La proyección térmica o rociado térmico es una tecnología que implica calentar un material que está en forma de polvo o alambre y llevarlo a un estado fundido o semifundido, para luego propulsarlo mediante una corriente de gas o aire comprimido y depositarlo sobre un sustrato metálico, cerámico o polimérico, que tenga condiciones de rugosidad adecuadas. La investigación realizó la caracterización electroquímica mediante las técnicas de espectroscopia de impedancia electroquímica y ruido electroquímico de una aleación Zn-15Al depositada sobre una fundición nodular grado 65-45-12 (2), por medio de la técnica de proyección térmica por llama con alambre, donde el recubrimiento de Zn-Al presenta buena homogeneidad, buena adherencia y una mejora sustancial en la resistencia a la corrosión.
<p>Three materials were made with mixtures of virgin expanded polystyrene (EPS) grade S3 and recycled material from multipurpose EPS packaging. The latter was subjected to washing and grinding in a blade mill, with percentages by weight of recycled material 10, 15, and 20%. The mechanical properties of these materials were evaluated by testing compressive strength and flexural, impact, and thermal properties using the techniques of differential scanning calorimetry and thermogravimetry. Hot plate and steady state temperature profiles in a non-steady state were simulated with Octave 3.6.4. The results obtained for the three mixtures showed little variation in the properties of compression, impact, glass transition, and thermal diffusivity with respect to the reference material. The regularity of the decline in mass loss as a function of temperature evidences homogeneity in the samples. The flexural strength decreased the maximum failure load compared to the virgin material, and the thermal conductivity exceeded 0.06W/mK, reducing their insulating capacity. These materials can be industrially manufactured in order to produce packaging, caissons, and spheres, among other things.</p>
Objective: In this work, niobium carbide (NbC) coatings were deposited on substrates of the tool steels AISI H13 and AISI D2 using thermo-reactive deposition/diffusion (TRD) in order to analyze their behavior against corrosion in a saline environment. Materials and methods: The niobium carbides were obtained using salt baths composed of borax pentahydrate, aluminum and ferroniobium. This mixture was heated at 1050 °C for 4 hours. The chemical composition was determined by X-ray fluorescence (XRF). The coatings were morphologically characterized using scanning electron microscopy (SEM), the crystal structure was analyzed using X-ray diffraction (XRD), and the electrochemical behavior was studied using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results and discussion: The XRF analysis indicated that the coatings contained 87.476 wt% Nb and 51.943 wt% Nb for the D2-substrate and the H13-substrate, respectively. The SEM images revealed that the morphology of the surface of the coatings was homogeneous. The XRD analysis established that the coatings were polycrystalline, and the electrochemical tests established that the corrosion resistance increased slightly in the covered substrates with respect to the uncoated steels, with the best results being obtained in the layers of niobium carbide deposited on AISI D2 steel. Conclusions: The analysis of corrosion resistance revealed that the coatings prepared on D2 steel have a higher corrosion resistance because they have fewer surface imperfections, which causes the coating to exhibit a dielectric behavior.
Películas delgadas de Ti-Zr-Si-N se depositaron sobre sustratos de acero inoxidable 316 L usando la técnica de co-sputtering reactivo. El análisis de la estructura se realizó mediante difracción de rayos X (DRX), el análisis morfológico se realizó por microscopía electrónica de barrido (MEB) y microscopía óptica 3D. Los estudios de oxidación cíclica se realizaron en un horno en ambiente seco con un total de 300 ciclos, cada uno con una tasa de calentamiento de 46 °C/min hasta lograr una temperatura de 600 °C, la cual fue sostenida durante 30 min y finalmente enfriado a 20 °C/min. Los recubrimientos mejoraron la resistencia a la corrosión del acero inoxidable a altas temperaturas en un 30% debido a la formación de óxidos protectores. En este trabajo se discute el mecanismo de corrosión por oxidación cíclica para los recubrimientos realizados.
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