Physical changes in rubbing surfaces on scuffing

Abstract

Cast-iron surfaces rubbing against steel have been found to develop a thin layer of a white constituent when scuffing occurs or is approached. This material has not been fully identified, but the results point to it having a basis of two phases, viz. cementite and a quenched high-carbon ferritic phase developed from austenite, resulting from the high temperature developed by rubbing. In the laboratory work, using a 4-ball apparatus modified to take piston ring segments, this white material was also obtained in some degree with mineral oil under milder conditions than those causing scuffing, but not with the castor oil which proved better in preventing scuffing in running-in an aero-engine. The work was carried out early in the war period and was not completed. These particular results, and a number of others, are recorded to draw attention to this phenomenon, which has also been noticed in the U.S.A., and may act also as pointers to the further work that should be carried out to elucidate the phenomena associated with the running-in of surfaces and scuffing.