JPS60200863A - Silicon nitride base ceramics - 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] This invention particularly relates to rolls and guide rollers.

Seal rings, rocker arm tips, nozzles.

This invention relates to silicon nitride-based ceramics suitable for wear-resistant parts such as dies or cutting tips.

Currently, silicon nitride-based ceramics having a composition consisting of silicon nitride and Y2O3, which is a sintering aid, are used. This silicon nitride-based ceramic exhibits relatively good performance when simply exposed to high temperatures and corrosive atmospheres, such as when used in turbine blades.

However, since silicon nitride has a strong affinity with iron and easily reacts with iron, when the silicon nitride-based ceramic is used in applications that cause friction with iron, wear progresses quickly.

Therefore, various studies have been conducted to reduce the affinity of the silicon nitride-based ceramics with iron and improve the wear resistance, and so far it has been found that the addition of T1 nitride is effective. There is. That is, silicon nitride-based ceramics having a composition consisting of silicon nitride, Ti nitride, and Y2O3 were known prior to the filing of this application. When the nitride is added to a silicon nitride-based ceramic raw material, it has the effect of improving the wear resistance of the resulting ceramic without significantly reducing its strength.

However, in the above two types of known ceramics,
The sintering aid reacts with silicon nitride and 5i02 on its surface, resulting in Y
-Since it remains as a Si-0-N glass, approximately 1000
Although the strength and hardness maintain sufficiently high values up to around ℃,
However, at high temperatures, the glass at the grain boundaries softens, resulting in a decrease in strength and hardness, leading to faster wear.

Therefore, the purpose of this invention is to
The strength is improved even at high temperatures (especially high temperatures).
An object of the present invention is to provide a silicon nitride-based ceramic having excellent hardness at temperatures as high as 00°C.

As a result of various studies, the present inventors found that the above object can be achieved by containing a specific amount of a specific whisker.

This invention was invented based on the above knowledge, and includes one or more types of whiskers selected from the group consisting of SiC, Si3N4, B4C and TiB2: 1 to 30.

One or more carbides and nitrides of Groups 4a and 5a of the Periodic Table of the Elements; 1 to 30.

Y2O3: 1 to 10%, with the remainder being silicon nitride (the above, weight %)
) is a silicon nitride-based ceramic.

The present invention will be explained in detail below.

(a) S i C, Si3N4, B4C, TiB
2. Whiskers These whiskers themselves have high hardness and strength from room temperature to high temperatures, and when combined with silicon nitride, they can remain in the whisker shape, and have a structure that is uniformly dispersed within the tissue, that is, a so-called fibrous structure. This structure serves as a strong stopper when external stress is applied, so the silicon nitride-based ceramic can be strengthened and hardened.

The average diameter of these whiskers is usually 01-5 μm, preferably 05-1.5 μm. The average length is usually 2 to 50 μm, but if it is too long, the mixing technique will be difficult and sintering defects will occur, so it is preferable not to exceed 20 μm, and the properties are even better if it is about 5 to 10 μm. of ceramics can be obtained.

If the amount of whiskers added is less than 1 inch, the desired high temperature strength and hardness at high temperatures cannot be obtained. On the other hand, if it exceeds 30 inches, the sinterability will deteriorate and the strength at room temperature will be too low, which is not preferable.

(b) Carbides and nitrides of groups 4a and 5a Group 4a of the periodic table of elements refers to the group consisting of Ti, Zr and I-1f, and group 5a refers to the group consisting of V, Nb and Ta. Therefore, 1r4 or more of the carbides and nitrides of groups 4a and 5a of the periodic table of elements is Ti.

Carbides of Zr, Hf, V, Nb and Ta (hereinafter referred to as TiC, ZrC, HfC, V C, NbC and T, respectively)
Indicated by aC. ) and Ti, Zr, Hf, V,
Nitride of Nb and Ta (hereinafter referred to as TiN, Z
rN, HfN, V N , NbN and '1' a
Indicated by N. ) is one or more of the following.

These are components that are effective in reducing the affinity with iron, and in turn are effective in improving wear resistance.

If the amount added is less than 1 t, the desired wear resistance cannot be obtained, and conversely, if it exceeds 30%, the sinterability becomes insufficient, leading to a decrease in room temperature strength, and the amount of silicon nitride is relatively small. If too much, the excellent high-temperature strength and side thermal shock properties of silicon nitride would be degraded, so the amount added was set to 1 to 30%.

(c) yzos This is an essential component that generates a liquid phase and promotes sintering. If the amount added is less than 1%, sintering will be insufficient;
If it exceeds 10%, the amount of liquid phase will be too large and the grain growth will also significantly decrease both strength and hardness.
%.

Next, a method for manufacturing the silicon nitride-based ceramic of the present invention will be described.

The whiskers may be mixed simultaneously with other raw material powders without being crushed, but the following mixing method is more preferable since a completely uniform structure can be obtained.

Commercially available whiskers are wet-passed through a 60-mesh sieve to remove whisker clumps, and the bottom of the sieve is used as a raw material. On the other hand, the other raw materials are sufficiently wet-mixed in a ball mill or the like to a desired composition, and the resulting mixed slurry is slightly diluted, and the required amount of the sieved whiskers is added and mixed.

This mixture is then dried in air or vacuum, shaped and sintered at about 1650-1800°C. Sintering is carried out under 1 atmosphere of nitrogen or by hot pressing in nitrogen.

When this sintered body is further hot isostatically pressed, its strength is further improved. Alternatively, the green compact from the molding process may be sintered under nitrogen gas pressure or hot isostatic pressing at once.

Hereinafter, the structure and effects of the present invention will be explained in detail by showing Examples and Comparative Examples.

Examples and comparative examples As raw materials, Si3N4 powder with an average particle size of 06 μm and ¥203 powder with an average particle size of 12 μm, both of which have particle sizes of 1 to 15
μm group 4a, 5a carbides, nitrides, average diameter 15μ
m, and whiskers with an average length of 15μ7n were used.

Only the whiskers were soaked in ethanol in advance, stirred lightly, passed through a 60-mesh sieve, and dried under reduced pressure. On the other hand, the powders other than the whiskers had the compositions shown in Table 1 and were back mixed in ethanol for 72 hours using a Lumil. This mixed slurry was stirred with ethanol, sieved whiskers were added thereto in an amount having the composition shown in Table 1, and the mixture was mixed with a stirrer for 6 hours. After drying under reduced pressure, It/
The sample was pressed at a pressure of 1.0 m and sintered at 1750° C. for 2 hours in 1 atm of nitrogen. This sintered body was further heated at 1700°C in nitrogen for 15
Hot isostatic pressing was carried out for 1 hour under the conditions of 00 to 9/(i).

Comparative ceramics whose compositions were outside the composition range of the present invention were also manufactured by the same method.

The Vickers hardness and transverse rupture strength of the obtained ceramics of the present invention, comparative ceramics, and conventional ceramics containing no whiskers and having the compositions listed in Table 1 were measured at room temperature and 1200°C, and the results are shown in Table 1. Indicated.

Further, the following cutting tests were carried out on each of them, and flank wear was measured, and the results are also shown in Table 1.

cutting test Work material: FC25 square material with a width of 150 mm x length of 400 mm.

Cutting method: milling cutting. Using a DN cutter with a diameter of 160 myn and a tip made of silicon nitride-based ceramics, cut the material so that the center of the cutter matches the upper middle of the width of the workpiece.

Cutting speed 300? rL/min Depth of cut 2 Feed per blade 0.17 Excitation/blade cutting time 60 minutes As is clear from Table 1, this release 1! J] ceramics are particularly excellent in transverse rupture strength and hardness at high temperatures, and are therefore suitably used for wear-resistant parts that require high-temperature strength and high-temperature hardness. Furthermore, from Table 1, it can be seen that the ceramics of the present invention have excellent wear resistance even when used as cutting tips.

Applicant: Mitsubishi Metals Corporation Agent Tomi 1) Kazuo and 1 other person

Claims (1)

[Claims] One or more whiskers selected from the group consisting of SiC, Si3N, B, C, and TiB2: 1 to 30%. One or more carbides and nitrides of Groups 4a and 5a of the Periodic Table of Elements: Groups 1 to 30. Y2O3: A silicon nitride-based ceramic containing 1 to 10 Y2O3, with the remainder being silicon nitride (weight %).