Effect of heat treatment on stress corrosion behavior of alloy 690 in caustic solution containing Pb

Microstructure of alloy 690 solid-solutioned at different temperatures was investigated by SEM and EBSD technique. The stress corrosion behavior of alloy 690 in NaOH solution containing Pb was studied by a constant strain method. SEM and EBSD results show that the micro structure of alloy 690 solutioned at 1100°C is more uniform. Alloy 690 mill treated at 1100°C has the higher proportion of low coincidence site lattice grain boundaries. The results of stress corrosion test at high temperature and high pressure condition show that alloy 690 treated at 1090°C exhibits higher stress corrosion sensitivity in the test solution. The alloy 690 solution-treated at the lower temperature has the lower proportion of low coincidence site lattice grain boundaries, which increases the stress corrosion sensitivity in NaOH solution containing Pb.