JP2000170768A - Sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member excellent in lubricating property, anti-friction property, and mechanical strength, and low in costs. SOLUTION: A material metal powder selected from a stainless steel, a heat-resistant steel, a copper, a copper alloy, an aluminum, an aluminum alloy, and the like, is sintered by a power metallurgy, to manufacture a backing material 11 with numerous dispersion pores 11b. On the surface 11a of the backing material 11, numerous backing dimples 11b' consisting of a part of the dispersion pores 11b are formed at random. By evaporating a material selected from an amorphous carbon, a diamond like carbon, a silicon carbide, a titanium carbide, a titanium nitride, a titanium carbonitride, a silicon nitride, and the like, a hard membrane 12 is formed on the surface 11a of the backing material 11, and dimples 10b corresponding to the backing dimples 11b' are formed on the surface (the sliding surface 10a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member used as a sealing element on a rotating shaft side or a stationary sealing element sliding on the rotating shaft in a mechanical seal or the like for sealing a fluid around a rotating shaft of an apparatus. is there.

[0002]

2. Description of the Related Art A mechanical seal is an end face in which a sliding member provided on a rotating shaft side and rotating with the rotating shaft and a stationary sliding member provided on a non-rotating housing side are orthogonal to the axis. The close sliding between the members prevents leakage of fluid around the shaft, and the sliding material is required to have excellent wear resistance and sliding characteristics. For this reason, as a material of the sliding material, a hard material such as silicon carbide or alumina having excellent wear resistance, or carbon having excellent self-lubricating properties is used.

When sliding between flat surfaces under lubrication with an isothermal incompressible fluid, if the flat surfaces are extremely smooth, a lubricating liquid film is theoretically not formed between the sliding surfaces in a steady state. In an actual mechanical seal, a lubricating liquid film is formed due to factors such as minute undulations generated on the sliding surface and surface roughness. However, during sliding, the waviness and surface roughness change due to frictional heat and the like, and a change in the thickness of the lubricating liquid film accompanying this change causes a change in the coefficient of friction and the amount of heat generated on the sliding surface. When the sliding material is used under severe conditions, such as a PV value, which is extremely high, the average value and the maximum value of the friction coefficient and the amount of heat generated by the sliding increase, so that minute deterioration or breakage of the sliding surface progresses.

For example, when a hard sliding material such as silicon carbide is used in combination with a sliding material made of carbon having self-lubricating properties, frictional heat causes a blister called blister on a sliding surface on the carbon side. It is known that worm-like abnormal wear often occurs. Such destruction of the sliding surface occurs because the liquid lubricating film between the sliding surfaces has completely disappeared.

Therefore, in recent years, a pore-dispersed sliding material having a large number of pores at a predetermined ratio has been developed in order to improve the sliding characteristics. As a typical example, a pore-dispersion sliding material made of, for example, a silicon carbide sintered body is disclosed in
066, etc. According to this kind of pore-dispersed sliding material, it is possible to effectively prevent the occurrence of blisters and the like on the sliding surface described above. This is because the lubricating liquid film is stabilized even under severe sliding conditions in which the lubricating liquid film tends to disappear, because a large number of concaves formed by pores exposed on the sliding surface function as a lubricating liquid pool. This is because lubrication and cooling are promoted.

[0006]

However, according to the above prior art, the silicon carbide sintered body is expensive, and moreover,
During the sintering process of silicon carbide, the synthetic resin powder to be added to the sintering material to form pores therein is decomposed by heating, which causes a problem that the sintering furnace is contaminated. Also, the silicon carbide sintered body has a small fracture toughness value,
In other words, because of its high brittleness, cracks are likely to occur due to impacts, and the strength of the pores is further reduced by forming pores inside. This may increase the wear and increase the amount of wear.

[0007] Although the above-mentioned problem has been described with respect to a sliding material made of a silicon carbide sintered body, a similar problem has been pointed out with respect to a sintered body of titanium carbide, titanium nitride, titanium carbonitride, silicon nitride and the like. You. In recent years, the inventors have studied the use of, for example, amorphous carbon or diamond-like carbon as a sliding material, which is extremely hard and has excellent solid lubricity and wear resistance as compared with a sliding material such as fired carbon. However, sintering of these materials is extremely difficult, and it is also difficult to form recesses on the surface.

The present invention has been made in view of the above problems, and its main technical problem is to provide an inexpensive sliding material having excellent lubricity, abrasion resistance and mechanical strength. To provide.

[0009]

In order to effectively solve the above-mentioned technical problems, a sliding member according to the present invention is made of a material obtained by sintering a metal powder and has a large number of pores dispersed therein. By forming a sliding surface on which a hard film is deposited on the surface of the base material, the sliding surface has a large number of dimples. That is, by forming the sliding surface with a hard film, the wear resistance is improved, and the dimples corresponding to the concave portions formed by the pores appearing on the surface of the base material function as a lubricating liquid pool, thereby improving the liquid lubricity. The base material is made of sintered metal powder to increase the fracture toughness value.

The base material is selected from stainless steel sintered by powder metallurgy, heat-resistant steel, copper, copper alloy, aluminum, aluminum alloy and the like. In the sintering process by powder metallurgy, dispersed pores are inevitably formed by bonding metal particles together in a solid state, so it is necessary to intentionally perform a pore forming operation in advance by mixing synthetic resin powder or the like. Therefore, contamination of the sintering furnace by the thermally decomposed synthetic resin can be prevented. The dispersed pores formed by the powder metallurgy generally have an average pore diameter of 5 to 100 μm and a porosity of 3 to 20%, but are determined in consideration of the use conditions of the sliding material. Can be

The hard film may be made of a hard material such as amorphous carbon, diamond-like carbon, silicon carbide, titanium carbide, titanium nitride, titanium carbonitride, silicon nitride, etc., in consideration of sliding conditions, characteristics of the fluid to be sealed, temperature, and the like. The selected material is deposited on the base material by CVD or PVD. The film thickness is determined in consideration of the sliding conditions, the target life, the bonding property with the metal material of the base material, and the like, but is generally several μm to several tens μm. In addition, diamond-like carbon is a general term for materials having intermediate properties (structure) between high-purity calcined carbon containing graphite and diamond, and is remarkably harder than carbon materials used as ordinary sliding materials. It is.

A large number of dimples present on the sliding surface hold a part of the liquid intervening as a hydrodynamic lubricating liquid film between the sliding surface and the sliding surface of the mating member, and form a lubricating liquid. Has the function of stabilizing the film. These dimples are formed on the surface of the hard film deposited thereon, corresponding to the many concave portions formed of a part of the pores appearing on the surface of the sintered metal as the base material. For this reason, even if the edge of the concave portion in the base material is sharply raised, the edge of the dimple finally formed on the sliding surface by vapor deposition of the hard film becomes a curved surface, so that the aggressiveness to the mating sliding material is obtained. (Grater action) is reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic enlarged perspective view of the vicinity of a sliding surface showing an embodiment of a sliding member according to the present invention. The sliding member 10 includes a base member 11 having a shape as a sliding ring of a mechanical seal, and a hard film 12 formed on an end surface of the base member 11 corresponding to the sliding surface 10a. Are formed with a large number of dimples 10b at random.

FIG. 2 is a flowchart showing a manufacturing process of the sliding member 10. That is, first, in step S1, a raw metal powder selected from stainless steel, heat-resistant steel, copper, copper alloy, aluminum, aluminum alloy and the like is mixed,
In the next step S2, the raw metal powder is filled into an annular molding space of a compression molding die apparatus, and compression molded at a predetermined pressure. Thereby, a powder compact having the shape of the sliding ring of the mechanical seal is preformed.

Next, in step S3, the powder compact taken out of the compression molding die apparatus is heated in a sintering furnace at a predetermined sintering temperature lower than the melting temperature of the raw material metal for a predetermined time, thereby forming a base. The material 11 is sintered. In step S4, recompression molding is performed to increase the dimensional accuracy of the sintered base material 11 and to increase the bonding strength of the metal particles. In step 5, the base material 11 serving as the sliding surface 10a is formed. Is flattened by polishing or the like. As described above, since the base material 11 obtained by sintering the metal powder is a porous sintered body having a large number of dispersed pores 11b therein, the dispersed surface is provided on the machined surface 11a. By exposing a part of the pores 11b, a large number of underlying dimples 11
b ′ exists randomly.

Next, in step 6, the surface 11a of the machined base material 11 is coated with amorphous carbon,
Diamond-like carbon, silicon carbide, titanium carbide,
A hard film is formed by depositing a material selected from titanium nitride, titanium carbonitride, silicon nitride, or the like by plasma CVD or PVD. Since this hard film is also deposited on the inner surface of the base dimple 11b existing on the surface, the surface of the formed hard film 12 (the sliding surface 10b) is formed.
In a), a dimple 10b having a smaller diameter and a smaller depth is formed corresponding to the base dimple 11b.

EXAMPLE By sintering stainless steel powder of SUS316 by powder metallurgy, a surface serving as a sliding surface of a base material made of a pore-dispersed material having an average pore diameter of 50 μm and a porosity of 8% was obtained. The sliding material on which a silicon carbide film with a thickness of 30 μm was formed by the CVD method was incorporated into a mechanical seal tester,
A sliding test was performed. The mating sliding material was made of a high-strength carbon material and had a flat sliding surface free of dimples, and the other conditions were as follows. Test conditions (1) Liquid to be sealed High viscosity oil (2) Sliding speed 15m / s (3) Surface pressure of sliding surface 0.35MPa (4) Temperature of liquid to be sealed -10 ° C (5) Sliding time 2 time

After the test, the carbon sliding surface of the mating material was observed. As a result, there was no occurrence of blisters in the form of carbon damage. Therefore, it was confirmed that the sliding material of the present invention can obtain excellent lubrication.

[0019]

According to the sliding material of the present invention, the dimple formed on the sliding surface has an appropriate control function of the thickness of the lubricating liquid film and the amount of leakage of the liquid to be sealed, and the sliding surface has a hard coating. Is applied to provide abrasion resistance, so that the same sliding characteristics can be obtained as a sliding material made entirely of a hard material of the same material as the hard coating, and the hard material is burned. Even a material that cannot be bonded can be used as a sliding material. In addition, since the base material is made of sintered metal by powder metallurgy, the fracture toughness value is higher than when the base material is made of ceramics.

Since there is a concave portion due to pores formed in the sintering process on the surface of the base material made of the sintered metal, it is necessary to process the base dimple for forming the dimple on the sliding surface made of the hard film. There is no. Further, the pores are
It is inevitably formed in the sintering process, and there is no need to add a synthetic resin powder for forming pores to the raw metal powder. Moreover, the metal powder material itself is cheaper than the ceramic material, so that the raw material and processing costs can be reduced to provide an inexpensive product, and the sintering furnace is not contaminated.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged cross-sectional perspective view of the vicinity of a sliding surface of a sliding material according to the present invention.

FIG. 2 is a flowchart showing a manufacturing process of the sliding material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sliding material 10a Sliding surface 10b Dimple 11 Base material 12 Hard film

Continued on the front page F-term (reference)

Claims (3)

[Claims] A base material (1) made of a material obtained by sintering metal powder and having a large number of pores (11b) dispersed therein.
By forming a sliding surface (10a) on which a hard film (12) is deposited on the surface (11a) of 1), the sliding surface (10a) has a large number of dimples (10b). Sliding material. 2. The base material (11) according to claim 1,
However, stainless steel, heat-resistant steel, sintered by powder metallurgy,
A sliding material characterized by being selected from copper, copper alloy, aluminum, aluminum alloy and the like. 3. Hard coating (12) according to claim 1.
Is selected from hard materials such as amorphous carbon, diamond-like carbon, silicon carbide, titanium carbide, titanium nitride, titanium carbonitride, silicon nitride, etc .;
A sliding material characterized by being formed by VD.