The surface integrity of turned and ground hardened bearing steel

The surface integrity of the machined component has received greater attention over the last 20 years, especially in relation to high performance materials. Due to the inherent differences between abrasive machining and single point cutting, distinct surface texture patterns will be produced, which together with the associated metallurgical alterations can lead to substantial variations in component service performance. The paper compares several aspects of finish turning against grinding of hardened bearing steel, more specifically surface texture, microstructural alterations, changes in microhardness, residual stresses distribution and fatigue life. The findings suggest that for the operating parameters tested the microstructural alterations observed were confined to an untempered martensitic layer often followed by an overtempered martensitic layer. Compressive residual stresses were induced when turning and grinding and the best fatigue resistance was obtained when turning using PCBN cutting tools followed by turning using mixed alumina tools and finally by grinding.