Examinando por Autor "Bedmar, J."

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    Impact of molten salts composition on the corrosion behavior of NiMoCr and CoNiCrAl coatings on L-PBF 316L stainless steel for CSP plants
    (Elsevier, 2024-04-30) Abu-warda, Najib; Bedmar, J.; García-Rodríguez, S.; Utrilla, M.V.; Torres, B.; Rams, J.
    The high-temperature corrosion performance of NiMoCr and CoNiCrAl coatings produced by high velocity oxy-fuel (HVOF) on laser powder bed fusion (L-PBF) 316L stainless steel substate has been evaluated in presence of three different molten salts used as thermal energy storage (TES) materials for concentrated solar power (CSP) plants. The coatings have an excellent oxidation resistance at 700 °C, showing a percentage of affected thickness lower than 2 %, due to the formation of a protective layer of Cr2O3 and Al2O3 in both NiMoCr and CoNiCrAl coatings, respectively. The carbonates-based molten salt accelerates the corrosion of the NiMoCr coating, affecting around 43 % of the coating thickness, due to the formation of chromates and the high depletion of Mo in the coating. In contrast, the effective protection shown by the CoNiCrAl coating is explained because the grown LiAlO2 after the lithiation process has a high capacity to act as a strong diffusion barrier for metal ions and inhibited the formation of chromates. In the presence of two different ZnCl2 and MgCl2-rich molten salts, the CoNiCrAl coating behaved worse than NiMoCr coating due to the breakage of the (Al,Cr)-rich oxide layer as a consequence of an active oxidation mechanism and due to the formation of voids along the entire thickness, which were identified in 100 % of the coating thickness. The superior corrosion resistance of the NiMoCr coating in presence of the chloride rich molten salts was attributed to the presence of Mo, which fixed the Cr and inhibited the diffusion of oxygen
  • Miniatura
    Ítem
    Microstructure and corrosion behavior of 316L stainless steel lattice and bulk parts manufactured by LPBF using fiber and CO2 lasers
    (Elsevier, 2024-08) García-Rodríguez, S.; Bedmar, J.; Abu-warda, N.; Torres, B.; Rams, J.
    AISI 316L stainless steel lattices were manufactured using two distinct Laser Powder Bed Fusion (LPBF) techniques: a commercial printer equipped with a fiber laser and a novel system equipped with a CO2 laser. Fiber laser systems produce parts exhibiting superior detail, finer cell size, and lower porosity compared to CO2 laser ones because of the stability of the laser beam and the higher absorptivity of the laser light by the material powder. Electrochemical tests indicated that lattices exhibited inferior corrosion resistance compared to solid counterparts for both manufacturing techniques. This disparity is caused by the distinct corrosion mechanisms exhibited by lattices and solid parts, as observed through Electrochemical Impedance Spectroscopy (EIS). The observed differences are attributed not only to the increased different specific surface areas but also to the distinctive morphologies formed in the material beneath the surface. CO2 LPBF lattices demonstrated higher corrosion sensitivity than the fiber LPBF lattices due to their distinct microstructure and the more prevalent presence of defects