Rolls-Royce extends successful research partnership

Rolls-Royce North American Technologies is extending its collaboration with The Ohio State University in their efforts to build a better jet engine.

This sponsored research on "Microstructural Investigation of Environmentally Assisted Crack Growth" focuses on the role of structural and compositional instabilities that occur during microstructural evolution, and how they influence the environmentally accelerated damage processes in nickel-based superalloys.

As jet engine manufacturers intensify their efforts to increase the operating temperature of turbine alloys above 700°C, concerns about the corrosion caused by oxygen and sulfur are moving to the forefront. Improving the operating temperature of disk alloys by only 25°C would translate into approximately a 10 percent increase in aircraft engine efficiency, resulting in cost savings in the billions and reduction of CO2 emissions for a fleet of aircraft during their service life.

“Unfortunately, the life of the rotating components in these engines, especially under the sustained and cyclic loading conditions experienced during a plane’s take off and landing, can be significantly reduced by the corrosive environment inside the engines,” said G. Babu Viswanathan, the program’s principal investigator and a senior research scientist at Ohio State’s Center for Electron Microscopy and Analysis (CEMAS). 

“The reduction in fatigue life at these punishing high temperatures is primarily caused by the absorption of oxygen into the materials, making them fail prematurely,” Viswanathan added.

The oxygen-induced damage is often also accentuated by the deformation caused by the creep-fatigue processes occurring simultaneously with the environmental damage. “This damage can only be mitigated if we understand where it causes changes to the local microstructure, in places such as grain boundaries, and at the relevant length scale.”

The kind of state-of-the-art instrumentation needed for this research is available at CEMAS.

“The aberration corrected Titan 60-300 kV (S)TEM microscopes, for example, are equipped with image Cs correctors, a monochromator and ChemiSTEM technology, and an ultrahigh resolution EELS spectrometer, and provide unparalleled capabilities for materials characterization down to sub-Ångstrom levels,” Viswanathan said. “It is the objective of this research program to use these state-of-the art capabilities in CEMAS and other testing facilities in the Department of Materials Science and Engineering to capture, assess and develop accurate descriptions of the early stages of environmentally induced damage buildup in nickel-based superalloys, and so develop solutions for mitigating or minimizing damage accumulation."

Joining Viswanathan on the project is Materials Science and Engineering (MSE) Professor Mike Mills. Based on efforts in the last two years, Rolls-Royce also has added support for computational modeling work to complement experimental results. Maryam Ghazisaeidi, an MSE assistant professor, will spearhead the modeling efforts on the project.