The "breaking-in" of lubricated surfaces

Abstract

Steel cylinders were slid against flat steel surfaces, which were prepared to various surface roughness values, in order to determine the mechanisms of "break-in" of lubricated surfaces. It was found that proper break-in of a surface is effected when a film of Fe3O4 about 400 A thick forms. The formation of Fe2O3 is to be avoided. In addition, it was found in laboratory experiments that proper breaking-in by sliding requires a specific initial surface roughness of about 0.1 [mu]m center-line average. Smoother and rougher surfaces failed quickly. It appears that the optimum surface roughness was one in which the asperities plastically deformed at a rate that was too slow for fast progression to low cycle fatigue failure but at a rate sufficient to accelerate the formation of oxides.