JPS63277578A - Production of sintered material having high density - Google Patents

Abstract

PURPOSE:To obtain a sintered material having high density and high uniformity, in high production efficiency, using a pressurized self-combustion sintering process, by mixing raw material powder with a lubricant convertible to the same composition as the components of the raw material powder. CONSTITUTION:Raw materials (e.g. a mixture of metallic titanium powder and carbon black) necessary for the production of a sintered article by pressurized self-combustion sintering process are mixed with a lubricant (e.g. stearic acid) convertible to the same composition as one or more components of the raw material powder. The mixed powder is compression-molded to obtain a molded article having excellent uniformity by the action of the lubricant and heat-treated to convert the lubricant in the molded article into one or more raw material components. The obtained molded article is ignited under pressure to start the combustion reaction to effect the simultaneous synthesis and sintered by the heat generated by the combustion process to obtain the objective sintered article having high density.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing ceramics or cermets such as titanium carbide, titanium carbide-alumina, and titanium carbide-titanium.

Conventional Technology Ceramics such as titanium carbide and titanium boride generally have a high melting point and high hardness, and are suitable for use under harsh conditions. In recent years, it has attracted attention not only as an abrasive and a tool, but also as a structural material.

Conventionally, in order to obtain these ceramics, a method has been used in which raw material powder is molded and fired at a high temperature of 1,600 to 2,200° C. for a long period of time. Since this method consumes a large amount of energy, efforts have been made to add various additives as sintering aids to lower the temperature required for densification. Recently, as a new method for sintering ceramics, powders of metal and nonmetallic elements (carbon, boron, etc.) are thoroughly mixed, then molded, and a part of the molded body is ignited under high pressure to start a reaction. The reaction propagates sequentially throughout the ignition point,
Pressure self-combustion sintering method (formerly known as gh Pressure SeIf-Comb) involves simultaneous synthesis of carbides and borides and production of sintered bodies during the propagation of the reaction.
Ustion Sintering Method)
; HPCS method) has been proposed. According to this method, high-purity ceramics can be obtained in an energy-saving process and in a short time. The ignition method is generally to ignite one point of the molded object using a filament or laser light (P, D, Zavitsanos and J, R, Morris Jr.
Zavitsanos and J, R, Morris
.

Jr.), Ceramic Engineering Science Proceedings (Ceram, Eng, Sci, Pro
c, > +4, [7-8], 624 (1983))
. Other methods include a method in which the outer periphery of the molded body is surrounded by a heater and the reaction is propagated from the surroundings, and a method in which electricity is applied directly to the molded body. (0, Yamada, Y, Miyamoto and M, Koizumi (0, Yamada, Y, Miyamoto an
dM. Koizuwi) r American Ceramic Society Bulletin (Am, Ceras, so
e, Bull, ), 64[2]319-2H198
5)) The detailed reaction mechanism of the self-combustion reaction is still largely unknown, and research is underway at various research institutes in Japan and abroad. A considerable amount of phenomenological data has been accumulated, and researchers have agreed on the effects of temperature and atmospheric pressure on combustion modes. There are two combustion modes: steady mode and unsteady mode.
Only in the former case can a uniform sintered body be obtained. In order to produce a uniform sintered body, the problem is how to burn it in a steady mode. It is known that the higher the temperature and atmospheric pressure, the more combustion will occur in a steady mode, but the combustion mode is also susceptible to other factors (it cannot be controlled solely by temperature and atmospheric pressure. Very sensitive to body condition.

When attempting to produce a dense sintered body by pressurized self-combustion reaction, compaction density is an important factor. R,W
, Rice et al. investigated the porosity of the product and the compacting density of the raw material powder before the self-combustion reaction, and found that if the compacting density was too low or too high, a dense sintered body could not be obtained, and that depending on each system. It is pointed out that there is an optimal molding density. (R,W,
Rice, G. Y., Richardson, J. M., Kunez, T., Schroter & W. J., McDonough (R.
, W., Rice, G., Y., Richardson, J.
M.Kunetz.

T, 5chroeter and Wl, Mc mouth on
(ough), proceedings on io t
h Annual Conference on Composite and Advanced Ceramic Materials (P
roceedings of theloth Ann
ual Conference on Composi
tes and Advanced Ceramic
Materials), I), 737-750, American Ceramic Society (The Amer
icanCeraIIIic 5ociety) (1
(986)) Therefore, in order to obtain a high-density sintered body, it is also necessary to control the compacting density.

Problems to be Solved by the Invention When raw material powder is pressure-molded, pressure distribution occurs in the compact, making it impossible to obtain a uniform compact. For this reason, naturally,
This non-uniform density in the molded body causes non-uniformity in the obtained sintered body. Also, microscopic non-uniformity in compact density can cause unsteady mode combustion. Generally, in powder metallurgy, a lubricant is used during pressure molding in order to obtain a uniform molded body. However, in the pressurized self-combustion reaction, these lubricants cause unsteady mode combustion, and moreover, the lubricants are incorporated into the products as impurities even after combustion.

The present invention solves these problems.

Means for Solving the Problems In a method of producing a sintered body using heat generated by compound formation, a lubricant that can be converted into the same composition as one or more of the components of the raw material powder by heat treatment is used. The lubricant is mixed into the raw material powder, the mixed powder is pressure-molded, the lubricant in the molded body is converted into one or more of the raw material components by heat treatment, and then the molded body is ignited under pressure to burn. The reaction is initiated and the heat generated as a result of the combustion process performs synthesis and simultaneous sintering.

Since a lubricant is mixed with the working raw material powder, the pressure molding process can be carried out smoothly, and of course the uniformity of each part of the molded product obtained is very high.Moreover, the lubricant in this molded product is Since it is converted into one or more of the raw material components by heat treatment before carrying out the pressurized self-combustion reaction, it does not interfere with the steady mode combustion.Therefore, the sintered body obtained by such a manufacturing method is There is almost no non-uniformity in the density of each part, and the density is very high.In addition, the content of impurities is naturally low.

Example Example 1 An attempt was made to produce titanium carbide from titanium and carbon powder.

Titanium metal powder with a particle size of 10 u@ and carbon black made from acetylene were mixed in a ratio of 1.0:0.
．． This mixed powder is mixed at a molar ratio of 9 and 10
1 wt, $ stearic acid was added to the mixture to make it zero, and the mixture was dry mixed for 1 hour. Uniaxial pressure molding was performed at a pressure of 100 MPa to produce a molded body with a diameter of 25 + ua and a height of 10 am. The molded body was heated in a vacuum at 600° C. for 5 hours while it was still under pressure. After the temperature was returned to room temperature, an argon atmosphere (1 atm) was created, and a tungsten heater provided at the bottom of the sample was energized to ignite the compact and start a combustion reaction. According to the results of powder X-ray diffraction, the obtained sintered body consists of a single phase of titanium carbide, and the density measured by the Archimedes method is 97.1z of the theoretical density.
Met. When the fractured surfaces of each part of the sintered body were observed using a scanning electron microscope, similar microstructures were observed everywhere.
It was confirmed that the entire sintered body had extremely high uniformity.

Example 2 An attempt was made to manufacture titanium carbide-titanium cermet from powders of titanium and carbon.

Metallic titanium powder with a particle size of 10 μ- and carbon black made from acetylene were dry mixed at a molar ratio of 1.0 and 0.6. Next, this mixed powder was adjusted to 100%, and 1wt of paraffin was added to the mixture and mixed dry for 1 hour. Uniaxial pressure molding was performed at a pressure of 100 MPa to produce a molded body similar to that in Example 1.

In an argon atmosphere with the molded body under pressure as it is 5
After heating at 00℃ for 10 hours and returning to room temperature,
In the same manner as in Example 1, the molded body was ignited to initiate a combustion reaction. The obtained sintered body consisted of two phases of titanium carbide and titanium, and no other subcomponents were observed. The density is 9 of the theoretical density
9.0*, which is very high (and the uniformity was also high.

Example 3 Alumina made from aluminum, titanium oxide, and carbon powder
An attempt was made to manufacture titanium carbide composite ceramics.

Metallic aluminum powder with particle size 10 μ- and particle size l.

2 μm titanium oxide (Ti02) and carbon black made from acetylene in a ratio of 4.0:3.0
: Mixed at a molar ratio of 2.7. Next, this mixed powder was adjusted to 100%, and 1 wt.$ of aluminum stearate was added and mixed in a dry manner for 1 hour. 80M
Uniaxial pressure molding was performed at a pressure of Pa to produce a molded product similar to that in Example 1. The compact was treated in the same process as in Example 1 and ignited under the same conditions. The obtained sintered body consists of two phases of alumina and titanium carbide,
No other accessory ingredients were observed. The density is the theoretical density of 97
．． 0, which is very high (and the uniformity was also high.

Comparative example 1 An attempt was made to produce titanium carbide from titanium and carbon powder.

Metallic titanium powder with a particle size of 1Oμ- and carbon black made from acetylene were mixed at a molar ratio of 1.0:0.9. Uniaxial pressure molding was performed at a pressure of 100 MPa to produce a molded body similar to that in Example 1. The compact was treated in the same process as in Example 1 and ignited under the same conditions. According to the results of powder X-ray diffraction, the obtained sintered body consists of a single phase of titanium carbide.
The density determined from the shape and weight was as low as the theoretical density of 84.72 (considerable non-uniformity was observed in the microstructure).

Comparative example 2 An attempt was made to produce titanium carbide from titanium and carbon powder.

Metallic titanium powder with a particle size of 10 μ- and carbon powder with a particle size of 42 nm are mixed at a molar ratio of 1.0:0.9,
Further, assuming that this mixed powder is 100 $, 1 wt, $
of stearic acid was added and dry mixed for 1 hour. 100
Uniaxial pressure molding was performed at a pressure of MPa to produce a molded body similar to that in Example 1. The compact was treated in the same process as in Example 1 and ignited under the same conditions. According to the results of powder X-ray diffraction, the obtained sintered body consisted of a single phase of titanium carbide, and the density determined from the shape and weight was the theoretical density of 73.0 zero.

Effects of the Invention According to the present invention, since one or more of the raw material components are converted by heat treatment and molded using a lubricant, the uniformity of the obtained molded product is extremely high.

Moreover, since the lubricant in the compact is converted into one or more of the raw material components by heat treatment before the pressurized self-combustion reaction, the combustion reaction becomes a steady mode, and the resulting sintered compact has a high density. This results in extremely high uniformity. Therefore, the high-density sintered body manufactured by the manufacturing method of the present invention is extremely suitable as a material for various substrates and tools.

Claims (2)

[Claims] (1) In a method of manufacturing a sintered body using heat generated by compound formation, a lubricant that can be converted into the same composition as one or more of the components of the raw material powder by heat treatment is added to the raw material powder. the mixed powder is pressed and molded, the lubricant in the molded body is converted into one or more of the raw material components by heat treatment, and then the molded body is ignited under pressure to initiate a combustion reaction; A method for producing high-density sintered bodies that performs simultaneous synthesis and sintering using the heat generated as a result of the combustion process. (2) The method for producing a high-density sintered body according to claim 1, wherein the lubricant is paraffin, a paraffin compound, or a salt of a paraffin compound.