JPS62292678A - Tib2 base composite ceramics and manufacture - 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 3. Detailed Description of the Invention (Technical Field) The present invention relates to TiBz (titanium boride)-based composite ceramics and a method for producing the same, and in particular to TiBz containing Altos.
The present invention relates to a high-strength ceramic body which can be subjected to electric discharge machining, and an advantageous method for producing the same.

(Background Art) In recent years, T i Bz ceramics have received attention for their metallic properties, excellent high melting point, and high strength properties, and also for their excellent high-temperature corrosion resistance and oxidation resistance. Therefore, it is expected to be used in high-temperature bearings, injection nozzles for internal combustion, and parts for processing molten nonferrous metals, and is attracting attention as a promising material that can be used under conditions that exceed the operating temperature limits of SiC and 5inN4. is bathed in

However, such TiBZ has poor sinterability, and it is difficult to obtain a high-density, high-strength material using it alone. Composites with carbides, nitrides, etc. have been studied. However, with these conventional methods, there is an inherent problem that it is not possible to obtain products with large dimensions or complex shapes.
It is desired to develop a new technique for obtaining a high-density, high-strength ceramic body from TiB2 material using a pressureless sintering method (pressureless sintering method) that does not have such problems.

(Structure of the Invention) The present invention has been made against the background of the above, and its main purpose is to provide a high-strength TiB-based composite ceramic that can be processed by electric discharge, and a method for producing the same. Another objective is to produce high-density, high-strength TiBZ by a pressureless sintering method under normal pressure rather than a hot press sintering method.
The object of the present invention is to provide a technology that can advantageously produce composite ceramics.

That is, in order to achieve the above-mentioned object, the present invention has the following features:
TiBz (titanium boride) is composited with Aj220 (alumina) and sintered, and the TiBz-based composite ceramic thus obtained preferably contains 15 to 90% by weight. It has a blending composition consisting of T i Bz of 10 to 85% by weight of AlzOx.

Further, such a TiBz-based composite ceramic according to the present invention preferably contains TiBz: 15 to 90% by weight and Aj
! It is manufactured by molding a composition having a blending composition of z03: 10 to 85% by weight into a predetermined shape and then sintering it at a temperature of 1700° C. or higher under normal pressure.

In short, as a result of various studies conducted by the present inventors regarding the pressureless sintering method of TiB2, the present invention has been made by blending a predetermined amount of Al zo3 with TiB2 and sintering it to achieve high density and high It was completed based on the discovery that it is possible to advantageously produce composite ceramics that are strong and suitable for electric discharge machining, and these T
iB2 and A12o3 are 15-90% by weight: 10-85
It will be blended in a ratio of 25 to 60 weight %:40 to 75 weight %. In addition,
If the blended amount of Al2O2 becomes too small, it becomes difficult to perform pressureless sintering, and density, strength, hardness, etc. each decrease, while AA! If the blending amount of . This causes problems such as making processing difficult.

Furthermore, the composition of Ti132 and Al z Os is as follows:
Generally, this is carried out in powder form, and the obtained composition having the above-mentioned composition is molded into a predetermined shape corresponding to the product shape in the same manner as the conventional manufacturing method of ceramic nox bodies. Become. For example, TiB, powder and α-Ae20. The powder is wet mixed at a predetermined ratio, dried, and uniaxially pressed using a mold, and then cold isostatically pressed (C
IP) processing to form a molded article corresponding to the desired product shape.

Next, the obtained T i B, .Al□03 composite molded body is subjected to a sintering operation at a temperature of 1700° C. or higher under normal pressure. That is, the desired TiB2-based composite ceramic (sintered body) is formed not by hot press sintering but by pressureless sintering.

Note that in this sintering operation, if the sintering temperature is lower than 1700° C., it becomes difficult to obtain a dense sintered body. The sintering time will be appropriately selected depending on the sintering temperature employed, but is generally about 1 hour or more, and the sintering atmosphere is usually an inert gas atmosphere such as Ar gas. will be used.

(Examples) Below, some examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is not limited in any way by the description of such examples. It goes without saying that this is not something you should accept.

In addition to the following examples and the above-mentioned specific description, the present invention includes various changes, modifications, and changes based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention. It should be understood that improvements and the like may be made.

Average particle size: 2.65μ TiB, powder, average particle size: 0
．． 4 μ of α-,1203 powder was blended in the proportions shown in Tables 1 and 2 below, wet mixed using a ball mill in ethyl alcohol, and then dried to obtain TiB, -Aj2□01 composition,
Using a mold, uniaxial pressure was applied at 30 MPa, and then 3
CIP treatment was carried out at 00 MPa, and each was molded into a predetermined molded body. Next, the various molded bodies obtained are subjected to a sintering operation for 1 hour at various temperatures within the range of 1600 to 1900°C in an Ar atmosphere under normal pressure to form various TiB-based composite ceramics. (Sintered body) was obtained.

The relative density, bending strength, hardness, coefficient of thermal expansion, weight gain on heating, and electrical resistance of the various sintered bodies thus obtained were measured, and the results are also shown in Tables 1 and 2 below. Ta. The heating weight increase was carried out to evaluate the oxidation resistance of the obtained sintered body, and was carried out at 1000℃×
It was measured by determining the weight increase (absolute value) due to heating in air for 36 hours.

Table 2 As is clear from the results in Tables 1 and 2, T
In the case of single iBZ, if the sintering temperature is below 1600°C (m27), the compact will not sinter, and
At 0°C (ll & L19) 73% of the theoretical density, and 18
It is recognized that at temperatures above 00°C (Ni 11.11), only a sintered body having a density of only 78% of the theoretical density can be obtained. And Aj! As the amount of zO+ added increases, the density of the sintered body increases monotonically, and the amount reaches 90%.
So, at 1600℃, (9)92%, at 1700℃
If this is the case, a relative density of 95% or more can be obtained. From this, in order to obtain a dense sintered body, 170
It is understood that a temperature of 0° C. or higher is required.

In addition, regarding the bending strength, TiBz alone is so weak that it is impossible to measure the strength at a sintering temperature of 1600°C, and a bending strength of 160 to 180 at a sintering temperature of 1700°C or higher.
It shows a roughly constant value of MPa. However, A 1
When z○3 is added to TiB2 and combined, the amount added increases monotonically at each temperature up to 50%, 300 MPa at 1800°C and 45 MPa at 1900°C.
It becomes 0 MPa. This result corresponds well to increasing sintered density. However, rather than this, Aβ2
As the amount of 03 added increases and the sintering temperature reaches 1800°C or higher, the strength decreases, and this tendency becomes even more pronounced at high temperatures. The reason is A7! This is due to grain growth of zos. And AI! zo3 added view: 50%
The maximum intensity value is obtained when . On the other hand, at a sintering temperature of 1700°C, the maximum strength is A jl! When the amount of zO3 added is 70%, it is 300 MPa, and if the amount is larger than this, it is recognized that the strength becomes weaker for the same reason.

Thus, by adding AfzO'+, T iB
It has become clear that a sintered body with strength 1.3 to 1.7 times higher than that of z alone can be obtained.

Next, the electrical resistance was measured N11l~7 and 9.10
Regarding the sintered body of , the electrical resistance of T i B z alone is 3X10-'Ω-Ca11, and it increases slightly as the amount of A1203 increases, but when the amount of Al2O3 is 8
Up to about 0%, it is about 104, and when the blending amount reaches 85%, it becomes 10-4, and further, at 90%, it becomes 3X1.
It is recognized that the resistance value is 0'Ω-b, and the resistance value increases rapidly from 109 to 10I0.

This is due to the discontinuity of the T i B z structure of the matrix, and therefore, it is recognized that electrical discharge machining becomes difficult unless the blending amount of Az, 03 is up to 90% in the sintered body.

(Effect of the invention) As is clear from the above explanation, the conventional TiB2
Because of its difficulty in sintering, it is customary for ceramics to be hot-press sintered with the addition of additives. By pressureless sintering at 1700°C or higher, it is possible to obtain a sintered body that has a strength up to three times that of TiB2 alone and can be processed by electric discharge machining. It has significant significance.

Claims (3)

[Claims] (1) A TiB_2-based composite ceramic that can be electrically discharge-machined, which is made by combining TiB_2 with Al_2O_3 and sintering it. (2) The TiB_2-based composite ceramic according to claim 1, having a blending composition of 15 to 90% by weight of TiB_2 and 10 to 85% by weight of Al_2O_3. (3) TiB_2: 15-90% by weight and Al_2O_3
: 10 to 85% by weight of a composition is formed into a predetermined shape, and then sintered at a temperature of 1700° C. or higher under normal pressure.