Effects of machining parameters on surface integrity of hard machined surfaces

Abstract

This study investigates the effects of machining parameters on the surface integrity of hard machined surfaces. The residual stress distribution of hard machined surfaces is characterized by compressive stresses in the range between 150 and 1000 MPa. Typically, residual stresses in the feed direction are more compressive above a depth of 12.7 μm, while residual stresses in the cutting direction are more compressive below a depth of 12.7 μm. The micro-hardness distribution of hard machined surfaces is characterized by a lower surface hardness and a stable bulk hardness. It is noted that a higher cutting speed induces a more softened layer. The machining-induced residual stress and micro-hardness distribution can increase the crack initiation life by 39 per cent, while increasing the crack propagation life by more than four times. Accordingly, it can increase the fatigue life by more than three times. The results are presented that demonstrate that the machining parameters significantly influence the residual stress and micro-hardness distribution of hard machined surfaces and that the fatigue performance of hard machined surfaces can be significantly enhanced by optimizing the machining parameters.