Mechanical Seal Friction Pair Material

Silicon carbide: Silicon carbide ceramic is a new material developed in recent years. It has a very low friction coefficient, high hardness, and good wear resistance. It has good chemical stability, heat resistance and thermal shock resistance.

Silicon carbide includes hot pressed silicon carbide, atmospheric pressure sintered silicon carbide and reaction sintered silicon carbide.

Cemented carbide: Cemented carbide is mainly tungsten carbide WC, including cobalt-based tungsten carbide WC-Co, nickel-based tungsten carbide WC-Ni and cobalt-nickel-based tungsten carbide WC-Co-Ni.

The characteristics of tungsten carbide: high hardness, good wear resistance; high mechanical strength, good bending resistance; high thermal conductivity and small expansion coefficient, the friction heat of the sealing surface is easily exported; cobalt-free cemented carbide has good corrosion resistance.

Mechanical auxiliary sealing materialsThe auxiliary seal of the mechanical seal is an important part to ensure reliable sealing and extend service life. Auxiliary seals include auxiliary sealing rings of dynamic and stationary rings. Its function is to ensure the seal between the stationary ring seat (gland) and the stationary ring between the sealed shaft and the moving ring, to compensate for the deflection and vibration of the sealing surface; to ensure that the end faces of the moving and stationary rings are tightly coupled and have floatability.

Mechanical seal requirements for auxiliary seal ring materials:

1) The material has good elasticity, especially good recovery properties and small permanent deformation;

2) It is not eroded by the fluid medium, and its expansion and contraction in the medium are not large;

3) Small friction factor and good wear resistance;

4) The use temperature range should be wide, and it should not stick, hard, brittle or lose elasticity at high and low temperatures;

5) It must have appropriate mechanical properties, such as tear strength, elongation, pressure resistance, etc., no significant deformation under pressure, and excellent tear resistance, wear resistance, pressure resistance, etc.;

6) Easy to process and can achieve high precision;

7) It has good resistance to medium corrosion, dissolution, swelling, aging, etc., and should not pollute the medium.

Materials used as auxiliary sealing rings include rubber, plastic, asbestos, expanded graphite, graphite and metal expansion rings. Rubber ring is the most widely used auxiliary sealing ring. Commonly used rubber sealing ring materials include nitrile rubber, fluorine rubber, silicone rubber, neoprene rubber, styrene-butadiene rubber, etc.

Nitrile rubber is a commonly used oil-resistant rubber. It is a copolymer of butadiene and acrylonitrile. According to the acrylonitrile content, it is divided into several types: low acrylonitrile (butyronitrile-18), medium acrylonitrile (butyronitrile-26) and high acrylonitrile (butyronitrile-40). The higher the acrylonitrile content, the better its oil resistance. Good, the tensile strength, hardness, wear resistance, and water resistance increase, and the breathability decreases. Subsequently, its solubility in polar solvents increases, its corrosion resistance is also affected, and its elasticity and cold resistance also become worse. Nitrile rubber is not resistant to flexing and has poor tear resistance.

Fluorine rubber has the advantages of high temperature resistance, oil resistance and chemical corrosion resistance. The most widely used fluorine rubber is fluorine-containing olefin copolymer, mainly types 26 and 23. Type 26 includes fluororubber-26 series emulsion copolymer of vinylidene fluoride and hexafluoropropylene and fluororubber-246 series terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoropropylene. Type 23 fluorine rubber is an amorphous rubber-like copolymer produced by suspension polymerization of vinylidene fluoride and chlorotrifluoroethylene at room temperature and 3.24MPa pressure. It cannot be used in liquid ammonia or ammonia water.

Silicone rubber is a polar polymer polymerized by dimethylsiloxane and other silicone monomers in the presence of acid or alkaline catalysts. Silicone rubber has high thermal stability, but it is polar and prone to ionic cracking under the action of acids and alkalis. Therefore, it has poor corrosion resistance and is not suitable for petroleum solvents (such as benzene, toluene, etc.), acetone, and ketone. Organic solvents such as ether.

PTFE has excellent chemical stability, oil resistance, solvent resistance, aging resistance and temperature resistance, and has a very low friction factor and certain strength, elasticity, flexibility and non-adhesion, so it is widely used in various temperature applications. , sealing rings under pressure and corrosive media conditions.

In summary, as auxiliary sealing materials, O-rings, gaskets and bellows made of rubber materials can be used in general media; V-rings and wedge-shaped rings made of polytetrafluoroethylene can be used in corrosive media. , gaskets and bellows, etc.; metal bellows can be used under high and low temperature conditions. The service temperature and corrosion resistance of the material should be considered when selecting.