The friction and wear behavior of WC coating on medical grade titanium alloys

The clinical success of artificial joints has provided remarkable benefit to patients with joint disorders. However, the long-term success of total joint prostheses has been frustrated by an unacceptable rate of aseptic loosening, the osteolysis induced by joint wear, metal ion release, and high risk of toxicity. In this article, a hard and wear resistance WC coating was formed on the surface of medical grade titanium alloys, using a plasma spraying system in order to solve the above clinic problems. The WC phase and micro-hardness were characterized with X-ray diffraction and Vickers hardness tester to evaluate the plasma spraying process and the mechanical properties of the coatings. Then, the friction and wear tests of WC coatings were performed on M-2000 block-on-ring tribological testing machine. After that, the tribological behavior of the modified titanium alloys was investigated by means of scanning electron microscopy. It was observed that a graded structure was formed on the surface of titanium alloy and exhibited good bonding between the coating and substrate. In addition, it was noticed that WC phase could significantly harden the surface of titanium alloys and decreased the wear factor from 38.5x10(-11) to 1.66x10(-11)kg/Nm. Finally, it was proved that adhesion and abrasive wear dominated the damage of titanium alloy, while the wear of WC coating was controlled by adhesion wear. All of the results indicated WC coating on titanium alloys with good bonding strength after plasma spraying was a potential candidate for the application of artificial joints from the understanding of wear resistance. Further investigation regarding biocompatibility and artificial joint simulation need to be conducted.