Niobium enrichment and environmental enhancement of creep crack growth in nickel-base superalloys
- Lehigh Univ., Bethlehem, PA (United States). Dept. of Mechanical Engineering and Mechanics
- Univ. of Maine, Orono, ME (United States). Lab. for Surface Science and Technology
In this paper, the possible role of niobium in the environmental enhancement of creep crack growth in nickel-base superalloys is further examined. The examination included (1) surface enrichment of Nb in a commercial Inconel 718; (2) a source of niobium and its interaction with oxygen; (3) preferential oxidation of Nb at the crack tip, and (4) correlations between environmental sensitivity and niobium concentration of nickel-base superalloys from the literature. The role of niobium was suggested by recent X-ray photoelectron spectroscopic (XPS) studies. The XPS studies show a significant increase in the concentration of niobium on the (001) surface of an Inconel 718 single crystal after heating at temperatures above 775 K. Considerable segregation of niobium was also found on the grain boundaries of a thermally aged commercial (polycrystalline) Inconel 718. The CCGR data showed significant enhancement by oxygen and water vapor at temperatures of 800--975 K where niobium enrichment occurred.
- OSTI ID:
- 55423
- Journal Information:
- Scripta Metallurgica et Materialia, Vol. 32, Issue 8; Other Information: PBD: 15 Apr 1995
- Country of Publication:
- United States
- Language:
- English
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