JPH0343229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a ceramic sliding member in which the sliding characteristics of ceramics are improved.

(Conventional technology and problems) In recent years, interest in ceramic materials has increased,
Ceramics are being applied to various sliding parts by focusing on their excellent wear resistance, corrosion resistance, heat resistance, heat insulation properties, etc. However, most of them are used in conditions where oil lubrication is abundant, and they are rarely used in areas where lubricating oil cannot be supplied or where lubricating oil cannot be retained. Furthermore, even if an attempt is made to lubricate parts exposed to high temperatures, the viscosity of the lubricating oil will drop significantly and the lubricating purpose cannot be achieved.

Since oil lubrication is not possible, solid lubricants have no choice but to rely on solid lubricants, but solid lubricants such as molybdenum disulfide and Teflon have many problems in terms of heat resistance and strength. Demand for structural members that cannot be lubricated with oil or that are exposed to high temperatures is increasing, and there are expectations for the development of a method to increase the sliding properties of ceramics, which have high wear resistance and heat resistance, as a base material.

(Means for solving the problem) As shown in Figs. 1 and 2, fine cavities 3 are formed by chemically or electrically eluting unreacted Si2 in the surface layer of reactive sintered SiC. A solid lubricant with excellent sliding properties is impregnated into the cavity 3 and fixed thereon to form a solid lubricant layer 4, which retains solid lubricity and has heat resistance and wear resistance. The present invention provides a new method for manufacturing a ceramic sliding member that combines ceramics with excellent properties such as ceramics and a solid lubricant that can maintain lubricity even under severe conditions where oil lubrication is impossible.

The reactively sintered SiC ceramic of the present invention, which serves as the base material, may be one that is produced by ordinary reactive sintering and has an unreacted Si portion.

It can be obtained by chemically eluting the Si portion with an acid, hydrofluoric acid, or a mixed acid thereof that reacts with Si in the cavity 3 of the surface layer of the reactive sintered SiC, or by eluting the Si portion by electrolysis using the reactive sintered SiC as an anode. It will be done. The electrolyte solution used for electrolysis may be a mixed acid containing hydrofluoric acid or an acid similar thereto.

As a solid lubricant for this cavity 3, zinc stearate, molybdenum disulfide, graphite, etc. are added mechanically by press-fitting, chemically by electrophoresis in a colloidal solution such as graphite, or physically by vapor deposition, sputtering, etc. A solid lubricant layer 4 is formed by impregnating and fixing a solid lubricant into the cavity using a method. The thickness t of the solid lubricant layer can be determined to be suitable for each application by appropriately setting the conditions for elution of unreacted Si2 forming the cavity 3 and the conditions for impregnating the solid lubricant.

(Example) In an example of the present invention, the characteristics of a ceramic sliding material according to the structure of the present invention will be explained based on the experimental data shown in FIGS. 3 to 5.

Example 1 The unreacted Si portion of reactive sintered SiC was eluted by a chemical method using a mixed acid of hydrofluoric acid and nitric acid.

Hydrofluoric acid (47%): Nitric acid: Water = 1:1:1
The unreacted Si of the reacted sintered SiC was eluted in a mixed acid with a ratio of .

The relationship between reaction time and elution depth is shown in Figure 3.
The elution depth at reaction times of 1 hour and 2 hours is
At 0.3 mm and 0.6 mm, the reaction time and elution depth are almost proportional.

Example 2 In Example 1, a sample having a cavity depth of 0.3 mm was impregnated with zinc stearate by the press injection method.

The impregnation method is based on the temperature of the stearic acid solution in the impregnation tank.
230℃, keeping the sample at the ambient temperature of 230℃ for 30 minutes.
After keeping the temperature at 230℃, immerse it in the liquid of the impregnation tank that has been reduced to -700mmHg or less, hold it for 5 minutes, and then reduce the pressure to 0.9
After pressurizing to Kg/cm ² and holding for 3 minutes, the impregnating liquid was drained and the liquid was drained by rotating centrifugal force and taken out.

The impregnation rate by this method was 90%.

Example 3 The unreacted Si portion of reactive sintered SiC was eluted by an electrical method using electrolysis.

Constant voltage electrolysis was carried out in an aqueous solution of 5% by volume of hydrofluoric acid (47%) and 5% by volume of nitric acid, with reaction sintered SiC as the anode and a Cu plate as the cathode.

The relationship between current density and elution amount per unit area is as shown in Figure 4.
The elution amount at 10 ^-2 A/cm ² is 7 and 12×10 ^-3 g, and the current density and elution amount are almost proportional.

Example 4 The sample of Example 3 with an elution depth of 0.3 mm was impregnated with graphite by a chemical method using electrophoresis.

Reactive sintered SiC in 0.5% by volume graphite solution
Electrophoresis was performed by applying a voltage using the Cu plate as an anode and the Cu plate as a cathode.

The impregnation rate was 85%.

Example 5 The samples of Examples 2 and 4 above were tested for lubricating properties.

Friction speed 0.23 with Pinghon disk friction tester
The test was conducted under the following conditions: m/s, load 20 kg/cm ² and no lubrication. The friction coefficient of the test results is as shown in FIG.

The friction coefficient value of reactive sintered SiC tested as a comparative example was 0.2, whereas the friction coefficient of zinc stearate-impregnated SiC was 0.1;
With graphite-impregnated SiC0.09, the friction coefficient was halved and the lubricity was greatly improved.

Effects According to the present invention, ceramics have excellent heat resistance,
Due to the synergistic effect of wear resistance and the low friction properties of solid lubricants, it can self-lubricate without supplying lubricating oil as a sliding member used under severe conditions where oil lubrication is impossible or in environments where use is undesirable. This has the remarkable effect that it is possible to obtain a sliding member with excellent properties such as wear resistance, corrosion resistance, and heat resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention. Figure 2: General cross-sectional diagram of ceramics. Third
Figure: Relationship diagram between reaction time and elution depth when unreacted Si is eluted using a chemical method. Figure 4: Relationship diagram between current density and elution amount when unreacted Si is eluted by an electrical method. Figure 5 Reactive sintered SiC and Si-Zn impregnation of the present invention
The friction coefficient of SiC and graphite-impregnated SiC is shown. 1: SiC particles, 2: unreacted Si, 3: cavity,
4: Solid lubricant layer.

Claims (1)

[Claims] 1 The base material is ceramics in which the unreacted Si in the surface layer of reactive sintered SiC is chemically or electrically eluted to form fine cavities and dispersed therein, and the cavities are filled with a solid material with excellent sliding properties. A method for manufacturing a reaction sintered SiC ceramic sliding member, characterized in that a solid lubricant layer is formed by impregnating and fixing a lubricant.