Environmental enhancement of creep crack growth in Inconel 718 by oxygen and water vapor

Journal Article · Sun May 15 00:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90257-7· OSTI ID:7303357

Valerio, P; Gao, M; Wei, R P ^[1]

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

Inconel 718 alloy is widely used in high temperature applications. Because of its sensitivity to environmentally enhanced crack growth at high temperatures, its use has been limited to modest temperatures (i.e., below 973 K). To improve its performance and to better predict its service life, it is important to develop a better understanding of the processes of crack growth at high temperatures in this alloy. It has been shown that the creep crack growth rates (CCGR) in air are at least two orders of magnitude faster than those in vacuum or inert environments. CCGR were also found to depend strongly on temperature. Fractographic studies showed that crack growth was intergranular in air and in vacuum with brittle appearing grain boundary separation in air and extensive cavity formation in vacuum. The increased CCGR in air has been attributed to the enhancement by oxygen; principally through enhanced cavity nucleation and growth by high-pressure carbon monoxide/dioxide formed by the reactions of oxygen that diffused into the material with the grain boundary carbides. The appropriateness of this mechanism, however, may be questioned by the absence of cavitation on the crack surfaces produced in air. As such the mechanism for crack growth needs to be re-examined. Because of the presence of moisture in air, the possible influence of hydrogen needs to be considered as well. In this study, preliminary experiments were conducted to examine the process of environmentally enhanced creep crack growth in Inconel 718 alloy in terms of possible mechanisms and rate controlling processes. Creep crack growth experiments were carried out in air, oxygen (from 2.67 to 100 kPa), moist argon (water vapor) and pure argon at temperatures from 873 to 973 K.

• OSTI ID: 7303357
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 30:10; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
CRACK PROPAGATION
CREEP
DATA
EXPERIMENTAL DATA
GRAIN BOUNDARIES
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL 718
INCONEL ALLOYS
INFORMATION
IRON ALLOYS
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM A
NUMERICAL DATA
SEGREGATION
TESTING