ROLE OF ETA PHASE EVOLUTION ON CREEP PROPERTIES OF NICKEL BASE SUPERALLOYS USED IN ADVANCED ELECTRIC POWER GENERATION PLANTS

Author

Ninad Mohale, Michigan Technological UniversityFollow

Date of Award

2021

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering (PhD)

Administrative Home Department

Department of Materials Science and Engineering

Advisor 1

Walter Milligan

Committee Member 1

Paul Sanders

Committee Member 2

Calvin White

Committee Member 3

Douglas Swenson

Committee Member 4

John Shingledecker

Abstract

Advanced fossil energy power generation plants require materials that withstand high temperatures and corrosive environments. One such material that is used in steam turbines is Nimonic 263. It is a nickel-base superalloy that is principally strengthened by gamma primephase (Ni₃(Ti, Al)) and has an L1₂structure. At extended times and at turbine operating temperatures however, eta (Ni₃Ti) phase is known to form at the expense of gamma prime. Eta has a complex DO₂₄structure and is the stable phase between 750°C and 900°C, but with slow kinetics of formation. Little is understood about eta phase, and it may negatively impact the strength and creep resistance of Nimonic 263.

The hypothesis of this project is that eta phase lowers the steady state creep rate of Nimonic 263. The aim of this project was to study the creep performance and deformation behavior of three related materials to isolate the effects of eta phase on steady state creep behavior in secondary creep regime. The three materials are:

1. Standard commercial Nimonic 263 containing only gamma prime
2. Standard commercial Nimonic 263 that has been heat-treated to contain both gamma primeand eta phases prior to creep testing
3. Modified Michigan Tech alloy based on Nimonic 263 that contains only eta and no gamma prime

Based on this improved understanding of creep deformation and failure mechanisms as a function of eta phase, existing creep models were modified to reflect eta phase effects in secondary creep. This modified model will improve life prediction and component design for advanced fossil energy power plant systems.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Recommended Citation

Mohale, Ninad, "ROLE OF ETA PHASE EVOLUTION ON CREEP PROPERTIES OF NICKEL BASE SUPERALLOYS USED IN ADVANCED ELECTRIC POWER GENERATION PLANTS", Open Access Dissertation, Michigan Technological University, 2021.

https://doi.org/10.37099/mtu.dc.etdr/1295