Microstructural changes around non-metallic inclusions caused by rolling-contact fatigue of ball-bearing steels

Abstract

Microstructural changes around non-metallic inclusions (sometimes called ‘butterflies') were studied using both optical and transmission electron microscopy. Large numbers of cyclic stresses cause the parent tempered martensite to disappear, along with the spherical cementite particles generally found in these through-hardened steels. The microstructural changes are described and the transformation products identified. Also, comparisons are made with similar events around crack tips, and a formation mechanism is proposed.