JPH0511062B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a composite sintered body of titanium oxycarbide and aluminum oxide. This composite sintered body is useful as a cutting tool material, a wear-resistant member, a heating element material that can be used in an oxidizing atmosphere, and an electrically conductive material. Prior art Al ₂ O ₃ has excellent properties such as high strength and high hardness, but has the drawback of low toughness. Therefore, by combining TiC, which has high toughness, high hardness, and high strength, we created TiC-
It is known to form an Al ₂ O ₃ composite sintered body. Furthermore, although TiC has excellent electrical conductivity, it has the disadvantage of poor oxidation resistance. Therefore, it is known that TiC--Al ₂ O ₃ conductive ceramics, which have both advantages, can be made by combining TiC with Al ₂ O ₃ , which has excellent oxidation resistance. However, both sintered bodies are manufactured by a hot press method using low temperature and high load. In other words, since TiC, one of the components, is difficult to sinter, it is necessary to sinter it at a high temperature in order to sinter it at normal pressure, and if you try to sinter it at a high temperature, Al ₂ O ₃ will evaporate. Because of this, it was not possible to obtain a dense composite sintered body.
It was manufactured using the method described above. As described above, the conventional method requires a high load, which makes the manufacturing equipment expensive, which increases the manufacturing cost accordingly, and makes it impossible to produce a sintered body with a complicated shape. Moreover, the obtained sintered body could only be a two-phase system of TiC-Al ₂ O ₃ . Purpose of the Invention The present invention was made in order to eliminate the drawbacks of the conventional method.The purpose of the present invention is to create a composite material with higher density than the conventional method which combines the advantages of titanium carbide and aluminum oxide using atmospheric pressure sintering as raw materials. The present invention provides a method for manufacturing a sintered body. Composition of the Invention As a result of intensive research to achieve the above object, the present inventor created a green compact containing a specific combination of titanium carbide powder and aluminum oxide powder, embedded this green compact in aluminum oxide powder, and neutralized it. Alternatively, it has been found that when pressureless sintering is performed at 1700 to 1900°C in a reducing atmosphere, a high-density composite sintered body that cannot be obtained by conventional methods can be obtained regardless of pressureless sintering. It was also found that the obtained sintered body was a composite sintered body of Ti oxycarbide and aluminum oxide. The present invention was completed based on these findings. The gist of the invention is titanium carbide powder 10-60% by weight
A homogeneous mixture of 90 to 40% by weight of aluminum oxide powder and aluminum oxide powder is formed into a green compact, the green compact is embedded in aluminum oxide powder, and the powder is heated under a neutral or reducing atmosphere.
The present invention provides a method for producing a composite sintered body of titanium oxycarbide and aluminum oxide, which is characterized by pressureless sintering at 1700 to 1900°C. The blending ratio of titanium carbide powder and aluminum oxide powder in the present invention is in the range of 10 to 60% by weight of titanium carbide and 90 to 40% by weight of aluminum oxide. If the titanium carbide powder is less than 10% by weight, the toughness, electrical conductivity, and hardness of the obtained sintered body will be low, and if it exceeds 60% by weight, it will not be highly dense.
The oxidation resistance will also be poor. The purpose of embedding the green compact in aluminum oxide powder is to control the sintering atmosphere, prevent evaporation of aluminum oxide from the green compact, prevent compositional changes, and increase densification. The sintered density of this green compact can be increased by mixing 0.5% by weight or less of MgO with respect to Al ₂ O ₃ . If the atmospheric pressure firing temperature is lower than 1700°C, the amount of evaporation of Al ₂ O ₃ will be small, but the driving force for mass transfer required for sintering will not be sufficient, and sintering will not be sufficient. If the temperature exceeds 1900℃, even if the molded green compact is embedded in Al ₂ O ₃ powder,
The amount of evaporation of Al ₂ O ₃ increases, which not only causes a change in composition, but also makes it impossible to obtain a dense sintered body. Therefore, it is necessary to sinter within the range of 1700 to 1900°C. The atmosphere needs to be neutral or reducing to prevent oxidation of the TiC. The sintered body obtained by the method of the present invention is a titanium oxycarbide TiC _x O _y (1<x<O, 1<y<O, 1
≦x+y≦0.5, 0.05≦y/x≦0.20), resulting in a composite sintered body of aluminum oxide. In TiC _x O _y , x+y is controlled by the non-stoichiometric nature of the raw material TiC. Further, the ratio of carbon to oxygen (y/x) becomes smaller when the sintering temperature is lower, and becomes larger when the sintering temperature is higher. In the present invention, the sintering temperature is 1700℃
At , y/x = 0.05, and at 1900°C, y/x = 0.20. Therefore, in the method of the present invention, 0.05≦y/x
≦0.20 is obtained. FIG. 1 is a diagram showing the relationship between the sintering temperature and the relative density of the obtained sintered body when the starting materials have a composition of 30% by weight of TiC and 70% by weight of Al ₂ O ₃ . The ○ mark indicates the case where the green compact is embedded in Al ₂ O ₃ powder, and the ● mark indicates the case of pressureless sintering without embedding. As shown in Figure 1, the evaporation of Al ₂ O ₃ is
The evaporation of Al ₂ O ₃ can be suppressed by embedding it in Al ₂ O ₃ powder, although it becomes severe at temperatures above 1700°C, and the effect increases as the temperature rises, resulting in a large relative density. However, when it exceeds 1900℃
Even if it is embedded with Al ₂ O ₃ powder, the evaporation of Al ₂ O ₃ cannot be suppressed, and a dense sintered body with a high relative density cannot be obtained. Figure 2 shows 1800% by changing the composition ratio of starting materials.
It is a relationship diagram with relative density in the case of normal pressure sintering at °C. The ○ mark indicates when the green compact is embedded in Al ₂ O ₃ powder, and the ● mark indicates when it is not embedded. Since the sintered body of the present invention needs to have the properties of titanium carbide, the amount of raw material titanium carbide needs to be 10% by weight or more. However, if the amount exceeds 60% by weight, a highly dense sintered body cannot be obtained. FIG. 3 shows a relationship between the room temperature conductivity of the sintered body and the composition of the sintered body (wt% of TiC _x O _y ). As is clear from this, the sintered body of the present invention has excellent electrical conductivity. Example 1 TiC powder with an average particle size of 1.5 μm and a TiC powder with an average particle size of 0.2 μm
Using Al ₂ O ₃ powder, the composition ratio of TiC is 10, 30,
A mixed powder having a concentration of 60% by weight was prepared, ethanol was added thereto, and wet mixing was performed for 24 hours. After drying this mixed powder, it was formed into a pellet-like compact by uniaxial pressure molding and isostatic pressing. This compact was embedded in Al ₂ O ₃ powder in a SiC crucible and heated and sintered at 1700 to 1900° C. in a high frequency induction heating furnace in an Ar flow. As a result, a dense sintered body with a relative density of 90 to 96% was obtained. Chemical analysis was performed on the obtained sintered body, and TiC
was found to have changed to titanium oxycarbide (TiC _x O _y ) in which oxygen was dissolved as a solid solution. Table -
1 with a composition of 30% by weight of TiC and 70% by weight of Al ₂ O ₃ ,
The composition of the sintered body at firing temperatures of 1700°C and 1900°C is shown.

[Table] Example 2 TiC powder with an average particle size of 1.5 μm and an average particle size of 0.2 μm
Using Al ₂ O ₃ powder, a mixed powder containing 30% and 60% by weight of TiC was prepared, and a powder compact was produced in the same manner as in Example 1. This was embedded in Al ₂ O ₃ powder and heated and sintered at 1850°C in an Ar flow. The composition of the obtained sintered body, and the three-point bending strength, Vickers hardness, and toughness of this sintered body are shown in Table 2. As this shows, it has high hardness, high toughness, and high strength, making it a material suitable for cutting tools, wear-resistant members, and structural materials. Further, the oxidation resistance was investigated by leaving this sintered body in the air at 1500° C. for 5 hours and examining the change in weight. The results are shown in Table-3. This sintered body has superior oxidation resistance compared to TiC sintered body. Further, FIG. 3 shows the relationship between the room temperature conductivity of the sintered body and the amount of oxycarbide in titanium.

【table】

[Table] Example 3 MgO powder with an average particle size of 0.2 μm was added to a mixed powder of TiC and Al ₂ O ₃ powders similar to those in Example ₁ mixed with 30% by weight of TiC and 70% by weight of Al ₂ O 3 _{. 3} was further mixed in an amount of 0.5% by weight. A powder compact was made from this mixture in the same manner as in Example 1, embedded in Al ₂ O ₃ powder, and heated and sintered at 1850° C. in an Ar flow. The obtained sintered body is
When MgO powder was not mixed, the relative density was 96%, whereas the relative density was 99%, making it highly dense. Chemical analysis of this sintered body revealed that its composition was TiC _0.85 O _0.15 30.3% by weight, Al ₂ O ₃ 69.4% by weight,
MgO was 0.3% by weight. Sintered body composition TiC without MgO addition _0.85
Compared to O _0.15 30.3% by weight, Al ₂ O ₃ 69.7% by weight,
No change in the chemical composition or weight composition of oxycarbide was observed. Effects of the Invention According to the method of the present invention, TiC powder and Al ₂ O _{3 powder} are used as raw materials, and by pressureless _{sintering , TiC} A composite sintered body with high density can be obtained. Therefore, there is no need for a high-pressure device as in the conventional method, and it is therefore possible to easily manufacture products with complex shapes.

[Brief explanation of drawings]

Figure 1 shows the relationship between sintering temperature and relative density for a sintered body with a raw material composition of 30% by weight of TiC and 70% by weight of Al ₂ O _3. Figure 2 shows the relationship between the amount of TiC in the raw material and the relative density of the resulting sintered body. Figure 3 shows a relationship between the room temperature conductivity of the sintered body and the amount of oxycarbide in titanium. ○ mark: When the green compact is embedded in Al ₂ O ₃ , ● mark: When the green compact is not embedded in Al ₂ O ₃ powder.

Claims (1)

[Claims] 1. A homogeneous mixture of 10 to 60% by weight of titanium carbide powder and 90 to 40% by weight of aluminum oxide powder is formed into a green compact, and this green compact is embedded in aluminum oxide powder to form a neutral Alternatively, a method for producing a composite sintered body of titanium oxycarbide and aluminum oxide, characterized by sintering under normal pressure at 1700 to 1900°C in a reducing atmosphere. 2. The method for producing a composite sintered body according to claim 1, wherein a small amount of magnesium oxide is blended into the green compact.