Unexpected friction behaviours due to capillary and adhesion effects

Abstract

In this present work, we show that pouring water into the interface of SiC sliding against the same SiC material makes the friction coefficient far exceed that governing initial dry friction, and a subsequent load increase causes a dramatic abnormal friction force decrease. With the load further increasing to a critical value, friction force sharply increases again. The small amounts of water in the interface generates a large capillary force, the capillary bridges break to cause micro-separation of interface increase to allow bulk water to enter the friction interface, and a squeezing out of the water film to form a strong adhesion force between SiC-SiC materials, are considered to be responsible for the three stages, respectively.