JPS6364975A - Manufacture of electroconductive sialon sintered body - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a sialon sintered body, and particularly a method for manufacturing a conductive sialon sintered body mainly composed of a β-sialon phase and a TiN phase. It is related to.

[Conventional technology]

β-sialon sintered bodies have been used in various fields in recent years because they have advantages such as excellent high-temperature strength and oxidation resistance, a small coefficient of thermal expansion, and very high thermal shock resistance. This β-sialon sintered body is 1, for example,
As is known from Japanese Patent Publication No. 391 or Japanese Patent Publication No. 58-52949, a first component consisting of silicon nitride, aluminum nitride, and alumina, and at least one of yttrium, scandium, cerium, lanthanum, and lanthanide family metals. It is obtained by molding a powder mixture consisting of a second component consisting of oxides of two elements, and sintering this molded body in a protective atmosphere with or without pressure.

However, the β-sialon sintered body has a drawback in workability, and although it is usually processed using a diamond grindstone, there is a problem in that the processing time and cost are extremely large.

For this reason, recently, among the β-sialons represented by the general formula Si, Al, OzN, -, especially 2 is 1. or 4
．． 2, 15-50% IV by volume
one or more compounds of oxides, nitrides, carbides, and borides of group a, Va, and VIa elements and/or 5iC1A
1. It has been proposed to obtain a sialon sintered body that can be electrically discharge-machined by imparting conductivity by adding one or more selected from C.
Publication No. 1).

[Problem that the invention seeks to solve]

In accordance with the above-mentioned known facts, the present inventor prepared a conductive sialon sintered body and conducted various experiments and studies to obtain a product with a complex shape by electrical discharge machining. It has been found that it is necessary to improve the process and obtain a sintered body with excellent workability.

In other words, as seen in Example 1.2.3, the conductive Sialon proposed above has an electrical resistivity of 1O-1 (Ω・c!1) or more in all cases, and electrical discharge machining is possible. It has become clear that there are problems such as slow processing speed and the impossibility of wire cutting a sintered body with a certain thickness or more.

Furthermore, as seen in the examples, the SiAlON proposed above is mainly based on hot press sintering, and the problem has also emerged that the shape of the product is extremely limited.

In view of the above circumstances, the present invention provides a method for manufacturing a conductive sialon sintered body that has better electrical discharge machinability and minimizes deterioration of the oxidation resistance, thermal shock resistance, etc. that β-sialon inherently has. The purpose is to

Means for Solving the Problem c] In order to achieve the above object, the present invention mainly uses Si, N
, powder, A1□O1 powder, AIN polytype powder (AI
(containing N), Sio, powder, and oxide or nitride powder of one or more MA group elements, and for these, 25 to
After adding 70% by volume of TiN powder, mixing and molding, this molded body is sintered at 1600-2000°C under normal pressure or pressurized nitrogen to form a mixture consisting mainly of β-sialon phase and TiN phase with the remainder being , Si, Al, one or more Ma group elements, O, N, in a method for obtaining a conductive sialon sintered body composed of a grain boundary phase consisting of
This is a method for producing a conductive sialon sintered body, characterized in that the N powder is obtained by a gas phase reaction.

1. TiN The most important feature of this manufacturing method is that TiN powder obtained by gas phase reaction is used as the TiN powder. Here, there are various methods for manufacturing TiN as shown in Table 1. Broadly speaking, ■ directly nitriding Ti
There are four methods: reducing and nitriding oTie, (2) nitriding T i H, and (2) converting T i N by gas phase reaction. The process that is currently being mass-produced here is the direct nitriding of Ti (2).The present inventor collected and studied TiN powder produced by various processes. The particle structure of the powder is shown in Figure 1 (the specific surface area is also shown), and it can be seen from this that the powder produced by the direct nitriding method contains a considerable amount of fine particles because the powder is pulverized in the form of lumps. Further, the specific surface area of the product reduced and nitrided from TiO□ is the same as that of the product obtained by direct nitridation, but the particle size is well matched. On the other hand, those produced by gas phase reactions have much finer particle sizes than those mentioned above.
The specific surface area is also approximately 7 times larger. Therefore, when conductive sialon was produced using these TiN powders, it was found that there was a large difference in electrical resistivity even when the same volume % was added.

That is, it has been found that when TiN produced by gas phase reaction is used, the electrical resistivity is extremely lower than when TiN produced by direct nitridation is used. The lower the electrical resistivity, the better the electrical discharge machinability, the higher the machining speed, and the higher the machining efficiency. In addition, the amount of TiN required to maintain the same electrical resistivity is small, and the oxidation resistance and
It becomes possible to improve thermal shock resistance.

The reason why the amount of TiN powder added is 25-70% by volume is that if it is less than 25% by volume, the contact between the TiN particles is insufficient, good electrical discharge machinability cannot be obtained, and the resistance This is because the variation in the ratio is also large, and if it exceeds 70% by volume, the characteristics inherent to β-sialon, such as oxidation resistance and high-temperature strength, will deteriorate significantly. More preferable T
The amount of iN is 30 to 50% by volume.

In addition, in the present invention, a Ma group element is added,
This is to enable normal pressure sintering, gas pressure sintering, etc. Here, the Ma group elements form a liquid phase during sintering and promote sintering. Since it is not solidly dissolved in β-SiAlON, it becomes the main component of the grain boundary phase in the sintered body. Although it is possible to use MgO or the like to bring about such an effect, it is preferable to use a Ma group element in order to maintain high high-temperature strength.

In addition, sintering is performed at normal pressure or pressurized nitrogen at a temperature of 1600 to 2000
Preferably, it is carried out at °C. If the sintering temperature is less than 1,600°C, densification will not proceed sufficiently, and if the sintering temperature exceeds 2,000°C, the generation of decomposition gas from the sintered body will be completely suppressed even when sintered in high-pressure nitrogen gas. cannot be suppressed.

Furthermore, instead of the oxides and nitrides of the MA group elements, substances that convert into these substances during sintering, such as nitrates, hydroxides, alkoxides, etc. of the MA group elements, may be used.

Furthermore, when molding the mixed powder in the present invention, molding methods such as injection molding, pressing, rubber pressing, and slip casting can be used, and the properties can be further improved by HIP treatment after sintering. It is also possible to perform heat treatment to strengthen the grain boundary phase.

〔Example〕

Example I Si□N4 powder (particle size 0.7μ, gelatinization rate 93%), A
IN polytype powder (crystal type 21R1 particle size 2 μm, 98
．． 8%), A1□0. Powder (particle size 0.5μ grave, 99.5
%), T20. Powder (particle size 1μ, 99.99%) was used and blended so that z = 0.5 in β-sialon (Y a Os amount was 7%).

On the other hand, three types of T i N with different manufacturing processes
After adding 35% by volume, mixing and molding, 1750
C. for 4 hours in a nitrogen atmosphere at 1 atmosphere.

Table 2 shows the electrical resistivity, density, and room temperature strength of the obtained sintered body.

Table 2 From these results, it can be seen that when using TiN produced by the TiO□ vapor phase synthesis method, the electrical resistance is greatly reduced even when the same amount of TiN is added.

Example 2 Using the same powder as in Example 1, it was blended to have a β-sialon composition of z = 0.4, and 31% by volume of Example 1 was added to this powder.
The T i N used in was added. After mixing and forming this,
Sintering was carried out at 1780° C. for 4 hours in a nitrogen atmosphere of 5 atm. The structure of the obtained sintered body is shown in FIG. 2, and the specific surface area and electrical resistivity of the raw material powder are shown in Table 3.

Table 3 From Figure 2, Ti in the sintered body made from T1Ni material A
It can be seen that the particle size of N is significantly smaller than those made from B and C.

Correspondingly, the electrical resistivity also decreases significantly.

Example 3 Using the same powder as in Example 1, it was blended to have a β-SiAlON composition with z = 0.5, and 20 to 75% by volume was added to this powder.
of T i N (B powder) was added. After mixing and molding, this was sintered at 1750°C for 4 hours in 1 atm nitrogen.Table 4 shows the relative density, electrical resistivity, and high temperature strength of the sintered body.
1100°C).

Table 4 From the above, Si3N, powder, Al, 03 powder, AIN polytype powder and/or Sin, powder, and compounds of one or more ma group elements and 25 to 70
In the manufacturing method for obtaining a conductive sialon sintered body by adding % by volume TiN powder, mixing, molding, and sintering, the electrical resistivity is low by using TiN made by gas phase reaction. It can be seen that a conductive sialon sintered body with excellent mechanical properties can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to manufacture a conductive siflone sintered body that has excellent electrical discharge machinability and minimizes deterioration of the oxidation resistance, thermal shock resistance, etc. of the original β-sialon. This makes it possible to drill holes with complex shapes that were impossible with conventional Sialons, expanding the range of applications for dies, structural members, etc., and also allowing SiAlons to be applied to fields such as heaters that utilize conductivity. becomes possible.

[Brief explanation of drawings]

Figure 1 is a micrograph showing the particle structure of TiN powder made by various processes, Figure 2 is a photomicrograph showing the particle structure of TiN powder A, B,
It is a micrograph showing the microstructure of a sintered compact made using C as a raw material. Fig. 1 Fig. 2 A, ' x 20 oO

Claims (1)

[Claims] A method for producing a conductive sialon sintered body whose conductive phase is a TiN phase, the method comprising using TiN powder obtained by a gas phase reaction.