Environmentally enhanced crack growth in nickel-based alloys at elevated temperatures

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:624247

Gao, M; Chen, S F; Chen, G S; Wei, R P ^[1]

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1. Lehigh Univ., Bethlehem, PA (United States). Dept. of Mechanical Engineering and Mechanics

A recent understanding of environmentally enhanced sustained-load crack growth in nickel-based superalloys at elevated temperatures is presented. This understanding is based on the results of coordinated studies of crack growth kinetics, surface chemistry, and microstructure in a commercial Inconel 718. The results suggest that environmental enhancement of sustained-load crack growth in Inconel 718 is associated with the formation and rupture of niobium oxides at grain boundary surfaces and is controlled mainly by the rate of oxidation and decomposition of niobium carbides at the grain boundaries. Data on other nickel-based alloys in the literature appear to support this suggested role of niobium. Initial results from a study of a niobium-free Ni-18Cr-18Fe alloy (its base composition is identical to Inconel 718) confirm the possible influence of niobium and the proposed mechanism. Some open issues for further investigation are discussed.

• OSTI ID: 624247
• Report Number(s): CONF-950618--; ISBN 0-8031-2413-9
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM ALLOYS
CRACK PROPAGATION
HEAT RESISTING ALLOYS
INCONEL 718
IRON ALLOYS
METALLURGICAL EFFECTS
MICROSTRUCTURE
NICKEL BASE ALLOYS
NIOBIUM
TEMPERATURE DEPENDENCE