The Corrosion Resistance And Biological Properties Of Diamond-like Carbon Film Prepared By PECVD

Diamond-like carbon（DLC）film with high hardness,low friction coefficient,excellent corrosion resistance and biocompatibility should be an ideal coating for biomedical stainless steel.However,due to the mismatch of the bond between DLC film and substrate and the difference in hardness and other mechanical properties between DLC and substrate,there is high residual stress and poor adhesion of DLC film.Which will lead to the existence of micropores in the DLC film and the electrolyte is easy to penetrate to the surface of the substrate,resulting in corrosion of substrate.Also,during the immersion process,the electrolyte reaches to the interface of DLC film and substrate will result in the peel of film.To meet the biological application of DLC film,corrosion-resistant DLC film with high resistivity,low residual stress and less micropores is required.In this paper,DLC films have been deposited by plasma-enhanced chemical vapor deposition method（PECVD）method using methane and argon.By adjusting the deposition power,CH₄rate,deposition pressure and substrate temperature,the influence of deposition parameters on corrosion resistance is investigated.By studying the EIS plots of DLC films deposited at different substrate temperature,the corrosion behavior of DLC film with different microstructure is discussed.At the same time,the influence of the microstructure of DLC film on its biological properties was studied by measuring its contact angle and antibacterial properties,so as to prepare a 316L stainless steel protective film for human implantation with excellent properties.The research results in this paper show that the deposition parameters of PECVD affect the structure of DLC films.Among them,the deposition power influences the structure of DLC films by affecting the dissociation degree of CH₄.When the power is lower than 75 W,a typical DLC film cannot be generated.Different CH₄ flow rates have little influence on the structure of DLC films.The deposition pressure affects the structure of DLC film by affecting the number and energy of reactants free radicals.When the pressure is 1.0 Pa,the degree of graphitization is the highest,the film is smooth and dense,and the corrosion resistance is increased.And the graphitization degree of DLC films deposited at 400°C by PECVD technology increases but still maintains a high resistivity,which can effectively reduce the internal stress of the films.This films exhibit less micropores,which greatly improves the corrosion resistance and long-term corrosion performance.At the same time,due to the formation of fine graphite in the film layer,the film surface energy is reduced,thus has a better antibacterial property.During simulated body fluid immersion,Ca₃（PO₄）₂ is generated on the surface of DLC,that is,the surface of the film has certain osteogenic ability and good biocompatibility.