Examinando por Autor "Múnez, Claudio J."

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Alternative low-power plasma-sprayed inconel 625 coatings for thermal solar receivers: Effects of high temperature exposure on adhesion and solar absorptivity
(Elsevier, 2022) Merino-Millan, David; Múnez, Claudio J.; Garrido-Maneiro, Miguel Ángel; Poza, Pedro
Over recent years, renewable energy technologies have focused on increasing performance and efficiency, and on the reduction of maintenance costs. In this work, thermal-sprayed Inconel 625 coatings have been studied as an alternative for concentrated solar power plants receivers. A low-power compact plasma spray system was used to deposit coatings onto two substrates: grade 22 ferritic steel and AISI 316 L austenitic steel. This system may be used for in-situ maintenance or repair purposes. The coatings were heat-treated at two temperatures: 520 ◦C and 800 ◦C, at different exposure times. The aim of this work was to evaluate the effect of this treatment on the adherence and solar absorptivity of the Inconel 625 coatings. The results showed that, at higher temperatures and longer exposure times, better adherence and absorptivity are achieved. Adherence values above 60 MPa were obtained due to diffusion in the coating-substrate interface. Additionally, absorptivity values above 93% were measured due to oxide formation on the coating surface during heat treatment. Furthermore, the highest temperature of the oxidized treatment reported the highest values of absorptivity. These results show that the developed Inconel 625 coatings could be considered as a possible alternative to improve the performance of concentrated solar power plants.
Hardness and Young's modulus evolution of low-power plasma sprayed Inconel 625 coatings exposed to high temperatures
(Elsevier, 2024-10-30) Merino-Millán, David; Garrido-Maneiro, Miguel Ángel; Múnez, Claudio J.; Poza, Pedro
The use of renewable energy sources has been increasing in recent years as it aims to balance the production of fossil fuels by 2050. Among the various alternatives, concentrated solar power plants are considered the most feasible due to their capability of storing energy. Ongoing research is conducted to enhance the performance of third-generation plants by achieving higher temperatures. It makes necessary to explore new materials. This research is focused on concentrated solar power plants with central tower receivers, for which coatings used nowadays do not withstand the new requirements. For this reason, an alternative plasma sprayed Inconel 625 coating has been proposed. This study confidently presents an analysis of the high temperature exposure effects on the coating's mechanical properties at two temperatures, 520 and 800 °C. The study focuses on the Young's modulus and hardness, and the results demonstrate a significant improvement in these properties due to the formation of secondary phases. Coating hardness increased gradually from 4.12 GPa to 5.3 GPa during exposition at 520 °C. In contrast, the increment was attained quickly during the first 24 h exposure at 800 °C, reaching 4.5 GPa, and then maintained for all times studied. The microstructure was characterized using transmission electron microscopy, which identified the presence of carbides and intermetallic phases. The application of these coatings will significantly enhance the performance of solar receivers due to their superior properties compared to the currently available Pyromark coatings