摘要
激光定向能量沉积316L不锈钢不同成形方向所呈现的不同组织结构对其电化学溶解行为具有至关重要的影响,进而使得电化学抛光表面产生差异。因此,本团队利用光学显微镜观测、X射线衍射分析和电子背散射衍射(EBSD)等分析方法,针对构件的正面、侧面和上表面的组织各向异性展开深入研究,通过电化学测试对不同表面在NaCl-乙二醇电解液中的电化学阳极溶解行为进行了系统研究,最后对激光定向能量沉积316L不锈钢的三个面进行射流电化学抛光。结果表明:激光定向能量沉积的三个表面在显微组织上存在显著的各向异性。三个面在NaCl-乙二醇电解液中的耐电化学溶解能力排序为上表面<正面<侧面。经过射流电化学抛光处理后,表面粗糙度均下降至0.2μm以下,达到了镜面效果。三个面在抛光后都存在降低镜面效果的暗区,枝晶间区域的Cr、Mo元素含量高于枝晶主干区域是导致这一现象的主要原因。中心线处的晶粒远小于其他区域,细小的晶粒减小了枝晶间区域与枝晶主干区域的腐蚀差异,在电化学抛光后呈现亮区。
Objective 316L stainless steel is widely used in the aerospace,biomedical,and nuclear power industries owing to its high corrosion resistance,ease of processing,adequate strength,and reasonable cost.Laser directed energy deposition(LDED)is an additive manufacturing technology that has the advantages of high flexibility,high processing efficiency,and high degreesoffreedom,making it suitable for manufacturing fine and complex components.However,fields such as aerospace,biomedical,and nuclear power require components that achieve low surface roughness.The main objective of this study is to utilize the jet electrochemical polishing method to postpolish an LDEDed 316L stainless steel surface.Before polishing,this study elucidates the anisotropy of the microstructure of the LDEDed front,top,and side faces,and analyzes the differences in their anodic dissolution behavior in a sodium chlorideglycol electrolyte,which provides a sufficient theoretical basis for the subsequent jet electrochemical polishing.The surface morphologies and microstructures of the different faces were analyzed in detail after polishing.The aim of this study is to provide an empirical and technical support for the polishing of LDEDed components to improve their surface quality.Methods The microstructural anisotropy of three faces—front,top,and side—of LDEDed 316L stainless steel was analyzed using optical microscopy(OM),Xray diffraction(XRD),and electron backscatter diffraction(EBSD)techniques.Then,the opencircuit potentials,polarization curves,and alternating current(AC)impedance curves of the three faces were measured using an electrochemical workstation to assess the anodic dissolution behavior of the individual surfaces in a sodium chlorideglycol electrolyte.A jet electrochemical polishing device was then utilized to polish the three faces with the facescan mode to reduce their roughness.The threedimensional morphology and surface roughness of the three faces were measured using a laser confocal microscope to evaluate the effect of polishing.Finally,scanning electron microscopy(SEM)was used to analyze the micromorphology and chemical composition.Results and Discussions The LDEDed 316L stainless steel shows significant anisotropy in the microstructure(Fig.4),physical phase(Fig.5),and texture(Fig.6).The results of the opencircuit potential(Fig.7),potentiodynamic polarization curves(Fig.8),and electrochemical impedance spectra(Fig.9)indicate that the corrosiondissolution behavior of the three different faces of the LDEDed 316L stainless steel exhibits anisotropy.Specifically,the corrosion resistance of the three faces decreases in the following order:top face<front face<side face.Scratches on the front,top,and side faces disappear after the jet electrochemical polishing surface sweep,all of which show good mirror effect(Fig.10).The roughness decreases from the original 1.057μm to 0.177μm,0.200μm,and 0.171μm,respectively(Fig.11).Bright and dark zones exist on all three faces after polishing(Fig.10),which are caused by the different microstructures of the bright and dark zones(Fig.12).SEM and energydispersive Xray spectroscopy(EDS)results(Fig.14)show that after jet electrochemical polishing,a large number of dendrites exist in the dark zone;dendrites in the bright zone are basically dissolved.Conclusions In this study,LDEDed 316L stainless steel was subjected to jet electrochemical polishing to reduce its roughness.First,the anisotropy of the microstructures of the front,top,and side faces was analyzed.Subsequently,the electrochemical anodic dissolution behaviors of the three faces in a sodium chlorideglycol electrolyte were analyzed.Finally,the three faces were subjected to jet electrochemical polishing with surface sweep mode to reduce their roughness to less than 0.2μm.The reasons for the appearance of bright and dark areas on the polished surfaces were elucidated by analyzing the microstructure and chemical composition of the bright and dark zones.
作者
吴国龙
黄煜杰
杨珍珍
王晔
王梁
姚建华
Wu Guolong;Huang Yujie;Yang Zhenzhen;Wang Ye;Wang Liang;Yao Jianhua(College of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310023,Zhejiang,China;Institute of Laser Advanced Manufacturing,Zhejiang University of Technology,Hangzhou 310023,Zhejiang,China;Collaborative Innovation Center Jointly Constructed by Provinces and Ministries for HighEnd Laser Manufacturing Equipment,Hangzhou 310023,Zhejiang,China)
出处
《中国激光》
北大核心
2025年第12期99-112,共14页
Chinese Journal of Lasers
基金
国家自然科学基金(U2130122,U22A20199)
国家重点研发计划(2024YFB4607101)
浙江省自然科学基金(LQ24E050017)。
