JPS6158861A - Silicon carbide material and manufacture - 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] Industrial Application Field The present invention is applicable to mechanical seals, plain bearings, etc. The present invention relates to a silicon carbide material particularly useful as a sealing sliding component and a method for producing the same.

Conventional technology In recent years, many ceramics have been developed and put into practical use as high-temperature structural materials. One of them, silicon carbide, has high strength at high temperatures and little strength deterioration, and is resistant to thermal shock. It has many advantages such as being strong against water, having excellent abrasion resistance, being lightweight, and having excellent corrosion resistance.In terms of manufacturing technology, the invention of the pressureless sintering method has made it easy to produce high quality products. Now that it has become possible to manufacture various products, development is progressing in a wide range of applications, including gas turbine parts, automobile engine parts, mechanical seals, and various bearings.

In the above-mentioned pressureless molding method, as disclosed in 1. Y Kaimei No. 50-78609, Japanese Patent Kokai No. 51-148712, etc., a sintering aid is added to submicron silicon carbide fine powder. , boron and/or aluminum
0.2 to 2% carbon, aluminum and/or their compounds when calculated as moxibustion, and 0.2 to 4% when calculated as carbon.
% of carbon and/or carbonizable rock material, both in the form of submicron fine powder, is molded into a powder with a density of 3.0 or more without pressure. This is a method of sintering into a high-density sintered body.

Problems to be Solved by the Invention The above-mentioned conventional methods for producing silicon carbide materials are intended for producing structural materials that place particular importance on strength, heat resistance, and oxidation resistance at high temperatures, and to this extent, they are not sufficient. It is excellent. However, when silicon carbide materials manufactured using this method are used as sliding parts such as mechanical seals or plain bearings, under conditions of insufficient lubrication, the coefficient of friction becomes extremely high, causing the sliding material to wear out quickly. It has the disadvantage that it is easily damaged and the main body itself is prone to wear and cracks.

JP-A-59-131577 discloses that a large free carbon phase is formed in a sintered body so that the i8 plane of the carbon phase with a diameter of 5 or more occupies 1.5 to 45% of the entire surface of the sintered body. A method for obtaining a silicon carbide material with a low coefficient of friction by .

As a result of various studies to solve the problem, we created a sintered body with low density (and therefore high porosity) by keeping the sintering temperature low in the above-mentioned pressureless sintering method. It has been found that a thermosetting synthetic 4A (low Y friction material can be obtained when impregnated with fat and cured).

The present invention is based on the above findings and consists of two inventions. The second aspect of the present invention is the invention of the silicon carbide material according to the first aspect of the present invention.
Method 1: A total amount of 0.2 to 2% by weight of one or more substances consisting of boron or aluminum alone or as a compound (however, in the case of compounds, the value converted to boron or aluminum), Sinterable powder consisting essentially of 0.2 to 4% by weight of submicron powder made of carbon or carbonizable organic material (however, in the case of carbonizable organic material, the value converted to carbon) and submicron powder of silicon carbide The mixture is molded, and the resulting molded product has a density of 2.4 to 2.8.
It is characterized in that it is heated and sintered in a non-oxidizing atmosphere until a 67 cm" sintered book is shaped, and the resulting sintered body is impregnated with a thermosetting synthetic resin and hardened.

The silicon carbide material according to the present invention is composed of two phases, a silicon carbide phase and a thermosetting synthetic resin phase, based on the above composition, and when used as a sliding material, it appears on the surface of the sliding part. The thermosetting synthetic resin part has a lubricating effect similar to that of an oil pot.

Next, a method for producing the silicon carbide material according to the second aspect of the present invention will be explained.

The submicron powders of silicon carbide used as a raw material, sintering aids such as boron (or its compounds), aluminum (or its compounds), carbon, and carbonizable organic materials are those used in conventional manufacturing methods. You can use the same one; nothing special is needed.

Boron and aluminum may be used in the form of a single substance or in the form of a compound, and boron and aluminum may be used either alone or in combination. Specific examples of suitable boron compounds and aluminum compounds Examples include boron carbide, boron nitride, boron phosphide, aluminum boride, and aluminum oxide.

The carbonizable organic material is preferably one that dissolves in various solvents and decomposes at high temperatures to produce carbon, with a high carbon yield. Specific examples thereof include phenol resin, 7-run resin, polyphenylene resin, There is also coal tar pitch.

The preferred blending ratio of the above sintering raw materials is as follows.

(2) 0.2 to 2% by weight of submicron powder consisting of boron or aluminum alone or as a compound (however, in the case of a compound, the value is converted to boron or aluminum). 2
If more than one species is used together, the total amount should be within the above range.

(2) Submicron powder made of carbon or carbonizable organic material: 0.2 to 4% by weight (however, in the case of carbonizable materials, the carbon equivalent value).

(2) Submicron silicon carbide powder is the remainder of the above components.

In addition to the above-mentioned sintering raw materials, in order to facilitate molding and give the molded body before sintering the strength necessary for handling, baingu, side light stearic acid, polyvinyl alcohol, and
- resin, acrylic resin, etc. can be used.

Each of the above raw materials (1) to (2) is mixed uniformly using a ball mill or the like, and then pine goo for molding is added, mixed, and molded into a desired shape. The molding can be carried out by various molding methods depending on the molded shape, such as press molding or rubber press at room temperature, hot extrusion molding or injection molding by adding a rather large amount of molding pine goo.

The compact is sintered in a vacuum or in a non-oxidizing atmosphere such as argon gas. The sintering temperature is about 1700~
2000°C is suitable. The sintering process is performed so that the density of the sintered book is approximately 2.4 to 2.8 H/am (the theoretical density is approximately 75
90%), but the sintering time required for this varies depending on the composition of the sintering materials, molding conditions, sintering temperature, etc., and must be confirmed through experiments. The density of the sintered body affects the amount of resin impregnated in the next thermosetting synthesis rig and resin impregnation process, and if the density is higher than 2.8 Fi7cm, there will be almost no pores and it will be possible to sufficiently impregnate 1J4 fat. On the other hand, the density is 2.4 g/
When less than c11+', the sintered body is too porous;
Even if impregnated with 434 fat, the product will have poor strength and wear resistance.

The sintered body obtained by cooling after sintering has a relatively low density as described above, so it has fine communicating holes.

This sintered body having pores is immersed in a thermosetting resin to fill the pores with the resin, and then heated to a temperature at which the resin hardens to harden the resin. Materials are obtained. Note that if all the pores of a sintered body having a density within the above range can be filled with resin, the amount of resin in the product will be about 9 to 17% by weight. In reality, it is difficult to fill all the pores with resin, and the amount of impregnation is often not close to the above-mentioned amount, but there is no problem.

Effects of the Invention As mentioned above, the silicon carbide material according to the present invention is composed of two phases: a silicon carbide material and an appropriate amount of thermosetting synthetic 141 fat phase, and since the latter has a lubricating effect, it is made of only a silicon carbide material. It exhibits a much lower coefficient of friction than conventional silicon carbide materials. On the other hand, does the silicon carbide material that occupies most of the surface have excellent wear resistance that is sufficient for practical use in many applications?1 The silicon carbide material of the present invention has both lubricity and wear resistance. However, it is an extremely excellent material for sliding parts. According to the manufacturing method of the present invention, the silicon carbide material having this preferable characteristic is subjected to high-density sintering by directly utilizing the conventional pressureless sintering method for manufacturing silicon carbide material. It is not necessary to make a body, but it can be manufactured easily.

The present invention will now be described with reference to Examples and Comparative Examples. Note that the values of carbonizable organic materials on each side are carbon equivalent values.

Example: 1.5% by weight of boron carbide fine powder with an average particle size of 0.4u...
A raw material mixture consisting of 5.6% by weight of novolac type phenolic resin, 1% by weight of stearic acid, and the remainder silicon carbide powder with an average particle size of 0.3 IJm was mixed in a wet ball mill using acetone as a dispersion medium, then dried and pulverized. did. The obtained powder had an inner diameter of 43 I at a pressure of 1.0 Lon/am”.
It was molded into a ring with Il+nX outer diameter of 65.5+om and thickness of 10IIIal, and was sintered by heating to 18SO'C in vacuum. The obtained sintered body has a density of 2.68 H/cu+
', it was porous.

This was impregnated with furan resin and then heated to harden the resin, yielding a silicon carbide material with a density of 2.88 g7 cm'' and a resin content of 7% by weight.

Comparative Example A molded body obtained from the same raw materials and the same molding method as in the example was sintered at 2100°C in a vacuum, and the density was 3.
A dense sintered body of 15 g 7 cm" was obtained (no resin impregnation was carried out).

A sliding test in hot water of 100'C was conducted on the sintered bodies from each side. The test conditions were a hydraulic pressure of 7 kg.
/am2・G, rotation speed 3600 rpm%PV value (surface pressure ×
Circumferential speed) 54.6Kg/cm”-m/sec.

The test was opened at 100 o'clock, and carbon impregnated with phenol resin was used as the mating material. The test results are shown in Table 1.

Table 1 Sample wear amount　　Mating material wear amount

Claims (3)

[Claims] (1) A silicon carbide material formed by filling the micropores of a low-density sintered body mainly made of silicon carbide with a thermosetting synthetic resin. (2) A total amount of 0.2 to 2% by weight of one or more substances consisting of a simple substance or a compound of boron or aluminum (however, in the case of a compound, the value converted to boron or aluminum), from carbon or a carbonizable organic material A sinterable powder mixture consisting essentially of 0.2 to 4% by weight of submicron powder (in the case of a carbonizable organic material, calculated as carbon) and submicron powder of silicon carbide is molded. The molded product is heated and sintered in a non-oxidizing atmosphere until a sintered body with a density of 2.4 to 2.8 g/cm^3 is formed,
A method for producing a silicon carbide material, which comprises impregnating the obtained sintered body with a thermosetting synthetic resin and curing it. (3) The silicon carbide material according to claim 1, in which silicon carbide accounts for 78 to 90% by weight of the total weight.