Fabrication and characteristics of ta-C biomaterial coatings on Ti–6Al–4V using metal plasma immersion ion implantation and deposition

We have formed amorphous diamond (ta-C) coatings on Ti–6Al–4V substrates using a metal plasma immersion ion implantation and deposition (MEPIIID) technique, and characterized the mechanical properties and biological compatibility of the coating material. The hemocompatibility of the coating compared favorably with that of low temperature isotropic (LTI) carbon, with kinetic clotting time and hemolysis rate approximately the same as for LTI carbon, and platelet consumption about twice that of the latter. The mechanical properties were good, with a microhardness greater than that of the uncoated metal substrates, and high adhesion of >0.75 GPa (interface shear stress) as estimated from a thermal quench method. Glancing-angle X-ray diffraction measurements indicated the presence of a TiC transition layer, suggesting the formation of a Ti/TiC/ta-C multilayer structure, leading in turn to good film–substrate adhesion. We conclude that this kind of amorphous diamond coating could provide benefit as a biocompatible hard coating for Ti–6Al–4V substrate material.