JPH0416565A - Conductive sialon sintered body and production thereof - Google Patents

Abstract

PURPOSE:To improve thermal impact resistance by mixing respectively specific ratios of raw materials of beta type sialon, nitride of Ti, Y2O3 and/or CeO2, oxide of Ni and/or oxide of Co, molding the mixture, and sintering the molding after heat treating in an N2 atmosphere. CONSTITUTION:The powder mixture formed by compounding Si3N4, AlN and Al2O3 in such a manner that the Z in the beta type sialon sintered body expressed by formula attains a prescribed value, and the nitride powder of Ti, such as TiN, are mixed to attain 22 to 50vol.% (hereafter %) of the total volume, >=1 kinds of the Y2O3 powder and CeO2 powder as sintering assistants are so mixed as to attain 0.2 to 5.4% of the total volume, and >=1 kinds of the oxide powder of Ni, such as NiO, and oxide powder of Co, such as Co3O4, are so mixed as to attain 0.3 to 2.1% of the total volume. The mixture is then molded. This molding is held for >=1 hours at 1550 deg.C to 1650 deg.C in an atm. or pressurized gaseous N2 atmosphere and is then held and sintered for >=2 hours at 1700 to 1840 deg.C, by which the conductive sialon sintered body having the high thermal impact resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sialon sintered body and a method for manufacturing the same.
) This relates to a conductive sintered body mainly composed of β-type SiAlON.

Conventional technology β-type sialon sintered bodies have the advantages of being relatively hard to adhere to metals such as iron, having excellent high-temperature strength and oxidation resistance, and having a small coefficient of thermal expansion and high thermal shock resistance. , in recent years, attempts have been made to apply it in various fields. If the β-type sialon sintered body has electrical conductivity, it is thought that the field of application of the current-carrying body 1 that performs rapid heating and cooling will further expand. However, the β-type sialon sintered body itself is an insulator and cannot be used as a current-carrying body as it is.

Recently, IVa, Va, VI a M in β-type sialon
It has been proposed to add oxides, nitrides, and carbides of elements to impart conductivity to obtain a sialon sintered body that can be subjected to electrical discharge machining (Japanese Patent Laid-Open No. 82-285177).

This also makes it possible to use β-type sialon as a current-carrying body.

Problems to be Solved by the Invention The present inventor conducted an experimental study to apply the conductive sintered body according to the above-mentioned known technology to a current-carrying body, and found that in order to improve thermal shock resistance, a conductive phase is required. It was concluded that it is desirable to reduce the amount of Ti nitride.

That is, Ti nitride has a larger coefficient of thermal expansion than Sialon. Therefore, the thermal shock resistance of the conductive Sialon sintered body depends on the amount of Ti nitride.

On the other hand, the specific resistance also depends on the amount of Ti nitride, and the smaller the amount of Ti nitride, the more the specific resistance increases and the more difficult it is for current to flow.

In view of the above circumstances, it is an object of the present invention to provide a thermal shock resistance higher than that of the prior art while ensuring a predetermined specific resistance.

Means to Solve the Problem 2 In order to achieve the objective, Mizuo 1's invention uses β-type sialon (Si6-2 uzO2NB-2) and T1 nitride in an amount of 22 to 50% by volume based on the total capacity. ,y,o3. C
One or more types of eO2 are 0.2 to 5.4 to the total capacity
% by volume, reaction products of one or more of N1 oxide and Co oxide and β-type sialon and/or Ti nitride should be 0.3 to 3.7 vol% based on the total capacity. This is a conductive sialon sintered body characterized by:

The reason why Ti nitride is used as a constituent is that it is a compound with electrical conductivity and a high melting point, and has little adverse effect on the sintering of Sialon. The amount of this compound is 22
The reason why it is set at ~50% by volume is that if it is less than 22% by volume, there are too few contact points between the conductive compound particles and the conductivity required for 1-current heating cannot be obtained, and if it exceeds 50% by volume, β-type SiAlON This is because the difficulty of adhesion with metal and the thermal shock resistance of the metal are impaired. The nitride wrinkles are more preferably 30 to 40% by volume.

Y2O3 and CeO2 are sintering aids for Sialon. The amount of these compounds ranges from 2 to 5.4% by volume.
．． If it is less than 2% by volume, the sintered body will not be densified, and 5.
If it exceeds 4% by volume, the glass phase increases and high temperature strength decreases. The modulus of these sintering aids is more preferably 1.1 to 4.
．． It is 1% by volume.

The N1 oxide and the Co oxide have the effect of promoting sintering between Ti nitride particles without relatively inhibiting the sintering of Sialon. If sintering between Ti nitride particles is promoted, the specific resistance will decrease. Therefore, the same specific resistance can be obtained with less Ti nitride without significantly deteriorating the mechanical properties of the sintered body. The Ni oxide and Co oxide form β-sialon and/or Ti during heating.
reacts with the nitride of, and after cooling a reaction product is formed.

The amount of the reaction product in the sintered body is set to 0.3 to 3.7% by volume by 2O. If it is less than 3% by volume, the proportion of Ti in contact with nitride particles is small and the resistivity reduction effect does not appear, and if it exceeds 3.7% by volume, the effect of the reaction product becoming the starting point of destruction is more pronounced. become. The amount of the reaction product is more preferably 0.6-2.5% by volume. Although the detailed chemical structure of the reaction product is unknown, it is thought to be a compound and/or solid solution consisting of Ni, Si, Ti2O, etc. when an oxide of i is added.

Furthermore, a method for manufacturing a conductive sialon sintered body, which is the second invention, is as follows.

That is, as a raw material for β-sialon, 5iJ4. One is a mixture or compound of MN, Idl, and Os, and has a predetermined value of Z as a β-sialon, and the other is a Ti nitride with a concentration of 22% of the total capacity.
~50% by volume, one or more of Y2O3, Ce02 (7) is 0.2~5.4% by volume based on the total capacity, N! oxide of Co, and one or more of the oxides of Co are 0.
A mixture consisting of 3 to 2.1% by volume is molded, and the molded body is heated to 1550~! under normal pressure or a pressurized nitrogen gas atmosphere. 65
After holding at 0℃ for more than 1 hour, 1700-1840℃
The conductive sialon sintered body of the present invention can be obtained by holding the sintered body for 2 hours or more and sintering it.

Note that the reason why the temperature is maintained at 1550 to 1850°C is to uniformly disperse the melt in the grain boundaries. If the temperature is lower than 1550°C, the melt will not be sufficiently dispersed. Also, Si, N, -
Once dissolved in the melt, it re-precipitates and grows into columnar crystals,
When the columnar knots 1 grow sufficiently and intertwine with each other to become densely charged, the β-sialon exhibits high strength.

At 1,650 to 1,700°C, 513M4 begins to dissolve and reprecipitate before the melt is fully dispersed.Moreover, in this temperature range, the growth of columnar crystals is insufficient and WK density cannot be achieved. S i
The dissolution and reprecipitation of 3N4 must be suppressed. Therefore, the temperature at this time needs to be 1650°C or lower.

Next, the reason for holding it at 1700-1840℃ is 17
If the sintering temperature is less than 1,840 degrees Celsius, densification will not proceed sufficiently for the reasons mentioned above, and if the temperature exceeds 1,840 degrees Celsius, decomposition of 5iJ4 cannot be suppressed unless nitrogen gas is at least 100 atm. At high pressures, it is necessary to eliminate open pores in the molded body in advance, which increases the number of manufacturing steps. In addition, when sintering in a pressurized nitrogen gas atmosphere, the nitrogen gas pressure is preferably 1.1 to 30 atm.

The Ni oxide and the Co oxide react with the β-sialon and/or the Ti nitride during heating, and a reaction product phase is formed after cooling. Ni oxide, G.

2O. If the amount is less than 3% by volume, the proportion of T1 in contact with the nitride particles will be small, and the sintering promotion effect will not appear.

Moreover, when the amount exceeds 2.1% by volume, the effect that the reaction product becomes the starting point of destruction becomes more pronounced. The amount of one or more of Ni oxide and Go oxide is more preferably 0.6 to 1.
．． 4% by volume.

Effects According to the present invention as described above, it has become possible to easily obtain a sintered body having the same resistivity and higher thermal shock resistance than the conventional conductive sialon sintered body. This is because the addition of Ni oxide and Co oxide promotes sintering between Ti nitride particles and increases the current path.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on examples.

Si3N4 powder (average particle size 0.5 gm, gelatinization rate 97%)
above), M2O3 powder (average particle size 0.2 pm),
AIN polytype powder (crystal type 21R, v average particle size 3 m
) of β-type sialon in the sintered body = 0.4
5. Additionally, Y2O3 is used as a sintering aid.
(+average particle size 0.6, Btm) and Ce07 (average particle size 1 gm) were blended in the proportions shown in Table 1.

In contrast, TiN (average particle size 1.5 gm) and N1
(7) Oxide (average particle size: 7 m) and Go oxide (average particle size: 10 mm) were added in the proportions shown in Table 1.

After mixing and molding these, 160°C in a normal pressure nitrogen gas atmosphere
After holding at 0°C for 2 hours, it was held at 1750°C for 5 hours for sintering, and then slowly cooled to room temperature. The room temperature bending strength, specific resistance, and thermal shock resistance of the sintered body thus obtained are shown in Table 1.Thermal shock resistance is the maximum quenching temperature difference ΔT ('C) at which no strength deterioration occurs by the underwater quenching method. It was evaluated by

(Left below) Effects of the Invention The present invention has made it possible to produce a sintered body with the same resistivity and higher thermal shock resistance than the conventional conductive sialon sintered body. Applicable force to the current carrying body that performs heating and cooling (possible).

Claims (2)

[Claims] (1) β-type sialon (Si_6_-_ZAl_ZO_
ZN_8_-_Z), Ti nitride is 22 to 50% by volume of the total capacity, one or more of Y_2O_3 and CeO_2 is 0.2 to 5.4% by volume of the total capacity, Ni oxide, A conductive sialon sintered product characterized in that a reaction product of one or more Co oxides and β-type sialon and/or Ti nitride is comprised of 0.3 to 3.7% by volume based on the total capacity. Concretion. (2) β-type sialon raw material and Ti nitride are 22 to 50% by volume of the total volume, Y_2O_3, CeO_2
One or more of these is 0.2 to 5.4% by volume of the total capacity
A mixture of 0.3 to 2.1% by volume of at least one of , Ni oxide, and Co oxide based on the total volume is molded, and this molded body is heated at normal pressure or in a pressurized nitrogen gas atmosphere. 15
After holding at 50~1650℃ for more than 1 hour, 1700~
A method for producing a conductive sialon sintered body, which comprises sintering at 1840°C for 2 hours or more.