Effect of laser polishing on the microstructure and mechanical properties of stainless steel 316L fabricated by laser powder bed fusion

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:802

Article

Chen, Lan^1,2  Richter, Brodan²  Zhang, Xinzhou^1,2  Bertsch, Kaila B.⁴  Thoma, Dan J.³  Pfefferkorn, Frank E.² 

[1] Jiangsu Univ, Sch Mech Engn, Zhenjiang 212013, Jiangsu, Peoples R China

[2] Univ Wisconsin, Dept Mech Engn, Madison, WI 53706 USA

[3] Univ Wisconsin, Dept Mat Sci & Engn, Madison, WI 53706 USA

[4] Lawrence Livermore Natl Lab, Mat Sci Div, Livermore, CA 94550 USA

关键词: Laser polishing;    Laser powder bed fusion;    Stainless steel;    Mechanical property;    Microstructure;   

DOI  :  10.1016/j.msea.2020.140579

来源: Elsevier

【 摘 要 】

While metal additive manufacturing has seen significant growth in recent years, the surfaces produced often need post-processing to improve surface finish, mitigate residual stresses, and remove surface-connected porosity. Laser polishing, by means of remelting a thin layer of the surface, is one post-processing method being investigated for surface finish improvements and other surface enhancements. In this work, the surface morphology and microstructure of laser powder bed fused (L-PBF) stainless-steel 316 L (316 L) before and after laser polishing are characterized by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scatter diffraction (EBSD), and transmission electron microscopy (TEM). In addition, the cross-sectional microhardness of the samples is measured and reported. Additionally, the as-built and laser-polished sample's tensile properties are characterized using uniaxial tension tests. The results indicate that the surface roughness of as-built 316 L (Sa = 4.84 mu m) can be substantially reduced through laser polishing (Sa = 0.65 mu m). After laser polishing, the average grain diameter is reduced and the proportion of low angle grain boundaries (2 degrees similar to 5 degrees) is increased in the L-PBF 316 L. The maximum sub-surface hardness reaches 262 HV, and both the tensile strength and ductility of 316 L are increased after laser polishing. This enhancement is attributed to thermal cycling stresses, grain refinement, the elimination of surface defects, and dislocation strengthening after laser polishing.

【 授权许可】

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