Sliding Characteristics of Silver Against Iron as Influenced by Oxygen Concentration

Friction, wear and metal transfer of the silver-iron friction couple have been studied as a function of oxygen percentage of the surrounding atmosphere at different levels of temperature. The results show that the replacement of high purity argon by a mixture of argon and oxygen causes an instantaneous increase in friction, followed by local transfer of silver to the iron surface and a high rate of wear. The observed effect is reversible. It is found that in the severe wear region the diffusion of oxygen towards the friction interface determines the wear rate, although visible oxidation does not occur. Experimental evidence strongly suggests that the formation of thin films of iron oxide is responsible for increased adhesion and metal transfer.