The effects of hard turning and deep rolling on surface integrity and fatigue life of deep groove ball bearings

Abstract

This experimental study consists of two main steps. In the first step, the effects of cutting conditions and tool geometry on cutting forces, roundness error and surface integrity (surface roughness, residual stresses, and subsurface phase transformations) were studied on 6208-type deep groove ball bearings. In the second step, performances of grinding (GR), hard turning (HT) and hard turning + deep rolling (DR) applied to the inner ring raceways are compared to each other in terms of surface roughness, roundness error, residual stresses, noise level and fatigue life. Experimental results in the first step showed that lower surface roughness, roundness error and higher compressive stresses are achieved by V-35 cutting insert. A remarkable result in the second step is that although DR process produces higher compressive stresses in deeper layers of work surface, the bearings possess lower fatigue life than HT and GR bearings due to their higher roundness error values.