Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion

Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.

激光粉末床熔融（LPBF）在致密金属结构的制造中已得到越来越多的应用。然而，LPBF合金的腐蚀相关性能，特别是环境辅助开裂性能，如腐蚀疲劳性能，尚未得到很好的理解。在这项研究中，使用电化学方法、高周疲劳和疲劳裂纹扩展测试，研究了LPBF 316L不锈钢在3.5 wt.%氯化钠溶液中的腐蚀和腐蚀疲劳特性。与传统制造的316L相比，LPBF 316L不锈钢表现出显著改善的腐蚀性能，这体现在点蚀电位和再钝化电位的提高以及裂纹萌生的延迟上。然而，打印参数对点蚀电位没有显著影响。LPBF样品在疲劳裂纹扩展过程中也表现出更强的再钝化能力。讨论了打印过程中引入的独特微观结构特征。腐蚀和腐蚀疲劳性能的提高归因于由位错网络形成的柱状/胞状亚晶粒的存在，这些亚晶粒作为传输防腐元素的高扩散路径。