Preparation Of Superhydrophobic Surface On Stainless Steel Via Laser-Chemical Processing And Its Wear/Corrosion Resistance

Stainless 316L steel has been widely applied in biomedicine,marine equipment,aerospace and petrochemical fields because of its good corrosion resistance.A dense oxide film will be formed on the surface of stainless steel,which has corrosion resistance.However,the complex corrosive environment will destroy the oxidized surface layer and accelerate the corrosion rate of stainless steel.The safe service of stainless steel is failed.Several nature organisms have been investigated on excellent micro-nano structures during long-term natural evolution history.For example,the superhydrophobic surface generated by the multi-level structure of lotus leaves makes it easy for water droplets to roll and to take away pollutants.The superhydrophobic technology based on the natural evolution is one of cutting-edge technologies involving biology,physics,chemistry,materials and machinery,etc.It can greatly improve the mechanical,chemical and physical properties of processed materials and surfaces.Endowing material with superhydrophobicity via micro-nano structures processing and surface energy reducing has been recognized as a potentially anti-corrosion method.Hence,it will be great significance for prolonging the service life of key stainless steel components with improving corrosion resistance of stainless steel 316L by constructing a superhydrophobic surface.Firstly,the stainless steel 316L is selected as the research object.The laser-chemical processing technology will be researched in viewpoints of the technical bottlenecks and preparation problems on superhydrophobic surfaces,such as high preparation cost,complicated operation process,environmental pollution,and difficulty in large-scale production.Two new superhydrophobic surface processing methods including nanosecond laser-chemical and femtosecond laser-chemical methods are proposed.Secondly,it is optimized for both nanosecond laser-chemical and femtosecond laserchemical processes.The superhydrophobicity of surface fabricated by the nanosecond laserchemical method is improved with optimizing the laser processing parameters and the surface microstructure.The surface composition is analyzed the mechanism of laser-induced stearic acid decomposition is discussed.The femtosecond laser ablation power and frequency are determined by calculating the ablation threshold during femtosecond laser-chemical processing.The scanning speed,the surface macrostructure type and size are optimized and selected.The surface hydrophobicity can be improved with proposed both processing technologies.Finally,the chemical stability of the fabricated surface is investigated by ultrasonic cleaning.The electrochemical corrosion of the cleaned surface is characterized by the potentiodynamic polarization curve.The wear resistance of the cleaned surface is measured by the accelerated test method.The results show that the chemical stability,corrosion resistance and wear resistance of the surfaces prepared by the two processes are better than those fabricated by stearic acid coating method.The chemical stability and corrosion resistance of the surface processed by the nanosecond laser-chemical method are more better than those processed by femtosecond laser-chemical method.The wear resistance of the surface processed by the femtosecond laser-chemical method is better than that of the nanosecond laser-chemical one.