Laser processed TiN reinforced Ti6Al4V composite coatings

The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-material interactions and tribological performance of TiN particle reinforced. Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-material interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10 N normal load. The results show that the composite coatings contain distinct TiN particles embedded in alpha + beta phase matrix. The average top surface hardness of Ti6Al4V alloy increased from 394 +/- 8 HV to 1138 +/- 61 HV with 40 wt% TiN reinforcement. Among the composite coatings, the coatings reinforced with 40 wt% TiN exhibited the highest wear resistance of 3.74 x 10(-6) mm(3)/Nm, which is lower than the wear rate, 1.04 x 10(-5) mm(3)/Nm, of laser processed CoCrMo alloy tested under identical experimental conditions. In vitro biocompatibility study showed that these composite coatings were non-toxic and provides superior cell-material interactions compared to Ti6Al4V control, as a result of their high surface energy. In summary, excellent in vitro wear resistance and biocompatibility of present laser processed TiN reinforced Ti6Al4V alloy composite coatings clearly show their potential as wear resistant contact surfaces for load bearing implant applications. (C) 2011 Elsevier Ltd. All rights reserved.