Fracture and fatigue crack-growth behavior of single crystal NiAl
- Stanford Univ., CA (United States). Dept. of Materials Science and Engineering
Single crystal intermetallics have significant potential for gas turbine applications where high temperature strength and oxidation resistance are required. With its low density, high thermal conductivity, and superior oxidation resistance, NiAl + X is a leading candidate as an alternative to conventional superalloys. Typical gas turbine applications will expose the material to significant cyclic and vibrational loading. However, very limited reliable fracture and subcritical crack-growth data currently exists, together with little fundamental understanding of damage and failure modes for NiAl single crystals, particularly at elevated temperatures. There is virtually no knowledge of what constitutes a fracture or fatigue-resistant microstructure or composition, and there is a real uncertainty in potential life-prediction procedures. Accordingly, this work describes progress made in characterizing fracture and fatigue crack-growth behavior in a Nial + Fe single crystal using fracture mechanics based techniques. The authors believe the fatigue crack-growth data presented in this paper to be quite unique, representing the first reported subcritical crack-growth data in such intermetallic single crystals. Surprisingly, their observations appear to indicate that under fatigue loading conditions. cracks may leave the low energy cleavage plane and actually propagate along higher index planes.
- Sponsoring Organization:
- Department of the Air Force, Washington, DC (United States)
- OSTI ID:
- 509204
- Journal Information:
- Scripta Materialia, Vol. 36, Issue 12; Other Information: PBD: 15 Jun 1997
- Country of Publication:
- United States
- Language:
- English
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