1. Oxidation-Assisted Crack Growth in Single-Crystal Superalloys during Fatigue with Compressive Holds
- Author
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Tresa M. Pollock, Ming Y. He, M. A. Lafata, and Rettberg Luke H
- Subjects
010302 applied physics ,Materials science ,Structural material ,Metallurgy ,Metals and Alloys ,Oxide ,02 engineering and technology ,Penetration (firestop) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Finite element method ,Superalloy ,Crack closure ,chemistry.chemical_compound ,Creep ,chemistry ,Mechanics of Materials ,0103 physical sciences ,Composite material ,0210 nano-technology ,Single crystal - Abstract
The mechanism of oxidation-assisted growth of surface cracks during fatigue with compressive holds has been studied experimentally and via a model that describes the role of oxide and substrate properties. The creep-based finite element model has been employed to examine the role of material parameters in the damage evolution in a Ni-base single-crystal superalloy Rene N5. Low-cycle fatigue experiments with compressive holds were conducted at 1255 K and 1366 K (982 °C and 1093 °C). Interrupted and failed specimens were characterized for crack depth and spacing, oxide thickness, and microstructural evolution. Comparison of experimental to modeled hysteresis loops indicates that transient creep drives the macroscopic stress–strain response. Crack penetration rates are strongly influenced by growth stresses in the oxide, structural evolution in the substrate, and the development of $$\gamma ^{\prime }$$ denuded zones. Implications for design of alloys resistant to this mode of degradation are discussed.
- Published
- 2017