Research On Selective Laser Melting And Electrochemical Polishing Of Stainless Steel Array Structures

Cellular materials,especially ordered porous structure materials,have good mechanical properties and functional properties,such as light weight,high specific strength,shock absorption,sound absorption and energy absorption.Currently,porous materials are becoming more and more popular in many fields including automobiles,aerospace,ships,construction,civil engineering,machinery,medical,energy and military.However,due to the complexity of its structure,the traditional process can not manufacture the porous structure with small inner hole or complex structure.The reasonable and feasible process for making complex porous material have been paid more and more attention.Selective Laser Melting(SLM),as a popular technology among 3D printing technologies,can be used to fabricate complex porous structures.However,in the powder based melting technology,the unmelted powder particles will stick to the solid-liquid solidification interface of the molten pool during the layer-by-layer forming process,resulting in a rough surface.The rough surfae is particularly serious in complex porous structures,so this has become one of the bottlenecks of this technology.For the preparation of porous structures,the main advantage of SLM is the freedom of desgin,which is benificial to achieve new functional applications.4To study the fabrication of metal porous electrodes by SLM in the energy field,which provides a guidance for the design and preparation of a new generation of porous electrodes.The SLM process was optimized from the single tracks to multi-tracks.The Bcc lattices without defacts(pores and cracks and deformation)were successfully prepared by using optimized SLM process.The microstrute of build Bcc latttices was studied.The numercial model to predict mechanical behaviors of Bcc lattices were defined.The deformation characteristics and failure mechanism of Bcc lattice structure were clarified,and the energy absorption characteristics of Bcc results with different relative densities were predicted.These findings will provide a guidance to design Bcc lattice structure for specific energy absorption application.A strategy of overpotential electrochemical polishing was developed for effectively smoothening SLM-fabricated surfaces,particularly for removing sticking particles.Here,the mechinism of overpotential electrochemical polishing(OECP)was studied.Then,A combination of overpotential and conventional electrochemical polishing(OECP+ECP)method was deveoped.It can significantly improve the polishing quality and reduce the amount of material removal.Importantly,this new polishing method can effectively improve the mechanical properties of the porous structure.The microlattices polished with this approach nearly doubled the specific compressive plateau stress and energy absorption over as-printed lattices.This work also demonstrates the capability of uniformly smoothening the inner surface of tubes.Moreover,the success of 4130 steel and Al Si10 Mg has indicated that this strategy could be applied to other metals,highlighting that our OECP method is broadly practical.performance and smoothsurfaced metals related functional applications.To meet the high electrode requirements of conductivity and mechanical strength in the energy field,the porous electrode with mesh array structure was designed in this paper.The mesh array structure with continuous framework was successfully fabricated by SLM and OECP techniques.The conductivity and tensile strength of the mesh array structure was about 10 times and 4 times compared with that of commercial stainless steel foams,respectively.Futhermore,a hollow porous cone array stucture with flow channels is designed.The nano-needles were deposited on the surface of the hollow porous array structure.A multi-scale three-dimensional electrode was fabricated.The electrode has excellent electron/ion/liquid transport properties as well as high electrochemical active surface area,high activity and excellent corrosion resistance.The electrochemical active surface area of the multi-scale electrode is 9 times that of the commercial stainless steel foames.Comparing with other electrodes in the same material,the hollow porous array electrode achieves the lowest overpotential among the reported values,and its durability time is more than 7 times that of the commercial stainless steel foames.