Tribocorrosion response in biological environments of multilayer TaN films deposited by HPPMS
Abstract Biomedical implant failure arises mainly from the degradation caused by tribological processes occurring in the corrosive environment the human body represents, known as tribocorrosion. The material loss and metal ion release resulting from tribocorrosion processes compromise the biocompatibility of metallic implants. The deposition of protective coatings on metallic substrates is a promising solution to overcome this problem. Pure titanium (Ti cp) is widely used as an implant material due to its excellent corrosion resistance and high biocompatibility. However, its mechanical properties must be improved in order to ensure a longer durability. For this purpose, TaN monolayer and multilayer coatings were deposited on medical grade Ti cp to enhance its tribocorrosion performance in simulated body fluids. TaN coatings were deposited by recently developed High Power Pulsed Magnetron Sputtering (HPPMS) technique. HPPMS enables the deposition of extremely dense coatings with superior properties compared to the ones grown by conventional sputtering. Columnar free TaN monolayer and multilayer films were developed exhibiting corrosion resistances in the MO range, one order of magnitude higher than for Ti cp. Friction coefficient of Ti cp was reduced from 0.58 to 0.25 while wear rate was considerably decreased. The determined material loss after tribocorrosion tests for Ti cp was 0.4 mm 3 It was reduced up to 1.55 x 10 3 mm 3 by the application of best performing TaN multilayer film.