Preparation And Microstructure As Well As Properties Study Of Diamond-Like Carbon Film By Liquid Phase Method

Stainless steel is widely used among the key structural parts of high-end equipment in the field of industrial production and living areas,however,due to the development of technology and society,the harsh conditions of the traditional production environment have severely restricted its application.Surface modification technology can effectively improve the surface properties of materials by preparing films,coatings,coatings or infiltration layers.It is an beneficial way to enhance the performance of stainless steel.Diamond-like carbon films,as a kind of film material with excellent properties no less than that of diamond structure,has been widely concerned.In this study,DLC films were prepared on stainless steel by liquid phase electrochemical deposition（LPCED）,and the structure and properties of DLC films were analyzed to explore the influence of different processes on its structure and performance.At the same time,based on the experimental results,different carbon structure models of DLC models are established,to explore the electronic structure as well as intrinsic mechanical properties of structures based on the first calculation principle.The experimental results show that the surface of the films grow continuously and have a dense distribution.With the extension of the deposition time,the roughness of the films is continuously reduced and the flatness is continuously improved.The phase composition of the film sample is mainly diamond-like carbon and a small amount of Cr₃C₂and Fe₃C impurity phase.After deposition for 15 min,the thickness reaches 8μm or so.For the same carbon source system,the process with carbon source volume fraction 40%is the best.To a certain extent,with the extension of time,it is beneficial to increase the sp³hybrid carbon in the thin film structure.Compared with stainless steel,the surface hardness of DLC film can be increased by 2～3times,up to 1283 HV_0.1（nano hardness is 13 GPa）,and its film-based bonding force grade is HF1.After DLC films were deposited,the surface friction coefficient of stainless steel decreased from 0.63 to 0.26,and the wear resistance is clearly ameliorated.Serious adhesion,abrasive particles and oxidative wear occurred on the untreated stainless steel,but moderate adhesive wear and abrasive wear,as well as mild oxidative wear,mainly occurred on the surface after deposition of DLC films.The corrosion resistance of the stainless steel has also been improved.With the extension of the deposition time,the corrosion resistance has shown an increasing trend as a whole.The results of semiconductor properties analysis show that the passivation films on the surface of DLC films were P-type semiconductor,and the acceptor charge concentration of the processed thin film samples is much smaller than that of the untreated substrate material,that is,the corrosion passivation film formed on the film samples is more stable and have better corrosion resistance.The first principle calculation shows that the DLC structure is between graphite and diamond,and the stability is the worst.The peaks of density of states of different carbon structures are contributed by the s orbital and p orbital of C;The band gap width of DLC structure broadens with the increase of structure density,which belongs to semiconductor property.The hardness calculation results show that the maximum hardness of DLC structure with density of 3.0 g/cm³is 28 GPa.At the same time,according to the average hardness and sp³hybrid bond content based on the experimental,it can be concluded that the structure model with a density of 2.8 g/cm³is the most consistent with the theoretical model of the experiment in this paper under the existing conditions.