On the Mechanism of Surface Quality Formation during Laser-Assisted Milling of GH4169 Alloy

Laser-assisted milling (LAM) holds great promise for difficult-to-machine materials, but its impact on surface integrity remains unclear. This study established an integrated framework combining a three-dimensional finite element thermal model with a piecewise mathematical model to predict peak temperatures during laser irradiation and validated the results through orthogonal cutting experiments. Compared with conventional milling (CM), LAM significantly reduced cutting forces: the maximum and average values of the radial force F x decreased by 38.7 and 52.5%, respectively; the axial force F z decreased by 36.2 and 69.2%, respectively; and the tangential force F y decreased by 18.7 and 19.6%, respectively. Furthermore, fluctuations in cutting forces were suppressed. LAM also improved surface integrity: surface roughness ( Rz ) was reduced by up to 68.2%, hardness distribution became more uniform, work hardening was suppressed, and residual stress fluctuations stabilized at approximately 7 times the previous level. Chip morphology changed from brittle fragments under CM to continuous spiral ribbons under LAM, with the average aspect ratio increasing from 6.05 to 9.9. Tool wear analysis showed that the average wear on the rake face and tool tip decreased by 8.7 and 5.9%, respectively, and the data dispersion was significantly reduced. These improvements are attributed to the laser-induced thermal softening effect, which reduces the material’s yield strength and promotes plastic flow. This study provides a quantitative basis for optimizing the parameters of laser-assisted milling of GH4169.