Study On Electrochemical Polishing Of 316L Stainless Steel Parts By Selective Laser Melting

Selective Laser Melting(SLM)is widely used in aerospace,precision manufacturing and other fields due to its advantages of forming complex structures.However,its poor surface quality and difficulty in direct application limit the further development of SLM.Electrochemical polishing has the advantage of being able to process complex structures and is considered an ideal process for post-processing of SLM parts.However,electrochemical polishing has high requirements on the quality of the polished surface.How to apply electrochemical polishing directly to SLM parts is an urgent problem to be solved.In this paper,by exploring the electrochemical polishing strategy,electrochemical polishing is directly applied to 316 L stainless steel parts prepared by SLM.Then,periodic defects are fabricated by adjusting the SLM forming process parameters,and the defects are fabricated into microstructures through the disadvantage of electrochemical polishing to create a butterfly-like superhydrophobic surface.Finally,the pit microstructure is directly formed by electrochemical polishing-assisted SLM,and a 3D superhydrophobic square tube with application value is fabricated.The main research contents are as follows:(1)The effect of electrochemical polishing strategy on the surface quality of stainless steel SLM parts is explored.A gradient voltage electrochemical polishing strategy is proposed to reduce the top and side surface roughness(Ra)from 12 ?m and10 ?m to 2.3 ?m and 1.7 ?m.The gradient voltage polishing strategy is extended to complex structures,and the inner surface roughness(Ra)of square and round tubes is successfully reduced to about 1 ?m.This strategy solves the problem of poor surface quality of complex SLM parts and provides a new method for post-processing of SLM complex parts.(2)Inspired by the superhydrophobic structure of butterfly wings.SLM is used to accumulate additive manufacturing of periodic defects one by one,and electrochemical polishing,chemical etching,and fluorosilane modification are used on the surface of SLM-prepared samples to process multi-scale non-smooth superhydrophobic surfaces imitating butterfly wing pits.The metal surface is fabricated by adding and subtracting materials to form a uniform pit-shaped micro-nano composite structure,and the corrosion resistance is significantly improved.Finally,a complex superhydrophobic groove with the application prospect of a flow surface is prepared,and its excellent selfcleaning performance is verified.This method combines the fabrication of additive and subtractive materials,which provides a new idea for the fabrication of stainless steel superhydrophobic structures.(3)Uniform pit microstructures are directly fabricated in both horizontal and vertical directions by electrochemical polishing-assisted SLM,a method that removes less metal and can form complex structures than pits fabricated from defects.The stainless steel superhydrophobic surface is obtained by chemical etching and fluorosilane modification.Finally,a 3D superhydrophobic square tube with application value is fabricated,and the inner surface of the square tube is uniform in superhydrophobicity and had strong self-cleaning ability.This provides a new method for anti-corrosion of pipelines.In this paper,aiming at the problem of poor surface quality of SLM parts,firstly,the gradient voltage electrochemical polishing strategy is used to successfully reduce the surface roughness.This strategy solves the problem of incompatibility between SLM complex parts and high surface quality,and provides a new idea for the postprocessing of SLM complex parts.Then,the bionic superhydrophobic surface is prepared by electrochemical polishing using periodic defects on the surface of SLM parts.Finally,the 3D superhydrophobic pipeline is successfully fabricated by electrochemical polishing-assisted SLM.The superhydrophobic surface preparation method proposed in this paper can be used to solve the problems of easy corrosion and icing on the inner surface of complex pipelines,and also provides a feasible solution for the preparation of 3D metal superhydrophobic surfaces.