Surface Integrity Difference between Hard Turned and Ground Surfaces and Its Impact on Fatigue Life

Surface integrity is the key for process selection of hard turning or grinding in industry. This study identifies the fundamental differences in the integrity of hard turned and ground surfaces and the subsequent impact on rolling contact fatigue life. The significant findings are: (a) mechanical deformation plays a larger role during hard turning than grinding, while the size effect in grinding induces higher surface hardness; and (b) a hard turned surface may have a more than 100% longer fatigue life than a ground one with an equivalent surface finish (Ra 0.07 μm) due to the very different characteristics of surface integrity.