JP2968293B2 - Method for producing silicon carbide carbon composite ceramics compact - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a silicon carbide carbon composite ceramic having excellent strength, hardness, fracture toughness, friction coefficient, wear resistance and the like.

[Prior art] Ceramics have excellent heat resistance, strength, hardness, abrasion resistance and corrosion resistance compared to metals, and are weighed.
Many high-temperature structural materials have been developed and put into practical use. For example, silicon carbide, which is one of them, has many advantages such as less deterioration in strength at high temperatures, excellent corrosion resistance, excellent wear resistance, and high thermal conductivity, so it can be used for automobile engine parts, mechanical seals, bearings, For parts requiring corrosion resistance, wear resistance and high-temperature strength such as control valves,
Application to precision sliding members such as magnetic head sliders is being studied.

However, since silicon carbide has a smaller fracture toughness than silicon nitride, zirconia, etc., it has a problem in reliability when used as a structural material. Further, the silicon carbide ceramic itself has a large coefficient of friction, and when it is used for a sliding member, there is a problem that the mating material is damaged or the dimensional accuracy is lost due to expansion due to frictional heat.

As means for solving these problems, Japanese Patent Application Laid-Open No. 63-1478
No. 80, "Silicon carbide-carbon composite material"
No. 58861 proposes “silicon carbide-based material and its production method”. However, these are obtained by impregnating and firing an organic polymer compound or a thermosetting resin on porous silicon carbide, but have insufficient mechanical strength and have practical problems.

[Problems to be Solved by the Invention] An object of the present invention is to provide a ceramic having excellent strength, hardness, fracture toughness, and abrasion resistance and a small friction coefficient.

[Means for Solving the Problems] In order to achieve the above object, it has been found that a combination of carbon containing a crystalline phase and an amorphous phase at a specific ratio and silicon carbide provides an excellent effect. Was reached.

That is, the present invention provides a method of wet-mixing silicon carbide, a carbon source and a sintering aid, calcining the mixture at 400 to 800 ° C. in an inert atmosphere, and then molding, and then subjecting the mixture to an inert atmosphere or vacuum.
Firing at 00 to 2300 ° C., containing 0.2 to 50 parts by weight of carbon (b) based on 100 parts by weight of silicon carbide (a), and laser Raman spectroscopy of the crystalline phase and amorphous phase of carbon (b) The peak area ratio of intensity is 0.1 to 10.0
It is intended to provide a method for producing a silicon carbide / carbon composite ceramics molded body, characterized in that: Further, the present invention provides a sliding machine component using the same.

The silicon carbide (a) used in the present invention serves as a ceramic matrix, and may be any of α and β crystal forms. The purity is preferably 90% by weight or more, more preferably 95% by weight or more, in order to prevent a decrease in density, deterioration of strength and fracture toughness, etc., and from the viewpoint of mechanical properties such as Young's modulus. The form of silicon carbide is preferably a powder having a particle size of 5 μm or less from the viewpoint of sinterability.

The carbon (b) in the composite ceramic of the present invention is a simple substance of carbon, and is composed of a crystalline phase and an amorphous phase. Specifically, as the simple substance of carbon, amorphous carbon, graphite and the like can be mentioned. These single crystal phases have peaks in the range of 1450 to 1700 cm ^-1 centered at around 1580 cm ^{-1 by} laser Raman spectroscopy. The amorphous phase is 1300 to 14 around 1360 cm ^-1
It has a peak up to 50 cm ^-1 . Examples of the crystal structure in the above crystal phase include a graphite type planar hexagonal structure, a surface body type structure and the like. The abundance ratio of the crystalline phase and the amorphous phase in the simple substance is 0.1 to 10.0 in the above peak area.
If the abundance is out of this range, the mechanical properties (ie, strength, hardness, etc.) are inferior, and therefore, it is not preferable.

In the composition of the composite ceramic of the present invention, the carbon (b) is used in an amount of 0.2 to 0.2 parts by weight based on 100 parts by weight of the carbon silicon (a).
It is 50.0 parts by weight, preferably 0.5 to 45.0 parts by weight. If it is less than 0.2 part by weight, there is no effect of reducing the coefficient of friction, and if it is more than 50.0 parts by weight, strength, hardness and abrasion resistance are inferior.

In the method for producing a composite ceramic of the present invention, the carbon (b) may be generated from an appropriate carbon source during the production process. That is, the silicon carbide, a carbon source described below, and, if necessary, commonly used additives and the like (for example, a known sintering aid such as a boron compound) are wet-mixed and calcined. This calcining step converts the carbon source into the carbon (b). Next, after granulation molding, firing is performed to produce a composite ceramic.

The wet mixing may be performed by a ball mill, a vibration mill, a planetary mill, or the like. The solvent used is preferably an organic solvent, for example, an aromatic solvent such as benzene, toluene, or xylene, an alcohol solvent such as methanol or ethanol, or a ketone solvent such as methyl ethyl ketone.

The calcining step is performed by heat-treating the wet-mixed mixture preferably at 400 to 800 ° C. under an inert atmosphere (for example, under an atmosphere of nitrogen gas, argon gas, or the like). If the temperature is lower than 400 ° C., it is not sufficiently converted to carbon (b). If the temperature is higher than 800 ° C., free sintering of the compounded particles occurs and re-dispersion during spray drying is difficult, which is not preferable.

The carbon source is not particularly limited as long as it is soluble or dispersible in the organic solvent used for wet mixing and can be converted to carbon (b) under the calcination conditions. Specific examples of such a carbon source include a furan resin, a phenol resin, and coal tar pitch.

In the above granulation molding, granulation may be performed by spray drying or the like. The molding may be performed by a mold molding method, a CIP method, a slip casting method, or the like.

The firing step is performed under an inert atmosphere or under vacuum,
It is desirable to carry out at 00 to 2300 ° C. If the firing temperature is out of this range, the density of the sintered body is reduced, and mechanical properties such as strength and hardness are deteriorated due to growth of particles of silicon carbide (a). As a firing method, a hot press, a HIP method, or the like may be used to increase the density.

The composite ceramics obtained as described above has excellent sliding properties and excellent wear resistance, and is extremely suitable as a sliding part. The sliding component has a movable part where the mechanical element is movable, and at least in a part that is in temporary or constant contact and relatively slides, at least the sliding surface is made of the silicon carbide carbon composite ceramic of the present invention. It needs to be. Specific examples of sliding parts include bearing retainers,
A mechanical seal, a flow valve for coal slurry, a drawing die and the like can be used.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Examples 1 to 17 and Comparative Examples 1, 4 to 7) A carbon source shown in Table 1, β-silicon carbide having a particle size of 0.5 μm (purity: 98 wt%), and B ₄ C 2 wt% as a sintering aid were vibrated. Ethanol wet mixed in a mill, 600 ° C under argon atmosphere
And calcined. After granulation by spray drying, molding was performed by a die molding method, and then firing was performed for 1 hour in a firing atmosphere and a firing temperature shown in Table 1. If necessary, this was hot-pressed under the pressure shown in Table 1 to produce each ceramic.

(Comparative Examples 2 and 3) A porous silicon carbide was impregnated with a phenol resin in which ethanol was dissolved, and calcined at 600 ° C. in an argon atmosphere, and then calcined for 1 hour in a calcining atmosphere and a calcining temperature shown in Table 1. To produce ceramics (Comparative Examples 2 and 3, respectively).

Table 1 shows the composition ratio of carbon (b) relative to 100 parts by weight of silicon carbide (a) in the ceramics of each of the above Examples and Comparative Examples. Also, carbon (b) measured by Raman spectroscopy
Table 1 shows the ratio between the crystalline phase and the amorphous phase. Further, the strength, hardness, Young's modulus, fracture toughness, friction coefficient, and wear resistance of each ceramic were tested, and the results are shown in Table 1.

When Example 1 was precision machined into a rolling bearing retainer and used, it showed no lubrication and long-term durability.

When Example 2 was applied to a mechanical seal, the sealability was better and the durability for a long time was exhibited as compared with the conventional material.

When Example 7 was used as a flow valve for coal slurry, the cutoff of the slurry was performed smoothly, the sliding characteristics were good, and the wear resistance was good.

When Example 11 was precision-processed and used as a magnetic head base material, the durability was good without damaging the partner medium.

When Example 16 was used as a twist ring, it exhibited lower wear and light durability than the conventional ceramics.

[Effects of the Invention] As is clear from the examples, the silicon carbide / carbon composite ceramics obtained by the present invention has a higher fracture toughness while maintaining strength and hardness as compared with conventional silicon carbide ceramics.
The improvement of the sliding characteristics is found, and it is industrially useful as various sliding machine parts.

Continuation of the front page (56) References JP-A-61-58862 (JP, A) JP-A-60-112670 (JP, A) JP-A-61-251576 (JP, A) JP-A-63-252964 (JP) , A) JP-A-55-47273 (JP, A) Edited by the Japan Society of Carbon Materials "Carbon Materials Experimental Technology (I)" (Showa 53-6-1) Science and Technology Company, p78-83 (58) Int.Cl. ⁶ , DB name) C04B 35/565-35/577

Claims (1)

(57) [Claims] 1. A method comprising the steps of: wet mixing silicon carbide, a carbon source and a sintering aid, calcining the mixture at 400 to 800 ° C. in an inert atmosphere,
Then, after molding, under an inert atmosphere or under vacuum, 1800 ~
Firing at 2300 ° C., containing 0.2 to 50 parts by weight of carbon (b) based on 100 parts by weight of silicon carbide (a), and measuring the laser Raman spectral intensity of the crystalline phase and amorphous phase of the carbon (b) A method for producing a silicon carbide / carbon composite ceramics molded body, wherein a peak area ratio is 0.1 to 10.0.