JPS59131575A - Abrasion resistant sliding material - 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 The present invention relates to wear-resistant sliding materials. For more details,
This invention relates to wear-resistant sliding materials that can be used up to high temperatures even without lubrication.

As a sliding material that can be used up to high temperatures without lubrication, graphite bearings have been used as sliding bearings. Graphite bearings have excellent chemical resistance and self-lubricating properties, so they can be used up to high temperatures without lubrication, but a major drawback is that they have a large porosity and therefore poor mechanical strength.

Therefore, for the purpose of reinforcing this mechanical strength, it is common practice to impregnate the pores with a thermosetting resin or a metal with a relatively low melting point. However, the impregnating material, resin or metal, expands, decomposes, melts, leaches, etc. under high temperature and high pressure. As a result, when impregnated with resin, the heat and humidity resistance is lower than 200°C due to deterioration and decomposition of the resin, and the difference in thermal expansion coefficient between graphite and resin causes the blistering phenomenon ( blistering phenomenon)
happens. Furthermore, when impregnated with metal, chemical resistance and corrosion resistance deteriorate, sliding properties also deteriorate, and seizure phenomenon occurs.

Furthermore, solid lubricant-dispersed sintered metal bearings are also used, in which graphite, molybdenum disulfide, etc. are uniformly dispersed in a bronze-based or iron-based metal base material using a powder metallurgy method. Compared to this, the mechanical strength is improved and it can be used up to Takagata without lubrication, but since the base is made of metal, it has poor chemical resistance and corrosion resistance, and is not only inferior in wear resistance at high temperatures, but also suffers from oxidation expansion. Therefore, there are drawbacks such as the inner diameter of the bearing shrinking and affecting the bearing clearance.

In addition to these, plastic bearings and sintered oil-impregnated bearings are also used, but with the exception of fluororesin bearings, these have a limited operating temperature that takes into consideration the heat resistance temperature of the material itself or the lifespan of the lubricating oil impregnated with it. In practice, it is used at temperatures of about 80-120°C or lower. In addition, fluororesin bearings not only have high heat and humidity resistance of about 250°C, but also have characteristics such as a low coefficient of friction and excellent chemical resistance, but on the other hand, they have the disadvantage of being soft and prone to creep. have. In particular, the higher the blood pressure or the higher the temperature, the greater the creep, causing problems such as deformation and outflow. Furthermore, the coefficient of thermal expansion is on the order of 10-5, which is one order of magnitude larger than that of metals, and because of such coefficient of thermal expansion and creep, it is often used practically at temperatures below 200°C.

The present invention provides a wear-resistant sliding material that does not exhibit any of these drawbacks, and the friction-resistant sliding material of the present invention, which is made of a glassy carbon material and a solid lubricant boron nitride, Self-lubricating properties are maintained up to about 450°C in the air without oil, and up to about 2500°C in an inert/semi-gas atmosphere.

Glassy carbon materials are produced by carbonizing a cured molded product of furan resin, phenol resin, or a mixture thereof in an inert atmosphere at a high temperature, generally at a temperature of about 1000°C or higher, and if necessary. It can be obtained by further graphitizing. In addition, a carbon precursor material having an oxygen functional group induced from a pitch with an adjusted hydrogen/carbon atomic ratio (Hlo) is powder-molded, then similarly fired and carbonized, and if necessary, this is further added to graphite. It can be obtained by converting

Graphitization treatment, which is performed as necessary, is performed by subjecting the fired material to high temperature treatment for a long time at about 2000 to 3000° C. using a graphitization furnace. However, glassy carbon materials are difficult to graphitize, and graphitization only slightly progresses even with such high-temperature heat treatment. Although the hardness decreases slightly due to the development of a graphite structure when the material causes metal-to-metal contact,
Improves lubricity.

These glassy carbon materials have a light specific gravity like graphite, but are very hard and strong, have excellent chemical resistance and corrosion resistance, and have a heat resistance of about 450°C in the air and in an inert gas atmosphere. It is a new carbon material with a high temperature of about 2,500°C and an extremely high specific strength, and has traditionally been used mainly for applications such as crucibles, boats, heaters, and electrodes.

Boron nitride, which is used as a solid lubricant to be blended into such a glassy carbon material, has extremely good lubricity because its crystal structure has a stack of hexagonal mesh planes similar to that of graphite. Moreover, its decomposition temperature is approximately 3000℃.
Therefore, it can be used at high temperatures of about 700 to 900°C in air and up to about 2800°C in an inert gas atmosphere.

Boron nitride is present in the blend with the glassy carbon material at about 5 to 5
It is used at a blending ratio of 0% by weight. If the usage rate is less than this, the resulting sliding material will lack lubricity, have a high coefficient of friction, and have poor wear resistance. On the other hand, if it is used in a higher proportion than this, the hardness will decrease and the bending strength will decrease.
Not only does it lack mechanical strength such as compressive strength,
As will be described later, this makes it difficult to harden or produce powder compacts for producing sliding materials.

The sliding material is manufactured by forming a uniform mixture of a glassy carbon material forming material and boron nitride into a predetermined shape, and then carbonizing the mixture at the firing temperature of the glassy carbon material forming material. When using a cured molded resin, a sliding material with a thickness of about 3711111 can only be produced from a compound with boron nitride alone, so carbon materials such as graphite or carbon precursors containing oxygen functional groups are generally used. It is used in the form of a coating on a molded body as a base material, which is formed from a fired product of the substance. In this case, since the resin is impregnated into the pores of the molded body made of a base material such as a carbon material, the coating is firmly adhered to the molded body, and at the same time, the strength of the molded body itself is improved thereby. 1. When an oxygen functional group-containing carbon precursor substance is used as a material for forming a glassy carbon material, a uniformly mixed powder of nitrogen and boron is powder-molded into a predetermined shape with an arbitrary thickness under pressure at room temperature. After that, firing and carbonization are performed. The sliding material manufactured in this way has sufficient mechanical strength because it is made of glassy carbon material, but in order to further improve it, it is necessary to add carbon fiber, A carbon-carbon composite material can also be obtained by blending graphite fibers or the like.

The sliding material according to the present invention is extremely hard and has high strength.
The substrate is made of heat-resistant glassy carbon material,
Because it contains boron nitride as a solid lubricant, it has excellent wear resistance and maintains lubricity up to approximately 450°C in the atmosphere and at high humidity of approximately 2500°C in an inert gas atmosphere. There is. Furthermore, it has excellent chemical resistance and corrosion resistance,
Since it is stable even at high temperatures, it does not suffer from the disadvantages of poor chemical resistance and corrosion resistance, or oxidation expansion, which were observed in conventional metal-impregnated graphite bearings and graphite-dispersed sintered metal bearings. . In addition, even at high temperatures, it does not suffer from the phenomenon of reeving seen in fluorine wood bearings, and its coefficient of thermal expansion is slightly lower than that of iron, making it easy to control the bearing clearance.

Next, the present invention will be explained with reference to examples.

Examples] - Oxygen functional group-containing carbon precursor material derived from pitch (
80 parts by weight (particle size 10μ or less) and 80 parts by weight (particle size 5
20 weight parts of uniformly mixed powder was powder-molded into a disc shape with a diameter of 60 cm and a thickness of 10 cm at room temperature at a molding pressure of 3000 r, and then heated at 30°C/hr in an inert atmosphere 'dM. The carbon precursor material was carbonized by raising the temperature to 1000° C. at a heating rate of .

Comparative Example 1 In Example 1, a disk was powder-molded and carbonized without using boron nitride.

The north characteristic values of the disk bodies (surface roughness 3s) fired in Example 1 and Comparative Example 1 were measured, and the results are shown in Table 1 below.

Table 1 Item Example 1 Comparative Example 1 Bulk density (A11) 1.72, 1.59 Open porosity (volume %) 5.4 4.3 Shore hardness (HS) 119 128 Bending strength (~) 820 910 compressive strength
(η) 4400 4900 Furthermore, using these fired disk bodies as test pieces, the friction and wear characteristics were examined using a Suzuki type friction and wear tester (thrust type tester). In the friction wear test, an inner diameter of 2Qfl1 was placed on this test piece.
71. A cylindrical mating material with an outer diameter of 25.6 mm (5450 carburized and quenched, hardness HRC 51 to 54, surface roughness 1s, sliding area 2i) was placed in a fixed manner, and the test piece was rotated under the following conditions. It was done by letting

Lubrication: None Rotation speed: Constant 40m/min (Rotation speed: 559 rpm
) Surface pressure: 0.5.3, 0.5.5.8.0 ~ (cumulative load) Operating time: Maintained at each surface pressure for 8 hours (32 hours in total) Atmosphere temperature: Normal humidity Furthermore, for comparison, Graphite-dispersed bronze-based sintered metal bearing material (Comparative Example 2), carbon fiber-filled fluororesin material (Comparative Example 3), and graphite material (Comparative Example 4) all have a surface roughness of 38.
), the friction and wear characteristics were similarly investigated.

The values of the coefficient of friction and the increased humidity for the cumulative cargo (and its calculated pv value) are both shown in the graph of FIG. The results of measuring the amount of wear of each test piece and its counterpart material at the end of 32 hours of operation are shown in Table 2 below.

Table 2 Example 1 0.002 0.8 ratio soft example 10
゜017 3.5 // 2 0.029 2.6 // 3
0.005 0.9// 4. 0.
012 2.3 From the results shown in Fig. 1 and Table 2, the sliding material according to the present invention has a lower coefficient of friction and lower temperature rise than the carbon fiber-filled fluororesin material at room temperature, and also has less wear. It can be seen that it can be used sufficiently as a dynamic material.

Example 2 Boron nitride (particle size 5
μ or less) was uniformly dispersed, and this dispersion was applied several times to the surface of the disc-shaped powder compact of Comparative Example 1 with a brush.
Each time, curing was repeated to form a film there. Then, the coating surface was polished to make it flat, and heated to 1500°C at a heating rate of 10 IC/hr in an inert gas atmosphere.
The temperature was raised to 100%, followed by calcination and carbonization.

A film about 17 mm thick is formed on the surface of the disk,
It was formed from a very hard glassy carbonaceous material containing 30% by weight boron nitride. This was heated to 300° C. using a water condensation type friction and wear tester (thrust type tester) equipped with a high-frequency heating device, and a friction and wear test was conducted. The test conditions were a rotation speed of 5 m/min, blood pressure of 8,
The procedure was the same as in Example 1 except that the operating time was changed to 100 hours. Note that similar tests were conducted on the materials of each of the comparative examples.

The amount of wear is shown in the graph in Figure 2, and the friction coefficient of each test piece just before the end of 100 hours of operation is shown in Table 3 below.
shown respectively.

Table 3 Example Friction coefficient Example 2 0.22 Comparative example 1 0.33 1/2 0.36 “ 3 0.32 // 4 0.28 From the results in Figure 2 and Table 3, the high temperature condition of 300°C It can be seen from the figure below that the sliding material according to the present invention has significantly less wear than other materials, and has a small and stable friction coefficient.Also, the sliding surface after the friction and wear test is When observed, other materials had clear sliding marks and severe unevenness, but the sliding material of the present invention had a smooth sliding surface and maintained a good frictional state during sliding. This confirms that

[Brief explanation of the drawing]

FIG. 1 is a graph showing the values of the friction coefficient and temperature rise with respect to the cumulative load (and its converted PV value) in the friction and wear test. Moreover, FIG. 2 is a graph showing the value of the amount of wear against the operating time in the friction and wear test. Representative Patent Attorney Yoshi 1) Toshio Total of 2 diagrams Open when driving (closed when driving)

Claims (1)

[Claims] 1. A wear-resistant sliding material comprising a glassy carbon material and a solid lubricant boron nitride. 2. The wear-resistant sliding material according to claim 1, which contains about 5 to 50% by weight of boron. 3. The wear-resistant sliding material according to claim 1 or 2, which is formed as a double bearing. 4. The wear-resistant sliding material according to claim 1 or 2, which is used as a sliding surface of a sliding bearing and is subject to bearing profiteering.