JPH0426563A - Ceramic sintered body having composite structure - Google Patents

Abstract

PURPOSE:To prolong the service life of the sintered body when used for cutting tools by enclosing the disperse phase obtained by dispersing whiskers in a ceramic matrix with a ceramic matrix phase free of whiskers. CONSTITUTION:The ceramic sintered body contains 10-60wt.% whiskers, the balance grain consisting essentially of metal oxide and inevitable impurities as mentioned below. Namely, the sintered body consists of the first phase as a mixture of the first hard grain consisting essentially of metal oxides and whiskers and the second phase contg. the second hard grain consisting essentially of metal oxides or the grain contg. an extremely small amt. of whiskers as compared with the first phase, and the first phase is enclosed by the second phase. For example, the first phase contains 30-60wt.% silicon carbide whiskers and the first hard grain consisting essentially of aluminum oxide, and the second phase consists of the second hard grain of aluminum oxide.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a composite structure that can be applied to cutting tool materials, wear-resistant tool materials, corrosion-resistant materials, and various mechanical parts and electrical parts. The present invention relates to a ceramic sintered body having the following characteristics.

(Prior Art) Whiskers and fibers are added to conventional materials to increase the strength of the materials. Among these, many studies have been conducted on fiber-reinforced ceramic TFRCI, which is made by containing whiskers in a ceramic matrix. Representative examples of this FRC include JP-A-61-174165 and JP-A-61.
There is a publication No.-274803.

(Problems to be Solved by the Invention) JP-A-61-174165 describes an alumina prepared by dispersing silicon carbide whiskers having a diameter of 1 μm or less and a length of 20 μm or less in an amount of 2 to 30% by volume in an alumina matrix. - A silicon carbide heat-resistant composite sintered body is disclosed. Furthermore, Japanese Patent Application Laid-Open No. 61-274803 discloses a reinforced ceramic cutting tool in which 2 to 40 volume percent of ceramic whiskers are dispersed within a ceramic matrix.

Of these two publications, the former suggests that the bending strength and hardness at high temperatures have been significantly improved, and that significant improvements can be expected as tips for cutting tools, while the latter actually suggests that the bending strength and hardness at high temperatures have been significantly improved. Although it is said to be extremely effective as a cutting tool material for cutting metal work materials,
Since both of these tools have whiskers simply dispersed in a matrix, there is a problem in that they do not have a satisfactory lifespan as a cutting tool.

The present invention solves the above-mentioned problems, and specifically, a whisker-dispersed phase formed by dispersing whiskers in a ceramic matrix is replaced with a ceramic matrix phase containing no whiskers or a trace amount of whiskers. The object of the present invention is to provide a ceramic sintered body that has a structure surrounded by a ceramic matrix phase containing .

(Means for Solving the Problems) The present inventors have found that from the viewpoint of the strength of FRC, the higher the content of whiskers, the better; however, for example, SiC whiskers tend to react with iron group metals and reduce wear resistance. In order to overcome this contradictory situation, it is preferable to reduce the content as much as possible because of the fact that the whisker-containing ceramic has strength and abrasion resistance that can be used as a material for cutting tools. While considering this, we found that the improvement in the strength of FRC is greatly influenced by the state of dispersion of whiskers in the sintered body, and that the dispersion of whiskers in the matrix is more important than dispersing them uniformly throughout the sintered body. By creating a structure in which a phase containing whiskers is densely surrounded by a matrix phase or a phase containing whiskers in a matrix, the strength and wear resistance are significantly improved, and it can be used as a cutting tool. This finding has shown that the lifespan of the battery is also significantly improved. Based on this knowledge, we have completed the present invention.

That is, the ceramic sintered body having a composite structure of the present invention is a ceramic sintered body consisting of whiskers of 10 to 60 W%, hard particles mainly composed of metal oxide, and inevitable impurities. The ceramic sintered body has a first phase consisting of a mixture of first hard particles mainly composed of metal oxide and whiskers, and a second phase mainly composed of metal oxide.
a second phase containing hard particles or whiskers that are enriched compared to the first phase in the second hard particles;
The first phase is also characterized by a structure in which the first phase is surrounded by the second phase.

The first phase in the ceramic sintered body having a composite structure of the present invention is a mixture of first hard particles and whiskers, and the size and shape of this phase will be described in detail later, but it is approximately 10 to several 100 μm. Of these, the metal oxide that is the main component of the first hard particles is
For example, specifically, aluminum oxide, zirconium oxide, chromium chloride, magnesium oxide, mullite (3A
2□03・2SiO, ] , spinel (MgO・＾＾2
tos1. The whiskers include silicon carbide whiskers, silicon nitride whiskers, titanium carbide whiskers, titanium nitride whiskers, boron carbide whiskers, and boron nitride whiskers. This can be cited as a representative example. Of these, 30 are in the first phase.
In the case of ~60% by weight of silicon carbide whiskers and the remainder of the first hard particles mainly composed of aluminum oxide,
This is preferable because the strength is significantly improved.

When the first hard particles in the first phase are made only of aluminum oxide, the strength is significantly improved. When the remaining aluminum oxide is used, the sintering is accelerated and the strength is significantly improved.

V, Nb, Ta, Cr, Mo, 11. When at least 30% by weight of at least one of Si carbides, nitrides, #-rides, Zr, Hf carbides, nitrides, carbonates, nitrides, and mutual solid solutions thereof, and the remainder is aluminum oxide, etc. is particularly preferred since it significantly improves wear resistance and strength.

The second phase in the ceramic sintered body having a composite structure of the present invention is composed of second hard particles mainly composed of a metal oxide, or has a whisker content that is poor compared to the second hard particles and the first phase. whiskers, specifically 1, for example 50% or less of the whisker content in the first phase, preferably 20%
This is a phase in which the following whiskers are mixed in the second hard particles.

The second hard particles in this second phase are 2, for example, 5, specifically,
If only aluminum oxide is present, zirconium oxide,
When it consists of 15 @ 1% or less of at least one of hafnium chloride or rare metal oxides and the remainder aluminum oxide, or T1, V, Nb, Ta, Cr
, Mo, L 5i (7) carbide, nitride, oxide,
Examples include cases in which the amount of at least one of Zr, 8F carbides, nitrides, carbonates, nitroxides, and mutual solid solutions thereof is 30% by weight or less, and the remainder is aluminum oxide. The second hard particles may have the same composition as the first hard particles, or may have different compositions.

The first phase and the second phase can be combined in various ways, for example, the first phase is silicon carbide whiskers in an amount of 30 to 60% and the remainder is first hard particles of aluminum oxide. The second phase is a combination of aluminum oxide with second hard particles (containing a small amount of silicon carbide whiskers), or the first phase is 30 to 60% by weight of iscar in silicon carbide.
and 15% by weight or less of at least one of zirconium oxide, hafnium mide, or an oxide of a rare metal, and 4a to 70% by weight of the remaining blue hard particles of aluminum oxide, and the second phase is Second hard particles of aluminum oxide (
or the first phase is 30 to 60% by weight of iscar in silicon carbide and 15% by weight of at least one of zirconium oxide, hafnium oxide, or an oxide of a rare earth metal. Below and the rest of the aluminum oxide part! It consists of hard particles of 40 to 70% by weight, and the second phase is TIV, Nb, Ta, Cr,
Mo, stomach, Si carbide, nitride, oxide, Zr
, 30% by weight or less of at least one of Hf carbides, nitrides, carbonates, nitrides, and mutual solid solutions thereof, and the remaining second hard particles of aluminum oxide (containing a trace amount of silicon carbide whiskers). Acceleration of sintering, especially when used in combination.

This is preferable because it significantly suppresses grain growth, improves wear resistance, improves heat resistance, and improves strength.

The first phase in the ceramic sintered body having a composite structure of the present invention is preferably in an oriented state, for example, in a cross section in one direction, it has a circular shape and/or a circular shape of about 10 to several 100 μm. On the other hand, in a cross section perpendicular to this cross section, the shape ranges from needle-like or rod-like to round-like. The area around this first phase is approximately 5 to 20 μm.
It consists of a structure in which a second phase having a width of m is surrounded in a continuous state.

When the content of whiskers in the ceramic sintered body having a composite structure of the present invention is less than 10% by weight, the strength improvement effect of the whiskers is weak. It is difficult to sinter, making it difficult to obtain a dense sintered body, resulting in a decrease in strength. For this reason, the amount of whiskers contained in the sintered body of the present invention is determined to be 10 to 60% by weight.

Although the ceramic sintered body having a composite structure of the present invention can be obtained by applying conventional powder metallurgy manufacturing methods, it is particularly important to granulate the composition components that will become the first phase. Preferably, the granulated powder is mixed with a powder of the composition components that will become the second phase, and then molded and sintered.

Among these, the size, shape, and hardness of the granulated powder used to form the first phase are important because they affect the size and shape of the first phase when it actually becomes a sintered body. It is something that comes.

(Function) The ceramic sintered body having a composite structure of the present invention has a first
The phase mainly contributes to improving the strength, and especially when the first phase contains at least one of zirconium oxide, hafnium oxide, or rare earth metal oxide, it has the effect of increasing the acceleration of sintering. , the second phase mainly contributes to improving the wear resistance, especially in the second phase, Ti, V, Nb,
Ta, Cr, Mo, WSi carbides, nitrides, oxides, Zr, Hf carbides.

When containing at least one of nitrides, carbonates, nitrides, and mutual solid solutions thereof, atomization,
The combination of the first phase and the second phase, surrounding the first phase with the second phase, and making the second phase continuous contributes to high hardness and wear resistance. This has the effect of increasing hardness, heat resistance, and oxidation resistance, as well as further increasing strength.

(Example) Example 1 A, 9aOi powder with an average particle size of 0.5 μm and an average particle size of 0.5 μm.
5 gm, average length 20 μm SiC whiskers [5
Using iC (denoted as II) as a starting material, first, using alumina balls, the composition components shown as the granulated powder for forming the first phase in Table 1 (the ratio of the components to the balls is I :
It was set as l. ) Wet mixing was carried out using a ball mill. After drying this mixture, 3% paraffin wax was added, and the mixture was granulated by a rolling method, and then sieved to obtain granulated powder for forming the first phase having a mesh size of -60 to +325. The composition components shown as the granulated powder for forming the second phase in Table 1 were additionally added to this granulated powder for forming the first phase, and mixed in a blender (1) to obtain a mixture. Fill this mixture into a carbon mold and
Atmosphere, 500 kgf/cm” pressure, 1850
50X by hot pressing by holding for 1 hour at ℃ 50X
A sintered body having dimensions and shape of 6III111 was obtained. The thus obtained sintered bodies of the present invention products 1 to 11 and comparative products 1 to 6 were cut into predetermined shapes, and the structures of each sample were observed with a metallurgical microscope. 5.Hisame product that missed the mark.
No. 6 is about 50 to 15 in which the structure in the cross section perpendicular to the press pressure direction of the hot press (Fig. 1) is composed of high whisker content.
It is a composite structure consisting of a circular and elliptical first phase of 0 μm and a continuous second phase surrounding this first phase, and the structure has a cross section parallel to the press pressure direction (Figure 2). It was a composite structure consisting of an acicular or rod-shaped first phase made of whiskers with a high content of whiskers, and a continuous second phase surrounding this first phase. On the other hand, comparative products 1 to 4, which correspond to conventional products,
Each section parallel to and perpendicular to the press pressure direction had a uniform single-phase structure throughout.

The first of the thus obtained invention products 1 to 11 and comparative product 5.6
The compositional components of the phase and the second phase were investigated by metallurgical microscopic observation, SEM observation, and EPM^ analysis, and found that they were approximately as shown in Table 1, with approximately 5% by weight of carbonization in the second phase. It contained silicon whiskers. This invention product 1~
11 and comparative products 1 to 6 as ISO standard SNG +204
08 (brehoning 0.I5+amX-25°), work material: Wasburoy, cutting speed:
l50m/min, depth of cut: 1. Omm, feed +
Cutting was performed under wet cutting conditions of 0.1 aim/rev until the chip broke or chipped, and the cutting time at that time was determined and is also listed in Table 1.

The following margin is Example 2 AβJ3 powder used in Example 1, 5iCfl! l and・
Zr0z (3mog%Y20.
Using the granulated powder shown in Table 2 as a starting material, the granulated powder for forming the first phase shown in Table 2 was wet mixed in a ball mill and granulated, and separately, the powder for forming the second phase shown in Table 2 was mixed in a ball mill. Wet mixing was performed, and then the granulated powder for forming the first phase and the powder for forming the second phase were mixed in a V blender as in Example I to obtain a mixture. This mixture is heated to an atmosphere of 200 to 50 kgf/
A sintered body was obtained by hot pressing at a pressure of 1,700 to 1,850° C. for 1 hour. The structures of the sintered bodies of the invention products 12 to 20 and comparative products 7 to 9 thus obtained were confirmed in the same manner as in Example 1, and a cutting test was conducted under the same conditions as in Example 1. Also listed in the table.

Below is the margin Example 3 β20 used in Example 1. Using SiC powder, SiC (wl) and TiC powder with an average particle size of 0.5 μm as starting materials, each sample consisting of the composition components shown in Table 3 was prepared in the same manner as in Example 1 to prepare products 21 to 29 and 29 of the present invention. Comparison product 1
0 to 12 sintered bodies were obtained. The structures of these sintered bodies were confirmed in the same manner as in Example 1, and the hardness was measured using a Vickers hardness tester, and the first phase of products 21 to 29 of the present invention was approximately 14 rJO.
~2600Hv, the second phase is 1900~2000Hv,
While the average hardness was about 2250-2350Hv,
Comparative product I2 had an approximately average overall hardness of 2300 Hv.

Next, the products 21 to 29 of the present invention and the comparative products IO to 12 were subjected to a cutting test under the same conditions as in Example 1, and the results are also listed in Table 3.

Below is the margin Example 4 Using the starting materials used in Examples 2 and 3, 38w
L%^Q gOi -60wt%5iC('I11-8
wL%Z'02 granulated powder and 70ton L%8ρ, (1,-3
Granulated powder of 0 wt% TiC was prepared in the same manner as in Example 1, and then the two granulated powders were mixed in a ratio of 1:1 using a V-blender to obtain a mixture. This mixture was hot-pressed at a pressure of 200 kgf/cm" and a temperature of 1700°C for 1 hour. The thus obtained product 30 of the present invention was examined in the same manner as in Example I and found to have a relative density of 100% and an average hardness of 2300 Hv. , the structure of the sintered body is 2 approximately 38wt% AI!, xis -60w
t%5iC(ll) -8wt%Zr0i first phase and 7
0wt%All gOi -30w1:%TiC [about 5
wt% SiC (W) content].

Next, a cutting test was conducted under the same conditions as in Example 1, and the cutting time (life time) until chipping was determined.
The time was 30 minutes.

(Effects of the Invention) The ceramic sintered body having a composite structure of the present invention is different from the conventional ceramic sintered body having a single-phase structure in which whiskers are uniformly dispersed and the ceramic sintered body outside the scope of the present invention. Abrasion resistant compared to

It has excellent fracture resistance, and as a result, when used as a cutting tool, it has the remarkable effect of improving the life by about 1.6 to 78 times. From this, the ceramic sintered body having a composite structure of the present invention can be used for cutting tool materials, wear-resistant materials and other tool materials, corrosion-resistant materials, machine parts materials, etc., in which conventional ceramic sintered bodies have been used. It is an industrially useful material that can be used not only as an electrical component material but also for purposes or shapes that could not be put to practical use due to insufficient strength.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the structure of the ceramic sintered body of the present invention obtained in Example 1 in a cross section perpendicular to the press pressure direction. Figure 2 is an example! FIG. 2 is a schematic diagram of the structure of the ceramic sintered body of the present invention obtained in a cross section parallel to the press pressure direction. In the figure, 1 indicates the first phase and 2 indicates the second phase. Patent applicant: Toshiba Tungaloy Corporation

Claims (7)

[Claims] (1) A ceramic sintered body consisting of 10 to 60% by weight of whiskers, remaining hard particles mainly composed of metal oxides, and unavoidable impurities. 1. A first phase consisting of a mixture of hard particles and whiskers, and a second phase consisting mainly of metal oxides.
a second phase comprising hard particles or whiskers that are enriched compared to the first phase in the second hard particles;
A ceramic sintered body having a composite structure, wherein the first phase is surrounded by a second phase. (2) The first phase contains 30 to 60 silicon carbide whiskers.
The ceramic sintered body having a composite structure according to claim 1, characterized in that the ceramic sintered body has a composite structure of 1% by weight and the remaining first hard particles mainly composed of aluminum oxide. (3) The first phase contains 30 to 60 silicon carbide whiskers.
% by weight and first hard particles whose main component is residual aluminum oxide, and wherein the second phase is comprised of second hard particles of aluminum oxide. Ceramic sintered body with structure. (4) The first phase contains 30 to 60 silicon carbide whiskers.
15% by weight or less of at least one of zirconium oxide, hafnium oxide, or rare earth metal oxide, and 40 to 70% of the remaining first hard particles of aluminum oxide.
% by weight.
A ceramic sintered body having a composite structure as described in 1. (5) The first phase contains 30 to 60 silicon carbide whiskers.
% by weight, 15% by weight or less of at least one of zirconium oxide, hafnium oxide, or rare earth metal oxide, and the remainder aluminum oxide, the first hard particles are 40 to 70% by weight.
% by weight, and wherein the second phase is comprised of second hard particles of aluminum oxide. (6) The second phase is Ti, V, Nb, Ta, Cr, Mo
, W, Si carbides, nitrides, oxides, Zr, Hf carbides, nitrides, carbonates, nitride oxides, and mutual solid solutions of these in an amount of 30% by weight or less, and the remaining aluminum oxide. A ceramic sintered body having a composite structure according to claim 1, characterized in that it is made of second hard particles. (7) The first phase contains 30 to 60 silicon carbide whiskers.
% by weight, 15% by weight or less of at least one of zirconium oxide, hafnium oxide, or rare earth metal oxide, and the remainder aluminum oxide, the first hard particles are 40 to 70% by weight.
% by weight, and the second phase is Ti, V, Nb,
At least one of carbides, nitrides, oxides of Ta, Cr, Mo, W, Si, carbides, nitrides, carbonates, nitrides of Zr, Hf, and mutual solid solutions thereof is 30% by weight or less. 2. A ceramic sintered body having a composite structure according to claim 1, wherein the ceramic sintered body is made of second hard particles of aluminum oxide.