Effect of inclusion geometry and matrix properties on rolling contact fatigue of steel

The work presented in this paper is aimed at studying the effect of inclusion geometry and matrix property on rolling contact fatigue of steel. Rolling contact has been stimulated in laboratory using a twin-disc machine and an on-line crack detection system. It has been shown that soft inclusions, although normally considered harmless, can be good sites for crack initiation and suitable paths for crack propagation. Enough evidence has been given to show that if inclusions can be maintained spherical, they may not affect rolling contact fatigue life. The mechanical properties of the matrix play an important role in helping or hindering the deformation of soft inclusions. Strong matrix around the inclusion makes it less likely for spherical shaped inclusions to transform to stringers, and as a result, preserves the geometry of inclusion. However, soft matrix enables deforming the inclusion and raises the stress concentration at the inclusion edges. (author). 25 refs., 7 figs. 2 tabs