| It is necessary to improve the service life for Titanium alloys with reasonable surface modification when they are used in the severe condition of the corrosion-wear coupling behavior as artificial joint material.Diamond-like film(DLC)has potential application in improving metal wear and corrosion resistance due to its excellent self-lubricating performance and chemical inertia.Therefore,the dry friction properties and tribology-corrosion properties in Hank's simulated body fluid of DLC films deposited on titanium alloys have been studied in this paper,which can provide theoretical and experimental basis for the application of DLC films in titanium alloy artificial joints.Firstly,the hydrogen DLC films have been deposited on surfaces of TC4 titanium alloys by plasma enhanced chemical vapor deposition.The dry friction properties of the tribo-pairs composed of DLC films and different ceramic/metal materials have been systematically investigated,and the mating ball used for tribocorrosion test has been selected.The results show that the ceramic balls with higher wear resistance could maintain stable carbon transfer film at the friction interface,while the carbon transfer film on the low hardness metal balls are easy to lose with the wear of balls,causing poorer lubrication effect,so the coefficients of friction ceramics/DLCs pairs are generally lower than those of metals/DLCs pairs.And Si C/DLC,Zr O2/DLC,304 SS/DLC and GCr15/DLC are relatively reasonable tribo-pairs because of their lower coefficients of friction and wear rates of balls and films.Secondly,with thermal oxidized(TO)titanium alloy sample as a reference,the tribology-corrosion properties of DLC film deposited on the titanium alloy surface and TO sample in Hank's simulated body fluids are systematically compared by friction and electrochemical tests.The results show that both DLC film and TO could improve the static corrosion and tribocorrosion properties of titanium alloy.The static corrosion tendency and static corrosion rate of DLC film are lower than those of TO,the coefficient of friction and wear rate of DLC film in the tribocorrosion test are far less than those of TO,and the open circuit potential under friction of DLC film is just about-0.27 V,so DLC film exhibits excellent wear and corrosion resistance property.It is mainly due to the strong chemical inertia,good density,high bonding force and surface wear resistance of DLC films,resulting in substrates being difficult to corrode by solution under friction.Finally,different nitrogen content doped DLC films have been prepared on surfaces of titanium alloys by adjusting the ratio of acetylene and nitrogen,and their dry friction properties and tribology-corrosion properties in Hank's simulated body fluid have been studied by friction and electrochemical tests.The results show that comparing with the undoped film,the dry friction performance and static corrosion resistance of the nitrogen doped DLC films are worse,which is mainly because much more sp2 sites caused by nitrogen doping in films leads to the increase of surface roughness,the decrease of elastoplastic index and the increase of electron migration speed.But the nitrogen doped DLC films exhibit more remarkable tribocorrosion properties than the undoped film in the tribocorrosion test,because bonding force between films and substrates are improved significantly by nitrogen doping,leading to less microcracks and breakage on the nitrogen doped films under friction,which reduces the corrosion effect of solution ions passing through the microcrack and the damaged areas of films.And the nitrogen doped DLC film prepared with nitrogen flow rate of 20 sccm has the best comprehensive performance. |
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