MMAE Seminar - The Impact of Oxidation on the Performance of Ni-based Superalloys Used in Turbine Disk Applications
Dr. Chantal K. Sudbrack from NASA Glenn Research Center, OH, will visit IIT on November 5th, 2014 to present a seminar "The Impact of Oxidation on the Performance of Ni-based Superalloys Used in Turbine Disk Applications."
Abstract
Due to excellent mechanical properties at elevated temperatures, hot section turbines in aviation gas engines are fabricated from advanced Ni-based γ'-superalloys. Higher operating temperatures are needed in key components like high-pressure turbine (HPT) and last-stage compressor disks to achieve substantial gains in fuel efficiency. Turbine disks are bulky and are regarded as critical components to flight safety; a failure is a serious hazard. Low cycle fatigue (LCF) is an important design criteria for turbine disks. Powder metallurgy (PM) superalloys, like René 142 in the GE90 engine, have led to major improvements in temperature performance through refractory additions (e.g. Mo, W) at the expense of environmental resistance (Al, Cr). Service conditions for aerospace disks can produce major cycle periods extending from minutes to hours and days with total service times exceeding 1,000 hours in aerospace applications. Some of the effects of service can be captured by extended exposures at elevated temperature prior to LCF testing. Above 500 °C, oxidation can reduce the fatigue life of disk alloys via accelerated crack initiation and growth at defects; cracking often tends to be intergranular, making grain boundary chemistry and characteristics important. NASA third-generation-from-now goals require peak rim temperatures of 815 °C, where durability is limited by time-dependent creep-fatigue-environment interactions and PM alloys are no longer suitable; hence NASA-GRC is pursuing a hybrid disk concept that consists of joining a low density single-crystal alloy rim to a PM alloy bore. This talk will cover various aspects of the impact of oxidation between 700 °C and 815 °C on the performance of coated and uncoated PM and single-crystal Ni-based superalloys with the above context in mind.
Biography
Key aspects in Dr. C. K. Sudbrack's research with NASA Glenn's turbine disk team include alloy development strategies, thermal barrier coatings, environmental damage mechanisms, processing relationships, additive manufacturing and microstructural predictions of commercial nickel-based superalloys. Sudbrack received her B.A. degree in Chemistry from Reed College and B.S. degree in Materials Science and Engineering from Columbia University in 1999, and a Ph.D. degree in Materials Science and Engineering from Northwestern University in 2004. Prior to joining NASA Glenn in 2009, she held post-doctoral research positions at Argonne National Laboratory and Northwestern University that leveraged her expertise in atom-probe tomography. Sudbrack has co-authored about 30 peer-reviewed journal articles, NASA technical reports and conference proceedings with over 300 citations. She actively works on technical programming for the TMS's High Temperature Alloys committee, and is currently serving a four-year appointment as the committee's JOM technical editor. Sudbrack enjoys mentoring and supporting a variety of research activities for undergraduate and graduate students.