JPS61163166A - Manufacture of silicon carbide composite sintered body - 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 This invention relates to a method for producing a silicon carbide sintered body, and in particular to a silicon carbide composite in which voids are filled with silicon (Si) and secondarily produced silicon carbide. The present invention relates to a method for manufacturing a sintered body.

BACKGROUND OF THE INVENTION Silicon carbide has excellent heat resistance and high hardness, so it is expected to be used as a high-temperature structural material for engine parts, turbine parts, and the like. In order to manufacture various parts using silicon carbide as a raw material, as is well known, the powder is molded into the desired shape using compression molding, injection molding, etc., and then sintered. It is necessary to give strength.

By the way, mechanical parts such as turbine engine parts have complex shapes, require high high-temperature strength, and also require good dimensions of 11 degrees, but various molding methods are being researched and developed. Nowadays, it has become possible to mold fairly complex shapes relatively easily.

On the other hand, conventionally known sintering methods for imparting strength include normal pressure sintering, pressure sintering, and reaction sintering. When manufacturing parts, these sintering methods have advantages and disadvantages, and it is not always possible to obtain a satisfactory sintered body.

The problem that the invention aims to solve is that mechanical parts such as turbine engine parts have complex shapes, so when they are made from silicon carbide, it is recommended to use the pressureless sintering method as the sintering method. considered preferable. However, although the pressureless sintering method can be easily applied to products with complex shapes, and the strength of the sintered body can be increased by adding auxiliary agents such as carbon and boron, the shrinkage due to firing is large, so the size This method has the disadvantage of poor accuracy, and furthermore, because the strength of the sintered body is high, processing for correcting dimensions is extremely difficult.

On the other hand, a reaction sintering method is known as a sintering method that causes small dimensional changes (shrinkage). In the reactive sintering method using silicon carbide as a raw material, after forming a mixture of SiC powder and carbon (C), molten Si or 3i gas is infiltrated into the compact and heated to raise the temperature. This method generates SiC and fills the voids with the remaining Si, but this method allows for good dimensional accuracy because the dimensional change is very small, but it does not have the problem of insufficient strength. There is.

In view of the above circumstances, it is an object of the present invention to provide a method by which a silicon carbide composite sintered body with good dimensional accuracy and high strength can be obtained.

Means for Solving the Problems In order to achieve the above object, the present invention is characterized in that pressureless sintering, machining, and reaction sintering are sequentially performed. More specifically, by subjecting a silicon carbide powder compact to pressureless sintering, a porous primary sintered body in which most of the pores are open is created, and the primary sintered body is machined by grinding, etc. The desired shape and dimensions are achieved through processing, and then carbon content is infiltrated into the pores of the primary sintered body.
This method is characterized in that the carbon content is then silicified by reaction sintering.

DETAILED DESCRIPTION OF THE INVENTION As mentioned above, the present invention is a method for obtaining a sintered silicon carbide body, and since silicon carbide is difficult to sinter, a suitable auxiliary agent (for example, boron and carbon) is added. Form into a predetermined shape. As the molding method, various conventionally known methods such as compression molding and injection molding can be employed depending on the shape to be obtained.

In addition, pressureless sintering is performed at a sintering temperature of 2000°C or higher (α-8i
This is carried out by heating to about 2100° C. for C and about 2200° C. for β-8iC, and setting the atmosphere at that time to a flow of a rare gas such as Ar gas or He gas at 1 atm.

The steps of forming and pressureless sintering up to this point are to obtain a primary sintered body with an open pore structure in which silicon carbide particles are intertwined. Other conditions may be determined as appropriate to meet the purpose.

Since the molded body shrinks due to pressureless sintering, the dimensions of the primary sintered body are irregular, and therefore, this is processed to obtain the desired product dimensions. In this case, since the primary aggregate is porous with the same pore structure, it can be easily ground with a device (tool) such as a normal surface grinder or cylindrical grinder using a diamond grindstone.

Reactive sintering is sintering in which carbon contained in a SiC molded body or sintered body reacts with molten metal Si or gas 5i to secondarily generate SIC. Since the reaction sintering is performed on the carbon, carbon can be supplied, for example, in the same way.

In other words, carbon such as carbon black is slurried using a liquid dispersion medium, the primary sintered body is covered with the slurry under reduced pressure, and the slurry is then turned into a pressurized state to be slurried into the pores. Just let it penetrate. When such a method is adopted, it is preferable to remove the dispersion medium before performing reaction sintering. Furthermore, when carbon is infiltrated into the pores in the form of a compound, it is preferable to carbonize the material prior to reaction and sintering. The carbon infiltrated into the pores in this way is silicified. This operation is carried out by heating the primary sintered body to a predetermined temperature in a heating furnace and bringing Si into contact with carbon in the pores. The Si content is molten metal S1 or gas S
i can be used, and such reactive sintering can be carried out by conventional methods.

Example Examples of this invention will be described below.

Molding: Commercially available β-8iC powder (manufactured by Showa Denko K.K., product name: B
1 wt % of carbon black and 1 wt % of amorphous boron were added as auxiliaries to -1) and compression molded at a pressure of 1.5 tons/crl to create a 5 x 5 x 50 (IIll) shaped product. Its bulk density is 1.75! J/C
It was ll13.

Primary sintering: The above-mentioned formed body is sintered in an argon (Ar > air flow).
It was heated to 200'C and fired for 30 minutes to obtain a primary sintered body. When the primary sintered body was examined, it was found that it had a structure in which plate-like particles were entangled and most of the pores were open, and the bulk density was 2.56 (J/C Shin 3).

Processing: The above primary sintered body was subjected to surface grinding using a diamond grindstone to obtain a shape of 3×4×45 (mm). No particular abnormality occurred during processing, and processing was easy.

Supply of carbon content: A slurry in which 40% by volume of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd., trade name: Dia Black E) is dispersed in ethyl alcohol is prepared in advance, and the primary sintered body is The primary sintered body was placed in an evacuated container, and slurry was dropped in that state to cover the primary sintered body with the slurry. Then, a pressure of 4 atmospheres was applied with compressed air to infiltrate the slurry into the pores. Thereafter, the dispersion medium, ethyl alcohol, was removed by taking it out from the container and heating and drying it. By performing the above operation once or several times, carbon black was sufficiently penetrated into the pores.

Reaction sintering: The primary sintered body containing carbon black was heated to 1450
The carbon in the pores was silicified by contacting with molten metal S1 in a vacuum furnace at .degree.

When the sintered body obtained by the above-mentioned series of operations was rubbed, it was found that the secondarily generated SiC and the infiltrated 3i
The voids were filled in, resulting in a dense structure. Further, when the unreacted metallic silicon adhering to the surface was removed by grinding and the dimensions were measured, no dimensional shrinkage was observed during reaction sintering to silicify the carbon content. The bulk density of the silicon carbide composite sintered body obtained as roughly described above is 3.
18! J/cm3, and its bending strength is 61k on average.
(Shows high strength at 1/i, and has a Weibull coefficient of 15.
8, which was much larger and more homogeneous than the generally known dense silicon carbide sintered bodies 6 to 8.

Effects of the Invention As is clear from the above explanation, according to the present invention, a sintered body to be a product is obtained by processing a primary sintered body to adjust its dimensions and then subjecting it to reaction sintering. A sintered body with good dimensional accuracy and high strength can be obtained. In addition, in this invention, processing to adjust the dimensions is performed on the porous primary sintered body, and after reaction sintering, it is only necessary to remove the excess 3i attached to the surface, so grinding etc. Machining is extremely easy, and since pressureless sintering, which is primary sintering, does not require obtaining a sintered body with a dense W1, its operation and management are easy.

Furthermore, in this invention, the primary sintered body obtained by pressureless sintering contains coarse pores, but since the pores are filled in the reaction sintering process, not only can the strength be increased,
It is possible to reduce variations in characteristics and improve reliability. Further, in this invention, since the total additive color of carbon and boron can be reduced, oxidation resistance can be improved.

Applicant: Toyota Motor Corporation Agent: Patent Attorney Yutaka 1) Hisashi Take (1 idiot)

Claims (1)

[Claims] A porous primary sintered body with an open pore structure is created by applying pressureless sintering to a silicon carbide powder compact molded into a predetermined shape, and after machining the primary sintered body into a predetermined shape,
A method for producing a silicon carbide composite sintered body, which comprises infiltrating carbon into the pores and then silicifying the carbon by reaction sintering.