ADVANCED MATERIALS & PROCESSES | APRIL 2025 5 RESEARCH TRACKS SPINEL HELPS SUPERALLOYS FACE EXTREME TEMPS A multi-institutional team including researchers at Virginia Tech discovered a promising candidate for a lubricant that works at extremely high temperatures: transition metal spinel oxides formed on nickel-chromium- base superalloys. Unlike common lubricants that break down under high heat, spinel oxide maintains lubrication up to 700°C, almost as hot as a metal forge. Enabling metallic materials to withstand higher temperatures could lead to innovations in metals manufacturing for industries like aerospace and nuclear energy. Spinels and spinel- structured oxides belong to a group of semiprecious gemstones sometimes found alongside rubies in rare rocks. The researchers found that the mineral possesses the unusual ability to self- lubricate under heat stress and friction. Yet it only appears to do so under specific circumstances, and only when paired with a certain superalloy. Demand for metal parts that resist wear at extremely high temperatures is becoming increasingly common in many industries. Solid lubricants such as thin layers of molybdenum disulfide and graphite on metal surfaces can help prevent this wear in some cases. However, none withstand temperatures greater than 600°C in tests, and not without corrosion. In the current study, researchers demonstrated a process by which an additively manufactured sample of Inconel 718 is lubricated by spinel at temperatures exceeding 600°C. Using a new approach, the team heat treated its surface before exposing it to these temperatures. The superalloy formed lubricating spinel-based oxides and did not thicken or lose friction tolerance. The scientists note that it could be the unique structure of spinel itself helping it outperform similar oxides as a lubricant. This research was supported by multiple grants from the National Science Foundation. nsf.gov. LEARNING WHY PLATINUM ELECTRODES CORRODE Scientists from Leiden University, the Netherlands, and the DOE’s SLAC National Accelerator Laboratory, Menlo Park, Calif., discovered the mysterious cause behind the rapid corrosion of platinum electrodes. The researchers believe this break- through could lead to applications such as more affordable green hydrogen Hydride formation on a platinum surface. Courtesy of Nature Materials, 2025, doi.org/10.1038/s41563-024-02080-y. production and more reliable electrochemical sensors. With most metals, being negatively polarized protects against corrosion. However, platinum electrodes can rapidly break down under these conditions. “If you take a piece of platinum and you apply a very negative potential, you can dissolve your platinum in a matter of minutes,” says Marc Koper, the Leiden team’s principal investigator. The team knew they would need to observe platinum as it was corroding in an electrolyte while making hydrogen, so they turned to SLAC’s Stanford Synchrotron Radiation Lightsource. There, SLAC researchers developed high- energy-resolution x-ray spectroscopy techniques that could penetrate the electrolyte and filter out other effects, allowing the team to focus on subtle changes in the platinum electrode during operation. Using these methods, researchers made the first-ever observations of platinum actively corroding, recording x-ray spectra from the negatively polarized electrode’s surface. Using computational models of platinum hydrides and platinides, the team simulated the spectra they would expect to see from each structure under the x-ray beam. Comparing the simulated spectra with the results of their experiment confirmed that only platinum hydride could have produced their results. www.universiteitleiden.nl. 2023 launch of NASA’s Crew-6 mission. Some rocket engines use superalloys such as Inconel for certain parts. Courtesy of SpaceX.
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