Surface and subsurface characteristics of laser polished Ti6Al4V titanium alloy

This paper aims at investigating the effects of laser power, laser pulse repetition rate and scan speed on the polished metal surface and subsurface characteristics. The influence of initial surface roughness of workpiece on the polishing performance was also taken into account. In this study, Ti6Al4V titanium alloy was selected as a specimen to be polished by a nanosecond pulse laser. The results revealed that the surface roughness was able to be improved by about 43% when the laser fluence of 1-3 J/cm(2) was applied. In addition, the proper polishing condition was dependent on the initial surface roughness of workpiece, and a better surface improvement was subjected to a lower initial surface roughness. A thick recast layer, high degree of oxidation and large heat-affected zone with lots of micro-cracks were obtained when too high laser power and slow scan speed were used in the polishing of titanium alloy. With regard to the findings of this study, the suggested polishing conditions could be applied for smoothing the different levels of initial surface roughness of titanium alloy and possibly other similar metals with less subsurface damage.