Ion beam assisted deposition was employed to improve the biological performances of Ti-6Al-4V as artificial joints. Interlayers of Ti oxide, Zr oxide, and calcium phosphate increased the adhesion strength of plasma-sprayed hydroxyapatite coatings to substrate by introducing chemical bonds at interfaces. Heat treatment also affected the adhesion strength, but changed the failure mechanism of HAp coatings from adhesive to cohesive type failure. The cytotoxicity of interlayers was measured with Swiss 3T3 fibroblasts by MTT method, and was comparable to that of the FDA approved Ti-6Al-4V. Titanium nitride was formed with evaporation of Ti and simultaneous bombardments of Ar/N₂ ion beam mixture. The stoichiometry was controlled by the arrival ratio of titanium atoms to nitrogen ions. TiN had the Vickers hardness of 2800 Hv and greatly improved the wear resistance of Ti-6Al-4V.