Topographical effects of laser surface texturing on various time-dependent wetting regimes in Ti6Al4V

Abstract

Laser surface texturing (LST) processes have great potential to alter surface wetting properties of widely known bioactive Ti–6Al–4V alloy. Micro-pillars arrays of different topography are produced by Nd:YAG laser of 1064 nm wavelength to investigate the influence of its physical and geometrical parameter on wettability. Micro-textures named as: THS (high density, square pillars of 30 × 30 μm), TMS (medium density, square pillars of 60 × 60 μm), TLS (low density, square pillars of 170 × 170 μm), TLL (low density, landscape pillars of 300 × 100 μm) and TLP (low density, portrait pillars of 100 × 300 μm) are produced to analyze the effect of texture areal density, aspect ratio and shape over surface wetting phenomenon. It is observed that on the flat textured surface shows hydrophilic and spontaneous wetting behavior up to 24 h after machining. Percentage increment in water contact angle (CA) value varies with time, maximum increase in CA was found to be in THS (215%) followed by TMS (197%), TLS (166%), TLP (144%) and TLL (122%) after 20 days of machining (as compared with the untextured surface). The response of the textured surface to spontaneous wetting behavior with respect to varying viscosity is also studied and validated through Washburn's model. It is found that early viscous regime of capillary rise in the textured surface can be altered by regulating the geometrical parameters of the micro-textures array. Time taken to rise up to 40 mm by low, medium and high viscosity fluids are 200 s, 600 s and 9334 s respectively. The texture (THS) with highest areal density micro-pillars of 60 μm width exhibits maximum capillary action.