Yang Yunzhi*, Chen Zhiqing, Ran Junguo# and Zheng Changqiong#

West China University of Medical Sciences , Chengdu ,610041 , China
mailbox@wcums.edu.cn

#Sichuan Union University , Chengdu , 610065 , China

Much of the orthopedic community now believe that the long term failure of total hip and knee prostheses is directly or indirectiy due to the production of wear particles, particularly polyethylene wear particles which are produced at the articulating interface between the metal component and the high molecular weight plastic component. These particles cause cellular events that contribute to the long-term loosing between the implant and the bone. At present, there are no good materials that can substitute ultra-high molecular polyethylene (UHMUPE), therefore the only way forward is finding a material for femoral heads or a friction- and wear- reducing coating on the metal to minimize the production of the polyethylene wear particles and dramatically extend hip implant life. Diamond like carbon (DLC) film, with its extreme smoothness, hardness, low coefficient of friction, and biocompatibility, is an excellent candidate for such an application. One of the key issues that may limit the utility of DLC film in this application is the adhesion of this material to common biomedical alloys, because the ceramics coating sometimes peels off due to the great thermal stress resulted from the property differences between coating and metal substrate. In this paper the design thought of functionally gradient materials (FGM) is used to reduce the thermal stress and improve the adhesion of DLC coating to metal substrate, in which the composition and morphology from metal substrate to ceramics coating is regulated and gradually changed to reduce the differcences of property and structure in the transition zone. In this paper the particularity of thin film is considered and the plane thermal stress model is frist established on the basis of plane stress hypothesis. And then the design of the DLC/titanium alloy (Ti6Al4V) biomedical coating for fermoral heads is carried out. The design parameters are (1) magnetron cosputtering temperature 200 C (2) deposition thichness 10 mm (3) interlayer number 10. The design results show that under the condition of the composition distribution coefficient 0.8, the thermal stress between coating and substrate is significantly alleviated compared with non-gradient coating and the adhesion is improved.

*This subject is supported by the Nature Science Fundation of China