Pulsed laser polishing of micro-milled Ti6Al4V samples

Pulsed laser micro-polishing (PLμμP) was investigated as a method to reduce the surface roughness of micro-milled Ti6Al4V samples. Thermal modeling was presented to estimate the melt depth and duration caused by a single laser pulse ranging from 50–1000 ns on a flat Ti6Al4V surface. Predictions of the spatial frequency domain that experiences significant amplitude reductions (i.e., polishing) agrees well with experiments. Polishing was performed using a 1064 nm Nd:YAG laser in Q-switch mode at a repetition rate of 4 kHz, 50–70 μm laser spot size, and pulse duration of 650 ns. Surface cracking was observed when polishing the samples in air, a result of oxides forming on the workpiece surface. To prevent oxidation during the laser polishing process Argon, an inert shielding gas that is heavier than air, was employed. Polishing results with Argon shielding demonstrated a reduction in average surface roughness by a factor of two. Two-dimensional polishing is demonstrated using a computer controlled optical scan head. In addition, the PLμμP process was used to effectively reduce surface scratches on Ti6Al4V samples.