KR100419059B1 - Fabrication method of SiC-Al2O3/Al composites - Google Patents

Abstract

The present invention relates to a method for producing a silicon carbide-alumina / aluminum composite, wherein 60 to 90% by weight of fused silica powder and 10 to 40% by weight of silicon carbide powder are mixed to produce a molded body, and then sintering the manufactured molded body. When the sintered molded body is reacted with the molten aluminum at 750 to 1,100 ° C., a silicon carbide-alumina / aluminum composite having excellent strength and fracture toughness can be easily manufactured.

Description

Fabrication method of SiC-Al2O3 / Al composites}

[TECHNICAL FIELD OF THE INVENTION]

The present invention relates to a method for producing a silicon carbide-alumina / aluminum composite, and more particularly, as a material resistant to fracture, it may be used where a wear resistant member, a structural member, or a mechanical impact is strongly applied. It relates to a method for producing a silicon carbide-alumina / aluminum composite having enhanced phosphorus fracture toughness.

[Private Technology]

Conventionally, a method of manufacturing a ceramic / metal composite is obtained by mixing a ceramic (SiC, Al ₂ O ₃ ) powder or whisker with a metal powder and heat-treating in an inert atmosphere, or obtaining a composite by forming a porous ceramic molded body and then melting the metal into the molded body. Was physically penetrated to prepare a composite. However, the method is difficult to secure the homogeneity of the composite, there was also a problem that a lot of difficulties in the manufacturing process.

Also, in the production of ceramic / metal composites, a method of obtaining a composite by directly reacting a molten metal with a gas phase and a method of obtaining a composite by a reaction between a ceramic molded body and a molten metal (molten metal substitution reaction method) have been studied. In the former method, it is difficult to control the shape or microstructure of the composite. In the latter method, the silica molded body and the molten aluminum are chemically reacted as shown in Scheme 1 below to obtain a composite relatively easily. Although there is an advantage of obtaining a complex close to, there was a complicated manufacturing process. Silica glass, mullite, or kaolin group minerals, etc. are used as the ceramic formed body used in the preparation of the composite by the substitution reaction of the molten metal.

Scheme 1

3SiO ₂ + 4Al → 2Al ₂ O ₃ + 3Si

In addition, a method of manufacturing a silicon carbide / aluminum composite by physically injecting molten aluminum into the porous silicon carbide sintered body when a high wear resistance silicon carbide is mixed with an aluminum metal has been used, but the manufacturing method has a complicated problem.

In order to solve the above problems of the prior art, the present invention provides a silicon carbide-silica-based molded body using silicon carbide powder and molten silica powder as starting materials instead of silica glass or silica sintered body, which is a molded product used for the substitution reaction of molten metal. It is an object of the present invention to provide a method for producing a silicon carbide-alumina / aluminum composite having excellent strength and fracture toughness by subjecting a resultant silicon carbide-silica-based molded article to molten aluminum.

Figure 1 shows the shape of the silicon carbide-alumina / aluminum composite prepared according to the present invention.

In order to achieve the above object, the present invention provides a molded article manufacturing step of producing a molded body by mixing 60 to 90% by weight of fused silica powder and 10 to 40% by weight of silicon carbide powder, a sintering step of sintering the manufactured molded article and the sintered molded body It provides a method for producing a silicon carbide-alumina / aluminum composite comprising a reaction step of reacting with the molten aluminum at 750 to 1,100 ℃.

Hereinafter, the present invention will be described in detail.

As the silica powder used in the present invention, it is preferable to use amorphous fused silica, and the higher the purity, the higher the purity. The particle size of the silica powder is preferably 20 microns or less considering the sinterability. In addition, the content of the silica powder in the molded body prepared by mixing the silica powder and silicon carbide powder is preferably from 60 to 90% by weight.

In addition, the silicon carbide powder used in the present invention is not significantly affected by the particle size, but it is preferable to use a powder of 45 microns or less, and the amount of the silicon carbide powder is prepared by mixing the silica powder and the silicon carbide powder. It is preferable that it is 10 to 40 weight% in a molded object.

In the present invention, a method of preparing a molded body by mixing the silica powder and silicon carbide powder may be used in general methods of manufacturing a molded body. Representative methods of the above method include a method of preparing a molded body by using a hydraulic molding machine by putting a mixed powder of silica and silicon carbide into a mold mold, and another method is to prepare a slurry from the silica powder and silicon carbide The method of manufacturing a molded object by slip-casting the said slurry to a gypsum mold is mentioned.

In another aspect, the present invention includes the step of sintering the molded body prepared above. The sintering is preferably used to sinter the molded body for about 2 hours at a temperature of 1,300 to 1,400 ℃ using an electric furnace and then to cool in the electric furnace. When the firing temperature is lower than 1,300 ° C., the porosity of the molded article is high, and thus, it is difficult to produce a homogeneous composite or a large reaction time. In addition, when the manufacturing temperature exceeds 1,400 ℃, the crystalline phase of the silica contained in the molded body is transferred from the amorphous phase to the crystalline (cristobalite) to generate microcracks inside the molded body, it is difficult to obtain a homogeneous composite.

The present invention also includes a reaction step of reacting the sintered molded body with the molten aluminum at 750 to 1,100 ℃. In order to make the silicon carbide-alumina / aluminum composite, an alumina crucible containing the manufactured molded body and metal aluminum is charged into a furnace at room temperature, and then heated at a rate of 10 ° C. or less per minute, and the molded body maintained in the furnace is reached at 750 to 1,100 ° C. After depositing in the molten aluminum for a certain time, the specimen is taken out of the molten aluminum to obtain a silicon carbide-alumina / aluminum composite. In the reaction of the molded body with the molten aluminum, the silica in the molded body is aluminized by the reaction of Scheme 1, and the precipitated metal silicon is dissolved in the metal aluminum or escapes into the molten aluminum. In this reaction, silicon carbide remains in the molded body to form a silicon carbide-alumina / aluminum composite. When the reaction temperature is less than 750 ℃ during the reaction, it takes a long time to melt the metal aluminum, the production rate of the composite by the reaction of the aluminum and the molded body is too slow. In addition, if it exceeds 1,100 ℃, the oxidation rate of the molten aluminum surface is fast and inefficient. The optimum reaction temperature of the reaction is 1,000 ° C.

1 shows a silicon carbide-alumina / aluminum composite prepared according to the present invention. In Fig. 1, ① represents the specimen appearance after the reaction step of the present invention, ② represents the cut surface of the specimen, ③ represents the silicon carbide-alumina / aluminum composite, and ④ represents the silicon carbide in the unreacted molded body state. -Shows a silica-based sintered body. The figure shows that silicon carbide-alumina / aluminum composites can be produced according to the ceramic shaped body shape.

Hereinafter, examples of the present invention will be described. However, the following examples are intended to illustrate the invention and the present invention is not limited by the following examples.

Example 1

A slurry was prepared by mixing 60 wt% of fused silica powder and 40 wt% of silicon carbide powder by ball milling in an alumina pot for 24 hours. The slurry was prepared into pellet-shaped specimens having a size of 15 ψ × 10 mm at a pressure of 50 MPa. The molded specimens were fired at a temperature range of 1,250 to 1,450 ° C., respectively, using an electric furnace. At this time, the temperature increase rate was 5 ° C. per minute, and the cooling was natural furnace cooling. The molded article thus obtained was reacted with aluminum melted at a temperature in the range of 700 to 1,100 ° C. for 5 hours to prepare a silicon carbide-alumina / aluminum composite.

[Examples 2 to 3 and Comparative Examples 1 to 5]

It was carried out in the same manner as in Example 1 with the same content as Table 1 below.

TABLE 1

Example Comparative example One 2 3 One 2 3 4 5 Composition of the molded body SiC 40 30 30 5 60 30 30 30 SiO ₂ 60 70 70 95 40 70 70 70 Firing temperature of molten silica (℃) 1400 1400 1300 1400 1400 1400 1450 1250 Characteristics of the molded body Relative Density (%) of Molded Body 93 95 90 95 82 90 95 73 Crystal phase of the car in the molded body Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Crystalline Amorphous Reaction temperature with metal aluminum (℃) 1000 800 1000 1000 1000 700 1100 1000 Reactivity and Complex Properties Produce thickness (mm / hr) 3.0 2.5 2.5 3.0 2.0 0.1 3.0 0.1 Appearance state of the complex Good Good Good Good Bad Unreacted Crack Unreacted Composite properties High strength, high wear resistance High strength High strength Lack of wear resistance, low strength - Strength deterioration -

In Table 1, the composites of Examples 1 to 3 have high strength and good appearance of the composite, but Comparative Examples 1 to 5 have low strength, and the reaction in the reaction step of the present invention is poor or the reaction is poor. It showed no result.

In Comparative Examples 1 and 2 in Table 1, the content of silicon carbide and silica in the composition of the molded product is out of the preferred range, and the content of silicon carbide in the molded product is not a problem in manufacturing the composite, but there is no effect of improving the wear resistance. When the content of silicon carbide exceeds 40% by weight, it is difficult to densify the molded body, and the content of metal aluminum in the composite is insufficient and the strength is difficult to express.

In addition, in Table 1, Comparative Example 3 is a reaction temperature outside the preferred range during the reaction between the ceramic molded body and the molten aluminum, because the metal aluminum is not sufficiently melted due to the low temperature is insufficient reactivity. In addition, although not described in the comparative example, if the reaction temperature exceeds 1,100 ℃, the oxidation rate of the surface of the molten aluminum during the complex formation reaction is not good.

In addition, in Table 1, Comparative Examples 4 and 5 are those in which the firing temperature of the molded body exceeds a preferable range. In Comparative Example 4, the firing temperature of the molded body is too high. In this case, the density of the sintered compact is sufficient, but due to the high firing temperature, As the phase transition of silica caused cracks in the molded body, it was not possible to produce a homogeneous composite. In the case of Comparative Example 5, because the firing temperature is too low, the porosity of the produced molded article is high, because of this, only the surface is reacted when the molded product is reacted with molten aluminum, it is impossible to produce a composite even if maintained for a long time.

As described above, when manufacturing the silicon carbide-alumina / aluminum composite according to the present invention, it is easier to manufacture than the method of physically impregnating molten aluminum in the ceramic substrate containing a lot of pores, the shape according to the shape of the ceramic molded body It can be modified, and the high strength and fracture toughness could be produced a silicon carbide-alumina / aluminum composite that can be used in structural materials or wear-resistant materials.

Claims (2)

Preparing a molded body by mixing 60 to 90% by weight of fused silica powder and 10 to 40% by weight of silicon carbide powder; Sintering the manufactured molded body; And Depositing the sintered molded body on the molten aluminum melt at 750 to 1,100 ° C. to form alumina according to the following reaction scheme: 3SiO ₂ + 4Al → 2Al ₂ O ₃ + 3Si Method for producing a silicon carbide-alumina / aluminum composite comprising a. The method of claim 1, wherein the sintering temperature in the sintering step is 1,300 to 1,400 ℃ manufacturing method of the silicon carbide-alumina / aluminum composite.