Study on surface morphology and residual stress in inclined milling of titanium alloy TC11

As high service performance requirements of critical aviation components, machining surface integrity gained attention from both academics and industrials. In this paper, the inclined milling experiments based on L₂₅(5⁶) orthogonal experimental design is carried out, in which surface roughness, morphology, and surface residual stress were tested. The tests showed that the feed rate per tooth has the most significant effect on the feed direction roughness, while the step width has the most significant effect on the step direction roughness; the milling speed has a significant effect on the feed direction residual stress, while the feed rate per tooth has the most significant effect on the step direction residual stress; the pattern of feed marks varies periodically. Then, a simplified simulation model is established to study the surface morphology formation mechanism. The simulation results agree with the influence trend of milling parameters on roughness. The prediction accuracy is validated through 3D roughness measured on supplemental tests in which only one insert is used in milling. By introducing runout error to surface morphology simulation for two typical experiments, the unexpected pattern of feed marks is simulated. Finally, correlated to the high-stress layer beneath the machined surface, a parameter called averaged last cutting depth (ALCD) is constructed, which is derived from the morphology simulation process. Statistical analysis shows that this parameter has a more significant correlation with residual stress than a popular parameter named undeformed chip volume (UCV).