THE SURFACE INTEGRITY OF TURNED AND GROUND HARDENED BEARING STEEL

The surface integrity of the machined component has received greater a ttention over the last 20 years, especially in relation to high perfor mance materials. Due to the inherent differences between abrasive mach ining and single point cutting, distinct surface texture patterns will be produced, which together with the associated metallurgical alterat ions can lead to substantial variations in component service performan ce. The paper compares several aspects of finish turning against grind ing of hardened bearing steel, more specifically surface texture, micr ostructural alterations, changes in microhardness, residual stresses d istribution and fatigue life. The findings suggest that for the operat ing parameters tested the microstructural alterations observed were co nfined to an untempered martensitic layer often followed by an overtem pered martensitic layer. Compressive residual stresses were induced wh en turning and grinding and the best fatigue resistance was obtained w hen turning using PCBN cutting tools followed by turning using mixed a lumina tools and finally by grinding.