Influence of a white layer on the performance of hard machined surfaces in rolling contact

Abstract

This study investigates the influence of a machining-induced white layer on the performance of hard machined surfaces in rolling contact. Based on the residual stress and microhardness distribution of a specimen without a white layer and one with a white layer, fatigue parameters are computed to investigate its effect on the fatigue performance. Fatigue tests are then performed to substantiate the computations. It is noted that the white layer moves the crack initiation depth to a deeper location at low maximum Hertzian stresses, whereas it moves the crack initiation depth to a shallower location at the highest maximum Hertzian stress. The white layer can increase the maximum shear stress at crack initiation depth by 54 per cent. The white layer can reduce the crack initiation life by 75 per cent, while reducing the crack propagation life by 89 per cent. Accordingly, it can reduce the fatigue life by 85 per cent. The effect of the white layer on crack initiation life, crack propagation life, and fatigue life decreases significantly as the loading increases. The presented results demonstrate that the white layer induces a highly variable change in fatigue parameters, and its effect on fatigue performance can be significantly lessened if the loading is increased.