EFFECTS OF DENDRITE ORIENTATION AND WATER CHEMISTRY ON STRESS CORROSION CRACKING PATH AND KINETICS OF ALLOY 182 WELD METAL IN HIGH-TEMPERATURE WATER

摘要

Stress corrosion cracking growth rates of Alloy 182 weld metals in T-S and T-L orientations in 288°C pure water with various dissolved oxygen and hydrogen concentrations were measured. High angle random boundaries are dominant in Alloy 182. Extensive inter-dendritic stress corrosion cracking paths on the side surfaces and fracture surfaces of both T-S and T-L orientation specimens. Crack growth rates of the T-S specimen are significantly higher than those of the T-L specimen under the same test conditions. The crack growth path in the T-S orientation specimen is apparently perpendicular to the applied loading direction, which appears to be parallel to the loading direction in the T-L specimen. The crack growth rate decreased significantly with decreasing dissolved oxygen concentration. Dissolved hydrogen in water would affect the crack tip interface condition thus cause a transient decreasing effect on the potential drop signal during crack growth monitoring.