NETL researchers are reporting a breakthrough in efforts to extend the life and improve the efficiency of energy-producing gas turbines by refining a process that can simulate how corrosion-causing thermally grown oxide (TGO) develops and causes cracking in the environmental barrier coatings (EBCs). This development is crucial for protecting next-generation turbine blades from thermal cycling damage.

Better coatings can lead to more effective and longer-lasting gas turbines.

The researchers reported their success in a paper published in the journal Acta Materials, titled “Phase-Field Modeling of Thermally Grown Oxide and Damage Evolution in Environmental Barrier Coatings.”

A gas turbine is a combustion engine at the heart of many power plants that can convert natural gas or other liquid fuels to mechanical energy. This energy then drives a generator that produces the electrical energy that moves along power lines to homes and businesses.

Gas turbines also power aircraft, trains, ships, pumps, gas compressors and tanks.

NETL researchers Tianle Cheng, Fei Xue, Yinkai Lei, Richard Oleksak, Ömer Doğan and Youhai Wen, who all are based at the laboratory’s Albany, Oregon, site, authored the paper.

According to the paper, “The pressing demand for improving the energy efficiency in gas turbines necessitates materials that can endure increasingly higher temperatures within oxidizing atmospheres. Current state-of-the-art structural materials in the hot sections of gas turbines are mainly nickel-based superalloys, complemented by thermal barrier coatings. For next-generation gas turbine engines, ceramic matrix composites protected by environmental barrier coatings is one promising material solution. Although some success has been achieved with current generation EBCs, development of more effective and durable EBCs remains of significant technological importance.”

Current state-of-the-art EBCs typically consist of a rare earth silicate topcoat and a metallic silicon bond coat that attaches the topcoat to the substrate. However, at high temperatures, oxygen penetrates the topcoat and reacts with the bond coat to form a TGO layer. 

Wen explained that more robust and efficient EBCs are needed to accommodate high-temperature oxidative environments.

“TGO layers spontaneously form in the EBC systems,” he said. “Those TGOs are critical factors in the degradation and failure of environmental barrier coatings, yet the detailed mechanisms of TGO growth remains unclear. NETL developed a comprehensive model that can simulate growth of TGO layers in environmental barrier coatings.”

In the NETL approach, researchers performed large-scale three-dimensional simulations to model the formation of interconnecting vertical/channel cracks, often called “mud cracks.” The simulations provide insights into the cracking of EBCs and its dependence on the coating system’s structure and properties.

“These results highlight the potential of the damage model as a useful tool for designing more durable EBCs, which are critical for next-generation gas turbines, especially those powered by sustainable fuels like hydrogen,” Wen said.

NETL is a U.S. Department of Energy national laboratory that drives innovation to deliver solutions for a secure energy future. Through its expertise and research facilities, NETL is advancing technologies to unleash America’s affordable, reliable, and secure domestic energy and natural resources.