Advantages of a New Hard Carbon for Water Pump Seals for Automotive Engines

Carbon-graphite and ceramic mating pair has been generally used as water pump mechanical seals of automotive engine. Silicon carbide materials are recently used in order to prevent damage of mechanical seal surfaces by hard solid substances in liquid to be sealed. The silicon carbide material has poor self-lubricity. As a result, seal surfaces sometimes seize or the secondary seal is damaged due to heat generation by friction, resulting in leakage. In order to overcome such a defect, a new carbon-graphite material, which is composed of carbon-graphite powder, chopped carbon fiber and resin, has been developed.

Wear resistance, cavitation erosion and sealing tests are performed. The results are compared with those obtained with usual carbon-graphite and silicon carbide. It is found that the carbon-graphite contained a certain amount of chopped carbon fiber has good performance as a material of water pump mechanical seals