Views: 2458 Author: Site Editor Publish Time: 2020-07-29 Origin: Site
At present, most of the seals, such as non contacting mechanical seal, pump seal, gland packing, spring seal, elastomer bellows seal, are made of metal materials, which leads to these seals have different degrees of defects. Due to its excellent mechanical properties, corrosion resistance and good tribological properties, silicon carbide is gradually developed and applied in many fields as a sealing material.
When the mechanical seal works under high pressure, the end face needs to bear a lot of load, which requires that the seal material must have high strength and rigidity, otherwise the end face will be deformed due to pressure, resulting in leakage or rapid wear, resulting in mechanical seal failure. Silicon carbide material is a kind of material with high strength, high rigidity and high elastic modulus, which is not easy to deform under high pressure and meets the use requirements.
In the high speed working condition, because of the high linear speed, the thermal wear and vibration of the friction pair will be an important problem in the working process. Therefore, it is required that the material used as rotary seal should have high strength and low density. In this way, the centrifugal force produced by the rotary seal at high speed is small, and the vibration and deflection caused by it are also small, so as to maintain the stable fit of the end face. Due to its low density, good thermal performance and small friction coefficient, silicon carbide has obvious advantages in high speed rotary seal materials, so it is widely used in high speed mechanical seal.
High temperature will change the performance of friction pair materials, make the end face deformed, reduce the hardness, and reduce the service life of mechanical seal. Therefore, the thermal deformation, high temperature strength and wear resistance of materials are the key issues to be considered when selecting sealing materials. The high temperature strength of silicon carbide is very good, so it will not creep at high temperature. Because of the self-lubricating function of silicon carbide ceramic, there will be no adhesive wear when rotating between the two end faces, so silicon carbide can be used for mechanical seal at high temperature.
Corrosion is the main reasons for the failure of friction pairs. This kind of corrosion will directly or rapidly cause the change of sealing performance, so the selection of sealing materials should be based on the characteristics of medium. Silicon carbide has good chemical stability and strong corrosion resistance, so it can be used in a variety of corrosive acid and alkaline medium.
The sealed fluid often contains solid particles, such as waste water, sea water, some easily crystallized chemical solutions, etc. These particles will not only seriously wear the end face, but also make the end face hot cracking. Silicon carbide has the characteristics of high hardness, wear resistance and heat crack resistance, so it is an ideal choice as one or two end face materials of mechanical seal.
Under normal conditions, dry friction will affect the performance of the seal. Dry friction will increase the friction coefficient, resulting in burning loss, thermal stress cracking and even leakage of the seal ring. Therefore, the seal material is required to have high temperature resistance and good tribological performance. And silicon carbide has such properties, so silicon carbide can fully meet the needs.