•Effect of Laser Processing Parameters on Microstructure and wear resistance.•Laser cladding of a Metco 1040 powder over a Hadfield steel.•Tribological behavior of the coating material assessed by ...pin-on-drum test.•Metco 1040 alloy has the same wear resistance as the Hadfield Steel.
Hardfacing of Ni and Co-based alloys has been widely applied to extend the lifespan of components that operating under severe conditions. The recent development of computational tools, such as Scorpeta from Oerlikon Metco, has allowed the design of alloys with customized properties. Metco 1040® (Fe-V-Mn-C) is a novel hardfacing alloy designed by the Scorpeta process to improve the abrasion and impact resistance of manganese steel substrates. However, few authors have addressed its wear performance. Therefore, the purpose of this study was to evaluate the effect of the processing parameters on the microstructure and wear resistance of the Metco 1040® alloy deposited by laser cladding on Hadfield steel. Single beads were deposited on Hadfield steel substrates according to a full factorial design of experiment (DOE), in which the laser power and deposition scanning speed were varied with 3 levels (32). Using some selected parameters, areas were covered by depositing parallel beads with an overlap of 30%, aimed at assessing the wear resistance through the “pin on drum” test. On applying the response surface method, it was found that the observed effects of the processing parameters (laser power and scanning speed) on the bead geometry (height, width and dilution) corroborate the current literature. For a given scanning speed, the higher the laser power the larger the carbide size and interdendritic spacing will be. The deposition parameters had no significant effect on the hardness or wear resistance of the coatings. However, the coating performance was significantly higher than that of Hadfield steel substrate. The findings reported herein suggest that the Metco 1040 alloy can be used to extend the lifespan of components of Hadfield steel.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this work was to evaluate the effect of different heat treatment routes on the microstructure and sliding wear resistance of Inconel 718 alloy deposited by laser cladding on an AISI 316 L ...stainless steel substrate. Three heat treatment conditions were tested: double aged, solubilized and double aged, and homogenized, solubilized and double aged. These conditions were compared between each other and the as built samples. Both as built and double aged conditions presented a dendritic microstructure. The solubilized and double aged samples exhibited a recrystallized characteristic, however still containing a dendritic structure. While the homogenized, solubilized and double aged samples reveled equiaxial grains with the total replacement of the dendrites. Regarding the top and cross-section hardness, the heat-treated claddings were superior (about 65% higher) when compared to the as built condition. The friction coefficient for all conditions were statistically equal, however the solubilized and double aged and homogenized, solubilized and double aged conditions showed better results of wear loss (about 25% lower) when compared to the as built condition, whereas the double aged condition displayed statistically equal results in relation to the others. The wear mechanisms were predominantly adhesive for the as built conditions, adhesive and abrasive for the double aged and mostly abrasive for the solubilized and double aged and homogenized, solubilized and double aged samples. The results presented confirmed the need for heat treatment to improve the hardness of the coating and, in addition, it can be concluded that the different heat treatment routes did not have significant impacts on wear resistance. Therefore, from the conditions tested in this study it is possible to assume that the double aged route is the most suitable, for the point of view of wear resistance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Resumo: O presente trabalho teve como objetivo determinar parâmetros de processamento a laser para deposição de revestimentos de Stellite 6 livres de descontinuidades e com geometria adequada sobre ...aço inoxidável austenítico. Revestimentos foram depositados com uma fonte de laser de diodo, equipada com um cabeçote coaxial contínuo, utilizando diferentes potências do feixe e velocidades de varredura. A geometria (largura, altura, ondulação e diluição) dos revestimentos foi medida por meio de análise da secção transversal. Esses dados obtidos foram utilizados para a modelagem do processo (superfície de resposta) e para estimar parâmetros otimizados (função desejabilidade), que foram posteriormente verificados experimentalmente. A microestrutura dos revestimentos depositados com os parâmetros otimizados foi caracterizada por microscopia óptica e eletrônica de varredura. A seleção adequada dos parâmetros resultou em revestimentos com bom acabamento, livre de descontinuidades superficiais e baixa diluição. Os resultados mostram que a potência do laser teve efeito significativo sobre a diluição, enquanto a velocidade influenciou na altura da camada depositada. A microestrutura resultante do revestimento é composta por dendritas ricas em cobalto e a região interdendrítica com carbonetos de cromo. Os resultados de dureza estão de acordo com o previsto na literatura.
Abstract: The present work aimed to determine laser processing parameters for deposition of defect-free Stellite 6 coatings and with suitable geometry on austenitic stainless steel. Coatings were deposited with a diode laser source, equipped with a continuous coaxial head, using different beam powers and scanning speeds. The geometry (width, height, undulation and dilution) of the coatings was measured by analyzing the cross section. These obtained data were used to model the process (response surface) and to estimate optimized parameters (function desirability), which were later verified experimentally. The microstructure of the coatings deposited with the optimized parameters was characterized by optical and scanning electron microscopy. The proper selection of parameters resulted in coatings with good surface finish, free of superficial defects and low dilution. The results show that the laser power had a significant effect on the dilution, while the speed influenced the height of the deposited layer. The microstructure resulting from the coating is composed of dendrites rich in cobalt and interdendritic region with chromium carbides. The hardness results are in line with the predicted in the literature.
The purpose of this study was to evaluate the effect of build direction on the mechanical properties of AISI 316L stainless steel using the Laser Directed Energy Deposition (L-DED) process, in the ...as-built and heat-treated conditions. The test specimens were manufactured in vertical and horizontal directions for tensile and impact tests. In addition, analysis test specimens cube-shaped were manufactured for microstructural and microhardness evaluation. The microstructure in the as-built condition showed a combination of cellular, equiaxial dendritic, cellular dendritic and columnar dendritic, while the microstructure in the heat-treated condition showed a homogeneous characteristic, composed by differently sized grains. The microhardness evaluation in the heat-treated condition presented a reduction of 26.52% compared to the as-build condition. The ultimate tensile strength of horizontal test specimens in the as-built condition was 4.86% higher than the heat-treated condition, whereas the ultimate tensile strength of vertical test specimens in the as-built condition was 5.55% higher than the heat-treated condition. The impact resistance of horizontal test specimens in the heat-treated condition was 12.36% higher than the as-built condition, whereas the impact resistance of vertical test specimens in the heat-treated condition was 18.92% higher than the as-built condition. Briefly, the build direction directly affects the mechanical properties of components manufactured through the L-DED process, and it is possible to improve certain mechanical properties, such as ductility and toughness, through heat treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The present work aimed to assess the combination of the use of an empirical-statistical model and design of experiments (DoE) to minimally validate the geometrical characteristics (dilution, coating ...height, waviness and porosity) of a laser-induced Inconel 625 coating on AISI 316L substrate. Employing the estimated laser processing parameters, a verification coating was deposited to assess its microstructure, microhardness and bending resistance. The statistical model showed to be an efficient computational tool for the planning of the design of experiments (DoE), resulting in errors less than 15% for all geometrical characteristics evaluated. The presence of some pores along the verification Inconel 625 coating was observed. Additionally, the verification coating showed good dilution and low waviness. Regarding the microstructure and microhardness, the verification coating showed a columnar dendritic microstructure, and its microhardness was about 110% higher than that observed for the AISI 316L substrate. Its resistance to bending was 30% higher when compared to that of the uncoated samples. By considering the experimental conditions explored within this work, one can state that the laser-cladded Inconel 625 coatings performed well on AISI 316L stainless steel substrate.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Gold NPs incorporated on CeO2 nanowires were produced by a simple approach.•CeO2-Au NPs as efficient catalysts towards the selective oxidation of thioanisole.•The control of physical ...and chemical parameters led to high active surface sites.•Strong metal–support interactions enabled higher concentration of oxygen vacancies.
Gold nanoparticles incorporated on ceria nanowires have been employed as efficient nanocatalysts for the selective oxidation of thioanisole. The control of both physical and chemical parameters as well as metal–support interactions are important factors that determine their performances. Considering their one-dimensional morphology with large surface area, thin diameters, high concentration of oxygen vacancies, and small Au NPs uniformly on the entire CeO2 surface with a high fraction of oxidized gold species, these characteristics make them favorable nanocatalysts for oxidation transformations. The CeO2-Au nanowires displayed improved performances towards the oxidation of thioanisole when compared to the pure CeO2 nanowires and commercial CeO2-Au catalysts. The CeO2-Au nanowires catalyzed the selective synthesis of methyl phenyl sulfoxide with up to 100 % of selectivity and high conversion. The impact of solvent and temperature during the catalytic reaction was also experimentally and theoretically investigated by DFT calculations, indicating a key role in the observed activities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Purpose: To evaluate the stability and arthrosis of the knee 10 to 15 years after arthroscopic-assisted anterior cruciate ligament (ACL) reconstruction with patellar tendon graft. Methods: From July ...1986 to March 1991, 82 patients underwent arthroscopic-assisted ACL reconstruction with patellar tendon graft. Of these, 62 returned for follow-up evaluation between November 2000 and April 2001. Four different physicians, blinded to each other’s examination findings, evaluated the radiologic as well as surgical results according to the International Knee Documentation Committee criteria and the Lysholm knee scoring scale. Results: There were 47 male and 15 female patients. The mean period between injury and surgery was 16 months (range, 2 weeks to 8 years). Results of radiographs were compared with the finding of meniscal lesions during surgery and with International Knee Documentation Committee test results. A statistically significant association ( P < .0001) was found between medial or lateral arthrosis of the knee and meniscal injury. In all patients the presence of tears in both menisci was associated with osteoarthrosis in both compartments (medial and lateral). Conclusions: In patients who underwent arthroscopic-assisted ACL reconstruction with patellar tendon graft who also had medial or lateral meniscectomy (or both), arthrosis of the respective compartments developed by 10 to 15 years after reconstruction. Meniscectomy was also associated with poorer results on objective tests of knee function, even with a stable knee joint. Level of Evidence: Level IV, therapeutic case series.
Background. Previous studies have suggested that guarana (Paullinia cupana) and açai (Euterpe oleracea) have antioxidant, anti-inflammatory, and proliferative properties, indicating their potential ...therapeutic action in wound healing. We produced a conjugated guarana-açai (GA) extract and tested its healing action on earthworms (Eisenia fetida) subjected to tail amputation by surgical incision. Methods. Extract from roasted guarana seeds and fresh açai seed berries was produced. The antioxidant and genoprotective capacity of GA extract was tested. The concentration with the most remarkable healing potential was used in subsequent tests. The last three posterior segments of the clitellate earthworm tail reared under standardized conditions were surgically amputated. Next, topical PBS or GA extract was applied to the surgical wound. The rate of cell migration and tissue regeneration at the local wound site was histologically evaluated after the procedure. Expression of the SOX4 gene that acts in epithelial-to-mesenchymal transition was determined by RT-qPCR. Results. Sixteen bioactive molecules, including some previously described substances, were identified. All tested concentrations exhibited antioxidant and genoprotective effects. The GA extract accelerated the healing processes as observed through macroscopic and histological analyses and increased expression of SOX4. Conclusion. The GA extract has a potential role in the healing of surgically induced wounds.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Barbatimão (Stryphnodendron adstringens, Mart.) is a native Brazilian species used in traditional medicine and some commercial preparations owing to its strong wound-healing activity. However, ...controversy regarding its use due to safety concerns over the potential genotoxic effect of this plant remains. In order to clarify this issue, the effect of hydroalcoholic extract of barbatimão in vitro on cell viability, DNA damage, and induction of apoptosis in two commercial cell lines of keratinocytes (HaCaT) and fibroblasts (HFF-1) was evaluated. Barbatimão stem bark hydroalcoholic extract (70% ethanol) was obtained and lyophilized for subsequent use in all experiments. The main bioactive molecules quantified by HPLC were gallic acid, caffeic acid, quercetin, catechin, and epigallocatechin gallate (EGCG). Barbatimão (0.024 to 1.99 mg/mL) was found to decrease cellular mortality as compared to the control group. GEMO assay, a noncellular DNA protocol that uses H2O2-exposed calf thymus DNA, revealed not only a genotoxic effect of barbatimão, but also a potential genoprotective action against H2O2-triggered DNA fragmentation. These results indicated that barbatimão at concentrations of 0.49 and 0.99 mg/mL, which are near to the levels found in commercial preparations, exerted an in vitro genoprotective effect on cells by decreasing the levels of DNA oxidation quantified by 8-hydroxy-2′-deoxyguanosine (8-OHdG) and reactive oxygen species (ROS) levels. Gene and protein apoptotic markers, quantified by qRT-PCR (BAX/Bcl-2 genes) and immunoassays (Caspases 3 and 8), respectively, also indicated a decrease in apoptotic events in comparison with control cells. Collectively, the results suggest that barbatimão could exert genoprotective and antiapoptotic effects on human keratinocytes and fibroblasts.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
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