STRUCTURAL ALTERATIONS OF BEARING STEELS UNDER ROLLING CONTACT FATIGUE

Abstract

Two types of structural alteration, the white etching constituent and the dark etching one, are revealed. The former originates at nonmetallic inclusions, mostly of alumina, and a microcrack is often seen to be associated with it. The white etching constituents grow in number and size with repeated cycles, but are suppressed at the depth where the dark etching zone forms. This depth also corresponds to that where shear stress becomes maximum. Each dark etching constituent of which the dark etching zone is ## is a variation of originalartensite leaves. The hardness of the dark etching constituent is lower than that of the original martensite. The mechanism of the decomposition of martensite is discussed.