of improving the mechanical properties of the sintered body. Such a SIC-Si3N4-based Akatsuki body of the present invention is
This makes it possible to manufacture complex-shaped mechanical parts that are used at high temperatures, and also makes it possible to efficiently manufacture large quantities of small parts from large sintered silk bodies. Example 1Si3
10 parts by weight of N4 powder (0.5-2mm), 5 parts by weight of Mg0 as a coagulation aid, and well-dispersed SIC whiskers (thickness 0.1-5mm, length 50-500mm) 5 parts by weight and 2 parts by weight of polyvinyl alcohol as a binder were added and thoroughly mixed to form a paste.

The obtained paste is formed into a thin plate shape by vacuum filtration method,
After drying at 13,030 for one hour, the material was brined at 180,000 under the pressure of a 300k9/c fin to obtain a sintered body with a relative density of 100%. Table 1 shows the specific resistance, room temperature strength, high temperature strength (1300°C), and hardness of the obtained composite. It is clear that the electrical conductivity of the sintered body of the present invention is high enough to allow electrical discharge machining, and it also has excellent mechanical properties, especially at high temperatures.

Example 2 An Akatsuki compact was obtained in the same manner as in Example 1, except that the amount of SIC whiskers relative to Si3N4 was changed to 4 parts by weight.

The physical properties of the obtained bran aggregates are also shown in Table 1. Comparative example
A sintered body was obtained in the same manner as in Example 1 except that 1SIC whiskers were not used.

The physical properties of the composite are shown in Table 1. Table 1

Claims (1)

[Claims] 1 Si_3N_4 contains 5 to 50% of the weight of Si_3N_4
Length 10-500 μm, thickness 0.1-10 within the range of %
SiC-Si_3N characterized by containing μm fibrous SiC crystals dispersed therein and having a specific resistance of 1Ω-cm or less
_4 series sintered composite ceramics.