JPS61178473A - Manufacture of si3n4 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 Field of Industrial Application This invention relates to a method for producing a Si3N4 sintered body, which is used as a component material for, for example, gasoline engines, gas turbine engines, etc.

Conventional technology In manufacturing Si3N4 sintered bodies, sintering is performed at as low a temperature as possible to directly reduce fuel costs.
Indirectly, there is the benefit of reducing wear and tear on furnace materials and kiln tools, so Y2O3 and ^Q20s
Alternatively, a sintering aid such as MIIO is added. By adding such a sintering aid, a liquid phase is generated at a low temperature during the sintering process, and sintering is performed by a viscous flow mechanism in which Si3N4 moves particle by particle, increasing the sintering speed. Therefore, conventionally, when producing 5iaN+ sintered bodies by pressureless sintering, Y203 and ^Q2 were used as sintering aids.
03 or 190 was added in a total amount of more than 6.0%.

On the other hand, as a method for producing ceramic powder sintered bodies, a pressure sintering method has been conventionally used in which powder is pressure-molded and simultaneously heated and sintered. This pressure sintering method has the advantage of causing plastic flow of the powder under high temperature and pressure, promoting densification, and has thus far been applied to the production of 5iaN4 sintered bodies. However, even in that case, it is necessary to increase the sintering speed, so sintering aids such as Y203 are used at 4.0%.
More than that was added.

Problems to be Solved by the Invention However, the above-described conventional method for manufacturing a Si3N+ sintered body had the following problems.

That is, as described above, when a sintering aid such as Y203 or ^Q203 is added, a liquid phase is generated at a low temperature during the sintering process, and this effect improves the sintering rate. However, on the other hand, there was a problem in that the obtained sintered body did not have sufficient high temperature strength. Specifically, it is a fact that when approximately 4.0% of sintering aid is added in the production of Si3N4 sintered bodies, the strength of the obtained sintered bodies decreases to about 53 to 70 ka/- at 1200°C. there were.

In addition, in the above conventional method for manufacturing a Si3N4 sintered body,
When the resulting sintered body is heated in an oxidizing atmosphere, there is a problem in that the weight increase due to oxidation is large and the properties of the sintered body change.

This invention has been made in view of the above-mentioned conventional circumstances, and provides a method for manufacturing a Si3N4 sintered body that can reduce oxidation gain during the sintering process of the Si3N+ sintered body and improve high-temperature strength. The purpose is to provide

The means for solving the problem, that is, the method for manufacturing 5iaN4 sintered bodies of the present invention, is to use 8i1203, Y203, MI
The average particle size of at least one type of O is 2JJll so that the total amount is 2.0% (weight%, the same hereinafter) or less.
It is characterized in that it is added to the following 5isN+ and pressure sintered in a non-oxidizing atmosphere.

Below, the average particle size of each mixed powder in the method of this invention,
Describe the reason for limiting the amount added.

(1) Average grain size of SisN+: 5ia When the average grain size of N4 exceeds 2.0 tones, the strength of the obtained sintered body is insufficient. Therefore, the average particle diameter of 5iaN+ needs to be 2.0 tones or less, more preferably 1.8 tones or less, and most preferably 1.5 tones or less.

(2) AI! 203, Y203.14110(F) Average particle size^g20s, Y203, MOOf) Average 'l
When the diameter exceeds l diameter ffi o and i diameter, the density and room temperature/high temperature strength of the obtained sintered body decrease. Therefore, eight Q203,
The average particle size of Y203 and MIO must be 0.1311 or less, more preferably 0.08 J3 or less, and most preferably o, os 4 or less.

(3) AI! 203, Y203, MIIO(7)
Total amount ^ Total amount of Q203, Y203 and MIO is 2.0
% or less because if the total amount exceeds 2.0%, the high-temperature strength of the resulting sintered body will decrease.

Now, in this invention, the above raw material powder is sintered under pressure in a non-oxidizing atmosphere.

Ar, N2, etc. can be used as the non-oxidizing atmosphere. Further, the pressure sintering can be performed by applying the well-known HP method or HIP method.

Example Examples of this invention are described below.

Example 1 Si3N with an average particle size of 0.3jJ, an average particle size of 0.03
-0.3% Y203, average particle size 0.02 pa^
0.6% of Q203 was added and sintered to obtain a 5iaN4 sintered body.

The sintering process is shown in Figure 1.

First, Si3N41! :Y203 and ^1203 f) Powders were mixed for 96 hours using a ball mill using plastic balls with ethanol as a medium, and the dried product was molded at a pressure of 200 ko/d to perform primary molding. After the next molded product was subjected to isostatic pressing at a pressure of 1200 kMd, the obtained molded product was heated at a temperature of 1700 to 1850°C in a nitrogen gas atmosphere of 10 ats for 400 mA.
It was opened and pressurized at a pressure of t-. The obtained sintered body was polished using a diamond grindstone and diamond paste. The final particle size of the diamond paste was one tone. Five test pieces of 4QX4X311 were made from the sintered body after polishing.
Zero pieces were cut out, and a three-point bending test was conducted on 40 pieces. Three-point bending tests were carried out in ambient air, with a span of 30+m and a crosshead speed of 0.5-1/m at room temperature and at temperatures of 1200<0>C. Also,
The remaining 10 pieces were placed in an atmosphere of 1200℃ and 45% humidity for 72 hours.
After standing for 0 hours, oxidation weight gain was measured.

Example 2 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder was obtained by adding 0.5% of Y2O3 with an average particle size of 0.03 JJII and 0.5% of ^1!203 with an average particle size of 0.02 to 5isN4 with an average particle size of 1.1JJI. Ta.

Example 3 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder is Si3N+ with an average particle size of 0.3-, 0.8% Y2O3 with an average particle size of 0.03, and 0.8% of Y2O3 with an average particle size of 0.02.
It was obtained by adding 0.8% of 8g203 of P.

Example 4 Using a mixed powder having the following composition, sintering was carried out in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were carried out.

The mixed powder is Si3N4 with an average particle size of 0.3 mm, 1.0% Y2O3 with an average particle size of 0.03 mm, and 1.0% of Y2O3 with an average particle size of 0.02 mm.
JJa!ノ＾Ih O3 added 1.0%l,,te41
7=.

Example 5 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder was obtained by adding 0.5% of Y 203 (average particle diameter 0.03 nf) and 1.5% of Alh 03 (average particle diameter 0.02 JJIl+7) to Si3N4 with an average particle diameter of 1.1 mm. Ta.

Comparative Example 1 A mixed powder having the following composition was sintered in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder is Si3N4 with an average particle size of 0.3JJ, 2.0% Y203 with an average particle size of 0.03JJ, and 2.0% of Y203 with an average particle size of 0.0JJ.
2 Obtained by adding 2.0% of JJ's ^1!202.

Comparative Example 2 A mixed powder having the following composition was sintered in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder is Si3N+ with an average particle size of 0.3 JJl, 5.0% Y2O3 with an average particle size of 0.03, and 5.0% of Y2O3 with an average particle size of 0.
02ya's ^Q203@ 5.0% addition Lr1).

Example 6 Using a mixed powder having the following composition, sintering was carried out in the same process as in Example 1, and the same three-point bending test and measurement of oxidation gain as in Example 1 were carried out.

The mixed powder was obtained by adding 0.8% of Y203 with an average particle size of 0.02% (7) and 0.8% of &JIIO with an average particle size of 0.015 to 5iaN4 with an average particle size of 1.1JJl. .

Example 7 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder is 5isN4 with an average particle size of 0.3JJll,
1.45% of ^1!203 with an average particle size of 0.02, an average particle size of 0.015 JJl (lflo 0.55% I added
r1l.

Example 8 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and measurement of fermentation weight gain as in Example 1 were performed.

The mixed powder is 5iaN+ with an average particle size of 1.1JJIl,
Average particle size 0.023711 (7) Y203 @ 1.0
%, average particle size 0.02 F(7)8lh 03 wo0.
73%, average particle size 0.015-0.5
It was obtained by adding 5%.

Comparative Example 3 Using a mixed powder with the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation gain measurement as in Example 1 were performed.

The mixed powder is Si3N4 with an average particle size of 0.3 degrees, 2.0% Y2O3 with an average particle size of 0.02 degrees, and 2.0% Y2O3 with an average particle size of 0.02 degrees.
JJII(7)^12203 t 1.45%, an average particle size of 0.015 mm was obtained by adding 0.55% of M2O.

Comparative Example 4 Using a mixed powder having the following composition, sintering was performed in the same process as in Example 1, and the same three-point bending test and oxidation weight gain measurement as in Example 1 were performed.

The mixed powder is 5isN4 with an average particle size of 0.3 mm, 3.0% Y2O3 with an average particle size of 0.02 JJ, and 3.0% of Y2O3 with an average particle size of 0.02 JJ.
02 ym^1!20s 2.19%, average particle size 0,
It was obtained by adding 0.81% of MgO of 0.015.

Tables 1 and 2 show the conditions for adding each component in each of the above Examples and Comparative Examples, as well as the density, three-point bending strength, and oxidation weight gain of the obtained sintered bodies.

As can be seen from Table 1, all of the sintered bodies (Oka 1 to NtlL5) obtained by the examples of the present invention had a 98%
%T-D or higher density, and all at 1200℃
The three-point bending strength was high at 92 μ/- or more, and the oxidation weight gain was low at 0.20 mu/d or less. On the other hand, Y2O3 and AI! Comparative Example 1 (m6
) had a sintered body density of about 99% T-D,
The three-point bending strength at 1200°C was as low as 70 ka/-, and the weight gain due to oxidation was as high as 0.51 mg/cd. In addition, Comparative Example 2 (llil
The sintered body of No. 17) had a density of about 99% TD, but the three-point bending strength was as low as 53 kM-, and the weight gain due to oxidation was extremely high at 2.1010/d. moreover,
As can be seen from Table 2, all of the sintered bodies (Hidden 8 to Na 10) obtained by the Examples of the present invention had 120
The three-point bending strength at 0°C was high at 92 ka/- or more, and the weight gain due to oxidation was low at 0.20 Q/d or less.

On the other hand, the sintered body of Comparative Example 3 (Na11) in which the addition amount of the sintering aid consisting of Y2O3, ^11203 and
The point bending strength was 71 kM-, lower than that of the example, and the oxidation weight gain was 0.60 I! la/at, which was higher than that of the example. Also, Y203 and ^1!203 and N
The sintered body of Comparative Example 4 (N1112) in which the amount of sintering aid consisting of 90% was 6.0% had a low three-point bending strength of 66 kg/- at 1200°C, and the weight gain due to oxidation was 1.6010.
/ci.

Effects of the Invention As described above, according to the method for manufacturing a Si3N+ sintered body of the present invention, Δg203 and Y2 are added to Si3N4 as sintering aids.
By adding at least one of O3 and IJ90 and keeping the total amount of them to 2.0% or less, the original benefit of improving the sintering speed by adding a sintering aid is secured. The excellent effect of improving the density and strength of the obtained sintered body, especially the high-temperature strength, can be achieved even when the sintered body is heated.

Moreover, the effect of reducing oxidation weight gain when placed in a high-temperature oxidizing atmosphere is achieved.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a sintering process in an embodiment of the present invention. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (and 1 other person) District 1

Claims (1)

[Claims] Al_2O_3 with an average particle size of 0.1 μm or less and Y_2O
_3, at least one type of MgO in total amount 2.
A method for producing a Si_3N_4 sintered body, which comprises adding Si_3N_4 with an average particle size of 2 μm or less so that the amount is 0% (weight %, the same applies hereinafter) or less, and sintering under pressure in a non-oxidizing atmosphere.