JP2958731B2 - Aluminum oxide based sintered body and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum oxide-based sintered body suitably used as a material requiring wear resistance, such as various tool materials and sliding members, and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum oxide is well known as a relatively inexpensive material having excellent wear resistance. A technique of adding tungsten carbide to further improve the wear resistance is also known.

[0003]

However, as described above, a material obtained by simply adding tungsten carbide to aluminum oxide has a large crystal grain size, and particles may fall off during wear. Also, the addition amount of tungsten carbide is 5w
When the content is less than t%, the effect of addition is poor.
Above, the mechanical strength is rather deteriorated.

Although the cause is not clear, the present inventors have found that it is presumed that the interfacial bond between aluminum oxide and tungsten carbide is weak and that aluminum oxide is not sufficiently atomized. An object of the present invention is to solve such problems and to provide an aluminum oxide-based sintered body having excellent mechanical strength and abrasion resistance and a method for producing the same.

[0005]

The means is that the silicon compound and the tungsten compound in the sintered body are, on a molar basis,
5% or more and 40% or less and 0.5% or more and 25% or less, respectively, in terms of SiC and metal W, and tungsten carbide particles having a W / SiC molar ratio of 4 or less and an average particle size of 0.5 μm or less as a crystal phase. Alternatively, there is provided an aluminum oxide-based sintered body having excellent wear resistance, wherein tungsten silicide particles are dispersed.

Another means is that, on a molar basis, the silicon compound and the tungsten compound in the sintered body are not less than 5% and not more than 40% and not less than 0.5% and not more than 25%, respectively, in terms of SiC and metal W; W / SiC is 4 or less in molar ratio, tungsten carbide particles or tungsten silicide particles having an average particle size of 0.5 μm or less are dispersed as a crystal phase, and silicon-containing glass is present at the grain boundary. An aluminum oxide-based sintered body having excellent wear resistance.

[0007] A preferable means for obtaining such an aluminum oxide-based sintered body is silicon carbide Si on a molar basis.
C is 5% or more and 40% or less, tungsten W is 0.5% or more and 25% or less, and the balance of the α-Al2O3 source is contained in terms of α-Al2O3. Then, a temperature of 1500 to 1900 in a non-oxidizing atmosphere
A method for producing an aluminum oxide-based sintered body, characterized by sintering at a temperature of ℃. Further, in the above manufacturing method, after sintering, a treatment by hot isostatic pressure (HIP) may be further performed.

Here, α-Al2O3 source includes α-Al2O3.
Temperature of 1500-1900 in non-oxidizing atmosphere as well as 2O3
Any substance can be used as long as it changes to α-Al2O3 by sintering at ℃, and examples thereof include γ-Al2O3 and boehmite. The mixing of the compounded powder may be performed by a usual means such as a wet ball mill. The sintering can be applied to either pressure sintering or non-pressure sintering.

[0009]

In the above sintered body, the dispersion of the tungsten carbide having an average particle size of 0.5 μm or less causes the aluminum oxide to be finely divided, and this fineness and the high wear resistance of the tungsten carbide itself are obtained. Act synergistically to improve wear resistance. When the silicon-containing glass is present at the grain boundary, the silicon-containing glass makes the aluminum oxide particles and the tungsten carbide particles adhere to each other, so that the interfacial bonding force between them is improved. Although tungsten carbide is generated with a wide starting composition, depending on the starting composition, tungsten silicide may be generated, which also improves wear resistance.

In the above manufacturing method, silicon carbide serves as a carbon source of tungsten carbide and a silicon source of tungsten silicide. Since carbon and silicon are uniformly coordinated at an atomic level in a raw material stage. Even if the composition is such that tungsten silicide is formed, tungsten carbide and tungsten silicide provide a uniform dispersion state. Tungsten is a tungsten source of a tungsten compound. And both silicon carbide and tungsten produce tungsten carbide and tungsten silicide finer than their particles,
Aluminum oxide is present in the grain boundaries or grains of the aluminum oxide to make the aluminum oxide finer, thereby suppressing deterioration in strength.
Therefore, expensive ultrafine particles are not required as a raw material.

[0011] However, silicon carbide and metal tungsten do not always completely react with each other, and silicon-containing glass may be by-produced or may remain as metal tungsten. Indeed, metallic tungsten improves thermal conductivity without adversely affecting strength and wear resistance. Therefore, depending on the use, it is preferable to leave them in an unreacted state. The quantitative ratio of the reaction product to the unreacted product can be controlled by the starting composition and the firing temperature.

When the content of silicon carbide is less than 5%, the content of tungsten is less than 0.5%, or the W / SiC ratio exceeds 4 on a molar basis, a sufficient amount of reaction products to improve wear resistance and strength is obtained. Does not occur. On the other hand, when silicon carbide exceeds 40%, sinterability deteriorates, and metallic tungsten becomes 25%
If it exceeds 3, segregation of the tungsten compound is likely to occur, resulting in a decrease in wear resistance.

[0013]

Example 1 Example 1 γ-Al2O3 (purity 99% or more and a small amount of γ-AlOOH
Containing Si and Al (OH) 3, average particle size 1 µm), SiC
(Β type, average particle size 0.3 μm) and W (average particle size 0.5
To 0.6 μm) by a wet ball mill using ethanol as a medium with a starting composition shown in Table 1, and hot-pressed in a carbon die at a pressure of 40 MPa and a temperature shown in Table 1 to obtain a sample of each of Samples 1 to 9. A compact was produced.

For comparison, a sintered body of Sample No. 10 was manufactured under the same manufacturing conditions as Sample Nos. 1 to 9 except that SiC and W were not used. The sintered body of Sample No. 11 was manufactured under the same manufacturing conditions as Sample Nos. 1 to 9, except that SiC was not used and WC (average particle size: 0.5 to 0.7 μm) was used instead of W. Was manufactured.

[0015]

[Table 1] With respect to the obtained sintered body, a constituent crystal phase was identified by an X-ray diffraction method, and a density was measured. Table 2 shows the results.
Shown in

[0016]

[Table 2] As can be seen from Table 2, γ-Al ₂ O ₃ is α-Al ₂ O
₃ and all samples were fully densified. When the surface of the sintered body of Sample No. 4 parallel to the pressing direction during hot pressing was observed with a transmission electron microscope, as shown in FIG. 1, most of the particles of tungsten carbide and tungsten silicide were raw materials. The particles were much smaller than silicon carbide and tungsten, and dispersed to 100 nm or less. In FIG. 1, the particles that look like light columns are aluminum oxide, and the black particles are tungsten compounds.

Next, the mechanical strength, fracture toughness and wear resistance of each sintered body were evaluated. Mechanical strength is JI
By measuring the S three-point bending strength, the fracture toughness is
Each was evaluated by measuring the fracture toughness value according to the F method (30 kgf of load, also measuring Vickers hardness). The wear resistance was measured by mounting a carbon steel ring having an outer diameter of 25 mm and an inner diameter of 20 mm on a mirror-finished sintered compact disk.
The two were immersed in oil while being pressed at 00 kgf, and a wear test was performed in which the disk was rotated at a speed of 500 rpm for 5 hours.
It was evaluated by measuring x). Table 3 shows the results.

[0018]

[Table 3] As can be seen from Table 3, the sintered bodies in the range of the present invention were all excellent in strength and wear resistance. On the other hand, the sintered bodies of Sample Nos. 7 and 8 were inferior in wear resistance because the W content exceeded 25%. The sintered body of sample number 9 is
Since the SiC content was less than 5%, the abrasion resistance was poor. The sintered bodies of Sample Nos. 10 and 11 were also inferior in wear resistance.

Example 2 α-Al 2 O 3 (purity 99.99% or more, average particle size 0.2
μm), SiC (β type, average particle size 0.3 μm), and W
(Average particle size: 0.5 to 0.6 μm) was mixed with a starting composition shown in Table 4 by a wet ball mill using ethanol as a medium, and then subjected to cold isostatic pressure (CIP) molding. The obtained molded body is fired in argon gas at normal pressure at the temperature shown in Table 4 and then subjected to hot isostatic pressure (HIP) treatment at a temperature shown in the same table using argon gas at 2000 atm as a medium. The sintered bodies of Sample Nos. 12 to 16 were manufactured.

[Table 4]

The obtained sintered body was evaluated in the same manner as in Example 1. Tables 5 and 6 show the results.
Shown in

[Table 5]

[0021]

[Table 6]

Example 3 A mixed powder after the wet ball mill having the same starting composition as the sample No. 4 in Example 1 was mixed in a nitrogen atmosphere at 1350 to 145.
By heat treatment at 0 ° C., part or all of γ-Al2O3 was changed to α-Al2O3. The heat-treated powder was again pulverized by a wet ball mill, molded in the same manner as in Example 2, fired at 1800 ° C.,
C. HIP treatment (the same conditions as in Sample No. 14 having the same starting composition) was performed. The density is also 4.
A dense sintered body of 74 g / cm3 could be produced. When the crystal phase of the produced sintered body was identified by an X-ray diffraction method, it was α-Al2O3, W5Si3, WC and Si2W.

[0023]

According to the present invention, a sintered body having a mechanical strength of 700 MPa or more and excellent wear resistance is obtained.

[Brief description of the drawings]

FIG. 1 is a structural photograph showing a crystal structure of a sintered body according to one embodiment of the present invention.

Claims (4)

(57) [Claims] (1) On a molar basis, the silicon compound and the tungsten compound in the sintered body are 5% or more and 40% or less and 0.5% or more and 25% or less, respectively, in terms of SiC and metal W, and W / SiC is An aluminum oxide-based sintered body excellent in wear resistance, characterized in that tungsten carbide particles or tungsten silicide particles having an average particle diameter of 0.5 μm or less are dispersed as a crystal phase in a ratio of 4 or less. 2. On a molar basis, the silicon compound and the tungsten compound in the sintered body are 5% or more and 40% or less and 0.5% or more and 25% or less in terms of SiC and metal W, respectively. Excellent in abrasion resistance characterized in that tungsten carbide particles or tungsten silicide particles having an average particle diameter of 0.5 μm or less are dispersed as a crystal phase and silicon-containing glass is present at the grain boundaries. Aluminum oxide based sintered body. 3. An amount of silicon carbide (SiC) of 5% or more on a molar basis.
0% or less, 0.5% or more and 25% or less of tungsten W, and the balance of α-Al2O3 source in terms of α-Al2O3.
A method for producing an aluminum oxide-based sintered body, comprising: mixing powder having a compounding composition having a / SiC ratio of 4 or less, followed by sintering at a temperature of 1500 to 1900 ° C in a non-oxidizing atmosphere. 4. An amount of silicon carbide of at least 5% on a molar basis.
0% or less, 0.5% or more and 25% or less of tungsten W, and the balance of α-Al2O3 source in terms of α-Al2O3.
An aluminum oxide-based sintered body characterized in that after mixing powder having a compounding composition having a / SiC ratio of 4 or less, sintering is performed at a temperature of 1500 to 1900 ° C. in a non-oxidizing atmosphere, and further subjected to hot isostatic pressure treatment. Manufacturing method.