Browsing by Author "Barrionuevo, German Omar"

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    Experimental and numerical investigation of sliding wear of heat-treated 316L stainless steel additively manufactured
    (2024) Barrionuevo, German Omar; Calvopina, Hector; Debut, Alexis; Perez-Salinas, Cristian
    Additive manufacturing (AM) of metal alloys using a laser as a machine tool is reaching levels of precision comparable to conventional processing methods. Stainless steel specimens fabricated by AM have been extensively evaluated in load-bearing applications, showing an adequate response concerning mechanical strength. However, research on wear behavior remains open to discussion. The present work evaluates the sliding wear response of 316L stainless steel fabricated by laser powder bed fusion in three conditions: (1) as-built, (2) stressrelieved at 550degree celsius, and (3) heat-treated at 1150degree celsius. A pin-on-disk tribometer and a nanoindentation tester were employed to assess the tribological response and compare it with the same cold drawing material. The wear track and volume loss were evaluated using a 3D surface profile meter. Furthermore, the finite element method was applied to validate the experimental results and obtain insights into the behavior of the pin and disk couple. The results show that the samples in the as-built condition exhibit higher wear resistance associated with higher hardness. Stress relief slightly alters the wear response, while heat treatment modifies the microstructure, reducing the sliding wear resistance. The wear of the heat-treated samples cannot be attributed to a single wear mechanism, a synergy between several sub-mechanisms, such as abrasion, adhesion, oxidation, and tribochemical reactions.
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    Microstructural differences and mechanical performance of stainless steel 316L conventionally processed versus a selective laser melted
    (2024) Barrionuevo, German Omar; La Fe-Perdomo, Ivan; Ramos-Grez, Jorge A.; Walczak, Magdalena; Mendez, Patricio F.
    Metal additive manufacturing (AM) has changed materials design and processing paradigms. However, as it is a layered manufacturing process and due to the complex material-laser interaction, the resulting microstructure differs from conventional counterpart alloys. Since the mechanical properties depend on the microstructure, the functional properties of mechanical components manufactured by laser powder bed fusion (LPBF) thus are significantly influenced by the processing parameters and the scanning strategy. The present research is focused on the microstructure differences between 316L stainless steel processed by LPBF and conventionally processed. Several characterization techniques were employed in this assessment, including optical and electron microscopies, X-ray diffraction, and spectrometry. A finite element analysis (FEA) was conducted to study grain boundaries and orientation and determine the thermal gradient and cooling rate. Moreover, welding-based algebraic models were used to calculate the cooling rate and the cell spacing. The FEA results show good agreement in the prediction of microstructural features, while the algebraic results values are of the same order of magnitude, with a relative error of less than 5% in determining the cell spacing (0.57 mu m). The additively manufactured specimen shows approximately the same ultimate tensile strength (622 MPa); however, a 40% increase in yield strength (532 MPa) and a higher microhardness is observed.
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    TENSILE/COMPRESSIVE RESPONSE OF 316L STAINLESS STEEL FABRICATED BY ADDITIVE MANUFACTURING
    (2024) Barrionuevo, German Omar; La Fe-Perdomo, Ivan; Caceres-Brito, Esteban; Navas-Pinto, Wilson
    Additive manufacturing has evolved from a rapid prototyping technology to a technology with the ability to produce highly complex parts with superior mechanical properties than those obtained conventionally. The processing of metallic powders by means of a laser makes it possible to process any type of alloy and even metal matrix composites. The present work analyzes the tensile and compressive response of 316L stainless steel processed by laser-based powder bed fusion. The resulting microstructure was evaluated by optical microscopy. Regarding the mechanical proppercentage of elongation before breakage, compressive strength and microhardness were determined. The results show that the microstructure is constituted by stacked micro molten pools, within which cellular sub-grains are formed due to the high thermal gradient and solidification rate. The compressive strength (1511.88 +/- 9.22 MPa) is higher than the tentest, the hardness increased by 23%.