51312-01641-Stress Corrosion Cracking of a Highly Cold Worked Alloy 690 in Deaerated High Temperature Water

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Product Number: 51312-01641-SG

ISBN: 01641 2012 CP

Author: Guoping Cao

Publication Date: 2012

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In this study tapered uniaxial tensile samples under constant load and bent ring samples under constant strain were used for evaluating the stress corrosion cracking (SCC) of two INCONEL alloys 600 and 690 in supercritical water. During exposure of the tapered tensile specimen in supercritical water the stress level is varied along the specimen which can help evaluate the threshold stress for SCC initiation. After being exposed in pure supercritical water at 400oC 25MPa and 15 ppb dissolved oxygen for 650 hours under a stress level of 150% yield strength Alloy 600 showed some slight stress corrosion cracking initiations. In the bent ring samples both alloys 600 and 690 showed stress corrosion cracking. It is interesting to see significant stress corrosion cracking in the Alloy 690 bent ring samples. The reason is probably that the tested Alloy 690 has a very low ductility (about 8%) as compared with standard 40-50% and the strain level during making the bent ring samples is too high for this Alloy 690. This unexpected stress corrosion cracking behavior in Alloy 690 in SCW will be studied by using alloys from different heats with different mechanical properties. The SCC initiation and growth of the Alloy 600 and 690 (different heats) in hydrogenated supercritical water are still in progress and the SCC performance of the two alloys will be presented.