JPS589071B2 - Manufacturing method of ceramic sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ceramic sintered body, and more particularly to a method for manufacturing a ceramic sintered body having excellent mechanical strength and thermal shock resistance.

Ceramic sintered bodies mainly composed of silicon nitride are 1
It exhibits excellent heat resistance, being able to withstand high temperatures up to 900℃. It also has excellent thermal shock resistance due to its low coefficient of thermal expansion.

Therefore, attempts have been made to apply this type of ceramic sintered body mainly composed of silicon nitride to structural parts such as gas turbine blades and nozzles that require high strength at high temperatures.

By the way, this type of ceramic sintered body... For example, a mixture of silicon nitride, yttrium monoxide, and aluminum monoxide is used as a raw material, and it is manufactured by a so-called hot pressing method or an atmospheric pressure sintering method.

For example, in the hot press method. The present inventors have previously revealed that a silicon nitride-based sintered body with excellent properties can be obtained by changing the grain boundaries from glassy (non-quality) to Si3N4.Y203 crystalline compound.

Also. Patent Application No. 113235/1984 and Patent Application No. 1983
As disclosed in No. 145, etc. A method for manufacturing ceramic powder materials that enables reduction of vitreous content in sintered bodies. Alternatively, it has been shown that good results can be obtained by using a silicon nitride powder containing a compound of Si3N4 and Y203 as a ceramic powder material that can further improve the high-temperature strength of the sintered body.

However, with these methods, it is difficult to obtain a dense sintered body using pressureless sintering, so it is difficult to obtain a sintered body with excellent mechanical strength and thermal shock resistance. In the case of hot press sintering. Although a sintered body with excellent mechanical strength and thermal shock resistance can be obtained, the shape of the sintered body is restricted. It also had the disadvantage of not being mass-produced.

The present invention is. The purpose of the present invention is to provide a method for manufacturing a ceramic sintered body that overcomes the drawbacks of the above-mentioned prior art, and as a result of intensive research into the above-mentioned points, the present inventors have
We have successfully developed a method for producing ceramic sintered bodies with excellent mechanical strength and thermal shock resistance using pressureless sintering. The present invention has now been completed.

The manufacturing method of the present invention provides a silicon nitride powder containing a tetragonal crystal phase of a compound of si3N4.¥2031=1. The maximum intensity ratio of the X-ray diffraction line of the crystal phase of the 813N4 ¥2031:1 compound to the silicon nitride crystal phase is 0.
．． 03-0.6 nitrogen silicon powder 75% by weight or more, aluminum oxide powder 1-10% by weight. A mixed powder consisting of 1 to 10 parts by weight of aluminum nitride powder and 0.5 to 5 parts by weight of at least one oxide powder selected from the group consisting of titanium oxide powder, magnesium oxide powder and zirconium oxide powder is formed, and then This is a method for producing a ceramic sintered body characterized by sintering at 1500 to 1900°C in a non-oxidizing atmosphere.

The maximum intensity ratio of the X-ray diffraction line of the tetragonal crystal phase of the Si3N4/Y2031:1 compound to the silicon nitride crystal phase is 0.
．． The silicon nitride powder having a nitrogen concentration of 0.3 to 0.6 is obtained by adding and mixing yttrium oxide of about 0.5 to 10 by weight to α-type silicon nitride powder, for example. Argon. Carbon monoxide. Under a non-oxidizing atmosphere such as nitrogen-ammonia gas, 1550-1
Heat treatment at 750℃ for about 30 minutes to 2 hours (crystallization treatment)
It can be obtained by

The Si3N4・￥2031:1 compound obtained in this way is. Vitreous (
(non-quality) is removed or reduced. As a result, the mechanical strength of the sintered body can be prevented from decreasing and the thermal shock resistance can be improved.

If the maximum intensity ratio of the diffraction line of the Si3N4 ￥2031:1 compound crystal phase to the silicon nitride crystal phase in X-ray diffraction analysis is smaller than 0.03, no contribution to the maximum intensity is recognized, and if it is larger than 0.06 However, the properties of silicon nitride itself are impaired. This results in a sintered body with high porosity, which impairs its properties as a high-strength, heat-resistant material.

In addition. In the present invention, the method for obtaining the silicon nitride powder in which the si3N4.¥203 compound is produced is as follows. Although not limited to the above method. Sis calculated from the amount of Y203 added
In relation to other additives, it is desirable that at least 50 yen of the N4 ￥203 compound is formed as a crystalline phase that can be detected linearly in It is preferable from the viewpoint of high-temperature strength and thermal shock resistance that it be produced as a crystalline phase detected in .

The silicon nitride powder containing the SisN4.¥2031:1 compound obtained in this way is used in a composition of 75% by weight or more, preferably 85% by weight or more; if it is less than 75% by weight, the high temperature strength and heat resistance of the ceramic sintered body are No improvement in sexual impact resistance was observed.

The other additive components, aluminum oxide powder and aluminum nitride powder, react with the si3N4.¥203 compound and other additives to promote sintering. In particular, aluminum nitride has the function of suppressing sublimation and grain growth of silicon nitride.

These aluminum oxide and aluminum nitride are commonly available ones, and both have a weight ratio of 1 to 10,
Preferably the weight coefficient is 1.5 to 7, and the total of both is 1.
It is preferable that the weight ratio is 5 or less.

If the amount exceeds 10% by weight, the high-temperature strength and thermal shock resistance of the sintered body will decrease, which is undesirable.
If the weight is less than 1, sintering will not proceed.

Moreover, aluminum oxide can also be added during the above-mentioned crystallization treatment.

Furthermore, another additive component, an oxide powder selected from the group consisting of titanium oxide powder, magnesium oxide powder, and zirconium oxide powder, promotes sintering. The sintered body is densified by improving the wettability of silicon nitride, the main component. This results in shorter sintering time and lower sintering temperature.

These oxides are one or two commonly available ones.
Use more than one type, and even if two or more types are used, the total weight is 0.5 to 5. Preferably, it is used in an amount of 1 to 3 parts by weight.

If the amount of these oxides exceeds 5 weight ratio, the high-temperature strength of the sintered body will be impaired, which is not preferable, and if it is less than 0.5 weight ratio, sintering will not proceed.

The mixture of these components is. This can be carried out using a conventional grinding mixer such as a ball mill using a solvent such as n-butyl alcohol.

A binder such as stearic acid is added to the mixed powder thus prepared, and the mixture is molded at about 500 to 1000 kg/cm2.

The molded body thus obtained was placed in a non-oxidizing atmosphere for 1
A ceramic sintered body is obtained by sintering at 500-1900°C, preferably 1600-1800°C for 1-2 hours.

Argon is used as a non-oxidizing atmosphere. Examples include nitrogen, carbon monoxide, nitrogen-ammonia gas, etc. In an oxidizing atmosphere, silicon nitride is oxidized at high temperatures and its properties are impaired.

If the sintering temperature is less than 1,500°C, it is difficult to produce a ceramic sintered body, and if it exceeds 1,900°C, the sintered body will decompose, which is not preferable.

It is also clear that a ceramic sintered body having the same properties can be obtained by hot press sintering under the same atmosphere and temperature conditions by applying a pressure of 50 to 500 kg/cI2.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Reference Examples.

Examples and Reference Examples Yttrium oxide (Y203) powder with an average particle size of 1 μm was added to silicon nitride powder with an average particle size of 1.2 μm containing 85% α-type phase silicon nitride (SlsN4) as shown in the table <0.2 to 15
The blended powder, which was added and mixed in the weight range (including reference examples), was heat-treated at 1650°C for 1 hour in a nitriding atmosphere.
A silicon nitride powder containing a Si3N4.¥203 compound was prepared.

In this powder, the ratio of the 813N4 ¥203 compound crystal phase to the Si3N4 crystal phase is 0 at the highest strength ratio in terms of the X-line.
．． Si3N4 is in the range of 0.01 to 0.80 (including reference examples) and calculated from the added amount of ¥203.
In all cases, a crystalline phase with a coefficient of 70 or higher was detected relative to the theoretical amount of Y203 compound formation.

This silicon nitride powder. Aluminum oxide powder (Al2e3) with an average particle size of 0.5μ. Aluminum nitride powder (AAN) with an average particle size of 1.5μ, titanium oxide powder (TiO2) with an average particle size of 1μ, magnesium oxide powder (MgO).
The composition ratio of zirconium oxide powder (Zr02) shown in the table (
Using n-butyl alcohol as a solvent, each material was ground and mixed for 24 hours in a rubber-lined ball mill to prepare 64 types of raw material powders, including reference examples.

Add and blend stearic acid (binder) to the raw material powder prepared above at a weight ratio of 7 to 700 kg/cr2/t.
Length 60un. under molding pressure. Width 40rn. A rod-shaped molded body with a thickness of 10 mw (for bending strength test). Diameter 30mm. A disk (for thermal shock resistance test) with a thickness of 10 mL was formed, respectively.

The molded product thus obtained was first subjected to heat treatment at 700°C. After volatilizing and removing the binder, 1700 min under nitriding gas atmosphere
Sintering was performed at ℃ to obtain a silicon nitride ceramic sintered body.

Density and bending strength (mechanical strength) of the ceramic sintered body obtained above. The results of measuring and thermal shock resistance are also shown in the table.

still. The densities in the table are relative densities (%) based on the theoretical density.
Yes. The bending strength values are based on a three-point bending strength test. The sample size was 3X3X30 (mi) and the test conditions were a crosshead speed of 0.5mm/mm. Span 20mn,
The temperature was room temperature, 1200° C., and all measurements at each temperature were performed four times, and the average value is shown.

Also. Thermal shock resistance value ΔTc is determined by putting the sintered body into water from a certain temperature and cooling it in air. The presence or absence of cracks was confirmed by fluorescence flaw detection, and the difference between the temperature at which cracks just started and the water temperature was expressed as ΔTc.

As is clear from the table, the sintered body obtained by the method of the present invention has properties comparable to pressure sintered bodies despite being sintered under pressure, and its density is 95 times higher than the theoretical density. Strength is 8 at room temperature
5kg/mm2 or more, 70kg/mm2 or more at 1200℃. The thermal shock resistance value ΔTc is approximately 500° C. or higher.

As explained above, it will be understood that the method for manufacturing a ceramic sintered body of the present invention does not require pressurization, and is therefore suitable for mass production, and a sintered body with excellent properties can be obtained using a sintering method that is very advantageous industrially. .

Claims (1)

[Claims] A silicon nitride powder containing a tetragonal crystal phase of an I S13N4 ￥2031:1 compound, wherein the si3N
4.Y2031=1 A silicon nitride powder having a maximum intensity ratio of the X-ray diffraction line of the crystal phase of the compound to the silicon nitride crystal phase of 0.03 to 0.6 by weight of 75 or more. Aluminum oxide powder 1-10 by weight, aluminum nitride powder 1-10
A mixed powder consisting of a weight factor and 0.5 to 5 weight factor of at least one oxide powder selected from the group consisting of titanium oxide powder, magnesium oxide powder, and zirconium oxide powder is molded. Then in a non-oxidizing atmosphere, 1500-1
A method for producing a ceramic sintered body, characterized by sintering at 900°C.