JPH01145371A - Highly wear-resistant c-b4c-based sliding member - Google Patents

Abstract

PURPOSE:To obtain the title sliding member outstanding in frictional and wear characteristics and mechanical strength along with giving excellent transferability and film-formability to the surface of facing materials, by press sintering of mixed powder made up of B4C powder and a carbonaceous component consisting of carbon powder and carbon fiber. CONSTITUTION:The objective sliding member can be obtained by sintering at >=2,000 deg.C under a pressure of >=100kg/cm<2>, mixed powder which has been prepared by mixing (A) 65-95wt.% of a carbonaceous component made up of (a) 95-70wt.% of carbon powder such as of coke, carbon black or artificial graphite and (b) 5-30wt.% of pitch- or PAN-based carbon fiber with a length of 10 to 500mu and (B) 35-5wt.% of B4C powder.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a C-BsC-based sliding material useful as a component for parts that generate friction due to sliding, such as bearings, cylinders, and sliding valves.
This relates to IJ members. More specifically, the present invention relates to a C-B4C sliding member suitable for use under conditions where it is difficult to use a fluid lubricant such as grease at high temperatures, so-called dry triboelectricity 1. be.

(Prior Art) In recent years, with the development of mechatronics, there has been an increasing demand for WI moving members that have good friction and wear characteristics, especially in high-temperature regions.

For sliding parts used in the high temperature range of 200 to 500°C, it is not possible to use fluid lubricants such as lubricating oil or grease between contact surfaces.1 Usually, solid materials such as graphite and molybdenum disulfide are A lubricant may be used. This solid lubricant generally does not have the fluidity and wettability of fluid lubricants, so when using it, means such as coating, impregnation, and pouring cannot be used.

Therefore, in the case of a solid lubricant, it must be applied by coating the friction surface with the solid lubricant, making the sliding member itself from the solid lubricant, or mixing it with other materials. In all of these methods, the lubricating effect is exerted only when a portion of the solid lubricant is transferred to the surface of the mating material on the sliding contact surface and a film of the required thickness is formed. Therefore, the quality of film formation on the surface of the mating material influences the friction and wear characteristics.

However, graphite, which has been commonly used as a solid lubricant, is an excellent solid lubricant in terms of its lubricity, non-melting properties, good thermal conductivity, and low coefficient of thermal expansion. No, because the adhesion to the other material and film-forming properties are insufficient, a! It cannot be said that the friction and abrasion characteristics are necessarily satisfactory, and when the component itself is made of graphite, the mechanical strength is low, so the surrounding area must be reinforced with metal or impregnated with metal to strengthen it. There is a difficulty in manufacturing that it must be done.

In addition, as a sliding member used under dry conditions.

Graphite impregnated with synthetic resin, mixed or coated with molybdenum disulfide or polytetrafluoroethylene have also been proposed, but these melt, thermally decompose, or oxidize at high temperatures, so they cannot be used at temperatures above 300°C. The disadvantage is that it cannot be used below.

(Problems to be Solved by the Invention) The purpose of the present invention is to overcome the drawbacks of conventional solid lubricants, exhibit good transferability and film-forming properties on the surface of mating materials, and have excellent properties in high-temperature regions. It is an object of the present invention to provide a sliding member that exhibits excellent friction and wear characteristics and high mechanical strength.

(Means for Solving the Problems) In order to solve the above problems, a 4C-B 4 C sliding member was proposed (Japanese Patent Laid-Open Publication No. 31355/1983).
However, although the sliding member obtained by this method exhibits excellent properties in terms of Al mechanical strength and wear coefficient at high temperatures, it is not possible to obtain a sufficiently satisfactory amount of wear from room temperature to high temperature. .

As a result of extensive research, the present inventors have discovered that by adding carbon fiber to the C-B4C sliding member, a C-B, C-based layered sliding member having excellent wear resistance can be obtained.

Next, one aspect of the present invention will be explained in detail.

Examples of the carbon powder used in the present invention include powders of amorphous carbon such as coke, anthracite, carbon black, and charcoal, and graphitic carbon powders such as artificial graphite, quiche graphite, and natural graphite. These may be used alone or in combination of two or more.

There are pitch-based and PAN-based carbon fibers, and either one or a mixture thereof may be used.

It is preferable to use PAN-based carbon having high strength and high elastic modulus. The length of carbon fiber is! If it is shorter than 0 ILm, it will be smaller than the carbon powder and sufficient effect cannot be obtained, and if it is longer than 500 ILm, it will inhibit the free movement of the carbon powder or boron carbide powder, so it is difficult to increase the density of the sintered body. 10 because it increases the fl friction coefficient and the amount of wear in order to reduce the graphite component exposed on the surface layer.
A range of ~500 m is preferred.

The reason why the amount of carbon fiber added was limited to 5% to 30% is that 5%
If it is less than 30%, it will not be effective, and if it is more than 30%, the length of the carbon spa will be limited, and the free movement of the carbon powder or boron carbide powder will be inhibited, so the resulting sintered body will become denser. This is undesirable as it will interfere.

In the present invention, such carbon powder and carbon fiber are mixed with 65 to 5 weight percent of boron carbide powder and 5 to 35 weight percent of boron carbide powder to form a powder for sintering. In addition, wet mixing is preferable for these mixing.

The powder for sintering obtained in this way was 100kg g7c.
m or more, preferably 150-300kg/c
under a pressure of 2000°C or more, preferably 2000°C or more
The sliding member of the present invention is obtained by sintering at 2300°C.

At this time, it is preferable to apply pressure until the temperature drops to 1500° C. after the completion of sintering.

Moreover, in this case, when raw coke is used as the carbon powder raw material, it can also be manufactured by adding a predetermined amount of boron carbide powder and carbon fiber to this and sintering it under normal pressure. Boron carbide serves as a sintering accelerator for carbon powder, and is contained in the resulting sintered body, which helps improve friction and wear characteristics, especially in high-temperature regions. Based on 5~35! Is it necessary to choose within the range of Tf amount %? The effect of boron carbide as a sintering accelerator appears at around 3% by weight, but at this level, all of the boron in boron carbide dissolves in carbon during the heating sintering process, and the resulting sintered body contains Therefore, improvements in mechanical strength, friction, and wear characteristics are insufficient. therefore,
In order to impart desirable properties to these sliding members, it is necessary to add at least 5% by weight of boron carbide.

This boron carbide is a hard substance and does not exhibit the same lubricating properties as graphite or molybdenum disulfide, but when incorporated into a graphite sintered body, when used as a sliding member, it will not lubricate the surface of the mating material. This tendency to promote the formation of a solid lubricating film, increase the durability of the coating in dry friction, and improve friction and wear properties is particularly noticeable in high temperature regions.

On the other hand, if the amount of boron carbide added exceeds 35% by weight, the coefficient of friction increases, the wear resistance decreases significantly, and
This will cause damage to the surface of the other material. in this way,
When the amount of boron carbide exceeds 35% by weight, the friction and wear characteristics deteriorate significantly.

It is thought that this is because wear particles caused by lacerations are present on the sliding surface with the mating material, and the wear gradually shifts to abrasive wear.

(Operation of the invention) Boron carbide dissolves in carbon powder and promotes graphitization, thereby lowering the coefficient of friction, but at the same time lowering the hardness of the sintered body. In general, hardness is an important factor in the coefficient of friction and amount of wear in sliding members.

If the hardness is low, the actual contact surface with the mating material increases, which increases the coefficient of friction and increases the amount of wear. The effect of carbon fiber in the sintered body containing carbon fiber in the present invention is that the true contact area is reduced due to the high strength and high rigidity properties of the basic fiber, resulting in a reduction in the coefficient of friction and the amount of wear. It is thought that this decreases the For this reason, it is preferable to add carbon fibers with higher strength and stiffness.

(Example) Next, the present invention will be explained in detail with reference to examples.

Example 1 B4C with a particle size of 1500 M e s h was added to 10 wt%,
10 to 30 pitch-based carbon fibers with an average length of 200 lm
80 to 60 wt% of calcined pitch coke powder with a particle size of 44 ILm was mixed in a ball mill using benzene as a dispersion medium, and dried to obtain a powder for sintering. This sintering powder was filled into a graphite mold to produce 300kg/crn'
The temperature was raised to 2200℃ under the pressure of
It was held for a time and sintered.

Then, after cooling to room temperature, it was taken out to obtain a carbon fiber-carbon: boron carbide-based sliding member. Table 1 shows these physical properties and sliding characteristics.

In addition, the measurement of the wear coefficient and amount of wear in the example.

Using a lead powder type thrust tester, length 45 mm, radius 45 m
A block-shaped WI moving member with a thickness of 5 mm and a thickness of 5 mm was applied to a stainless steel cylindrical body with an outer diameter of 1.25 mm, an inner diameter of 20 mm, and a length of 15 mm under conditions of a load of 20 kg/cm' and a speed of 5 m/min. This was done by sliding it. y
I depletion is the value after 2 hours of testing time.

Here, the specific wear rate is defined by a linear equation.

Hima 1F, rate = wear body m/(load/sliding distance) and,
For comparison, a sample to which no carbon fiber was added was also shown as a comparative example.

Example 2 A PA containing BaC and calcined pitch coke shown in Example 1 at 10 wt% and 80 wt%, respectively, and an average length of 10 roll m.
A sintered body was obtained in the same manner as in Example 1 except that 10 wt% of N-based carbon was added. The bulk weight of this sintered body is 2.11g/c
c, Chicoa hardness is 61, bending strength is 800kg
/c ni', the coefficient of friction is 0.22. Specific wear rate is o
, 6 x 10-'mm''/kg.

Furthermore, Table 2 shows the friction coefficients at high temperatures for the formulations listed in -.

(Hereinafter, blank space) Table 2 (Effects of the invention) As shown above, the resistance to jI! according to the present invention! The C-B4C sliding member, which has excellent wear resistance, is an excellent material that can significantly improve wear resistance without sacrificing the excellent sliding properties and strength at high temperatures that conventional graphite/boron carbide composites have. It is a sliding member.

Therefore, the present invention greatly contributes to industry.

Patent applicant Director of Industrial Technology Agency IBIDEN Co., Ltd. Designated representative of the Director of the Agency of Industrial Science and Technology ■Director of General Industrial Technology Testing Institute, Institute of Industrial Technology Sub-agent of the Director of the Agency of Industrial Science and Technology

Claims (1)

[Claims] 1). C-B_4C with excellent wear resistance characterized by being made of a sintered body of a mixture of 65 to 95% by weight of carbon powder and carbon fiber as carbon components and 5 to 35% by weight of boron carbide powder. System sliding members. 2). C having excellent abrasion resistance according to claim 1, wherein the carbon fiber is 5 to 30% by weight.
-B_4C sliding member. 3). The C-B_4C sliding member with excellent wear resistance according to claim 1 or 2, wherein the carbon fiber has a length of 10 to 500 μm.