JPS63147880A - Silicon carbide-carbon composite material - 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 (Field of Industrial Application) The present invention relates to a silicon carbide composite material that is particularly useful as a sealed sliding part such as a mechanical seal.

(Conventional technology and its problems) Among the many ceramics developed in recent years, pressureless sintered silicon carbide has excellent wear resistance and corrosion resistance, so it is suitable for sealing and sliding applications such as mechanical seals. Applications have been actively developed in the parts field as well.

As a method for manufacturing a silicon carbide sintered body, for example, JP-A-50
There are methods described in JP-A-78609, JP-A-51-148712, and the like. However, when the dense silicon carbide sintered body obtained by the above manufacturing method is used as a sliding part, the coefficient of friction becomes high under conditions of insufficient lubrication, causing severe wear of the sliding partner material, and the silicon carbide sintered body The structure itself also had the disadvantage of being prone to cracking.

As a method to improve this drawback, Japanese Patent Application Laid-Open No. 61-58136
In Publication No. 1, silicon carbide powder containing a sintering aid is sintered at a relatively low temperature to obtain a porous sintered body of silicon carbide (hereinafter referred to as a porous body), which is impregnated with a thermosetting resin. A method for obtaining a sliding material is described. If the sliding material obtained by the above method has a porous material density of 2.4 g/d or less, its strength, durability, and abrasion resistance are insufficient even after resin impregnation. I am using it. However, in that case, since the resin content was as low as 7% by weight, the lubricating effect of the impregnated resin was also insufficient.

Furthermore, in Japanese Patent Application Laid-Open No. 59-131577, the coefficient of friction is reduced by forming a free carbon phase in a sintered body and exposing carbon particles on the surface. However, addition of excessive Yuryu carbon with large particle size hinders sintering, making it difficult to obtain a homogeneous sintered body with high wear resistance.

(Objective of the Invention) An object of the present invention is to solve the above-mentioned drawbacks and to provide a sliding member that has good wear resistance due to the sufficient lubricating action of carbon contained therein.

(Technical means for solving the problem) The present invention provides a porous body in which silicon carbide powder is bonded by inorganic substances mainly composed of Si and C, which is produced by thermal decomposition of an organic silicon compound, and can be converted into carbon by heating. The present invention relates to a silicon carbide-carbon composite material impregnated with an organic polymer compound and carbonized.

In the present invention, the silicon carbide powder may be either α or β, and there are no special restrictions on purity or particle size.
In order to maintain the strength of the porous body, it is desirable to use submicron powder.

For organic silicon compounds, under an inert gas atmosphere.

The material used is one that can be converted into an inorganic material mainly consisting of Si and C by heat treatment at 1000° C. or higher. Particularly preferred are organosilicon polycondensates whose main skeleton components are bonds between silicon and carbon. For example, JP-A-51-126300
No. 52-112700, Japanese Patent Application Laid-Open No. 1972-112700
Polymeric organosilicon compounds mainly consisting of a carbosilane skeleton described in Japanese Patent Laid-Open No. 57-16029 and Japanese Patent Application Laid-Open No. 57-16029 are suitable for use in the present invention.

The organic polymer compound is not particularly limited as long as it can be converted into carbon by heating, but from the viewpoint of economy and high carbonization rate, thermosetting resins such as phenolic, furan, and epoxy resins, Alternatively, pitch and tar are suitable.

The silicon carbide-carbon composite material of the present invention can be obtained by the following manufacturing method.

First, an organic silicon compound is mixed with silicon carbide powder as a binder. The silicon carbide powder and the organic silicon compound are mixed using a pressure kneader, etc. At this time, in order to improve moldability,
For example, higher fatty acids may be added as a lubricant.

Next, the obtained mixture is molded into a desired shape by extrusion molding or the like, and this is fired to obtain a porous body.

Firing temperature is 1200~2200″C1-especially 1600~
2200°C is desirable. If the temperature is too low, the strength of the porous body will be insufficient.

The porous body in the present invention is a porous body in which silicon carbide powder is bonded by an inorganic substance mainly composed of Si and C produced by thermal decomposition of an organic silicon compound without using a sintering aid, and therefore has a 1.8 to 2 Although it has a low density of .4 g/cj, it has a high strength of 25 to 35 kg/-.

Next, the porous body is impregnated with an organic polymer compound.

Impregnation of the porous body with the organic polymer compound is carried out by a conventional method, for example, by immersing the porous body in the organic polymer compound under vacuum. Alternatively, by pressurizing the organic polymer using a hydrostatic press or the like, the M of the pores can be reduced! Part A can be sufficiently impregnated with the organic polymer compound.

Next, the porous body impregnated with the organic polymer compound is heated at 700 to 2200°C in an inert atmosphere and carbonized, thereby obtaining a silicon carbide-carbon composite material with excellent wear resistance. Furthermore, by repeating the impregnation-carbonization operation, a silicon carbide-carbon composite material in which the porous body sufficiently contains carbon can be obtained.

(Example) Hereinafter, the present invention will be explained in Examples.

Example 1 81 parts by weight of silicon carbide powder having an average particle size of 0.3 μm, 10 parts by weight of polytitanocarbosilane, and 9 parts by weight of stearic acid were mixed for 90 minutes using a pressure kneader. After pulverizing the obtained mixture, a pipe-shaped molded product was obtained by extrusion molding. The temperature of this molded body was gradually raised to 550°C, and after degreasing the stearic acid, one piece was fired at 50°C, and the outer diameter was 44nm.
A sintered body of m+ and an inner diameter of 30 (goods) was obtained. This sintered body is a porous body with a density of 2.05 g/- and a bending strength of 34.1
'sg/-. This sintered body was cut to a thickness of 10 mm to obtain a porous ring.

This porous ring was impregnated with a resol type phenolic resin and then heated to 800° C. in a nitrogen atmosphere to carbonize it. This impregnation-carbonization process was repeated three times, resulting in a density of 273 g.
/ oa composite ring was obtained.

A sliding test was conducted on the obtained composite ring in hot water at 100° C. using phenol resin-impregnated carbon as a mating material. Test conditions are hydraulic pressure 7 kg/cA, rotation speed 5
000 r p rn, 200 hours. The amount of wear was 1 μm on the composite material DIjJO and 0.2 μm on the mating material side.

Comparative Example 1 A mixture consisting of 1.5 parts by weight of boron carbide powder as a sintering aid, 5.6 parts by weight of resol type phenolic resin, 1 part by weight of stearic acid, and the balance consisting of silicon carbide powder was mixed in ethanol using a wet ball mill. Ethanol was distilled off and the mixture was ground. The obtained powder is 1. Oton /(,H
After hydrostatic pressing at a pressure of 1,850° C., the sintered body was fired at 1850° C. in a vacuum to obtain a sintered body having an outer diameter of 44 mm, an inner diameter of 3 Om, and a thickness of 10 ffD11. The density of this porous body is: 175 g/ca,
The bending strength was 15.0 kg/-. When this porous body was impregnated with phenolic resin and cured in the same manner as in Example 1, the density was 2.93 g/aa and the resin content was 6.3.
%Met. As a result of a sliding test conducted under the same conditions as in Example 1, the amount of wear was found to be
．． 2 μm.

Comparative Example 2 To crushed powder having the same composition as Comparative Example 1, 5 parts by weight of carbon powder with an average particle size of 15 μm was added, mixed in a wet ball mill, dried, and crushed to obtain crushed powder with excess carbon.

After the obtained powder was hydrostatically pressed at a pressure of 1.0 tOn/-, the compact was sintered at 2100°C in a vacuum. The obtained sintered body had a density of 188 g/cj and a bending strength of 20. .5
kg/-, and the density was low. As a result of performing a sliding test under the same conditions as in Example], the amount of wear on the sintered body side was 0.3μ
m, and the counterpart material side was 1.0 μm.

(Effects of the Invention) The silicon carbide-carbon composite material according to the present invention is composed of silicon carbide and impregnated carbon, and due to the lubricating action of the latter, it exhibits a much lower coefficient of friction than silicon carbide alone. The silicon carbide-carbon composite material has sufficient strength and hardness, and therefore the silicon carbide-organic polymer composite material of the present invention is an excellent sliding member that has both lubricity and wear resistance. . Furthermore, when manufacturing a silicon carbide porous body, there is almost no shrinkage, which is advantageous in manufacturing sliding members with high dimensional accuracy.

Claims (2)

[Claims] (1) A porous sintered body of silicon carbide in which silicon carbide powder is bonded by an inorganic substance mainly composed of Si and C, which is produced by thermal decomposition of an organic silicon compound, is impregnated with an organic polymer compound that can be converted into carbon by heating. , a silicon carbide-carbon composite material made by carbonization. (2) The density of the silicon carbide porous sintered body is 1.8 to 2.4 g
/cm^3 The silicon carbide-carbon composite material according to claim 1.