Diamond Carbon Film Deposition On CoCrMo Alloy Artificial Joint

Recently, the CoCrMo alloy and ultra-high molecular-weight polyethylene (UHMWPE) prosthesis are the most widely artificial joint. The main reason leading to the failure of artificial joint is the UHMWPE debris from wear process. Consequently, amorphous hydrogenated carbon (a-C:H) films have been deposited on Co-Cr-Mo alloy substrates by electron cyclotron resonance plasma enhance chemical vapor deposition (ECR-PECVD).The a-C:H film was fabricated successfully by the mixture of acetylene and hydrogen. The effects of hydrogen flow and bias voltage to the structures and properties of the films were studied. The microstructures of the a-C:H film were measured by visible Raman spectra and Fourier transform infrared (FTIR) spectroscopy. The adhesion force was measured by scratch test and wear resistance was evaluated by reciprocating wear test.The results indicate that the structure of the film is affected by the hydrogen flow rate and bias voltage strongly. On the condition of the same bias voltage(-400V), the deposition rate of the film decreases, while the residual stress, the hardness and the sp3 bonding content of the film increase with the hydrogen flow rate; on the condition of the same flow rate of hydrogen(40sccm), the deposition rate and the hydrogen content of the film increase with the decreasing of bias pulse voltage, and the polymeric vibration model appeares in the film at-100V bias voltage. The adhesion force and wear resistance increase with the bias voltage.Various transition layers, including ta-C film by filtered cathodic vacuum arc(FCVA) and nitriding layer by plasma immersion ion implantation(PIII) were used in order to improve the interfacial adhesion. The results indicate that the adhesion force of the a-C:H film increases remarkably due to the transition layers.In order to decrease the H content and increase the mechanical properties, the ta-C:H films were fabricated by the mixture of acetylene and argon. The effects of bias voltage to the deposition of ta-C:H films were studied. The results show that the sp3 content and the hardness of the ta-C:H film decrease and the residual stress of ta-C:H film increases with the bias. The ta-C:H film fabricated at-800V bias pulsed voltage has the outstanding wear resistance. The effects of different substrates (glass, silicon, Co-Cr-Mo alloy) to the deposition of the ta-C:H films were studied. The results indicate that the film fabricated on glass wafer is soft because of high H content; the films fabricated on the silicon wafer and CoCrMo alloy are hard with high sp3 content.The CoCrMo alloy modified by ECR-PECVD and FCVA were both slid against the UHMWPE in 25% calf serum in distilled water in room temperature. The a-C:H and ta-C films reduce the wear of CoCrMo alloy.