Femtosecond laser polishing of titanium surfaces

A femtosecond laser with a wavelength of 515 nm is used to perform polishing operations on the surface of titanium metal to analyze the formation mechanism of surface morphology in the processed area under different laser parameters. By changing the laser focus position to suppress the formation of a hump-like structure, the processing quality is significantly improved and the optimal laser parameter window for polished titanium metal is obtained. It is found that when the laser focus is on the surface of the sample, the size of the bump-like structure increases with the increment of the number of processed layers and gradually spreads from the scratch of the sample to the whole processed area. At an energy density of 25.88 J/cm², the positive defocus amount gradually increases in the range from 0 to 2.5 mm, and then the hump-like structure gradually decreases until it disappears completely, while the polishing depth increases from 38.94 μm to 108.02 μm. The surface roughness is reduced from the original 1.496 μm to 0.314 μm when the defocus amount is 2.5 mm.