JPH01212278A - Production of ceramics parts - Google Patents

Abstract

PURPOSE:To obtain the subject parts having excellent impact resistance and reliability at a high yield by presintering an Si3N4 molding contg. Y2O3, CeO2 and ZrO2 as a sintering assistant in an inert gaseous atmosphere of a prescribed temp., then changing temp. conditions and subjecting the molding to a hot isostatic treatment which acts commonly as regular sintering. CONSTITUTION:The molding obtd. by adding 2-30wt.% sintering assistant contg. 30-70wt.% ZrO2 and >=1wt.% Y2O3 and CeO2 to the Si3N4 powder then mixing and molding the mixture is first presintered in the inert gaseous atmosphere kept at 1,370-1,600 deg.C. This molding is then subjected to the hot isostatic treatment which acts commonly as normal sintering in the inert gaseous atmosphere kept at <=1,750 deg.C.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing ceramic components.

(Prior art) Ceramics, especially 5isN4 ceramics, have been used for example in engine parts of vehicles such as automobiles because they have strong high-temperature strength and excellent impact resistance compared to other ceramics. It is used in practical applications as parts that require wear resistance, such as As a method for manufacturing such 5i3No ceramics,
For example, as disclosed in JP-A-60-122783, 5isN* is sintered and then surface-treated.
Next, by performing heat treatment in an N2 gas atmosphere,
A method is known to reduce variations in strength after machining.

However, although 5i3Ns ceramics have excellent impact resistance as mentioned above, their impact resistance is lower than that of metals other than ceramics, for example, only about 115 that of cast iron, and the conventional method described above Although it is possible to reduce the variation in the strength of the obtained ceramic after the force I'l-L, no improvement has been made in terms of impact resistance. Therefore, when ceramics obtained by this method are applied to an apex seal attached to the top of a rotor in a rotary piston engine of a vehicle such as an automobile, the apex seal is exposed to high-pressure combustion gas and is exposed to planetary rotation. Since they are subjected to various restraining forces associated with exercise, there may be cases where they cannot withstand these harsh conditions.

Under these circumstances, the present inventor found that when Y2O1, Cen2, and Zr0t were added as sintering aids to 5ilN4 powder and sintered in two stages at a predetermined temperature, the impact resistance value of the sintered body was significantly increased. I found out.

(Problems to be Solved by the Invention) However, in the -F sintering method, micropores remain in the sintered body, and the sintered body has uneven impact resistance. has grown larger. Therefore, a thermostatic pressure treatment (hereinafter referred to as 1', HTP treatment) was performed in order to remove fine pores in the sintered body. However, the impact resistance deteriorated.

The present invention was made in view of the following circumstances, and its purpose is to improve the reliability of ceramic components with excellent impact resistance.

(Means and effects for solving the problem) In order to achieve this object, the present invention uses Yt as a sintering aid.
A 5ilN4 molded body containing Os, Cent, and ZrO2 was first sintered in an inert gas atmosphere at 1370 to 1600°C, and then hot-sintered in an inert gas atmosphere at 1750°C or higher, which also served as main sintering. This is a method of manufacturing a ceramic component characterized by performing a hydraulic treatment.

With the configuration described above, the ceramic structure is transformed into HI, which also serves as main sintering in the post-stage sintering process, by the pre-stage sintering.
The density becomes suitable for P treatment, and by performing HIP treatment which also serves as main sintering after the pre-stage sintering, it is possible to eliminate micropores in the sintered body. Therefore, the ceramic component not only has excellent impact resistance but also has improved reliability.

To explain more specifically, sintering aid Y2O3, CeO
x and Z r 02 are preferably set in the range of 2 to 30 % of the amount of insects in the entire mixed raw material. If the proportion of the sintering aid in the mixed raw material is too large, it will promote abnormal grain growth of Si3N and particles during sintering, causing a decrease in strength, and the grain boundary layer will become large, resulting in a decrease in the Charpy value. This is because, while the ratio of the sintering aid to the mixed raw material decreases, sintering becomes difficult if the proportion of the sintering aid in the mixed raw material decreases too much.

The proportion of ZrO2 in the sintering aid is 30 to 70% by weight
It is preferable to set it to . Z r in the sintering aid
This is because if the proportion of Ot becomes too large, sintering will be hindered, while if the proportion of ZrO2 in the sintering aid becomes too small, sintering will become difficult.

The proportion of YzOs and Cent in the sintering aid is
Preferably it is at least 1% by weight. This is because if the sintering aid does not contain Y2O3 and CeO2, the Charpy value will be low.

The reason why the pre-stage sintering is performed is to ensure that the HIP treatment, which also serves as the main sintering in the post-process, is performed effectively, as described above. The sintering temperature of this first stage sintering is 1370~1
The sintering temperature is set at 600℃, which is 1370℃.
If it is less than that, the ceramic structure will not be properly densified,
This is because if the sintering temperature exceeds 1600° C., even if the main sintering temperature is appropriate, abnormal grain growth of 5isN* particles occurs, and no improvement in mechanical properties can be expected, resulting in a low Charpy value for both.

The reason why the sintering temperature for main sintering is 1750℃ or less is because
This is because if the temperature is 1750°C or higher, abnormal grain growth is promoted, resulting in a decrease in Charpy value.

The above sintering temperature can be supported by the following experiment.

That is, 5isN* powder with a gelatinization rate of 91% and an average particle size of 0.5 μm was used as a sintering aid with an average particle size of 0.5 μm or less as Yt o2 , C, e
Ot and 7. rOt were respectively prepared, and these were mixed so that the composition ratios were as shown in Table 1.

Next, using a 5isNs ball and a nylon resin pot, the above-mentioned mixed powder with ethanol added was mixed and ground in a vibration mill for 25 hours, and the slurry obtained by this mixed grinding was vacuum-dried to form a dry powder. The particle size of this dry powder was adjusted to 300 μm or less to obtain a mixed raw material.

Thereafter, this mixed raw material was set in a carbon die, and a pressure of 200 kgf/cm' was applied using a hot press to form a predetermined molded product.

Thereafter, each molded body was subjected to a first sintering process in an N2 gas atmosphere under the sintering conditions shown in Table 1 below to densify the ceramic structure to a density of 80% or more.
The HIP treatment, which also serves as the final sintering of the stages, was carried out for 200 min in an N2 atmosphere.
It was carried out under atmospheric pressure.

Each sintered body obtained in this way was
A Charpy impact test was conducted on the test piece. The test data is shown in Table 1.

(Left below) The sintering time for 1111 stage sintering depends on the suitability of the ceramic structure.
It is preferable to leave it for 1 hour or more in order to achieve thorough densification.
1st thing.

The sintering time of the main sintering is preferably set within 2 hours in order to prevent abnormal grain growth of 5i3No particles.

The reason why we decided to perform HIP treatment as well as the main sintering was as follows.]
1; This is to eliminate fine pores in cooperation with the first-stage sintering without reducing the impact resistance value. This H [
It is preferable that the P treatment be performed in an N2 atmosphere at a pressure of 200 atmospheres or more.

(Example) Hereinafter, the present invention will be explained in detail.

Add Y20x powder 2 as a sintering aid to the commercially available 5isN* powder
．． 4% of Cen2 powder, 3.6% of Z'02 powder, and 6% of Z'02 powder were added, and this was mixed in an organic solvent using a vibrating mill.
After mixing for 5 hours, the resulting slurry was dried and granulated, and the particle size was adjusted and used as a raw material. After sintering it under the conditions shown in Table 2, it was processed into each specimen size and its characteristics were examined.

(The following is a blank space) As a result, since Example 1.2 did not meet the conditions of the present invention, it was possible to obtain stable and superior impact resistance.

On the other hand, as in Comparative Example 1, 5isO*-Yt
Ox -Cent-ZrOt system under specific conditions (1500
After densification at ~1600℃! Those sintered at temperatures higher than 750°C had good characteristic values. However, in the process of Comparative Example 1, the yield was very poor when processing into parts. In addition, the strength of the materials obtained in this way varies widely, and the materials at the lower limit of strength were examined under an electron microscope.
SF, M) IQ analysis revealed that micropores were present at the fracture origin. Therefore, when HIP treatment was performed as in Comparative Example 2 to remove these pores, the characteristics clearly deteriorated (see Table 2).

In addition, the sintered body of Comparative Example 1 was reheated (1350°C, N
2) did. In this case as well, the characteristics deteriorated.

In addition, in the case of Comparative Example 3, good characteristics could not be obtained as shown in Table 2, and the sintered body of Comparative Example 3 was used as the sintered body of Comparative Example 4.
As shown in the figure, even with the HIP treatment, good results could not be obtained because the pre-stage sintering temperature exceeded the predetermined sintering temperature in the process of Comparative Example 3.

Add 3 Y2O3 powder as a sintering aid to the commercially available 5isN* powder.
%, CeO powder 3%, and ZrO2 powder 6%, and further, 15% of fibrous SiC single crystal was added externally to prepare a material powder. This powder was heated to 1450 ml in N2 gas.
After being densified (relative density 91%) at 200 kgf/am2 for 2 hours at ℃, this was processed into a test piece with a size of 55 mm and subjected to HIP treatment at 1650 ℃ and 2000 atm, which resulted in sufficient densification. After grinding the test piece, a Charpy impact test was performed and the impact was 0.27 [kgf·m7cm21].

On the other hand, the conventional method, namely 1800℃χIhr,
The test pieces manufactured under 200 kgf/cm' in N2 gas could only be processed in half of the number of samples in this example from the same type M material components, and the Charpy value was O, l 9 [
kg-m/cm2].

(Effect of the invention) As is clear from the above description, the present invention has been made.

Ceramic parts with excellent impact resistance and high reliability can be manufactured with a high yield.

Claims (1)

[Claims] (1) Y_2O_3, CeO_2, Zr as sintering aids
1370-1 Si_3N_4 molded body containing O_2
First stage sintering in an inert gas atmosphere at 600°C, then
A method for manufacturing ceramic parts, characterized in that hot isostatic pressure treatment is performed in an inert gas atmosphere at a temperature of 1750° C. or lower, which also serves as main sintering.