Effects of carbides on susceptibility of alloy 600 to stress corrosion cracking in high-temperature water

The electrochemical behavior of sensitized, carburized, and mill-annealed alloy 600 (UNS N06600) was studied in hydrogenated, aerated, and high-temperature (250 to 350 C) dilute aqueous solutions. In high-temperature water at high anodic potentials, the current density (DC) from carbide dissolution was higher than DC 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. These studies have been conducted in environments similar to those in the steam generators of pressurized water reactors (PWR) in nuclear power plants