Recent Advances in Sliding Contacts including Space Applications

Drastic wear under very dry high altitude or space conditions is considered to be due to a lack of a contact film. When this film is absent, electron exchange between metallic members can produce metallic bonds which are of the same order of magnitude in strength as those of soft metals. The contact between a metal and graphite also exhibits considerable bond strength. Such bonds result in galling, seizure, high wear rates, and in some cases, the end result is poor electrical conduction. Graphite alone is not sufficient to provide a suitable contact film for sliding conduction under space conditions. It is an electron conductor, and it is therefore possible that it can make weak metallic bonds with the metals in the absence of moisture or organic vapors. A large list of chemical compounds, some of which are laminar, like graphite, and some of which are not, like lithium carbonate, can prevent drastic wear.