Abstract
The fatigue properties and microstructural evolution of 316 L stainless steel (316LSS) manufactured by laser powder bed fusion (L-PBF) were systematically studied and compared with its wrought counterpart. The as-built L-PBF 316LSS shows a pronounced heterogeneity, not only structurally but also chemically, with a unique microstructure of highly serrated grain boundaries, bimodal grain structure, nano-precipitates, solidification cell structures, and chemical segregations. The microindentation test showed that the hardness of the as-built L-PBF 316LSS reached 2.589 GPa, which was about 1.6 times higher than that of the wrought solution annealed counterpart, and the sparser slip steps around indentations revealed its greater dislocation storage capability. The S-N curves indicated that the fatigue resistance of the as-built L-PBF 316LSS was significantly better than that of the wrought solution annealed samples, and this was ascribed to its unique microstructural characteristics, especially the pre-existing high-density dislocations and chemical microsegregation within cellular solidification features. Furthermore, the enhanced planar slip in L-PBF 316LSS by its unique microstructure, especially the formation of deformation twins, delays the strain localization and restrains slip band generation, thereby significantly inhibiting crack initiation, and contributing greatly to the fatigue performance. The unique cell structure appears to be more effective in improving the low-cycle fatigue performance of L-PBF 316LSS due to the enhanced ductility.
Highlights
As one of the most promising technologies in the field of metal additive manufacturing (AM), laser powder bed fusion (L-PBF) known as selective laser melting (SLM) has attracted huge attention (Deng et al, 2021; Liu et al, 2018)
For face-centered cubic (FCC) crystals, the texture is dominant in L-PBF alloys, because it is easier to grow along the temperature gradient (Cui et al, 2022b)
Sun et al (Sun et al, 2018b) reported that fine-grained texture was introduced while texture was weakened as the scanning strategy was varied for L-PBF 316 L stainless steel (316LSS)
Summary
As one of the most promising technologies in the field of metal additive manufacturing (AM), laser powder bed fusion (L-PBF) known as selective laser melting (SLM) has attracted huge attention (Deng et al, 2021; Liu et al, 2018). International Journal of Plasticity 149 (2022) 103172 stainless steels (Cui et al, 2021a) and high entropy alloys (Kim et al, 2022), the L-PBF components usually exhibit an overwhelming advantage in terms of mechanical properties over the structures manufactured by other traditional processes (Liu et al, 2018; Nakada et al, 2010; Wang et al, 2018). The reliability and deformation mechanism of these L-PBF austenitic stainless steels under cyclic loading conditions still require in-depth research. Some intrinsic defects, such as lack-of-fusion (LOF) (Darvish et al, 2016), surface roughness (Kahlin et al, 2020; Yu et al, 2020), keyhole collapse (Cunningham et al, 2019) and gas porosity (Svensson et al, 2010) etc., can be introduced during the L-PBF process, which notably affect the fatigue properties of AM parts. To the best of the authors’ knowledge, the effect of unique microstructure characteristics on the fatigue properties of AM alloys is still poorly understood
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
