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The susceptibility of alloy 600 (UNS N06600) to stress corrosion cracking (SCC) in hydrogenated high-temperature water was studied as a function of the degree of cold work (CW) of the alloy and the temperature of the solution. Cracks did not nucleate in smooth specimens during constant extension rate testing (CERT). However, cracking susceptibility increased as the degree of CW by bending increased. An extrapolation was made to predict cracking susceptibility in smooth non-CW conditions. The activation energy (Q) for the crack growth rate (CGR) was calculated for two CW conditions in the temperature ranges between 315°C and 350°C and 270°C to 350°C. Results showed there was no unique value of Q. Analysis of Q values suggested that the CGR depended primarily on events occurring inside the alloy, which were enhanced by processes occurring in the metal-electrolyte interface.

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The electrochemical behavior of sensitized, carburized, and mill-annealed alloy 600 (UNS N06600) was studied in hydrogenated, aerated, and high-temperature (250°C to 350°C) dilute aqueous solutions. In high-temperature water at high anodic potentials, the current density (CD) from carbide dissolution was higher than CD from matrix dissolution. In oxidizing environments, intergranular stress corrosion cracking propagated in alloy 600 by dissolution of continuous or semicontinuous carbides at the grain boundary, in sensitized and non-sensitized materials.