Structural Studies of Bearing Steel Undergoing Cyclic Stressing.

A report is made on a metallurgical investigation of the failure mechanisms which operate in bearing steels during cyclic stressing. It describes the findings and conclusions reached under this investigation regarding the microstructural changes which accompany fatigue and the nature of fatigu crack initiation and propagation mechanisms. It describes findings from observations of bearing surfaces by electron and light microscopy techniques and relates microstructural and morphological changes with lubrication phenomena. Experimental studies of run-in of rolling bearing steel surfaces are described, in which EHD film changes and surface morphology are monitored. Optical film shape measurements showing the effect of surface defects on EHD film are presented and interpreted. Statistical data on the relative density of non-metallic inclusions in different bearing grade steels is presented and correlated with endurance life. (Author)