High-Temperature Oxidation of Superalloy C-263 of Rings for Aircraft Engines

The present investigation was conducted to study the oxidation kinetics of nickel-based superalloy 263, used in the manufacture of rings for aircraft engines. For carrying out this study, we first conducted microstructural characterization of the pieces using the techniques of optical microscopy, scanning electronic microscopy, and X-ray diffraction. Subsequently, using the thermogravimetric analysis, the kinetic oxidation of the metal was performed in a temperature range between 700 and 1000°C, using atmospheres of O2. The results of the micrographs show the formation of a protective oxide film on the surface of the material in different oxidizing agents. Finally, it was found that the kinetics of high-temperature oxidation of the superalloy C-263 obeys the parabolic rate law

Comportamiento a la Corrosión del Acero API X70 Soldado por el Proceso de Doble Arco Sumergido Inmerso en Diferentes Medios Corrosivos

Los aceros API X70 son aplicados en fabricación y construcción de tuberías para el transporte de hidrocarburos, sin embargo, a un lapso de tiempo se degradan debido al medio ambiente al cual están expuestos; influyendo en la velocidad y tipo de corrosión sobre las superficies del metal base (MB), zona afectada por el calor (ZAC) y zona de fusión (ZF). A fin de conocer y evaluar la susceptibilidad a la corrosión en uniones del acero API X70 sometido a diferentes medios corrosivos, varias pruebas se llevaron a cabo por el proceso de soldadura de doble arco sumergido (DSAW, por sus siglas en inglés), las cuales fueron inmersas en diferentes electrolitos: Cloruro de Sodio (NaCl al 3,5%) y Agua (H2O) a temperatura ambiente para conocer su comportamiento. Se utilizaron técnicas electroquímicas de ruido electroquímico (RE) y curvas de polarización cíclica (CPC) para obtener velocidad y tipo de corrosión producida en cada una de las muestras analizadas, incluyendo las tres zonas: MB, ZAC y ZF. Además, se utilizaron técnicas de caracterización como microscopía óptica (MO) y microscopía electrónica de barrido (MEB) para el análisis superficial. La mayoría de las soldaduras presentan corrosión mixta, con mayores velocidades de corrosión en 3,5% de NaCl

Simulations of a micro positioner and PCB design for measurement of SQUIDs

Resumen del trabajo presentado a la XII Reunión del grupo de física de la materia condensada de la RSEF (GEFES), celebrada en Salamanca del 1 al 3 de febrero de 2023.In this work, we present the design and fabrication of a micro positioner based on two complementary approaches. The first one employs capacitive actuators to implement movement in the x-y plane. On the other hand, C-MOS compatible piezoelectric materials will be used to control the displacement along the z axis. Here we present preliminary simulations performed with COMSOL Multiphysics that allow us to fine tune the geometrical parameters of the positioner considering different types of materials. In addition to that, simulations are used to estimate the resistance, Von Mises stress, shear forces, torsion forces and elastic constant which serve to calculate the final effective displacement and response of the device. The resulting micro positioners will be combined with ultrasensitive magnetic sensors such nanoSQUIDs (Superconducting QUantum Interference Devices). In this way, it will be possible to displace nanometric samples in close vicinity to the most sensitive regions of the nanoSQUID, to perform scanning magnetic imaging and reference measurements. In this poster, we present the progress made so far in this doctoral thesis work.Peer reviewe

Cobertura vegetal y la distribución de islas de calor/oasis urbanos en Hermosillo, Sonora

The case of an arid Northwest city of Mexico is studied with the general objective of assessing the influence of the percentage of vegetation cover (VC) in Land Surface Temperature (LST) and mapping its spatial distribution, through a geographic information system using remote sensing data. Results showed: 1) on average, 12% (min. 0 to max. 59%) of a city block is covered with vegetation, 38% of the blocks had % VC ≤ 10; 2) the LST regression model estimated temperatures range from 37 to 45°C, the main explanatory variable was % VC, increasing % VC in 10 is associated with cooling effect of 1.1 °C. The spatial heterogeneity in the distribution of LST can be interpreted as the human effect modifying the climate on a small scale; this creates internal diurnal oasis.Se analiza el caso de Hermosillo, una ciudad del noroeste árido de México. El objetivo general es conocer la influencia del porcentaje de cobertura vegetal (CV) en la temperatura superficial del suelo (LST) y su distribución espacial a través de un sistema de información geográfica, utilizando datos de teledetección remota. En cuanto a los resultados, destaca en primer lugar que en promedio el porcentaje de CV en manzanas urbanas es de 12 por ciento (rango 0 a 59%), con un 38 por ciento de éstas con una CV ≤ 10 por ciento. En segundo lugar, que el modelo para estimar la LST detectó temperaturas promedio por manzana entre los 37 y 45°C, la principal variable explicativa fue el porcentaje de CV. Aumentar la CV en un 10 por ciento tendría el potencial de disminuir la LST en 1.1 °C. La heterogeneidad espacial en la distribución de la LST puede interpretarse como el efecto del ser humano modificando el clima a pequeña escala, esto crea un mosaico interno de oasis urbanos diurnos

Corrosion Resistance Measurement of 316L Stainless Steel Manufactured by Selective Laser Melting

Selective laser melting (SLM) technology is ushering in a new era of advanced industrial production of metal components. It is of great importance to understand the relationship between the surface features and electrochemical properties of manufactured parts. This work studied the influence of surface orientation on the corrosion resistance of 316L stainless-steel (SS) components manufactured with SLM. The corrosion resistance of the samples was measured using linear polarization resistance (LPR) and electromechanical noise (EN) techniques under three different environments, H2O, 3.5 wt.% NaCl, and 20% H2SO4, analyzing the horizontal (XY) and vertical (XZ) planes. The microstructure and morphology of the samples were obtained by optical (OM) and scanning electron microscopy (SEM). The obtained microstructure showed the grains growing up from the fusion line to the melt pool center and, via SEM-EDS, the presence of irregular and spherical pores was observed. The highest corrosion rate was identified in the H2SO4 solution in the XZ plane with 2.4 × 10−2 mm/year and the XY plane with 1.31 × 10−3 mm/year. The EN technique along with the skewness factor were used to determine the type of corrosion that the material developed. Localized corrosion was observed in the NaCl electrolyte, for the XY and XZ planes (−1.65 and −0.012 skewness factors, respectively), attacking mainly the subgrains of the microstructure and, in some cases, the pores, caused by Cl ions. H2O and H2SO4 solutions presented a uniform corrosion mechanism for the two observed orientations. The morphology identified by SEM was correlated with the results obtained from the electrochemical techniques

Transformation temperatures and electrochemical behavior of polycrystalline Fe-Doped Ni-Mn-Ga and Co-Ni-Ga Alloys

"The effect of Fe addition on martensitic transformation temperatures and electrochemical behavior was studied in polycrystalline Ni51.4Mn24.8-XGa23.8FeX alloys (1<x<2.2) and Co38.3Ni32.1Ga29.6 as alternative to Ni-Mn-Ga alloys which are used as ferromagnetic shape memory alloys. The analysis of corrosion rates was conducted by cyclic polarization curves with potentiostat-galvanostat equipment. The corrosion morphologies were also analyzed by scanning electron microscopy (SEM). The kinetics of corrosion was found to decrease with increasing Fe content in the alloy, while the martensitic transformation temperatures increased with increasing Fe content. The Co38.3Ni32.1Ga29.6 alloy shows i(corr) lower than the Ni-Mn-Ga alloy. From results, the studied alloys exhibited a general dissolution in the anodic branch where a spontaneous passive zone occurred at certain potential and some elements like Co, Mn and also Ni were present in a higher percentage in corrosion deposits.

Corrosion Resistance of Titanium Alloys Anodized in Alkaline Solutions

Titanium alloys present superior electrochemical properties due to the generation of the TiO2 passive layer. The ability to generate an oxide passive layer depends on the anodized alloy. This work mainly studies the corrosion resistance of the alloys Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V anodized in NaOH and KOH at 1 M and 0.025 A/cm2 of current density. The electrochemical techniques were performed in a conventional three-electrode cell exposed to electrolytes of NaCl and H2SO4. Based on ASTM-G61 and G199, cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN) techniques were used. The results indicated that Ti-6Al-2Sn-4Zr-2Mo anodized on NaOH presented a higher passivity range than anodized on KOH, relating to the high reactivity of Na+ ions. The former anodized alloy also demonstrated a higher passive layer rupture potential. In EN, the results showed that Ti-6Al-4V anodized in KOH presented a trend toward a localized process due to the heterogeneity of anodized porosity and the presence of V in the alloy