Badea Teodor-Adrian, Dombrovschi Mădălin
Romanian Research and Development Institute for Gas Turbines COMOTI, 220D Iuliu Maniu Av., 061126 Bucharest, Romania.
Materials (Basel). 2025 Apr 28;18(9):1996. doi: 10.3390/ma18091996.
Nickel-based superalloys are extensively used in high-temperature applications because of their exceptional oxidation and corrosion resistance. However, their performance in aggressive environments containing molten salts, such as NaSO and VO, remains a critical challenge. This study investigated the hot corrosion behavior of Inconel 718, Udimet 710, Nimonic 75, and Inconel 625, focusing on the role of the alloying elements in the corrosion layers and degradation mechanisms. The superalloys were exposed to 50/50 wt.% NaSO-VO at 900 °C for 8, 48, and 96 h, and their corrosion resistance was evaluated through weight gain measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). These results indicate that Mo is a key factor in accelerating degradation, with Inconel 625 exhibiting the highest weight gain owing to the formation of thermally unstable Mo-rich phases. Fe also negatively impacted the stability of the protective scale of Inconel 718, contributing to an increased corrosion rate. In contrast, Nimonic 75 exhibited the best resistance, forming more of the NiCrO spinel phase through the reaction of CrO with NiO from the high Ni and Cr contents in the corrosive layers. These findings highlight the importance of alloy composition in optimizing corrosion resistance and suggest that using superalloys with lower Mo and Fe contents and higher Cr and Ni concentrations can significantly enhance the durability of superalloys in molten salt environments.
镍基高温合金因其出色的抗氧化和耐腐蚀性能而广泛应用于高温领域。然而，它们在含有熔盐（如NaSO和VO）的侵蚀性环境中的性能仍然是一个关键挑战。本研究调查了Inconel 718、Udimet 710、Nimonic 75和Inconel 625的热腐蚀行为，重点关注合金元素在腐蚀层中的作用和降解机制。将这些高温合金在900℃下暴露于50/50 wt.%的NaSO-VO中8、48和96小时，并通过重量增加测量、扫描电子显微镜（SEM）和能量色散X射线光谱（EDS）评估它们的耐腐蚀性。这些结果表明，Mo是加速降解的关键因素，Inconel 625由于形成热不稳定的富Mo相而表现出最高的重量增加。Fe也对Inconel 718的保护氧化皮的稳定性产生负面影响，导致腐蚀速率增加。相比之下，Nimonic 75表现出最佳的耐腐蚀性，通过腐蚀层中高Ni和Cr含量的CrO与NiO反应形成更多的NiCrO尖晶石相。这些发现突出了合金成分在优化耐腐蚀性方面的重要性，并表明使用Mo和Fe含量较低且Cr和Ni浓度较高的高温合金可以显著提高高温合金在熔盐环境中的耐久性。
