Caracterización microestructural de recubrimientos NiCoCrAlYTa obtenidos por láser coaxial y por refusión láser sobre AISI 316L

[ES] En este estudio se ha evaluado la microestructura de recubrimientos NiCoCrAlYTa depositados mediante la técnica de laser cladding coaxial, y en recubrimientos obtenidos por proyección térmica de alta velocidad (HVOF) y refundidos por láser, ambos sobre láminas de acero inoxidable AISI 316L. Se ha analizado la microestructura, variación de microdureza y composición química, mediante microscopía óptica, microscopía electrónica de barrido (MEB) y microanálisis por espectroscopía de energía dispersiva (EDS). Los recubrimientos obtenidos no presentan macro defectos importantes y existe una buena unión metalúrgica con el sustrato; no obstante, existe una estructura dendrítica columnar no homogénea que depende del procesado láser. Los análisis evidencian la disolución y mezcla de elementos químicos relevantes con el NiCr que generan una variación gradual entre sustrato y recubrimiento que influye en el endurecimiento observado en la intercara del recubrimiento. Se logra la densificación de los recubrimientos HVOF eliminando la porosidad inicial y mejorando su acabado superficial, diferencias en la disolución de elementos químicos han sido encontradas para las dos técnicas utilizadas, debido al espesor del recubrimiento obtenido y los parámetros láser utilizados.[EN] In this study the microstructure of NiCoCrAlYTa coatings deposited by coaxial laser cladding technique, and laser remelted coatings obtained previously by high velocity oxy fuel thermal spraying (HVOF), both on sheets of stainless steel AISI 316L, were evaluated. Optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy microanalysis have been used to analyze the chemical composition, microstructure, and microhardness. A coatings without cracks or macro pores and a good metallurgical bond with the substrate through the dilution zone was obtained; yet there is no a homogeneous columnar dendrite structure that depends of laser processing parameters. The analysis evidenced the dilution and mixing of relevant chemical elements such as Fe, Co, Al and Ta with Ni-Cr, generating a gradual variation between substrate and coating which influence the hardening observed at the interface of the coating. The densification is achieved by removing HVOF coating initial porosity and improving the surface finish, differences in the chemicals components dissolution have been found for the two techniques employed, influence by the thickness coating and by the laser parameters.Pereira Falcón, JC.; Candel Bou, JJ.; Amado, J.; Amigó Borrás, V. (2014). Caracterización microestructural de recubrimientos NiCoCrAlYTa obtenidos por láser coaxial y por refusión láser sobre AISI 316L. Revista Colombiana de Materiales. Especial(5):127-132. http://hdl.handle.net/10251/91890S127132Especial

Mixing Bandt-Pompe and Lempel-Ziv approaches: another way to analyze the complexity of continuous-states sequences

In this paper, we propose to mix the approach underlying Bandt-Pompe permutation entropy with Lempel-Ziv complexity, to design what we call Lempel-Ziv permutation complexity. The principle consists of two steps: (i) transformation of a continuous-state series that is intrinsically multivariate or arises from embedding into a sequence of permutation vectors, where the components are the positions of the components of the initial vector when re-arranged; (ii) performing the Lempel-Ziv complexity for this series of `symbols', as part of a discrete finite-size alphabet. On the one hand, the permutation entropy of Bandt-Pompe aims at the study of the entropy of such a sequence; i.e., the entropy of patterns in a sequence (e.g., local increases or decreases). On the other hand, the Lempel-Ziv complexity of a discrete-state sequence aims at the study of the temporal organization of the symbols (i.e., the rate of compressibility of the sequence). Thus, the Lempel-Ziv permutation complexity aims to take advantage of both of these methods. The potential from such a combined approach - of a permutation procedure and a complexity analysis - is evaluated through the illustration of some simulated data and some real data. In both cases, we compare the individual approaches and the combined approach.Comment: 30 pages, 4 figure

Trends in arsenic levels in PM10 and PM2.5 aerosol fractions in an industrialized area

Arsenic is a toxic element that affects human health and is widely distributed in the environment. In the area of study, the main Spanish and second largest European industrial ceramic cluster, the main source of arsenic aerosol is related to the impurities in some boracic minerals used in the ceramic process. Epidemiological studies on cancer occurrence in Spain points out the study region as one with the greater risk of cancer. Concentrations of particulate matter and arsenic content in PM10 and PM2.5 were measured and characterized by ICP-MS in the area of study during the years 2005-2010. Concentrations of PM10 and its arsenic content range from 27 to 46 mu g/m(3) and from 0.7 to 6 ng/m(3) in the industrial area, respectively, and from 25 to 40 mu g/m(3) and from 0.7 to 2.8 ng/m(3) in the urban area, respectively. Concentrations of PM2.5 and its arsenic content range from 12 to 14 mu g/m(3) and from 0.5 to 1.4 ng/m(3) in the urban background area, respectively. Most of the arsenic content is present in the fine fraction, with ratios of PM2.5/PM10 in the range of 0.65-0.87. PM10, PM2.5, and its arsenic content show a sharp decrease in recent years associated with the economic downturn, which severely hit the production of ceramic materials in the area under study. The sharp production decrease due to the economic crisis combined with several technological improvements in recent years such as substitution of boron, which contains As impurities as raw material, have reduced the concentrations of PM10, PM2.5, and As in air to an extent that currently meets the existing European regulations.The authors are grateful to Ilmo. Ayuntamiento de L'Alcora for the financial support through the 07I055 project, Generalitat Valenciana for their support and collaboration, and Miss Miriam Rubio Renau for her assistance in the laboratory work. 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Laser Cladding of MCrAlY coatings on stainless steel

MCrAlY alloys (where M stands for Ni,Co or both) are commonly used as overlay protective coatings in gas turbine engine components against high temperature oxidation and corrosion. The protective effect of these alloys is due to the formation of a continuous thermally stable oxide layer on the coating surface. In this work several types of MCrAlY alloys, differing in their elemental composition, have been deposited on austenitic stainless steel by means of laser cladding. The microstructure of the coatings have been characterized by SEM-EDS and XRD. As expected, elemental composition compatible with γ-Ni/γ'-Ni3Al, β-Ni/β'-NiAl or γCo/β-(Co,Ni)Al phases are observed in hypoeutectic or hypereutectic microstructures depending on the alloy composition. The high temperature oxidation behavior of the coatings was evaluated by air furnace oxidation tests at 1100ºC for 200 h. The oxidized surface of the samples was examined by SEM-EDS and the oxides present identified by theoretical stoichiometric calculations. Results indicate the formation of a uniform Al3O2 protective oxide scale with NiO, CoO, Y2O3/YAlO3 and Cr2O3 oxide inclusions.Tobar, M.; Amado, J.; Yáñez, A.; Pereira Falcón, JC.; Amigó Borrás, V. (2014). Laser Cladding of MCrAlY coatings on stainless steel. Physics Procedia. 56(C):276-283. doi:10.1016/j.phpro.2014.08.172S27628356

Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

[EN] The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed. © 2011 Published by Elsevier Ltd.This works has been done under the financial support of Xunta de Galicia, project reference 08DPI024CT, Programa de Diseno y Produccion Industrial.Amado Paz, JM.; Tobar Vidal, MJ.; Yañez Casal, AJ.; Amigó Borrás, V.; Candel Bou, JJ. (2011). Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding. Physics Procedia. 12(1):338-344. https://doi.org/10.1016/j.phpro.2011.03.043S33834412

Dynamical complexity of short and noisy time series: Compression-Complexity vs. Shannon entropy

Shannon entropy has been extensively used for characteriz- ing complexity of time series arising from chaotic dynamical systems and stochastic processes such as Markov chains. However, for short and noisy time series, Shannon entropy performs poorly. Complexity measures which are based on lossless compression algorithms are a good substitute in such scenarios. We evaluate the performance of two such Compression-Complexity Measures namely Lempel-Ziv complexity(LZ)andEffort-To-Compress( ETC)onshorttimeseriesfrom chaoticdynamicalsystemsinthepresenceofnoise.Both LZ and ETC outperform Shannon entropy (H) in accurately characterizing the dynamical complexity of such systems. For very short binary sequences (which arise in neuroscience applications), ETC has higher number of distinct complexity values than LZ and H, thus enabling a finer resolution. For two-state ergodic Markov chains, we empirically show that ETC converges to a steady state value faster than LZ. Compression-Complexity measures are promising for applications which involve short and noisy time series

Permutation entropy: One concept, two approaches

Since C. Bandt and B. Pompe introduced permutation entropy in 2002 for piecewise strictly monotonous self-maps of one-dimensional intervals, this concept has been generalized to ever more general settings by means of two similar, though not equivalent, approaches. The first one keeps the original spirit in that it uses “sharp” dynamics and the corresponding ordinal partitions. The second uses symbolic (or “coarse-grained” dynamics with respect to arbitrary finite partitions, as in the conventional approach to the Kolmogorov-Sinai entropy of dynamical systems. Precisely, one of the main questions along these two avenues refers to the relation between permutation entropy and Kolmogorov-Sinai entropy. In this paper the authors will explain the underpinnings of both approaches and the latest theoretical results on permutation entropy. The authors also discuss some remaining open questions