Optimizing Ni-base Superalloys for Environmental Fracture Resistance and Preventing Catastrophic Failures
Abstract
Ni-base superalloys are commonly chosen for their high strength since they maintain high resistance to both environmental fracture and corrosion. Unfortunately, failures of these alloys have occurred in seawater service with no known root cause. The correlation between environmental fracture mechanisms, microstructure, environment factors for Ni-base alloys is not well understood. Using a combination of experimental and modeling approaches, we demonstrate that shear slip accumulation and high interfacial stresses can occur near grain boundary precipitates, particularly -phase, with precipitate distribution affecting their extent. We explicitly simulated the driving force for hydrogen transport towards a fracture process zone within the material microstructure ahead of an advancing crack by including dislocation transport, trapping, and diffusion driven by stress gradients within the microstructure. The results show that trapping by immobile dislocations can also strongly influence the location of the highest hydrogen concentration, moving it towards the interior of the material. Experimentally measured assisted crack growth rates of various Inconel 718 grades and other high strength alloys measured in seawater at open circuit, under cathodic protection or during alternate immersion are reported.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 16, 2024
- Accession Number
- AD1226825
Entities
People
- Attilio Arcari
- Derek J. Horton
- James A Wollmershauser
- M.A. Zikry
- Mary E. Parker
- Muh-jang Chen
- Patrick G. Callahan
- Ramgopal Thodla
Organizations
- North Carolina State University
- United States Naval Research Laboratory