Study On Structure And Tribological Properties Of Nano-Composite Diamond-Like Carbon Films

Diamond-like carbon(DLC)film is a new type of lubricating material with excellent properties such as high hardness,low friction coefficient,high wear resistance and good chemical stability,and it is expected to meet application requirements under severe working conditions.However,its defects(such as higher internal stress,environmental dependence of tribological properties,etc.)limit its application in practice.Studies have shown that nano-composite DLC films have high strength and toughness,and excellent tribological properties in a variety of environments.This provides ideas for solving the above problems.Therefore,in this paper,Si-doped,Si-Ag and Si-Cu doped DLC films were prepared by RF magnetron sputtering.The influences of doping elements and their contents on the chemical compositions,microstructures and mechanical properties of the films were investigated.The tribological properties of different nanocomposite DLC films were studied.The related tribological mechanisms were explored.The main results are listed as follows:(1)A series of DLC composite films with different Si contents were prepared by RF magnetron sputtering coating technology.The effect of Si content on the film composition,microstructure,mechanical,and tribological properties in simulated acid rain was investigated.The results show that with the increase of Si content,the content of sp3 C in the film increases.When the Si content is 8.33 at.%,there is Si C formed and the film has excellent mechanical properties.Such films have excellent tribological properties in acid rain and can generate silicic acid lubricating phases at the frictional interface under low-load,low-speed,and short-term sliding conditions.(2)The effects of Si and Ag elements co-doped on the structure and properties of DLC films were investigated.The results show that the doped Si elements mainly exist as Si-Si bonds,Si-C bonds and Si-O bonds,Ag element exists as metal phases in the films.When the Si content is 8.24 at.%,the film exhibits low friction coefficient in the atmosphere,which is related to the higher hardness,high H3/E2 and H/E ratio of the film.In addition,the friction coefficients of the film change little in different atmospheres,including the air,Ar,and O2 gas.This convinceds that the two-element doping film reduce the sensitivity of the tribological behavior to different atmospheres.(3)The tribological properties and corrosion resistance of single-doped Si/DLC films and Si(Ag)/DLC films in the atmosphere were compared.It was found that Si-Ag co-doped DLC films have more excellent tribological properties and better corrosion resistance.(4)The effects of co-doping of Si and Cu on the structure and mechanical properties of DLC films were investigated.The results show that Cu is mainly present in the film as a metal phase and a small portion of copper oxide,Si elements mainly exist as Si-Si bonds,Si-C bonds and Si-O bonds.The film(A2 film)with a Cu content of 1.95 at.% has a higher hardness(8.01 GPa)and elastic modulus(58.24 GPa).This is associated with the small amount of Cu incorporation into the film causing an increased sp3 C content.Compared with Si(Ag)/DLC films,these films have better elastic recovery.