STRUCTURAL STUDIES OF BEARING STEEL UNDERGOING CYCLIC STRESSING
Abstract
The microstructural changes seen in bearing steels after prolonged cyclic stressing are reviewed. It is shown that these changes arise from both plastic flow and the diffusion of carbon. The regions of plastic flow appear under the electron transmission microscope, as cell structures and under the light microscope as light etching bands, designated deformation bands. Carbon diffusion is shown by the development of large carbides which grow during cycling. These are designated lenticular carbides. Microstructural alterations are seen as a bulk material phenomenon where the calculated shear stress exceeds an estimated threshold value of 120,000 psi. They also develop locally around stress raisers. It is shown that stress raisers severe enough to cause the growth of deformation bands are also frequently involved in the nucleation of fatigue failures. Sequences of photographs are shown which illustrate various stages of failure initiation at four types of microscopic defects: Debris dents, grinding furrows, surface pits of unknown origin, and non-metallic inclusions.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 20, 1967
- Accession Number
- AD0816316
Entities
People
- Alvin D. Eberhardt
- John A. Martin
- Salvatore F. Borgese