Effect of laser polishing on the microstructure and mechanical properties of stainless steel 316L fabricated by laser powder bed fusion
Effect of laser polishing on the microstructure and mechanical properties of stainless steel 316L fabricated by laser powder bed fusion
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DOI：
10.1016/j.msea.2020.140579
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发表时间：
2021-01-20
期刊：
影响因子：
6.4
通讯作者：
Pfefferkorn, Frank E.
中科院分区：
文献类型：
--
作者：
Chen, Lan;Richter, Brodan;Pfefferkorn, Frank E.
虽然近年来金属增材制造取得了显着增长，但所生产的表面通常需要后处理，以改善表面光洁度，减轻残余应力，并消除表面连接的孔隙。激光抛光，通过重熔表面的薄层，是一种后处理方法正在研究的表面光洁度改善和其他表面增强。采用光学显微镜（OM）、扫描电镜（SEM）、电子背散射衍射（EBSD）和透射电镜（TEM）对激光粉末床熔合（L- pbf）不锈钢316l （316l）激光抛光前后的表面形貌和微观结构进行了表征。此外，还测量并报告了样品的横截面显微硬度。此外，使用单轴拉伸测试表征了成品和激光抛光样品的拉伸性能。结果表明，激光抛光（Sa = 0.65 mu m）可显著降低316 L合金（Sa = 4.84 mu m）的表面粗糙度。激光抛光后，L- pbf 316 L的平均晶粒直径减小，低角度晶界（2度近似于5度）比例增加，亚表面硬度最高达到262 HV，激光抛光后316 L的抗拉强度和塑性均有所提高。这种增强归因于热循环应力、晶粒细化、表面缺陷的消除和激光抛光后的位错强化。
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.