Browsing by Subject "stainless steel 316L"
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Item Competing Influence of Porosity and Microstructure on the Fatigue Property of Laser Powder Bed Fusion Stainless Steel 316L(University of Texas at Austin, 2017) Zhang, Meng; Sun, Chen-Nan; Zhang, Xiang; Chin Goh, Phoi; Wei, Jun; Li, Hua; Hardacre, DavidCrack initiation constitutes a large portion of the total life for parts under high cycle fatigue loading. Materials made by the laser powder bed fusion (L-PBF) process contain unavoidable process-induced porosity whose effect on the mechanical properties needs to be considered for fatigue applications. Results from this work show that not all pores in L-PBF parts promote fatigue crack initiation. The length scale of local microstructure defects, i.e. grain boundary, could be larger than the pores and in such cases they are the primary cause for crack initiation. Samples were produced in this work to demonstrate the critical defect size responsible for the transition between the porosity-driven and microstructure-driven failure modes.Item Effects of Spatial Energy Distribution on Defects and Fracture of LPBF 316L Stainless Steel(University of Texas at Austin, 2019) Jost, Elliott; Miers, John; Robinson, Aron; Moore, David; Saldana, ChristopherMeasures of energy input and spatial energy distribution during laser powder bed fusion additive manufacturing have significant implications for the build quality of parts, specifically relating to formation of internal defects during processing. In this study, scanning electron microscopy was leveraged to investigate the effects of these distributions on the mechanical performance of parts manufactured using laser powder bed fusion as seen through the fracture surfaces resulting from uniaxial tensile testing. Variation in spatial energy density is shown to manifest in differences in defect morphology and mechanical properties. Computed tomography and scanning electron microscopy inspections revealed significant evidence of porosity acting as failure mechanisms in printed parts. These results establish an improved understanding of the effects of spatial energy distributions in laser powder bed fusion on mechanical performance.Item Fatigue Performance of Additively Manufactured Stainless Steel 316L for Nuclear Applications(University of Texas at Austin, 2019) Beard, William; Lancaster, Robert; Adams, Jack; Buller, DaneAdditive manufacturing (AM) is a rapidly growing technology which is extending its influence into many industrial sectors such as aerospace, automotive and marine. Recently the nuclear sector has considered AM in the production of nuclear reactor components due to its possible advantages over conventional manufacturing routes. This includes considerable cost savings due to less material wastage, the ability to produce complex near net shape components that conventional manufacturing processes are unable to achieve and a reduced manufacturing time. Initially, Stainless Steel 316L (SS316L) manufactured by laser powder bed fusion (LPBF) has been identified as a potential candidate. However, due to the transient nature of the microstructure it is now of fundamental importance to assess and understand the mechanical behaviour of the LPBF material. This paper will highlight some of the recent research at Swansea University in investigating the variation on the fatigue characteristics between wrought SS316L and LPBF processed SS316L material. This will include an extensive microstructural and fractographic investigation. As LPBF material looks to replace conventionally manufactured equivalents, an understanding of how build integrity and orientation affects the mechanical properties of AM material is critical. Wrought and vertical LPBF material are to be assessed to understand how the microstructure controls the fatigue performance of LPBF SS316L material.Item A Parametric Study on Grain Structure in Selective Laser Melting Process for Stainless Steel 316L(University of Texas at Austin, 2017) Sun, Dongwei; Li, Xuxiao; Tan, WendaLaser Selective Melting (SLM) process is used in this work to produce 3-dimensional samples of Stainless Steel (SS) 316L. The effects of laser power, scanning speed, and laser scanning strategy on the track morphology and grain structure are investigated. As the laser heat input is increased by increasing laser power and/or decreasing laser scanning speed, the surface morphology of the SLM track will vary according to the extent of powder melting, and the grain size will increase correspondingly. Different laser scanning strategies can produce different grain patterns, and a noticeable porosity can be found if the scanning strategy is not appropriate. The grains in the bottom layers of the built samples inherit the crystallographic orientations from the substrate through epitaxial growth; nucleation takes places in the top layers and introduces new grains of random crystallographic orientations into the built samples.