Chemical and mechanochemical degradations of ultrafast laser surface structured Ti6Al4V in simulated body fluid environment

In the present study, the effect of ultrafast laser surface structuring of Ti6Al4V (using a Ti: Sapphire laser with a pulse duration of 100 fs and 3000 fs) on its surface topography, nanomechanical properties, tribocorrosion property, and bioactivity has been undertaken. Surface structuring leads to defect-free periodic surface structures with shockwave-induced compressive residual stresses and grain refinement (subgrain size of 5.2 mu m) as compared to as received Ti6Al4V (26 mu m). There is a significant enhancement in nano hardness (5600-5800 MPa) and Young's modulus (139 - 148 GPa) as compared to as received Ti6Al4V ((nano hardness of 3800 MPa), (Young's modulus of 117 GPa)) due to laser surface structuring. The tribocorrosion kinetics were significantly reduced in laser surface structured Ti6Al4V as compared to as received one. The individual influence of tribocorrosion property was established. A detailed microstructural study and immersion studies showed the presence of a higher fraction of calcium phosphate deposition in surface-structured samples (0.0432-0.0461 mg/cm2 after 7 days) as compared to as received Ti6Al4V (0.018 mg/cm2 after 7 days). The presence of hydroxyapatite has been confirmed by X-ray photoelectron spectroscopic analysis.