JPH01201067A - Wear-resistant composite material - Google Patents

Abstract

PURPOSE:To improve erosion resistance and wear characteristics in a composite material comprising Al2O3 as a matrix and SiC particles a dispersible material, by specifying particle size of SiC particles and the amount of the particles added and making a specific high density. CONSTITUTION:This wear-resistant composite material consists of 20-50vol.% SiC particles having 0.5-2.0mu average particle diameter and the rest of Al2O3 and has >=98% relative density. The composite material is obtained by blending Al2O3 powder with SiC powder and sintering the mixture. In the case, when the average particle diameter of SiC is <0.5mu, a composite material containing 50vol.% SiC can not be processed to have the above-mentioned density even by hot press, etc. and when >2.0mu, the composite material is slightly sintered in a dense state. When the content of SiC is <20vol.%, improvement in erosion resistance and wear characteristics is insufficient and when >50vol.%, a dense sintered material is not obtained. When relative density is <98%, hardness is insufficient and erosion resistance is not obtained even if SiC content is 40-50vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to wear-resistant materials, particularly to ceramic composites that are excellent against wear caused by collisions of solid particles (erosion wear).

[Conventional technology]

High-speed rotating bodies such as turbine blades are worn out by SiO□ fine particles, which are airborne dust particles. Also,
Coal-using plants are severely hampered by wear caused by coal dust. It is known that it is desirable that a material that is excellent against such erosion wear be hard. Among the hard materials, Bs C is one of the ceramics.
, S i C1A2□O, , Si, N4, etc., and Ba
C and SiC are particularly hard materials, and Alto3 is known as a material with relatively high hardness and low cost. The wear resistance of these materials is usually evaluated by the ratio of the volume of the worn material to the volume of collided fine particles (abrasive grains) (this is called the wear rate (c/a+7)).

Regarding the above ceramics, the abrasive grains to be collided with SiC
The size of the abrasive grains is approximately 500 μm, and the collision speed of the abrasive grains is 2.
When tested at 50 to 300 m/sec and a collision angle of 80°, the wear rate was B4C: 27X 10-'cuf/c.
nf, Sic: 18X10-'cal/ci,
All Owl: 39-45 XIO-'
cU/crA, Sl3N4: 27-59
X 10-'Cnl/c+11.

These wear rates are excellent among many ceramic materials, but in high-speed rotating objects such as dust exhaust equipment,
Materials with lower wear rates are desired.

Conventionally, Af has been used as a material with improved wear resistance.

A composite using 03 as a matrix and SiC particles as a dispersion material is known (Atsushi Nakate, Akira Shinhara-1 Toshio Hirai,
Al2O2sic? 1. Microstructure and mechanical properties of composite materials,
Ceramics Association Magazine 94 (8L 767-772.1986)
. However, this composite is approximately 2-8μ as SiC particles.
We use large particles with a maximum diameter of approximately 30 m.
% by volume, and does not solve the problem of anti-erosion wear.

[Description of the first invention] The first invention (the invention described in the claims) is intended to provide a practical material that is excellent against wear such as erosion wear caused by collision of solid particles.

The wear-resistant composite of the first invention has an average particle size of 0.5 to 2.
It consists of 20 to 50 volume % of silicon carbide particles of 0 μm and the balance is alumina, and is characterized by having a relative density of 98% or more.

The composite of the first invention has high hardness and excellent toughness, and has excellent wear resistance such as erosion wear resistance. Furthermore, the composite of the first invention is excellent not only in erosion wear but also in friction wear and grinding wear. The composite of the first invention having such excellent properties can be used as a material for high-speed rotating bodies such as turbine blades or coal-using plants.

[Description of the Second Invention] Hereinafter, an invention that embodies the first invention (referred to as the second invention) will be described.

The composite according to the second invention is composed of silicon carbide (SiC) particles and alumina (Affi203),
A desirable form is A2□0. In this state, SIC particles are dispersed inside. The more uniform the dispersion of the SiC particles, the better the wear resistance of the composite.

The average particle diameter of the SiC particles is selected from the range of 0.5 to 2.0 μm. The reason why this average particle size is set in the above range is due to problems in manufacturing the composite of the present invention, as described below.

The composite of the present invention can be manufactured by mixing AlzOz powder and SiC powder and sintering this mixture. In the sintering of the mixture, it is AltO that is sintered.
z, SiC inhibits sintering. For this reason, Si
The particle size of C is an important factor in obtaining a dense composite. If the particle size of SiC is small, even if the amount of SiC is the same, Al
This increases the possibility of inhibiting sintering of zO*. For this reason, SiC
The lower limit of the average particle size of the particles is limited to 0.5 μm.

When this average particle size is substantially smaller than 0.5 μm,
Even by hot pressing or HIP, a composite containing 50% by volume of SiC cannot be densified to a relative density of 98% or more. Also, if the particle size of SiC is too large, S
A bridge is formed where the iC particles are in contact with each other, and it becomes difficult for A120z to enter between the bridges, making it difficult to sinter densely. Therefore, the upper limit is set to 2 μm.

By the way, the hardness of ceramics varies depending on the load to be measured and the magnification of the reading device, so it cannot be determined uniquely. However, the hardness of SiC is usually 27 to 30 ONm-
", the hardness of Al2O:l is 17 to 20 ONm-". Since the hardness of the composite is generally qualitatively additive, the hardness of the composite increases as the proportion of SiC added increases. In addition, SiC acts as an obstacle to crank progress during fracture, thereby increasing the toughness of the composite. Therefore, the SiC content is closely related to erosion wear resistance.

In the second invention, the content of SiC in the composite is 2
0 to 50% by volume. This is because if the SiC content is less than 20% by volume, the improvement in erosion and wear resistance is insufficient. When the content of SiC exceeds 50% by volume,
A dense sintered body cannot be obtained, and the wear resistance of the composite is reduced.

Note that SiC has two types of crystal forms, α type and β type, but in the present invention, either the α type or the β type may be used, or a mixture of both may be used.

Further, the relative density of the composite according to the second invention is 98% or more. This is because if the relative density is less than 98%, even if the SiC content is as high as 40 to 50% by volume, the hardness will not be large enough, and as a result, excellent erosion resistance will not be obtained. be.

Note that the composite of the second invention contains 5i used during production.
Oz, alkaline earth metal oxides, and mixtures thereof, etc.
A conventional A2□03 sintering aid may be included.

Next, as a method for producing a composite according to the present invention, Al
There is a method of mixing zOx powder and SiC powder and then sintering this mixture.

The above-mentioned mixture of both powders includes a predetermined amount of Altos powder and SiC powder.
Weigh the powder, mix and dry using a conventional method. A1. z
Since both Os and SiC are inert to water, there is no need to use alcohol as a mixed solvent during mixing, as with Si3N4, and water is sufficient. Although a dryer may be used for drying, a spray dryer is usually used. The dried mixed powder is densely sintered by a normal sintering method, a hot press method, a HIP method, a gas pressure sintering method, or a combination of these methods. However, this mixed powder is difficult to sinter as described below, so
Particularly preferably, sintering is performed by a hot press method or a HIP method.

In the sintering of the mixed powder described above, A2□03 undergoes grain growth during the sintering process, but SiC does not undergo grain growth and exists in the composite as SiC particles similar to the raw material. Therefore, the average particle size of the SiC particles in the composite is the same as the average particle size of the starting material SiC powder, 0.5 to 2 μm.

Further, the A2□03 powder is not particularly limited as long as it can yield a dense composite containing 20 to 50% by volume of SiC particles, but it is preferable that it is a raw material that is easily sintered. Therefore, the average particle size of AffzO3 is 1
It is desirable that it is less than μm. Since chemical purity does not significantly affect erosion wear resistance, Aj2. O,
of normal purity is sufficient. Further, in order to aid the sintering of A2□03, an appropriate amount of SiO□, which is a usual sintering aid for A l z Os, an alkaline earth metal oxide, or a composite thereof may be added.

〔Example〕

The present invention will be explained in detail below.

Example 1 As shown in Table 1, a mixed powder obtained by mixing and drying 50 volume % of six kinds of SiC powders having different average particle diameters (50% by volume) with a diameter of 0.4 μm was heated at a temperature of 1850° C. and a pressure of 25 MNm. −”,
Hot pressing was carried out under conditions of pressurization time of 1 hour.

SiC in the obtained composite existed as particles having the same average particle size as the SiC powder used as the starting material. The resulting composite was subjected to an erosion test using SiC abrasive grains. Abrasive grains with an average size of 500 μm are used, and the collision conditions are at a speed of 250 to 30
The speed was 0 m/sec and the angle was 80°. The results are shown in Table 1.

The average particle size of SiC particles in the composite is 0.28 μm, 0,
48 μm and smaller than 0.5 μm (sample NαC1,
In C2), the relative density did not reach 98%, so the Vickers hardness was low and the erosion wear rate was high. Furthermore, even when the average particle size of the SiC particles was as large as 3.0 μm (sample No., C3), the relative density was as low as 97%, the hardness was decreased, and the erosion wear rate was also high. On the other hand, the average particle size of SiC particles is 0.65
μm, 1.0 μm, 2.0 μm (sample Nα1
-3) all had relative densities of 98% or more, high hardness, and good erosion abrasion resistance.

Example 2 With the blending ratio shown in Table 2, the average particle size was 0°65μ.
m SiC powder and the remainder A12oz powder (average particle size 0.
The mixed powder obtained by mixing and drying the powder (4 μm) using a conventional method was hot-resisted at a temperature of 1850° C., a pressure of 30 MNm'', and a pressurizing time of 2 hours.

The SiC in the resulting composite has an average particle size of 0.65 μm.
existed as particles.

Further, an erosion test was conducted on the obtained composite under the same conditions as in Example 1. The results are shown in Table 2.

When the blending amount of SiC is 0.10% by volume (sample NαC4
, C5) had a sufficiently dense relative density of 99.5%, but neither hardness nor toughness were sufficiently large, and the erosion wear rate was large. In addition, when the blending amount of SiC is 55% by volume (sample N (LC6)), it does not finish densely,
Therefore, the hardness was low and the erosion wear resistance was also poor. On the other hand, the blended amount of SiC is 20.30
．． In the case of 40.50 volume% (sample Nα4.5.6.7)
Both have a relative density of 98% or more, high toughness, and excellent erosion and wear resistance.

In Example 1.2, SiC abrasive grains with an average particle size of 500 μm were used as colliding particles, but even if the abrasive grains have different sizes, Ant O3, mullite, etc. may be used as the abrasive grains. However, the tendency of erosion resistance was the same.

Claims (1)

[Claims] 20 to 5 silicon carbide particles with an average particle size of 0.5 to 2.0 μm
A wear-resistant composite comprising 0% by volume and the remainder alumina, and having a relative density of 98% or more.