SCC OF ALLOY 690 AND ITS WELD METALS

摘要

Alloy 690 base metal, HAZ and weld metal were tested in representative PWR primary water at 290 to 360 °C. Intergranular cracking was observed in all materials. Growth rates as high as 1.2 x 10 mm/s were observed in the S-L orientation with microstructural banded material after cold rolling or forging to align the planes of banding, rolling and cracking. However, not all banded material has exhibited such high growth rates. Growth rates on homogeneous Alloy 690, including extruded CRDM tubing, often showed growth rates in the range of 2 — 8 x 10~(-8) mm/s in cold worked condition and an S-L orientation. Crack growth rates in some Alloy 690 tests were in the range of 1 to 10 x 10~(-9) mm/s, primarily in orientations other than S-L. For cracks aligned along the HAZ, growth rates as high as 1.2 x 10~(-8) mm/s were observed. Alloy 152/52/52i weld metals always exhibited low growth rates, apart from a weld that was further cold worked by 20%, which grew at 7 x 10~(-9) mm/s.