Laser Preparation Of Superhydrophobic Surface On Titanium Alloy And Its Anti-Icing Performance

Ti6Al4V titanium alloys play an irreplaceable role in the aerospace field because of the excellent mechanical properties.Titanium alloys are hydrophilic materials,water and pollutants are easy to adsorb on devices surface made by titanium alloys.Besides,the surface often freeze at low temperatures,which affects the normal operation of the equipment.The superhydrophobicity of solid surfaces can reduce the wetting of water droplets on surface,and inhibit the heat exchange between water droplets and surface,which provides an idea for improving the self-cleaning and anti-icing performance of titanium alloys surfaces.Therefore,in this paper,nanosecond UV laser was used to construct rough structures on titanium alloy surfaces,and the superhydrophobic titanium alloy surfaces were prepared after chemical treatment.Finally,the anti-icing performance was explored under low temperature environment.Two typical surface characteristic structures,pits and grooves,were designed,the superhydrophobic surface on titanium alloy was obtained by nanosecond laser texturing and low surface energy modification.The surface morphology was characterized by scanning electron microscopy(SEM)and three-dimensional video microscopy(3d-vcm).The results show that the micro bulges and granular nano-structures are formed on the surface of characteristic structure under the irradiation of laser.After processing,the roughness of the titanium alloy surface increases,compounded with the low surface energy material layer,which make titanium alloy surface superhydrophobic.The micro-nano rough structures made by nanosecond laser on titanium alloy substrate is an important factor to improve surface hydrophobicity.The effects of laser scanning times and scanning spacing on the surface morphology and wettability of titanium alloy surfaces were analyzed.The results reveal that the change of micro-nano composite structures on surface of titanium alloys is the main factor for the change of surface contact angle and rolling angle with different laser processing parameters.The size parameters of surface characteristic structures and nanostructures are mainly affected by the number of laser scanning,and the scanning spacing mainly controls the distance between pits/grooves and the distribution or density of nanostructures on titanium alloys surface.The results show that the crater surface morphology on pits structure is obvious and the granular structure is small when the laser scanning spacing is 50 μm and the number of scans is 15.And the superhydrophobicity of surface on titanium alloy is most excellent,the static contact angle of the sample surface is 155.9 ° and the rolling angle is only 3.4 °.When grooves structure are constructed by laser with laser scanning spacing of 50 μm and laser scanning times of 5,the grooves shape are regular and nano-structures are densely distributed.The hydrophobicity of structures on titanium alloy surfaces is most excellent.The contact angle in the vertical and parallel directions of the grooves is 156.8 ° and 155.5 °respectively,and the rolling angle is 4.3 ° and 5.4 ° respectively.A homemade experimental device at low temperature was built to explore the freezing characteristics of droplets on surfaces with different wettability,including smooth hydrophilic,hydrophobic and superhydrophobic titanium alloy surfaces.The freezing process and freezing time of water droplets on the supercooled surfaces were observed and analyzed,and the effects of microstructures and wettability on the freezing time of water droplets on titanium alloy surfaces were preliminarily explored.It can be indicated that the freezing time of water droplets can be greatly delayed on the surface of pitted and grooved superhydrophobic titanium alloy surfaces for a certain temperature range.When the surface temperature is stable at-5℃,it takes only 18.3 s for water droplets on surface of a smooth titanium alloy hydrophilic surfaces to complete freezing,while the freezing time of pits and grooves are 1567.9 s and 1385.4 s respectively,indicating that the titanium superhydrophobic alloy surfaces prepared by nanosecond laser have excellent anti-icing performance.