| 1. |
- Bernal, Ximena E., et al.
(författare)
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Empowering Latina scientists
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Quiceno, Enrique, et al.
(författare)
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Customized Ti6Al4V implants by EBM : design, manufacturing and surface treatments
- 2022
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Ingår i: Proceedings. - 9786289528718 ; , s. 381-388
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Konferensbidrag (refereegranskat)abstract
- Subtractive manufacturing methods such as machining have been conventionally used to produce standard metallic implants for bone replacement in materials such as Co-Cr and Ti-based alloys. The production of a customized implant with complex geometries using conventional machining techniques such as CNC requires specification equipment (5 or 6 axes), where the manufacturing process is difficult, limiting the mass production of customized products. New advanced metal additive manufacturing (AM) methods allow patient-specific implants obtaining, in which the Engineering for Transformation implant geometry can be designed to fit to a specific patient from the information of a CT scan. Besides this flexibility in the design, AM offers a cleaner production with less generation of scrap, low energy consumption and lower CO2 release. Electron Beam Melting (EBM) is one of the most used AM methods in the implant industry. In EBM, an electron beam is used to melt metal powder layer by layer in a vacuum protective environment, following a digital 3D model. Titanium alloys, specifically Ti6Al4V, have been the most widely used biomaterial in biomedical applications of orthopedic implants. In general, implants for biomedical applications require postmanufacturing surface modification to improve their performance, biocompatibility and fixation with the surrounding tissues in the area where they are implanted. Formation of anodic layers is one of the surface modifications that have become essential due to the high demands of implant applications and in order to enhance chemical and mechanical properties of the surface specimen. The most common anodizing developments were performed on Ti6Al4V alloy surfaces manufactured by conventional technologies such as forging and conventional machining. The project explores the feasibility of EBM of metal implants prototypes manufacturing for the Colombian healthcare market. 3D implant models were obtained, and then manufactured using EBM in Ti6Al4V alloy. A PEO process to surface modification with the aim to improve the biocompatibility of the manufactured implants by EMB process were demonstrated.
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| 3. |
- Ramirez, Angie, et al.
(författare)
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Biotribological behavior of Ti6Al4V alloy fabricated by EBM and subsequently anodized
- 2022
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Ingår i: Proceedings. - 9786289528718 ; , s. 404-410
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Konferensbidrag (refereegranskat)abstract
- Hip joints can be damaged by metabolic (degenerative disease) or mechanical (fracture) causes, limiting their functioning. To restore joint movement, the joint must be replaced by a hip prosthesis. Lubrication, friction and wear phenomena occur in the joints, which, in turn, are often responsible for the failure of the prosthesis, causing its loosening. The aim of the present study is to evaluate the biotribological behavior of a prototype Ti6Al4V hip prosthesis made-up by electron beam melting (EBM) additive manufacturing and subsequently surface modified by anodizing. Once the prototype was obtained, some samples were polished for biotribological tests and others for anodizing. The biotribological tests were performed in a ball-ondisk tribometer using 6 mm diameter alumina counterbodies. Wear tracks of 2 mm in diameter were obtained, using SBF solution at a temperature of 37 °C as the medium. The samples fabricated by EBM and subsequently anodized showed the highest values of friction coefficients, while the samples madeup by forging and EBM showed similar friction coefficients, while the anodized samples showed the lowest wear rate followed by the samples manufactured by EBM.
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| 4. |
- Vargas, Carlos, et al.
(författare)
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The Effect Of Microstructure And Anisotropy Of Different Ti-6al-4v AlloysSubstrates Over Their Surface Modification By Plasma Electrolytic Oxidation
- 2022
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Ingår i: Abstracts E-book.
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Konferensbidrag (refereegranskat)abstract
- Ti-6Al-4V is one of the widely used load-bearing implant materials due to its unique set of combinatorial properties such as biocompatibility and enhanced mechanical properties. However, after being implanted, these biomaterials can trigger difficulties in patients due to infections mainly caused by bacterial adhesion. Their good corrosion performance is mainly explained by the formation of a dense and passive oxide layer on their surface. Nevertheless, this oxide film alone does not have enough surface characteristics like bioactivity, antimicrobial activity, corrosion resistance, osseointegration, roughness, biocompatibility, fatigue, and wear to provide good performance for biomedical applications. For that reason, others surface modifications on these alloys are required. In that direction, the surface modification of plasma electrolytic oxidation (PEO) is of great interest given its low cost and environmentally friendly nature. PEO had been widely studied on Ti-6Al-4V alloys, especially on substrates made by conventional manufacturing like forged. However, currently, most implants are manufactured by additive manufacturing techniques (electron beam melting, selective laser melting) and the effect of PEO on substrates manufactured by these techniques has not been completely studied, especially by the electron beam melting technique. In this work, the morphology, chemical composition, and phase composition of the PEO coatings on substrates manufactured by the EBM technique were analyzed by Scanning Electron Microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD). PEO coatings characteristics like thicknesses, pore sizes, and layer homogeneity along the built direction of the printed part and its transversal direction were measured with the purpose to evaluate the effect of the anisotropic of printed substrates over the PEO layer growth. For comparative analysis, PEO coatings on the forged substrates were evaluated to analyze the effect of different microstructures with respect to substrates manufactured by the EBM technique. According to previous microstructure characterization of substrates, the analysis shows a differential growth of the anodic layer on substrates manufactured by EBM due to the presence of beta and alpha phases in Ti-6Al-4V and the difference in grain size related to the build direction of the printed part and its transversal direction.
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| 5. |
- Botero, Carlos Alberto, et al.
(författare)
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Microstructural and mechanical evaluation of a cr-mo-v cold-work tool steel produced via electron beam melting (Ebm)
- 2021
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a highly alloyed cold work tool steel, Uddeholm Vanadis 4 Extra, was manufactured via the electron beam melting (EBM) technique. The corresponding material microstructure and carbide precipitation behavior as well as the microstructural changes after heat treatment were characterized, and key mechanical properties were investigated. In the as-built condition, the mi-crostructure consists of a discontinuous network of very fine primary Mo-and V-rich carbides dispersed in an auto-tempered martensite matrix together with ≈15% of retained austenite. Adjusted heat treatment procedures allowed optimizing the microstructure by the elimination of Mo-rich carbides and the precipitation of fine and different sized V-rich carbides, along with a decrease in the retained austenite content below 2%. Hardness response, compressive strength, and abrasive wear properties of the EBM-manufactured material are similar or superior to its as-HIP forged counterparts manufactured using traditional powder metallurgy route. In the material as built by EBM, an impact toughness of 16–17 J was achieved. Hot isostatic pressing (HIP) was applied in order to further increase ductility and to investigate its impact upon the microstructure and properties of the material. After HIPing with optimized protocols, the ductility increased over 20 J.
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| 6. |
- Botero, Carlos Alberto, et al.
(författare)
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Microstructure and nanomechanical behavior of modified 316L-based materials fabricated using EBM
- 2018
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Konferensbidrag (refereegranskat)abstract
- Stainless steel 316L based materials modified by the additions of iron-based wear-resistant alloys (Colferoloy@ 103 and 139) used for thermal spray coatings applications were fabricated by EBM. Process parameters were tailored to fabricate compact specimens of 1cm3 in an Arcam A2 (Arcam AB, Mölndal, Sweden) at Mid Sweden University. Microstructural features of the materials obtained were characterized by OM and SEM in polished and etched samples. Nanoindentation tests carried out at different penetration depths were performed on selected areas of the polished specimens to evaluate the materials micro/nano mechanical behavior and to establish correlations with the observed microstructure.
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| 7. |
- Botero, Carlos Alberto, et al.
(författare)
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Nanoscratch Testing of 3Al2O3·2SiO2 EBCs : Assessment of Induced Damage and Estimation of Adhesion Strength
- 2023
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Ingår i: Ceramics. - : MDPI AG. - 2571-6131. ; 6:1, s. 664-677
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the structural integrity of mullite (3Al2O3·2SiO2) films, deposited on silicon carbide (SiC) substrates using chemical vapor deposition (CVD), was investigated via increasing load nanoscratch tests. The films were configured by mullite columns of stoichiometric composition growing from a silica-rich layer in contact with the SiC substrate. Controlled damage was induced in the 3Al2O3·2SiO2 films at relatively low scratch loads. Radial and lateral cracking were applied until final delamination and repeated chipping were achieved as the load increased. The intrinsic integrity of the 3Al2O3∙2SiO2 film and the performance of the coated 3Al2O3·2SiO2/SiC system, regarded as a structural unit, were analyzed. With the aid of advanced characterization techniques at the surface and subsurface levels, the configuration and morphology of the damage induced in the coated system by the nanoscratch tests were characterized, and the scratch damage micromechanisms were identified. Finally, the adhesion of the film, in terms of energy of adhesion and interfacial fracture toughness, was determined using different models proposed in the literature. The results from this investigation contribute to the understanding of the mechanical performance and structural integrity of EBC/SiC-based systems, which over the past few years have increasingly been implemented in novel applications for gas turbines and aircraft engines.
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| 8. |
- Botero Vega, Carlos Alberto, et al.
(författare)
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Additive Manufacturing of a Cold-Work Tool Steel using Electron Beam Melting
- 2020
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 19:5, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Metal additive manufacturing (AM) is on its way to industrialization. One of the most promising techniques within this field, electron beam melting (EBM), is nowadays used mostly for the fabrication of high‐performance Ti‐based alloy components for the aerospace and medical industry. Among the industrial applications envisioned for the future of EBM, the fabrication of high carbon steels for the tooling industry is of great interest. In this context, the process windows for dense and crack‐free specimens for a highly alloyed (Cr–Mo–V) cold‐work steel powder are presented in this article. High‐solidification rates during EBM processing lead to very fine and homogeneous microstructures. The influence of process parameters on the resulting microstructure and the chemical composition is investigated. In addition, preliminary results show very promising mechanical properties regarding the as‐built and heat‐treated microstructure of the obtained material.
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| 9. |
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| 10. |
- Koptioug, Andrei, 1956-, et al.
(författare)
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Compositionally-tailored steel-based materials manufactured by electron beam melting using blended pre-alloyed powders
- 2020
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 771
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the prospects of additive manufacturing (AM) in metal, using the powder bed fusion (PBF) method Electron Beam Melting (EBM) in fabrication specific steel-based alloys for different applications. The proposed approach includes manufacturing of metals from blended pre-alloyed powders for achieving in situ alloying and the material microstructure tailoring by controlling electron beam energy deposition rate EBM tests were conducted with the blends of 316L stainless steel and Colferoloys 103 and 139, corrosion- and abrasion-resistant iron based materials commonly used for plasma spray coating. Thorough microstructure analysis of the manufactured sample was carried out using electron microscopy and measurements of microhardness and elastic modulus was carried out using nanoindentation. It is concluded that implementation of blended powder pathway in PBF AM allows to widen the scope of available materials through diminishing the dependence on the availability of pre-alloyed powders. Together with beam energy steering this pathway also allows for an effective sample microstructure control at different dimensional scales, resulting in components with unique properties. Therefore, the implementation of ‘blended powder pathway’ in PBF AM provides a possibility of manufacturing components with the composite-like and homogeneous zones allowing for the microstructure control and effectively adding a “4th dimension” to “3D printing".
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