Classification of Metallic Materials from a Viewpiont of Their Antiwear Behavior

Abstract

The mode of dry sliding wear of metals is classified as severe wear or mild wear. From a distinct difference between wear rates in the severe and mild wear, it is deduced that the most important character to be possessed in “antiwear materials,” is that the wear mode must be mild wear. Severe wear appears in most all metallic materials. The metals in which mild wear appears are, on the contrary, limited. The mild wear is promoted by chemisorption of oxygen molecules onto fresh surfaces generated during wear processes. Backed with this fundamental principle, it is deduced that the elemental metals in which mild wear appears are transition metals includung rare earth metals, because these metals have a high chemisorption activity for surrounding gas molecules. Extending this theory to materials other than pure elements, it is deduced that semiconductors, some ceramics, amorphous alloys, quenched steels and some intermetallic compounds can be classified as antiwear materials.