Tribological Properties And Wear Mechanism Of The DLC Films Under Different Currents

The development of miniaturization and high precision of mechanical and electrical systems requires that sliding electrical contact materials have excellent electrical properties and low friction and wear resistance.When the device size is small,adhesion and friction caused by sliding electrical contact may cause serious friction and wear problems in MEMS.Therefore,the basic factor that determines the long life and stable operation of the sliding electrical contact element is the lubrication and wear resistance of the electrical contact material,and the tribological performance of the electrical contact material is affected by the current and the sliding motion.Diamond like carbon?DLC?film has been widely used in various transmission machinery as a surface protective material as its high hardness,high elastic modulus,excellent antifriction and wear resistance,good light transmission,strong chemical stability and biocompatibility.As a well-known element with good conductivity in friction materials,Cu is widely used in industrial applications,and Ti is one of the most effective elements to reduce the internal stress and increase the adhesion between DLC film and substrate,so the doping of Cu and Ti may change the tribological properties of DLC film.In this paper,the composition,microstructure,mechanical properties,the morphology of wear scars and wear tracks,as well as the composition of the transfer film on the surface of wear scars were characterized by some analytical methods.The results show that:?1?The results of friction and wear tests were exactly different for DLC film,Cu/DLC film and Ti/DLC film under different currents.The friction coefficients changed obviously and the wear rate increased as the current increased for DLC film,Cu/DLC film,and Ti/DLC film.?2?When the DLC film,Cu/DLC film and Ti/DLC film against with GCr15 ball under different current-carrying conditions,the friction coefficient of DLC film and Cu/DLC film first decreases and then increases with the increase of current,which obtain the relatively low value under 1A current due to the surface of wear scars has formed the compact lubrication film in the process of friction and sliding.In the case of Ti-DLC film,when the current intensity enhanced from 0A to 2A,the friction coefficient monotonically increased,which was due to the friction heat and Joule heat destroy the lubricating film in the friction process.The wear rate of DLC film,Cu/DLC film and Ti/DLC film increased with the increase of current,which is because a large number of hard oxide fragments at higher temperature make the films suffered more serious damage.In addition,the wear rate of Ti/DLC film is the largest and the Cu/DLC film is the smallest among the three films under the same current carrying conditions.?3?When the DLC film,Cu/DLC film and Ti/DLC film against with Cu ball under different current-carrying conditions,the friction test results showed that the friction coefficient of DLC film and Cu/DLC film changed little under different current,while the friction coefficient of Ti/DLC film decreases when sliding under high current carrying conditions.The wear rate of DLC film,Cu/DLC film and Ti/DLC film increased with the increase of current.The wear rate of Ti/DLC film increases sharply with the increase of current,which is due to the formation of TiO₂,a hard oxide particle,in the sliding process of Ti/DLC film.TiO₂ is not conducive to friction and lubrication in the atmospheric environment,which will aggravate the wear degree of the film.