Preparation And Properties Of Hard Protective Coatings In Seawater Environment

Friction and wear of key tribo-pairs is the bottleneck for long-life stable operation of mechanical system in seawater.Improving the surface properties of a material is an important method that extends service life of machine parts under harsh condition.In this study,a series of Cu doped diamond-like carbon?Cu/DLC?composite coatings,Cu and MoS₂ co-doped diamond-like carbon??Cu,MoS₂?/DLC?composite coatings and CrN/CrCN multilayer coatings were prepared on stainless steel surfaces by physical vapor deposition techniques.The coatings with different composition and microstructure were achieved by process designs.The microstructure,mechanical properties,corrosion resistance and tribological mechanism of the coatings in seawater environment were discussed systematically.The main findings were as follows:1.Diamond-like carbon coatings with various Cu contents?Cu/DLC coatings?were successfully deposited on stainless steel substrates via magnetron sputtering techniques.The effects of Cu dopant on the microstructure,tribological performance,mechanical properties,antifouling ability and corrosion resistant of Cu/DLC composite coatings were systematically investigated.The tribological performance and adhesion strength of Cu/DLC coatings were significantly improved due to the addition of Cu.In particular,the antifouling test demonstrated that the algae adhesion rate of Cu/DLC coatings could reduce from 6.87%to 0.82%.The corrosion resistant of Cu/DLC coatings was significantly enhanced by the addition of Cu due to the graphitization.Meanwhile,the Cu nanoparticles could form a dense two-phase structure with amorphous carbon network to create a physical barrier,and the best anti-corrosion performance was obtained at the Cu content of 7.4 at.%.These indicates that the as-prepared Cu/DLC coatings could be suitable for using as a promising protective material in marine environments.2.the?Cu,MoS₂?/DLC coatings with various Cu contents were prepared on stainless steel substrates by magnetron sputtering technique.The effects of Cu contents on microstructure,mechanical,tribological,anticorrosion and antifouling properties of coatings were systematically investigated.As the increase of Cu content,the surface roughness and sp²/sp³ ratio of?Cu,MoS₂?/DLC coatings presented an uptrend.Meanwhile,the hardness and elastic modulus of coatings gradually displayed a downtrend.Overall,the microstructure,mechanical properties,tribological properties,corrosion properties and antifouling properties of DLC coatings could be improved by co-doping Cu and MoS₂.The?Cu,MoS₂?/DLC coating with 7.6 at.%Cu content could exhibit the optimal multi-functional protection in marine environment.3.CrN,CrCN monolayer and CrN/CrCN multilayer coatings were deposited on stainless steels substrates by multi-arc ion plating technology,the microstructure,mechanical properties and tribocorrosion behaviors of the three coatings were systematically compared.Results revealed that the CrN/CrCN multilayered coating presented a high content of graphite-like phase and hard Cr-C compounds,which might play a key role enhancing lubrication and hardness.In particular,tribocorrosion tests in artificial seawater showed that the as-deposited CrN/CrCN multilayered coating could demonstrate significant improvement of tribocorrosion resistance compared to the CrN and CrCN monolayers coatings.The multilayer architecture design could effectively interrupt cracks propagation and prevent and/or slow corrosive media from reaching the substrates.Also,the friction lubricating film formed by hard Cr-C phase and self-lubricating graphite phase could effectively improve the coating's lubrication and tribocorrosion resistance.