JPS62148367A - Abrasion resistance, high strength, high toughness and high hardness ceramic sintered body 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 Field of Application) The present invention relates to a high strength, high toughness, high hardness ceramic sintered body with excellent wear resistance and a method for manufacturing the same. A novel high-strength, high-toughness, high-hardness ceramic sintered body, which is made by using zirconium oxide as a substrate and dispersing zirconium oxide therein, and is suitable for wear-resistant jigs such as dies, cutting tools, and mechanical seals, and a method for manufacturing the same. Regarding.

(Prior Art) Conventionally, for example, in the field of ceramic tools, Al2
Alumina-based tools containing 99% or more of O, and 20 to 40
% of titanium carbide has been put into practical use as an alumina ceramic tool. However, although this ceramic tool has excellent hardness and heat resistance, it has inferior toughness (transverse rupture strength) and low thermal conductivity compared to cemented carbide tools, so its uses are limited.

In order to solve such problems with alumina ceramic tools, various sintered ceramic bodies have been proposed in recent years that have improved toughness by using alumina as a matrix and dispersing zirconium oxide therein. The sintering raw material composition in which zirconium oxide is dispersed in alumina is
After sintering this, during the cooling process, the zirconium oxide dispersed in the alumina undergoes a phase transition from tetragonal to monoclinic, and at this time, due to volume expansion, fine racks are created in the sintered body. It is said that the fine racks prevent the propagation of main cracks due to stress applied to the sintered body, resulting in the sintered body having excellent toughness. Also,
The sintered body also contains tetragonal crystals in a non-equilibrium state, so when the main crack due to stress reaches this zirconium oxide, the crystal structure of the zirconium oxide undergoes a phase transition from tetragonal to monoclinic, and the tip of the crack Relaxation of stress is also said to be one of the reasons for toughness.

Furthermore, recently, as described in JP-A-57-100976 and JP-A-59-190259, oxides of certain elements, such as Y2O3, MgO1CaO, etc., have been used together with zirconium oxide. Partially stabilized oxidation by adding an appropriate amount to zirconium oxide and making it a solid solution in zirconium oxide during the sintering process, making the crystal structure of a part or the main part of zirconium oxide into a tetragonal crystal with a metastable phase at room temperature. Sintered bodies containing zirconium have also been proposed.

In the alumina ceramic sintered body containing such partially stabilized zirconium oxide, the tetragonal zirconium oxide undergoes a phase transition to monoclinic crystal due to stress, and due to the resulting stress relaxation, compared to the alumina-based sintered body described above, It has high strength, high toughness, and excellent transverse rupture strength, but on the other hand, since it contains zirconium oxide, the hardness decreases and the i5
tI''&purity is inferior to that of alumina-based materials, and is not suitable for use as a cutting tool for high-hardness steel, for example.

On the other hand, titanium carbide and titanium nitride are well known as ceramic sintering raw materials for forming a high-hardness sintered body. On the other hand, these sintered bodies made only of titanium compounds have low strength and toughness, so they are susceptible to chipping and cannot be put to practical use as wear-resistant sintered bodies. In particular, these titanium compounds with a particle size of about 5 μm have poor sinterability, so hot pressing at 1700°C or higher is usually required to obtain a sintered body. Inferior in strength and toughness. On the other hand, when a titanium compound with a grain size of 2 μm or less is hot pressed at a temperature of about 1600° C., significant grain growth occurs at the same time as densification, and as a result, the resulting sintered body is inferior in both strength and toughness.

(Purpose of the Invention) As a result of intensive research to solve the above-mentioned problems in conventional ceramic sintered bodies, the present inventors dispersed zirconium oxide in fine titanium carbide and/or titanium nitride, and compared the results. We have discovered that by sintering at a relatively low temperature, it is possible to obtain a high-strength, high-toughness, and high-hardness ceramic sintered body that has homogeneous and fine fibers and has excellent wear resistance, and has developed the present invention. This is what we have come to.

Therefore, an object of the present invention is to provide a wear-resistant, high-strength, high-toughness, high-hardness ceramic sintered body formed by dispersing zirconium oxide in fine titanium carbide and/or titanium nitride, and a method for manufacturing the same.

(Structure of the Invention) The wear-resistant, high-strength, high-toughness, high-hardness ceramic sintered body according to the present invention is selected from the group consisting of zirconium oxide in an amount of 5 to 30% by volume, and the remainder being titanium carbide and titanium nitride having an average particle size of 2 μm or less. and unavoidable impurities.

Furthermore, the ceramic sintered body according to the present invention preferably contains Y2O3,10 and Ca in addition to zirconium oxide.
It contains at least one oxide selected from the group consisting of O in an amount of 0.1 to 5 mol % based on zirconium oxide.

Both titanium carbide and titanium nitride used in the present invention need to have an average particle size of 2 μm or less. When the average particle size exceeds 2 μm, it is difficult to obtain a dense sintered body by sintering at 1650° C. or lower. That is, according to the present invention, by dispersing zirconium oxide in titanium carbide and/or titanium nitride with an average particle size of 2 μm or less and sintering this at a relatively low temperature, a uniform fine structure is obtained. It is possible to obtain a ceramic sintered body that not only has high hardness but also has good strength and toughness. Particularly from this point of view, titanium carbide and titanium nitride preferably have an average particle size of 1.5 μm or less.

The ceramic sintered body according to the present invention contains zirconium oxide in a range of 5 to 30% by volume. When this amount is less than 5% by volume, the effect of suppressing grain growth of titanium carbide and titanium nitride during sintering of the raw material composition is insufficient, and the resulting sintered body has poor strength and toughness. It will be inferior. On the other hand, when the amount exceeds 30% by volume, the resulting sintered body does not have satisfactory hardness because zirconium oxide has low hardness, as described above.

In addition to the above-mentioned titanium carbide and/or titanium nitride and zirconium oxide, the ceramic or sintered body of the present invention preferably contains at least one oxide selected from the group consisting of Y2O3, MgO and CaO. It is contained in a range of 0.1 to 5 mol% based on. As mentioned above, when the above oxide is sintered with zirconium oxide, it forms a solid solution in zirconium oxide, making the crystal structure of zirconium oxide tetragonal, and in a stress field, this tetragonal product becomes monoclinic. Transfer and try to relieve stress. Therefore, when the amount of the above oxide is less than 0.1 mol%, a sufficient amount of tetragonal zirconium oxide is not generated in the sintered body, so the effect of improving toughness is poor;
If an excessive amount is added beyond the zirconium oxide, the zirconium oxide is stabilized, and not only does the stress relaxation effect due to the phase transition from tetragonal to monoclinic described above not occur, but also the phase transition from tetragonal to monoclinic occurs during sintering. Because fine racks are not dispersed in the sintered body due to the phase transition to , the effect of preventing crack propagation in a stress field is not exhibited, and the toughness is not improved.

The ceramic sintered body according to the present invention has the following features:
5 to 30% by volume of zirconium oxide and preferably, in addition to the zirconium oxide, a small amount (both 0.1 to 5% by mole, based on the zirconium oxide) of one oxide selected from the group consisting of Y2O3, MgO and CaO. A sintering raw material composition consisting of at least one selected from the group consisting of titanium carbide and titanium nitride and unavoidable impurities, with the remainder having an average particle size of 2 μm or less, is heated at a temperature of 1400 to 1.
It can be obtained by hot pressing at 650° C. and a pressure of 100 kg/cd or more.

In the method of the present invention, in order to obtain a dense sintered body by sintering the sintering raw material composition, the hot pressing temperature must be at least 1400°C. However, 16
When the temperature exceeds 50°C, titanium carbide and titanium nitride react with zirconium oxide to form zirconium carbide and zirconium nitride, respectively. As a result, zirconium oxide is lost, and zirconium oxide carbon (hydrogen and nitride) The grain growth suppressing effect of titanium is not expressed.Furthermore, during sintering, a small pressure (of 100 kg/cl) is required, and it is difficult to obtain a dense sintered body under a pressure lower than this. The upper limit of is not particularly limited, due to the strength of the graphite mold used for sintering
Usually, 500 kg/cI11 is practical. In order to obtain a dense sintered body, sintering must be carried out at the above-mentioned temperature and pressure for usually 10 minutes or more. However, sintering for too long is not preferable because grain growth of titanium carbide and titanium nitride occurs.

(Effects of the Invention) As described above, the ceramic sintered body according to the present invention is made by dispersing a predetermined amount of zirconium oxide in fine titanium carbide and/or titanium nitride. As a result of suppressing growth, it has a homogeneous fine structure, has high hardness and excellent wear resistance, and the tetragonal zirconium oxide contained in the sintered body utilizes stress in the stress field, preventing crack propagation. It has high strength and high toughness.

In particular, sintered bodies made of dispersed titanium nitride have lower thermal conductivity at high temperatures than conventional alumina-based materials, and also have a low chemical affinity for iron, so they are not suitable for steel materials. Less wear due to adhesion under contact wear conditions.

Furthermore, according to the method of the present invention, such a ceramic sintered body can be obtained by sintering at a relatively low temperature.

(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example ■ (Example using titanium carbide) Example 1 85% by volume of titanium carbide powder with an average particle size of 1.0 μm and 15% by volume of zirconium oxide powder containing 3 mol% of Y2O3 based on zirconium oxide were mixed with ethanol. After wet mixing for 5 hours using a vibration mill as a dispersion medium, the resulting slurry was spray-dried to obtain a raw material composition to be sintered.

This raw material composition was filled into a graphite mold (cross-sectional area: 56 x 56 mm), and the temperature was 1600°C and the pressure was 250 kg.
Hot pressed for 0 minutes.

The sintered body thus obtained was extremely dense, and its relative density (ratio of measured density to theoretical density) was 99.1%. In addition, the bending strength (3-point bending, Suba 7301+1) is 92 kg/mmz, and the fracture toughness value is +c.
(Vickers indentation method) was 6.4 HPam172 and Vickers hardness was 2460 kg/mm2, indicating high strength, high toughness, and high hardness. Furthermore, using Incorne 750 as the wear test material, the specific wear amount measured by the Okoshi method was 1.2 x 10-6 mm.
The weight was 27 kg, and it was shown that the wear resistance was also low.

Examples 2 to 9 and Comparative Examples 1 to 6 As shown in Table 1, a predetermined amount of titanium carbide powder with an average particle diameter of 1.0 μm and (Y2
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder (containing either Ch, O, or CaO) was used and sintered under Condition F shown in Table 1. Table 1 shows the properties of each of the sintered bodies thus obtained.

Example 10 and Comparative Example 7 As shown in Table 1, predetermined amounts of titanium carbide powder with an average particle size of 2.0 μm and Y2O were used as sintering raw material compositions.
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder containing .

Table 1 shows the properties of each of the sintered bodies thus obtained.

Comparative Examples 8 to 10 As sintering raw material compositions, predetermined amounts of titanium carbide powder with an average particle size of 5.0 μm and Y2O were used as shown in Table 1.
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder containing No. 3 was used and sintered under the conditions shown in Table 1.

The properties of each sintered body obtained in this way are
Shown in the table.

Example ■ (Example using titanium nitride) Example 1 85% by volume of titanium nitride powder with an average particle size of 1.0 μm and 15% by volume of zirconium oxide powder containing 3 mol% of Y2O3 powder based on zirconium oxide were carried out. After wet mixing and spray drying in the same manner as in Example 1, it was filled into graphite molds at a temperature of 1600'C and a pressure of 250 kg/cn.
Pot press for 30 minutes at T.

The sintered body thus obtained was extremely dense, and its relative density (ratio of measured density to theoretical density) was 99.5%. In addition, the bending strength (3-point bending, span 30mm) is 114 kg/mm2, and the fracture toughness value is 1
．． (Vickers indentation method) is 6.2MPamI/z,
The Vickers hardness was 1750 kg/mm2, indicating high strength, high toughness, and high hardness.

Furthermore, using SO5304 steel as the wear test material, the specific wear amount measured by the Great War style wear test method was 0.8X 1
The weight was 0-6 mm and 27 kg, and it was shown that the wear resistance was also low.

Examples 2 to 9 and Comparative Examples 1 to 6 As shown in Table 2, a predetermined amount of titanium nitride powder with an average particle size of 1.0 μm and (Yz
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder (containing either Oi, MgO or CaO) was used and sintered under the conditions shown in Table 2. Table 2 shows the properties of each of the sintered bodies thus obtained.

Example 10 and Comparative Example 7 As shown in Table 2, predetermined amounts of titanium nitride powder with an average particle size of 2.0 μm and Y2O were used as sintering raw material compositions.
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder containing No. 3 was used and sintered under the conditions shown in Table 2.

The properties of each sintered body obtained in this way are
Shown in the table.

Comparative Examples 8 to 10 As sintering raw material compositions, predetermined amounts of titanium nitride powder with an average particle size of 5.0 μm and Y2O were used as shown in Table 2.
The process was carried out in the same manner as in Example 1, except that zirconium oxide powder containing No. 3 was used and sintered under the conditions shown in Table 2.

The properties of each sintered body obtained in this way are
Shown in the table.

Comparative Examples 11 and 12 In order to compare with the ceramic sintered body according to the present invention, an alumina sintered body containing zirconium oxide and a cemented carbide (WC
-10%Co) properties are shown in Table 2.

Claims (4)

[Claims] (1) High strength and wear resistance characterized by comprising 5 to 30% by volume of zirconium oxide, the balance being at least one member selected from the group consisting of titanium carbide and titanium nitride with an average particle size of 2 μm or less, and unavoidable impurities. High toughness and high hardness ceramic sintered body. (2) Zirconium oxide 5-30% by volume, Y_2O_3
, MgO and CaO, based on zirconium oxide, at least one oxide selected from the group consisting of 0.1 to 5
A wear-resistant, high-strength, high-toughness, high-hardness ceramic sintered body characterized by comprising at least one member selected from the group consisting of titanium carbide and titanium nitride, with the remainder having an average particle diameter of 2 μm or less, and unavoidable impurities. . (3) A composition consisting of 5 to 30 volume % of zirconium oxide, the remainder being at least one selected from the group consisting of titanium carbide and titanium nitride with an average particle size of 2 μm or less, and unavoidable impurities at a temperature of 1400 to 1650 °C and a pressure 100k
A method for producing a wear-resistant, high-strength, high-toughness, high-hardness ceramic sintered body, which comprises hot pressing at g/cm^2 or more. (4) Zirconium oxide 5-30% by volume, Y_2O_3
, MgO and CaO, based on zirconium oxide, at least one oxide selected from the group consisting of 0.1 to 5
A composition consisting of at least one member selected from the group consisting of titanium carbide and titanium nitride with an average particle size of 2 μm or less and unavoidable impurities is heated at a temperature of 1400 to 16 mol%.
A method for producing a wear-resistant, high-strength, high-toughness, high-hardness ceramic sintered body, characterized by hot pressing at 50°C and a pressure of 100 kg/cm^2 or more.