Open AccessAEM investigations of primary water SCC in nickel alloys
Author(s) -
J. S. Fish,
Duncan Perry,
N. Lewis,
C. D. Thompson,
Wenjing Yang
Publication year - 1997
Language(s) - English
Resource type - Reports
DOI - 10.2172/319835
Subject(s) - intergranular corrosion , grain boundary , materials science , metallurgy , carbide , microstructure , corrosion , cracking , stress corrosion cracking , void (composites) , nickel , composite material
The microstructure of nickel alloys, particularly the grain boundary composition and intergranular precipitates, plays an important role in high temperature primary water stress corrosion cracking (SCC) performance. Analytical electron microscopy (AEM) was used to examine SCC cracks in Alloys 600 and X-750 to investigate the role of grain boundary precipitates, dislocations and oxides in primary water SCC (PWSCC). Analysis of oxides by AEM and ESCA/Auger indicates that the crack tip oxides are different than the oxides formed on the outer surfaces. Comparison of heats with good and poor SCC resistance has identified metallurgical features that affect cracking. These AEM results show that the mechanism of PWSCC in nickel-base alloys does not involve void formation or blunting of the crack tip near intergranular carbides. The role of grain boundary composition, the interaction of cracks with carbides and other intergranular precipitates, and observations from AEM examinations ahead of the crack tip are discussed in relation to the mechanism of SCC