Magnetron-sputtered TixNy thin films applied on titanium-based alloys for biomedical applications: Composition-microstructure-property relationships

Progress in tissue engineering and regenerative medicine necessitates the use of novel materials with promising bio-surface for biomedical applications. In this work, TixNy thin films are applied on biological TC4 substrates in a mixed atmosphere of Ar and N-2 via magnetron sputtering system for the protection of TC4 alloy. The effects of N/Ti ratio on the phase structure, growth orientation, contact angle, and the mechanical and corrosion performances of thin films are discussed by implementation of composition-microstructure-property interrelationships. The phase structure of TixNy thin films is changed from amorphous-like to single phase Ti2N structure with increasing N/Ti ratio. In the same direction, the growth orientation changed from (112) to (200). The contact angle of TC4 alloy increased by applying TixNy thin films on the substrate. TixNy thin films prepared at higher N/Ti ratios resulted in higher contact angle, mechanical properties, corrosion resistance and biocompatibility. The hardness value of the films varied between 7.5 to 28 GPa, while the Young's modulus, EIT, of the films ranged from 152 to 476 GPa. The maximum protection efficiency in SBF solution was found to be about 99.4%. Based on equivalent circuit model of MG63 cell, the TiN-4 exhibited the nearest similarity with best biocompatibility. The results of this work uncovered the critical roles of nitrogen content and growth orientation on the mechanical and biological properties of TixNy thin films. The upshots illuminate the appropriate properties of such system, which can be potentially used in different application such as metal orthopedic and neural electrodes. Development of such surface-coated titanium alloy showing superior corrosion resistance and biocompatibility can pave the way towards advanced bio-coatings with multifaceted features.