Solid-Liquid Composite Lubrication Tribochemical Mechanism Of Si Doped DLC Films

The incorporation of silicon into the diamond-like carbon film can increase the disorder of the film,significantly change the internal structure of the film,and further improve the mechanical and tribological properties of the film.In this paper,two kinds of silicon-doped diamond-like carbon films with low silicon content and high silicon content were prepared by ion-vapor deposition technique.Friction and wear test of a-C:H:Si films were tested at 80�C using the CSM-TRN friction and wear tester.The variable load tribological properties under base oil?PAO?,base oil+molybdenum dialkyldithiocarbamate?PAO+MoDTC?and base oil+zinc dialkyldithiophosphate?PAO+ZDDP?were studied.Using scanning electron microscopy,atomic force microscopy,Raman spectroscopy,and X-ray photoelectron spectroscopy,the surface morphology,chemical composition,and microstructure of the film before and after the friction and wear test were analyzed,and the high and low silicon contents were compared and analyzed in depth.The relationalship of frictional properties,load,the frictional reaction film formation and frictional chemical mechanism of a-C:H:Si films under MoDTC and ZDDP conditions were analyzed.The friction interactions were analyzed.The results are as follows:?1?Compared with a-C:H:Si-h films,less C-Si bond is formed in a-C:H:Si-l films,the sp³/sp² ratio and disorder are lower,and the bonding strength is stronger.Under PAO conditions,the overall friction coefficient of low Si content films is lower than that of high Si content films,and there is no significant difference under virous load.Only slight graphitization occurs at 7 N,resulting in a lower coefficient of friction and a significantly lower degree of wear under different loads than high Si content film due to the poor bonding strength.?2?Under the condition of MoDTC,MoS₂ and MoO_x,Mo_xC,SiO_x and other hard particles are decomposed by MoDTC at the interface of low silicon content film.The hard particles increase the graphitization.The joint action with MoS₂ leads to the decrease of friction coefficient and the increase of wear.MoS₂ and MoO_x,Mo_xC,SiO_x and other hard particles are also generated at the interface of the high-silicon films,but the high silicon content suppresses the occurrence of graphitization,and the MoS₂ and hard particles are mixed into a solid lubricant to reduce the friction coefficient.At the same time,the degree of wear has also declined.?3?Under the condition of ZDDP,the ZDDP of the a-C:H:Si-l film has a low degree of decomposition.The friction reaction film is mainly composed of a small amount of long-chain zinc phosphate,zinc sulfide,and zinc oxide.A small amount of friction reaction film is equivalent to a micro-convex body.The increase in the coefficient of friction.The ZDDP decomposition at the interface of a-C:H:Si-h film is larger,and more SiO_x and SiC hard particles are generated,which promotes the growth of the tribofilm and the formation of more short-chain phosphate,and the antiwear effect is improved.Friction reaction film formed a large plaque,and the area increased with the increase of the load,and the difference in the generation rate of the friction reaction film was the main reason for the difference in the amount of wear under high and low load.