The friction of copper-nickel and iron-sulfur alloys in air and vacuum

Abstract

The friction of unlubricated copper-nickel and iron-sulfur alloys is studied with a pin-on-disc machine in air and in vacuum for determining the frictional characteristics of a typical solid solution alloy and a typical two phase alloy. The friction of copper-nickel alloys on themselves is slightly reduced by alloying but even more so by the surface oxides. The friction of copper-nickel alloys on steel plates is not reduced by alloying but increased by the surface oxides. The friction of iron-sulfur alloys on steel plates is decreased or increased depending on the nature of the iron sulfide film. It is hypothesized that oxides and other phases in metals can either reduce friction by preventing metal-to-metal contact or increase friction by becoming embedded in the surface. These two effects can occur at the same time; and the hardness of the oxide or the second phase, that of the matrices and the compatibility of the metals forming the friction couple determine which one of these effects will predominate.