SYMPOSIA PAPER Published: 01 January 1988

Creep Crack Growth of Alloy 800H in Controlled-Impurity Helium


The creep crack growth behavior of Alloy 800H has been characterized at temperatures of 677C (1250F) and 732C (1350F) in controlled-impurity helium. Cold-worked material in various recrystallized conditions, expected to be encountered in elevated-temperature service, was tested in center-cracked tension specimen form under constant load. The tests were conducted under dominantly steady-state conditions where the estimated transition time to steady-state creep for each test is a small fraction of the total test time. The results indicate that the crack-tip field parameter, C*, as was experimentally measured, is a good descriptive parameter for the steady-state creep crack growth rate of this material. In fact, the crack growth rate, da/dt, versus C* data from all five tests spanning three different material conditions, two temperatures, and three orders of magnitude of crack growth rates appeared to consolidate into a single straight line on a logarithmic plot. The metallographic results show that crack extension occurs dominantly by the intergranular creep camage mechanisms anticipated in service.

Author Information

Foulds, JR
Failure Analysis Associates, Palo Alto, CA
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Developed by Committee: E08
Pages: 112–126
DOI: 10.1520/STP26773S
ISBN-EB: 978-0-8031-5063-8
ISBN-13: 978-0-8031-1174-5