Enhancement of boiling performance on a surface modified by micro/millimeter-posts and nanoparticles

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Effects of elevated temperature exposure on the residual stress state and microstructure of PVD Cr coatings on SiC investigated via in situ X-ray diffraction and transmission electron microscopy

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A novel approach for manufacturing oxide dispersion strengthened (ODS) steel cladding tubes using cold spray technology

A novel fabrication method of oxide dispersion strengthened (ODS) steel cladding tubes for advanced fast reactors has been investigated using the cold spray powder-based materials deposition process. Cold spraying has the potential advantage for rapidly fabricating ODS cladding tubes in comparison with the conventional multi-step extrusion process. A gas atomized spherical 14YWT (Fe-14%Cr, 3%W, 0.4%Ti, 0.2%Y, 0.01%O) powder was sprayed on a rotating cylindrical 6061-T6 aluminum mandrel using nitrogen as the propellant gas. The powder lacked the oxygen content needed to precipitate the nanoclusters in ODS steel, therefore this work was intended to serve as a proof-of-concept study to demonstrate that free-standing steel cladding tubes with prototypical ODS composition could be manufactured using the cold spray process. The spray process produced an approximately 1-mm thick, dense 14YWT deposit on the aluminum-alloy tube. After surface polishing of the 14YWT deposit to obtain desired cladding thickness and surface roughness, the aluminum-alloy mandrel was dissolved in an alkaline medium to leave behind a free-standing ODS tube. The as-fabricated cladding tube was annealed at 1000 °C for 1 h in an argon atmosphere to improve the overall mechanical properties of the cladding. Keywords: Oxide dispersion strengthened steel, 14YWT powder, Cold spray process, ODS tube manufacturin

In-situ synthesis of nitrides and oxides through controlling reactive gas atmosphere during laser-powder bed fusion of Fe-12Cr-6Al

This study endeavors to investigate the feasibility of in situ synthesis of nitrides and oxides within Fe-12Cr-6Al alloys through precise modulation of reactive gas atmosphere during the Laser-Powder Bed Fusion process. A focused study on elucidating the effects of critical process parameters, such as laser power, scanning speed, and hatch distance, was undertaken to discern their impact on the material's microstructure, oxygen/nitrogen content, and hardness. Synthesis of nano-sized AlN and Al2O3 precipitates within the Fe-12Cr-6Al matrix was achieved when nitrogen was used for a process gas. A rise in laser power from 120 W to 200 W, coupled with a reduction in scanning speed from 1200 mm/s to 400 mm/s, resulted in decreased porosity and an increase in grain size. Additionally, all printed samples showed lower oxygen content compared to the initial powder, while nitrogen ratios were notably higher. A marginal increase of the Vickers hardness value, from 240 ± 4.5 to 266 ± 3 HV, was observed as the laser power increased and the scanning speed decreased. The hardness values were higher than those obtained from different production methods with identical compositions. These compelling results suggest a positive impact of nitride precipitates and oxide precipitates to improve hardness values

Pre-Oxidation Effect of a Zirconium-silicide Sputtered Surface on Boiling Performance and Oxidation Resistance

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Enhancement of flow boiling performance of Zirconium-Silicide ATF by electrophoretic deposition (EPD)

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Initial study on thermal stability of cold spray tantalum coating irradiated with deuterium for fusion applications

International audienceRemoval of neutral hydrogen atoms in the plasma edge reduces the number of charge exchange events and thus, the net energy losses in the plasma, significantly improving performance of fusion devices. Effective control of the residual pressure of hydrogen isotopes (HIs) in the plasma edge may be achieved by utilizing a hydrogen absorbing first wall interface capable of withstanding the harsh fusion environment. In this study, we have investigated tantalum (Ta) coating deposited by cold spray technology on 316L stainless steel substrate as a potential plasma-facing material surface. High fluence low energy deuterium plasma irradiation experiments and subsequent thermal annealing cycles associated with thermal desorption spectrometry (TDS) demonstrated superior structural stability of the Ta coating. TDS experiments revealed the outgassing of deuterium (as measure of its retention) for cold spray Ta coatings to be three times higher than bulk Ta and two orders of magnitude greater than bulk polycrystalline W. X-ray photoelectron spectroscopy revealed evolution of oxidation states upon deuterium irradiation and a partial recovery of the metallic signature of Ta after the thermal treatment at 1100 K