The differences between silicon carbide and alloys on the mechanical seal end face of the Chinese ATACH Industrial Water Pump Factory

For chemical media, ATACH industrial pumps usually recommend using alloy-silicon carbide sealing surfaces. 

In fact, for plain water, silicon carbide-graphite sealing surfaces are fully capable of performing the task. 

In the end face of mechanical seals for centrifugal pumps, silicon carbide and alloys (typically referring to hard alloys such as tungsten carbide) are two core friction pair materials, which have significant differences in performance and are suitable for different working conditions.

Main differences

• ‌Hardness and wear resistance‌: Silicon carbide has extremely high hardness, second only to diamond, and has excellent wear resistance, especially suitable for use in media containing particles or abrasive substances. Hard alloys (such as tungsten carbide) also have high hardness and good wear resistance, but are usually slightly lower than silicon carbide.

• ‌Corrosion resistance‌: Silicon carbide has extremely strong corrosion resistance to most chemical media (including concentrated nitric acid, sulfuric acid, hydrochloric acid, etc., strong corrosive liquids), and is only sensitive to hydrogen fluoride and other few media. The corrosion resistance of hard alloys is relatively better, but in strong corrosive environments, it may not be as good as silicon carbide, and often requires surface treatment or alloying to improve.

• ‌Impact resistance and toughness‌: The toughness of hard alloys is better than that of silicon carbide, capable of withstanding certain mechanical impact and vibration. Silicon carbide is a hard and brittle material, with poor mechanical impact resistance. When subjected to impact or improperly installed, it is more likely to crack.

• ‌Thermal conductivity and friction coefficient‌: The thermal conductivity of hard alloys is usually better than that of silicon carbide, which helps to dissipate heat quickly in high-speed or high-temperature working conditions. The friction coefficient of silicon carbide is lower, and it has good self-lubrication properties, which can form an efficient sealing combination with graphite and other materials.

• ‌Applicable working conditions‌: Silicon carbide is an ideal choice for corrosive media, high temperatures, and high wear environments, especially performing well in clean or weakly corrosive fluids. Hard alloys are more suitable for medium corrosion, environments with impact or vibration, and are a more versatile material.

Common pairing methods

• ‌Silicon carbide with graphite‌: This is one of the most commonly used combinations, combining the high wear resistance and corrosion resistance of silicon carbide with the excellent self-lubrication of graphite, suitable for most clean water and chemical media.

• ‌Silicon carbide with itself‌: Used for high wear, high purity or particle-containing media, it is a "hard against hard" pairing, with excellent wear resistance, but requires high installation accuracy.

• ‌Hard alloys with graphite‌: Suitable for medium corrosion, occasions requiring good toughness, a traditional and reliable combination.

• ‌Hard alloys with hard alloys‌: Used for high load, high impact working conditions, but with a higher friction coefficient, attention should be paid to heat dissipation.

In conclusion, the choice between silicon carbide or alloys should be determined based on the properties of the medium (corrosiveness, particle content), temperature, pressure, impact load, and cost.