Study on surface quality of ultrasonic assisted underwater laser polishing

Abstract

Surface polishing is a critical factor in optimizing the practical utility of laser additive manufacturing (LAM) parts. This study explores the use of nanosecond pulsed lasers for polishing the surface of laser-directed energy deposition (LDED) TA15 titanium alloy. Various polished surfaces are achieved by adjusting laser processing parameters. Analytical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), laser confocal microscopy, and ultra-depth of field microscopy, are employed to assess phase composition, oxidation levels, and surface roughness under different laser polishing conditions. The study also investigates changes in surface properties and the underlying mechanisms that occur during laser polishing. Microhardness tests and room temperature tensile tests are conducted to evaluate the compressive strength and tensile strength of the TA15 alloy's surface after laser polishing. The results demonstrate that different laser polishing methods yield varying surface quality and mechanical properties. Notably, ultrasonic assisted underwater laser polishing (UWP) exhibits significantly lower surface roughness Ra (3.035 μm) and Sa (3.172 μm) compared to air laser polishing (AP) and underwater laser polishing (WP), indicating improved surface quality and enhanced surface strength and plasticity.