A diverse research team has created innovative protective coatings that enable turbine engines to operate at elevated temperatures, offering potential benefits for both the environment and human health.
A research team from the University of Virginia has designed new coatings that let turbine engines function at increased temperatures before any components start to fail.
“Engines that operate at higher temperatures are more efficient,” mentioned Elizabeth J. Opila, a professor and the chair of UVA’s Department of Materials Science and Engineering, who is a key researcher in this project.
Turbine engines are commonly associated with powering aircraft, but they are also utilized in stationary applications, such as electricity generation. These engines burn fuel to make turbine blades spin, which transforms mechanical energy into electrical power.
“Higher temperatures lead to more effective work output from heat input,” Opila explained. “This potential has sparked interest in coatings that can protect against the harmful gases produced during combustion at these elevated temperatures that may harm turbine blades.”
Improved efficiency results in decreased fuel use and lowered emissions and operating expenses, which is one reason why the U.S. Department of Energy’s ARPA-E ULTIMATE program supported this team’s efforts. Their findings were published in the October issue of Scripta Materialia.
Challenges with Current High-Temperature Materials
Currently, there are two main types of materials used in the hot sections of turbine engines:
- Coated nickel-based superalloys can withstand temperatures up to around 2,200°F, which is still far from the DOE’s target of nearly 3,300°F.
- Ceramic composites utilize multiple coating layers to shield against damage from oxidation, a chemical reaction that takes place when exposed to air and moisture. However, these systems are restricted by the melting point of silicon, a layer that melts at 2,577°F.
The UVA-led group investigated a different material type known as refractory metal alloys. While these metals were extensively researched in the 1960s for their durability and heat resistance, they were largely overlooked due to inadequate oxidation resistance.
The researchers aimed to protect these alloys by testing rare earth oxides—natural chemical compounds with remarkably strong protective qualities—to develop a versatile coating solution.
“By merging various rare earth oxides, we can enhance the protective properties of the underlying substrate using just a single coat,” stated Kristyn Ardrey, a Ph.D. graduate of Opila’s lab and the main author of the study. “This approach enabled us to improve performance without relying on complex multi-layer coatings.”
Collaborative Team Effort
Opila’s lab devised and analyzed new combinations of rare earth elements like yttrium, erbium, and ytterbium. To determine the most effective combinations and boost performance, they collaborated with UVA associate professors Bi-Cheng Zhou and Prasanna Balachandran, who specialize in computer simulations and machine learning methods.
The team applied the coatings to alloys through two established manufacturing techniques. The first involves heating the material until it melts before spraying it on, while the second method uses a liquid mixture that dries and hardens on application. The researchers evaluated the effectiveness of each method under extreme heat and reactive situations, such as exposure to high-temperature steam.
They also collaborated with Professor Patrick Hopkins’ ExSiTE Lab at UVA, which focuses on measuring heat resistance and material strength using lasers.
“This was a truly cooperative endeavor,” Opila remarked. “The use of machine learning and computational techniques allowed us to examine a wide variety of potential material combinations, and Patrick’s lab played a crucial role in assessing the physical properties of the materials we created.”
Further Improvements Required
As one of the pioneering research groups to test multicomponent rare earth oxides, the team recognizes that additional testing and refinement are essential. They plan to use computer simulations to continue enhancing the coatings and explore the most effective application methods.
Nonetheless, their findings mark a significant advancement in turbine engine technology, benefitting everyone involved.
“Minimizing fuel usage and emissions while enhancing engine effectiveness benefits not only sectors like energy and aviation,” Opila concluded. “It also contributes to a cleaner environment and reduced costs for everyday consumers.”
