Study On Tribology And Corrosion Resistance Of Ti-DLC Film

The surface wear and corrosion of the key transmission parts of the mechanical systems are the key to affecte its service life and reliability.The goal pursued by scholars in the field of surface engineering is to improve the surface performance of this type of parts to meet the requirements of long-life and high-reliability service.Diamond-like carbon(DLC)films have found a wide range of applications in machinery,automobile,aviation and other fields in recent years,due to their unique properties such as high hardness,low friction coefficient,wear resistance,chemical stability,etc.However,the composition and structure of the DLC film have significant effects on their tribological behavior and corrosion resistance.Doping DLC film with Ti element can effectively regulate the amorphous carbon structure,internal stress and binding force,and then improve the friction,wear and corrosion resistance of DLC film under different service conditions.However,due to the influence of the preparation process and deposition parameters,there are still differences in the research on the influence law and mechanism of the optimal doping amount on the microstructure,tribological properties and corrosion resistance of the DLC film.In this paper,Ti-DLC films with different Ti doping content(1.82 wt.%-18.29 wt.%)were prepared by adjusting the Ti target current in the plasma system of the ionic enhanced physical vapour deposition device with the unbalanced magnetron sputtering system.The carbon-based structure of Ti-DLC film,the size and content of Ti C nanocrystals were characterized by Raman spectroscopy(Raman)and transmission electron microscope(TEM),respectively.The friction and wear performance of Ti-DLC film and the corrosion resistance in 3.5 wt.% Na Cl solution were evaluated by reciprocating friction and wear testing machine and electrochemical workstation.The research results show that the size and relative proportion of a large number of Ti C nanocrystals embedded in the amorphous carbon-based network structure are closely related to the tribological properties of the Ti-DLC film.When the Ti doping amount is1.82 wt.%,the Ti-DLC film exhibits the most excellent tribological properties through the effective regulation of the carbon-based structure of the film and the alleviation of the internal stress of the film by the Ti C nanocrystals.However,the doping of Ti element intensifies the self-corrosion rate of DLC film.The results of first-principles calculations show that the formation of the interface between the Ti C nanocrystalline structure and the carbon matrix reduces the total energy of the system in the process of Cl atom penetration into the film,and accelerates the failure of the DLC film.In view of the accidental damage such as cracks,peeling,etc.that the DLC film may appear under severe conditions that may damage the integrity of the film and affect the tribological performance and corrosion resistance of the film,the surface of DLC films was pre-fabricated with different degrees of damage by using large load scratch tester,and the effect of the degree of damage on the tribological properties and corrosion resistance of the DLC film was studied.The research results show that,compared with the complete film,the slight damage structure of the DLC film surface can play a role in the collection of wear debris,reduce the contact pressure at the friction interface,slow down the softening of the film surface due to graphitization in the friction sliding process,and improve Friction and wear properties of the film.However,with the increase of the damage depth,the DLC film surface appears different degrees of cracking,peeling and other defects,which accelerate the corrosion failure of the film.Further failure mechanism research results show that the different degrees of cracking and peeling of the film surface cause corrosive Cl-ions to contact the stainless steel surface more easily,promote the occurrence of stainless steel pitting reaction,and reduce the corrosion protection performance of the film.