JPS59199577A - Heat resistant silicon nitride 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 The present invention relates to heat-resistant silicon nitride used in heat-resistant structural materials, machining materials, particularly cutting tools, wear-resistant materials, and corrosion-resistant materials, and a method for producing the same.

Silicon nitride is a compound with strong covalent bonding, and it has been known that it decomposes and evaporates at high temperatures, has low reactivity due to the small self-diffusion coefficient of Confucian atoms, and has a history of grain formation compared to ionic crystals and metal crystals. Because the ratio of field energy to surface energy is large, it is a material that is difficult to be occupied by non-concentrations. For this reason, even if nitrided silicon cord is sintered by the irradiated pressure Shintsu sintering method, the sintered body is not preferred, and generally MgO, Y2O3, Al2O3. Al
A dense sintered body is obtained by adding a sintering aid such as N and applying pressure using reactive sintering or liquid phase sintering or hot isostatic pressing (HIP). In this way, MgO,Y
2O3, Al2O3. S with added AlN sintering aid
In the i3N4 sintered body, lower silicate occurs at the grain boundaries of Si3N4, and this lower silicate becomes a liquid phase at a low temperature and becomes Si3N4.
Although it promotes sintering, it has the disadvantage that it remains in the grain boundary phase even after sintering, reducing the high temperature strength of the sintered body. In order to improve this drawback, a method has been proposed in which lower silicates remaining in the Si3N4 grain boundary phase are crystallized by heat treatment to improve the strength of the sintered body. However, when the Si3N4 sintered body is experimentally sintered in a small shape, the second phase, which is mainly composed of these lower silicates or a sintering aid made by crystallizing these lower silicates by heat treatment, becomes Si3N4 grains. There were no major problems because they were dispersed relatively uniformly in the interfacial phase, but when complex or large shapes were sintered to promote industrialization, Si3N4 was sintered and sintered as a material. Due to poor reactivity with the auxiliary agent and problems with cooling speed caused by the enlargement of the sintering furnace, the second phase of the oxide-based auxiliary agent, which is mainly composed of gold, is unevenly distributed in the Si3N4 grain boundary phase. The problem of segregation arises. As described above, due to the poor reactivity between Si3N4 and the sintering aid and the segregation of the second phase, which is mainly composed of the sintering aid, variations in the properties within the Si3N4 sintered body become large and the strength decreases. There is a problem that it is difficult to industrialize because it causes a problem.

The present invention solves the above-mentioned drawbacks and problems, and
By facilitating the reactivity between 3N4 and the sintering aid, the second phase, which is mainly composed of the sintering aid, can be uniformly dispersed in a sintered body with a complex or large shape, and the second phase Si3N
The object of the present invention is to provide a silicon nitride sintered body in which the properties of the sintered body are improved by increasing the bonding strength with No. 4, and a method for manufacturing the same.

The heat-resistant silicon nitride sintered body of the present invention contains 0.5 to 25% by weight of at least one of a nitride and an oxynitride of a rare earth element and B.
The silicon nitride sintered body is made of 0.5 to 25 tons of at least one of oxides, nitrides, and oxynitrides of Al, Ga, and the remainder silicon nitride and unavoidable impurities. Among these nitrogen-containing sintering aids, nitrogen-containing compounds of rare earth elements in particular have a lower decomposition temperature than oxide-based sintering aids, and are activated at low temperatures. Hard phase Si3N
In addition, since the movement of anion ions is very small in this reaction, the nitrogen-containing sintering aid can be partially dissolved in Si3N4, and the sintering aid can be added to the Si3N4 flow field. is uniformly dispersed to promote sintering, and after sintering, the nitrogen contained in the sintering aid combines the second phase formed mainly with the sintering aid and the Si3N4 hard phase. In order to increase strength, it is possible to prevent problems such as segregation of sintering aids, uneven firing, residual pores, and abnormal formation of Si3N4 particles that occur with oxide-based sintering aids, and to improve the strength of the second phase and Si3N.
A heat-resistant silicon nitride composite sintered body that is dense and has a high degree of sizing, and can be easily sintered homogeneously even with complex or large shapes because the internal stress caused by the anisotropy is small. It becomes easy to manufacture. Among the sintering aids used here, the nitrides and oxynitrides of fudozuke elements include B, At, and Ga.
During the baking process, Si3N4 grain boundaries are uniformly penetrated and dispersed together with oxides, nitrides, and oxynitride compounds.
The bond between Si3N4 and the second phase is strengthened by the formation of a homogeneous second phase mainly composed of sintering aids surrounding the 3N4 particles, and the mutual diffusion of the hardwood in this second phase and the grains in Si3N4. It also contributes to the properties of the sintered body, prevents segregation of the second phase, and improves the high-temperature strength of the sintered body after sintering. On the other hand, at least one wax of oxides, nitrides, and acid oxides of B, Al, and Ga, which is used as a sintering aid, facilitates the formation of a phase-free phase and promotes the abolition of Si3N4. Formation of a homogeneous second phase mainly consisting of rare earth elements and Si of this second phase
The bond-mediated effect with silicon in 3N4 contributes to the same properties of the sintered body.

In the method for producing a heat-resistant silicon nitride sintered body of the present invention, it is desirable to use Si3N4 powder, which is difficult to imitate as much as possible, as a starting material. 0.5 to 25% by weight of powder of B, Al, Ga, and 0.5 to 25% of first wood of at least one of oxides, nitrides, and oxynitrides of B, Al, Ga, or rare earth elements may be blended. A composite compound powder consisting of at least one of nitrides and oxynitrides of B, Al, and Ga, and at least one of oxides, nitrides, and oxynitrides of B, Al, and Ga, and Si3N
It may be used as a starting material by blending B and A with at least one of nitrides and oxynitrides of rare earth elements.
l, at least one of Ga oxides, nitrides, and oxynitrides;
Composite compound powder consisting of Germany and Si3N4 and Si3N4
A composite compound powder consisting of and Sj3N4 powder may be blended as a starting material, and if a composite compound powder with a reduced enzyme content is used as a starting material, the structure of the baked box will become columnar or acicular. Sintered clay with a small aspect ratio particle shape has improved soil heat resistance, so it can be used to prevent locally severe thermal shocks such as cutting tools. When used for additional purposes, it is desirable to use summer seedling compound powder as a starting material.

In the uninvented method for producing a heat-resistant silicon nitride yarn sintered body, Si3N4 powder, which is used as a starting material in order to make the rough surface area of the sintered body a structure with a small aspect ratio, is used as a raw material that is free of taint. It is desirable that Si3N4 powder contains Al, Fe blue, or Si3N4 powder as an unavoidable impurity.
The amount of impurities mixed in from the container and these balls when mixed and crushed with Al2O3 holes and superalloy balls etc. when the blended powder is placed in a container is 5. If it is less than 1% by weight, the properties of the heat-resistant silica sintered body can be sufficiently maintained by adjusting the hardwood partial pressure during the nitrogen incorporation of the starting material used as a sintering aid and the sintering process. I can do something. For example, carbides, nitrides, carbonitrides, etc. of group IVa elements, group Va elements, and group VIa elements of the periodic table that are mixed in from cemented carbide balls used during mixing and pulverization are used in the sintered compact of the present invention. There is a sequential process that is useful for improving wear resistance, and SiO2 mixed in from the starting raw material lowers the original decomposition temperature of Si3N4 in the hard buying phase, causing a reaction between Si3N4 and the sintering aid at the low temperature side. Al and Fe group elements mixed in from the starting materials and the container and ball during mixing and pulverization promote the interdiffusion reaction between silicon in Si3N4 and become sintering aids. It tends to support dispersion.

Also, Be, Mg, and Ca are group IIa elements of the periodic table.

These are Sr, Ba, Ra and group Ia elements. Li, Na.

Since K oxides, nitrides, and oxynitrides promote the formation of a crystalline phase and contribute to densification, they can be polished to the extent that the properties of the non-inventive hemorrhagic silicon nitride sintered body are not deteriorated. Si3N4 as a starting material used here is α-Si
3N4. β-Si3N4. Amorphous Si3N4 or a mixture of these Si3N4 having different crystal structures in any ratio may be used. In addition, at least one of nitrides and oxynitrides of rare earth elements as a sintering aid, B, Al
．． At least one of the oxides, nitrides and acid oxides of Ga, the nitrogen-containing compound may be a stoichiometric compound or a non-stoichiometric compound, and at this time the nitrogen-containing compound of rare earth elements is visible in the atmosphere. Since it is easily oxidized, it is necessary to handle it in a state filled with an inert gas such as nitrogen gas, but it is preferable to use a composite compound containing B, Al, and Ga elements.

In the coin making method of the present invention, the starting materials of various materials are mixed and crushed and packed in a sintering mold in the state of mixed powder to make a universal compact, or in a forming mold to a compacting rate,
The molded body is made into a molded body by pre-sintering at a temperature lower than the pre-forming temperature, or the molded body is molded after pre-sintering in a non-containing atmosphere including vacuum. (including sintering), sintering by methods such as frequency pressure sintering, toichi pressure sintering, gas pressure sintering, and hot pressing, or by combining these sintering methods with isostatic pressing. A method of promoting densification of the sintered body can also be used. Although the sintering temperature varies depending on the sintering method or the ingredients, a sufficiently oxidized sintered body can be obtained within a temperature range of 1500°C to 1900°C.

The rare earth elements used here are Toma, Sc, and Y.

, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,
It is a general term for 17 elements: Tb, Dy, Ho, Er, Tm, Yb, and Lu.

Here I will explain why I added the ridge straight limit.

At least one of rare earth element nitrides and oxynitrides is 0
．． If it is less than 5% by weight, the sieve temperature frequency of the second phase formed mainly from the sintering aid will be too high, and the strength of the sintered body itself will decrease, and if it exceeds 25% by weight, the relative strength will increase. Si3
Since the weight of N4 decreases, the hardness of the sintered body decreases, and the wear resistance and heat resistance decrease, so the content was set at 0.5 to 25% by weight.

The sintering promotion effect of Si3N4 is weak when at least one of the oxides, oxides, and oxynitrides of B, Al, and Ga is present at 0.5%, and the bond between Si3N4 particles and Futochi Motoki. The mediating effect becomes weak, and when the amount exceeds 25% by weight, the amount of Si3N4 becomes relatively small, and melon-grade anal acid walls are formed in the second phase formed by using the filler as a living body. 0.5 to 25, which easily reduces the hardness and strength of the buttock body.
It was expressed as ``death %''.

Next, a detailed description will be given according to an example.

Example 1 Si3N4 (approximately 40% amorphous S) with an average diameter of 1 μm
mixture of i3N4, α-Si3N4, and β-Si3N4),
Si3N4 with an average toughness of 2 μm (approximately 95% α-Si3N4
and β-Si3N4), Si3 with an average particle size of 5ttm
N4 (approximately 70% α-Si3N4 and β-Si3N4) and YN.

Y3O3N, B2O3, BN, B3O3N, Al2O3
Using the entire powder bed of AlN, Al3O3N, and Ga2O3, each sample was mixed in the proportions shown in Table 1, and the combined samples were placed in a stainless steel container along with a hexane bath medium WC-based superalloy ball. It was mixed and ground in a . The crushed bladder bed was filled into a 100 x 100 mm square carbon mold punched with BN powder, and the inside of the furnace was replaced with N2 gas.
Pressure sintering was carried out at a temperature of 900° C. for 60 to 120 minutes. The manufacturing quality of each sample was shown to the first person, and the obtained sintered body was divided into the center and the outer periphery and cut into approximately 13 x 13 x 5 mm. The Al2O3-Si3N4 bond was determined by comparison, and the results are shown in Table 2.

As a result of Table 2, the uninvented heat-resistant silicon nitride sintered body has high thermal shock resistance and fracture toughness (KiC), and is superior to the Y2O3-Al2O3-Si3N4-based sintered body, which is a proprietary product. In comparison, we were able to confirm that there was less variation between the center and the outer periphery of the sintered body, and that even a large sintered piece could be sintered homogeneously. The thermal impact test conducted here shows the temperature at which the sample can withstand without cranking by holding the sample at the volume temperature for 2 minutes and then immersing the sample in water at approximately 20℃ (room temperature), and the fracture toughness value is It was determined from the crack length, the size of the indentation, and the Vickers hardness caused by the Vickers indentation with a 30 kg loader.

When the outer periphery of sample number 2 was confirmed by X-ray diffraction and fluorescent X-rays, it was found that it contained Co and W, and W formed tungsten silicide. It was considered.

Example 2 1 μm Si3N4 and YSjO2N used in Example 1,
AlYN2, Al2YO3N, YSi4O2N5 and Y
A composite compound of Al2Si3O3N5 was mixed as in the third coating, and mixed powder of each sample was prepared in the same manner as in Example 1.

This mixed powder was compacted according to the manufacturing conditions of Example 1, and various custom orders for the obtained sintered body were obtained in the same manner as in Example 1, and the results are shown in the fourth column.

Example 3 Using the 1 μm Si3N4 used in Example 1, various rare earth compounds, and compounds of B, Al, and Ga, the mixture was blended as shown in Table 5, and the mixed powder of each sample was prepared in the same manner as Actual Example 1. did. This mixed wood powder was sintered according to the manufacturing conditions of Example 1, and the molding properties of the obtained sintered body are shown in Table 6. The notes for the sintered body were obtained in the same manner as in Example 1.

Example 4 The 1 μm Si3N4 used in Example 1 and the non-stoichiometric compounds YN0.85, Y3(03N)0.95 and AlN0.
90 and Al2O3 were combined as in Example 7, and a mixed example tree of each sample was prepared in the same manner as in Example 1. This mixed powder was sintered under the same condition as in Example 1, and the sintering conditions were approximately 10 kg/
cm3N2 gas pressure sintering or subsequent HI using Ar gas
8.
Show it on your clothes. Takao Uke's glaring kimono was used in the same way as in Example 1 and was made longer.

Actual flow example 5 Implemented as a substitute for Fukiryokusenkotaikohi of Nashinina strange rock 2 of Example 1, sample number 13 of Fusen example 2, sample town number 22 of Example 3, and sample strange rock 25 of Example 4 Y2 achieved the same results as Example 1.
Using an O3-Al2O3-Si3N4 sintered body, each deactivated body was cut into a central part and an outer part, and then CIS standard SN
Molded into P432 and SNCN54ZTN and next (A)
and (B) perform a cutting test at the vehicle, and use the 9th cup of rice.
As shown in 6.

(A) FC35 (350ψmm x 1500mm)
Cutting speed 600m/min Depth of cut 1.5mm Depth 0.7mm/rev Cutting time
30min Chip shape SNP432 (B) Cutting test with milling cutter High quality cutting material Hadako Kabura (HRC45) Cutting speed with black skin
270m/min Depth of cut 4.5mm Table feed 600mm/min Single blade wheel feed 0.20mm/rev Chip shape SNCN5
As a result of Table 9 of 4ZTN, the heat-resistant Danya-formed silicon hemlock of the present invention is Y2O3-Al2O3-Sj3, which is a comparable product in terms of wear resistance by turning and durability by milling.
It is better placed than the N4 fired body, and there is almost no difference in cutting performance and various characteristics between the center and the outer periphery of the corpse body, which has a large shape. Because of this, Tochishina and its manufacturing method lead to the unconventional production of dish-heated structural materials, which often have large shapes and irregular shapes, and materials for mechanical work, which are made with a large number of individual tumors. This was confirmed.

Patent distributor: Toho Tungaloy Co., Ltd.

Claims (2)

[Claims] (1) At least one hydride and oxynitride of cloth cheek yarn (containing Sc, Y and lanthanide elements) 0.5 to 25
A heat-resistant silicon nitride characterized by comprising: 0.5 to 25% by weight of at least one oxidized product of B, Al, and Ga, 0.5 to 25% by weight of an oxidized product of B, Al, and Ga, a residual silicon compound, and unavoidable impurities. Unglazed sintered body. (2) At least 1 year old 0, 5 to 25 of the pharyngeal proboscis and relatives of the earthen elements (Sc, Y and lanthanide originals)
A mixed powder consisting of 0.5% to 25% by weight of at least one of the oxides, oxides, and nitrides of B, At, and Ga, and the remainder silicon nitride and unavoidable impurities is made into a powder compact or compact. 1. A method for producing a heat-resistant silicon nitride sintered body, comprising heating and sintering it at 1500° C. to 1900° C. in a non-oxidizing atmosphere.