JPS63218584A - Ceramic sintered body - 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 [Objective of the Invention (Industrial Application Field) The present invention relates to a ceramic sintered body containing silicon nitride as a main component and having excellent mechanical strength even at high temperatures.

(Prior art) Ceramic sintered bodies containing silicon nitride as a main component are 19
It has excellent heat resistance up to 00°C and has a low coefficient of thermal expansion, so it has excellent thermal shock resistance and is suitable for various applications such as gas turbine blades and automobile parts. Attempts are being made to apply it to high-strength, heat-resistant parts. Furthermore, since it has excellent corrosion resistance against molten metal, it has also been put into practical use as a molten metal resistant material.

By the way, silicon nitride itself has extremely poor sinterability, and various sintering methods have been tried.

At present, methods for producing ceramic sintered bodies containing silicon nitride as a main component can be roughly divided into densification sintering using additives and reaction sintering using a nitriding reaction. Among these sintering methods, the former densification sintering using additives forms a liquid phase at grain boundaries by adding a metal compound with a lower melting point than silicon nitride, and this liquid phase causes particle rearrangement. This is a method for easily obtaining a dense silicon nitride sintered body. Additives that act as sintering aids include Mg, AJ! , Y, Sc, La, and Ce oxides are known and used alone or in combination. Among these sintering aids, yttrium oxide-aluminum oxide systems are often used. This yttrium oxide-aluminum oxide system is used with the addition of aluminum nitride, or with the addition of a gold R oxide such as titanium oxide or magnesium oxide.

(Problems to be Solved by the Invention) By the way, as mentioned above, the method of sintering silicon nitride using a sintering aid once forms a liquid phase, and this liquid phase facilitates the rearrangement of particles. Although this is a method for obtaining a dense silicon nitride sintered body, this liquid phase partially remains as a glass phase at the grain boundaries even after sintering. If there is a large residual amount of a low melting point compound such as the glass phase, there is a problem that destruction occurs at high temperatures due to the presence of the low melting point compound present at the grain boundaries.

Ceramic sintered bodies containing nitride/arsenic as a main component produced using conventional sintering aids are not necessarily fully satisfactory in terms of high-temperature strength and hardness, and furthermore, these A silicon nitride sintered body with improved properties is strongly desired.

The present invention has been made to solve these difficulties, and an object of the present invention is to provide a ceramic sintered body containing silicon nitride as a main component, which has significantly improved high-temperature strength and hardness.

[Constitution of the Invention (Means for Solving Problems)] The ceramic sintered body of the present invention contains 0.5 to 10% by weight of rare earth oxide and 0.5 to 10% by weight of aluminum nitride as sintering aids.
10% by weight and oxides or silicides of magnesium, cobalt or nickel, oxides, carbides or silicides of chromium, carbides of molybdenum or tungsten!
1171 or 0.5 to 10% by weight of at least one selected from the group consisting of silicide, zirconium oxide, carbide, silicide or boride, titanium oxide, carbide, silicide, nitride or boride. , the remainder being silicon nitride, and 0.0% of a rare earth oxide as a sintering aid.
5-10% by weight, aluminum nitride 0.5-10% by weight
, magnesium, cobalt or nickel oxides or silicides, chromium oxides, carbides or silicides,
At least one member selected from the group consisting of molybdenum or tungsten carbides, zirconium oxides, carbides, silicides, or borides, and titanium oxides, carbides, silicides, nitrides, or borides. A ceramic mixture containing 0.5 to 10% by weight of at least one selected from the group consisting of oxides, carbides, or silicides of hafnium, niobium, or tantalum, and the remainder consisting of silicon nitride. It is characterized by being made by molding and firing.

The silicon nitride used in the present invention preferably has an average particle size of 1 μm or less and has a constituent phase of 80% or more of α phase. The finer the average particle size is, the higher the sintering property is, so it is preferable.
It has a great effect of uniformly dispersing the sintering aid in the range of μm or less.

Examples of rare earth oxides used in the present invention include yttrium oxide, cesium oxide, and neodymium oxide, which may be used alone or as a mixture. Note that, as these rare earth oxides, rare earth compounds that become oxides when heated can also be used. Among these, yttrium oxide in particular makes the crystal grains of the obtained sintered body long columnar,
It is preferable because it contributes to high toughness and hardness, and
These rare earth oxides and oxides or silicides of magnesium, cobalt or nickel, oxides, carbides or silicides of chromium, carbides or silicides of molybdenum or tungsten, oxides, carbides, silicides or boron of zirconium or titanium At least 1M of metal compound components selected from the group consisting of oxides (including compounds that become oxides, silicides, carbides, and borides when heated) both function as sintering accelerators, and also form grain boundaries after sintering. remains as a compound with a high melting point. The amount of rare earth oxide added is 0.5 to 10% by weight of the total ceramic mixture.
, particularly preferably in the range of 1 to 7.5% by weight, and the amount of the other metal compounds mentioned above is preferably 1 to 7.5% by weight of the total ceramic mixture.
This is because the mechanical strength and thermal shock resistance of the sintered body obtained within this range are particularly excellent. In addition, when using a zirconium oxide, the amount of yttrium oxide contained as a stabilizer is also taken into consideration.

Aluminum nitride, which is another additive component in the present invention, contributes to recrystallization of the formed liquid phase, thereby increasing mechanical strength at high temperatures, and
Although it also contributes to the promotion of sintering, it is selected from the range of 0.5 to 10% by weight, particularly preferably from 1 to 7. It is in the range of 5% by weight.

The ceramic sintered body containing silicon nitride as a main component of the present invention contains at least one metal selected from hafnium, niobium, or tantalum oxides, carbides, or silicides as the sintering aid. Preferably 1% to 0.5% to 10% by weight of the compound in the total ceramic mixture
It may be added in an amount of up to 7.5% by weight, resulting in even better high-temperature strength.

The total amount of these components added as sintering aids is preferably in the range of 4 to 20% by weight based on the total ceramic mixture, and if the added amount is less than 4% by weight, the effect of promoting liquid phase sintering will be reduced. If the content exceeds 20% by weight, the inherent properties of silicon nitride may be impaired.

In the present invention, a mixture containing the above components in a composition ratio within a predetermined range is first molded into a desired shape, and then heated under an inert atmosphere for 1600 m
Sinter at temperatures between 1900°C and 1900°C. Note that this sintering can also be performed using the so-called atmospheric pressure sintering method to obtain a silicon nitride-based sintered body that is dense, has excellent high-temperature strength, and is highly hard, but other sintering methods such as atmospheric pressure sintering A sintered body having similar performance can also be obtained by a hot pressing method, a hot isostatic sintering method (HIP), or a combination thereof.

(Function) The constituent phases of the ceramic sintered body containing silicon nitride as a main component of the present invention vary depending on the added components and amounts, but are typically as shown in Table 1. A compound with a high melting point is formed, and the remaining amount of a compound with a low melting point such as a glass phase becomes extremely small.

(Example) The present invention will be explained below with reference to Examples.

Example 1 Silicon nitride (95% α phase) powder 8 with an average particle size of 0.8 μm
8% by weight, 5% by weight of yttrium oxide powder with an average particle size of 0.9 μm, 5% by weight of aluminum nitride powder with an average particle size of 1.0 μm, and 2% by weight of magnesium oxide powder with an average particle size of 0.5 μm were prepared in a ball mill. Mixing was carried out for about 24 hours to prepare the raw material powder.Next, 5 parts by weight of binder was added to 100 parts by weight of this raw material powder, and about 11,000 tons were mixed.
/ci molding pressure length 50n x width 50n x thickness In
After degreasing in a nitrogen gas atmosphere at 700°C for 1 hour, pressureless sintering was performed at 1750°C in a nitrogen gas atmosphere for 2 hours to form silicon nitride. A ceramic sintered body with the main component was fabricated.

Using the ceramic sintered body thus obtained, the bending strength and hardness at room temperature and 1200° C. were measured, and the results were as shown in Table 2.

In addition, Comparative Example 1 in the table is listed for comparison with the present invention, and the silicon nitride powder, yttrium oxide powder, and magnesium oxide powder used in Example 1 were each
This is a ceramic sintered body produced under the same conditions as Example 1 using raw material powder containing 3% by weight, 5fc, 1%, and 2% by weight.

Table 2 The bending strength values in the table are based on a 3-point bending strength test, sample size 4mm: x 3n x 40n, test conditions: crosshead speed 0.5n/min, span 30U.
The measurements at each temperature were performed four times and the average value is shown.

Examples 2 to 10 The silicon nitride powder, yttrium oxide powder, aluminum nitride powder and magnesium oxide powder or magnesium silicide powder with an average particle size of 0.8 μm used in Example 1 were each used in the composition ratios shown in Table 3. Raw material powders were prepared by mixing under the same conditions as in the example, and sintering was performed under the conditions shown in Table 3 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 3.

Note that the numerical values representing the composition in the table indicate weight % (the same applies hereinafter).

(Left space below) Examples 11 to 20 The silicon nitride powder, yttrium oxide powder, and aluminum nitride powder used in Example 1 and the metal compounds shown in Table 4 were used in the same composition ratios as shown in Table 4, respectively, as in Example 1. Raw material powders were prepared by mixing under the conditions, and sintering was performed under the conditions shown in Table 4 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 4.

(Left space below) Examples 21 to 30 The silicon nitride powder, yttrium oxide powder, and aluminum nitride powder used in Example 1 and the metal compounds shown in Table 5 were used in the same composition ratios as shown in Table 5, respectively, as in Example 1. Raw material powders were prepared by mixing under the conditions, and sintering was performed under the conditions shown in Table 5 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 5.

(Leaving space below) Table 5 Umbrella 1: Average particle size 1μ 112: Average particle size 1μ - Kou 3:
'l' ni noakito 1μ-den 4: ! l'J-eyebrow t↑1
μ■ Examples 31 to 40 The silicon nitride powder, yttrium oxide powder, and aluminum nitride powder used in Example 1 and the metal compounds shown in Table 6 were prepared under the same conditions as in Example 1 using the composition ratios shown in Table 6. The raw material powders were prepared by mixing and sintered under the conditions shown in Table 6 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 6.

(Blank below) 111Fill Examples 41 to 50 The silicon nitride powder, yttrium oxide powder, and aluminum nitride powder used in Example 1 and the metal compounds shown in Table 7 were mixed into Example 1 and the metal compounds shown in Table 7 in the composition ratios shown in Table 7, respectively. Raw material powders were prepared by mixing under the same conditions, and sintering was performed under the conditions shown in Table 7 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 7.

(Left below) ++5: Average grain t! 08 μm Examples 51 to 60 The silicon nitride powder, yttrium oxide powder, and aluminum nitride powder used in Example 1, and the metal compounds shown in Table 8 were used in the composition ratios shown in Table 8 under the same conditions as Example 1. The raw material powders were prepared by mixing and sintering was performed under the conditions shown in Table 8 to produce ceramic sintered bodies.

Using the ceramic sintered body thus obtained, bending strength and hardness were measured under the same conditions as in Example 1. The results are also shown in Table 8.

(Leaving space below) -5: Average particle size 07μm Umbrella 6: Average particle size 0.8μm - Umbrella 7: Average particle size 1μm Medium 8: Average particle size 1μm -9: Average Fi2 diameter O, Sμ Maro Umbrella 10: Average grain size O, Sμ [
Effects of the Invention As explained above, the ceramic sintered body of the present invention has excellent mechanical strength and high hardness even at high temperatures, and is suitable for various high-strength heat-resistant members.

Claims (8)

[Claims] (1) 0.5-10% by weight of rare earth oxide as a sintering aid
, 0.5-10% by weight of aluminum nitride and oxides or silicides of magnesium, cobalt or nickel, oxides, carbides or silicides of chromium, carbides or silicides of molybdenum or tungsten, oxides, carbides or silicides of zirconium. Forming a ceramic mixture containing 0.5 to 10% by weight of at least one selected from the group consisting of titanium oxides, borides, titanium oxides, carbides, silicides, nitrides, and borides, with the remainder being silicon nitride. , a ceramic sintered body characterized by being formed by firing. (2) The ceramic sintered body according to claim 1, wherein the total amount of the sintering aid added is in the range of 4 to 20% by weight in the ceramic mixture. (3) The ceramic sintered body according to claim 1 or 2, wherein the rare earth oxide is yttrium oxide. (4) The ceramic sintered body according to any one of claims 1 to 3, wherein the average grain size of silicon nitride is 1 μm or less. (5) 0.5-10% by weight of rare earth oxide as a sintering aid
, 0.5-10% by weight of aluminum nitride, oxides or silicides of magnesium, cobalt or nickel, oxides, carbides or silicides of chromium, carbides or silicides of molybdenum or tungsten, oxides, carbides or silicides of zirconium. 0.5 to 10% by weight of at least one selected from the group consisting of titanium oxides, borides, titanium oxides, carbides, silicides, nitrides, and borides
and 0.5 to 10% by weight of at least one selected from the group consisting of oxides, carbides, or silicides of hafnium, niobium, or tantalum, and the remainder is silicon nitride, which is formed by molding and firing a ceramic mixture. A ceramic sintered body characterized by: (6) The ceramic sintered body according to claim 5, wherein the total amount of the sintering aid added is in the range of 4 to 20% by weight in the ceramic mixture. (7) The ceramic sintered body according to claim 5 or 6, wherein the rare earth oxide is yttrium oxide. (8) The ceramic sintered body according to any one of claims A to 7, wherein the average grain size of silicon nitride is 1 μm or less.