Effect of femtosecond laser processing atmosphere on micro-nano structures and wetting properties of Ti6Al4V surface

Femtosecond laser processing was carried out to build the hydrophobic micro-nano structure on Ti6Al4V titanium alloy, and the effect of processing atmosphere, i.e., air and nitrogen, on the geometric dimension feature, distribution, element content, and the hydrophobic property was investigated. Results showed that the disordered micro-hump structure was induced in air, while micro-spindle structure with regular geometrical morphology formed in nitrogen. The size of micro-nano structure induced in air is larger than that in nitrogen, and both of them increased with the laser energy density. The micro-hump structure surface induced in air exhibited better hydrophobicity (water contact angle of 144.6°) than that in nitrogen. Processing in nitrogen could effectively inhibit the oxidation of the micro-nano structure, providing a breakthrough to improve the surface hydrophobic stability by reducing the micro-nano structure size and the surface polar metal oxides.