Integrated experimental and theoretical approach for corrosion and wear evaluation of laser surface nitrided, Ti-6Al-4V biomaterial in physiological solution.

A laser based surface nitriding process was adopted to further enhance the osseo-integration, corrosion resistance, and tribological properties of the commonly used bioimplant alloy, Ti-6Al-4V. Earlier preliminary osteoblast, electrochemical, and corrosive wear studies of laser nitrided titanium in simulated body fluid clearly revealed improvement of cell adhesion as well as enhancement in corrosion and wear resistance but mostly lacked the in-depth fundamental understanding behind these improvements. Therefore, a novel integrated experimental and theoretical approach were implemented to understand the physical phenomena behind the improvements and establish the property-structure-processing correlation of nitrided surface. The first principle and thermodynamic calculations were employed to understand the thermodynamic, electronic, and elastic properties of TiN for enthalpy of formation, Gibbs free energy, density of states, and elastic properties of TiN were investigated. Additionally, open circuit potential and cyclic potentio-dynamic polarization tests were carried out in simulated body fluid to evaluate the corrosion resistance that in turn linked with the experimentally measured and computationally predicted surface energies of TiN. From these results, it is concluded that the enhancement in the corrosion resistance after laser nitriding is mainly attributed to the presence of covalent bonding via hybridization among Ti (p) and N (d) orbitals. Furthermore, mechanical properties, such as, Poisson׳s ratio, stiffness, Pugh׳s ductility criteria, and Vicker׳s hardness, predicted from first principle calculations were also correlated to the increase in wear resistance of TiN. All the above factors together seem to have contributed to significant improvement in both wear and corrosion performance of nitride surface compared to the bare Ti-6Al-4V in physiological environment indicating its suitability for bioimplant applications.

Laser induced nitrogen enhanced titanium surfaces for improved osseo-integration.

The osseo-integration, corrosion resistance, and tribological properties of the commonly used bioimplant alloy Ti-6Al-4V were enhanced using a laser-based surface nitridation process. The biomedical properties of the laser nitrided Ti-6Al-4V were investigated using experimental and computational methodologies. Electrochemical analysis of laser nitrided titanium in simulated body fluid (SBF) was performed to assess the biomedical characteristics in near-human body conditions. Additionally, the corrosive wear performance of these laser nitrided samples was evaluated using pin-on-disk geometry with a zirconia pin counter surface in SBF to mimic the biological scenario. Osteoblast studies were conducted to evaluate cell affinity towards titanium nitrided bioimplant material. Cells adhered to all substrates, with high viability. Initial cell adhesion was revealed by focal adhesion formation on all substrates. Cells can proliferate on samples treated with 1.89 and 2.12 × 10(6) J/m(2) laser conditions, while those treated with 1.70 × 10(6) J/m(2) inhibited proliferation. Thus, microstructural and phase observations, electrochemical analyses, corrosive wear evaluation, and cell behavior analysis of laser nitrided surface of bioimplant material (Ti-6Al-4V) indicated that laser nitriding greatly improves the performance of bioimplant material.