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Round Robin Tensile Testing of 50% cold worked Nitronic 60

Carroll, J.D.; Casias, Zachary; Rodelas, Jeffrey

This report documents recent experiments on the structural properties of Nitronic 60, Level 5 (cold worked to approximately 50% reduction in diameter). Material from two different vendors was examined. Different cold working approaches by the two vendors resulted in inhomogeneous material properties that varied as a function of distance from the center of the rod. Measurements were compared to Sandia specifications (7343200-7343207). The effect of several parameters on structural properties was examined, including lot-to-lot variability, lot diameter, radial location of tensile bars, tensile bar size, and cold working method. Most significantly, the apparent tensile strength, yield strength, and ductility were found to all vary with radial distance from the center of the bar.

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TYPE SAND Report YEAR 2019
DOIOSTI

Evolution of 316L stainless steel feedstock due to laser powder bed fusion process

Additive Manufacturing

Heiden, Michael J.; Deibler, Lisa A.; Rodelas, Jeffrey; Koepke, Joshua R.; Tung, Daniel J.; Saiz, David J.; Jared, Bradley H.

Some of the primary barriers to widespread adoption of metal additive manufacturing (AM) are persistent defect formation in built components, high material costs, and lack of consistency in powder feedstock. To generate more reliable, complex-shaped metal parts, it is crucial to understand how feedstock properties change with reuse and how that affects build mechanical performance. Powder particles interacting with the energy source, yet not consolidated into an AM part can undergo a range of dynamic thermal interactions, resulting in variable particle behavior if reused. In this work, we present a systematic study of 316L powder properties from the virgin state through thirty powder reuses in the laser powder bed fusion process. Thirteen powder characteristics and the resulting AM build mechanical properties were investigated for both powder states. Results show greater variability in part ductility for the virgin state. The feedstock exhibited minor changes to size distribution, bulk composition, and hardness with reuse, but significant changes to particle morphology, microstructure, magnetic properties, surface composition, and oxide thickness. Additionally, sieved powder, along with resulting fume/condensate and recoil ejecta (spatter) properties were characterized. Formation mechanisms are proposed. It was discovered that spatter leads to formation of single crystal ferrite through large degrees of supercooling and massive solidification. Ferrite content and consequently magnetic susceptibility of the powder also increases with reuse, suggesting potential for magnetic separation as a refining technique for altered feedstock.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus
Results 26–50 of 144
Results 26–50 of 144
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