Browsing by Subject "316L stainless steel"

Now showing 1 - 7 of 7

Additive Manufacturing of ODS Steels Using Powder Feedstock Atomized with Elemental Yttrium
(University of Texas at Austin, 2023) Yang, Seongun; Xu, Donghua; Yan, Dongqing; Albert, Marc; Pasebani, Somayeh
This study investigates the microstructure and mechanical properties of an austenitic ODS steel produced by the Laser Directed Energy Deposition (LDED) process using powder feedstock atomized with elemental yttrium. The Microstructure of the samples was characterized by electron microscopy, and mechanical properties were measured using a tensile test and nanoindentation. Further, the thermal stability of the LDEDproduced ODS steels were evaluated. As-printed samples showed a cellular structure with Si-Mn-Y-Oenriched nanoparticles that were found to be amorphous. After 100 hours at 1000°C in an argon atmosphere, a partially recrystallized microstructure with a decrease in the number density of Y-O-enriched nanoparticles with crystalline structure was revealed. The as-printed (600 W, 600 mm/min) samples exhibited an ultimate tensile strength of 774 MPa and an elongation at a break of 22%. A lower ultimate tensile strength of 592 MPa and higher elongation of 42% was measured after 100 hours at 1000°C.
Additively Manufactured 316L Stainless Steel: Effect of Heat Treatment on Microstructure and Tensile Properties
(2022) Lee, Seungjong; Ghiaasiaan, Reza; Shao, Shuai; Gradl, Paul R.; Shamsaei, Nima
The microstructure and tensile properties of 316L stainless steel (SS) fabricated using the laser powder directed energy deposition (LP-DED) after various heat treatment (HT) steps such as stress-relief (SR), solution annealing (SA), and hot isostatic pressing (HIP) are characterized. Microstructures before and after HTs are analyzed using both optical and scanning electron microscopy (SEM). Both quasi-static uniaxial tensile and hardness tests are performed to measure mechanical properties. The tensile results indicate that the non-heat treated (NHT) condition possesses higher strengths but lower ductility as compared to the other HT conditions (i.e., SR, SA, HIP, SR+SA, and SR+HIP). By employing the two-step HT conditions (i.e., SR+SA and SR+HIP), no significant changes on tensile properties as compared to the individual single-step HT conditions (i.e., SA or HIP) are observed. The findings suggest that two-step HTs are not required for LP-DED 316L SS unless HIP is needed to minimize volumetric defect contents.
Analysis of the Shielding Gas Dependent L-PBF Process Stability by Means of Schlieren and Shadowgraph Techniques
(University of Texas at Austin, 2019) Hoppe, B.; Enk, S.; Schleifenbaum, J.H.
Ensuring a robust and reproducible Laser Powder Bed Fusion (L-PBF) process depends on the design of the shielding gas flow in the corresponding manufacturing system. The gas flow assures the removal of particles from the process zone that emerge from the interaction with the laser irradiation. Minor disturbances may influence the stability of the L-PBF-Process and cause defects in final parts produced. The objective of this work comprises visualizing the convection processes and particle dynamics to analyze their influence on process stability. Therefore, a high speed camera based Schlieren and Shadowgraph setup is used to visualize convection flows as well as trajectories of metallic condensate and particles with up to 10,568 fps. This arrangement allowed investigating the influence of shielding gas flow conditions on single melt tracks. Corresponding results and studies on the interaction between laser irradiation and particles in varying shielding gas flow conditions are contents of this work.
Comparison of Rotating-Bending and Axial Fatigue Behaviors of LB-PBF 316L Stainless Steel
(University of Texas at Austin, 2019) Shrestha, Rakish; Simsiriwong, Jutima; Shamsaei, Nima
Additive manufactured (AM) materials are prone to internal defects such as entrapped gas pores and lack of fusions along with having a rough surface. There are different types of fatigue tests that are used to characterize the effects of such defects on the structural integrity of AM parts. The present study aims to investigate the effect of stress gradient on the fatigue behavior of 316L stainless steel (SS), fabricated using a laser beam powder bed fusion (LB-PBF) process. Axial fatigue tests are performed on as-built (non-machined) LB-PBF 316LSS round specimens with uniform gage section, while rotating bending fatigue tests are conducted on hourglass specimens (i.e. reduced gage section). Fatigue tests revealed that the specimens subjected to the axial loading exhibited lower fatigue resistance compared to the specimens failed under rotating bending test. Such differences in the fatigue life was attributed to the variation in the stress distribution resulting from different loading types and its effect on the fatigue crack propagation. Fractography analysis conducted to determine the failure mechanism showed that all of the cracks initiated from the surface of the specimen irrespective to the loading conditions. Furthermore, fracture surface observed for LB-PBF 316L SS specimens resembled a typical fracture surface of notched specimens, which supports the fact that for the as-built specimens cracks initiates from the micro-notches as a result of layer wise fabrication in AM process.
The Impact of the Printed Part Geometry on the Shrinkage and the Density of 316L Stainless Steel Parts Printed by FFF/FDM Technology
(2022) Obeidat, Suleiman; Nervis, Joe Jr.; Ma, Junkun
Investigation of the Scan Strategy and Property of 316L Stainless Steel-Inconel 718 Functionally Graded Materials Fabricated by Selective Laser Sintering
(University of Texas at Austin, 2015) Zhou, Y.; Zhou, X.; Teng, Q.; Wei, Q.S.; Shi, Y.S.
316L stainless steel and Inconel 718 alloy functionally graded materials were fabricated by selective laser melting with a novel approach which combined powder-bed with powder-feed pattern. Two different scanning strategies have been used to form the steel/Ni FGMs. The interfacial characteristics were analyzed by scanning electron microscopy and energy dispersive spectroscopy. Quantitative evidence of good bonding at the interface was obtained from the tensile and shear tests of the steel/Ni FGMs.
A Methodology for the Embedding of Sensors in Components Manufactured Using Metal Laser Powder Bed Fusion
(University of Texas at Austin, 2021) Uí Mhurchadha, S.M.; Huynh, M.P.; Quinn, P.T.; Tomaz, I.; Raghavendra, R.
This paper presents a methodology for the embedding of a sensor in a 316L stainless steel component during the laser powder bed fusion process. The aim of this study is to overcome the drawbacks of traditional sensor attachment to the surface of a component via placing sensors into a part during the manufacturing process. A methodology for the embedding process that ensures the functionality of the sensor within the component is presented and a preliminary investigation into the effect of the embedding process on the manufactured part quality preformed. An off-the-self accelerometer was embedded into a turbine and tested under rotational loading conditions. The interface microstructure where the print was stopped is also studied to investigate the effect of the sensor embedding methodology on material properties. The embedded sensor is capable of detecting off-axis rotation and over-speed of the turbine, two critical loading conditions that cause failure in turbines.